ALCA December 2016
You also want an ePaper? Increase the reach of your titles
YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.
THE<br />
OF THE AMERICAN<br />
LEATHER CHEMISTS ASSOCIATION<br />
<strong>December</strong> <strong>2016</strong> Vol. CXI, No. 12 J<strong>ALCA</strong> 111(12), 427-462, <strong>2016</strong><br />
Contents<br />
113th Annual<br />
Convention<br />
to be held at the<br />
Pinehurst Resort<br />
Village of Pinehurst, NC<br />
June 13-16, 2017<br />
For more information go to<br />
www.leatherchemists.org/<br />
annual_meeting.asp<br />
Synthesis and Application of a New Phosphate Ester Based on<br />
Nonionic Amphiphilic Polyurethane as Leather Fatliquoring Agent............. 427<br />
by Hanping Li, Yong Jin, Baozhu Fan, Rui Qi and Xinfeng Cheng<br />
Minimization of Chromium Discharge in Leather Processing by<br />
using Methanesulfonic Acid: A Cleaner Pickling-masking-chrome<br />
Tanning System..................................................................................................... 435<br />
by Chunxiao Zhang, Fuming Xia, Biyu Peng, Qing Shi,<br />
Dominic Cheung and Yongbin Ye<br />
Development of Chrome-free Tanning in Supercritical CO 2<br />
Fluid<br />
using Zr-Al-Ti Complex....................................................................................... 447<br />
by Xinhua Liu, Feng Li, Qin Huang, Wiehua Dan and Nianhua Dan<br />
Studies on the use of Bi-functional Enzyme for Leather Making............... 455<br />
by G. Jayakumar, M. Sathish, R. Aravindhan and J. Raghava Rao<br />
Lifelines................................................................................................................... 461<br />
<strong>ALCA</strong> and Industry News<br />
Call for Papers – 113th Annual Convention, June 13-16, 2017................... 462<br />
ISSN: 0002-9726<br />
Communications for Journal Publication<br />
Manuscripts, Technical Notes and Trade News Releases should contact<br />
Mr. Robert F. White, Journal Editor, 1314 50th Street, Suite 103, Lubbock, TX 79412, USA.<br />
E-mail: jalcaeditor@prodigy.net Mobile phone: (616) 540-2469<br />
Contributors should consult the Journal Publication Policy at<br />
http://www.leatherchemists.org/journal_publication_policy.asp
BUCKMAN LEATHER TECHNOLOGIES<br />
Optimize wetblue consistency.<br />
Maximize process efficiency.<br />
Quality leather begins with consistent wetblue. And that begins with Buckman<br />
Beamhouse & Tanyard Systems. We bring you the products<br />
and processes you need to ensure consistency, make<br />
crust and finishing easier, and produce superior leather<br />
more sustainably and efficiently.<br />
Contact your Buckman representative today<br />
to discuss all the benefits of Buckman<br />
Beamhouse & Tanyard Systems, or visit us at<br />
www.buckman.com.<br />
© 2013 Buckman Laboratories International, Inc. All rights reserved.
JOURNAL OF THE<br />
AMERICAN LEATHER CHEMISTS ASSOCIATION<br />
Proceedings, Reports, Notices, and News<br />
of the<br />
AMERICAN LEATHER CHEMISTS ASSOCIATION<br />
OFFICERS<br />
David Peters, President<br />
DLP Advisors<br />
8206 Santa Rosa Court<br />
Sarasota, FL 34243<br />
Mike Bley, Vice-President<br />
Eagle Ottawa – Lear<br />
2930 Auburn Road<br />
Rochester Hills, MI 48309<br />
Shawn Brown<br />
Quaker Color<br />
201 S. Hellertown<br />
Quakertown, PA 18951<br />
Joseph Hoelfer<br />
The Dow Chemical Company<br />
400 Arcola Rd.<br />
Collegeville, PA 19426<br />
COUNCIL<br />
Jeffrey D. Miller<br />
GST AutoLeather, Inc.<br />
31601 Industrial Road<br />
Livonia, MI 48150<br />
Andreas W. Rhein<br />
Tyson Foods, Inc.<br />
800 Stevens Port Drive<br />
Dakota Dunes, SD 57049<br />
Beat Schelling<br />
Wickett & Craig of America<br />
120 Cooper Rd.<br />
Curwensville, PA 16833<br />
Katie Thudium<br />
Eagle Ottawa – Lear<br />
2930 Auburn Road<br />
Rochester Hills, MI 48309<br />
Dr. Meral Birbir<br />
Department of Biology<br />
Marmara University<br />
Istanbul, Turkey<br />
Chris Black<br />
Consultant<br />
St. Joseph, Missouri<br />
Dr. Eleanor M. Brown<br />
Eastern Regional<br />
Research Center<br />
U.S. Department of Agriculture<br />
Wyndmoor, Pennsylvania<br />
Kadir Donmez<br />
Leather Research Laboratory<br />
University of Cincinnati<br />
Cincinnati, Ohio<br />
Dr. Anton Ela’mma<br />
Retired<br />
Perkiomenville, Pennsylvania<br />
Elton Hurlow<br />
Buckman International<br />
Memphis, Tennessee<br />
Prasad V. Inaganti<br />
Wickett and Craig of America<br />
Curwensville, Pennsylvania<br />
Steve Lange<br />
Leather Research Laboratory<br />
University of Cincinnati<br />
Cincinnati, Ohio<br />
Xue-Pin Liao<br />
National Engineering Laboratories<br />
Sichuan University<br />
Chengdu, China<br />
Dr. Cheng-Kung Liu<br />
Eastern Regional<br />
Research Center<br />
U.S. Department of Agriculture<br />
Wyndmoor, Pennsylvania<br />
EDITORIAL BOARD<br />
John Moore<br />
Retired<br />
Petaluma, California<br />
Dr. Edwin H. Nungesser<br />
Dow Chemical Company<br />
Spring House, Pennsylvania<br />
Dr. J. Raghava Rao<br />
Central Leather<br />
Research Institute<br />
Chennai, India<br />
Andreas W. Rhein<br />
Tyson Foods, Inc.<br />
Dakota Dunes, South Dakota<br />
Dr. Bi Shi<br />
National Key Laboratories<br />
Sichuan University<br />
Chengdu, China<br />
George Stockman<br />
Retired<br />
Clemson, SC<br />
Maryann M. Taylor<br />
Eastern Regional<br />
Research Center<br />
U.S. Department of Agriculture<br />
Wyndmoor, Pennsylvania<br />
Dr. Palanisamy<br />
Thanikaivelan<br />
Central Leather<br />
Research Institute<br />
Chennai, India.<br />
Brandon Yoemans<br />
S. B. Foot Tanning Co.<br />
Red Wing, Minnesota<br />
PAST PRESIDENTS<br />
G. A. Kerr, W. H. Teas, H. C. Reed, J. H. Yocum, F. H. Small, H. T. Wilson, J. H. Russell, F. P. Veitch, W. K. Alsop, L. E. Levi, C. R. Oberfell, R. W. Griffith, C. C. Smoot,<br />
III, J. S. Rogers, Lloyd Balderson, J. A. Wilson, R. W. Frey, G. D. McLaughlin, Fred O’Flaherty, A. C. Orthmann, H. B. Merrill, V. J. Mlejnek, J. H. Highberger, Dean<br />
Williams, T. F. Oberlander, A. H. Winheim, R. M. Koppenhoefer, H. G. Turley, E. S. Flinn, E. B. Thorstensen, M. Maeser, R. G. Henrich, R. Stubbings, D. Meo, Jr., R.<br />
M. Lollar, B. A. Grota, M. H. Battles, J. Naghski, T. C. Thorstensen, J. J. Tancous, W. E. Dooley, J. M. Constantin, L. K. Barber, J. J. Tancous, W. C. Prentiss, S. H.<br />
Feairheller, M. Siegler, F. H. Rutland, D.G. Bailey, R. A. Launder, B. D. Miller, G. W. Hanson, D. G. Morrison, R. F. White, E. L. Hurlow, M. M. Taylor, J. F. Levy, D.<br />
T. Didato, R. Hammond, D. G. Morrison, W. N. Mullinix, D. C. Shelly, W. N. Marmer, S. S. Yanek, D. LeBlanc, C.G. Keyser, A.W. Rhein, S. Gilberg, S. Lange, S. Drayna<br />
THE JOURNAL OF THE AMERICAN LEATHER CHEMISTS ASSOCIATION (USPS #019-334) is published monthly by The American Leather Chemists Association,<br />
1314 50th Street, Suite 103, Lubbock, Texas 79412. Telephone (806)744-1798 Fax (806)744-1785. Single copy price: $8.50 members, $17.00 non-member. Subscriptions: $175 for<br />
hard copy plus postage and handling of $60 for domestic subscribers and $70 for foreign subscribers; $175 for ezine only; and $195 for hard copy and ezine plus postage and handling<br />
of $60 for domestic subscribers and $70 for foreign subscribers.<br />
Periodical Postage paid at Lubbock, Texas and additional mailing offices. Postmaster send change of addresses to The American Leather Chemists Association, 1314 50th Street,<br />
Suite 103, Lubbock, Texas 79412.<br />
Website: www.leatherchemists.org E-mail: <strong>ALCA</strong>@leatherchemists.org<br />
COPYRIGHT <strong>2016</strong>. THE AMERICAN LEATHER CHEMISTS ASSOCIATION
427<br />
Synthesis and Application of a New Phosphate<br />
Ester Based on Nonionic Amphiphilic Polyurethane<br />
as Leather Fatliquoring Agent<br />
by<br />
Hanping Li, A,B Yong Jin, A,B * Baozhu Fan, C,D Rui Qi C,D and Xinfeng Cheng C,D<br />
A<br />
Key Laboratory of Leather Chemistry and Engineering, Ministry of Education,<br />
Sichuan University, Chengdu 610065, China<br />
B<br />
National Engineering Laboratory for Clean Technology of Leather Manufacture,<br />
Sichuan University, Chengdu 610065, China<br />
C<br />
Chengdu Institute of Organic Chemistry, Chinese Academy of Science, Center of Polymer Science and Technology,<br />
Chengdu 610041, China<br />
D<br />
University of Chinese Academy of Sciences,<br />
Beijing 100049, China<br />
Abstract<br />
A new polyurethane phosphate ester (PUP-2) was successfully<br />
synthesized based on a nonionic amphiphilic polyurethane<br />
(PU-2). The structures and properties of PU-2 and PUP-2 were<br />
characterized by FTIR and surface tensiometer. The fatliquoring<br />
experiments were carried out in three different groups (treated with<br />
PUP-2 alone, with the complex of hexadecyl phosphate ester (SLP)<br />
and PUP-2, or with the complex of SLP, PUP-2 and other<br />
commercialized fatliquoring agents, respectively). The physical and<br />
organoleptic properties of the resultant leathers were investigated<br />
and SEM was carried out in the study of fiber splitting. The leathers<br />
treated in the three different fatliquoring experiments all did not<br />
have fatty spew defect. Furthermore, the resultant leathers treated<br />
with PUP-2 alone or with the complex of SLP and PUP-2 had the<br />
advantage of resistance to yellowing. This new phosphate ester<br />
meets the requirements for the leathers with a good performance in<br />
resistance to yellowing and avoiding fatty spew defect.<br />
Introduction<br />
Currently a wide variety of fatliquoring agents are being used in<br />
leather manufacturing. 1-3 Phosphorylated fatliquoring agents are<br />
widely used due to the advantages of low toxicity, low stimulation<br />
and good biodegradability. 4, 5 Most of the phosphate esters used<br />
at present are natural phosphate esters or synthetic phosphate<br />
esters which are usually synthesized based on modified natural<br />
oils or high-carbon alcohols. 6, 7<br />
However, the natural phospholipids have some disadvantages<br />
such as easy to mildew, dull color and low emulsion stability. 8,9 In<br />
addition, the synthetic phosphate esters based on modified<br />
natural oils can be oxidized due to the carbon-carbon double<br />
bonds of natural oils, 10 thus resulting in the poor performance of<br />
leathers and limiting their applications. What’s more, although<br />
the high-carbon alcohol phosphate esters can improve the oil<br />
feeling, waxy feeling and waterproofness of leathers, they usually<br />
result in fatty spew formation on the leather surface when the<br />
temperature is low, which can be attributed to their low<br />
emulsification, poor permeability and high freezing point. Thus,<br />
it was really necessary for the leather industry to develop a new<br />
phosphate ester with higher emulsification, richer permeability,<br />
lower freezing point and no carbon-carbon double bonds to be<br />
substituted for the traditional ones.<br />
In this paper, a new polyurethane phosphate ester (PUP-2) was<br />
prepared, which consists of the soft molecular chains. And<br />
carbon-carbon double bonds are not involved here, too.<br />
Moreover, the nonionic amphiphilic structural features can<br />
improve the permeability and stability of the resultant<br />
fatliquoring emulsions. The above advantages of the<br />
polyurethane phosphate ester are in accord with the growing<br />
demand for the leathers with the good properties of resistance to<br />
yellowing and avoiding fatty spew defect.<br />
*Corresponding author e-mail: jinyong@scu.edu.cn<br />
Manuscript received March 25, <strong>2016</strong>, accepted for publication June 14, <strong>2016</strong>.<br />
J<strong>ALCA</strong>, VOL. 111, <strong>2016</strong>
Phosphate Ester as Fatliquoring Agent 428<br />
Experimental<br />
Materials<br />
Isophorone diisocyanate (IPDI), polyethylene glycol monomethyl<br />
ether (MPEG, Mn=750 g/mol) and polyoxypropylene ether<br />
(PPG, Mn=2000 g/mol), AR grade, were purchased from<br />
Shanghai Chemical Reagents Corporation, China. Dibutyltin<br />
dilaurate (DBTDL), phosphorus pentoxide (P 2<br />
O 5<br />
) and<br />
hexadecanol, AR grade, were purchased from Ke Long Chemical<br />
Corporation, China. SWA, FG-B, FL-71, NL-20, HN01, A18, JM,<br />
JMK, OF, FS-90, melamine, dicyandiamide, dispersing tannin,<br />
chestnut and protein filler, purchased from Dowell Technology<br />
Co., Ltd., were used as industrial grade. Wattle extract, industrial<br />
grade, was purchased from UNITY Corporation, Argentina. PF<br />
aldehyde, industrial grade, was purchased from Zschimmer &<br />
Schwarz Chemicals. Basic chromium sulphate, industrial grade,<br />
was purchased from Ming Feng Chemical Corporation, China.<br />
Wet blue bovine hides were purchased from Da Fan Jiu Leather<br />
Corporation, China. Other chemicals were of analytical grade<br />
and used as received. All of them were used without further<br />
purification.<br />
Synthesis of Hexadecyl Phosphate Ester (SLP),<br />
PU-2 and PUP-2<br />
A certain amount of hexadecanol was plunged into a 100 ml<br />
three-necked flask equipped with a stirrer and a thermometer at<br />
50°C. Under the high-speed stirring, a quantitative amount of<br />
P 2<br />
O 5<br />
with a mole ratio of ROH: P 2<br />
O 5<br />
=3: 1 which was divided into<br />
four same parts was added with an internal of 10 min. After all<br />
of P 2<br />
O 5<br />
was added and dispersed completely, the system was<br />
heated up to 85°C and maintained for 5 h. Then, a small amount<br />
of water with a mole ratio of P 2<br />
O 5:<br />
H 2<br />
O=1: 1 was added at 30°C.<br />
After 1.5 h, the product of SLP was obtained.<br />
The calculated amount of MPEG and DBTDL (a mole ratio of<br />
MPEG: DBTDI=1: 0.002) were placed in a four-necked flask<br />
equipped with a thermometer and a mechanical stirrer. While<br />
stirring heated to 60°C, the calculated amount of IPDI with a<br />
mole ratio of MPEG: IPDI=1: 1 was added dropwise into the<br />
flask. The reaction was carried out at 60°C for 4 h. PPG-2000<br />
with a mole ratio of MPEG: PPG-2000=1: 1 was then added and<br />
allowed to react for another 2 h at 80°C. The nonionic<br />
amphiphilic diblock polyurethane (PU-2) was obtained.<br />
A certain amount of PU-2 was plunged into a 100 ml threenecked<br />
flask equipped with a stirrer and a thermometer at 50°C.<br />
A quantitative amount of P 2<br />
O 5<br />
with a mole ratio of PU-2: P 2<br />
O 5<br />
=1:<br />
2 which was divided into four same parts was added with an<br />
internal of 10 min. After all of the P 2<br />
O 5<br />
was added and dispersed<br />
completely, the system was heated up to 85°C and maintained<br />
for 5 h. After the reaction, mixture was cooled to 30°C,<br />
a calculated amount of water was added with a certain<br />
Scheme 1. Synthesis of PU-2 and PUP-2.<br />
mole ratio (H 2<br />
O: P 2<br />
O 5<br />
=2: 1) by stirring. After 1.5 h, the polyurethane<br />
phosphate ester (PUP-2) was prepared. The preparation of PU-2 and<br />
PUP-2 is shown schematically in Scheme 1.<br />
Application on Leathers<br />
The wet blue bovine hid was cut into two pieces (200mm x<br />
150mm), which had the symmetry along the spine to make sure<br />
the same fiber woven status. One was treated with fatliquoring<br />
agents and the other one was not as a comparison. The retanning<br />
and fatliquoring process of leathers is shown in Table I, and the<br />
three ways of fatliquoring were carried out as follows:<br />
Experiment 1- Treated with PUP-2 alone, its weight was 2%, 4%,<br />
8% or 12% of wet blue bovine hide’s weight respectively.<br />
Experiment 2- Treated with the complex of SLP and PUP-2, and<br />
the total weight of them was 8% of wet blue bovine hide’s weight.<br />
There were four weight ratios between SLP and PUP-2, SLP:<br />
PUP-2=1:9, SLP: PUP-2=2:8, SLP: PUP-2=3:7 or SLP: PUP-2=4:6,<br />
respectively.<br />
Experiment 3- Treated with the complex of SLP, PUP-2 and other<br />
commercialized fatliquoring agents. The weight of SLP and<br />
PUP-2 was 2% of wet blue bovine hide’s weight, and the<br />
commercialized fatliquoring agents accounted for the remaining<br />
6% (2.5%JM, 1.5%JMK,1.5%FS-90 and 0.5%OF, respectively).<br />
Description of the Experimental Tests<br />
FTIR Characterization<br />
The FTIR spectrum was recorded with a Thermo Fisher Nicolet<br />
6700 spectrophotometer in KBr pellets. The range of 400-4000<br />
cm -1 was scanned and the result was recorded.<br />
J<strong>ALCA</strong>, VOL. 111, <strong>2016</strong>
429 Phosphate Ester as Fatliquoring Agent<br />
Surface Tension Measurement<br />
The surface tension was determined by a BZY-1 automatic<br />
tensiometer, which was configured with a platinum plate and a<br />
sample cell. The platinum plate was rinsed with ethanol and<br />
deionized water several times and then flamed with an alcohol<br />
lamp to get rid of the contaminants before and after every test.<br />
After calibrating the tensiometer, a quantitative of the product<br />
solution, which was stabilized for at least 24h, was measured<br />
three times at 25°C, and the final surface tension value of the<br />
product was determined by an average of the three values.<br />
Physical and Organoleptic Properties Test<br />
The final leathers were sampled and conditioned according to<br />
the standard method. 11 With a tensile machine AI-7000S<br />
(GOTECH TESTING MACHINES INC, Taiwan), the physical<br />
properties, such as tensile strength, tear strength and elongation<br />
12, 13<br />
were tested with the standard methods.<br />
The softness, grain tightness and lubricating sense of the treated<br />
resultant leathers were assessed as the organoleptic properties<br />
with hand and visual examinations by three different qualified<br />
leather technologists and reported as an average value. They<br />
were visually examined and measurements were given on a scale<br />
of 0-10 points for each functional property, where higher points<br />
indicate better properties exhibited.<br />
Fatty Spew Test<br />
The leathers which were treated with PUP-2 alone (8%, w/w), the<br />
complex of SLP and PUP-2 (SLP: PUP-2=3: 7, 8%, w/w), or the<br />
complex of SLP, PUP-2 (SLP: PUP-2=3: 7, 2%, w/w) and other<br />
commercialized fatliquoring agents (6%, w/w) were respectively<br />
placed at a temperature of -37°C for a week.<br />
Resistance to Yellowing<br />
Testing: The resistance to yellowing of leathers was tested with a<br />
Q-LAB QUV resistant to climate testing equipment (GOTECH<br />
TESTING MACHINES INC, Taiwan). The test was conducted<br />
according to ISO 105-B02 standard method 2: 50°C, 65%RH,<br />
Xenon arc test lamp, 7 IR filter and 42 W/m 2 . 14<br />
Table I<br />
Retanning and fatliquoring process.<br />
Process Amount Product Time Temperature pH<br />
200% Water<br />
Wash<br />
0.05-0.2% Formic acid<br />
0.20% SWA<br />
40 min<br />
0.10% FG-B Check pH (4.0)<br />
Drain & Wash<br />
100% Water<br />
0.50% FL-71 10 min<br />
2% NL-20 30 min 40°C<br />
Check pH (4.5)<br />
2% Wattle extract 40 min<br />
Retanning<br />
0.2-0.4% Formic acid 20 min Check pH (3.8)<br />
3% Chrome<br />
30min<br />
4% ANO1<br />
2% PF aldehyde 60 min<br />
0.50% Sodium formate 20 min<br />
0.35-0.6% Sodium bicarbonate 30 min Check pH (4.1)<br />
Table I continued on following page.<br />
J<strong>ALCA</strong>, VOL. 111, <strong>2016</strong>
Phosphate Ester as Fatliquoring Agent 430<br />
Table I continued.<br />
Drain & Wash & Pile over night<br />
150% Water<br />
2% NL-20<br />
1% Sodium formate<br />
20 min<br />
0.50% Sodium bicarbonate 60 min Check pH (5.2)<br />
80% Water<br />
40°C<br />
3% A18 20 min<br />
1.50% Melamine<br />
Filling<br />
1.50% Dicyandiamide<br />
0.50% Dispersing tannin<br />
40 min<br />
1.50% Wattle extract<br />
1.50% Chestnut<br />
1% JM<br />
1% JMK<br />
60 min<br />
30 min<br />
40°C<br />
100% Water 65°C<br />
0.40% Formic acid 20 min<br />
45°C<br />
0.1-0.4% Formic acid 40 min Check pH (4.1)<br />
Drain & Wash<br />
Fatliquoring<br />
100% Water<br />
2% Protein filler 20 min<br />
x% Fatliquor agent 40 min<br />
0.25% Formic acid 30 min<br />
55°C<br />
0.25% Formic acid 30 min Check pH (3.8-4.0)<br />
Drain & Wash<br />
Hook to dry, Stake<br />
Evaluation: An X-RiteColor Premier 8200 spherical<br />
spectrophotometer (X-Rite, USA) was used to measure the<br />
coloring of leather samples. Spectral reflectance values were<br />
measured between 400-700 nm range with 20nm intervals, and<br />
16 readings were obtained for each sample. The reflectance<br />
readings were converted to CIE L*a*b* values with related<br />
formulas, and color differences were calculated by CIELAB 1967<br />
color difference formula listed in Eq.1. 15<br />
ΔE= [(L-L 0<br />
) 2 + (a-a 0<br />
) 2 + (b-b 0<br />
) 2 ] 1/2 (1)<br />
J<strong>ALCA</strong>, VOL. 111, <strong>2016</strong>
431 Phosphate Ester as Fatliquoring Agent<br />
The CIELAB 1976 color difference formula calculates the linear<br />
distance between the coordinates of the sample and target color,<br />
and this difference is shown by ΔE.<br />
Scanning Electron Microscopic Analysis (SEM)<br />
A JSM-5900LV scanning electron microscope (Shimadzu, Japan)<br />
was used for the analysis. The micrographs for the cross section<br />
were obtained by operating the SEM at low vacuum with an<br />
accelerating voltage of 20kV at the same magnification level.<br />
Results and Discussion<br />
Characterization of Synthetic Chemicals<br />
FTIR of SLP, PU-2 and PUP-2<br />
As shown in Figure 1, the common structures of PU-2 and<br />
PUP-2 were evidenced by the common peaks at 3444-3480 cm -1 ,<br />
2867-2869 cm -1 , 1720-1639 cm -1 and 1108-1105 cm -1 related to<br />
different common groups (N-H, C-H, C=O, and C-O-C,<br />
respectively). The characteristic peaks of phosphate ester at 1151-<br />
1295 cm -1 and 1015-1028 cm -1 ascribed to P=O and P-O-C were<br />
observed for PUP-2 and SLP. The results indicated that SLP,<br />
PU-2 and PUP-2 were all synthesized successfully.<br />
Surface Tension of PUP-2 and PU-2<br />
From the results of surface tension shown in Figure 2, it was very<br />
clear that the surface tension was lower in PUP-2 solution than<br />
in PU-2 solution at every same concentration. Meanwhile, the<br />
CMC of the PUP-2 was much lower than that of PU-2 according<br />
to the CMC data (4.12 ×10 -6 mol/L for PUP-2 and 1.01×10 -5 mol/L<br />
for PU-2). The results indicated that PUP-2 was more effective in<br />
reducing surface tension, which suggested that PUP-2 might play<br />
a good role in fatliquoring process. A possible explanation was<br />
that hydrophobic groups in PUP-2 were closer between each<br />
other because of the phosphorylation. 16<br />
Characterization of Resultant Leathers<br />
Physical and Organoleptic Properties of Leathers<br />
The resultant leathers were treated with different amounts of<br />
PUP-2 alone (Experiment 1), with the complex of SLP and PUP-2<br />
in different weight ratios (Experiment 2), or with the complex of<br />
SLP, PUP-2 and other commercialized fatliquoring agents<br />
(Experiment 3), and their physical and organoleptic properties<br />
were tested. As seen from Figure 3, Figure 4 and Table II, the<br />
leathers treated with three different kinds of PUP-2 based<br />
fatliquoring agents showed a clearly improvement in physical<br />
(tensile strength, elongation and tear strength) and organoleptic<br />
properties (softness, lubricating sense and grain tightness)<br />
compared with non-fatliqured leathers, especially when PUP-2<br />
alone (8%, w/w) or the complex of SLP and PUP-2 (SLP: PUP-<br />
2=3:7, 8%, w/w) was applied.<br />
SEM Analysis<br />
SEM studies of the grain pattern of leathers are given in Figure<br />
5, at a magnification of ×1000. As compared with the A, the fiber<br />
splitting of B, C, and D were comparatively better in SEM. The<br />
fatliquoring agents based on PUP-2 penetrated deeply resulting<br />
in better fiber splitting and softness due to its nonionic<br />
amphiphilic structure and soft molecular chains.<br />
Fatty Spew Test<br />
Fatty spew formation was not observed on the surface of three<br />
kinds of leathers which were treated with PUP-2 alone, the<br />
complex of SLP and PUP-2, or the complex of SLP, PUP-2 and<br />
other commercialized fatliquoring agents. It can be attributed to<br />
the soft C-O-C bonds of PUP-2 with a low freezing point and the<br />
nonionic amphiphilic structure resulting in better dispersion and<br />
deeper penetration of fatliquoring agents as reported by Nashy. 17<br />
Figure 1. FT-IR spectra of SLP, PU-2 and PUP-2.<br />
Figure 2. Surface tension at different concentrations of PU-2 and PUP-2.<br />
J<strong>ALCA</strong>, VOL. 111, <strong>2016</strong>
Phosphate Ester as Fatliquoring Agent 432<br />
Resistance to Yellowing<br />
Reflectance measurements were carried out for all combination<br />
leathers. The ‘L’, ‘a’ and ‘b’ values used as the parameters to<br />
assess color are given in Table III. ‘L’ represents whiteness, which<br />
on a scale of 0-100; and 100 means pure white. ‘a’ represents red<br />
and green axis, where ‘a’ >0 means red and ‘a’ 0 means yellow<br />
and ‘b’
433 Phosphate Ester as Fatliquoring Agent<br />
a little decrease in white and a little increase in green. However,<br />
the increase of ‘b’ value from I, II and III was 2-4, which meant<br />
an increase in yellow tones when exposed to light. As a result, the<br />
increase of ‘ΔE’ value from I, II and III was 3-5. As seen from the<br />
Table III, the changes of ‘b’ and ‘ΔE’ mainly happened between<br />
0-6 hours. Compared with II and III, I, which was the nonfatliquored<br />
leathers, also had a 2-4 change on ‘b’ and 3-5 on ‘ΔE’,<br />
which meant that the change of ‘b’ and ‘ΔE’ of II and III was not<br />
attributed to SLP or PUP-2. However, the natural phospholipids,<br />
which usually contain the unsaturated acids, are prone to<br />
oxidation 18-21 and the oxidation reaction always leads to the<br />
performance of yellowing. 22-24 In summary, the leathers treated<br />
with PUP-2 alone (8%, w/w) or the complex (SLP: PUP-2=3:7, 8%,<br />
w/w) all showed a good performance in resistance to yellowing.<br />
It can be attributed to no unsaturated carbon-carbon double<br />
bonds, which were easily oxidized. 25<br />
Figure 4. Physical properties of leathers treated with the complex<br />
of SLP and PUP-2 in different weight ratios, or with the complex of<br />
SLP, PUP-2 (SLP: PUP-2=3:7, 2%, w/w) and other commercialized<br />
fatliquoring agents (6%, w/w). (The Y axis is a normalized scale for all<br />
three measured values.)<br />
Figure 5. SEM images of the cross section of leathers. (A) Nonfatliqured<br />
leathers, 1000× (B) Leathers treated with PUP-2 alone<br />
(8%, w/w), 1000×. (C) Leathers treated with the complex of SLP and PUP-<br />
2 (SLP: PUP-2=3:7, 8%, w/w), 1000×. (D) Leathers treated the complex<br />
of SLP, PUP-2 (SLP: PUP-2=3:7, 2%, w/w) and other commercialized<br />
fatliquoring agents (6%, w/w), 1000×.<br />
Table III<br />
Yellowing resistance of resultant leathers.<br />
Time (h) I II III<br />
L a b ΔE L a b ΔE L a b ΔE<br />
0 77.54 -0.52 9.56 76.94 -1.62 10.31 77.74 -2.18 10.41<br />
6 76.28 -0.93 12.91 3.52 76.63 -1.84 13.38 3.09 77.26 -2.33 13.24 2.95<br />
12 75.34 -1.04 13.40 4.46 76.29 -2.24 13.64 3.45 76.85 -2.71 13.39 3.13<br />
24 75.20 -1.39 13.64 4.78 76.04 -2.92 13.95 3.97 76.70 -3.24 13.89 3.78<br />
Δ6 -1.26 -0.41 3.26 -0.31 -0.22 3.07 -0.84 -0.15 2.83<br />
Δ12 -2.20 -0.52 3.84 -0.65 -0.62 3.33 -0.89 -0.35 2.98<br />
Δ24 -2.34 -0.87 4.08 -0.90 -1.30 3.64 -1.04 -1.06 3.48<br />
I: Non-fatliquored leathers (the comparison of the leather treated with 8% PUP-2).<br />
II: Leathers treated with PUP-2 alone (8%, w/w).<br />
III: Leathers treated with the complex of SLP and PUP-2 (SLP: PUP-2=3:7, 8%, w/w).<br />
J<strong>ALCA</strong>, VOL. 111, <strong>2016</strong>
Phosphate Ester as Fatliquoring Agent 434<br />
Conclusions<br />
A new phosphorylated ester (PUP-2) was successfully<br />
synthesized, which was effective in reducing surface tension and<br />
had a good performance in improving physical and organoleptic<br />
properties of resultant leathers. The fatty spew formation was<br />
not observed on the surface of three kinds of leathers treated<br />
with PUP-2 based fatliquoring agents. Meanwhile, since all basic<br />
raw materials of PUP-2 do not contain carbon-carbon double<br />
bonds, the leathers treated with PUP-2 alone (8%, w/w) or the<br />
complex of SLP and PUP-2 (SLP: PUP-2=3:7, 8%, w/w) had a<br />
good resistance to yellowing. Therefore, PUP-2 completely meets<br />
the requirements of resistance to yellowing and avoiding fatty<br />
spew defect for leathers.<br />
Acknowledgements<br />
This work was financially supported by the National High-tech<br />
Research and Development Projects (863) (2013AA06A306),<br />
National Natural Science Foundation of China (21474065) and<br />
Sichuan Province Leaders in Academic and Technical Training<br />
Project Funding (2015/100-5).<br />
References<br />
1. Wang, X. C., Feng, J. Y and An, H. R.; Phosphate modified<br />
lanolin fatliquors produced by a sustained-release method.<br />
JSLTC 88, 228-230, 2004.<br />
2. Ornes, C.L.; Studies of fatliquoring: II. The influence of type<br />
of oil, degree of sulfation, and neutralization level of fatty<br />
acids on some physical properties of shoe upper leather.<br />
J<strong>ALCA</strong> 55, 372-386, 1960.<br />
3. Ornes, C.L.; Studies of fatliquoring: III. The influence of<br />
oil level, neutralization, and vegetable mordanting on some<br />
physical properties of side upper leather. J<strong>ALCA</strong> 57, 107-115,<br />
1962.<br />
4. Fan, B. Z., Jin, Y and Qi R.; Research progress on phosphate<br />
leather fatliquoring agent based on natural oils and fats.<br />
China Leather 44, 37-38, 2015.<br />
5. Kalyanaraman, B., Kameswari, K. S. B., Sudharsan, N. M<br />
and Priyadharsini, P.; Biodegradation of lecithin-based<br />
fatliquor: optimization of food to microbes ratio and<br />
residence time. J<strong>ALCA</strong> 103, 1-10, 2013.<br />
6. S. Kanth., S. Sadulla., J. Rao., B. Madhan., G. Balaji and R.<br />
Aravindhan.; Glove leather manufacture from sheepskins:<br />
Influence of fatliquors and syntans on the gloving<br />
properties. J<strong>ALCA</strong> 108, 182-190, 2008.<br />
7. Zheng, S. J., Cao, X. Y., Li, X. B and Li, Bo.; Research of<br />
property of leather based high-carbon alcohol phosphate<br />
ester fatliquoring agents with different structure and<br />
components. Journal of Qiqihar University 22, 82-84, 2006.<br />
8. Xing, X. B.; A summary and discussion about preparation<br />
of fatliquors with phospholipid. China Leather 26, 8-9, 1997.<br />
9. Baskar, G., Vijayalakshmi, K., Parthasarathy, K., Rao, V.<br />
V. M., Jayaraman, K. S and Rajadurai, S.; Development<br />
of phosphorylated fatliquors and their application in the<br />
manufacture. J<strong>ALCA</strong> 86, 159-165, 1991.<br />
10. Ozgunay, H.; Lightfastness properties of leathers tanned<br />
with various vegetable tannins. J<strong>ALCA</strong> 103, 345-351, 2008.<br />
11. IUP 2, Sampling. JSLTC 84, 303-309, 2000.<br />
12. IUP 6, Measurement of tensile strength and percentage of<br />
elongation. JSLTC 84, 317-321, 2000.<br />
13. IUP 8, Measurement of tear load-double edge load, JSLTC<br />
84, 327-329, 2000.<br />
14. International standard ISO 105-B02:2000/Amd.2.2000 (E),<br />
Color fastness to artificial light: Xenon are fading lamp test.<br />
15. CIE (Commission Internationale de L’Eclairage), Official<br />
Recommendation on Uniform Color Spaces Color<br />
Difference Equations Metric Color Terms, 1976.<br />
16. Miao, Q., Jin, Y and Dong, Y.; Surface behavior and micelle<br />
morphology of novel nonionic polyurethane bolaform<br />
amphiphilic block copolymers, Journal of Polimer Research<br />
06,911-921, 2010.<br />
17. Nashy, E. S. H. A and Abo-Elwafa, G. A.; Highly Stable<br />
Nonionic Fatliquors Based on Ethoxylated Overused<br />
Vegetable Oils. Journal of the American Oil Chemists Society<br />
88, 1611-1620, 2011.<br />
18. Song, H. B and Li, Z. J.; Chemical modification of nature<br />
phospholipids and characteristics of products. West Leather<br />
28, 27-32, 2006.<br />
19. Liu, D. C and Ma, F. C.; Soybean Phospholipids. INTECH<br />
Open Access Publisher, 2011.<br />
20. Hu. S., Li. Z. Q and Cheng H. M.; Review of Phospholipid<br />
Fatliquors. West leather 5, 22-24, 2001.<br />
21. Peter, V. H and Armin, W.; The use of natural and synthetic<br />
phospholipids as pharmaceutical excipients. European<br />
Journal of Lipid Science & Technology 116, 1088–1107, 2014.<br />
22. Puntener, A.; The influence of fatliquors on the lightfastness<br />
of dyed leather. J<strong>ALCA</strong> 91, 126-135, 1996.<br />
23. Liu, C. K., Latona, N. P and Lee, J.; Glutaraldehyde-tanned<br />
leather treated with tocopherol. J<strong>ALCA</strong> 100, 102-110, 2005.<br />
24. Gao. H., Fang. Y. J and Cheng, H. J.; Synthesis and Application<br />
of a New Sulfonated Soybean Phospholipid Faliquoring<br />
Agent. LEATHER SCIENCE AND ENGINEERING 3, 49-52,<br />
1999.<br />
25. Shimizu, T., Komatsuzaki, S and Hirabayashi, K.;<br />
Synthesis, Structure, and Complexation Behavior of 14-and<br />
28-Membered Partially Unsaturated Thiacrown Ethers.<br />
Heteroatom Chemistry 22, 287-293, 2011.<br />
J<strong>ALCA</strong>, VOL. 111, <strong>2016</strong>
435<br />
Minimization of Chromium Discharge in Leather<br />
Processing by using Methanesulfonic Acid:<br />
A Cleaner Pickling-masking-Chrome Tanning System<br />
by<br />
Chunxiao Zhang, 1 Fuming Xia, 1 Biyu Peng, 1,2 * Qing Shi, 3 Dominic Cheung 3 and Yongbin Ye 4<br />
1<br />
National Engineering Laboratory for Clean Technology of Leather Manufacture,<br />
Sichuan University, Chengdu 610065, P. R. China<br />
2<br />
Key Lab. of Leather Chemistry and Engineering of Ministry of Education, Sichuan University,<br />
Chengdu, Sichuan 610065, P. R. China<br />
3<br />
BASF Advanced Chemicals Co., Ltd.,<br />
Pudong, Shanghai, 200137, P. R. China<br />
4<br />
Zhejiang Tongtianxing Group J.S.Co., Ltd.,<br />
Quzhou, Zhejiang, 324022, P.R. China<br />
Abstract<br />
Chrome tanning is the most important and widely used tanning<br />
method in leather manufacture hitherto. However, chromium<br />
discharge may be a serious environmental concerned pollutant<br />
in leather processing, which originates from both chrome<br />
tanning and post-tanning operations. In order to minimize the<br />
emissions of chromium from the whole leather processing, a<br />
novel leather processing method integrating high chromium<br />
exhaustion and low chromium leaching-out based on the<br />
application of methanesulfonic acid (MSA) was designed and<br />
optimized. The results indicated that, being superior to the<br />
conventional processes, the chrome tanning and retanning<br />
processes with MSA were conducted at a high beginning pH<br />
(5.0) smoothly and the total chromium utilization ratio was<br />
increased to 95.8% from 81.0% in the novel processes.<br />
Accordingly, the total Cr dosage was decreased by 26.7% around,<br />
the residual Cr concentrations in each chrome-containing<br />
wastewater was decreased by 44%-85%, varying with the<br />
operations, and the total Cr discharge generated in the whole<br />
leather processing was reduced by 83.8% around, from 2.737 kg/t<br />
salted-wet hide to 0.443kg/t salted-wet hide before next chrome<br />
precipitation treatment. The area yields, mechanical properties<br />
and organoleptic properties of the leather from the new method<br />
were comparable with that from conventional processes.<br />
Introduction<br />
Chrome tanning is the technology of using a chrome tanning<br />
agent, basic chromium sulfate (BCS), to convert the pelts to<br />
leathers. Conventionally, in order to achieve good penetration of<br />
chromium into pelts, a “pickling-masking-tanning” process is<br />
adopted. The pelts are acidified to pH 2.5-3.2 with formic acid<br />
and sulfuric acid in slat solution before tanning, named pickling,<br />
to lower the reactivity of the carboxyl groups of collagen, and<br />
chromium complexions are also modified by added ligands,<br />
typically carboxylates, to reduce the affinities of them towards<br />
collagen, named masking. 1,2 The relative affinities of ligands to<br />
chrome ions from potential masking agents are listed as follows:<br />
hydroxide > oxalate > citrate > lactate > malonate > maleate ><br />
phthalate >glycolate> tartrate > succinate >adipate> acetate ><br />
carboxyl of collagen >formate> sulfite > sulfate > chloride ><br />
nitrate > chlorate. 1 According to the above list, the affinity of<br />
formate to chromium ion is a little weaker than that of the<br />
carboxyl of collagen, so it is chosen as the dominant masking<br />
agent. However, only 60%-80% of the offering chrome is<br />
effectively utilized in the conventional chrome tanning process.<br />
As a result, the chrome concentration in spent float is in a range<br />
of 1,000-3,000mg/L, 3 causing a significant disposal problem.<br />
Therefore, cleaner chrome tanning processing, i.e., maximizing<br />
the chrome uptake and minimizing the residual amount of<br />
chrome in floats, is a matter of great concern to all tanners.<br />
*Corresponding author e-mail: pengbiyu@scu.edu.cn; Tel.+86-28-85401208.<br />
Manuscript received March 23, <strong>2016</strong>, accepted for publication June 30, <strong>2016</strong>.<br />
J<strong>ALCA</strong>, VOL. 111, <strong>2016</strong>
Methanesulfonic Acid for Cleaner Tanning System 436<br />
The low chrome utilization ratio in the conventional chrome<br />
tanning process can be probably attributed to that the lower<br />
affinity of the masked chromium complex ions with carboxyls of<br />
collagen side chain. The adding of organic acids in pickling and<br />
carboxylates during tanning introduces relatively large<br />
quantities of carboxylates into the tanning float, which may<br />
produce rather strong masking effects to chromium ions,<br />
resulting from the strong coordinating ability of carboxylates<br />
with chromium ion. Hence, the possibility of carboxyls of<br />
collagen entering into the inner spheres of chromium complex<br />
ions to substituted existing organic ligands is decreased<br />
accordingly. The uptake ratio of chrome is kept a rather low<br />
level. Many researches on optimizing masking agents have been<br />
done. Carboxylates with different molecular structure, including<br />
aliphatic and aromatic dicarboxylates, 4,5 low molecular weight<br />
polyacrylates, 6 and so on, were chosen as masking agents.<br />
Though these kinds of masking agents can increase the<br />
chromium exhaustion to a certain degree, it is difficult to achieve<br />
the chromium utilization ratio beyond 85%, and the leather is<br />
often negatively affected by the irrelevant application of the<br />
additives. Therefore, it may be deduced that the current picklingmasking-tanning<br />
system is not beneficial to high-exhaustion of<br />
chrome.<br />
Theoretically, taking every effort to promote the reaction activity<br />
between chrome and collagen can improve the tanning<br />
effectiveness. For example, resulting from the increase of both<br />
the dissociation degree of carboxyl of collagen side chain and the<br />
hydrolyzation degree of chromium ion at a high pH, it is<br />
beneficial to the uptake of chromium by collagen when the bated<br />
pelts are directly chrome tanned or after preprocessed with<br />
syntans at a high beginning pH over 6.0, 7-9 called non-pickling<br />
chrome tanning. However, the excessive fast combination of<br />
chromium on pelt surface will cause difficult penetration of<br />
chromium and bad hand feeling of leather when tanning at the<br />
high initial pH. Hence, to find a new kind of acid with weaker<br />
affinity to chromium than formic acid to establish a novel<br />
pickling-masking-chrome tanning system, which can well<br />
balance the competing process rates of Cr penetration and<br />
reaction with collagen when chrome tanning is conducted at a<br />
reasonably highly initial pH value, will be a possible approach to<br />
achieve high-exhaustion of chrome and minimize chrome<br />
discharge in chrome tanning.<br />
Methanesulfonic acid (MSA) is a kind of organic strong acid. For<br />
there is an electron donor, methyl, connecting directly with<br />
sulfur atom, its pKa value (-0.6) is higher than sulfuric acid<br />
(pKa=-3.0), and much lower than formic acid (pKa=3.68) and<br />
acetic acid (pKa=4.76) 10 , thus the acidity of MSA is weaker than<br />
common inorganic acids, and stronger than most of organic<br />
acids. MSA has been used in electroplate industry to substitute<br />
sulfuric acid as it is considered as a “green acid” due to its<br />
environmental advantages: far less corrosive and easily<br />
biodegradable. 11 Though the structure and geometric parameters<br />
of the Cr (III) complex ions of sulfate and methanesulfonate are<br />
rather similar, forming Cr (III) complexes is more easily in<br />
methanesulfonate solution than sulfate solution, 12 and Cr (III)<br />
complex ions in methanesulfonate are more stable. 13-15 Therefore,<br />
the coordination ability of methanesulfonate toward Cr(III) is<br />
stronger than sulfate. It can be deduced that pickling with MSA<br />
has the potential to well balance the contradiction of the highexhaustion<br />
and penetration of chromium during chrome<br />
tanning, theoretically.<br />
According to the above analysis, a novel pickling-maskingchrome<br />
tanning system based on the application of MSA was<br />
designed to achieve the high-exhaustion of chrome. The process<br />
parameters were optimized, such as initial tanning pH value,<br />
dosage of chrome, and the leather quality was evaluated. The<br />
chrome discharge in the whole leather processes was also traced.<br />
Experimentals<br />
Materials and Instruments<br />
Salted-wet cattle hides from Sichuan, China, were purchased<br />
from a local tannery (Chengdu Xinshi Leather Industry Co.,<br />
Ltd.). Methanesulfonic acid (MSA, 70%) was offered by<br />
BASF-AE. Chromium (III) sulfate hydrate (Cr 2<br />
(SO 4<br />
) 3·6H 2<br />
O, CP)<br />
was purchased from Aladdin Co.. Chromosal B (a chromium<br />
tanning agent with 33% of basicity and 26% of Cr 2<br />
O 3<br />
content)<br />
was purchased from LANXESS Inc. The following applied<br />
leather chemicals, including syntans, fatliquors, polymers, filling<br />
agents, etc. were industrial grade and from Sichuan Dowell<br />
Science & Technology Co., Ltd. The other chemicals were<br />
analytic grade.<br />
Ultraviolet and Visible Spectrophotometer (TU-1810PC, Beijing<br />
Purkinje General Instrument Co., LTD, China), Stainless<br />
Experimental Drum (GSD400-4, Wuxi Xinda Light Industry<br />
Machinery Co., Ltd. China), Inductively Coupled Plasma<br />
Emission Spectrometer (AES-ICP, 2100DV, Perkin Elmer Inc.<br />
America), Precision Slice Machine (C520L, Camog (a) Inc.,<br />
Italy), Desktop Scanning Electron Microscope (Phenom Pro,<br />
Phenom World Inc., Netherland).<br />
Evaluation of the Masking Effect of MSA to Chromium Ion<br />
The appropriate chromium(III) sulfate hydrate (11.6g) was<br />
dissolved in deionized water (250.00ml) to get a solution with Cr<br />
concentration of was 0.2mol/L. Samples (20.00ml) were removed<br />
and mixed with MSA at different ratios. As a control, the molar<br />
ratio of formic acid to chromium was 1:1. The solutions were<br />
then aged by standing at room temperature (20-22°C) for<br />
3 hours. A solution of NaHCO 3<br />
(5%, w/w) was added slowly with<br />
magnetic stirring for 30min to adjust the pH to 4.0. The total<br />
volumes were diluted to 100.00ml respectively. Have been aged<br />
J<strong>ALCA</strong>, VOL. 111, <strong>2016</strong>
437 Methanesulfonic Acid for Cleaner Tanning System<br />
for 12 hours at 40°C, the ultraviolet-visible spectrum analysis<br />
was conducted at the wave lengths from 700nm to 350nm at<br />
0.5nm interval respectively.<br />
Substituting Sulfuric Acid and/or Formic Acid with<br />
MSA in Pickling<br />
Salted-wet cattle hides were conducted soaking, fleshing, liming,<br />
splitting, deliming and bating procedures as normal processes.<br />
A whole grain-layer limed cattle hide with thickness of 3.0 mm<br />
after splitting was divided into pieces adjacently and<br />
symmetrically, and they were distributed to different tanning<br />
groups for evaluating and comparing tanning effects. The bated<br />
pelts were put into drums and soaked in 50% of water at 23°C<br />
(based on the weight of limed hides, the same below) and pickled<br />
to pH 2.9 around with a certain amount of MSA, the mixtures of<br />
formic acid and MSA, or sulfuric acid and MSA, respectively, in<br />
the presence of 6.0% (w/v) of NaCl. After pickling overnight,<br />
6.0% Chromosal B together with 1.0% of sodium formate was<br />
added into each drum. When chrome completely penetrated into<br />
hide inner-layer after running for about 180min at 23°C, the pH<br />
was basified to around 4.0 with NaHCO 3<br />
solution carefully. Then<br />
a certain amount of hot water (60°C) was added to make the total<br />
water offer be total 200% of limed hide weight. After running for<br />
another 120 min at 40°C, the drums were stayed overnight. The<br />
next day, the pH of tanning liquors was adjusted to 4.0±0.1 once<br />
more. The Cr contents in spent tanning liquors were determined.<br />
Optimization of Processing Parameters of MSA Pickling-<br />
Chrome Tanning<br />
The adjacent and symmetrical bated pelts were prepared and<br />
pickled to different pH with varying amounts of MSA. After<br />
pickling overnight, chrome tanning was carried out with a<br />
varying offer amount of Chromosal B, with or without using<br />
sodium formate. All other operations were the same as above. As<br />
a control, two groups of pelts were pickled as per the conventional<br />
method (formic acid 0.5% and sulfuric acid 1.0-1.2%) and were<br />
tanned with 6.5% of Chromosal B alone or the combinations of<br />
5.0% of Chromosal B and 0.5% of sodium formate respectively.<br />
The Cr contents in spent tanning liquors were determined. Cr<br />
distribution, shrinkage temperature values (Ts) and the<br />
appearances of the chrome-tanned leather were determined and<br />
compared.<br />
Tracing Chrome Discharge in Whole Leather Wet-end<br />
Processing Based on MSA Pickling-chrome Tanning<br />
Bated pelts were divided into two groups. Among them, a whole<br />
piece of grain-layer limed cattle hide was cut into two half sides<br />
along with the backbone line, symmetrically, and they were<br />
distributed to different tanning groups for evaluating and<br />
comparing tanning effects. As shown in Table I, the two groups<br />
of pelts were chrome tanned with a conventional picklingchrome<br />
tanning process (No. i) and MSA pickling-chrome<br />
tanning process (No. ii), respectively. After stacked and aged for<br />
7 days, the tanned leathers were carried out sammying, shaving<br />
(thickness 1.1-1.2 mm), and wetting as the normal operations.<br />
Then the shaved tanned leathers were put in drums and<br />
conducted with a normal (No. i) and a modified (No. ii) chrome<br />
retanning processes correspondingly. Then the chrome retanned<br />
leathers were neutralized, retanned with syntans, dyed and<br />
fatliquored as the normal procedures for shoe upper leather, and<br />
was also used to substitute formic acid to fix syntans, dyestuff<br />
and fatliquors in No. ii process. The chromium concentrations<br />
in chromium-containing wastewaters were analyzed and the<br />
main leather properties were also measured.<br />
Determination of Chromium Concentration in Spent<br />
Tanning Liquors<br />
The spent tanning liquors were filtered with 100 mesh filter<br />
cloth and digested with the mixture of hydrochloric acid and<br />
nitric acid at 120°C for 120min. The digestion solutions were<br />
appropriately diluted and their chromium concentrations were<br />
measured with AES-ICP. The chromium concentrations of spent<br />
tanning liquors were calculated.<br />
Determination of Chromium Content and Distribution<br />
in Leather<br />
The chrome-tanned leather samples of each tanning group were<br />
taken out in the adjacent and symmetrical parts of the same<br />
hide, and washed thoroughly to remove uncombined chromium<br />
salt. Then the samples were freeze-dried at -55°C and 20pa<br />
vacuum for 24hours. The dried leathers were averagely split into<br />
three layers using Precision Slice Machine. A certain quantity of<br />
the dried leather sample was completely digested with the<br />
mixture of nitric acid and chloride acid at 120°C for 120min.<br />
The digestion solutions were appropriately diluted and their<br />
chromium concentrations were measured with AES-ICP. The<br />
chromium content in each layer of the leather was calculated.<br />
Scanning Electron Microscopy (SEM) Analysis<br />
The samples of the dried crust leathers of each tanning group<br />
were viewed microscopically using Desktop Phenom Pro<br />
Desktop Scanning Electron Microscope. Then the pattern of<br />
both the grain on the surfaces and the collagen fibril on the<br />
section were evaluated.<br />
Test of Physical and Mechanical Properties of Crust Leather<br />
Dried crust leather samples of each tanning group were taken<br />
out in the adjacent and symmetrical parts of the same hide for<br />
testing physical and mechanical properties. The dichloromethane<br />
extracts were evaluated as per ISO 4048-2008. Samples were<br />
conditioned as per IUP method (IUP 2, 2000). Physical<br />
properties such as tensile strength, elongation at break, tear<br />
strength and bursting strength were examined as per the<br />
standard procedures (IUP 6, 2000; IUP 8, 2000; IUP 9, 1996).<br />
J<strong>ALCA</strong>, VOL. 111, <strong>2016</strong>
Methanesulfonic Acid for Cleaner Tanning System 438<br />
Table I<br />
Leather making processes for shoe upper leather.<br />
Operations Chemicals Dosages (%) Parameters Comments<br />
Bating<br />
Pickling Water 50 23°C<br />
NaCl 6.0 10 min<br />
No. i HCOOH 0.5 30 min<br />
H 2<br />
SO 4<br />
1.1 180 min<br />
No. ii MSA 0.9 180 min<br />
Overnight No. i pH 2.96; No. ii pH 4.86<br />
Cr- tanning<br />
No. i Chromosal B 6.5<br />
HCOONa 0.5 180 min Cr penetrate evenly<br />
No. ii Chromosal B 4.5 180 min Cr penetrate evenly<br />
Basifying NaHCO 3<br />
X 180 min 30 min interval<br />
Overnight<br />
Water (60°C) 150 120 min Stable at 40°C<br />
Draining Cr sewage 200%<br />
Stacking<br />
7 days<br />
Sammying Cr sewage 20%<br />
Shaving<br />
Thickness 1.1-1.2 mm<br />
Wetting Water (40°C) 200<br />
Nonionic wetting agent 0.3<br />
Nonionic degreasing agent 0.1<br />
NaHCO 3<br />
0.3 120 min pH 4.5<br />
Draining Cr sewage 200%<br />
Cr-retanning Water (40°C) 200<br />
No. i HCOOH 0.5 120 min pH 3.5 around<br />
Chromosal B 3.5<br />
HCOONa 0.5<br />
Table I continued on following page.<br />
J<strong>ALCA</strong>, VOL. 111, <strong>2016</strong>
439 Methanesulfonic Acid for Cleaner Tanning System<br />
Table I continued.<br />
NaHCO 3<br />
X 120 min pH 4.2 around<br />
No. ii Chromosal B 3.5<br />
MSA-Na 0.5 90 min<br />
NaHCO 3<br />
X 120 min pH 4.2 around<br />
Overnight<br />
Draining Cr sewage 200%<br />
Neutralizing Water 150 40°C<br />
Neutralizing Syntans 1.5 30min<br />
NaHCO 3<br />
1.0 90min pH 5.1<br />
Draining Cr sewage 150%<br />
Organic retanning/<br />
Filling<br />
Water 150 40°C<br />
Synthetic Fatliquor 2.0 30min<br />
Polyacrylate Retanning Agents 9.0 60min<br />
Polysulfone Syntan 4.0<br />
All the chemicals were diluted<br />
with 3 times hot water<br />
Polynaphthalene Sulphonate 2.0<br />
Melamine Resin 3.0<br />
Protein Filling 3.0<br />
Vegetable Tannin 3.0 90min<br />
No. i HCOOH 0.5<br />
No. ii MSA 0.5 30min pH4.5 around<br />
Draining Cr sewage 200%<br />
Washing Water 200 10min Cr sewage 200%<br />
Fatliquoring/<br />
Dyeing<br />
Water 150 55°C<br />
+ Dyestuffs 3.0 30min<br />
+ Mixture of Fatliquors 10.0<br />
All chemicals were diluted<br />
with 3 times hot water<br />
No. i HCOOH 1.5 90min pH3.6 around<br />
No. ii MSA 1.8 90min pH3.6 around<br />
Draining Cr sewage 200%<br />
Vacuum Drying, Hanging Drying, Stacking as conventional methods<br />
J<strong>ALCA</strong>, VOL. 111, <strong>2016</strong>
Methanesulfonic Acid for Cleaner Tanning System 440<br />
Results and Discussions<br />
The Masking Effect of Methanesulfonic Acid (MSA) on<br />
Chromium Ions<br />
UV-Vis is the most common technique for characterizing Cr(III)<br />
species. The positions of the two peaks are changeable depending<br />
on ligands associated to chromium ion, and the slight variations<br />
in the wavelengths are attributed to the fact that Cr(III) reacted<br />
with different ligands. 16 In order to evaluate the masking effect<br />
of MSA towards chromium ions, UV-Vis spectral studies of<br />
chromium sulfate solutions with different ratios of MSA at pH<br />
4.0 were conducted, and the results are showed in Figure 1 and<br />
Table II.<br />
Two fairly strong absorptions of [Cr(H 2<br />
O) 6<br />
] 3+ complex are known<br />
in the visible and near-ultraviolet region from 700nm to 350nm.<br />
These peaks correspond to two transitions from ground states to<br />
the excited states: 4 A 2g<br />
→ 4 T 2g<br />
and 4 A 2g<br />
→ 4 T 1g<br />
. 17 The spectrum is the<br />
characteristic of [Cr(H 2<br />
O) 6<br />
] 3+ complex in which Cr(III) ion is<br />
octahedral, and the water molecules in this complex could be<br />
replaced by various ligands present in the solution, resulting the<br />
color change of the solution from green to blue. 15 The results in<br />
Figure 1 and Table II indicate that the two peaks are slightly<br />
shifted to the blue region by 0.5nm to 1.5nm, varying with the<br />
concentrations of MSA, meaning that one or more water<br />
molecules in the inner sphere of Cr(III) complex are replaced<br />
with MSA, forming the MSA-complexes of Cr(III). Therefore,<br />
the affinity of MSA to Cr(III) is stronger than that of sulfuric<br />
acid. But the peaks in formic acid solution are obviously shifted<br />
by 3.5nm and 7.0nm respectively, indicating the formation of the<br />
stronger formic acid-complexes of Cr(III), for the affinity of<br />
carboxyl is much stronger than that of methanesulfonate to<br />
Cr(III). Therefore, the masking effect of MSA on chromium ions<br />
is between sulfate and formate.<br />
The Influence of Pickling with MSA on Chrome Tanning<br />
In order to pre-search the possibility of establishing a new<br />
pickling-chrome tanning system, MSA was used to completely<br />
or partially substitute sulfuric acid and/or formic acid in pickling<br />
process, and the influences of pickling methods on chrome<br />
tanning effects were examined firstly. The results are shown in<br />
Table III.<br />
The results in Table III show that MSA pickling can increase<br />
chromium uptake to a certain degree, comparing with<br />
conventional pickling. The improving effect of replacing sulfuric<br />
acid with MSA on chromium exhaustion, i.e. combining MSA<br />
and formic acid in pickling (No.2), isn’t as evident as substituting<br />
formic acid (No.3). The chromium uptake arrives at 79% when<br />
pickling with MSA alone. The reason may be ascribed to the<br />
strong masking effect of formate toward Cr(III) ions as the<br />
results above (Figure 1 and Table II). Although there is no adding<br />
of formic acid in pickling method No.3 and No.4, the added 1.0%<br />
of sodium formate in tanning processing still produces enough<br />
masking effect toward Cr(III), which significantly negatively<br />
influences the complex ability of masked chromium ions with<br />
collagen carboxyls. In order to illustrate the impact of masking<br />
effect on chromium uptake, only MSA was used in pickling<br />
without adding formic acid and formate (No.5), and the result<br />
shows that the chromium uptake is remarkably raised to<br />
Figure 1. UV-Vis spectrum of chromium (III) ion in different<br />
concentrations of ligands.<br />
Table II<br />
Measured wavelength of the two peaks in the UV-Vis spectrum of<br />
chromium solutions with different concentrations of ligands.<br />
Ratio of masking agent to<br />
chromium (mol/mol)<br />
MSA<br />
HCOOH<br />
0:1 0.5:1 1:1 2:1 3:1 1:1<br />
λ max,1 423.0 422.5 422.5 422.0 421.5 419.5<br />
λ max,2 583.5 583.0 583.0 583.0 583.0 576.5<br />
J<strong>ALCA</strong>, VOL. 111, <strong>2016</strong>
441 Methanesulfonic Acid for Cleaner Tanning System<br />
86%, whilst the residual chromium concentration is decreased to<br />
335mg/L. The results indicate that the excessively strong<br />
masking effect toward chromium ion from an overdose of<br />
formate is not beneficial to the combination of chrome by<br />
collagen, and MSA pickling exhibits good effect on improving<br />
the high exhaustion of chrome in the case of no addition of any<br />
other masking agents.<br />
Optimizing of Parameters of MSA Pickling-chrome<br />
Tanning Process<br />
According to the above results (Table III), the application of<br />
MSA can promote the absorption of chromium, hence, aiming at<br />
minimizing chromium discharge to a maximum degree, the<br />
main control parameters of MSA pickling-chrome tanning<br />
process, including pickling pH, masking agent and chrome<br />
offers, were further investigated. The results in Table IV show<br />
that, though the Cr offer is raised by about 30% in method No.6,<br />
from 0.89% to 1.16%, comparing with method No.7, the Cr<br />
uptake ratio is increased to 80% from 75% of method No.7, in<br />
which (No.7) 0.5% of sodium formate is added together with<br />
chrome powder. This further illustrates that the strong masking<br />
effects from formate to Cr(III) ion negatively influence the<br />
combination of chrome by collagen. The only difference between<br />
methods No.8 and No.6 is the kind of used acid in pickling, but<br />
the Cr uptake ratio in methods No.8 is much higher, which<br />
further indicates that MSA pickling can promote chrome<br />
exhaustion. This advantage can be mainly ascribed to the<br />
moderate masking effects of MSA towards Cr(III) ion. In order<br />
to minimize chromium discharge to a maximum degree, the<br />
initial tanning pH is raised to 5.0, and the offer is reduced to<br />
0.81% (method No.9) in consideration of the much enough Cr<br />
content in the leather from MSA process with a regular Cr offer<br />
(method No.8). As expected, the Cr exhaustion is further<br />
enhanced to 95%, and the shrinkage temperature (Ts) reaches to<br />
107°C, which can satisfy the requirement of chrome tanning<br />
standard accordingly, the residual Cr concentration in<br />
wastewater is further reduced to 115mg/L from 372mg/L.<br />
However, combining formic acid even at a rather low level of<br />
0.15% in method No.10 makes more Cr resided in wastewater<br />
than in method No.9. This indicates the negative effects of<br />
formate on chromium absorption over again.<br />
Figure 2. Cr contents and distributions of chrome tanned leathers with<br />
different pickling methods.<br />
Table III<br />
Influence of pickling with different acids on chrome uptake.<br />
Pickling methods<br />
No.1<br />
FA a +SA b<br />
No.2<br />
MSA+FA<br />
No.3<br />
MSA+SA<br />
No.4<br />
MSA-I<br />
No.5<br />
MSA-II<br />
Acid dosage (%)<br />
FA a 0.6,<br />
+SA b 0.9<br />
MSA 2.2,<br />
+FA 1.2<br />
MSA 1.5,<br />
+SA 0.5<br />
MSA 3.1 MSA 3.1<br />
Pickling pH 2.9±0.1 2.9±0.1 2.9±0.1 2.9±0.1 2.9±0.1<br />
Tanning end pH 4.1±0.1 4.1±0.1 4.1±0.1 4.1±0.1 4.1±0.1<br />
Cr offer (%) 1.07 1.07 1.07 1.07 1.07<br />
Sodium formate offer c (%) 1.00 1.00 1.00 1.00 0<br />
Cr in waste bath (mg/L) 1074±10 1040±10 914±8 799±8 335±5<br />
Cr uptake ratio (%) 72 73 77 79 86<br />
a<br />
FA-formic acid; b SA-sulfuric acid; c Sodium formate was added together with chrome powder.<br />
J<strong>ALCA</strong>, VOL. 111, <strong>2016</strong>
Methanesulfonic Acid for Cleaner Tanning System 442<br />
As mentioned before, there is a worry about Cr penetration into<br />
the inner layer of pelts when chrome tanning conducted at a high<br />
initial pH and with a low offer of Cr, hence, the chromium<br />
contents and distributions in chrome-tanned leathers from the<br />
above methods in Table IV were further investigated. The results<br />
are illustrated in Figure 2.<br />
Figure 2 indicates that the Cr content of chrome-tanned leather<br />
is consistent with the corresponding calculated value according<br />
to the data in Table IV. The addition of sodium formate in<br />
conventional process can improve the uniformity of Cr<br />
distribution in leather, but the combined Cr amount is decreased<br />
obviously, comparing method No.6 and No.7. In the MSA<br />
pickling process, being attributed to the moderate masking<br />
effect of MSA towards Cr(III) ions, there is no negative influence<br />
on the penetration and distribution of chromium in the leather.<br />
Chrome tanning at a high initial pH of about 5.0 with MSA, the<br />
penetration of chromium is not hindered, and the “excessive<br />
surface tanning effect” is not observed, and the addition of other<br />
masking agents is not necessary. Hence, raising initial tanning<br />
pH and appropriate reduction Cr offer in MSA pickling-tanning<br />
process is a practicable approach to further decrease chromium<br />
discharge.<br />
Tracing Chrome Discharge in Whole Leather<br />
Wet-end Processing<br />
The efficiency of the novel pickling-chrome tanning method<br />
with MSA was further evaluated on improving chrome tanning<br />
and leather quality in comparison with the conventional process.<br />
Because chrome in wet-blue leather will also leach out at varying<br />
levels in the following post-tanning operations, including<br />
wetting, neutralizing, organic retanning/filling and dyeing/<br />
fatliquoring, the emission of chromium was also traced in whole<br />
leather wet-end processing. 18<br />
In the novel process, the pelts was pickled with MSA to a<br />
relatively high pH value of about 4.9 and tanned with a reduced<br />
Cr offer and without adding any other masking agent, and then<br />
Figure 3. The effectiveness of the novel process on improving Cr distribution.<br />
Table IV<br />
Influence of pickling pH and Cr offering in MSA pickling on chrome tanning.<br />
Pickling methods<br />
Conventional<br />
MSA<br />
No.6 No.7 No.8 No.9 No.10<br />
Acid dosage (%)<br />
FA a 0.50<br />
+SA b 1.10<br />
FA 0.50<br />
+SA 1.00<br />
MSA 3.00 MSA 1.00<br />
FA 0.15<br />
+MSA 0.70<br />
Pickling pH 2.9±0.1 2.9±0.1 2.9±0.1 5.0±0.1 5.0±0.1<br />
Basification pH 4.1±0.1 4.1±0.1 4.1±0.1 4.1±0.1 4.1±0.1<br />
Chromosal B (Cr) offer (%) 6.5 (1.16) 5.0 (0.89) 6.5 (1.16) 4.5 (0.81) 4.0 (0.72)<br />
Sodium formate offer c (%) 0 0.50 0 0 0<br />
Cr in waste water (mg·L -1 ) 864±8 802±8 372±4 155±3 224±3<br />
Cr uptake ratio (%) 80 75 91 95 91<br />
Shrinkage temperature (°C) 120±2 112±1 118±2 107±2 107±1<br />
a<br />
FA-formic acid; b SA-sulfuric acid; c Sodium formate was added together with chrome powder<br />
J<strong>ALCA</strong>, VOL. 111, <strong>2016</strong>
443 Methanesulfonic Acid for Cleaner Tanning System<br />
retanned with 0.63% of Cr offer and 0.5% of sodium<br />
methanesulfonate to substitute sodium formate at pH 4.5. The<br />
tanning effects are shown in Table V and Figure 3.<br />
The results show that the novel chrome tanning process is going<br />
well at a high beginning pH of 4.9. As shown in Table V, the Cr<br />
absorption ratio in the novel process is increased to 94% from<br />
75% in the conventional process, and the residual Cr in spent<br />
tanning float is reduced to 166.6mg/L from 1076.6mg/L (see<br />
Table VI), correspondingly, which are consistent with the results<br />
of No.9 method in Table IV. On basis of the novel picklingchrome<br />
tanning, the next chrome retanning operation was a<br />
little modified, i.e., wet-blue leather was conducted retanned<br />
with methanesulfonate as the masking agent at initial pH 4.5<br />
around. Further, the chrome uptake rate is increased to 96%<br />
from 76% in the conventional retanning process. All in all, both<br />
the novel tanning and retanning process with MSA exhibit<br />
obvious effectiveness on increasing chrome exhaustion.<br />
As shown in Figure 3, though the total Cr offer was reduced by<br />
30% (from 1.16% to 0.81%) in the novel MSA pickling-tanning<br />
process, the average Cr content of the chrome tanned leather is<br />
only a little lower than that from the conventional tanning<br />
process, and there is no obvious difference in the average Cr<br />
contents and Ts of the retanned leather between the two<br />
processes. This can be ascribed to the high exhaustion of chrome<br />
in the novel processes. Therefore, the total Cr offer can be<br />
obviously decreased. The Cr distribution in the vertical section<br />
of the leather retanned with novel process is more uniform than<br />
that in the leather from conventional retanning process, and the<br />
Cr content in the grain layer is not remarkable higher than in the<br />
middle layer. This once again proves that chromium penetrating<br />
into the inner layer is not hindered when tanning at the high<br />
beginning pH in the novel process. The area yield of leather is<br />
also not diminished (see Table V); hence no excessive tanning<br />
effectiveness has happened in the novel process.<br />
As mentioned before, besides the high-concentration chromecontaining<br />
effluents from tanning, sammying and chrome<br />
retanning, all the spent liquors from following post-tanning<br />
operations contain chrome resulting from the releasing of<br />
chrome from leather. All the chrome-containing effluents<br />
should be treated to decrease the Cr concentration to lower than<br />
1.5mg/L before discharged into sewage system in China,<br />
according to the strict statutory limits. Hence, the chrome<br />
discharge in whole leather wet-end processing was traced.<br />
Generally, a certain amount of formic acid is added to lower pH<br />
to promote the combination and fixation of anionic chemicals,<br />
such as anionic syntans, dyestuffs and fatliquors, in the posttanning<br />
processes. MSA was also used to substitute formic acid<br />
in the post-tanning processes of wet-blue leather from the novel<br />
pickling-chrome tanning and retanning methods, and the Cr<br />
concentrations of the spent liquors from main wet-end processes<br />
are shown in Table VI.<br />
Table V<br />
Effects of MSA pickling to a high pH on chrome tanning and retanning.<br />
Operations<br />
Pickling<br />
methods<br />
Acid dosage<br />
(%)<br />
Pickling pH<br />
Cr offer<br />
(%)<br />
Ts (°C)<br />
Cr uptake<br />
rate (%)<br />
Yield of leather a<br />
(sq.ft/kg)<br />
Cr-tanning<br />
Conventional<br />
FA 0.5;<br />
SA 1.1;<br />
Na-FA b 0.5<br />
2.9±0.1 1.16 118±2 75 3.10<br />
MSA MSA 0.9 4.9±0.1 0.81 107±2 94 3.10<br />
Cr- retanning<br />
Conventional<br />
FA 0.5;<br />
Na-FA b 0.5<br />
3.5±0.1 0.63 124±2 76 7.54<br />
MSA Na-MSA c 0.5 4.5±0.1 0.63 121±2 96 7.52<br />
a <br />
yield of leather in Cr tanning=areas of wet-blue (sq.ft)/weight of limed hide (kg);<br />
yield of leather in Cr retanning=areas of final leather (sq.ft)/ weight of shaved leather (kg).<br />
b<br />
Na-FA: sodium formate; added together with chrome powders.<br />
c<br />
Na-MSA: sodium methanesulfonate; added together with chrome powders.<br />
J<strong>ALCA</strong>, VOL. 111, <strong>2016</strong>
Methanesulfonic Acid for Cleaner Tanning System 444<br />
It can be seen that the chromium concentration of each<br />
wastewater is decreased by 46.1%-84.5%, the total chromium<br />
discharge amount is reduced by 83.8%, and the total Cr<br />
utilization ratio is increased to 95.8% from 81.0% in the novel<br />
technology of integrating application of MSA in picklingchrome<br />
tanning and post-tanning processes, comparing with<br />
the corresponding one from the conventional processes. Not<br />
only does the novel leather making process using MSA increase<br />
chromium exhaustion during chrome tanning and retanning,<br />
but also decrease chromium leaching out in post-tanning<br />
operations effectively, hence, the total Cr discharge is minimized.<br />
Operations<br />
Table VI<br />
Tracing Cr discharge in whole<br />
leather wet-end processing a<br />
No. i a<br />
Conventional<br />
(mg·L -1 )<br />
No. ii a<br />
Novel<br />
(mg·L -1 )<br />
Decrease<br />
rate (%)<br />
chrome tanning 1076±10 167±2 84.5<br />
Samming 465±3 107±3 77.0<br />
Wetting 16±2 7±1 58.9<br />
Chrome retanning 541±6 88±2 83.7<br />
Neutralizing 18±2 7±2 62.7<br />
Washing 9±2 5.0±1 43.8<br />
Moreover, considering that the residual Cr concentration was<br />
very low in the spent tanning liquor, it can be recycled directly in<br />
pickling process after simply filtrated. It is expected that the<br />
main problems of recycling the conventional spent chrome<br />
tanning liquor, such as dark color and rough grain of chrome<br />
tanned leather, from the high-concentration residual chromium<br />
will be overcome. Also, the chrome-containing sludge generated<br />
from alkali-precipitation of low concentration chromecontaining<br />
wastewater from post-tanning processes will be<br />
dramatically decreased. The further research is ongoing.<br />
Comparison of Leather Properties<br />
One of the main factors affecting the acceptability of a novel<br />
leather making method by tanners is whether it can improve or<br />
at least keep the original properties of the final leather. Hence<br />
the main properties of the leathers from the adjacent and<br />
symmetrical parts of a same hide respectively conducted the<br />
processing procedures of No. i and No. ii in Table I were<br />
evaluated by scanning electron microscope, and the results are<br />
shown in Figure 4.<br />
As mentioned before, excessive binding and depositing of<br />
chrome on the surface of leather resulting in wrinkled grain is a<br />
potential risk for tanning at a high initial pH. The electron<br />
micrographs illustrate that the grain pattern is a little smoother<br />
of the leather from MSA processing than conventional<br />
processing, and there is no any deposition of chromium on<br />
surface and inside the hair pores, hence, the excessive tanning<br />
effect in leather surface does not happen. The fiber bundles are<br />
well separated and their diameters are finer, and there is less<br />
Organic retanning/<br />
Filling<br />
29±2 12±1 57.3<br />
Washing 15±2 8±1 46.1<br />
Dyeing/Fatliquoring 41±2 15±2 64.2<br />
The input and output of the Cr in whole process<br />
(kg/t salted-wet hide) b<br />
Total Cr offer 14.411 10.561 26.7<br />
Total Cr discharge 2.737 0.443 83.8<br />
Total Cr utilization<br />
ratio (%)<br />
81.0 95.8 -<br />
a<br />
The process parameter of No. i and No. ii seen Table I;<br />
b<br />
1.0t salted-wet hide was changed into 1.1t limed hide<br />
and 0.262t shaved grain chrome-tanned leather, and the<br />
samming water amount is 200 kg/t.<br />
Figure 4. SEM images of the grain pattern (×300) and vertical sections<br />
(×1000, ×5000) of the crust leather.<br />
J<strong>ALCA</strong>, VOL. 111, <strong>2016</strong>
445 Methanesulfonic Acid for Cleaner Tanning System<br />
densely blocky adhesion between fibers of the leather from MSA<br />
processing than the other one, which can be attributed to that<br />
the inner layer is well tanned, and the chemical used in posttanning<br />
processing are well absorbed and penetrate into the<br />
inner layer.<br />
Actually, it is found that the absorptions of anionic chemicals,<br />
especially dyestuffs and fatliquors, were obvious improved in the<br />
novel processing through observing the color depths and the<br />
turbidities of spent floats. The content of fatliquor in leather is<br />
higher and the distribution is more even as illustrated in<br />
Figure 5. The higher fatliquor content in middle layer may result<br />
from higher content of chrome (see Figure 4).Hence, the leather<br />
is softer and with better physical-mechanical performances, as<br />
shown in Table VII.<br />
The Pilot-scale Experiment Results<br />
In order to verify the acceptability of the novel pickling-chrome<br />
tanning method with MSA, the pilot-scale experiments were<br />
conducted in Tongtianxing Leather Co., which is the biggest<br />
furniture leather plant in China. Bating pelts of Ireland cowhides<br />
were taken out from the tannery production line of furniture<br />
leather, and conducted pickling with 1.0% MSA to pH of 4.5, and<br />
then tanning with 0.85% of Cr offer based on the weight of limed<br />
pelts of 2.5-2.8mm thickness. Satisfactorily, the same results with<br />
laboratory experiments were obtained. The twice repeated results<br />
indicated that the residual Cr concentration in the spent tanning<br />
liquor was 270mg/L. As the control, it was 2608mg/L from the<br />
tannery tanning float, tanning with 1.16% Cr offer as per<br />
conventional methods. The Cr content in leather was 3.15%, a little<br />
lower than the control, 3.31%, and the shrinkage temperature<br />
reached to 95°C, in the case of Cr offer decreased by 26.7%.<br />
The wet-blue leathers were post-tanned and finished as per the<br />
tannery’s furniture leather procedures. The resultant leathers<br />
passed through the examination of the quality inspectors from<br />
the tannery. Skilled tanners commented that, in the aspects of<br />
organoleptic properties comparing with the tannery products,<br />
the leather was more stretching, the fullness and softness were<br />
better, and the grain pattern of the final leather was more<br />
uniform. In their opinions, pickling-tanning method with MSA<br />
is interesting and commercially acceptable.<br />
Conclusion<br />
The novel pickling-masking-chrome tanning system with MSA<br />
can remarkably increase the chromium exhaustion without<br />
impairing Cr penetration in both chrome tanning and retanning,<br />
resulting from the suitable and moderate masking effect of the<br />
MSA ligand towards Cr(III) ion. Accordingly, the total chrome<br />
offer can be reduced by about 26.7%, and the total Cr utilization<br />
ratio can be increased to 95.8% from 81.0% around, resulting in<br />
the total chromium emission in the whole leather processing is<br />
reduced by 83.8%, comparing with the conventional process.<br />
The area yield, physical and organoleptic properties of the<br />
leather are comparable with those from conventional processes.<br />
Acknowledgment<br />
Figure 5. Fatliquor content in the final leather (dichloromethane extracts).<br />
Samples<br />
Table VII<br />
Physical properties of crust leathers.<br />
Tensile<br />
strength<br />
(N/mm 2 )<br />
Tear strength<br />
(N/mm)<br />
Elongation<br />
at break (%)<br />
Conventional 7.5±1.2 25.6±5.7 45.7±4.7<br />
MSA 7.9±0. 9 32.0±3.4 56.7±3.2<br />
This work was financially supported by BASF Advanced<br />
Chemical Co., Ltd. and the National Key Technology R&D<br />
Programs of the Ministry of Science and Technology<br />
(2014BAE02B01). Tongtianxing Leather Co., China provided the<br />
required conditions for pilot-scale experiments.<br />
References<br />
1. Anthony, D.C.; Tanning chemistry: the science of leather,<br />
RSC Publishing, Cambridge UK, pp.177-258, 2011.<br />
2. Anthony, D.C.; Modern tanning chemistry. Chem. Soc. Rev.<br />
26, 111-126, 1997.<br />
J<strong>ALCA</strong>, VOL. 111, <strong>2016</strong>
Methanesulfonic Acid for Cleaner Tanning System 446<br />
3. Sundar, V. J., Rao, J.R. and Muralidharan, C.; Cleaner<br />
chrome tanning-emerging options. J. Clean. Prod. 10, 69-<br />
74, 2002.<br />
4. Chen, W.Y., Li, G.Y.; Tanning chemistry, China Light<br />
Industry Press, Beijing China, pp. 85-89, 2001.<br />
5. Gregori, J., Marsal, A., Manich, A.M. and Cot, J.;<br />
Optimization of the chrome tanning process – influence of<br />
3 types of commercially available masking agents. JSLTC.<br />
77, 147-150, 1993.<br />
6. Luan, S.F., Liu, Y., Fan, H.J., Shi, B. and Duan Z.J.; A novel<br />
pre-tanning agent for high exhaustion chromium tannage.<br />
JSLTC. 91, 149-153, 2007.<br />
7. Thannikaivelan, P., Kanthimathi, M., Rao, J.R. and Nair,<br />
B.; A novel formaldehyde-free synthetic chrome tanning<br />
agent for pickle-less chrome tanning: comparative study on<br />
syntan versus modified basic chromium sulfate. JSLTC. 97,<br />
127-136, 2002.<br />
8. Chen, J.P., Gong, Y. and Chen, W. Y.; Study on the softness<br />
of pickle and pickle-less chrome tanning leather. 7 th Asian<br />
International Conference of Leather Science and Technology,<br />
Chengdu China, 675-678, 2006.<br />
9. Suresh, V., Kanthimathi, M., Thanikaivelan, P., Raghava,<br />
J.R. and Unni, B.N.; An improved product-process for<br />
cleaner chrome tanning in leather processing. J. Clean.<br />
Prod. 9, 483-491, 2001.<br />
10. Bnownstrin, S., Stillman, A.E.; Proton resonance shifts of<br />
acids in liquid sulfur dioxide. J. Phys. Chem. 63, 2061-2062,<br />
1956.<br />
11. Michael, D., Gernon, Min, W., Thomas, B. and Patrick<br />
J.; Environmental benefits of methanesulfonic acid:<br />
comparative properties and advantages. Green Chemistry.<br />
1(3), 127-140, 1999<br />
12. Kityk, A.A., Protsenko, V.S. and Danilov, F.I.; Voltammetry<br />
Study of Cr(III)/Cr(II) system in methanesulfonate and<br />
sulfate solutions: temperature dependences. J. Electroanal.<br />
Chem. 689, 269-275, 2013.<br />
13. Protsenko, V., Danilov, F.; Kinetics and mechanism of<br />
chromium electrodeposition from formate and oxalate<br />
solutions of Cr(III) compounds. Electrochimica Acta 54,<br />
5666-5672, 2009.<br />
14. Protsenko, V.S., Kityk, A.A. and Danilov, F.I.; Kinetics<br />
and mechanism of chromium electrodeposition from<br />
methanesulfonate solutions of Cr(III) Salts. Surf. Eng. Appl.<br />
Ekect. 50, 384-389, 2014.<br />
15. Protsenko, V.S., Kityk, A.A. and Danilov, F.I.; Voltammetry<br />
study of Cr(III)/Cr(II) system in aqueous methanesulfonate<br />
solutions. J. Electroanal. Chem. 661, 213-218, 2011.<br />
16. Maher, J., Fathi, A., Safa, S. and Awni, K.; Monitoring<br />
chromium of content in tannery wastewater. J. Argent.<br />
Chem. Soc. 97, 77-87, 2009.<br />
17. Protsenko, V.S., Kityk, A.A. and Danilov, F.I.;<br />
Electroreduction of Cr(III) ions in methanesulphonate<br />
solution on Pb electrode. E-J CHEM 8, 1714-1719, 2011.<br />
18. Zhou, J., Hu, S.X., Wang, Y.N., He, Q., Liao, X.P., Zhang,<br />
W.H. and Shi, B.; Release of chrome in tanning and post<br />
tanning processes. JSLTC. 96, 157-161, 2011.<br />
J<strong>ALCA</strong>, VOL. 111, <strong>2016</strong>
447<br />
Development of Chrome-free Tanning in<br />
Supercritical CO 2<br />
Fluid using Zr-Al-Ti Complex<br />
by<br />
Xinhua Liu, 1,2 Feng Li, 1,2 Qin Huang, 1,2 Weihua Dan, 1,2 * and Nianhua Dan 1,2 *<br />
1<br />
Key Laboratory of Leather Chemistry and Engineering of Ministry of Education, Sichuan University,<br />
Chengdu, 610065, P.R. China<br />
2<br />
National Engineering Laboratory for Clean Technology of Leather Manufacture, Sichuan University,<br />
Chengdu, 610065, P.R. China<br />
Abstract<br />
In the current study, a green technology for the leather tanning<br />
process was developed, based on Zr-Al-Ti complex as a tanning<br />
agent in supercritical CO 2<br />
fluid (SCF-CO 2<br />
). The operating<br />
parameters in the tanning process, including dosage of the<br />
tanning agent, reaction time, tanning temperature and tanning<br />
pressure, were optimized using the orthogonal testing method.<br />
The physicochemical properties, morphological features,<br />
organoleptic properties, hydrothermal stability and microscopic<br />
fibrous construction of the Zr-Al-Ti tanned leather were also<br />
evaluated. The results showed that the optimum process<br />
conditions were: a tanning agent dosage of 40% of the bated pelt<br />
weight, a tanning time of 1.5h, a final temperature of 40°C and a<br />
reaction pressure of 8.5 MPa. The shrinkage temperature, tear<br />
strength, tensile strength and elongation at break of Zr-Al-Ti<br />
tanned leather in water media and in SCF-CO 2<br />
exhibited no<br />
statistically significant differences. However, SEM and<br />
histological observations revealed that the fiber bundles of<br />
leather tanned using the Zr-Al-Ti complex tanning agent in<br />
SCF-CO 2<br />
seemed to disperse more unevenly compared to those<br />
in water media, as well as conventional chrome tanned leather.<br />
Moreover, the degree of “opening up” of the fiber bundles and<br />
the visible interspace among them in the Zr-Al-Ti tanned leather<br />
in SCF-CO 2<br />
seemed to be much larger. Based on these results, we<br />
infer that the chrome-free tanning process in SCF-CO 2<br />
may<br />
endow similar leather characteristics compared to Zr-Al-Ti<br />
tanned leather in a water medium, which could effectively<br />
reduce the discharge of waste water compared to a conventional<br />
chrome tanning process, thus contributing to the development<br />
of a greener, or cleaner, technology for the leather tanning<br />
process.<br />
Introduction<br />
In recent years, concerns over environmental issues have led to<br />
many greener, or cleaner, approaches to leather tanning<br />
processes in the leather industry. 1-4 At present, chrome(III) is<br />
still recognized as endowing leather with unmatchable<br />
hydrothermal stability and excellent organoleptic properties;<br />
hence, its use as a tanning agent is widespread in the industry. 5<br />
Nevertheless, chrome tanning has some negative attributes,<br />
including: the possibility that uncombined residues of trivalent<br />
chromium in leather may be transformed into hexavalent<br />
chromium in some extreme conditions due to the insufficient<br />
penetration and combination of the chrome tanning agent; 6 such<br />
agents could give rise to concerns about water treatment issues<br />
related to BOD and COD; in some countries, chromium<br />
resources may be limited and even restricted to certain purposes<br />
only. 7,8 Therefore, the development of an eco-friendly chromefree<br />
tanning agent is of key importance for leather tanning.<br />
9, 10<br />
The Zr-Al-Ti complex tanning agent, abbreviated DMT-II, is a<br />
novel chrome-free tanning agent, which has been prepared by<br />
our group based on the interactions of metal molecules through<br />
coordination bonds. 11, 12 According to our previous study, 11 the<br />
combination of the three metal ions in solution results in the<br />
regeneration of a more complex multi-heteronuclear composite,<br />
which may be conducive to the tanning process. Moreover, it has<br />
been confirmed that DMT-II can endow leather with appropriate<br />
hydrothermal stability and superior organoleptic properties,<br />
comparable to chrome tanning agents. 12<br />
*Corresponding authors’ e-mail: lamehorse-8@163.com (N. Dan), danweihua_scu@126.com (W. Dan);<br />
Tel.: +86 28 85408988; fax: +86 28 85408988.<br />
Manuscript received October 29, 2015, accepted for publication May 10, <strong>2016</strong>.<br />
J<strong>ALCA</strong>, VOL. 111, <strong>2016</strong>
Chrome-free Tanning in Supercritical CO 2<br />
448<br />
Reduction or elimination of sewage discharge at the source<br />
might solve certain contaminant concerns in the leather<br />
manufacturing industry. 13 Supercritical CO 2<br />
fluid (SCF-CO 2<br />
) has<br />
been utilized extensively in many areas, such as printing, dyeing,<br />
and cleaning. 14-16 In recent years, the technology of leather<br />
manufacturing based on SCF-CO 2<br />
has also been explored, with<br />
its core principle being the use of SCF-CO 2<br />
instead of water as a<br />
medium in the different parts of the leather manufacturing<br />
process. 17,18 It has been reported that the penetration, distribution<br />
uniformity and combination of the chemical reagents used in<br />
each working procedure seem to be promoted significantly<br />
under SCF-CO 2<br />
, 19, 20 as the fluid can effectively control reactivity<br />
and reaction selectivity owing to its high compatibility, high<br />
dispersion, and low viscosity. 21 Therefore, the chemical reagents<br />
used in the process exhibit relatively high levels of utilization.<br />
Moreover, as CO 2<br />
can provide an inert chemical microenvironment,<br />
these reagents may be much more easily recycled<br />
in SCF-CO 2<br />
.<br />
In the present study, SCF-CO 2<br />
was used instead of water as a<br />
medium in the chrome-free Zr-Al-Ti tanning process. The<br />
process conditions, including dosage of the tanning agent,<br />
reaction time, tanning temperature and pressure of the reaction<br />
caldron were optimized using the orthogonal testing method. In<br />
addition, the physicochemical properties, morphological<br />
features, organoleptic properties, hydrothermal stability,<br />
chemical components, and microscopic fibrous construction of<br />
the Zr-Al-Ti tanned leather were further studied. Our aim is to<br />
explore the feasibility of an anhydrous or micro water tanning<br />
method using supercritical CO 2<br />
fluid as the medium and<br />
Zr-Al-Ti complexes as a chrome-free tanning agent, with a view<br />
to the sustainable development of cleaner leather<br />
manufacturing process and effluent.<br />
modifications. 11 A brief description of the preparation process is<br />
as follows: first, zirconium sulphate, aluminum sulphate,<br />
titanium sulphate and citric acid, in a ratio of 5:4:1:2 (w/w), were<br />
dissolved in 1 L of water under continuous magnetic stirring.<br />
Then, the mixture was heated and maintained at a constant<br />
temperature of 90° C for 30 minutes. Finally, the solution was<br />
dried using spray drying (GPL5, Sichuan Wang Chang Drying<br />
Equipment Co. Ltd.) to obtain the DMT-II.<br />
Leather Tanning Process<br />
The tanning process was carried out using bated cow pelts with<br />
a pH of 7.0–7.5. The bated cow pelts were soaked in the Zr-Al-Ti<br />
complex tanning solutions with different concentrations (based<br />
on the pelt weight) for 12 h and then drained for 30 min.<br />
Subsequently, the flesh side of the pelts was further soaked in a<br />
sodium bicarbonate solution with a stock concentration of 30<br />
mg/ml. Finally, the pretreated pelts were placed in the<br />
supercritical CO 2<br />
fluid reaction unit to undergo the tanning<br />
reaction. The detailed operating conditions for the tanning<br />
process are shown in Table I according to the design principles<br />
Figure 1. Schematic of the SCF-CO 2<br />
reaction unit.<br />
Experimental Procedures<br />
Materials<br />
The bated cattle pelts used in the tanning process were selfprepared<br />
according to the method describe in our previous<br />
report. 12 The chemicals used for the synthesis of DMT-II and for<br />
tanning the leather were of analytical grade and purchased from<br />
Chengdu Kelong Reagent Chemical Factory, P. R. China. In<br />
addition, the supercritical CO 2<br />
fluid equipment, with operating<br />
temperatures between −20 and 300° C , was designed in-house.<br />
Figure 1 shows a schematic of the SCF-CO 2<br />
reaction unit. The<br />
maximum operating pressure and effective working volume of<br />
the equipment were 20 MPa and 1000 mL, respectively.<br />
Preparation of Zr-Al-Ti Complex Tanning Agent<br />
The Zr-Al-Ti complex tanning agent (DMT-II) was self-prepared<br />
according to the method detailed in a previous study, with slight<br />
Level<br />
Table I<br />
The factors and levels of orthogonal tests<br />
for the Zr-Al-Ti complex tanning process.<br />
Tanning<br />
time /h<br />
Factors<br />
Tanning<br />
temperature<br />
/°C<br />
Tanning<br />
pressure /<br />
MPa<br />
DMT-II<br />
offer /% a<br />
1 2 45 9.5 24<br />
2 1.5 40 8.5 32<br />
3 1 35 7.5 40<br />
a<br />
The DMT-II tanning solution was used in the tanning<br />
process and its dosage was based on the limed pelt after<br />
weight gain to 1.2 times.<br />
J<strong>ALCA</strong>, VOL. 111, <strong>2016</strong>
449 Chrome-free Tanning in Supercritical CO 2<br />
of the orthogonal test method. Simultaneously, samples of<br />
chrome-free tanned leather and chrome tanned leather, both<br />
using water as the medium, were also prepared as a control,<br />
based on the methods from our previous report. 12<br />
Shrinkage Temperature Analysis<br />
The shrinkage temperature of the leather specimens from each<br />
tanning group was measured using a MSW-YD4 shrinkage<br />
meter from the Yangguang Research Institute of the Shanxi<br />
University of Science Technology, according to the Chinese<br />
Industrial Standard QB/T 2713-2005.<br />
ICP Analysis<br />
The leather specimens from each tanning group were split into<br />
three layers (grain layer, middle layer, and flesh layer) with the<br />
same thickness, using a precise splitting machine. Each layer of<br />
the leather specimens was placed in a drying oven for over 4<br />
hours, following which a certain number of the dried samples<br />
were digested and further analyzed using an inductively coupled<br />
plasma (ICP) spectrometer (Optima 2100DV, Germany). The<br />
homogeneous degree of DMT-II in the leather specimens was<br />
calculated using the following formula (1).<br />
where A 2<br />
represents the metal ion content of the middle layer,<br />
and A 1<br />
and A 3<br />
are the metal ion contents of the grain layer and<br />
flesh layer, respectively.<br />
Microstructure Characteristics<br />
Scanning Electron Microscope Observation<br />
The leather specimens from each tanning group were sampled in<br />
official sampling position. The samples were lyophilized in a<br />
vacuum chamber (0.05 bar) for 48 hours and their cross sections<br />
were observed microscopically using a scanning electron<br />
microscope (SEM, Hitachi S3000N, Hitachi, Ltd., Japan). 12 All<br />
the specimens were coated with aurum and imaged at an<br />
accelerating voltage of 5 kV.<br />
Histological Observation<br />
The leather specimens from each tanning group were sampled<br />
adjacently and symmetrically from the same hide, and fixed in a<br />
10% formaldehyde solution for more than 24 hours. The crossand<br />
longitudinal- sections of the specimens were prepared using<br />
a CM1950 freezing microtome (Leica, Germany) to a thickness<br />
of 12 µm, and adhered to glass slides. Morphologic observation<br />
was performed using the Van Giesen staining method with<br />
picric acid and fuchsin acid. Finally, an E400 optical microscope<br />
(Nikon, Japan) was used to carry out a histological examination<br />
of the stained samples. 12<br />
(1)<br />
Physical-mechanical Properties and Organoleptic Assessment<br />
The dried crust leather samples from each tanning group were<br />
tested using an AI-7000S Versatile Material Experiment Machine<br />
(Gotech High Technology Co. Ltd., Taiwan, China) according to<br />
the standard procedures for testing physical and mechanical<br />
properties. Physical properties such as tensile strength,<br />
elongation at break, and tear strength were examined as per the<br />
standard procedures IUP 6 (2000), IUP 8 (2000), and IUP 9<br />
(1996). 22 Further, the specimens from each tanning group were<br />
assessed by hand for softness, grain tightness, grain smoothness,<br />
strength, and fullness, through the visual examination of<br />
experienced tanners, who have worked in the leathermanufacturing<br />
industry for more than ten years.<br />
Chemical Composition Analysis<br />
The leather specimens from each tanning group were subjected<br />
to chemical composition analysis to determine the moisture,<br />
sulfate ash, and fat content, according to the methods laid out by<br />
the Chinese Industrial Standard QB/T 2706-2722 (2005).<br />
Results and Discussion<br />
Orthogonal Experiment Analysis<br />
Table II shows the results of orthogonal experiments determined<br />
by the shrinkage temperature, Ts. The influence of the tanning<br />
conditions on the shrinkage temperature of the leather specimens<br />
from each tanning group are directly reflected by the R values. As<br />
shown in Table II and Figure 2, the tanning conditions for the<br />
shrinkage temperature of the leather specimens, ranked in order<br />
from the most to the least influential, are: (DMT-II offer) ><br />
(tanning time) > (tanning temperature) > (tanning pressure).<br />
Figure 2 shows the effects of each tanning operating condition on<br />
the shrinkage temperature of the leather specimens. The Ts values<br />
increased dramatically for DMT-II dosages of less than 32%. As<br />
the DMT-II offer was increased, the Ts tended towards a steady<br />
value; however, operating under these conditions would be more<br />
costly. Generally, with an increasing concentration of DMT-II, the<br />
coordination probability between carboxyl groups in collagen<br />
fibrils and DMT-II would increase, 12 thus increasing the combined<br />
amount of DMT-II and further improving the shrinkage<br />
temperature. Furthermore, our previous study indicated that the<br />
reaction between collagen fibrils and DMT-II reaches chemical<br />
equilibrium when the DMT-II offer reaches 40%. 12 In addition,<br />
when the tanning process starts within 1 h, the penetration of the<br />
tanning agent could promptly penetrate into the leather. By<br />
prolonging the rotation time to 1.5 h, the combination of the<br />
tanning agent with the carboxyl of the collagen chains approaches<br />
an equilibrium point. Furthermore, increasing the tanning<br />
temperature accelerates the hydrolysis and polycomplexation of<br />
the DMT-II molecules, 12 resulting in bigger molecular dimensions;<br />
this may promote the permeation of DMT-II into the pelts and<br />
J<strong>ALCA</strong>, VOL. 111, <strong>2016</strong>
Chrome-free Tanning in Supercritical CO 2<br />
450<br />
further the combination of the metal complex with the collagen.<br />
However, when the tanning temperature is set too high, DMT-II<br />
molecules might become too large and react with the collagen too<br />
early, leading to the case hardening of leather, 23 which would<br />
negatively affect the permeation of DMT-II molecules. In<br />
summary, taking into account the cost and tanning results, the<br />
optimum operating conditions of the Zr-Al-Ti tanning process in<br />
SCF-CO 2<br />
were determined to be: a tanning agent dosage of 40% of<br />
the bated pelt weight, a tanning time of 1.5 h, a final temperature<br />
of 40°C, and a reaction pressure of 8.5 MPa.<br />
Shrinkage Temperature Analysis<br />
The shrinkage temperature determines the thermostability of<br />
leather. Table III shows the shrinkage temperatures of the leather<br />
specimens from each tanning group. The shrinkage temperature<br />
of the Zr-Al-Ti tanned leather in SCF-CO 2<br />
increased by around<br />
24 °C compared to the bated cattle skin, which indicates that the<br />
hydrothermal stability of leather may be efficiently improved by<br />
the tanning agent. 24 Note that the shrinkage temperature of the<br />
Zr-Al-Ti tanned leather in SCF-CO 2<br />
was somewhat lower than<br />
that in the water fluid. This may be because the pelts could not<br />
achieve sufficient mechanical interaction in the SCF-CO 2 reaction<br />
unit compared to the conventional drum. On the other hand,<br />
though the combination of the DMT-II in the tanned leather<br />
under SCF-CO 2<br />
was higher, as confirmed by the ICP analysis,<br />
the effective combination with collagen fibrils (i.e. the multipoint<br />
attachment) was insufficient. 17 Additionally, as is well known,<br />
hydrolysis and polymerization of metal tanning agents usually<br />
occur in an aqueous medium; thus, the aforementioned reaction<br />
of the Zr-Al-Ti tanning agent would be inhibited to some extent<br />
in SCF-CO 2<br />
, leading to a lower shrinkage temperature.<br />
Therefore, the tanning process taking place in an almost<br />
anhydrous environment may be very beneficial for saving<br />
tanning water and reducing tanned effluent discharge. At the<br />
same time, unlike for the conventional chrome tanning process,<br />
there was no need to introduce any additional sodium<br />
bicarbonate to increase alkalinity in the tanning process<br />
occurring in the SCF-CO 2<br />
reactor. Meanwhile, 1.5 h of tanning<br />
time, which was significantly lower than that of the Zr-Al-Ti<br />
tanned leather in water fluid, was quite enough in the SCF-CO 2<br />
.<br />
This would undoubtedly substantially save on energy<br />
consumption and labor costs.<br />
Table II<br />
Results of orthogonal experiments.<br />
Tanning time /h<br />
Tanning<br />
temperature / ° C<br />
Pressure /MPa Dosage /% Ts / °C<br />
1 2 45 9.5 24 82.0<br />
2 2 40 8.5 32 87.5<br />
3 2 35 7.5 40 83.3<br />
4 1.5 40 9.5 40 85.7<br />
5 1.5 35 8.5 24 84.8<br />
6 1.5 45 7.5 32 86.7<br />
7 1 35 9.5 32 83.6<br />
8 1 45 8.5 40 84.3<br />
9 1 40 7.5 24 82.8<br />
K 1<br />
84.3 83.7 84.3 83.2<br />
Ts<br />
K 2<br />
85.7 85.5 85.3 85.9<br />
K 3<br />
83.6 84.3 83.9 84.4<br />
R 2.1 1.8 1.4 2.7<br />
Significance<br />
DMT-II offer > Tanning time > Tanning temperature > Tanning Pressure<br />
J<strong>ALCA</strong>, VOL. 111, <strong>2016</strong>
451 Chrome-free Tanning in Supercritical CO 2<br />
ICP Analysis<br />
Table IV shows the ICP results for the Zr-Al-Ti tanned leathers<br />
in the SCF-CO 2<br />
and water fluids. The DMT-II contents of each<br />
layer of the tanned leather in SCF-CO 2<br />
were higher compared to<br />
those in water, which indicates that the penetration and<br />
combination of the DMT-II is promoted under SCF-CO 2<br />
.<br />
Moreover, the DMT-II in the tanned leather exhibited a<br />
significantly higher homogeneous degree in the SCF-CO 2<br />
compared to the water.<br />
Physical-mechanical Properties Analysis<br />
Table V shows the results of the physical-mechanical property<br />
analysis for the Zr-Al-Ti tanned leathers in the SCF-CO 2<br />
and<br />
water fluids, and the conventional chrome tanned leather. The<br />
tear strengths, tensile strengths and elongation at break of the<br />
three samples were not very different, and ensures that all three<br />
fulfilled the fundamental requirements for the mechanical<br />
strength of leathers. 12 However, it is still noteworthy that the<br />
Zr-Al-Ti tanned leather in SCF-CO 2<br />
exhibited a slightly lower<br />
tensile strength than the other two specimens, while possessing<br />
the highest elongation at break.<br />
The organoleptic properties of the three different leathers were<br />
also evaluated. All of the professional, skilled tanners consulted<br />
in this study believed that there were no visible differences<br />
among these leathers in respect to the strength, fullness and<br />
hand feeling; some differences were noted in respect to the<br />
softness, grain tightness and grain smoothness. More<br />
specifically, the softness and grain smoothness of the Zr-Al-Ti<br />
tanned leather in SCF-CO 2<br />
was superior to that in water, while its<br />
grain tightness exhibited a slight inferiority.<br />
Chemical Composition Analysis<br />
The chemical compositions of the leather specimens from each<br />
tanning group were studied using the methods outlined in the<br />
Chinese Industrial Standard QB/T 2706-2722 (2005), as shown<br />
in Table VI. According to the proximate composition results, the<br />
moisture content of the Zr-Al-Ti tanned leather in SCF-CO 2<br />
was<br />
slightly higher compared with that in the water. Generally, the<br />
moisture content of leather or fur should be between 12–18%, as<br />
the density, thickness, area, and tensile strength of the leather<br />
vary greatly with the moisture content. Leathers with lower<br />
moisture content appear much harder and crisper, whereas those<br />
with higher moisture content tend to be much easier to deform<br />
and mildew. A higher content of sulfated ash was found in the<br />
Zr-Al-Ti tanned leather in SCF-CO 2<br />
compared to that in the<br />
water, which might suggest that the amount of infiltration and<br />
combination of DMT-II was significantly higher due to more<br />
loosely weaved collagen fibrils. Meanwhile, the Zr-Al-Ti tanned<br />
leather in SCF-CO 2<br />
exhibited lower dichloromethane extract<br />
Figure 2. The effect of each tanning operating condition on the shrinkage temperature of the leather specimens.<br />
J<strong>ALCA</strong>, VOL. 111, <strong>2016</strong>
Chrome-free Tanning in Supercritical CO 2<br />
452<br />
content, as the SCF-CO 2<br />
was able to extract a small amount of<br />
grease from the bated pelts. As is well known, the<br />
dichloromethane extract content of leather is closely associated<br />
with its water resistance performance, extensibility and<br />
breathability. The lower dichloromethane extract content may be<br />
beneficial for the breathability of the leather, especially when<br />
used as shoe upper leather. In addition, the Zr-Al-Ti tanned<br />
leather in SCF-CO 2<br />
was found to have a significantly higher<br />
protein content than that in water fluid, which indicates that the<br />
tanning process in supercritical CO 2<br />
fluid does not excessively<br />
damage the basic framework of collagen fibrils in leather.<br />
Overall, the chemical compositions of the two leathers were<br />
similar but still showed some differences, which may be closely<br />
related to their specific leather properties.<br />
Microstructure Characteristics<br />
SEM Analysis<br />
The scanning electron micrographs of the leather specimens<br />
from each tanning group, presented in Figure 3, show that the<br />
degree of “opening up” of the fiber bundles in the Zr-Al-Ti<br />
tanned leathers in both media were higher compared to the<br />
bated pelts. Moreover, no apparent dense blocky crystals of<br />
DMT-II were observed between the collagen fibers, which<br />
indicates that all the inner layers were well tanned. 21 The fiber<br />
bundles of these two leathers were weaved very tightly and the<br />
fibrous clearance was relatively close. As a result, the<br />
tanning effects achieved by DMT-II were clearly apparent<br />
compared to the bated pelts, which implies that the DMT-II<br />
tanning process was conducted successfully in the SCF-CO 2<br />
.<br />
Specimens<br />
Table III<br />
Shrinkage temperatures of the leather<br />
specimens from each tanning group.<br />
Table IV<br />
ICP results for the leather specimens<br />
from each tanning group.<br />
Ts / ° C<br />
Bated cattle pelts 63.7 ± 2.1<br />
Zr-Al-Ti tanned leather in SCF-CO 2<br />
87.4 ± 2.6<br />
Zr-Al-Ti tanned leather in water fluid 94.6 ± 3.5<br />
conventional chrome leather 105.1 ± 5.3<br />
Table V<br />
The mechanical properties of each leather specimen.<br />
Specimens<br />
Tear strength/<br />
(N/mm)<br />
Tensile<br />
strength/MPa<br />
Elongation at<br />
break /%<br />
Zr-Al-Ti<br />
tanned<br />
leather in<br />
SCF-CO 2<br />
Zr-Al-Ti<br />
tanned<br />
leather in<br />
water fluid<br />
Chrome<br />
tanned<br />
leather<br />
45.7 ± 3.5 44.8 ± 2.8 46.4 ± 1.3<br />
10.6 ± 0.6 13.7 ± 1.6 12.3 ± 1.1<br />
95.2 ± 3.7 75.3 ± 6.0 78.9 ± 5.5<br />
Table VI<br />
Chemical compositions of each leather.<br />
Specimens<br />
Layer<br />
classification<br />
DMT-II<br />
content /<br />
(mg/g)<br />
homogeneous<br />
degree of<br />
DMT-II<br />
Specimens<br />
Zr-Al-Ti<br />
tanned<br />
leather in<br />
SCF-CO 2<br />
Zr-Al-Ti<br />
tanned<br />
leather in<br />
water fluid<br />
Chrome<br />
tanned<br />
leather<br />
Zr-Al-Ti<br />
tanned<br />
leather in<br />
water fluid<br />
Grain layer 36.32<br />
Middle layer 32.86<br />
Flesh layer 36.89<br />
Zr-Al-Ti Grain layer 37.65<br />
SCF-CO 2 Flesh layer 37.12<br />
tanned<br />
leather in<br />
Middle layer 35.13<br />
89.77%<br />
93.97%<br />
Moisture /% 15.91 ± 2.52 14.98 ± 2.31 13.13 ± 1.98<br />
Sulfated ash /% 17.95 ± 1.28 16.70 ± 2.13 6.93 ± 1.65<br />
Dichloromethane<br />
extracts /%<br />
0.78 ± 0.02 1.05 ± 0.05 2.31 ± 0.59<br />
Protein /% 48.66 ± 3.12 36.50 ± 2.91 38.79 ± 2.61<br />
J<strong>ALCA</strong>, VOL. 111, <strong>2016</strong>
453 Chrome-free Tanning in Supercritical CO 2<br />
Histological Analysis<br />
Histological examination mainly showed the intact total framework<br />
of the cross and longitudinal sections of the three different<br />
specimens, as shown in Figures 4 and 5. The degree of “opening up”<br />
of the fiber bundles and the visible interspace among them seemed<br />
to be much larger in the SCF-CO 2<br />
specimen compared to the one in<br />
water, which may be beneficial for the infiltration and combination<br />
of DMT-II, since most of the penetration time is determined by the<br />
efficiency of DMT-II assimilating into the collagen fibrils. 25 In this<br />
case, the CO 2<br />
can directly infiltrate the grain and reticular layers of<br />
crust leathers, which should have a positive impact on the<br />
penetration of the DMT-II. In addition, the fibrils of the Zr-Al-Ti<br />
tanned leather in SCF-CO 2<br />
seemed to be more loosely weaved,<br />
which corresponds with the results of the physical-mechanical<br />
property and organoleptic assessment analyses. Based on these<br />
results, it may be inferred that the gaps between the collagen fiber<br />
bundles would be increased in the SCF-CO 2<br />
due to its function of<br />
“decentralizing fibers.”<br />
Figure 3. Scanning Electron Microscope cross sections of crust leathers:<br />
(1) Bated cattle skin (×200); (2) Zr-Al-Ti tanned leather in SCF-CO 2<br />
(×200); (3) Zr-Al-Ti tanned leather in water fluid (×200).<br />
Conclusions<br />
A green technology for a leather tanning process in supercritical<br />
CO 2<br />
fluid media (SCF-CO 2<br />
) was developed and evaluated based<br />
on Zr-Al-Ti complex as tanning agent. The operating conditions<br />
of the tanning process were optimized using the orthogonal test<br />
method, with the following conditions found to be optimal: a<br />
tanning agent dosage of 40% of the bated pelt weight, a tanning<br />
time of 1.5 h, a final temperature of 40° C and a reaction pressure<br />
of 8.5 MPa. The shrinkage temperature of the Zr-Al-Ti tanned<br />
leather in water media and in the SCF-CO 2<br />
exhibited no<br />
statistically significant differences. ICP analysis confirmed that<br />
the distribution uniformity and combination of the Zr-Al-Ti<br />
tanned leather in SCF-CO 2<br />
was better compared to the<br />
conventional Zr-Al-Ti tanned leather in water fluid. The slightly<br />
lower tensile strength and higher elongation at break of the<br />
Zr-Al-Ti tanned leather in SCF-CO 2<br />
were due to its more loosely<br />
woven fibrils. Meanwhile, histological observations showed that<br />
the degree of “opening up” of fiber bundles, and the visible<br />
interspace among them in the Zr-Al-Ti tanned leather in<br />
SCF-CO 2<br />
seemed to be much larger compared to that in the<br />
water fluid. SEM analysis confirmed that all the inner layers<br />
were well tanned. As a whole, the fundamental properties and<br />
microscopic fibrous construction of the Zr-Al-Ti tanned leather<br />
in SCF-CO 2<br />
exhibited no remarkable differences compared to<br />
the conventional Zr-Al-Ti tanned leather in water. However, this<br />
chrome-free process could help with waste water treatment by<br />
eliminating the chromium discharge at the source, thus<br />
contributing to the development of sustainable leather<br />
manufacturing processes.<br />
Figure 5. Histological observation of the cross sections of crust leathers<br />
j. Bated cattle skin (×40), m. Bated cattle skin (×100);<br />
k. Zr-Al-Ti tanned leather in SCF-CO 2<br />
(×40), n. Zr-Al-Ti tanned leather<br />
in SCF-CO 2<br />
(×100);<br />
i. Zr-Al-Ti tanned leather in water fluid (×40), o. Zr-Al-Ti tanned<br />
leather in water fluid (×100).<br />
Figure 4. Histological observation of the longitudinal sections of<br />
crust leathers.<br />
a. Bated cattle skin (×40), d. Bated cattle skin (×100), g. Bated cattle<br />
skin (×200);<br />
b. Zr-Al-Ti tanned leather in SCF-CO 2<br />
(×40), e. Zr-Al-Ti tanned leather<br />
in SCF-CO 2<br />
(×100), h. Zr-Al-Ti tanned leather in SCF-CO 2<br />
(×200);<br />
c. Zr-Al-Ti tanned leather in water fluid (×40), f. Zr-Al-Ti tanned leather<br />
in water fluid (×100), i. Zr-Al-Ti tanned leather in water fluid (×200).<br />
J<strong>ALCA</strong>, VOL. 111, <strong>2016</strong>
Chrome-free Tanning in Supercritical CO 2<br />
454<br />
Acknowledgement<br />
This work is supported by the National Natural Science<br />
Foundation of China (contract grant numbers 51473001 and<br />
21276164).<br />
References<br />
1. Covington A.D.; Tanning Chemistry: the Science of Leather.<br />
RSC Publishing, Cambridge, UK, 2011.<br />
2. Karlheinz F., Rainer K., Mitchell J. W.; Glyoxylic acid: an<br />
interesting contribution to clean technology. J<strong>ALCA</strong> 88,<br />
402-413, 1993.<br />
3. John S. V., Raghava R. J., Muralidharan C.; Cleaner chrome<br />
tanning emerging options. J. Clean. Prod. 10, 69-74, 2002.<br />
4. Träubel, H.; A new approach to tanning-an unconventional<br />
attempt. J<strong>ALCA</strong> 100, 304-316, 2005.<br />
5. Morera, J. M., Bacardit, A., Ollé, L., Bartolí, E., Borràs, M.<br />
D.; Minimization of the environmental impact of chrome<br />
tanning: A new process with high chrome exhaustion.<br />
Chemosphere 69, 1728-1733, 2007.<br />
6. Murthy, Y. R., Tripathy, S. K., Kumar, C. R.; Chrome ore<br />
beneficiation challenges & opportunities-A review. Miner.<br />
Eng. 24, 375-380, 2011.<br />
7. Levina, A., Lay, P. A.; Chemical properties and toxicity of<br />
chromium(III). Chem. Res. Toxicol. 21, 563-571, 2008.<br />
8. Leafe, M. K.; Leather Technologists Pocket Book, J. Soc.<br />
Leather Technol. Chem., U.K., 1999<br />
9. Luo, J. X., Feng, Y. J., Shan, Z. H.; Complex Combination<br />
Tannage with Phosphonium Compounds, Vegetable<br />
Tannins and Aluminium Tanning Agent. J. Soc. Leather<br />
Technol. Chem. 95, 215, 2011.<br />
10. Shi B., Wang X. C.; Cleaner Leather Production Technologies<br />
and Principles, Chemical Industry Press, Beijing, China, 87-<br />
93, 2010.<br />
11. Wang K., Jia S., Dan N., et al; Separation and Analysis of Zr-<br />
Al-Ti Complex Tanning Agent Solution Components. J. Soc.<br />
Leather Technol. Chem. 97, 80-83, 2013.<br />
12. Wang K., Xiao S., Liu M., et al; Chrome-free Tanning–A<br />
Non-Pickle Process Using a Zr-Al-Ti Complex Tanning<br />
Agent. J. Soc. Leather Technol. Chem. 96, 141-147, 2012.<br />
13. Luo, J. X., Feng, Y. J. and Shan, Z. H., Complex Combination<br />
Tannage with Phosphonium Compounds, Vegetable<br />
Tannins and Aluminium Tanning Agent. J. Soc. Leather<br />
Technol. Chem. 95, 215, 2011.<br />
14. Jun J. H., Sawada K., Takagi T., Kim G. B., Park C. H., Ueda<br />
M.; Effects of pressureand temperature on dyeing acrylic<br />
fibers with basic dyes in supercritical carbon dioxide. Color.<br />
Technol. 121, 25-28, 2005<br />
15. Hurren D.; Supercritical fluid extraction with CO2. Filtr.<br />
Separat. 36, 25, 1996.<br />
16. Guan Z., DeSimone J. M., Elsbernd C. S.; Synthesis of<br />
fluoropolymers in supercritical carbon dioxide. Science 257,<br />
945-947, 1992.<br />
17. Manfred R., Eckhard W., Bijoern J., et al; Free of water<br />
tanning using CO 2<br />
as process additive – An overview on the<br />
process development. J. of Supercritical Fluids 66, 291-296,<br />
2012.<br />
18. Renner M., Weidner E., Brandin G.; High-pressure carbon<br />
dioxide tanning. Chem. Eng. Res. Des. 87, 287-996, 2009.<br />
19. Marsal A., Celma P. J., Cot J., et al.; Supercritical CO2<br />
extraction as a clean degreasing process in the leather<br />
industry. J. of Supercritical Fluids 16, 217-223, 2000.<br />
20. Yang Q., Qin S., Chen J., et al.; Supercritical carbon dioxideassisted<br />
loosening preparation of dry leather. J. Appl. Polym.<br />
Sci. 113, 4015-4022, 2009.<br />
21. Behles J. A., DeSimone J. M.; Developments in CO 2<br />
research.<br />
Pure and Appl. Chem. 73, 1281-1285, 2001.<br />
22. Zhang, C., Lin J., Jia X., Peng B.; A salt-free and chromium<br />
discharge minimizing tanning technology: the novel<br />
cleaner integrated chrome tanning process, J. Clean. Prod.<br />
http://dx.doi.org/10.1016/j.jclepro.2015.07.155, 2015.<br />
23. Wang K., Dan W., Liu M., et al.; Optimization and design<br />
of tanning process using Zr-Al-Ti complex tanning agent.<br />
XXXII. International Congress of IULTCS. 2013<br />
24. Chen D., Wang K., Dan N., et al.; Flame Resistance of<br />
Leather Tanned by Zr-Al-Ti Complex Tanning Agent. J. Soc.<br />
Leather Technol. Chem. 58, 213-218, 2013.<br />
25. Covington A.D.; Theory and mechanism of tanning:<br />
present thinking and future implications for industry, J.<br />
Soc. Leather Technol. Chem. 85, 24–34, 2000.<br />
J<strong>ALCA</strong>, VOL. 111, <strong>2016</strong>
455<br />
Studies on the use of Bi-functional Enzyme for Leather Making<br />
by<br />
G. C. Jayakumar, 1 M. Sathish, 1 R Aravindhan 2 * and J. Raghava Rao 1 *<br />
1<br />
Chemical Laboratory<br />
2<br />
Leather Process Technology Division<br />
Central Leather Research Institute, Council of Scientific & Industrial Research<br />
Adyar, Chennai, India<br />
Abstract<br />
Preparation of skin or hide for tanning involves several unit<br />
processes/operations. This results in the generation of significant<br />
quantity of solid and liquid wastes, which is of major concern for<br />
the leather fraternity. However, several alternate technologies are<br />
available to address this issue. One of the well explored systems<br />
is application of enzymes in conventional leather processing. In<br />
the present research, application of bi-functional enzymefibrozyme<br />
(mixture of protease and amylase) for leather<br />
processing was studied. The present study relies upon the<br />
characteristic evaluation methods to ascertain the efficiency of<br />
enzymes in unhairing and fiber opening. Initially, various<br />
concentrations of enzymes were applied to cow hides by drum<br />
method. In this approach, 3.5% of fibrozyme is optimized for<br />
efficient removal of hair and proteoglycans. This is based on the<br />
organoleptic evaluation of enzyme treated pelts. The efficiency of<br />
enzyme was primarily evaluated through staining technique.<br />
Moreover, physical strength parameters were measured to assess<br />
the impact on fibers due to enzyme treatment. Morphological<br />
evaluation was carried out to confirm that there is no coalescent<br />
or distortion of fibers after enzyme treatment. Hydrothermal<br />
stability of experimental wet blue leather was found to be 108ºC,<br />
which confirms better exhaustion and fixation of chromium. The<br />
study provides an avenue for integrated enzymatic dehairing and<br />
fiber opening using a single formulation of protease and amylase.<br />
Introduction<br />
Development of cleaner technologies for leather manufacture is one<br />
of the emerging fields of research to attain the eco-labelling. 1 It is a<br />
real challenge to attain paradigm shift in adopting modern<br />
technologies in traditional sector like leather. 2 There are several unit<br />
processes and operations involved to clean the matrix. Pretanning<br />
is carried out primarily to prepare the skins/hides for tanning. In<br />
conventional leather making, liming and reliming steps are very<br />
imperative as it is prerequisite to remove hair, flesh and to open up<br />
the fiber bundles for the diffusion of chemicals. Lime-sulfide<br />
process is extensively used in terms of hair removal due to its high<br />
efficiency. However, generation of pollution due to this process<br />
cause serious health hazard to the workers as well as the<br />
environment. Sulfide assisted process also leads to the degradation<br />
of hairs, which results in high COD in the effluent. Several alternate<br />
technologies have been designed to reduce the pollution load.<br />
Application of enzymes in leather processing is one such option,<br />
which aids in the reduction of the pollution load, increase the<br />
efficiency of the process thereby reducing the duration. 2-3 Protease,<br />
amylase and lipase are the three major enzymes that are widely used<br />
in bio-processing methods. Conventional reliming process takes a<br />
minimum of one day to few days depending on the type of end<br />
product. However, enzyme assisted fiber opening considerably<br />
reduce the duration and effectively scissors the proteoglycans. 4-5<br />
Amylase helps in the fiber opening and effective removal of the<br />
adipose tissue from the skin/hide.<br />
In the present study, a technical evaluation method has been<br />
formulated in order to evaluate the efficacy of the enzymes in<br />
leather processing. Staining technique is employed to understand<br />
the role of protease and amylase in leather making. Proteaseamylase<br />
mixture is treated with cow hides at various<br />
concentrations and their organoleptic properties have been<br />
evaluated and the offer of enzyme is optimized. The present<br />
study provides a new dimensional approach in analytical<br />
methods to assess the leather properties.<br />
Experimental<br />
Materials<br />
Wet salted cow hides were used as raw materials during this<br />
study. All chemicals used for leather processing were of<br />
commercial grade while the chemicals used for the analysis of<br />
spent liquors were of analytical grade. Fibrozyme (formulated<br />
protease and amylase product having protease activity - 100 U/g,<br />
amylase activity - 1000 U/g) was supplied by Southern Petro<br />
Chemicals Industries Corporation (United Alacrity), Chennai.<br />
Bovine Serum Albumin (BSA), Mucin, Folin ciocelatu reagent,<br />
Periodic acid was procured from Sigma-Aldrich, India and other<br />
analytical chemicals were procured from SD Fine Chem Ltd., India.<br />
*Authors for correspondence e-mail: (J. Raghava Rao) clrichem@mailcity.com; (R Aravindhan) aravindhanr78@gmail.com;<br />
Tel: + 91 44 2441 1630; Fax: + 91 44 2491 1589<br />
Manuscript received March 3, <strong>2016</strong>, accepted for publication May 27, <strong>2016</strong>.<br />
J<strong>ALCA</strong>, VOL. 111, <strong>2016</strong>
Bi-functional Enzyme 456<br />
Quantification on the Release of Protein,<br />
Proteoglycan Processes<br />
Five wet salted cow hides were taken and cut in to sides. The left<br />
halves were processed for enzymatic unhairing and fiber opening<br />
process as given in Table I and the right halves were used as<br />
control, where, lime sulphide method was employed for dehairing<br />
and conventional reliming using lime was carried out for fiber<br />
opening. The pH of the float was adjusted using sodium carbonate<br />
to 8.5-9.0 before addition of enzyme for effective unhairing<br />
treatment. The spent liquor collected after the unhairing and fiber<br />
opening from both control and experimental processes were<br />
filtered through Whattman filter paper (cellulose filters, 0.25 psi<br />
wet burst, thickness-180 μm, pore size-11 μm). The filtered<br />
samples were then estimated for the release of protein and<br />
proteoglycan. 6 Proteins are estimated as described by Bradford<br />
method, 7 where a standard graph was prepared using BSA and the<br />
amount of protein present in the sample sourced from the control<br />
and experimental processes was estimated.<br />
For the estimation of proteoglycans, Schiff’s assay method was<br />
carried out, 8 where the periodate oxidizable glycoconjucates can<br />
be estimated. Standard graph was prepared using mucin as<br />
working standard and the amount of proteoglycan present in the<br />
samples were estimated.<br />
Staining Techniques<br />
Haematoxylin and Eosin (H&E) staining is a routinely used<br />
technique in histopathology laboratories as it provides the<br />
pathologist/researcher a very detailed view of the tissue. H&E<br />
staining is considered to be a critical assay to study the tissue<br />
samples. This technique was carried out for staining the relimed<br />
pelt (control) and fibrozyme treated pelt, to understand the<br />
changes brought about in the fibers. From each sample the color<br />
images were acquired with a light microscope and digital camera<br />
running under image analysis program. 9<br />
Chrome Tanning<br />
The enzyme treated pelts were washed thoroughly and pickled. The<br />
deliming and bating processes were eliminated for the enzyme<br />
based process as the pH of the enzyme treated pelts was around 8±1.<br />
In addition, no lime was also used during the fiber opening process.<br />
The pickled pelts were subsequently processed for conventional<br />
chrome tanning using 8% BCS as given in Table II. The spent liquor<br />
was collected to analyze the exhaustion of chromium, which is an<br />
indirect measure of fiber opening in the hide matrix. The control<br />
pelts were conventionally processed in to chrome tanned leather by<br />
carrying out deliming, bating and pickling.<br />
Determination of Shrinkage Temperature<br />
The shrinkage temperature, which is a measure of hydrothermal<br />
stability of leather, is determined using a Theis shrinkage tester. 10<br />
A 2 cm 2 samples from control and experimental leathers was cut<br />
and clamped between the jaws of the clamp, and was immersed<br />
in a solution of water: glycerol mixture (3:1). The temperature of<br />
the solution was gradually increased and the solution was kept<br />
under stirring using a mechanical stirrer. The temperature at<br />
which the leather shrinks was noted and determined as the<br />
shrinkage temperature.<br />
Post Tanning Process<br />
Control and experimental leathers were shaved to a uniform<br />
thickness of 1.1±0.1 mm and converted in to an upper crust leather<br />
Table I<br />
Process recipe for fibrozyme enzyme application.<br />
Process Chemicals % Time (h) Remarks<br />
Soaking I Water 300<br />
Water 300<br />
Soaking II<br />
Sodium carbonate 0.4<br />
2<br />
Adjust the pH of soak liquor<br />
to 9-9.5 and left overnight<br />
Biocide 0.1<br />
Enzyme treatment Water 30<br />
Fibrozyme 2.5-4<br />
6<br />
Adjust the bath pH to 9-9.5.<br />
No. of cycles – 6 (10’ run and 50’<br />
stop and left overnight)<br />
Washing Wetting agent 0.2 10 Dry drumming<br />
Washing Water 100<br />
Wetting agent 0.2<br />
10<br />
J<strong>ALCA</strong>, VOL. 111, <strong>2016</strong>
457 Bi-functional Enzyme<br />
by following the post tanning recipe provided in Table III. After<br />
post tanning operations, the leathers were piled overnight. Next<br />
day, the leathers were set, hooked to dry, staked and buffed.<br />
Evaluation of Physical and Organoleptic<br />
Properties of Leathers<br />
The samples for physical testing were obtained as per IULTCS<br />
methods. 11 The samples were conditioned at 80°F and 65% R.H.<br />
for 48 h. 12 Physical properties such as tensile strength, %elongation,<br />
tear strength and grain crack strength were determined as per<br />
standard procedures. 13,14 Each value reported is an average of four<br />
measurements. The crust leathers were further assessed for<br />
softness, grain smoothness, fullness and general appearance by<br />
tactile evaluation. Three experienced tanners rated the leathers on<br />
a scale of 0-10 points for each functional property.<br />
Scanning Electron Microscopic (SEM) Analysis<br />
of Processed Leathers<br />
Samples from control and experimental pelts and from the<br />
respective crust leathers were cut from the official sampling<br />
position. 11 Samples were first washed in water. Subsequently, the<br />
samples were dehydrated gradually using acetone and methanol as<br />
per standard procedures. 15 A Quanta 200 series scanning electron<br />
microscope was used for the analysis. The micrographs for the grain<br />
surface and cross section were obtained by operating the SEM at an<br />
accelerating voltage of 5 KV with different magnification levels.<br />
Results and Discussion<br />
Optimization of Enzyme Application<br />
The amount of enzyme used for the experiment has been<br />
calculated based on the enzyme activity. Drum based deharing<br />
Table II<br />
Process recipe for chrome tanning process.<br />
and fiber opening has been employed during the study. After<br />
ensuring thorough soaking, 2.5-4% of enzyme (w/w based on<br />
soaked weight) has been used for the experiment. The enzyme<br />
treatment has been carried out for 12 h with 10 min of<br />
intermittent running. The visual and organopleptic assessment<br />
of the dehaired and fiber opened pelts have been carried out and<br />
the results are depicted in Figure 1. The observations have been<br />
compared with that of the control pelts processed employing<br />
conventional liming and reliming processes. It could be observed<br />
from the figure that at concentrations less than 3.5%, complete<br />
hair removal has not been achieved. Hence a minimum of 3.5%<br />
of enzyme is required to achieve complete unhairing. During the<br />
process, no objectionable odor has been observed. Moreover, the<br />
fiber opening and grain smoothness have been observed to be<br />
better at higher concentration and has been observed to be better<br />
than that of the control pelts. Hence, based on assessment rating,<br />
3.5% of fibrozyme is being optimized for further studies.<br />
Proteoglycan Release After Enzyme Treatment<br />
Opening up of fiber bundles is a crucial step in leather making.<br />
Ever since, the quote “Leathers are made in lime yard” always<br />
signifies the importance of opening up of fiber bundles to<br />
fibrillar level in order to enhance the uptake of chemicals added<br />
during tanning and post tanning processes. Conventional<br />
reliming process depends on the plumpness brought about due<br />
to the difference in concentration gradient inside and outside the<br />
pelts. However, in the case of enzyme assisted process, release of<br />
proteoglycans is considered to be the indirect measurement of<br />
fiber opening. As, in the latter case, no visual changes can be<br />
observed except for a clean pelt after removal of short hairs. The<br />
amount of proteins and proteoglycans released during the<br />
control and experimental trials are provided in Table IV. It could<br />
be observed that a significant quantity of protein and<br />
proteoglycans have been released from the skin, which is an<br />
Chemicals % Offer Time Remarks<br />
Pickle liquor 50<br />
Chrome<br />
tanning agent<br />
8 2-3 h<br />
Check pH<br />
2.8-3.0<br />
Check<br />
penetration<br />
Water 50 30 min<br />
Sodium<br />
formate<br />
1 15 min<br />
Sodium<br />
bicarbonate<br />
1-1.5<br />
4x15 min<br />
+ 1 h<br />
Check pH<br />
3.8-4.0<br />
Water 50<br />
Drain/washed<br />
Aged for 48 h<br />
Figure 1. Assessment rating of fibrozyme treated and control pelts<br />
J<strong>ALCA</strong>, VOL. 111, <strong>2016</strong>
Bi-functional Enzyme 458<br />
Table III<br />
Post-tanning recipe for the manufacture<br />
of upper leather from wet blue.<br />
Process/chemicals %<br />
Washing<br />
Duration<br />
(min)<br />
Remarks<br />
Water 100 10 Drained<br />
Neutralization<br />
Water 150<br />
Sodium formate 1.0 10<br />
Sodium bicarbonate 1.0 3x15+45<br />
Washing<br />
pH – 5.0 - 5.2,<br />
Drained.<br />
Water 200 15 Drained<br />
Retanning, Dyeing and Fat liquoring<br />
Water 100<br />
Grain tightening<br />
acrylic syntan<br />
Semi-synthetic<br />
fatliquor<br />
4.0 30<br />
3.0 45<br />
Acid dye 3.0 30<br />
Synthetic fatliquor 4.0<br />
Phenol –naphthalene<br />
based syntan<br />
5.0<br />
Mixed in hot<br />
water<br />
indication that the enzyme has cleaved proteoglycans and aided<br />
in opening up of the fiber bundles. This is in accordance with<br />
the visual assessment made in the earlier section.<br />
Histological Examination of the Control and<br />
Experimental Pelts<br />
The pelts obtained after fiber opening by employing both<br />
conventional reliming and fibrozyme treatment have been<br />
subjected to histological examination by adopting Hematoxylin<br />
and Eosin (H&E) staining technique. By employing this<br />
technique, a clear picture about the opening up of the fiber<br />
bundles could be obtained. The H&E stained images of raw cow<br />
hide, conventionally relimed and enzyme treated cow pelts are<br />
shown in Figure 2 (a-c). Collagen fibers being acidophilic, reacts<br />
with the eosin dye and are stained pink. From the figure a wellorganized<br />
collagen fiber could be seen in all three raw materials.<br />
Apart from this, it is also clearly observed that the level of<br />
separation/opening of the fibers varied distinctly with respect to<br />
the type of sample. Stained image of raw hide (2a) showed<br />
compact fiber orientation as compared to relimed (2b) and<br />
enzyme treated pelt (2c). Moreover, the splitting of fibers in case<br />
of the enzyme treated pelt was better, which is evident from the<br />
higher distance between the collagen fibers.<br />
Stratigraphic Distribution of Chromium<br />
in Wet Blue Leathers<br />
The layer wise distribution of chrome content in both control<br />
and experimental wet blue leathers was assessed to estimate the<br />
chrome penetration and distribution, which would in turn<br />
provide a substantiate evidence on the level of opening up of the<br />
fibers. Chrome content in grain, middle and flesh layer has been<br />
determined to be 3.59, 3.51 and 3.64% Cr 2<br />
O 3<br />
, respectively and the<br />
average chrome content in the leather has been found to be 3.62%<br />
Cr 2<br />
O 3<br />
. The uniform distribution of chrome content in the leather<br />
Melamine syntan 6.0 60<br />
Semi-synthetic<br />
fatliquor<br />
4.0 30<br />
Wattle 4.0 30<br />
Formic acid 1.5 4x10+20<br />
Washing 100 15<br />
The dye<br />
exhaustion<br />
was checked.<br />
Drained.<br />
Drained. Crust<br />
leathers were set<br />
twice, hooked to<br />
dry, conditioned,<br />
and staked.<br />
Figure 2. Photomicrographs of H&E stained raw (A), relimed (B) and<br />
fibrozyme (C) treated cow hides<br />
J<strong>ALCA</strong>, VOL. 111, <strong>2016</strong>
459 Bi-functional Enzyme<br />
confirms the through-through penetration. This is possible only<br />
when the uniform and efficient opening up of the fiber bundles<br />
have been achieved. Also, the chrome exhaustion has been found<br />
to be 75% with the shrinkage temperature of 108ºC.<br />
Visual Assessment of Wet Blue Leathers<br />
The wet blue leathers obtained from control and experimental trials<br />
were visually assessed by experienced tanners. Various parameters<br />
such as color of the wet blue, chrome patches, grain smoothness and<br />
general appearances have been used for assessing the wet blue<br />
leathers. The results are provided in Table V. It could be observed<br />
from the table that the rating of the experimental wet blue is in the<br />
range of 8-9, which indicates that the fibrozyme based deharing and<br />
fiber opening has not deteriorated the quality of the final leather.<br />
Specifically, no grain damage has been observed in the case of<br />
enzyme treated (Experiment) wet blue leathers. The general<br />
assessment also indicates that the enzyme processed leathers are on<br />
par to that of conventionally chrome tanned leathers.<br />
Physical Characteristics of Crust Leather<br />
The strength characteristics like tensile, tear and grain crack<br />
strength of the crust leathers processed from control and<br />
experimental wet blue leathers have been analyzed. The tensile,<br />
tear and the grain crack strength of the experimental upper<br />
Table IV<br />
Release of protein and proteoglycans in the spent liquor.<br />
Process<br />
Protein<br />
(mg/g of raw wt)<br />
Proteoglycans<br />
(mg/g of raw wt)<br />
Enzyme Liquor 26.8±0.5 4.7±0.3<br />
Wash liquor<br />
(10 min) I<br />
Wash liquor<br />
(10 min) II<br />
9.2±0.3 1.8±0.2<br />
3.2±0.4 1.1±0.3<br />
leather have been determined to be 270 Kg/cm 2 , 50 Kg/cm, 43 Kg<br />
with distension of 9.28 mm, respectively. Similarly values of 265<br />
Kg/cm 2 , 40 Kg/cm, 32 Kg with distension of 9.00 mm,<br />
respectively has been obtained for control leathers. Hence, it<br />
could be inferred that the fibrozyme treatment has not affected<br />
the final leather quality, rather proper opening up of the fiber<br />
bundles has aided in obtaining higher strength characteristics.<br />
Organoleptic Properties of Crust Leathers<br />
The control and experimental crust leathers have been assessed<br />
by experienced tanners for their organoleptic properties.<br />
Table VI<br />
Organoleptic property of cow upper leather.<br />
Parameters Control Experimental<br />
Softness 8±1 8±1<br />
Roundness 8±1 9±0.5<br />
Fullness 7±1 8±1<br />
Grain tightness 8±1 8±1<br />
Color uniformity 7±0.5 7±1<br />
Strength 8±0.5 8±1<br />
Grain smoothness 7±1 8±1<br />
General appearance 7±1 7±2<br />
*rating on a scale of 1–10 with 10 being the best<br />
Table V<br />
Visual assessment data of the wet blue leather.<br />
Parameter Control Experimental<br />
Color of the wet blue 8±1 8±1<br />
Chrome patches Nil Nil<br />
Grain smoothness 8±0.5 9±0.5<br />
General appearances 8±0.5 8±0.5<br />
*rating on a scale of 1–10 with 10 being the best<br />
Figure 3. Scanning Electron Microscopy images of curst leathers of<br />
cow hide: a) Grain and b) Cross-section of fibrozyme treated leathers<br />
c) Grain and d) Cross-section of control leathers<br />
J<strong>ALCA</strong>, VOL. 111, <strong>2016</strong>
Bi-functional Enzyme 460<br />
The leathers have been assessed for various organoleptic<br />
properties such as softness, roundness, fullness, grain tightness,<br />
color uniformity, strength, grain smoothness and general<br />
appearance. The results are provided in Table VI. It could be<br />
observed from the table that the experimental leathers are on par<br />
with that of the control leathers in terms of grain tightness, grain<br />
smoothness, roundness, dye affinity and strength. In addition, it<br />
was also observed that there were no grain damage and the<br />
experimental leathers are softer than the control leathers.<br />
Scanning Electron Microscopy Evaluation<br />
Scanning electron microscopic (SEM) images of the control and<br />
experimental pelts are provided in Figure 3 (a-d). Figure 3a and c<br />
shows the grain pattern of the control and experimental pelts,<br />
respectively. It could be observed that the grain layer of both the pelts<br />
is devoid of any hair. Also, the grain is found to be smooth and does<br />
not show any damage. Fig. 3b and d shows the cross sectional view of<br />
the control and experimental pelts, respectively. It could be observed<br />
from the figure that the fiber bundles have better opened up structure.<br />
Hence, it could be inferred that the fibrozyme could be effectively used<br />
for both dehairing and fiber opening of cow hides in a single step.<br />
Conclusions<br />
In the present study, a single step enzymatic dehairing and fiber<br />
opening of cow hides has been established. Offer of enzyme has been<br />
optimized to 3.5% (w/w) based on the soaked weight of the cow<br />
hides. From the hand evaluation properties, the enzyme treated pelts<br />
have shown clean and complete removal of hairs and the skin is<br />
devoid of any scud or short hairs. The stratigraphic distributions of<br />
chromium in control and experimental wet blue leathers have been<br />
found to be uniform throughout the cross section of the leather. An<br />
average chrome content of 3.62% and shrinkage temperature of<br />
108ºC has been obtained for the experimental leathers. The visual<br />
and organoleptic assessment of the experimental leathers has been<br />
rated high by the experienced tanners. The physical strength met the<br />
upper leather norms. The morphological evaluation of experimental<br />
pelts through SEM also substantiates that there is no coalescence and<br />
distortion of fibers due to enzyme treatment. The H&E staining<br />
technique also confirmed the complete opening up of the fiber<br />
bundles in the experimental leathers. Thus this single step<br />
methodology could be successfully implemented in tanneries. This<br />
method not only saves time but also completely eliminates the use of<br />
lime and sulphide in leather processing.<br />
Acknowledgement<br />
Financial support from CSIR, New Delhi under 12 th plan project<br />
“S&T Revolution in Leather with a Green Touch” (STRAIT -<br />
CSC 0201) is greatly acknowledged. CSIR-CLRI Communication<br />
No. A/<strong>2016</strong>/CHL/CSC0201/1202.<br />
References<br />
1. Saurabh, S., Richi, V. M., Rekha, K., Jasmine, I., Rajendra,<br />
K.S.; Enzyme mediated beam house operations of leather<br />
industry: a needed step towards greener technology. Journal<br />
J. Clean. Prod. 54, 315-322, 2013<br />
2. Ramasami, T., Prasad, B.G.S.; Environmental Aspects of<br />
Leather Processing, Proc LEXPO XV (ILTA, Calcutta) 43-<br />
71, 1991.<br />
3. Venba, R., Kanth, S., Chandrababu, N.; Novel approach<br />
towards high exhaust chromium tanning - Part I: Role of<br />
Enzymes in the Tanning Process. J<strong>ALCA</strong> 103, 401-411, 2008<br />
4. Dettmer, A., Schacker Dos Anjos, P., Gutterres, M.; Enzymes<br />
in the Leather Industry, a special review paper. J<strong>ALCA</strong>. 108<br />
Number: 4 Page: 146-158 Year: 2013<br />
5. Andrioli, E., Gutterres, M.; Associated use of enzymes and<br />
hydrogen peroxide for cowhide hair removal. J<strong>ALCA</strong>. 109,<br />
41-48, 2014<br />
6. Saravanan, P., Shiny Renitha, T., Gowthaman, M.K.,<br />
Kamini, N.R.; Understanding the chemical free enzyme<br />
based cleaner unhairing process in leather manufacturing.<br />
J. Clean. Prod. 79, 258-264, 2014.<br />
7. Bradford, M.M.; A rapid and sensitive for the quantitation<br />
of microgram quantities of protein utilizing the principle of<br />
protein-dye binding. Anal. Biochem.72, 248-254, 1976.<br />
8. Madhan, B., Rao, J.R., Nair, B.U.; Studies on the removal<br />
of interfibrillary materials Part-I: removal of protein,<br />
proteoglycan, glycosoaminoglycans from conventional pretanning<br />
process. J<strong>ALCA</strong> 105, 2010.<br />
9. Jayakumar G.C., Sivaraman, G., Saravanan, P., Mohan,<br />
R., Rao, J.R.; Cohesive system for enzymatic unhairing<br />
and fiber opening: an architecture towards eco-benign<br />
pretanning operation. J. Clean. Prod. 83, 428-436, 2014.<br />
10. Fathima, N. N., Rao J. R., Nair, B.; Augmentation of garment<br />
sheepskin type properties in goatskins: Role of chromiumsilica<br />
tanning agent. JSLTC 87, 227-232, 2003.<br />
11. IUP 2, Sampling, JSLTC 84, 303, 2000.<br />
12. IUP 6, Measurement of tensile strength and percentage<br />
elongation, JSLTC 84, 317-321, 2000.<br />
13. IUP 8, Measurement of tear load-double edge tear, JSLTC<br />
84, 327-329, 2000.<br />
14. SLP 9 (IUP 9), Measurement of Distension and Strength of<br />
Grain by the Ball Burst test, Official methods of analysis,<br />
The Society of Leather Technologists and Chemists,<br />
Northampton, 1996.<br />
15. Usharani, N., Jayakumar, G.C., Rao, J.R., Chandrasekaran,<br />
B., Nair, B.U.; A microscopic evaluation of collagen-bilirubin<br />
interactions: in vitro surface phenomenon. Microsc. 253,<br />
109-18, 2014<br />
J<strong>ALCA</strong>, VOL. 111, <strong>2016</strong>
461<br />
Lifelines<br />
Hanping Li, a postgraduate, is working at Key Laboratory of<br />
Leather Chemistry and Engineering of Ministry of Education,<br />
Sichuan University, China, and mainly engaging in the research<br />
of green leather chemicals and environment friendly functional<br />
materials.<br />
Yong Jin, professor, is currently working as a scientist and teacher<br />
at the National Engineering Laboratory for Clean Technology of<br />
Leather Manufacture, Sichuan University, China. He obtained his<br />
PhD degree at the Chengdu Institute of Organic Chemistry,<br />
Chinese Academy of Science, China, in 2003. His main research<br />
areas include green leather chemicals and cleaner leather making<br />
technology, environment friendly functional materials.<br />
Baozhu Fan, a postgraduate, is working at the Chengdu Institute<br />
of Organic Chemistry, Chinese Academy of Science, China, and<br />
specializing in the research of surfactant materials.<br />
Rui Qi, a doctor, is working at the Chengdu Institute of Organic<br />
Chemistry, Chinese Academy of Science, China, and mainly<br />
engaging in the research of polymer self-assembly and<br />
environment friendly functional materials.<br />
Xinfeng Cheng, a doctor, is working at the Chengdu Institute of<br />
Organic Chemistry, Chinese Academy of Science, China, and<br />
mainly engaging in the research of intelligent polymer and<br />
environment friendly functional materials.<br />
Chunxiao Zhang, PhD candidate from Sichuan University,<br />
majoring in leather chemistry and engineering. Focusing on the<br />
cleaner production of leather making, the researching fields<br />
contain salt-free pickling, high exhaustion chrome tanning,<br />
ammonia-free deliming and the application of enzyme in tanyard.<br />
Fuming Xia is a postgraduate student in Sichuan University and<br />
studying in the Key Lab of Leather Chemistry and Engineering<br />
of Ministry of Education in Sichuan University. Focuses on<br />
researching the technologies of salt-free pickling and high<br />
chrome exhaustion tanning.<br />
Biyu Peng, see J<strong>ALCA</strong> 110, 2015<br />
Qing Shi, graduated from Donghua University China, 2002,<br />
with focus on engineering of dyeing and finishing. 2005/10—<br />
2015/7 worked BASF for textile auxiliary finishing technical<br />
support, 2015/7 until now, worked in BASF for new development<br />
of surfactant and polymer.<br />
Dominic Cheung, graduated from Hong Kong Polytechnic<br />
University in 1987 and major in textile chemistry. Worked in<br />
Ciba for textile dyes and chemicals areas, covering various<br />
functions from lab to technical marketing and later worked for<br />
Huntsman in setting up R&D center for textile chemicals in<br />
Guangzhou. Right now, serves the Care Chemicals Division on<br />
industry marketing for textile & leather in BASF.<br />
Ye Yongbin, Bachelor, graduated from Sichuan University.<br />
Working in Zhejiang Tongtianxing Group J. S. Co., Ltd. In<br />
charge of the new product research and development.<br />
Xinhua Liu. as a doctoral student in the Key Laboratory of<br />
Leather Chemistry and Engineering of Ministry of Education in<br />
Sichuan University, he is focusing on the extraction and<br />
modification of collagen for versatile applications.<br />
Feng Li. as a master in the Key Laboratory of Leather Chemistry<br />
and Engineering of Ministry of Education in Sichuan University,<br />
his research focuses on the preparation and evaluation of<br />
chrome-free tanning agents and their applications.<br />
Qin Huang. as a master in the Key Laboratory of Leather<br />
Chemistry and Engineering of Ministry of Education in Sichuan<br />
University, his research focuses on the preparation and<br />
evaluation of chrome-free tanning agents and their applications.<br />
Weihua Dan, as a professor in the Key Laboratory of Leather<br />
Chemistry and Engineering of Ministry of Education in Sichuan<br />
University, his research focuses on the development of ecological<br />
leather and fur, and the preparation and evaluation of collagenbased<br />
biomaterials.<br />
Nianhua Dan, as a lecturer in the Key Laboratory of Leather<br />
Chemistry and Engineering of Ministry of Education in Sichuan<br />
University, his research focuses on the development of ecological<br />
leather and fur, and the synthesis and modification of leather<br />
chemicals.<br />
Gladstone C. Jayakumar, see J<strong>ALCA</strong> 106, 68, 2011<br />
M. Sathish, see J<strong>ALCA</strong> 110, 379, 2015<br />
R. Aravindhan, see J<strong>ALCA</strong> 106, 208, 2011<br />
J. Raghava Rao, see J<strong>ALCA</strong> 93, 156, 1998<br />
J<strong>ALCA</strong>, VOL. 111, <strong>2016</strong>
462<br />
Call For Papers<br />
for the 113th Annual Convention of the<br />
American Leather Chemists Association<br />
Pinehurst Resort, Village of Pinehurst, NC<br />
June 13-16, 2017<br />
If you have recently completed or will shortly be completing research studies relevant to hide<br />
preservation, hide and leather defects, leather manufacturing technology, new product<br />
development, tannery equipment development, leather properties and specifications, tannery<br />
environmental management, or other related subjects, you are encouraged to present the<br />
results of this research at the next annual convention of the Association to be held at the<br />
Pinehurst Resort Village of Pinehurst, NC, June 13-16, 2017.<br />
Abstracts are due by April 1, 2017.<br />
Full Presentations are due by June 1, 2017.<br />
They are to be submitted by e-mail to the <strong>ALCA</strong> Vice-President and Chair of the<br />
Technical Program:<br />
Mike Bley<br />
Eagle Ottawa - Lear<br />
2930 Auburn Road<br />
Rochester Hills, MI 48309<br />
E-mail: mbley@lear.com<br />
In accordance with the<br />
Association Bylaws,<br />
all presentations are<br />
considered for<br />
publication by<br />
The Journal of the<br />
American Leather<br />
Chemists Association.<br />
The Abstract should begin with the title in capital letters, followed by the authors’ names. An<br />
asterisk should denote the name of the speaker, and contact information should be provided<br />
that includes an e-mail address. The abstract should be no longer than 300 English words,<br />
and in the Microsoft Word format.<br />
Full Presentations at the convention will be limited to 25 minutes. In accordance with the<br />
Association Bylaws, all presentations are considered for publication by The Journal of the<br />
American Leather Chemists Association. They are not to be published elsewhere, other than<br />
in abstract form, without permission of the Journal Editor. For further paper preparation<br />
guidelines please refer to the J<strong>ALCA</strong> Publication Policy on our website: leatherchemists.org.<br />
Full Presentations are to be submitted by e-mail to the J<strong>ALCA</strong> editor:<br />
Robert F. White<br />
Journal Editor<br />
The American Leather Chemists Association<br />
E-mail: jalcaeditor@prodigy.net<br />
Mobile Phone (616) 540-2469<br />
J<strong>ALCA</strong>, VOL. 111, <strong>2016</strong>
ENZYME TECHNOLOGY ENERGIZED BY<br />
In the beamhouse process there is a great deal of innovation potential – and that can have a positive<br />
impact on your business success. In partnership with Novozymes, LANXESS has developed the Peltec ®<br />
X-Zyme technology, a completely new, enzyme-based soaking and unhairing solution that overcomes<br />
current beamhouse challenges. Just by deploying two novel enzymes you can run the beamhouse<br />
process more effi ciently, signifi cantly reduce both effl uent load and the amount of basic chemicals used,<br />
and at the same time produce extremely clean pelts of the highest quality. www.lanxessleather.com<br />
Peltec ®<br />
X-Zyme<br />
LXS_X-ZYME_Anzeige_ENG_203x266_140514.indd 1 14.05.14 15:03
your dreams,<br />
our tools<br />
together<br />
we go beyond<br />
ERRETRE SPA Via Ferraretta, 1 - 36071 Arzignano VI - ITALY<br />
Phone +39 0444 478312 - Fax +39 0444 478308 - info@erretre.com - www.erretre.com
Few people realize that Leather Making is the world’s oldest manufacturing<br />
process, thus the world’s oldest industry. Tanning—the process of converting<br />
hides and skins into leather—is also the world’s first science.<br />
Also, because of the pure craftsmanship involved, tanning may well<br />
be the world’s first art form.<br />
Anyone who doubts that a<br />
sheepskin has up to 30,000<br />
fibers per square inch has<br />
only to count them.<br />
NOTHING TAKES THE<br />
PLACE OF LEATHER<br />
INDEX TO ADVERTISERS<br />
<strong>ALCA</strong> Annual Meeting................................. Inside Back Cover<br />
Biosk.............................................................................................. II<br />
Biosk.............................................................................................VI<br />
Buckman Laboratories.................................Inside Front Cover<br />
Chemtan......................................................................................III<br />
Chemtan...................................................................... Back Cover<br />
Erretre........................................................................................... V<br />
Elementis................................................................................... VII<br />
Lanxess.........................................................................................IV
www.CHEMTAN.com<br />
Made with<br />
WATERPROOF<br />
TECHNOLOGY<br />
Tel: (603) 772-3741 • Fax: (603) 772-0796 • www.CHEMTAN.com