Reactive Dyes

Kaliakor Dye Managers Workshop
Reactive
Dyes
Dr Kelvin N Tapley
Department of Colour Chemistry
University of Leeds, Leeds, UK
September 2003
Outline
•History
• General Features
• Advantages & Disadvantages
• Factors influencing performance
• Common Types of Reactive Dyes
• Reactions of Reactive Dyes
• Application Methods
•Summary
1

History
• Cyanuric chloride reaction with cotton and then amines
• Remazol (vinyl sulphone) chemistry intorduced
• 1956 Rattee + Stephen (ICI) “first” reactive dyes
– chlorotriazines
• Various developments – including new chemical types
• 1980’s Mixed bifunctional dyes (esp. Sumitomo – Sumifix Supra
dyes)
General Features of a Reactive Dye
Molecule
W = water solubilising group
D = chromophore
B = bridging group
RG = reactive group
X = leaving group
2

Advantages?
• Full Colour Gamut
• Brilliant, bright colours
• Colvalent fixation high WashFastness (WF)
• Varying reactivities
– Various temperatures
including low energy (cold dyeing)
• Various methods of application
• Inexpensive to apply (but dyes expensive)
Disadvantages?
• Incomplete fixation (problem with hydrolysis)
• Need for wash-off (for high WF)
• Need for high concentrations of salt
– Affect natural balance of watercourses
• High pH
• Some dyes are “AOX” – potentially harmful to
the environment
3

Importance of Washing Fastness (WF)
The major issues
• Loss of colour fading problems
• Transfer of colorants to “adjacent” fabrics leads
to staining problems
• NB some of the WF tests have got tougher!
Laundry washing
Poor wash fastness
4

During the laundry process the fabric is subjected to some
severe conditions and very often dye is “beaten” from the
fabric.
This results in dye entering the washing liquors.
Once in the washing liquors 3 things can happen to the
dye...
1. Re-adsorb onto original fibre
2. Adsorb to a different substrate
3. Remain in the wash liquor
Degree of staining
=
affinity of dye for original fibre
+
affinity of dye for adjacent fibre
+
affinity for water
(staying in solution)
5

Factors that affect the dyeing
of cotton with reactive dyes
Cotton
Pre-treatment
Auxiliaries
Reactive dye
Dyebath (liquor ratio/flow)
Method:
eg.Temperature and duration
of dyeing
Factors Influencing the Performance
of Reactive Dyes
• Molecular structure of Dye
– Number of reactive groups
– Chemical nature of reactive groups
– Molecular mass (size)
– Number of sulphonic acid groups
– Ratio of sulphonic acid groups to aromatic carbons
• hydrophobic – hydrophilic balance
– Linear / planar structure (shape)
– Other functional groups present
– Realtive positions of functional groups (incl. reactive groups)
Plus characteristics and quantity of impurities / additives
6

Factors Influencing the Performance
of Reactive Dyes
• Material being dyed
– Chemical type (assume cellulosic)
– (Macro) physical structure (yarn, fabric, garment)
– (Micro) physical structure (crystallinity vs
amorphous)
– Material preparation or damage prior to coloration
• Exposure to physical, chemical and biological agents
Pre-treatment
It is easy to appreciate that what happens to the fabric before
dyeing will affect dyeing itself !
Pre-treatment is crucial to a dyer if he wants to achieve right-
first-time time dyeings. After pre-treatment he can trust his fabric.
Pre-treatment for cotton
principally involves:
Scouring and bleaching
7

Scouring
Essentially cleaning!
removal of waxes, fatty acids etc.
Scoured
Exhaustion
Unscoured
Time
Definition of scour: To remove natural impurities, dirt or grease
from (cloth or fibers) by means of a detergent.
Factors Influencing the Performance
of Reactive Dyes
• Application conditions
– Quality of the water employed
– Temperature programme employed
– pH programme employed (incl type + conc of alkali)
– Electrolyte programme employed
– Any other additives/chemicals present (eg. Auxiliaries)
– Liquor to materials ratio (LR)
– Chemical (incl Dye) addition programme employed
– Agitation / liquor circulation method
– Time – at each stage
[Rinse/Wash/After treatment conditions are also important]
8

Factors Influencing the Performance
of Reactive Dyes
• Application conditions – the “Human Factor”
– You may not be using an optimum method
– Do you / your operatives actually do what you say you do?
– Try to identify real / potential problem areas, for example:
• Volume of water used (LR). Why?
• Housekeeping
• Use of Chemicals (dyes, electrolyte, alkali, auxiliaries)
• Temperature (including storing/dissolving dyes)
• Time
Types of Reactive Dyes
[Some examples!]
9

Sulphatoethyl sulphone dyes
O
NH 2
SO 3
Na
O
N
H
SO 2
CH 2
CH 2
OSO 3
Na
Vinyl sulphone dye (Remazol Brilliant Blue R, C.I. Reactive Blue 19)
Monochloro-s-triazine dyes
Cl
SO 3
Na
N
N
N
N
OH
HN
N
N
H
NaSO 3
SO 3
Na
Monochloro-s-triazine dye (Procion Red H-3B, C.I. Reactive Red 3)
10

Bis (monochloro-s-triazine) dyes
Cl
Cl
SO 3
Na
N
N
N
N
NaSO 3
OH HN
N N
N
N
H
H
N NH
N
NaSO 3
SO 3
Na
NaSO 3
OH
N N
SO 3
Na
Bis(monochloro-s-triazine) dye (Procion Red HE-3B, C.I. Reactive Red 120)
2,4-difluoro-5-chloro-pyrimidine dyes
F
N
N
N
H
Cl
F
SO 3
Na
SO 3
Na
H
OH N
NaSO 3
N N
O
SO 3
Na
2,4-difluoro-5-chloro-pyrimidine dye
(Levafix Brilliant Red E 3BA, C.I. Reactive Red 147)
11

2,4,5-trichloro-pyrimidine dyes
Cl
SO 3
Na
Cl
N
N
N
OH
HN
N
Cl
NaSO 3
SO 3
Na
Trichloro pyrimidine dye (Drimarene Red Z 2B, C.I. Reactive Red 17)
Mixed Bifunctional reactive dyes
eg.
Dye
NH
N
N
Cl
N
N
H
SO 2
CH 2
CH 2
OSO 3
Na
General structure of Sumifix Supra dyes
MCT-SES or MCT-VS
[Reactron Supra F dyes are similar]
12

Reactions of Reactive Dyes
[Some examples!]
Nucleophilic
addition
Reactive
group
The reactive group is usually the
vinylsulphone group
SO 2 -CH= CH 2
Sulphone (SO2)
Vinyl (CH = CH2)
13

Nucleophilic addition
DYE
O
S
O
H H
-
O
C C OSO 3
Na
DYE S CH
H H
O
CH 2
DYE
O
S
O
-
CH
H
C
H
O
Cellulose
+
NaHSO 4
DYE S
Cellulose O -
O
O
CH
+
CH 2
H 2
O
DYE
O
S
O
H
C
H
H
C
H
O
Cellulose
+ OH-
ß-elimination of ß-sulphatoethylsulphone to
vinyl sulphone and reaction with cellulose.
Nucleophilic
substitution
Reactive
group
The reactive groups is usually a
halogenated heterocyclic group
Cl
N
Cl
N
N
e.g.
a dichloro-s-triazine reactive
group
14

Nucleophilic substitution
Dye
N
H
N
N
Cl
N
Cl
..
+ X -
Dye
N
H
N
N
X
Cl
N
Cl
- Cl -
OR
Dye
Dye
N
H
N
H
N
N
N
N
Cl
N
O
Cellulose
Cl
N
OH
Competing nucleophilic substitution reactions of s-triazine dyes
Separation of bis-Monochlorotriazinyl Reactive
Dyes and Hydrolysates in Dyehouse Effluent by
Capillary Zone Electrophoresis
0.43
0.33
0.23
0.13
0.03
6 10 14 18 22
Time / minutes
15

• Continuous
Application Methods
– eg. Pad - Thermofix
• Semi-Continuous
– eg. Pad - Batch
• Batchwise Exhaustion *
– eg. Winch, Jet, Package and Beam Dyeing
•Printing
– eg. Print - Thermofix
Typical dyeing conditions for a bifunctional
monochlorotriazine dye
16

Typical dyeing conditions for a bifunctional
dichlorotriazine dye
Typical dyeing conditions for a bifunctional
sulphatoethyl sulphone dye
17

Summary
• Dominant dye class for cotton
• Importance of nature and number of reactive
groups ( covalent fixation)
• Different types/chemistries
many different application methods
• Problem of dye hydrolysis
• Potential impact on environment
Acknowledgements
Department of
Colour Chemistry,
University of Leeds
DFID
K.Tapley@leeds.ac.uk
www.leeds.ac.uk/ccd
Department of Colour Chemistry, University of Leeds, Leeds, LS2 9JT
18

Questions ?
19