Multifunctional propyleneimines-new generation of crosslinkers for ...

ARTICLE IN PRESS
International Journal of Adhesion & Adhesives 24 (2004) 503–511
Multifunctional propyleneimines-new generation of crosslinkers for
solvent-based pressure-sensitive adhesives
Zbigniew Czech*
Polymer Institute, Technical University of Szczecin, K. Pulaskiego 10, Szczecin 70-322, Poland
Accepted 21 January 2004
Abstract
This article describes work with the goal of crosslinking pressure sensitive acrylic adhesives (PSA) and a new generation of
crosslinkers based on multifunctional propyleneimine derivates. Crosslinking of PSA is an established technology used in many
industrial manufacturing processes. New applications and technical specifications stimulate the continuous development of new
crosslinking agents with very interesting properties. These new crosslinkers influence physico-mechanical properties of acrylic PSA
such as tack, peel resistance (adhesion) and shear strength (cohesion). The weak point of propyleneimine crosslinkers is their very
short potlife.
r 2004 Elsevier Ltd. All rights reserved.
Keywords: Multifunctional propyleneimines; Crosslinking; Crosslinking agents; Acrylic; Pressure sensitive adhesives
1. Introduction
Crosslinking is a most important process, attractive
for the chemist, informative for the physicist and helpful
for the user in the joint development of tailored pressure
sensitive acrylic adhesives (PSAs). This applies in
general to solvent-based PSAs acrylics.
In general, PSAs are used increasingly for coating of
PSA tapes, labels, decorative films and similar selfadhesive
articles. The PSAs must have certain properties.
Besides good surface adhesion the PSAs should
have good stability against light, oxygen, moisture and
plasticizer and the adhesion characteristic should be
constant over a very large temperature range.
The crosslinking of PSAs is a useful process in the
repertoire of general procedures for many applications.
Polymeric networks or crosslinked systems consist of
interconnected macromolecules, which expand into all
three dimensions due to the length of the starting
polymeric chains, only small amounts of a crosslinking
additive are needed to accomplish complete crosslinking,
i.e. a crosslinking covering the total volume of the
PSA. The larger the starting molecules, the larger the
*Fax: +48-97-483-49-08.
E-mail address: psa czech@wp.pl (Z. Czech).
probability that they participate in the network concentration
with a given amount of crosslinking additive.
Therefore, parts with lower molecular weight tend to
remain without ties to the network when a low crosslinking
degree is applied because of normal polydispersal
characteristic of polymers.
The physico-chemical and mechanical properties of
PSAs based on acrylate acid esters are determined to a
large degree by the type and amount of crosslinking
agent which is added to the copolymer. It is known that
an acrylate copolymer which has no crosslinking or is
crosslinked only by hydrogen bridges, has in sufficient
thermo-mechanical stability and is practically useless as
a PSA [1].
The crosslinking can be considered as a critical factor
in the formulation of the PSA in the application stage.
The generated crosslinked connections inhibit the
mobility of the polymer molecules extensively by
chemical bondings in the network of the polymeric
PSA. A crosslinked PSA therefore cannot melt anymore.
Perhaps it becomes somewhat softer at increased
temperature, but does not melt. Rather it undergoes
decomposition above a certain temperature.
With the help of crosslinking agents an increase in
cohesion may be accomplished during the drying of the
PSA coating in the drying step. Logically the tackifying
0143-7496/$ - see front matter r 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.ijadhadh.2004.01.005

504
ARTICLE IN PRESS
Z. Czech / International Journal of Adhesion & Adhesives 24 (2004) 503–511
properties of the PSA coat, such as tack and peel
adhesion decrease (Fig. 1).
The time span, which can be utilized after the
crosslinking agent containing PSAs is set up, is called
pot life. After a second time span the so-called gel point
is reached, and the PSA can no longer be modified. This
process is illustrated below (Fig. 2).
The curve in general applies to each crosslinking
agent containing PSA system. That means that a fast
crosslinking systemhas actually a short pot life, and a
slow crosslinking systemhas a long pot life. Fast
crosslinking PSA systems for industrial use with short
pot life are often used with two-component applicationequipment,
which mix and add the reactive components
right before the coating [4].
In order to develope the solvent-based PSA crosslinking,
various multifunctional chemical compounds
with respectively reactive groups are used as the
following list illustrates:
* metal acidesters [5],
* metal chelates [6],
* metal salts [7],
tack, adhesion
25
20
15
10
5
0
tack
cohesion
crosslinker amount
adhesion
Fig. 1. Crosslinkage density influence on tack, peel, adhesion and
cohesion [2].
viscosity (Pas)
12
10
8
6
4
2
coating level
pot life
gel point
0
0 1 2 3 4 5 6 7
time (h)
Fig. 2. Viscosity dependence of time by crosslinker containing PSAs
[3].
cohesion
* polyfunctional isocyanates [8],
* organofunctional silanes [9],
* polycarbodiimides [10],
* polyfunctional ethyleneimines [11],
* polyfunctional propyleneimines [12],
* amino resins [13],
* epoxy resins [14].
1.1. Multifunctional propyleneimine derivatives
In order to achieve optimum crosslinking efficiency,
the known terrain of crosslinkers was widened by the
introduction of a new generation of crosslinkers, multifunctional
propyleneimines derived from 2-methylaziridine
containing saturated unstable rings with nitrogen
atoms.
Such compounds react with the carboxyl groups or
isocyanate groups of the polymer by opening the ring.
This classifies themas crosslinkers.
The crosslinking of carboxyl group containing pressure
sensitive adhesives is carried out under room
temperature, an increase of temperature accelerates the
crosslinking process. Because of the high reactivity of
polyaziridines the pot life of propyleneimine containing
PSA formulations is quite limited and lies in the range of
2– 8 h which is lower than the pot life of polyisocyanate
containing adhesives. This problemcan be overcome by
mixing the adhvesive mass and the crosslinker directly
prior to the coating step. In comparison to metal acid
esters or metal chelates the crosslinking yield of multifunctional
propyleneimines is so high that no afterreactions
like brittleness or a decline of peel resistance
due to ongoing crosslinking occur.
1.2. Reaction mechanism of crosslinking
The crosslinking of pressure sensitive adhesives with
multifunctional propyleneimines is mainly based on the
carboxyl groups offered by the vinylcarbonic acids
within the polymeric chain. The oxygen of the nucleophilic
carboxyl group causes the opening of the tense
propyleneimine rings while the hydrogen atoms accompanying
the carboxyl groups protonate the nitrogen
atoms (Fig. 3).
Such a crosslinking variation involves the following
consideration (Fig. 4).
Concidering the carbon-cation-structure the variant
2 seems to be the most realistic path backing the
reaction mechanism shown above.
General multifunctional propyleneimine groups containing
compounds are known for over 35 years. Along
with the progress in the field of organic synthesis the
chemical structure of propyleneimine crosslinkers was
adapted to the developments in polymer chemistry. The
application of such crosslinkers is product oriented and
only mentioned for special formulations. In the early

ARTICLE IN PRESS
Z. Czech / International Journal of Adhesion & Adhesives 24 (2004) 503–511 505
O
O
Polymer C OH
N R N HO C Polymer
CH 3 CH 3
O
H H
O
Polymer C O
CH 3
N R N
CH 3
O C Polymer
H O O
2 C
CH 2
N C R C N
H 3 C HC
CH CH 3
Fig. 5. Structure of bisamide crosslinking agents.
O
Polymer C
O
CH 3 CH
CH 2 NH R NH CH 2 CH CH 3
O
O
C
Polymer
CH
H 2 C
3 CH 3
CH
N
N 2
O C N CH CH
HC
2 C CH 2 CH 2 CH 2 N C O CH
CH
CH 3
3 CH 3
O CH 3 CH 3 O
Polymer C O CH CH 2 NH R NH CH 2 CH O C
Polymer
Fig. 3. Crosslinking of carboxylated PSA initiated by propyleneimine.
O
CH 3 CH 3
O
H 2 C
CH 2
N C NH CH 2 C CH 2 CH CH 2 CH 2 NH C N
HC
CH
CH
CH 3
3
CH 3
Fig. 6. Synthesis of multifunctional propyleneimine from isocyanates
wit 2-methyl-aziridine.
CH 2
1
CH 2
H 1
CH 3 CH NH R
instable carbon cation
N R
2
CH 2
CH 3 CH CH 2 NH R
stable carbon-cation
CH 3
Fig. 4. Crosslinking mechanism by propyleneimines [1].
Cl
CH 2
3x HN
+
CH CH
N
3
N
Cl
N
Cl
CH 3
CH 3
N N N
N N
N
CH 3
Fig. 7. 2,4,6-Tris(1-methylaziridinyl)-1,3,5-triazine (tripropylenemelamine).
1980s, 3M was particularly active in this sector
presenting new ideas about structure and application
of polyfunctional propyleneimines [15].
Regarding their chemical structure the multifunctional
propyleneimine crosslinkers can be prepared by
the following reactions.
Reaction products from multifunctional carboxylic acid
chlorides and propyleneimine: This range of crosslinking
agents is also known as bisamide crosslinking agents
(BCA) (Fig. 5).
Reaction products from multifunctional isocyanates and
propyleneimine: This reaction is based upon the reactivity
of the propyleneimine ring and the N¼C¼O-groups
(Fig. 6).
Propyleneimines based on s-triazine: As a result of the
reaction between propyleneimine and cyanuric acid
chloride or tris-(2-carboxyethyl)isocyanurate we find
the following crosslinker (Fig. 7).
Reaction products from multifunctional acrylates and
propyleneimine: Propyleneimine reacts with the double
bond of the acryloyl group (Fig. 8).
Propyleneimines with central heteroatoms: Mainly
phosphorus and sulfur serve as heteroatoms (Fig. 9).
H 3 C
H 3 C
C 3
H 7
N
N
H 2 C
CH
2. Experimental part
O
C
O
CH 2 CH 2 C
O R O C CH
The following experiments were conducted in order to
study the influence of diverse propyleneimines such
crosslinkers on other important properties of pressure
sensitive adhesive such as tack, adhesion and cohesion.
O
CH 2
O
O R O C CH 2 CH 2 N
Fig. 8. Reaction of 2-methylaziridine with acryloyl group.
O N
P
N
CH 3
O
O
CH 3 N CH 2 S CH 2 C
CH
N
3
Fig. 9. Propyleneimines with heteroatom.
C
N
CH 3
CH 3
CH 3

506
ARTICLE IN PRESS
Z. Czech / International Journal of Adhesion & Adhesives 24 (2004) 503–511
The basic acrylic PSA was prepared from65 parts 2-
ethylhexyl acrylate, 30 parts methyl acrylate and 5 parts
acrylic acid by polymerization in a typical organic
solvent like ethyl acetate. The solid content was about
50% by weight and 2,2 0 -azo-diisobutyronitrile content
was 0.1 wt%. Facing the high reactivity of propyleneimine
crosslinker the addition of isopropyl alcohol is
necessary.
2-Ethylhexyl acrylate, methyl acrylate, acrylic acid,
isopropyl alcohol and 2,2 0 -azo-diisobutyronitrile are
purchased fromTokyo Chemical Industry Co. (Japan).
The investigated crosslinking agents are available from:
Permutex XR-2500 (Stahl/Holland), Neocryl CX-100
(ICI/England), Trazidin VN (Tramaco/Germany) and
MAPO (Arsynco/USA). Others propylenimine crosslinkers
were synthesized at Technical University in
Szczecin.
Tack, adhesion and cohesion of investigated acrylic
pressure-sensitive adhesives were measured according to
AFERA 4015 (tack), 4001 (adhesion) and 4012 (cohesion).
The synthesized PSAs were crosslinked with investigated
multifunctional propyleneimines, at levels of 0.1–
0.5 wt%. Since the crosslinking reaction proceeds at
room temperature, the propyleneimine must be added
and mixed just before the coating operation with 60 g/
m 2 on polyester foil. After mixing, these materials have a
pot life of up to 2–6 h before they gel and become
unusable.
3. Results and discussion
3.1. Influence of reaction products from multifunctional
carboxylic acid chlorides and propyleneimine on tack,
adhesion and cohesion
The examples for typical reaction products from
multifunctional carboxylic acid chlorides and propyleneimine
are bis-, tri- or tetra-propylencarbonic acid
amides.
It was the aimto examine the influence of diverse
synthetized multifunctional acid amides N,N-bis-propylenadipic
acid amide (Fig. 10), 1,1 0 -azelaoyl-bis-(2-
methylaziri-dine) (Fig. 11), N,N 0 ,N 00 ,N 000 -tetrapropylene-1,2,3,4-butanetetracarbonic
acid amide (Fig. 12)
and N,N 0 -bis-propylenisophthalic acide amide (Fig. 13)
as crosslinkers on tack, adhesion and cohesion of
crosslinked PSA acrylics.
The details of the investigations carried out are
presented in Figs. 14–18.
As can be seen in Figs. 14 and 15, the tack and
adhesion are considerably reduced and cohesion at 20 C
and at 70 C are improved by the increase of propylenimines
concentration. The best crosslinking agent
according to tack and adhesion was 1,1 0 -azelaoyl-bis-
O
O
H 2 C
CH 2
N C CH 2 CH 2 CH 2 CH 2 C N
CH 3 HC CH CH 3
Fig. 10. N,N 0 -bis-propyleneadipic acid amide (BPAA).
O
O
H 2 C
CH 2
N C (CH 2 ) 7 C N
CH 3 HC
CH CH 3
Fig. 11. 1,1 0 -Azelaoyl-bis-(2-methylaziridine) (ABMA).
H 2 C
O
HC
N C CH 2 CH
CH 3
O C
N
H 2 C
CH 3 HC CH 2
CH 3
(2-methylaziridine) (ABMA) with long heptene-chain.
The best crosslinker for increase of cohesion of PSAs
was tatra functional N,N 0 ,N 00 ,N 000 -tetrapropylene-1,2,3,4-
butanetetracarbonic acid amide (TPBA). A very good
balance between tack, adhesion and cohesion was
achieved with aromatic propyleneimine N,N 0 -bis-propyleneisophthalic
acid amide (BPIA).
N
C
CH
CH
O
CH 2
O
C
N
CH 2
CH
CH 3
Fig. 12. N,N 0 ,N 00 ,N 000 -Tetrapropylene-1,2,3,4-butanetetracarbonic acid
amide (TPBA).
tack (N)
24
20
16
12
CH 3
N
O
C
O
C
N
CH 3
Fig. 13. N,N 0 -Bis-propyleneisophthalic acid amide (BPIA).
8
4
0
ABMA
BPAA
BPIA
TPBA
0.1 0.2 0.3 0.4 0.5
propyleneimine amount (wt.%)
Fig. 14. Tack dependence of propyleneimine concentration.

ARTICLE IN PRESS
Z. Czech / International Journal of Adhesion & Adhesives 24 (2004) 503–511 507
adhesion (N)
24
20
16
12
8
4
ABMA
BPAA
BPIA
TPBA
0
0.1 0.2 0.3 0.4 0.5
propyleneimine amount (wt.%)
Fig. 15. Adhesion dependence of propyleneimine concentration.
3.2. Influence of reaction products from multifunctional
isocyanates and propyleneimine on tack, adhesion and
cohesion
The synthesis of this kind of multifunctional aliphatic,
cycloaliphatic or aromatic propylenimines is based upon
the reaction of aliphatic, cycloaliphatic or aromatic
multifunctional isocyanates with propyleneimine. The
influence of the following investigated propylenimine
crosslinking agents: 1,6-hexamethylendipropyleneurea
(Fig. 18), N,N 0 -bis-propylene-1,4-cyclohexanedicarboxylic
acid amide (Fig. 19), dicyclohexylmethane-bis-
4,4 0 -dipropyleneurea (Fig. 20) and toluene-2,6-dipropylene-urea
(Fig. 21) on tack, adhesion and cohesion was
tested.
120
TPBA
cohesion (N) (20˚C)
100
80
60
40
20
BPIA
ABMA
BPAA
CH 3
N
O
C N
CH 3
C
Fig. 19. N,N 0 -Bis-propylene-1,4-cyclohexanedicarboxylic acid amide
(PCHA).
O
0
0,1 0,2 0,3 0,4 0,5
propyleneimine amount (wt.%)
Fig. 16. Cohesion at 20 C dependence of propyleneimine concentration.
O
O
CH 3
N C NH
CH 2 NH C N
CH 3
Fig. 20. Dicyclohexylmethane-bis-4,4 0 -dipropyleneurea (DCDU).
cohesion (N) (70˚C)
40
35
30
25
20
15
10
5
0
BPIA
TPBA
ABMA
BPAA
0.1 0.2 0.3 0.4 0.5
propyleneimine amount (wt.%)
Fig. 17. Cohesion at 70 C dependence of propyleneimine concentration.
H 2 C
HC
CH 3
N
O
C
NH
(CH 2 ) 6
NH
O
C
N
CH 2
CH
CH 3
Fig. 18. 1,6-Hexamethylenedipropyleneurea (HMPU).
tack (N)
24
20
16
12
8
4
0
CH 3
O
O
N C NH
NH C N
CH 3
CH 3
Fig. 21. Toluene-2,6-dipropyleneurea (TDPU).
HMPU
PCHA
DCDU
TDPU
0.1 0.2 0.3 0.4 0.5
propyleneimine amount (wt.%)
Fig. 22. Effect of propyleneimine amount on tack.

508
ARTICLE IN PRESS
Z. Czech / International Journal of Adhesion & Adhesives 24 (2004) 503–511
The results of tack, adhesion and cohesion of acrylics
pressure-sensitive adhesives are presented in Figs. 22–24.
As expected, the increase of propyleneimine content
affects negatively the adhesiveness and positively the
cohesion of PSA. The best crosslinker according to
cohesion was aromatic propyleneimine toluene-2,6-
dipropylene-urea (TDPU). The best balance between
tack, adhesion and cohesion was achieved with cycloaliphatic
propyleneimine N,N 0 -bis-propylene-1,4-cyclohexanedicarboxylic
acid amide (PCHA).
adhesion (N)
cohesion (N) at 20˚C and 70 ° C
20
16
12
8
4
0
120
100
80
60
40
20
0
HMPU
TDPU
PCHA
DCDU
0.1 0.2 0.3 0.4 0.5
propyleneimine amount (wt.%)
Fig. 23. Effect of propyleneimine amount on adhesion.
20 ° C
70˚C
0.1 0.2 0.3 0.4 0.5 0.6
propyleneimine amount (wt.%)
HMPU
PCHA
DCDU
TDPU
HMPU
PCHA
DCDU
TDPU
Fig. 24. Effect of propyleneimine amount on cohesion at 20 C and
70 C.
N
N
N
N
N
CH 3
3.3. Influence of propyleneimines based on s-triazine on
tack, adhesion and cohesion
As a result of the reaction between propyleneimine
and cyanuric acid chloride or tris-(2-carboxyethyl)isocyanurate
the following crosslinkers are investigated
(Figs. 25 and 26).
The influence of the investigated propyleneimine
crosslinking agents based on s-triazine: 2,4,6-tris(1-
methylaziridinyl)-1,3,5-triazine (tripropylenemelamine)
(Fig. 25) and 2,4,6-tris(propylenepropionic acid
amide)-1,3,5-triazine (Fig. 26) on tack, adhesion and
cohesion was tested and presented in Figs. 27–29.
The obtained PSA acrylics containing propyleneimine
crosslinking agents based on s-triazine have very good
CH 3
tack (N)
adhesion (N)
24
20
16
12
8
4
0
20
16
12
8
N
O
C
CH 2
CH 2
CH 2 CH 2 C N
O
N
CH CH 2 C
N N
O
TPAA
TMTT
0.1 0.2 0.3 0.4 0.5
propyleneimine amount (wt.%)
Fig. 27. Tack dependence of propyleneimine content.
TPAA
TMTT
CH 3
CH 3
Fig. 26. 2,4,6-Tris(propylenepropionic acid amide)-1,3,5-triazine
(TPAA).
N
CH 3
CH 3
N
Fig. 25. 2,4,6-Tris(1-methylaziridinyl)-1,3,5-triazine (tripropylenemelamine)
(TMTT).
4
0
0.1 0.2 0.3 0.4
0.5
propyleneimine amount (wt.%)
Fig. 28. Adhesion dependence of propyleneimine content.

ARTICLE IN PRESS
Z. Czech / International Journal of Adhesion & Adhesives 24 (2004) 503–511 509
cohesion (N) at 20˚C and 70˚C
120
100
80
60
40
20
0
20˚C
70˚C
TMTT
TPAA
TMTT
TPAA
0.1 0.2 0.3 0.4 0.5
propyleneimine amount (wt.%)
Fig. 29. Cohesion dependence of propyleneimine content.
tack, adhesion and cohesion. The increase of crosslinkers
concentration from0.1 to 0.5 wt% decreases the
tack and adhesion performance by factor about 3–4 in
comparison to initial value. The best cohesion was
achieved with 2,4,6-tris(1-methylaziridinyl)-1,3,5-triazine
(tripropylenemelamine) (TMTT).
CH 3
N
N P O
CH 3
N
CH 3
Fig. 30. Tris-(1-(2-methylaziridynyl)phosphinoxide (MAPO).
S
N P N
CH 3 CH 3
N
CH 3
Fig. 31. Tris-1-(2-methyl)aziridinylphosphinesulfide (TAPS).
O
3.4. Influence of propyleneimines with central heteroatom
on tack, adhesion and cohesion
P
N
N
CH 3
Mainly phosphorus and sulfur serve as heteroatoms
(Figs. 30–32).
Performance qualities of the investigated propyleneimine
crosslinking agents with central heteroatom on
tack, adhesion and cohesion of acrylic PSAs are
described in Figs. 33–35.
The increase of propyleneimine crosslinker concentration
containing central heteroatomdecrease the peel
properties such as tack and adhesion and increase of
course the cohesion at 20 C and 70 C. The best
cohesion and also the low tack and adhesion were
achieved with tris-1-(2-methyl)aziridinylphosphinesulfide
(TAPS). In general, it can be said that the use of
propyleneimines as crosslinker with P¼S group gave the
better cohesion that the use of propyleneimines with
P¼O group.
3.5. Reaction products from multifunctional acrylates
and propyleneimine
Some classical compounds of this section are shown in
Ref. [16]. The table below comprises the characteristics
of propyleneimine crosslikners being offered in the
market (Table 1).
These three crosslinkers have been compared by using
a synthesized polyacrylate PSA at a coating weight of
60 g/m 2 on polyester foil. The performance of crosslinked
pressure sensitive adhesives are presented in
Table 2.
tack (N)
CH 3
Fig. 32. N,N 0 -Bis-propanephosphonic acid diamide (BPAD).
16
12
8
4
0
BPAD
MAPO
TAPS
0.1 0.2 0.3 0.4 0.5
propyleneimine amount (wt.%)
Fig. 33. Tack dependence of propyleneimine content.
As can be seen fromthe Table 2, Permutex XR-2500
is a more useful crosslinker than Trazidin VN and
Neocryl CX-100. While the cohesion of crosslinked
PSAs is comparrable for the both crosslinkers
Permutex XR-2500 and Trazidin VN, the tack and
adhesion tested at 20 C and 70 C are higher in the case
of Permutex XR-2500 introduction. As shown Permutex
XR-2500 provides high-quality crosslinked polyacrylic
PSAs.

510
ARTICLE IN PRESS
Z. Czech / International Journal of Adhesion & Adhesives 24 (2004) 503–511
3.6. Potlife of pressure-sensitive adhesives containing
multifunctional propylene-imines
It was also followed up the shell life of investigated
PSA crosslinked with the best crosslinker propyleneimine
Permutex XR-2500 with 0.1, 0.2 and 0.3 wt%
(Fig. 36).
As can be seen in Fig. 36 the PSAs are general only
processable in the time area between 5 and 7 h. The
potential risk of gelation is quite difficult to convert
propyleneimine containing adhesives.
adhesion (N)
16
12
8
4
0
BPAD
MAPO
TAPS
0.1 0.2 0.3 0.4 0.5
propyleneimine amount (wt.%)
Fig. 34. Adhesion dependence of propyleneimine content.
4. Conclusions
Fromthe evaluaction of the experiments discussed in
this article, it can be concluded that:
* Fromthe reaction products between multifunctional
carboxylic acid chlorides and propyleneimine
Table 2
Important properties of crosslinked PSA
Cros.-conc. (wt%) Tack (N) Adhesion (N) Cohesion (N)
20 C 70 C 20 C 70 C
Permutex XR-2500
0.1 24.0 19.5 13.5 90 30
0.2 21.5 17.0 10.5 >90 40
0.3 18.5 14.5 8.0 >90 40
Trazidin VN
0.1 23.5 18.0 12.0 90 30
0.2 18.5 16.0 10.0 >90 40
0.3 16.5 14.5 7.5 >90 40
Neocryl CX-100
0.1 20.0 24.0 18.0 90 20
0.2 17.0 18.0 9.0 >90 35
0.3 15.0 16.0 6.5 >90 40
cohesion (N) (20 ° C and 70 ° C)
120
100
80
60
40
20
20 ° C
70 ° C
TAPS
MAPO
BPAD
TAPS
MAPO
BPAD
viscosity (Pas)
20
15
10
5
0.3wt.%
0.2wt.%
0.1wt.%
gel
gel
max. coating viscosity
gel
0
0.1 0.2 0.3 0.4 0.5 0.6
propyleneimine amount (wt.%)
Fig. 35. Cohesion at 20 C and 70 C dependence of propyleneimine
content.
0
0 1 2 3 4 5 6 7 8 9
viscosity run (h)
Fig. 36. Potlife of PSAs containing crosslinker propyleneimine
Permutex XR-2500.
Table 1
Properties of commerciall propyleneimine crosslinkers
Properties
Propyleneimine crosslinker
Permutex XR-2500 Trazidin VN Neocryl CX-100
Chemical name
Trismethylolpropane-tris-(Nmethyl-ziridinyl)propionate
Polyfunctional propyleneimine
derivative
Polyfunctional propyleneimine
derivative
Molecular mass (Da) 467 475 470
pH 10.5 8y9 8.5y9.5
Appearance Clear, yellowish liquid Light liquid Light liquid
Viscosity 25 C (mPa s) 200 220 180
Solubility
In ethylacetate, alcohol and in aromates, limited solubility in aliphates.

ARTICLE IN PRESS
Z. Czech / International Journal of Adhesion & Adhesives 24 (2004) 503–511 511
the greatest influence of tack, adhesion and
cohesion in the case of aromatic propyleneimine
was observed.
* Fromthe reaction products between multifunctional
isocyanates and propyleneimine the best results
of cohesion was achieved with aromatic propyleneimnine
crosslinker and the best adhesion and tack
performance with cycloaliphatic propyleneimine.
* The use of propyleneimines based on s-triazine the s-
triazine derivatives with longer carbon chain are
better for softly PSAs than s-triazine crosslinkers
with ‘‘short structure’’.
* In general the propyleneimine crosslinkers with
central heteroatomin the chemical structure are
stronger than other investigated in this publication
propylenimine compounds. They are very interesting
for cohesive acrylic PSAs.
* From the investigated commercial reaction products
from multifunctional acrylates and propyleneimine
Permutex XR-2500 was the best crosslinker for
acrylics PSAs with the best balanced performance
between tack, adhesion and cohesion.
* The solvent-based PSAss acrylics containing multifunctional
propyleneimines have a very short potlife
froma few hours.
References
[1] Czech Z. Crosslinking of acrylic pressure-sensitive adhesives.
Politechnika Szczecinska, Szczecin, 1999 (ISBN 83-87423-18-1).
[2] Zosel A. Int J Adhes Adhes 1998;4:268.
[3] Milker R, Czech Z. Adh.asion 1985;3:29–32.
[4] Milker R, Czech Z. Adh.asion 1989;6:20–5.
[5] US Patent 3,886,126, 1975.
[6] US Patent 3,769,254, 1973.
[7] US Patent 3,886,126, 1975.
[8] EP 0 071 142, 1984.
[9] EP 0 355 991, 1989.
[10] Bron WT. Waterborne, Higher-Solids and Polder Coatings
Symposium, New Orleans, vol. 2. 1994. p. 9–11.
[11] US Patent 3,993,716, 1970.
[12] EP, 0 206 669, 1986.
[13] DE, 21 34 688, 1971.
[14] EP, 0 655 490, 1994.
[15] US Patent 5,296,277, 1992, 3M.
[16] US Patent 4,490,505, 1981, 3M.