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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.
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