Preparation Of Photoinitator Grafting Onto SBS And Application In UV Crosslinkable Pressure Sensitive Adhesive

UV crosslinkable pressure sensitive adhesive (PSA) based on SBS (styrene-butadiene-styrene) triblock copolymer have attracted much researchers′attention. A chemical crosslinking network of SBS formed after UV irradiation can be introduced to enhance the adhesion of the PSA. However, the photoinitiator, was blended with SBS by conventional preparation method in[0] the UV crosslinkable PSA system, arising many problems. First, the photoinitiator molecular has weak compatibility with SBS and other additives. Second, toxicologically hazardous cleavage products are formed. Third, there are still many problems with migration of excess photoinitiator. Thus, plenty of researches were focused on UV crosslinking system, including using electron beam curing technology, or synthesizing low-toxic and hard-decomposing photoinitiators which show good compatibility with SBS, or grafting of photoinitiators onto polymer main chains. The main ideal of this paper is to improve the UV crosslinkable PSA system by grafting copolymerization of photoinitiators onto SBS. Conducting studies as follows:(1)A kind of maleimide of 4-maleimidobenzophenone (MBP) was synthesized by the condensation of maleic anhydride (MAH) and 4-Aminobenzophenone (4-ABP). MBP was characterized by 1HNMR and FTIR.(2)MBP was grafted onto SBS through free radical polymerization initiated by benzoperoxide (BPO). The grafted polymer SBS-g-MBP was characterized by FTIR analysis. The grafting efficiency was relatively compared by the peak area ratio of the carbonyl vibration band.(3)The relationship between gel fraction of SBS-g-MBP after UV irradiation and grafting efficiency of MBP was disscused. The influence of preparation processing conditions was investigated by different feeding mode, N2 input, BPO concentration, MBP concentration and the grafting reaction time.(4)The grafted polymer was suitable to prepared solvent-based UV crosslinkable PSA by blending with other additives in toluene. The mixture was tested for their pressure sensitive adhesive property on kraft paper by UV irradiation. The FTIR of the tapes after UV irradiation and the change in the glass transition temperature Tg of the polybutadiene block indicated the crosslingking reaction of the tapes. Accroding to the recommendatory scheme reported in the literature, 180°peel strength, persistent adhesion property and initial adhesion property of the crosslinked samples were measured. The results were compared with the technical requirements of Chinese kraft paper pressure-sensitive adhesives tapes (HG/T 2408-92). The performance index of modifated PSA tapes can reach balance by changing KN-4006 concentration. The optimized scheme of the UV crosslinkable PSA was evaluated.