Synthesis Of Copolymerizable Photoinitiator Used For UV Curing Systems

The photoinitiator is an important component for UV curing system. However, conventional small molecular photoinitiators can easily volatilize and migrate in the process of preservation and application, which will not only reduce photopolymerization efficiency, but also bring smelly odor and toxicity to the final products. In the application of food and drugs, the migration of small molecular photoinitiators and their photolytic fragments is strictly forbidden. In this paper, a new kind of copolymerizable photoinitiator used for UV curing systems has been synthesized and discussed. This new type copolymerizable photoinitiator can polymerize with other monomers to form a long-chain molecular, which will solve the problem of small photoinitiator residual and the migration of photolytic fragments.According to the photoinitiation mechanism of photoinitiators, structure of copolymerizable photoinitiator(UV-I) has been designed. 2-HEA, HDI and 4- dihydroxybenzophenone have been chosen as raw materials to synthesis UV-I with N,N-dimethyl formamide as solvent and Dibutylin Dilaurate as catalyst. The synthesis process can be divided into two steps. The first step was conduct by 2-EHA and HDI and the second step started when 4- dihydroxybenzophenone was added. The reaction processing conditions and synthesis methods have been researched. Besides, the FTIR, 1H-NMR and UV spectrum analysis indicate that the synthetic final product is just the target product UV-I.To characterize the initiation performance of UV-I, the UV curing acrylic pressure-sensitive adhesive has been employed in this paper. The composition of pressure-sensitive adhesive(PSA) system is: CN966H9030%, BA20%, 2-HEA20% and VAc30%. The PSA was cured by high-pressure mercury lamp with an exposure distance of 10cm. The 180°peel adhesion, ATR-FTIR and DSC spectrum of PSA indicate that the UV-I can initiate photoreaction. When the content of UV-I was 1.0% and UV curing time was 20s, PSA system can be cured completely.After treating under ageing process, the 180°peel adhesion of PSA reduced little, which indicates that the PSA have good aging performance. This also demonstrates that UV-I have excellent photoinitiation performance and the UV curing products with UV-I possess well resistance to weather.