Free Radical UV-Curable Release Coatings Without Silicon Monomers Using Poly(methylhydrosiloxane) Co-Initiator

摘要

To ensure easier removal of adhesive, backing materials can be coated with a release film. UV-curable release coatings based on acrylate or epoxy silicone oligomers represent an increasing proportion of release liners available on the market. In order to alleviate their current problems of recycling, metal contamination and initiator insolubility, we have developed a synthetic methodology able to reduce silicone content below 1 wt%. Silicon monomer-free, our approach relies on a type II radical photoinitiator consisting of benzophenone and poly(methylhydrosiloxane) (PMHS, 1600 g/mol), a silicone derivative with the general structure O-Si(H)(CH3). The ability for PMHS to act as co-initiator in radical photopolymerization is revealed by real-time Fourier transform IR spectroscopy. Release properties are evaluated through a probe tack experiment using a commercial pressure sensitive adhesive. Using 1,6-hexanediol diacrylate as resin, release properties are achieved at 1 wt% PMHS, and can be also maintained with poly(ethylene glycol) diacrylate, or tripropylene glycol diacrylate monomers. A ten times decrease in adhesion energy is observed when PMHS is used against a non-reactive silicone thanks to chemical bonding between co -initiator and polymer network.