Ultraviolet crosslinkable copolymers

摘要

Preparation of crosslinked pressure-sensitive adhesives comprises two-stage or multi-stage free-radical addition polymerization of at least two copolymerizable monomers in the presence of a polyvalent mercaptan(s), producing block copolymers containing a polyvalent thioether unit(s); coating of the polymer from the melt on a backing; and crosslinking of the polymer on the backing by irradiation with ultraviolet radiation. Preparation of crosslinked pressure-sensitive adhesives partly based on block copolymers comprising a polyvalent thioether unit(s), comprises: (1) two-stage or multi-stage free-radical addition polymerization of at least two copolymerizable monomers in the presence of a polyvalent mercaptan(s), monomer(s) comprising a functional group which on irradiation with ultraviolet rays initiates a UV crosslinking, the polymerization producing block copolymers containing a polyvalent thioether unit(s); (2) coating of the polymer from the melt on a backing; and (3) crosslinking of the polymer on the backing by irradiation with ultraviolet radiation. An independent claim is also included for block copolymers obtained by two-stage or multi-stage free-radical addition polymerization of at least two copolymerizable monomers in the presence of a polyvalent mercaptan(s). The block copolymers are of formula [R 1,iP 1,iS] mX[SP 2,jR 2,j] m. i : 1 to n; j : 1 to m; n, m : integers; P 1,ipolymer segments from a monomer group comprising first monomers A and/or copolymer segments from a monomer group comprising first monomers A and third monomers C, where the I segments P 1can have different lengths and different chemical compositions; P 2,jpolymer segments from a monomer group comprising second monomers B and/or copolymer segments from a monomer group comprising second monomers B and third monomers C, where the j segments P 2can have different chemical compositions; R 1,I, R 2,jradicals capping the segments P 1,iand P 2,j; X : linking unit, with X(S) n+m=polyvalent thioether unit, the valency being at least n+m. At least one of the segments P 1,iand/or P 2,icontains copolymerized monomers C. The monomers C contain the functional groups which on irradiation with UV rays initiate a UV crosslinking.