Pressure-sensitive adhesive

Claim 1

A composition consisting essentially of an optically clear blend of (1) a water-soluble polymer of a vinyl lactam having the structure ##STR5## in which X represents an alkylene bridge having three to five carbon atoms, or a copolymer thereof with 1 to 80 mole percent of copolymerizable monomer containing a polymerizable ethylenic unsaturation, and (2) a tacky water-insoluble copolymer comprising (A) an ester or a mixture of esters having the structure ##STR6## in which R' represents hydrogen or methyl and R 1 represents alkyl having from 1 to 14 carbon atoms and (B) from 1 to 12% by weight, based on the tacky copolymer of an ethylenic monomer containing an acid group, said vinyl lactam polymer or copolymer being present in an amount from 1 to 30% by weight of the blend and having a glass transition temperature from 20° to 150° C., and the tacky copolymer having a glass transition temperature below 0° C. and being present in an amount from 70 to 99% by weight of the blend and being substantially free from cross-linking and having a viscosity less than 50,000 cps at 350° F. so that it possesses by itself insufficient cohesive strength to be useful as a pressure-sensitive adhesive, said blend having a viscosity less than 100,000 cps at 350° F.