Azlactone-containing pressure-sensitive adhesives

Claim 1

A composite structure comprising: (a) two substrates, and (b) coated between said substrates a pressure-sensitive, normally-tacky, adhesive interpolymer which is the product of simultaneous polymerization of ethylenically-unsaturated monomers which comprise (1) from about 70 to 90 molar parts of monomers consisting of (a) 69-100 mole percent of an acrylic acid ester of at least one non-tertiary alkyl alcohol, the molecules of said alcohol containing 1-14 carbon atoms, the average being 5-12 carbon atoms, (b) 31-0 mole percent of at least one monomer selected from the group consisting of vinyl acetate, styrene, vinyl ethers, and alkyl methacrylates, the alkyl group having 1 to 14 carbon atoms, and (c) 10-0 mole percent of at least one monomer selected from the group consisting of acrylamide, methacrylamide, acrylonitrile, methacrylonitrile, and N-vinyl pyrrolidone, and (2) from 25 to 5 molar parts of at least one alkenyl azlactone monomer having the formula I ##STR6## wherein R 1 is hydrogen or methyl; R 2 is selected from a single bond, --R 3 --, or ##STR7## in which R 3 is a substituted or unsubstituted alkylene group having 1 to 12 carbon atoms, and W is --O--, --S--, or --NH--; R 4 and R 7 are independently selected from a single bond, methylene, or substituted methylene having 1 to 12 carbon atoms; R 5 and R 6 are independently substituted or unsubstituted alkyl or cycloalkyl having 1 to 12 carbon atoms, aryl or aralkyl having 6 to 12 carbon atoms, or R 5 and R 6 taken together with the carbon to which they are joined forming a 5- or 6-membered carbocyclic ring or R 5 and R 6 each may be hydrogen when at least one of R 4 and R 7 is methylene; and (3) from 25 to 5 molar parts of at least one acrylic-functional carboxylic acid monomer selected from acrylic acid, methacrylic acid, itaconic acid, maleic acid, or an N-acryloylamino acid; said interpolymer exhibiting a glass transition temperature (Tg) of less than -15° C., with the proviso that said substituting groups are unreactive with said azlactone ring and said monomers having been polymerized in a medium free of alcohol and other crosslinking agents capable of reacting with the azlactone ring.