Printing ink copolymers

Claim 1

A composition of matter comprising an aqueous dispersion of a four component copolymer of: (1) an alkyl ester of acrylic acid, (2) an alkyl ester of methacrylic acid wherein at least one of the alkyl substituents of the ester components has at least four carbon atoms, and wherein the sum of the carboxylate esters (1) and (2) are from 50 to 80 percent by weight of the copolymer, (3) an ethylenically-unsaturated nitrile containing from three to five carbon atoms, (4) an ethylenically-unsaturated carboxylic acid, present in from 2 to 15 percent by weight of said copolymer, containing from three and six carbon atoms, and said nitrile component present in an amount greater than the carboxylic acid component on a mole ratio basis, (5) a water soluble or water dispersible coalescent agent comprising an ether selected from the group consisting of mono-alkyl ethers of ethylene glycol and their higher molecular weight homologues and (6) a mixture of water-dispersible surfactants derived from hydroxyl terminated polyethylene oxide adducts prepared from (1) linear aliphatic primary alcohols and (2) linear alkyl-substituted phenols, the resulting copolymer having a glass-transition temperature and minimum film formation temperature of less than 80° C. and the pH of the aqueous dispersion being below about 8.5, whereby essentially all of the carboxylic acid groups present are in the unionized carboxylic acid form.