Patent ID: 6489387
Filing Date: 2002-12-03
Classification: C08F,C08L,C09J

Abstract:
Pressure-sensitive adhesive (PSA) copolymers which, when coated and dried as a film, resist water whitening, formed by polymerizing in emulsion a mixture of monomers comprisingat least one alkyl acrylate ester of an alcohol containing 4 to 8 carbon atoms, the total amount of alkyl acrylate esters being about 55 to about 85% by weight of the mixture of monomers; at least one polar comonomer, the total amount of polar comonomers being about 1 to about 10% by weight of the mixture of monomers; and at least one partially water soluble comonomer selected from the group consisting of methyl acrylate, ethyl acrylate, methyl methacrylate, and vinyl acetate, the total amount of partially water soluble comonomers being about 8 to about 25% by weight of the mixture of monomers; polymerization being carried out in an aqueous media in the presence of at least one nonionic surfactant containing at least 8 moles of ethylene oxide per mole of nonionic surfactant and at least one anionic surfactant containing up to 4 moles of ethylene oxide per mole anionic surfactant, wherein the weight ratio of nonionic surfactant to anionic surfactant is at least 1.5:1; said emulsion thereafter neutralized by the addition of at least one base to a pH greater than 7; said copolymers, when cast as a film on a clear, 2 mil thick, biaxially oriented polypropylene film at a coat weight of 20 to 22 g/m2, dried, and immersed in water of at least 95Â° C. for 10 minutes, and then laminated to a clear, 2 mil thick polyester film, having an opacity of about 5% or less as determined with a spectrocolorimeter.