Water whitening-resistant pressure-sensitive adhesives

摘要

Acrylic emulsion PSA polymers which when cast as a film resist water whitening by hot or ambient temperature water are provided, and are formed by copolymerizing a monomer mixture comprising at least one alkyl acrylate ester of an alcohol containing at least four carbon atoms, at least one polar comonomer and at least one partially water soluble comonomer present in an amount of at least about 7% by weight of the monomers. Polymerization is carried out in the presence of at least one nonionic surfactant containing at least about 8 moles of ethylene oxide per mole nonionic surfactant and at least one anionic surfactant containing up to about 10 moles ethylene oxide per mole anionic surfactant. There is added to the product of polymerization at least one base to produce an emulsion having a pH greater than 7 and containing particles having a mean "volume-average" particle diameter of up to about 210 nm as determined by laser light scattering. An electrolyte is post-polymerization added to stabilize opacity of the adhesive films cast from the emulsion. Applications include autoclavable labels, wet-stick container labels, fleet marking labels and battery labels.