Acrylic emulsion polymers for removable pressure sensitive adhesive applications

United States Patent（美國專利號）：  8580875

Abstract：An improved aqueous acrylic emulsion pressure sensitive adhesive (PSA) composition of improved sheer strength includes an aqueous acrylic emulsion including at least one hydrophobic monomer, at least one hydrophilic monomer, and at least one hydrogen bonding monomer; and a peel control additive. The PSA composition is substantially devoid of phosphate-based surfactants.

Background：When the adhesive coated film face stock is removed from the release sheet, the adhesive must exhibit initial tack and peel performance when pressure-applied to a substrate. The substrate bearing the adhesively-bound film face stock may be subjected to a variety of manufacturing operations over time. Thermal cycling of the substrate is a condition to which high performance, pressure sensitive adhesives must be designed to confront. When the film face stock is removed from the substrate, removal must be clean, i.e. no visible trace of the adhesive should remain on the substrate. Heat aging of the film face stock/substrate laminate, however, tends to cause the adhesive to "build", that is, the necessity to utilize excessive force to remove the film face stock. Thus, the adhesive should stick well initially, but not so well that its later removal is difficult. Then too, the adhesive must possess shelf life, viscosity, etc., making it compatible with existing coating and handling techniques utilized in the art. 

More particularly, some commercial acrylic PSA's utilize phosphate-based surfactants as peel control agents (see, for example, U.S. Pat. No. 5,416,134); however, foam control may become an issue with these surfactants. The disclosed PSA replaces such foamy additives with a modification of the acrylic polymer to control peel without foam issues.

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