Abstract: Removable pressure sensitive adhesive compositions having enhanced resistance to water-whitening comprising a crosslinked aqueous emulsion polymer are disclosed. The crosslinked aqueous emulsion polymer comprises (a) at least one hydrophobic monomer; (b) greater than 1 wt. % of at least one hydrophilic monomer; (c) greater than 3 wt. % of at least one mono-olefinically unsaturated monomer having an aldehyde or ketone group; (d) optionally at least one partially hydrophilic monomer; and (e) an effective amount of at least one water-soluble or water-dispersible polymerizable surfactant; wherein the crosslinked aqueous emulsion polymer is crosslinked with an effective amount of at least one polyhydrazide crosslinker, the wt.

Abstract: In forming pressure sensitive adhesive microspheres by copolymerizing a non-ionic monomer of an alkyl acrylate or alkyl methacrylate ester of a non-tertiary alcohol and an ionic monomer copolymerizable with said non-ionic monomer, non-free radically polymerizable acid is present during the polymerization to promote formation of solid rather than hollow microspheres and to reduce residual unconverted ionic monomer. These microspheres exhibit reduced adhesive transfer in downstream use as a repositionable pressure sensitive adhesive. A water soluble initiator is optionally added to the polymerization mixture after achieving about 90% conversion of the non-ionic monomer to further reduce residual unconverted ionic monomer.

Abstract: In forming pressure sensitive adhesive microspheres by copolymerizing a non-ionic monomer of an alkyl acrylate or alkyl methacrylate ester of a non-tertiary alcohol and an ionic monomer copolymerizable with said non-ionic monomer, non-free radically polymerizable acid is present during the polymerization to promote formation of solid rather than hollow microspheres and to reduce residual unconverted ionic monomer. These microspheres exhibit reduced adhesive transfer in downstream use as a repositionable pressure sensitive adhesive. A water soluble initiator is optionally added to the polymerization mixture after achieving about 90% conversion of the non-ionic monomer to further reduce residual unconverted ionic monomer.