AQUEOUS POLYMER DISPERSION AND PROCESS

摘要

PROBLEM TO BE SOLVED: To provide tackified PSAs that have a core-shell structure and are stable under high shear.SOLUTION: A multi-step process for preparing an aqueous dispersion of heterogeneous polymer particles by mini-emulsion polymerization comprises the step (I) of (a) forming a mixture comprising (i) water, (ii) at least one stabilizer (such as a surfactant and a hydrophobic co-stabilizer), (iii) at least one tackifier (such as polyterpenes, rosin resins and/or hydrocarbon resins), and (iv) at least one α,&bgr;-ethylenically unsaturated monomer; (b) applying high shear to the mixture from the step (a) to form an essentially stable mini-emulsion comprising an aqueous continuous phase and stabilized droplets dispersed therein of an average diameter from about 10 to about 1000 nm; (c) polymerizing the monomer within the droplets in the presence of a free radical initiator; and (d) adding further monomer to the dispersed phase to form a dispersion; and the step (II) of using the dispersion from the step (I) as a seed to form a dispersion of heterogeneous polymer particles in a subsequent emulsion polymerization.