Aqueous polymer dispersions, their preparation and use

Abstract

Described is a process for preparing aqueous polymer dispersions by at least two-stage free-radical aqueous emulsion polymerization of ethylenically unsaturated monomers, comprising: 1. a first polymerization stage, 1, in which a first monomer composition M(1) is polymerized in accordance with a monomer feed technique by adding a free-radical polymerization initiator I(1), giving an aqueous dispersion of a polymer P(1), and 2. a further polymerization stage, 2, in which 2a. a monomer composition M(2) whose makeup is different than that of the monomer composition M(1) is added in undiluted form to the aqueous dispersion of the polymer P(1), and 2b. the monomer composition M(2) is polymerized, and 3. if desired, steps 2a and 2b are repeated to carry out further polymerization stages, i, the total amounts of the monomer M(2) making up from 0.1 to 20% by weight of the monomers M(1) polymerized in stage 1 and the addition of the monomer mixture M(2) not taking place before the end of the addition of the monomer mixture M(1), wherein the polymerization in polymerization stage 2 and any further polymerization stages takes place in the presence of residual amounts of the initiator I(1) added in the 1st stage or by adding further initiator I(1) and from the beginning of step 1 to the end of step 2b in the last polymerization stage the temperature in the reaction vessel is at least 70° C., and also the use of these polymer dispersions for preparing pressure sensitive adhesives.

Dependencies are inferred from the claim text.