Patent ID: 6031038
Filing Date: 2000-02-29
Classification: B27K,C04B,C08F,C08L,C09D,Y10T

Abstract:
An aqueous polymer emulsion, comprising:A) at least one dispersed polymer A obtained by polymerizing a composition 1 comprising at least one monomer having at least one ethylenically unsaturated group by a free radical aqueous emulsion polymerization method to a conversion of at least 90% by weight, based on the monomer composition 1 to be polymerized (polymerization stage 1), followed by polymerizing, in the presence of the product of polymerization stage 1, a composition 2 comprising at least one monomer having at least one ethylenically unsaturated group by a free radical aqueous emulsion polymerization method (polymerization stage 2), with the proviso thata) the composition 1 is such that random copolymerization of the composition 1 alone provides a polymer 1 whose glass transition temperature tends to the Tg.sup.1 with increasing molecular weight,b) the composition 2 is such that random copolymerization of the composition 2 alone provides a polymer 2 whose glass transition temperature tends to the Tg.sup.2 with increasing molecular weight,c) the difference between Tg.sup.1 and Tg.sup.2 is at least 20.degree. C.,d) the amount of that composition 1 or 2 which has the lower Tg is from 40 to 90% by weight, based on the total amount of the compositions 1 and 2, ande) in addition to the monomers of the compositions 1 and 2, at least one adhesion-promoting monomer which differs from these monomers and has at least one ethylenically unsaturated group and at least one group of the formula I ##STR7## where X is O or S and R.sup.1 and R.sup.2 are both hydrogen or C.sub.1 -C.sub.5 -alkyl or both together form a bridging C.sub.2 -C.sub.4 -alkylene group which may be monosubstituted or disubstituted by C.sub.1 -C.sub.4 -alkoxy or hydroxyl,is polymerized, in stage 1 or stage 2 or distributed over both polymerization stages in an amount of from 0.1 to 30% by weight, based on the total amount of the monomers to be polymerized,B) at least one chemical compound B having at least two unprotected reversibly protected aldehyde groups, with the proviso that the molar ratio R of all the groups of formula I contained in the aqueous polymer emulsion to the total molar amount of unprotected or reversibly protected aldehyde groups contained in the aqueous polymer emulsion in the form of compounds B is from 0.1:1 to 10:1, andC) in the absence of carboxylic hydrazide.