Aqueous polymer emulsion
AssigneeBASF SE
InventorsRoland Baumstark, Michael Portugall, Rolf Dersch, Enrique Schweigger
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Abstract
An aqueous polymer emulsion is obtained by polymerizing first a monomer composition 1 in a first polymerization stage and then a monomer composition 2 in a polymerization stage 2, in each case by the free radical aqueous emulsion polymerization method, one of the two monomer compositions essentially comprising hard monomers and the other monomer composition essentially comprising soft monomers, and, in addition to the monomer compositions 1 and 2, nitrogen-containing adhesion-promoting monomers being polymerized, at least 20 mol % of the total amount of the adhesion-promoting monomers being polymerized in polymerization stage 1.
Claims46
An aqueous polymer emulsion obtained by polymerizing in a first polymerization stage monomers 1 having at least one ethylenically unsaturated group by free radical aqueous emulsion polymerization to a conversion of at least 90% by weight, based on the monomers 1 to be polymerized, and then polymerizing, in the presence of the product mixture of the first polymerization stage, monomers 2 having at least one ethylenically unsaturated group in a second free radical aqueous emulsion polymerization stage, with the proviso that
- a) the monomers 1 are such that their random copolymerization alone would give a polymer 1 whose glass transition temperature tends to the limit Tg.sup.1 with increasing molecular weight,
- b) the monomers 2 are such that their random copolymerization alone would give a polymer 2 whose glass transition temperature tends to the limit 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) in addition to the monomers of the monomers 1 and 2, at least one adhesion-promoting monomer which differs from these monomers 1 and 2 and contains at least one ethylenically unsaturated group and at least one amino, ureido or N-heterocyclic group is polymerized in an amount of from 0.1 to 10% by weight, based on the total amount of the monomers to be polymerized,
- e) from 20 to 100 mol % of the total amount of the adhesion-promoting monomers to be polymerized according to d) are polymerized in the first polymerization stage and
- f) the amount of the monomers of the polymer having the lower limit Tg.sup.1 is from 40 to 90% by weight, based on the total amount of the monomers 1 and 2.
Dependencies are inferred from the claim text.