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US 6,605,662 B2Granted
Multistage aqueous dispersion of polymer particles having a soft core and hard shell
AssigneeBASF SE
InventorsCheng-Le Zhao, Joachim Roser, Eckehardt Wistuba, Bernhard Schuler, Klemens Mathauer
Life of this patent
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Abstract
A process for preparing aqueous polymer dispersions comprises first of all subjecting ethylenically unsaturated monomers to free-radical aqueous emulsion polymerization to prepare an aqueous dispersion of a polymer 1 having a glass transition temperature Tg1, then dissolving further, comparatively hard monomers in the dispersed particles of the polymer 1, and subsequently carrying out free-radical polymerization of said monomers dissolved in said particles.
Claims17
An aqueous polymer dispersion obtained by a process, comprising:
- polymerizing monomers having at least one ethylenically unsaturated group by the method of free-radical aqueous emulsion polymerization to give a polymer 1, in dispersed distribution in the aqueous medium;
- and
- free-radical polymerizing further monomers in one or more successive polymerization stages i, in the presence of the polymer 1 that is in disperse distribution in the aqueous medium, with the proviso that
- a) the polymer 1 has a glass transition temperature Tg1;
- b) the monomers polymerized in each of the polymerization stages i are such that isolated random copolymerization of these monomers would give a polymer i whose glass transition temperature tends with increasing molecular weight toward the limit value Tgi;
- c) for each Tgi the difference Tgi-Tg1 is ≧10° C.;
- d) the amount of the monomers polymerized to prepare the polymer 1 in disperse distribution, based on the amount of all of the monomers polymerized in the process is ≧92% by weight and ≧99.9% by weight;
- e) the total amount of the monomers polymerized in all polymerization stages i, based on the total amount of all of the monomers polymerized in the process, is ≧0.1% by weight to 8% by weight;
- f) in each of the polymerization stages i, the addition of the monomers i to the polymerization vessel is made such that at no time up to the end of the addition does the degree of polymerization Ui of monomers i exceed 50 mol-%;
- g) the total amount of the monomers polymerized to prepare the polymer 1, apart from the monomers having two conjugated ethylenically unsaturated groups, does not include more than 5% by weight of monomers having more than one ethylenically unsaturated group;
- and
- wherein in each of the polymerization stages i the monomers are added in pure form.
9 more elements
A polymer obtained by a process, comprising:
- polymerizing monomers having at least one ethylenically unsaturated group by the method of free-radical aqueous emulsion polymerization to give a polymer 1, in dispersed distribution in the aqueous medium;
- and
- free-radical polymerizing further monomers in one or more successive polymerization stages i, in the presence of the polymer 1 that is in disperse distribution in the aqueous medium, with the proviso that
- a) the polymer 1 has a glass transition temperature Tg1;
- b) the monomers polymerized in each of the polymerization stages i are such that isolated random copolymerization of these monomers would give a polymer i whose glass transition temperature tends with increasing molecular weight toward the limit value Tgi;
- c) for each Tgi the difference Tgi-Tg1 is 10° C.;
- d) the amount of the monomers polymerized to prepare the polymer 1 in disperse distribution, based on the amount of all of the monomers polymerized in the process is ≧92% by weight and ≦99.9% by weight;
- e) the total amount of the monomers polymerized in all polymerization stages i, based on the total amount of all of the monomers polymerized in the process, is 0.1% by weight to 8% by weight;
- f) in each of the polymerization stages i, the addition of the monomers i to the polymerization vessel is made such that at no time up to the end of the addition does the degree of polymerization Ui of monomers i exceed 50 mol-%;
- g) the total amount of the monomers polymerized to prepare the polymer 1, apart from the monomers having two conjugated ethylenically unsaturated groups, does not include more than 5% by weight of monomers having more than one ethylenically unsaturated group;
- and
- wherein in each of the polymerization stages i the monomers are added in pure form.
9 more elements
Dependencies are inferred from the claim text.