Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Patent
1988-05-20
1989-11-14
Foelak, Morton
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Cellular products or processes of preparing a cellular...
521 54, 521 57, 521134, 523201, 525301, 525902, C08J 928, C08F26504
Patent
active
048808423
ABSTRACT:
Multi-stage polymer particles containing one or more void space(s) therein are produced by sequential emulsion polymerization of an essentially low-acid earlier polymer stage, encapsulation of said low-acid polymer stage with at least a final polymer stage, contacting said polymer particles with a non-polymeric carboxylic acid to permit the acid to be absorbed into said low-acid polymer stage and swelling the polymer particles by contacting the particles with an aqueous base. The low-acid polymer stage is formed by emulsion polymerizing a monomer system comprising ethylenically unsaturated monomer(s) and containing less than 5% by weight of monomer(s) containing acid functionality. The low-acid polymer stage is subsequently encapsulated by one or more polymer stages by emulsion polymerizing ethylenically unsaturated monomer(s) in the presence of the low-acid polymer stage. The final stage has a glass transition temperature (Tg) of about 50.degree. C. or greater, and the total polymer stages having a Tg of about 50.degree. C. or greater comprise about 60% or more by weight of the polymer particles. A non-polymeric carboxylic acid is absorbed into the polymer particles and the resultant particles are contacted with base at a pH sufficient to swell the particles with water at a temperature near or above the Tg of the neat polymer or plasticized polymer of the final polymer stage. When dried the particles contain void space(s) therein which produce(s) opacity in compositions in which the particles are contained.
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Kowalski Alexander
Vogel Martin
Battle Carl W.
Foelak Morton
Rohm & Haas Company
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