Process for preparing multi-stage polymer emulsions and multi-stage polymers formed therefrom

CAFC
  • US 6,252,004 B1
  • Filed: 10/14/1999
  • Issued: 06/26/2001
  • Est. Priority Date: 11/05/1997
  • Status: Expired due to Term
First Claim
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1. A process for preparing emulsion polymer particles comprising:

  • (a) providing an aqueous emulsion of (i) multi-stage emulsion polymer, comprising a core stage polymer and a shell stage polymer, wherein the core stage polymer comprises, as polymerized units, from 5 to 100 percent by weight, based on the weight of the core stage polymer, of hydrophilic monoethylenically unsaturated monomer, and from 0 to 95 percent by weight, based on the weight of the core stage polymer, of at least one nonionic monoethylenically unsaturated monomer; and

    wherein the shell stage polymer comprises, as polymerized units, at least 50 percent by weight of nonionic monoethylenically unsaturated monomer;

    (b) adding an effective amount of one or more polymerization inhibitors or reducing agents to substantially stop any polymerization;

    (c) providing monomer at a level of at least 0.5 percent by weight based on the weight of the multi-stage emulsion polymer;

    (d) adding swelling agent; and

    (e) reducing the level of monomer by at least fifty percent.

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