Stable emulsion polymers and methods of preparing same

Claim 1

In a process for producing a latex, which comprises the steps of: (a) reacting latex-forming monomers under predetermined emulsion-polymerization reaction conditions to form a hydrophilic, first-stage polymer; and (b) contacting the first-stage polymer with an effective amount of at least one hydrophobic, latex-forming monomer under predetermined emulsion-polymerization reaction conditions to form a hydrophobic, second-stage polymer, wherein the second-stage hydrophobic polymer partitions into the first-stage hydrophilic polymer thereby producing an inverted core-shell emulsion polymer, wherein the improvement comprises the additional step of adjusting the pH of the inverted core-shell emulsion polymer by an amount effective to dissolve the first-stage hydrophilic polymer, the first-stage hydrophilic polymer being dissolvable and the second-stage hydrophobic polymer being insoluble upon adjustment of pH, for thereby producing a stabilized latex comprising a continuous aqueous phase containing the first-stage hydrophilic polymer and a discontinuous phase containing discrete, stabilized particles of the second-stage hydrophobic polymer.