Process for making vinyl pyrrolidone/vinyl acetate copolymers having a very low residual vinyl pyrrolidone monomer level within a short production cycle
AssigneeISP Investments Inc.
InventorsDrupesh Patel, Paul Taylor, John Mc Kittrick
Life of this patent
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Abstract
Vinyl pyrrolidone/vinyl acetate copolymers having a very low residual vinyl pyrrolidone monomer level, i.e. <100 ppm, preferably only 50 ppm, are made within an advantageously short production cycle, by post-treating an aqueous solution of the copolymer at an elevated temperature of about 120–150° C., preferably about 130° C., under pressure, in the presence of a high temperature initiator, for a period of about 1–4 hours, preferably 2 hours.
Claims5
A process of making vinyl pyrrolidone (VP)/vinyl acetate (VA) copolymers having a very low residual VP level of <100 ppm based upon the amount of VP used which comprises copolymerizing VP and VA in isopropanol (IPA) solvent in the presence of a low temperature radical initiator, continuously stripping the IPA while simultaneously adding water to form an aqueous solution of the copolymer, and post-heating said aqueous solution at about 120–150° C. in the presence of a high temperature initiator, for a period of 1–4 hours.
Dependencies are inferred from the claim text.