Patent ID: 7388069

Claim:
A process to produce a film comprising poly(vinyl alcohol), the process comprising the steps of: dissolving a poly(vinyl alcohol) polymer or copolymer in a solvent to produce a casting solution; casting the casting solution onto a casting form; removing the solvent to produce the film comprising poly(vinyl alcohol), wherein prior to producing the casting solution, the poly(vinyl alcohol) polymer or copolymer is first purified by a continuous purification process comprising the steps of: providing a crude homogeneous poly(vinyl alcohol) solution consisting essentially of water, poly(vinyl alcohol) polymer or copolymer, impurities, wherein the crude homogeneous poly(vinyl alcohol) solution has a pH of about 5 to about 6.9; directing the crude homogeneous poly(vinyl alcohol) solution at a temperature of about 25° C. to about 100° C. through a column comprising a macroreticular polymeric cation exchange resin comprising the hydrogen form of a sulfonic acid; and collecting a purified aqueous poly(vinyl alcohol) solution at a pH of between 3 and 6.9 from the column, wherein a 50 micrometer thick film produced from the purified aqueous poly(vinyl alcohol) solution has an APHA color value of 50 or less after the film has been heated at 150° C. for 60 minutes.