| abstract |
What is described herein is a process for preparing a lightly-crosslinked copolymer of (a) vinyl pyrrolidone (VP) and (b) dimethylaminopropyl methacrylamide (DMAPMA) under more reproducible conditions. Suitably the weight ratio of (a):(b) is 50-95:50-5, preferably 80:20. The copolymer has a Brookfield viscosity of 5,000 to 45,000 cps; preferably 10,000 to 30,000 cps, and a haze of <100 NTU; it includes about 0.1 to 0.5 wt. %, preferably 0.2 to 0.4 wt. %, of a cross-linking agent based upon the total weight of the monomers in the copolymer. |