Patent ID: 9260546
Filing Date: 2016-02-16
CPC Classification: A61K,A61Q,C08F

Claim Text:
1. A process for producing a vinyllactam polymer having K values of 10 to 150, the process comprising the steps in the sequence set forth: a) polymerizing one or more N-vinyllactams and optionally further monomers via free-radical polymerization with a free-radical initiator in an aqueous liquid, wherein the polymerization process is performed as batch process, as semi-batch process or as continuous process; b) using at least one base to maintain the pH during the polymerization in a range from 5 to 11; c) optional postpolymerization, wherein a further initiator is added; d) optional purification by stripping with gas, thermal distillation and/or steam distillation; e) treating the vinyllactam polymer with a sulfur component selected from the group consisting of sulfurous acid, sulfur dioxide and one or more salts of sulfurous acid, wherein the pH of a water-containing phase with which the polymer comes into contact during the treatment with the sulfur component has a value of less than 6, and keeping the polymer in contact with the water-containing phase comprising the sulfur component at this pH for a period between 10 minutes and 5 hours, and then optional repeat of step d); f) optionally adding at least one base to set a desired pH in the range from 4 to 9; g) optional purification by filtering; and h) optional drying to form a free-flowing powder.