Producing aqueous solutions of vinyllactam polymers and powders thereof

摘要

Described is a process for producing aqueous solutions of vinyllactam polymers and solids obtainable therefrom by drying, especially polyvinylpyrrolidone, said process comprising using one or more sulfur components selected from the group consisting of sulfur dioxide, sulfurous acid and one or more salts of sulfurous acid, to reduce residual monomer. Also described are vinyllactam polymers obtainable by the process which have good stability in storage, the use of these vinyllactam polymers, and articles of manufacture and preparations comprising these vinyllactam polymers or obtained by use thereof.

主权项

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.