GB778201A - Process for producing water-insoluble threads of polyvinyl alcohol - Google Patents

Abstract

Threads of polyvinyl alcohol, which may still contain acetyl groups, are stretched, dried, heated under tension and treated with an aqueous solution containing formaldehyde and either hydrogen chloride or perchloric acid or containing formaldehyde, hydrogen chloride and perchloric acid. The solution may also contain an alkali chloride and a perchlorate and may be applied to the threads in one or more baths. The treatment may be effected in one bath at one temperature or at a continuously increasing temperature or in a number of baths at the same or successively increasing temperatures. In examples, the threads are produced by wet or dry spinning methods and are stretched, dried, heated under tension and treated in baths containing: (1) formaldehyde, hydrochloric acid and sodium chloride at 70 DEG C.; (2) formaldehyde, perchloric acid and sodium chloride at temperatures of 20 DEG C., successively raised to 70 DEG C. and 90 DEG C.; (3) in a first bath, formaldehyde, hydrochloric acid and potassium chloride at 20 DEG C., in a second bath, formaldehyde, hydrochloric acid and sodium chloride at 70 DEG C. and in a third bath formaldehyde and hydrochloric acid; (4) formaldehyde, hydrochloric acid, perchloric acid, sodium perchlorate and sodium chloride at a temperature continuously raised from 20 DEG to 80 DEG C., and (5) formaldehyde, hydrochloric acid and sodium perchlorate at 80 DEG C.