GB791775A - Process for the production of artificial threads and films from viscose - Google Patents

Abstract

In the production of artificial threads and films from viscose, from 0.01 to 1 per cent by weight of a condensation product, formed by the reaction of ammonia with an aldehyde containing two or more carbon atoms in the molecule in a 2 : 1 molar ratio, is added to a viscose of gamma value 42 or over, and the viscose is extruded into an aqueous coagulating bath containing 40-65 g./l. of sulphuric acid and over 30 g./l. of zinc sulphate. Thereafter the threads or films so formed are stretched by 80-120 per cent in a second aqueous bath at about 90 DEG C. containing 2-10 g./l. of sulphuric acid. The aldehyde may be acetaldehyde, crotonaldehyde or acrolein and, with ammonia and acetaldehyde, the molar ratio may alternatively be 1 : 1 or, with ammonia and acrolein, it may be 3 : 1. The viscose preferably contains 7-8 per cent of cellulose and 5-7 per cent of caustic soda. The coagulation bath preferably contains 160-200 g./l. of sodium sulphate and is advantageously at a temperature of 45-70 DEG C. In an example, a viscose containing 7.3 per cent of cellulose, 6.3 per cent of caustic soda and, based on the cellulose, 40 per cent of carbon bisulphide, with an addition of 0.2 per cent of a crotonaldehyde and ammonia condensation product (molar ratio 1 : 2) and having a gamma value of 42, is spun into an aqueous coagulating bath containing 65 g./l. of sulphuric acid, 245 g./l. of sodium sulphate and 50 g./l. of zinc sulphate. The filaments thus produced are stretched by 90 per cent in a second aqueous bath at 92 DEG C. containing 5 g./l. of sulphuric acid. The condensation product may be used without having been isolated from the reaction mixture. The threads produced have improved resistance to abrasion.