GB657686A - Improvements in or relating to a method for improving the strength of artificial insolubilised protein filaments - Google Patents

Abstract

Artificial protein filaments which have been rendered insoluble by treatment with saline solutions adapted to form monomeric thioformaldehyde or the trimer thereof in situ, these solutions containing formaldehyde or a compound which will yield formaldehyde under the conditions of the treatment, a salt of a reducing sulphur acid in which the atomic proportion reckoned on the anhydrous salt of oxygen, if present, to sulphur, does not exceed 2 : 1, and an acid which does not oxidize the salt of the sulphur acid and which is completely ionized in dilute aqueous solution, are treated under tension with an aqueous solution of mercuric chloride, whereby the strength of the filaments is increased. The filaments are preferably stretched to about 350 per cent of their original lenth, while undergoing treatment with the mercuric chloride solution, preferably at a temperature of 70-80 DEG C. and preferably in the presence of hydrochloric acid. In the example filaments formed by extruding an aged solution of groundnut protein in an aqueous solution of sodium hydroxide into an aqueous sulphuric acid-sodium sulphate coagulating bath in known manner are rendered insoluble by treatment in a saturated sodium chloride solution containing formaldehyde, hydrochloric acid and sodium sulphide. The filaments are then washed free from acid and dried at 110 DEG C. The insolubilized tow thus obtained is then stretched for about 30 minutes to a point just short of breakage in a bath consisting of a 3 per cent solution of mercuric chloride in 0.1 normal aqueous hydrochloric acid at 70 DEG C. The tow, which may now be 350-450 per cent of its original length, is then washed in running water and dried at 108 DEG C. The thus insolubilized filaments are increased in wet strength by about 60 per cent and in elongation at break when dry by about 200 per cent. The elongation at break of the wet filaments is decreased by 50 per cent. Specifications 533,952 and 639,342 are referred to.