GB787588A - Improvements in or relating to a method for insolubilising artificial filaments, threads, fibres and the like of regenerated protein - Google Patents

Abstract

Insolubilized artificial filaments are produced from a bundle of regenerated protein filaments (obtained by spinning an aqueous solution of natural protein into an aqueous acidified saline coagulating bath followed by an aqueous saline relaxing bath), by treating the bundle with an acidified aqueous solution having a pH up to 4 (preferably 1.5 to 3) of at least one salt, said salt being such that, if the bundle is immersed in an aqueous solution thereof and then washed and dried, it contains discrete filaments, then treating the bundle with an acidified aqueous solution of formaldehyde in the presence of at least one of the salts at a pH not over 3.0 (preferably not over 1.5), washing the bundle free from salts, impregnating the filaments of the bundle with an acidified aqueous solution of formaldehyde which is free from salts, stretching the filaments, holding the filaments in the stretched condition while undergoing drying at least for such a period of time that they no longer tend to shrink, and heating the bundle while the filments are free to relax to a temperature and for a time to effect insolubilization. The salts may be alkali metal salts of hydrochloric, sulphuric or phosphoric acid, or ammonium, magnesium or aluminium, sulphate or sodium zirconyl sulphate. The salt solution should preferably have a concentration of over 5 per cent and may contain, for example, 24 per cent of sodium sulphate, 20 per cent of magnesium sulphate and 6 per cent of aluminium sulphate or 10 per cent of sodium zirconyl sulphate. The formaldehyde solution may contain 10-20 grams of formaldehyde per 100 cc. of solution. The drying of the filaments may be effected at 15-160 DEG C. and insolubilization at 140-220 DEG C. In an example a bundle of filaments formed by spinning a solution of groundnut protein is stretched 400 per cent in a coagulating bath, relaxed in a bath containing 24 per cent of sodium sulphate and 2.5 per cent of sodium chloride at pH 8 to 9 for 5 minutes at 25 DEG C., treated in a bath containing 24 per cent of sodium sulphate adjusted to pH 4 with sulphuric acid for 10 minutes at 70 DEG C., then treated in a bath containing 24 per cent of sodium sulphate and 1.5 per cent of formaldehyde adjusted to pH 2 with sulphuric acid for 5 minutes at 50 DEG C., washed with water and dried at 80 DEG C. The filaments are then impregnated with a 10 per cent formaldehyde solution brought to pH 1.0 with hydrochloric acid, mangled, stretched 300 per cent in air, dried while stretched at 80 DEG C. until they no longer tend to shrink, and heat-treated for 30 minutes at 160 DEG C., while free to relax. Specifications 513,910, 533,952, 597,497, 605,830, 623,460, 642,359, 741,497, 742,261, 742,890, 758,560, 770,662 and 785,881 are referred to.