GB758560A - Improvements in or relating to a method for insolubilising artificial filaments obtained by the spinning of solutions of proteins - Google Patents

Abstract

Artificial filaments, obtained by spinning a solution of protein to form a bundle of protein filaments and hardening the filaments by treating them with a hardening agent, are insolubilized by impregnating the bundle of hardened filaments with an aqueous solution of formaldehyde having a pH greater than 6, and heating the bundle to such a temperature and for such a period of time that the filaments do not dissolve within 90 minutes in an aqueous solution of 0.1 per cent sulphuric acid and 0.25 per cent sodium sulphate at 97 DEG C. Preferably, after the impregnation with the aqueous formaldehyde solution the filaments are stretched, e.g. 200 per cent, and are held in the stretched condition while undergoing drying at least long enough that they no longer tend to shrink, prior to heating them to insolubilize them. The drying of the filaments, whether or not in the stretched condition, may be done at 15-160 DEG C. and the insolubilization at 120-180 DEG C. The pH of the formaldehyde solution may be 6.5-11 and preferably 6.5-7.5 or 9.5-11 and its concentration may be 10-37 grams formaldehyde per 100 c.c. of solution. The pH of the formaldehyde solution may be adjusted between 6.5 and 7.5 by means of sodium borate, aluminate, stannate, tungstate or hydroxide, ammonium hydroxide, potassium chromate or pyridine, or between 9.5 and 11 by means of sodium stannate, aluminate or hydroxide. The hardening agent is preferably an aqueous solution of formaldehyde which may also contain a high concentration of sodium chloride or sulphate and have a pH of about 4.5. The hardened filaments may be treated while still wet or after having been dried. Preferably, if the filaments are to be stretched while wet, the formaldehyde hardening should be effected in 10-15 minutes at 50 DEG C. In an example, filaments produced by spinning a matured alkaline solution of peanut globulin in an aqueous acid saline coagulating bath and relaxed in a concentrated aqueous saline bath are hardened for 7 minutes at 50 DEG C. in a bath consisting of 20 per cent sodium sulphate, 2.5 sodium chloride and 1.5 formaldehyde at pH 5, mangled, washed in water and dried at 80 DEG C. The filaments are then impregnated with 10 per cent formaldehyde solution adjusted to pH 7.5 with sodium hydroxide, mangled, dried at 80 DEG C. and heat treated for 30 minutes at 160 DEG C. Specifications 513,910, 533,952, 596,536, 597,497, [all in Group IV], 605,830, 623,460, 642,359, 654,513 and 708,057 are referred to.