NL70666C - - Google Patents

Abstract

521,148. Artificial silk &c. COURTAULDS, Ltd., and WORMELL, R. L. Oct. 13, 1938, No. 29703. [Class 2 (ii)] Threads which have been formed by extrusion of a solution of casein or like protein substance, e.g. soya bean protein, into a coagulant and have been thereafter treated with a hardening agent are further treated with a salt solution adjusted if necessary as regards its acidity, which brings the pH of the threads to a value at or about the isoelectric point of the protein. The excess moisture is removed from the threads and the latter are then heated in the presence of moisture. The salts used have a buffering action in solution over a pH range in the region of the isoelectric point of the protein, e.g. in the casein about pH 4.6. Sodium phosphate, phthalate, lactate, borate, or acetate, or aluminium acetate or substances forming it, e.g. aluminium sulphate and sodium or calcium acetate maybe used. If acetic acid is liberated in the formation of the solution it may be neutralized with sodium carbonate. The hardening solution may be aluminium sulphate solution or formaldehyde solution. After the hardening treatment the threads may be subjected to the treatment with salt solution with or without intermediate drying. Heating in presence of moisture may be effected in a closed container at a temperature of at least 50‹C. In an example a solution of casein in caustic soda solution is extruded into a salt and acid bath and the fibres are hardened with a solution containing aluminium sulphate, sodium carbonate and acetate, and formaldehyde. The fibres are washed and dried and then immersed in a solution of aluminium acetate made by mixing aluminium sulphate solution with lime and acetic acid, filtering off the calcium sulphate, and adding soda ash to neutralize excess acetic acid. The fibres are removed, whizzed free from excess liquor and heated in a closed vessel. In another example, casein fibres are hardened with aluminium sulphate, stapled, and then treated with a solution of sodium acetate, formaldehyde, and acetic acid. In another example, casein fibres on a conveyer are hardened with a solution of aluminium and sodium sulphates and formaldehyde. The fibres are then stretched in a solution of sodium acetate and acetic acid, wound up on a reel in a bath containing sodium acetate, acetic acid, and formaldehyde. The wound fibres are left in a closed vessel for several hours and then heated. They are then placed in cold water.