Patent GB-977945-A (GB)
Title: A method of producing fibres, filaments or films from regenerated cellulose
IPC: C02F1/52
Filed: 1961-10-17
Abstract: 977,945. Viscose spinning. PHRIX-WERKE A.G. Oct. 17, 1961 [Oct. 21,1960], No. 37224/61. Heading B5B. Regenerated cellulose filaments, fibres or films are made by extruding a viscose containing a viscose-soluble compound of arsenic and/or antimony into an aqueous spinning bath containing sulphuric acid, sodium sulphate and preferably zinc sulphate, the coagulated extrudate if in the form of filaments being stretched in a secondary bath and preferably cut to staple lengths, and the filaments or staple lengths being decomposed in conventional manner and finished without an alkaline aftertreatment, and the resultant filaments, staple lengths or films are finally treated in an aqueous solution of a salt of a metal which forms difficultly soluble sulphides for the purpose of converting the arsenic and/or antimony sulphide contained in the filaments, staple lengths or films. In this way a variety of coloured filamentary materials may be made. Thus the viscose may contain a trivalent arsenic compound in an amount up to 15% calculated as arsenic trioxide, based on the alpha cellulose. Specified salts are those of copper, lead, mercury, silver, platinum, gold, tin, cadmium, cobalt, nickel, iron, zinc, bismuth or antimony (if the filament, fibre or film contains arsenic sulphide), which are preferably used at pH 0-4, and those of iron, cobalt, nickel, zinc and cadmium, preferably used at pH 4-8, in the presence of buffer salts of strong alkalis with weak acids. Conversion treatment of the sulphides may be performed at 80-100‹ C. In a preferred method the conversion reaction between the filamentary materials containing arsenic and/or antimony sulphide and metal salts, especially salts of silver, copper, cadmium, zinc, cobalt and nickel, is performed in the presence of a mono- or polyvalent organic amine at pH 8-14, especially pH 7.5-10. The resulting metal sulphide containing filamentary materials, if coloured, may be after-treated with a salt of cadmium or zinc. Alternatively, the metal sulphide containing filamentary materials may be after-treated with an alkaline solution, preferably dilute sodium hydroxide, at an elevated temperature. In a modification, filamentary materials containing arsenic and/or antimony sulphide are treated with a compound of a metal, especially zinc, which is capable of displacing arsenic or antimony from its sulphide compound, and the products further treated with a salt of a metal having a greater affinity for sulphide sulphur than the metal used in performing the first treatment. Alternatively, filamentary materials containing arsenic and/or antimony sulphide are treated with a compound of a metal capable of forming an alkali-insoluble sulphide, and this treatment is followed by a further reaction of the sulphide-containing material with a salt of metal at pH 8-14. Pigments may be incorporated in the spun material prior to spinning. In examples, the metal salts are used in the form of their acetates, or salts of the metals with mineral acids are used in the presence of buffer salts of strong alkalis with weak acids.