Patent GB-991496-A (GB)
Title: Polyvinyl chloride textile fibres and method of manufacturing
IPC: C21C5/52
Filed: 1963-04-08
Abstract: 991,496. Polyvinyl chloride filaments. A.C.S.A. APPLICAZIONI CHIMICHE S.p.A. April 8, 1963 [April 6, 1962; Sept. 27, 1962 (2); Nov. 14, 1962 (2)], No. 13936/63. Heading B5B. A solution of a high DS vinyl chloride polymer in cyclohexanone is wet spun into a coagulating bath comprising cyclohexanone and the resulting filaments stretched and heat-treated, the method being characterized in that:- (a) the spinning solution is formed by dissolving in cyclohexanone at a temperature between 110‹ C. and 156‹ C. the high-DS vinyl chloride polymer of a mean molecular weight between 50,000 and 120,000 in an amount providing a gel-free solution containing between 15 and 20% by weight of said polymer; (b) the gel-free solution is supplied to and through the spinneret at a temperature above the gelation temperature; (c) the filaments are stretched to a draw ratio of at least 7 at a temperatue between room temperature and 100‹ C.; (d) the heat-treatment comprises conditioning the stretched filaments at a temperature between 180‹ and 220‹ C. over a period between 0.I and 10 sees. while keeping the stretched filaments under tension; and then relaxing the conditioned filaments at a temperature between 100‹ and 120‹ C. over a period between 1 and 60 mins. High-DS vinyl chloride polymers are defined as those obtained by low-temperature polymerization which have a D635 to D693 absorption ratio of at least 1À8, this rate being defined as the degree of syndiotacticity (DS). Both vinyl chloride homopolymers, and copolymers containing at least 85% vinyl chloride, with e.g. vinyl acetate, methyl acrylate or methyl methacrylate or vinylidene chloride, prepared by low-temperature polymerization may be used. Up to 15% of cyclohexanonesoluble polymers or copolymers having basic groups in their molecular structure, e.g. a 50/50 copolymer of acrylonitrile and 2-methyl-5-vinyl pyridine, may be incorporated to improve receptivity towards acidic dyes, while up to about 2% of acidic monomers e.g. cinnamic acid, itaconic acid, or sodium-p-sulphoxyphenyl-vinyl ether may be incorporated to enhance receptivity towards basic dyes. A stabilizing agent may be added to the cyclohexanone at the solution-forming stage, said agent being selected from the following compounds:-  (a) Phenates of zinc, barium or cadmium. (b) Tin-organic compounds having structural formulµ where R 1  and R 2  are selected from alkyl, aryl, and aralkyl radicals, ,R 3  and R 4  from alkyl and acyl radicals, and R 5  and R 6  from alkyl radicals. Examples include dibutyl-Sn-mercaptans, dibutyl-Sn-maleate and dibutyl-Sn-oxide, added in a proportion of 0À1 to 2.0% by weight based on the high-DS P.V.C. The coagulating bath may be held at a temperature not exceeding 80‹ C., especially between 40‹ and 70‹ C., and preferably comprises a ternary solution of 15-50% by weight cyclohexanone, correspondingly 70-20% water, the balance being provided by a mutual solvent for cyclohexanone and water, e.g. methyl alcohol, ethyl alcohol, isopropyl alcohol, tert.-butyl alcohol, polyethylene glycol of molecular weight 400-1500, acetone, acetic acid, nitric acid, sulphuric acid, phosphoric acid and hypophosphorous acid. After removal from the coagulating bath and stretching either in a single stage at 98-100‹ C.; or in three or four stages each at a temperature not exceeding 100‹ C., suitably in hot water or saturated steam, the stretched filaments may be treated with an aqueous finishing bath and then dried at 100-140‹ C.; the filaments being kept under tension meanwhile. Stabilizing agent may be added to the finishing bath in an amount making up for loss of said agent from the filaments in the coagulating bath. Heat-conditioning may be effected in superheated steam or inert gas, and relaxation may be effected in an autoclave or in a continuous-treatment chamber through which steam is circulated. Fibres so made have a tensile strength of at least 2.5 g./ denier, elongation at break of 25-60%, boiling water shrinkage of less than 2%, shrinkage in trichloroethylene at 40‹ C. of less than 2% and flex-abrasion resistance exceeding 600 cycles. In the apparatus of Fig. 1, cyclohexanone and high-DS polyvinyl chloride are supplied to the mixer 21, maintained at 110-156‹ C., and the solution pumped by pump 22 to spinneret 23, both the mixer 21, pump 22 and spinneret 23 as well as the solution-conveying conduits being surrounded by a heating jacket 44, and the face of the spinneret 23 being immersed just below the level of the coagulating bath 24. The filaments are stretched between roller pairs 25, 27 while passing through the hot water tray 26, passed through finishing bath 30, rollers 28 having the same peripheral speed as rollers 27, dried by passing over the internally heated rolls 31, conditioned in chamber 32 to which superheated steam is supplied from superheater 33, and delivered by the rolls 29 to the container 34, preferably made of foraminated sheet metal, which is then placed in an autoclave to effect relaxation of the filaments.