Patent GB-1006040-A (GB)
Title: Production of polyacrylonitrile fibres
IPC: D01F6/18
Filed: 1964-05-28
Abstract: 1,006,040. Polyacrylonitrile filaments. JAPAN EXLAN CO. Ltd. May 28, 1964 [June 5, 1963], No. 22174/64. Heading B5B. In the wet-spinning of polyacrylonitrile filaments, the coagulated polyacrylonitrile filaments containing a proportion by weight of solvent not exceeding 1À5 times the dry weight of polymer are dried until their water content is less than 1À5 times the weight of said solvent, the dried filaments stretched in a medium which will not appreciably extract said solvent, and the stretched filaments washed and dried. Homopolymers of acrylonitrile, copolymers of acrylonitrile with other olefinic monomers, block polymers, graft polymers and mixtures of said polymers may be used. Specified monomers include vinyl acetates vinyl esters of other monocarboxylic acids, acrylic acid, acrylic esters such as methyl acrylate and ethyl acrylate; methacrylic acid, methacrylic esters such as methyl methacrylate; vinyl chloride, vinylidene chloride, styrene, methacrylonitrile, vinylidene cyanide, vinyl pyridine and its substituted derivaties, other vinyl-substituted nitrogen-containing heterocyclic compounds such as vinyl imidazole; aliphatic and aromatic sulphonic acids having an unsaturated bond such as styrene sulphonic acid, allyl sulphonic acid and methallyl sulphonic acid and monoolefinic monomers capable of copolymerizing with acrylonitrile. Pigments, anti-colouring agents, stabilizers, plasticers and other conventional additives may be added to the polymer. The spinning solvent may be an organic solvent having a boiling point higher than that of water, e.g. N,N-dimethyl formamide, N,N,-dimethylacetamide, ethylene carbonate and dimethyl sulphoxide, or a concentrated aqueous solution of an inorganic salt, e.g. sodium thiocyanate, calcium thiocyanate, sodium perchlorate, calcium perchlorate, zinc chloride or lithium chloride. Coagulating baths specified include dilute aqueous solutions of the spinning solvent or non-solvents for the polymer and coagulation may be effected at room temperature. Stretching is preferably effected in hot air and washing in water. Crimping, application of finishing agents and cutting are then carried out, and the fibres dried. In Examples: (1) an acrylonitrile/ methyl acrylate/methacryl sulphonic acid copolymer is dissolved in 46% aqueous sodium thiocyanate and spun into 12% aqueous sodium thiocyanate at 20 C. The coagulated filaments are immersed in 4% aqueous sodium thiocyanate, removed, dried in air at 50 C., stretched in hot air, washed in cold water and dried at 150 C. (2) Coagulated gel filaments made as in (1) are immersed in 5% aqueous sodium thiocyanate, removed, dried, stretched in hot water, washed in hot water and dried at 105 C. (3) An acrylonitrile/methyl acrylate copolymer is dissolved in 50% aqueous sodium thiocyanate and spun into 75% aqueous sodium thiocyanate at 15 C. The coagulated filaments are dried at 50 C., stretched in hot air at 105 C., washed in cold water and dried at 105 C. (4) Dried gel filaments made as in (2) but before being subjected to stretching are stretched while being heated between infra-red lamps, washed with water and dried at 105 C. In general, stretch ratios of 5À3-9À9 and stretching temperatures of 60-200 C. are used. Filaments so made are dense, have a smooth surface, circular cross-section and a silk-like touch and lustre.