Patent GB-1235021-A (GB)
Title: Acrylonitrile polymer fibers
IPC: D01F6/18
Filed: 1969-05-30
Abstract: 1,235,021. An improved polyacrylonitrile fibre and its manufacture. MITSUBISHI RAYON CO. Ltd. 30 May, 1969 [19 June, 1968], No. 27662/69. Heading B5B. [Also in Division C3] Polyacrylonitrile filaments are produced by dissolving in a solvent a blend of 50 to 95 parts of an acrylonitrile-methacrylonitrile copolymer containing 40 weight per cent or less of methacrylonitrile and 50 to 5 parts of an acrylonitrile polymer containing 95 to 50 weight per cent acrylonitrile, the remainder being monomers which decrease the crystallinity of the acrylonitrile polymer (decry stallizing monomers), wet or dry-spinning the resulting solution, stretching the thus formed filaments followed by relaxing. A list of decrystallizing monomers is given in the Specification, and they may be illustrated from the examples which use vinyl acetate in combination with p-sulphophenyl methallyl ether and methyl acrylate in combination with sodium p-vinyl benzene sulphonate or sodium methallyl sulphonate. The acrylonitrile/methacrylonitrile copolymer preferably has a specific viscosity of 0À13 to 0À18 and the acrylonitrile polymer has a specific viscosity of 0À10 to 0À25, both measured in dimethylformamide at 25‹ C. and at a concentration of 0À1 g./100 ml. The solvent for the polymer blend may be selected from N,N<SP>1</SP>- dimethylformamide, N,N<SP>1</SP>-dimethylacetamide, dimethylsulphoxide, and γ-butyrolactone. In the preferred embodiment for dry spinning a spinning solution of 15 to 35 weight per cent polymer blend in dimethylformamide, with a viscosity of 500 to 2500 poises at 50‹ C. is extruded through a spinneret at 80‹ to 170‹ C. into an atmosphere at 80‹ to 300‹ C. at a draft ratio of 0À4 : 1 to 50 : 1 and the filaments thus formed are stretched from 1À5 : 1 to 7 : 1 in water above 60‹ C. The stretched filaments containing 0À3 to 10 times the weight of water of the dried filaments may thereafter be treated in a slack state with an atmosphere of temperature and humidity within the range enclosed by the points on Fig. 7 (not shown) and thereafter dried at 100‹ to 200‹ C. and heat treated at 80‹ to 280‹ C. in a slack state to shrink the filaments more than 7%. In the preferred embodiment for wet-spinning a spinning solution of 10 to 30 weight per cent polymer blend in an organic solvent, with a viscosity of 50 to 2000 poises at 50‹ C. is extruded through a spinneret into a coagulation bath containing the same organic solvent at a draft ratio of from 0À3 : 1 to 10 : 1 and the filaments thus formed are stretched 1À5 : 1 to 10 : 1 in boiling water. The stretched filaments containing 0À3 to 3 times the weight of water of the dried filaments may thereafter be treated in a slack state with an atmosphere of temperature and humidity within the range enclosed by the points on Fig. 7 (not shown) and further dried at 80‹ to 200‹ C. to shrink the filaments more than 7%. The acrylonitrile polymer fibres thus produced have a Young's Modulus in water at 90‹ C. of at least 1À5 g./d., good antifibrillation properties (F value as defined in Specification of not more than 2À0) and at least 70% dye absorption when dyed in a bath containing 5% owf of Deorlene Blue 5G at 100‹ C. for 2 hours. The knitted fabrics have improved dimensional stability and antipilling properties.