Patent GB-1109729-A (GB)
Title: Method for the production of polyacrylonitrile conjugate filaments
IPC: D01F8/08
Filed: 1966-09-22
Abstract: 1,109,729. Conjugate polyacrylonitrile filaments. JAPAN EXLAN CO. Ltd. 22 Sept., 1966 [25 Sept., 1965], No. 42418/66. Heading B5B. In a process for the production of a helically crimped conjugate filament there are concurrently spun at least two solutions differing in concentration, of polyacrylonitrile or of a copolymer of acrylonitrile with an ethylenically unsaturated monomer copolymerizable therewith, the resulting spun gel filament is stretched, dried without tension at a temperature below 80‹ C. and the dried filament steamed in a relaxed but confined state at a temperature of at least 110‹ C. The polymers used are composed mainly of acrylonitrile, and include copolymers of acrylonitrile with vinyl monomers copolymerizable therewith, as well as blends with other polymers. Such vinyl monomers and other ethylenically unsaturated compounds copolymerizable with acrylonitrile include vinyl acetate, vinyl chloride, vinylidene chloride, acrylic acid, methacrylic acid, and other acrylic acid derivatives, acrylamide, N-methylolacrylamide and homologues thereof, vinylpyridine and homologues thereof, allyl sulphonic acid, methallyl sulphonic acid and its derivatives, as well as all other monomers copolymerizable with acrylonitrile. Preferably, the difference in concentration of the polymer solutions is greater than 2% by weight, and the filament to be steamed is arranged in a container and the container is then turned through 90 degrees, so that the parallel lengths of filaments become parallel with the direction of the force of gravity, in which state the tension forces acting on the individual filaments are minimized. The container may suitably be made of wire netting or foraminated plates, and the filament may be packed into the container at an apparent density of from 0À2 to 0À005 g. per c.c. Suitably, the polymer is dissolved in an aqueous solution of sodium thiocyanate, nitric acid, zinc chloride, dimethylformamide or dimethylsulphoxide and the resulting spinning solution is wet-spun employing an aqueous coagulating bath. In an example, a copolymer consisting of 90% acrylonitrile, 9À5% methyl acrylate, and 0À5% sodium methallyl sulphonate is dissolved in 49% aqueous solutions of sodium thiocyanate to prepare two kinds of spinning solutions, the copolymer concentrations of which are respectively 8À5 and 11%. Equal parts of the spinning solutions are extruded through an extrusion apparatus into a 10% aqueous solution of sodium thiocyanate at 0‹ C., and the resulting filament is washed with water at 30‹ C. and then stretched in boiling water to nine times its initial length. Tows of this filament are then dried in hot air streams at 40‹, 60‹ and 80‹ C., respectively, under no tension, for 60 minutes. The samples are then allowed to fall in parallel folds into a container of foraminated plates, so that each fold of the tow measures about 20 cms. and the apparent density of the filament is about 0À05 g. per c.c. The container is closed with a foraminated cover and then turned through 90 degrees. In this state, the filament is subjected to a crimp-setting and heat-relaxation treatment in saturated water vapour for 10 minutes at 125‹ C. The treated filaments are then stretched 20% in hot water at 95‹ C. and at room temperature until the crimps disappear completely. When the individual filaments are immersed in hot water at 95‹ C. in a relaxed state, the three-dimensional coiled crimps are restored.