Patent GB-870701-A (GB)
Title: Treatment of polyacrylonitrile textile articles
IPC: D06M15/244
Filed: 1959-12-21
Abstract: A permanent finish is imparted to polyacrylonitrile textile articles, i.e. threads, fibres and yarns consisting of polymers of which at least 85% by weight is acrylonitrile and woven, knitted or made-up articles produced from these threads, fibres or yarns, by impregnating them with a composition consisting of a latent solvent for the textile article and a polymer which is soluble, at least on heating, in the solvent, at a temperature below that at which the textile article spontaneously dissolves in the latent solvent, and then drying the impregnated article at a temperature at least equal to the temperature at which the textile article dissolves in the latent solvent.  A "latent solvent" is defined as being a liquid which does not spontaneously dissolve the textile article below a certain temperature but does dissolve it at higher temperatures, it being possible to keep the textile article in the latent solvent below the said temperature for at least one hour without modification and then to effect dissolution by simply heating the mass.  Specified latent solvents when the textile article consists of an acrylonitrile homopolymer are dimethylformamide, dimethylacetamide, dimethyl sulphoxide and g -butyrolactone and mixtures thereof.  The polymer, which is preferably used at a concentration of 0,1-15% by weight in the latent solvent, may be a cellulose derivative, e.g. cellulose acetate, or a completely synthetic polymer, e.g. a polyolefine, a vinyl polymer, e.g. polyvinyl acetate and polyvinyl chloride, or an acrylic polymer, a soluble polymer containing 85-100% by weight of acrylonitrile and up to 15% by weight of another copolymerizable ethylenically unsaturated monomer being particularly suitable.  After impregnation excess liquid may be removed from the textile article prior to drying, which may be carried out at temperatures higher than 100 DEG C.  The textile article may be shaped, e.g. folded, crimped, calendered or embossed, before, during or after immersion in the treatment solution but before drying.  Examples III, VI and VII describe the treatment of tubes woven from highbulk "Helanca" (Registered Trade Mark) type polyacrylonitrile thread to which are imparted circularly disposed pleats prior to or after impregnation with a solution of polyacrylonitrile in dimethylformamide but prior to drying, the tubes being suitable for arterial prosthesis. Specification 825,183 also is referred to.ALSO:A tube woven from high-bulk Helanca-type polyacrylonitrile threads (the word "Helanca" is a Registered Trade Mark), suitable for use as an arterial prosthesis, is impregnated with a solution of polyacrylonitrile in dimethyl formamide at 25 DEG  C., prior to or after imparting thereto circularly disposed pleats, and then dried at 120 DEG  C.  The tube may be pleated by pulling it on to a glass rod, arranging it in folds along the rod and steaming, and then impregnated with the polyacrylonitrile solution, or the tube may be impregnated with the polyacrylonitrile solution, arranged in folds along the glass rod and then dried at 120 DEG  C.  Specification 825,183 is referred to.