GB656467A - Manufacture of artificial fibres - Google Patents

Abstract

In the manufacture of fibres and like structures from synthetic linear hydroxylated polymers, having at least one alcoholic hydroxyl group per 2.5 carbon atoms but not more than one hydroxyl group per 2 carbon atoms of the polymer chain, an aqueous solution of the polymers is coagulated in an aqueous solution of an inorganic salt and the wet spun filaments are drawn to at least twice their initial length, under tension, which produces molecular orientation along the filament axes to an extent such that they are insufficiently softened by water to cause sticking of the filaments upon drying. The drawn filaments are then washed with water to remove the salt and dried while maintained at at least twice their initial length. The synthetic polymers used include polyvinyl alcohol and hydrolysed polyvinyl ester polymers and copolymers having hydroxyl to chain carbon ratios within the range specified. In addition the hydrolysed copolymers of vinyl esters with ethylene or vinyl chloride can be employed. The polymers are dissolved in hot aqueous solution, usually to the extent of 5-20 per cent by weight, to which small proportions of water-soluble aliphatic alcohols, amines or mercaptans may be added. For difficulty soluble polymers, mixtures of an alkali metal hydroxide and carbon bisulphide may be used as adjuvants. The coagulating bath is an aqueous, nearly saturated, solution of one or more inorganic alkali metal salts such as sodium sulphate, disodium hydrogen phosphate or potassium sulphate in a salt such as ammonium chloride or zinc sulphate. An aqueous solution of mono-sodium dihydrogen phosphate having a specific gravity of about 1.4 at 25 DEG C. is preferred. From 0.005 to 0.05 per cent by weight of a cationic surface-active agent such as acetyl trimethyl pyridinium bromide may be present, the bath being usually saturated with the agent. The bath temperature is usually 5-80 DEG C. and the drawing tension is at least 0.05 gram per denier. The tensioning of the yarn is stated to produce molecular orientation of the polymers along the filament axes and a description is given of the method used for determining the "orientation numbers" of yarns which have been subjected to varying degrees of tension. Data are furnished showing the "orientation numbers" corresponding with various tensions. Examples are given, and Specification 499,334, [Group III], is referred to.