GB995848A - Oxymethylene polymer filaments of high strength - Google Patents

Abstract

High tenacity filaments are made by extruding a liquid comprising an oxymethylene polymer, at a temperature such that substantially no gas formation by thermal degradation of the polymer occurs, through a spinning orifice, solidifying the extruded polymer into filamentary form and stretching the material in two successive drawing operations. There may be used an oxymethylene polymer having in the molecule successively recurring units of the formula <FORM:0995848/C3/1> where n is an integer from 0-5 and is 0 in from 75-99.5% of the recurring units, and preferably such a polymer having successively recurring units of the formula (-O-CH2-(CH2)n-), where n is an integer from 0-2 and is 0 in from 75-99.5% of the recurring units. Melt, dry-and wet-spinning processes are described. The extruded liquid may be a melt which contains besides the oxymethylene polymer, up to 50% by weight, especially 1-40%, based on the weight of polymer, of a substance which reduces the viscosity of the molten polymer, especially a formamide, e.g. formamide itself, N,N-dimethyl formamide and N-methyl-N-phenyl formamide. Other suitable substances are phenols, e.g. phenol, 3,4-xylenol, #s-cyclohexyl phenol and a -naphthol; halogen substituted aliphatic hydrocarbons, e.g. sym.-tetra-chloroethane and ethylene dibromide; lactones, e.g. g -butyrolactone; aromatic amines, e.g. aniline and #s-toluidine, and aryl phosphates, e.g. tricrysyl phosphate and trixylenyl phosphate. The oxymethylene polymer may also include one or more thermal stabilizers, preferably in a proportion of 0.05-10% by weight of the polymer. A suitable stabilizer system is a combination of an antioxidant, for example a phenolic compound, especially a substituted bis-phenol, and an ingredient to inhibit chain scission, generally a compound or polymer containing trivalent nitrogen atoms. Suitable alkylene bis-phenols are those having 1-4 carbon atoms in the alkylene group and 0-2 alkyl substituents on each benzene ring, each alkyl substituent having 1-4 carbon atoms, e.g. 2,21-methylene bis-(4-methyl-6-tert. butyl phenol) and 4,41-butylidene bis - (6 - tert. butyl - 3 - methyl phenol). Other phenolic stabilizers specified include 2,6-ditert. butyl-4-methyl phenol, octyl phenol and p-phenyl phenol. Suitable scission inhibitors include carboxylic polyamides, polyurethanes, substituted polyacrylamides, polyvinyl pyrrolidone, hydrazides, compounds having 1-6 amide groups, proteins, compounds having tertiary amine and terminal amide groups, compounds having amidine groups, cycloaliphatic amine compounds and aliphatic acyl-ureas. Those specified include malonamide and cyanoguanidine. Melt-spinning may be carried out at 140-230 DEG C., in the absence of a viscosity reducing substance, temperatures up to 40 DEG C. lower being used in the presence of such a substance, and the filaments formed may be wound up at 1-250 ft. per sec. Solution spinning temperatures of 125-210 DEG C. may be used, the polymer concentration in the solution being 5-25% by weight. Suitable spinning solvents include dimethyl formamide, benzyl alcohol, anisole and butyro lactone. Such spinning solutions may be dry-spun, or, where lower temperatures are used, may be wet-spun into a non-solvent liquid, e.g. water, hydrocarbons, and alcohols. The filamentary material may be stretched continuously with the spinning process or as a separate operation, suitably 3-15 times the original length at 60-160 DEG C., especially 120-150 DEG C., in the first stage, and 1.05-6 times the drawn length, especially 1.05-2 times, at 100-165 DEG C., especially 150-160 DEG C., in the second stage. Conventional drawing means are used. Filaments so made have a tenacity exceeding 7 g./denier, e.g. 9-14 g./denier, a modulus between 50-180 g./denier and an elongation of 10-25%.