Patent GB-979342-A (GB)
Title: Production of filamentary materials from difficultly meltable condensation polymers
IPC: D01F6/60
Filed: 1961-02-22
Abstract: 979,342. Synthetic filaments. CELANESE CORPORATION OF AMERICA. Feb. 22, 1961 [Feb. 25, 1960; Jan. 23, 1961], No. 6466/61. Heading B5B. Filamentary materials are made from difficultly meltable synthetic linear polymers having repeating -CO.NR- groups in the molecule, where R is hydrogen or a monovalent organic radical, by extruding a solution of such a polymer in sulphuric acid of at least 80% by weight concentration through an orifice into an acidic liquid coagulant to form the filamentary material, stretching it while still swollen with sulphuric acid and thereafter washing free from sulphuric acid and drying the stretched product. Difficultly meltable polymers include polyamides melting above 275‹ C., polyurethanes and polyureas melting above 179‹ C., especially above 210‹ C., and in general polymers containing cyclic groups, e.g. m- and p-phenylene cycloalkylene groups, e.g. 1,4-cyclohexylene and/or heterocyclic groups, e.g. piperazylene, as an integral part of the chain. A long list of suitable polymers is given. The polymer may be a polyamide melting above 275‹ C., preferably a poly-(polymethylene) terephthalamide in which the polymethylene groups contain 2-10 carbon atoms, e.g. polyhexamethylene terephthalamide, and may be dissolved in sulphuric acid of 95-100% concentration to give a polymer solution of 5-30% by weight concentration. A spinning temperature between 20‹ C. and 100‹ C. is preferred. Aqueous sulphuric acid of 40-60% by weight concentration may be used as the coagulant, maintained at 40- 60‹ C., the coagulant temperature and concentration being such as to fall within the closed area between curves A and B in Fig. 1. Aqueous formic and acetic acids may also be used as coagulants, suitably in concentrations of 52-68% by weight and 52% to 63% by weight respectively at temperatures of about 20‹ C., or in lower concentrations at higher temperatures. After being withdrawn from the coagulant the filaments may be further stretched in water or aqueous sulphuric acid of up to 30% by weight concentration at temperatures up to the boiling point of the solution. After washing free from acid, filaments may also be stretched in air while heated to an elevated temperature. Other liquid heating media which may be used for stretching include tetralin, toluene, heptane, benzene, methanol, methanol/ water mixtures, acetone, acetone/water mixtures and ethylene glycol. The filaments may subsequently be annealed, e.g. polyhexamethylene terephthalamide filaments may be annealed at 270‹ C. for a period of 5 minutes. In a preferred method, the solution is extruded downwards into the coagulant to form filaments which are passed round a guide where the filaments are substantially coagulated and are drawn upwards and out of the coagulant so as to stretch the filaments, the guide preventing the tension in the filaments passing back to the material leaving the extrusion orifice to an extent sufficient to cause breakage. In Fig. 2, spinning solution is supplied through pipe 10 to spinneret 11, below the surface of the coagulant 12. The filaments formed are pulled around guide 15 and taken up by the positivelydriven godet roll 16. The angle α may be varied from 5-70 degrees and the distance A varied from 12-100 inches, being preferably from 20-70 inches. Filaments of poly-(polymethylene) terephthalamides melting above 275‹ C. and having a tensile factor of at least 10, e.g. polyhexamethylene terephthalamides having tensile factors of from 10 to 25 may be made by the process of the invention. Specification 977,405 is referred to.