GB552227A - Extrusion of synthetic polymeric materials - Google Patents

Abstract

552,227. Extruding synthetic polymeric substances ; polyamides. DU PONT DE NEMOURS & CO., E. I. Sept. 19, 1941, No. 12026. Convention date, April 23. [A Specification was laid open to inspection under Sect. 91 of the Acts, Oct. 5, 1942.] [Classes 2 (ii) and 2 (iii)] [Also in Group V] Thermoplastic polymerized aliphatic hydrocarbons or compositions containing the same are extruded at temperatures substantially above their normal decomposition temperatures, whereby improved properties, e.g. freedom from cracking, are obtained. Polymerized ethylene (decomposition temperature 220‹C.) is extruded at 250‹C., an interpolymer of ethylene and vinyl acetate containing 10 per cent. of vinyl acetate (175‹C.) at 225‹C., an interpolymer of ethylene and methyl methacrylate containing 15 per cent. of the latter (210‹C.) at 250‹C., and an interpolymer of isobutylene and butadiene containing 20 per cent. of the latter (160‹C.) at 180‹C. The material is passed quickly through the extrusion orifice, e.g. around a wire passing therethrough, and is then cooled rapidly. The decomposition temperature of any given composition may be ascertained by heating it in a test-tube and noting the point at which a slight darkening or change of colour occurs. Specification 538,716 [Group V], is referred to. The Specification as open to inspection under Sect. 91 describes also the extrusion, at temperatures above their decomposition temperatures, of compositions containing polyvinyl halogen-containing materials and of compositions containing synthetic linear polyamides. Thus, (a) granules of a composition comprising 60 per cent. polyvinyl chloride plasticized with 40 per cent. tricresylphosphate are extruded at 185‹C. (b) the composition of (a), plus filler, is extruded at 180-190‹C. (c) polyvinyl chloride (decomposition temperature 165‹C.) is extruded at 180-185‹C.; (d) a composition containing 67 parts of polyvinyl chloride, 33 of tricresylphosphate and 0.2 of urea is extruded on to wire; (e) a composition containing 67 parts of a copolymer of vinyl chloride and methyl acrylate, 33 of tricresyl phosphate and 0.02 of urea (decomposition temperature 168‹C.) is extruded at 175‹C.; (f) a composition containing 75 parts of vinyl chloride/vinyl acetate interpolymer (85 chloride, 15 acetate), 25 of tricresyl phosphate and 0.75 of calcium stearate (decomposition .temperature 132‹C.) is extruded at 160‹C.; (g) a composition containing 72.5 per cent. polyhexamethylene adipamide, 12.5 per cent. polyhexamethylene sebacamide and 15 per cent. N-, ethyl-, ortho- and paratoluene sulphonamide as plasticizer is extruded at 240‹C.; (h) a composition comprising 65 per cent. polyhexamethylene adipamide, 25 per cent. polyhexamethylene sebacamide and 15 per cent. N, ethyl-, ortho- and paratoluene sulphonamide is extruded at 235‹C. The decomposition temperature for polyvinyl halogen-containing compositions may be determined by test-tube, as above, and for polyamides may be determined by spreading a thin line of finely-ground polyamide across a melting bar and noting the temperature at which charring takes place within 15 minutes. In extruding polyamide compositions the apparatus may be heated by oil or diphenyl. This subject-matter does not appear in the Specification as accepted.