Patent GB-1145932-A (GB)
Title: Cushioning structure
IPC: D04H3/16
Filed: 1967-05-09
Abstract: 1,145,932. Cellular filaments; laminates. E. I. DU PONT DE NEMOURS & CO. 9 May, 1967 [23 June, 1966], No. 21518/67. Headings B5B and B5N. [Also in Divisions B2, B6, C3 and D1] A bonded web used as a carpet underlay is composed of randomly disposed cellular filamentary polymeric material. The cells in the filaments contain 6-40% wt. of an impermeant inflatant. The filaments, other than where they are distorted at the interfilamentary bonds, have a density of 0À008-0À06 g./c.c. The average ratio of the volume of the filaments to the total volume of the web is at least 0À4. Either continuous or staple filaments can be used. Preferably, (a) the undistorted filament portions have a major cross-sectional dimension of 0À635-6À35 mm. and a length : thickness ratio of at least 20 and (b) the web has a thickness of 0À25-2À5 cm. with a weight of filamentary material of 34 to 340 g./m.<SP>2</SP> The filaments can be made of polyolefins, e.g. linear polyethylene or stereo-regular polypropylene, polyamides, e.g. nylon-6, polyesters, e.g. polyethylene, terephthalate and polyhalohydrocarbons, e.g. polyvinyl chloride. The impermeant inflatant can be sulphur hexafluoride and fluorinated aliphatic or cycloaliphatic compounds, with or without ether or nitrogen linkages, e.g. perfluorocyclobutane, sym-dichlorotert tetrafluoroethane, chlorotrifluoromethane, dichlorodifluoromethane trichlorotrifluoroethane and chloropentafluoroethane. The web can be formed by air-laying filaments using water to assist in collection of the filaments. The web can be bonded by melting the filaments with a moving melting blade (Example VI) or by adhesive, e.g. polyurethane, a mixture of natural rubber, butadiene-styrene copolymer, sulphur, antioxidant, e.g. zinc oxide, surfactant and dispersant and/or a mixture of ethylenevinyl acetate copolymer and talc. The binder is applied to the web in solution as an aqueous dispersion or as a froth which is gelled in situ by CO 2 . The web, with or without prior bonding, can be heated, pressed and embossed. The web bonded with a thermoplastic binder can be expanded between spaced-apart metal plates by heating, Example V. The surfaces of the web can be covered with nets, non-woven fabrics, paper and foils of open-cell foams or films, such as those of polyethylene, polypropylene, polyvinyl chloride, polyurethane and polyethylene terephthalate. The foils can be bonded during a hot-embossing procedure, see Example III. Foamable compositions of rubber, polyurethane or neoprene containing an isocyanate can be coated on to the web, see Example VII. In order to silence the noise generated by filaments rubbing together during compression, the web, with or without prior bonding, can be dipped in an aqueous suspension containing polymethylsiloxanes, dibutyltindilaureate and zinc 2-ethyl hexoate, Example II. Formation of cellular filaments.-In Example I a heated mixture of dried polyethylene terephthalate, trichlorotrifluoroethane, perfluorocyclobutane and a foaming agent, e.g. methylene chloride, ethylene chloride, dichloroform or carbon tetrachloride is extruded into filaments. The extruding vessel has 5 holes each 0À003 x 0À006 inch and a sandwich of 50 and 325 mesh screens upstream of the holes. The mixture is shaken at 213 C. and extruded using nitrogen at 1200 p.s.i.g. The collapsed filaments are heated to 120 C. to diffuse air into the closed cells of the filaments. The cells also contain some of the halohydrocarbons as inflatant. In Example II samples of webs produced similarly to those of Example I can be autoclaved with a mixture of methylene chloride and perfluorocyclobutane resulting in only the latter fluorocarbon being present in the cells as inflatant. In Example III, perfluorocyclobutane is introduced into chopped cellular filaments by immersing them in a bath containing methylene chloride and perfluorocyclobutane. In Example VI collapsed filaments are made by extruding a methylene chloride solution of polyethylene terephthalate through a single 0À075 inch diameter hole. Extrusion was at 800 p.s.i.g. and 206-208 C. A pack of 20, 100 and 200 mesh screens was placed upstream of the hole. The filament is formed into a web which is then immersed in a mixture of methylene chloride and perfluorocyclobutane. The web is then removed and heated. The web produced contains the fluorocarbon as inflatant within the filament cells. Alternative filament polymers and inflatants are given above.