Patent GB-1113921-A (GB)
Title: Production of flexible materials
Inventor: CLARKE DENNIS IVOR
IPC: D04H1/4291
Filed: 1964-07-22
Abstract: Microporous flexible materials are produced by forming a mixture of an emulsion of a silicone-oil with a rubber latex and one or more vulcanizing agents for the rubber, the silicone oil preferably being present in amounts of at least 6% by weight, gelling the mixture so obtained and heating the gelled mixture to effect vulcanization of the rubber under conditions such that escape of water from the gelled mixture is substantially prevented.  The rubber may be a natural rubber latex, a graft copolymer of natural rubber and methyl methacrylate, or a synthetic rubber latex based on, e.g., a copolymer of styrene and butadiene, polyisoprene, polyisobutylene, polybutadiene or a copolymer of ethylene and propylene with or without a third monomer conferring unsaturation.  The silicone oil is preferably a linear methyl polysiloxane having a viscosity in the range from 10 to 12,500 cSt. at 25 DEG  C.  The mixture is preferably gelled under hot water or in an atmosphere of steam.  The ungelled mixture, e.g. a mixture based on natural rubber, may be used to impregnate a compressed reticulated polyether polyurethane foam (Example 3).ALSO:Microporous flexible materials are produced by forming a mixture of an emulsion of a silicone-oil with a rubber latex and one or more vulcanising agents for the rubber, the silicone oil preferably being present in amounts of at least 6% by weight, gelling the mixture so obtained and heating the gelled mixture to effect vulcanisation of the rubber under conditions such that escape of water from the gelled mixture is substantially prevented.  The rubber may be a natural rubber latex, a graft copolymer of natural rubber and methyl methacrylate, or a synthetic rubber latex based on e.g. a copolymer of styrene and butadiene, polyisoprene, polyisobutylene, polybutadiene or a copolymer of ethylene and propylene with or without a third monomer conferring unsaturation. The silicone oil is preferably a linear methyl polysiloxane having a viscosity in the range from 10 to 12,500 cSt at 25 DEG C.  The mixture is preferably gelled under hot water or in an atmosphere of steam.  The ungelled mixture may be used to coat a fabric, e.g. in Example 8 an open-mesh rayon fabric is coated by spreading using a doctor blade with a mixture of natural rubber latex, curing agents, several dimethyl polysiloxanes of different viscosities, aqueous NH4Cl and a pigment, and the coating is gelled and cured in a steam oven.  In Example 3 the ungelled mixture is used to impregnate a compressed microcellular polyurethane foam.  The products obtained are water-impermeable but water-vapour permeable.ALSO:Microporous flexible materials are produced by forming a mixture of an emulsion of a silicone-oil with a rubber latex and one or more vulcanising agents for the rubber, the silicone oil preferably being present in amounts of at least 6% by weight, gelling the mixture so obtained and heating the gelled mixture to effect vulcanisation of the rubber under conditions such that escape of water from the gelled mixture is substantially prevented.  The rubber may be a natural rubber latex, a graft copolymer of natural rubber and methyl methacrylate, or a synthetic rubber latex based on e.g. a copolymer of styrene and butadiene, polyisoprene polyisobutylene, polybutadiene or a copolymer of ethylene and propylene with or without a third monomer conferring unsaturation.  The silicone oil is preferably a linear methyl polysiloxane having a viscosity in the range from 10 to 12,500 cSt at 25 DEG  C.  The vulcanising agent may be sulphur and potassium oleate, di-beta naphthyl -para-phenylenediamine, zinc diethyl dithio carbamate, zinc mercapto benzthiazolen, zinc oxide and ammonium chloride may also be present.  The mixture is preferably gelled under hot water or in an atmosphere of steam. The ungelled mixture may be used to impregnate a fibrous mat, e.g. a consolidated mat of interpenetrated crimped continuous fibres or crimped or uncrimped staple fibres, or an extruded net.  The mat can be formed by carding, cross-lapping or air-laying.  The mat may be needled and may be joined from several layers. Specified fibres which may be used are nylon, polyethylene terephthalate, polyacrylonitrile, polyolefin, rayon and silk fibres.  In examples, compositions based on natural rubber latex are used to impregnate a composite web of polypropylene staple fibre needled to a web of crimped nylon fibre.  The surface of impregnated sheet can be buffed.  The product when gelled is water-impermeable but water vapour-permeable and may be used as a leather-substitute.