Abstract: To provide the heat-meltable fluorine-containing resin fiber having excellent intermingling property and various materials for fiber products obtained therefrom. The heat-meltable fluorine-containing resin such as ETFE having a branched structure is used solely or mixed to other fiber such as an electrically conductive fiber to be formed into a non-woven fabric.

Abstract: A material for electrode which is excellent in electric conductivity, gas permeability, water repellency and chemical resistance and has enhanced handling property, moldability and processability is provided. A gas diffusion electrode for a fuel battery which is obtained by using a non-woven fabric comprising a fluorine-containing resin fiber and electrically conductive fiber as a material for electrode is formed.

Abstract: To provide various members such as filter cloth for dust collection which assures small pressure loss and easy shaking down of dust particles and is excellent in friction property and mechanical strength, sliding member excellent in sliding property, water repellent member excellent in water repellency, non-sticking member excellent in non-sticking property and member for supplying mold releasing agent in electrophotographic apparatuses which is excellent in air permeability, heat resistance and oil resistance, and provide a multilayered felt used therefor and a process for producing the multilayered felt. The multilayered felt is obtained by placing a layer of a web comprising polytetrafluoroethylene staple fibers on at least one surface of a felt and then joining the polytetrafluoroethylene staple fibers and fibers which form the felt by intermingling through water jet needling and/or needle punching.

Abstract: The split PTFE yarn and PTFE filament which are bulky and excellent in the feeling and have good intermingling property can be obtained and the cotton-like PTFE materials can be produced therefrom efficiently at a low percentage of dropped fibers. Further the filter cloth for dust collection which is obtained from those cotton-like materials has a high collection efficiency. The present invention can provide the split yarn having a network structure and obtained by splitting a uniaxially stretched PTFE film in the stretched direction with a needle blade roll; the filament having branches and obtained by cutting the network structure of the split yarn in a longitudinal direction; the methods of production thereof; the method of producing the cotton-like materials by cutting the split yarn or filament and then opening; and a filter cloth for dust collection obtained from the cotton-like materials.

Abstract: An unsintered polytetrafluoroethylene tape for sealing screw joints is described. The tape is obtained by uniaxially stretching an unsintered body of a composition comprising 75 to 25 wt. parts of polytetrafluoroethylene fine powder and 25 to 75 wt. parts of inorganic powder which has new Mohs hardness of 3 or less and substantially no water absorption. The tape has excellent heat stability and sealing properties like a conventional polytetrafluoroethylene tape for screw joint sealing, but the required amount of PTFE can be decreased. Furthermore, by compounding a specific inorganic filler, the tape does not suffer from limitations regarding stretching conditions, and does not abrade or damage the screw.

Abstract: To provide a PTFE composite fiber having remarkably improved thermal bonding property, PTFE cotton-like materials which can be used for producing a non-woven fabric by thermal bonding method, processes for production thereof, a process for producing a split yarn, a process for producing a monofilament and a process for producing a multifilament having loop and/or branched structure.A thermofusing resin layer is provided on the surface of the PTFE fiber. After lamination of the PTFE film and the thermofusing resin film, uniaxial stretching is carried out at a temperature between the melting points of the respective films.

Abstract: The present invention provides cotton-like mixed materials containing the PTFE fibers and other fibers uniformly and being excellent in intermingling property, non-woven fabrics obtained from the cotton-like mixed materials, and a process for preparation thereof.The split yarn having a network structure and obtained by splitting the uniaxially stretched PTFE film with the needle blade rolls in the stretched direction and the other continuous filament are fed simultaneously to the needle blade rolls rotating at high speed.

Abstract: To provide a PTFE composite fiber having remarkably improved thermal bonding property, PTFE cotton-like materials which can be used for producing a non-woven fabric by thermal bonding method, processes for production thereof, a process for producing a split yarn, a process for producing a monofilament and a process for producing a multifilament having loop and/or branched structure.A thermofusing resin layer is provided on the surface of the PTFE fiber. After lamination of the PTFE film and the thermofusing resin film, uniaxial stretching is carried out at a temperature between the melting points of the respective films.

Abstract: A porous polytetrafluoroethylene film which is excellent as an air filter used in clean rooms in a semiconductor industry, which is suitable for the collection of microparticles floating in a gas such as air and exhibits a low pressure drop is provided. The film has an average pore size of from 0.2 to 0.4 .mu.m and exhibits a pressure drop of from 20 to 50 mmH.sub.2 O when air is passed through it at a flow rate of 5.3 cm/sec. The film is prepared by stretching biaxially unsintered polytetrafluoroethylene at specific temperatures.

Abstract: To provide a fluorine-containing resin molded article surface-modified by irradiating, onto a surface thereof, a laser beam having a wavelength of 150 to 370 nm through a basic solution, preferably an aqueous basic solution. The surface-modified fluorine-containing resin molded article is excellent in adhesion to not only organic materials but also metals.

Abstract: A process for producing a multilayer polytetrafluoroethylene porous membrane is disclosed, which process comprises at least two layers having different average pore diameters, the process comprising the steps of: filling the inside of a cylinder of an extruding mold distinctively with at least two kinds of polytetrafluoroethylene fine powders with each of which a liquid lubricant has been mixed; paste-extruding the powders to obtain a multilayer extrudate, which is then optionally rolled; removing the liquid lubricant from the multilayer extrudate or the rolled multilayer extrudate to obtain an unsintered multilayer structure; subsequently heating the unsintered multilayer structure at a temperature not lower than the melting point of sintered polytetrafluoroethylene to obtain a semisintered multilayer structure; and then stretching the semisintered multilayer structure at least monoaxially.

Abstract: A porous PTFE film having a thin thickness and good permeability is produced by coating an emulsion of polytetrafluoroethylene on a substrate surface, in particular, a porous polytetrafluoroethylene substrate which has not been heated at a melting point of unsintered polytetrafluoroethylene or higher, heating the coated substrate at a temperature not lower than a melting point of sintered polytetrafluoroethylene to semi-sinter polytetrafluoroethylene, optionally removing the semi-sintered polytetrafluoroethylene film from the substrate, and then stretching the semi-sintered film at least in one direction.

Abstract: A process for producing a multilayer polytetrafluoroethylene porous membrane comprising at least two layers having different average pore diameters is disclosed, the process comprising the steps of: filling the inside of a cylinder of an extruding mold distinctively with at least two kinds of polytetrafluoroethylene fine powders with each of which a liquid lubricant has been mixed; subsequently paste-extruding the powders to obtain a multilayer extrudate, which is then optionally rolled; and then stretching the extrudate or the rolled extrudate at least monoaxially after the liquid lubricant is removed therefrom or without removing the liquid lubricant.

Abstract: A laminate consisting essentially of a metal film or sheet and a film or sheet of a fluorine-containing polyimide (1), a composite sheet consisting essentially of a fluorohydrocarbon polymer substrate impregnated with a fluorine-containing polyimide (2), and a laminate consisting essentially of a metal film or sheet and the above composite sheet, the polyimide (1) and (2) being defined in the specification.