Abstract: Provided is a material that can be easily biaxially oriented, homogeneously stretched even with a high draw ratio, and formed into a PTFE porous membrane with low pressure loss. The present invention relates to a polytetrafluoroethylene mixture comprising: a fibrillable modified polytetrafluoroethylene; and a fibrillable polytetrafluoroethylene homopolymer, the polytetrafluoroethylene homopolymer having strength at break of 25 N or higher.

Abstract: A non-woven fabric of the present invention is composed primarily of entangled fluoropolymer fibers. In addition, the non-woven fabric of the present invention may be pressure and heat treated, or may be subject to elongation. This provides the non-woven fabric with superior mechanical characteristics.

Abstract: This electrical insulating board 1 comprises a cloth substrate 3 and web layers 5. The web layers 5 made of fluororesin fibers and are stacked on both sides of the cloth substrate 3 and bonded there by entangling. In addition, to at least one side surface of web layers 5, heat treatment at a temperature of melting point of fluororesin fiber or more is applied under pressure.

Abstract: There is provided an adhesive tape or sheet which makes it possible to maintain an adhesion strength for a long period of time, is excellent in sliding property and can be used cut to a desired size and shape in case of need. The adhesive tape or sheet or a cut tape thereof comprises a non-woven fabric of a fluorine-containing resin fiber having, partly or wholly on its one surface, an adhesive layer or a pressure sensitive adhesive layer through or not through a substrate layer.

Abstract: A method of laminating at least two gas permeable sheet materials includes: (1) providing at least a first gas permeable sheet material, wherein at least a portion of at least a surface region of the first sheet material is thermoplastic material; (2) providing at least a second gas permeable sheet material of polytetrafluoroethylene; (3) superposing the sheet materials; and (4) contacting the sheet materials with a heating means to heat the thermoplastic material to a temperature from 140° to 230° C., so as to melt the thermoplastic material and laminate the sheet materials to one another, without the application of direct pressure in the thickness direction of the sheet materials during the contacting step so as to form a gas permeable laminate.

Abstract: A filter medium with excellent flame-resistant properties and an air filter unit using the same are provided which have a flame-resistant air permeable supporting material on at least one surface of a polytetrafluoroethylene (PTFE) porous film and which can be used as a ceiling device, etc.

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: An object is to provide a polytetrafluoroethylene (PTFE) porous composite film which has substantially no defect portion.There is provided the PTFE porous composite film by stretching a composite along its width direction which composite is composed of at least two overlapped films longitudinally stretched at a temperature not higher than a melting point of a sintered PTFE material, each film being obtained by paste-extruding and semi-sintering thereafter a PTFE produced by emulsion polymerization.

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: Cotton-like polytetrafluoroethylene materials are obtained by opening a uniaxially stretched article of molded polytetrafluoroethylene by a mechanical force. Those cotton-like materials comprise the 5 to 150 mm long fibers having branches and crimps and non-uniform section. The cotton-like materials are excellent in intermingling property and can be easily made into non-woven fabrics.

Abstract: A filter apparatus that is compact and that provides a large filtration area includes filter elements each constructed in cylindrical form by spirally winding a filter medium. Such medium includes a porous membrane of a polytetrafluoroethylene having a pore diameter of 0.1 to 5 .mu.m and low pressure loss and one or a pair of sheets composed of fibers made of a thermally melting synthetic resin. One end of the cylindrical filter element is connected to a respective through hole in a rigid support plate, and the opposite end is blocked.