Abstract: An air filter medium includes a fluororesin porous membrane and an air-permeable supporting member stacked on the fluororesin porous membrane. The fluororesin porous membrane has a pressure loss of 80 Pa or less when air is passed at a flow rate of 5.3 cm/s. The fluororesin porous membrane has a PF of 20 or more, the PF being determined from a formula PF={?log((100?collection efficiency (%))/100)}/(pressure loss (Pa)/1000) using the pressure loss and a collection efficiency determined using NaCl particles having a particle size of 0.1 ?m. The fluororesin porous membrane has a thickness of 10 ?m or more. A dust-holding capacity of polyalphaolefin particles having a number median diameter of 0.25 ?m is 15.0 g/m2 or more when air containing the polyalphaolefin particles is continuously passed through the fluororesin porous membrane at a flow rate of 5.3 cm/s and pressure loss increases by 250 Pa.

Abstract: The present invention provides a polymer electrolyte membrane having excellent strength, a small dimensional change, and a low membrane resistance. The polymer electrolyte membrane includes a porous film having pores and a polymer electrolyte contained in the pores. The porous film is obtained by copolymerizing tetrafluoroethylene and an ethylenic comonomer to provide polytetrafluoroethylene and then stretching the polytetrafluoroethylene. The porous film has an average pore size of greater than 0.20 ?m.

Abstract: The present invention provides a porous body having high strength, a small pore size, and excellent homogeneity. The porous body of the present invention includes polytetrafluoroethylene and has a microstructure that includes nodes and fibrils. The microstructure further includes, in addition to the nodes and the fibrils, fused points where a fibril that links two nodes and another fibril that links another two nodes are fused with each other.

Abstract: The present invention provides a polymer electrolyte membrane having excellent strength, a small dimensional change, and a low membrane resistance. The polymer electrolyte membrane includes a porous film and a polymer electrolyte. The porous film has a fibril/node area ratio of 90/10 to 75/25.

Abstract: The present invention provides a polymer electrolyte membrane having excellent strength, a small dimensional change, and a low membrane resistance. The polymer electrolyte membrane includes a porous film and a polymer electrolyte. The porous film has a fibril/node area ratio of 90/10 to 75/25.

Abstract: The present invention provides a polymer electrolyte membrane having excellent strength, a small dimensional change, and a low membrane resistance. The polymer electrolyte membrane includes a porous film having pores and a polymer electrolyte contained in the pores. The porous film is obtained by copolymerizing tetrafluoroethylene and an ethylenic comonomer to provide polytetrafluoroethylene and then stretching the polytetrafluoroethylene. The porous film has an average pore size of greater than 0.20 ?m.

Abstract: The present invention provides a porous body having high strength, a small pore size, and excellent homogeneity. The porous body of the present invention includes polytetrafluoroethylene and has a microstructure that includes nodes and fibrils. The microstructure further includes, in addition to the nodes and the fibrils, fused points where a fibril that links two nodes and another fibril that links another two nodes are fused with each other.

Abstract: The present invention aims to provide a biaxially stretched porous membrane having high strength, a small pore size, and excellent homogeneity. The biaxially stretched porous membrane of the present invention includes polytetrafluoroethylene obtained by copolymerizing tetrafluoroethylene and perfluoro(methyl vinyl ether).

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: 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: 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.