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: 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: An embossed air filter filtration medium has at least one porous film and a plurality of air-permeable support materials supporting the at least one porous film. The least one porous film includes a fibril-formable polytetrafluoroethylene, a non-fibril-forming and non-hot-melt-processable component, and a non-fibril-forming and hot-melt-processable component having a melting point below 320° C. Surfaces of both sides of the air filter filtration medium are formed by two air-permeable support materials of the air-permeable support materials. The air filter filtration medium has a plurality of embossed projections. The embossed air filter filtration medium may be part of a filter pack, which may be part of an air filter unit. The embossed air filter filtration medium is manufactured by laminating air-permeable support materials on the at least one porous film and embossing the air filter filtration medium to form the projections.

Abstract: A filter medium includes a porous film and a support material supporting the porous film. The porous film includes polytetrafluoroethylene, has an average pore diameter of at least 2.5 ?m, and has a porosity of at least 95%. A pressure loss is less than 100 Pa when air is passed through the filter medium at a velocity of 5.3 cm/sec. A collection efficiency of NaCl particles is at least 95% when air including NaCl particles with a particle diameter of 0.3 ?m is passed through the filter medium at a velocity of 5.3 cm/sec. A PF value is at least 30, where PF={?log [(100?collection efficiency (%))/100]/pressure loss (Pa)}×1000. A dust holding capacity of polyalphaolefin particles held in the filter medium is at least 15 g/m2 when air including polyalphaolefin particles with a count median diameter of 0.25 ?m is continuously passed through the filter medium at a velocity of 5.3 cm/sec and pressure loss reaches 300 Pa.

Abstract: A composition, a mixed power and a material for molding have polytetrafluoroethylene as a main component. Each includes polytetrafluoroethylene that can be fibrillated, a non-hot melt processable component that is not fibrillated, and a hot melt processable component with a melting point of lower than 320° C. that is not fibrillated. The hot melt processable component is contained at equal to or more than 0.1% by weight but less than 20% by weight of a total weight. A filtering medium for an air filter includes a porous membrane made of these components, and an air permeable support. The porous membrane is manufactured, by mixing these components, extruding the mixture, rolling and drawing.

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: This invention relates to a multi-stage stretching operation for production of expanded stretched porous polytetrafluoroethylene (ePTFE) fibrous materials with minimal node size and minimized filament sizes. A plurality of stretching or expansions may be implemented on the film including combinations of MDO and TDO stretches including at least two longitudinal stretches and at least one transverse stretch. Subsequent stretches occur at rates generally less than a prior similar longitudinal or transverse type of expansion.

Abstract: Provided is a material that can be easily biaxially oriented, homogeneously stretched even with a high draw ratio, and formed into a polytetrafluoroethylene porous membrane with low pressure loss. The present invention relates to a polytetrafluoroethylene mixture comprising: a modified polytetrafluoroethylene; and a fibrillable polytetrafluoroethylene homopolymer, the modified polytetrafluoroethylene having an extrusion pressure to a cylinder, at a reduction ratio of 1600, of 70 MPa or higher.

Abstract: A filter medium for an air filter unit for collecting dust from an airflow includes a pre-collection layer, a principal collection layer and an air-permeable cover layer. The pre-collection layer collects a part of the dust in the air flow. The principal collection layer includes a porous polytetrafluoroethylene film. The principal collection layer is positioned on a downstream side of the air flow relative to the pre-collection layer to collect dust that passes through the pre-collection layer. The air-permeable cover layer is positioned as an outermost surface layer of the filter medium on an upstream side of the air flow to allow dust in the air flow to pass through. The air-permeable cover layer is configured to suppress deformation of a surface of the filter medium caused by pressing force from an outside. Preferably, an air filter unit includes the filter medium in a zigzag shape.

Abstract: Provided is a material that can be easily biaxially oriented, homogeneously stretched even with a high draw ratio, and formed into a polytetrafluoroethylene porous membrane with low pressure loss. The present invention relates to a polytetrafluoroethylene mixture comprising: a modified polytetrafluoroethylene; and a fibrillable polytetrafluoroethylene homopolymer, the modified polytetrafluoroethylene having an extrusion pressure to a cylinder, at a reduction ratio of 1600, of 70 MPa or higher.

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 filter medium includes a porous film and a support material supporting the porous film. The porous film includes polytetrafluoroethylene, has an average pore diameter of at least 2.5 ?m, and has a porosity of at least 95%. A pressure loss is less than 100 Pa when air is passed through the filter medium at a velocity of 5.3 cm/sec. A collection efficiency of NaCl particles is at least 95% when air including NaCl particles with a particle diameter of 0.3 ?m is passed through the filter medium at a velocity of 5.3 cm/sec. A PF value is at least 30, where PF={?log [(100?collection efficiency (%))/100]/pressure loss (Pa)}×1000. A dust holding capacity of polyalphaolefin particles held in the filter medium is at least 15 g/m2 when air including polyalphaolefin particles with a count median diameter of 0.25 ?m is continuously passed through the filter medium at a velocity of 5.3 cm/sec and pressure loss reaches 300 Pa.

Abstract: A method of manufacturing a filter medium that has a PF value that exceeds 32, the PF value calculated from the pressure loss and the collection efficiency of the filter medium according to the following formula: PF=[?log(permeability (%)/100)/(pressure loss (Pa)]×1000[Formula 1] in which permeability (%)=100?collection efficiency (%). In this method, 380 ml or more of a liquid lubricant at 20° C. is added per 1 kg of a PTFE fine powder, this compound is processed into a tape shape and elongated to obtain a PTFE porous film, and an air permeable support member is heat laminated to at least one surface of the PTFE porous film.

Abstract: A method of manufacturing a filter medium that has a PF value that exceeds 32, the PF value calculated from the pressure loss and the collection efficiency of the filter medium according to the following formula:

Abstract: An air filter medium is provided with a porous film made from a polytetafluoroethylene, and a non-woven fabric laminated on at least one side of the porous film. The non-woven fabric has an apparent density satisfying the following equation: apparent density (g/cm3)<1.5×(basis weight (g/m2)/1000)+0.11. The filter medium is produced by a process that includes a first step of producing a porous film formed from a polytetrafluoroethylene, and a second step of laminating a non-woven fabric on at least one side of the porous film on heating roll that has undergone a non-adhesive treatment. The filter medium is used to manufacture an air filter pack, while the air filter pack is used to manufacture an air filter unit.

Abstract: An air filter medium comprising a porous polytetrafluoroethylene film and an air-permeable support member laminated on at least one surface of said porous film and having a PF1 value exceeding 22, which is calculated according to the following formula: PF1=[−log(Penetration (%)/100)/Pressure loss (mmH2O)]×100 in which the penetration (%)=100−Collection efficiency from a pressure loss (unit: mmH2O) measured when an air is flowed through the air filter medium at a flow velocity of 5.3 cm/sec. and a collection efficiency (unit: %) measured using dioctyl phthalate having a particle size of 0.10 to 0.12 &mgr;m. This air filter medium has a low pressure loss and a high collection efficiency.