Abstract: A porous filter includes a porous laminate in which a plurality of biaxially stretched porous sheets made of PTFE are stacked. The Gurley number G and the bubble point B (kPa) of the porous laminate satisfy the following expressions (1) and (2): log G>3.7×10?3×B?0.8??(1) log G<4.9×10?3×B+0.45??(2).

Abstract: A porous polytetrafluoroethylene film comprising a fluororesin containing polytetrafluoroethylene as a main component, wherein an envelope surface area of resin fibers included per film having an area of 1 m2 and a thickness of 25 ?m is 4,000 m2 or more, and a melting point peak is 333° C. or lower.

Abstract: A porous filter includes a porous laminate in which a plurality of biaxially stretched porous sheets made of PTFE are stacked. The Gurley number G and the bubble point B (kPa) of the porous laminate satisfy the following expressions (1) and (2): log G>3.7×10?3×B?0.8??(1) log G<4.9×10?3×B+0.45??(2).

Abstract: Provided is a method for producing a porous polytetrafluoroethylene film having good chemical resistance, good heat resistance, a high porosity, and good dimensional stability. The method for producing a porous polytetrafluoroethylene film includes a stretching step of stretching a sheet-like molded body composed of a fluororesin containing polytetrafluoroethylene as a main component in a longitudinal direction and/or a lateral direction at a temperature lower than a melting point of the fluororesin to make a porous fluororesin film, and, after the stretching step, an annealing step of holding the porous fluororesin film in a shape-fixed state, and maintaining the porous fluororesin film at a temperature lower than the melting point of the fluororesin but not lower than a temperature 30° C. lower than the melting point for 1 to 20 hours.

Abstract: Provided is a method for producing a porous polytetrafluoroethylene film having good chemical resistance, good heat resistance, a high porosity, and good dimensional stability. The method for producing a porous polytetrafluoroethylene film includes a stretching step of stretching a sheet-like molded body composed of a fluororesin containing polytetrafluoroethylene as a main component in a longitudinal direction and/or a lateral direction at a temperature lower than a melting point of the fluororesin to make a porous fluororesin film, and, after the stretching step, an annealing step of holding the porous fluororesin film in a shape-fixed state, and maintaining the porous fluororesin film at a temperature lower than the melting point of the fluororesin but not lower than a temperature 30° C. lower than the melting point for 1 to 20 hours.

Abstract: A porous polytetrafluoroethylene film comprising a fluororesin containing polytetrafluoroethylene as a main component, wherein an envelope surface area of resin fibers included per film having an area of 1 m2 and a thickness of 25 ?m is 4,000 m2 or more, and a melting point peak is 333° C. or lower.

Abstract: In a filter for microfiltration, a filtration layer is protected so as not to be damaged. A porous multi-layer filter, which is a laminated body of three porous stretched PTFE sheets that have been biaxially stretched in the longitudinal and transverse directions, includes a filtration layer as a middle layer, a protection layer stacked on one surface of the filtration layer on the liquid-to-be-treated inflow side, and a support layer stacked on another surface of the filtration layer, in which the one surface and the other surface of the filtration layer are fusion-bonded to the protection layer and the support layer at boundaries therebetween, pores of the protection layer and pores of the support layer three-dimensionally communicate with pores of the filtration layer, and the mean pore size of pores of the filtration layer is smaller than the mean pore size of pores of each of the protection layer and the support layer.

Abstract: Provided is a porous multilayer filter which can trap ultrafme particles and in which permeability is high and treatment can be performed at a high flow rate. A porous multilayer filter is characterized by including a support layer 2 composed of a porous expanded PTFE sheet, and a filtration layer 3 composed of a porous expanded PTFE sheet which is different from that of the support layer 2, wherein at least a liquid-to-be-treated inflow surface of the filtration layer 3 is subjected to hydrophilization treatment, the filtration layer 3 and the support layer 2 are fusion-bonded to each other at a boundary therebetween to form a multilayer structure, pores of the support layer 2 three-dimensionally communicate with pores of the filtration layer 3, and pores surrounded by a fibril skeleton of the filtration layer 3 are smaller than pores of the support layer 2.