Abstract: Provided is a porous membrane including polytetrafluoroethylene and/or modified polytetrafluoroethylene having a small pore diameter, thin film thickness, high porosity, and high strength; and a method for manufacturing the same. The porous membrane including polytetrafluoroethylene and/or modified polytetrafluoroethylenehas bubble point of isopropyl alcohol according to JIS K3832 of 600 kPa or more, and tensile strength according to JIS K6251 of 90 MPa or more.

Abstract: The problem of the present invention is to provide a novel polytetrafluoroethylene porous film having a small pore diameter, small film thickness, high porosity, and high strength, and a production method thereof. The present invention provides a polytetrafluoroethylene porous film, wherein a bubble point in isopropyl alcohol (IPA) according to JIS K3832 is not less than 400 kPa, and a tensile strength based on JIS K6251 is not less than 50 MPa.

Abstract: Provided is a porous polytetrafluoroethylene (PTFE) membrane having a PF value of 36 or more and a mass per unit area of 0.90 g/m2 or less. The PF value is determined by the following equation: PF value={?log(PT (%)/100)/(PL(Pa)/9.8)}×100. PT (permeability) is determined by PT (%)=100?CE (%), CE (collection efficiency) is determined by a value measured using dioctyl phthalate particles with a particle diameter of 0.10 ?m to 0.20 ?m under a condition of a permeate flow rate of 5.3 cm/sec, and PL (pressure loss) is determined by a value measured under a condition of a permeate flow rate of 5.3 cm/sec. This porous PTFE membrane is suitable for air filter media.

Abstract: Provided is a porous polytetrafluoroethylene (PTFE) membrane having a PF value of 36 or more and a mass per unit area of 0.90 g/m2 or less. The PF value is determined by the following equation: PF value={?log(PT (%)/100)/(PL(Pa)/9.8)}×100. PT (permeability) is determined by PT (%)=100?CE (%), CE (collection efficiency) is determined by a value measured using dioctyl phthalate particles with a particle diameter of 0.10 ?m to 0.20 ?m under a condition of a permeate flow rate of 5.3 cm/sec, and PL (pressure loss) is determined by a value measured under a condition of a permeate flow rate of 5.3 cm/sec. This porous PTFE membrane is suitable for air filter media.

Abstract: A first unsintered sheet made of PTFE having a standard specific gravity of 2.16 or more and a second unsintered sheet made of PTFE having a standard specific gravity of less than 2.16 are laminated, and a pressure is applied to a resulting laminated body so as to obtain a pressure-bonded article. The pressure-bonded article is stretched in a specified direction at a temperature lower than a melting point of PTFE, and then the pressure-bonded article is stretched further in the specified direction at a temperature equal to or higher than the melting point of PTFE or heated to a temperature equal to or higher than the melting point of PTFE. Thereafter, the pressure-bonded article stretched in the specified direction is stretched in a width direction perpendicular to the specified direction at a temperature lower than the melting point of PTFE.

Abstract: First, a first porous body is manufactured by stretching, in a uniaxial direction, a sheet made of polytetrafluoroethylene having a standard specific gravity of 2.155 or more, and a second porous body is manufactured by stretching, in biaxial directions, a sheet made of polytetrafluoroethylene. Next, the first porous body is integrated with the second porous body by stretching a laminate of the first porous body and the second porous body in the same direction as the uniaxial direction while heating the laminate at a temperature equal to or higher than a melting point of polytetrafluoroethylene. Thus, a porous polytetrafluoroethylene membrane is produced.

Abstract: The present invention provides a polytetrafluoroethylene (PTFE) porous membrane having, when an arbitrary in-plane direction of the membrane is taken as a first direction, and an in-plane direction orthogonal to the first direction is taken as a second direction, a strength of 20 N/mm2 or more, an elongation percentage at breakage of 200% or less, and a ratio of the elongation percentage in the second direction with respect to the elongation percentage in the first direction of 0.5 to 2.0, in a tensile test performed in the first direction and in the second direction. The PTFE porous membrane of the present invention is less elongated due to an external force and has small anisotropy in elongation.

Abstract: A first unsintered sheet made of PTFE having a standard specific gravity of 2.16 or more and a second unsintered sheet made of PTFE having a standard specific gravity of less than 2.16 are laminated, and a pressure is applied to a resulting laminated body so as to obtain a pressure-bonded article. The pressure-bonded article is stretched in a specified direction at a temperature lower than a melting point of PTFE, and then the pressure-bonded article is stretched further in the specified direction at a temperature equal to or higher than the melting point of PTFE or heated to a temperature equal to or higher than the melting point of PTFE. Thereafter, the pressure-bonded article stretched in the specified direction is stretched in a width direction perpendicular to the specified direction at a temperature lower than the melting point of PTFE.

Abstract: First, a first porous body is manufactured by stretching, in a uniaxial direction, a sheet made of polytetrafluoroethylene having a standard specific gravity of 2.155 or more, and a second porous body is manufactured by stretching, in biaxial directions, a sheet made of polytetrafluoroethylene. Next, the first porous body is integrated with the second porous body by stretching a laminate of the first porous body and the second porous body in the same direction as the uniaxial direction while heating the laminate at a temperature equal to or higher than a melting point of polytetrafluoroethylene. Thus, a porous polytetrafluoroethylene membrane is produced.

Abstract: A process for separating methane from a gaseous mixture containing methane and carbon dioxide by concentration is disclosed, which comprises contacting said gaseous mixture with a membrane comprising a film of a polyimide resin having a repeating unit represented by formula (I): ##STR1## wherein R.sup.1 represents a divalent aromatic, alicyclic or aliphatic hydrocarbon group, or a divalent organic group composed of these hydrocarbon groups linked via a divalent organic linking group. The membrane exhibits excellent selective permeability to carbon dioxide, enabling efficient and stable separation of methane.

Abstract: A thermopervaporation apparatus comprising a microporous membrane which is impervious to liquids while readily allowing the vapor to pass therethrough, the passage of a hot feed solution situated on one side of said microporous membrane, a porous spacer disposed on at least part of the other side of said microporous membrane, and a heat-transmission wall disposed on said spacer, in such a manner that the vapor of the component to be separated from the feed solution permeates said membrane, diffuses to said heat-transmission wall through said spacer and is cooled on said heat-transmission wall to form a condensate which is withdrawn through said spacer, thereby improving a yield of the condensate.