Nitto-denko Corporation

Nitto Electric Industrial Co., Ltd.

Shunichi Shimatani

Masaaki Mori

Michiharu Yamamoto

Yuri Horie

Akio Iwama

Akira Shimazu

Atsuo Yoshimura

Shoji Kimura

Akira Sanami

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/mor less. The PF value is determined by the following equation: PF value={&#x2212;log(PT (%)/100)/(PL(Pa)/9.8)}&#xd7;100. PT (permeability) is determined by PT (%)=100&#x2212;CE (%), CE (collection efficiency) is determined by a value measured using dioctyl phthalate particles with a particle diameter of 0.10 &#x3bc;m to 0.20 &#x3bc;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.

Porous polytetrafluoroethylene membrane and air filter medium

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.

Polytetrafluoroethylene porous membrane, method for producing same, and waterproof air-permeable filter

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.

Porous polytetrafluoroethylene membrane, method for producing the same, and water-proof air permeable filter

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.

Process for separating methane using permeable membrane

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.

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Osaka, Japan

Shunichi Shimatani