Fluororesin thin film, fluororesin composite, porous fluororesin composite, manufacturing methods thereof, and seperation membrane element

Abstract

There are provided a fluororesin thin film which is composed of a fluororesin, which has a thickness of 20 μm or less and a Gurley's number of 300 seconds or more, and which includes no defects, such as voids and/or cracks; a method for manufacturing the fluororesin thin film in which after a fluororesin dispersion including a dispersing medium and a fluororesin powder dispersed therein is applied on a flat and smooth foil, the dispersing medium is dried, and the fluororesin powder is sintered; the fluororesin dispersion; a fluororesin composite including a porous base material and the fluororesin thin film; a manufacturing method thereof a porous fluororesin composite formed by stretching the fluororesin composite; and a separation membrane element using the porous fluororesin composite.

1 . A fluororesin thin film produced by a process comprising the steps of applying a fluororesin dispersion including a dispersing agent and a fluororesin powder dispersed therein on a flat and smooth film, and then drying the dispersing agent and sintering the fluororesin to form a fluororesin thin film removably provided with the flat and smooth film or a fluororesin thin film by removing the flat and smooth film, wherein the thickness of the fluororesin thin film is 20 μm or less and the Gurley's number thereof after the flat and smooth film is removed is 300 seconds or more. 
   
   
       2 . The fluororesin thin film according to  claim 1 , wherein the Gurley's number is 1,000 seconds or more. 
   
   
       3 . The fluororesin thin film according to  claim 1 , wherein no IPA permeation is detected by an IPA permeation test at 25° C. 
   
   
       4 . The fluororesin thin film according to  claim 1 , wherein the fluororesin is one selected from the group consisting of polytetrafluoroethylene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polychlorotrifluoroethylene, tetrafluoroethylene-ethylene copolymer, chlorotrifluoroethylene-ethylene copolymer, polyvinylidene fluoride, and polyvinyl fluoride or is a mixture including at least two thereof. 
   
   
       5 . The fluororesin thin film according to  claim 1 , wherein the fluororesin is a resin primarily composed of polytetrafluoroethylene. 
   
   
       6 . The fluororesin thin film according to  claim 5 , wherein the fluororesin is a mixture including polytetrafluoroethylene and tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, and a volume ratio of the tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer is less than 20% with respect to the volume of the mixture. 
   
   
       7 . A method for manufacturing a fluororesin thin film comprising the steps of: applying a fluororesin dispersion including a dispersing medium and a fluororesin powder dispersed therein on a flat and smooth film; then drying the dispersing medium and sintering the fluororesin powder; and subsequently removing the flat and smooth film. 
   
   
       8 . The method for manufacturing a fluororesin thin film according to  claim 7 , wherein the flat and smooth film is a metal film. 
   
   
       9 . A fluororesin dispersion comprising: a dispersing medium; and a fluororesin powder which is dispersed therein and which is primarily composed of polytetrafluoroethylene. 
   
   
       10 . The fluororesin dispersion according to  claim 9 , wherein a mixture of a polytetrafluoroethylene powder and a thermoplastic fluororesin powder is dispersed in the dispersing medium. 
   
   
       11 . The fluororesin dispersion according to  claim 10 , wherein the thermoplastic fluororesin powder is a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer powder, and a volume ratio of the tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer powder is less than 20% with respect to the volume of the mixture. 
   
   
       12 . The fluororesin dispersion according to  claim 9 , further comprising a nonionic water-soluble polymer having a molecular weight of 10,000 or more. 
   
   
       13 . The fluororesin dispersion according to  claim 9 , further comprising an anionic surfactant having a concentration of 0.5 to 30 mg/ml. 
   
   
       14 . A fluororesin composite comprising: a porous base material; and the fluororesin thin film according to  claim 1  formed on one surface of the base material. 
   
   
       15 . The fluororesin composite according to  claim 14 , further comprising a metal foil on a surface of the fluororesin thin film opposite to the porous base material. 
   
   
       16 . A fluororesin composite comprising: two porous base materials; and the fluororesin thin film according to  claim 1  provided therebetween. 
   
   
       17 . A method for manufacturing the fluororesin composite according to  claim 14 , comprising the steps of applying a fluororesin dispersion including a dispersing medium and a fluororesin powder dispersed therein between a flat and smooth film and a porous base material; then drying the dispersing medium and sintering the fluororesin powder. 
   
   
       18 . A method for manufacturing the fluororesin composite according to  claim 14 , comprising the steps of applying a fluororesin dispersion including a dispersing medium and a fluororesin powder dispersed therein on a flat and smooth film; then drying the dispersing medium and sintering the fluororesin powder to form a fluororesin thin film; and after the fluororesin thin film is formed, adhering the fluororesin thin film to a porous base material. 
   
   
       19 . A porous fluororesin composite manufactured by stretching a fluororesin composite, wherein the fluororesin composite has a porous base material and a fluororesin thin film formed on one surface thereof, and the fluororesin thin film is composed of a fluororesin and has a thickness of 20 μm or less and a Gurley's number of 300 seconds or more. 
   
   
       20 . A porous fluororesin composite manufactured by stretching a fluororesin composite, wherein the fluororesin composite has two porous base materials and a fluororesin thin film provided therebetween, and the fluororesin thin film is composed of a fluororesin and has a thickness of 20 μm or less and a Gurley's number of 300 seconds or more. 
   
   
       21 . A separation membrane element using the porous fluororesin composite according to  claim 19  as a separation membrane. 
   
   
       22 . (canceled) 
   
   
       23 . (canceled) 
   
   
       24 . A method for manufacturing the fluororesin composite according to  claim 15 , comprising the steps of applying a fluororesin dispersion including a dispersing medium and a fluororesin powder dispersed therein between a flat and smooth film and a porous base material; then drying the dispersing medium and sintering the fluororesin powder. 
   
   
       25 . A method for manufacturing the fluororesin composite according to  claim 16 , comprising the steps of applying a fluororesin dispersion including a dispersing medium and a fluororesin powder dispersed therein between a flat and smooth film and a porous base material; then drying the dispersing medium and sintering the fluororesin powder. 
   
   
       26 . A method for manufacturing the fluororesin composite according to  claim 15 , comprising the steps of: applying a fluororesin dispersion including a dispersing medium and a fluororesin powder dispersed therein on a flat and smooth film; then drying the dispersing medium and sintering the fluororesin powder to form a fluororesin thin film; and after the fluororesin thin film is formed, adhering the fluororesin thin film to a porous base material. 
   
   
       27 . A method for manufacturing the fluororesin composite according to  claim 16 , comprising the steps of: applying a fluororesin dispersion including a dispersing medium and a fluororesin powder dispersed therein on a flat and smooth film; then drying the dispersing medium and sintering the fluororesin powder to form a fluororesin thin film; and after the fluororesin thin film is formed, adhering the fluororesin thin film to a porous base material. 
   
   
       28 . A separation membrane element using the porous fluororesin composite according to  claim 20  as a separation membrane.