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PTFE aqueous emulsion AND PROCESS FOR ITS PREPARATION, polytetrafluoroethylene aqueous dispersion obtained by using such an aqueous emulsion polytetrafluoroethylene fine powder and stretch the porous material
PTFE aqueous emulsion AND PROCESS FOR ITS PREPARATION, polytetrafluoroethylene aqueous dispersion obtained by using such an aqueous emulsion polytetrafluoroethylene fine powder and stretch the porous material
1. A method for producing an aqueous polytetrafluoroethylene emulsion, which comprises carrying out emulsion polymerization of tetrafluoroethylene by using at least one fluorinated emulsifier selected from the group consisting of C4-8 fluorinated carboxylic acid having in its backbone from 1 to 4 oxygen atoms of ether units, and salts thereof, for preparing an aqueous emulsion comprising microparticles of PTFE having an average primary particle size in the range from 0.1 to 0.3 microns, where at the beginning of the emulsion polymerization of tetrafluoroethylene in the emulsion polymerization include a (polyfluoroalkyl) ethylene (a) represented by the following formula (1) and / or comonomer (b), characterized by constant r copolymerizable monomerTFE in the range of 0.1 to 8 when copolymerized with tetrafluoroethylene, allowing their administration in a quantity ranging from 0.001 to 0.01% by weight. based on the final amount of polytetrafluoroethylene obtained,; CH2= CH-Rf1 (1), ;wherein Rf1 It represents C1-10 polyfluoroalkyl group.;2. A method for producing an aqueous polytetrafluoroethylene emulsion according to claim 1, wherein the average primary particle size of polytetrafluoroethylene in the microparticles is in the range from 0.2 to 0.3 microns.;3. A method for producing an aqueous polytetrafluoroethylene emulsion according to claim 1 wherein the (polyfluoroalkyl) ethylene (a) is at least one member selected from the group consisting of CH2= CH- (CF2)2F, CH2= CH- (CF2)4F and CH2= CH- (CF2)6F.;4. A method for producing an aqueous polytetrafluoroethylene emulsion according to claim 1, wherein the comonomer (b) is at least one member selected from the group consisting of the following formula (2), the following formula (3), perfluoro (2 methylene-4-methyl-1,3-dioxolane), perfluoro (2,2-dimethyl-1,3-dioxole) and perfluoro (5-methoxy-1,3-dioxole); CF2= CF-O- (CF2)nCF = CF2 (2) ;where n is an integer of 1 or 2;; CF2= CF-O-Rf2 (3) ;wherein Rf2 It represents C12 a perfluoroalkyl group).;5. The aqueous polytetrafluoroethylene emulsion obtained by the process of claim 1.;6. The polytetrafluoroethylene aqueous dispersion obtained by adding to an aqueous polytetrafluoroethylene emulsion according to claim 5 nonionic surfactant for stabilization, followed by concentration, wherein a content of polytetrafluoroethylene microparticles ranges from 50 to 70% by weight.;7. The PTFE fine powder obtained by coagulating a PTFE aqueous emulsion according to claim 5, which retains the stress relaxation time equal to at least 500 seconds.;8. polytetrafluoroethylene fine powder according to claim 7, characterized by a standard specific gravity in the range of 2,135 to 2,155.;9. The stretched porous material obtained by extruding a paste of polytetrafluoroethylene fine powder according to claim 7, followed by stretching.
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