Tetrafluoroethene-based fluoropolymers of low gel content, methods of making the fluoropolymers, methods of extruding the fluoropolymers into articles, and extruded articles comprising the fluoropolymers.

Tetrafluoroethene-based fluoropolymers of low gel content, methods of making the fluoropolymers, methods of extruding the fluoropolymers into articles, and extruded articles comprising the fluoropolymers.

(Problem) To provide an electrolyte film for fuel cells, capable of achieving both low resistance (film thinning) and high dimensional stability.

(Solution) An electrolyte film for fuel cells, the electrolyte film comprising a polymeric electrolyte and a polytetrafluoroethylene (PTFE) porous film, characterized in that a material having an elastic modulus higher than that of the material constituting the PTFE porous film is composited on the inside surfaces of pores of the PTFE porous film, and the composited PTFE porous film has an elastic modulus of at least 150 MPa.

(Problem) To provide an electrolyte film for fuel cells, capable of achieving both low resistance (film thinning) and high dimensional stability.

(Solution) An electrolyte film for fuel cells, the electrolyte film comprising a polymeric electrolyte and a polytetrafluoroethylene (PTFE) porous film, characterized in that a material having an elastic modulus higher than that of the material constituting the PTFE porous film is composited on the inside surfaces of pores of the PTFE porous film, and the composited PTFE porous film has an elastic modulus of at least 150 MPa.

A conductive composition for electrode is provided that is excellent in conductivity and dispersibility. Further, an electrode for lithium ion secondary battery with lower plate resistance and a lithium ion secondary battery excellent in rate characteristics are provided that use this conductive composition. A conductive composition for electrode, including: carbon nanofiber with a median diameter D50 value by volume from 0.1 to 8 μm; an active material; and a binder enables production of an electrode for lithium ion secondary battery with lower plate resistance and a lithium ion secondary battery excellent in rate characteristics.

The invention pertains to a method for making a fluoropolymer comprising an aqueous emulsion polymerization of one or more fluorinated monomers wherein said aqueous emulsion polymerization is carried out in the presence of at least one cyclic fluorocompound of the following formula (I): ##STR00001##
wherein X.sub.1, X.sub.2, X.sub.3, equal or different from each other are independently selected among H, F, and C.sub.1-6 (per)fluoroalkyl groups, optionally comprising one or more catenary or non-catenary oxygen atoms; L represents a bond or a divalent group; R.sub.F is a divalent fluorinated C.sub.1-3 bridging group; Y is a hydrophilic function selected among anionic functionalities, cationic functionalities and non-ionic functionalities.

A method for producing a fluoropolymer by solution polymerization or dispersion polymerization, the method including: in the presence of an initiator, a chain transfer agent, and a solvent, (i) homopolymerizing tetrafluoroethylene; or (ii) randomly copolymerizing tetrafluoroethylene and at least one of a monomer represented by the following formula (1) or a monomer represented by the following formula (2). The chain transfer agent includes at least one selected from dithioester compounds, dithiocarbamate compounds, trithiocarbonate compounds and xanthate compounds. The fluoropolymer contains 50 to 100 mol % of a polymerized unit based on the tetrafluoroethylene. The formula (1): CF.sub.2═CR.sup.1R.sup.2 wherein R.sup.1 and R.sup.2 are as defined herein, the formula (2): CH.sub.2═CR.sup.3R.sup.4 wherein R.sup.3 and R.sup.4 are as defined herein.

A method for producing a fluoropolymer by solution polymerization or dispersion polymerization, the method including: in the presence of an initiator, a chain transfer agent, and a solvent, (i) homopolymerizing tetrafluoroethylene; or (ii) randomly copolymerizing tetrafluoroethylene and at least one of a monomer represented by the following formula (1) or a monomer represented by the following formula (2). The chain transfer agent includes at least one selected from dithioester compounds, dithiocarbamate compounds, trithiocarbonate compounds and xanthate compounds. The fluoropolymer contains 50 to 100 mol % of a polymerized unit based on the tetrafluoroethylene. The formula (1): CF.sub.2═CR.sup.1R.sup.2 wherein R.sup.1 and R.sup.2 are as defined herein, the formula (2): CH.sub.2═CR.sup.3R.sup.4 wherein R.sup.3 and R.sup.4 are as defined herein.

A method for producing a fluorosulfonyl group-containing compound to obtain a compound represented by the following formula 5 from a compound represented by the following formula 1 as a starting material and a method for producing a fluorosulfonyl group-containing monomer in which the fluorosulfonyl group-containing compound is used: ##STR00001##
wherein R.sup.1 and R.sup.2 are a C.sub.1-3 alkylene group, and R.sup.F1 and R.sup.F2 are a C.sub.1-3 perfluoroalkylene group.

A method for producing a fluorosulfonyl group-containing compound to obtain a compound represented by the following formula 5 from a compound represented by the following formula 1 as a starting material and a method for producing a fluorosulfonyl group-containing monomer in which the fluorosulfonyl group-containing compound is used: ##STR00001##
wherein R.sup.1 and R.sup.2 are a C.sub.1-3 alkylene group, and R.sup.F1 and R.sup.F2 are a C.sub.1-3 perfluoroalkylene group.