An object of the present invention it to provide a novel fluororesin that has excellent mechanical strength and chemical resistance, and very low permeability at high temperature. The fluorine resin is a copolymer that includes copolymerized units derived from tetrafluoroethylene, vinylidene fluoride, and an ethylenically unsaturated monomer other than tetrafluoroethylene and vinylidene fluoride. The fluororesin has a storage modulus E′, as measured at 170° C. by a dynamic viscoelasticity analysis, in the range of 60 to 400 MPa.

To provide a method for producing a fluorinated polymer which does not require an emulsifier as an essential component while an aqueous medium with little environmental burden is used.

A method for producing a fluorinated polymer, which comprises polymerizing at least one fluorinated monomer selected from tetrafluoroethylene, chlorotrifluoroethylene and vinylidene fluoride, in an aqueous medium in the presence of a first polymer having units based on a compound represented by the following formula (1):

CXY═CR.sup.1-L-R.sup.2  (1)

wherein X and Y are each independently a hydrogen atom, a halogen atom or a methyl group, R.sup.1 is a hydrogen atom, a halogen atom or a C.sub.1-3 alkyl group, L is —CO—O—*, —O—CO—* or —O—, provided that * represents the binding position to R.sup.2, and R.sup.2 is a cyclic alkyl group, a monovalent aromatic hydrocarbon group or a C.sub.1-6 linear alkyl group, provided that the C.sub.1-6 linear alkyl group as R.sup.2 may have an etheric oxygen atom in a carbon-carbon bond, and the hydrogen atom in the cyclic alkyl group, the monovalent aromatic hydrocarbon group or the C.sub.1-6 linear alkyl group as R.sup.2 may be replaced with a halogen atom.

Crosslinked rubber of the present invention is a crosslinked product of a copolymer having units based on tetrafluoroethylene and units based on propylene, of which the total light transmittance is from 60 to 100%. Or, crosslinked rubber of the present invention is a crosslinked product of a copolymer having units based on tetrafluoroethylene and units based on a perfluoro(alkyl vinyl ether), of which the total light transmittance is from 70 to 100%.

Crosslinked rubber of the present invention is a crosslinked product of a copolymer having units based on tetrafluoroethylene and units based on propylene, of which the total light transmittance is from 60 to 100%. Or, crosslinked rubber of the present invention is a crosslinked product of a copolymer having units based on tetrafluoroethylene and units based on a perfluoro(alkyl vinyl ether), of which the total light transmittance is from 70 to 100%.

To provide a fluorinated copolymer composition whereby a crosslinked rubber article having a low compression set at high temperature can be formed, and a crosslinked rubber article.

The fluorinated copolymer composition of the present invention comprises a fluorinated copolymer, an organic peroxide, a compound having at least two polymerizable unsaturated bonds and a phosphorus compound having a melting point of 60° C. or lower.

To provide a fluorinated copolymer composition whereby a crosslinked rubber article having a low compression set at high temperature can be formed, and a crosslinked rubber article.

The fluorinated copolymer composition of the present invention comprises a fluorinated copolymer, an organic peroxide, a compound having at least two polymerizable unsaturated bonds and a phosphorus compound having a melting point of 60° C. or lower.

The purpose of the present invention is to provide a fluororesin film or fluororesin laminate excellent in heat resistance and excellent in interlayer adhesion to an object to be laminated, such as a prepreg, a method for producing a hot pressed laminate using said film or laminate, and a method for producing a printed circuit board. The fluororesin film contains a fluororesin having a melting point of from 260 to 380° C., and has an arithmetic average roughness Ra of at least 3.0 nm when inside of 1 μm.sup.2 of at least one surface thereof in the thickness direction is measured by an atomic force microscope. The laminate 1 has a layer A10 containing said fluororesin and a layer B12 made of another substrate, wherein the layer A10 has an arithmetic average roughness Ra of at least 3.0 nm when inside of 1 μm.sup.2 of a second surface 10b thereof is measured by an atomic force microscope.

The invention pertains to a thermoplastic fluoropolymer composition comprising one or more polymer A comprising recurring units derived from ethylene and recurring units derived from halogenated monomers selected from chlorotrifluoroethylene (CTFE) and tetrafluoroethylene (TFE) and one or more polymer B comprising recurring units derived from ethylene, recurring units derived from halogenated monomers selected from CTFE and TFE, and recurring units derived from hexafluoroisobutylene (HFIB) and/or perfluoropropylvinylether (PPVE). The resulting composition allows to manufacture films having exceptional transparency and good mechanical properties which can be used for examples as architectural films.

The invention pertains to a thermoplastic fluoropolymer composition comprising one or more polymer A comprising recurring units derived from ethylene and recurring units derived from halogenated monomers selected from chlorotrifluoroethylene (CTFE) and tetrafluoroethylene (TFE) and one or more polymer B comprising recurring units derived from ethylene, recurring units derived from halogenated monomers selected from CTFE and TFE, and recurring units derived from hexafluoroisobutylene (HFIB) and/or perfluoropropylvinylether (PPVE). The resulting composition allows to manufacture films having exceptional transparency and good mechanical properties which can be used for examples as architectural films.

A binder for a secondary battery containing a fluorine-containing polymer (A) and polyvinylidene fluoride (B). The fluorine-containing polymer (A) contains a polymerized unit based on vinylidene fluoride, a polymerized unit based on tetrafluoroethylene, and a polymerized unit based on a monomer (2-2) represented by the following formula (2-2): ##STR00001##
wherein R.sup.5, R.sup.6, and R.sup.7 are each independently a hydrogen atom or a C1-C8 hydrocarbon group; R.sup.8 is a C1-C8 hydrocarbon group; and Y.sup.1 is an inorganic cation or an organic cation. Also disclosed is an electrode mixture and an electrode for a secondary battery including the binder, and a secondary battery including the electrode.