Abstract: A method for producing particles of a fluorinated polymer (A) which has either one or both of structural units (u1) derived from tetrafluoroethylene and structural units (u2) having no sulfonic acid type functional group and having a cyclic structure and fluorine atoms, and which has structural units (u3) having a sulfonic acid type functional group, wherein the proportion of the structural units (u1) is from 0 to 82 mol % in all structural units in the fluorinated polymer (A), the method including: (i) preparing solution or dispersion of the fluorinated polymer (A) having the fluorinated polymer (A) dissolved or dispersed in a solvent (B); and (ii) mixing the solution or dispersion of the fluorinated polymer (A) and a solvent (C) to aggregate the fluorinated polymer (A) to form particles of the fluorinated polymer (A).

Abstract: A method for producing a fluorinated polymer, which comprises carrying out polymerization in a container capable of polymerizing a monomer in a pressurized state, in the presence of at least one of specific four organic peroxides, in a polymerization medium containing at least one fluorinated solvent (B) having a boiling point at normal pressure of at most 60° C., using at least a fluorinated monomer (C) having a boiling point at normal pressure higher than said fluorinated solvent (B), and tetrafluoroethylene, at a temperature of at most 70° C. and at least the boiling point at normal pressure of a fluorinated solvent (B) having the lowest boiling point at normal pressure among said fluorinated solvent (B).

Abstract: A method for producing a fluorinated polymer, which comprises carrying out polymerization in a container capable of polymerizing a monomer in a pressurized state, in the presence of at least one of specific four organic peroxides, in a polymerization medium containing at least one fluorinated solvent (B) having a boiling point at normal pressure of at most 60° C., using at least a fluorinated monomer (C) having a boiling point at normal pressure higher than said fluorinated solvent (B), and tetrafluoroethylene, at a temperature of at most 70° C. and at least the boiling point at normal pressure of a fluorinated solvent (B) having the lowest boiling point at normal pressure among said fluorinated solvent (B).

Abstract: To provide an optical member having an excellent transparency and heat resistance and further having favorable light resistance as compared with a molded product made of a conventional ethylene/tetrafluoroethylene copolymer, a process for producing the same, and an article provided with the optical member. An optical member made of a molded product containing a crosslinked product of an ethylene/tetrafluoroethylene copolymer comprising units (A) based on tetrafluoroethylene, units (B) based on ethylene and units (C) based on CH2?CH—CnF2n+1 (wherein n is an integer of from 2 to 10), wherein the molar ratio ((A)/(B)) of the above units (A) to the above units (B) is from 50/50 to 66/34, and the molar ratio ((C)/{(A)+(B)}) of the above units (C) to the sum of the above units (A) and the above units (B) is from 4.0/100 to 10/100.

Abstract: To provide a method for recovering an anionic fluorinated emulsifier, whereby an anionic fluorinated emulsifier adsorbed on a basic ion exchange resin can be simply and efficiently recovered. A mixed liquid of an aqueous inorganic acid solution, a fluorinated medium and a non-fluorinated medium, is contacted to a basic ion exchange resin having an anionic fluorinated emulsifier adsorbed thereon, to recover a liquid phase containing the fluorinated medium, or an aqueous inorganic acid solution is contacted to a basic ion exchange resin having an anionic fluorinated emulsifier adsorbed thereon, then a mixed liquid of a fluorinated medium and a non-fluorinated medium is contacted thereto, and thereafter the basic ion exchange resin and a liquid phase are separated to recover the liquid phase, whereupon from each liquid phase, an acid of the anionic fluorinated emulsifier is recovered.

Abstract: To provide an optical member having an excellent transparency and heat resistance and further having favorable light resistance as compared with a molded product made of a conventional ethylene/tetrafluoroethylene copolymer, a process for producing the same, and an article provided with the optical member. An optical member made of a molded product containing a crosslinked product of an ethylene/tetrafluoroethylene copolymer comprising units (A) based on tetrafluoroethylene, units (B) based on ethylene and units (C) based on CH2?CH—CnF2n+1 (wherein n is an integer of from 2 to 10), wherein the molar ratio ((A)/(B)) of the to above units (A) to the above units (B) is from 50/50 to 66/34, and the molar ratio ((C)/{(A)+(B)}) of the above units (C) to the sum of the above units (A) and the above units (B) is from 4.0/100 to 10/100.

Abstract: To provide a method for recovering an anionic fluorinated emulsifier, whereby an anionic fluorinated emulsifier adsorbed on a basic ion exchange resin can be simply and efficiently recovered. A mixed liquid of an aqueous inorganic acid solution, a fluorinated medium and a non-fluorinated medium, is contacted to a basic ion exchange resin having an anionic fluorinated emulsifier adsorbed thereon, to recover a liquid phase containing the fluorinated medium, or an aqueous inorganic acid solution is contacted to a basic ion exchange resin having an anionic fluorinated emulsifier adsorbed thereon, then a mixed liquid of a fluorinated medium and a non-fluorinated medium is contacted thereto, and thereafter the basic ion exchange resin and a liquid phase are separated to recover the liquid phase, whereupon from each liquid phase, an acid of the anionic fluorinated emulsifier is recovered.

Abstract: To obtain a nonwoven fabric which is excellent in the heat resistance and the chemical resistance, of which the fiber diameter is small, and which is excellent in the mechanical strength at a temperature at which it is used; and an electrolyte membrane which is excellent in the dimensional stability when it is swollen by water, and of which an increase in the resistance by a reinforcing material is suppressed. A nonwoven fabric 28 containing fibers 26 of an ethylene/tetrafluoroethylene copolymer having a storage elastic modulus E? at 25° C. of at least 8×108 Pa and a melt viscosity measured at 300° C. of higher than 60 Pa·s and at most 300 Pa·s, wherein the average fiber diameter of the fibers is from 0.01 to 3 ?m; and an electrolyte membrane reinforced by the nonwoven fabric 28.

Abstract: A polymer electrolyte membrane made of a polymer has a low electrical resistance, high heat resistance and is strong against repeats of swelling and shrinkage. Thus, a membrane/electrode assembly for polymer electrolyte fuel cells having high power generation performance and excellent in durability can be provided. For a polymer electrolyte membrane 15 or for a catalyst layer 11 constituting electrodes 13 and 14, a polymer comprising units (U1) and units (U2) is used: Q1, Q2: a perfluoroalkylene group which may have —O— or the like; Rf1, Rf2: a perfluoroalkyl group which may have —O—; X: an oxygen atom or the like; a: 0 or the like; Y, Z: a fluorine atom, or a monovalent perfluoroorganic group such as —CF3; S: 0 to 1; and t: 0 to 3.

Abstract: To obtain a nonwoven fabric which is excellent in the heat resistance and the chemical resistance, of which the fiber diameter is small, and which is excellent in the mechanical strength at a temperature at which it is used; and an electrolyte membrane which is excellent in the dimensional stability when it is swollen by water, and of which an increase in the resistance by a reinforcing material is suppressed. A nonwoven fabric 28 containing fibers 26 of an ethylene/tetrafluoroethylene copolymer having a storage elastic modulus E? at 25° C. of at least 8×108 Pa and a melt viscosity measured at 300° C. of higher than 60 Pa·s and at most 300 Pa·s, wherein the average fiber diameter of the fibers is from 0.01 to 3 ?m; and an electrolyte membrane reinforced by the nonwoven fabric 28.

Abstract: A polymer electrolyte membrane made of a polymer having a low electrical resistance, high heat resistance and is strong against repeats of swelling and shrinkage. Thus, a membrane/electrode assembly for polymer electrolyte fuel cells having high power generation performance and excellent in durability can be provided.

Abstract: A polymer electrolyte membrane made of a polymer has a low electrical resistance, high heat resistance and is strong against repeats of swelling and shrinkage. Thus, a membrane/electrode assembly for polymer electrolyte fuel cells having high power generation performance and excellent in durability can be provided. For a polymer electrolyte membrane 15 or for a catalyst layer 11 constituting electrodes 13 and 14, a polymer comprising units (U1) and units (U2) is used: Q1, Q2, Q3: a perfluoroalkylene group which may have —O— or the like; Rf1, Rf2: a perfluoroalkyl group which may have —O—; X1, X2: an oxygen atom or the like; a, b: 0 or the like; Y1, Y2: a fluorine atom or a monovalent perfluoroorganic group; and s, t: 0 to 1.

Abstract: A polymer electrolyte membrane made of a polymer has a low electrical resistance, high heat resistance and is strong against repeats of swelling and shrinkage. Thus, a membrane/electrode assembly for polymer electrolyte fuel cells having high power generation performance and excellent in durability can be provided. For a polymer electrolyte membrane 15 or for a catalyst layer 11 constituting electrodes 13 and 14, a polymer comprising units (U1) and units (U2) is used: Q1, Q2: a perfluoroalkylene group which may have —O— or the like; Rf1, Rf2: a perfluoroalkyl group which may have —O—; X: an oxygen atom or the like; a: 0 or the like; Y, Z: a fluorine atom, or a monovalent perfluoroorganic group such as —CF3; S: 0 to 1; and t: 0 to 3.

Abstract: A fluorine-containing copolymer containing polymer units (A) based on tetrafluoroethylene or chlorotrifluoroethylene, polymer units (B) based on ethylene, polymer units (C) based on vinyl acetate and polymer units (D) based on a compound represented by the general formula CH2═CX(CF2)nY wherein each of X and Y which are independent of each other, is a hydrogen atom or a fluorine atom, and n is an integer of from 2 to 10, wherein (A)/(B) is from 20/80 to 80/20 in a molar ratio, (C)/((A)+(B)) is from 1/1,000 to 15/100 in a molar ratio, (D)/((A)+(B)) is from 1/1,000 to 15/100 in a molar ratio, and the volumetric rate of flow is from 1 to 1,000 mm3/sec.

Abstract: A method for producing a fluorinated polymer containing fluoroolefin units as the main constituting units, wherein CF.sub.3 (CF.sub.2).sub.n CH.sub.2 CH.sub.3 or CF.sub.3 (CF.sub.2).sub.n H, wherein n is an integer of from 1 to 8), the is used as the polymerization medium, and CF.sub.2 ClCF.sub.2 CHClF and/or CF.sub.3 CF.sub.2 CHCl.sub.2 as a chain transfer agent.Using the polymerization medium which is less likely to bring about an environmental destruction, it is possible to obtain a fluorinated polymer excellent in the heat resistance, solvent resistance, chemical resistance, etc. Further, the above chain transfer agent has good compatibility with the polymerization medium which scarcely brings about the environmental destruction, whereby it is possible to efficiently produce a fluorinated polymer excellent in the heat resistance and solvent resistance.