Abstract: The present invention has for its object to provide a method of producing fluoropolymers with high productivity under comparatively low temperature and low pressure conditions which are conducive to reduced cost of commercial-scale production equipment. The present invention is directed to a method of producing a fluoropolymer which comprises polymerizing a radical polymerizable monomer in a defined reaction-field, said radical polymerizable monomer comprising a fluorine-containing ethylenic monomer and said defined reaction-field being in supercriticality-expression state with a monomer density [?m]-monomer critical density [?0] ratio of [?m/?0] not less than 1.1.

Abstract: To a fluorine-containing polymer, 0.1 to 10% of a compound having an alkali metal or an alkaline earth metal in terms of the number of atoms of the alkali metal or the alkaline earth metal based on the total number of the above terminal groups, 0.1 to 10% of ammonia in terms of the number of ammonia molecules based on the total number of the above terminal groups, or 0.1 to 10% of a compound having an ammonium group in terms of the number of the ammonium groups based on the total number of the above terminal groups is added, and heated at a temperature of at least 200° C. in an atmosphere containing moisture. By this process, unstable terminal groups such as terminal carboxylic acid groups and coloration caused by such terminal groups are effectively removed from the fluorine-containing polymer, and furthermore unstable bonds in the backbones can be removed. The obtained fluorine-containing polymer contains 1.

Abstract: The present invention has for its object to provide a method of producing fluoropolymers with high productivity under comparatively low temperature and low pressure conditions which are conducive to reduced cost of commercial-scale production equipment. The present invention is directed to a method of producing a fluoropolymer which comprises polymerizing a radical polymerizable monomer in a defined reaction-field, said radical polymerizable monomer comprising a fluorine-containing ethylenic monomer and said defined reaction-field being in supercriticality-expression state with a monomer density [?m]?monomer critical density [?0] ratio of [?m/?0] not less than 1.1.

Abstract: To a fluorine-containing polymer, 0.1 to 10% of a compound having an alkali metal or an alkaline earth metal in terms of the number of atoms of the alkali metal or the alkaline earth metal based on the total number of the above terminal groups, 0.1 to 10% of ammonia in terms of the number of ammonia molecules based on the total number of the above terminal groups, or 0.1 to 10% of a compound having an ammonium group in terms of the number of the ammonium groups based on the total number of the above terminal groups is added, and heated at a temperature of at least 200° C. in an atmosphere containing moisture. By this process, unstable terminal groups such as terminal carboxylic acid groups and coloration caused by such terminal groups are effectively removed from the fluorine-containing polymer, and furthermore unstable bonds in the backbones can be removed. The obtained fluorine-containing polymer contains 1.

Abstract: A melt-processable fluorine-containing polymer is melt kneaded with a kneader which has a residence time of at least 10 minutes, a usable volume ratio (usable space in a container/space in a container) of larger than 0.3, and a power factor K of less than 8000, the power factor K being represented by the formula: K=Pv/&mgr;/n2 in which Pv is a power requirement per unit volume (W/m3), &mgr; is a melt viscosity (Pa.s), and n is a rotation speed (rps), to effectively remove terminal groups and bonds in the backbones, which are unstable during melt kneading, from the melt-processable fluorine-containing polymer, and obtain a colorless fluorine-containing polymer.

Abstract: To a fluorine-containing polymer, 0.1 to 10% of a compound comprising an alkali metal or an alkaline earth metal in terms of the number of atoms of the alkali metal or the alkaline earth metal based on the total number of the above terminal groups, 0.1 to 10% of ammonia in terms of the number of ammonia molecules based on the total number of the above terminal groups, or 0.1 to 10% of a compound having an ammonium group in terms of the number of the ammonium groups based on the total number of the above terminal groups is added, and heated at a temperature of at least 2000C in an atmosphere containing moisture. By this process, unstable terminal groups such as terminal carboxylic acid groups and coloration caused by such terminal groups are effectively removed from the fluorine-containing polymer, and furthermore unstable bonds in the backbones can be removed. The obtained fluorine-containing polymer contains 1.

Abstract: A melt-processable fluorine-containing polymer is melt kneaded with a kneader which has a residence time of at least 10 minutes, a usable volume ratio (usable space in a container/space in a container) of larger than 0.3, and a power factor K of less than 8000, the power factor K being represented by the formula: K=Pv/&mgr;/n2 in which Pv is a power requirement per unit volume (W/m3), &mgr; is a melt viscosity (Pa.s), and n is a rotation speed (rps), to effectively remove terminal groups and bonds in the backbones, which are unstable during melt kneading, from the melt-processable fluorine-containing polymer, and obtain a colorless fluorine-containing polymer.

Abstract: A melt-processable fluorine-containing polymer is melt kneaded with a kneader which has a residence time of at least 10 minutes, a usable volume ratio (usable space in a container/space in a container) of larger than 0.3, and a power factor K of less than 8000, the power factor K being represented by the formula: K=Pv/&mgr;/n2 in which Pv is a power requirement per unit volume (W/m3), &mgr; is a melt viscosity (Pa.s), and n is a rotation speed (rps), to effectively remove terminal groups and bonds in the backbones, which are unstable during melt kneading, from the melt-processable fluorine-containing polymer, and obtain a colorless fluorine-containing polymer.

Abstract: To provide the stabilization method, in which unstable groups of melt-processable fluorine-containing polymer having unstable groups can be stabilized rapidly and effectively, and even if the obtained stabilized polymer is melt-molded, an obtained molded article is free from bubbles and cavity and no coloration arises. The method of stabilizing a fluorine-containing polymer by melt-kneading a melt-processable fluorine-containing polymer having unstable groups in a kneader having a stabilization treatment zone which satisfies the following conditions: (1) an oxygen-containing gas is present in the stabilization treatment zone, (2) water is present in the stabilization treatment zone, and (3) an absolute pressure in the stabilization treatment zone is adjusted to a pressure of 0.

Abstract: A melt-processable fluorine-containing polymer is melt kneaded with a kneader which has a residence time of at least 10 minutes, a usable volume ratio (usable space in a container/space in a container) of larger than 0.3, and a power factor K of less than 8000, the power factor K being represented by the formula: K=Pv/&mgr;/n2 in which Pv is a power requirement per unit volume (W/m3), &mgr; is a melt viscosity (Pa.s), and n is a rotation speed (rps), to effectively remove terminal groups and bonds in the backbones, which are unstable during melt kneading, from the melt-processable fluorine-containing polymer, and obtain a colorless fluorine-containing polymer.

Abstract: A process for preparing a fluoropolymer by the batchwise polymerization of a monomer mixture containing tetrafluoroethylene, in which, after the initiation of a reaction, the monomers are reacted under conditions such that the monomer mixture is supplemented to a polymerization system in an amount more than the amount of the monomers consumed and simultaneously the excessive unreacted monomers are discharged from the polymerization system to maintain the monomer composition in the polymerization system substantially the same as that of the composition of the monomer mixture initially charged, and the monomer mixture supplemented to the polymerization system contains a compound suppressing the autoexplosion of the monomers.

Abstract: A process for preparing a fluoropolymer by the batchwise polymerization of a monomer mixture containing tetrafluoroethylene, in which, after the initiation of a reaction, the monomers are reacted under conditions such that the monomer mixture is supplemented to a polymerization system in an amount more than the amount of the monomers consumed and simultaneously the excessive unreacted monomers are discharged from the polymerization system to maintain the monomer composition in the polymerization system substantially the same as that of the composition of the monomer mixture initially charged, and the monomer mixture supplemented to the polymerization system contains a compound suppressing the autoexplosion of the monomers.

Abstract: Coagulated particles having a low water content are separated and recovered from an emulsified dispersion of fluorine-containing polymer particles. A solid-liquid separation method comprising: a step for adding a coagulant in an emulsified dispersion of fluorine-containing polymer particles to coagulate the fluorine-containing polymer particles with stirring and obtain a slurry of coagulated particles, a step for filtrating the slurry, and a step for pressing the obtained cake. It is preferable to continuously carry out the filtration step and pressing step with a filter press or a belt press. Also a washing step may be provided after the filtration step.

Abstract: A method for preparing a tetrafluoroethylene/hexafluoropropylene copolymer by polymerizing tetrafluoroethylene and hexafluoropropylene in an aqueous medium using a di(fluoroacyl) peroxide as a polymerization initiator characterized in that a fluoroalkylcarboxylic acid is added gives a stable molecular weight of the tetrafluoroethylene/hexafluoropropylene copolymer and an increased utilization efficiency of the polymerization initiator.