A method for producing a fluoropolymer powder including (A1) adding, to a fluoropolymer aqueous dispersion obtained by polymerization using a carboxylic acid type hydrocarbon surfactant, and an acid to adjust a pH to 4.0 or less and cause coagulation to thereby obtain a wet fluoropolymer powder containing a fluorine-containing compound represented by the following general formula (1A), and (B1) heat-treating the wet fluoropolymer powder at a temperature higher than 150° C. and lower than 240° C.: General Formula (1A): H—(CF.sub.2).sub.m—COOH wherein m is 3 to 19.

A method for producing a fluoropolymer powder including (A1) adding, to a fluoropolymer aqueous dispersion obtained by polymerization using a carboxylic acid type hydrocarbon surfactant, and an acid to adjust a pH to 4.0 or less and cause coagulation to thereby obtain a wet fluoropolymer powder containing a fluorine-containing compound represented by the following general formula (1A), and (B1) heat-treating the wet fluoropolymer powder at a temperature higher than 150° C. and lower than 240° C.: General Formula (1A): H—(CF.sub.2).sub.m—COOH wherein m is 3 to 19.

[Problem to be Solved]

Provided are an aqueous dispersion of a fluoroolefin and the like that do not corrode vessels and enable a copolymer to be given at a high conversion ratio and high productivity from the fluoroolefin as a raw material monomer.

[Solution]

An aqueous dispersion containing: a fluoroolefin (a) represented by the following general formula (1); a surfactant (c) represented by the following general formula (2); and a dispersion medium containing water, wherein the aqueous dispersion has a cumulant diameter of 250 to 2,000 nm, and the aqueous dispersion has a pH of 2.0 to 7.0:

CF.sub.2═CF—[O—CF.sub.2—CF(CF.sub.3)].sub.n—O—[CF.sub.2].sub.m—Z   (1) wherein n represents an integer of 0 or more and 2 or less, m represents an integer of 2 or more and 4 or less, and Z represents CF.sub.3, SO.sub.2F, or COOH.sub.3, and

CF.sub.3—[CF.sub.2].sub.m—O—[CF(CF.sub.3)—CF.sub.2—O].sub.n—CF(CF.sub.3)—Z   (2) wherein m represents an integer of 0 to 2, n represents an integer of 0 to 6, Z represents COOM, wherein N represents H, Li, Na, K, or NR.sub.4, wherein R represents H or a linear alkyl group having 1 to 4 carbon atoms.

[Problem to be Solved]

Provided are an aqueous dispersion of a fluoroolefin and the like that do not corrode vessels and enable a copolymer to be given at a high conversion ratio and high productivity from the fluoroolefin as a raw material monomer.

[Solution]

An aqueous dispersion containing: a fluoroolefin (a) represented by the following general formula (1); a surfactant (c) represented by the following general formula (2); and a dispersion medium containing water, wherein the aqueous dispersion has a cumulant diameter of 250 to 2,000 nm, and the aqueous dispersion has a pH of 2.0 to 7.0:

CF.sub.2═CF—[O—CF.sub.2—CF(CF.sub.3)].sub.n—O—[CF.sub.2].sub.m—Z   (1) wherein n represents an integer of 0 or more and 2 or less, m represents an integer of 2 or more and 4 or less, and Z represents CF.sub.3, SO.sub.2F, or COOH.sub.3, and

CF.sub.3—[CF.sub.2].sub.m—O—[CF(CF.sub.3)—CF.sub.2—O].sub.n—CF(CF.sub.3)—Z   (2) wherein m represents an integer of 0 to 2, n represents an integer of 0 to 6, Z represents COOM, wherein N represents H, Li, Na, K, or NR.sub.4, wherein R represents H or a linear alkyl group having 1 to 4 carbon atoms.

An aqueous dispersion comprising a tetrafluoroethylene core-shell polymer and at least one surfactant corresponding to the general formula R.sub.10-[CH.sub.2CH.sub.20].sub.n[R.sub.20].sub.m-R.sub.3 wherein R.sub.1 represents a linear or branched aliphatic hydrocarbon group having at least 8 carbon atoms, preferably 8 to 18 carbon atoms, R2 represents an alkylene having 3 carbon atoms, R3 represents hydrogen, a C1-C3 alkyl group, or a C1-C3 hydroxyalkyl group, n has a value of 0 to 40, m has a value of 0 to 40 and the sum of n+m is at least 2, wherein the dispersion is free of fluorinated emulsifiers or contains them in an amount of less than 50 ppm based on the weight of the dispersion and wherein the core-shell polymer contains an outer shell of tetrafluoroethylene homopolymer. Further provided are methods of making the dispersions, coating compositions comprising the dispersions and article coated by the coating composition.

An aqueous dispersion comprising a tetrafluoroethylene core-shell polymer and at least one surfactant corresponding to the general formula R.sub.10-[CH.sub.2CH.sub.20].sub.n[R.sub.20].sub.m-R.sub.3 wherein R.sub.1 represents a linear or branched aliphatic hydrocarbon group having at least 8 carbon atoms, preferably 8 to 18 carbon atoms, R2 represents an alkylene having 3 carbon atoms, R3 represents hydrogen, a C1-C3 alkyl group, or a C1-C3 hydroxyalkyl group, n has a value of 0 to 40, m has a value of 0 to 40 and the sum of n+m is at least 2, wherein the dispersion is free of fluorinated emulsifiers or contains them in an amount of less than 50 ppm based on the weight of the dispersion and wherein the core-shell polymer contains an outer shell of tetrafluoroethylene homopolymer. Further provided are methods of making the dispersions, coating compositions comprising the dispersions and article coated by the coating composition.

An aqueous dispersion comprising a tetrafluoroethylene core-shell polymer and at least one surfactant corresponding to the general formula R.sub.10-[CH.sub.2CH.sub.20].sub.n[R.sub.20].sub.m-R.sub.3 wherein R.sub.1 represents a linear or branched aliphatic hydrocarbon group having at least 8 carbon atoms, preferably 8 to 18 carbon atoms, R2 represents an alkylene having 3 carbon atoms, R3 represents hydrogen, a C1-C3 alkyl group, or a C1-C3 hydroxyalkyl group, n has a value of 0 to 40, m has a value of 0 to 40 and the sum of n+m is at least 2, wherein the dispersion is free of fluorinated emulsifiers or contains them in an amount of less than 50 ppm based on the weight of the dispersion and wherein the core-shell polymer contains an outer shell of tetrafluoroethylene homopolymer. Further provided are methods of making the dispersions, coating compositions comprising the dispersions and article coated by the coating composition.

A fluoropolymer composition production method for producing a fluoropolymer composition containing a fluoropolymer, the method which includes polymerizing a fluoromonomer in a reactor in the presence of a fluorine-containing surfactant, a polymerization initiator, and an aqueous medium to prepare an aqueous dispersion comprising a fluoropolymer; feeding an inert gas to the reactor; and subjecting to a heat treatment the aqueous dispersion in the reactor to give a fluoropolymer composition, wherein a temperature of the heat treatment is 35° C. or higher and a time of the heat treatment is 15 minutes or more.

A fluoropolymer composition production method for producing a fluoropolymer composition containing a fluoropolymer, the method which includes polymerizing a fluoromonomer in a reactor in the presence of a fluorine-containing surfactant, a polymerization initiator, and an aqueous medium to prepare an aqueous dispersion comprising a fluoropolymer; feeding an inert gas to the reactor; and subjecting to a heat treatment the aqueous dispersion in the reactor to give a fluoropolymer composition, wherein a temperature of the heat treatment is 35° C. or higher and a time of the heat treatment is 15 minutes or more.

Provided is a fluoropolymer composition production method for producing a fluoropolymer composition containing a fluoropolymer, the method which includes polymerizing a fluoromonomer in a reactor in the presence of a fluorine-containing surfactant, a polymerization initiator, and an aqueous medium to prepare an aqueous dispersion containing a fluoropolymer; after the aqueous dispersion is prepared, removing from the reactor the fluoromonomer remaining in the reactor, or recovering the aqueous dispersion in the reactor and accommodating the aqueous dispersion in a container different from the reactor; adding a radical generator to the aqueous dispersion; and subjecting to a heat treatment the aqueous dispersion comprising the radical generator to give a fluoropolymer composition.