PROCESS FOR PRODUCING ELASTIC FLUOROCOPOLYMER AND CROSSLINKED FLUORORUBBER

Abstract

A process for producing an elastic fluorocopolymer, which comprises emulsion-polymerizing at least one fluoromonomer (a) selected from the group consisting of tetrafluoroethylene, hexafluoropropylene, vinylidene fluoride and a perfluorovinyl ether represented by CF2═CF—O—Rf (wherein Rf is a C1-8 perfluoroalkyl group or a perfluoro(alkoxyalkyl) group), a vinyl ester monomer (b) represented by the formula CR1R2═CR3COOCH═CH2 (wherein each of R1 and R2 which are independent of each other, is a hydrogen atom, a C1-10 alkyl group or a C1-10 alkoxyalkyl group containing an etheric oxygen atom, and R3 is a hydrogen atom, a fluorine atom or a methyl group), and as the case requires, at least one hydrocarbon monomer (c) selected from the group consisting of ethylene, propylene and a vinyl ether represented by CH2═CH—O—R4 (wherein R4 is a C1-8 alkyl group or an alkoxyalkyl group), in an aqueous medium to produce an elastic fluorocopolymer latex, adjusting the pH of the elastic fluorocopolymer latex to from 1 to 9, and coagulating the elastic fluorocopolymer latex to isolate an elastic fluorocopolymer.

Description

Claims

1. A process for producing an elastic fluorocopolymer, which comprises emulsion-polymerizing at least one fluoromonomer (a) selected from the group consisting of tetrafluoroethylene, hexafluoropropylene, vinylidene fluoride and a perfluorovinyl ether represented by CF2═CF—O—Rf (wherein Ris a C1-8 perfluoroalkyl group or a perfluoro(alkoxyalkyl) group), a vinyl ester monomer (b) represented by the formula CR1R2═CR3COOCH═CH2 (wherein each of R1 and R2 which are independent of each other, is a hydrogen atom, a C1-10 alkyl group or a C1-10 alkoxyalkyl group containing an etheric oxygen atom, and R3 is a hydrogen atom, a fluorine atom or a methyl group), and as the case requires, at least one hydrocarbon monomer (c) selected from the group consisting of ethylene, propylene and a vinyl ether represented by CH2═CH—O—R4 (wherein R4 is a C1-8 alkyl group or an alkoxyalkyl group), in an aqueous medium to produce an elastic fluorocopolymer latex, adjusting the pH of the elastic fluorocopolymer latex to from 1 to 9, and coagulating the elastic fluorocopolymer latex to isolate an elastic fluorocopolymer.

2. The process for producing an elastic fluorocopolymer according to claim 1, wherein R2 and R3 in the vinyl ester monomer (b) are hydrogen atoms.

3. The process for producing an elastic fluorocopolymer according to claim 1, wherein the vinyl ester monomer (b) is at least one member selected from the group consisting of vinyl methacrylate and vinyl crotonate.

4. The process for producing an elastic fluorocopolymer according to claim 1, wherein in the elastic s fluorocopolymer, the ratio of repeating units (l) based on the fluoromonomer (a) to repeating units (n) based on the hydrocarbon monomer (c) is such that (n)/(l)=30/70 to 70/30 (molar ratio).

5. The process for producing an elastic fluorocopolymer according to claim 1, wherein the fluoromonomer (a) is tetrafluoroethylene, the hydrocarbon monomer (c) is propylene, and in the elastic fluorocopolymer, the ratio of repeating units (l) based on the fluoromonomer (a) to repeating units (n) based on the hydrocarbon monomer (c) is such that (n)/(l)=40/60 to 60/40 (molar ratio).

6. The process for producing an elastic fluorocopolymer according to claim 1, wherein in the elastic fluorocopolymer, the ratio of repeating units (l) based on the fluoromonomer (a), repeating units (m) based on the vinyl ester monomer (b) and repeating units (n) based on the hydrocarbon monomer (c) is such that (m)/((l)+(n))=0.0001 to 0.1 (molar ratio).

7. The process for producing an elastic fluorocopolymer according to claim 1, wherein the pH is from 1 to 8.

8. The process for producing an elastic fluorocopolymer according to claim 1, wherein the pH at the time of the emulsion polymerization is from 1 to 8.

9. An elastic fluorocopolymer, which is obtained by the process for producing an elastic fluorocopolymer as defined in claim 1.

10. A crosslinked fluororubber, which is obtained by cross-linking an elastic fluorocopolymer obtained by the process for producing an elastic fluorocopolymer as defined in claim 1.