Process for producing aqueous fluoropolymer dispersion and aqueous fluoropolymer dispersion

• US 20070135558A1
• Filed: 10/29/2004
• Published: 06/14/2007
• Est. Priority Date: 10/31/2003
• Status: Active Grant

• Current Assignee: Daikin Industries Ltd
• Original Assignee: Daikin Industries Ltd
• Inventors: Shimizu, Tetsuo, Sawauchi, Chie, Tsuda, Nobuhiko, Sawada, Yasuhiko
• Granted Patent: US 7,696,268 B2
• Time in Patent Office: Days
• US Class Current: 524/544
• CPC Class Codes: C08F 14/18 Monomers containing fluorine
• CPC Class Codes: C08F 14/26 Tetrafluoroethene
• CPC Class Codes: C08F 2/16 Aqueous medium
• CPC Class Codes: C08F 214/26 Tetrafluoroethene
• CPC Class Codes: C08F 6/16 Purification
• CPC Class Codes: C08F 6/20 Concentration
• CPC Class Codes: C08L 27/12 containing fluorine atoms

Abstract

The present invention provides a method of producing a fluoropolymer aqueous dispersion by which the fluorine-containing emulsifier contained in the fluoropolymer aqueous dispersion as obtained after polymerization can be efficiently removed as well as a fluoropolymer aqueous dispersion low in fluorine-containing emulsifier concentration. The present invention is a method of producing a fluoropolymer aqueous dispersion which comprises carrying out a concentration treatment comprising a concentration operation of a pretreatment fluoropolymer aqueous dispersion, wherein the pretreatment fluoropolymer aqueous dispersion is obtained by carrying out a polymerization in an aqueous medium in the presence of a fluorine-containing surfactant (A), the fluorine-containing surfactant (A) is a fluorine-containing surfactant having an octanol/water partition coefficient of 1.5 to 3.5.

Claims

1. A method of producing a fluoropolymer aqueous dispersion which comprises carrying out a concentration treatment comprising a concentration operation of a pretreatment fluoropolymer aqueous dispersion, wherein said pretreatment fluoropolymer aqueous dispersion is obtained by carrying out a polymerization in an aqueous medium in the presence of a fluorine-containing surfactant (A), said fluorine-containing surfactant (A) is a fluorine-containing surfactant having an octanol/water partition coefficient of 1.5 to 3.5.

2. The method of producing a fluoropolymer aqueous dispersion according to claim 1, wherein the ratio [M¹/M⁰] between the mass [M⁰] of the fluorine-containing surfactant (A) in the pretreatment fluoropolymer aqueous dispersion and the mass [M¹] of the fluorine-containing surfactant (A) removed by carrying out the concentration operation once is not lower than 0.5.

3. The method of producing a fluoropolymer aqueous dispersion according to claim 1, wherein the ratio [M¹/M⁰] between the mass [M⁰] of the fluorine-containing surfactant (A) in the pretreatment fluoropolymer aqueous dispersion and the mass [M¹] of the fluorine-containing surfactant (A) removed by carrying out the concentration operation once is not lower than 0.6.

4. The method of producing fluoropolymer aqueous dispersion according to claim 1, wherein the ratio [M¹/M⁰] between the mass [M⁰] of the fluorine-containing surfactant (A) in the pretreatment fluoropolymer aqueous dispersion and the mass [M¹] of the fluorine-containing surfactant (A) removed by carrying out the concentration operation once is not lower than 0.7.

5. The method of producing a fluoropolymer aqueous dispersion according to claim 1, wherein the fluoropolymer aqueous dispersion has a solid matter concentration of 30 to 80% by mass.

6. The method of producing a fluoropolymer aqueous dispersion according to claim 1, wherein the fluorine-containing surfactant (A) has an octanol/water partition coefficient of 1.5 to 3.0.

7. The method of producing a fluoropolymer aqueous dispersion according to claim 1, wherein a fluoropolymer constituting the pretreatment fluoropolymer aqueous dispersion comprises a tetrafluoroethylene homopolymer and/or a modified polytetrafluoroethylene.

8. The method of producing a fluoropolymer aqueous dispersion according to claim 1, wherein a fluoropolymer constituting the pretreatment fluoropolymer aqueous dispersion is a perfluoropolymer.

9. A fluoropolymer aqueous dispersion which is obtained by the method of producing a fluoropolymer aqueous dispersion according to claim 1.

12. A fluoropolymer powder which is obtained by drying a wet powder obtained by coagulation of the fluoropolymer aqueous dispersion according to claim 9.

13. A fluoropolymer molding which is obtained by carrying out a molding/processing using the fluoropolymer aqueous dispersion according to claim 9.

14. A fluoropolymer molding which is obtained by carrying out a molding/processing using the fluoropolymer powder according to claim 12.

10. A fluoropolymer aqueous dispersion containing a particle comprising a fluoropolymer dispersed in an aqueous medium, wherein said fluoropolymer aqueous dispersion contains a fluorine-containing surfactant (A) in an amount of not smaller than 0.1 ppm but not greater than 5% by mass and has a solid matter concentration of 30 to 80% by mass, said fluorine-containing surfactant (A) has an octanol/water partition coefficient of 1.5 to 3.5.

11. The fluoropolymer aqueous dispersion according to claim 10, wherein the fluorine-containing surfactant (A) is the one caused to be present in carrying out a polymerization in the aqueous medium for obtaining the fluoropolymer.