Aqueous fluoropolymer dispersion

Abstract

An object of the present invention is to provide an aqueous fluoropolymer dispersion inhibited from viscosity rising and excellent in mechanical stability in spite of a low fluorinated surfactant concentration. The invention provides an aqueous fluoropolymer dispersion comprising particles of a fluoropolymer as dispersed in an aqueous medium wherein a fluorinated surfactant (A) having a molecular weight lower than 1000 amounts to not higher than 100 ppm of the mass of the fluoropolymer, the aqueous fluoropolymer dispersion containing an anionic surfactant (B) other than the fluorinated surfactant (A) as well as a water-soluble polymer (C).

1 . An aqueous fluoropolymer dispersion comprising a particle of fluoropolymer as dispersed in an aqueous medium wherein a fluorinated surfactant (A) having a molecular weight lower than 1000 amounts to not higher than 100 ppm of the mass of the fluoropolymer, said aqueous fluoropolymer dispersion containing an anionic surfactant (B) other than said fluorinated surfactant (A) as well as a water-soluble polymer (C). 
     
     
         2 . The aqueous fluoropolymer dispersion according to  claim 1 , wherein the anionic surfactant (B) is selected from the group consisting of (1) sulfosuccinic acid alkyl esters or salts thereof, and/or sulfosuccinic acid fluoroalkyl esters or salts thereof, (2) fluorinated surfactants (a) other than the fluorinated surfactant (A), which have a molecular weight lower than 1000, and (3) nonfluorinated anionic surfactants having an acid group and showing a pKa value lower than 4. 
     
     
         3 . The aqueous fluoropolymer dispersion according to  claim 2 , wherein the nonfluorinated anionic surfactant having an acid group and showing a pKa value lower than 4 is selected from the group consisting of sulfonic acids and carboxylic acids, and salts thereof. 
     
     
         4 . The aqueous fluoropolymer dispersion according to  claim 2 , wherein the nonfluorinated anionic surfactant having an acid group and showing a pKa value lower than 4 comprises an aliphatic carboxylic acid or a salt thereof. 
     
     
         5 . The aqueous fluoropolymer dispersion according to  claim 2 , wherein the nonfluorinated anionic surfactant having an acid group and showing a pKa value lower than 4 comprises a saturated or unsaturated aliphatic carboxylic acid of 9 to 13 carbon atoms in which a —OH group is optionally substituted for a terminal H, or a salt thereof. 
     
     
         6 . The aqueous fluoropolymer dispersion according to  claim 2 , wherein the fluorinated surfactant (a) is a fluorinated anionic surfactant (a1) of 4 to 7 carbon atoms. 
     
     
         7 . The aqueous fluoropolymer dispersion according to  claim 2 , wherein the anionic surfactant (B) comprises (1) sulfosuccinic acid alkyl esters or salts thereof, and/or sulfosuccinic acid fluoroalkyl esters or salts thereof. 
     
     
         8 . The aqueous fluoropolymer dispersion according to  claim 2 , wherein the sulfosuccinic acid alkyl esters or salts thereof and/or the sulfosuccinic acid fluoroalkyl esters or salts thereof are a sulfosuccinic acid alkyl ester or a salt thereof represented by the following general formula (I):
   R 1 —OCOCH(SO 3 A)CH 2 COO—R 2   (I)   
       (wherein R 1  and R 2  are the same or different and each represents an alkyl group of 4 to 12 carbon atoms and A represents an alkali metal, an alkaline earth metal or NH 4 ), or a sulfosuccinic acid fluoroalkyl ester or a salt thereof represented by the following general formula (II):
   Rf 1 —R 3 —OCOCH(SO 3 A)CH 2 COO—R 4 —Rf 2   (II) 
 
       (wherein Rf 1  and Rf 2  are the same or different and each represents a perfluoroalkyl group of 1 to 6 carbon atoms, which optionally has a terminal hydrogen atom, R 3  and R 4  are the same or different and each represents an alkylene group of 1 to 5 carbon atoms and A represents an alkali metal, an alkaline earth metal or NH 4   + ). 
     
     
         9 . The aqueous fluoropolymer dispersion according to  claim 8 , wherein the sulfosuccinic acid alkyl esters or salts thereof and/or the sulfosuccinic acid fluoroalkyl esters or salts thereof is the sulfosuccinic acid alkyl ester represented by the general formula (I) or the salt thereof, in which R 1  and R 2  in the general formula (I) are the same or different and each is an alkyl group of 8 to 12 carbon atoms. 
     
     
         10 . The aqueous fluoropolymer dispersion according to  claim 1 , wherein the anionic surfactant (B) amounts to 5 to 5000 ppm of the mass of the fluoropolymer. 
     
     
         11 . The aqueous fluoropolymer dispersion according to  claim 1 , wherein the anionic surfactant (B) amounts to 5 to 500 ppm of the mass of the fluoropolymer. 
     
     
         12 . The aqueous fluoropolymer dispersion according to  claim 1 , wherein the water-soluble polymer (C) comprises at least one polymer selected from the group consisting of polyacrylic acid, polyacrylic acid derivatives, polyvinylpyrrolidone, poly(vinyl methyl ether), poly(vinyl alcohol), poly(ethylene oxide) and poly(ethylene oxide) copolymers. 
     
     
         13 . The aqueous fluoropolymer dispersion according to  claim 1 , wherein the water-soluble polymer (C) has a molecular weight of 5000 to 20000000. 
     
     
         14 . The aqueous fluoropolymer dispersion according to  claim 1 , wherein the water-soluble polymer (C) has a molecular weight of 50000 to 1000000. 
     
     
         15 . The aqueous fluoropolymer dispersion according to  claim 1 , wherein the fluorinated surfactant (A) is a fluorinated anionic surfactant (A1) of 7 to 10 carbon atoms. 
     
     
         16 . The aqueous fluoropolymer dispersion according to  claim 1 , wherein the particle of fluoropolymer amounts to 30 to 70% by mass of the aqueous fluoropolymer dispersion. 
     
     
         17 . The aqueous fluoropolymer dispersion according to  claim 1 , wherein the viscosity at 25° C. is 0.01 to 0.16 Pa·s. 
     
     
         18 . The aqueous fluoropolymer dispersion according to  claim 1 , wherein the anionic surfactant (B) is an aliphatic carboxylic acid or salt thereof and the water-soluble polymer (C) is a block copolymer derived from ethylene oxide and propylene oxide. 
     
     
         19 . The aqueous fluoropolymer dispersion according to  claim 1 , which is a dispersion for dispersion spinning method. 
     
     
         20 . The aqueous fluoropolymer dispersion according to  claim 1 , which is a dust suppressant.