METHOD FOR PRODUCING FLUOROPOLYMER AQUEOUS DISPERSION LIQUID

Abstract

The present invention provides a method for producing a fluoropolymer aqueous dispersion having a significantly small particle size and excellent dispersion stability. The present invention relates to a method for producing an aqueous dispersion containing at least one fluoropolymer selected from the group consisting of polytetrafluoroethylene and melt-fabricable fluororesins excluding polytetrafluoroethylene. The method includes polymerizing a fluoromonomer in an aqueous medium in the presence of a fluorosurfactant and a polymerization initiator. The fluorosurfactant has a concentration in the aqueous medium of not lower than 0.8 times the critical micelle concentration of the fluorosurfactant.

Claims

1. A method for producing an aqueous dispersion containing at least one fluoropolymer selected from the group consisting of polytetrafluoroethylene and melt-fabricable fluororesins excluding polytetrafluoroethylene, the method comprising: polymerizing a fluoromonomer in an aqueous medium in the presence of a fluorosurfactant and a polymerization initiator, the fluorosurfactant having a concentration in the aqueous medium of not lower than 0.8 times the critical micelle concentration of the fluorosurfactant.

2. The method for producing a fluoropolymer aqueous dispersion according to claim 1, wherein the fluorosurfactant has Log POW of 3.4 or lower.

3. The method for producing a fluoropolymer aqueous dispersion according to claim 1, wherein the fluorosurfactant is at least one selected from the group consisting of: fluorine-containing compounds represented by the following formula (1):
X(CF.sub.2).sub.m1Y(1) wherein X is H or F; ml is an integer of 3 to 5; and Y is SO.sub.3M, SO.sub.4M, SO.sub.3R, SO.sub.4R, COOM, PO.sub.3M.sub.2, or PO.sub.4M.sub.2, where M is H, NH.sub.4, or an alkali metal and R is a C1-C12 alkyl group; and fluorine-containing compounds represented by the following formula (3):
CF.sub.3OCF(CF.sub.3)CF.sub.2OCF(CF.sub.3)COOX(3) wherein X is a hydrogen atom, NH.sub.4, or an alkali metal atom.

4. The method for producing a fluoropolymer aqueous dispersion according to claim 1, wherein the polymerization is performed in the absence of a fluorine-containing compound represented by the following formula (2):
X(CF.sub.2).sub.m2Y(2) wherein X is H or F; m2 is an integer of 6 or greater; and Y is SO.sub.3M, SO.sub.4M, SO.sub.3R, SO.sub.4R, COOM, PO.sub.3M.sub.2, or PO.sub.4M.sub.2, where M is H, NH.sub.4, or an alkali metal and R is a C1-C12 alkyl group.

5. The method for producing a fluoropolymer aqueous dispersion according to claim 1, wherein the fluoropolymer has a volume average particle size of not smaller than 0.1 nm but smaller than 20 nm.

6. The method for producing a fluoropolymer aqueous dispersion according to claim 1, wherein the polymerization initiator is at least one selected from the group consisting of persulfates and organic peroxides.

7. The method for producing a fluoropolymer aqueous dispersion according to claim 1, wherein the polymerization initiator is used in an amount corresponding to 1 to 5,000 ppm of the aqueous medium.

Description

EXAMPLES

[0159] Next, the present invention is described below referring to, but not limited to, examples.

[0160] The values in the examples are determined as follows.

Volume Average Particle Size

[0161] The volume average particle size is determined by dynamic light scattering (DLS). The dynamic light scattering (DLS) measurement was performed using ELSZ-1000S (Otsuka Electronics Co., Ltd.) at 25 C. A fluoropolymer aqueous dispersion having a fluoropolymer solid content of 1.0 mass % was used as a sample. The applied refractive index of the solvent (water) was 1.3328 and the viscosity of the solvent (water) was 0.8878 mPa.Math.s. The measurement was performed using 660-nm laser as a light source and the light scattered from the sample was detected at 165 which is close to the backscattering angle. One measurement included 70 accumulations, and the data was imported over about 3 minutes. In accordance with the scattering intensity of the sample, the device automatically adjusted the intensity of the laser light applied to the sample and the position of measurement so as to give an optimal scattering intensity (10000 to 50000 cps).

[0162] Based on the resulting autocorrelation function, the ELSZ-1000 software provided the average particle size (d) and the polydispersity index (PI) by the Cumulant method adapted to the autocorrelation function. Still, the information regarding the particle size distribution is insufficient.

[0163] Thus, in order to obtain the particle size distribution, the histogram method was performed in which approximation is performed by causing a limited number of j to represent the distribution. The non-linear least squares method used in the approximation was a modified Marquardt method. The resulting particle size distribution is a distribution dependent to the scattering intensity, and thus converted into a weight distribution by the Rayleigh-Gans-Debye function. The average value in the weight distribution was defined as the weight average particle size. The specific gravity of the particles in the sample is identical regardless of the particle size. Thus, the weight average particle size is considered as equivalent to the volume average particle size.

Modified Amount

[0164] The modified amount was determined by appropriate combination of NMR, FT-IR, elemental analysis, and X-ray fluorescence analysis in accordance with the type of the monomer.

Melting Point

[0165] The melting point was determined as a temperature corresponding to the local maximum on a heat-of-fusion curve obtained by heating 3 mg of a sample having no history of being heated up to 300 C. or higher using a differential scanning calorimeter (DSC) at a temperature-increasing rate of 10 C./min.

Initial Pyrolysis Temperature

[0166] The initial pyrolysis temperature was determined as a temperature at which the amount of a sample was reduced by 1 mass % when 10 mg of the sample was heated from room temperature at a temperature-increasing rate of 10 C./min using a thermogravimetric-differential thermal analysis (TG-DTA) device (trade name: TG/DTA6200, Seiko Instruments Inc.).

Solid Content

[0167] The solid content of the pre-condensation aqueous dispersion obtained by polymerization was a value corresponding to the proportion (in terms of percentage) of the mass of residue after heating (which was prepared by drying 1 g of the aqueous dispersion in a forced air oven at 150 C. for 60 minutes) relative to the mass (1 g) of the aqueous dispersion.

[0168] The solid content of the condensed fluoropolymer aqueous dispersion was a value corresponding to the proportion (in terms of percentage) of the mass of residue after heating (which was prepared by drying 1 g of the aqueous dispersion in a forced air oven at 300 C. for 60 minutes) relative to the mass (1 g) of the aqueous dispersion.

Melt Flow Rate (MFR)

[0169] The MFR was determined as the mass (g/10 min) of the polymer flowed out of a nozzle (inner diameter: 2 mm, length: 8 mm) per 10 minutes determined using a melt indexer (Yasuda Seiki Seisakusho Ltd.) by the method in conformity with ASTM D1238 at a predetermined measurement temperature and load depending on the type of the fluoropolymer (for example, the temperature was 372 C. for PFA and FEP, 297 C. for ETFE, and 380 C. for PTFE, and the load was 5 kg for PFA, FEP, ETFE, and PTFE).

[0170] If the amount of the polymer flowed out was very slight and was difficult to measure, it was regarded as 0.2 g/10 min or less.

Evaluation of Dispersion Stability

Storage Stability Test

[0171] First, 30 g of the fluoropolymer aqueous dispersion maintained at 25 C. was put in a container for exclusive use, and then stirred at 5000 rpm for five minutes using a centrifuge (himac CT15D, Hitachi Koki Co., Ltd.) equipped with a rotor (RT15A7 model), separating the precipitation layer from the fluoropolymer aqueous dispersion layer. The fluoropolymer aqueous dispersion layer was isolated and the solid content was determined. The precipitation amount was then calculated from the difference between the solid content in the fluoropolymer aqueous dispersion layer and the original solid content in the fluoropolymer aqueous dispersion used. The precipitation amount was determined in terms of proportion (mass %) relative to the amount of the fluoropolymer contained in the fluoropolymer aqueous dispersion used. The lower the proportion is, the better the storage stability is.

Mechanical Stability Test

[0172] First, 100 g of the fluoropolymer aqueous dispersion maintained at 65 C. was circulated for two hours at a discharge flow rate of 10 L/h using a peristaltic pump (roller pump RP-2000, Tokyo Rikakikai Co, Ltd.) equipped with a tube (Tygon tube) having an inner diameter of 4.76 mm and an outer diameter of 7.94 mm. Then, the fluoropolymer aqueous dispersion was filtered through a 200-mesh stainless steel net. The amount of the substance remaining on the net was measured in terms of proportion (mass %) relative to the amount of the fluoropolymer contained in the fluoropolymer aqueous dispersion used. The lower the proportion is, the better the mechanical stability is.

Example 1

[0173] A 1-L glass reactor equipped with a stirrer was charged with 530 g of deionized water, 30 g of paraffin wax, and 49.5 g of an ammonium perfluorohexanoate (APFH) dispersant. Next, the contents of the reactor were heated up to 85 C. and sucked, and simultaneously the reactor was purged with a TFE monomer, thereby removing the oxygen in the reactor. Then, 0.03 g of ethane gas was added to the reactor, and the contents were stirred at 540 rpm. The TFE monomer was added to the reactor until the inner pressure reached 0.73 MPaG. An initiator prepared by dissolving 0.110 g of ammonium persulfate (APS) in 20 g of deionized water was charged into the reactor, and the pressure in the reactor was adjusted to 0.83 MPaG. The charging of the initiator was followed by a decrease in the pressure, which means that the start of the polymerization was observed. The TFE monomer was added to the reactor to maintain the pressure, and the polymerization was continued until about 140 g of the TFE monomer was consumed in the reaction. Thereafter, the gas in the reactor was discharged until the pressure reached normal pressure. The contents were then taken out of the reactor and cooled down. The supernatant paraffin wax was removed from the resulting PTFE aqueous dispersion.

[0174] The resulting PTFE aqueous dispersion had a solid content of 20.9 mass % and a volume average particle size of 1.2 nm.

[0175] Nitric acid was added to the resulting PTFE aqueous dispersion, and the mixture was vigorously stirred until coagulation occurred. The resulting coagulum was washed with deionized water, and then dried at 150 C. Thereby, PTFE powder was obtained. This PTFE powder had a MFR of 16.7 g/10 min, a melting point of 327.2 C., and an initial pyrolysis temperature at 1 mass % of 473.0 C.

[0176] Deionized water was added to the resulting PTFE aqueous dispersion to adjust the solid content to 5.0 mass %, and the storage stability thereof was evaluated. The precipitation amount was 0.1 mass %.

[0177] APFH, which is the same dispersant as used in the polymerization, was added to the PTFE aqueous dispersion to adjust the amount of the dispersant to 10.0 mass %. Deionized water was further added to the dispersion to adjust the solid content to 5.0 mass %, and the mechanical stability was evaluated. The mesh-up amount was 0.1 mass %.

[0178] Then, 100 g of the resulting PTFE aqueous dispersion was uniformly mixed with 2.0 g of a surfactant, and the mixture was passed through a column filled with an ion exchange resin. The resulting aqueous dispersion was maintained at 60 C., and the condensed phase provided by phase separation was collected. This condensed phase had a solid content of 62 mass %. Water and a surfactant were further added to the condensed phase to give a solid content of 60 mass % and a surfactant content of 8 mass %, and the pH was adjusted to 9.7.

Control Example

[0179] The polymerization was performed in the same manner as in Example 1 except that the amount of the ammonium perfluorohexanoate (APFH) dispersant was not 49.5 g as in Example 1 but 55.0 g. The resulting PTFE aqueous dispersion had a solid content of 20.5 mass % and a volume average particle size of 0.9 nm.

[0180] In comparison with Example 1, the amount of change in the fluorosurfactant concentration in the aqueous medium was 10000 ppm and the amount of change in the volume average particle size was 0.3 nm. Thus, the amount of change in the volume average particle size was 0.03 nm per 1000 ppm of the fluorosurfactant in the aqueous medium.

Example 2

[0181] The polymerization was performed in the same manner as in Example 1 except that the polymerization temperature was not 85 C. as in Example 1 but 70 C.

Example 3

[0182] The polymerization was performed in the same manner as in Example 1 except that the amount of the ammonium persulfate (APS) initiator was not 0.110 g as in Example 1 but 0.028 g.

Example 4

[0183] The polymerization was performed in the same manner as in Example 1 except that the amount of the ammonium persulfate (APS) initiator was not 0.110 g as in Example 1 but 0.006 g, the amount of the ammonium perfluorohexanoate (APFH) dispersant was not 49.5 g but 55.0 g, and the polymerization was continued until about 40 g of the TFE monomer was consumed in the reaction.

Example 5

[0184] The polymerization was performed in the same manner as in Example 1 except that the amount of the ammonium persulfate (APS) initiator was not 0.110 g as in Example 1 but 0.006 g, the amount of the ammonium perfluorohexanoate (APFH) dispersant was not 49.5 g but 27.5 g, and the polymerization was continued until about 10 g of the TFE monomer was consumed in the reaction.

Example 6

[0185] The polymerization was performed in the same manner as in Example 4 except that the amount of the ammonium perfluorohexanoate (APFH) dispersant was not 55.0 g as in Example 4 but 26.4 g.

Example 7

[0186] The polymerization was performed in the same manner as in Example 4 except that the amount of the ammonium perfluorohexanoate (APFH) dispersant was not 55.0 g as in Example 4 but 25.9 g.

Example 8

[0187] The polymerization was performed in the same manner as in Example 4 except that 55.0 g of the ammonium perfluorohexanoate (APFH) dispersant as in Example 4 was replaced by 20.9 g of an ammonium 2,3,3,3-tetrafluoro-2-[1,1,2,3,3,3-hexafluoro-2-(trifluoromethoxy)propoxy]-propanoate (CF.sub.3OCF(CF.sub.3)CF.sub.2OCF(CF.sub.3)COONH.sub.4) (PMPA) dispersant.

Example 9

[0188] The polymerization was performed in the same manner as in Example 8 except that the amount of the ammonium 2,3,3,3-tetrafluoro-2-[1,1,2,3,3,3-hexafluoro-2-(trifluoromethoxy)propoxy]-propanoate (CF.sub.3OCF(CF.sub.3)CF.sub.2OCF(CF.sub.3)COONH.sub.4) (PMPA) dispersant was not 20.9 g as in Example 8 but 13.8 g.

Example 10

[0189] The polymerization was performed in the same manner as in Example 8 except that the amount of the ammonium 2,3,3,3-tetrafluoro-2-[1,1,2,3,3,3-hexafluoro-2-(trifluoromethoxy)propoxy]-propanoate (CF.sub.3OCF(CF.sub.3)CF.sub.2OCF(CF.sub.3)COONH.sub.4) (PMPA) dispersant was not 20.9 g as in Example 8 but 10.5 g.

Example 11

[0190] A 6-L stainless steel reactor equipped with a stirrer was charged with 2860 g of deionized water, 104 g of paraffin wax, and 288.0 g of an ammonium perfluorohexanoate (APFH) dispersant. Next, the contents of the reactor were heated up to 85 C. and sucked, and simultaneously the reactor was purged with a TFE monomer, thereby removing the oxygen in the reactor. Then, 0.08 g of ethane gas was added to the reactor, and the contents were stirred at 250 rpm. The TFE monomer was added to the reactor until the inner pressure reached 0.25 MPaG. An initiator prepared by dissolving 0.029 g of ammonium persulfate (APS) in 20 g of deionized water was charged into the reactor, and the pressure in the reactor was adjusted to 0.30 MPaG. The charging of the initiator was followed by a decrease in the pressure, which means that the start of the polymerization was observed. The TFE monomer was added to the reactor to maintain the pressure, and the polymerization was continued until about 250 g of the TFE monomer was consumed in the reaction. Thereafter, the gas in the reactor was discharged until the pressure reached normal pressure. The contents were then taken out of the reactor and cooled down. The supernatant paraffin wax was removed from the resulting PTFE aqueous dispersion.

[0191] The resulting PTFE aqueous dispersion had a solid content of 6.0 mass % and a volume average particle size of 2.5 nm.

[0192] A portion of the resulting PTFE aqueous dispersion was frozen in a freezer. The frozen PTFE aqueous dispersion was left to stand until the temperature reached 25 C., and thereby a coagulated powder was obtained. The wet coagulated powder was washed with deionized water and then dried at 150 C. This PTFE powder had a MFR of 0.2 g/10 min or lower, a melting point of 329.5 C., and an initial pyrolysis temperature at 1 mass % of 490.8 C.

Example 12

[0193] The polymerization was performed in the same manner as in Example 11 except that 0.08 g of the ethane gas as in Example 11 was replaced by 0.10 g of PMVE.

Example 13

[0194] The polymerization was performed in the same manner as in Example 11 except that 0.08 g of the ethane gas as in Example 11 was replaced by 0.49 g of HFP, the reactor at a pressure of 0.30 MPaG was replaced by a reactor at a pressure of 0.20 MPaG, and the polymerization was continued until about 200 g of the TFE monomer was consumed in the reaction.

Example 14

[0195] The polymerization was performed in the same manner as in Example 4 except that 0.03 g of the ethane gas as in Example 4 was replaced by 0.41 g of PPVE.

Example 15

[0196] A 1-L glass reactor equipped with a stirrer was charged with 530 g of deionized water, 30 g of paraffin wax, and 55.0 g of an ammonium perfluorohexanoate (APFH) dispersant. Next, the contents of the reactor were heated up to 85 C. and sucked, and simultaneously the reactor was purged with a TFE monomer, thereby removing the oxygen in the reactor. Then, 0.03 g of ethane gas and 0.20 g of perfluorohexylethylene (PFHE) were added to the reactor, and the contents were stirred at 540 rpm. The TFE monomer was added to the reactor until the inner pressure reached 0.73 MPaG. An initiator prepared by dissolving 0.006 g of ammonium persulfate (APS) in 20 g of deionized water was charged into the reactor, and the pressure in the reactor was adjusted to 0.83 MPaG. The charging of the initiator was followed by a decrease in the pressure, which means that the start of the polymerization was observed. The TFE monomer was added to the reactor to maintain the pressure, and the polymerization was continued until about 40 g of the TFE monomer was consumed in the reaction. Thereafter, the gas in the reactor was discharged until the pressure reached normal pressure. The contents were then taken out of the reactor and cooled down. The supernatant paraffin wax was removed from the resulting PTFE aqueous dispersion.

[0197] The resulting PTFE aqueous dispersion had a solid content of 6.6 mass % and a volume average particle size of 1.6 nm.

[0198] A portion of the resulting PTFE aqueous dispersion was frozen in a freezer. The frozen PTFE aqueous dispersion was left to stand until the temperature reached 25 C., and thereby a coagulated powder was obtained. The wet coagulated powder was washed with deionized water, and then dried at 150 C. This PTFE powder had a MFR of 0.2 g/10 min or lower, a melting point of 329.3 C., and an initial pyrolysis temperature at 1 mass % of 465.5 C.

Example 16

[0199] The polymerization was performed in the same manner as in Example 15 except that the polymerization temperature was not 85 C. as in Example 15 but 70 C., the amount of the ammonium persulfate (APS) initiator was not 0.006 g but 0.110 g, the amount of the ammonium perfluorohexanoate (APFH) dispersant was not 55.0 g but 44.0 g, 0.20 g of the perfluorohexylethylene (PFHE) was replaced by 1.12 g of perfluoro[3-(1-methyl-2-vinyloxy-ethoxy)propionitrile] (CNVE), and the polymerization was continued until about 140 g of the TFE monomer was consumed in the reaction.

Example 17

[0200] The polymerization was performed in the same manner as in Example 16 except that 44.0 g of the ammonium perfluorohexanoate (APFH) dispersant as in Example 16 was replaced by 22.0 g of an ammonium 2,3,3,3-tetrafluoro-2-[1,1,2,3,3,3-hexafluoro-2-(trifluoromethoxy)propoxy]-propanoate (CF.sub.3OCF(CF.sub.3)CF.sub.2OCF(CF.sub.3)COONH.sub.4) (PMPA) dispersant.

Example 18

[0201] The polymerization was performed in the same manner as in Example 15 except that 0.20 g of the perfluorohexyl ethylene (PFHE) as in Example 15 was replaced by 0.18 g of CTFE.

Example 19

[0202] The polymerization was performed in the same manner as in Example 15 except that the amount of the ammonium persulfate (APS) initiator was not 0.006 g as in Example 15 but 0.110 g, the amount of the ammonium perfluorohexanoate (APFH) dispersant was not 55.0 g but 49.5 g, 0.20 g of the perfluorohexylethylene (PFHE) was replaced by 8.80 g of PPVE, and the polymerization was continued until about 160 g of the TFE monomer was consumed in the reaction.

Example 20

[0203] The polymerization was performed in the same manner as in Example 16 except that the amount of the ammonium persulfate (APS) initiator was not 0.110 g as in Example 16 but 1.100 g.

Example 21

[0204] The polymerization was performed in the same manner as in Example 16 except that 44.0 g of the ammonium perfluorohexanoate (APFH) dispersant as in Example 16 was replaced by 33.0 g of a perfluoropolyether alkyl acid ammonium salt dispersant (C.sub.3F.sub.7OCF(CF.sub.3)COONH.sub.4) (PFPE).

Example 22

[0205] The polymerization was performed in the same manner as in Example 4 except that 55.0 g of the ammonium perfluorohexanoate (APFH) dispersant as in Example 4 was replaced by 100.0 g of an ammonium perfluoropentanoate (APFP) dispersant and the polymerization was continued until about 140 g of the TFE monomer was consumed in the reaction.

Example 23

[0206] The polymerization was performed in the same manner as in Example 4 except that 55.0 g of the ammonium perfluorohexanoate (APFH) dispersant as in Example 4 was replaced by 7.7 g a perfluoroalkyl alkylene sulfonic acid dispersant (C.sub.6F.sub.13(CH.sub.2).sub.2SO.sub.3H) (6,2-PFAS).

Example 24

[0207] The polymerization was performed in the same manner as in Example 4 except that 55.0 g of the ammonium perfluorohexanoate (APFH) dispersant as in Example 4 was replaced by 5.0 g a perfluoroalkyl alkylene sulfonic acid dispersant (C.sub.6F.sub.13(CH.sub.2).sub.2SO.sub.3H) (6,2-PFAS).

Example 25

[0208] The polymerization was performed in the same manner as in Example 4 except that 55.0 g of the ammonium perfluorohexanoate (APFH) dispersant as in Example 4 was replaced by 3.9 g of a perfluoroalkyl alkylene sulfonic acid dispersant (C.sub.6F.sub.13(CH.sub.2).sub.2SO.sub.3H) (6,2-PFAS).

Comparative Example 1

[0209] The polymerization was performed in the same manner as in Example 8 except that the amount of the ammonium 2,3,3,3-tetrafluoro-2-[1,1,2,3,3,3-hexafluoro-2-(trifluoromethoxy)propoxy]-propanoate (CF.sub.3OCF(CF.sub.3)CF.sub.2OCF(CF.sub.3)COONH.sub.4) (PMPA) dispersant was not 20.9 g as in Example 8 but 8.8 g.

Comparative Example 2

[0210] The polymerization was performed in the same manner as in Example 4 except that the amount of the ammonium perfluorohexanoate (APFH) dispersant was not 55.0 g as in Example 4 but 22.0 g.

[0211] Table 1 and Table 2 show the polymerization conditions and the evaluation results on the PTFE aqueous dispersions in the respective examples.

TABLE-US-00001 TABLE 1 Initiator Emulsifier Modifier Chain-transfer agent Temperature Pressure Type Amount Type Amount Type Amount Type Amount C. MPaG g g g g Example 1 85 0.83 APS 0.110 APFH 49.5 Ethane 0.03 Example 2 70 0.83 APS 0.110 APFH 49.5 Ethane 0.03 Example 3 85 0.83 APS 0.028 APFH 49.5 Ethane 0.03 Example 4 85 0.83 APS 0.006 APFH 55.0 Ethane 0.03 Example 5 85 0.83 APS 0.006 APFH 27.5 Ethane 0.03 Example 6 85 0.83 APS 0.006 APFH 26.4 Ethane 0.03 Example 7 85 0.83 APS 0.006 APFH 25.9 Ethane 0.03 Example 8 85 0.83 APS 0.006 PMPA 20.9 Ethane 0.03 Example 9 85 0.83 APS 0.006 PMPA 13.8 Ethane 0.03 Example 10 85 0.83 APS 0.006 PMPA 10.5 Ethane 0.03 Example 11 85 0.30 APS 0.029 APFH 288.0 Ethane 0.08 Example 12 85 0.30 APS 0.029 APFH 288.0 PMVE 0.10 Example 13 85 0.20 APS 0.029 APFH 283.0 HFP 0.49 Example 14 85 0.83 APS 0.006 APFH 55.0 PPVE 0.41 Example 15 85 0.83 APS 0.006 APFH 55.0 PFHE 0.20 Ethane 0.03 Example 16 70 0.83 APS 0.110 APFH 44.0 CNVE 1.12 Ethane 0.03 Example 17 70 0.83 APS 0.110 PMPA 22.0 CNVE 1.12 Ethane 0.03 Example 18 85 0.83 APS 0.006 APFH 55.0 CTFE 0.18 Ethane 0.03 Example 19 85 0.83 APS 0.110 APFH 49.5 PPVE 8.80 Ethane 0.03 Example 20 70 0.83 APS 1.100 APFH 44.0 CNVE 1.12 Ethane 0.03 Example 21 70 0.83 APS 0.110 PFPE 33.0 CNVE 1.12 Ethane 0.03 Example 22 85 0.83 APS 0.006 APFP 100.0 Ethane 0.03 Example 23 85 0.83 APS 0.006 6,2-PFAS 7.7 Ethane 0.03 Example 24 85 0.83 APS 0.006 6,2-PFAS 5.0 Ethane 0.03 Example 25 85 0.83 APS 0.006 6,2-PFAS 3.9 Ethane 0.03 Comparative 85 0.83 APS 0.006 PMPA 8.8 Ethane 0.03 Example 1 Comparative 85 0.83 APS 0.006 APFH 22.0 Ethane 0.03 Example 2

TABLE-US-00002 TABLE 2 Amount of change Volume Initial in volume average Dispersion stability* average Modified pyrolysis particle size Storage stability Mechanical particle amount Melting temper- Solid per 1000 ppm of (precipitation stability size MFR Type Amount point ature content fluorosurfactant amount) (mesh-up amount) nm g/10 min mol % C. C. mass % nm/1000 ppm mass % mass % Example 1 1.2 16.7 327.2 473.0 20.9 0.03 0.1 0.1 Example 2 2.2 6.3 328.5 477.5 20.5 0.01 0.1 0.2 Example 3 1.4 2.3 329.7 486.9 21.8 0.02 0.2 0.2 Example 4 3.3 0.2 or less 329.4 487.4 6.6 0.05 0.2 0.1 Example 5 4.7 0.4 328.6 478.8 1.4 0.05 0.1 0.1 Example 6 10.7 0.2 or less 327.6 490.1 6.1 1.60 4.3 1.5 Example 7 19.7 0.2 or less 327.6 489.8 5.9 23.76 7.8 2.3 Example 8 4.8 0.2 or less 328.6 489.1 7.4 0.05 0.2 0.7 Example 9 8.9 0.2 or less 328.6 487.3 6.9 0.49 3.7 1.4 Example 10 15.3 0.2 or less 328.9 491.3 6.8 3.52 6.3 1.9 Example 11 2.5 0.2 or less 329.5 490.8 6.0 0.03 0.2 0.2 Example 12 3.4 0.2 or less PMVE 0.022 332.8 496.7 6.6 0.05 0.2 0.2 Example 13 2.2 0.2 or less HFP 0.133 331.8 485.3 3.9 0.03 0.2 0.2 Example 14 1.4 0.2 or less PPVE 0.23 326.7 487.9 6.7 0.02 0.1 0.2 Example 15 1.6 0.2 or less PFHE 0.144 329.3 465.5 6.6 0.03 0.1 0.2 Example 16 1.3 0 CNVE 0.22 330.3 463.8 20.6 0.02 0.1 0.2 Example 17 0.9 0 CNVE 0.62 329.2 450.4 20.7 0.01 0.1 0.2 Example 18 2.8 0.2 or less CTFE 0.28 329.4 489.2 6.4 0.03 0.2 0.2 Example 19 4.6 210 PPVE 1.37 319.8 434.4 22.7 0.11 1 8 0.7 Example 20 2.6 0 CNVE 0.16 325.9 461.7 20.9 0.03 0.2 0.2 Example 21 2.2 0 CNVE 0.18 328.7 466.5 19.8 0.02 0.2 0.2 Example 22 2.9 0.2 or less 330.8 476.9 20.5 0.03 0.3 0.6 Example 23 2.7 0.2 or less 327.5 488.1 6.9 0.03 0.3 0.5 Example 24 4.8 0.2 or less 327.3 473.6 7.0 0.16 2.3 0.9 Example 25 9.7 0.2 or less 327.9 477.7 6.8 1.09 4.0 1.8 Comparative 109.7 0.2 or less 328.0 492.6 6.9 1.19 21.7 5.1 Example 1 Comparative 90.2 0.2 or less 327.5 491.6 7.1 1.47 19.8 4.6 Example 2 *Solid content was 1.0 mass % in each of Examples 5 and 13

INDUSTRIAL APPLICABILITY

[0212] The method for producing a fluoropolymer aqueous dispersion of the present invention can provide an aqueous dispersion which contains fluoropolymer particles having a significantly small particle size and which is excellent in dispersion stability. The fluoropolymer aqueous dispersion produced by the production method of the present invention and the fluoropolymer fine powder produced from the aqueous dispersion can suitably be used as, for example, additives for a variety of molding materials, coating materials, cosmetics, wax, grease, and toners; electrode binders for secondary batteries and fuel cells; hardness adjustors for electrode binders; and water-repellents for electrode surfaces.