JP2012241128A - Method for producing fluoropolymer - Google Patents

Abstract

A novel production method for producing a fluoropolymer using a polymerization solvent having a low global warming potential is provided.
A process for producing a fluoropolymer comprising the following formula:
R ¹ —O—CX ¹ Z ¹ — (CY ¹ Y ² ) _a —CX ² X ³ X ⁴ (1)
(In the formula, R ¹ represents a non-fluorinated alkyl group or a perfluoroalkyl group having 1 to 3 carbon atoms, a represents an integer of 0 to 3, and X ^{1 to} X ⁴ and Y ^{1 to} Y ² each represents Independently, it represents a hydrogen atom, a fluorine atom, or an alkyl group or fluoroalkyl group having ¹ to 3 carbon atoms, and Z ¹ represents a fluorine atom or an alkyl group or fluoroalkyl group having 1 to 3 carbon atoms. However, at least one of X ^{1 to} X ⁴ is a hydrogen atom, at least one is a fluorine atom, and when R ¹ is a perfluoroalkyl group, at least one of X ^{2 to} X ⁴ is a hydrogen atom. And a fluoromonomer is polymerized in the presence of the fluorinated ether represented by formula (1).
[Selection figure] None

Description

The present invention relates to a method for producing a fluoropolymer.

As a method for producing a fluoropolymer, an emulsion polymerization method or a suspension polymerization method is known. In these polymerization methods, perfluorocarbon (PFC) or chlorofluorocarbon (CFC) has been used as a polymerization medium. However, PFC and CFC have a large global warming potential (GWP), and it is preferable to reduce the amount used. Therefore, a solvent that replaces PFC and CFC has been proposed.

In Patent Document 1, carbon, fluorine, at least one hydrogen atom, at least the same number of fluorine atoms as the hydrogen atom, at least two adjacent —CH ₂ — groups are contained, and any primary carbon is a hydrogen atom. There has been proposed a polymerization process comprising contacting a fluoromonomer with a solvent that should not contain a methyl group (—CH ₃ ) except for the —CF ₂ OCH ₃ atomic group, which does not have a hydrogen atom.

In Patent Document 2, in producing a fluoropolymer by polymerization in a polymerization medium, F (CF ₂ ) ₄ OCH ₃ , F (CF ₂ ) ₄ OC ₂ H ₅ , (CF ₃ ) ₂ CFOCH are used as the polymerization medium. ₃ , a method for producing a fluorine-containing polymer characterized by using a (perfluoroalkyl) alkyl ether such as F (CF ₂ ) ₃ OCH ₃ has been proposed.

In Patent Document 3, in a method for producing a fluorinated polymer in which a fluorine monomer is radically polymerized in a polymerization medium, CF ₃ CH ₂ OCF ₂ CHF ₂ , CHF ₂ CF ₂ CH ₂ OCF ₂ CHF ₂ , CF are used as the polymerization medium. ₃ CF ₂ CH ₂ method of producing a fluoropolymer, which comprises using a hydro fluoroalkyl ether such as OCF ₂ CHF ₂ is proposed.

In Patent Document 4, in producing an ethylene-tetrafluoroethylene copolymer by polymerization in a polymerization medium, the polymerization medium has 3 to 10 carbon atoms containing a fluorine atom and one or more hydrogen atoms equal to or less than the number of fluorine atoms as the polymerization medium. There has been proposed a method for producing an ethylene-tetrafluoroethylene copolymer, characterized by using hydrofluorocarbon and using a saturated hydrocarbon or a partially fluorinated saturated hydrocarbon having 3 to 10 carbon atoms as a chain transfer agent.

JP 7-504224 JP 11-92507 A JP 2005-29704 A JP-A-6-298810

An object of the present invention is to provide a novel production method for producing a fluoropolymer using a polymerization solvent having a low global warming potential.

That is, the present invention is a method for producing a fluoropolymer, which has the following formula:
R ¹ —O—CX ¹ Z ¹ — (CY ¹ Y ² ) _a —CX ² X ³ X ⁴ (1)
(In the formula, R ¹ represents a non-fluorinated alkyl group or a perfluoroalkyl group having 1 to 3 carbon atoms, a represents an integer of 0 to 3, and X ^{1 to} X ⁴ and Y ^{1 to} Y ² each represents Independently, it represents a hydrogen atom, a fluorine atom, or an alkyl group or fluoroalkyl group having ¹ to 3 carbon atoms, and Z ¹ represents a fluorine atom or an alkyl group or fluoroalkyl group having 1 to 3 carbon atoms. However, at least one of X ^{1 to} X ⁴ is a hydrogen atom, at least one is a fluorine atom, and when R ¹ is a perfluoroalkyl group, at least one of X ^{2 to} X ⁴ is a hydrogen atom. The fluoromonomer is polymerized in the presence of the fluorine-containing ether represented by formula (1).

The above fluorine-containing ethers are CF ₃ OCF ₂ CF ₂ H, CF ₃ OCF ₂ CF ₂ CF ₂ H, CF ₃ CF ₂ OCF ₂ CHF ₂ , CH ₃ OCF ₂ CHF ₂ , CH ₃ OCF ₂ CF ₂ CHF ₂ , CH It is preferably at least one selected from the group consisting of ₃ CH ₂ OCF ₂ CHF ₂ and CH ₃ OCH (CF ₃ ) ₂ .

The fluoromonomer is preferably polymerized by a suspension polymerization method.

The fluoropolymer is preferably a melt-processable fluoropolymer.

The above fluoropolymers are polyvinylidene fluoride, tetrafluoroethylene / vinylidene fluoride copolymer, tetrafluoroethylene / vinylidene fluoride / hexafluoroethylene copolymer, tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer, tetrafluoroethylene. / Hexafluoroethylene copolymer and at least one selected from the group consisting of ethylene / tetrafluoroethylene copolymer are preferable.

The present invention provides the following formula:
R ¹ —O—CX ¹ Z ¹ — (CY ¹ Y ² ) _a —CX ² X ³ X ⁴ (1)
(In the formula, R ¹ represents a non-fluorinated alkyl group or a perfluoroalkyl group having 1 to 3 carbon atoms, a represents an integer of 0 to 3, and X ^{1 to} X ⁴ and Y ^{1 to} Y ² each represents Independently, it represents a hydrogen atom, a fluorine atom, or an alkyl group or fluoroalkyl group having ¹ to 3 carbon atoms, and Z ¹ represents a fluorine atom or an alkyl group or fluoroalkyl group having 1 to 3 carbon atoms. However, at least one of X ^{1 to} X ⁴ is a hydrogen atom, at least one is a fluorine atom, and when R ¹ is a perfluoroalkyl group, at least one of X ^{2 to} X ⁴ is a hydrogen atom. It is also a polymerization solvent characterized by comprising a fluorine-containing ether represented by

The present invention provides the following formula:
R ¹ —O—CX ¹ Z ¹ — (CY ¹ Y ² ) _a —CX ² X ³ X ⁴ (1)
(In the formula, R ¹ represents a non-fluorinated alkyl group or a perfluoroalkyl group having 1 to 3 carbon atoms, a represents an integer of 0 to 3, and X ^{1 to} X ⁴ and Y ^{1 to} Y ² each represents Independently, it represents a hydrogen atom, a fluorine atom, or an alkyl group or fluoroalkyl group having ¹ to 3 carbon atoms, and Z ¹ represents a fluorine atom or an alkyl group or fluoroalkyl group having 1 to 3 carbon atoms. However, at least one of X ^{1 to} X ⁴ is a hydrogen atom, at least one is a fluorine atom, and when R ¹ is a perfluoroalkyl group, at least one of X ^{2 to} X ⁴ is a hydrogen atom. It is also a composition characterized by comprising a fluorine-containing ether represented by formula (1) and a polymerization initiator.

Since the production method of the present invention has the above-described configuration, it is environmentally friendly and can produce a fluoropolymer having physical properties comparable to those of conventional production methods using perfluorocarbon or chlorofluorocarbon.
Since the solvent and composition for polymerization of the present invention have the above-mentioned constitution, they are environmentally friendly, and can be used for the production of fluoropolymers, thereby allowing conventional polymerization solvents and compositions containing perfluorocarbon and chlorofluorocarbon to be used. A fluoropolymer having comparable physical properties can be produced.

The method for producing a fluoropolymer of the present invention is characterized by polymerizing a fluoromonomer in the presence of a specific fluorine-containing ether.

The fluorine-containing ether has the following formula:
R ¹ —O—CX ¹ Z ¹ — (CY ¹ Y ² ) _a —CX ² X ³ X ⁴ (1)
(In the formula, R ¹ represents a non-fluorinated alkyl group or a perfluoroalkyl group having 1 to 3 carbon atoms, a represents an integer of 0 to 3, and X ^{1 to} X ⁴ and Y ^{1 to} Y ² each represents Independently, it represents a hydrogen atom, a fluorine atom, or an alkyl group or fluoroalkyl group having ¹ to 3 carbon atoms, and Z ¹ represents a fluorine atom or an alkyl group or fluoroalkyl group having 1 to 3 carbon atoms. However, at least one of X ^{1 to} X ⁴ is a hydrogen atom, at least one is a fluorine atom, and when R ¹ is a perfluoroalkyl group, at least one of X ^{2 to} X ⁴ is a hydrogen atom. It is expressed by.

The fluorine-containing ether preferably has a total carbon number of 4 to 8, more preferably 4 to 6, and still more preferably 4.
The fluorine-containing ether preferably has a total number of fluorine atoms of 50% or more based on the total number of hydrogen atoms and fluorine atoms.
The fluorine-containing ether has a low global warming potential and low chain mobility. By using the above-mentioned fluorine-containing ether, a fluoropolymer having a high molecular weight and excellent in solvent resistance and chemical resistance can be efficiently produced.

R ¹ in the above formula (1) preferably has 1 carbon.
The a is preferably an integer of 0 to 3, and more preferably 0 or 1.
Y ^{1 to} Y ² are preferably fluorine atoms.

The fluorine-containing ethers, among _{others, CF 3 OCF 2 CF 2 H} , CF 3 OCF 2 CF 2 CF 2 H, CH 3 OCF 2 CHF 2, CF 3 CF 2 OCF 2 CHF 2, CH 3 OCF 2 CF 2 CHF ₂ , at least one selected from the group consisting of CH ₃ CH ₂ OCF ₂ CHF ₂ and CH ₃ OCH (CF ₃ ) ₂ is preferred.

The fluorine-containing ether preferably has a boiling point of 35 to 85 ° C. When the boiling point of the fluorinated ether is within the above range, it is easy to separate and recover the fluorinated ether from water after polymerization.

The fluorine-containing ether can be used as a polymerization solvent. The amount used can be appropriately selected depending on the type and characteristics of the target polymer. You may use the said fluorine-containing ether mixed with another polymerization solvent. Further, a polymerization initiator may be dissolved in the above-mentioned fluorine-containing ether and charged into the polymerization reactor.

The polymerization of the fluoromonomer can be performed by a known polymerization method, and examples thereof include an emulsion polymerization method, a suspension polymerization method, a solution polymerization method, a bulk polymerization method, and the like, and the polymerization is performed by an emulsion polymerization method or a suspension polymerization method. It is preferable to perform polymerization by suspension polymerization.

Examples of the fluoromonomer include tetrafluoroethylene [TFE], vinylidene fluoride [VdF], chlorotrifluoroethylene [CTFE], vinyl fluoride [VF], hexafluoropropylene [HFP], and hexafluoroisobutene [HFIB]. , CH ₂ = CX ⁶ (CF ₂ ) _n X ⁷ (wherein X ⁶ is H or F, X ⁷ is H, F or Cl, and n is an integer of 1 to 10). Body, CF ₂ = CF-ORf ¹ (wherein Rf ¹ represents a perfluoroalkyl group having 1 to 8 carbon atoms) perfluoro (alkyl vinyl ether) [PAVE], CF ₂ = CF-OCH ₂ -Rf ² (wherein, Rf ² represents. a perfluoroalkyl group having 1 to 5 carbon atoms) alkyl perfluorovinyl ether derivative represented by, trifluoperazine Ethylene, trifluoro propylene, tetrafluoropropylene, pentafluoropropylene, trifluoperazine Rob Ten tetrafluoro isobutene, and be at least one selected from the group consisting of iodine-containing fluorinated vinyl ethers preferred.

The fluoropolymer is preferably a fluororesin. The fluororesin is not particularly limited as long as it has a clear melting point.

The fluoropolymer preferably has a melting point of 100 to 347 ° C, and more preferably 150 to 322 ° C. The melting point can be determined as a temperature corresponding to the maximum value in the heat of fusion curve when the temperature is raised at a rate of 10 ° C./min using a DSC apparatus (manufactured by Seiko).

The fluoropolymer preferably has a melt flow rate [MFR] of 1 to 100 g / 10 min. The MFR is a value that can be measured in accordance with ASTM D 3307 under a load of 5.0 kg. The measurement temperature depends on the melting point of the fluoropolymer.

The fluoropolymer includes tetrafluoroethylene [TFE], vinylidene fluoride [VdF], chlorotrifluoroethylene [CTFE], vinyl fluoride [VF], hexafluoropropylene [HFP], hexafluoroisobutene [HFIB], ^{_{CH 2 = CX 6 (CF 2}} ) n X 7 ( wherein, ^{X 6} represents H or F, ^{X 7} is H, F or Cl, n is an integer of from 1 to 10.) the monomer represented by, CF ₂ = CF-ORf ¹ perfluoro (. wherein, Rf ¹ is representative of the perfluoroalkyl group having 1 to 8 carbon atoms) represented by (alkyl vinyl ether) _{[PAVE], CF 2 = CF-OCH 2} - Rf ² (wherein, Rf ² represents. a perfluoroalkyl group having 1 to 5 carbon atoms) alkyl perfluorovinyl ether derivative represented by trifluoroacetic ethyl It is preferable to have a polymer unit based on at least one fluoromonomer selected from the group consisting of ethylene, trifluoropropylene, tetrafluoropropylene, pentafluoropropylene, trifluorobutene, tetrafluoroisobutene, and iodine-containing fluorinated vinyl ether .

The fluoropolymer may have a polymerization unit based on a non-fluorinated monomer, and has a repeating unit derived from an ethylenic monomer having 5 or less carbon atoms from the viewpoint of maintaining heat resistance, chemical resistance, and the like. This is also a preferred form. The fluoropolymer comprises polymerized units based on at least one non-fluorinated monomer selected from the group consisting of ethylene, propylene, 1-butene, 2-butene, alkyl vinyl ether, vinyl chloride, vinylidene chloride and unsaturated carboxylic acid. It is also preferable to have it.

Examples of the fluoropolymer include polytetrafluoroethylene [PTFE], polychlorotrifluoroethylene [PCTFE], ethylene [Et] / TFE copolymer [ETFE], Et / chlorotrifluoroethylene [CTFE] copolymer, CTFE. / TFE copolymer, TFE / HFP copolymer [FEP], TFE / PAVE copolymer [PFA], and at least one selected from the group consisting of polyvinylidene fluoride [PVdF] More preferably, it is a melt-processable fluoropolymer, more preferably at least one selected from the group consisting of ETFE, FEP and PFA.

The ETFE preferably has an Et unit: TFE unit molar ratio of 20:80 to 80:20. When the Et unit content is less than 20:80, productivity may be poor, and when the Et unit content exceeds 80:20, corrosion resistance may be deteriorated. More preferably, the molar ratio of Et units: TFE units is 35:65 to 55:45. ETFE is a copolymer containing polymerized units based on TFE and polymerized units based on Et, and may have polymerized units based on other fluoromonomer or non-fluorinated monomer.

The other fluoromonomer or non-fluorinated monomer is not particularly limited as long as it can be added to both Et and TFE, but a fluorine-containing vinyl monomer having 3 to 10 carbon atoms is easy to use. For example, hexafluoroisobutylene CH ₂ = CFC ₃ F ₆ H, HFP, and the like. Among them, the following general formula:
CH ₂ = CH-Rf ⁴
A fluorine-containing vinyl monomer represented by the formula (wherein Rf ⁴ represents a perfluoroalkyl group having 4 to 8 carbon atoms) is also one preferred form. Non-fluorinated monomers include the following general formula:
CH ₂ = ^{CH-R 4}
(In the formula, R ⁴ is not particularly limited in carbon number and may contain an aromatic ring, and may contain a carbonyl group, an ester group, an ether group, an amide group, a cyano group, a hydroxyl group or an epoxy group. R ⁴ does not contain a fluorine atom).

In addition, ETFE is an Et / TFE / HFP copolymer, which is also a preferred form, and has other fluoromonomer (excluding HFP) or polymerized units based on non-fluorinated monomers. There may be. The other fluoromonomer and non-fluorinated monomer are preferably 10 mol% or less, more preferably 5 mol% or less of the whole polymer. Et unit: TFE unit: Molar ratio of monomer units based on other fluoromonomer and non-fluorinated monomer is 31.5-54.7: 40.5-64.7: 0.5-10 Is preferred.

In the FEP, the HFP unit is more than 2% by mass, preferably 20% by mass or less, and more preferably 10 to 15% by mass.

As PAVE in said PFA, what has a C1-C6 alkyl group is preferable, and PMVE, PEVE, or PPVE is more preferable. The PFA has a PAVE unit of more than 2% by mass and preferably 5% by mass or less, and more preferably 2.5 to 4.0% by mass.

The FEP or PFA may be further polymerized with other monomers as long as it has the above-described composition. Examples of the other monomer include PAVE in the case of the FEP, and HFP in the case of the PFA. The said other monomer can use 1 type (s) or 2 or more types.

The other monomer to be polymerized with the FEP or PFA varies depending on the type, but it is usually preferably 1% by mass or less of the mass of the fluoropolymer (A). A more preferred upper limit is 0.5% by mass, and a still more preferred upper limit is 0.3% by mass.

The content of each monomer unit of the copolymer described above can be calculated by appropriately combining NMR, FT-IR, elemental analysis, and fluorescent X-ray analysis depending on the type of monomer.

In the production method of the present invention, the polymerization is carried out by charging the polymerization reactor with the above-mentioned fluorine-containing ether, fluoromonomer and other additives as necessary, stirring the contents of the reactor, and then subjecting the reactor to the predetermined polymerization. It can be carried out by maintaining the temperature and then adding a predetermined amount of a polymerization initiator to start the polymerization reaction. It is also possible to charge a polymerization solvent, a surfactant, a chain transfer agent, a radical scavenger and the like different from the fluorine-containing ether. The polymerization may be batch polymerization, semi-batch polymerization or continuous polymerization.

Examples of the polymerization solvent different from the fluorine-containing ether include water; fluorine-free organic solvents such as alcohols, ethers, and ketones; and fluorine-containing organic solvents having a boiling point of 40 ° C. or lower. For example, when carrying out suspension polymerization, a fluorine-containing organic solvent such as C318 can be used.

As the polymerization initiator, known oil-soluble and / or water-soluble polymerization initiators can be used. Furthermore, the polymerization can be started as a redox in combination with a reducing agent or the like. The concentration of the polymerization initiator is appropriately determined depending on the type of monomer, the molecular weight of the target fluoropolymer, and the reaction rate.

The polymerization initiator may be dissolved in the fluorine-containing ether and charged into the polymerization reactor.

Examples of the chain transfer agent include hydrocarbons such as isopentane, n-pentane, n-hexane, and cyclohexane; alcohols such as methanol and ethanol; halogenated hydrocarbons such as carbon tetrachloride, chloroform, methylene chloride, and methyl chloride. Can be used.

In the production method of the present invention, the polymerization temperature is not particularly limited, but is preferably 0 to 100 ° C, and more preferably 30 to 90 ° C. The polymerization pressure is not particularly limited, but is preferably 0.1 to 10 MPa, and more preferably 0.5 to 5 MPa.

The production method of the present invention may include a step of recovering the fluoropolymer after polymerizing the fluoromonomer. When an aqueous dispersion containing a fluoropolymer is obtained by polymerization, the fluoropolymer may be recovered by coagulating, washing and drying the fluoropolymer contained in the aqueous dispersion. When the fluoropolymer is obtained as a slurry by polymerization, the fluoropolymer may be recovered by removing the slurry from the polymerization reactor, washing, and drying. By drying, the fluoropolymer can be recovered in the form of powder.

The present invention provides the following formula:
R ¹ —O—CX ¹ Z ¹ — (CY ¹ Y ² ) _a —CX ² X ³ X ⁴ (1)
(In the formula, R ¹ represents a non-fluorinated alkyl group or a perfluoroalkyl group having 1 to 3 carbon atoms, a represents an integer of 0 to 3, and X ^{1 to} X ⁴ and Y ^{1 to} Y ² each represents Independently, it represents a hydrogen atom, a fluorine atom, or an alkyl group or fluoroalkyl group having ¹ to 3 carbon atoms, and Z ¹ represents a fluorine atom or an alkyl group or fluoroalkyl group having 1 to 3 carbon atoms. However, at least one of X ^{1 to} X ⁴ is a hydrogen atom, at least one is a fluorine atom, and when R ¹ is a perfluoroalkyl group, at least one of X ^{2 to} X ⁴ is a hydrogen atom. It is also a polymerization solvent characterized by comprising a fluorine-containing ether represented by

Preferred fluorine-containing ethers are as described above. The polymerization solvent of the present invention can be used to produce a fluoropolymer by polymerizing a fluoromonomer.

The present invention provides the following formula:
R ¹ —O—CX ¹ Z ¹ — (CY ¹ Y ² ) _a —CX ² X ³ X ⁴ (1)
(In the formula, R ¹ represents a non-fluorinated alkyl group or a perfluoroalkyl group having 1 to 3 carbon atoms, a represents an integer of 0 to 3, and X ^{1 to} X ⁴ and Y ^{1 to} Y ² each represents Independently, it represents a hydrogen atom, a fluorine atom, or an alkyl group or fluoroalkyl group having ¹ to 3 carbon atoms, and Z ¹ represents a fluorine atom or an alkyl group or fluoroalkyl group having 1 to 3 carbon atoms. However, at least one of X ^{1 to} X ⁴ is a hydrogen atom, at least one is a fluorine atom, and when R ¹ is a perfluoroalkyl group, at least one of X ^{2 to} X ⁴ is a hydrogen atom. It is also a composition characterized by comprising a fluorine-containing ether represented by formula (1) and a polymerization initiator.

Preferred fluorine-containing ethers are as described above. The compositions of the present invention can be used to polymerize fluoromonomers to produce fluoropolymers.

Next, the present invention will be described with reference to examples, but the present invention is not limited to such examples.

Each numerical value of the examples was measured by the following method.

[Melting point]
Using a differential scanning calorimeter [DSC] (trade name: RDC220, manufactured by Seiko Denshi), 3 mg of the sample was heated from room temperature to 300 ° C. at 10 ° C./min, and then cooled to room temperature at −10 ° C./min. The temperature at the melting peak when the temperature was raised again from room temperature at 10 ° C./min was taken as the melting point.

[MFR]
Based on ASTM D 3307-01, using a melt indexer (manufactured by Toyo Seiki Co., Ltd.), the mass of the polymer flowing out per 10 minutes from a nozzle having an inner diameter of 2 mm and a length of 8 mm under a 5 kg load (g / 10 minutes) Was MFR.

[Example 1]
Distilled water (0.945 L) was charged into an autoclave with an internal volume of 4 L and sufficiently purged with nitrogen. Then, 945 g of hexafluoropropylene (HFP) was charged, and the system was maintained at 29 ° C. and a stirring speed of 580 rpm. Thereafter, 110 g of tetrafluoroethylene (TFE) and 2 g of methanol were charged, and then 12 g of an 8 wt% solution of 7H-dodecafluoroheptanoyl peroxide / hexafluoroisopropyl methyl ether (CH ₃ OCH (CF ₃ ) ₂ ) was added. Polymerization was started. Polymerization was continued by adding 12 g of an 8 wt% solution of 7H-dodecafluoroheptanoyl peroxide / hexafluoroisopropyl methyl ether every 2 hours. Since the internal pressure decreased with the progress of polymerization, tetrafluoroethylene (TFE) was continuously supplied to maintain the internal pressure at 0.931 MPaG. Then, 110 g of a total amount of tetrafluoroethylene (TFE) was charged, and stirring was continued for 6 hours. Then, after releasing the pressure to return to atmospheric pressure, the reaction product was washed with water and dried to obtain 120 g of fluororesin (TFE / HFP copolymer) powder. The melting point was 263 ° C. and the MFR value measured at 372 ° C. was 20.

[Example 2]
The same method as in Example 1 except that 1,1,2,2,3,3-hexafluoropropyl trifluoromethyl ether (CF ₃ OCF ₂ CF ₂ CF ₂ H) was used instead of hexafluoroisopropyl methyl ether Polymerization was carried out at The reaction product was washed with water and dried to obtain 115 g of fluororesin powder. The melting point of the obtained fluororesin (TFE / HFP copolymer) was 261 ° C., and the MFR value measured at 372 ° C. was 11.

[Example 3]
1.28 L of distilled water was charged into an autoclave with an internal volume of 4 L, and after sufficiently purging with nitrogen, 880 g of hexafluoroisopropyl methyl ether (CH ₃ OCH (CF ₃ ) ₂ ) was charged, and the system was stirred at 35 ° C. The speed was kept at 580 rpm. Thereafter, 231 g of tetrafluoroethylene, 7.5 g of ethylene, 2.38 g of (perfluorobutyl) ethylene, and 2.6 g of cyclohexane were charged, and then 3.5 g of di-n-propyl peroxydicarbonate was added to start polymerization. did. Since the internal pressure decreased with the progress of polymerization, a mixed gas of tetrafluoroethylene / ethylene = 57.0 / 43.0 mol% was continuously supplied to maintain the internal pressure at 1.2 MPaG. Then, a total amount of 6.9 g of perfluorobutylethylene was continuously charged, and stirring was continued until the supply amount of the tetrafluoroethylene / ethylene mixed gas reached 130 g. Then, after releasing the pressure to return to atmospheric pressure, the reaction product was washed with water and dried to obtain 135 g of a fluororesin (TFE / Et copolymer) powder. The melting point of the obtained fluororesin was 254 ° C., and the MFR value measured at 297 ° C. was 18.

[Example 4]
The same method as in Example 3 except that 1,1,2,2,3,3-hexafluoropropyl trifluoromethyl ether (CF ₃ OCF ₂ CF ₂ CF ₂ H) was used instead of hexafluoroisopropyl methyl ether Polymerization was carried out at The reaction product was washed with water and dried to obtain 132 g of fluororesin (TFE / Et copolymer) powder. The melting point of the obtained fluororesin was 254 ° C., and the MFR value measured at 297 ° C. was 14.

[Comparative Example 1]
Distilled water (0.945 L) was charged into an autoclave with an internal volume of 4 L and sufficiently purged with nitrogen. Then, 945 g of hexafluoropropylene (HFP) was charged, and the system was maintained at 29 ° C. and a stirring speed of 580 rpm. Thereafter, 90 g of tetrafluoroethylene (TFE) and 2 g of methanol were charged, and then 7H-dodecafluoroheptanoyl peroxide / 2,2,3,3-tetrafluoropropyl methyl ether (CH ₃ OCH ₂ CF ₂ CF ₂ H). Polymerization was started by adding 12 g of an 8 wt% solution. Polymerization was continued by adding 12 g of an 8 wt% solution of 7H-dodecafluoroheptanoyl peroxide / 2,2,3,3-tetrafluoropropyl methyl ether every 2 hours. Since the internal pressure decreased with the progress of polymerization, tetrafluoroethylene (TFE) was continuously supplied to maintain the internal pressure at 0.932 MPaG. Then, a total amount of 50 g of tetrafluoroethylene (TFE) was charged, and stirring was continued for 6 hours. Then, after releasing the pressure to return to atmospheric pressure, the reaction product was washed with water and dried to obtain 50 g of a fluororesin (TFE / HFP copolymer) powder. The melting point was 261 ° C., and the MFR value measured at 372 ° C. was too high to be measured.

[Comparative Example 2]
Polymerization was carried out in the same manner as in Example 1 except that 1,1,1,3,3-pentafluorobutane (CH ₃ CF ₂ CH ₂ CF ₃ ) was used instead of hexafluoroisopropyl methyl ether. The reaction product was washed with water and dried to obtain 115 g of fluororesin (TFE / HFP copolymer) powder. The melting point was 261 ° C. and the MFR value measured at 372 ° C. was 9.5.

[Comparative Example 3]
Polymerization was carried out in the same manner as in Example 3 except that 1,1,1,3,3-pentafluorobutane (CH ₃ CF ₂ CH ₂ CF ₃ ) was used instead of hexafluoroisopropyl methyl ether. The reaction product was washed with water and dried to obtain 134 g of a fluororesin (TFE / Et copolymer) powder. The melting point of the obtained fluororesin was 255 ° C., and the MFR value measured at 297 ° C. was 12.2.

Claims (7)

A method for producing a fluoropolymer comprising the following formula:
R ¹ —O—CX ¹ Z ¹ — (CY ¹ Y ² ) _a —CX ² X ³ X ⁴ (1)
(In the formula, R ¹ represents a non-fluorinated alkyl group or a perfluoroalkyl group having 1 to 3 carbon atoms, a represents an integer of 0 to 3, and X ^{1 to} X ⁴ and Y ^{1 to} Y ² each represents Independently, it represents a hydrogen atom, a fluorine atom, or an alkyl group or fluoroalkyl group having ¹ to 3 carbon atoms, and Z ¹ represents a fluorine atom or an alkyl group or fluoroalkyl group having 1 to 3 carbon atoms. However, at least one of X ^{1 to} X ⁴ is a hydrogen atom, at least one is a fluorine atom, and when R ¹ is a perfluoroalkyl group, at least one of X ^{2 to} X ⁴ is a hydrogen atom. And a fluoromonomer is polymerized in the presence of the fluorinated ether represented by formula (1). Fluorine-containing ethers are CF ₃ OCF ₂ CF ₂ H, CF ₃ OCF ₂ CF ₂ CF ₂ H, CF ₃ CF ₂ OCF ₂ CHF ₂ , CH ₃ OCF ₂ CHF ₂ , CH ₃ OCF ₂ CF ₂ CHF ₂ , CH ₃ CH ₂ OCF ₂ CHF _{2 and,, CH 3 OCH (CF 3} ) at least one method of manufacturing according to claim 1 wherein the fluoropolymer is selected from the group consisting of _2. The method for producing a fluoropolymer according to claim 1 or 2, wherein the fluoromonomer is polymerized by a suspension polymerization method. The method for producing a fluoropolymer according to claim 1, 2 or 3, wherein the fluoropolymer is a melt-processable fluoropolymer. Fluoropolymers include polyvinylidene fluoride, tetrafluoroethylene / vinylidene fluoride copolymer, tetrafluoroethylene / vinylidene fluoride / hexafluoroethylene copolymer, tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer, tetrafluoroethylene / The method for producing a fluoropolymer according to claim 1, 2, 3, or 4, which is at least one selected from the group consisting of a hexafluoroethylene copolymer and an ethylene / tetrafluoroethylene copolymer. Following formula:
R ¹ —O—CX ¹ Z ¹ — (CY ¹ Y ² ) _a —CX ² X ³ X ⁴ (1)
(In the formula, R ¹ represents a non-fluorinated alkyl group or a perfluoroalkyl group having 1 to 3 carbon atoms, a represents an integer of 0 to 3, and X ^{1 to} X ⁴ and Y ^{1 to} Y ² each represents Independently, it represents a hydrogen atom, a fluorine atom, or an alkyl group or fluoroalkyl group having ¹ to 3 carbon atoms, and Z ¹ represents a fluorine atom or an alkyl group or fluoroalkyl group having 1 to 3 carbon atoms. However, at least one of X ^{1 to} X ⁴ is a hydrogen atom, at least one is a fluorine atom, and when R ¹ is a perfluoroalkyl group, at least one of X ^{2 to} X ⁴ is a hydrogen atom. A polymerization solvent characterized by comprising a fluorine-containing ether represented by the formula: Following formula:
R ¹ —O—CX ¹ Z ¹ — (CY ¹ Y ² ) _a —CX ² X ³ X ⁴ (1)
(In the formula, R ¹ represents a non-fluorinated alkyl group or a perfluoroalkyl group having 1 to 3 carbon atoms, a represents an integer of 0 to 3, and X ^{1 to} X ⁴ and Y ^{1 to} Y ² each represents Independently, it represents a hydrogen atom, a fluorine atom, or an alkyl group or fluoroalkyl group having ¹ to 3 carbon atoms, and Z ¹ represents a fluorine atom or an alkyl group or fluoroalkyl group having 1 to 3 carbon atoms. However, at least one of X ^{1 to} X ⁴ is a hydrogen atom, at least one is a fluorine atom, and when R ¹ is a perfluoroalkyl group, at least one of X ^{2 to} X ⁴ is a hydrogen atom. A composition comprising a fluorine-containing ether and a polymerization initiator.