CN109476785B

CN109476785B - Fluorine-containing polymer composition, fluorine resin coating material, and coated article

Info

Publication number: CN109476785B
Application number: CN201780043675.6A
Authority: CN
Inventors: 原祐二; 鹫见直子; 广野高生
Original assignee: Asahi Glass Co Ltd
Current assignee: AGC Inc
Priority date: 2016-07-14
Filing date: 2017-07-13
Publication date: 2021-08-20
Anticipated expiration: 2037-07-13
Also published as: WO2018012577A1; JP6927216B2; CN109476785A; JPWO2018012577A1

Abstract

Provided is a fluoropolymer composition having excellent storage stability. A fluoropolymer composition comprising a fluoropolymer and a solvent, wherein the fluoropolymer comprises a fluoroolefin unit and a cyclohexyl vinyl ether unit, and the area ratio AR determined by an area ratio calculation method is 0.1-3%.

Description

Fluorine-containing polymer composition, fluorine resin coating material, and coated article

Technical Field

The present invention relates to a fluorine-containing polymer composition, a fluorine-containing resin coating material, and a coated article.

Background

The composition containing the fluorine-containing polymer and the solvent is suitable as a raw material for a fluororesin coating material. The fluoropolymer contained in the fluoropolymer composition generally contains a fluoroolefin unit and a unit based on a monomer other than the fluoroolefin unit.

Patent document 1 discloses a fluoropolymer composition containing a fluoropolymer comprising a fluoroolefin unit and a cyclohexyl vinyl ether unit and a solvent.

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 61-174210

Disclosure of Invention

Problems to be solved by the invention

In recent years, further improvement in storage stability of a fluoropolymer composition used as a raw material of a fluororesin coating has been demanded in accordance with expansion of the use thereof. Here, the storage stability means that the mass average molecular weight of the fluoropolymer contained in the fluoropolymer composition does not increase under a heating environment.

The present inventors have made studies on the storage stability of a fluoropolymer composition comprising a fluoropolymer containing fluoroolefin units and cyclohexyl vinyl ether units and a solvent by referring to the method described in patent document 1, and as a result, have found that the recent level of demand may not be satisfied.

The present invention has been made in view of the above problems, and an object thereof is to provide a fluoropolymer composition having excellent storage stability, and a method for producing a fluoropolymer.

Another object of the present invention is to provide a fluororesin coating material containing the fluoropolymer composition, and a coated article.

Means for solving the problems

The present inventors have conducted extensive studies to solve the above problems, and as a result, have found that the storage stability is affected by the presence of specific impurity components in the fluoropolymer composition, and further that a desired effect can be obtained by adjusting the amount thereof to a predetermined range, thereby completing the present invention.

Namely, the present invention is as follows.

[1] A fluoropolymer composition comprising a fluoropolymer and a solvent (wherein toluene and acetone are not included), wherein the fluoropolymer comprises fluoroolefin units and cyclohexyl vinyl ether units, and wherein the area ratio AR determined by the following area ratio calculation method is 0.1-3%.

Area ratio calculation method: the method for producing a fluorinated polymer composition comprises adding 200 parts by mass of acetone to 100 parts by mass of the fluorinated polymer composition to prepare a diluted solution obtained by diluting the fluorinated polymer composition, adding 1% by mass of toluene to the diluted solution to prepare a sample solution, performing gas chromatography using the obtained sample solution, extracting a peak having a peak area 0.5 times or less of that of a toluene-derived peak, setting the total of the peak areas of the extracted peaks as an area A, setting the total of the peak areas of the extracted peaks as an area B, and setting the value obtained by the following formula (1) as an area ratio AR.

Formula (1): area ratio AR (%) (area B/area a) × 100

[2] The fluoropolymer composition according to [1], wherein the content of the fluoroolefin unit is 30to 70 mol% based on the total units contained in the fluoropolymer, and the content of the cyclohexyl vinyl ether unit is 10 to 50 mol% based on the total units contained in the fluoropolymer.

[3] The fluoropolymer composition according to [1] or [2], wherein the area ratio AR is 0.1 to 1.5%.

[4] The fluoropolymer composition according to any one of [1] to [3], wherein the fluoroolefin unit is a tetrafluoroethylene unit or a chlorotrifluoroethylene unit.

[5] The fluoropolymer composition according to any one of [1] to [4], wherein the fluoropolymer further comprises a unit having a crosslinkable group.

[6] The fluoropolymer composition according to [5], wherein the unit having a crosslinkable group is a unit having a hydroxyl group.

[7] The fluoropolymer composition according to any one of [1] to [6], wherein the fluoropolymer further comprises a unit based on a 4 th monomer other than the fluoroolefin, the cyclohexyl vinyl ether and the monomer having a crosslinkable group.

[8] The fluoropolymer composition according to [7], wherein the 4 th monomer-based unit is a unit based on a monomer having no fluorine atom.

[9] A process for producing a fluoropolymer, which comprises polymerizing a monomer mixture comprising a fluoroolefin and cyclohexyl vinyl ether to produce a fluoropolymer, wherein the cyclohexyl vinyl ether is purified to obtain cyclohexyl vinyl ether having an area ratio of 0.15% or less of compounds contained in the cyclohexyl vinyl ether and having a boiling point lower than that of cyclohexanol, and the purified cyclohexyl vinyl ether is used in the polymerization.

Area ratio: in the measurement of cyclohexyl vinyl ether by gas chromatography, the ratio of the sum of peak areas of peaks derived from a component appearing on a time side shorter than the retention time of cyclohexanol to the sum of peak areas of all peaks in the obtained gas chromatography is obtained.

[10] The method for producing a fluoropolymer according to [9], wherein the monomer mixture is polymerized in the presence of a solvent or a dispersion medium.

[11] A process for producing a fluoropolymer, which comprises polymerizing a monomer mixture comprising a fluoroolefin and cyclohexyl vinyl ether in the presence of a radical polymerization initiator, an alkali metal carbonate and a polymerization solvent, wherein the polymerization solvent is a mixed solvent of an alcohol having 1 to 6 carbon atoms and an organic solvent having a boiling point higher than that of the alcohol by 20 ℃ or more, the alkali metal carbonate precipitated by removing the alcohol by distillation under reduced pressure from the reaction mixture after the polymerization is removed, and the removal by distillation under reduced pressure of the alcohol is carried out under conditions in which the temperature and the reduced pressure which are generally used for the removal by distillation under reduced pressure of the alcohol are exceeded and the organic solvent is not removed by distillation under reduced pressure, thereby producing a fluoropolymer in which the alcohol is dissolved in the organic solvent.

[12] The process according to [11], wherein the organic solvent is an organic solvent having a boiling point of 110 ℃ or higher, the alcohol is ethanol, and the ethanol is distilled off under reduced pressure at a temperature of 65 ℃ or higher and a reduced pressure of 45Torr or lower.

[13] The process for producing a fluoropolymer according to [11] or [12], wherein the cyclohexyl vinyl ether contains a compound having a boiling point lower than that of cyclohexanol, and the area ratio of the compound is 0.15% or less.

[14] A fluororesin coating comprising the fluoropolymer composition according to any one of the above [1] to [8 ].

[15] A coated article comprising an article and a coating film formed on the article with the fluororesin coating material according to [14 ].

ADVANTAGEOUS EFFECTS OF INVENTION

The present invention can provide a fluoropolymer composition having excellent storage stability.

Further, the present invention can provide a fluororesin coating material and a coated article containing the fluoropolymer composition.

Detailed Description

The terms used in the present invention have the following meanings.

The "unit" is a generic name of a radical derived from the monomer 1 molecule directly formed by polymerization of the monomer and a radical obtained by chemically converting a part of the radical. The content (mol%) of each unit relative to the total units contained in the polymer was determined by analyzing the polymer by nuclear magnetic resonance. The unit based on a specific monomer is represented by adding "unit" to the monomer name.

The "number average molecular weight" and the "mass average molecular weight" are values measured by gel permeation chromatography using polystyrene as a standard substance. The "number average molecular weight" is also referred to as "Mn", and the "mass average molecular weight" is also referred to as "Mw".

The "intermediate particle size" refers to a particle size of 50 mass% in which the mass% is accumulated from the side having a smaller particle size.

The fluoropolymer composition of the present invention (hereinafter also referred to as "the present composition") is characterized in that the range of the area ratio AR obtained by the area ratio calculation method described in detail later is within a predetermined range.

The present inventors have studied the prior art and found that specific components (impurity components) contained in a small amount in the present composition adversely affect the storage stability of the composition. Specifically, the present composition inherently contains impurity components derived from the monomer used for producing the fluoropolymer. Examples of the impurity component include a cyclohexanol residue used in the synthesis of cyclohexyl vinyl ether, and a byproduct residue generated in the synthesis of cyclohexyl vinyl ether. Among them, the present inventors have found that components mainly appearing in a shorter time than the retention time of cyclohexanol (not including acetone, toluene, and the like as described below) in gas chromatography measurement (hereinafter, also referred to as "GC measurement") affect the storage stability of the present composition.

Therefore, the present inventors have found that when the content of the above-mentioned components is controlled to a predetermined amount or less, the storage stability is improved. The reason why the component is associated with the storage stability is not clear, but it is presumed that the component promotes the crosslinking of the fluoropolymers in the present composition, and the storage stability is deteriorated.

First, a method of calculating the area ratio AR (hereinafter, also referred to as "area ratio calculation method") will be described in detail.

In the area ratio calculation method, measurement was performed by GC. The sample solutions for GC assay were prepared as follows.

First, a fluoropolymer composition was prepared, and 200 parts by mass of acetone was added to 100 parts by mass of the fluoropolymer composition to prepare a diluted solution in which the fluoropolymer composition was diluted.

Subsequently, toluene was added to the diluted solution in an amount of 1 mass% based on the total mass of the diluted solution to prepare a sample solution. As will be described later, toluene was added as a reference for extracting peaks of minor components contained in the fluoropolymer composition in the GC measurement.

Subsequently, GC measurement was performed using the obtained sample solution.

The GC measurement was carried out under the following conditions using a gas chromatograph (detector: FID) manufactured by Agilent Technologies.

1.0 μ L (sample injection amount), split (injection mode), He (carrier gas), 240 ℃, (injection port temperature), 199.9kPa (pressure), (total flow rate) 179mL/min, (split ratio) 100: 1. (split flow rate) 174mL/min, (column) capillary column, DB1301 (length 60m X inner diameter 0.25mm, film thickness 1.00 μm), (column pressure) 199.9kPa, (column flow rate) 1.7mL/min, (average linear velocity) 29.0cm/sec, (column oven temperature program) at 40 ℃ for 10 minutes, then 10 ℃/min temperature rise, 250 ℃ for 25 minutes, (detector) hydrogen Flame Ionization Detection (FID), (detector temperature) 250 ℃.

First, a peak having a peak area 0.5 times or less the peak area of the toluene-derived peak was extracted from the gas chromatogram obtained by GC measurement. Here, a peak area derived from a peak of toluene added in a predetermined amount to the present composition is taken as a reference, and a peak related to a minor component contained in the present composition is extracted. The amount of acetone added to the sample solution is larger than that of toluene, and thus the acetone peak appears as a peak larger than that of toluene and is excluded at the time of extraction. In addition, since the solvent content in the present composition is generally higher than that of toluene, peaks corresponding to the solvent are excluded during extraction. That is, by the extraction, a peak associated with a minor component (mainly an impurity component) contained in the present composition can be extracted.

Next, the total of peak areas of the extracted peaks is defined as an area a.

In addition, the total of peak areas of peaks derived from a component appearing on a shorter time side than the retention time of cyclohexanol among the extracted peaks was defined as an area B. Since the peaks originally extracted do not include a solvent-derived peak, an acetone-derived peak, and a toluene-derived peak, the peak area of the solvent-derived peak, the peak area of the acetone-derived peak, and the peak area of the toluene-derived peak are not included in the calculation of the area B.

In the calculation of the area B, the retention time of cyclohexanol may be obtained in advance by performing GC measurement using a cyclohexanol monomer in order to calculate the retention time of cyclohexanol.

Using the obtained area a and area B, the area ratio AR is obtained by the following formula (1).

Formula (1): area ratio AR (%) (area B/area a) × 100

From the viewpoint of storage stability of the present composition, the area ratio AR in the present composition is in the range of 0.1 to 3%, preferably 0.1 to 3.0%, more preferably 0.1 to 1.5%, and particularly preferably 0.1 to 1.0%.

When the area ratio AR exceeds 3%, the storage stability of the present composition is poor. The lower limit (0.1%) of the area ratio AR is a technical limit that can remove trace components in the present composition. In order to make the area ratio AR less than 0.1%, cyclohexyl vinyl ether having a very high purity and being expensive must be used, which is disadvantageous in terms of industry.

The composition contains a fluoropolymer containing a predetermined unit and a solvent.

The fluoropolymer comprises fluoroolefin units and cyclohexyl vinyl ether units. In the following, cyclohexyl vinyl ether is also referred to as "CHVE".

The fluoroolefin is an olefin in which 1 or more hydrogen atoms are substituted with fluorine atoms. In the fluoroolefin, 1 or more of the hydrogen atoms not substituted by fluorine atoms may be substituted by chlorine atoms.

As the fluoroolefin, CF is preferred₂＝CF₂、CF₂＝CFCl、CF₂＝CFCF₃And CF₂＝CH₂More preferably CF₂＝CF₂(tetrafluoroethylene) and CF₂CFCl (chlorotrifluoroethylene).

The fluoroolefin may be used alone in 1 kind, or may be used in combination in 2 or more kinds.

The content of the fluoroolefin unit is preferably 30to 70 mol%, more preferably 40 to 60 mol%, and particularly preferably 45to 55 mol% based on the total units contained in the fluoropolymer. When the content of the fluoroolefin unit is 30 mol% or more, the coating film formed from the fluororesin coating material of the present invention (hereinafter, also referred to as "the present coating film") is more excellent in weather resistance. When the content of the fluoroolefin unit is 70 mol% or less, the fluoropolymer has more excellent solubility and dispersibility in a solvent.

The content of the CHVE unit is preferably 10 to 50 mol%, more preferably 10 to 45 mol%, and particularly preferably 15to 40 mol% based on the total units contained in the fluoropolymer. When the content of the CHVE unit is 10 mol% or more, the fluoropolymer is more excellent in solubility and dispersibility in a solvent. When the content of the CHVE unit is 50 mol% or less, the coating film has excellent weather resistance.

The fluoropolymer may contain units other than fluoroolefin units and CHVE units. Hereinafter, the monomer other than the fluoroolefin and CHVE is referred to as "other monomer", and the unit based on the other monomer is referred to as "other unit".

The number of other units contained in the fluoropolymer may be 2 or more. The other units may be units having fluorine atoms or units having no fluorine atoms. The other unit may be a unit having a crosslinkable group described later. The unit other than the unit having a crosslinkable group in the other units is the 4 th unit. The fluoropolymer preferably comprises at least 1 other unit.

As the other unit, a unit having no fluorine atom is preferable. In addition, as the unit having no fluorine atom contained in the fluoropolymer, at least 2 other units including a unit having a crosslinkable group and a 4 th unit (i.e., a unit having no crosslinkable group) are more preferable.

The other monomer having no fluorine atom may be a compound having no fluorine atom and having a polymerizable group, and specific examples thereof include a vinyl ether having no fluorine atom, an allyl ether having no fluorine atom, a vinyl ester having no fluorine atom, an allyl ester having no fluorine atom, an α -olefin having no fluorine atom, an acrylic ester having no fluorine atom, and a methacrylic ester having no fluorine atom.

The monomer having no fluorine atom is preferably a vinyl monomer having no fluorine atom, more preferably a vinyl ether having no fluorine atom or a vinyl ester having no fluorine atom, from the viewpoint of reactivity with a fluoroolefin.

As one of suitable modes of the other monomer having no fluorine atom, a monomer having a crosslinkable group (hereinafter, also referred to as "monomer I") can be mentioned. As described in detail later, when the fluoropolymer has a crosslinkable group, the coating film can be further improved in weather resistance, water resistance, chemical resistance, heat resistance, and the like by adding a curing agent to the fluororesin coating material.

The crosslinkable group is preferably a functional group having an active hydrogen (e.g., a hydroxyl group, a carboxyl group, or an amino group), a hydrolyzable silyl group (e.g., an alkoxysilyl group), or the like, and particularly preferably a hydroxyl group.

Examples of the monomer I include hydroxyalkyl vinyl ethers, hydroxyalkyl vinyl esters, hydroxyalkyl allyl ethers, hydroxyalkyl allyl esters, hydroxyalkyl acrylates, and hydroxyalkyl methacrylates, and hydroxyalkyl vinyl ethers are preferred from the viewpoint of copolymerizability with fluoroolefins and weather resistance of the present coating film.

Specific examples of the monomer I include 2-hydroxyethyl vinyl ether, 4-hydroxybutyl vinyl ether, cyclohexanedimethanol monovinyl ether, 2-hydroxyethyl allyl ether, 2-hydroxyethyl acrylate and 2-hydroxyethyl methacrylate.

The monomer I may be used alone in 1 kind, or may be used in combination of 2 or more kinds.

A suitable embodiment of the monomer I is a monomer represented by the following formula (2).

Formula (2) CH₂＝CX¹(CH₂)_n1-Q¹-R¹-Y

In the formula, X¹Is a hydrogen atom or a methyl group.

n1 is 0 or 1.

Q¹Is an oxygen atom, -C (O) O-or-O (O) C-, preferably an oxygen atom.

R¹Is an alkylene group having 2 to 20 carbon atoms, preferably cyclohexane-1, 4-dimethylene group or n-nonylene group, optionally having a branched structure or a ring structure.

Y is a crosslinkable group, preferably a hydroxyl group, a carboxyl group or an amino group, more preferably a hydroxyl group.

From the viewpoint of storage stability of the present composition, the content of the unit based on the monomer I is preferably 0to 20 mol%, more preferably 0to 18 mol%, and particularly preferably 0to 15 mol% based on the total units contained in the fluoropolymer.

A suitable embodiment of the monomer forming the 4 th unit includes a monomer having no fluorine atom, no cyclic hydrocarbon group, and no crosslinkable group (hereinafter, also referred to as "monomer II").

Examples of the monomer II include vinyl ethers having no fluorine atom, cyclic hydrocarbon group and crosslinkable group, allyl ethers having no fluorine atom, cyclic hydrocarbon group and crosslinkable group, vinyl esters having no fluorine atom, cyclic hydrocarbon group and crosslinkable group, allyl esters having no fluorine atom, cyclic hydrocarbon group and crosslinkable group, olefins having no fluorine atom, cyclic hydrocarbon group and crosslinkable group, acrylic esters having no fluorine atom, cyclic hydrocarbon group and crosslinkable group, and methacrylic esters having no fluorine atom, cyclic hydrocarbon group and crosslinkable group.

Specific examples of the monomer II include nonyl vinyl ether, 2-ethylhexyl vinyl ether, hexyl vinyl ether, ethyl vinyl ether, n-butyl vinyl ether, t-butyl vinyl ether, ethyl allyl ether, hexyl allyl ether, vinyl esters of carboxylic acids (e.g., acetic acid, butyric acid, pivalic acid, benzoic acid, and propionic acid), allyl esters of carboxylic acids (e.g., acetic acid, butyric acid, pivalic acid, benzoic acid, and propionic acid), ethylene, propylene, and isobutylene.

The monomer II may be used alone in 1 kind, or may be used in combination of 2 or more kinds.

A suitable embodiment of the monomer II is a monomer represented by the following formula (3).

Formula (3) CH₂＝CX²(CH₂)_n2-Q²-R²

In the formula, X²Is a hydrogen atom or a methyl group.

n2 is 0 or 1.

Q²Is an oxygen atom, -C (O) O-or-O (O) C-.

R²The alkyl group is an alkyl group having 2 to 20 carbon atoms and optionally having a branched structure.

From the viewpoint of storage stability of the present composition, the content of the unit based on the monomer II is preferably 0to 50 mol%, more preferably 5to 45 mol%, and particularly preferably 15to 40 mol% based on the total units contained in the fluoropolymer.

The content of the fluoroolefin unit, the CHVE unit, the unit based on the monomer I, and the unit based on the monomer II is preferably 30to 70 mol%, 10 to 50 mol%, 0to 20 mol%, and 0to 50 mol%, respectively, in this order, based on the total units contained in the fluoropolymer.

The Mn of the fluoropolymer is preferably 3000 to 40000.

The Mw of the fluoropolymer is preferably 5000 to 100000, more preferably 5000 to 80000.

The ratio of change in Mw of the fluoropolymer before and after heating ((Mw after heating)/(Mw before heating)) when the fluoropolymer is heated at 70 ℃ for 2 weeks is preferably 1.50 or less, more preferably 1.40 or less, and particularly preferably 1.30 or less, from the viewpoint of storage stability of the fluoropolymer. The lower limit of the rate of change in Mw is usually 1.0.

When the Mw change ratio is 1.50 or less, the viscosities of the fluoropolymer composition and the fluorine-containing coating material can be appropriately maintained, and the workability when forming a coating film from the fluorine-containing coating material is excellent.

The present composition contains the above-mentioned fluoropolymer and a solvent. The solvent contained in the present composition is a solvent other than the solvents (toluene and acetone) used for the measurement of the area ratio AR by the area ratio calculation method. At least a part of the solvent contained in the present composition is preferably a solvent used for producing the fluoropolymer from the monomer mixture. Examples of the solvent include water and an organic solvent.

As will be described later, in the method for producing a fluoropolymer, an alcohol and an organic solvent other than an alcohol are generally used as a solvent used for polymerization of a monomer mixture (hereinafter, also referred to as "polymerization solvent"). The solvent in the present composition is preferably an organic solvent other than alcohol, which is used as the polymerization solvent. The organic solvent is preferably an organic solvent having a boiling point higher than that of the alcohol used as the solvent for polymerization.

The organic solvent in the present composition preferably contains at least 1 organic solvent selected from the group consisting of an aromatic hydrocarbon solvent, a ketone solvent, an ether ester solvent, an ester solvent, and a weak solvent. The organic solvent is preferably an organic solvent capable of dissolving the fluoropolymer, and the present composition is preferably a solution containing the fluoropolymer and the organic solvent for dissolving the fluoropolymer.

The ether ester is a compound having both an ether bond and an ester bond in the molecule. In addition, the weak solvent refers to a solvent classified as a third organic solvent in the national work safety and health act.

The aromatic hydrocarbon solvent is preferably xylene, ethylbenzene, aromatic naphtha, tetralin, Solvesso #100 (registered trademark of Exxon chemical Co., Ltd.), Solvesso #150 (registered trademark of Exxon chemical Co., Ltd.), etc., and more preferably xylene and ethylbenzene.

The ketone solvent is preferably acetone, methyl ethyl ketone, methyl amyl ketone, methyl isobutyl ketone, ethyl isobutyl ketone, diisobutyl ketone, cyclohexanone, or the like.

The ether ester solvent is preferably ethyl 3-ethoxypropionate, propylene glycol monomethyl ether acetate, methoxybutyl acetate, etc.

The ester solvent is preferably methyl acetate, ethyl acetate, n-propyl acetate, isobutyl acetate, n-butyl acetate, etc.

The weak solvent is at least 1 selected from the group consisting of gasoline, coal tar naphtha (including solvent naphtha), petroleum ether, naphtha, refined light solvent gasoline (petroleum benzine), turpentine, mineral spirits (including mineral diluent, petroleum spirit, white spirit, mineral turpentine), and the like, and mineral spirits are preferable in that the flash point is at least room temperature.

The solvent may be only 1 kind of solvent, or may be a mixed solvent of 2 or more kinds.

The content of the solvent in the present composition is preferably 30to 70% by mass, more preferably 45to 70% by mass, based on the total mass of the present composition.

The present composition may contain a residue of a monomer used for obtaining a fluoropolymer or a component of a raw material used for producing the monomer, and these components may correspond to the above-mentioned minor components (impurity components).

Specific examples of the monomer residue used for obtaining the fluoropolymer include a cyclohexyl vinyl ether residue and a residue of the monomer I (such as 4-hydroxyvinyl ether).

Specific examples of the raw material used for producing the monomer include cyclohexanol used for producing cyclohexyl vinyl ether.

The present invention also provides 2 a production method for producing a fluoropolymer having excellent storage stability. The production method 1 in the production method of the present invention is a method of purifying CHVE before polymerization and producing a fluoropolymer using the purified CHVE. The 2 nd production method in the production method of the present invention is a method comprising: after polymerizing the monomer to produce the fluoropolymer, when the alcohol, which is a part of the polymerization solvent, is distilled off from the reaction mixture, the distillation is performed under severer conditions than those usually required for the removal of the alcohol, and the impurity components are also removed at the same time, thereby producing the fluoropolymer.

The fluoropolymer obtained by any of the production methods of the present invention has a high storage stability because of a small content of impurity components derived from monomers and the like, and has little viscosity change in a solvent solution or the like. Further, by simultaneously carrying out the production methods 2, the content of impurity components can be further reduced as compared with the case of carrying out the individual production methods.

Any of the production methods of the present invention is a method suitable for producing the fluoropolymer composition of the present invention. However, the production method of the present invention is not limited to the production of the present composition, and the fluoropolymer obtained by the production method of the present invention may be used for the production of fluoropolymer solutions or dispersions other than the present composition.

The production method of the present invention will be described below by taking the production of the present composition as an example.

The first production process of the present invention is a process for producing a fluoropolymer by polymerizing a monomer mixture containing a fluoroolefin and CHVE, wherein CHVE is purified to give CHVE having an area ratio of 0.15% or less of a compound having a boiling point lower than that of cyclohexanol simultaneously contained in CHVE, and the purified CHVE is used for the polymerization.

Area ratio: in the measurement of CHVE by gas chromatography, the ratio of the sum of peak areas of peaks derived from a component appearing on a time side shorter than the retention time of cyclohexanol to the sum of peak areas of all peaks in the obtained gas chromatography is calculated.

The present inventors have found that most of components appearing on the shorter time side than the retention time of cyclohexanol in the GC measurement are low boiling compounds contained in CHVE used as a raw material. The low boiling point compound is considered to be at least a part of the impurity components that lower the storage stability of the fluoropolymer solution. Therefore, when the amount of the low boiling point compound simultaneously contained in CHVE is reduced by distillation of CHVE, a fluoropolymer having excellent storage stability can be produced. In addition, the area ratio AR in the fluoropolymer composition of the invention can be reduced. That is, the fluoropolymer composition of the present invention can be produced by the production method 1.

The area ratio is preferably 0.1% or less, more preferably 0.05% or less, and particularly preferably 0.01% or less. The lower limit is not particularly limited, and is 0%.

For the method of producing a fluoropolymer by polymerizing a monomer mixture comprising a fluoroolefin and CHVE, a known method can be used except that purified CHVE is used. As the polymerization medium, a solvent or a dispersion medium can be used, and an organic solvent capable of dissolving the produced fluoropolymer is preferably used. Further, the same production method as the below-described production method 2 is preferable except for the conditions for removing the alcohol by distillation under reduced pressure, and the below-described production method 2 including the conditions for removing the alcohol by distillation under reduced pressure is more preferable.

The second production method of the present invention is a method for producing a fluoropolymer, comprising polymerizing a monomer mixture containing a fluoroolefin and CHVE in the presence of a radical polymerization initiator, an alkali metal carbonate and a polymerization solvent, wherein the polymerization solvent is a mixed solvent of an alcohol having 1 to 6 carbon atoms and an organic solvent having a boiling point higher than that of the alcohol by 20 ℃ or more (hereinafter, also referred to as "high-boiling organic solvent"), the alkali metal carbonate precipitated by removing the alcohol by distillation under reduced pressure from the reaction mixture after polymerization is removed, and the removal by distillation under reduced pressure of the alcohol is carried out under conditions in which the temperature and the reduced pressure normally used for the removal by distillation under reduced pressure of the alcohol are exceeded and the organic solvent is not removed by distillation under reduced pressure, to obtain a fluoropolymer dissolved in the organic solvent.

In the 2 nd production method, in order to remove the alcohol having 1 to 6 carbon atoms, more severe removal conditions than usual alcohol removal conditions are set in order to remove the low boiling point compound at the same time. For example, in the vacuum distillation removal of alcohol, the vacuum distillation removal is performed under lower pressure and higher temperature conditions, thereby simultaneously removing low boiling point compounds. On the other hand, in order that the high-boiling organic solvent is not removed at the time of alcohol removal, it is preferable that the difference in boiling point between the alcohol used and the high-boiling organic solvent is large, and the boiling point of the high-boiling organic solvent is preferably 30 ℃ or higher, more preferably 50 ℃ or higher than the boiling point of the alcohol used in combination.

The alcohol having 1 to 6 carbon atoms is preferably ethanol, and when ethanol is used, more specifically, the distillation under reduced pressure is preferably carried out at a temperature of 65 ℃ or higher (upper limit is preferably 85 ℃) and under reduced pressure of 45Torr or lower (preferably 30Torr or lower, lower limit is preferably 5 Torr).

In addition, the area ratio AR in the polymer composition of the present invention can be reduced by the production method 2. That is, the fluoropolymer composition of the present invention can be produced by the production method 2.

From the viewpoint of productivity, the production method 2 of the present invention preferably includes the following steps 1 to 3.

Step 1 (polymerization step): and a step of copolymerizing a monomer mixture containing a fluoroolefin and CHVE in the presence of a radical polymerization initiator, an alkali metal carbonate, and a polymerization solvent which is a mixed solvent of an alcohol having 1 to 6 carbon atoms and a high-boiling organic solvent, in a state in which at least a part of the alkali metal carbonate is dissolved in the polymerization solvent, to obtain a solution of a fluoropolymer.

Step 2 (deposition step): and a step of removing the alcohol from the fluoropolymer solution to reduce the alcohol content and thereby precipitate an alkali metal carbonate.

Step 3 (removal step): and a step of filtering the fluoropolymer solution obtained in the step 2 to remove the precipitated alkali metal carbonate, thereby obtaining a fluoropolymer dissolved in a high-boiling organic solvent.

The monomer mixture in step 1 may contain, if necessary, monomers other than the fluoroolefin and CHVE (monomer I, monomer II, etc.).

Specific examples of the alkali metal carbonate used in step 1 include potassium carbonate.

In the step 1, the mass ratio of the alkali metal carbonate to the total monomers in the monomer mixture (alkali metal carbonate/total monomers in the monomer mixture) is preferably 0.005/1 to 0.013/1, more preferably 0.008/1 to 0.012/1. When the mass ratio of potassium carbonate to the total monomers in the monomer mixture is 0.005/1 or more, the copolymerization reaction proceeds smoothly, and when the mass ratio of potassium carbonate to the total monomers in the monomer mixture is 0.013/1 or less, the coloration of the resulting fluoropolymer solution can be suppressed while ensuring the polymerization stability.

The polymerization solvent in step 1 may include alcohols having 1 to 6 carbon atoms and high-boiling organic solvents, and any solvent used in conventionally known polymerization may be used in addition to these solvents.

In the case of producing the present composition, since a special treatment such as solvent replacement is not necessary, it is preferable to use the same solvent as the high boiling point organic solvent in the polymerization solvent as the solvent contained in the present composition and use the fluoropolymer solution obtained in step 3 as it is as the present composition.

Specific examples of the alcohol having 1 to 6 carbon atoms include methanol, ethanol, n-propanol, isopropanol, t-butanol, pentanol, and hexanol, and ethanol is preferable in view of solubility of potassium carbonate.

Examples of the high-boiling organic solvent in the polymerization solvent include organic solvents having a boiling point higher than that of the alcohol in the polymerization medium by 20 ℃ or more, such as aromatic hydrocarbon solvents, alcohol solvents other than the alcohol having 1 to 6 carbon atoms, ketone solvents, ether ester solvents, and poor solvents. Specific examples of the aromatic hydrocarbon solvent, ketone solvent, ether ester solvent, and weak solvent are organic solvents satisfying a condition of high boiling point among the solvents preferably contained in the present composition.

Specific examples of the alcohol solvent other than the alcohol having 1 to 6 carbon atoms include octanol and dodecanol.

The high-boiling organic solvent is more preferably an aromatic hydrocarbon solvent, an ether ester solvent, or an alcohol solvent other than an alcohol having 1 to 6 carbon atoms, and particularly preferably an aromatic hydrocarbon solvent.

When the alcohol having 1 to 6 carbon atoms is ethanol (bp: 78 ℃), the high-boiling organic solvent is preferably an organic solvent having a boiling point of 110 ℃ or higher, and specifically aromatic hydrocarbon solvents such as toluene (bp: 110 ℃), ethylbenzene (bp: 136 ℃), and xylene (bp: 138 to 144 ℃).

The content of the C1-6 alcohol is preferably 10-95% by mass, more preferably 20-90% by mass, based on the total mass of the polymerization solvent.

It is preferable that the monomer mixture is copolymerized by solution polymerization in the presence of a radical polymerization initiator, an alkali metal carbonate, and the polymerization solvent in a state where at least a part of potassium carbonate is dissolved.

The "state in which at least a part of the alkali metal carbonate is dissolved" means a state in which a part of the alkali metal carbonate is dissolved in the solvent, but may be dispersed (including suspended or precipitated) in a state in which at least a part of the alkali metal carbonate is not dissolved.

Specific examples of the radical polymerization initiator include azo initiators (e.g., 2 '-azobisisobutyronitrile, 2' -azobiscyclohexanecarbonitrile, 2 '-azobis (2, 4-dimethylvaleronitrile), and 2, 2' -azobis (2-methylbutyronitrile)), ketone peroxides (e.g., cyclohexanone peroxide), hydrogen peroxide (e.g., t-butyl peroxide), diacyl peroxides (e.g., benzoyl peroxide), dialkyl peroxides (e.g., di-t-butyl peroxide), peroxyketals (e.g., 2-di (t-butyl peroxide) butane), alkyl peresters (e.g., t-butyl peroxypivalate (PBPV)), and peroxycarbonate peroxide initiators (e.g., diisopropyl peroxydicarbonate).

When the Mn and Mw of the fluoropolymer need to be adjusted, a conventionally known chain transfer agent may be added as needed.

The polymerization reaction is preferably carried out at a polymerization temperature of 65 ℃. + -. 10 ℃ for a polymerization time of 6 to 36 hours. The polymerization temperature may be appropriately set depending on the initial decomposition temperature and half-life of the initiator to be used. After cooling, the polymerization reaction is stopped by using a polymerization inhibitor such as hydroquinone monomethyl ether and the like.

The step 2 is a step of removing the alcohol solvent having 1 to 6 carbon atoms from the fluoropolymer solution obtained in the step 1, preferably reducing the alcohol solvent to 0to 0.03 mass% relative to the polymerization solvent, and precipitating the alkali metal carbonate in the solution.

Examples of the method for removing the alcohol having 1 to 6 carbon atoms include a method of concentrating the alcohol by a vacuum distillation apparatus under reduced pressure and heating.

Preferably, the pre-filtration is performed before removing the C1-6 alcohol. The preliminary filtration is performed for the purpose of substantially filtering off the alkali metal carbonate or the modified product thereof dispersed in a solid form (including floating or precipitated) in the solution of the fluoropolymer. When the prefiltering is not performed, they may be removed in the removal step described below.

The step 3 is a step of filtering the fluoropolymer solution obtained in the precipitation step from which the alcohol solvent having 1 to 6 carbon atoms has been removed, and removing the alkali metal carbonate precipitated, thereby obtaining a fluoropolymer dissolved in an organic solvent.

Examples of the filtration method include filtration using diatomaceous earth. The diatomaceous earth may be exemplified by diatomaceous earth having an intermediate particle size of 25 to 40 μm, and the amount thereof to be used is preferably 0.05 to 0.10g/cm based on the filtration area²。

The filtration is particularly preferably as follows: the diatomaceous earth was used to transfer liquid to a pressure filter equipped with filter paper No.63 for viscous liquid, and the liquid was filtered under a pressure of 0.01 to 0.5MPa, and the liquid was circulated until the appearance of the filtrate became clear by visual observation.

The present composition can be suitably used for a fluororesin coating (clear coating, etc.).

The fluororesin coating of the present invention can be prepared by further adding a coating compounding ingredient such as a curing agent and a resin other than the fluoropolymer to the present composition.

The fluororesin coating may be a one-component type coating or a two-component type coating. In the case of the two-pack type, the curing agent is preferably mixed immediately before use.

In the case where the fluorine-containing polymer contains a unit based on the monomer I, the curing agent is preferably one which can crosslink with the crosslinkable group of the monomer I.

When the crosslinkable group of the monomer I is a hydroxyl group, the curing agent is preferably a curing agent for coating materials such as a room-temperature curing type isocyanate curing agent, a thermosetting type blocked isocyanate curing agent, and a melamine curing agent.

The content of the curing agent in the fluororesin coating is preferably 1 to 100 parts by mass, more preferably 1 to 50 parts by mass, per 100 parts by mass of the fluoropolymer.

As the resin other than the fluoropolymer, a known resin blended in a fluororesin coating material can be suitably used.

In order to improve the drying property of the coating film, CAB (cellulose acetate butyrate), NC (nitrocellulose), or the like may be blended. In addition, a coating resin such as a polymer of acrylic acid or an ester thereof, polyester, or the like may be blended in order to improve the gloss, hardness, and coating applicability of the present coating film.

Further, if necessary, known components blended in the coating material, such as a silane coupling agent, an ultraviolet absorber, a curing accelerator, a light stabilizer, a colorant, and a matting agent, may be blended as additives.

The coated article of the present invention is obtained by forming a coating film on the surface of an article with the fluororesin coating material of the present invention.

Specific examples of the coated article include transportation equipment (automobiles, electric cars, aircraft, etc.), civil engineering members (bridge members, iron towers, etc.), industrial equipment (waterproof material sheets, tanks (tank), ducts, etc.), building members (building exterior, doors, window and door members, monuments, poles, etc.), road members (road center barriers, guardrails, sound insulation walls, etc.), communication equipment, electric and electronic components, surface sheets for solar cell modules, and back sheets.

The film thickness of the coating film is preferably 10 to 200 μm, more preferably 10 to 100 μm.

The fluororesin coating may be applied directly to the surface of the article, or may be applied after subjecting the surface of the article to a known surface treatment (e.g., a primer treatment).

Specific examples of the coating method of the fluororesin coating material include spray coating, air spray coating, brush coating, dipping method, and a method using a roll coater or a flow coater.

The drying temperature after coating is preferably about 15to 300 ℃.

Examples

The present invention will be described in detail below with reference to examples. However, the present invention is not limited to these examples.

The evaluation methods and materials used in the examples are shown below.

< calculation of area ratio AR >

Calculated by the area ratio calculation method described above.

The fluoropolymer compositions produced in examples and comparative examples described below were prepared, and 200 parts by mass of acetone (and a special grade reagent manufactured by Wako pure chemical industries, Ltd.) was added to 100 parts by mass of the fluoropolymer composition to prepare a diluted solution in which the fluoropolymer composition was diluted.

Subsequently, toluene (and a special grade reagent manufactured by Wako pure chemical industries, Ltd.) was added to the diluted solution in an amount of 1 mass% based on the total mass of the diluted solution to prepare a sample solution. The obtained sample solution was subjected to GC measurement under the above-mentioned conditions using 6850series II (Detector: FID) manufactured by Agilent Technologies. From the obtained chromatogram, the area ratio AR was determined by the method described above. The retention time of cyclohexanol was confirmed by measuring cyclohexanol (and a special grade reagent manufactured by Wako pure chemical industries, Ltd.).

< evaluation of storage stability >

The fluoropolymer compositions produced in examples and comparative examples described below were placed in a sealed container and heated in an oven set at 70 ℃ for 2 weeks. The change rate of Mw of the fluoropolymer before and after heating was evaluated.

Mw change rate (Mw after heating)/(Mw before heating)

For the measurement of Mw, the following apparatus was used: EcoSEC HLC-8320GPC, available from Tosoh corporation, was prepared by diluting a fluoropolymer composition with tetrahydrofuran and adjusting the concentration of the fluoropolymer to 1 mass% as a sample solution for Mw evaluation.

<CHVE>

In the following examples and comparative examples, CHVE1 to 3 described in Table 1 below were used. The column of "area ratio (%) of compound having a boiling point lower than that of cyclohexanol" in table 1 indicates: the ratio (area ratio) of the sum of peak areas of peaks derived from a component appearing on a shorter time side than the retention time of cyclohexanol in a gas chromatogram to the sum of peak areas of all peaks, which was obtained by performing the above-described GC measurement using each CHVE. The lower the area ratio, the lower the proportion of components having a boiling point lower than that of cyclohexanol.

CHVE3 was a commercial product, CHVE1 was CHVE obtained by distilling CHVE3 (distillation yield 70%), and CHVE2 was obtained by distilling CHVE3 (distillation yield 90%).

[ Table 1]

TABLE 1

(example 1)

Xylene (587g), ethanol (168g), Ethyl Vinyl Ether (EVE) (206g), 4-hydroxy vinyl ether (HBVE) (129g), cyclohexyl vinyl ether 1(CHVE1) (208g), potassium carbonate (11g), and tert-butyl peroxypivalate (PBPV) (3.5g) were charged into a stainless steel pressure-resistant reactor (internal volume 2500mL) equipped with a stirrer, and dissolved oxygen in the liquid was removed by pressure-purging and degassing with nitrogen.

Then, Chlorotrifluoroethylene (CTFE) (660g) was introduced, and the temperature was gradually raised, and the reaction was continued while maintaining the temperature at 65 ℃. After 12 hours the reactor was water cooled to stop the reaction. After the reaction solution was cooled to room temperature, the unreacted monomers were removed, and the reactor was opened.

The obtained reaction solution was transferred to a pressure filter equipped with filter paper No.63 for viscous liquid, potassium carbonate was filtered off under a pressure of 0.05MPa, and then 0.1g of hydroquinone monomethyl ether (HQMME) was added. Then, ethanol in the reaction solution was distilled off by a vacuum distillation apparatus under reduced pressure heating at 65 ℃ and 45 Torr. Next, 0.06g/cm of a filtration area was added to the reaction mixture²The resulting diatomaceous earth (medium particle size: 30.1 μm) was mixed and stirred, and then the mixture was transferred to a pressure filter equipped with filter paper No.63 for viscous liquid, and the mixture was filtered 2 times under a pressure of 0.02MPa to remove the diatomaceous earth, thereby obtaining fluoropolymer composition P1.

Thereafter, the concentration of the fluoropolymer in the fluoropolymer composition P1 was adjusted so that the mass concentration of the fluoropolymer became 60 mass%, thereby obtaining a fluoropolymer composition 1.

Then, the fluoropolymer composition 1 was analyzed by the GC measurement, and the area ratio AR was found to be 0.8%.

(example 2)

Fluoropolymer composition 2 was obtained in the same manner as in example 1, except that CHVE2 was used in place of CHVE 1.

Subsequently, the fluoropolymer composition 2 was analyzed by the GC measurement, and the area ratio AR was 3.0%.

(example 3)

Xylene (587g), ethanol (168g), EVE (206g), HBVE (129g), CHVE2(208g), potassium carbonate (11g) and PBPV (3.5g) were charged into a stainless steel pressure-resistant reactor (internal volume 2500mL) equipped with a stirrer, and dissolved oxygen in the liquid was removed by pressurization, purging and degassing with nitrogen.

Subsequently, CTFE (660g) was introduced and the temperature was gradually raised, and the reaction was continued while maintaining the temperature at 65 ℃. After 12 hours the reactor was water cooled to stop the reaction. After the reaction solution was cooled to room temperature, the unreacted monomers were removed, and the reactor was opened.

The resulting reaction solution was transferred to a pressure filter equipped with filter paper No.63 for viscous liquid, potassium carbonate was filtered off under a pressure of 0.05MPa, and then 0.1g of HQMME was added. Then, ethanol in the reaction solution was distilled off by a vacuum distillation apparatus under reduced pressure heating at 65 ℃ and 15 Torr. Next, 0.06g/cm of a filtration area was added to the reaction mixture²The resulting diatomaceous earth (medium particle size: 30.1 μm) was mixed and stirred, and then the mixture was transferred to a pressure filter equipped with filter paper No.63 for viscous liquid, and the mixture was filtered 2 times under a pressure of 0.02MPa to remove the diatomaceous earth, thereby obtaining fluoropolymer composition P3.

Thereafter, the concentration of the fluoropolymer in the fluoropolymer composition P3 was adjusted so that the mass concentration of the fluoropolymer became 60 mass%, thereby obtaining a fluoropolymer composition 3.

Subsequently, the fluoropolymer composition 3 was analyzed by the GC measurement, and the area ratio AR was found to be 1.3%.

Comparative example 1

Fluoropolymer composition 4 was obtained in the same manner as in example 1, except that CHVE3 was used in place of CHVE 1.

Subsequently, the fluoropolymer composition 4 was analyzed by the gas chromatography measurement, and the area ratio AR was found to be 5.0%.

The fluoropolymer compositions obtained in the above examples and comparative examples were used to evaluate the storage stability. The results are shown in Table 2 below.

[ Table 2]

TABLE 2

As shown in table 2, it was confirmed that the present composition showing a predetermined area ratio AR was excellent in storage stability.

The entire contents of the specification, claims and abstract of japanese patent application 2016-.

Claims

1. A fluoropolymer composition comprising a fluoropolymer and a solvent, wherein the solvent does not contain toluene or acetone, wherein the fluoropolymer comprises a fluoroolefin unit and a cyclohexyl vinyl ether unit,

an area ratio AR of 0.1 to 3% as determined by the following area ratio calculation method,

area ratio calculation method: preparing a diluted solution by diluting the fluoropolymer composition by adding 200 parts by mass of acetone to 100 parts by mass of the fluoropolymer composition, preparing a sample solution by adding 1% by mass of toluene to the diluted solution, performing gas chromatography using the obtained sample solution, extracting a peak having a peak area that is 0.5 times or less of a peak area derived from toluene, setting the total sum of the peak areas of the extracted peaks as an area A, setting the total sum of the peak areas of the extracted peaks as an area B, and setting a value obtained by the following formula (1) as an area ratio AR,

formula (1): area ratio AR (%) (area B/area a) × 100;

the fluoropolymer has an Mw change rate of 1.50 or less before and after heating when the fluoropolymer is heated at 70 ℃ for 2 weeks, where the Mw change rate is (Mw after heating)/(Mw before heating).

2. The fluoropolymer composition according to claim 1, wherein the content of the fluoroolefin unit is 30to 70 mol% based on the total units contained in the fluoropolymer,

the content of the cyclohexyl vinyl ether unit is 10 to 50 mol% based on the total units contained in the fluoropolymer.

3. The fluoropolymer composition according to claim 1 or 2, wherein the area ratio AR is 0.1 to 1.5%.

4. The fluoropolymer composition of claim 1 or 2, wherein the fluoroolefin units are tetrafluoroethylene units or chlorotrifluoroethylene units.

5. The fluoropolymer composition according to claim 1 or 2, wherein the fluoropolymer further comprises a unit having a crosslinkable group.

6. The fluoropolymer composition according to claim 5, wherein the unit having a crosslinkable group is a unit having a hydroxyl group.

7. The fluoropolymer composition according to claim 1 or 2, wherein the fluoropolymer further comprises units based on a 4 th monomer other than fluoroolefin, cyclohexyl vinyl ether and a monomer having a crosslinkable group.

8. The fluoropolymer composition according to claim 7, wherein the units based on the 4 th monomer other than the fluoroolefin, the cyclohexyl vinyl ether, and the monomer having a crosslinkable group are units based on a monomer having no fluorine atom.

9. The fluoropolymer composition according to claim 1, wherein the process for producing a fluoropolymer comprises polymerizing a monomer mixture comprising a fluoroolefin and cyclohexyl vinyl ether to produce a fluoropolymer, wherein the cyclohexyl vinyl ether is purified to give a cyclohexyl vinyl ether having an area ratio of 0.15% or less of compounds contained in the cyclohexyl vinyl ether and having a boiling point lower than that of cyclohexanol, and the purified cyclohexyl vinyl ether is used in the polymerization,

area ratio: a ratio of a sum of peak areas of peaks derived from a component appearing on a shorter time side than a retention time of cyclohexanol to a sum of peak areas of all peaks in the obtained gas chromatogram in measurement of cyclohexyl vinyl ether by a gas chromatogram;

the content of the cyclohexyl vinyl ether unit is 15to 50 mol% with respect to the total units contained in the fluoropolymer.

10. The fluoropolymer composition of claim 9, wherein the monomer mixture is polymerized in the presence of a solvent or dispersion medium.

11. The fluoropolymer composition according to claim 1, wherein the process for producing the fluoropolymer comprises polymerizing a monomer mixture comprising a fluoroolefin and cyclohexyl vinyl ether in the presence of a radical polymerization initiator, an alkali metal carbonate and a polymerization solvent, wherein the polymerization solvent is a mixed solvent of an alcohol having 1 to 6 carbon atoms and an organic solvent having a boiling point higher than that of the alcohol by 20 ℃ or more, the alkali metal carbonate precipitated by removing the alcohol by distillation under reduced pressure from the reaction mixture after polymerization is removed, and the removal by distillation under reduced pressure of the alcohol is carried out under conditions in which the temperature and the reduced pressure which are generally used for the removal by distillation under reduced pressure of the alcohol are exceeded and the organic solvent is not removed by distillation under reduced pressure, to obtain the fluoropolymer dissolved in the organic solvent;

the organic solvent is an organic solvent having a boiling point of 110 ℃ or higher, the alcohol is ethanol, and the ethanol is distilled off under reduced pressure at a temperature of 65 ℃ or higher and a reduced pressure of 45Torr or lower.

12. The fluoropolymer composition according to claim 11, wherein the cyclohexyl vinyl ether contains a compound having a boiling point lower than that of cyclohexanol and the area ratio of the compound is 0.15% or less,

13. A fluororesin coating comprising the fluoropolymer composition according to any one of claims 1 to 12.

14. A coated article comprising an article and a coating film formed on the article from the fluororesin coating material according to claim 13.