JP2015067826A - Method for producing fluorine-containing copolymer solution, method for producing coating material composition and fluorine-containing copolymer solution - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a fluorine-containing copolymer solution that suppresses gelation during the polymerization in the production of the fluorine-containing copolymer solution, imparts good storage stability to a copolymer solution and suppresses discoloration of the copolymer solution, to provide a fluorine-containing copolymer solution and to provide a method for producing a coating material composition containing the fluorine-containing copolymer solution.SOLUTION: The method for producing a fluorine-containing copolymer solution has a step of polymerizing a monomer mixture including (a) a fluoroolefin and (b) a monomer having a crosslinkable group in an organic solvent. The polymerization is conducted in the presence of a metal alkoxide in an amount of 0.02-2.0 pts.mass based on 100 pts.mass of the total mass of the monomer mixture.

Description

  The present invention relates to a method for producing a fluorine-containing copolymer solution, a method for producing a coating composition containing the fluorine-containing copolymer solution, and a fluorine-containing copolymer solution.

The fluorine-containing copolymer is suitably used as a coating resin. However, when a fluorine-containing copolymer solution is produced, if a monomer having a crosslinkable group is used as a monomer, there is a problem that gelation tends to occur during polymerization.
In addition, the coating resin is required to be colorless in a solution state after polymerization, and to have good storage stability when stored in a varnish (paint resin solution) state. Furthermore, it is preferable not to be colored during storage.

  Patent Document 1 relates to a method for producing a fluorinated copolymer, wherein a monomer mixture containing a fluoroolefin and an alkyl vinyl ether is mixed with an alkali metal carbonate in a polymerization medium containing a lower alkylbenzene and a component having a lower boiling point than the lower alkylbenzene. It is described that the copolymerization in the presence of a salt provides smooth progress of the copolymerization reaction and storage stability of the varnish containing the produced copolymer. An example of an alkali metal carbonate is potassium carbonate.

Patent Document 2 relates to a method for producing a fluorine-containing copolymer having a hydroxyl group. A monomer mixture containing a fluoroolefin and a vinyl ether having a hydroxyl group is converted into a metal oxide, a metal hydroxide, and an anion exchange resin. A method of radical polymerization in the presence of at least one selected from the group consisting of the above is described. Hydrotalcite is mentioned as a preferable example of the metal hydroxide. Thus, it is described that an effect of preventing gelation during polymerization can be obtained.
Patent Document 3 relates to a method for producing a fluorine-containing copolymer having a hydroxyl group. A monomer mixture containing a fluoroolefin and a vinyl ether having a hydroxyl group contains a 2,2,6,6-tetrasubstituted piperidinyl group. A method of radical polymerization in the presence of a compound is described. Thus, it is described that an effect of preventing gelation during polymerization can be obtained.

JP 61-174210 A Japanese Patent Laid-Open No. 1-229011 JP 62-292814 A

As described in Patent Document 1, addition of alkali metal carbonate during copolymerization of the fluorine-containing copolymer has an effect of suppressing gelation during polymerization, but the alkali metal carbonate is dissolved in an organic solvent. Therefore, it is necessary to provide a step of filtering the added alkali metal carbonate after the completion of the polymerization, and there is a problem that the production process becomes complicated.
Moreover, since the metal oxide, metal hydroxide, and anion exchange resin described in Patent Document 2 are not dissolved in an organic solvent, a filtration step after polymerization is required as in Patent Document 1.
Furthermore, according to the method described in Patent Document 3, although polymerization proceeds without gelation, a nitrogen-containing compound is added to the polymerization system, so that the fluorine-containing copolymer solution after polymerization is colored. There is.
As described above, when producing a fluorinated copolymer solution, there is a need for a method that prevents gelation during polymerization and that can suppress the coloring of the fluorinated copolymer solution after polymerization without requiring filtration. Such a method is not yet known.

  The present invention has been made in view of the above circumstances, and when producing a fluorine-containing copolymer solution, gelation during polymerization can be prevented, and coloring of the fluorine-containing copolymer solution after polymerization can be suppressed. Provided are a method for producing a fluorine-containing copolymer solution, a method for producing a coating composition containing the fluorine-containing copolymer solution, and a fluorine-containing copolymer solution.

  In order to solve the above-mentioned problems, the present inventors have intensively studied. As a result, the presence of a specific amount of metal alkoxide at the time of copolymerization prevents gelation at the time of polymerization of the fluorine-containing copolymer, and the fluorine-containing after polymerization. The inventors have found that coloring of the copolymer solution can be suppressed, and have reached the present invention.

That is, the present invention is as follows.
(1) A method for producing a fluorinated copolymer solution comprising a step of polymerizing a monomer mixture containing a fluoroolefin (a) and a monomer (b) having a crosslinkable group in an organic solvent. There,
The said polymerization is performed in presence of 0.02-2.0 mass part metal alkoxide with respect to 100 mass parts of total mass of the said monomer mixture, The manufacturing method of the fluorine-containing copolymer solution characterized by the above-mentioned.

(2) The manufacturing method of the fluorine-containing copolymer solution as described in said (1) whose said metal alkoxide is alkali metal alkoxide.
(3) The manufacturing method of the fluorine-containing copolymer solution as described in said (1) or (2) whose said crosslinkable group is a hydroxyl group.

(4) The manufacturing method of the fluorine-containing copolymer solution as described in any one of said (1)-(3) in which the said monomer (b) contains hydroxyalkyl vinyl ethers.
(5) Production of the fluorinated copolymer solution according to any one of (1) to (4), wherein the monomer mixture further contains a monomer (c) having no crosslinkable group. Method.

(6) The fluorine-containing copolymer is composed of 30 to 70 mol% of the structural units based on the fluoroolefin (a) and 5 to 40 mol% of all the structural units in the fluorine-containing copolymer. The structural unit based on the monomer (b) having the crosslinkable group and the structural unit based on the monomer (c) having no crosslinkable group of 0 to 45 mol%, as described in (5) above A method for producing a fluorine-containing copolymer solution.

(7) Content of the said metal alkoxide is any one of said (1)-(6) which is 0.1-1.0 mass part with respect to 100 mass parts of total mass of the said monomer mixture. A method for producing a fluorine-containing copolymer solution.
(8) The organic solvent is one or more organic solvents (d) selected from the group consisting of aromatic hydrocarbon solvents, ketone solvents, ether ester solvents, weak solvents, alcohol solvents, and fluorine-containing solvents. The manufacturing method of the fluorine-containing copolymer solution as described in any one of said (1)-(7) which is.

(9) The fluorine-containing copolymer solution obtained by the production method according to any one of (1) to (8) above, from a group consisting of a curing agent and a resin other than the fluorine-containing copolymer. The manufacturing method of the coating composition characterized by including the process of mix | blending the 1 or more types of coating composition component (e) chosen.

(10) containing a fluorine-containing copolymer having a structural unit based on the fluoroolefin (a) and a structural unit based on the monomer (b) having a crosslinkable group, an organic solvent, and a metal alkoxide. A characteristic fluorine-containing copolymer solution.

  According to the method for producing a fluorine-containing copolymer solution of the present invention, the method for producing a coating composition containing the fluorine-containing copolymer solution, and the fluorine-containing copolymer solution, when producing the fluorine-containing copolymer solution, Gelation at the time of polymerization can be suppressed, and filtration of insoluble matters is unnecessary, and coloring of the fluorine-containing copolymer solution after polymerization and the coating composition containing the fluorine-containing copolymer solution can be reduced. Moreover, the storage stability of the fluorine-containing copolymer solution obtained by the method for producing a fluorine-containing copolymer solution of the present invention is good.

<1> Method for Producing Fluorine-Containing Copolymer Solution of the Present Invention The method for producing the fluorine-containing copolymer solution of the present invention comprises a fluoroolefin (a) and a monomer (b) having a crosslinkable group. And a step of polymerizing the monomer mixture in an organic solvent, and the polymerization is performed in the presence of 0.02 to 2.0 parts by mass of a metal alkoxide with respect to 100 parts by mass of the total mass of the monomer mixture. It is characterized by being performed by.
Below, each component of the monomer mixture used for the polymerization in the present invention, metal alkoxide, polymerization method, and the resulting fluorine-containing copolymer solution (hereinafter also referred to as “fluorine-containing copolymer (A) solution”). ) Etc. will be described.

  The monomer component used for the polymerization in the present invention is a monomer mixture containing a fluoroolefin (a) and a monomer (b) having a crosslinkable group. The monomer mixture may further contain a monomer (c) having no crosslinkable group, if necessary.

[Fluoroolefin (a)]
The fluoroolefin (a) in the present invention is a compound in which part or all of the hydrogen atoms bonded to the carbon atoms of the olefin hydrocarbon are substituted with fluorine atoms. You may have a substituent atom or substituent other than a fluorine atom. The number of fluorine atoms contained in the fluoroolefin (a) is preferably 2 or more, more preferably 2 to 6, and still more preferably 3 to 4. When the number of fluorine atoms is 2 or more, the resulting coating film has sufficient weather resistance.
Examples of the fluoroolefin (a) include tetrafluoroethylene, chlorotrifluoroethylene, vinylidene fluoride, hexafluoropropylene and the like. Tetrafluoroethylene and chlorotrifluoroethylene are particularly preferred.

The amount of the fluoroolefin (a) used for the polymerization in the present invention is preferably from 30 to 70 mol%, more preferably from 40 to 60 mol%, more preferably from 45 to 45 mol%, based on all monomers contained in the monomer mixture. 55 mol% is more preferable.
The fluoroolefin (a) used for the polymerization in the present invention may be used alone or in combination of two or more.

[Monomer (b) having a crosslinkable group]
The monomer (b) having a crosslinkable group in the present invention is a monomer other than the fluoroolefin (a) and a monomer having a double bond copolymerizable with the fluoroolefin (a).
Specifically, the monomer (b) having a crosslinkable group is preferably a monomer having the structure of the following formula 1.
Formula _{1: CH 2 = CX (CH} 2) n -Q-R-Y
(X is a hydrogen atom or a methyl group, n is 0 or 1, Q is an oxygen atom, a group represented by —C (O) O—, or a group represented by —O (O) C—. R is an alkylene group having 2 to 20 carbon atoms which may have a branched structure and / or a ring structure, and Y is a crosslinkable functional group.)
The crosslinkable group is preferably a functional group having active hydrogen such as a hydroxyl group, a carboxyl group, or an amino group; a hydrolyzable silyl group such as an alkoxysilyl group;

  The monomer (b) having a crosslinkable group is preferably a compound in which the crosslinkable functional group represented by Y in Formula 1 is a hydroxyl group, a carboxyl group, or an amino group, and more preferably a compound that is a hydroxyl group. . In the monomer (b) having a crosslinkable group, R in Formula 1 is preferably an alkylene group having 2 to 20 carbon atoms which may have a branched structure and / or a ring structure. An alkylene group is more preferred. 2-10 are preferable, as for carbon number of this alkylene group, 2-6 are more preferable, and 2-4 are more preferable. The monomer (b) having a crosslinkable group preferably contains a vinyl ether having a crosslinkable group, wherein Q in Formula 1 is an oxygen atom.

Monomers (b) having a crosslinkable group include hydroxyalkyl vinyl ethers, hydroxyalkyl carboxylic acid vinyl esters, hydroxyalkyl allyl ethers, hydroxyalkyl carboxylic acid allyl esters, or (meth) acrylic acid hydroxyalkyl esters. Are preferred.
It is preferable that the hydroxyalkyl group and the hydroxyallyl group in the hydroxyalkylcarboxylic acid vinyl ester and the hydroxyalkylallylcarboxylic acid ester are each bonded to the carbon atom of the carbonyl group of the ester bond.

  Specific examples of the monomer (b) having a crosslinkable group include hydroxyalkyl vinyl ethers such as 2-hydroxyethyl vinyl ether (HEVE), hydroxymethyl vinyl ether (HMVE), 4-hydroxybutyl vinyl ether (HBVE); Hydroxyalkyl allyl ethers such as allyl ether; (meth) acrylic acid hydroxyalkyl esters such as hydroxyethyl (meth) acrylate are preferred. Hydroxyalkyl vinyl ethers are more preferable because of excellent copolymerizability and good weather resistance of the formed coating film. In particular, 4-hydroxybutyl vinyl ether (HBVE) is preferable.

The amount of the monomer (b) having a crosslinkable group used for the polymerization in the present invention is preferably 5 to 40 mol%, and 8 to 35 mol%, based on all monomers contained in the monomer mixture. More preferred.
The crosslinking monomer (b) used in the polymerization in the present invention may be used alone or in combination of two or more.

[Monomer (c) having no crosslinkability]
The monomer mixture may contain a monomer (c) having no crosslinkable group.
Specifically, the monomer (c) having no crosslinkable group is preferably a monomer having the structure of the following formula 2.
Formula _{2: CH 2 = CX (CH} 2) n -Q-R-H
(X is a hydrogen atom or a methyl group, n is 0 or 1, Q is an oxygen atom, a group represented by —C (O) O—, or a group represented by —O (O) C—. R is an alkylene group having 2 to 20 carbon atoms which may have a branched structure and / or a ring structure.)

As the monomer (c) having the structure of Formula 2, a compound in which R in Formula 2 is an alkylene group having 2 to 20 carbon atoms which may have a branched structure and / or a ring structure is preferable. Specifically, alkyl vinyl ethers, alkyl carboxylic acid vinyl esters, alkyl allyl ethers, alkyl carboxylic acid allyl esters or (meth) acrylic acid alkyl esters are preferred. The alkyl group in the alkylcarboxylic acid vinyl esters and alkylcarboxylic acid allyl esters is preferably bonded to the carbon atom of the carbonyl group of the ester bond.
In addition, in this specification, description with "(meth) acrylic acid" represents either acrylic acid or methacrylic acid.

As specific examples of the monomer (c) having no crosslinkability, ethyl vinyl ether (EVE), cyclohexyl vinyl ether (CHVE), 2-ethylhexyl vinyl ether (2EHVE) and the like are preferable.
In particular, when the monomer mixture contains cyclohexyl vinyl ether (CHVE), the resulting copolymer has high rigidity, is soluble in a solvent, is easy to apply, especially when applied to paints, and provides a hard coating film. More preferable in terms.

  The amount of the monomer (c) having no crosslinkability used for the polymerization in the present invention is preferably 0 to 45 mol%, and preferably 3 to 35 mol%, based on all monomers contained in the monomer mixture. More preferably, 5-30 mol% is further more preferable.

  The monomer (c) used for the polymerization in the present invention may be used alone or in combination of two or more.

[Organic solvent]
The organic solvent used for the polymerization in the present invention is not particularly limited, and is generally used for polymerization such as a hydrocarbon solvent, an aromatic hydrocarbon solvent, an alcohol solvent, an ester solvent, an ether solvent, a ketone solvent, and the like. Can be used.
The organic solvent is at least one organic solvent (d) selected from the group consisting of aromatic hydrocarbon solvents, ketone solvents, ether ester solvents, weak solvents, alcohol solvents, and fluorine-containing solvents. preferable.

  Aromatic hydrocarbon solvents include toluene, xylene, ethylbenzene, aromatic petroleum naphtha, tetralin, turpentine oil, Solvesso # 100 (Exxon Chemical Co., Ltd. registered trademark), Solvesso # 150 (Exxon Chemical Co., Ltd. registered trademark) Etc.

As the ketone solvent, acetone, methyl ethyl ketone (MEK), methyl amyl ketone (MAK), methyl isobutyl ketone, ethyl isobutyl ketone, diisobutyl ketone, cyclohexanone and isophorone are preferable.
The ether ester solvent is a compound having both an ether bond and an ester bond in the molecule. As the ether ester solvent, ethyl 3-ethoxypropionate (EEP), propylene glycol monomethyl ether acetate, and methoxybutyl acetate are preferable.
The weak solvent is a kind of hydrocarbon solvent, and is an organic solvent classified as a third type organic solvent in the classification of organic solvents by the Industrial Safety and Health Law. Weak solvents include gasoline, coal tar naphtha (including solvent naphtha), petroleum ether, petroleum naphtha, petroleum benzine, turpentine oil, mineral spirit (including mineral thinner, petroleum spirit, white spirit and mineral turpentine), paraffinic It is a solvent comprising at least one selected from the group consisting of a solvent and a naphthenic solvent.
As a weak solvent, since a flash point is room temperature or more, mineral spirits (including mineral thinner, petroleum spirit, white spirit and mineral terpenes) are preferable.

As the alcohol solvent, those having 4 or less carbon atoms are preferable, and specifically, ethanol, tert-butanol, and iso-propyl alcohol are preferable.
The fluorine-containing solvent is preferably at least one selected from the group consisting of hydrochlorofluorocarbons, hydrofluorocarbons, hydrofluoroethers and hydrofluoroalcohols. Of these, hydrochlorofluorocarbons, hydrofluorocarbons and hydrofluoroethers are preferred.

Examples of the hydrochlorofluorocarbon include 1,3-dichloro-1,1,2,2,3-pentafluoropropane and 1,1-dichloro-2,2,3,3,3-pentafluoropropane.
The _{hydrofluorocarbons, CF 3 CF 2 CF 2 CF} 2 CH 2 CH 3, CF 3 CF 2 CF 2 CF 2 CF 2 CF 2 CH 2 CH 3, CF 3 CF 2 CHFCHFCF 3, CF 3 CH 2 CF 2 CH 3 Etc.

Examples of the hydrofluoroether include CF ₃ CH ₂ OCF ₂ CF ₂ H, CF ₃ CH ₂ OCF ₂ CFHCF ₃ , (CF ₃ ) ₂ CHOCF ₂ CF ₂ H, CF ₃ CH ₂ OCHFCHF ₂ , and CF ₃ (CF ₂ ) _3. OCH ₃ , CF ₃ (CF ₂ ) ₄ OCH ₃ , CF ₃ (CF ₂ ) ₃ OCH ₂ CH ₃ , CF ₃ (CF ₂ ) ₄ OCH ₂ CH ₃ , (CF ₃ ) ₂ CFCF ₂ OCH ₂ CH ₃ etc. Can be mentioned.
Examples of the hydrofluoroalcohol include 2,2,2-trifluoroethanol, 2,2,3,3-tetrafluoropropanol, 1,1,1,3,3,3-hexafluoroisopropanol, 2,2,3, Examples include 3,3-pentafluoropropanol.

  From the viewpoint of reducing environmental burden, ketone solvents such as acetone, methyl ethyl ketone (MEK), methyl amyl ketone (MAK), methyl isobutyl ketone, ethyl isobutyl ketone, diisobutyl ketone, cyclohexanone, isophorone, and ethyl 3-ethoxypropionate ( EEP), ether ester solvents such as propylene glycol monomethyl ether acetate and methoxybutyl acetate are preferred. These solvents are solvents corresponding to the PRTR method and HAPs regulations. Similarly, from the viewpoint of reducing environmental burden, it is also preferable to use a weak solvent such as a paraffin solvent or a naphthene solvent.

  The organic solvent (d) may be used alone or in combination of two or more.

The organic solvent used for the polymerization particularly preferably contains an alcohol solvent having 4 or less carbon atoms. When the organic solvent contains an alcohol solvent having 4 or less carbon atoms, it is considered that the effect of preventing gelation is further enhanced in the polymerization reaction due to the increased solubility of the metal alkoxide.
When the alcohol solvent having 4 or less carbon atoms is used in combination with another solvent, the content of the alcohol solvent having 4 or less carbon atoms is preferably 5 to 30% by mass in the total organic solvent.
As the organic solvent in the present invention, a solvent other than the organic solvent (d) and / or the organic solvent (d) is used, but only one kind of the solvent other than the organic solvent (d) and the organic solvent (d) may be used. Two or more of these may be used in combination.
Examples of the solvent other than the organic solvent (d) include hydrocarbon solvents, ester solvents, ether solvents and the like.

[Metal alkoxide]
The polymerization in the present invention is carried out in the presence of a metal alkoxide. Examples of the metal alkoxide include alkali metal alkoxides and alkaline earth metal alkoxides.
Examples of the alkali metal of the alkali metal alkoxide include sodium and potassium. Specific alkali metal alkoxides include sodium methoxide, sodium ethoxide, sodium n-propoxide, sodium i-propoxide, sodium n-butoxide, sodium t-butoxide, and other sodium alkoxides; potassium methoxide, potassium ethoxide Potassium alkoxides such as potassium n-propoxide, potassium i-propoxide, potassium n-butoxide, potassium t-butoxide, and the like.
Examples of the alkaline earth metal of the alkaline earth metal alkoxide include barium.

Specific examples of the alkaline earth metal alkoxide include barium t-butoxide.
Examples of other metal alkoxide metals include magnesium and aluminum.
Specific examples include magnesium diethoxide, magnesium dii-propoxide, aluminum-2-propylate; and the like.
From the viewpoint of solubility during polymerization, alkali metal alkoxides, particularly sodium methoxide, sodium ethoxide, sodium t-butoxide, potassium methoxide, potassium ethoxide, and potassium t-butoxide are preferred.

The usage-amount of a metal alkoxide is 0.02-2.0 mass parts with respect to the total mass (100 mass parts) of a monomer mixture. The amount used is preferably 0.1 parts by mass or more, and more preferably 0.2 parts by mass or more. The amount used is preferably 1.5 parts by mass or less, more preferably 1.0 part by mass or less, and further preferably 0.5 parts by mass or less.
When the amount of metal alkoxide used is not less than the above value with respect to 100 parts by mass of the monomer mixture, gelation at the time of polymerization is suppressed, the copolymerization reaction proceeds smoothly, and is not more than the above value. And coloring of the fluorine-containing copolymer solution after polymerization can be reduced.

[Polymerization method]
In the present invention, the polymerization is carried out in the presence of a metal alkoxide, the fluoroolefin (a), the monomer (b) having the crosslinkable group, and the monomer (c) having no crosslinkable group if necessary. A monomer mixture containing is polymerized in an organic solvent. The amount of each component used for the polymerization is as described above. Moreover, it is preferable to add a polymerization initiator.

  As the polymerization initiator, 2,2′-azobisisobutyronitrile, 2,2′-azobiscyclohexane carbonate nitrile, 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2′- Azo initiators such as azobis (2-methylbutyronitrile); ketone peroxides such as cyclohexanone peroxide, hydroperoxides such as tert-butyl hydroperoxide, diacyl peroxides such as benzoyl peroxide, di -Dialkyl peroxides such as tert-butyl peroxide, peroxyketals such as 2,2-di- (tert-butylperoxy) butane, alkyl peresters such as tert-butyl peroxypivalate (PBPV) , Diisopropyl peroxydicarbonate, etc. Peroxide initiators par carbonates; and the like.

Specifically, the polymerization in the present invention is preferably carried out by any of the following methods.
(I) A method in which a total monomer mixture, an organic solvent, a metal alkoxide, and a polymerization initiator are charged and polymerized. The order of preparation can be set as appropriate.

(Ii) a monomer (b) having a crosslinkable group, a monomer (c) having no crosslinkable group, and a polymerization initiator in a reactor charged with an organic solvent, a fluoroolefin (a), and a metal alkoxide Is added continuously or dividedly. The monomer (b) having a crosslinkable group, the monomer (c) having no crosslinkable group, and a polymerization initiator may be mixed together with an organic solvent and added together, and the charging order can be appropriately set.

(Iii) A method in which the total monomer mixture and the polymerization initiator are added to the reactor charged with the organic solvent and the metal alkoxide, respectively, continuously or dividedly. The monomer mixture and the polymerization initiator may be mixed with an organic solvent and added together, and the charging order can be appropriately set.

(Vi) An organic solvent and a metal alkoxide were charged, and a part of the fluoroolefin (a), the monomer (b) having a crosslinkable group, and the monomer (c) having no crosslinkable group were charged. In the reaction vessel, the remaining amount of the fluoroolefin (a), the monomer (b) having a crosslinkable group and the monomer (c) having no crosslinkable group, the polymerization initiator, is continuously or divided. To add. For the remainder of the fluoroolefin (a), the monomer (b) having a crosslinkable group and the monomer (c) having no crosslinkable group, the polymerization initiator is mixed with an organic solvent and added together. The order of preparation may be set as appropriate.

In addition, the addition method of a metal alkoxide will not be restrict | limited especially if it exists at the time of superposition | polymerization, You may add at the time of superposition | polymerization, or may melt | dissolve in the organic solvent at the time of superposition | polymerization, and may add continuously.
As a result of the above polymerization, a fluorine-containing copolymer solution in which the fluorine-containing copolymer is dissolved in an organic solvent is obtained. According to the production method of the present invention, coloring of the fluorinated copolymer solution after polymerization can be reduced.

  In the method for producing a fluorinated copolymer solution of the present invention, after the polymerization, a step of removing the insoluble matter in the obtained fluorinated copolymer solution after polymerization is not required. If present, it is preferable to remove insoluble matter present in the fluorinated copolymer solution by performing solid-liquid separation such as filtration as necessary. When a solution containing an insoluble material is used for a coating material, the appearance (gloss and transparency) of the coating film may be deteriorated.

[Fluorine-containing copolymer (A) solution]
The fluorine-containing copolymer (A) in the fluorine-containing copolymer (A) solution obtained by the production method of the present invention is based on the structural unit based on the fluoroolefin (a) and the monomer (b) having crosslinkability. It has a structural unit based on the structural unit and, if necessary, the monomer (c) having no crosslinkable group.
The fluorinated copolymer (A) preferably has 30 to 70 mol% of structural units based on the fluoroolefin (a) with respect to all the structural units in the fluorinated copolymer (A). It is more preferable to have mol%, and it is more preferable to have 45-55 mol%.
When the fluoroolefin (a) is 30 mol% or more with respect to all the structural units in the fluorine-containing copolymer (A), the weather resistance is good, and when it is 70 mol% or less, it is dissolved in a solvent or a diluent. Good sex.
The structural unit based on the fluoroolefin (a) contained in the fluorinated copolymer (A) may be only one type or two or more types.

Further, the fluorinated copolymer (A) has 5 to 40 mol% of structural units based on the crosslinkable monomer (b) with respect to all the structural units in the fluorinated copolymer (A). It is preferable to have 8 to 35 mol%.
When the content of the crosslinkable monomer (b) is 5 mol% or more with respect to all the structural units in the fluorinated copolymer (A), it is sufficient to obtain a coating film having high hardness. A sufficient amount of the crosslinkable group is introduced into the fluorine-containing copolymer (A). Moreover, even if it is a high solid content type as content of the monomer (b) which has crosslinkability is 40 mol% or less, sufficient low viscosity can be maintained.
The structural unit based on the monomer (b) having a crosslinkable group contained in the fluorinated copolymer (A) may be only one type or two or more types.

Further, when the fluorine-containing copolymer (A) has a structural unit based on the monomer (c) having no crosslinkable group, the above-mentioned components are added to all the structural units in the fluorine-containing copolymer (A). It is preferable to have 0 to 45 mol% of structural units based on the monomer (c) having no crosslinkable group, more preferably 3 to 35 mol%, and even more preferably 5 to 30 mol%.
By including the monomer (c) having no crosslinkability in the fluorinated copolymer (A), the hardness and flexibility of the obtained coating film can be appropriately adjusted. When the amount of the monomer (c) is 45 mol% or less with respect to all the structural units in the fluorinated copolymer (A), it is sufficient for obtaining a coating film having good weather resistance and high hardness. An amount of crosslinkable groups is introduced into the copolymer.
The structural unit based on the monomer (c) having no crosslinkable group contained in the fluorine-containing copolymer (A) may be only one type or two or more types.
In order to make the composition of the fluorinated copolymer (A) in the above range, the amount ratio of each monomer in the monomer mixture used in the polymerization of the fluorinated copolymer (A) is set to the above range. Good.

The molecular weight of the fluorine-containing copolymer (A) obtained by the production method of the present invention is not particularly limited, but when the fluorine-containing copolymer (A) solution is used for coating, the number of fluorine-containing copolymers (A) The average molecular weight (Mn) is preferably 3000 to 9000. When Mn is 3000 or more, the resulting coating film has excellent weather resistance, and when Mn is 9000 or less, sufficient solubility is obtained even in a coating composition having a high concentration of the fluorinated copolymer (A). This is preferable because it can be realized and a low viscosity can be realized.
In order to make the average molecular weight of the fluorine-containing copolymer (A) fall within the above range, the polymerization temperature may be adjusted or a chain transfer agent may be added. When adjusting the polymerization temperature, the polymerization temperature may be in the range of 60 to 75 ° C.
Here, the number average molecular weight (Mn) of the fluorine-containing copolymer (A) is a number average molecular weight (Mn) measured by gel permeation chromatography (GPC) using polystyrene as a standard substance.

In general, it is known that a fluorinated copolymer may become unstable due to thickening when stored in a solution state and cause problems when used as a paint. However, the fluorine-containing copolymer (A) solution obtained by the production method of the present invention does not increase in viscosity even when stored in a solution state and has good stability.
The fluorine-containing copolymer (A) solution in the present invention is obtained by concentrating the fluorine-containing copolymer (A) solution after polymerization or diluting with an organic solvent that is the same as or different from the organic solvent used in the polymerization, The density may be adjusted. Moreover, all the solvent of the fluorine-containing copolymer (A) solution after superposition | polymerization is remove | excluded, and what was dried again may melt | dissolve in the same or different organic solvent as the organic solvent used by superposition | polymerization. In any case, when the content of the metal alkoxide in the fluorine-containing copolymer (A) solution is 0.1 to 1.0 part by mass with respect to 100 parts by mass of the fluorine-containing copolymer, the solution state Even if it is stored at a temperature, there is no increase in viscosity or the like, and the effect of good stability is obtained.

  The solid content concentration of the fluorinated copolymer (A) in the fluorinated copolymer (A) solution at the time of storage is not particularly limited, but it is a solid content concentration suitable for use as, for example, a paint, 40 to 80 A range of mass% is preferred.

<2> Manufacturing method of coating composition The manufacturing method of the coating composition of the present invention includes a curing agent and a fluorine-containing copolymer solution obtained by the above-described method for manufacturing a fluorine-containing copolymer solution. It includes a step of containing at least one paint blending component (e) selected from the group consisting of resins other than copolymers.

[Fluorine-containing copolymer solution]
The step of obtaining the fluorine-containing copolymer solution in the method for producing a coating composition of the present invention may be performed by the method for producing a fluorine-containing copolymer (A) solution.
Although the solid content concentration in the fluorine-containing copolymer (A) solution in the method for producing a coating composition of the present invention is not particularly limited, for example, a solid content concentration suitable for use as a coating is 40 to 80% by mass. A range is preferred.

Hereinafter, each component of the coating compounding component (e) composed of one or more selected from the group consisting of resins other than the curing agent and the fluorine-containing copolymer will be described.
[Curing agent]
As the curing agent, a curing agent capable of crosslinking with the crosslinkable group in the fluorine-containing copolymer (A) is preferable.
When the crosslinkable group is a hydroxyl group, the curing agent is preferably a coating curing agent such as an isocyanate curing agent, a blocked isocyanate curing agent, or a melamine curing agent.

As the isocyanate curing agent, non-yellowing isocyanates such as hexamethylene diisocyanate and isophorone diisocyanate are preferable.
As the blocked isocyanate curing agent, those obtained by blocking the isocyanate group of the isocyanate curing agent with caprolactam, isophorone, β-diketone or the like are preferable.
As the melamine curing agent, melamine etherified with a lower alcohol such as butylated melamine, epoxy-modified melamine, and the like are preferable.

When the crosslinkable group is a carboxy group, the curing agent is preferably a coating curing agent such as a melamine curing agent, an amine curing agent, an isocyanate curing agent, or an epoxy curing agent.
When the crosslinkable group is an amino group, the curing agent is preferably a coating curing agent such as an isocyanate curing agent or an epoxy curing agent.

1-100 mass parts is preferable with respect to 100 mass parts of the fluorine-containing copolymer in a coating composition, and, as for content of the hardening | curing agent in the manufacturing method of the coating composition of this invention, 1-50 mass parts is more. preferable.
When the curing agent is 1 part by mass or more, the resulting coating film has excellent solvent resistance and sufficient hardness, and when the curing agent is 100 parts by mass or less, it has excellent workability and excellent impact resistance. .

  The coating composition in the present invention may be a one-pack type paint or a two-pack type paint. In the case of the two-component type, the curing agent is mixed immediately before use.

[resin]
The resin blended as the paint blending component (e) is a resin other than the fluorocopolymer obtained by the method for producing the fluorocopolymer solution of the present invention, and a known resin blended in the paint is appropriately used. be able to.
Examples of the resin other than the fluorine-containing copolymer include CAB (cellulose acetate butyrate) and NC (nitrocellulose) in order to improve the drying property of the coating film. Moreover, in order to improve the gloss of a coating film, hardness, and the workability of a coating material, resin, such as an acrylic resin and a polyester resin, is mentioned.

[Other ingredients]
In the step of containing the paint blending component (e) in the method for producing a paint composition of the present invention, in addition to the paint blending component (e), an organic solvent for paint, a colorant, a silane coupling agent, an ultraviolet absorber, Known components such as a curing accelerator, a light stabilizer, and a matting agent can be blended as necessary.
In order to adjust the concentration to an appropriate level as a paint, an organic solvent for paint may be added. The organic solvent for paint may be the organic solvent used in the polymerization in the method for producing the fluorine-containing copolymer (A) solution, or other organic solvent.
Examples of the colorant include inorganic pigments such as carbon black and titanium oxide having good weather resistance; organic pigments such as phthalocyanine blue, phthalocyanine green, quinacridone red, indanthrene orange, and isoindolinone yellow; dyes and the like.

As a method of coating using the coating composition in the present invention, any method such as spray coating, air spray coating, brush coating, dipping method, roll coater, flow coater and the like can be applied.
Examples of the material of the article to be coated include inorganic substances such as concrete, natural stone, and glass; metals such as iron, stainless steel, aluminum, copper, brass, and titanium; and organic substances such as plastic, rubber, adhesive, and wood.
It is also suitable for coating organic and inorganic composite materials such as FRP, resin reinforced concrete, and fiber reinforced concrete.

  Articles to be painted include transportation equipment such as automobiles, trains and aircraft; civil engineering members such as bridge members and steel towers; industrial equipment such as waterproof sheets, tanks and pipes; building exteriors, doors, window gate members, monuments, Examples include building members such as poles; road parts such as road median strips, guardrails, and soundproof walls; communication equipment; electrical and electronic parts; surface sheets for solar cell modules, and backsheets.

<3> Method for Producing Fluorine-Containing Copolymer Solution The present inventors used a metal alkoxide used in the method for producing a fluorinated copolymer solution of the present invention as a fluorinated copolymer produced by a known method. It has also been found that when added to an organic solvent solution, it has storage stability and anti-coloring effects.
Another aspect of the present invention is a method for producing a fluorinated copolymer solution, which comprises adding a metal alkoxide to an organic solvent solution of the fluorinated copolymer (hereinafter referred to as “second invention”). It is.

Specifically, the method for producing the fluorine-containing copolymer solution of the second invention (hereinafter also referred to as “fluorine-containing copolymer (B) solution”) comprises the steps of: It has the process of adding 0.1-1.0 mass part metal alkoxide with respect to 100 mass parts of total mass of the said fluorine-containing copolymer, It is characterized by the above-mentioned.
The fluorine-containing copolymer in the second invention (hereinafter also referred to as fluorine-containing copolymer (B)) is not particularly limited. The fluorine-containing copolymer (A) obtained by the above-mentioned method for producing a fluorine-containing copolymer (A) solution can also be used, and it has been produced by other known methods, for example, the method described in Japanese Patent No. 1563615. Things can also be used. The constitutional unit of the fluorine-containing copolymer to be used is not particularly limited.

The fluorine-containing copolymer (B) in the second invention is preferably a fluorine-containing copolymer having a structural unit based on a fluoroolefin and a structural unit based on a monomer having a crosslinkable group.
Examples of the fluoroolefin in the second invention include the same as the fluoroolefin (a), and the preferred embodiments are also the same. Examples of the monomer having a crosslinkable group in the second invention include the same monomers as the monomer (b) having the crosslinkable group, and preferred embodiments are also the same.
The crosslinkable group in the monomer having a crosslinkable group is preferably a functional group having an active hydrogen such as a hydroxyl group, a carboxyl group, or an amino group; a hydrolyzable silyl group such as an alkoxysilyl group; preferable.

The fluorine-containing copolymer (B) may have a structural unit based on a monomer having no crosslinkable group, if necessary. Examples of the monomer having no crosslinkable group in the second invention include the same monomers as the monomer (c) having no crosslinkable group, and preferred embodiments are also the same.
As a composition of the fluorine-containing copolymer (B) in 2nd invention, the same composition as the said fluorine-containing copolymer (A) is mentioned, A preferable aspect is also the same.

In the second invention, the fluorine-containing copolymer (B) solution to which the metal alkoxide is added is concentrated in the polymerized fluorine-containing copolymer solution or diluted with the same or different organic solvent as the organic solvent used in the polymerization. Alternatively, the density may be adjusted. Alternatively, all of the organic solvent in the fluorinated copolymer solution after polymerization may be removed and the dried product may be dissolved again in the same or different organic solvent as used in the polymerization.
As an organic solvent in a fluorine-containing copolymer (B) solution, the same organic solvent in the manufacturing method of said fluorine-containing copolymer can be used.
In the fluorine-containing copolymer (B) solution to which the metal alkoxide is added, the solid content concentration of the fluorine-containing copolymer is not particularly limited. For example, the solid content concentration suitable for use as a paint is 40 to 80% by mass. The range of is preferable.

As a metal alkoxide in 2nd invention, the same thing as the metal alkoxide in the manufacturing method of said fluorine-containing copolymer (A) solution can be used. The preferred embodiment is also the same.
The addition amount of the metal alkoxide in the second invention is preferably 0.1 to 1.0 part by mass with respect to the total mass (100 parts by mass) of the fluorine-containing copolymer in the fluorine-containing copolymer (B) solution. . The added amount is more preferably 0.2 parts by mass or more. If the content of the metal alkoxide is at least this value, the storage stability will be good.
Further, the addition amount is more preferably 1.0 part by mass or less, and further preferably 0.5 part by mass or less. If the content of the metal alkoxide is not more than this value, the coloring of the solution can be suppressed.

  In the fluorine-containing copolymer (B) solution obtained by the second invention, the coating compounding component (e) and other components are added in the same manner as in the method for producing the fluorine-containing copolymer (A) solution. Thus, a coating composition can be produced.

<4> Fluorine-containing copolymer solution The present invention comprises a fluorine-containing copolymer having a structural unit based on a fluoroolefin (a) and a structural unit based on a monomer (b) having a crosslinkable group, an organic solvent, And a fluorinated copolymer solution characterized by containing a metal alkoxide.

  The content of the metal alkoxide is preferably 0.1 to 1.0 part by mass with respect to 100 parts by mass of the fluorinated copolymer from the viewpoint of storage stability, More preferably. Storage stability is favorable in it being the said range.

  The fluorine-containing copolymer solution of the present invention can be obtained by the method for producing the fluorine-containing copolymer (A) solution of the present invention or the method for producing the fluorine-containing copolymer (B) solution of the second invention. Although obtained, it is not limited to this.

The fluorine-containing copolymer has a structural unit based on the fluoroolefin (a) and a structural unit based on the monomer (b) having a crosslinkable group, and the single unit having the crosslinkable group and the fluoroolefin (a). It can be obtained by polymerizing a monomer mixture containing the monomer (b). The monomer mixture may further contain a monomer (c) having no crosslinkable group.
As a composition of a fluorine-containing copolymer, the same composition as the said fluorine-containing copolymer (A) is mentioned, Although a preferable aspect is also the same, it is not limited to this.

Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples. Parts and% are shown on a mass basis unless otherwise specified.
<Production Example 1 of fluorinated copolymer solution>
A fluorine-containing copolymer solution was prepared with the formulation shown in Table 1. The numerical values in the columns of fluoroolefin (a), monomer (b) and monomer (c) of the monomer mixture in the table are the ratio (parts by mass) of each monomer in the monomer mixture. The description in parentheses is mol%. The numerical value in the column of metal alkoxide is a ratio (unit: part by mass) to 100 parts by mass of the total mass of the monomer mixture.

[Example 1]
In a stainless steel pressure resistant reactor having an internal volume of 2500 mL equipped with a stirrer, ethanol 18 parts by mass, xylene 64 parts by mass, ethyl vinyl ether (EVE) 29 parts by mass (40 mol%), 4-hydroxy vinyl ether (HBVE) 12 parts by mass Parts (10 mol%), 0.10 parts by weight of sodium methoxide, and 0.5 parts by weight of tert-perbutyl pivalate (PBPV) are added, and dissolved oxygen in the liquid is removed by pressurizing / purging with nitrogen and degassing. Removed. Next, 59 parts by mass (50 mol%) of chlorotrifluoroethylene (CTFE) was introduced, the temperature was gradually raised, and the reaction was continued while maintaining the temperature at 65 ° C. After 12 hours, the reactor was cooled with water to stop the reaction. After cooling the reaction solution to room temperature, the unreacted monomer was purged, the resulting reaction solution was distilled under reduced pressure to remove ethanol, and the fluorinated copolymer A-1 having a solid content concentration of 60.2% was obtained. A solution was obtained.
The number average molecular weight (Mn) of the obtained fluorine-containing copolymer was 8,000.

[Example 2]
In Example 1, the formulation was changed as shown in Table 1, and the same except that sodium ethoxide was used instead of sodium methoxide. A solution was obtained. In this example, cyclohexyl vinyl ether (CHVE) was further used.
The number average molecular weight (Mn) of the obtained fluorine-containing copolymer was 7500.

[Example 3]
In Example 1, the formulation was changed as shown in Table 1, and the same procedure was performed except that potassium t-butoxide was used instead of sodium methoxide, and the fluorine-containing copolymer A- having a solid content concentration of 60.2% was used. Three solutions were obtained. In this example, cyclohexyl vinyl ether (CHVE) was used instead of ethyl vinyl ether (EVE).
The number average molecular weight (Mn) of the obtained fluorine-containing copolymer was 8,000.

[Example 4]
In Example 1, the blending was changed as shown in Table 1, and the solid content concentration was changed to 60.50, except that 0.20 parts by mass of sodium t-butoxide was used instead of 0.10 parts by mass of sodium methoxide. A 3% fluorine-containing copolymer A-4 solution was obtained. In this example, cyclohexyl vinyl ether (CHVE) was further used.
The number average molecular weight (Mn) of the obtained fluorine-containing copolymer was 8,500.

[Example 5]
In Example 1, the formulation was changed as shown in Table 1, and the solid content concentration was changed to 60. 5 in the same manner except that 0.50 part by mass of sodium t-butoxide was used instead of 0.10 part by mass of sodium methoxide. A 2% fluorine-containing copolymer A-5 solution was obtained. In this example, cyclohexyl vinyl ether (CHVE) was further used.
The number average molecular weight (Mn) of the obtained fluorine-containing copolymer was 7500.

[Example 6]
In Example 1, the formulation was changed as shown in Table 1, and the solid content concentration was changed to 60.70, except that 1.0 part by mass of potassium t-butoxide was used instead of 0.10 parts by mass of sodium methoxide. A 3% fluorine-containing copolymer A-6 solution was obtained. In this example, cyclohexyl vinyl ether (CHVE) was further used.
The number average molecular weight (Mn) of the obtained fluorine-containing copolymer was 8,000.

[Comparative Example 1]
In Example 1, sodium methoxide was not added, the formulation was changed as shown in Table 1, and the others were the same as in Example 1. As a result, a gel-like fluorine-containing copolymer B-1 insoluble in a solvent was obtained. A solution was obtained.

[Comparative Example 2]
In Example 1, in place of 0.10 parts by mass of sodium methoxide, 1.00 parts by mass of methanol was added, the formulation was changed as shown in Table 1, and the others were the same as in Example 1. An insoluble gel-like fluorine-containing copolymer B-2 solution was obtained.

[Comparative Example 3]
In Example 3, 0.10 parts by mass of potassium t-butoxide was changed to 0.01 parts by mass of sodium t-butoxide, and the rest was the same as in Example 3 except that the fluorine content was highly viscous with a solid content concentration of 60.2%. A copolymer B-3 solution was obtained.

[Comparative Example 4]
In Example 3, 0.10 parts by mass of potassium t-butoxide was changed to 2.50 parts by mass of sodium t-butoxide, and the rest was the same as in Example 3 except that the fluorine-containing copolymer having a solid content concentration of 60.3% was used. A B-4 solution was obtained.
The number average molecular weight (Mn) of the obtained fluorine-containing copolymer was 8,000.

[Comparative Example 5]
In Example 4, 0.20 parts by mass of sodium t-butoxide was changed to 5.00 parts by mass of potassium t-butoxide, and the rest was the same as in Example 4, except that the fluorine-containing copolymer having a solid content concentration of 60.5% was used. A B-5 solution was obtained.
The number average molecular weight (Mn) of the obtained fluorine-containing copolymer was 7500.

[Comparative Example 6]
In Example 3, 0.10 parts by mass of potassium t-butoxide was changed to 1.00 parts by mass of potassium carbonate, and polymerization was performed in the same manner as in Example 3. After the polymerization, the residue of potassium carbonate was filtered to obtain a fluorinated copolymer B-6 solution having a solid concentration of 60.5%.
The number average molecular weight (Mn) of the obtained fluorine-containing copolymer was 8,000.

[Evaluation]
(Polymerization behavior of fluorine-containing copolymer)
Visually, the viscosity of the copolymer was evaluated according to the following criteria. The results are shown in Table 1.
Viscosity increases in the order of None <None (with insoluble content) <Thickening <Gel.

(Presence or absence of coloring of the solution after polymerization)
About the obtained fluorine-containing copolymer (A-1 to A-6, B-1 to B-6) solution, the presence or absence of coloring was visually evaluated. The results are shown in Table 1.

(Storage stability of fluorine-containing copolymer solution)
After the obtained fluorinated copolymer (A-1 to A-6, B-1 to B-6) solution was stored at 70 ° C. for 14 days, the solution was visually observed to check for gelation. Evaluated. The results are shown in Table 1.
Evaluation ○: No gelation Δ: Slightly thickened (Viscosity: Initial value × 1.5 to 2 times)
X: Gelled (viscosity: initial value x 2 times or more)

From the results of Table 1, the fluorine-containing copolymer solutions of the examples in which copolymerization was performed in the presence of a specific amount of metal alkoxide can suppress gelation during polymerization and are excellent in coloration suppression. I understand that. The effect of suppressing coloring was higher in Examples 1 to 5 in which the addition amount of the metal alkoxide was 0.1 parts by mass, 0.2 parts by mass, and 0.5 parts by mass. In addition, in Examples 4 to 6 in which the addition amount of the metal alkoxide was 0.2 parts by mass, 0.5 parts by mass, and 1.0 parts by mass with respect to 100 parts by mass of the total mass of the monomer mixture. The storage stability of the polymer was good.
On the other hand, in Comparative Examples 1 and 2 to which no metal alkoxide was added and Comparative Example 3 in which the amount of metal alkoxide added was small, gelation could not be suppressed.
In Comparative Example 6 using potassium carbonate instead of metal alkoxide, gelation during polymerization was suppressed, but the storage stability was not good.
In Comparative Examples 4 and 5, gelation during polymerization was suppressed, but the result of color suppression was not good.
In addition, the coating film obtained with the solution of the Example obtained a white favorable coating film.

<Production Example 2 of fluorinated copolymer solution>
A fluorine-containing copolymer solution was prepared with the formulation shown in Table 2. The numerical values in the columns of fluoroolefin (a), monomer (b) and monomer (c) of the monomer mixture in the table are the ratio (parts by mass) of each monomer in the monomer mixture. The description in parentheses is mol%. The numerical value in the column of stabilizers other than metal alkoxide is a ratio (unit: parts by mass) to 100 parts by mass of the total mass of the monomer mixture. Moreover, the numerical value in the column of the metal alkoxide added after superposition | polymerization is a ratio (unit: mass part) with respect to 100 mass parts of total mass of the obtained fluorine-containing copolymer.

[Reference Example 1]
A stainless steel pressure-resistant reactor having an internal volume of 2500 mL equipped with a stirrer, ethanol 18 parts by mass, xylene 64 parts by mass, ethyl vinyl ether (EVE) 29 parts by mass (40 mol%), tert-hydroxy vinyl ether (HBVE) 12 parts by mass Part (10 mol%), 1.0 part by mass of potassium carbonate, and 0.5 part by mass of perbutyl pivalate (PBPV) were added, and dissolved oxygen in the liquid was removed by pressurization / purging with nitrogen and deaeration. Next, 59 parts by mass (50 mol%) of chlorotrifluoroethylene (CTFE) was introduced, the temperature was gradually raised, and the reaction was continued while maintaining the temperature at 65 ° C. After 12 hours, the reactor was cooled with water to stop the reaction. After cooling the reaction solution to room temperature, the unreacted monomer was purged, and the reaction solution obtained was distilled under reduced pressure to remove ethanol, and then filtered through a mesh to remove potassium carbonate residue, sodium 0.10 parts by mass of methoxide was added to obtain a fluorine-containing copolymer C-1 solution having a solid content concentration of 60.3%.
The number average molecular weight (Mn) of the obtained fluorine-containing copolymer was 8,000.

[Reference Example 2]
In Reference Example 1, the composition was changed as shown in Table 2 to obtain a fluorinated copolymer. After filtration through a mesh, 0.4 mass part of sodium ethoxide was used instead of 0.10 mass part of sodium methoxide. In the same manner as in Reference Example 1, a fluorinated copolymer C-2 solution having a solid content concentration of 60.2% was obtained.
The number average molecular weight (Mn) of the obtained fluorine-containing copolymer was 7500.

[Reference Example 3]
In Reference Example 1, the composition was changed as shown in Table 2 to obtain a fluorinated copolymer, and after filtration through a mesh, 0.40 part by mass of potassium t-butoxide was substituted for 0.10 part by mass of sodium methoxide. A fluorine-containing copolymer C-3 solution having a solid content concentration of 60.3% was obtained in the same manner as in Reference Example 1 except that it was used.
The number average molecular weight (Mn) of the obtained fluorine-containing copolymer was 8,000.

[Reference Example 4]
In Reference Example 1, the composition was changed as shown in Table 2 to obtain a fluorinated copolymer, and after filtration through a mesh, the solid content concentration was 60. A 3% fluorine-containing copolymer D-1 solution was obtained.
The number average molecular weight (Mn) of the obtained fluorine-containing copolymer was 8,000.

[Reference Example 5]
In Reference Example 1, the composition was changed as shown in Table 2 to obtain a fluorinated copolymer. After filtration through a mesh, 0.05 mass part of potassium t-butoxide was substituted for 0.10 mass part of sodium methoxide. A fluorine-containing copolymer D-2 solution having a solid content concentration of 60.2% was obtained in the same manner as in Reference Example 1 except that it was used.
The number average molecular weight (Mn) of the obtained fluorine-containing copolymer was 7000.

[Reference Example 6]
In Reference Example 1, the composition was changed as shown in Table 2 to obtain a fluorinated copolymer, and after filtration through a mesh, 1.50 parts by mass of potassium t-butoxide was substituted for 0.10 parts by mass of sodium methoxide. A fluorine-containing copolymer D-3 solution having a solid content concentration of 60.4% was obtained in the same manner as in Reference Example 1 except that it was used.
The number average molecular weight (Mn) of the obtained fluorine-containing copolymer was 8,000.

[Reference Example 7]
In Reference Example 1, the composition was changed as shown in Table 2 to obtain a fluorinated copolymer, and after filtration through a mesh, 0.50 parts by mass of potassium t-butoxide was used instead of 0.10 parts by mass of sodium methoxide. A fluorine-containing copolymer C-4 solution having a solid content concentration of 60.5% was obtained in the same manner as in Reference Example 1 except that it was used.
The number average molecular weight (Mn) of the obtained fluorine-containing copolymer was 8,000.
[Reference Example 8]
In Reference Example 1, the formulation was changed as shown in Table 2, and tinuvin stabilizer (product name: Tinuvin 144, manufactured by Ciba Japan Co., Ltd.) was used instead of potassium carbonate as a stabilizer during polymerization. A fluorinated copolymer C-5 solution having a solid content concentration of 60.2% was obtained in the same manner as in Reference Example 1 except that the fluorinated copolymer was obtained.
The number average molecular weight (Mn) of the obtained fluorine-containing copolymer was 8,000.

[Reference Example 9]
In Reference Example 1, the formulation was changed as shown in Table 2, and tinuvin stabilizer (product name: Tinuvin 144, manufactured by Ciba Japan Co., Ltd.) was used instead of potassium carbonate as a stabilizer during polymerization. A fluorine-containing copolymer having a solid content concentration of 60.3% was obtained in the same manner as in Reference Example 1 except that 0.10 parts by mass of sodium methoxide was replaced with 0.40 parts by mass after filtration through a mesh. A copolymer C-6 solution was obtained.
The number average molecular weight (Mn) of the obtained fluorine-containing copolymer was 7000.

[Evaluation]
About the obtained fluorine-containing copolymer (C-1 to C-6, D-1 to D-3) solution, the same as above, the presence or absence of coloring of the polymerization behavior and the solution after polymerization, and after the addition of the metal alkoxide The appearance, storage stability and the presence or absence of coloring after 14 days at 70 ° C. were evaluated. The measurement results are shown in Table 2.
In addition, the external appearance after metal alkoxide addition and the presence or absence of coloring after 70 degreeC x 14 days were evaluated by visual observation similarly to the presence or absence of coloring of the solution after polymerization.

From the results in Table 2, the fluorine-containing copolymer solutions of Reference Examples 1 to 3 and 7 to 9 in which a specific amount of metal alkoxide was added after polymerization were excellent in storage stability. It turns out that the reference examples 1-3 are further excellent in coloring suppression.
On the other hand, Reference Example 4 in which the metal alkoxide was not added after polymerization was inferior in storage stability.
In Reference Example 5, although the metal alkoxide was added after the polymerization, the result of storage stability was poor because the addition amount was small. In Reference Example 6, although metal alkoxide was added after polymerization, coloring was not suppressed because of the large amount of addition.

Claims (10)

A method for producing a fluorinated copolymer solution comprising a step of polymerizing a monomer mixture containing a fluoroolefin (a) and a monomer (b) having a crosslinkable group in an organic solvent,
The said polymerization is performed in presence of 0.02-2.0 mass part metal alkoxide with respect to 100 mass parts of total mass of the said monomer mixture, The manufacturing method of the fluorine-containing copolymer solution characterized by the above-mentioned.   The method for producing a fluorine-containing copolymer solution according to claim 1, wherein the metal alkoxide is an alkali metal alkoxide.   The method for producing a fluorinated copolymer solution according to claim 1, wherein the crosslinkable group is a hydroxyl group.   The manufacturing method of the fluorine-containing copolymer solution as described in any one of Claims 1-3 in which the said monomer (b) contains hydroxyalkyl vinyl ethers.   The manufacturing method of the fluorine-containing copolymer solution as described in any one of Claims 1-4 in which the said monomer mixture contains the monomer (c) which does not have a crosslinkable group further.   The fluorine-containing copolymer is composed of 30 to 70 mol% of the structural unit based on the fluoroolefin (a) and 5 to 40 mol% of the crosslinkability with respect to all the structural units in the fluorine-containing copolymer. The fluorine-containing copolymer according to claim 5, comprising a structural unit based on the monomer (b) having a group and a structural unit based on the monomer (c) having no crosslinkable group of 0 to 45 mol%. A method for producing a polymer solution.   Content of the said metal alkoxide is 0.1-1.0 mass part with respect to 100 mass parts of total mass of the said monomer mixture, The fluorine-containing copolymer as described in any one of Claims 1-6. A method for producing a solution.   The organic solvent is one or more organic solvents (d) selected from the group consisting of aromatic hydrocarbon solvents, ketone solvents, ether ester solvents, weak solvents, alcohol solvents, and fluorine-containing solvents. The manufacturing method of the fluorine-containing copolymer solution as described in any one of Claims 1-7.   To the fluorine-containing copolymer solution obtained by the production method according to any one of claims 1 to 8, at least one selected from the group consisting of a curing agent and a resin other than the fluorine-containing copolymer. The manufacturing method of the coating composition characterized by having the process of mix | blending a coating composition component (e).   It contains a fluorine-containing copolymer having a structural unit based on a fluoroolefin (a) and a structural unit based on a monomer (b) having a crosslinkable group, an organic solvent, and a metal alkoxide. Fluorine-containing copolymer solution.