WO2017122701A1 - Fluororesin-containing solution, process for producing fluororesin-containing solution, coating composition, and coated article - Google Patents

Abstract

The present invention addresses the problem of providing a fluororesin-containing solution which has excellent storage stability and can form coating films excellent in terms of glossiness immediately after film formation. Furthermore, the present invention addresses the problem of providing a process for producing the fluororesin-containing solution, a coating composition, and a coated article. The fluororesin-containing solution of the present invention comprises: a fluororesin comprising a fluoropolymer that comprises units based on chlorotrifluoroethylene; an aminated compound; and an organic solvent. The fluororesin-containing solution has a chlorine ion concentration, as determined by the following chlorine ion concentration measurement method, of 50 mass ppm or less. Chlorine ion concentration measurement method: the fluororesin-containing solution is mixed with xylene to prepare a sample solution; the obtained sample solution is mixed with water; the resultant mixture is subjected to phase separation into a xylene phase and an aqueous phase, and the aqueous phase is recovered; and the chlorine ion concentration in the recovered water is determined by ion chromatography.

Description

Fluororesin-containing solution, method for producing fluororesin-containing solution, coating composition, and coated article

The present invention relates to a fluororesin-containing solution, a method for producing a fluororesin-containing solution, a coating composition, and a coated article.

Conventionally, fluororesins obtained by copolymerizing fluoroolefins alone or with other monomers are known. A solution obtained by dissolving such a fluororesin in an organic solvent (a fluororesin-containing solution) is used, for example, as a raw material for a paint.
As such a fluororesin-containing solution, Patent Document 1 discloses a fluoropolymer having a unit based on a fluoroolefin, a compound having a 2,2,6,6-tetrasubstituted piperidyl group, and an organic solvent. A fluororesin-containing solution is disclosed.

International Publication No. 2015/056751 Pamphlet

In recent years, regarding the performance of the coating film, further improvement in gloss has been demanded.
The present inventors produced a coating composition using a fluororesin-containing solution containing a fluororesin composed of a fluoropolymer having a unit based on chlorotrifluoroethylene as described in Patent Document 1. As a result of examining the glossiness of the coating film obtained using this coating composition, it was confirmed that the glossiness immediately after film formation does not satisfy the high level required recently.
As a result of studying the cause, the present inventors have found that the decrease in gloss immediately after film formation is related to the concentration of chlorine ions detected by subjecting the fluororesin-containing solution to a predetermined treatment. is doing.
Moreover, the fluororesin-containing solution is also required to have excellent storage stability.

The present invention has been made in view of the above problems, and an object thereof is to provide a fluororesin-containing solution capable of forming a coating film having excellent storage stability and excellent gloss immediately after film formation. Another object of the present invention is to provide a method for producing a fluororesin-containing solution, a coating composition, and a coated article.

As a result of earnestly examining the above problems, the present inventor has found that a desired effect can be obtained by using a fluororesin-containing solution whose chlorine ion concentration detected by the detection method described in detail later is a predetermined value or less. The headline, the present invention has been reached.
That is, the present inventor has found that the above problem can be solved by the following configuration.

This invention is the following invention regarding the fluororesin containing solution, the manufacturing method of a fluororesin containing solution, a coating composition, and a coated article.
[1] A fluororesin-containing solution containing a fluororesin composed of a fluoropolymer having a unit based on chlorotrifluoroethylene, an amino group-containing compound, and an organic solvent, the following method for measuring chloride ion concentration The fluororesin containing solution whose chlorine ion concentration calculated | required by is 50 mass ppm or less.
Chlorine ion concentration measurement method: The fluororesin-containing solution and xylene are mixed to prepare a sample solution. After mixing the obtained sample solution and water, phase separation is performed into a xylene phase and a water phase. The aqueous phase is recovered and the concentration of chloride ions in the recovered water is measured by ion chromatography.
[2] The fluororesin-containing solution according to [1], wherein the content of the amino group-containing compound is 0.1 to 2.0 parts by mass with respect to 100 parts by mass of the fluororesin.
[3] The fluororesin-containing solution according to [1] or [2], wherein the content of units based on the chlorotrifluoroethylene is 40 to 60 mol% with respect to all units of the fluoropolymer.
[4] The fluororesin-containing solution according to any one of [1] to [3], wherein the chlorine ion concentration is 3 mass ppm or more.

[5] In the presence of an amino group-containing compound and hydrotalcite, a monomer component containing chlorotrifluoroethylene is polymerized in an organic solvent to obtain a fluorine-containing polymer-containing mixture, and then the fluorine-containing polymer A method for producing a fluororesin-containing solution by removing insoluble components derived from the hydrotalcite from a polymer-containing mixture,
The ratio of the mass of the hydrotalcite to the mass of the amino group-containing compound (the mass of hydrotalcite / the mass of the amino group-containing compound) at the start of polymerization of the monomer component is 1 to 4. A method for producing a fluororesin-containing solution.
[6] The process according to [5], wherein hydrotalcite is added to the fluoropolymer-containing mixed solution after the polymerization and before the filtration.
[7] The amount of the amino group-containing compound at the start of polymerization is 0.1 to 2.0 parts by mass with respect to 100 parts by mass of the monomer component. Production method.
[8] The production method of any one of [5] to [7], wherein the amount of chlorotrifluoroethylene in the monomer component is 40 to 60 mol% with respect to the total monomer components.
[9] The method according to any one of [5] to [8], wherein the fluororesin-containing solution does not substantially contain hydrotalcite.
[10] The production method of any one of [5] to [9], wherein the chlorine ion concentration determined by the following chlorine ion concentration measurement method in the produced fluororesin-containing solution is 50 mass ppm or less.
Chlorine ion concentration measurement method: The fluororesin-containing solution and xylene are mixed to prepare a sample solution. After mixing the obtained sample solution and water, phase separation is performed into a xylene phase and a water phase. The water is collected, and the chlorine ion concentration in the collected water is measured by ion chromatography.

[11] The production method of [10], wherein the chlorine ion concentration is 3 mass ppm or more.
[12] A coating composition comprising the fluororesin-containing solution according to any one of [1] to [4].
[13] A coating composition comprising a fluororesin composition obtained by removing the organic solvent from the fluororesin-containing solution of any one of [1] to [4].
[14] The coating composition according to [13], wherein the coating composition is a powdered coating composition.
[15] A coated article comprising a base material and a coating film formed on the base material with the coating composition according to any one of [12] to [14].

According to the present invention, it is possible to provide a fluororesin-containing solution capable of forming a coating film having excellent storage stability and excellent gloss immediately after film formation. Moreover, according to this invention, the manufacturing method of a fluororesin containing solution, a coating composition, and a coated article can also be provided.

In this specification, “unit based on monomer” means an atomic group directly formed by polymerization of one monomer molecule and an atomic group obtained by chemically converting a part of the atomic group. It is a generic name. Hereinafter, the unit based on the monomer is also simply referred to as “unit”.
The content (mol%) of each unit of the fluoropolymer can be determined by analyzing the fluoropolymer by nuclear magnetic resonance spectroscopy, but can also be estimated from the charged amount of each monomer.
The “crosslinkable group” means a group capable of forming a crosslinked structure by reacting with a curing agent, or a group capable of forming a crosslinked structure by reacting with each other.
In the present specification, the number average molecular weight and the mass average molecular weight are values obtained in terms of polystyrene by a gel permeation chromatography (GPC) method. The number average molecular weight is also referred to as Mn.
“Hydrotalcite” means a layered double hydroxide represented by the following formula.
[Mg ²⁺ _1-x Al ³⁺ _x (OH) ₂ ] ^{x +} [CO ₃ ²⁻ _{x / 2} · mH ₂ O] ^x−
However, x is 0.2 to 0.33, and m is 0 to 2.
“(Meth) acrylate” is a general term for acrylate and methacrylate.
The “ether ester solvent” means a compound having both an ether bond and an ester bond in the molecule.

Hereinafter, the fluororesin-containing solution, the method for producing the fluororesin-containing solution, the coating composition, and the coated article of the present invention will be described in detail.

[Fluorine resin-containing solution]
The fluororesin-containing solution of the present invention includes a fluororesin comprising a fluoropolymer having units based on chlorotrifluoroethylene (CF ₂ = CFCl, hereinafter also referred to as “CTFE”), an amino group-containing compound, and an organic solvent. The chlorine ion concentration calculated | required by the following chlorine ion concentration measuring methods is 50 mass ppm or less.
Chlorine ion concentration measurement method: The above fluororesin-containing solution and xylene are mixed to prepare a sample solution. After mixing the obtained sample solution and water, the xylene phase and the water phase are phase-separated. The aqueous phase is recovered and the concentration of chloride ions in the recovered water is measured by ion chromatography.
In the following, the above-described chlorine ion concentration measurement method is also referred to as “predetermined measurement method”, and the chlorine ion concentration means the chlorine ion concentration obtained by the predetermined measurement method.
The fluororesin-containing solution of the present invention is excellent in storage stability and can form a coating film excellent in gloss immediately after film formation. The details of this reason have not yet been clarified, but it is thought that this is mainly due to the following reasons.

In the present invention, a fluororesin composed of a fluoropolymer having units based on CTFE is used.
Inventors manufactured a coating composition using a fluororesin-containing solution containing a fluoropolymer having a unit based on CTFE according to a method specifically described in Patent Document 1, and the coating composition The glossiness of the coating film obtained using the above was examined (see Comparative Example 1 described later). As a result, the present inventors have found that the gloss immediately after the coating film is formed decreases.
The present inventors have found that the chlorine ion concentration of the fluororesin-containing solution and the decrease in gloss of the coating film immediately after film formation are closely related. Specifically, as shown also in the Example mentioned later, when the chlorine ion concentration was made into the predetermined value or less, it discovered that the coating film excellent in the glossiness immediately after film-forming was obtained.
Although the detailed reason why chlorine ions are related to the glossiness of the coating film is unknown, at the time of coating film formation, acid-derived components (such as chlorine ions derived from hydrogen chloride) are localized on the coating film surface. There is a difference in curing speed between the coating surface and the inside of the coating film, or the fluororesin gels and melt fluidity deteriorates before film formation during baking coating, and a uniform coating film may not be formed It is considered that the glossiness deteriorates due to such reasons.
Note that “immediately after film formation” refers to within 24 hours from the production of the coating film.

In addition, since the fluororesin-containing solution of the present invention contains an amino group-containing compound, it is presumed that the fluororesin can exist stably in the solution. As a result, it is considered that the fluororesin-containing solution is prevented from increasing in viscosity over time and the storage stability of the fluororesin-containing solution is excellent.

Patent Document 1 discloses a specific mode for producing a fluororesin-containing solution containing a fluoropolymer having a unit based on CTFE, using an amino group-containing compound and hydrotalcite. The present inventors have found that the chlorine ion concentration in the embodiment is high. The reason is not necessarily clear, but is considered as follows.
First, it is considered that the chlorine ions contained in the fluororesin-containing solution are mainly due to the decomposition of CTFE generated during the polymerization of CTFE.
If an amino group-containing compound is present in the presence of such a chlorine ion, a hydrochloride is formed between the amino group-containing compound and the chlorine ion. In addition, when hydrotalcite is present in such a situation, chlorine ions are also adsorbed on hydrotalcite. That is, in the specific embodiment of Patent Document 1, both salt formation between chlorine ions and amino group-containing compounds and adsorption of chlorine ions to hydrotalcite proceed.

Hydrotalcite is separated from the fluoropolymer after polymerization by filtration or the like. Therefore, it is adsorbed by hydrotalcite and chlorine ions are removed from the system. On the other hand, the chloride ion salt-forming with the amino group-containing compound remains in the system as it is. That is, the amount of chlorine ions contained in the fluororesin-containing solution is affected by the amount of amino group-containing compound and hydrotalcite used. Specifically, when the amount of the amino group-containing compound used is larger than the amount of hydrotalcite used, a large amount of chloride ions salted with the amino group-containing compound remain in the system, and as a result, the chlorine ion concentration Therefore, the present inventors have found that the desired effect cannot be obtained.
In the present invention, as described in detail later, in the production of the fluororesin-containing solution, the amount of use of hydrotalcite relative to the amount of use of the amino group-containing compound is set as a predetermined ratio, and the amount of chlorine ions removed from the system and the amount remaining in the system Therefore, it is considered that the chlorine ion concentration of the fluororesin-containing solution can be reduced, and as a result, a desired effect can be obtained.

The fluoropolymer in the present invention preferably has units based on CTFE and further has units other than the above units (hereinafter also referred to as other units).
The other unit is a unit based on a fluoroolefin other than CTFE, a unit based on a monomer having a crosslinkable group (hereinafter also referred to as “monomer 1”), or a unit having no fluorine atom and no crosslinkable group. A unit based on a monomer (hereinafter also referred to as “monomer 2”) is preferable, and a unit based on monomer 1 or a unit based on monomer 2 is more preferable. The fluorine-containing polymer particularly preferably has both a unit based on the monomer 1 and a unit based on the monomer 2.

The number of fluorine atoms contained in the fluoroolefin other than CTFE is preferably 2 or more, more preferably 2 to 6, and further preferably 3 to 4. When the number of fluorine atoms is 2 or more, the resulting coating film has excellent weather resistance.
Fluoroolefins other than CTFE _{is, CF 2 = CF 2, CH} 2 = CF 2, _or, preferably _{CH 2 = CFCF 3, CF 2} = CF 2 is particularly preferred.
Two or more fluoroolefins other than CTFE may be used.

Monomer 1 is a monomer having a crosslinkable group.
The crosslinkable group is preferably a functional group having active hydrogen (a hydroxyl group, a carboxy group, an amino group or the like), a hydrolyzable silyl group (such as an alkoxysilyl group), an epoxy group or an oxetanyl group.
The monomer 1 is preferably a monomer represented by the formula CH ₂ = CX ¹ (CH ₂ ) _n1 -Q ¹ -R ¹ -Y ¹ . In the formula, X ¹ is a hydrogen atom or a methyl group, n1 is 0 or 1, Q ¹ is a single bond, an etheric oxygen atom, —C (O) O— or —O (O) C— R ¹ is an alkylene group having 2 to 20 carbon atoms, an alkylene group containing an etheric oxygen atom having 2 to 20 carbon atoms, or an alkylene group having 6 to 20 carbon atoms having a ring structure, and Y ¹ is It is a crosslinkable group.
X ¹ is preferably a hydrogen atom.
n1 is preferably 0.
Q ¹ is preferably an oxygen atom or —O (O) C—, and more preferably an oxygen atom.
R ¹ is preferably a linear alkylene group having 1 to 10 carbon atoms. The alkylene group preferably has 1 to 6 carbon atoms, more preferably 2 to 4 carbon atoms.
Y ¹ is preferably a hydrolyzable silyl group, a hydroxyl group, a carboxy group or an amino group, more preferably a hydroxyl group, a carboxy group or an amino group, and even more preferably a hydroxyl group.

Specific examples of the monomer 1 include hydroxyalkyl vinyl ether (2-hydroxyethyl vinyl ether, hydroxymethyl vinyl ether, 4-hydroxybutyl vinyl ether, etc.), hydroxyalkyl vinyl ester, hydroxyalkyl allyl ether (hydroxyethyl allyl ether, etc.), hydroxy Alkyl allyl ester, hydroxyalkyl (meth) acrylate (hydroxyethyl (meth) acrylate, etc.), etc. are mentioned. It is preferable that the hydroxyalkyl group and the hydroxyallyl group in the hydroxyalkyl vinyl ester and the hydroxyalkyl allyl ester are each bonded to the carbon atom of the carbonyl group of the ester bond.
Monomer 1 is preferably hydroxyalkyl vinyl ether or hydroxyalkyl allyl ether, more preferably hydroxyalkyl vinyl ether, and 4-hydroxybutyl vinyl ether is preferred from the viewpoint of excellent copolymerizability and excellent weather resistance of the formed coating film. Particularly preferred.
Two or more monomers 1 may be used.

The monomer 2 is a monomer having no fluorine atom and a crosslinkable group.
As the monomer 2, a monomer represented by the formula CH ₂ = CX ² (CH ₂ ) _n2 -Q ² -R ² is preferable. However, in the formula, X ² is a hydrogen atom or a methyl group, n2 is 0 or 1, Q ² is a single bond, an oxygen atom, —C (O) O— or —O (O) C—. R ² is an alkyl group having 2 to 20 carbon atoms, an alkyl group containing an etheric oxygen atom having 2 to 20 carbon atoms, or an alkyl group having 6 to 20 carbon atoms having a ring structure.
X ² is preferably a hydrogen atom.
n2 is preferably 0.
Q ² is preferably an oxygen atom or —O (O) C—, and more preferably an oxygen atom.
R ² is preferably an alkyl group having 1 to 10 carbon atoms or an alkyl group having 6 to 20 carbon atoms having a ring structure, more preferably an alkyl group having 1 to 6 carbon atoms or a cycloalkyl group having 6 to 12 carbon atoms. An alkyl group having 2 to 4 carbon atoms or a cycloalkyl group having 6 to 10 carbon atoms is particularly preferable.

Specific examples of the monomer 2 include alkyl vinyl ether, cycloalkyl vinyl ether, alkyl vinyl ester, alkyl allyl ether, alkyl allyl ester, alkyl (meth) acrylate, and the like. The alkyl group in the alkyl vinyl ester and the alkyl allyl ester is preferably bonded to the carbon atom of the carbonyl group of the ester bond.
Monomer 2 is preferably alkyl vinyl ether or cycloalkyl vinyl ether, more preferably ethyl vinyl ether, cyclohexyl vinyl ether, or 2-ethylhexyl vinyl ether, when the fluororesin has high rigidity, is soluble in an organic solvent, and is applied to a paint. In particular, cyclohexyl vinyl ether is particularly preferable because it is easy to construct and provides a hard coating film.
Two or more monomers 2 may be used.

The proportion of units based on CTFE in the fluoropolymer is preferably from 40 to 60 mol%, more preferably from 45 to 55 mol%, based on the total units of the fluoropolymer. If this ratio is 40 mol% or more, it is excellent in the weather resistance of the coating film obtained. If this ratio is 60 mol% or less, it is excellent in the solubility to an organic solvent or a diluent.

In the case where the fluoropolymer has units based on the monomer 1 and units based on the monomer 2, the total ratio is preferably 40 to 60 mol% with respect to the total units of the fluoropolymer. 45 to 55 mol% is more preferable.
Therefore, when the units other than the units based on CTFE are only units based on monomer 1 and units based on monomer 2, the total ratio of units based on monomer 1 and units based on monomer 2 is: The amount is preferably 40 to 60 mol%, more preferably 45 to 55 mol%, based on the total units of the fluoropolymer.

The proportion in the case of having units based on the monomer 1 is preferably 5 to 40 mol%, more preferably 8 to 35 mol%, based on the total units of the fluoropolymer. When the proportion is 5 mol% or more, a sufficient amount of crosslinkable groups are introduced into the fluoropolymer to obtain a coating film having high hardness. If this ratio is 40 mol% or less, even if it is a high solid content type, sufficient low viscosity can be maintained as a fluororesin containing solution.
The proportion in the case of having units based on the monomer 2 is preferably more than 0 mol% and 45 mol% or less, more preferably 3 to 45 mol%, more preferably 20 to 45 mol, based on all units of the fluoropolymer. % Is more preferable. If it has this unit, the hardness and softness | flexibility of the coating film obtained can be adjusted suitably. If the said ratio is 45 mol% or less, it will become easy to introduce | transduce into a fluoropolymer sufficient quantity in order to obtain a coating film with excellent weather resistance and high hardness.

When having a unit based on a monomer other than a unit based on CTFE, a unit based on monomer 1 and a unit based on monomer 2, the proportion of the unit is based on the total units of the fluoropolymer, 20 mol% or less is preferable and 10 mol% or less is more preferable.

The Mn of the fluoropolymer is preferably 3,000 to 50,000, more preferably 5,000 to 30,000. If Mn of a fluoropolymer is more than the said lower limit, it will be excellent in the water resistance of a coating film, salt water resistance, etc. If Mn of a fluoropolymer is below the said upper limit, it will be excellent in the surface smoothness of a coating film.

The fluororesin-containing solution of the present invention does not substantially contain hydrotalcite. The fact that hydrotalcite is substantially not included means that the amount of hydrotalcite contained in the fluorine fat-containing liquid of the present invention is less than 0.1% by mass, and is usually 0.01% by mass or less. Is preferred. The lower limit of the amount of hydrotalcite is 0% by mass.

The amino group-containing compound in the present invention is not particularly limited as long as it is a compound containing an amino group. In the present specification, the “amino group-containing compound” includes an aspect in which a salt is formed with hydrogen chloride (HCl). That is, the “amino group-containing compound” includes hydrochlorides of amino group-containing compounds.

Examples of the amino group include a primary amino group (—NH ₂ ), a secondary amino group, and a tertiary amino group.
Secondary amino groups are mono-substituted amino group represented by the formula -NHR N ^{(R N} is a monovalent substituent), specific examples of R ^N is an alkyl group, an aryl group, an acetyl group, a benzoyl Group, benzenesulfonyl group, tert-butoxycarbonyl group and the like. Specific examples of the secondary amino group include secondary amino groups in which R is an alkyl group such as methylamino group, ethylamino group, propylamino group, and isopropylamino group, and R such as phenylamino group and naphthylamino group. Examples include secondary amino groups that are aryl groups. Also, R ^N hydrogen atom, further acetyl group, a benzoyl group, benzenesulfonyl group, may be substituted with a tert- butoxycarbonyl group.
The tertiary amino group is a di-substituted amino group represented by the formula —NR ^N1 R ^N2 (R ^N1 and R ^N2 are monovalent substituents). Specific examples of R ^N1 and R ^N2 include R ^N And the same. Specific examples of the tertiary amino group include a dimethylamino group, a diethylamino group, a dibutylamino group, an ethylmethylamino group, a diphenylamino group, and a methylphenylamino group.

An amino group also includes an alicyclic amino group. An alicyclic amino group is an alicyclic group containing at least one nitrogen atom in the ring.
The alicyclic amino group is preferably a 5- to 7-membered alicyclic amino group such as a pyrrolidyl group, piperidyl group, piperazyl group, or azepanyl group, and particularly a 6-membered alicyclic amino group (piperidyl group). preferable. The hydrogen atom in the alicyclic amino group may be further substituted with a substituent (alkyl group, aryl group, etc.).
The 6-membered alicyclic amino group is preferably a piperidyl group or a piperidyl group having a substituent, more preferably a piperidyl group having a substituent, further preferably a tetra-substituted piperidyl group, and 2,2,6,6-tetra A substituted piperidyl group is particularly preferred.

Two or more amino group-containing compounds may be used.
The amino group-containing compound is preferably a compound represented by the following formula (a compound having a 2,2,6,6-tetrasubstituted piperidyl group).

R ¹¹ to R ¹⁴ are each independently an alkyl group having 1 to 18 carbon atoms (methyl group, ethyl group, propyl group, dodecyl group, stearyl group, etc.), cycloalkyl group (cyclopentyl group, cyclohexyl group, etc.), substituted alkyl group (2-hydroxyethyl group, 2-methoxycarbonylethyl group, 3-hydroxypropyl group, etc.), an aryl group (phenyl group, naphthyl group) or an aralkyl group (a phenethyl group, a benzyl group, etc.), R ¹¹ And R ¹² , or R ¹³ and R ¹⁴ may form an aliphatic ring having 3 to 6 carbon atoms. As R ¹¹ to R ¹⁴ , an alkyl group having 1 to 18 carbon atoms is preferable, and a methyl group is particularly preferable from the viewpoint of cost and availability.

R ¹⁵ represents a hydrogen atom, an alkyl group (methyl group, ethyl group, propyl group, butyl group, dodecyl group, stearyl group, etc.), a substituted alkyl group (2-hydroxyethyl group, 2-methoxycarbonylethyl group, 2-acetoxy group). Ethyl group, 2- (3-methoxycarbonylpropionyloxy) ethyl group, 3-hydroxypropyl group, etc.), aryl group (phenyl group, naphthyl group, hydroxyphenyl group, etc.), aralkyl group (phenethyl group, benzyl group, hydroxy group) An enylalkyl group or the like) or a cycloalkyl group (such as a cyclohexyl group).

R ¹⁶ is a hydrogen atom, hydroxyl group, alkyl group (methyl group, ethyl group, propyl group, butyl group, dodecyl group, stearyl group, etc.), substituted alkyl group (2-hydroxyethyl group, 2-methoxycarbonylethyl group, 2 -Acetoxyethyl group, 2- (3-methoxycarbonylpropionyloxy) ethyl group, 3-hydroxypropyl group, etc.), aryl group (phenyl group, naphthyl group, etc.), aralkyl group (phenethyl group, benzyl group, etc.), ester bond Containing group (acetoxy group, propionyloxy group, butyryloxy group, lauroyloxy group, substituted alkylcarbonyloxy group, benzoyloxy group, substituted benzoyloxy group, etc.), amino group containing group (alkoxycarbonylamino group, N-monoalkylcarbamoylamino) Group, N, N-dialkylcarbamoy Or a 2,2,6,6-tetrasubstituted piperidyl group-containing group. R ¹⁶ may be a combination of two or more of these groups.

Specific examples of the amino group-containing compound include 2,2,6,6-tetramethylpiperidine, 1,2,2,6,6-pentamethylpiperidine, 4-hydroxy-2,2,6,6-tetramethyl. Piperidine, 4-hydroxy-1,2,2,6,6-pentamethylpeviridine, 1-ethyl-2,2,6,6-tetramethylpiperidine, 1-ethyl-4-hydroxy-2,2,6 , 6-tetramethylpiperidine, 1-butyl-4-hydroxy-2,2,6,6-tetramethylpiperidine, 1-dodecyl-2,2,6,6-tetramethylpiperidine, 1-phenyl-2,2 , 6,6-tetramethylpiperidine, 1- (2-hydroxyethyl) -2,2,6,6-tetramethylpipericin, 1- (6-hydroxyethyl) -4-hydroxy-2,2,6, 6- Tramethylpiperidine, 4-acetoxy-2,2,6,6-tetramethylpiperidine, 4-acetoxy-1,2,2,6,6-pentamethylpiperidine, 1- (2-acetoxyethyl) -4-acetoxy -2,2,6,6-tetramethylpiperidine, 1- (2-benzoyloxyethyl) -4-benzoyloxy-2,2,6,6-tetramethylbiperidine, 4-ethyl-2,2, 6,6-tetramethylpiperidine, 4-ethyl-1,2,2,6,6-pentamethylpiperidine, 4-butyl-2,2,6,6-tetramethylpiperidine, 4-octyl-2,2, 6,6-tetramethylpiperidine, 4-dodecyl-2,2,6,6-tetramethylpiperidine, 4-stearyl-2,2,6,6-tetramethylpiperidine, 4-stearyl-1 2,2,6,6-pentamethylpiperidine, methyl 1,2,2,6,6-pentamethyl-4-piperidyl sebacate, bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, etc. Is mentioned.

Examples of the amino group-containing compound in which R ¹⁶ is a 2,2,6,6-tetrasubstituted piperidyl group-containing group include 2,2,6,6-tetramethylpiperidine (4-hydroxy-2,2,6) having a hydroxyl group. , 6-tetramethylpiperidine, 4-hydroxy-1,2,2,6,6-pentamethylpiperidine, 1- (2-hydroxyethyl) -4-hydroxy-2,2,6,6-tetramethylpiperidine, 1- (2-hydroxyethyl) -2,2,6,6-tetramethylpiperidine etc.) and polybasic acids (succinic acid, adipic acid, sebacic acid, azelaic acid, decane-1,10-dicarboxylic acid, phthalate Acid, isophthalic acid, terephthalic acid, trimellitic acid, malonic acid, substituted malonic acid, etc.) obtained by reacting two or more 2,2,6,6-tetramethylpiperidis per molecule Examples include an amino group-containing compound containing a nyl group, specifically, a compound represented by the following formula.
However, n3 is an integer of 1-20.

The content of the amino group-containing compound is preferably 0.1 to 2.0 parts by weight, more preferably 0.5 to 2.0 parts by weight, with respect to 100 parts by weight of the fluororesin. 5 parts by mass is more preferable. When the content is 0.1 part by mass or more, the fluororesin-containing solution is more difficult to gel during or after the polymerization of the monomer component, and the storage stability of the fluororesin-containing solution is more excellent. Further, if the content is 2.0 parts by mass or less, the discoloration of the solution during storage of the fluororesin-containing solution (for example, yellowing or cloudiness) and the increase in the molecular weight of the fluoropolymer are further suppressed, The storage stability of the fluororesin-containing solution is more excellent.

The organic solvent in the present invention is not particularly limited as long as it is an organic solvent that can dissolve the fluororesin. From the group consisting of an aromatic hydrocarbon solvent, a ketone solvent, an ester solvent, an alcohol solvent, and an ether ester solvent. One or more organic solvents selected are preferred.

The aromatic hydrocarbon solvent is preferably toluene, xylene, ethylbenzene, aromatic petroleum naphtha, teraline, or turpentine oil. A commercially available product can be used as the aromatic hydrocarbon solvent, and Solvesso (registered trademark) # 100 (manufactured by Exxon Chemical Co., Ltd.), Solvesso (registered trademark) # 150 (manufactured by Exxon Chemical Co., Ltd.), and the like can be used.
The ketone solvent is preferably acetone, methyl ethyl ketone, methyl amyl ketone, methyl isobutyl ketone, ethyl isobutyl ketone, diisobutyl ketone, cyclohexanone, or isophorone.
The ester solvent is preferably methyl acetate, ethyl acetate, n-propyl acetate, isobutyl acetate, or tert-butyl acetate.
The alcohol solvent is preferably an alcohol having 4 or less carbon atoms, and preferably ethanol, tert-butyl alcohol, or iso-propyl alcohol.
The ether ester solvent is preferably ethyl 3-ethoxypropionate, propylene glycol monomethyl ether acetate, or methoxybutyl acetate.

Two or more organic solvents may be used. Moreover, the organic solvent same as the organic solvent used as a polymerization solvent may be sufficient, and a different organic solvent may be sufficient as it.
From the viewpoint of improving the solubility of the fluororesin, the content of the organic solvent is preferably contained so that the solid content concentration in the fluororesin-containing solution is 40 to 80% by mass.

The fluororesin-containing solution of the present invention may contain components other than those described above (for example, general-purpose resin components such as acrylic resin and polyester resin) within a range in which the effects of the present invention can be sufficiently exhibited.

In the fluororesin-containing solution of the present invention, the chlorine ion concentration determined by a predetermined measurement method is 50 mass ppm or less. The chlorine ion concentration is more preferably 40 mass ppm or less, further preferably 30 mass ppm or less, and particularly preferably 10 mass ppm or less. The lower limit is preferably 1 ppm by mass, and particularly preferably 3 ppm by mass.
When the chlorine ion concentration is 50 mass ppm or less, the coating film obtained using the fluororesin-containing solution of the present invention is excellent in gloss immediately after film formation. On the other hand, when the chlorine ion concentration exceeds 50 ppm by mass, the gloss immediately after film formation becomes insufficient.
In particular, when the chlorine ion concentration is 3 to 30 ppm by mass, the flowability of the coating composition obtained using the fluororesin-containing solution is excellent. When the coating composition obtained using the fluororesin-containing solution has excellent flow properties, the coating composition is formed when the powder composition coated on the substrate is melted to form a coating film (cured film). This is preferable in that a smooth and uniform coating film (cured film) can be obtained.
If the chlorine ion concentration is 30 mass ppm or less, generation of hydrogen chloride due to heat generation during pulverization (desolvation) of the fluororesin-containing solution and baking coating can be suppressed. Thereby, it is estimated that the gelation of the fluororesin contained in the coating composition is suppressed and the flowability of the coating composition is improved.

In the present invention, the chlorine ion concentration is measured by a predetermined measurement method, that is, the fluororesin-containing solution of the present invention and xylene are mixed to prepare a sample solution, and the obtained sample solution and water are mixed. Thereafter, the xylene phase and the water phase are phase-separated to recover the water phase, and the chloride ion concentration in the recovered water is measured by ion chromatography.
More specifically, the chloride ion concentration is measured as follows.
First, the fluororesin-containing solution of the present invention and xylene are mixed and stirred to obtain a sample solution. The amount of the fluororesin-containing solution is 0.5 g with respect to 5 mL of xylene.
Next, the sample solution and pure water are mixed and stirred to obtain a mixed solution. The amount of pure water is 3 mL with respect to the sample solution addition amount of 4.9 g.
Next, the mixed solution is centrifuged to separate the mixed solution into a water phase and a xylene phase, and the xylene phase is removed to obtain a separated solution. Further, the separated liquid is centrifuged to separate the residual xylene (xylene phase) and water (water phase), and the xylene phase is removed to recover the water phase.
Next, a measurement solution is prepared by adding pure water to the collected water (water phase) and diluting it, and the chloride ion concentration is measured by ion chromatography.
In any of the centrifuges, a known centrifuge (specifically, a device according to the trade name “Table Top Cooling Centrifuge 5500” manufactured by Kubota Corporation) is used, and the centrifuge conditions are 12000 rpm. 5 minutes.
In addition, the measurement by ion chromatography is performed by using, for example, an apparatus according to ion chromatograph ICS-1500 (trade name, manufactured by Dionex).

Specific measurement conditions for the chloride ion concentration by ion chromatography are as follows. The detected amount is measured by the peak area ratio with respect to a standard solution with a known concentration, and the amount of chloride ion (Cl ⁻ ) is converted. Further, the limit of determination of chlorine ions (Cl ⁻ ) is 0.6 ppm or less.
<Ion chromatographic conditions>
Apparatus: Analytical column using ICS-1500 suppressor manufactured by Dionex, Inc .: Dionex IonPac AS14 Inner diameter 4.0 mm × Length 50 mm
Guard column: Dionex IonPac AG14 ID 4.0 mm x length 250 mm
Eluent: 3.5 mmol Na ₂ CO ₃ , 1.0 mmol NaHCO ₃
Flow rate: 1.5ml / min

[Method for producing fluororesin-containing solution]
In the method for producing a fluororesin-containing solution of the present invention, a monomer component containing CTFE is polymerized in an organic solvent in the presence of an amino group-containing compound and hydrotalcite to obtain a fluoropolymer-containing mixed solution. Then, the insoluble component derived from the hydrotalcite is removed from the fluorine-containing polymer-containing mixed solution to produce a fluororesin-containing solution.
The ratio of the amount of hydrotalcite to the amount of amino group-containing compound (the amount of hydrotalcite / the amount of amino group-containing compound) is 1 to 4 at the start of polymerization of the monomer component.
Furthermore, it is preferable that the chlorine ion concentration calculated | required by the predetermined measuring method is 50 mass ppm or less.
According to the method for producing a fluororesin-containing solution of the present invention, a fluororesin-containing solution excellent in storage stability can be obtained, and a coating film excellent in gloss immediately after film formation can be formed.
Hereinafter, the process of superposing | polymerizing is called a superposition | polymerization process and the process of filtering is called a filtration process, and each process is demonstrated in detail.

The monomer component in the polymerization step is polymerized by a so-called solution polymerization method. The order of adding each component to the polymerization system can be appropriately selected. As the monomer component, monomer 1 and monomer 2 can also be used in addition to CTFE.
The details of the amino group-containing compound, CTFE, and fluororesin in the polymerization step are as described above, and a description thereof is omitted.
Examples of the organic solvent include organic solvents similar to the organic solvents described in the section of the fluororesin-containing solution. The organic solvent in the polymerization step may be the same as or different from the organic solvent contained in the fluororesin-containing solution of the present invention.

The hydrotalcite in the polymerization step is excellent in adsorption of chlorine ions and is easily available, so Mg ₆ Al ₂ (OH) ₁₆ CO ₃ .4H ₂ O (in the above-described formula representing hydrotalcite, x = 0.25, m = 0.5), or Mg _4.5 Al ₂ (OH) ₁₃ CO ₃ .3.5H ₂ O (in the above-described formula representing hydrotalcite, x = 0.308, m = 0.538) is preferable.
Two or more hydrotalcites may be used.
The particle size of the hydrotalcite is preferably 5 to 500 μm, more preferably 5 to 110 μm. If the hydrotalcite particle size is 5 μm or more, removal by filtration becomes easy. If the particle size of hydrotalcite is 500 μm or less, the surface area per unit mass is large, and the effect of hydrotalcite is more exhibited.
The particle size of hydrotalcite is measured in accordance with JIS K 0069 “Chemical product screening test method”.

In the polymerization step, the monomer component is preferably polymerized by the action of the polymerization initiator.
As polymerization initiators, azo initiators (2,2′-azobisisobutyronitrile, 2,2′-azobiscyclohexane carbonate nitrile, 2,2′-azobis (2,4-dimethylvaleronitrile), 2,2'-azobis (2-methylbutyronitrile), peroxide initiators (ketone peroxide (cyclohexanone peroxide, etc.), hydroperoxide (tert-butyl hydroperoxide, etc.), diacyl peroxide (penzoyl peroxide, etc.) , Dialkyl peroxides (di-tert-butyl peroxide, etc.), peroxyketals (2,2-di- (tert-butylperoxy) butane, etc.), alkyl peresters (tert-butyl peroxypivalate, etc.), percarbonates (diisopropyl) Peroxydicarbonate Etc.)}.

At the start of polymerization in the polymerization step, the ratio of hydrotalcite mass (hydrotalcite mass / amino group-containing compound mass) to the mass of the amino group-containing compound is 1 to 4, and 1.0 to 3 is 1.0 to 2 is particularly preferable.
If this ratio is 1 or more, the chlorine ion concentration can be adjusted to a predetermined range as described in the section of the fluororesin-containing solution, and the gloss of the coating film immediately after film formation is excellent. Moreover, if this ratio is 4 or less, it is easy to suppress clogging of the filter medium when removing insoluble components in the filtration step.

The amount of the amino group-containing compound is preferably from 0.1 to 2.0 parts by weight, more preferably from 0.5 to 2.0 parts by weight, based on 100 parts by weight of the monomer component. 5 parts by mass is more preferable. When the amount is 0.1 parts by mass or more, the fluororesin-containing solution becomes more difficult to gel during or after the polymerization of the monomer component, and the storage stability of the fluororesin-containing solution is more excellent. Further, if the amount is 2.0 parts by mass or less, the discoloration of the solution (for example, yellowing or cloudiness) during storage of the fluororesin-containing solution and the increase in the molecular weight of the fluororesin can be further suppressed, and the fluororesin-containing The storage stability of the solution is better.

The amount of CTFE in the monomer component is preferably 40 to 60 mol%, more preferably 45 to 55 mol%, based on the total monomer components. When the amount of CTFE is 40 mol% or more, the resulting coating film has excellent weather resistance. When the amount of CTFE is 60 mol% or less, the solubility in organic solvents and diluents is excellent.
When monomer 1 and monomer 2 are included as monomer components, the total amount is preferably 40 to 60 mol%, more preferably 45 to 55 mol%, based on the total monomer components.
Therefore, when the monomer components other than CTFE are only monomer 1 and monomer 2, the total amount of monomer 1 and monomer 2 is 40 to 60 mol relative to the total monomer components. % Is preferable, and 45 to 55 mol% is more preferable.

The amount of monomer 1 in the monomer component is preferably 5 to 40 mol%, more preferably 8 to 35 mol%, based on the total monomer components. When the amount is 5 mol% or more, a sufficient amount of crosslinkable groups is introduced into the fluoropolymer to obtain a coating film having high hardness. If this amount is 40 mol% or less, even if it is a high solid content type, a low viscosity can be maintained as a fluororesin-containing solution.
The amount of monomer 2 in the monomer component is preferably more than 0 mol% and 45 mol% or less, more preferably 3 to 45 mol%, further preferably 20 to 45 mol%, based on the total monomer components. preferable. If the monomer 2 is used, the hardness and softness | flexibility of the coating film obtained can be adjusted suitably. When the amount is 45 mol% or less, it becomes easy to introduce a sufficient amount of crosslinkable groups into the fluoropolymer to obtain a coating film having excellent weather resistance and high hardness.
In the case of a monomer component containing monomers other than CTFE, monomer 1 and monomer 2, the amount of the monomer is preferably 20 mol% or less with respect to the total monomer components. The mol% or less is more preferable.

In the filtration step in the present invention, hydrotalcite that is an insoluble component that does not dissolve in the organic solvent and adsorbs chlorine ions generated in the polymerization step (that is, an insoluble component derived from hydrotalcite) is removed. The removal is performed by a solid-liquid separation process such as filtration.
The fluororesin-containing solution obtained by the production method of the present invention preferably has a chlorine ion concentration measured by a predetermined measurement method of 50 mass ppm or less. Since a more preferable range and effect of the chlorine ion concentration are as described in the section of the fluororesin-containing liquid, description thereof is omitted.
Moreover, it is preferable that the fluororesin containing solution obtained by the manufacturing method of this invention does not contain hydrotalcite substantially. “Substantially free of hydrotalcite” means that the amount of hydrotalcite contained in the fluorine-containing solution is less than 0.1% by mass, and is usually preferably 0.01% by mass or less. . The lower limit of the amount of hydrotalcite is 0% by mass.

In the production method of the present invention, hydrotalcite may be added to the fluoropolymer-containing mixed solution after the polymerization step and before the filtration step. Furthermore, after hydrotalcite addition, you may stir-process before a filtration process. Thereby, the said chlorine ion density | concentration can be made lower and the glossiness immediately after film-forming of the coating film obtained is more excellent. In addition, the storage stability of the fluororesin-containing solution tends to be more excellent.
The amount of hydrotalcite to be added is preferably 0.1 to 3.0 parts by mass, and more preferably 0.5 to 2.0 parts by mass with respect to 100 parts by mass of the produced fluoropolymer. If the amount is within the above range, the above-described effects are more manifested.

[Coating composition]
The coating composition of the present invention is a coating composition obtained using the fluororesin-containing solution of the present invention. The coating composition of the present invention may be in the form of a liquid or powder (so-called powder coating composition).

The liquid coating composition is a coating composition containing the above-described fluororesin-containing solution, and preferably contains a curing agent in addition to the fluororesin-containing solution.
Examples of the curing agent include an isocyanate curing agent, a blocked isocyanate curing agent, and an amino resin.
The isocyanate-based curing agent is preferably a non-yellowing isocyanate (for example, hexamethylene diisocyanate, isophorone diisocyanate, etc.).
The blocked isocyanate-based curing agent is preferably a curing agent in which the isocyanate group of the isocyanate-based curing agent is blocked with caprolactam, isophorone, β-diketone or the like.

The amino resin is a reaction product (methylol melamine or the like) of an amine (melamine, guanamine, urea or the like) and an aldehyde (formaldehyde or the like) or a derivative thereof (alkyl etherified methylol melamine or the like). Examples of amino resins include melamine resins, guanamine resins, urea resins, sulfoamide resins, and aniline resins.

The content of the curing agent is preferably 1 to 100 parts by mass and more preferably 1 to 50 parts by mass with respect to 100 parts by mass of the fluororesin in the coating composition. If a hardening | curing agent is 1 mass part or more, it is excellent in the solvent resistance and hardness of a coating film. If it is 100 parts by mass or less, the processability and impact resistance of the coating film are excellent.

The liquid coating composition may further contain components other than those described above. Examples of such components include colorants, resins other than the above-described fluororesins, silane coupling agents, ultraviolet absorbers, curing catalysts, and the like.

The coating composition of the present invention may also be a coating composition containing the fluororesin composition obtained by removing the organic solvent from the fluororesin-containing solution of the present invention. This coating composition may be a liquid coating composition obtained by dissolving the fluororesin composition in a solvent or dispersing it in a dispersion medium. Preferably, it is a coating composition containing a fluororesin composition not containing a liquid medium such as the organic solvent. As a coating composition containing a fluororesin composition not containing a liquid medium, a powdery coating composition (so-called powder coating composition) is preferable.

The powdery coating composition contains a fluororesin composition obtained by removing the organic solvent from the fluororesin-containing solution of the present invention to form a powder. The powdery fluororesin composition can be produced by subjecting the fluororesin-containing composition of the present invention to known treatments such as drying treatment and pulverization treatment.
In addition to the said fluororesin composition, it is preferable that a powder-form coating composition contains a hardening | curing agent. About a hardening | curing agent, it is the same as that of the liquid coating composition mentioned above, and abbreviate | omits description.
Moreover, the powdery coating composition may further contain components other than those described above. Such a component is the same as the liquid coating composition described above, and a description thereof is omitted.

[Coated articles]
The coated article of this invention has a base material and the coating film formed on the said base material with the said coating composition.
Examples of the coating method include spray coating, air spray coating, brush coating, dipping method, electrostatic coating method, roll coating, flow coating and the like.
The coating film may be a film (melted film) obtained by applying a known melting treatment after coating on the substrate.

Examples of the material for the substrate include inorganic substances, organic substances, and organic-inorganic composite materials. Examples of the inorganic material include concrete, natural stone, glass, metal (iron, stainless steel, aluminum, copper, brass, titanium, etc.). Examples of the organic material include plastic, rubber, adhesive, and wood. Examples of the organic / inorganic composite material include fiber reinforced plastic, resin reinforced concrete, and fiber reinforced concrete.
The shape, size, etc. of the substrate are not particularly limited.
Applications of the coated articles of the present invention include transportation equipment (automobiles, trains, aircraft, etc.), civil engineering members (bridge members, steel towers, etc.), industrial equipment (waterproofing material sheets, tanks, pipes, etc.), construction materials (building exteriors) , Doors, window gates, monuments, poles, etc.), road components (road median strips, guardrails, sound barriers, etc.), communication equipment, electrical equipment, electronic equipment, solar cell module surface sheets, for solar cell modules A back sheet etc. are mentioned.

Hereinafter, the present invention will be described in detail with reference to examples. However, the present invention is not limited to these examples.
The compounding quantity of each component in the table | surface mentioned later shows a mass reference | standard.
The solid content concentration of the fluororesin-containing solution was determined by measuring the heating residue according to JIS K 5601-1-2 (established in 2009).
Mn of the fluororesin contained in the fluororesin-containing solution was measured by GPC (manufactured by Tosohichi Corporation, HLC-8220). Tetrahydrofuran was used as a developing solvent, and polystyrene was used as a standard substance.

[Fluorine resin-containing solution]
Each fluororesin-containing solution of Examples and Comparative Examples was prepared as follows.

<Preparation of fluororesin-containing solution of Example 1>
A stainless steel pressure-resistant reactor having an internal volume of 2500 mL equipped with a stirrer was charged with 7.32 g of an amino group-containing compound (manufactured by BASF, trade name “TINUVIN292”, bis (1,2,2,6,6-pentamethyl- 4-piperidyl) separate and a mixture of methyl 1,2,2,6,6-pentamethyl-4-piperidylsepacate (mass ratio 3: 1)), 7.32 g of hydrotalcite (manufactured by Kyowa Chemical Industry Co., Ltd., Product name “KW500”, particle size: 45 μm or less: 38%, 45-7 μm: 35%, 75-106 μm: 21%, 106-500 μm: 6%), 746 g of xylene, 153 g of 4-hydroxybutyl vinyl ether, 601 g Of cyclohexyl vinyl ether, and dissolved oxygen in the liquid was removed by deaeration with nitrogen. Further, 701 g of CTFE was introduced into the reactor, the temperature was gradually raised, and when the temperature reached 65 ° C., 4.1 g of tert-butyl peroxypivalate (polymerization initiator) was intermittently added. The polymerization was allowed to proceed.
After 24 hours, the reaction was stopped by cooling the reactor with water. After cooling the reaction solution to room temperature, the unreacted monomer is purged, insoluble components of the obtained reaction solution are removed by filtration using diatomaceous earth as a filter medium, and an appropriate amount of xylene is added to obtain a solid content concentration of 60. 0.0% of the fluororesin-containing solution of Example 1 was obtained.
The Mn of the fluoropolymer contained in the fluororesin-containing solution of Example 1 was 15500.

<Preparation of fluororesin-containing solution of Example 2>
Polymerization was carried out in the same manner as in the preparation of the fluororesin-containing solution in Example 1, and hydrotalcite KW500 was further added to the resulting reaction liquid, followed by stirring for 1 hour, and then filtering insoluble components using diatomaceous earth as a filter medium. Then, an appropriate amount of xylene was added to obtain a fluororesin-containing solution of Example 2 having a solid content concentration of 60.0%.
The Mn of the fluoropolymer contained in the fluororesin-containing solution of Example 2 was 15500.

<Preparation of fluororesin-containing solutions of Examples 3 to 5 and Comparative Example 1>
Except that the addition amount of at least one of the amino group-containing compound and hydrotalcite added at the time of polymerization was changed to the amount shown in Table 1, the same operation as in the preparation of the fluororesin-containing solution of Example 1 was carried out. The fluorine-containing resin solutions of Examples 3 to 5 and Comparative Example 1 were obtained.
The Mn values of the fluoropolymers contained in the fluororesin-containing solutions of Examples 3 to 5 and Comparative Example 1 were 15100, 14900, 14800, and 15400, respectively.

<Examples 6 to 7>
The amino group-containing compound added at the time of polymerization was changed from TINUVIN 292 to TINUVIN 770DF (trade name, manufactured by BASF, bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate) or diethanolamine, and the amino group-containing compound and Except that the amount of hydrotalcite added was changed to the amount shown in Table 1, the same operations as in the preparation of the fluorine-containing solution of Example 1 were performed to obtain fluorine-containing resin solutions of Examples 6 to 7.
The Mn values of the fluoropolymers contained in the fluororesin-containing solutions of Examples 6 to 7 were 15000 and 14900, respectively. Moreover, content of the hydrotalcite in the fluororesin containing solution obtained in each above example was 0.01 mass% or less.

<Preparation of fluororesin-containing solution of Comparative Example 2>
A fluororesin-containing solution of Comparative Example 2 was obtained in the same manner as in the preparation of the fluororesin-containing solution of Example 1, except that no amino group-containing compound was added during the polymerization.
The Mn of the fluoropolymer contained in the fluororesin-containing solution of Comparative Example 2 was 16400.

<Preparation of fluororesin-containing solution of Comparative Example 3>
The same operation as in the preparation of the fluororesin-containing solution of Example 2 except that the amount of the amino group-containing compound added during the polymerization was changed to the amount shown in Table 1 and no hydrotalcite was added during the polymerization. The fluororesin-containing solution of Comparative Example 3 was obtained.
The Mn of the fluoropolymer contained in the fluororesin-containing solution of Comparative Example 3 was 15600.

<Chlorine ion concentration>
The chlorine ion concentration of each fluororesin-containing solution was measured by the following procedure.
0.5 g of each fluororesin-containing solution and 5 mL of xylene were placed in a PP (polypropylene) tube and shaken by hand for 1 minute to obtain a sample solution in which the fluororesin-containing solution was completely dissolved in xylene. .
Next, 3 mL of pure water was added to the sample solution and shaken vigorously by hand to obtain a mixed solution.
Subsequently, the mixture was centrifuged to separate water and xylene, and then the xylene phase (upper layer) was removed from the mixture using a micropipette.
Further, the mixed liquid from which the xylene phase was removed was centrifuged to separate residual xylene (xylene phase) and water (water phase). Any centrifugation was performed for 5 minutes at 12000 rpm using a centrifuge (trade name “Table Top Cooling Centrifuge 5500”, manufactured by Kubota).
Next, a measurement liquid was prepared by diluting the separated and recovered water (aqueous layer) 5 times or 10 times with pure water, and the chloride ion concentration of the measurement liquid was measured by ion chromatography. The measurement by ion chromatography was performed using an ion chromatograph ICS-3000 (trade name, manufactured by Thermo Fisher). The measurement conditions by ion chromatography are as follows.

Specifically, the detected amount was measured by the peak area ratio with respect to a standard solution with a known concentration, and the amount of chlorine ions (Cl ⁻ ) was converted. The limit of quantification was 0.6 ppm or less for chlorine ions (Cl ⁻ ).
(Ion chromatograph conditions)
Apparatus: Analytical column using ICS-1500 suppressor manufactured by Dionex: Dionex IonPac AS14 Inner diameter 4.0 mm × length 50 mm
Guard column: Dionex IonPac AG14 ID 4.0 mm x length 250 mm
Eluent: 3.5 mmol Na ₂ CO ₃ , 1.0 mmol NaHCO ₃
Flow rate: 1.5mL / min
The measurement results of the above chlorine ion concentration are summarized in Table 1.

[Evaluation test]
The following evaluation tests were carried out using the respective fluororesin-containing solutions.

<Storage stability>
Each fluororesin-containing solution is heated at 70 ° C. for 2 weeks, Mn is measured before and after heating, and (Mn after heating) / (Mn before heating) is stored based on the rate of increase in molecular weight. Each sex was evaluated.

<Glossiness immediately after film formation>
Each fluororesin-containing solution was evaporated to dryness and pulverized to obtain a powdery fluororesin composition. With respect to 100 parts by mass of each of the obtained powdery fluororesin compositions, 67 parts by mass of titanium oxide (manufactured by DuPont, Ti-Pure (registered trademark) R960), blocked isocyanate curing agent (Evonik) Vestagon (registered trademark) B1530) 25 parts by mass, dibutyltin dilaurate xylene solution (10,000-fold diluted product) 0.012 parts by mass, degassing agent benzoin 0.8 parts by mass, surface Add 2 parts by weight of a modifier (BYK (registered trademark) -360P, manufactured by Big Chemie) and mix for about 10 to 30 minutes using a high-speed mixer (manufactured by Amagasaki Co., Ltd.) to obtain powdery mixtures. It was.
Using a twin screw extruder (manufactured by Thermo Prism, 16 mm extruder), the powdery mixture was melt-kneaded at a barrel set temperature of 120 ° C. to obtain pellets. Next, the pellets are pulverized at room temperature using a pulverizer (manufactured by FRITSCH, rotor speed mill P14), and classified by a 150 mesh sieve to obtain powder coating compositions having an average particle diameter of about 40 μm. It was.
Using each powder coating composition, one surface of an aluminum plate subjected to chromate treatment is electrostatically coated with an electrostatic coating machine (GX3600C, manufactured by Onoda Cement Co., Ltd.) and held at 200 ° C. for 20 minutes. did. Then, this was left to cool to room temperature to obtain an aluminum plate with a coating film (cured film) having a thickness of 55 to 65 μm.
Using a gloss meter (Nippon Denshoku Industries Co., Ltd., PG-1M), the 20 ° glossiness of the surface of the coating film was measured 24 hours after the coating film was formed.

<Flowability>
Each fluororesin-containing solution was evaporated to dryness and pulverized to obtain a powdery fluororesin composition. Using a tablet molding machine, 0.5 g of a powdery fluororesin composition was molded into tablets under conditions of a pressure of 20 MPa and 10 seconds.
The tablet-like fluororesin composition was affixed to an aluminum plate using a double-sided tape, heated at 200 ° C. for 20 minutes with an inclination of 60 degrees, and the flowed distance was measured. Based on the distance which flowed, flow property was evaluated according to the following criteria.
◎: Flow distance is 100 mm or more ○: Flow distance is 60 mm or more and less than 100 mm Δ: Flow distance is 30 mm or more and less than 60 mm ×: Flow distance is less than 30 mm

<Evaluation results>
The results of the above evaluation tests are shown in Table 1. In addition, the numerical value in the bracket | parenthesis in Table 1 shows content (mass part) of each component with respect to 100 mass parts of fluororesin content (solid content).

As shown in Table 1, since all of the fluororesin-containing solutions of the examples have a chlorine ion concentration of 50 ppm by mass or less, the coating film prepared by using the coating composition obtained by using this solution has a composition of The gloss of the coating film immediately after the film was excellent. Moreover, all of the fluororesin-containing solutions of the examples were excellent in storage stability.
Further, the comparison of Examples 1 to 7 showed that the flow properties were excellent when the chlorine ion concentration was 3 to 30 ppm by mass (Examples 4 and 5).

On the other hand, the fluororesin-containing solutions of Comparative Example 1 and Comparative Example 3 had a chlorine ion concentration exceeding 50 ppm by mass. Therefore, the coating film produced using the coating composition obtained by using this solution was immediately after film formation. The gloss of the coating film was insufficient.
Here, in Comparative Examples 1 and 3, the ratio of the amount of hydrotalcite to the amount of the amino group-containing compound when polymerizing the fluororesin was outside the range of 1 to 4. For this reason, it is considered that the chlorine ion amount discharged out of the fluororesin-containing solution as an insoluble component together with hydrotalcite is reduced, and the chlorine ion concentration is increased.

In addition, the fluororesin-containing solution of Comparative Example 2 had a low chlorine ion concentration, but did not contain an amino group-containing compound, so the storage stability was poor (the fluororesin-containing solution gelled after heating, Mn could not be measured). Moreover, when producing the coating composition obtained using the fluororesin-containing solution of Comparative Example 2, gelation occurred, the powder composition could not be produced, and glossiness immediately after film formation could not be evaluated.
The entire contents of the specification, claims and abstract of Japanese Patent Application No. 2016-005279 filed on Jan. 14, 2016 are incorporated herein as the disclosure of the specification of the present invention. It is.

Claims (15)

1. A fluororesin-containing solution comprising a fluororesin comprising a fluoropolymer having a unit based on chlorotrifluoroethylene, an amino group-containing compound, and an organic solvent,
   A fluororesin-containing solution having a chlorine ion concentration determined by the following chlorine ion concentration measurement method of 50 mass ppm or less.
   Chlorine ion concentration measurement method: The fluororesin-containing solution and xylene are mixed to prepare a sample solution. After mixing the obtained sample solution and water, phase separation is performed into a xylene phase and a water phase. The aqueous phase is recovered and the concentration of chloride ions in the recovered water is measured by ion chromatography.
2. 2. The fluororesin-containing solution according to claim 1, wherein the content of the amino group-containing compound is 0.1 to 2.0 parts by mass with respect to 100 parts by mass of the fluororesin.
3. 3. The fluororesin-containing solution according to claim 1, wherein the content of the units based on the chlorotrifluoroethylene is 40 to 60 mol% with respect to the total units of the fluoropolymer.
4. The fluororesin-containing solution according to any one of claims 1 to 3, wherein the chlorine ion concentration is 3 mass ppm or more.
5. In the presence of an amino group-containing compound and hydrotalcite, a monomer component containing chlorotrifluoroethylene is polymerized in an organic solvent to obtain a fluorine-containing polymer-containing mixture, and then the fluorine-containing polymer is contained. A method for producing a fluororesin-containing solution by removing insoluble components derived from the hydrotalcite from a mixed solution,
   The ratio of the mass of the hydrotalcite to the mass of the amino group-containing compound (the mass of hydrotalcite / the mass of the amino group-containing compound) at the start of polymerization of the monomer component is 1 to 4. A method for producing a fluororesin-containing solution.
6. The production method according to claim 5, wherein hydrotalcite is added to the fluoropolymer-containing mixed solution after the polymerization and before the filtration.
7. The production method according to claim 5 or 6, wherein the amount of the amino group-containing compound at the start of polymerization is 0.1 to 2.0 parts by mass with respect to 100 parts by mass of the monomer component.
8. The production method according to any one of claims 5 to 7, wherein the amount of chlorotrifluoroethylene in the monomer component is 40 to 60 mol% with respect to the total monomer components.
9. The production method according to any one of claims 5 to 8, wherein the fluororesin-containing solution does not substantially contain hydrotalcite.
10. The production method according to any one of claims 5 to 9, wherein the chlorine ion concentration obtained by the following chlorine ion concentration measurement method in the produced fluororesin-containing solution is 50 mass ppm or less.
    Chlorine ion concentration measurement method: The fluororesin-containing solution and xylene are mixed to prepare a sample solution. After mixing the obtained sample solution and water, phase separation is performed into a xylene phase and a water phase. The water is collected, and the chlorine ion concentration in the collected water is measured by ion chromatography.
11. The manufacturing method according to claim 10, wherein the chlorine ion concentration is 3 mass ppm or more.
12. A coating composition comprising the fluororesin-containing solution according to any one of claims 1 to 4.
13. A coating composition comprising a fluororesin composition obtained by removing an organic solvent from the fluororesin-containing solution according to any one of claims 1 to 4.
14. The coating composition according to claim 13, wherein the coating composition is a powdered coating composition.
15. A coated article having a base material and a coating film formed on the base material with the coating composition according to any one of claims 12 to 14.