JP2020007491A - Powder coating composition, powder coating, method for producing powder coating, method for producing base material with coating film, and base material with coating film - Google Patents

Abstract

To provide a powder coating composition that makes it possible to produce a powder coating that can form a coating film with excellent impact resistance and has excellent blocking resistance; and provide a powder coating, a method for producing a powder coating, a method for producing a base material with a coating film, and a base material with a coating film.SOLUTION: A powder coating composition contains: a fluorine-containing polymer containing a unit based on fluoroolefin and a unit having a carboxy group; and a low-boiling organic solvent with a boiling point of less than 150°C. The content of the low-boiling organic solvent is 0.001-2 pts.mass relative to the fluorine-containing polymer 100 pts.mass. A high-boiling organic solvent with a boiling point of 150°C or more is not contained therein, or if it is contained, its content is less than 1.5 pts.mass relative to the fluorine-containing polymer 100 pts.mass.SELECTED DRAWING: None

Description

  The present invention relates to a powder coating composition, a powder coating, a method for producing a powder coating, a method for producing a substrate with a coating, and a substrate with a coating.

In recent years, powder coatings containing a fluoropolymer have been widely studied in the coatings field.
Patent Document 1 discloses a powder coating material containing 0.005 to 2% by weight of a high-boiling organic solvent (C1) having a boiling point of 150 to 300 ° C. at normal pressure. It is described that by leaving a high-boiling solvent (C1) in the powder coating, it is possible to prevent the formation of coating defects such as armpits and pinholes at the time of baking and hardening, and to improve the coating film appearance. I have.

JP 2003-082295 A

In recent years, the performance required of powder coating materials containing a fluoropolymer has been further improved. For example, a powder coating material capable of forming a coating film having more excellent impact resistance on a substrate has been demanded. Further, there is a demand for a powder coating having excellent blocking resistance, which can suppress generation of lumps during storage of the powder coating.
The present inventors have found that a coating film formed using the powder coating described in Patent Document 1 has poor impact resistance.

  The present invention has been made in view of the above-mentioned problems, and a powder coating composition, a powder coating, and a powder coating capable of forming a coating film having excellent impact resistance and producing a powder coating having excellent blocking resistance. It is an object of the present invention to provide a method for producing a substrate, a method for producing a coated substrate, and a substrate with a coated film.

  The present inventors have conducted intensive studies on the above problems, and as a result, including a fluoropolymer containing a unit based on a specific monomer, a low-boiling organic solvent having a boiling point of less than 150 ° C, and having a boiling point of 150 ° C. When a powder coating composition having a high boiling point organic solvent as described above is used, the content of which is less than a predetermined amount, a coating film having excellent impact resistance can be formed, and a powder coating having excellent blocking resistance can be formed. Have been found, and the present invention has been achieved.

  That is, the present inventors have found that the above-described problems can be solved by the following configuration.

[1] A powder coating composition comprising a fluoropolymer comprising a unit based on a fluoroolefin and a unit having a carboxy group, and a low-boiling organic solvent having a boiling point of less than 150 ° C,
The content ratio of the low boiling organic solvent is 0.001 to 2 parts by mass relative to 100 parts by mass of the fluoropolymer, and
Does not contain a high-boiling organic solvent having a boiling point of 150 ° C. or higher, or when it contains, the content of the high-boiling organic solvent is less than 1.5 parts by mass with respect to 100 parts by mass of the fluoropolymer. A powder coating composition comprising:
[2] The composition according to [1], wherein the ratio of the weight average molecular weight to the number average molecular weight of the fluoropolymer is 1.0 to 5.0.
[3] The composition according to [1] or [2], wherein the content of the unit having a carboxy group is 3 to 30 mol% with respect to all units contained in the fluoropolymer.
[4] The fluorine-containing polymer further comprises units based on a monomer represented by the formula X ² -Z ^2, A composition according to any one of [1] to [3].
The symbols in the formula have the following meanings.
X ² _{is, CH 2 = CHC (O)} O-, CH 2 = C (CH 3) C (O) O-, CH 2 = CHOC (O) -, CH 2 = CHCH 2 OC (O) -, CH ₂ = CHO- or _CH 2 = CHCH ₂ is O-.
Z ² is a monovalent hydrocarbon group having 1 to 24 carbon atoms.
[5] Any one of [1] to [4], wherein the glass transition temperature of the fluoropolymer is 40 to 120 ° C, and the melt viscosity at 170 ° C of the fluoropolymer is 20 to 100 Pa · s. A composition according to claim 1.
[6] The composition according to any one of [1] to [5], wherein the fluoropolymer has an acid value of 25 to 80 mgKOH / g.
[7] The composition according to any one of [1] to [6], wherein the low-boiling organic solvent contains an alcohol.
[8] The composition according to any one of [1] to [7] and a curing agent, wherein the curing agent contains an epoxy group, a carbodiimide group, an oxazoline group, or a β-hydroxyalkylamide group in one molecule. A powder coating which is a compound having at least two.
[9] The powder coating according to [8], further comprising a non-fluorine resin, wherein the non-fluorine resin is at least one selected from the group consisting of a polyester resin, a (meth) acrylic resin, a urethane resin, and an epoxy resin. .
[10] A method for producing a powder coating, comprising pulverizing the composition according to any one of [1] to [7] to obtain a powder coating.
[11] A method for producing a powder coating, wherein the composition according to any one of [1] to [7] is melt-kneaded, then cooled, and then pulverized to obtain a powder coating.
[12] A powder coating according to [8] or [9] is applied to a substrate to form a powder coating layer, and the powder coating layer is heat-treated to form a coating film on the substrate A method for producing a coated substrate.
[13] A coated substrate, comprising: a substrate; and a coating film formed on the substrate by the powder coating material according to [8] or [9].

  ADVANTAGE OF THE INVENTION According to this invention, the powder coating composition which can form the coating film excellent in impact resistance, and can manufacture the powder coating excellent in blocking resistance, the powder coating material, and the manufacturing method of the base material with a coating film , And a coated substrate.

The meanings of the terms in the present invention are as follows.
The numerical range represented by using “to” means a range including the numerical values described before and after “to” as the lower limit and the upper limit.
“(Meth) acrylate” is a generic term for acrylate and methacrylate, and “(meth) acryl” is a generic term for “acryl” and “methacryl”.
The “unit” is a general term for an atomic group formed directly by polymerization of a monomer and based on one molecule of the monomer, and an atomic group obtained by chemically converting a part of the atomic group. The content (mol%) of each unit with respect to all units contained in the polymer can be determined by analyzing the polymer by a nuclear magnetic resonance spectroscopy.
The “acid value” and “hydroxyl value” are values measured according to the method of JIS K 0070-3 (1992), respectively.
"Number average molecular weight" and "weight average molecular weight" are values measured by gel permeation chromatography using polystyrene as a standard substance. "Number average molecular weight" is also called "Mn", and "weight average molecular weight" is also called "Mw".
"Glass transition temperature" is the midpoint glass transition temperature measured by differential scanning calorimetry (DSC). “Glass transition temperature” is also referred to as “Tg”.
The “melt viscosity” means the value of the melt viscosity of a sample at 170 ° C. when the temperature is measured from 130 ° C. to 200 ° C. at a rate of 10 ° C./min using a rotary rheometer. I do.
“Powder” means a collection of a plurality of particles. The average particle diameter of the particles constituting the powder is measured on a volume basis using a known particle size distribution measuring device (manufactured by Sympatec, trade name “Helos-Rodos” or the like) using a laser diffraction method as a measurement principle. Is a value at a cumulative frequency of 50% calculated from the particle size distribution of.
The “boiling point” is a temperature at which the liquid starts to boil at normal pressure (1 atm, 101325 Pa).
The “film thickness” is a value measured using an eddy current film thickness meter (trade name “EDY-5000”, manufactured by Sanko Electronics Co., Ltd.).

  The powder coating composition of the present invention (hereinafter, also referred to as “the present composition”) includes a unit based on fluoroolefin (hereinafter, also referred to as “unit F”) and a unit having a carboxy group (hereinafter, “unit 1”). ).). Further, the present composition contains a low-boiling organic solvent having a boiling point of less than 150 ° C (hereinafter, also referred to as “low-boiling organic solvent”), and a high-boiling organic solvent having a boiling point of 150 ° C or more (hereinafter, referred to as “high-boiling organic solvent”). If it does not contain, or contains, a high-boiling point organic solvent, the content is less than 1.5 parts by mass per 100 parts by mass of the fluoropolymer. The content of the low boiling organic solvent is 0.001 to 2 parts by mass based on 100 parts by mass of the fluoropolymer.

A coating film (hereinafter, also referred to as “the present coating film”) formed by heating a powder coating material (hereinafter, also referred to as “the present coating material”) produced using the present composition has an impact resistance. Excellent. The present inventors presume the reason for this as follows.
In a fluoropolymer having a carboxy group, an apparently bonded high molecular weight is likely to be generated due to an interaction generated between the carboxy groups. If such a high molecular weight substance is mixed in the coating film, it is considered that the impact given to the coating film is hardly absorbed. On the other hand, if the powder coating composition contains a low-boiling organic solvent, the low-boiling organic solvent reduces the interaction between the carboxy groups in the fluoropolymer and suppresses the generation of high molecular weight polymers. As a result, it is considered that a coating film having excellent impact resistance can be formed.
On the other hand, when the high-boiling organic solvent is contained in the powder coating composition in a predetermined amount or more, the high-boiling organic solvent has a poor effect of relaxing the interaction between carboxy groups, and the impact resistance of the formed coating film is poor. Can not be improved.
In addition, the present coating is excellent in blocking resistance. The present inventors presume the reason for this as follows.
If the content of the low-boiling organic solvent is too large relative to the total mass of the fluoropolymer, the blocking resistance of the powder coating is adversely affected. Therefore, it is considered that by setting the content of the low boiling point organic solvent within a predetermined range, good blocking resistance can be maintained.

Fluoroolefins are olefins in which one or more of the hydrogen atoms have been replaced by fluorine atoms. In the fluoroolefin, one or more hydrogen atoms not substituted with a fluorine atom may be substituted with a chlorine atom.
Specific examples of the _{fluoroolefin, CF 2 = CF 2, CF} 2 = CFCl, CF 2 = CHF, CH 2 = CF 2, CF 2 = CFCF 3, CF 2 = CHCF 3, CF 3 CH = CHF, CF 3 CF = CH ₂ and the like. Fluoroolefins, from the viewpoint of _{copolymerizability, CF 2 = CF 2, CF} 2 = CFCl, CF 3 CH = CHF, the CF 3 CF = CH _{2 Preferably,} CF 2 = CFCl is particularly preferred. Two or more fluoroolefins may be used in combination.
From the viewpoint of the weather resistance of the present coating film, the content of the unit F is preferably from 20 to 70 mol%, particularly preferably from 40 to 60 mol%, based on all units contained in the fluoropolymer.

  The unit 1 may be a unit based on a monomer having a carboxy group (hereinafter, also referred to as “monomer 1”), and an acid is added to a hydroxyl group of a fluoropolymer including a unit having a hydroxyl group described later. A unit obtained by reacting an anhydride (such as succinic anhydride) and converting a part or all of the hydroxyl groups to a carboxy group may be used. The unit 1 is preferably a unit based on a monomer having a carboxy group from the viewpoint of blocking resistance of the present coating composition. Unit 1 has no fluorine atom.

The unit 1 is a unit based on the monomer 1 from the viewpoint of suitably imparting an acid value to the fluoropolymer, in particular, from the viewpoint of obtaining a fluoropolymer having an acid value without a hydroxyl value. Is preferred. When the fluoropolymer has an acid value without a hydroxyl value, the fluoropolymer of the present invention can be more stably powdered.
Examples of the monomer 1 include an unsaturated carboxylic acid, (meth) acrylic acid, and a monomer obtained by reacting a polycarboxylic acid or an acid anhydride thereof with a hydroxy group of the above-mentioned monomer having a hydroxy group. No.
The monomer 1 is preferably a monomer represented by the formula X ¹ -Y ¹ .
X ¹ _{is, CH 2 = CH-, CH (} CH 3) = CH- or _{CH 2 = C (CH 3)} - and _is, CH 2 = CH- or _{CH (CH} 3) = CH- are preferred.
Y ¹ is a carboxy group or a monovalent saturated hydrocarbon group having 1 to 12 carbon atoms having a carboxy group, and is preferably a carboxy group or a carboxyalkyl group having 1 to 10 carbon atoms.

As specific examples of the monomer 1, CH ₂ ＣＨCHCOOH, CH (CH ₃ ) ＝ CHCOOH, CH ₂ ＣC (CH ₃ ) COOH, a compound represented by the formula CH ₂式 CH (CH ₂ ) _n1 COOH ( However, n1 shows the integer of 1-10.).
As the monomer 1, two or more kinds may be used in combination.

When the present coating composition contains a curing agent, the carboxy group of unit 1 serves as a crosslinking point, and the crosslinking reaction between the fluoropolymers proceeds via the curing agent, and the hardness of the coating film is improved. Film properties such as water resistance, water resistance, chemical resistance, and heat resistance are improved.
The content of the unit 1 is preferably 3 to 30 mol%, more preferably 4 to 20 mol%, and more preferably 5 to 20 mol%, based on all the units contained in the fluoropolymer, in that the impact resistance of the coating film is more excellent. -10 mol% is particularly preferred.

From the viewpoint of the surface smoothness of the coating film, the fluoropolymer is at least one selected from vinyl ether, vinyl ester, allyl ether, allyl ester, and (meth) acrylate, which does not have a crosslinkable group. A unit based on a certain monomer (hereinafter, also referred to as “monomer 2”) (hereinafter, also referred to as “unit 2”) may be included. In addition, the monomer 2 and the unit 2 do not have a fluorine atom. Further, examples of the crosslinkable group include a carboxy group, a hydroxyl group, an amino group, an alkoxysilyl group, and the like.
Monomer 2 is preferably a monomer represented by the formula ^X 2 -Z ^2.
X ² _{is, CH 2 = CHC (O)} O-, CH 2 = C (CH 3) C (O) O-, CH 2 = CHOC (O) -, CH 2 = CHCH 2 OC (O) -, CH ₂ ＣＨCHO— or CH ₂ ＣＨCHCH ₂ O—, and from the viewpoint of excellent copolymerizability with the unit F, CH ₂ ＣＨCHOC (O) —, CH ₂ ＣＨCHCH ₂ OC (O) —, CH ₂ CHO- or _{CH 2} = CHCH 2 O- are preferred.

Z ² is a monovalent hydrocarbon group having 1 to 24 carbon atoms. The monovalent hydrocarbon group may be linear or branched. Further, the monovalent hydrocarbon group may have a ring structure or may have a ring structure. Further, the monovalent hydrocarbon group may be a monovalent saturated hydrocarbon group or a monovalent unsaturated hydrocarbon group.
The monovalent hydrocarbon group is preferably an alkyl group, a cycloalkyl group, a cycloalkylalkyl group, an aryl group or an aralkyl group, and is an alkyl group having 2 to 12 carbon atoms, a cycloalkyl group having 6 to 10 carbon atoms, An aryl group having 10 to 10 or an aralkyl group having 7 to 12 carbon atoms is particularly preferred.
Specific examples of the alkyl group include a methyl group, an ethyl group, a tert-butyl group, a hexyl group, a nonyl group, a decyl group, and a dodecyl group.
Specific examples of the cycloalkyl group include a cyclohexyl group.
Examples of the cycloalkylalkyl group include a cyclohexylmethyl group.
Specific examples of the aralkyl group include a benzyl group.
Specific examples of the aryl group include a phenyl group and a naphthyl group.

Z ² is an alkyl group having 4 to 8 carbon atoms represented by the formula —C (Z ²¹ ) ₃ from the viewpoint of increasing the Tg of the fluoropolymer (however, three Z ^21s each independently have a carbon number An alkyl group having 1 to 5 carbon atoms), a cycloalkyl group having 6 to 10 carbon atoms, a cycloalkylalkyl group having 6 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, or an aralkyl group having 7 to 12 carbon atoms. preferably, from the viewpoint of weather resistance of the coating film, a cycloalkyl group of formula ^{-C (Z} _{21) 3} alkyl group carbon atoms or a 4 to 8 carbon atoms represented by 6 to 10 are particularly preferred.

The monomer 2 may be used in combination of two or more kinds.
Specific examples of the monomer 2 include ethyl vinyl ether, tert-butyl vinyl ether, 2-ethylhexyl vinyl ether, cyclohexyl vinyl ether, vinyl acetate, vinyl pivalate, and vinyl neononanoate (trade name “Veoba 9” manufactured by HEXION). , Neodecanoic acid vinyl ester (manufactured by HEXION, trade name "Veoba 10"), benzoic acid vinyl ester, tert-butyl (meth) acrylate, and benzyl (meth) acrylate.
When the fluoropolymer contains the unit 2, the content of the unit 2 is preferably from 1 to 70 mol%, particularly preferably from 10 to 50 mol%, based on all units contained in the fluoropolymer.

The fluorinated polymer may include a unit (hereinafter, also referred to as “unit 3”) based on a monomer having a hydroxyl group (hereinafter, also referred to as “monomer 3”). Unit 3 has no fluorine atom.
However, it is preferable that the fluoropolymer does not contain the unit 3 from the viewpoint of the blocking resistance of the present coating composition.
Monomer 3 include allyl alcohol, or a hydroxyl group, vinyl ethers, vinyl esters, allyl ethers, allyl esters or (meth) acrylic acid ester, from the viewpoint of excellent copolymerizability with the unit F, wherein X ³ monomer or an allyl alcohol represented by -Y ³ are preferred.
X ³ represents CH ₂ ＣＨCHC (O) O—, CH ₂ ＣC (CH ₃ ) C (O) O—, CH ₂ ＣＨCHOC (O) —, CH ₂ ＣＨCHCH ₂ OC (O) —, CH ₂ = CHO- or _CH 2 = CHCH ₂ is O-.
Y ³ is a monovalent saturated hydrocarbon group having 2 to 12 carbon atoms and having a hydroxyl group. The monovalent saturated hydrocarbon group may be linear or branched. Further, the monovalent saturated hydrocarbon group may have a ring structure or may have a ring structure.
The monovalent saturated hydrocarbon group is preferably an alkyl group having 2 to 6 carbon atoms or an alkyl group containing a cycloalkylene group having 6 to 8 carbon atoms.

The monomer _{3, CH 2 = CHOCH 2 -cycloC} 6 H 10 -CH 2 OH, CH 2 = CHCH 2 O-CH 2 -cycloC 6 H 10 -CH 2 OH, CH 2 = CHOCH 2 CH 2 OH, CH ₂ ＣＨCHCH ₂ OCH ₂ CH ₂ OH, CH ₂ ＣＨCHOCH ₂ CH ₂ CH ₂ CH ₂ OH, CH ₂ ＣＨCHCH ₂ OCH ₂ CH ₂ CH ₂ CH ₂ OH, and the like. Incidentally, "- cycloC ₆ H ₁₀ -" represents cyclohexylene, "- cycloC ₆ H ₁₀ -" binding site is usually 1,4.
Two or more monomers 3 may be used in combination. Further, as described above, the hydroxyl group of the fluoropolymer containing the unit 3 may be converted into a carboxy group before use.

  When the fluoropolymer contains unit 3, the content of unit 3 is preferably less than 35 mol%, more preferably less than 20 mol%, and more preferably less than 5 mol%, based on all units contained in the fluoropolymer. Particularly preferred.

The fluoropolymer contains 20 to 70 mol%, 3 to 30 mol%, and 0 to 70 mol% of the unit F, the unit 1 and the unit 2 in this order with respect to all units of the fluoropolymer. Is preferred.
The acid value of the fluoropolymer is preferably from 5 to 150 mgKOH / g, more preferably from 10 to 100 mgKOH / g, still more preferably from 25 to 80 mgKOH / g, and still more preferably from 30 to 60 mgKOH / g, from the viewpoint of the impact resistance of the coating film. g is particularly preferred.
When the fluorinated polymer is a fluorinated polymer having a hydroxyl value, the hydroxyl value of the fluorinated polymer is preferably 100 mgKOH / g or less, more preferably 50 mgKOH / g, and still more preferably 5 mgKOH, from the viewpoint of the stability of the coating composition. / G or less is particularly preferred. The lower limit is usually 0 mgKOH / g.

Tg of the fluoropolymer is preferably from 40 to 120 ° C, more preferably from 50 to 100 ° C, and particularly preferably from 50 to 80 ° C, from the viewpoint that the anti-blocking property of the present coating composition is more excellent.
The melt viscosity at 170 ° C. of the fluoropolymer is preferably from 1 to 200 Pa · s, more preferably from 20 to 100 Pa · s, and particularly preferably from 20 to 95 Pa · s. When the melt viscosity is 1 Pa · s or more, the impact resistance of the present coating film is more excellent. When the melt viscosity is 200 Pa · s or less, the surface smoothness of the present coating film is more excellent.

The melt viscosity is preferably set within the above range by controlling the molecular weight (particularly Mw) of the fluoropolymer and the type and content of the unit contained in the fluoropolymer.
Mw of the fluoropolymer is preferably from 15,000 to 75,000, particularly preferably from 25,000 to 60,000. When the Mw of the fluoropolymer is 15,000 or more, the impact resistance and the solvent resistance of the present coating film are more excellent. When the Mw of the fluoropolymer is 75,000 or less, the surface smoothness of the coating film is more excellent.

The ratio of Mw to Mn of the fluoropolymer (Mw / Mn) is preferably from 1.0 to 5.0, more preferably from 2.0 to 4.0, from the viewpoint that the impact resistance of the present coating film is more excellent. , 2.5 to 3.5 are particularly preferred.
Mn and Mw of the fluorinated polymer can be set within the above ranges by adopting a solution polymerization method as a method for producing the fluorinated polymer or by appropriately selecting a polymerization solvent.
Two or more fluoropolymers may be used in combination.

As a specific example of the method for producing the fluoropolymer, a method of copolymerizing a monomer (fluoroolefin and monomer 1) in the presence of a solvent and a radical polymerization initiator may be mentioned. In addition, you may add the monomer 2 and the monomer 3 further.
Specific examples of the polymerization method in the method for producing a fluoropolymer include a solution polymerization method, a suspension polymerization method, and an emulsion polymerization method. Among these, the solution polymerization method is preferable from the viewpoint of easily controlling the Mw of the fluoropolymer and the content of the unit 1 within a predetermined range.
The solvent is preferably alcohol, and specific examples thereof include ethanol, butyl alcohol, propanol, and butanol. The alcohol is superior in the solubility of the monomer 1 as compared with a non-polar solvent such as xylene. Therefore, if alcohol is used as the polymerization solvent, the unit 1 can be easily introduced into the fluoropolymer in an appropriate amount.

Specific examples of the radical polymerization initiator include peroxydicarbonate, peroxyester, ketone peroxide, peroxyketal, peroxycarbonate ester, diacyl peroxide, and dialkyl peroxide.
The reaction temperature in the polymerization is usually 0 to 130 ° C., the reaction pressure is usually 0 to 1.0 MPa, and the reaction time is usually 1 to 50 hours.

The composition contains 0.001 to 2% by mass of the low boiling point organic solvent based on 100 parts by mass of the fluoropolymer. The composition is preferably a solid in the form of powder or pellets.
The boiling point of the low-boiling organic solvent is less than 150 ° C, and from the viewpoint that the impact resistance of the present coating film and the blocking resistance of the present coating material are well-balanced and excellent, 50 to 145 ° C is preferable, and 75 to 100 ° C is more preferable. , 80 to 90 ° C is particularly preferred.

Specific examples of the low-boiling organic solvent include alcohols having a boiling point of less than 150 ° C (methanol, ethanol, n-propanol, isopropanol, n-butanol, tert-butyl alcohol, isobutyl alcohol, pentanol, etc.), and a boiling point of 150 ° C. Esters having a boiling point of less than 150 ° C., ketones having a boiling point of less than 150 ° C. (methyl ethyl ketone, acetone, etc.), aromatic hydrocarbons having a boiling point of less than 150 ° C. (toluene, xylene, etc.), and having a boiling point of 150 ° C. Glycol ethers (eg, methyl cellosolve, ethyl cellosolve, propylene glycol monomethyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether) having a boiling point of less than 150 ° C. (petroleum ether, pentane, hexane) Cyclohexane, heptane, octane, methylcyclohexane, ethylcyclohexane, and the like).
Two or more low boiling organic solvents may be used in combination.
Among them, the present composition preferably contains an alcohol as a low-boiling organic solvent, more preferably contains ethanol or tert-butyl alcohol, and particularly preferably contains tert-butyl alcohol.
The low-boiling organic solvent preferably contains an alcohol and a low-boiling organic solvent other than alcohol from the viewpoints of the blocking resistance of the present coating composition and the impact resistance of the present coating film. As the low-boiling organic solvent other than the alcohol, an aromatic hydrocarbon is preferable. As a combination of an alcohol and a low-boiling organic solvent other than the alcohol, a combination of ethanol or tert-butyl alcohol and xylene is preferable, and a combination of tert-butyl alcohol and xylene is particularly preferable.
When the low-boiling organic solvent contains an alcohol and a low-boiling organic solvent other than the alcohol, the alcohol and the low-boiling organic solvent other than the alcohol are added to the total mass of the low-boiling organic solvent in the order of 60 to 95, respectively. %, Preferably 5 to 40% by weight, particularly preferably 70 to 85% by weight and 15 to 30% by weight.

  In the present composition, the content ratio of the low boiling organic solvent is 0.001 to 2 parts by mass, preferably 0.01 to 1.8 parts by mass, and more preferably 0.05 to 1.8 parts by mass with respect to 100 parts by mass of the fluoropolymer. -1.5 mass parts is more preferable, and 0.1-1.0 mass parts is especially preferable.

  From the viewpoint of the impact resistance of the present coating film, the present coating does not contain a high-boiling organic solvent having a boiling point of 150 ° C. or higher, or, if it contains, the high-boiling organic solvent to 100 parts by mass of the fluoropolymer. And less than 1.5 parts by weight. When the present composition contains a high-boiling organic solvent, the content of the high-boiling organic solvent is preferably less than 1.0 part by mass, more preferably less than 0.05 part by mass, based on 100 parts by mass of the fluoropolymer. It is more preferably, less than 0.01 part by mass, particularly preferably less than 0.001 part by mass. When the present composition contains a high boiling organic solvent, the ratio of the mass of the high boiling organic solvent to the mass of the low boiling organic solvent (mass of the high boiling organic solvent / mass of the low boiling organic solvent) is 0.75 or less. Preferably, it is 0.01 or less, more preferably 0.005 or less.

  Tg of the present composition is preferably from 40 to 120 ° C, more preferably from 50 to 100 ° C, and particularly preferably from 50 to 80 ° C, from the viewpoint of better blocking resistance of the present coating composition. The Tg of the present composition can be adjusted by the content of the low-boiling organic solvent and the high-boiling organic solvent in the present composition.

  The amount of change in Mw / Mn of the fluoropolymer in the composition before and after heating the composition at 130 ° C. for 20 minutes (absolute value of the difference between Mw / Mn before heating and Mw / Mn after heating) ) Is preferably 0.01 or less, more preferably 0.001 or less, and particularly preferably 0.0005 or less. When the variation is within the above range, the composition is excellent in thermal stability and the uniformity of a coating film formed using a powder coating manufactured from the composition is excellent. Excellent impact properties.

As a method for confirming whether or not the present composition contains a predetermined amount of a low-boiling organic solvent, the following method may be mentioned.
1.0 g of the present composition is thinly spread on an aluminum foil, and heated at 130 ° C. for 20 minutes. From the weight change of the present composition before and after heating, the content of the solvent in the present composition is determined. . In addition, by collecting and analyzing components generated in the process of heating the present composition, the type and content of the solvent contained in the present composition can be confirmed.
Examples of a method for confirming whether the present composition contains a predetermined amount of a high-boiling organic solvent include pyrolysis gas chromatography and pyrolysis gas chromatography mass spectrometry.
Further, when the raw material and the charged amount when producing the present composition are known, and when the present composition is produced in a closed system in which the solvent does not evaporate, the low boiling point organic compound in the present composition is used. The content of the solvent or the high boiling point organic solvent may be calculated from the raw materials and the charged amount.

Specific examples of the method for producing the present composition include the following methods.
Production method 1: A method of mixing the fluoropolymer and a low-boiling organic solvent to obtain the present composition.
Production method 2: a method of spray-drying a mixed solution or dispersion containing a fluoropolymer and a low-boiling organic solvent to obtain a powdery present composition.

  In the production method 1, the solvent is distilled off from the solution containing the fluoropolymer and the solvent obtained by the above-mentioned production method of the fluoropolymer to obtain a fluoropolymer, and the obtained fluoropolymer is obtained. It is preferable to obtain the present composition by mixing the coalesced organic solvent with a low-boiling organic solvent. In this case, it is preferable that the fluoropolymer obtained by distilling off the solvent is pulverized into a powder form from the viewpoint that the low boiling point organic solvent uniformly acts on the fluoropolymer.

  In the manufacturing method 2, the method described in JP-A-2003-105270 can be used as appropriate. In the production method 2, the content of the low-boiling organic solvent in the mixed solution before spray-drying and the content of the Drying conditions may be appropriately adjusted.

  The present composition is preferably obtained by the production method 1 from the viewpoint that the content of the low-boiling organic solvent and the high-boiling organic solvent in the present composition is easily adjusted. In particular, when the present composition is subjected to melt kneading described below to obtain the present coating material, the use of the present composition reduces the interaction between the carboxy groups of the fluoropolymer even in the process of melt kneading. Since the state is maintained, the present coating composition is more excellent in the blocking resistance and the impact resistance of the present coating film.

  The paint includes the composition. In light of the weather resistance of the present coating film, the present coating material has a content of the fluoropolymer of 5 to 90% by mass (preferably 15 to 80% by mass, more preferably 20 to 50% by mass based on the total mass of the present coating material). ) May be included in the composition.

  The paint may include components other than the composition. Components other than the present composition include a resin having no fluorine atom (hereinafter, also referred to as “non-fluorine resin”), a curing agent, and an additive.

Non-fluorinated resins contained in this paint include alkyd resins, amino alkyd resins, polyester resins, epoxy resins, urethane resins, epoxy polyester resins, polyvinyl acetate resins, (meth) acrylic resins, vinyl chloride resins, phenolic resins, and modified polyesters. Resins, acrylic silicone resins, silicone resins and the like.
As the non-fluorinated resin, a polyester resin, a (meth) acrylic resin, a urethane resin or an epoxy resin is preferable, and from the viewpoint of the substrate adhesion of the coating film, the non-fluorinated resin and the fluoropolymer are hardly mixed and separated. From the viewpoint of ease, a polyester resin or a (meth) acrylic resin is particularly preferable.

  Specific examples of the polyester resin include “CRYLCOAT (trade name) 4642-3”, “CRYLCOAT (trade name) 4890-0”, and “CRYLCOAT (trade name) 4842-3” manufactured by Daicel Ornex, Inc. "Yupika coat (trade name) GV-740", "Yupika coat (trade name) GV-175", and "Uralac (trade name) 1680" manufactured by DSM. .

  Specific examples of the (meth) acrylic resin include “FINEDIC (trade name) A-249”, “FINEDIC (trade name) A-251”, and “FINEDIC (trade name) A-266” manufactured by DIC. "Almatex (trade name) PD6200" and "Almatex (trade name) PD7310" manufactured by Mitsui Chemicals, Inc., and "Sanpex PA-55" manufactured by Sanyo Chemical Industries.

  Specific examples of the epoxy resin include “Epicoat (trade name) 1001”, “Epicoat (trade name) 1002”, “Epicoat (trade name) 4004P” manufactured by Mitsubishi Chemical Corporation, and “Epiclon (trade name)” manufactured by DIC Corporation. 1050 "," Epiclon (trade name) 3050 "," Epototo (trade name) YD-012 "," Epototo (trade name) YD-014 ", manufactured by Nippon Steel & Sumitomo Metal Corporation," Denacol (trade name, manufactured by Nagase ChemteX Corporation) " EX-711 "and" EHPE3150 "manufactured by Daicel Corporation.

  The urethane resin is a mixture of a polyol (acrylic polyol, polyester polyol, polyether polyol, propylene glycol, etc.) and an isocyanate compound, or a resin obtained by reacting the mixture. As the urethane resin, a resin obtained by reacting a mixture of a powdered polyol (acrylic polyol, polyester polyol, polyether polyol) and a powdered isocyanate is preferable.

When the present coating material contains a non-fluorine resin, the non-fluorine resin on the substrate side, from the viewpoint of easily obtaining a coating film in which the fluoropolymer is disposed on the coating film surface side, from the viewpoint of the SP value of the fluoropolymer, The difference from the SP value of the non-fluororesin is preferably 0.4 to 16 (J / cm ³ ) ^{1/2 in} absolute value.
When the present coating composition contains a non-fluorine resin, the mass ratio of the fluoropolymer to the non-fluorine resin in the present coating composition (the mass of the fluoropolymer / the mass of the other resin) is 0.3 to 3.5. Preferably, 0.35 to 3 are particularly preferred.

  As the curing agent contained in the present coating material, a compound having two or more epoxy groups, carbodiimide groups, oxazoline groups, or β-hydroxyalkylamide groups in one molecule is preferable. Since the fluoropolymer in the present invention has a carboxy group based on the unit 1, if the present coating material contains a curing agent capable of reacting with the carboxy group, physical properties such as weather resistance, acid resistance, and concealing property of the present coating film are reduced. Better.

Compounds having two or more epoxy groups in one molecule include bisphenol type epoxy compounds (A type, F type, S type, etc.), diphenyl ether type epoxy compounds, hydroquinone type epoxy compounds, naphthalene type epoxy compounds, biphenyl type epoxy compounds, Fluorene type epoxy compound, hydrogenated bisphenol A type epoxy compound, bisphenol A nucleated polyol type epoxy compound, polypropylene glycol type epoxy compound, glycidyl ester type epoxy compound, glycidylamine type epoxy compound, glyoxal type epoxy compound, alicyclic type epoxy compound And alicyclic polyfunctional epoxy compounds and heterocyclic epoxy compounds (such as triglycidyl isocyanate).
Specific examples of the compound having two or more epoxy groups in one molecule include triglycidyl isocyanurate (hereinafter referred to as “TGIC”), “TM239” in which a methylene group is introduced into a glycidyl group portion of TGIC (Nissan Chemical Industries, Ltd. "TEPIC-SP" which is an epoxy compound having a triazine skeleton (trade name of Nissan Chemical Industries, Ltd.), "PT-910" which is a mixture of glycidyl trimellitate and glycidyl terephthalate (a product of HUNTSMAN) Name).

  Specific examples of the compound having two or more carbodiimide groups in one molecule include alicyclic carbodiimides, aliphatic carbodiimides, aromatic carbodiimides, and multimers and modified products thereof.

Specific examples of the compound having two or more oxazoline groups in one molecule include an addition-polymerizable oxazoline having a 2-oxazoline group and a polymer of the addition-polymerizable oxazoline.
Specific examples of the compound having two or more oxazoline groups in one molecule include Nippon Shokubai's Epocros WS-500, WS-700, K-2010, K-2020, and K-2030 (all trade names). No.

  Specific examples of the compound having two or more β-hydroxyalkylamide groups in one molecule include N, N, N ′, N′-tetrakis- (2-hydroxyethyl) -adipamide (PrimidXL-552, manufactured by EMS). , N, N, N ', N'-tetrakis- (2-hydroxypropyl) -adipamide (Primid QM 1260, manufactured by EMS).

Two or more curing agents may be used in combination.
As the curing agent, in addition to the above-mentioned compounds, a compound having two or more isocyanate groups in one molecule, a compound having two or more blocked isocyanate groups in one molecule, or the like may be included.
When the present coating composition contains a curing agent, the content of the curing agent is preferably from 1 to 100 parts by mass, particularly preferably from 1 to 50 parts by mass, based on 100 parts by mass of the fluoropolymer in the present coating composition.

  The paint may include additives. The additive is a component other than the present composition, the non-fluorinated resin and the curing agent. Specific examples of additives include curing catalysts, pigments, ultraviolet absorbers (various organic ultraviolet absorbers, inorganic ultraviolet absorbers, etc.), light stabilizers (hindered amine light stabilizers, etc.), matting agents (ultrafine powder synthesis) Silica, etc.), leveling agent, surface conditioner (improves the surface smoothness of the coating film), degassing agent, plasticizer, filler, heat stabilizer, thickener, dispersant, antistatic agent, anti-static agent Examples include a rust agent, a silane coupling agent, an antifouling agent, and a stain-reducing agent.

Pigments that may be included in the present coating composition as additives include rust-preventive pigments, extender pigments, and color pigments.
Specific examples of the rust preventive pigment include zinc cyanamide, zinc oxide, zinc phosphate, calcium magnesium phosphate, zinc molybdate, barium borate, and zinc cyanamide zinc.
Specific examples of the extender include talc, barium sulfate, mica, and calcium carbonate.

Specific examples of the coloring pigment include quinacridone, diketopyrrolopyrrole, isoindolinone, indanthrone, perylene, perinone, anthraquinone, dioxazine, benzimidazolone, triphenylmethanequinophthalone, anthrapyrimidine, graphite, phthalocyanine, and halogenated. Examples include phthalocyanine, azo pigments (azomethine metal complex, condensed azo, etc.), titanium oxide, carbon black, iron oxide, copper phthalocyanine, and condensed polycyclic pigments.
Examples of the coloring pigments include bright pigments. Specific examples thereof include metal particles (metals such as aluminum, zinc, copper, bronze, nickel, titanium, and stainless steel and alloys thereof), mica particles (mica powder), Examples include pearl particles, graphite particles, glass flakes, and scale-like iron oxide particles.
When the present paint contains a pigment, the content of the pigment is preferably more than 0% by mass and 40% by mass or less based on the total mass of the present paint.

  The content of the fluoropolymer in the present coating composition is preferably 5 to 90% by mass, more preferably 15 to 80% by mass, and particularly preferably 20 to 50% by mass, based on the total mass of the present coating composition. When the content of the fluoropolymer is within the above range, the weather resistance of the present coating film is further improved.

As the present paint, the present composition may be used as the present paint in the form of a powder, and the present composition is melt-kneaded, then cooled, and then pulverized. You may. In any case, components other than the present composition (non-fluorinated resin, curing agent, additives) may be added at any timing.
The temperature of the melt-kneading is preferably from 80 to 130 ° C, particularly preferably from 100 to 125 ° C. The kneading time is usually 1 to 15 minutes.

In the production of the present coating composition, a low-boiling organic solvent may be added. In this case, the content of the low boiling organic solvent in the present coating composition is 0.001 to 2 parts by mass (preferably 0.01 to 1.8 parts by mass) based on 100 parts by mass of the fluoropolymer. Parts, more preferably 0.05 to 1.5 parts by mass, particularly preferably 0.1 to 1.0 parts by mass).
In the production of the present coating composition, a high-boiling organic solvent may be added, but from the viewpoint of the blocking resistance of the present coating composition, it is preferable not to add it. When a high-boiling organic solvent is added in the production of the present coating composition, the high-boiling organic solvent has a content of the high-boiling organic solvent in the present coating composition of less than 1.5 parts by mass relative to 100 parts by mass of the fluoropolymer. (More preferably less than 1.0 part by mass, further preferably less than 0.05 part by mass, particularly preferably less than 0.01 part by mass, and most preferably less than 0.001 part by mass). preferable.

The present coating material preferably comprises a powdery pulverized product obtained by melt-kneading the present composition and components other than the present composition and pulverizing the composition. The average particle size of the present coating composition is preferably from 1 to 100 μm. The lower limit is particularly preferably 25 μm. The upper limit is particularly preferably 50 μm.
When the average particle size is 1 μm or more, the aggregating property of the present coating composition is low, and the coating is easy to be performed uniformly during powder coating. When the average particle size is 100 μm or less, the surface of the present coating film is excellent and the appearance of the present coating film is good.

The substrate with a coating film of the present invention has a substrate and a coating film formed on the substrate with the coating material.
Specific examples of the material of the substrate include an inorganic substance, an organic substance, and an organic-inorganic composite material.
Specific examples of the inorganic substance include concrete, natural stone, glass, and metal (iron, stainless steel, aluminum, copper, brass, titanium, and the like).
Specific examples of the organic substance include plastic, rubber, adhesive, and wood.
Specific examples of the organic-inorganic composite include fiber-reinforced plastic, resin-reinforced concrete, fiber-reinforced concrete, and the like.
In addition, a substrate that has been subjected to a known surface treatment (for example, chemical conversion treatment) may be used as the substrate. Further, a resin layer (polyester resin, acrylic resin, or the like) may be formed on the surface of the base material.

Among the above, the substrate is preferably a metal, and particularly preferably aluminum. The aluminum base material has excellent anticorrosion properties, is lightweight, and is suitable for building materials such as exterior members.
The shape and size of the substrate are not particularly limited.
Specific examples of the base material include a building panel such as a composite panel, a curtain wall panel, a curtain wall frame and a window frame, an automobile member such as a tire wheel, a construction machine, and a motorcycle frame.

  The thickness of the present coating film is preferably from 20 to 1,000 μm, particularly preferably from 20 to 500 μm. For applications such as members for high-rise buildings such as aluminum curtain walls, 20 to 90 μm is preferable. For applications requiring high weather resistance, such as outdoor units of air conditioners, signal poles, and signs installed along the coast, 100 to 200 μm is preferable.

  In the method for producing a coated substrate according to the present invention, the present coating composition is applied to a substrate to form a powder coating layer, and the powder coating layer is heat-treated to form the present coating layer on the substrate. Is preferred.

The powder coating layer is preferably formed by applying the present coating composition on a substrate by a coating method such as an electrostatic coating method, an electrostatic spraying method, an electrostatic immersion method, a fluid immersion method, or a spraying method. The electrostatic coating method using a powder coating gun is particularly preferable from the viewpoint that the surface smoothness and the concealing property of the present coating film are more excellent.
Specific examples of the powder coating gun include a corona charging type coating gun and a friction charging type coating gun. The corona charging type coating gun is a coating gun which sprays a powder coating by corona discharge treatment. The triboelectric coating gun is a coating gun that sprays a powder coating by triboelectric treatment.

When heat-treating the powder coating layer, it is preferable to heat the powder coating layer on the base material to form a molten film made of a powder coating melt on the base material. The formation of the molten film may be performed simultaneously with the formation of the powder coating layer on the base material, or may be performed separately after the formation of the powder coating layer.
The heating temperature (hereinafter, also referred to as “baking temperature”) and the heating maintaining time (hereinafter, also referred to as “baking time”) for heating and melting the present coating material and maintaining the molten state for a predetermined time are determined by the present invention. It is appropriately set according to the type and composition of the raw material components of the paint, the desired film thickness of the present coating film, and the like.

When the present coating composition contains a curing agent, for example, the carboxy group of the fluoropolymer in the present coating composition reacts with the curing agent to cure the present coating film. The reaction between a carboxy group and a curing agent as described above (such as a compound having two or more epoxy groups, carbodiimide groups, oxazoline groups, or β-hydroxyalkylamide groups in one molecule) uses a curing agent having an isocyanate group. There is an advantage that a high temperature (about 200 ° C.) is not required.
The baking temperature is preferably from 120 to 190 ° C, particularly preferably from 140 to 180 ° C. The baking time is usually 2 to 60 minutes.
It is preferable to cool the molten film formed on the substrate to 20 to 25 ° C. to form the present coating film. Cooling may be rapid cooling or slow cooling. Slow cooling is preferred from the viewpoint of more excellent substrate adhesion of the present coating film.

  Hereinafter, the present invention will be described in detail with reference to examples. However, the present invention is not limited to these examples. In addition, the compounding quantity of each component in the table | surface mentioned later shows a mass reference | standard. Examples 1 to 3 are Examples, and Examples 4 to 6 are Comparative Examples.

<Production example of fluoropolymer>
Methyl ethyl ketone (870 g), CF ₂ = CFCl (501 g), vinyl pivalate (474 g), and 10-undecylenic acid (111 g) were placed in an autoclave (2.7 L in internal volume, made of stainless steel, equipped with a stirrer; the same applies hereinafter). ) Was introduced into an autoclave, the temperature was raised, and the temperature was maintained at 65 ° C. The pressure at this point was 0.50 MPa.
A 20% by mass xylene solution of tert-butyl peroxypivalate (hereinafter, also referred to as “polymerization initiator solution”) (4 mL) was added into the autoclave, and polymerization was started. During the polymerization, a polymerization initiator solution (53 mL) was continuously added. The polymerization was continued under stirring, and after 21 hours, the autoclave was cooled with water to stop the polymerization, and then the solution in the autoclave was filtered to obtain a solution containing a fluoropolymer. The obtained solution was vacuum-dried at 65 ° C. for 24 hours to remove the solvent, further vacuum-dried at 130 ° C. for 20 minutes, and the obtained block-shaped fluoropolymer was pulverized to a powdery form. Was obtained. The fluoropolymer was a polymer containing 40 mol%, 51 mol%, and 9 mol% of units based on CF ₂ビ ニ ル CFCl, units based on pivalic acid vinyl ester, and units based on 10-undecylenic acid in this order.
The Tg of the fluoropolymer was 57.0 ° C., the Mw was 34,366, the Mn was 10,735, and the acid value was 35 mgKOH / g.

[Examples 1 to 6]
(Production of composition)
The solution shown in Table 1 was added to 100 parts by mass of the powdery fluoropolymer, in the amount shown in Table 1, to obtain each powdery composition.
Solutions of Examples 1, 2 and 5: tert-butyl alcohol (t-BuOH, boiling point: 82 ° C.) and xylene (Xy, boiling point: 144 ° C.) are added in this order to the total mass of the low-boiling organic solvent for 75 times. Solution containing 2% by weight and 25% by weight. Solution of Example 3: Tetrahydrofuran (THF, boiling point: 66 ° C.)
The solution of Example 4: tert-butyl alcohol (t-BuOH, boiling point: 82 ° C.) and xylene (Xy, boiling point: 144 ° C.), based on the total weight of the low boiling organic solvent, were 75% by weight and 25% in this order. % By mass, and a high-boiling organic solvent (Solvesso 150 (S-150, boiling point: 180 to 217 ° C.), manufactured by ExxonMobil)
-Solution of Example 6: Solvesso 150 (S-150, boiling point: 180-217 ° C), manufactured by ExxonMobil

(Manufacture of powder paint)
50 g of each of the obtained compositions, 4.3 g of a curing agent (a compound having two or more epoxy groups in one molecule, manufactured by HUNTSMAN, PT-910 (trade name)), and a surface conditioner (manufactured by BYK Chemie, 0.85 g of BYK-360P (trade name), 0.35 g of a degassing agent (benzoin), and a pigment (a titanium oxide pigment having a titanium oxide content of 89% by mass. Ti-Pure R960 (manufactured by DuPont) 29.2 g) were mixed for about 10 to 30 minutes using a high-speed mixer (manufactured by Yuzaki Co., Ltd.). Next, the obtained mixture was melt-kneaded at a barrel setting temperature of 120 ° C. using a twin-screw extruder (16 mm extruder manufactured by Thermo Prism) to obtain a melt. After cooling the melt, it was pulverized at 25 ° C. using a pulverizer (manufactured by FRITSCH, product name: Rotor Speed Mill P14) to obtain a powdery pulverized material, and classified by 150 mesh to obtain an average particle. Each powder coating having a diameter of about 40 μm was obtained.

(Production of coating film)
Each of the obtained powder coatings was subjected to electrostatic coating using an electrostatic coating machine (manufactured by Onoda Cement Co., Ltd., GX3600C) on one surface of an aluminum plate (substrate) that had been subjected to a chromate treatment. For 20 minutes to obtain a powder coating molten film. The melted film was allowed to cool to room temperature to obtain an aluminum plate with a coating having a thickness of 55 to 65 μm, and the obtained aluminum plate with a coating was evaluated as a test piece. Details are shown in Table 1.

(Evaluation)
<Δ (Mw / Mn) of fluoropolymer>
Each composition was heated at 130 ° C. for 20 minutes, and Mn and Mw of the fluorinated polymer in the heated composition were measured to calculate Mw / Mn. The absolute value of the difference between Mw / Mn before heating and Mw / Mn before heating was defined as Δ (Mw / Mn). The smaller Δ (Mw / Mn), the better the thermal stability of the composition and the better the uniformity of the coating film formed by using the powder coating produced from the composition, and thus the more excellent the impact resistance of the coating film. it is conceivable that.
The Mn and Mw of the fluoropolymer contained in the composition before and after heating were determined in terms of polystyrene using a high-speed GPC apparatus (Tosoh Corporation, column TSKgelG 400XL).

<Blocking resistance of powder coatings>
The powder coating was placed in a sealed glass bottle and stored at 30 ° C., and the time until the powder coating blocked was evaluated.
A: No blocking occurs even after 15 days.
B: Blocking is observed in one day or more and less than 15 days.
C: Blocking is observed in less than one day.

<Impact resistance of coating film>
It was determined by a DuPont impact test (JIS K 5600-5-3). Using a DuPont impact tester, a weight was dropped on the coating surface of the test piece, and the presence or absence of cracks or cracks on the coating surface was observed.
A: No cracking or cracking occurs even when dropped from a height of 50 cm or more.
B: If it falls from a height of 20 cm or more and less than 50 cm, no crack or crack occurs.
C: Cracks and cracks occur even when dropped from a height of less than 20 cm.

Table 1 shows the results.
In Table 1, the column of “content (g)” means the content (g) of “low-boiling organic solvent” or “high-boiling organic solvent” with respect to 100 g of the fluoropolymer.

  As shown in Table 1, it was confirmed that when the powder coating material contained a predetermined amount of a low-boiling organic solvent, a coating film having excellent impact resistance could be formed.

Claims (13)

A fluorine-containing polymer containing a unit based on a fluoroolefin and a unit having a carboxy group, and a powder coating composition containing a low-boiling organic solvent having a boiling point of less than 150 ° C,
The content ratio of the low-boiling organic solvent is 0.001 to 2 parts by mass with respect to 100 parts by mass of the fluoropolymer, and
Does not contain a high-boiling organic solvent having a boiling point of 150 ° C. or higher, or if it contains, the content of the high-boiling organic solvent is less than 1.5 parts by mass with respect to 100 parts by mass of the fluoropolymer. A powder coating composition comprising:   The composition according to claim 1, wherein the ratio of the weight average molecular weight to the number average molecular weight of the fluoropolymer is 1.0 to 5.0.   3. The composition according to claim 1, wherein the content of the unit having a carboxy group is 3 to 30 mol% based on all units contained in the fluoropolymer. 4. It said fluoropolymer further comprises units derived from a monomer represented by the formula X ² -Z ^2, composition according to any one of claims 1 to 3.
The symbols in the formula have the following meanings.
X ² _{is, CH 2 = CHC (O)} O-, CH 2 = C (CH 3) C (O) O-, CH 2 = CHOC (O) -, CH 2 = CHCH 2 OC (O) -, CH ₂ = CHO- or _CH 2 = CHCH ₂ is O-.
Z ² is a monovalent hydrocarbon group having 1 to 24 carbon atoms.   The glass transition temperature of the said fluoropolymer is 40-120 degreeC, The melt viscosity in 170 degreeC of the said fluoropolymer is 20-100 Pa.s, The Claims any one of Claims 1-4. Composition.   The composition according to any one of claims 1 to 5, wherein the fluorine-containing polymer has an acid value of 25 to 80 mgKOH / g.   The composition according to any one of claims 1 to 6, wherein the low boiling organic solvent comprises an alcohol.   A composition comprising the composition according to any one of claims 1 to 7 and a curing agent, wherein the curing agent has two or more epoxy groups, carbodiimide groups, oxazoline groups, or β-hydroxyalkylamide groups in one molecule. Powder paint that is a compound.   The powder coating according to claim 8, further comprising a non-fluorine resin, wherein the non-fluorine resin is at least one selected from the group consisting of a polyester resin, a (meth) acrylic resin, a urethane resin, and an epoxy resin.   A method for producing a powder coating, wherein a powder coating is obtained by crushing the composition according to claim 1.   A method for producing a powder coating, wherein the composition according to any one of claims 1 to 7 is melt-kneaded, then cooled, and then pulverized to obtain a powder coating.   A powder coating layer is formed by applying the powder coating composition according to claim 8 or 9 on a substrate, and a heat treatment is performed on the powder coating layer to form a coating film on the substrate. To produce a coated substrate.   A base material with a coating film, comprising: a base material; and a coating film formed on the base material by the powder coating material according to claim 8.