WO2015190462A1

WO2015190462A1 - Fluorine-containing coating and exterior member

Info

Publication number: WO2015190462A1
Application number: PCT/JP2015/066568
Authority: WO
Inventors: 俊齋藤; 将崇相川; 修平尾知
Original assignee: 旭硝子株式会社
Priority date: 2014-06-09
Filing date: 2015-06-09
Publication date: 2015-12-17

Abstract

　Provided are: a fluorine-containing coating that contains titanium oxide as a pigment and has superior weather resistance; and an exterior member provided with said coating.　The fluorine-containing coating is formed from a powder coating material containing a fluororesin (A) and a titanium oxide pigment (B), and has a gloss retention (%) of at least 50%, as measured in the fluorine-containing coating by means of an accelerated weathering test (α). The accelerated weathering test (α) involves subjecting the fluorine-containing coating to xenon arc radiation using a xenon weathering tester. Other than exposing the fluorine-containing coating to 1 mass% hydrogen peroxide instead of water, the test was conducted in accordance with method 1 of JIS K 5600-7-7.　For the gloss retention, the ratio (%) of the value of the 60° glossiness of the fluorine-containing coating after being subjected to xenon arc radiation for 40 hours to the value of the 60° glossiness of the fluorine-containing coating prior to xenon arc radiation was used.

Description

Fluorine-containing coating film and exterior member

The present invention relates to a fluorine-containing coating film and an exterior member provided with the fluorine-containing coating film.

In recent years, global-scale environmental destruction problems such as global warming, ozone layer destruction, and acid rain have been greatly highlighted. International environmental pollution measures have been called out, and various regulations have been implemented from the viewpoint of environmental protection. In particular, the release of organic solvents (VOC) into the atmosphere has become a major problem, and the movement to remove organic solvents (de-VOC) has become active along with the trend of strengthening VOC regulations in each industry. In the paint industry, as an alternative to conventional organic solvent-type paints, there is a growing expectation for powder paints as environmentally friendly paints that do not contain VOCs at all and do not require exhaust treatment or wastewater treatment and can be recovered and reused. Yes.

As the powder coating, acrylic resin powder coating, polyester resin powder coating, or epoxy resin powder coating is mainly used. However, cured films formed using these powder paints have the disadvantage of poor weather resistance.

As a resin excellent in weather resistance, a fluororesin is generally known. Patent Document 1 describes a powder paint comprising a composition containing a hydroxyl group-containing fluororesin and a polyuretdione curing agent or a block isocyanate curing agent as a powder coating containing a fluororesin.
Patent Document 2 describes a powder coating containing a fluororesin, a polyester resin, a curing agent, and an ultraviolet absorber.

JP 2003-105269 A WO2014 / 067283

However, when the present inventors examined, when the titanium oxide was mix | blended with the conventional powder coating material of patent document 1 as a pigment, the formed coating film said that it was hard to express the weather resistance as expected. A problem was found.
Moreover, although the weather resistance of the formed coating film improved in the powder coating material of patent document 2, it was not yet enough.

An object of the present invention is to provide a fluorine-containing coating film excellent in weather resistance even for a coating film formed of a powder paint, and an exterior member provided with the fluorine-containing coating film.

The present invention has the following configurations [1] to [8].
[1] A fluorine-containing coating film formed from a powder paint containing a fluororesin (A) and a titanium oxide pigment (B),
A fluorine-containing coating film having a gloss retention (%) of 50% or more as measured in a fluorine-containing coating film having undergone the following accelerated weather resistance test (α).
[Accelerated weather resistance test (α)]
This is a test in which xenon arc radiation is applied to a fluorine-containing coating film using a xenon weather meter, except that 1% by mass hydrogen peroxide solution is sprayed on the fluorine-containing coating film instead of water, according to JIS K 5600-7-7. Perform according to Method 1. However, the relative humidity in the test is 70% RH, the black panel temperature is 50 ° C., the irradiation intensity of the xenon light source is 80 W / m ² in the wavelength range of 300 to 400 nm, the spraying time of hydrogen peroxide water is 3 minutes, Next, the drying time is repeated for 2 minutes.
[Gloss retention]
Calculated according to JIS K 5600-4-7: 1999 (ISO 2813: 1994), the fluorine-containing coating film after 40 hours of xenon arc radiation with respect to the 60 ° gloss value of the fluorine-containing coating film immediately before xenon arc radiation Of 60 ° gloss value (unit:%).
[2] The fluorine-containing coating film according to [1], wherein the smoothness visual judgment of the surface smoothness determined using the standard plate for visual judgment of the smoothness of the powder coating film by the powder coating institute is 6 or more. .
[3] The fluorine-containing coating film according to [1] or [2], wherein a color difference (ΔE) between immediately before the xenon arc radiation and after 40 hours of the xenon arc radiation is 5.0 or less.
[4] The fluorine-containing coating film according to any one of [1] to [3], wherein the titanium oxide pigment (B) is a coated titanium oxide pigment having a titanium oxide content of 80 to 92% by mass. .
[5] The powder coating composition according to any one of [1] to [4], wherein the powder coating further contains 0.1 to 15.0 parts by mass of a surface conditioning agent (F) with respect to 100 parts by mass of the fluororesin (A). The fluorine-containing coating film as described in any one of Claims.
[6] The containing resin according to [1] to [5], wherein the fluororesin (A) is at least one selected from polyvinylidene fluoride, a hydroxyl group-containing fluoropolymer and a carboxy group-containing fluoropolymer. Fluorine coating.
[7] The powder coating material further includes at least one curing agent selected from the group consisting of a β-hydroxyalkylamide curing agent, a triglycidyl isocyanurate curing agent, and a blocked isocyanate curing agent (D The fluorine-containing coating film according to any one of [1] to [6].
[8] Any one of [1] to [7], wherein the powder coating further includes at least one non-fluorine resin (C) selected from the group consisting of an acrylic resin, a polyester resin, and an epoxy resin. The fluorine-containing coating film according to item.
[9] An exterior member provided with the fluorine-containing coating film according to any one of [1] to [8] on a substrate.

The fluorine-containing coating film of the present invention is excellent in weather resistance even if it is a coating film formed of a powder coating containing titanium oxide as a pigment. The exterior member of the present invention includes a fluorine-containing coating film having excellent weather resistance.

The following definitions of terms apply throughout this specification and the claims.
"Glass transition temperature" means the midpoint glass transition temperature measured by the differential scanning calorimetry (DSC) method.
“(Meth) acrylate” is a general term for acrylate and methacrylate, and “(meth) acryl” is a general term for “acrylic” and “methacrylic”.
The “unit” means a polymer unit derived from a monomer that exists in the polymer and constitutes the polymer. The unit derived from the monomer resulting from addition polymerization of a monomer having a carbon-carbon unsaturated double bond is a divalent unit generated by cleavage of the unsaturated double bond. The unit derived from a polyvalent carboxylic acid compound constituting the polyester resin is a unit derived from a polyhydric alcohol compound, which is a monovalent or higher unit obtained by removing a hydroxyl group from at least one carboxy group of the polyvalent carboxylic acid compound. Is a monovalent or higher unit obtained by removing a hydrogen atom from at least one hydroxyl group of a polyhydric alcohol compound. Moreover, what unitally converted the structure of a unit after polymer formation is also called a unit.
Hereinafter, in some cases, a unit derived from an individual monomer is referred to as a name obtained by adding “unit” to the monomer name.

[Fluorine-containing coating film]
The fluorine-containing coating film of the present invention is a fluorine-containing coating film formed from a powder paint containing a fluororesin (A) and a titanium oxide pigment (B), and the following accelerated weather resistance test (α) is performed. The gloss retention measured in the passed fluorine-containing coating film is 50% or more, and the weather resistance is excellent. In particular, since the accelerated weather resistance test (α) simulates the weather in a high temperature and high humidity region, the coating film having a gloss retention of 50% or more according to the accelerated weather resistance test (α) is particularly Excellent weather resistance in hot and humid areas.
The fluorine-containing coating film preferably has a gloss retention of 60% or more after the accelerated weathering test (α) described below, more preferably 70% or more, and particularly preferably 75% or more.

[Accelerated weather resistance test (α)]
This is a test in which xenon arc radiation is applied to a fluorine-containing coating film using a xenon weather meter, except that 1% by mass hydrogen peroxide solution is sprayed on the fluorine-containing coating film instead of water, according to JIS K 5600-7-7. Perform according to Method 1. However, the relative humidity in the test is 70% RH, the black panel temperature is 50 ° C., the irradiation intensity of the xenon light source is 80 W / m ² in the wavelength range of 300 to 400 nm, the spraying time of hydrogen peroxide water is 3 minutes, Next, the drying time is repeated for 2 minutes.

In addition, as a repeating procedure of spraying and drying on the fluorine-containing coating film, cycle A described later is adopted. The xenon arc radiation 40 hours is the total radiation time. In the present invention, 2 hours of radiation is repeated 20 times for a total of 40 hours. After each irradiation, a cleaning process for 30 minutes is performed to clean the surface of the fluorine-containing coating film with water such as ion exchange water. Xenon arc radiation stops during cleaning. And after each washing | cleaning process, a glossiness and the following color difference are measured.

The glossiness is calculated according to JIS K 5600-4-7: 1999 (ISO 2813: 1994), and after 40 hours of xenon arc radiation with respect to the 60 ° gloss value of the fluorine-containing coating film immediately before xenon arc radiation. The ratio of the 60 ° gloss value of the fluorine-containing coating film is defined as the gloss retention (unit:%).
The fluorine-containing coating film of the present invention has a color difference (ΔE) between just before the xenon arc radiation and after 40 hours of the xenon arc radiation being excellent in weather resistance, so 5.0 or less is preferable, and 3.0 The following is more preferable, and 2.0 or less is particularly preferable.
The color measurement of the fluorine-containing coating film is performed using a color difference meter in accordance with JIS K 5600-4-5: 1999, and the color difference is calculated in accordance with JIS K 5600-4-6: 1999.

Furthermore, if the fluorine-containing coating film has good surface smoothness, irregular reflection due to unevenness on the surface can be suppressed, so that there is less variation in glossiness and higher glossiness. Also, if the surface has large irregularities, the fluorine-containing coating tends to deteriorate from the convex part, the outermost resin is peeled off, and the internal titanium oxide pigment is exposed to promote the deterioration of the entire fluorine-containing coating. It will be. Therefore, if the surface smoothness of the fluorine-containing coating film is good, the gloss retention is also excellent.
The surface smoothness of the fluorine-containing coating film can be determined using a standard plate (1 to 10) for visually determining the smoothness of the powder coating film by a powder coating institute (PCI). The numerical value of the standard version for visual judgment of smoothness indicates that the larger the numerical value, the better the surface smoothness. As the surface smoothness of the fluorine-containing coating film of the present invention, the visual smoothness determination by PCI is preferably 6 or more, more preferably 7 or more, and particularly preferably 8 or more.

The water contact angle of the fluorine-containing coating film is preferably 1 to 55 degrees, particularly preferably 3 to 50 degrees. If the water contact angle is equal to or greater than the lower limit, the powder coating film (1) is less likely to be eroded by the organic acid component derived from bird droppings and insect carcasses, and to the surface of the powder coating film (1). Generation of mold is suppressed (generation of mold leads to poor appearance). If a water contact angle is below the said upper limit, it will be excellent in stain resistance.

The thickness of the fluorine-containing coating film is preferably 20 to 1,000 μm, more preferably 20 to 500 μm, and particularly preferably 20 to 300 μm. 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 addition, when the thickness of a fluorine-containing coating film is thick, the thickness can be achieved by selecting the below-mentioned fluidized immersion method.

[Powder paint]
The powder paint in the present invention contains a fluororesin (A) and titanium oxide (B). The powder coating material may further contain one or more of a non-fluororesin (C), a curing agent (D), a curing catalyst (E), and other components (H) described later, if necessary.

(Fluororesin (A))
As a fluororesin (A), the homopolymer or copolymer which has a unit based on a fluoro olefin is mentioned.
The fluoroolefin is a compound in which one or more hydrogen atoms of a hydrocarbon-based olefin (general formula C _n H _2n ) are substituted with a fluorine atom.
The carbon number n of the fluoroolefin is preferably 2-8, and particularly preferably 2-6.
The number of fluorine atoms contained in the fluoroolefin is preferably 2 or more, particularly preferably 3 to 4. If the number of fluorine atoms is 2 or more, the cured film has excellent weather resistance.
In the fluoroolefin, one or more hydrogen atoms not substituted with fluorine atoms may be substituted with chlorine atoms. When the fluoroolefin has a chlorine atom, it is easy to disperse pigments (especially colored organic pigments such as cyanine blue and cyanine green) in the fluororesin (A). Moreover, the glass transition temperature of the fluororesin (A) can be preferably designed to be 30 ° C. or higher, and blocking of the cured film can be suppressed.

The fluoroolefin is preferably at least one selected from the group consisting of tetrafluoroethylene (hereinafter referred to as “TFE”), chlorotrifluoroethylene (hereinafter referred to as “CTFE”), hexafluoropropylene and vinyl fluoride. , TFE, or CTFE are particularly preferred.
A fluoroolefin may be used individually by 1 type, and may use 2 or more types together.
Examples of the homopolymer having a unit based on a fluoroolefin include polyvinylidene fluoride (hereinafter referred to as “PVDF”), polyvinyl fluoride, polychlorotrifluoride and the like. PVDF is particularly preferred from the viewpoints of excellent adhesion to a substrate (particularly an aluminum substrate) and easy fixing of an aluminum curtain wall with a sealing agent.

When the fluororesin (A) is a copolymer, it is a copolymer containing units based on fluoroolefin and units having a reactive group from the viewpoint of excellent antifouling properties, water resistance, acid resistance, and alkali resistance. It is preferable. Furthermore, the copolymer may have units other than the units based on fluoroolefin and the units having reactive groups.
The unit having a reactive group may be a unit obtained by polymerizing a monomer having a reactive group, and a compound that decomposes a part of the copolymer or gives a reactive group to a functional group of the copolymer May be a unit obtained by reacting.
Examples of the reactive group include a hydroxyl group, a carboxy group, and an amino group. In particular, when an isocyanate curing agent (particularly a blocked isocyanate curing agent) is used as a curing agent described later, the curing rate is excellent, the pigments are easily dispersed, and the gloss is high (60 ° gloss is 60% or more). Of these, a hydroxyl group and a carboxy group are preferable.

Examples of the monomer having a hydroxyl group include allyl alcohol, hydroxyalkyl vinyl ether (2-hydroxyethyl vinyl ether, 4-hydroxybutyl vinyl ether, cyclohexanediol monovinyl ether, etc.), hydroxyalkyl allyl ether (2-hydroxyethyl allyl ether, etc.). And vinyl hydroxyalkanoate (such as vinyl hydroxypropionate) and hydroxyalkyl (meth) acrylate (such as hydroxyethyl (meth) acrylate).

Examples of the monomer having a carboxyl group include (meth) acrylic acid, carboxyl alkyl vinyl ether, carboxyl allyl ether, and the like.
Further, when a carboxyl group can be brought into the functional group of the copolymer, for example, after obtaining a copolymer containing units based on the monomer having a hydroxyl group, the copolymer and an acid anhydride are reacted. Thus, an ester bond and a carboxyl group can be obtained.
The acid anhydride is preferably a compound having a molecular weight of 90 to 200, a compound having 4 to 15 carbon atoms, and a compound having a melting point of 20 to 180 ° C. from the viewpoint of excellent reactivity with a hydroxyl group.

Examples of the acid anhydride include dibasic acid anhydrides. Dibasic acid anhydrides include succinic anhydride (molecular weight: 100.1, melting point: 120 ° C., carbon number: 4), glutaric anhydride (molecular weight: 114.1, melting point: 52 ° C., carbon number: 5) Itaconic anhydride (molecular weight: 112.1, melting point: 67 ° C., carbon number: 5), 1,2-cyclohexanedicarboxylic anhydride (hexahydrophthalic anhydride) (molecular weight: 154.0, melting point: 35 ° C., carbon number 8), cis-4-cyclohexene-1,2-dicarboxylic anhydride (molecular weight: 152.0, melting point: 66 ° C., carbon number: 8), phthalic anhydride (molecular weight: 148.1, melting point: 131 ° C., Carbon number: 8), 4-methylhexahydrophthalic anhydride (molecular weight: 168.0, melting point: 22 ° C., carbon number: 9), 1,8-naphthalic anhydride (molecular weight: 198.2, melting point: 17 ° C.) , Carbon number: 11), anhydrous male Phosphate (molecular weight: 98.1, mp: 52.6 ° C., the number of carbon atoms: 4), and the like.
As the dibasic acid anhydride, succinic anhydride is particularly preferable from the viewpoint of solubility and easy reaction with a hydroxyl group.

Examples of other units include units based on fluorine-containing monomers other than fluoroolefin, units based on monomers having no fluorine atom and reactive group, and the like.
Examples of fluorine-containing monomers other than fluoroolefins include fluoro (alkyl vinyl ether).
As the monomer having no fluorine atom or reactive group, a vinyl monomer is preferable because it is excellent in alternating copolymerization with a fluoroolefin and can increase the polymerization yield.
In addition, the vinyl monomer is preferable because it has little influence on the cured film even if it remains unreacted and can be easily removed in the production process.
Examples of vinyl monomers include vinyl ether, allyl ether, carboxylic acid vinyl ester, carboxylic acid allyl ester, and olefin.

Examples of the vinyl ether include cycloalkyl vinyl ether (cyclohexyl vinyl ether (hereinafter referred to as “CHVE”)), alkyl vinyl ether (nonyl vinyl ether, 2-ethylhexyl vinyl ether, hexyl vinyl ether, ethyl vinyl ether, n-butyl vinyl ether, tert-butyl vinyl ether). Etc.).
Examples of allyl ethers include alkyl allyl ethers (ethyl allyl ether, hexyl allyl ether, etc.).

Examples of carboxylic acid vinyl esters include vinyl esters of carboxylic acids (such as acetic acid, butyric acid, pivalic acid, benzoic acid, and propionic acid). Further, Veova-9, Veova-10 (both manufactured by Shell Chemical Co., Ltd.) and the like that are commercially available as vinyl esters of carboxylic acids having a branched alkyl group may be used.
Examples of carboxylic acid allyl esters include allyl esters of carboxylic acids (such as acetic acid, butyric acid, pivalic acid, benzoic acid, and propionic acid).
Examples of the olefin include ethylene, propylene, isobutylene and the like.

As other units, a unit based on cycloalkyl vinyl ether is preferable and a unit based on CHVE is preferable in that the glass transition temperature of the fluororesin (A) can be designed to be 30 ° C. or higher and blocking of the cured film can be suppressed. Particularly preferred.
As other units, a unit having a linear or branched alkyl group having 3 or more carbon atoms is preferable from the viewpoint of excellent flexibility of the cured film.
Other units may be used alone or in combination of two or more.

Examples of the fluororesin (A) include TFE-perfluoro (alkyl vinyl ether) copolymer (hereinafter referred to as “PFA”), TFE-hexafluoropropylene copolymer, TFE-perfluoro (alkyl vinyl ether) -hexafluoropropylene. And a copolymer, an ethylene-TFE copolymer (hereinafter referred to as “ETFE”), an ethylene-CTFE copolymer, and the like.
Especially, as a combination of the monomer which forms the unit which comprises a fluororesin (A), the following combination (1) is preferable from the point of a weather resistance, adhesiveness, a softness | flexibility, and blocking resistance, 2) is more preferable, and the combination (3) is particularly preferable.

Combination (1)
Fluoroolefin: TFE or CTFE,
Monomer having a hydroxyl group: hydroxyalkyl vinyl ether,
Monomer having no fluorine atom and reactive group: one or more selected from cycloalkyl vinyl ether, alkyl vinyl ether and carboxylic acid vinyl ester.
Combination (2)
Fluoroolefin: TFE or CTFE,
Monomer having a hydroxyl group: hydroxyalkyl vinyl ether,
Monomer having no fluorine atom and reactive group: CHVE or tert-butyl vinyl ether.
Combination (3)
Fluoroolefin: CTFE,
Monomer having a hydroxyl group: hydroxyalkyl vinyl ether,
Monomer having no fluorine atom and reactive group: CHVE or tert-butyl vinyl ether.

The proportion of units based on fluoroolefin is preferably from 30 to 70 mol%, particularly preferably from 40 to 60 mol%, based on the total units (100 mol%) in the copolymer. If the unit based on a fluoroolefin is more than the said lower limit, a cured film will be excellent in a weather resistance. If the unit based on fluoroolefin is not more than the above upper limit, when the cured film has a single-layer structure, the adhesiveness between the layer and the substrate is excellent, and when the cured film has a two-layer structure, the fluororesin (A) It is excellent in adhesion between the formed layer and a layer formed of the non-fluororesin (C) described later.

The proportion of units having a reactive group is preferably from 0.5 to 20 mol%, particularly preferably from 1 to 15 mol%, based on the total units (100 mol%) in the copolymer. When the proportion of the unit having a reactive group is at least the lower limit, when the cured film has a single layer structure, the adhesiveness between the layer and the substrate is excellent, and when the cured film has a two-layer structure, a fluororesin ( The adhesion between the layer formed by A) and the layer formed by the non-fluororesin (C) described later is excellent. If the ratio of the unit having a reactive group is not more than the above upper limit value, the scratch resistance of the cured film is excellent.

The proportion of other units is preferably 20 to 60 mol%, particularly preferably 30 to 50 mol%, based on the total units (100 mol%) in the copolymer. When the proportion of other units is equal to or higher than the lower limit, the glass transition temperature of the fluororesin (A) can be set in an appropriate range, and the powder coating can be easily manufactured. If the proportion of other units is less than or equal to the above upper limit, when the cured film has a single layer structure, the adhesion between the layer and the substrate is excellent, and when the cured film has a two-layer structure, the fluororesin (A) It is excellent in adhesion between the formed layer and a layer formed of the non-fluororesin (C) described later.

The melting point of the fluororesin (A) is preferably 300 ° C. or lower, more preferably 200 ° C. or lower, and particularly preferably 180 ° C. or lower. When the melting point of the fluororesin (A) is not more than the above upper limit, the surface smoothness of the cured film is further improved.
The glass transition temperature of the fluororesin (A) is preferably 30 ° C. or higher, and particularly preferably 35 ° C. or higher, from the viewpoint that the powder coating is easy to produce and blocking is easily prevented. On the other hand, the glass transition temperature of the fluororesin (A) is preferably 150 ° C. or lower, more preferably 120 ° C. or lower, and particularly preferably 100 ° C. or lower from the viewpoint that the surface smoothness of the formed cured film can be further improved.

The number average molecular weight of the fluororesin (A) is preferably 3,000 to 50,000, particularly preferably 5,000 to 30,000. When the number average molecular weight is not less than the lower limit, the cured film is excellent in water resistance and salt water resistance. When the number average molecular weight is not more than the above upper limit, the surface smoothness of the cured film is further improved.

The hydroxyl value of the fluororesin (A) is preferably from 5 to 100 mgKOH / g, particularly preferably from 10 to 80 mgKOH / g. When the hydroxyl value is not less than the lower limit, when the cured film has a single-layer structure, the adhesiveness between the layer and the substrate is excellent, and when the cured film has a two-layer structure, it is formed of the fluororesin (A). Excellent adhesion between the layer and a layer formed of the non-fluororesin (C) described later. When the hydroxyl value is less than or equal to the above upper limit value, the crack resistance of the cured film is excellent under a temperature cycle at a high temperature of 100 ° C. or higher and a low temperature of 10 ° C. or lower. The hydroxyl value is measured according to JIS K1557-1 (2007 edition).
When the fluororesin (A) has a carboxy group, the acid value of the fluororesin (A) is preferably from 0.1 to 50 mgKOH / g, more preferably from 1.0 to 4.0 mgKOH / g. If the acid value of a fluororesin (A) is more than the said lower limit, it will be effective in the dispersibility improvement of a pigment, and if it is below the said upper limit, a cured film will be excellent in moisture resistance. The acid value is measured according to JIS K 5601-2-1 (2009).
As the fluororesin (A), any fluororesin that can be used as a powder coating can be used as appropriate. Specifically, Lumiflon 710, 710F (trade name, manufactured by Asahi Glass Co., Ltd.), Zeffle (trade name, manufactured by Daikin Industries, Ltd.), Kyner (trade name, manufactured by Arkema Co., Ltd.), ZB-F1000 (trade name, manufactured by Dalian Shinkoku Co., Ltd.) Product), Etaflon (trade name, manufactured by Eternal Co., Ltd.), and DS203 (trade name, manufactured by Todake Shinshu Co., Ltd.).

(Titanium oxide pigment (B))
Titanium oxide pigment refers to a pigment containing titanium oxide. Titanium oxide pigment (B) tends to advance the photocatalytic reaction in a hot and humid region. The photocatalytic reaction is promoted by moisture and ultraviolet rays.
As the titanium oxide pigment (B), a coated titanium oxide pigment (B1) surface-treated with one or more of silica, alumina, zirconia, selenium, organic components (polyol, etc.) is preferable. The coated titanium oxide pigment (B1) is a titanium oxide that has been surface-treated so that the photocatalytic reaction does not easily proceed, and has excellent weather resistance. For example, even when bubbles are left behind during the formation of the powder coating film and rainwater or the like enters the bubbles, the photocatalytic reaction with titanium oxide hardly proceeds. Therefore, the obtained fluorine-containing coating film is excellent in weather resistance, and the above-mentioned gloss retention (%) by the accelerated weather resistance test (α) falls within the above range. Further, the above-described color difference tends to be in the above range.

The coated titanium oxide pigment (B1) is particularly preferably one whose titanium oxide content is adjusted to 80 to 92% by mass. If titanium oxide content is more than the said lower limit, it will be excellent in the whiteness of a fluorine-containing coating film. If the titanium oxide content is less than or equal to the above upper limit value, the photocatalytic reaction is further suppressed, and the above-described gloss retention (%) by the accelerated weather resistance test (α) tends to be in the above range. Further, the above-described color difference tends to be in the above range.
The coated titanium oxide pigment (B1) may be used alone or in combination of two or more.

Commercially available coated titanium oxide pigments (B1) include “Taipaque (trade name) PFC105” (titanium oxide content: 87% by mass) and “Taipaque (trade name) CR95” (containing titanium oxide) manufactured by Ishihara Sangyo Co., Ltd. Amount: 90% by mass), “D918” (titanium oxide content: 85% by mass) manufactured by Sakai Chemical Co., Ltd., “Ti-Pure (trade name) R960” (titanium oxide content: 89% by mass) manufactured by DuPont "Ti-Select (trade name)" (titanium oxide content: 90% by mass).

In the powder coating according to the present invention, when the coated titanium oxide pigment (B1) is used as the titanium oxide pigment (B), the coating treatment is not performed or the coating treatment is not sufficient even if the coating treatment is performed. The titanium pigment (B2) (hereinafter, also simply referred to as “titanium oxide pigment (B2)”) may be included, but it is preferably not included from the viewpoint of weather resistance. When the titanium oxide pigment (B2) is included, the titanium oxide pigment (B2) is preferably 30 parts by mass or less and more preferably 20 parts by mass or less with respect to 100 parts by mass of the coated titanium oxide pigment (B1). Specifically, the titanium oxide pigment (B2) is a titanium oxide pigment having a titanium oxide content of more than 92 mass% and not more than 100 mass%.

(Non-fluorine resin (C))
Examples of the non-fluororesin (C) include at least one selected from the group consisting of acrylic resins, polyester resins, polyurethane resins, epoxy resins, and silicone resins. Among them, the point of excellent adhesion to the substrate, the fluororesin (A) and the non-fluororesin (C) can be easily separated when formed into a coating film, and the surface layer is formed with a layer of the fluororesin (A). From the viewpoint of excellent weather resistance, an acrylic resin or a polyester resin is preferable, and a polyester resin is particularly preferable.

<Acrylic resin>
The acrylic resin is a polymer having units based on (meth) acrylate. As an acrylic resin, what has reactive groups, such as a carboxy group, a hydroxyl group, and a sulfo group, is mentioned. The acrylic resin can improve the dispersibility of the pigment.
The glass transition temperature of the acrylic resin is preferably 30 to 60 ° C, more preferably 32 to 58 ° C. If the glass transition temperature is equal to or higher than the lower limit, blocking is difficult. If the glass transition temperature of the acrylic resin is not more than the above upper limit value, the surface smoothness of the cured film is further improved.

The number average molecular weight of the acrylic resin is preferably 5,000 to 100,000, particularly preferably 30,000 to 100,000. If the number average molecular weight of the acrylic resin is not less than the lower limit, blocking is difficult. If the number average molecular weight of the acrylic resin is not more than the upper limit, the surface smoothness of the cured film can be further improved.
The mass average molecular weight of the acrylic resin is preferably 6,000 to 150,000, more preferably 40,000 to 150,000, and particularly preferably 60,000 to 150,000. If the mass average molecular weight of the acrylic resin is not less than the lower limit, blocking is difficult. If the mass average molecular weight of the acrylic resin is not more than the above upper limit value, the surface smoothness of the cured film can be further improved.

When the acrylic resin has a carboxy group, the acid value of the acrylic resin is preferably 30 to 400 mgKOH / g, more preferably 35 to 300 mgKOH / g. If the acid value of the acrylic resin is not less than the lower limit, there is an effect of improving the dispersibility of the pigment. If the acid value of an acrylic resin is below the said upper limit, a cured film will be excellent in moisture resistance.

Commercially available acrylic resins include “Fine Dick (trade name) A-249”, “Fine Dick (trade name) A-251”, “Fine Dick (trade name) A-266” manufactured by DIC, Mitsui Chemicals, Inc. “Almatex (trade name) PD6200” manufactured by the company, “Almatex (trade name) PD7310”, “Sanpex PA-55” manufactured by Sanyo Chemical Industries, Ltd., and the like.

<Polyester resin>
The polyester resin has a unit based on a polyvalent carboxylic acid compound and a unit based on a polyhydric alcohol compound, and if necessary, a unit other than these two types of units (for example, a unit based on a hydroxycarboxylic acid compound). You may have. The polyester resin has at least either a carboxy group or a hydroxyl group at the end of the polymer chain.
Examples of the polyvalent carboxylic acid compound include phthalic acid, isophthalic acid, terephthalic acid, naphthalene dicarboxylic acid, trimellitic acid, pyromellitic acid, phthalic anhydride, and the like. From the point that the cured film has excellent weather resistance, isophthalic acid Is preferred.

As the polyhydric alcohol compound, an aliphatic polyhydric alcohol or an alicyclic polyhydric alcohol is preferable, and an aliphatic polyhydric alcohol is more preferable from the viewpoint of excellent adhesion to the substrate and flexibility of the cured film.
Examples of polyhydric alcohol compounds include ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, and 1,5-pentanediol. Neopentyl glycol, spiro glycol, 1,10-decanediol, 1,4-cyclohexanedimethanol, trimethylolethane, trimethylolpropane, glycerin, pentaerythritol and the like.
As the polyhydric alcohol, neopentyl glycol, 1,2-pentanediol, 1,5-pentanediol, trimethylolpropane and the like are preferable, and neopentylglycol or trimethylolpropane is particularly preferable from the viewpoint of easy availability.

Commercially available polyester resins include “CRYLCOAT (trade name) 4642-3” and “CRYLCOAT (trade name) 4890-0” manufactured by Daicel Ornex Corporation, “GV-250” and “GV- 740 "," GV-175 "and the like.

[Curing agent (D)]
The curing agent (D) refers to a compound having two or more reactive groups, and at least one of the reactive groups is a reactive group that can react with the reactive group of the fluororesin (A). The curing agent (D) is preferably contained in the powder coating material when the fluororesin (A) has a reactive group (hydroxyl group, carboxy group, etc.). The curing agent (D) cures the fluororesin (A) by reacting with the reactive group to crosslink the fluororesin (A) or to increase the molecular weight. Since it is preferable that the reactive group of the curing agent (D) does not react with the reactive group of the fluororesin (A) at room temperature, it is a reactive group that can react when the powder coating is heated and melted. Is preferred. For example, a blocked isocyanate group is preferable to an isocyanate group having a highly reactive group at room temperature. The blocked isocyanate group is released from the blocking agent when the powder coating is heated and melted to form an isocyanate group, and the isocyanate group acts as a reactive group.

As the curing agent (D), known compounds can be used. For example, blocked isocyanate curing agents, amine curing agents (melamine resin, guanamine resin, sulfoamide resin, urea resin, aniline resin, etc.), β -Hydroxyalkylamide type curing agents and triglycidyl isocyanurate type curing agents. A blocked isocyanate curing agent is particularly preferred from the viewpoint of excellent adhesion to the substrate, workability of the product after coating, and water resistance of the fluorine-containing coating film.
When all the hydroxyl groups of the fluororesin (A) are converted to carboxy groups, the curing agent is preferably a β-hydroxyalkylamide curing agent or a triglycidyl isocyanurate curing agent.
A hardening | curing agent (D) may be used individually by 1 type, and may use 2 or more types together.

The softening temperature of the curing agent (D) is preferably 10 to 120 ° C, particularly preferably 40 to 100 ° C. When the softening temperature is equal to or higher than the lower limit, the powder coating is difficult to cure at room temperature, and it is difficult to form a granular lump. If the softening temperature is not more than the above upper limit value, when the composition is melt-kneaded to produce a powder, the curing agent (D) can be easily dispersed homogeneously in the powder, and the surface of the resulting fluorine-containing coating film can be smoothed. Excellent in properties, strength, moisture resistance, etc.

The blocked isocyanate curing agent is preferably a solid at room temperature.
As the blocked isocyanate curing agent, a polyisocyanate obtained by reacting an aliphatic, aromatic or araliphatic diisocyanate with a low molecular weight compound having active hydrogen is reacted with a blocking agent, Those produced by masking are preferred.

Diisocyanates include tolylene diisocyanate, 4,4′-diphenylmethane isocyanate, xylylene diisocyanate, hexamethylene diisocyanate, 4,4′-methylene bis (cyclohexyl isocyanate), methylcyclohexane diisocyanate, bis (Isocyanate methyl) cyclohexane isophorone diisocyanate, dimer acid diisocyanate, lysine diisocyanate and the like.

Low molecular weight compounds having active hydrogen include water, ethylene glycol, propylene glycol, trimethylolpropane, glycerin, sorbitol, ethylenediamine, ethanolamine, diethanolamine, hexamethylenediamine, isocyanurate, uretidione, a low molecular weight polyester containing a hydroxyl group, Examples include polycaprolactone.

Examples of the blocking agent include alcohols (methanol, ethanol, benzyl alcohol, etc.), phenols (phenol, crezone, etc.), lactams (caprolactam, butyrolactam, etc.), and oximes (cyclohexanone, oxime, methyl ethyl ketoxime, etc.).

(Curing catalyst (E))
The curing catalyst (E) accelerates the curing reaction and imparts good chemical performance and physical performance to the fluorine-containing coating film.
When a blocked isocyanate curing agent is used, the curing catalyst (E) is preferably a tin catalyst (such as tin octylate, tributyltin laurate, dibutyltin dilaurate).
A hardening catalyst (E) may be used individually by 1 type, and may use 2 or more types together.

(Surface conditioner (F))
The surface conditioner (F) can be appropriately used as long as it improves the surface smoothness of the fluorine-containing coating film. In a fluorine-containing film using a powder coating, the glass transition temperature of the fluororesin (A) tends to be high in order to suppress blocking. Moreover, when forming the coating film which consists of a melt of a powder coating material, it is easy to contain air and it is difficult to fully obtain the surface smoothness of a fluorine-containing film.
In order to improve the surface smoothness of the fluorine-containing coating, a leveling agent that is unevenly distributed on the surface of the fluorine-containing coating, a plasticizer that lowers the melt viscosity of the fluororesin (A), and an inorganic that fills the gaps in the fluorine-containing coating Examples include fine particles.

(Leveling agent)
Commercially available leveling agents include trade names “BYK (trade name) -361N”, “BYK (trade name) -360P”, “BYK (trade name) -364P”, “BYK (trade name)” manufactured by Big Chemie. -368P "," BYK (product name) -3900P "," BYK (product name) -3931P "," BYK (product name) -3933P "," BYK (product name) -3950P "," BYK (product name) " -3951P "," BYK (trade name) -3955P ", and the like.

(Plasticizer)
As the plasticizer, a plasticizer having a cyclic hydrocarbon group in the molecule is preferable. The cyclic hydrocarbon group may be an alicyclic hydrocarbon group or an aromatic hydrocarbon group. When the plasticizer has a cyclic hydrocarbon group, compatibility with the resin component is improved, and the plasticizer is less likely to bleed out on the surface of the coating film. Therefore, blocking of the coating film can be suppressed, and a coating film having excellent coating film appearance and surface smoothness can be obtained.

The melting point of the plasticizer is preferably 60 to 200 ° C., more preferably 60 to 180 ° C., and particularly preferably 70 to 160 ° C. If melting | fusing point is more than the lower limit of the said range, blocking of a coating film can be suppressed. Further, the plasticizer is melted to fill the gaps between the resins, and a coating film having excellent coating film appearance and surface smoothness can be obtained. When the melting point of the plasticizer is not more than the upper limit of the above range, the melt viscosity of the molten film is lowered, and a coating film having excellent coating film appearance and surface smoothness can be obtained.

The molecular weight of the plasticizer is preferably 200 to 1,000, more preferably 220 to 980, and particularly preferably 240 to 960. If the molecular weight of the plasticizer is at least the lower limit of the above range, the volatility is low, the effect of reducing the melt viscosity of the molten film is sufficiently exerted, and a coating film with excellent coating film appearance and surface smoothness is obtained. Cheap. If the molecular weight of the plasticizer is not more than the upper limit of the above range, the plastic effect is suppressed from being excessively exhibited, and the coating film is prevented from being blocked.

Examples of the plasticizer include the following. Dicyclohexyl phthalate (melting point: 68 ° C., molecular weight: 330), hexabromocyclododecane (melting point: 180 ° C., molecular weight: 641), tribenzoic acid glyceride (melting point: 68 ° C., molecular weight: 404), tetrabenzoic acid pentaerythritol (melting point) : 108 ° C., molecular weight: 552), 1,4-cyclohexanedimethanol dibenzoate (melting point: 118 ° C., molecular weight: 352).

(Inorganic fine particles)
Examples of the inorganic fine particles include fine particles of silica, alumina, zirconia, and talc. The average particle diameter of the inorganic fine particles is preferably 0.01 to 500 nm, more preferably 0.05 to 400 nm, and particularly preferably 0.1 to 300 nm.
Examples of the inorganic fine particles include the following.
Silica: Product name “AEROSIL (trade name) R972” (manufactured by Evonik), Alumina: Product name “A-42” (manufactured by Showa Denko KK), Zirconia: Product name “ELCOM V-9” (manufactured by JGC Catalysts and Chemicals) ), Talc: Product name "NANO-ACE" (Matsuo Sangyo Co., Ltd.)

(Other ingredients (H))
The other components (H) of the powder coating in the present invention are fluororesin (A), titanium oxide (B), non-fluororesin (C), curing agent (D), curing catalyst (E), surface conditioner ( Components other than F).
Other components (H) include ultraviolet absorbers, light stabilizers, matting agents, surfactants (nonionic, cationic, or anionic), degassing agents (air entrained in powders, curing agents (C1) ) To remove the blocking agent, moisture, etc. coming out of the coating film from staying inside the powder coating film, although it is usually a solid, it becomes very low viscosity when melted. , Fillers, heat stabilizers, dispersants, antistatic agents, rust preventives, silane coupling agents, antifouling agents, antifouling treatment agents, and other pigments other than the titanium oxide pigment (B). .

[Ultraviolet absorber]
As the ultraviolet absorber, either an organic ultraviolet absorber or an inorganic ultraviolet absorber can be used.
An ultraviolet absorber may be used individually by 1 type, or may be used in combination of 2 or more type.
Examples of organic ultraviolet absorbers include salicylic acid ester ultraviolet absorbers, benzotriazole ultraviolet absorbers, benzophenone ultraviolet absorbers, and cyanoacrylate ultraviolet absorbers.

As the organic ultraviolet absorber, a compound having a molecular weight of 200 to 1,000 is preferable. If the molecular weight is 200 or more, it is difficult to volatilize in the process of forming the fluorine-containing coating film and can remain in the fluorine-containing coating film. If the molecular weight is 1,000 or less, it is easy to disperse in the fluorine-containing coating film.

As the organic ultraviolet absorber, a compound having a melting point of 50 to 150 ° C. is preferable. When the melting point is 50 ° C. or higher, it is difficult to volatilize in the process of forming the fluorine-containing coating film and can remain in the fluorine-containing coating film. When the melting point is 150 ° C. or lower, the film easily melts in the process of forming the fluorine-containing coating film and is easily dispersed in the fluorine-containing coating film.

As the organic ultraviolet absorber, a compound having a volatilization temperature of 180 to 450 ° C. is preferable, and a compound having a 220 to 400 ° C. is particularly preferable. Since a temperature condition of 150 to 220 ° C. is required in the process of forming the powder coating film (1), it is difficult to volatilize within the above range and can remain in the fluorine-containing coating film.

Examples of inorganic ultraviolet absorbers include filler-type inorganic ultraviolet absorbers containing ultraviolet absorbing oxides (such as zinc oxide and cerium oxide).
As the inorganic ultraviolet absorber, composite particles of zinc oxide and titanium oxide, composite particles of cerium oxide and titanium oxide, composite particles of zinc oxide and cerium oxide, composite particles of titanium oxide, zinc oxide and cerium oxide are preferable.

[Light stabilizer]
As the light stabilizer, a hindered amine light stabilizer is preferable, and a hindered amine light stabilizer having a molecular weight of 300 to 5,000 and a melting point of 50 to 250 ° C. is more preferable. A hindered amine light stabilizer having a molecular weight of 400 to 4,000 and a melting point of 60 to 200 ° C. is more preferable from the viewpoint of uniformly diffusing into the composition at the time of kneading.

As the light stabilizer, a compound having a volatilization temperature of 180 to 450 ° C. is preferable, and a compound having a temperature of 220 to 400 ° C. is particularly preferable. Since a temperature condition of 150 to 220 ° C. is required in the process of forming the fluorine-containing coating film, it is difficult to volatilize and stay in the fluorine-containing coating film within the above range.
A light stabilizer may be used individually by 1 type and may use 2 or more types together.

Commercially available hindered amine light stabilizers include “Tinuvin (trade name) 111FDL” (molecular weight: 2,000 to 4,000, melting point: 115 to 150 ° C.) and “Tinuvin (trade name) 144” manufactured by BASF. (Molecular weight: 685, melting point: 146 to 150 ° C.), “Tinuvin (trade name) 152” (molecular weight: 756.6, melting point: 83 to 90 ° C.), “Sanduvor (trade name) 3051 powder” manufactured by Clariant ( Molecular weight: 364.0, melting point: 225 ° C.), “Sanduvor (trade name) 3070 powder” (molecular weight: 1,500, melting point: 148 ° C.), “VP Sanduvor (trade name) PR-31” (molecular weight: 529, Melting point: 120 to 125 ° C.).

As the pigment other than the titanium oxide pigment (B), at least one selected from the group consisting of luster pigments, rust preventive pigments, colored pigments and extender pigments is preferable.
The bright pigment is a pigment for brightening the coating film. Examples of the bright pigment include aluminum powder, nickel powder, stainless steel powder, copper powder, bronze powder, gold powder, silver powder, mica powder, graphite powder, glass flake, and scale-like iron oxide powder.

The rust preventive pigment is a pigment for preventing the corrosion and alteration of the base material with respect to the base material that requires the antirust property. As the rust preventive pigment, a lead-free rust preventive pigment having a low environmental load is preferable. Examples of lead-free rust preventive pigments include cyanamide zinc, zinc oxide, zinc phosphate, calcium magnesium phosphate, zinc molybdate, barium borate, and calcium cyanamide zinc.

The color pigment is a pigment for coloring the coating film. Examples of the color pigment include carbon black, iron oxide, phthalocyanine blue, phthalocyanine green, quinacridone, isoindolinone, benzimidazolone, dioxazine and the like.

The extender pigment is a pigment for improving the hardness of the fluorine-containing coating film and increasing the thickness of the fluorine-containing coating film. It is also preferable to add it because the cut surface of the fluorine-containing coating film can be cleaned when a coated article such as a building exterior member is cut. Examples of extender pigments include talc, barium sulfate, mica, and calcium carbonate.

[Content of each component]
The content of each component contained in the powder coating in the present invention is preferably as follows.
The content of the titanium oxide pigment (B) in the powder coating is preferably 20 to 250 parts by mass, particularly preferably 50 to 220 parts by mass with respect to 100 parts by mass of the fluororesin (A). If it exists in the said range, the above-mentioned gloss retention (%) of the fluorine-containing coating film by an accelerated weather resistance test ((alpha)) will become easily in the said range. Further, the above-described color difference tends to be in the above range.
When the powder coating material contains the non-fluororesin (C), the content of the non-fluororesin (C) is preferably 10 to 90 parts by mass, and 20 to 80 parts by mass with respect to 100 parts by mass of the fluororesin (A). Part is more preferable, and 30 to 70 parts by weight is particularly preferable.

When the powder coating material contains a curing agent (D), the content of the curing agent (D) is preferably 1 to 50 parts by mass, preferably 3 to 30 parts by mass with respect to 100 parts by mass of the fluororesin (A). Particularly preferred.
When the curing agent (D) is a blocked isocyanate curing agent, the fluororesin (A) preferably has a hydroxyl group. The content of the blocked isocyanate curing agent is preferably such that the molar ratio of the isocyanate group to the hydroxyl group of the fluororesin (A) is 0.05 to 1.5, preferably 0.8 to 1.2. The amount is particularly preferred. When the molar ratio is not less than the lower limit, the degree of curing of the powder coating is increased, and the hardness and chemical resistance of the fluorine-containing coating film are excellent. When the molar ratio is not more than the above upper limit, the fluorine-containing coating film is not easily brittle, and the heat resistance, chemical resistance, moisture resistance and the like are excellent.

When the powder coating contains the curing catalyst (E), the content of the curing catalyst (E) is 0.0001 based on 100 parts by mass of the total solid content other than the titanium oxide pigment (B) of the powder coating. Up to 10.0 parts by mass is preferred. If content of a curing catalyst (E) is more than the said lower limit, a catalyst effect will be fully easy to be acquired. If the content of the curing catalyst (E) is not more than the above upper limit value, the gas such as air entrained in the powder coating during the melting and curing process of the powder coating is likely to escape, and the content of the curing catalyst (E) is caused by the remaining gas. Little decrease in heat resistance, weather resistance and water resistance of fluorine coating.

When the powder coating material contains the surface conditioner (F), the content of the surface conditioner (F) is preferably 0.1 to 15.0 parts by mass with respect to 100 parts by mass of the fluororesin (A). 1.0 to 10.0 parts by mass is more preferable, and 1.5 to 8.0 parts by mass is particularly preferable. When the surface conditioner (F) is in the above range, the surface smoothness is excellent, and the above-described gloss retention (%) of the fluorine-containing coating film by the accelerated weather resistance test (α) tends to be in the above range.
When the powder coating contains another component (H), the total content of the other components (H) is preferably 45% by mass or less, and 30% by mass or less in the powder coating (100% by mass). Particularly preferred.

<Production method of powder paint>
The powder coating can be produced by a known method. For example, the following method is mentioned.
Method I: A method in which the fluororesin (A) and titanium oxide (B) as raw materials are each pulverized in advance and then mixed.
Method II: A method in which these raw materials are mixed in a solid state and then pulverized into a powder.
Method III: A method in which these raw materials are mixed in a solid state, then melt-kneaded, cooled to form a lump, and pulverized into a powder.
Among these, the method III is preferable because a cured film having excellent homogeneity can be obtained by uniformly distributing each component in the obtained powder.

The mixing of the raw materials may be liquid or dry blend, and can be performed using a known mixer. Examples of the mixer include a high-speed mixer, a V-type mixer, an inverting mixer, a high-speed mixer, a double cone mixer, a kneader, a dumpler mixer, a mixing shaker, a drum shaker, and a rocking shaker.

The melt-kneading can be performed using various types of extruders such as a single shaft, a twin shaft, and a planetary gear. The mixture of each component is kneaded in a heated and melted state, and each component is made uniform. The extruded melt-kneaded product is preferably cooled to pellets.
The pellets can be pulverized using a known pulverizer. Examples of the type of pulverizer include a pin mill, a hammer mill, and a jet mill.
Classification is preferably performed after pulverization. When performing classification, it is preferable to remove at least one of particles having a particle diameter of less than 10 μm and particles having a particle diameter exceeding 100 μm. Examples of the classification method include a screening method and an air classification method.

The particle size of the particles contained in the powder coating is preferably about 25 to 50 μm with a 50% average volume particle size distribution, for example. The particle size of the particles is measured using a generally used particle size measuring instrument. Examples of the format of the particle size measuring device include a format that captures a potential change when passing through a pore, a laser diffraction method, an image determination format, a sedimentation velocity measurement method, and the like.
When the powder coating material in the present invention includes a non-fluororesin (C), a curing agent (D), a curing catalyst (E), and other components (F), mixing, melt-kneading, and pulverization are similarly performed. be able to.

<Method for producing fluorine-containing coating film>
A fluorine-containing coating film can be manufactured with the manufacturing method which has the following process (1) and process (2).
Step (1) A step of coating a base material with a powder coating material to form a coating film made of a melt of the powder coating material.
Step (2) A step of cooling the coating film to form a fluorine-containing coating film.

(Process (1))
A powder coating is applied to the base material to form a coating film made of a melt of the powder coating on the base material. In the coating film, when a reactive component is contained in each layer, a curing reaction occurs.

The coating film consisting of the powder coating melt may be formed at the same time as the coating of the powder coating on the substrate. After the powder coating is adhered to the substrate, the powder coating is heated and melted on the substrate. May be formed.
If the powder coating contains a reactive component, the curing reaction of the reactive component starts almost simultaneously with the powder coating being heated and melted. It is necessary to heat and melt the powder coating after the powder coating adheres to the substrate.

A heating temperature (hereinafter also referred to as “baking temperature”) and a heating maintenance time (hereinafter also referred to as “baking time”) for heating and melting the powder coating material and maintaining the molten state for a predetermined time are: It is appropriately set depending on the type and composition of the raw material components of the powder coating material, the desired thickness of the fluorine-containing coating film, and the like. In particular, the baking temperature is preferably set according to the reaction temperature of the curing agent (D). For example, the baking temperature when a blocked polyisocyanate curing agent is used as the curing agent (D) is preferably 170 to 210 ° C. The baking time is preferably 5 to 120 minutes, particularly preferably 10 to 60 minutes.
When the powder coating material does not contain the curing agent (D), the heating temperature and the heating maintenance time are determined according to the melting point of the fluororesin (A) and the like.

Examples of coating methods include electrostatic coating, electrostatic spraying, electrostatic dipping, spraying, fluid dipping, spraying, spraying, thermal spraying, plasma spraying, and the like. Even when the coating film is made thin, an electrostatic coating method using a powder coating gun is preferable from the viewpoint of excellent surface smoothness of the coating film and excellent concealability of the fluorine-containing coating film.

Examples of the powder coating gun include a corona charging type coating gun and a friction charging type coating gun. The corona electrification type coating gun sprays powder paint after corona discharge treatment. The friction charging type coating gun sprays a powder coating after friction charging.
The discharge amount of the powder paint from the powder coating gun is preferably 50 to 200 g / min.
The distance from the tip of the gun portion of the powder coating gun to the substrate is preferably 150 to 400 mm from the viewpoint of coating efficiency.

When a corona charging type gun is used, the load voltage applied to the components constituting the powder coating by corona discharge treatment is preferably −50 to −100 kV, and the coating efficiency (the ratio at which the powder coating adheres to the substrate) From the viewpoint of excellent appearance of the coating film, −60 to −80 kV is preferable.
When using a frictional charging type coating gun, the internally generated current value of the powder coating by the frictional charging treatment is preferably 1 to 8 μA from the viewpoint of excellent coating efficiency and appearance of the coating film.

When the electrostatic coating method is carried out industrially, for example, an unpainted mirror (base material) and a grounded conductive horizontal belt conveyor for grounding are installed in the coating room. Lay down and install a gun at the top of the painting chamber. The coating pattern width is preferably 50 to 500 mm, the operation speed of the gun is preferably 1 to 30 m / min, and the conveyor speed is preferably 1 to 50 m / min, and conditions suitable for the purpose may be selected from the above range.

As a coating method, the fluid immersion method is preferable from the viewpoint that a relatively thick fluorine-containing coating film can be formed.
In the fluidized dipping method, a substrate whose coating surface is heated to a temperature equal to or higher than the melting temperature of the powder coating material in a fluid tank in which the powder coating material that is flowing and supported by a gas such as air is accommodated. After the powder is adhered to the coated surface of the base material and melted to form a coating film with a predetermined thickness on the base material, the coated base material is taken out of the fluid tank, and in some cases for a predetermined time. It is preferable to maintain the molten state of the coating and then cool.

In the fluid immersion method, the temperature in the fluidized tank is preferably 15 to 55 ° C, and the temperature of gas such as air blown into the fluidized tank in order to fluidize the powder is also preferably 15 to 55 ° C. The temperature of at least the coated surface of the substrate when immersed in the fluidized tank is preferably 300 to 450 ° C., and the time for which the substrate is immersed in the fluidized tank is preferably 1 to 120 seconds. The substrate taken out from the fluidized tank is preferably maintained at a temperature of 150 to 250 ° C. for 1 to 5 minutes.

(Process (2))
The molten coating film is cooled to room temperature (20 to 25 ° C.) to form a fluorine-containing coating film.
The cooling after baking may be either rapid cooling or slow cooling.

[Exterior material]
The exterior member of the present invention is a member provided with the fluorine-containing coating film of the present invention on a substrate. As a base material, what consists of metals, such as aluminum, iron, magnesium, for example, is preferable, and aluminum is especially preferable from the point which is excellent in corrosion resistance, is lightweight, and has the performance excellent in building material uses, such as an exterior member.
The shape, size, etc. of the substrate are not particularly limited.
As an exterior member of the present invention, it is only necessary to provide a base material with a fluorine-containing coating film. Specifically, aluminum composite panels, aluminum panels for curtain walls, aluminum frames for curtain walls, aluminum window frames, etc. Examples include exterior members such as exterior members, petroleum tanks, natural gas tanks, ceramic building materials, housing exterior materials, automobile members, aircraft members, railway vehicle members, solar cell BS members, wind power generation towers, wind power generation blades, and the like.

Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to these examples. Examples 1, 3 to 6 are examples, and examples 2, 7, and 8 are comparative examples.

<Measurement method, evaluation method>
[Surface smoothness of coating film]
The determination was made using a standard plate for visual determination of the smoothness of the coating film by PCI (Powder Coating Institute). There are 10 types of standard plates, 1 to 10, and the smoothness is excellent as the number increases.

[Accelerated weather resistance test (α)]
Under the following test conditions, in accordance with JIS K 5600-7-7 (Method 1), xenon arc radiation is performed using a xenon weather meter, and an exposure test is performed. However, 1 wt% hydrogen peroxide solution is sprayed on the fluorine-containing coating film of the test piece instead of water to give wetness.
(Test conditions for accelerated weathering test)
The accelerated weather resistance test (α) was performed according to the following procedure (cycle A).
procedure:
(1a) A test piece provided with a fluorine-containing coating film is prepared.
(2a) Fix the test piece into the tank of the xenon weather meter test device.
(3a) The relative humidity in the tank is 70% RH, the black panel temperature is 50 ° C., and the irradiance of the xenon lamp (light source) is 80 W / m ² in the wavelength range of 300 to 400 nm. Adjust the hydrogen water respectively.
(4a) Under the above conditions, the xenon weather meter is operated continuously for 2 hours.
(5a) The spray of the hydrogen peroxide solution during operation is sprayed for 3 minutes and then stopped for 2 minutes, and this is repeated 24 times (that is, the spray liquid spraying and drying cycle is spraying time 3 minutes-drying 2 minutes.) During drying, the coating film surface of the test piece is monitored to be 30 ± 1.0 ° C. with a platinum resistance thermometer thermometer.
(6a) Thereafter, the operation under the above conditions is stopped, and the surface of the fluorine-containing coating film of the test piece is spray-washed with ion-exchanged water for 30 minutes. During the cleaning, xenon arc radiation stops.
(7a) (4a) to (6a) are repeated 4 times (10 hours in total. Xenon arc radiation is 8 hours in total).
(8a) Then, a test piece is taken out, a water droplet is removed, and glossiness is measured.
(9a) (7a) to (8a) are repeated 5 cycles (total 50 hours (excluding time required for (8a)), and xenon arc radiation total time is 40 hours.)

[Gloss retention (%) and color difference (ΔE)]
The gloss retention (%) and color difference (ΔE) are calculated from the results before and after the accelerated weather resistance test (α). The specific evaluation is as follows.
The gloss retention (%) was measured in accordance with JIS K 5600-4-7: 1999 (ISO 2813: 1994), and the 60 ° gloss value of the fluorine coating immediately before xenon arc radiation was defined as 100%. The ratio of the 60 ° gloss value of the fluorine-containing coating film after 40 hours of xenon arc radiation is calculated. From the calculated gloss retention, weather resistance was evaluated according to the following criteria. The gloss meter uses “PG-1M” manufactured by Nippon Denshoku Industries Co., Ltd.
(Gloss retention)
◎: 90% or more ○: 70% or more and less than 90% △: 50% or more and less than 70% ×: less than 50% (variation when measuring gloss retention)
Difference between maximum value and minimum value when measuring 5 points ○: Less than 5.0 Δ: 5.0 or more and less than 10.0 ×: 10.0 or more

In the accelerated weather resistance test (α), the color difference (ΔE) between immediately before xenon arc radiation and 40 hours after xenon arc radiation was also determined as follows.
That is, a color difference meter (manufactured by Nippon Denshoku Industries Co., Ltd.) was used to measure the color measurement of the surface of the fluorine-containing coating film immediately before xenon arc radiation and to measure the color measurement of the surface of the fluorine-containing coating film 40 hours after xenon arc radiation. , SA4000). The measurement was based on JIS K 5600-4-5: 1999. Then, based on JIS K 5600-4-6: 1999, the color difference (ΔE) before and after the emission was calculated, and the weather resistance was evaluated according to the following criteria.
(Color difference)
◎: ΔE is less than 2.0 ○: ΔE is 2.0 or more and less than 3.5 △: ΔE is 3.5 or more and less than 5.0 ×: ΔE is 5.0 or more

<Each component used for preparation of powder paint>
[Fluororesin (A)]
Fluorine resin (A-1): hydroxyl group-containing fluoropolymer (manufactured by Asahi Glass Co., Ltd., Lumiflon (trade name) LF710F, hydroxyl value: 51.3 mg KOH / g, glass transition temperature: 55 ° C., number average molecular weight: 10,000).
Fluororesin (A-2): PVDF (manufactured by SHENZHOU NEWMATERIAL (Tougaku), PVDF DS203, mass average molecular weight: 270,000, number average molecular weight: 160,000).

[Coated titanium oxide pigment (B1) and titanium oxide pigment (B2)]
Titanium oxide pigment (B1-1): Taipure R960 (trade name, manufactured by DuPont, titanium oxide content: 89% by mass, coated metal: silica, alumina).
Titanium oxide pigment (B1-2): Taipei PFC105 (trade name, manufactured by Ishihara Sangyo Co., Ltd., titanium oxide content: 87% by mass, coating metal: silica, alumina, zirconia).
Titanium oxide pigment (B1-3): D918 (trade name, manufactured by Sakai Chemical Co., Ltd., titanium oxide content: 85% by mass, coating metal: silica, alumina, zirconia).
Titanium oxide pigment (B2-4): Taipei CR97 (trade name, manufactured by Ishihara Sangyo Co., Ltd., titanium oxide content: 93% by mass, coated metal: alumina, zirconia).
Titanium oxide pigment (B2-5): TR-81 (trade name, manufactured by Huntsman, titanium oxide content: 93% by mass, coated metal: alumina, zirconia).

[Non-fluorine resin (C)]
Polyester resin: CRYLCOAT 4890-0 (trade name, manufactured by Daicel Ornex)

[Curing agent (D)]
Curing agent (D): Blocked isocyanate curing agent (Evonik's Vestagon (trade name) B1530).

[Curing catalyst (E)]
Curing catalyst (E): xylene solution of dibutyltin dilaurate (diluted 10,000 times).
[Surface conditioner (F)]
Plasticizer: 1,4-cyclohexanedimethanol dibenzoate (manufactured by EASTMAN, Benzoflex (trade name) 352)
Leveling agent for powder coatings: (BYK (trade name) -360P, manufactured by Big Chemie)

[Other additives (H)]
Degassing agent: benzoin.

[Examples 1, 2, 4 to 8]
Each component shown in Table 1 was mixed for about 10 to 30 minutes using a high-speed mixer (manufactured by Amagasaki Co., Ltd.) in the parts by mass shown in Table 1 to obtain a powdery mixture. The mixture was melt kneaded at a barrel setting temperature of 120 ° C. using a twin-screw extruder (manufactured by Thermo Prism, 16 mm extruder) to obtain powder pellets. Next, the obtained pellets were pulverized at room temperature using a pulverizer (manufactured by FRITSCH, rotor speed mill P14), classified by a 150 mesh sieve, and the average particle size (50% average volume particle size distribution) was about A 40 μm powder coating was obtained.
The obtained powder coating material was electrostatically coated with an electrostatic coating machine (GX3600C, manufactured by Onoda Cement Co., Ltd.) on one side of the chromate-treated aluminum plate, and held in a 200 ° C. atmosphere for 20 minutes. It was allowed to cool to room temperature to obtain an aluminum plate having a fluorine-containing coating film having a thickness of 55 to 65 μm. As a result of the accelerated weather resistance test (α) using the obtained fluorine-containing coated aluminum plate as a test piece, the gloss retention and color difference described in Table 1 were obtained. The results are shown in Table 1.

[Example 3]
(Manufacturing method of acrylic resin)
2 g of 200 mL of deionized water and reactive emulsifier (manufactured by Sanyo Kasei Kogyo Co., Ltd., Eleminol (trade name) JS-2, succinic acid ester derivative) in a 1 L 4-neck flask equipped with a condenser and a thermometer 2 g of polyoxyethylene nonylphenyl ether (10 mol addition of ethylene oxide) were introduced. When the temperature reached 80 ° C. in a warm bath under a nitrogen stream, 20 mL of a 2 mass% aqueous solution of ammonium persulfate was added. A mixture of 140.2 g of methyl methacrylate, 80.0 g of ethyl methacrylate, and 0.2 g of n-lauryl mercaptan as a chain transfer agent was added dropwise over 1 hour. Immediately after that, 2 mL of a 2 mass% aqueous solution of ammonium persulfate was added to initiate the reaction. After 3 hours, the temperature in the flask was raised to 85 ° C. and held for 1 hour, and then filtered through a 300-mesh wire mesh to obtain a blue-white aqueous dispersion. The aqueous dispersion was frozen and coagulated at −25 ° C., dehydrated and washed, and then vacuum dried at 80 ° C. to obtain 209.2 g of a white powdery acrylic resin. The obtained acrylic resin had a glass transition temperature of 56.6 ° C., a mass average molecular weight of 92,000, and a number average molecular weight of 43,000.

Each component shown in Table 1 was used in parts by mass shown in Table 1 to obtain a powder coating material of Example 3. A powder paint was obtained in the same manner as in Examples 1, 2, 4 to 8, except that the barrel set temperature was 190 ° C. when obtaining the pellets.
The obtained powder coating material was electrostatically coated on one surface of an aluminum plate subjected to chromate treatment with an electrostatic coating machine (GX3600C, manufactured by Onoda Cement Co., Ltd.) and held in a 250 ° C. atmosphere for 20 minutes. The plate was allowed to cool to room temperature to obtain an aluminum plate having a powder coating film having a thickness of 55 to 65 μm. As a result of the accelerated weather resistance test (α) using the obtained powder coated aluminum plate as a test piece, the gloss retention and color difference described in Table 1 were obtained. The results are shown in Table 1.

As shown in Table 1, in Examples 1 and 3 to 6, the gloss retention by the accelerated weather resistance test (α) is 50% or more, and the plasticizer and titanium oxide content is 80 to 92% by mass. Was a powder paint. Further, they had good gloss retention variation and color difference (ΔE) as measured in the accelerated weather resistance test (α).

The fluorine-containing coating film of the present invention is useful as a coating film provided on articles (base materials) used outdoors, and in particular, exterior members (aluminum composite panels, aluminum panels for curtain walls, aluminum frames for curtain walls, This is useful as a fluorine-containing coating provided on an aluminum window frame.

Japanese Patent Application No. 2014-118759 (Application Date: June 9, 2014), Japanese Patent Application No. 2014-177541 (Application Date: September 1, 2014) and Japanese Patent Application No. 2015-0405534 (Application Date). : March 2, 2015), the entire contents of the specification, claims, drawings and abstract are hereby incorporated by reference as the disclosure of the specification of the present invention.

Claims

A fluorine-containing coating film formed from a powder paint containing a fluororesin (A) and a titanium oxide pigment (B),
A fluorine-containing coating film having a gloss retention (%) of 50% or more as measured in a fluorine-containing coating film having undergone the following accelerated weather resistance test (α).
[Accelerated weather resistance test (α)]
This is a test in which xenon arc radiation is applied to a fluorine-containing coating film using a xenon weather meter, except that 1% by mass hydrogen peroxide solution is sprayed on the fluorine-containing coating film instead of water, according to JIS K 5600-7-7. Perform according to Method 1. However, the relative humidity in the test is 70% RH, the black panel temperature is 50 ° C., the irradiation intensity of the xenon light source is 80 W / m 2 in the wavelength range of 300 to 400 nm, the spraying time of hydrogen peroxide water is 3 minutes, Next, the drying time is repeated for 2 minutes.
[Gloss retention]
Calculated according to JIS K 5600-4-7: 1999 (ISO 2813: 1994), the fluorine-containing coating film after 40 hours of xenon arc radiation with respect to the 60 ° gloss value of the fluorine-containing coating film immediately before xenon arc radiation Of 60 ° gloss value (unit:%).
The fluorine-containing coating film according to claim 1, wherein the smoothness visual judgment of the surface smoothness determined using the standard plate for visual judgment of the smoothness of the powder coating film by the powder coating institute is 6 or more.
The fluorine-containing coating film according to claim 1 or 2, wherein a color difference between immediately before the xenon arc radiation and 40 hours after the xenon arc radiation is less than 5.0.
The fluorine-containing coating film according to any one of claims 1 to 3, wherein the titanium oxide pigment (B) is a coated titanium oxide pigment having a titanium oxide content of 80 to 92 mass%.
The powder coating material according to any one of claims 1 to 4, further comprising 0.1 to 15.0 parts by mass of a surface conditioning agent (F) with respect to 100 parts by mass of the fluororesin (A). The fluorine-containing coating film described.
The fluororesin (A) is at least one selected from the group consisting of polyvinylidene fluoride, a hydroxyl group-containing fluoropolymer, and a carboxy group-containing fluoropolymer. The fluorine-containing coating film according to item.
The powder coating material further comprises at least one curing agent (D) selected from the group consisting of a β-hydroxyalkylamide curing agent, a triglycidyl isocyanurate curing agent, and a blocked isocyanate curing agent. The fluorine-containing coating film according to any one of claims 1 to 6, further comprising:
The powder coating material according to any one of claims 1 to 7, further comprising at least one non-fluorine resin (C) selected from the group consisting of an acrylic resin, a polyester resin, and an epoxy resin. Fluorine-containing coating film.
An exterior member provided with the fluorine-containing coating film according to any one of claims 1 to 8 on a base material.