Method for producing powder coating composition, method for forming coating film and toning method

Abstract

To provide a method for producing a powder coating composition capable of achieving a coating film exhibiting a smooth and uniform hue and further to provide a method for forming a coating film using such powder coating composition and a method for toning the powder coating composition.SOLUTION: There is provided a method for producing a powder coating composition which comprises: a step of preparing a clear powder coating composition and two or more primary color powder coating compositions; a step of mixing the clear powder coating composition and a cationic compound (D) selected from a cationic polymer, stearyl trimethylammonium chloride and cetylpyridinium chloride to obtain a premixture 1; a step of mixing the premixture 1 with each of the two or more primary color powder coating compositions to obtain two or more premixtures 2; and a step of mixing the two or more premixtures 2 to obtain a powder coating composition.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present disclosure relates to a method for producing a powder coating composition, a method for forming a coating film, and a method for matching a color. [Background technology]

[0002] In recent years, awareness of reducing environmental load has increased, and there is a demand for replacing conventional products with environmentally friendly products. Among them, powder coating compositions do not contain organic solvents, are easy to recover, and have excellent environmental adaptability, so they are widely used for coating home appliances, automobile parts, steel furniture, etc. Powder coating compositions are usually mixed with multiple colored powder coating compositions to produce a wide range of hues, and are applied to substrates with an electrostatic coating gun or the like.

[0003] For example, Patent Document 1 describes a color matching method in which primary color powder paints suitable for matching to a target color are sequentially selected and combined from a group of achromatic primary color powder paints and a group of chromatic primary color powder paints. Patent Document 2 describes that when mixing and applying two or more powder coatings of different hues, the mass median particle size is set to 1 to 50 μm and the mass distribution variation coefficient is set to 50% or less before the colors are matched. Patent Document 3 describes how, when mixing and applying two or more powder paints of different hues, the difference in the electrostatic charge of the two or more powder paints is set to 5.0 μC / g or less before the colors are mixed. Patent Document 4 describes a method for matching the color of powder paints, which includes a step of dry-blending two or more primary color powder paints of different colors, each having an average particle size of 20 μm or less, to match the colors, and a step of granulating the blend to a particle size within a range suitable for painting by heating the blend with stirring to a temperature at which the particle surfaces melt but the interiors of the particles do not melt. Patent Document 5 describes a composite powder paint obtained by granulating and drying a plurality of primary color powder paints differing in hue and / or type of film-forming resin using a liquid binder, and describes that the liquid binder has a softening temperature of 20 to 200°C and is a liquid binder in which a binder compound having a self-crosslinking functional group and / or a functional group that reacts complementarily with a functional group possessed by the primary color powder paint is dissolved or dispersed in a solvent that does not dissolve the raw powder paint. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2002-155223 A [Patent Document 2] Japanese Patent Application Publication No. 10-219142 [Patent Document 3] Japanese Patent Application Publication No. 10-072557 [Patent Document 4] JP 2000-281978 A [Patent Document 5] International Publication No. 2006 / 057241 Summary of the Invention [Problem to be solved by the invention]

[0005] According to a conventional color matching method, a color-matched powder coating composition (also called a "color-matched powder coating composition") is prepared by mixing powder coating compositions having different hues. The color-matched powder coating composition thus obtained is applied to a substrate by an electrostatic coating gun or the like, and then baked to form a coating film.

[0006] However, when a coating film is formed from such a toned powder coating composition, unevenness may occur in the coating film to a degree that can be recognized by the naked eye, and the hue of the obtained coating film may be uneven. Furthermore, it is necessary to prepare a powder coating composition containing fine powder of each required hue, and the assortment of such compositions is enormous. Therefore, it is not easy to obtain a coating film of a smooth and uniform hue from the toned powder coating composition by toning two or more powder coating compositions with different hues.

[0007] The present disclosure has been made in view of the above circumstances, and aims to provide a method for producing a powder coating composition capable of realizing a coating film exhibiting a smooth and uniform hue. Further, the present disclosure aims to provide a method for forming a coating film using the powder coating composition, and a method for adjusting the color of the powder coating composition. [Means for solving the problem]

[0008] The present disclosure includes the following aspects. [1] Providing a clear powder coating composition and two or more primary color powder coating compositions; The clear powder coating composition; Cationic polymer, stearyltrimethylammonium chloride, and cetylpyridinium chloride a step of mixing the cationic compound (D) to obtain a premixture 1; mixing the premix 1 with each of the two or more primary color powder coating compositions to obtain two or more premixes 2; A step of mixing the two or more premixes 2 to obtain a powder coating composition; A method for producing a powder coating composition comprising the steps of: [2] The method according to [1], wherein the two or more primary color powder coating compositions each have a different hue and / or tone. [3] The method for producing a coating composition according to [1] or [2], wherein the clear powder coating composition and the primary color powder coating composition have an average particle size (D50) of 40 μm or less. [4] The method according to any one of [1] to [3], wherein the cationic compound (D) has an amino group and / or a quaternary ammonium salt group, and the softening point of the cationic compound (D) is 30° C. or higher and 180° C. or lower. [5] The method according to any one of [1] to [4], wherein the clear powder coating composition and the cationic compound (D) are mixed by a wet method. [6] The step of mixing the clear powder coating composition with a cationic compound (D) to obtain a preliminary mixture 1 includes the steps of: mixing the cationic compound (D) with water and / or a hydrophilic solvent to obtain a solution of the cationic compound; mixing the clear powder coating composition with the solution of the cationic compound to obtain a mixture containing a premixture 1; and removing water and / or hydrophilic solvent from the mixture to obtain a premixture 1; The method for producing the same according to any one of [1] to [5], [7] The method according to any one of [1] to [6], wherein the primary color powder coating composition is prepared by mixing a coating film-forming resin (A) and a color pigment (B1). [8] The method according to any one of [1] to [7], wherein the clear powder coating composition is prepared by mixing a coating film-forming resin (A) with an extender pigment (B2). [9] The method according to any one of [1] to [8], wherein the coating film-forming resin (A) contains a polymer having at least one functional group selected from an acid group, a hydroxyl group, and an epoxy group.

[10] The production method according to any one of [1] to [9], wherein the clear coating composition and the primary color powder coating composition further contain a curing agent (C).

[11] A method for forming a coating film, comprising applying a powder coating composition obtained by the production method according to any one of [1] to

[10] to an object to be coated.

[12] 1. A method for matching a powder coating composition, comprising: Providing a clear powder coating composition and two or more primary color powder coating compositions; The clear powder coating composition; Cationic polymer, stearyltrimethylammonium chloride, and cetylpyridinium chloride a step of mixing the cationic compound (D) to obtain a premixture 1; mixing the premix with each of the two or more primary color powder coating compositions to obtain two or more premixes 2; A step of mixing the two or more premixes 2 to prepare a powder coating composition; A color matching method comprising: Effect of the Invention

[0009] According to the present disclosure, it is possible to provide a method for producing a powder coating composition capable of realizing a coating film exhibiting a smooth and uniform hue. Furthermore, the present disclosure can also provide a method for forming a coating film using such a powder coating composition, and a method for adjusting the color of the powder coating composition. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The method for producing the powder coating composition of the present disclosure includes: Providing a clear powder coating composition and two or more primary color powder coating compositions; The clear powder coating composition; Cationic polymer, stearyltrimethylammonium chloride, and cetylpyridinium chloride a step of mixing the cationic compound (D) to obtain a premixture 1; mixing the premix 1 with each of the two or more primary color powder coating compositions to obtain two or more premixes 2; A step of mixing the two or more premixes 2 to obtain a powder coating composition; Includes.

[0011] In the present disclosure, a powder coating composition obtained by mixing two or more types of premixtures 2 is also referred to as a "toned powder coating composition."

[0012] Hereinafter, the "cationic compound selected from a cationic polymer, stearyltrimethylammonium chloride, and cetylpyridinium chloride" will be simply referred to as the cationic compound. Also,In the present disclosure, the process of mixing the clear powder coating composition with the cationic compound (D) is also referred to as the "first granulation process", the process of mixing the pre-mixture 1 with each of two or more primary color powder coating compositions is also referred to as the "second granulation process", and the process of mixing the two or more pre-mixtures 2 is also referred to as the "third granulation process".

[0013] According to the manufacturing method of the powder coating composition of the present disclosure, a coating film showing a smooth and uniform hue can be realized. Furthermore, even on a coating object having depth, a coating film having a uniform hue and a uniform gloss can be obtained, and the obtained coating film can have high smoothness. Although the present disclosure should not be interpreted as being limited to a specific theory, the reason why the manufacturing method of the present disclosure exhibits such an effect is considered to be as follows. That is, in the manufacturing method of the present disclosure, a clear coating composition and a cationic compound are mixed in advance to form a premixture, and a positively charged premixture 1 is used. It is considered that by mixing the premixture 1 with the raw powder coating composition, the positively charged particles (premixture 1) and the negatively charged particles (primary color powder coating composition) are uniformly and electrostatically attracted to each other, and thus an electrically neutral premixture 2 is obtained. It is considered that by further mixing two or more types of such premixtures 2, the distribution bias caused by the type of color pigment, etc. is suppressed, different particles can be uniformly mixed, and a coating film having a uniform hue and uniform gloss can be realized. The uniformity of the hue of the coating film can be evaluated based on the cosmetic properties, uniformity of hue, saturation and brightness, and uniformity of gloss, in addition to mottled appearance, surface unevenness, color separation, etc. on the coating film surface.

[0014] In addition, since the clear coating composition and the primary color powder coating composition are electrostatically bonded via the cationic compound, the powder coating composition after color matching can be easily disintegrated when forming a coating film, resulting in good coating film formability and allowing the formation of a smooth coating film. Furthermore, it is believed that such a coating film has the desired gloss and is less mottled.

[0015] On the other hand, the conventional manufacturing method of a powder coating composition with a toned color is mainly a dry blend method in which a plurality of powder coating compositions are mixed at room temperature or under heating, or a bonding method in which a plurality of powder coating compositions are mixed with a binder. However, when the powder coating composition after the toning by the dry blending method is applied using an electrostatic coating gun or the like to form a coating film, the desired hue and gloss may not be obtained due to differences in the properties (shape, particle size, specific gravity, etc.) of each powder coating composition and differences in coating conditions such as the shape of the coated object. In addition, when a coating film is formed from the powder coating composition after the toning by the bonding method, a smooth coating surface may not be formed, possibly because the particles of the powder coating composition are bonded to each other. The following describes in detail the embodiments of the present invention, but the scope of the present invention is not limited to these embodiments.

[0016] In the method for producing a powder coating composition of the present disclosure, first, a clear powder coating composition and two or more primary color powder coating compositions are prepared.

[0017] (Step of Preparing Primary Color Powder Coating Composition) The primary color powder coating composition may be any powder coating composition having uniform hue, saturation and gloss.

[0018] The two or more primary color powder coating compositions preferably have different hues and / or tones. This allows a toned powder coating composition having a different hue or tone from the primary color powder coating composition to be produced. The number of types of primary color powder coating compositions may be two or more, and may be, for example, preferably 2 to 10 types, more preferably 2 to 8 types.

[0019] The primary color powder coating composition preferably contains at least a film-forming resin (A), and more preferably contains a film-forming resin (A) and a color pigment (B1). Such a primary color powder coating composition is not limited to those containing only one type of film-forming resin (A) and / or one type of color pigment (B1).

[0020] (Coating film forming resin (A)) The film-forming resin (A) preferably contains a polymer having at least one curable functional group selected from an acid group, a hydroxyl group, and an epoxy group. This is believed to facilitate film formation and allow the primary color powder coating composition to be relatively negatively charged. As a result, the preliminary mixture 1 and the two or more primary color powder coating compositions are more likely to interact with each other at the particle level, and the resulting color-matching powder coating composition is believed to be capable of forming a coating film that exhibits a smoother and more uniform hue. Examples of the acid group include a carboxy group, a sulfonic acid group, and a phosphoric acid group, with the carboxy group being preferred.

[0021] The film-forming resin (A) is a film-forming component, and may be, for example, a non-reactive resin such as polyolefin resin (polyethylene, polypropylene, etc.), polyamide resin (nylon resin, etc.), or vinyl chloride resin; or a reactive resin such as epoxy resin, amine resin, acid anhydride resin, polyester resin, melamine resin, acrylic resin, polyester resin / epoxy resin, or polybasic acid resin. The film-forming resin (A) preferably contains one or more selected from acrylic resin, epoxy resin, and polyester resin. For example, from the viewpoint of weather resistance, acrylic resin, or polyester resin may be used, and from the viewpoint of physical performance of the coating film, polyester resin may be used. More specifically, for example, it may be one or more selected from the group consisting of polyester resin having a curable functional group, epoxy resin having a curable functional group, and acrylic resin having a curable functional group.

[0022] The acrylic resin may be a polymer of a monomer mixture containing a (meth)acrylic monomer. The monomer mixture preferably contains a monomer having a functional group capable of reacting with the curing agent (C) described below, and preferably contains a monomer having a functional group capable of reacting with the curing agent (C) and another vinyl monomer copolymerizable with the monomer.

[0023] The monomer containing a functional group capable of reacting with the curing agent (C) may be a monomer containing one or more groups selected from an epoxy group, an acid group, and a hydroxyl group, and preferably a monomer containing one or more groups selected from an epoxy group, a carboxy group, and a hydroxyl group.

[0024] The monomer having an epoxy group includes glycidyl (meth)acrylate. The monomer having a carboxy group includes (meth)acrylic acid. Examples of the monomer having a hydroxyl group include hydroxyl group-containing (meth)acrylic acid esters such as 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, 2-hydroxy-2-methylpropyl (meth)acrylate, 5-hydroxypentyl (meth)acrylate, and 6-hydroxyhexyl (meth)acrylate; addition reaction products of the hydroxyl group-containing (meth)acrylic acid esters with ε-caprolactone, etc. The monomer having a functional group can be used alone or in combination of two or more kinds. In the present disclosure, (meth)acrylic acid means acrylic acid and / or methacrylic acid.

[0025] Examples of other vinyl monomers copolymerizable with the monomer having a functional group include (meth)acrylic acid esters such as methyl (meth)acrylate, ethyl (meth)acrylate, n-, iso-, and tert-butyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and lauryl (meth)acrylate; and aromatic vinyl monomers such as styrene, α-methylstyrene, and vinyltoluene. These vinyl monomers may be used alone or in combination of two or more.

[0026] The content of the acrylic resin in the coating film-forming resin (A) may be preferably 30 parts by mass or more and 100 parts by mass or less, per 100 parts by mass of the total amount of the coating film-forming resin (A).

[0027] The epoxy resin is preferably an epoxy resin having an average of one or more epoxy groups per molecule, and specific examples thereof include bisphenol type epoxy resins (A type, B type, F type, etc.); novolac type phenolic resins such as phenol novolac type epoxy resins and cresol novolac type epoxy resins; reaction products of phenol novolac or o-cresol novolac with bisphenol type epoxy resins (A type, B type, F type, etc.) and epichlorohydrin; reaction products of phenol novolac or o-cresol novolac with bisphenol type epoxy resins (A type, B type, F type, etc.). These epoxy resins can be used alone or in combination of two or more.

[0028] The content of the epoxy resin contained in the coating film-forming resin (A) may be preferably 30 parts by mass or more and 100 parts by mass or less in 100 parts by mass of the total amount of the coating film-forming resin (A).

[0029] The polyester resin may be a condensation polymer of an acid component mainly composed of a polycarboxylic acid and an alcohol component mainly composed of a polyhydric alcohol.

[0030] Examples of the acid component include terephthalic acid, isophthalic acid, phthalic acid, trimellitic acid, pyromellitic acid and their anhydrides, aromatic dicarboxylic acids such as 2,6-naphthalenedicarboxylic acid and 2,7-naphthalenedicarboxylic acid and their anhydrides, saturated aliphatic dicarboxylic acids such as succinic acid, adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, and 1,4-cyclohexanedicarboxylic acid and their anhydrides, lactones such as γ-butyrolactone and ε-caprolactone, aromatic oxymonocarboxylic acids such as p-oxyethoxybenzoic acid, and corresponding hydroxycarboxylic acids, among which terephthalic acid and isophthalic acid are preferred. In addition, from the viewpoint of weather resistance, the content of isophthalic acid in the acid component is preferably 60% by mass or more, and more preferably 80% by mass or more. The acid components can be used alone or in combination of two or more.

[0031] The alcohol components include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,2-pentanediol, 1,4-pentanediol, 1,5-pentanediol, 2,3-pentanediol, 1,4-hexanediol, 1,5-hexanediol, 1,6-hexanediol, 2,5-hexanediol, 3-methyl-1,5-pentanediol, 1,12-dodecanediol, and 1,8-octadecanediol. Examples of the alcohol component include ethanol, diethylene glycol, triethylene glycol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, alkylene oxide adducts of bisphenol A, alkylene oxide adducts of bisphenol S, linear or branched glycols such as neopentyl glycol, trimethylolpropane, glycerin, and trihydric or higher polyhydric alcohols such as pentaerythritol, and among these, ethylene glycol, neopentyl glycol, and 1,6-hexanediol are preferred. Each of the alcohol components may be used alone or in combination of two or more.

[0032] In one embodiment, the film-forming resin (A) may contain one polyester resin, and in another embodiment, it may contain two or more polyester resins. When the film-forming resin (A) contains two or more polyester resins, the mass ratio of the content of the first polyester resin to the content of the second polyester resin may be 3 / 7 to 7 / 3.

[0033] The content of the polyester resin contained in the coating film-forming resin (A) may be preferably 30 parts by mass or more and 100 parts by mass or less in 100 parts by mass of the total amount of the coating film-forming resin (A).

[0034] In the primary color powder coating composition, the film-forming resin (A) may be used alone or in combination of two or more. In one embodiment, the film-forming resin (A) may contain a polyester resin and an epoxy resin. In this embodiment, the mass ratio of the polyester resin to the epoxy resin may be 3 / 7 to 7 / 3.

[0035] The acid value of the film-forming resin (A) may be preferably 10 mgKOH / g or more and 500 mgKOH / g or less, more preferably 20 mgKOH / g or more and 400 mgKOH / g or less, and even more preferably 25 mgKOH / g or more and 300 mgKOH / g or less. In one embodiment, the acid value of the film-forming resin (A) may be preferably 300 mgKOH / g or more. The hydroxyl value of the film-forming resin (A) may be preferably 5 mgKOH / g or more and 200 mgKOH / g or less, more preferably 10 mgKOH / g or more and 150 mgKOH / g or less, and even more preferably 15 mgKOH / g or more and 100 mgKOH / g or less. In one embodiment, the hydroxyl value of the film-forming resin (A) may be preferably 40 mgKOH / g or more, more preferably 60 mgKOH / g or more. The epoxy equivalent of the film-forming resin (A) may be preferably 250 g / mol or more and 600 g / mol or less, more preferably 350 g / mol or more and 500 g / mol or less. In the present disclosure, the acid value and hydroxyl value of a resin refer to the acid value of the solid content and the hydroxyl value of the solid content, respectively, and can be measured in accordance with JIS K 0070. In the present disclosure, the epoxy equivalent can be measured by the hydrochloric acid-pyridine method. When the coating film-forming resin (A) contains two or more resins, the acid value, hydroxyl value and epoxy equivalent may be the average value of the acid value, hydroxyl value and epoxy equivalent of each resin.

[0036] By having the acid value, hydroxyl value or epoxy equivalent of the coating film-forming resin (A) within the above range, it is believed that the surface of the primary color powder coating composition can be appropriately negatively charged, and the clear powder coating composition and two or more primary color powder coating compositions can be mixed more uniformly, making it easier to adjust the color and granulate. In two or more primary color powder coating compositions, the acid value, hydroxyl value or epoxy equivalent of the film-forming resins (A) contained therein may be the same or different.

[0037] The weight average molecular weight of the coating film-forming resin (A) may be preferably 5,000 or more and 500,000 or less, more preferably 5,000 or more and 100,000 or less, and even more preferably 10,000 or more and 50,000 or less. In one embodiment, the weight average molecular weight of the resin having an epoxy group may be preferably 5,000 or more and 100,000 or less, and more preferably 10,000 or more and 50,000 or less. In this disclosure, the weight average molecular weight is a polystyrene equivalent value determined by gel permeation chromatography.

[0038] The softening point of the coating film-forming resin (A) may be, for example, 80° C. or more and 130° C. or less, and preferably 90° C. or more and 120° C. or less. Being within the above range has the advantage that the pigment dispersibility during the production of the powder coating composition is good, and the storage stability of the obtained powder coating composition is good. In addition, the softening point in this disclosure means the Vicat softening temperature measured in accordance with JIS K 7206, with a test load of 10 N and a heating rate of 50° C. / hour.

[0039] The content of the film-forming resin (A) contained in the primary color powder coating composition is preferably 40 parts by mass or more and 70 parts by mass or less, more preferably 45 parts by mass or more and 70 parts by mass or less, per 100 parts by mass of the primary color powder coating composition. When the content of the film-forming resin (A) in the primary color powder coating composition is within the above range, various physical properties such as adhesion to the substrate and water resistance are good, and a coating film of the desired hue and brightness can be obtained. In two or more primary color powder coating compositions, the compositions of the film-forming resins (A) contained therein (types, amounts, and ratios when two or more types of film-forming resins (A) are contained) may be the same or different.

[0040] (Color pigment (B1)) As the color pigment (B1), inorganic or organic pigments that are usually used in powder coatings can be used. The color pigment (B1) can be appropriately selected depending on the hue, brightness, etc. of the coating film. For example, the hue of the coating film can be controlled by using a chromatic pigment, and the brightness and saturation of the coating film can be controlled by using an achromatic pigment. Furthermore, the gloss of the coating film can be controlled by the particle size and content of the color pigment (B1).

[0041] Examples of chromatic inorganic pigments include red iron oxide, chrome titanium yellow, yellow iron oxide, etc., and examples of achromatic inorganic pigments include titanium oxide, carbon black, etc. Examples of chromatic organic pigments include azo, perylene, condensed azo, nitro, nitroso, phthalocyanine, anthraquinone, quinacridone, dioxane, etc., and more specifically, examples of azo pigments include lake red, fast yellow, disazo yellow, permanent red, etc., examples of nitro pigments include naphthol yellow, etc., examples of nitroso pigments include pigment green B, naphthol green, etc., examples of phthalocyanine pigments include phthalocyanine blue, phthalocyanine green, etc., examples of anthraquinone pigments include indanthrene blue, dianthraquinonyl red, etc., examples of quinacridone pigments include quinacridone red, quinacridone violet, etc., and examples of dioxane pigments include carbazole dioxazine violet, etc.

[0042] In the primary color powder coating composition, the content of the color pigment (B1) may be preferably from 0.05 to 90 parts by mass, more preferably from 0.1 to 80 parts by mass, relative to 100 parts by mass of the total amount of the coating film-forming resin (A). In one embodiment, it may be, for example, from 1 to 75 parts by mass, and further from 3 to 70 parts by mass. In the primary color powder coating composition, the content of the color pigment (B1) may vary depending on the type of the color pigment (B1). For example, the content of the inorganic color pigment (B1) may be 0.05 to 90 parts by mass, 10 to 80 parts by mass, or even 15 to 70 parts by mass relative to 100 parts by mass of the total amount of the coating film-forming resin (A), and the content of the organic color pigment (B1) may be 0.05 to 40 parts by mass, or even 0.05 to 30 parts by mass relative to 100 parts by mass of the total amount of the coating film-forming resin (A). In two or more primary color powder coating compositions, the composition of the color pigment (B1) contained therein (type, amount, and ratio when two or more types of color pigment (B1) are contained) may be the same or different.

[0043] (Hardening agent (C)) The primary color powder coating composition of the present invention may contain a curing agent (C) as necessary. In this embodiment, the primary color powder coating composition is produced by mixing the film-forming resin (A), the color pigment (B1) and the curing agent (C). The order of mixing is not particularly limited, and the film-forming resin (A), the color pigment (B1) and the curing agent (C) may be mixed simultaneously, or the film-forming resin (A) and the color pigment (B1) may be mixed in advance, and then the mixture may be further mixed with the curing agent (C).

[0044] The curing agent (C) is not particularly limited and may be a known curing agent (C) used in powder coatings. Examples of the curing agent (C) include polycarboxylic acid compounds, acid anhydrides, amino group-containing compounds, epoxy group-containing compounds, β-hydroxyalkylamide compounds (HAA), blocked isocyanate compounds, and amino resins. In one embodiment, when the coating film-forming resin (A) contains a polymer having an epoxy group, the curing agent (C) is preferably one or more selected from polyvalent carboxylic acid compounds, acid anhydrides, and amino group-containing compounds. In another embodiment, when the coating film-forming resin (A) contains a polymer having an acid group, the curing agent (C) is preferably one or more selected from epoxy group-containing compounds and β-hydroxyalkylamide compounds. In yet another embodiment, when the coating film-forming resin (A) contains a polymer having a hydroxyl group, the curing agent (C) is preferably a blocked isocyanate compound or an amino resin.

[0045] When matte properties are taken into consideration, the primary color powder coating composition (B) preferably contains, for example, at least one selected from the group consisting of β-hydroxyalkylamide compounds, blocked isocyanates, and melamine compounds.

[0046] Examples of the polycarboxylic acid compound include aliphatic polycarboxylic acids such as adipic acid, sebacic acid, azelaic acid, decanedicarboxylic acid, hexadecanedicarboxylic acid, eicosanedicarboxylic acid, and tetraeicosanedicarboxylic acid; aromatic polycarboxylic acids such as isophthalic acid and trimellitic acid; alicyclic polycarboxylic acids such as hexahydrophthalic acid and tetrahydrophthalic acid; and among these, decanedicarboxylic acid is preferred. These may be used alone or in combination of two or more.

[0047] Examples of the acid anhydride include the following aliphatic, alicyclic, and aromatic acid anhydrides. Examples of the aliphatic acid anhydride include succinic anhydride, maleic anhydride, citraconic anhydride, polyadipic anhydride, polyazelaic anhydride, polysebacic anhydride; dodecenyl succinic anhydride, which is liquid at room temperature, poly(ethyloctadecanedioic) anhydride, and poly(phenylhexadecanedioic) anhydride. Examples of the alicyclic acid anhydride include hexahydrophthalic anhydride, tetrahydrophthalic anhydride, methylcyclohexene dicarboxylic anhydride, HET acid anhydride, himic anhydride, methylcyclohexene tricarboxylic anhydride; and methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, methyl himic anhydride, which are liquid at room temperature. Examples of aromatic acid anhydrides include phthalic anhydride, trimellitic anhydride, pyromellitic anhydride, tetrabromophthalic anhydride, tetrachlorophthalic anhydride, benzophenone tetracarboxylic anhydride, ethylene glycol bis(anhydrotrimellitate), and glycerol tris(anhydrotrimellitate).

[0048] Examples of the amino group-containing compound include dicyandiamide, polyamine compounds, imidazole, etc. Examples of the polyamine compound include polyhydrazide compounds such as adipic acid dihydrazide and sebacic acid dihydrazide. Examples of the imidazole include imidazole compounds containing an alkyl group or a substituted alkyl group as a substituent, such as 2-methylimidazole, 2-ethylimidazole, 2-heptadecylimidazole, 1-benzyl-2-methylimidazole, and 1-(2-cyanoethyl)-2-undecylimidazole; imidazole compounds containing an aminotriazine ring, such as 1-[2-(4,6-diamino-1,3,5-triazin-2-yl)ethyl]-2-methylimidazole and 1-[2-(4,6-diamino-1,3,5-triazin-2-yl)ethyl]-2-ethyl-4-methylimidazole; and salts of imidazole and carboxylic acid, such as a salt of 1-cyanoethyl-2-ethyl-4-methylimidazole and trimellitic acid or a salt of 1-cyanoethyl-2-methylimidazole and trimellitic acid. The polyvalent carboxylic acid compound, the acid anhydride and the amino group-containing compound can be used in combination with a known curing accelerator to adjust the curing speed. The curing accelerator is not particularly limited, but examples thereof include tertiary amines such as triethylamine and benzyldimethylamine, imidazoles such as 2-methylimidazole and 2-ethyl-4-methylimidazole and their precursors, imidazoline compounds, quaternary ammonium salts such as tetramethylammonium bromide and benzyltrimethylammonium bromide, phosphines such as triphenylphosphine and n-butyltriphenyl, and phosphonium salts.

[0049] The epoxy group-containing compound is a compound having one or more epoxy groups in one molecule, and examples thereof include triglycidyl isocyanurate, the epoxy resins, and epoxy group-containing acrylic resins.

[0050] The β-hydroxyalkylamide compound (HAA) can be a compound represented by the following formula (I):

[0051] [ka] (In the formula, R 1 is a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, R 2 represents an alkylene group having 1 to 12 carbon atoms). An example of such a compound that is commercially available is Primid XL-552.

[0052] The blocked isocyanate compound refers to blocked isocyanates in which the isocyanate groups are blocked with a blocking agent to prevent them from exhibiting activity at or below a certain temperature, and uretdiones in which isocyanate groups are reacted with each other to form uretdione rings to prevent them from exhibiting activity. The blocked isocyanate compound is a polyisocyanate compound in which the isocyanate group is blocked with a blocking agent.

[0053] Examples of the polyisocyanate compound include aliphatic diisocyanate compounds such as hexamethylene diisocyanate, trimethylene diisocyanate, 1,4-tetramethylene diisocyanate, pentamethylene diisocyanate, lysine diisocyanate, and 1,3-butylene diisocyanate; alicyclic diisocyanate compounds such as isophorone diisocyanate, 4,4'-methylenebis(cyclohexyl isocyanate), methylcyclohexane-2,4-(or -2,6-) diisocyanate, 1,3-(or 1,4-)di(isocyanatomethyl)cyclohexane, 1,4-cyclohexane diisocyanate, 1,3-cyclopentane diisocyanate, and 1,2-cyclohexane diisocyanate; xylylene diisocyanate, metaxylylene diisocyanate, tetramethylxylylene diisocyanate, tolylene diisocyanate, 4,4' aromatic diisocyanate compounds such as diphenylmethane diisocyanate, (m- or p-)phenylene diisocyanate; polyisocyanate compounds having three or more isocyanate groups, such as triphenylmethane-4,4',4"-triisocyanate; adducts obtained by reacting a polyisocyanate compound in an amount such that the amount of isocyanate groups is in excess with respect to the hydroxyl groups of a polyol, such as ethylene glycol, propylene glycol, 1,4-butylene glycol, polyalkylene glycol, trimethylolpropane, hexanetriol, etc.; biuret type adducts and isocyanuric ring type adducts, such as hexamethylene diisocyanate, isophorone diisocyanate, tolylene diisocyanate, xylylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 4,4'-methylenebis(cyclohexylisocyanate), etc.

[0054] Examples of blocking agents used to block the polyisocyanate compound include phenol-based, lactam-based, oxime-based, pyrazole-based, triazole-based, etc. Specific examples of these blocking agents include phenol-based blocking agents such as phenol, cresol, xylenol, nitrophenol, chlorophenol, ethylphenol, hydroxydiphenyl, t -butylphenol, methyl hydroxybenzoate, etc.; lactam blocking agents include ε-caprolactam, δ-valerolactam, γ-butyrolactam, β-propiolactam, etc.; oxime blocking agents include acetamide oxime, formamide oxime, acetone oxime, methyl ethyl ketone oxime, butanone oxime, methyl isobutyl ketone oxime, methyl amyl ketone oxime, diacetyl monooxime, benzophenone oxime, cyclohexanone oxime, methylhexanone oxime, etc.; pyrazole blocking agents include 1,2-pyrazole, 3,5-dimethylpyrazole, etc.; triazole blocking agents include 1H-1,2,4-triazole, 1H-1,2,3-triazole, 1H-1,2,4-triazole-3-thiol, 1H-1,2,3-triazolo[4,5-b]pyridine, etc.

[0055] Examples of the amino resin include melamine resin, urea resin, and benzoguanamine resin. The amino resin is obtained by condensing an amino compound with an aldehyde compound and then etherifying the resulting mixture with a lower monohydric alcohol. Examples of the amino resin include melamine, urea, and benzoguanamine. Examples of the aldehyde compound include formaldehyde and acetaldehyde. Examples of the lower monohydric alcohol include methanol, ethanol, propanol, and butanol.

[0056] The curing agent (C) may contain other curing agents (C). Examples of the curing agent (C) include polyisocyanate compounds such as tris(2,3-epoxypropyl)isocyanate, tolylene diisocyanate, and xylylene diisocyanate, or blocked isocyanate groups at the molecular terminals of prepolymers thereof with conventional blocking agents such as lactam compounds and oxime compounds; epoxy curing agents such as bisphenol A diglycidyl ether; alkoxysilane curing agents such as methoxysiloxane oligomers and ethoxysilane oligomers; polyaziridine curing agents such as adipic acid dihydrazide and succinic acid dihydrazide; and oxazoline curing agents such as 1,4-bis(2-oxazolinyl-2)-benzene and 1,2,4-tris(2-oxazolinyl-2)-benzene.

[0057] In one embodiment, the primary color powder coating composition may contain, as the film-forming resin (A), a polyester or acrylic resin having a hydroxyl group, and, as the curing agent (C), a blocked isocyanate blocked with at least one blocking agent selected from the group consisting of oxime-based, pyrazole-based, and triazole-based blocking agents.

[0058] In this embodiment, the average hydroxyl value of the hydroxyl-containing polyester or acrylic resin is preferably 40 mgKOH / g or more, and more preferably 60 mgKOH / g or more, from the viewpoint of the matting effect. The blocked isocyanate is preferably a blocked isocyanate blocked with at least one blocking agent selected from the group consisting of methyl isobutyl ketone oxime, methyl ethyl ketone oxime, 1,2-pyrazole, 3,5-dimethylpyrazole, 1H-1,2,4-triazole, 1H-1,2,3-triazole, 1H-1,2,4-triazole-3-thiol, and 1H-1,2,3-triazolo[4,5-b]pyridine. In order to obtain a sufficient matte effect, the blocked isocyanate preferably has a dissociation temperature of the blocking agent or uretdione ring of 160° C. or less, more preferably 140° C. or less.

[0059] The amount of the curing agent (C) in the primary color powder coating composition varies depending on the type of the coating film-forming resin (A) and the curing agent (C), and can be appropriately set. For example, the amount of the curing agent (C) is preferably 1 part by mass or more and 200 parts by mass or less, more preferably 5 parts by mass or more and 100 parts by mass or less, per 100 parts by mass of the total amount of the coating film-forming resin (A). In one embodiment, when a film-forming resin (A) having a hydroxyl group is used as the film-forming resin (A) of the primary color powder coating composition, it is preferable to use the blocked isocyanate as the curing agent (B), and the content of the blocked isocyanate may be preferably 10 parts by mass or more and 80 parts by mass or less, more preferably 15 parts by mass or more and 60 parts by mass or less, per 100 parts by mass of the film-forming resin (A) having a hydroxyl group.

[0060] The curing agent (C) in the present disclosure is preferably used in an amount such that the equivalent ratio (hereinafter also referred to as the "equivalent ratio of reactive groups") between the total of acid groups, hydroxyl groups, and epoxy groups contained in the coating film-forming resin (A) and the total of groups capable of reacting with acid groups, hydroxyl groups, and epoxy groups (e.g., acid groups, hydroxyl groups, amino groups, and isocyanate groups) contained in the curing agent (C) is, for example, preferably 0.1 or more and 3 or less, more preferably 0.8 or more and 1.2 or less.

[0061] In one embodiment, the primary color powder coating composition may contain a resin having a hydroxyl group and a resin having an epoxy group as the coating film-forming resin (A), and may contain a carboxyl group-containing compound and a blocked isocyanate as the curing agent (C). By using such a primary color powder coating composition, a higher matte effect can be obtained and popping and show-through can be prevented. Here, "popping" refers to a coating abnormality formed by foaming on the surface or inside of the coating film when applying the powder coating composition, and "see-through" refers to a situation in which the surface of the coated object is not sufficiently concealed by the coating film, allowing the surface of the coated object to be seen through the coating film.

[0062] In the same embodiment, the resin having an epoxy group may be an acrylic resin having an epoxy group and / or an epoxy resin, and from the viewpoint of the matte effect, it is preferably an acrylic resin having an epoxy group.

[0063] In the same embodiment, the blocked isocyanate may be any of the blocked isocyanates described above, and preferably includes a blocked isocyanate blocked with ε-caprolactam. The content of the blocked isocyanate blocked with ε-caprolactam may be preferably 20% by mass or more, more preferably 50% by mass or more, based on 100% by mass of the total amount of the blocked isocyanates. When the content is within the above range, foaming can be suppressed.

[0064] The content of the blocked isocyanate is preferably 15 parts by mass or more and 60 parts by mass or less, more preferably 20 parts by mass or more and 60 parts by mass or less, based on 100 parts by mass of the total amount of the resin having a hydroxyl group, the resin having an epoxy group, and the carboxy group-containing compound. When the content of the blocked isocyanate is within the above range, a good matting effect is obtained, and foaming on the surface or inside of the coating film can be suppressed.

[0065] Furthermore, in the same embodiment, the molar ratio of epoxy groups to carboxy groups (epoxy groups / carboxy groups) contained in the primary color powder coating composition may be preferably 0.5 to 2.0, more preferably 0.8 to 1.2. When the ratio is within the above range, the resulting coating film may have good matte properties and water resistance. In two or more primary color powder coating compositions, the composition of the curing agent (C) that may be contained (type, amount, and ratio when two or more types of curing agent (C) are contained) may be the same or different.

[0066] In the same embodiment, the combination of the film-forming resin (A) and the curing agent (C) is preferably such that the film-forming resin (A) contains a polyester resin having a hydroxyl group and / or an acrylic resin having a hydroxyl group, and the curing agent (C) contains a blocked isocyanate blocked with at least one blocking agent selected from the group consisting of oxime-based, pyrazole-based and triazole-based blocking agents; or the film-forming resin (A) contains a resin having a hydroxyl group and a resin having an epoxy group, and the curing agent (C) contains a carboxyl group-containing compound and a blocked isocyanate. In the above two combinations, the molar ratio of the hydroxyl group and the blocked isocyanate contained in the film-forming resin (A) (hydroxyl group / blocked isocyanate) is preferably 0.5 or more and 2.0 or less, more preferably 0.8 or more and 1.2 or less. When the ratio is within the above range, the matte effect and the physical properties of the resulting coating film are good.

[0067] (curing catalyst) The primary color powder coating composition may further contain a curing catalyst. By containing the curing catalyst, it is easy to adjust the gel time (the time until the coating film is cured). Examples of the curing catalyst include tin-based catalysts, imidazole compounds, imidazoline compounds, metal complexes of imidazole compounds and / or imidazoline compounds, tertiary phosphine compounds, quaternary phosphonium salts, and quaternary ammonium salts.

[0068] Examples of the tin catalyst include dibutyltin dilaurate, dibutyltin distearate, tin bis(2-ethylhexanoate), n-butyltris(2-ethylhexanoate), di-n-butylbis(2-ethylhexanoate), di-n-butylbis(2,4-pentanedionate), dioctyldilauryltin, tetra-n-butyltin, tetra-n-octyltin, dibutyltin diacetate, tetrabutyldiacetoxydistannoxane, tin acetylacetone, dibutyltin oxide, and dimethyltin oxide.

[0069] The imidazole compound is not particularly limited, and examples thereof include alkyl imidazoles such as 2-ethyl-4-methylimidazole, 1-methylimidazole, 1,2-dimethylimidazole, 2-methylimidazole, 2-ethylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, and 2-isopropylimidazole; carbamylalkyl-substituted imidazoles such as 1-(2-carbamylethyl)imidazole; and 1-cyanoethyl-2-methylimidazole. Examples of the imidazoles include cyanoalkyl-substituted imidazoles such as 2-phenylimidazole, 2-phenyl-4-methylimidazole, aromatic-substituted imidazoles such as 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, alkenyl-substituted imidazoles such as 1-vinyl-2-methylimidazole, allyl-substituted imidazoles such as 1-allyl-2-ethyl-4-methylimidazole, and polyimidazoles, and preferably, alkylimidazoles and aromatic-substituted imidazoles.

[0070] The imidazoline compound is not particularly limited, but examples thereof include 2-phenylimidazole, 2-methylimidazoline, 2-undecylimidazoline, and 2-heptadecylimidazoline.

[0071] Examples of the metal complex of the imidazole compound and / or the imidazoline compound include a complex of the imidazole compound or the imidazoline compound with a metal salt. The metal salt is not particularly limited, but examples thereof include a complex of a metal such as copper, nickel, cobalt, calcium, zinc, zirconium, silver, chromium, manganese, tin, iron, titanium, antimony, or aluminum with a salt such as chloride, bromide, fluoride, sulfate, nitrate, acetate, malate, stearate, benzoate, or methacrylate.

[0072] The tertiary phosphine compound is not particularly limited, but examples thereof include triphenylphosphine, tritolylphosphine, and the like.

[0073] The quaternary phosphonium salt is not particularly limited, but examples thereof include benzyltriphenylphosphonium chloride, butyltriphenylphosphonium bromide, ethyltriphenylphosphonium iodide, and ethyltriphenylphosphonium bromide.

[0074] The quaternary ammonium salt is not particularly limited, but examples thereof include tetraethylammonium chloride, tetraethylammonium bromide, and benzyltrimethylammonium bromide.

[0075] The curing catalyst may be, for example, 0.0001 parts by mass or more and 10 parts by mass or less in 100 parts by mass of each primary color powder coating composition. By keeping the content of the curing catalyst within the above range, the gel time of the obtained powder coating composition can be adjusted to a desired range.

[0076] (Other additives) The primary color powder coating composition may further contain other additives. As the other additives, additives commonly used in the field of powder coatings can be used, such as heat stabilizers, light stabilizers, slip agents, lubricants, plasticizers, antistatic agents, crystal nucleating agents, flow agents such as acrylate polymers, crosslinking accelerators such as various catalysts and organic tin compounds, pinhole inhibitors such as benzoin, extender pigments, modifiers, surface conditioners, ultraviolet absorbers, antioxidants, and popping inhibitors. When these additives are contained, the amount of each can be 0.1 parts by mass or more and 5 parts by mass relative to 100 parts by mass of the coating film-forming resin (A).

[0077] By including the above-mentioned extender pigment, it is possible to easily adjust the specific gravity of the primary color powder coating composition and to improve the mechanical properties of the resulting coating film. Examples of the extender pigment include talc, silica, calcium carbonate, barium sulfate, etc.

[0078] In the primary color powder coating composition, the content of the extender pigment may be preferably from 0 to less than 15 parts by mass, more preferably from 0 to less than 10 parts by mass, and even more preferably from 0 to less than 5 parts by mass, per 100 parts by mass of the total amount of the coating film-forming resin (A).

[0079] The modifier may be a resin different from the film-forming resin (A), and examples thereof include polyester resin, polyethylene resin, modified polyethylene resin, epoxy resin, ethylene vinyl acetate resin, ethylene ethyl acrylate resin, ethylene acrylic acid resin, nylon, etc. Among these, thermoplastic resins having a relatively low softening point, such as polyethylene resin, modified polyethylene resin, and ethylene acrylic acid resin, are preferred. The content of the modifier may be preferably 0.1 parts by mass or more and 50 parts by mass or less, based on 100 parts by mass of the film-forming resin (A).

[0080] The surface modifier can adhere to the surface of the powder coating material and control the fluidity and electrostatic charge of the powder coating material. Examples of the surface modifier include inorganic fine particles such as silica and aluminum oxide (alumina); and organic particles such as acrylic resin. The particle diameter of the surface modifier can be, for example, 1 μm or more and 50 μm or less. The content of the surface modifier can be, for example, 0.01 parts by mass or more and 5 parts by mass or less in 100 parts by mass of each primary color powder coating composition. In the manufacturing method disclosed herein, the surface modifier is not essential, and even if the surface modifier is not added, a powder coating composition capable of realizing a coating film showing a smooth and uniform hue can be manufactured.

[0081] The primary color powder coating composition may have an average particle size (D50) of preferably 1 μm or more and 40 μm or less, more preferably 1 μm or more and 25 μm or less, even more preferably 5 μm or more and 23 μm or less, and even more preferably 5 μm or more and 20 μm or less. When the primary color powder coating composition has an average particle size (D50) in the above range, a coating film showing a smoother and more uniform hue is easily obtained.

[0082] In the present disclosure, unless otherwise specified, the average particle size refers to the volume average particle size (D50). The volume average particle size (D50) can be measured using a particle size measuring device such as a laser diffraction / scattering type particle size distribution measuring device (Microtrack, manufactured by Nikkiso Co., Ltd.).

[0083] (Preparation of Primary Color Powder Coating Composition) The primary color powder coating composition may be prepared by purchasing a commercial product, or may be prepared by manufacturing. The primary color powder coating composition can be manufactured by a known method. For example, it can be manufactured by a manufacturing method including mixing the coating film-forming resin (A) with the color pigment (B1), curing agent (C), curing catalyst, and other additives used as necessary (mixing step), melt-kneading the obtained mixture (melting kneading step), and cooling the obtained melt-kneaded product (cooling step) and pulverizing (pulverizing step), and the manufacturing method may further include classifying the obtained pulverized product.

[0084] The order of mixing the film-forming resin (A), the color pigment (B1), the curing agent (C), the curing catalyst, and other additives is not particularly limited. In one embodiment, the film-forming resin (A) and the color pigment (B1) are mixed with the curing catalyst and other additives, and then mixed with the curing agent (C), but is not limited thereto. The mixing can be carried out using a super mixer, a ribbon blender, a drum blender, a Henschel mixer, etc. The mixing is preferably carried out at room temperature, for example, at 10 to 40°C, preferably 15 to 35°C.

[0085] The melt kneading can be carried out using a kneader such as a kneader or an extruder. The heating temperature during melt kneading is lower than the bake hardening temperature, and is a temperature at which at least a part of the raw materials can be melted and the whole can be kneaded, and is generally preferably about 80 to 140°C. In one embodiment, the kneading is carried out at a temperature of 80 to 120°C. In the present invention, when melt kneading is performed, the kneading temperature is higher than the granulation temperature in the second and third granulation steps described below, for example, higher than the softening point of the film-forming resin (A) having the highest softening point among the film-forming resins (A) contained in the primary color powder coating composition.

[0086] The melt kneaded product can be cooled, for example, by a cooling roll, a cooling conveyor, or the like. The obtained solidified product can be pulverized in one step or in two or more steps. For example, the product can be coarsely pulverized and then finely pulverized. The pulverization can be performed using a pulverizing device such as a hammer mill or a jet impact mill.

[0087] By the classification, large particles and small particles can be removed, and the particle size distribution can be narrowed. For example, an air classifier, a vibration sieve, an ultrasonic sieve, etc. can be used for the classification. By the classification, the average particle size of the obtained particles may be adjusted to 15 to 30 μm.

[0088] (Step of Preparing Clear Powder Coating Composition) The clear powder coating composition may be any composition that has a reduced effect on the hue, chroma, and gloss of the resulting powder coating composition. The clear powder coating composition preferably contains at least a film-forming resin, and more preferably contains a film-forming resin and an extender pigment (B2). The clear powder coating composition is not limited to one that contains only one type of film-forming resin and / or one type of extender pigment (B2).

[0089] As the film-forming resin used in the clear powder coating composition, any of the resins described as the film-forming resin (A) used in the primary color powder coating composition can be used. The film-forming resin may be used alone or in combination of two or more kinds.

[0090] In the film-forming resin used in the clear powder coating composition, the content of the acrylic resin may be preferably 30 parts by mass or more and 100 parts by mass or less in 100 parts by mass of the total amount of the film-forming resin.

[0091] In the film-forming resin used in the clear powder coating composition, the content of the epoxy resin may be preferably 30 parts by mass or more and 100 parts by mass or less in 100 parts by mass of the total amount of the film-forming resin.

[0092] The film-forming resin used in the clear powder coating composition may contain one of the polyester resins, and in another embodiment, may contain two or more of the polyester resins. When the film-forming resin contains two or more of the polyester resins, the mass ratio of the first polyester resin to the second polyester resin may be 3 / 7 to 7 / 3.

[0093] In the film-forming resin used in the clear powder coating composition, the content of the polyester resin may be preferably 30 parts by mass or more and 100 parts by mass or less in 100 parts by mass of the total amount of the film-forming resin.

[0094] The acid value of the film-forming resin used in the clear powder coating composition may be preferably 10 mgKOH / g or more and 500 mgKOH / g or less, more preferably 20 mgKOH / g or more and 400 mgKOH / g or less, and even more preferably 25 mgKOH / g or more and 300 mgKOH / g or less. In one embodiment, the acid value of the film-forming resin used in the clear powder coating composition may be preferably 300 mgKOH / g or more. The hydroxyl value of the film-forming resin used in the clear powder coating composition may be preferably 5 mgKOH / g or more and 200 mgKOH / g or less, more preferably 10 mgKOH / g or more and 150 mgKOH / g or less, and even more preferably 15 mgKOH / g or more and 100 mgKOH / g or less. In one embodiment, the hydroxyl value of the film-forming resin used in the clear powder coating composition may be preferably 40 mgKOH / g or more, more preferably 60 mgKOH / g or more. The epoxy equivalent of the film-forming resin used in the clear powder coating composition may be preferably 250 g / mol or more and 600 g / mol or less, more preferably 350 g / mol or more and 500 g / mol or less.

[0095] When the acid value, hydroxyl value or epoxy equivalent of the coating film-forming resin used in the clear powder coating composition is within the above range, the surface of the clear powder coating composition can be appropriately negatively charged, and adhesion to the cationic compound (D) described below can be improved.

[0096] The weight average molecular weight of the film-forming resin used in the clear powder coating composition may be preferably 5,000 to 500,000, more preferably 5,000 to 100,000, and even more preferably 10,000 to 50,000. In one embodiment, the weight average molecular weight of the resin having an epoxy group may be preferably 5,000 to 100,000, and more preferably 10,000 to 50,000.

[0097] The softening point of the film-forming resin used in the clear powder coating composition may be, for example, from 80° C. to 130° C., and preferably from 90° C. to 120° C. If it is within the above range, there are advantages in that the pigment dispersibility is good during the production of the clear powder coating composition, and the storage stability of the obtained clear powder coating composition is good.

[0098] The content of the film-forming resin contained in the clear powder coating composition is preferably 40 parts by mass or more and 70 parts by mass or less, more preferably 45 parts by mass or more and 70 parts by mass or less, per 100 parts by mass of the clear powder coating composition. When the content of the film-forming resin in the clear powder coating composition is within the above range, various physical properties such as adhesion to a substrate and water resistance can be good.

[0099] (Extender pigment (B2)) As the extender pigment (B2), a powder coating material that is generally used in powder coating materials can be used. By including the above, it is possible to easily adjust the specific gravity of the clear powder coating composition, and also to improve the mechanical properties of the resulting coating film.

[0100] Examples of extender pigments (B2) include talc, clay, calcium carbonate, magnesium carbonate, barium sulfate, silicon dioxide, silicic acid, silicates, aluminum oxide hydrate, calcium sulfate, gypsum, mica, micaceous iron oxide (MIO), glass flakes, suzolite mica, and clarite mica.

[0101] In the clear powder coating composition, the content of the extender pigment (B2) may be preferably from 5 to 90 parts by mass, more preferably from 10 to 80 parts by mass, and even more preferably from 20 to 70 parts by mass, per 100 parts by mass of the total amount of the coating film-forming resins.

[0102] The clear powder coating composition may contain a curing agent as required. As such a curing agent, any of the curing agents described as the curing agent (C) that may be contained in the primary color powder coating composition may be used.

[0103] In the clear powder coating composition, the amount of the curing agent varies depending on the type of the coating film-forming resin and the curing agent, and can be appropriately set. For example, the amount of the curing agent is preferably 1 part by mass or more and 200 parts by mass or less, more preferably 5 parts by mass or more and 100 parts by mass or less, relative to 100 parts by mass of the total amount of the coating film-forming resin. In one embodiment, when a film-forming resin having a hydroxyl group is used as the film-forming resin of the clear powder coating composition, it is preferable to use the blocked isocyanate as a curing agent, and the content of the blocked isocyanate can be preferably 10 parts by mass or more and 80 parts by mass or less, more preferably 15 parts by mass or more and 60 parts by mass or less, per 100 parts by mass of the film-forming resin having a hydroxyl group.

[0104] In the clear powder coating composition, the curing agent is preferably used in an amount such that the equivalent ratio (hereinafter also referred to as the "equivalent ratio of reactive groups") between the total of acid groups, hydroxyl groups, and epoxy groups contained in the coating film-forming resin and the total of groups capable of reacting with acid groups, hydroxyl groups, and epoxy groups (e.g., acid groups, hydroxyl groups, amino groups, and isocyanate groups) contained in the curing agent is, for example, preferably 0.1 or more and 3 or less, more preferably 0.8 or more and 1.2 or less.

[0105] In one embodiment, the clear powder coating composition may contain a resin having a hydroxyl group and a resin having an epoxy group as a coating film-forming resin, and may contain a carboxyl group-containing compound and a blocked isocyanate as a curing agent. By using such a clear powder coating composition, a higher matte effect can be obtained and popping and see-through can be prevented.

[0106] In the same embodiment, the resin having an epoxy group may be an acrylic resin having an epoxy group and / or an epoxy resin, and from the viewpoint of the matte effect, it is preferably an acrylic resin having an epoxy group.

[0107] In the same embodiment, the blocked isocyanate may be any of the blocked isocyanates described above, and preferably includes a blocked isocyanate blocked with ε-caprolactam. The content of the blocked isocyanate blocked with ε-caprolactam may be preferably 20% by mass or more, more preferably 50% by mass or more, based on 100% by mass of the total amount of the blocked isocyanates. When the content is within the above range, foaming can be suppressed.

[0108] The content of the blocked isocyanate is preferably 15 parts by mass or more and 60 parts by mass or less, more preferably 20 parts by mass or more and 60 parts by mass or less, based on 100 parts by mass of the total amount of the resin having a hydroxyl group, the resin having an epoxy group, and the carboxy group-containing compound. When the content of the blocked isocyanate is within the above range, a good matting effect is obtained, and foaming on the surface or inside of the coating film can be suppressed.

[0109] Furthermore, in the same embodiment, the molar ratio of epoxy groups to carboxy groups (epoxy groups / carboxy groups) contained in the clear powder coating composition may be preferably 0.5 to 2.0, more preferably 0.8 to 1.2. When the ratio is within the above range, the resulting coating film may have good matte properties and water resistance.

[0110] In the same embodiment, the combination of the film-forming resin and the curing agent is preferably a combination in which the film-forming resin contains a polyester resin having a hydroxyl group and / or an acrylic resin having a hydroxyl group, and the curing agent contains a blocked isocyanate blocked with at least one blocking agent selected from the group consisting of oxime-based, pyrazole-based and triazole-based blocking agents; or a combination in which the film-forming resin contains a resin having a hydroxyl group and a resin having an epoxy group, and the curing agent contains a carboxyl group-containing compound and a blocked isocyanate. In the above two combinations, the molar ratio of the hydroxyl group and the blocked isocyanate contained in the film-forming resin (hydroxyl group / blocked isocyanate) can be preferably 0.5 or more and 2.0 or less, more preferably 0.8 or more and 1.2 or less. When the ratio is within the above range, the matte effect and the physical properties of the resulting coating film are good.

[0111] (curing catalyst) The clear powder coating composition may further contain a curing catalyst. As such a curing catalyst, any of the curing catalysts described as the curing catalyst that can be contained in the primary color powder coating composition can be used.

[0112] The curing catalyst may be, for example, 0.0001 parts by mass or more and 10 parts by mass or less in 100 parts by mass of the clear powder coating composition. By keeping the content of the curing catalyst within the above range, the gel time of the obtained powder coating composition can be adjusted to a desired range.

[0113] (Other additives) The clear powder coating composition may further contain other additives. As other additives, additives commonly used in the field of powder coatings can be used, such as heat stabilizers, light stabilizers, slip agents, lubricants, plasticizers, antistatic agents, crystal nucleating agents, flow agents such as acrylate polymers, crosslinking accelerators such as various catalysts and organic tin compounds, pinhole inhibitors such as benzoin, coloring pigments, modifiers, surface conditioners, ultraviolet absorbers, antioxidants, and popping inhibitors. When these additives are contained, the amount of each can be 0.1 parts by mass or more and 5 parts by mass relative to 100 parts by mass of the coating film-forming resin.

[0114] In the clear powder coating composition, the content of the coloring pigment may be preferably 0 parts by mass or more and less than 3 parts by mass, more preferably 0 parts by mass or more and less than 0.1 parts by mass, and even more preferably 0 parts by mass or more and less than 0.05 parts by mass, relative to 100 parts by mass of the coating film-forming resin.

[0115] The average particle diameter (D50) of the clear powder coating composition is preferably 1 μm or more and 70 μm or less, more preferably 3 μm or more and 60 μm or less, even more preferably 5 μm or more and 50 μm or less, and even more preferably 10 μm or more and 40 μm or less. When the average particle diameter (D50) of the clear powder coating composition is within the above range, a coating film showing a smoother and more uniform hue is easily obtained. (Preparation of clear powder coating composition) The clear powder coating composition may be prepared by purchasing a commercial product, or may be prepared by manufacturing. The clear powder coating composition may be manufactured by a known method. For example, the clear powder coating composition may be manufactured by a manufacturing method including mixing the film-forming resin with the body pigment (B2) used as necessary, a curing agent, a curing catalyst, and other additives (mixing step), melt-kneading the obtained mixture (melting kneading step), and cooling the obtained melt-kneaded product (cooling step) and pulverizing (pulverizing step), and the manufacturing method may further include classifying the obtained pulverized product.

[0116] The order of mixing the film-forming resin, the body pigment (B2) used as necessary, the curing agent, the curing catalyst and other additives is not particularly limited. In one embodiment, the film-forming resin and the body pigment (B2) are mixed with the curing catalyst and other additives, and then the curing agent is further mixed, but the order is not limited thereto. The mixing can be carried out using a super mixer, a ribbon blender, a drum blender, a Henschel mixer, etc. The mixing is preferably carried out at room temperature, for example, at 10 to 40°C, preferably 15 to 35°C.

[0117] The melt kneading can be carried out using a kneader such as a kneader or an extruder. The heating temperature during melt kneading is lower than the bake hardening temperature, and is a temperature at which at least a part of the raw materials can be melted and the whole can be kneaded, and is generally preferably about 80 to 140°C. In one embodiment, the kneading is carried out at a temperature of 80 to 120°C. In the present invention, when melt kneading is performed, the kneading temperature is higher than the granulation temperature in the second and third granulation steps described below, for example, at a temperature higher than the softening point of the film-forming resin having the highest softening point among the film-forming resins contained in the clear powder coating composition.

[0118] The melt kneaded product can be cooled, for example, by a cooling roll, a cooling conveyor, or the like. The obtained solidified product can be pulverized in one step or in two or more steps. For example, the product can be coarsely pulverized and then finely pulverized. The pulverization can be performed using a pulverizing device such as a hammer mill or a jet impact mill.

[0119] By the classification, large particles and small particles can be removed, and the particle size distribution can be narrowed. For example, an air classifier, a vibration sieve, an ultrasonic sieve, etc. can be used for the classification. By the classification, the average particle size of the obtained particles may be adjusted to 3 to 60 μm.

[0120] (First granulation process) Next, the clear powder coating composition and the cationic compound (D) are mixed to obtain a preliminary mixture 1. This allows the surface of the clear powder coating composition to be positively charged.

[0121] (Cationic Compound (D)) In the present disclosure, the cationic compound (D) contains an amine base or a quaternary ammonium base. Cationic polymer, stearyltrimethylammonium chloride and cetylpyridinium chloride means.

[0122] The cationic polymerExamples of compounds that can be used as the catalyst include polyamide polyamine-epichlorohydrin condensates, condensates of amines and epichlorohydrin, polyallylamine hydrochloride, polyethyleneimine, polyamidine, naturally occurring cationic polymer Examples of such polymers include cationized chitin, chitosan, starch, and cellulose, polymers and copolymers of acrylates, methacrylates, acrylamides, and the like having a quaternary ammonium base, polymers and copolymers of diallyldimethylammonium chloride, and poly(vinylbenzyltrimethylammonium chloride).

[0123] The cationic polymer The weight average molecular weight of the cationic polymer may be preferably 100 or more and 10,000 or less, more preferably 200 or more and 6,000 or less, and even more preferably 300 or more and 6,000 or less. polymer By having the number average molecular weight of the cationic polymer and the clear powder coating composition, the color of the resulting coating film can be made more uniform, and the occurrence of mottled patterns can be further suppressed.

[0124] The cationic polymer The amine value of the cationic amine salt may be greater than 0 mgKOH / g, preferably from 1 mgKOH / g to 900 mgKOH / g, more preferably from 20 mgKOH / g to 700 mgKOH / g. polymer By having the amine value of the cationic amine compound in the above range, polymer and the clear powder coating composition, the color of the resulting coating film can be made more uniform, and the occurrence of mottled patterns can be further suppressed. In the present disclosure, the amine value can be measured in accordance with JIS K 7237.

[0125] The cationic polymer is preferably in a solid state at room temperature (25°C). polymer is in a solid state at room temperature, blocking can be suppressed during storage of the resulting premixture 1 and the color-matched powder coating composition. polymerThe softening point of the cationic polymer may be preferably 30° C. or higher, more preferably 30° C. or higher and 250° C. or lower, even more preferably 50° C. or higher and 180° C. or lower, and even more preferably 80° C. or higher and 160° C. or lower. polymer By having the softening point of the cationic polymer in the above range, polymer and the clear powder coating composition can be mixed more uniformly, the hue of the resulting coating film can be made more uniform, and the occurrence of mottled patterns can be further suppressed. In addition, there is also an advantage that the smoothness of the resulting coating film can be further improved.

[0126] The content of the cationic compound (D) may be preferably 0.01 to 10 parts by mass, more preferably 0.02 to 8 parts by mass, and even more preferably 0.03 to 6 parts by mass, based on 100 parts by mass of the total clear powder coating composition. By using the cationic compound (D) in the above range, the charge on the particle surface of the clear powder coating composition can be made appropriately positive, the hue of the resulting coating film can be made more uniform, and the occurrence of mottled patterns can be further suppressed.

[0127] The mixing of the clear powder coating composition and the cationic compound (D) is not particularly limited, and can be carried out by a dry method or a wet method.

[0128] In one embodiment, when the mixing is carried out dry, the solid cationic compound (D) may be added while mixing the clear powder coating composition.

[0129] In another embodiment, when the mixing is performed in a wet manner, the cationic compound (D) may be dissolved in a solvent in advance to prepare a cationic compound solution. Then, the cationic compound solution may be added while mixing the clear powder coating composition. In such an embodiment, it is preferable to remove the solvent after mixing the clear powder coating composition and the cationic compound solution. Therefore, in order to remove the solvent, the mixing may be continued until the solvent evaporates and the entire mixture is powdered. In addition, the mixture of the clear powder coating composition and the cationic compound solution may be subjected to a decompression treatment (preferably vacuum suction) to remove the solvent. The solvent used to prepare the cationic compound solution is not particularly limited, and examples thereof include alcohol solvents such as methanol, ethanol, isopropyl alcohol, butanol, water, and mixtures of water and alcohol solvents.

[0130] The mixing can be carried out using a mixer such as a super mixer, a ribbon blender, a drum blender, a Henschel mixer, etc. When a rotary mixer is used, the rotation speed may be 3 to 2,000 rpm.

[0131] The mixing step is preferably carried out at a temperature in the range of -5 to 50°C. Within this range, the primary color powder coating composition can be uniformly mixed, and the mottled pattern in the resulting coating film can be further suppressed. The mixing time in the mixing step can be, for example, preferably 10 minutes or more and 2 hours or less, more preferably 30 minutes or more and 1 hour or less.

[0132] (Second granulation process) In the second granulation step, the premix 1 is mixed with each of the two or more primary color powder coating compositions to obtain two or more premixes 2.

[0133] It is believed that at least a part of the cationic compound is attached to the particle surface of the clear powder coating composition in the premixture 1. It is believed that by mixing the premixture 1 with each of the two or more primary color powder coating compositions, the clear powder coating composition and the primary color powder coating composition can be bonded on a particle-by-particle basis, and an electrically neutral premixture 2 can be obtained.

[0134] The mass ratio of premix 1 to each primary color powder coating composition may be, for example, preferably 1 / 50 to 50 / 10, more preferably 1 / 20 to 20 / 10, and even more preferably 1 / 10 to 15 / 10. When the mass ratio is within the above range, premix 1 and each primary color powder coating composition can be mixed more uniformly, and the occurrence of mottled patterns in the resulting coating film can be further suppressed.

[0135] The mixing means of the preliminary mixture 1 and each primary color powder coating composition is not particularly limited. For example, a dry mixer such as a Henschel mixer, a ribbon blender, a drum blender, or a super mixer may be used. When a rotary mixer is used, the rotation speed may be 3 to 2,000 rpm. The ratio of the rotation speed during mixing in the first granulation step to the rotation speed during mixing in the second granulation step (rotation speed in the first granulation step / rotation speed in the second granulation step) may be preferably 0.1 to 10, more preferably 0.2 to 5. The larger the ratio, the better the uniformity of the hue tends to be, and the smaller the ratio, the better the smoothness of the resulting coating film tends to be.

[0136] Mixing of the premix 1 with each primary color powder coating composition is preferably carried out at room temperature. The mixing temperature may be preferably 10°C or higher and 40°C or lower, more preferably 15°C or higher and 35°C or lower. The mixing time is not particularly limited, and is, for example, 1 minute to 30 minutes. Mixing conditions can be appropriately set depending on the types of the clear powder coating composition, cationic compound (D) and primary color powder coating composition used, and the premix 2 is prepared by mixing so that the primary color powder coating composition is uniformly dispersed.

[0137] (Third granulation process) In the third granulation step, two or more kinds of premixtures 2 are mixed to obtain a toned powder coating composition. The premixture 2 may be a positively charged clear powder coating composition and a primary color powder coating composition bonded together at the particle level. By further mixing two or more kinds of such premixtures 2, it is believed that the uneven distribution caused by differences in color pigments can be suppressed, and a toned powder coating composition having uniform hue, saturation and gloss can be obtained.

[0138] Here, the particles of the color-matched powder coating composition obtained in the third granulation step can be pulverized into primary particles by vigorously stirring.

[0139] More specifically, for example, when the toning powder coating composition is stirred for about 1 minute at a peripheral speed of the stirring blade of 10 m / s or more, most of the particles of the toning powder coating composition can return to the state of primary particles having an average particle diameter equivalent to the average particle diameter of the clear powder coating composition primary color powder coating composition measured before granulation. Thus, in the present disclosure, granulation means preparation of particles that can be broken down into a primary particle state by applying a certain impact. As a result, in the obtained coating film, in addition to the effect of being able to smooth the surface, contributing to the minimization of mottling, and reducing or preventing problems such as surface unevenness and color separation, it can have high color reproducibility, such as cosmetic properties, and being able to reproduce the required uniform hue, uniform saturation, and uniform brightness.

[0140] The mass ratio of premix 2 of 1 to another premix 2 may be, for example, preferably 1 / 10 to 50 / 10, more preferably 2 / 10 to 20 / 10, and even more preferably 5 / 10 to 15 / 10. When the mass ratio is within the above range, premix 2 of 1 and another premix 2 can be mixed more uniformly, and the occurrence of mottled patterns in the obtained coating film can be further suppressed.

[0141] There is no particular limitation on the means for mixing the two or more types of preliminary mixture 2. For example, a dry mixer such as a Henschel mixer, a ribbon blender, a drum blender, or a super mixer may be used. When a rotary mixer is used, the rotation speed may be 3 to 2,000 rpm.

[0142] The mixing of two or more kinds of premixtures 2 is preferably carried out at room temperature. The mixing temperature may be preferably from 10° C. to 40° C., more preferably from 15° C. to 35° C. The mixing time is not particularly limited, and is, for example, from 1 minute to 30 minutes. The mixing conditions can be appropriately set depending on the type of premixture 2 used, and the two or more primary color powder coating compositions are mixed so as to be uniformly dispersed, thereby preparing a color-matched powder coating composition.

[0143] The color-matched powder coating composition obtained by the production method of the present disclosure does not need to be further classified, but may be further classified if necessary.

[0144] Although the first granulation step, the second granulation step, and the third granulation step have been described above, these steps may be repeated multiple times. For example, the color-matching powder coating composition may be used as the primary color powder coating composition. Specifically, the n-1th color-matching powder coating composition (where n is an integer of 2 or more) may be mixed with the cationic compound (D) to obtain the nth preliminary mixture 2, and two or more selected from the 1st to nth preliminary mixtures 2 may be further mixed to obtain the nth color-matching powder coating composition.

[0145] The pigment mass concentration in the color-matched powder coating composition may be preferably from 10% by mass to 50% by mass, more preferably from 20% by mass to 40% by mass.

[0146] The average particle size (D50) of the color-matching powder coating composition may be preferably 10 μm or more and 50 μm or less, more preferably 12 μm or more and 40 μm or less, and even more preferably 15 μm or more and 30 μm or less. In addition, the ratio of the average particle diameter (D50) of the color-matching powder coating composition to the average particle diameter (D50) of the entire primary color powder coating composition (average particle diameter of the color-matching powder coating composition / average particle diameter of the primary color powder coating composition) may be preferably 1 or more and 2 or less, more preferably 1 or more and 1.5 or less, and even more preferably 1 or more and 1.2 or less.

[0147] According to the manufacturing method of the present disclosure, in the obtained color-matching powder coating composition, two or more primary color powder coating compositions are aggregated via the clear powder coating composition and the cationic compound (D) present on its surface. Therefore, when measuring the average particle size, the color-matching powder coating composition can be crushed, and the particle size range is considered to be the same range as that of the primary color powder coating composition. As a result, the productivity of coating film formation can be improved. Furthermore, it is considered that the coating property can be made uniform, and the occurrence of color separation, color unevenness, gloss unevenness, etc. can be greatly suppressed or prevented.

[0148] <Coating film formation method> The present disclosure further includes a method for forming a coating film, which comprises applying the color-matched powder coating composition obtained by the above-mentioned production method to an object to be coated.

[0149] The substrate is not particularly limited, and specific examples thereof include iron plates, steel plates, aluminum plates, ceramic plates, and the like, as well as surface-treated versions of these. Further examples include members formed from these in complex shapes. Specific examples of the substrate include steel furniture, electronic parts, office automation equipment, home appliances, building materials, and automobile parts. A surface-treated substrate may also be used. The coating film formed on the substrate may be a single layer of the toned powder coating composition obtained by the toning method of the present invention, or the toned powder coating composition may be applied as a topcoat on an undercoat. The undercoat coating that forms the undercoat can be a known one such as an electrodeposition coating or a primer.

[0150] The method for applying the toned powder coating composition is not particularly limited, and may be any method well known to those skilled in the art, such as spray coating, electrostatic powder coating, fluidized bed coating, etc. From the viewpoint of coating efficiency, electrostatic powder coating is preferred. The coating film thickness (dry coating film thickness) when applying the color-matching powder coating composition may be preferably 20 μm or more and 100 μm or less, more preferably 40 μm or more and 70 μm or less, from the viewpoint of preventing the coating film from becoming mottled and transparent and also preventing the generation of bubbles on the surface or inside of the coating film.

[0151] The temperature and time of baking after application of the toning powder coating composition will vary depending on the type and amount of the curing agent (C) used, but the temperature is preferably 120 to 140° C., more preferably 140 to 220° C., for example 150 to 200° C., and in one embodiment 175 to 195° C., from the viewpoint of preventing the generation of bubbles on the surface or inside of the coating film. The baking time can be appropriately set depending on the baking temperature.

[0152] <Method of mixing powder coating composition> The present disclosure provides a method for matching a powder coating composition, comprising: Providing a clear powder coating composition and two or more primary color powder coating compositions; The clear powder coating composition; Cationic polymer, stearyltrimethylammonium chloride, and cetylpyridinium chloride a step of mixing the cationic compound (D) to obtain a premixture 1; A step of mixing the premix with each of the two or more primary color powder coating compositions to obtain two or more premixes 2; A step of mixing the two or more premixes 2 to prepare a powder coating composition; A color-matching method including the above is also included in the technical scope.

[0153] Each of the above steps can be carried out under the conditions described above using the raw materials and means described above as the method for producing the powder coating composition. According to this color-matching method, two or more primary color powder coating compositions can be uniformly mixed, and a color-matching powder coating composition that can realize a coating film showing a smooth and uniform hue can be obtained.

[0154] The coating film formed from the color-matched powder coating composition obtained by the present invention exhibits a smooth and uniform hue. In addition, according to the manufacturing method of the present invention, two or more different pigments are evenly dispersed in the resulting coating film, which leads to improved cosmetic properties and minimal mottling. Furthermore, since the method has excellent charge control technology, it is possible to suppress or reduce surface unevenness and contribute to eliminating color separation. In addition, since it is possible to control the gloss, the number of primary colors can be minimized. EXAMPLES

[0155] The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these.

[0156] (Production Example 1-1) Production Example of Primary Color Powder Coating Composition 1 120.0 parts by mass of (A-1) as the coating resin (A), 20.0 parts by mass of (C-1) as the curing agent (C), 80.0 parts by mass of (B1-1) as the color pigment (B1), 0.6 parts by mass of KF-54 as the surface conditioner, 1.6 parts by mass of benzoin as the popping inhibitor, and 0.6 parts by mass of dibutyltin dilaurate as the curing catalyst were mixed at 20° C. for 3 minutes using a Supermixer (manufactured by Kawata Corporation). A mixture was prepared by this process.

[0157] The mixture was then kneaded at 100°C and 100 rpm using a Buss Co-Kneader (Buss Co., Ltd.), rolled and cooled with a cooling roller attached to the device, and pulverized and classified using a pulverizer ACM10A (Hosokawa Micron Co., Ltd.) to obtain a powder with an average particle size (D50) of 20 μm.

[0158] 150.0 parts by mass of the obtained powder and 0.5 parts by mass of AEROSIL R972 (manufactured by Nippon Aerosil Co., Ltd.) as a flowability modifier were mixed uniformly in a Henschel mixer to prepare primary color powder coating composition 1 (average particle size (D50): 20 μm). The average particle size (D50) was measured using a particle size analyzer Microtrac HRA model 9320-X100 (manufactured by Nikkiso Co., Ltd.).

[0159] (Manufacturing Examples 1-2 to 1-15) Primary color powder coating compositions 2 to 15 were prepared in the same manner as in Production Example 1-1, except that the film-forming resin (A), color pigment (B1) and curing agent (C) were changed as shown in Tables 1A and 1B. The raw material composition in each production example and the average particle size (D50) of the obtained primary color powder coating composition are shown in Tables 1A and 1B. In Tables 1A and 1B, the "equivalent ratio of reactive groups" refers to the equivalent ratio between the total of the acid group, hydroxyl group and epoxy group contained in the film-forming resin (A) and the total of the groups (e.g., acid group, hydroxyl group, amino group and isocyanate group) that can react with the acid group, hydroxyl group and epoxy group contained in the curing agent (C).

[0160] [Table 1A]

[0161] [Table 1B]

[0162] (Production Example 2-1) Production Example of Clear Powder Coating Composition 1 120.0 parts by mass of (A-1) as the coating resin (A), 20.0 parts by mass of (C-1) as the curing agent (C), 80.0 parts by mass of (B2-1) as the body pigment (B2), 0.6 parts by mass of KF-54 as the surface conditioner, 1.6 parts by mass of benzoin as the popping inhibitor, and 0.6 parts by mass of dibutyltin dilaurate as the curing catalyst were mixed at 20° C. for 3 minutes using a Supermixer (manufactured by Kawata Corporation). A mixture was prepared by this process.

[0163] The mixture was then kneaded at 100°C and 100 rpm using a Buss Co-Kneader (Buss Co., Ltd.). The mixture was then rolled and cooled using a cooling roller attached to the device, and pulverized and classified using a pulverizer ACM10A (Hosokawa Micron Co., Ltd.) to prepare clear powder coating composition 1 (average particle size (D50): 20 μm).

[0164] (Manufacturing Examples 2-2 to 2-7) Clear powder coating compositions 2 to 7 were prepared in the same manner as in Production Example 2-1, except that the film-forming resin (A), extender pigment (B2) and curing agent (C) were changed as shown in Table 2. The raw material composition in each production example and the average particle size (D50) of the obtained clear powder coating composition are shown in Table 2. In Table 2, the "equivalent ratio of reactive groups" means the equivalent ratio between the total of acid groups, hydroxyl groups and epoxy groups contained in the film-forming resin (A) and the total of groups capable of reacting with acid groups, hydroxyl groups and epoxy groups (e.g., acid groups, hydroxyl groups, amino groups and isocyanate groups) contained in the curing agent (C).

[0165] [Table 2]

[0166] (Production Example of Powder Coating Composition 1) Example 1 <First granulation process> (Production Example 3-1) Production Example of First Granule 1 First, 2.0 parts by mass of stearyltrimethylammonium chloride (D-1) as the cationic compound (D) was mixed with 98.0 parts by mass of water and stirred until the solution became transparent when visually observed, to prepare an aqueous solution of the cationic compound. Next, 100 parts by mass of the clear powder coating composition 1 was charged into a mixing agitator 5XDMV-Qr (manufactured by Shinagawa Kogyosho Co., Ltd.), and while mixing at 20 rpm, 25.0 parts by mass of the aqueous solution 1 of the cationic compound (0.5 parts by mass as the solid content of (D-1)) was sprayed and added over 5 minutes. After that, mixing was continued for 60 minutes under the same conditions to obtain a first granule 1 (preliminary mixture 1).

[0167] <Second granulation process> (Production Example 41-1) Production Example of Second Granule 1-1 While stirring 10.0 parts by mass of the first granule 1 under the same conditions, 90.0 parts by mass of the primary color powder coating composition 1 was added and mixed for 5 minutes to obtain a second granule 1-1 (preliminary mixture 21-1).

[0168] (Production Example 42-1) Production Example of Second Granule 2 A second granulation product 2-1 (preliminary mixture 22-1) was obtained in the same manner as in the second granulation step 1, except that the primary color powder coating composition 1 was changed to primary color powder coating composition 2.

[0169] <Third granulation process> (Production Example 5-1) Production Example of Powder Coating Composition 1 The second granule 1 (100.0 parts by mass) and the second granule 2 (100.0 parts by mass) obtained above were stirred and mixed for 5 minutes under the same conditions as above to obtain a powder coating composition 1 (toned powder coating composition 1). The above series of production was carried out at 20°C (room temperature).

[0170] (Formation of coating film) The substrate was a 0.8×70×150 mm JIS G 3141 (SPCC-SD) cold-rolled steel plate that had been subjected to zinc phosphate treatment and then solvent degreased. The powder coating composition 1 prepared above was applied to this substrate using an electrostatic powder coating applicator OPTI hand gun (manufactured by Graco) under conditions of discharge rate of 120 g / min, set voltage of 100 kV, set current of 70 μA, free ion removal, and gun distance of 15 cm, so that the film thickness was 50-60 μm, and the substrate was baked at 180° C. for 20 minutes for testing.

[0171] (Examples 2 to 23, Comparative Example 1) (Manufacturing Examples 3-2 to 3-16) Except for changing the cationic compound, primary color powder coating composition, and granulation conditions as shown in Table 3, the same procedure as in Example 1 (Production Example 3-1) was carried out to prepare first granules 2 to 16.

[0172] (Production Examples 41-2 to 41-19 and Production Examples 42-2 to 42-19) Second granules 1-2 to 1-19 and second granules 2-2 to 2-19 were prepared in the same manner as in Example 1 (Production Examples 41-1 and 42-1), except that the first granule, primary color powder coating composition, and granulation conditions were changed as shown in Table 4. In addition, in Production Examples 41-19 and 42-19, clear powder coating composition 1 was used instead of the first granule.

[0173] (Manufacturing Examples 5-2 to 5-23) Except for changing the second granule 1-1, the second granule 2-1 and the production conditions as shown in Table 5, powder coating compositions 2 to 23 were prepared in the same manner as in Example 1 (Production Example 5-1). Coating films to be tested were prepared in the same manner as in Example 1, except that the powder coating compositions were changed as shown in Tables 5A and 5B. The blending amounts shown in Tables 1A to 5 are the solid content amounts of each.

[0174] Comparative Example 2 First, 2.0 parts by mass of the other polymer (d-1) and 98.0 parts by mass of methanol were mixed and stirred until the solution became transparent to the naked eye, thereby preparing polymer solution 1. Next, 100.0 parts by mass of the clear powder coating composition 1 was charged into a mixing agitator 5XDMV-Qr (manufactured by Shinagawa Kogyosho Co., Ltd.), and while mixing at 20 rpm, 300.0 parts by mass of the polymer solution 1 (6.0 parts by mass as the solid content of (d-1)) was sprayed and added over 5 minutes. Thereafter, mixing was continued for 60 minutes under the same conditions to obtain a first granule 13. While stirring 10.0 parts by mass of the first granule 13 under the same conditions, 90.0 parts by mass of the primary color powder coating composition 13 was added and mixed for 5 minutes to obtain a second granule 1-15. Further, a second granule 2-15 was obtained in the same manner as in the second granulation step 1, except that the primary color powder coating composition 13 was changed to primary color powder coating composition 14. Furthermore, 100.0 parts by mass of the second granule 1-15 obtained above and 100.0 parts by mass of the second granule 2-15 obtained above were stirred and mixed for 5 minutes under the same conditions as above to obtain a powder coating composition 25. The series of production steps described above was carried out at 20°C (room temperature). Thereafter, in the same manner as in Example 1, a coating film to be subjected to testing was obtained.

[0175] Comparative Example 3 First, 40.0 parts by mass of the other polymer (d-2) and 60.0 parts by mass of water were mixed and stirred until the solution became visually transparent, to prepare polymer solution 2. Next, 100.0 parts by mass of the clear powder coating composition 1 was charged into a mixing agitator 5XDMV-Qr (manufactured by Shinagawa Kogyosho Co., Ltd.), and while mixing at 20 rpm, 300.0 parts by mass of the polymer solution 2 (6.0 parts by mass as the solid content of (d-2)) was sprayed and added over 5 minutes. Thereafter, mixing was continued for 60 minutes under the same conditions to obtain a first granule 14. While stirring 10.0 parts by mass of the first granule 14 under the same conditions, 90.0 parts by mass of the primary color powder coating composition 14 was added and mixed for 5 minutes to obtain a second granule 1-16. Further, a second granule 2-16 was obtained in the same manner as in the second granulation step 1, except that the primary color powder coating composition 14 was changed to primary color powder coating composition 15. Furthermore, 100.0 parts by mass of the second granule 1-16 obtained above and 100.0 parts by mass of the second granule 2-16 obtained above were stirred and mixed for 5 minutes under the same conditions as above to obtain a powder coating composition 26. The series of production steps described above was carried out at 20°C (room temperature). Thereafter, in the same manner as in Example 1, a coating film to be subjected to testing was obtained.

[0176] Comparative Example 4 First, 5.0 parts by mass of the other polymer (d-3) and 95.0 parts by mass of water were mixed and stirred until the mixture was visually homogenous, to prepare polymer dispersion 3. Next, 100.0 parts by mass of the clear powder coating composition 1 was charged into a mixing agitator 5XDMV-Qr (manufactured by Shinagawa Kogyosho Co., Ltd.), and while mixing at 20 rpm, 300.0 parts by mass of the polymer dispersion 3 (6.0 parts by mass as the solid content of (d-3)) was sprayed and added over 5 minutes. After that, mixing was continued for 60 minutes under the same conditions to obtain a first granule 15. While stirring 10.0 parts by mass of the first granule 15 under the same conditions, 90.0 parts by mass of the primary color powder coating composition 13 was added and mixed for 5 minutes to obtain a second granule 1-17. Further, a second granule 2-17 was obtained in the same manner as in the second granulation step 1, except that the primary color powder coating composition 13 was changed to the primary color powder coating composition 15. Furthermore, 100.0 parts by mass of the second granule 1-17 obtained above and 100.0 parts by mass of the second granule 2-17 obtained above were stirred and mixed for 5 minutes under the same conditions as above to obtain a powder coating composition 27. The series of productions described above was carried out at 20°C (room temperature). Thereafter, in the same manner as in Example 1, a coating film to be subjected to testing was obtained.

[0177] Comparative Example 5 First, 3.0 parts by mass of the other polymer (d-4) and 97.0 parts by mass of water were mixed and stirred until the mixture was visually homogenous, to prepare polymer dispersion 4. Next, 100.0 parts by mass of the clear powder coating composition 6 was charged into a mixing agitator 5XDMV-Qr (manufactured by Shinagawa Kogyosho Co., Ltd.), and while mixing at 20 rpm, 300.0 parts by mass of the polymer dispersion liquid 4 (6.0 parts by mass as the solid content of (d-4)) was sprayed and added over 5 minutes. After that, mixing was continued for 60 minutes under the same conditions to obtain a first granule 16. While 10.0 parts by mass of the first granule 16 was stirred under the same conditions, 90.0 parts by mass of the primary color powder coating composition 3 was added and mixed for 5 minutes to obtain a second granule 1-18. Further, a second granule 2-18 was obtained in the same manner as in the second granulation step 1, except that the primary color powder coating composition 3 was changed to the primary color powder coating composition 4. Furthermore, 100.0 parts by mass of the second granule 1-18 obtained above and 100.0 parts by mass of the second granule 2-18 obtained above were stirred and mixed for 5 minutes under the same conditions as above to obtain a powder coating composition 28. The series of productions described above was carried out at 20°C (room temperature). Thereafter, in the same manner as in Example 1, a coating film to be subjected to testing was obtained.

[0178] Details of the raw materials used are shown below. Film-forming resin (A): (A-1) FineDic M8020 (DIC Corporation, polyester resin having hydroxyl groups), hydroxyl value: 30 mg KOH / g, softening point: 110°C (A-2) FineDic M8023 (DIC Corporation, polyester resin having hydroxyl groups), hydroxyl value: 40 mg KOH / g, softening point: 106°C (A-3) GV-126 (manufactured by Nippon U-Pica Co., Ltd., polyester resin having a carboxyl group), acid value: 30 mg KOH / g, softening point: 120°C (A-4) A278 (DIC Corporation, acrylic resin with epoxy groups), epoxy equivalent: 480g / eq, softening point: 103℃ (A-5) NT-114 (Nippon Steel Chemical & Material Co., Ltd., epoxy resin), epoxy equivalent: 440g / eq, softening point: 96℃ Color pigments (B1): (B-1) Tipaque CR90 (manufactured by Ishihara Sangyo Kaisha, titanium oxide) (B-2) Mitsubishi Carbon Black MA100 (Mitsubishi Chemical Corporation, carbon black) (B-3) Firstgen Blue NK (DIC, blue organic pigment) (B-4) Pacific Red 2020 (manufactured by Nagase & Co., Ltd., red organic pigment) (B-5) TAROX synthetic iron oxide HY-100 (manufactured by Titanium Industries, a yellow inorganic pigment) Extender pigment (B2): (B2-1) Precipitated barium sulfate 100 (Sakai Chemical Industry Co., Ltd., barium sulfate) (B2-2) Calcium Carbonate Super 2000 (Maruo Calcium Co., Ltd., calcium carbonate) (B2-3) Talc MS410 (Talc, manufactured by Maruo Calcium Co., Ltd.) Hardener(C): (C-1) VESTAGON B1530 (Evonik Industries, blocked isocyanate), NCO equivalent: 280g / eq (C-2) Primid XL-552 (EMS Co., Ltd., β-hydroxyalkylamide (HAA)) (C-3) GV-230 (Japan U-Pica Corporation, polyester resin), acid value: 48 mg KOH / g (C-4) Dodecanedicarboxylic acid (DDDA) (manufactured by Tokyo Chemical Industry Co., Ltd., polycarboxylic acid compound) (C-5) Dicyandiamide (Tokyo Chemical Industry Co., Ltd., amino group-containing compound) Cationic compounds (D): (D-1): Kotamin 86P Conc. (Kao Corporation, stearyl trimethylammonium chloride), softening point: 95 to 104°C, weight average molecular weight: 333, amine value: 168 mgKOH / g, solid content: 100% by mass (D-2) Cetylpyridinium chloride (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), softening point: 80 to 84°C, weight average molecular weight: 358, amine value: 157 mgKOH / g, solid content: 100% by mass (D-3) Polylysine (manufactured by JNC Corporation), softening point: 172°C, weight average molecular weight: 4,700, amine value: 600 mgKOH / g, solid content: 100% by mass (D-4) Koyo Chitosan (manufactured by Koyo Chemical Co., Ltd., chitosan), softening point: 200°C or higher, weight average molecular weight: 100,000, amine value: 298 mgKOH / g, solid content: 100% by mass Other polymers: (d-1) Phenolic resin YS Polystar TH130 (manufactured by Tohshin Chemical Industry Co., Ltd., phenolic resin), softening point: 125 to 135°C, amine value: 0 mgKOH / g, solid content: 100% by mass (d-2) Polyethylene glycol 4000 (Tokyo Chemical Industry Co., Ltd., polyethylene glycol), softening point: 54 to 58° C., weight average molecular weight: 2,700 to 3,400, amine value: 0 mg KOH / g, solid content concentration: 5% by mass (aqueous solution) (d-3) EMUSTAR-0136 (paraffin wax, manufactured by Nippon Seiro Co., Ltd.), softening point: 60°C, average particle size: 0.50 μm or less, amine value: 0 mgKOH / g, solid content concentration: 40 mass% (aqueous dispersion) (d-4) A-6001 (manufactured by Resitex, acrylic resin emulsion), softening point: 70 to 80°C, amine value: 0 mgKOH / g, solids concentration: 63 to 67% by mass (aqueous dispersion) Other Additives: Surface conditioner: KF-54 (Shin-Etsu Chemical Co., Ltd., silicone-based) Underarm anti-aging agent: Benzoin (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) Flow control agent: AEROSIL R972 (Nippon Aerosil Co., Ltd., silica)

[0179] [Table 3] [Table 4]

[0180] The following evaluations were carried out on the coating films obtained in the above-mentioned Examples 1 to 23 and Comparative Examples 1 to 5. The obtained evaluation results are shown in Tables 5A and 5B.

[0181] (Evaluation method) 1) Resistance to color separation The coating films obtained in the Examples and Comparative Examples were visually observed for mottling and evaluated for color-shift resistance. The evaluation criteria were as follows: △ or higher was considered to be acceptable. A: When viewed from a distance of 50 cm, the mottled color pattern is not recognizable. ○: When viewed from a distance of 50 cm, a mottled pattern of color tones is slightly discernible. Δ: When viewed from a distance of 50 cm, the mottled pattern of color tones is clearly recognizable, but when viewed from a distance of 80 cm, it is not recognizable or is only slightly recognizable. ×: When viewed from a distance of 80 cm, the mottled color pattern is clearly recognizable.

[0182] 2) Smoothness The arithmetic mean waviness (Wa value) of the coating films obtained in the examples and comparative examples was measured in accordance with JIS B 0601 using a surface roughness measuring instrument Surfcom TOUCH50 (manufactured by Tokyo Seimitsu Co., Ltd.) to evaluate the smoothness of the coating films. The evaluation criteria are as follows. The measurement conditions were cutoff value: 0.8 mm, scanning speed: 2 mm / s. A score of △ or higher was considered to be acceptable. ◯: Wa is less than 0.9. △: Wa is 0.9 or more and less than 1.1. ×: Wa is 1.1 or more.

[0183] [Table 5A]

[0184] [Table 5B]

[0185] Examples 1 to 23 are examples of the present disclosure, and the resulting coating films exhibited a smooth and uniform hue. On the other hand, in Comparative Example 1, which does not include the first granulation step, color separation was not suppressed, the coating film appeared mottled, and a uniform hue could not be obtained. Comparative Examples 2 to 5 are examples in which no cationic compound was used, and the resulting coating films were inferior in color-changing resistance and / or smoothness. [Industrial Applicability]

[0186] The manufacturing method and coating film formation method of the present disclosure can provide a coating film that is smooth and exhibits a uniform hue, and therefore the manufacturing method of the present disclosure can be applied to general industrial applications such as home appliances, automobile parts, and steel furniture.

Claims

1. Providing a clear powder coating composition and two or more primary color powder coating compositions; A step of mixing the clear powder coating composition with a cationic polymer (D) to obtain a preliminary mixture 1; A step of mixing the premix 1 with each of the two or more primary color powder coating compositions to obtain two or more premixes 2; A step of mixing the two or more premixes 2 to obtain a powder coating composition; A method for producing a powder coating composition comprising the steps of:

2. The method according to claim 1 , wherein the two or more primary color powder coating compositions each have a different hue and / or tone.

3. The method according to claim 1, wherein the clear powder coating composition and the primary color powder coating composition have an average particle size (D50) of 40 μm or less.

4. The method according to claim 1 , wherein the cationic polymer (D) has an amino group and / or a quaternary ammonium salt group, and the softening point of the cationic polymer (D) is 30° C. or higher and 180° C. or lower.

5. The method according to claim 1, wherein the clear powder coating composition and the cationic polymer (D) are mixed in a wet manner.

6. The step of mixing the clear powder coating composition with a cationic polymer (D) to obtain a preliminary mixture 1 includes the steps of: mixing the cationic polymer (D) with water and / or a hydrophilic solvent to obtain a cationic polymer solution; mixing the clear powder coating composition with the cationic polymer solution to obtain a mixed solution containing a premixture 1; and removing water and / or hydrophilic solvent from the mixture to obtain a premixture 1; The method of claim 1 , comprising:

7. 2. The method of claim 1, wherein the primary color powder coating composition is prepared by mixing a film-forming resin (A) and a color pigment (B1).

8. 2. The method according to claim 1, wherein the clear powder coating composition is prepared by mixing the film-forming resin (A) and the extender pigment (B2).

9. The method according to claim 1 , wherein the coating film-forming resin (A) comprises a polymer having at least one functional group selected from an acid group, a hydroxyl group, and an epoxy group.

10. The method according to claim 1 , wherein the clear coating composition and the primary color powder coating composition further comprise a curing agent (C).

11. A method for forming a coating film, comprising applying a powder coating composition obtained by the production method according to any one of claims 1 to 10 to an object to be coated.

12. A method for matching a powder coating composition, comprising the steps of: Providing a clear powder coating composition and two or more primary color powder coating compositions; A step of mixing the clear powder coating composition with a cationic polymer (D) to obtain a preliminary mixture 1; mixing the premix with each of the two or more primary color powder coating compositions to obtain two or more premixes 2; A step of mixing the two or more premixes 2 to prepare a powder coating composition; A color matching method comprising:

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