Method for producing powder coating composition, method for forming coating film, and method for matching color

Abstract

To provide a manufacturing method of a powder coating composition that enables a coating film exhibiting a smooth and even color tone to be achieved.SOLUTION: A manufacturing method of a powder coating composition of the present disclosure includes steps of: preparing two or more types of primary color powder coating compositions; obtaining a preliminary mixture by mixing some of the two or more types of primary color powder coating compositions with cationic polymer (D); and obtaining the powder coating composition by mixing the preliminary mixture with a balance of the two or more types of primary color powder coating compositions.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 colors. [Background technology]

[0002] In recent years, awareness of reducing environmental impact has increased, and there has been a demand for replacement with environmentally friendly products. Among these, powder coating compositions are widely used for coating home appliances, automobile parts, steel furniture, etc., because they are environmentally friendly, such as being free of organic solvents and being easy to recover. Such powder coating compositions are usually prepared by combining a plurality of pigmented powder coating compositions to produce a wide range of hues, and are then applied to an object to be coated using an electrostatic coating gun or the like.

[0003] For example, Patent Document 1 describes a color matching method for combining two or more powder paints of different colors to match a target color, in which primary color powder paints suitable for matching to the 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 a powder coating used in a coating method in which two or more powder coatings of different hues are mixed and applied, and describes that the two or more powder coatings have a mass median particle size of 1 to 50 μm and a mass distribution variation coefficient of 50% or less, and are then matched. Patent Document 3 describes a powder coating used in a coating method in which two or more powder coatings of different hues are mixed and applied, and describes how the difference in electrostatic charge between the two or more powder coatings is set to 5.0 μC / g or less before the colors are mixed. Patent Document 4 describes a method for matching powder paint colors, which includes a step of dry-blending two or more different primary color powder paints with an average particle size of 20 μm or less to match the colors, and a step of heating this blend with stirring to a temperature at which the particle surfaces melt but the interiors of the particles do not melt, thereby granulating the blend to a particle size within a range suitable for painting. 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 is a liquid binder having a softening temperature of 20 to 200°C, 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, there is a problem that a coating film that is smooth enough to be recognized by the naked eye is not obtained, and the hue of the obtained coating film is not uniform. Furthermore, it is necessary to prepare a powder coating composition containing a 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 such a 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] preparing two or more primary color powder coating compositions; A part of the two or more primary color powder coating compositions; Cationic polymer, stearyltrimethylammonium chloride, and cetylpyridinium chloride a step of mixing the cationic compound (D) to obtain a premixture; and mixing the premix with the remainder of the two or more primary color powder coating compositions to obtain a powder coating composition. [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 according to [1] or [2], wherein the primary color powder coating composition has an average particle size (D50) of 25 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 50°C or higher and 180°C or lower. [5] The method according to any one of [1] to [4], wherein mixing of a part of the two or more primary color powder coating compositions with the cationic compound (D) is carried out in a dry manner. [6] The method for producing a premixture by mixing a portion of the two or more primary color powder coating compositions with a cationic compound (D) is carried out by mixing the cationic compound (D) with water and / or a hydrophilic solvent to obtain a solution of the cationic compound, mixing a portion of the primary color powder coating compositions with the solution of the cationic compound to obtain a mixed liquid containing a premixture, and removing water and / or hydrophilic solvent from the mixed liquid to obtain the premixture. [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 colorant (B). [8] The method according to [7], 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. [9] The method for producing the primary color powder coating composition according to [7] or [8], further comprising a curing agent (C).

[10] 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 [9] to an object to be coated.

[11] A method for matching a powder coating composition, comprising: Producing two or more primary color powder coating compositions, each having a different hue and / or shade; At least a portion of the two or more primary color powder coating compositions; Cationic polymer, stearyltrimethylammonium chloride, and cetylpyridinium chloride a cationic compound (E) to obtain a premix; mixing said pre-mixture with the remainder of said two or more primary color powder coating compositions to mix a powder coating composition. 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 two or more primary color powder coating compositions; At least one of the two or more primary color powder coating compositions; Cationic polymer, stearyltrimethylammonium chloride, and cetylpyridinium chloride a cationic compound to obtain a premix; mixing the premix with the remainder of the two or more primary color powder coating compositions to obtain a powder coating composition. Hereinafter, the "cationic compound selected from a cationic polymer, stearyltrimethylammonium chloride, and cetylpyridinium chloride" will be simply referred to as the cationic compound. Also, Hereinafter, the primary color powder coating composition used to obtain a preliminary mixture by mixing with a cationic compound is also referred to as the "first primary color powder coating composition", and the remaining primary color powder coating composition used to obtain a powder coating composition by mixing with the preliminary mixture is also referred to as the "second primary color powder coating composition". In addition, the process of mixing the first primary color powder coating composition with a cationic compound is also referred to as the "first granulation process", and the process of mixing the pre-mixture with the second primary color powder coating composition is also referred to as the "second granulation process".

[0011] 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, one of the primary color powder coating compositions and a cationic compound are mixed in advance to form a preliminary mixture, and another primary color powder coating composition is further mixed into the preliminary mixture. The surface of the primary color powder coating composition mixed with the cationic compound is positively charged, while the surface of the remaining primary color powder coating composition added additionally is negatively charged. Therefore, it is considered that the positively charged particles and the negatively charged particles are electrostatically agglomerated and granulated.

[0012] As a result, different particles selectively aggregate with each other, and particles of the same color are unlikely to aggregate with each other, so that even under various coating conditions, it can contribute to minimizing mottling, and in addition to the effect of reducing or preventing problems such as surface unevenness and color separation, it is possible to have high color reproducibility, such as cosmetic properties, reproducing the required uniform hue, uniform saturation, and uniform brightness. In addition, since the aggregation between the first primary color powder coating composition and the second powder coating composition is electrostatically bonded via the cationic compound, the toning powder coating composition can be easily disintegrated when forming a coating film, and as a result of good coating film formability, a smooth coating film can be formed, and further, such a coating film is thought to have a desired gloss and little mottling.

[0013] On the other hand, the conventional manufacturing method of a powder coating composition with a toned color is mainly a dry blending 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.

[0014] (Step of Preparing Primary Color Powder Coating Composition) In the method for producing a powder coating composition of the present disclosure, first, two or more primary color powder coating compositions are prepared. The primary color powder coating compositions may be any powder coating composition having uniform hue, saturation, and gloss, and are not limited to those containing only one type of film-forming resin (A) and / or one type of colorant (B).

[0015] 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.

[0016] 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 colorant (B).

[0017] (Coating film forming resin (A)) The coating 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 makes it easier to form a coating film, and the primary color powder coating composition can be relatively negatively charged, which is thought to facilitate interaction with the cationic compound described below. As a result, in the premix, the surface of the first powder coating composition can be relatively positively charged, which facilitates interaction with the second powder coating composition at the particle level, and the resulting toning powder coating composition is thought 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, and the carboxy group is preferred.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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 coating film-forming resin (A).

[0024] 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.

[0025] 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 coating film-forming resin (A).

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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 coating film-forming resin (A).

[0031] 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.

[0032] 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.

[0033] By having the acid value, hydroxyl value or epoxy equivalent of the 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, making it easier to mix the first powder coating composition and the second powder coating composition more uniformly and to adjust the color and granulate the composition. The acid value, hydroxyl value or epoxy equivalent of the film-forming resin (A) contained in the first primary color powder coating composition and the acid value, hydroxyl value or epoxy equivalent of the film-forming resin (A) contained in the second primary color powder coating composition may be the same or different.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] (Color pigment (B)) As the colorant (B), inorganic or organic pigments that are usually used in powder coatings can be used. The colorant (B) 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 colorant (B).

[0038] 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.

[0039] In the primary color powder coating composition, the content of the colorant (B) may be preferably from 0.05 to 75 parts by mass, more preferably from 0.1 to 70 parts by mass, relative to 100 parts by mass of the coating film-forming resin (A). In one embodiment, it may be, for example, from 1 to 70 parts by mass, and even from 3 to 70 parts by mass. In the primary color powder coating composition, the content of the colorant (B) may vary depending on the type of colorant (B). For example, the content of the inorganic colorant (B) may be 0.05 to 75 parts by mass, 10 to 70 parts by mass, or even 15 to 70 parts by mass, relative to 100 parts by mass of the coating film-forming resin (A), and the content of the organic colorant (B) may be 0.05 to 20 parts by mass, or even 0.05 to 10 parts by mass, relative to 100 parts by mass of the coating film-forming resin (A). In two or more primary color powder coating compositions, the composition of the colorant (B) contained therein (type, amount, and ratio when two or more types of colorant (B) are contained) may be the same or different.

[0040] (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 colorant (B) and the curing agent (C). The order of mixing is not particularly limited, and the film-forming resin (A), the colorant (B) and the curing agent (C) may be mixed simultaneously, or the film-forming resin (A) and the colorant (B) may be mixed in advance, and then the mixture may be further mixed with the curing agent (C).

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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).

[0045] 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.

[0046] 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.

[0047] The β-hydroxyalkylamide compound (HAA) can be a compound represented by the following formula (I):

[0048] [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.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] The amount of the curing agent (C) in the primary color powder coating composition varies depending on the types 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 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.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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. 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.

[0061] 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.

[0062] 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.

[0063] (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.

[0064] 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.

[0065] 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.

[0066] The imidazoline compound is not particularly limited, but examples thereof include 2-phenylimidazole, 2-methylimidazoline, 2-undecylimidazoline, and 2-heptadecylimidazoline.

[0067] 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.

[0068] The tertiary phosphine compound is not particularly limited, but examples thereof include triphenylphosphine, tritolylphosphine, and the like.

[0069] The quaternary phosphonium salt is not particularly limited, but examples thereof include benzyltriphenylphosphonium chloride, butyltriphenylphosphonium bromide, ethyltriphenylphosphonium iodide, and ethyltriphenylphosphonium bromide.

[0070] The quaternary ammonium salt is not particularly limited, but examples thereof include tetraethylammonium chloride, tetraethylammonium bromide, and benzyltrimethylammonium bromide.

[0071] 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.

[0072] (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).

[0073] 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.

[0074] 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).

[0075] 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.

[0076] The primary color powder coating composition may have an average particle size (D50) of preferably 1 μm or more and 25 μm or less, 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.

[0077] 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.).

[0078] (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 may be manufactured by a known method. For example, the primary color powder coating composition may be manufactured by a manufacturing method including mixing the coating film-forming resin (A) with the colorant (B), curing agent (C), curing catalyst, and other additives used as necessary (mixing step), melt-kneading the obtained mixture (melting and 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.

[0079] The order of mixing the film-forming resin (A) and the colorant (B), curing agent (C), curing catalyst and other additives used as necessary is not particularly limited. In one embodiment, the film-forming resin (A) and the colorant are mixed with the curing catalyst and other additives, and then the mixture is further 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.

[0080] 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 granulation step 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.

[0081] 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.

[0082] 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.

[0083] (First granulation process) Next, a part of the two or more primary color powder coating compositions is mixed with a cationic compound (D) to obtain a preliminary mixture, whereby the surface of a part of the primary color powder coating compositions (first primary color powder coating composition) can be positively charged.

[0084] The part of the two or more primary color powder coating compositions means a part of two or more parts to be mixed among the two or more primary color powder coating compositions, and may be a part or all of one primary color powder coating composition, or may include two or more primary color powder coating compositions. In a preferred embodiment, the part of the two or more primary color powder coating compositions may be a part or all of one primary color powder coating composition.

[0085] (Cationic Compound (D)) In the present disclosure, the cationic compound (D) contains an amine base or a quaternary ammonium base. Cationic polymer, stearyltrimethylammonium chloride, cetylpyridinium chloride means...

[0086] The cationic polymer Examples 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 polymerExamples 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).

[0087] 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 3,000 or less. polymer By having the number average molecular weight of the cationic polymer and the first primary color powder coating composition can be mixed more uniformly, so that the color of the resulting coating film can be made more uniform and the occurrence of mottled patterns can be further suppressed.

[0088] 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 first primary color powder coating composition can be mixed more uniformly, so that 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.

[0089] 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 obtained color-matching powder coating composition. polymer The softening point of the cationic polymer may be preferably 30° C. or higher and 180° C. or lower, more preferably 50° C. or higher and 170° 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, polymerThe first primary color 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. Note that when the first primary color powder coating composition is mixed with the cationic compound (D), there is usually no change in the hue or saturation of the first primary color powder coating composition.

[0090] The content of the cationic compound (D) may be preferably 0.01 to 2 parts by mass, more preferably 0.02 to 1 part by mass, and even more preferably 0.03 to 0.5 parts by mass, based on 100 parts by mass of the primary color powder coating composition (first primary color powder coating composition and second primary color powder coating composition) used in the preparation of the toned powder coating composition. By using the amount of the cationic compound (D) within the above range, the charge on the particle surface of the first primary color powder coating composition can be made moderately positive, the hue of the resulting coating film can be made more uniform, and the occurrence of mottled patterns can be further suppressed.

[0091] The mixing of the first primary color 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.

[0092] In one embodiment, when the mixing is carried out dry, the solid cationic compound (D) may be added while mixing the first primary color powder coating composition.

[0093] In another embodiment, when the mixing is performed in a wet manner, the cationic compound (D) is dissolved in a solvent in advance to prepare a cationic compound solution. The cationic compound solution may then be added while mixing the first primary color powder coating composition. In such an embodiment, it is preferable to remove the solvent after mixing the first primary color 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 first primary color 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, and butanol; water; and a mixture of water and an alcohol solvent.

[0094] 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.

[0095] 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 occurrence of mottled patterns 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.

[0096] (Second granulation process) In the second granulation step, the pre-mixture is mixed with the remainder of the two or more primary color powder coating compositions to obtain a powder coating composition. It is believed that the cationic compound is adhered to the particle surfaces of the first primary color powder coating composition contained in the pre-mixture, and by mixing this pre-mixture with the remainder of the two or more primary color powder coating compositions (second primary color powder coating composition), the first primary color powder coating composition and the second primary color powder coating composition are bonded on a particle-by-particle basis and toned, and are granulated to obtain a toned powder coating composition.

[0097] Here, the particles of the color-matched powder coating composition obtained in the second granulation step can be pulverized into primary particles by vigorously stirring. 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 original color powder coating composition measured before granulation. Thus, in the present disclosure, granulation means preparation of particles that can be crushed into a state of primary particles 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.

[0098] The mass ratio of the first primary color powder coating composition to the second primary color powder coating composition 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, the first primary color powder coating composition and the second 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.

[0099] The mixing means of the preliminary mixture and the second 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.

[0100] The mixing temperature when mixing the preliminary mixture and the second primary color powder coating composition is preferably room temperature. The mixing temperature may be preferably 10°C or more and 40°C or less, more preferably 15°C or more and 35°C or less. The mixing time is not particularly limited, and is, for example, 1 minute to 30 minutes. The mixing conditions can be appropriately set according to the type of primary color powder coating composition used, and the color-matching powder coating composition is prepared by mixing two or more primary color powder coating compositions so that they are uniformly dispersed.

[0101] 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.

[0102] In the above, the first granulation step and the second granulation step have been described, but these steps may be repeated several times. That is, the toned powder coating composition may be used as the first or second primary color powder coating composition. In one embodiment, the first toned powder coating composition may be mixed with a cationic compound to obtain a premixture, and the premixture and the primary color powder coating composition may be mixed to obtain the second toned powder coating composition. Alternatively, the primary color powder coating composition may be mixed with a cationic compound to obtain a premixture, and the premixture and the first toned powder coating composition may be mixed to obtain the second toned powder coating composition. Furthermore, the first toned powder coating composition may be mixed with a cationic compound to obtain a premixture, and the premixture and the second toned powder coating composition may be mixed to obtain the third toned powder coating composition.

[0103] 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.

[0104] 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.

[0105] According to the manufacturing method of the present disclosure, in the obtained color-matching powder coating composition, the first primary color powder coating composition and the second primary color powder coating composition are aggregated via a cationic compound. Therefore, when measuring the average particle size, the color-matching powder coating composition is 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, since the coating property can be made uniform, the occurrence of color separation, color unevenness, gloss unevenness, etc. can be greatly suppressed or prevented.

[0106] <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.

[0107] 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.

[0108] 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 thickness (dry coating thickness) when applying the color-matching powder coating composition is 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 uneven and transparent and preventing the generation of bubbles on the surface or inside of the coating film.

[0109] 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.

[0110] <Method of mixing powder coating composition> The present disclosure provides a method for matching a powder coating composition, comprising: Producing two or more primary color powder coating compositions, each having a different hue and / or shade; At least a portion of the two or more primary color powder coating compositions; Cationic polymer, stearyltrimethylammonium chloride, and cetylpyridinium chloride a cationic compound to obtain a premix; and mixing the premix with the remainder of the two or more primary color powder coating compositions to form a powder coating composition.

[0111] 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.

[0112] The coating film formed from the color-matching 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, improved hiding power, and minimal mottling. Furthermore, since the electrostatic control technology is also excellent, surface unevenness can be suppressed or reduced, and color separation can also be eliminated. In addition, since gloss can be controlled, the number of primary colors can be minimized. EXAMPLES

[0113] The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto. In the examples, "parts" and "%" are by weight unless otherwise specified.

[0114] (Production Example 1) 120 parts by mass of (A-1) as the coating resin (A), 20 parts by mass of (C-1) as the curing agent, 80 parts by mass of (B-1) as the colorant (B), 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). Through this process, a mixture was prepared.

[0115] 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 19 μm. 150 parts by mass of the obtained powder and 0.45 parts by mass of AEROSIL R972 (manufactured by Nippon Aerosil Co., Ltd.) as a flowability modifier were uniformly mixed in a Henschel mixer to prepare primary color powder coating composition 1. The average particle size (D50) of the obtained primary color powder coating composition was 19 μm. The average particle size (D50) was measured using a particle size analyzer Microtrac HRA model 9320-X100 (manufactured by Nikkiso Co., Ltd.).

[0116] (Examples 2 to 13) Primary color powder coating compositions 2 to 16 were prepared in the same manner as in Example 1, except that the film-forming resin (A), colorant (B), curing agent (C) and other additives were changed as shown in Table 1. 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 Table 1. In Table 1, "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 (e.g., acid groups, hydroxyl groups, amino groups and isocyanate groups) that can react with acid groups, hydroxyl groups and epoxy groups contained in the curing agent (C).

[0117] [Table 1]

[0118] (Production of Powder Coating Composition) Example 1 <First granulation process> (Example) First, as the cationic compound (D-1), 1.0 part by mass of stearyltrimethylammonium chloride was mixed with 100 parts by mass of water and stirred until the solution became transparent to the naked eye to prepare an aqueous solution of the cationic compound. 100 parts by mass of the primary color powder coating composition 1 was charged into a mixer / agitator 5XDMV-Qr (manufactured by Shinagawa Kogyosho Co., Ltd.), and while mixing at 20 rpm, 16 parts by mass of the aqueous solution of the cationic compound was sprayed and added over 5 minutes. Thereafter, mixing was continued for 60 minutes under the same conditions to obtain a first granule. Next, while stirring the first granules under the same conditions, 100 parts by mass of the raw powder coating composition 2 was added and mixed for 5 minutes to obtain a powder coating composition. The series of production steps was carried out at 20° C. (room temperature).

[0119] (Formation of coating film) The substrate was a 0.8 x 70 x 150 mm JIS G 3141 (SPCC-SD) cold-rolled steel plate that had been zinc phosphate-treated and then solvent-degreased. This substrate was coated with a powder paint electrostatic applicator OPTI hand gun (Graco) at a discharge rate of 120 g / min, a set voltage of 100 kV, a set current of 70 μA, free ion removal, and a gun distance of 15 cm, to a film thickness of 50-60 μm, and baked at 180°C for 20 minutes, for testing.

[0120] (Examples 2 to 9, 11 to 16) A coating film was formed in the same manner as in Example 1, except that the cationic compound, primary color powder coating composition, and granulation conditions were changed as shown in Table 2. The blending amounts shown in Table 2 are the solid content amounts of each. Example 10 In the first granulation step, 100 parts by mass of primary color powder coating composition 1 and 0.2 parts by mass of cationic compound (D-2) were mixed for 3 minutes at 1,200 rpm using a super mixer (manufactured by Kawata Co., Ltd.) to obtain a first granule. Next, while stirring the first granule under the same conditions, 100 parts by mass of the raw powder coating composition 2 was added and mixed for 5 minutes to obtain a powder coating composition. The series of production was carried out at 25°C (room temperature).

[0121] Comparative Example 1 100 parts by mass of primary color powder coating composition 1 and 100 parts by mass of primary color powder coating composition 2 were charged into a mixer agitator 5XDMV-Qr (manufactured by Shinagawa Kogyosho Co., Ltd.) and mixed at 20 rpm for 5 minutes to obtain a powder coating composition. The series of production was carried out at 25°C (room temperature).

[0122] Comparative Example 2 First, 2 parts by mass of the other polymer (d-1) and 98 parts by mass of methanol were mixed and stirred until the mixture became visually transparent to prepare a polymer solution. 100 parts by mass of primary color powder coating composition 1 and 100 parts by mass of primary color powder coating composition 2 were charged into a mixer / stirrer 5XDMV-Qr (manufactured by Shinagawa Kogyosho Co., Ltd.), and 100 parts by mass of the polymer solution was sprayed over 10 minutes while stirring at 20 rpm. Then, mixing was continued for 60 minutes under the same conditions to obtain a powder coating composition.

[0123] Comparative Example 3 100 parts by mass of primary color powder coating composition 1 and 100 parts by mass of primary color powder coating composition 2 were charged into a mixer / stirrer 5XDMV-Qr (manufactured by Shinagawa Kogyosho Co., Ltd.), and while stirring at 20 rpm, 4 parts by mass of the polymer solution was sprayed over 10 minutes. Thereafter, mixing was continued under the same conditions for 60 minutes to obtain a powder coating composition.

[0124] Comparative Example 4 100 parts by mass of primary color powder coating composition 1 and 100 parts by mass of primary color powder coating composition 2 were charged into a mixing stirrer 5XDMV-Qr (manufactured by Shinagawa Kogyosho Co., Ltd.), and while stirring at 20 rpm, 0.5 parts by mass of other polymer (d-3) was sprayed over 10 minutes. Then, mixing was continued for 60 minutes under the same conditions to obtain a powder coating composition.

[0125] Comparative Example 5 100 parts by mass of primary color powder coating composition 1 and 100 parts by mass of primary color powder coating composition 2 were charged into a mixing stirrer 5XDMV-Qr (manufactured by Shinagawa Kogyosho Co., Ltd.), and while stirring at 20 rpm, 3 parts by mass of other polymer (d-4) was sprayed over 10 minutes. Then, mixing was continued for 60 minutes under the same conditions to obtain a powder coating composition.

[0126] Details of the raw materials used are shown below. (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℃ Colorant (B) (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) 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 Concentrate (Kao Corporation, stearyl trimethylammonium chloride), softening point: 95-104°C, weight average molecular weight: 333, amine value: 168mgKOH / g (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 (D-3) Polylysine (JNC Corporation), softening point: 172°C, weight average molecular weight: 4,700, amine value: 600mgKOH / g (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 Other polymers: (d-1) Dry transparent white lacquer (Nippon Shellac Kogyo Co., Ltd., shellac resin), softening point: 70 to 75°C, amine value: 0 mgKOH / g (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, solid content concentration: 5% by mass (aqueous solution), amine value: 0 mgKOH / g (d-3) EMUSTAR-0136 (paraffin wax, manufactured by Nippon Seiro Co., Ltd.), softening point: 60°C, average particle size: 0.50 μm or less, solid content concentration: 40% by mass (water dispersion), amine value: 0 mgKOH / g (d-4) A-6001 (manufactured by Resitex, acrylic resin emulsion), softening point: 70 to 80°C, solid content: 63 to 67% by mass (water dispersion), amine value: 0 mgKOH / g Other Additives: Surface conditioner: KF-54 (Shin-Etsu Chemical Co., Ltd., silicone-based) Armpit prevention agent: Benzoin (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) Flow control agent: AEROSIL R972 (Nippon Aerosil Co., Ltd., silica) Extender pigment: Precipitated barium sulfate 100 (Sakai Chemical Industry Co., Ltd., barium sulfate)

[0127] The following evaluations were carried out on the coating films obtained in the above-mentioned Examples 1 to 16 and Comparative Examples 1 to 5. The obtained evaluation results are shown in Tables 2 and 3.

[0128] <Colorfastness> The coating films obtained in the Examples and Comparative Examples were visually observed for mottling and evaluated for color separation resistance. The evaluation criteria were as follows: △ or higher was considered to be acceptable. ◎: When viewed from a distance of 50 cm, the mottled color pattern is not recognizable ○: When viewed from a distance of 50 cm, the color mottling is slightly discernible △: When viewed from a distance of 50 cm, the mottled color pattern is clearly recognizable, but Unrecognizable or barely recognizable when viewed from a distance of 80 cm ×: When viewed from a distance of 80 cm, the mottled color pattern is clearly visible

[0129] <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.

[0130] [Table 2]

[0131] [Table 3]

[0132] Examples 1 to 16 are examples of the present disclosure, and the resulting coating films exhibited a smooth and uniform hue. On the other hand, Comparative Example 1 is an example that does not include the first granulation step, and 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 a smooth coating film could not be obtained. [Industrial Applicability]

[0133] 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. A method for producing a coating composition comprising the steps of: preparing two or more negatively charged primary color powder coating compositions; mixing a portion of the two or more primary color powder coating compositions with a cationic compound (D) selected from a cationic polymer, stearyltrimethylammonium chloride, and cetylpyridinium chloride to obtain a positively charged preliminary mixture; and mixing the premix with the remainder of the two or more primary color powder coating compositions to obtain a powder coating composition; The two or more primary color powder coating compositions each contain at least the same or different film-forming resin (A), The coating film-forming resin (A) includes a polymer having at least one curable functional group selected from an acid group, a hydroxyl group, and an epoxy group. The method for producing a powder coating composition, wherein the amount of the cationic compound (D) is 0.01 parts by mass or more and 2 parts by mass or less per 100 parts by mass in total of the two or more primary color powder coating compositions.

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 primary color powder coating composition has an average particle size (D50) of 25 μm or less.

4. The method according to claim 1, 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 50° C. or higher and 180° C. or lower.

5. The method according to claim 1 , wherein the mixing of the part of the two or more primary color powder coating compositions with the cationic compound (D) is carried out in a dry manner.

6. 2. The method according to claim 1, wherein mixing a portion of the two or more primary color powder coating compositions with a cationic compound (D) to obtain a pre-mixture is carried out by mixing the cationic compound (D) with water and / or a hydrophilic solvent to obtain a solution of the cationic compound, mixing a portion of the primary color powder coating compositions with the solution of the cationic compound to obtain a mixed liquid containing a pre-mixture, and removing water and / or the hydrophilic solvent from the mixed liquid to obtain the pre-mixture.

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

8. The method according to claim 1 , wherein the primary color powder coating composition further comprises a curing agent (C).

9. 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 8 to an object to be coated.

10. A method for matching a powder coating composition, comprising the steps of: Producing two or more primary color powder coating compositions each having a different hue and / or tone and being negatively charged; mixing at least a portion of the two or more primary color powder coating compositions with a cationic compound (D) selected from a cationic polymer, stearyltrimethylammonium chloride, and cetylpyridinium chloride to obtain a positively charged preliminary mixture; mixing the premix with the remainder of the two or more primary color powder coating compositions to form a powder coating composition; The two or more primary color powder coating compositions each contain at least the same or different film-forming resin (A), The coating film-forming resin (A) contains a polymer having at least one curable functional group selected from an acid group, a hydroxyl group, and an epoxy group, The color matching method, wherein the amount of the cationic compound (D) is 0.01 parts by mass or more and 2 parts by mass or less per 100 parts by mass in total of the two or more primary color powder coating compositions.

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