Powder coating material composition, coated film, coated product and method for producing powder coating material composition

Abstract

To provide a powder coating material composition enabling suppression of color separation, a coated film formed by using the powder coating material composition, a coated article provided with the coated film, and a method for producing the powder coating material composition.SOLUTION: According to one aspect of the present invention, there is provided a powder coating material composition comprising at least a first powder coating material 10 and a second powder coating material 20 having tinge different from that of the first powder coating material 10, wherein the surface 10A of the first powder coating material 10 and the surface 20A of the second powder coating material 20 have the same electric charge polarity, and the first powder coating material 10 and the second powder coating material 20 each include a paint powder 11, 21 and a coating layer 12, 22 covering at least a portion of the paint powder 11, 21, the coating layers 12, 22 comprising at least one of a cationic polymer-containing layer 12A, 22A including a cationic polymer and an anionic polymer-containing layer 12B, 22B including an anionic polymer.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a powder coating composition, a coating film, a coated article, and a method for producing a powder coating composition. [Background technology]

[0002] Conventionally, liquid paints using organic solvents have been used as paints. However, in recent years, from the viewpoints of environmental conservation, including the reduction of volatile organic compound (VOC) emissions, and consideration for people's health, powder coating compositions, which are paints that do not contain organic solvents, have been attracting attention.

[0003] Powder coating compositions use coating powder, and the powder coating composition is applied in a dry state to an object to be coated by spraying or the like, and then baked to form a coating film (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-161162 Summary of the Invention [Problem to be solved by the invention]

[0005] Currently, it is desirable to mix two or more powder coatings of different colors to achieve a desired color in powder coating compositions. However, when a coating film is formed on an object to be coated using a powder coating composition containing two or more powder coatings of different colors, even if the powder coatings are mixed uniformly, there is a risk of the coating film having different colors, i.e., so-called color separation.

[0006] The present invention has been made to solve the above problems, and aims to provide a powder coating composition that can suppress color separation, a coating film formed using this powder coating composition, a coated article having this coating film, and a method for producing the powder coating composition. [Means for solving the problem]

[0007] [1] A powder coating composition comprising at least a first powder coating material and a second powder coating material having a different color from the first powder coating material, wherein the surfaces of the first powder coating material and the second powder coating material have the same electrostatic polarity, and the first powder coating material and the second powder coating material each comprise a coating powder and a coating layer covering at least a portion of the coating powder, and each coating layer comprises at least one of a cationic polymer-containing layer containing a cationic polymer and an anionic polymer-containing layer containing an anionic polymer.

[0008] [2] The powder coating composition according to [1], wherein each of the coating layers has a portion where one or more of the cationic polymer-containing layers and one or more of the anionic polymer-containing layers are laminated.

[0009] [3] The powder coating composition according to [2], wherein each of the coating layers has a portion in which the cationic polymer-containing layer and the anionic polymer-containing layer are alternately laminated.

[0010] [4] The powder coating composition according to any one of [1] to [3], wherein the surface of the first powder coating and the surface of the second powder coating are both surfaces of the anionic polymer-containing layer.

[0011] [5] A coating film formed using the powder coating composition described in any one of [1] to [4] above.

[0012] [6] A coated article comprising an object to be coated and the coating film described in [5] formed on the object to be coated.

[0013] [7] A method for producing a powder coating composition containing at least a first powder coating material and a second powder coating material having a color different from that of the first powder coating material, the method comprising: forming a coating layer on the surface of the first powder coating material, the coating layer including at least one of a cationic polymer-containing layer containing a cationic polymer and an anionic polymer-containing layer containing an anionic polymer, and covering at least a portion of the first powder coating material; forming a coating layer on the surface of the second powder coating material, the coating layer including at least one of a cationic polymer-containing layer containing a cationic polymer and an anionic polymer-containing layer containing an anionic polymer, and covering at least a portion of the second powder coating material, to form a second powder coating material having a surface with the same electrostatic polarity as that of the first powder coating material; and dry-blending the first powder coating material and the second powder coating material.

[0014] [8] The method for producing a powder coating composition according to [7], wherein the coating layer of the first powder coating material and the coating layer of the second powder coating material each have a portion in which one or more of the cationic polymer-containing layers and one or more of the anionic polymer-containing layers are laminated.

[0015] [9] The method for producing a powder coating composition according to [8], wherein the coating layer of the first powder coating material and the coating layer of the second powder coating material each have a portion in which the cationic polymer-containing layer and the anionic polymer-containing layer are alternately laminated.

[0016]

[10] The method for producing a powder coating composition according to any one of [7] to [9], wherein the surface of the first powder coating and the surface of the second powder coating are surfaces of the anionic polymer-containing layer. [Effects of the Invention]

[0017] The powder coating composition, coating film, and coated article according to the present invention can suppress color separation, and the method for producing the powder coating composition can provide a powder coating composition that can suppress color separation. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1A is a schematic diagram of a first powder coating material according to an embodiment, and FIG. 1B is a schematic diagram of a second powder coating material according to an embodiment. [Figure 2] FIG. 2 is a schematic diagram of the coating film and coated product according to the embodiment. [Figure 3] FIG. 3A is a scanning electron microscope photograph of the powder coating contained in the powder coating composition of Example 3, and FIG. 3B is a scanning electron microscope photograph of the powder coating contained in the powder coating composition of Comparative Example 2. [Figure 4] FIG. 4A is a photograph of the coated product according to Example 1, and FIG. 4B is a photograph of the coated product according to Example 2. [Figure 5] FIG. 5A is a photograph of a coated product according to Comparative Example 1, and FIG. 5B is a photograph of a coated product according to Comparative Example 2. [Figure 6] Figure 6 is a graph showing the surface potentials of the red paint powder / poly(diallyldimethylammonium chloride) layer (hereinafter referred to as the "PDDA layer"), red paint powder / PDDA layer / poly(sodium 4-styrenesulfonate) layer (hereinafter referred to as the "PSS layer"), red paint powder / PDDA layer / PSS layer / PDDA layer, red paint powder / PDDA layer / PSS layer / PDDA layer / PSS layer, and blue paint powder / PDDA layer, blue paint powder / PDDA layer / PSS layer, blue paint powder / PDDA layer / PSS layer / PDDA layer, and blue paint powder / PDDA layer / PSS layer / PDDA layer / PSS layer. DETAILED DESCRIPTION OF THE INVENTION

[0019] The powder coating composition, coating film, coated article, and method for producing the powder coating composition according to embodiments of the present invention will be described below. Fig. 1A is a schematic diagram of a first powder coating according to this embodiment, and Fig. 1B is a schematic diagram of a second powder coating according to this embodiment. Fig. 2 is a schematic diagram of a coating film and a coated article according to this embodiment.

[0020] <<<Powder coating composition>>> The powder coating composition contains two or more types of powder coatings that are different in color from each other. Specifically, it is a dry blend of at least a first powder coating and a second powder coating that is different in color from the first powder coating. The powder coating composition is not particularly limited as long as it contains two types of powder coatings that are different in color, and may contain three or more, four or more, or five or more types of powder coatings that are different in color. When the powder coating composition contains three types of powder coatings with different colors, it contains, in addition to the first and second powder coatings, a third powder coating having a color different from the first and second powder coatings; when it contains four types of powder coatings with different colors, it contains, in addition to the first, second and third powder coatings, a fourth powder coating having a color different from the first, second and third powder coatings; and when it contains five types of powder coatings with different colors, it contains, in addition to the first, second, third and fourth powder coatings, a fifth powder coating having a color different from the colors of the first, second, third and fourth powder coatings. In the following, the first and second powder coating materials will be described, but the third, fourth, and fifth powder coating materials are similar to the first and second powder coating materials except that they have different colors. In this specification, a "powder coating composition" refers to a composition containing two or more powder coating materials that are different in color from each other, and is different from the "composition for coating powder" used to form the coating powder described below. In this specification, "different colors" refers to differences in one or more of lightness, saturation, and hue.

[0021] <<First powder coating and second powder coating>> The first powder paint 10 and the second powder paint 20 shown in Figures 1A and 1B have different colors. The first powder paint 10 comprises a first paint powder 11 (hereinafter, the "first paint powder 11" may also be referred to as "paint powder 11") and a coating layer 12 that covers at least a portion of the first paint powder 11. The second powder paint 20 comprises a second paint powder 21 (hereinafter, the "second paint powder 21" may also be referred to as "paint powder 21") and a coating layer 22 that covers at least a portion of the second paint powder 21.

[0022] The average particle diameter (D 50 The average particle diameter (D) of the first powder coating material 10 and the second powder coating material 20 is not particularly limited, but is 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. 50 When the average particle diameter (D ) of the first powder coating material 10 and the second powder coating material 20 is within the above range, it becomes easier to obtain a coating film that exhibits a smoother and more uniform hue. 50 ) can be measured, for example, by a particle size measuring device such as a laser diffraction / scattering particle size distribution measuring device ("Microtrac" manufactured by Microtrac Bell Co., Ltd.).

[0023] The surface 10A of the first powder paint 10 and the surface 20A of the second powder paint 20 have the same charge polarity. For example, if the surface 10A of the first powder paint 10 has a negative charge polarity, the surface 20A of the second powder paint 20 also has a negative charge polarity, and if the surface 10A of the first powder paint 10 has a positive charge polarity, the surface 20A of the second powder paint 20 also has a positive charge polarity. The surface 10A of the first powder coating material 10 and the surface 20A of the second powder coating material 20 may be either positively or negatively charged as long as they have the same charge polarity. However, in powder coating using powder coating, the powder coating is often negatively charged before being applied to the substrate. Therefore, if the surface 10A of the first powder coating material 10 and the surface 20A of the second powder coating material 20 have a positive charge polarity, when the surface 10A of the first powder coating material 10 and the surface 20A of the second powder coating material 20 are negatively charged, the positive charges of the first powder coating material 10 and the second powder coating material 20 are offset by the negative charges, which may reduce the adhesive strength of the first powder coating material 10 and the second powder coating material 20 to the substrate. For this reason, it is preferable that the surface 10A of the first powder coating material 10 and the surface 20A of the second powder coating material 20 have a negative charge polarity.

[0024] The absolute value of the difference in surface potential (zeta potential) between the surface 10A of the first powder coating material 10 and the surface 20A of the second powder coating material 20 is preferably 10 mV or less. If the absolute value of this difference is 10 mV or less, charging performance can be made uniform and color separation can be further suppressed. The upper limit of the absolute value of this difference is more preferably 5 mV or less, 3 mV or less, or 1 mV or less. The lower limit of the absolute value of this difference may be 0 mV or more.

[0025] The surface potential of the surface 10A of the first powder coating material 10 is measured in an aqueous solution. Specifically, the surface potential is measured using a Zetasizer Advance PRO manufactured by Malvern Panalytical Co., Ltd., with the first powder coating material 10 dispersed in the aqueous solution. The surface potential of the surface 20A of the second powder coating material 20 is measured in the same manner as the surface potential of the surface 10A of the first powder coating material 10.

[0026] <Paint powder> The paint powders 11 and 21 preferably contain at least a resin (A), and more preferably contain a resin (A) and a color pigment (B). The paint powders 11 and 21 are not limited to those containing only one type of resin (A) and / or only one type of color pigment (B). The paint powders 11 and 21 can be formed from a paint powder composition containing a resin (A), more preferably a paint powder composition containing a resin (A) and a color pigment (B). The paint powder composition may contain a curing agent (C).

[0027] (Resin (A)) The 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. Examples of the acid group include a carboxyl group, a sulfonic acid group, and a phosphoric acid group, and the carboxyl group is preferred.

[0028] The resin (A) is a coating film-forming component, and examples thereof include non-reactive resins such as polyolefin resins (polyethylene, polypropylene, etc.), polyamide resins (nylon resin, etc.), and vinyl chloride resins; and reactive resins such as epoxy resins, amine resins, acid anhydride resins, polyester resins, melamine resins, acrylic resins, polyester resin / epoxy resins, and polybasic acid resins. The resin (A) preferably contains one or more resins selected from acrylic resins, epoxy resins, and polyester resins. For example, from the viewpoint of weather resistance, acrylic resins and polyester resins may be used, and from the viewpoint of the physical properties of the coating film, polyester resins may be used. More specifically, the resin (A) may be one or more resins selected from the group consisting of polyester resins having curable functional groups, epoxy resins having curable functional groups, and acrylic resins having curable functional groups.

[0029] 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-based monomer copolymerizable with the monomer.

[0030] Examples of the monomer containing a functional group capable of reacting with the curing agent (C) include monomers containing one or more groups selected from an epoxy group, an acid group, and a hydroxyl group, and preferably monomers containing one or more groups selected from an epoxy group, a carboxy group, and a hydroxyl group.

[0031] Examples of the monomer having an epoxy group include glycidyl (meth)acrylate. Examples of the monomer having a carboxy group include (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. In the present disclosure, (meth)acrylic acid means acrylic acid and / or methacrylic acid.

[0032] Examples of other vinyl monomers copolymerizable with the functional group-containing monomer 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 can be used alone or in combination of two or more.

[0033] The content of the acrylic resin contained in the resin (A) may be preferably 30 parts by mass or more and 100 parts by mass or less, based on 100 parts by mass of the total amount of the resin (A).

[0034] The epoxy resin is preferably an epoxy resin having an average of one or more epoxy groups per molecule, and specific examples 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; and 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.

[0035] The content of the epoxy resin contained in the 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 resin (A).

[0036] 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.

[0037] Examples of acid components 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. Of these, terephthalic acid and isophthalic acid are preferred. From the viewpoint of weather resistance, the content of isophthalic acid in the acid component is preferably 60% by mass or more, more preferably 80% by mass or more. The acid components can be used alone or in combination of two or more.

[0038] 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 suitable alcohol components include linear or branched glycols such as diethylene glycol, triethylene glycol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, alkylene oxide adducts of bisphenol A, alkylene oxide adducts of bisphenol S, neopentyl glycol, and trihydric or higher polyhydric alcohols such as trimethylolpropane, glycerin, and pentaerythritol, with ethylene glycol, neopentyl glycol, and 1,6-hexanediol being preferred. Each of the alcohol components can be used alone or in combination of two or more.

[0039] In one embodiment, resin (A) may contain one polyester resin, and in another embodiment, it may contain two or more polyester resins. When 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.

[0040] The content of the polyester resin contained in the 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 resin (A).

[0041] In the coating powder composition, the resin (A) may be used alone or in combination of two or more. In one embodiment, the resin (A) may contain a polyester resin and an epoxy resin. In such an embodiment, the mass ratio of the polyester resin to the epoxy resin may be 3 / 7 to 7 / 3.

[0042] The acid value of the 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 resin (A) may be preferably 300 mgKOH / g or more. The hydroxyl value of the 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 resin (A) may be preferably 40 mgKOH / g or more, more preferably 60 mgKOH / g or more. The epoxy equivalent of the 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 resin (A) contains two or more resins, the acid value, hydroxyl value, and epoxy equivalent weight may be the average value of the acid value, hydroxyl value, and epoxy equivalent weight of each resin.

[0043] In two or more types of compositions for paint powder, the acid value, hydroxyl value or epoxy equivalent of the resins (A) contained therein may be the same or different.

[0044] The weight average molecular weight of the 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.

[0045] The softening point of resin (A) may be, for example, 80°C or higher and 130°C or lower, and preferably 90°C or higher and 120°C or lower. Having a softening point within this range has the advantage of improving pigment dispersibility during production of the coating powder composition and improving the storage stability of the resulting coating powder composition. Note that the softening point in this disclosure refers to the Vicat softening temperature measured in accordance with JIS K 7206, using a test load of 10 N and a heating rate of 50°C / hour.

[0046] The content of resin (A) in the composition for paint powder is preferably 40 to 70 parts by mass, more preferably 45 to 70 parts by mass, per 100 parts by mass of the composition for paint powder. When the content of resin (A) in the composition for paint powder is within the above range, a coating film having good physical properties such as adhesion to the substrate and water resistance, and having the desired hue and brightness can be obtained. In two or more types of compositions for paint powder, the compositions of the resins (A) contained therein (types, amounts, and ratios when two or more types of resins (A) are contained) may be the same or different.

[0047] (Color pigment (B)) The color pigment (B) can be any inorganic or organic pigment typically used in powder coatings. Examples of inorganic pigments include titanium oxide, red iron oxide, chrome titanium yellow, yellow iron oxide, and carbon black. Examples of organic pigments include azo, perylene, condensed azo, nitro, nitroso, phthalocyanine, anthraquinone, quinacridone, and dioxane pigments. Specific examples of azo pigments include Lake Red, Fast Yellow, Disazo Yellow, and Permanent Red. Nitro pigments include Naphthol Yellow. Nitroso pigments include Pigment Green B and Naphthol Green. Phthalocyanine pigments include Phthalocyanine Blue and Phthalocyanine Green. Anthraquinone pigments include Indanthrene Blue and Dianthraquinonyl Red. Quinacridone pigments include Quinacridone Red and Quinacridone Violet. Dioxane pigments include Carbazole Dioxazine Violet.

[0048] The content of the color pigment per 100 parts by mass of the resin may be preferably 0.05 parts by mass or more and 90 parts by mass or less, more preferably 0.1 parts by mass or more and 80 parts by mass or less, relative to 100 parts by mass of the total amount of the resin (A). In one embodiment, for example, it may be 1 part by mass or more and 75 parts by mass or less, or even 3 parts by mass or more and 70 parts by mass or less. In the paint powder composition, the content of the color pigment (B) may vary depending on the type of color pigment (B). For example, the content of the inorganic color pigment (B) 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 resin (A), and the content of the organic color pigment (B) 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 resin (A). In two or more types of compositions for paint powder, the composition of the color pigment (B) contained therein (type, amount, and ratio when two or more types of color pigment (B) are contained) may be the same or different.

[0049] (Hardening agent (C)) When the coating powders 11 and 21 contain a reactive resin, they may also contain a curing agent (C). In this embodiment, the coating powder composition is produced by mixing the resin (A), the color pigment (B), and the curing agent (C). The order of mixing is not particularly limited, and the resin (A), the color pigment (B), and the curing agent (C) may be mixed simultaneously, or the resin (A) and the color pigment (B) may be mixed in advance, and then the mixture may be further mixed with the curing agent (C).

[0050] The curing agent can be any known curing agent that corresponds to the functional group of the reactive resin used, without any particular limitation, such as polycarboxylic acid compounds, acid anhydrides, amino group-containing compounds, epoxy group-containing compounds, β-hydroxyalkylamide compounds (HAA), blocked isocyanate compounds, amino resins, etc. In one embodiment, when the resin (A) contains a polymer having an epoxy group, the curing agent (C) is preferably one or more selected from polycarboxylic acid compounds, acid anhydrides, and amino group-containing compounds. In another embodiment, when the 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 resin (A) contains a polymer having a hydroxyl group, the curing agent (C) is preferably a blocked isocyanate compound or an amino resin.

[0051] When matte properties are taken into consideration, the coating powder composition preferably contains, for example, at least one selected from the group consisting of β-hydroxyalkylamide compounds, blocked isocyanates, and melamine compounds.

[0052] 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; and alicyclic polycarboxylic acids such as hexahydrophthalic acid and tetrahydrophthalic acid. Among these, decanedicarboxylic acid is preferred. These compounds may be used alone or in combination of two or more.

[0053] Examples of the acid anhydride include the following aliphatic, alicyclic, and aromatic acid anhydrides. Examples of aliphatic acid anhydrides 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 alicyclic acid anhydrides include hexahydrophthalic anhydride, tetrahydrophthalic anhydride, methylcyclohexenedicarboxylic anhydride, HET acid anhydride, himic acid anhydride, and methylcyclohexenetricarboxylic anhydride; and methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, and methyl himic acid 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).

[0054] Examples of the amino group-containing compound include dicyandiamide, polyvalent amine compounds, imidazole, etc. Examples of the polyvalent amine compound include polyhydrazide compounds such as adipic acid dihydrazide and sebacic acid dihydrazide. Examples of imidazoles 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 curing rate of the polycarboxylic acid compound, the acid anhydride and the amino group-containing compound can be adjusted by using them in combination with a known curing accelerator.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.

[0055] 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.

[0056] The β-hydroxyalkylamide compound (HAA) can be a compound represented by the following formula (I):

[0057] [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 a commercially available product of such a compound is Primid XL-552.

[0058] The blocked isocyanate compound refers to blocked isocyanates in which the isocyanate group is blocked with a blocking agent to prevent the compound from showing activity at a certain temperature or below, and uretdiones in which isocyanate groups are reacted with each other to form uretdione rings to prevent the compound from showing activity. The blocked isocyanate compound is a polyisocyanate compound in which the isocyanate group is blocked with a blocking agent.

[0059] Examples of polyisocyanate compounds 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 and (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 number of isocyanate groups is in excess relative to the hydroxyl groups of a polyol such as ethylene glycol, propylene glycol, 1,4-butylene glycol, polyalkylene glycol, trimethylolpropane, or hexanetriol; biuret-type adducts and isocyanuric ring-type adducts of hexamethylene diisocyanate, isophorone diisocyanate, tolylene diisocyanate, xylylene diisocyanate, 4,4'-diphenylmethane diisocyanate, and 4,4'-methylenebis(cyclohexyl isocyanate), etc.

[0060] Examples of blocking agents used to block polyisocyanate compounds 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 such as ε-caprolactam, δ-valerolactam, γ-butyrolactam, β-propiolactam, etc.; oxime blocking agents such as 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 such as 1,2-pyrazole and 3,5-dimethylpyrazole; and triazole blocking agents such as 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. Examples of the amino resin include melamine resin, urea resin, and benzoguanamine resin. The amino resin can be obtained by condensing an amino compound with an aldehyde compound and then etherifying the condensed product 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.

[0061] The curing agent (C) may contain other curing agents (C). Examples of such curing agents (C) include blocked isocyanate-based curing agents in which the terminal isocyanate groups of polyisocyanate compounds such as tris(2,3-epoxypropyl)isocyanate, tolylene diisocyanate, and xylylene diisocyanate, or prepolymers thereof, are blocked with a conventional blocking agent such as a lactam compound or an oxime compound; epoxy-based curing agents such as bisphenol A diglycidyl ether; alkoxysilane-based curing agents such as methoxysiloxane oligomers and ethoxysilane oligomers; polyaziridine-based curing agents such as adipic acid dihydrazide and succinic acid dihydrazide; and oxazoline-based curing agents such as 1,4-bis(2-oxazolinyl-2)-benzene and 1,2,4-tris(2-oxazolinyl-2)-benzene.

[0062] In one embodiment, the coating powder composition may contain, as the 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.

[0063] In this embodiment, the average hydroxyl value of the polyester or acrylic resin having hydroxyl groups is preferably 40 mgKOH / g or more, more preferably 60 mgKOH / g or more, from the viewpoint of achieving a matte finish. 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. To achieve a sufficient matte effect, the dissociation temperature of the blocking agent or uretdione ring of such a blocked isocyanate is preferably 160° C. or lower, more preferably 140° C. or lower.

[0064] The amount of curing agent (C) in the coating powder composition varies depending on the types of resin (A) and curing agent (C), and can be set appropriately. For example, the amount of 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 resin (A). In one embodiment, when a resin (A) having a hydroxyl group is used as the resin (A) of the coating powder 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 resin (A) having a hydroxyl group.

[0065] Furthermore, 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 resin (A) and the total of groups reactive with acid groups, hydroxyl groups, and epoxy groups (for example, 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.

[0066] In one embodiment, the coating powder composition may contain a hydroxyl group-containing resin and an epoxy group-containing resin as the resin (A), and a carboxyl group-containing compound and a blocked isocyanate as the curing agent (C). Use of such a coating powder composition can provide a higher matte effect and prevent popping and show-through. Here, "popping" refers to a coating defect formed by foaming on or inside the coating film during application of the coating powder composition, and "show-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.

[0067] 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 matte effect, it is preferably an acrylic resin having an epoxy group.

[0068] 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 is preferably 20% by mass or more, more preferably 50% by mass or more, based on 100% by mass of the total amount of blocked isocyanates. When the content is within the above range, foaming can be suppressed.

[0069] The content of the blocked isocyanate is preferably 15 to 60 parts by mass, more preferably 20 to 60 parts by mass, 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 achieved, and foaming on the surface or inside of the coating film can be suppressed.

[0070] Furthermore, in the same embodiment, the molar ratio of epoxy groups to carboxy groups (epoxy groups / carboxy groups) contained in the coating powder composition may 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 resulting coating film may have good matte properties and water resistance. In two or more types of compositions for paint powder, the composition of the curing agent (C) that can be contained (type, amount, and ratio when two or more types of curing agent (C) are contained) may be the same or different.

[0071] In the same embodiment, the combination of resin (A) and curing agent (C) is preferably such that resin (A) contains a polyester resin having hydroxyl groups and / or an acrylic resin having hydroxyl groups, and curing agent (C) contains a blocked isocyanate blocked with at least one blocking agent selected from the group consisting of oxime-, pyrazole-, and triazole-based blocking agents; or such that resin (A) contains a resin having hydroxyl groups and a resin having epoxy groups, and curing agent (C) contains a carboxyl group-containing compound and a blocked isocyanate. In these two combinations, the molar ratio of hydroxyl groups to blocked isocyanate in resin (A) (hydroxyl groups / blocked isocyanate) is preferably 0.5 to 2.0, more preferably 0.8 to 1.2. By keeping this ratio within the above range, the resulting coating film has a good matte effect and good coating properties.

[0072] (curing catalyst) The coating powder composition may further contain a curing catalyst. The inclusion of a curing catalyst makes it easy to adjust the gel time (the time until the coating film hardens). 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.

[0073] Examples of the tin catalyst include dibutyltin dilaurate, dibutyltin distearate, tin bis(2-ethylhexanoate), n-butyltris(2-ethylhexanoate), tin di-n-butylbis(2-ethylhexanoate), tin di-n-butylbis(2,4-pentanedionate), dioctyldilauryltin, tetra-n-butyltin, tetra-n-octyltin, dibutyltin diacetate, tetrabutyldiacetoxydistannoxane, tin acetylacetone, dibutyltin oxide, and dimethyltin oxide.

[0074] The imidazole compound is not particularly limited, and examples thereof include alkylimidazoles 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 alkyl-substituted imidazoles include cyanoalkyl-substituted imidazoles such as 2-phenylimidazole, 2-phenyl-4-methylimidazole, aromatic-substituted imidazoles such as 2-phenylimidazole, 2-phenyl-4-methylimidazole, and 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, but preferred are alkylimidazoles and aromatic-substituted imidazoles.

[0075] The imidazoline compound is not particularly limited, but examples thereof include 2-phenylimidazole, 2-methylimidazoline, 2-undecylimidazoline, and 2-heptadecylimidazoline.

[0076] Examples of the metal complex of the imidazole compound and / or imidazoline compound include a complex of the imidazole compound or the imidazoline compound with a metal salt. Such metal salts are not particularly limited, but include those composed of a metal such as copper, nickel, cobalt, calcium, zinc, zirconium, silver, chromium, manganese, tin, iron, titanium, antimony, or aluminum and a salt such as chloride, bromide, fluoride, sulfate, nitrate, acetate, malate, stearate, benzoate, or methacrylate.

[0077] The tertiary phosphine compound is not particularly limited, but examples thereof include triphenylphosphine and tritolylphosphine.

[0078] The quaternary phosphonium salt is not particularly limited, but examples thereof include benzyltriphenylphosphonium chloride, butyltriphenylphosphonium bromide, ethyltriphenylphosphonium iodide, and ethyltriphenylphosphonium bromide.

[0079] The quaternary ammonium salt is not particularly limited, but examples thereof include tetraethylammonium chloride, tetraethylammonium bromide, and benzyltrimethylammonium bromide.

[0080] The curing catalyst may be, for example, 0.0001 to 10 parts by mass per 100 parts by mass of each coating powder composition. By ensuring that the curing catalyst content is within the above range, the gel time of the resulting coating powder composition can be adjusted to a desired range.

[0081] (Other additives) The coating powder composition may further contain other additives. Examples of the other additives include those commonly used in the field of powder coatings, such as heat stabilizers, light stabilizers, slip agents, lubricants, plasticizers, antistatic agents, crystal nucleating agents, flow control agents such as acrylate polymers, crosslinking accelerators such as various catalysts and organic tin compounds, anti-pinhole agents such as benzoin, extender pigments, modifiers, surface conditioners, ultraviolet absorbers, antioxidants, and anti-foaming agents. When these additives are contained, the amount thereof may be 0.1 to 5 parts by mass per 100 parts by mass of the resin (A).

[0082] The inclusion of the extender pigment makes it easier to adjust the specific gravity of the coating powder composition and improves the mechanical properties of the resulting coating film. Examples of the extender pigment include talc, silica, calcium carbonate, and barium sulfate.

[0083] In the paint powder composition, the content of the extender pigment may be preferably 0 parts by mass or more and less than 15 parts by mass, more preferably 0 parts by mass or more and less than 10 parts by mass, and even more preferably 0 parts by mass or more and less than 5 parts by mass, relative to 100 parts by mass of the total amount of resin (A).

[0084] The modifier may be a resin different from resin (A), such as 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 to 50 parts by mass per 100 parts by mass of resin (A).

[0085] The surface modifier can adhere to the surface of the powder coating and control the fluidity and chargeability of the powder coating. Examples of the surface modifier include inorganic particles such as silica and aluminum oxide (alumina); and organic particles such as acrylic resin. The particle diameter of such a 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 per 100 parts by mass of each coating powder composition. Note that the use of a surface modifier is not essential in the manufacturing method disclosed herein; even without the addition of a surface modifier, a coating powder composition can be manufactured that can produce a coating film that exhibits a smooth and uniform hue.

[0086] <Coating layer> The coating layers 12, 22 cover at least a portion of the paint powder 11, 21. In this specification, "covering" means that the coating layer covers 50% or more of the surface of the paint powder, assuming the surface area of ​​the paint powder to be 100%, and is different from being scattered. The fact that the coating layers 12, 22 cover at least a portion of the paint powder 11, 21 can be confirmed by observing the cross sections of the first powder paint and the second powder paint using a scanning electron microscope (SEM). The coating layers 12, 22 preferably cover 80% or more, 85% or more, or 90% or more of the surface of the paint powder 11, 21. Note that the coating layers 12, 22 do not have to cover the entire surface of the paint powder as long as they cover 50% or more of the surface of the paint powder 11, 21, and the coating layers 12, 22 may have holes or defects.

[0087] The coating layers 12, 22 include at least one of a cationic polymer-containing layer 12A, 22A containing a cationic polymer and an anionic polymer-containing layer 12B, 22B containing an anionic polymer. The surface 10A of the first powder coating 10 and the surface 20A of the second powder coating 20 have the same charge polarity. For example, if the surface 10A of the first powder coating 10 is the surface of the anionic polymer-containing layer 12B, the surface 20A of the second powder coating 20 is also the surface of the anionic polymer-containing layer 22B. If the surface 10A of the first powder coating 10 is the surface of the cationic polymer-containing layer 12A, the surface 20A of the second powder coating 20 is also the surface of the cationic polymer-containing layer 22A. The surface 10A of the first powder coating 10 shown in FIG. 1A is the surface of the anionic polymer-containing layer 12B, and the surface 20A of the second powder coating 20 shown in FIG. 1B is the surface of the anionic polymer-containing layer 22B.

[0088] The coating layers 12 and 22 preferably have a portion where one or more cationic polymer-containing layers 12A and 22A and one or more anionic polymer-containing layers 12B and 22B are laminated. By having such a laminated portion, the charging polarity of the surface of the coating layers 12 and 22 can be adjusted. The coating layers 12 and 22 more preferably have a laminated structure consisting of one or more cationic polymer-containing layers 12A and 22A and one or more anionic polymer-containing layers 12B and 22B, as shown in FIGS. 1A and 1B. The coating layers may also have a single-layer structure consisting of either a cationic polymer-containing layer or an anionic polymer-containing layer.

[0089] Paint powders often have a negatively charged polarity, and from the standpoint of negatively charging the surface 10A of the first powder paint 10 and the surface 20A of the second powder paint 20, it is preferable that the coating layers 12, 22 are laminated so that the innermost layer is the cationic polymer-containing layer 12A, 22A and the outermost layer is the anionic polymer-containing layer 12B, 22B. However, the coating layers 12, 22 may also be laminated so that the innermost layer is the anionic polymer-containing layer 12B, 22B and the outermost layer is the cationic polymer-containing layer 12A, 22A.

[0090] More preferably, the coating layers 12, 22 have portions where the cationic polymer-containing layers 12A, 22A and the anionic polymer-containing layers 12B, 22B are alternately laminated. Such alternately laminated portions of the coating layers 12, 22 allow the formation of uniform coating layers 12, 22 and reduce the areas of the surfaces of the paint powders 11, 21 that are not covered by the coating layers 12, 22. When such alternately laminated portions are present, the number of cationic polymer-containing layers 12A, 22A and the anionic polymer-containing layers 12B, 22B in the laminated portions may be two or more, three or more, or four or more. More preferably, the coating layers 12, 22 have a structure where the cationic polymer-containing layers 12A, 22A and the anionic polymer-containing layers 12B, 22B are alternately laminated.

[0091] Since paint powders often have a negatively charged polarity, and from the viewpoint of negatively charging the surface 10A of the first powder paint 10 and the surface 20A of the second powder paint 20, it is preferable that the coating layers 12, 22 have portions alternately laminated such that the innermost layer of the coating layers 12, 22 is a cationic polymer-containing layer 12A, 22A, and the outermost layer of the coating layers 12, 22 is an anionic polymer-containing layer 12B, 22B. However, the coating layers 12, 1A has a portion where the cationic polymer-containing layer 12A, the anionic polymer-containing layer 12B, the cationic polymer-containing layer 12A, the anionic polymer-containing layer 12B, the cationic polymer-containing layer 12A, the anionic polymer-containing layer 12B are alternately laminated in this order from the paint powder 11, 21 side.

[0092] When the coating layer 12, 22 is composed of one cationic polymer-containing layer 12A, 22A or anionic polymer-containing layer 12B, 22B, the thickness of the cationic polymer-containing layer 12A, 22A or the anionic polymer-containing layer 12B, 22B is preferably 1 nm or more and 10 nm or less. If the thickness is within the above range, the difference in surface potential can be reduced, and color separation between the first powder coating material 10 and the second powder coating material 20, which have different colors, can be suppressed.

[0093] When the coating layers 12, 22 have a laminated or alternating laminated structure consisting of one or more cationic polymer-containing layers 12A, 22A and one or more anionic polymer-containing layers 12B, 22B, the thickness of each of the cationic polymer-containing layers 12A, 22A and the anionic polymer-containing layers 12B, 22B is preferably 1 nm or more and 10 nm or less. If the thickness is within the above range, the difference in surface potential can be reduced, and color separation between the first powder coating material 10 and the second powder coating material 20, which have different colors, can be suppressed.

[0094] It is preferable that the cationic polymer or anionic polymer contained in the coating layer 12 of the first powder coating material 10 is the same as the cationic polymer or anionic polymer contained in the coating layer 22 of the second powder coating material 20. By using the same cationic polymer or anionic polymer in the coating layers 12 and 22, the difference in surface potential can be further reduced.

[0095] (Cationic polymer-containing layer) The cationic polymer-containing layers 12A and 22A are layers containing a cationic polymer. The cationic polymer is not particularly limited, but examples thereof include polydiallyldimethylammonium chloride, polyvinylpyrrolidone, polyethyleneimine, polyallylamine, and other polyamines, polyamides such as poly(N-isopropylacrylamide), and natural polycations such as chitosan and chitin. Among these, polydiallyldimethylammonium chloride is preferred because of its high water solubility and the commercially available cationic polymers with various molecular weights.

[0096] The weight-average molecular weight of the cationic polymer is preferably 1,000 or more. If the weight-average molecular weight of the cationic polymer is 1,000 or more, a cationic polymer-containing layer consisting of one molecular layer can be formed. The lower limit of the weight-average molecular weight of the cationic polymer is more preferably 5,000 or more, 10,000 or more, or 100,000 or more, and the upper limit may be 1,000,000 or less, 500,000 or less, or 100,000 or less. The weight-average molecular weight of the cationic polymer can be measured by GPC (gel permeation chromatography) method.

[0097] When the cationic polymer is an amine-based polymer, the amine value of the cationic polymer is preferably 0.1 mgKOH / g or more and 1000 mgKOH / g or less. When the amine value of the cationic polymer is within the above range, color separation of the resulting coating film can be suppressed. The lower limit of the amine value of the cationic polymer is more preferably 0.5 mgKOH / g or more, 1 mgKOH / g or more, or 100 mgKOH / g or more, and the upper limit may be 750 mgKOH / g or less, 500 mgKOH / g or less, or 300 mgKOH / g or less. The amine value of the cationic polymer can be measured by titration with an aqueous potassium hydroxide solution.

[0098] (Anionic polymer-containing layer) The anionic polymer-containing layers 12B and 22B are layers containing an anionic polymer. Examples of anionic polymers include, but are not limited to, polysulfones such as sodium polystyrene sulfonate and polyvinyl sulfate, synthetic polyanions such as polyacrylic acid and polymethacrylic acid, polyalcohols such as polyvinyl alcohol, and natural polyanions such as alginic acid, chondroitin sulfate, heparin, cellulose sulfate, dextran sulfate, carboxymethylcellulose, and gelatin. Among these, sodium polystyrene sulfonate is preferred because it is highly water-soluble and commercially available in a variety of molecular weights.

[0099] The weight-average molecular weight of the anionic polymer is preferably 1,000 or more. If the weight-average molecular weight of the anionic polymer is 1,000 or more, an anionic polymer-containing layer consisting of one molecule can be formed. The lower limit of the weight-average molecular weight of the anionic polymer is more preferably 5,000 or more, 10,000 or more, or 100,000 or more, and the upper limit may be 1,000,000 or less, 500,000 or less, or 100,000 or less. The weight-average molecular weight of the anionic polymer can also be measured by GPC (gel permeation chromatography).

[0100] <<<Method for producing powder coating composition>>> The powder coating composition can be obtained as follows. First, coating powders 11 and 21 are obtained. Coating powders 11 and 21 may be prepared by purchasing commercially available products, or by manufacturing using the coating powder composition. The coating powder composition can be manufactured by a known method. For example, the coating powder composition can be manufactured by a manufacturing method including mixing the resin (A) with, if necessary, a color pigment (B), a curing agent (C), a curing catalyst, and other additives (mixing step), melt-kneading the resulting mixture (melt-kneading step), and cooling the resulting melt-kneaded mixture (cooling step) and pulverizing it (pulverizing step). This manufacturing method may further include classifying the resulting pulverized product.

[0101] The order of mixing the resin (A) with the color pigment (B), curing agent (C), curing catalyst, and other additives used as needed is not particularly limited. In one embodiment, the resin (A), color pigment (B), curing catalyst, and other additives may be mixed, and then the mixture may be further mixed with the curing agent (C), but this is not limiting. The mixing can be carried out using a super mixer, ribbon blender, drum blender, Henschel mixer, etc. The mixing is preferably carried out at room temperature, for example, at 10 to 40°C, preferably 15 to 35°C.

[0102] The melt-kneading can be carried out using a kneading machine 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 portion of the raw materials can be melted and the entire raw materials 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.

[0103] The melt-kneaded product can be cooled, for example, with a cooling roll, a cooling conveyor, or the like. The resulting solidified product can be pulverized in one step or in two or more steps. For example, coarse pulverization can be followed by fine pulverization. The pulverization can be carried out using a pulverizer such as a hammer mill or a jet impact mill.

[0104] By the classification, large particles and small particles can be removed, and the particle size distribution can be narrowed. For classification, for example, an air classifier, a vibration sieve, an ultrasonic sieve, etc. can be used. By the classification, the average particle size of the obtained particles can be adjusted to 15 to 30 μm.

[0105] Next, a coating layer 12 containing at least one of a cationic polymer-containing layer 12A and an anionic polymer-containing layer 12B and covering at least a portion of the paint powder 11 is formed on the surface of the paint powder 11 to form a first powder paint 10. Also, a coating layer 22 containing at least one of a cationic polymer-containing layer 22A and an anionic polymer-containing layer 22B and covering at least a portion of the paint powder 21 is formed on the surface of the paint powder 21 to form a second powder paint 20.

[0106] The coating layers 12, 22 can be formed, for example, by a dry process or a wet process. In one embodiment, when the coating layers 12, 22 are formed by a dry process, the solid cationic polymer and the solid anionic polymer may be added while mixing the paint powders 11, 21.

[0107] In another embodiment, when the coating layers 12, 22 are formed by a wet process, a polymer solution is prepared by dissolving a cationic polymer or an anionic polymer in a solvent. A solution in which a cationic polymer is dissolved in a solvent is referred to as a cationic polymer solution, and a solution in which an anionic polymer solution is dissolved in a solvent is referred to as an anionic polymer solution. The polymer solution may then be added to the coating powders 11, 21 while they are being mixed.

[0108] The concentration of the cationic polymer in the cationic polymer solution and the concentration of the anionic polymer in the anionic polymer solution are preferably 0.0001% by mass or more and 10% by mass or less, respectively.

[0109] The solvent for the cationic polymer solution and the anionic polymer solution is not particularly limited, but examples thereof include water, alcohols such as ethanol, isopropyl alcohol, and butanol, mixed solvents of water and alcohols, cellosolve, ketones, etc. Among these, water and alcohols are preferred from the viewpoints of safety and productivity.

[0110] After preparing the cationic polymer-containing solution and the anionic polymer-containing solution, the cationic polymer-containing solution is first added to the dispersion in which the coating powder 11 has been dispersed, or the coating powder 11 is added to the cationic polymer-containing solution, and the mixture is stirred at a temperature of 1°C to 50°C (e.g., room temperature) using a stirring device (e.g., a Planetary Mixer manufactured by Asada Iron Works Co., Ltd.). Stirring can be performed, for example, at a rotation speed of 3 rpm to 2000 rpm for a stirring time of 10 minutes to 120 minutes. This results in a coating powder 11 / cationic polymer-containing layer 12A in which at least a portion of the coating powder 11 is coated with the cationic polymer-containing layer 12A. The coating powder 11 / cationic polymer-containing layer 12A contained in the cationic polymer-containing solution is then washed, for example, by vacuum filtration using water, and the solvent contained in the cationic polymer-containing solution is removed, recovering the coating powder 11 / cationic polymer-containing layer 12A. Furthermore, by the same procedure, a coating powder 21 / cationic polymer-containing layer 22A in which at least a part of the coating powder 21 is covered with the cationic polymer-containing layer 22A is obtained.

[0111] Next, the coating powder 11 coated with the cationic polymer-containing layer 12A is added to the anionic polymer-containing solution and stirred at a temperature of 1°C to 50°C (e.g., room temperature) using, for example, the stirring device described above. Stirring can be performed, for example, at a rotation speed of 3 rpm to 2000 rpm for a stirring time of 10 minutes to 120 minutes. This results in a coating powder 11 / cationic polymer-containing layer 12A / anionic polymer-containing layer 12B in which at least a portion of the coating powder 11 / cationic polymer-containing layer 12A is further coated with the anionic polymer-containing layer 12B. The coating powder 11 / cationic polymer-containing layer 12A / anionic polymer-containing layer 12B contained in the anionic polymer-containing solution is then washed, for example, by vacuum filtration using water, and the solvent contained in the anionic polymer-containing solution is removed, recovering the coating powder 11 / cationic polymer-containing layer 12A / anionic polymer-containing layer 12B. Furthermore, a coating powder 21 / cationic polymer-containing layer 22A / anionic polymer-containing layer 22B can be obtained by coating at least a portion of the coating powder 21 / cationic polymer-containing layer 22A with an anionic polymer-containing layer 22B using a similar procedure. In this embodiment, it is preferable to remove the solvent after mixing the powder coating and the polymer solution. Therefore, the mixing may be continued until the solvent evaporates and the entire mixture is powdered. Alternatively, the mixture of the powder coating and the polymer solution may be subjected to a reduced pressure treatment (preferably vacuum suction) to remove the solvent.

[0112] The above steps are repeated to obtain a combination of paint powder 11 / cationic polymer-containing layer 12A / anionic polymer-containing layer 12B / cationic polymer-containing layer 12A / anionic polymer-containing layer 12B, which is then dried, for example, by air drying. This results in a first powder paint 10 including paint powder 11 and a coating layer 12 consisting of cationic polymer-containing layer 12A / anionic polymer-containing layer 12B / cationic polymer-containing layer 12A / anionic polymer-containing layer 12B that coats paint powder 11. Similarly, the above steps are repeated to obtain a combination of paint powder 21 / cationic polymer-containing layer 22A / anionic polymer-containing layer 22B / cationic polymer-containing layer 22A / anionic polymer-containing layer 22B, which is then dried. This results in a second powder paint 20 comprising paint powder 21 and a coating layer 12 consisting of a cationic polymer-containing layer 22A / anionic polymer-containing layer 22B / cationic polymer-containing layer 22A / anionic polymer-containing layer 22B that coats the paint powder 21.

[0113] Finally, the resulting first powder coating material 10 and second powder coating material 20 are mixed in a desired ratio by dry blending to obtain a powder coating composition. The mass ratio of the first powder coating material 10 to the second powder coating material 20 can 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. By having the mass ratio within this range, the first powder coating material and the second powder coating material can be mixed more uniformly, and color separation in the resulting coating film can be further suppressed.

[0114] The mixing means is not particularly limited. For example, dry mixers such as a Henschel mixer, ribbon blender, drum blender, or super mixer may be used. When a rotary mixer is used, the rotation speed may be 3 rpm or more and 2,000 rpm or less. Mixing is preferably performed at 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 may be, for example, 1 minute to 30 minutes. Mixing conditions can be appropriately set depending on the types of first powder coating material 10 and second powder coating material 20 used, and the powder coating composition is prepared by mixing the first powder coating material 10 and the second powder coating material 20 so that they are uniformly dispersed. The powder coating composition obtained by the manufacturing method of the present disclosure does not need to be further classified, but may be further classified if necessary.

[0115] <<<Paint films and painted products>>> The powder coating composition is used to form a coating film or a coated article. The coated article 30 shown in Figure 2 comprises an object to be coated 40 and a coating film 50 formed on the surface of the object to be coated 40 using the powder coating composition.

[0116] When forming a coating film 50 or a coated product 30 using the powder coating composition, the powder coating composition is first applied to the surface of the substrate 40 to form a coating film. In this specification, the film formed after the coating composition is applied and before drying or curing is referred to as the "coating film," and the film formed after drying or curing is referred to as the "coating film." As a method for applying the powder coating composition to the surface of the substrate 40, any method known in the field of powder coatings can be used as appropriate. For example, electrostatic powder spraying, fluidized bed immersion, electrostatic fluidized bed immersion, etc. can be preferably used. The thickness of the coating film can be adjusted as appropriate, for example, between 10 μm and 1000 μm.

[0117] After a coating film is formed on the surface of the object 40, the object with the coating film is placed in a furnace or the like and heated, for example, at a temperature of 120°C to 250°C for 5 to 60 minutes. This melts the first powder coating material 10 and the second powder coating material 20, forming a coating film 50 on the surface of the object 40, and obtaining a coated product 30. The thickness of the coating film may be adjusted as appropriate, for example, between 10 μm and 1000 μm.

[0118] The inventors conducted extensive research into the color separation phenomenon in paint films and discovered that the electrostatic charge of the powder paints plays a role in the color separation phenomenon. Specifically, significant differences in the surface potentials of the powder paints can lead to color separation in the paint film. According to this embodiment, the surface 10A of the first powder paint 10 and the surface 20A of the second powder paint 20 have the same electrostatic charge polarity. The first powder paint 10 and the second powder paint 20 each contain powder coatings 11, 21 and coating layers 12, 22 that at least partially cover the powder coatings 11, 21. The coating layers 12, 22 contain at least one of a cationic polymer-containing layer 12A and an anionic polymer-containing layer 12B. This reduces the difference in surface potential between the first powder paint 10 and the second powder paint 20. This suppresses color separation in the paint film 50.

[0119] Color difference is the color difference ΔE of the coating film. * It can be evaluated by calculating ΔE * -1.0<ΔE * When ΔE <1.0 is satisfied, color separation can be suppressed. * is in accordance with JIS Z 8781-4:2013. ΔE * is measured by a method conforming to JIS Z 8781-4:2013 * a * b * L in color space * value, a * value, b * It can be calculated from the value of L based on the following formula (1). * value, a * value, b *The value can be measured using a known color measurement method. For example, a spectrophotometer (Konica Minolta Inc. "CR-400", light source: D65) is used to measure the color value at angles of 25°, 45°, and 75°, assuming that the light receiving unit perpendicular to the coating film is at 0°, at positions 50 mm from the top to the bottom of a coating film formed on the entire surface of one side of a test plate 300 mm long from top to bottom, at the center, and at positions 50 mm from the bottom to the top.

number

[0120] Because the cationic polymer-containing layers 12A, 22A and the anionic polymer-containing layers 12B, 22B are formed using a cationic polymer-containing solution and an anionic polymer-containing solution, the cationic polymer and the anionic polymer spread easily, and at least a portion of the paint powders 11, 21 can be coated with the cationic polymer-containing layers 12A, 22A and / or the anionic polymer-containing layers 12B, 22B. However, as long as the cationic polymer-containing layer and / or the anionic polymer-containing layer can be formed in the gas phase, it is not necessary to use a cationic polymer-containing solution and an anionic polymer-containing solution. [Example]

[0121] To explain the present invention in detail, the following examples are provided, but the present invention is not limited to these. Fig. 3A is a scanning electron microscope photograph of the powder coating contained in the powder coating composition of Example 3, and Fig. 3B is a scanning electron microscope photograph of the powder coating contained in the powder coating composition of Comparative Example 2. Fig. 4A is a photograph of the coated product of Example 1, Fig. 4B is a photograph of the coated product of Example 2, Fig. 5A is a photograph of the coated product of Comparative Example 1, and Fig. 5B is a photograph of the coated product of Comparative Example 2. Fig. 6 is a graph showing the surface potentials of red paint powder / PDDA layer, red paint powder / PDDA layer / PSS layer, red paint powder / PDDA layer / PSS layer / PDDA layer, red paint powder / PDDA layer / PSS layer / PDDA layer, red paint powder / PDDA layer / PSS layer / PDDA layer / PSS layer, and blue paint powder / PDDA layer, blue paint powder / PDDA layer / PSS layer, blue paint powder / PDDA layer / PSS layer / PDDA layer, and blue paint powder / PDDA layer / PSS layer / PDDA layer / PSS layer.

[0122] Example 1 First, 3.75 parts by mass of polyester resin-based red paint powder ("Bilucia Alti RA05 without charge control agent," manufactured by Nippon Paint Industrial Coatings Co., Ltd.; hereafter referred to simply as "red paint powder") was added to pure water at room temperature and dispersed by stirring at 280 rpm for 30 minutes using a stirrer ("Microstar 7.5 control," manufactured by IKA Corporation) at room temperature to obtain a red paint powder dispersion. Polyvinylpyrrolidone (PVP, weight-average molecular weight: 360,000) was added as a cationic polymer to water at room temperature to obtain a PVP-containing solution containing 0.5% PVP. The PVP-containing solution was then added to the red powder dispersion at room temperature to obtain a PVP-containing solution containing 20 parts by mass of the PVP-containing solution per 80 parts by mass of the red paint powder dispersion. The PVP-containing solution containing the red paint powder contained 3% by mass of red paint powder and 0.1% by mass of PVP.

[0123] The PVP-containing solution containing the red paint powder was stirred at room temperature for 20 minutes at 280 rpm using the stirring device, and then filtered under reduced pressure to obtain a red paint powder / PVP layer in which the red paint powder was coated with a PVP layer.The red paint powder / PVP layer was then washed with pure water and air-dried.

[0124] Furthermore, polyvinyl alcohol (PVA, weight-average molecular weight: 66,000-79,200) was added to pure water at room temperature as an anionic polymer to obtain a PVA-containing solution containing 0.5% by mass of PVA. 3.75 parts by mass of the red paint powder / PVP layer was then added to pure water at room temperature and dispersed by stirring at 280 rpm using the stirrer. The red paint powder / PVP layer dispersion was then added to the PVA-containing solution at room temperature so that the PVA-containing solution was 20 parts by mass per 80 parts by mass of the red paint powder / PVP layer dispersion. In the PVA-containing solution containing the red paint powder / PVP layer, the red paint powder / PVP layer content was 3% by mass and the PVA content was 0.1% by mass.

[0125] The PVA-containing solution containing the red paint powder / PVP layer was stirred at room temperature using the above-mentioned stirring device at a rotation speed of 280 rpm for 20 minutes, and then filtered under reduced pressure to obtain a red paint powder / PVP layer / PVA layer in which the red paint powder / PVP layer was further coated with a PVA layer, and the resulting layer was washed with pure water.

[0126] The red paint powder / PVP layer / PVA layer was then air-dried to obtain a red powder paint having a two-layer coating layer consisting of the red paint powder and a PVP / PVA layer covering the red paint powder.

[0127] In addition, a blue powder paint having blue paint powder and a two-layer coating layer consisting of a PVP layer / PVA layer covering the blue paint powder was obtained using a polyester resin-based blue paint powder ("Bilucia Alti BA05 no charge control agent added" manufactured by Nippon Paint Industrial Coatings Co., Ltd., hereinafter simply referred to as "blue paint powder") in the same manner as above.

[0128] Thereafter, the red powder coating and the blue powder coating were mixed in a mass ratio of 1:1 by dry blending using a Henschel mixer at room temperature at a rotation speed of 1200 rpm for 1 minute to obtain a powder coating composition.

[0129] <Example 2> First, 3.75 parts by mass of polyester resin-based red paint powder ("Bilucia Alti RA05 without charge control agent," manufactured by Nippon Paint Industrial Coatings Co., Ltd.; hereafter referred to simply as "red paint powder") was added to pure water at room temperature and dispersed by stirring at 280 rpm for 30 minutes using a stirrer ("Microstar 7.5 control," manufactured by IKA Corporation) to obtain a red paint powder dispersion. Polyvinyl alcohol (PVA, weight-average molecular weight: 66,000-79,200) was added as an anionic polymer to water at room temperature to obtain a PVA-containing solution containing 0.5% PVA. The PVA-containing solution was then added to the red powder dispersion at room temperature to obtain a PVA-containing solution containing 20 parts by mass of the PVA-containing solution per 80 parts by mass of the red paint powder dispersion. The PVA-containing solution containing the red paint powder contained 3% by mass of red paint powder and 0.1% by mass of PVP.

[0130] The PVA-containing solution containing the red paint powder was stirred at room temperature using the above-mentioned stirring device at a rotation speed of 280 rpm for 20 minutes, and then filtered under reduced pressure to obtain a red paint powder / PVA layer in which the red paint powder was coated with a PVA layer, which was then washed with pure water.

[0131] Thereafter, the red paint powder / PVA layer was air-dried to obtain a red powder paint having a single-layer coating layer consisting of the red paint powder and a PVA layer covering the red paint powder.

[0132] In addition, a blue powder paint having blue paint powder and a single-layer coating layer consisting of a PVA layer covering the blue paint powder was obtained using a polyester resin-based blue paint powder ("Bilucia Alti BA05 no charge control agent added" manufactured by Nippon Paint Industrial Coatings Co., Ltd., hereinafter simply referred to as "blue paint powder") in the same manner as above.

[0133] Thereafter, the red powder coating and the blue powder coating were mixed in a mass ratio of 1:1 by dry blending using a Henschel mixer at room temperature at a rotation speed of 1200 rpm for 1 minute to obtain a powder coating composition.

[0134] Example 3 First, 3.75 parts by weight of polyester resin-based red paint powder ("Bilucia Alti RA05 without charge control agent," manufactured by Nippon Paint Industrial Coatings Co., Ltd.; hereafter referred to simply as "red paint powder") was added to pure water at room temperature and dispersed by stirring at 280 rpm for 30 minutes using a stirrer ("Microstar 7.5 control," manufactured by IKA Corporation) at room temperature to obtain a red paint powder dispersion. Also, 0.5 parts by weight of poly(diallyldimethylammonium chloride) (PDDA, weight-average molecular weight: 200,000-350,000) as a cationic polymer and 14.61 parts by weight of NaCl were added to water at room temperature to obtain a PDDA-containing solution containing 0.5% by weight of PDDA. The PDDA-containing solution was then added to the red powder dispersion at room temperature so that 20 parts by weight of the PDDA-containing solution was added to 80 parts by weight of the red paint powder dispersion, obtaining a PDDA-containing solution containing red paint powder. In the PDDA-containing solution containing the red paint powder, the content of the red paint powder was 3 mass %, and the content of PDDA was 0.1 mass %.

[0135] The PDDA-containing solution containing the red paint powder was stirred at room temperature for 20 minutes at 280 rpm using the stirrer described above, and then filtered under reduced pressure to obtain a red paint powder / PDDA layer in which the red paint powder was coated with a PDDA layer.The red paint powder / PDDA layer was then washed with pure water and allowed to air dry.

[0136] In addition, 0.5 parts by mass of poly(sodium 4-styrenesulfonate) (PSS, weight-average molecular weight: 220,000) as an anionic polymer and 14.61 parts by mass of NaCl were added to pure water at room temperature to obtain a PSS-containing solution with a PSS content of 0.5% by mass. Then, 3.75 parts by mass of the red paint powder / PDDA layer were added to pure water at room temperature and dispersed by stirring at 280 rpm using the stirrer. The PSS-containing solution was then added to the red paint powder / PDDA layer dispersion at room temperature so that the PSS-containing solution was 20 parts by mass per 80 parts by mass of the red paint powder / PDDA layer dispersion. In the PSS-containing solution containing the red paint powder / PDDA layer, the red paint powder / PDDA layer content was 3% by mass and the PSS content was 0.1% by mass.

[0137] The PSS-containing solution containing the red paint powder / PDDA layer was stirred at room temperature for 20 minutes at 280 rpm using the stirrer described above, and then filtered under reduced pressure to obtain a red paint powder / PDDA / PSS layer in which the red paint powder / PDDA layer was further coated with a PSS layer. This was then washed with pure water and allowed to air dry.

[0138] Next, 3.75 parts by mass of the resulting red paint powder / PDDA layer / PSS layer was added to pure water at room temperature and dispersed by stirring at 280 rpm using the stirrer described above.The PDDA-containing solution was then added to the red paint powder / PDDA layer / PSS layer dispersion at room temperature.In the PDDA-containing solution containing the red paint powder / PDDA layer / PSS layer, the red paint powder / PDDA layer / PSS layer content was 3% by mass and the PDDA content was 0.1% by mass.

[0139] The PDDA-containing solution containing the red paint powder / PDDA layer / PSS layer was stirred at room temperature for 20 minutes at 280 rpm using the stirrer described above, and then filtered under reduced pressure to obtain a red paint powder / PDDA layer / PSS layer / PDDA layer in which the PSS layer / PDDA layer-coated red paint powder was further coated with a PDDA layer, which was then washed with pure water.The red paint powder / PDDA layer / PSS layer / PDDA layer was then air-dried.

[0140] Next, 3.75 parts by mass of the obtained red paint powder / PDDA layer / PSS layer / PDDA layer was added to pure water at room temperature and dispersed by stirring at 280 rpm using the stirrer, and then the red paint powder / PDDA layer / PSS layer / PDDA layer dispersion was added to the PSS-containing solution. In the PSS-containing solution to which the red paint powder / PDDA layer / PSS layer / PDDA layer was added, the red paint powder / PDDA layer / PSS layer / PDDA layer content was 3 mass% and the PSS content was 0.1 mass%.

[0141] The PSS-containing solution containing red paint powder / PDDA layer / PSS layer / PDDA layer was stirred at room temperature for 20 minutes at a rotation speed of 280 rpm using the above-mentioned stirring device, and then filtered under reduced pressure to obtain a red paint powder / PDDA layer / PSS layer / PDDA layer in which the red paint powder / PDDA layer / PSS layer / PDDA layer was further coated with a PSS layer, and this was then washed with pure water.

[0142] The red paint powder / PDDA layer / PSS layer / PDDA layer / PSS layer was then air-dried to obtain a red powder paint having the red paint powder and a four-layer coating layer consisting of a PDDA layer / PSS layer / PDDA layer / PSS layer covering the red paint powder.

[0143] In addition, a blue powder coating was obtained using a polyester-based blue paint powder ("Bilucia Alti BA05 no charge control agent added" manufactured by Nippon Paint Industrial Coatings Co., Ltd., hereinafter simply referred to as "blue paint powder") in the same manner as above, having blue paint powder and a four-layer coating layer consisting of a PDDA layer / PSS layer / PDDA layer / PSS layer covering the blue paint powder.

[0144] Thereafter, the red powder coating and the blue powder coating were mixed in a mass ratio of 1:1 by dry blending using a Henschel mixer at room temperature at a rotation speed of 1200 rpm for 1 minute to obtain a powder coating composition.

[0145] <Comparative Example 1> In Comparative Example 1, a polyester resin-based red paint powder ("Bilyusia Alti RA05, no charge control agent added," manufactured by Nippon Paint Industrial Coatings Co., Ltd.) and a polyester resin-based blue paint powder ("Bilyusia Alti BA05, no charge control agent added," manufactured by Nippon Paint Industrial Coatings Co., Ltd.) were mixed in a weight ratio of 1:1 by dry blending using a Henschel mixer at room temperature at a rotation speed of 1200 rpm for 1 minute to obtain a powder coating composition.

[0146] <Comparative Example 2> In Comparative Example 2, a polyester resin-based red paint powder containing silica as a charge control agent ("Bilyusia Alti RA05 Charge Control Agent with Silica Added" manufactured by Nippon Paint Industrial Coatings Co., Ltd.) and a polyester resin-based blue paint powder containing silica as a charge control agent ("Bilyusia Alti BA05 Charge Control Agent with Silica Added" manufactured by Nippon Paint Industrial Coatings Co., Ltd.) were mixed in a mass ratio of 1:1 by dry blending using a Henschel mixer at room temperature at a rotation speed of 1200 rpm for 1 minute to obtain a powder coating composition.

[0147] <SEM observation of powder coating> The powder coatings contained in the powder coating compositions of Example 3 and Comparative Example 2 were observed using a scanning electron microscope (SEM). The observation conditions were as follows: For the powder coating contained in the powder coating composition of Example 3, the powder coating was crushed in a mortar and a cross section was prepared. Next, the surface of the powder coating, including its cross section, was coated with osmium on carbon tape. The osmium coating was performed using a "Neoc-ST Osmium Coater" manufactured by Meiwafosis Co., Ltd., by evacuating the chamber to 2 Pa or less, then introducing osmium oxide gas to 6 Pa, generating plasma at 5 mA for 10 seconds, and coating the surface of the powder coating, including its cross section, with osmium. The osmium-coated powder coating was then observed at 2000x magnification using a scanning electron microscope ("JSM-7000F" manufactured by JEOL Ltd.). Furthermore, the powder coating contained in the powder coating composition according to Comparative Example 2 was observed at a magnification of 3500 times using a scanning electron microscope (JEOL Ltd., "JSM-7000F").

[0148] As shown in Figure 3A, the coating layer was a continuous layer that covered the paint powder in the powder coating composition of Example 3. In contrast, as shown in Figure 3B, the powder coating in the powder coating composition of Comparative Example 2 had silica as a charge control agent scattered throughout the paint powder.

[0149] <Coating film formation> Coating films were formed using the powder coating compositions of Examples 1 and 2 and Comparative Examples 1 and 2. The coating films were formed as follows. First, a 0.8 × 90 × 300 mm JIS G 3141 (SPCC-SD) cold-rolled steel plate was used as the substrate. The steel plate had been zinc phosphate-treated and then solvent-degreased. Powder coating composition 1 prepared above was applied to one entire surface of the substrate using an electrostatic powder coating applicator, OPTI Handgun (manufactured by 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 coating thickness of 50 to 60 μm. The coating was then baked at 180°C for 20 minutes and subjected to testing. The resulting coating films are shown in Figures 4A, 4B, 5A, and 5B.

[0150] As shown in Figure 5A, color separation was observed in the coating film formed using the powder coating composition of Comparative Example 1. Furthermore, as shown in Figure 5B, color separation was also observed in the coating film formed using the powder coating composition of Comparative Example 2. This confirms that color separation cannot be suppressed by the charge control agent. In contrast, as shown in Figures 4A and 4B, color separation was not observed in the coating films formed using the powder coating compositions of Examples 1 and 2.

[0151] <ΔE * Calculation and color-coded evaluation The coating films according to Examples 1 and 2 and Comparative Examples 1 and 2 formed by the above <Coating Film Formation> were each measured for ΔE using a spectrophotometer ("CR-400" manufactured by Konica Minolta, Inc., light source: D65). * Specifically, the spectrophotometer was used to measure L at a position 50 mm from the top end of the coating film to the bottom end, at the center, and at a position 50 mm from the bottom end to the top end. * , a * , b * The L at a position 50 mm away from the top edge of the coating film was measured three times and the average value was calculated. * value, a * value, b * value and L at a position 50 mm away from the bottom edge of the coating * value, a* value, b * Calculate the average value of each of these L * value, a * value, b * Value and L at the center position * value, a * value, b * The color difference ΔE is calculated as a color classification index based on the above formula (1). * The results shown in Table 1 were obtained. In the color classification evaluation, -1.0<ΔE * <1.0 is considered a pass, ΔE * ≦-1.0 or ΔE * A value of ≧1.0 was considered a failure. [Table 1]

[0152] <Coating layer surface potential measurement> The surface potentials of the red paint powder / PDDA layer, red paint powder / PDDA layer / PSS layer, red paint powder / PDDA layer / PSS layer / PDDA layer, red paint powder / PDDA layer / PSS layer / PDDA layer, red paint powder / PDDA layer / PSS layer / PDDA layer / PSS layer, and blue paint powder / PDDA layer, blue paint powder / PDDA layer / PSS layer, blue paint powder / PDDA layer / PSS layer / PDDA layer, and blue paint powder / PDDA layer / PSS layer / PDDA layer / PSS layer obtained during the preparation of the powder coating composition of Example 3 were measured in aqueous solution. Specifically, the red paint powder and blue paint powder coated with these coating layers were dispersed in aqueous solution, and the surface potentials of the red paint powder and blue paint powder coated with these coating layers were measured using a Zetasizer Advance PRO (manufactured by Malvern Panalytical). The resulting surface potentials are shown in Figure 6.

[0153] From the graph of FIG. 6, it was confirmed that the surface potential could be adjusted by covering the surfaces of the red paint powder and the blue paint powder with a coating layer. [Explanation of symbols]

[0154] 10...First powder coating 10A, 20A…Surface 11, 21…Paint powder 12, 22...coating layer 12A, 22A...Cationic polymer-containing layer 12B, 22B...anionic polymer-containing layer 20…Second powder coating 30...painted products 40…Object to be painted 50...Paint film

Claims

1. A powder coating composition comprising at least a first powder coating material and a second powder coating material having a color different from that of the first powder coating material, the surface of the first powder paint and the surface of the second powder paint have the same charge polarity; the first powder coating material and the second powder coating material each include a coating powder and a coating layer covering at least a portion of the coating powder; The powder coating composition, wherein each of the coating layers comprises at least one of a cationic polymer-containing layer containing a cationic polymer and an anionic polymer-containing layer containing an anionic polymer.

2. 2. The powder coating composition according to claim 1, wherein each of the coating layers has a portion where one or more of the cationic polymer-containing layers and one or more of the anionic polymer-containing layers are laminated.

3. 3. The powder coating composition according to claim 2, wherein each of the coating layers has a portion where the cationic polymer-containing layer and the anionic polymer-containing layer are alternately laminated.

4. The powder coating composition according to claim 1 , wherein the surface of the first powder coating material and the surface of the second powder coating material are both surfaces of the anionic polymer-containing layer.

5. A coating film formed using the powder coating composition according to any one of claims 1 to 4.

6. An object to be painted, The coating film according to claim 5 formed on the object to be coated. A painted product comprising:

7. A method for producing a powder coating composition comprising at least a first powder coating material and a second powder coating material having a color different from that of the first powder coating material, forming a coating layer on the surface of the first paint powder, the coating layer including at least one of a cationic polymer-containing layer containing a cationic polymer and an anionic polymer-containing layer containing an anionic polymer, and covering at least a portion of the first paint powder, to form a first powder paint; forming a coating layer on the surface of the second paint powder, the coating layer including at least one of a cationic polymer-containing layer containing a cationic polymer and an anionic polymer-containing layer containing an anionic polymer, and covering at least a portion of the second paint powder, to form a second powder paint having a surface with the same charge polarity as the surface of the first powder paint; and dry-blending the first powder coating material and the second powder coating material.

8. 8. The method for producing a powder coating composition according to claim 7, wherein the coating layer of the first powder coating and the coating layer of the second powder coating each have a portion in which one or more cationic polymer-containing layers and one or more anionic polymer-containing layers are laminated.

9. 9. The method for producing a powder coating composition according to claim 8, wherein the coating layer of the first powder coating material and the coating layer of the second powder coating material each have a portion in which the cationic polymer-containing layer and the anionic polymer-containing layer are alternately laminated.

10. 8. The method for producing a powder coating composition according to claim 7, wherein the surface of the first powder coating material and the surface of the second powder coating material are surfaces of the anionic polymer-containing layer.

Images