Powder coating compositions, coating films, and coated bodies

Abstract

To provide a powder coating composition, etc., that can form a coating film that is glossy and has excellent brilliance, and is also excellent in terms of recovery and reuse. [Solution] The powder coating composition of the present invention contains resin-containing powder particles (A), a luminous pigment (B), and a binder (C), wherein the binder (C) has a central coordinate (δ) in the Hansen solubility sphere HSS which determines solubility with the solvent to be mixed. d , δ p , δ h When the interaction distance R is (19.0, 7.0, 5.0), a The resin is dissolved or dispersed in solvent (D) having a value of 20 or higher, has a Tg of 30°C or higher, and a weight-average molecular weight of 1,000 to 100,000.

Description

[Technical Field]

[0001] This invention relates to powder coating compositions, coating films, and coated bodies. [Background technology]

[0002] Conventionally, thermosetting powder coatings containing fluororesin, non-fluororesin, and pigments are known as powder coatings that have weather resistance and adhesion to substrates. When a glossy pigment is used as the pigment in this powder coating, a glossy coating film can be formed (see, for example, Patent Document 1). As a method for forming the coating film, for example, electrostatic powder coating is used.

[0003] Generally, the resin powder and the luminous pigments (e.g., metallic pigments) that make up powder coatings have significantly different electrostatic charges. Therefore, when electrostatic powder coating is performed using powder coatings containing both resin powder and luminous pigments, separation is likely to occur between the resin powder and the luminous pigments during coating. This separation can lead to a decrease in the aesthetic appeal of the resulting coating film. Furthermore, the separation can easily alter the pigment content of the powder coating before and after application. This change in pigment content can easily alter the color tone of the coating film obtained using recycled powder coatings compared to those obtained using powder coatings before reuse, making recycling (recovery and reuse) of powder coatings difficult.

[0004] In response to this, various proposals have been made in the past. For example, Patent Documents 2 and 3 disclose a method (bonding method) in which the surface of a thermosetting resin powder and a metallic pigment are attached to each other with an adhesive binder in order to avoid the separation phenomenon between the thermosetting resin powder and the metallic pigment. Furthermore, the examples in Patent Documents 2 and 3 disclose the use of a terpene-based resin as the binder.

[0005] Furthermore, Patent Document 4 discloses a bonding method for resin powders, particularly fluororesin powders. Specifically, Patent Document 4 discloses a powder coating containing resin powders comprising fluororesin and non-fluororesin, a glossy pigment, and a binder, wherein a method is disclosed for adhering the glossy pigment to the surface of a thermosetting resin powder using a binder consisting of a surfactant with a melting point of 25°C or higher. The examples in Patent Document 4 disclose the use of a fluoro-based halogen-containing solvent as the solvent for the binder. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2011-12119 [Patent Document 2] Japanese Patent Publication No. 2004-175813 [Patent Document 3] Patent No. 3926270 [Patent Document 4] Patent No. 6841235 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] When using terpene-based resins as adhesive binders in the examples of Patent Documents 2 and 3, it is necessary to dissolve the terpene-based resin in a low-polarity solvent such as n-heptane. However, since these low-polarity solvents generally also dissolve fluororesins, problems tend to arise when used with thermosetting resin powder particles containing fluororesins. Specifically, when the above low-polarity solvent is used with thermosetting resin powder particles containing fluororesins, some of the fluororesin dissolves and the thermosetting resin powders bind together, which may increase the particle size of the thermosetting resin powder, reduce paintability, or degrade the appearance of the coating film.

[0008] Furthermore, generally, the fluoro-based halogen-containing solvents used in the examples of Patent Document 4 dissolve fluororesins. Therefore, if the above-mentioned fluoro-based halogen-containing solvent is used with thermosetting resin powder particles containing fluororesins, there is a risk that the particle size of the thermosetting resin powder will increase, the paintability will decrease, and the appearance of the coating film will deteriorate, similar to the case where low-polarity solvents of Patent Documents 2 and 3 are used.

[0009] Furthermore, when the powder coating is a powder coating containing a resin having a carboxyl group, there was a problem that the gloss of the coating film tended to decrease when the binders disclosed in Patent Documents 2 to 4 were used.

[0010] In a powder coating composition for bonding methods, containing resin-containing powder particles, a glossy pigment, and a binder, it is desirable to include a solvent that dissolves the binder but does not dissolve the resin in the resin-containing powder particles. In contrast, the powder coating compositions disclosed in Patent Documents 2 to 4 can only be used in bonding methods when they relate to specific combinations of resins and binders. In this industry, from the viewpoint of design flexibility for powder coating compositions, there is a desire for a bonding method that can be broadly applied to various types of resin-containing powder particles.

[0011] The present invention has been made in view of the above problems, and aims to provide a powder coating composition that enables the formation of a coating film having gloss and excellent luster, and moreover, has excellent recoverability and reusability. The present invention also aims to provide a coating film and a coated body formed using the above powder coating composition. [Means for solving the problem]

[0012] The present inventors have found that in a powder coating composition containing resin-containing powder particles, a glossy pigment, and a binder, the Hansen solubility parameter (HSP) (δ d , δ p , δ h A specific Hansen lysis sphere is formed using ), and the binder interacts with the center coordinates of the specific Hansen lysis sphere at an interaction distance R. aWhen the resin is soluble or dispersible in a solvent with a solubility parameter of 20 or more, it has been possible to form a coating film having luster and excellent brightness, and moreover, the inventors have succeeded in developing a powder coating composition excellent in recyclability, thus completing the present invention.

[0013] (1) The powder coating composition according to the present invention is a powder coating composition containing resin-containing powder particles (A), a bright pigment (B), and a binder (C), wherein the binder (C) has a central coordinate (δ d , δ p , δ h ) in a Hansen solubility sphere (HSS) for discriminating solubility in a solvent to be mixed of (19.0, 7.0, 5.0), and an interaction distance R a is a resin that is soluble or dispersed in a solvent (D) with an interaction distance R

[0014] of 20 or more, has a Tg of 30°C or more, and a weight average molecular weight of 1,000 to 100,000. a (2) The binder (C) is preferably a resin that is soluble or dispersed in a solvent (D) with an interaction distance R

[0015] of 30 or more.

[0016] (3) The binder (C) preferably has a Tg of 40°C or more.

[0017] (4) The resin (A1) constituting the resin-containing powder particles (A) is preferably a resin obtained by reacting one or more binder resins (A11) selected from the group consisting of fluororesins, polyester resins, and acrylic resins with one or more curing agents (A12) selected from the group consisting of compounds having an epoxy group or polymers thereof, amide compounds, and isocyanate compounds.

[0018] (5) The solvent (D) is preferably one or more solvents selected from the group consisting of water, ethylene glycol, and methanol.

[0019] (7) The luminous pigment (B) is preferably in the form of flake-shaped aluminum pieces.

[0020] (8) The coating film according to the present invention is formed using the powder coating composition.

[0021] (9) The coated body according to the present invention comprises a substrate and a coating film formed on the surface of the substrate using the powder coating composition. [Effects of the Invention]

[0022] According to the present invention, it is possible to provide a powder coating composition that can form a coating film having a glossy and excellent luster, and moreover, has excellent recoverability and reusability. Furthermore, according to the present invention, it is possible to provide a coating film formed using the above powder coating composition, and a coated body having this coating film. [Brief explanation of the drawing]

[0023] [Figure 1] This figure illustrates a method for creating a Hansen lysis sphere with specific central coordinates and a specific interaction radius R0 on a Hansen 3D graph using HSP(δd, δp, δh). [Figure 2] This figure shows a group of solvents that dissolve a specific resin (virtual resin X) used to form Hansen soluble spheres, and a group of solvents that do not dissolve the resin (virtual resin X). [Figure 3] This figure shows a group of solvents that dissolve a specific resin (virtual resin X) used to form a Hansen lysis sphere, a group of solvents that do not dissolve the resin (virtual resin X), and a solvent located at an interaction distance Ra from the central coordinates (CC) of the specific Hansen lysis sphere. [Modes for carrying out the invention]

[0024] Embodiments of the present invention will be described below with reference to the drawings. Note that the shapes and sizes in the drawings have been modified as appropriate for the sake of explanation. Therefore, the present invention is not limited to the shapes shown in the drawings.

[0025] [Powder coating composition] The powder coating composition according to the present invention contains resin-containing powder particles (A), a luminous pigment (B), and a binder (C).

[0026] (Resin-containing powder particles (A)) The resin-containing powder particles (A) contain at least a resin (A1). The resin (A1) contains at least a binder resin (A11) and may optionally contain a curing agent (A12). Here, the curing agent (A12) is a compound or polymer that reacts with the binder resin (A11). Preferably, the curing agent (A12) does not react during the preparation of the resin-containing powder particles (A) but reacts when forming a film using the powder coating composition.

[0027] The resin-containing powder particles (A) are prepared, for example, by melt-kneading a mixture containing at least a binder resin (A11) and a curing agent (A12) as needed, followed by cooling and pulverizing to include resin (A1). The mixture may further contain additives such as surface modifiers and lubricants (A2), coloring pigments (A3), etc., as needed.

[0028] If the mixture further contains additive (A2), the resulting resin-containing powder particles (A) will contain resin (A1) and components derived from additive (A2). Here, "components derived from additive (A2)" means additive (A2) itself, or reaction products of additive (A2) with other components.

[0029] Furthermore, if the mixture further contains a coloring pigment (A3), the resulting resin-containing powder particles (A) will contain the resin (A1) and the coloring pigment (A3).

[0030] Furthermore, if an additive (A2) and a coloring pigment (A3) are further included, the resulting resin-containing powder particles (A) will consist of resin (A1), components derived from additive (A2), and coloring pigment (A3).

[0031] <Binder resin (A11)> As the binder resin (A11), for example, one or more selected from the group consisting of fluororesins, polyester resins, and acrylic resins may be used, and multiple types of binders may be combined and blended.

[0032] The fluororesin used in the binder resin (A11) is a fluorine-containing copolymer obtained by polymerizing or copolymerizing fluorine-containing monomers.

[0033] As for fluororesins, for example, those that are solid at room temperature and have a softening point of 50 to 150°C are used.

[0034] Examples of fluorine-containing monomers include vinyl fluoride, vinylidene fluoride, trifluoroethylene, tetrafluoroethylene, bromotrifluoroethylene, chlorotrifluoroethylene, pentafluoropropylene, hexafluoropropylene, and (per)fluoroalkyltrifluorovinyl ethers (where the (per)fluoroalkyl group has 1 to 18 carbon atoms).

[0035] Fluororesins may be copolymerized from fluorine-containing monomers and polymerizable monomers other than fluorine-containing monomers. Examples of polymerizable monomers include vinyl ethers, olefins, allyl ethers, vinyl esters, allyl esters, (meth)acrylic acid esters, and crotonic acid esters.

[0036] Examples of polymerizable monomers include, Alkyl vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, butyl vinyl ether, isobutyl vinyl ether, cyclohexyl vinyl ether, and chloroethyl vinyl ether; Olefins such as ethylene, propylene, 1-butene, isobutylene, cyclohexene, vinyl chloride, and vinylidene chloride; Styrene, α-methylstyrene, and other styrene monomers; Alkyl allyl ethers such as methyl allyl ether, ethyl allyl ether, butyl allyl ether, and cyclohexyl allyl ether; Vinyl fatty acid esters such as vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl valerate, vinyl hexanoate, vinyl octanoate, and vinyl versatate; Fatty acid allyl esters such as allyl propionate and allyl acetate; (meth)acrylic acid esters such as methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, and cyclohexyl (meth)acrylate; (meth)acrylamides such as (meth)acrylamide; cyano group-containing monomers such as acrylonitrile and 2,4-dicyabutene-1; Dienes such as isoprene and butadiene Polymerizable monomers such as the above are used.

[0037] The fluororesin may have reactive sites that react with curing agents, etc. Furthermore, the fluororesin may be a copolymer of one or more of the above-mentioned fluorine-containing monomers and polymerizable monomers with a monomer containing a reactive group.

[0038] Examples of monomers containing reactive groups include: Monomers containing functional groups such as hydroxyl groups, carboxyl groups, amide groups, amino groups, nitrile groups, glycidyl groups, and isocyanate groups are used. Examples of reactive group-containing monomers include hydroxyl group-containing monomers, carboxyl group-containing monomers, amino group-containing monomers, amide group-containing monomers, nitrile group-containing monomers, glycidyl group-containing monomers, and isocyanate group-containing monomers.

[0039] Examples of hydroxyl group-containing monomers include, Allyl alcohol; Hydroxyalkyl vinyl ethers such as 2-hydroxyethyl vinyl ether, 3-hydroxypropyl vinyl ether, 4-hydroxybutyl vinyl ether, and 4-hydroxycyclohexyl vinyl ether; Hydroxyalkyl allyl ethers such as 2-hydroxyethyl allyl ether, 3-hydroxypropyl allyl ether, 4-hydroxybutyl allyl ether, and 4-hydroxycyclohexyl allyl ether; Hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate; Esters of hydroxyalkyl carboxylic acids such as vinyl hydroxyacetate, vinyl hydroxyisobutyrate, vinyl hydroxypropionate, vinyl hydroxybutyrate, vinyl hydroxyvalerate, and vinyl hydroxycyclohexylcarboxylate with vinyl alcohols; Hydroxyalkyl allyl esters such as hydroxyethyl allyl ester, hydroxypropyl allyl ester, hydroxybutyl allyl ester, and hydroxyisobutyl allyl ester. These are used.

[0040] Furthermore, carboxyl group-containing monomers include (meth)acrylic acid and carboxyalkyl allyl esters. Amino group-containing monomers include aminoalkyl vinyl ethers and aminoalkyl allyl ethers. Amide group-containing monomers include (meth)acrylamide and N-methyl(meth)acrylamide. Nitrile group-containing monomers include (meth)acrylonitrile. Glycidyl group-containing monomers include glycidyl allyl ether and glycidyl(meth)acrylate. Isocyanate group-containing monomers include vinyl isocyanate and isocyanate ethyl acrylate.

[0041] The fluororesin used in this invention preferably has a fluorine content of 10 to 70% by mass.

[0042] Furthermore, when using a curing agent component (A12) that reacts with hydroxyl groups, the hydroxyl value of the fluororesin is preferably 10 to 100 mgKOH / g, and more preferably 30 to 70 mgKOH / g.

[0043] When using a curing agent component (A12) that reacts with carboxyl groups, the acid value of the fluororesin is preferably 1 to 80 mgKOH / g, and more preferably 10 to 60 mgKOH / g.

[0044] The polyester resin used in the binder resin (A11) is obtained by reacting a carboxylic acid and a polyhydric alcohol by a known method, and is a solid resin at room temperature. The softening point of the polyester resin is preferably 100 to 150°C.

[0045] Examples of carboxylic acid components containing carboxylic acids include polycarboxylic acids such as phthalic acid, isophthalic acid, terephthalic acid, naphthalenedicarboxylic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebatic acid, 1,9-nonanedicarboxylic acid, 1,10-decanedicarboxylic acid, 1,12-dodecanedicarboxylic acid, 1,2-octadecanedicarboxylic acid, maleic acid, fumaric acid, cyclohexanedicarboxylic acid, hexahydrophthalic acid, tetrahydrophthalic acid, trimellitic acid, and pyromellitic acid, as well as lower alkyl esters of these polycarboxylic acids and their anhydrides, or hydroxycarboxylic acids such as malic acid, tartaric acid, 1,2-hydroxystearic acid, and parahydroxybenzoic acid.

[0046] Examples of polyhydric alcohols include ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,9-nonanediol, 1,10-decanediol, neopentyl glycol, spiroglycol, 1,4-cyclohexanedimethanol, trimethylolethane, trimethylolpropane, glycerin, and pentaerythritol.

[0047] Polyester resin can be produced using the above-mentioned carboxylic acid component and polyhydric alcohol as raw materials by conventional methods for producing polyester resin for powder coatings. For example, the above-mentioned raw materials can be used in appropriate combinations and mixing ratios, and after carrying out esterification or transesterification reactions at 200-280°C according to conventional methods, a polycondensation reaction can be carried out at 230-290°C using a catalyst under reduced pressure, and then a depolymerization reaction can be carried out with the alcohol component to produce polyester resin.

[0048] From the viewpoint of controlling melt viscosity, polyester resins are preferable if their number-average molecular weight is 8000 or less and their weight-average molecular weight is 10000 to 20000.

[0049] When a curing agent component (A12) that reacts with hydroxyl groups is used, the hydroxyl value of the polyester resin is preferably 20 to 100 mg KOH / g, more preferably 30 to 80 mg KOH / g.

[0050] Furthermore, when a curing agent component (A12) that reacts with carboxyl groups is used, the acid value of the polyester resin is preferably 1 to 80 mg KOH / g, more preferably 10 to 60 mg KOH / g.

[0051] Furthermore, with regard to powder coatings containing fluororesin and polyester resin, if the melt viscosity of the polyester resin used is 3.5 Pa·s (190°C) or less, and the slope obtained from the Arrhenius plot of temperature and viscosity between 100 and 120°C (when the melt viscosity is measured using a rheometer at a cooling rate of 10°C / min from 200°C) is 15,000 or more, then the fluororesin component tends to be unevenly distributed on the surface of the coating film during film formation. When the fluororesin component is unevenly distributed on the surface of the coating film in this way, the weather resistance of the coating film is improved.

[0052] The above slope is calculated, for example, by the following method. First, viscosity is measured using a rheometer ARES manufactured by T.A. Instruments under the following measurement conditions: a 40 mm diameter parallel plate, a gap width of 1.0 mm, a frequency of 9.42 rad / s, and a strain of 1.0%. Next, the obtained measurement results are plotted on a graph with the reciprocal of temperature T (K), 1 / T, on the horizontal axis and the logarithm of viscosity V, lnV, on the vertical axis (Arrhenius plot). Then, the slope of the resulting straight line between 100 and 120°C is determined, and this value is taken as the above slope.

[0053] The above inclination is more preferably 16000 to 20000 from the viewpoint of facilitating layer separation of the coating film.

[0054] The acrylic resin used in the binder resin (A11) is a resin that is solid at room temperature and is a polymer of acrylic acid esters or methacrylic acid esters. As the acrylic resin, for example, a polymer obtained by polymerizing one or more acrylic components selected from acrylic acid, methacrylic acid, and their esters, amides, and nitriles is used. In addition, as the acrylic resin, a polymer obtained by polymerizing an acrylic component with a non-acrylic component such as styrene is also used. From the viewpoint of controlling melt viscosity, the acrylic resin is preferable if it has a softening point of 100 to 150°C, a number average molecular weight of 8000 or less, and a weight average molecular weight of 10000 to 20000.

[0055] Examples of acrylic components include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, sec-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, dodecyl (meth)acrylate, n-amyl (meth)acrylate, isoamyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, cyclohexyl (meth)acrylate, phenyl (meth)acrylate. (Meth)acrylate monomers such as acrylate, benzyl (meth)acrylate, methoxyethyl (meth)acrylate, ethoxyethyl (meth)acrylate, methoxypropyl (meth)acrylate, and ethoxypropyl (meth)acrylate, as well as functional group-containing monomers such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl acrylate, 2-aminoethyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, 3-aminopropyl (meth)acrylate, 2-butylaminoethyl (meth)acrylate, glycidyl (meth)acrylate, and allyl glycidyl ether, are used.In addition, acrylic components can also be acrylic acid and methacrylic acid; amide monomers such as acrylamide and methacrylate; and alkoxysilyl group-containing monomers such as γ-(meth)acryloxypropyltrimethoxysilane, γ-(meth)acryloxypropyltriethoxysilane, β-(meth)acryloxyethyltrimethoxysilane, β-(meth)acryloxyethyltriethoxysilane, γ-(meth)acryloxypropylmethyldimethoxysilane, γ-(meth)acryloxypropylmethyldiethoxysilane, γ-(meth)acryloxypropylmethyldipropoxysilane, γ-(meth)acryloxybutylphenyldimethoxysilane, γ-(meth)acryloxypropyldimethylmethoxysilane, and γ-(meth)acryloxypropyldiethylmethoxysilane.

[0056] The proportion of acrylic components to the total components of the acrylic resin is, for example, 40 to 100% by mass.

[0057] Examples of non-acrylic components include carboxyl group-containing monomers such as fumaric acid, maleic acid, maleic anhydride, itaconic acid, crotonic acid, and vinyl versatic acid; aromatic monomers such as styrene, methylstyrene, chlorostyrene, methoxystyrene, and vinyltoluene; olefin monomers such as ethylene and propylene; vinyl monomers such as vinyl acetate and vinyl chloride; amide monomers such as maleic acid amide; alkoxysilyl group-containing monomers such as vinyltrimethoxysilane, vinyltriethoxysilane, vinylmethyldimethoxysilane, and vinylmethyldiethoxysilane; and dialkyl fumarates, allyl alcohols, vinylpyridine, and butadiene.

[0058] When a curing agent component (A12) that reacts with hydroxyl groups is used, the hydroxyl value of the acrylic resin is preferably 20 to 100 mg KOH / g, more preferably 30 to 80 mg KOH / g.

[0059] Furthermore, when a curing agent component (A12) that reacts with carboxyl groups is used, the acid value of the acrylic resin is preferably 1 to 80 mg KOH / g, more preferably 10 to 60 mg KOH / g.

[0060] <Hardening agent (A12)> As the curing agent (A12), one or more selected from the group consisting of compounds having an epoxy group or polymers thereof, amide compounds, and isocyanate compounds are used.

[0061] As for compounds having epoxy groups, compounds having multiple epoxy groups in the molecule are preferred, and triglycidyl isocyanurate is a typical example. Polymers containing epoxy groups (hereinafter also referred to as epoxy resins) include bisphenol-type epoxy resins such as bisphenol A-type epoxy resins and bisphenol F-type epoxy resins, naphthalene-type epoxy resins, biphenyl-type epoxy resins, novolac-type epoxy resins, cyclic aliphatic epoxy resins, glycidylamine-type resins, heterocyclic epoxy resins, and polyfunctional epoxy resins. These can be used alone or in combination.

[0062] Examples of epoxy resins used include solid epoxy resins synthesized from bisphenol A and epihalohydrins such as epichlorohydrin, and solid epoxy resins obtained by the extension reaction of bisphenol A with epoxy resins derived from bisphenol A, divalent phenols, and epihalohydrins.

[0063] Examples of epoxy resins available on the market include jER1004, jER1004F, jER1007, and jER4005P from Mitsubishi Chemical Corporation; EPICLON3050 and EPICLON4050 from DIC Corporation; EPOTOTE YD014D from Nippon Steel & Sumitomo Metal Chemical Corporation; and EPONANYANPES-904 from Nanya Plastics Co., Ltd.

[0064] The softening point of the epoxy resin is not particularly limited, but is preferably 60 to 150°C. The epoxy equivalent of the epoxy resin is also not particularly limited, but is preferably 400 to 3000.

[0065] As the epoxy resin, a mixture of multiple epoxy resins with different epoxy equivalents can be used. When mixing multiple epoxy resins, it is preferable to combine an epoxy resin with an epoxy equivalent of 1000 or less with an epoxy resin with an epoxy equivalent of 1000 or more.

[0066] Furthermore, the epoxy resin typically has a difference of 300 or more, preferably 500 or more, and more preferably 800 or more, between the epoxy resin with the minimum epoxy equivalent (A-min) and the epoxy resin with the maximum epoxy equivalent (A-max).

[0067] As an amide compound, for example, β-hydroxyalkylamide is used. From the viewpoint of low-temperature curing properties and the water resistance of the coating film obtained by painting, the β-hydroxyalkylamide is preferably a β-hydroxyalkylamide having two or more functional groups per molecule. From the viewpoint of low-temperature curing properties and the water resistance of the coating film obtained by painting, the β-hydroxyalkylamide is more preferably N,N-di(β-hydroxyethyl)acetamide, bis(β-hydroxyethyl)adipoamide, bis(β-hydroxypropyl)adipoamide, bis[N,N-di(β-hydroxyethyl)]adipoamide, or bis[N,N-di(β-hydroxypropyl)]adipoamide. The equivalent amount of hydroxylamide groups to carboxyl groups in the resin of the β-hydroxyalkylamide is preferably 0.5 to 1.5 equivalents.

[0068] For example, blocked isocyanate compounds are used as isocyanate compounds. Preferably, isocyanate compounds that are solid at room temperature are used.

[0069] Blocked isocyanate compounds are easy to produce because they can be manufactured, for example, by reacting aliphatic, aromatic, or aromaticaliphatic diisocyanates with a low-molecular-weight compound having active hydrogen to obtain polyisocyanates, and then reacting these polyisocyanates with a blocking agent to mask them.

[0070] Examples of diisocyanates used include tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, xylylene diisocyanate, hexamethylene diisocyanate, 4,4'-methylenebis(cyclohexyl isocyanate), methylcyclohexane diisocyanate, bis(isocyanate-methyl)cyclohexane, isophorone diisocyanate, dimer acid diisocyanate, and lysine diisocyanate.

[0071] Examples of low molecular weight compounds containing active hydrogen include water, ethylene glycol, propylene glycol, trimethylolpropane, glycerin, sorbitol, ethylenediamine, ethanolamine, diethanolamine, hexamethylenediamine, as well as isocyanurates, urethidione, low molecular weight polyesters containing hydroxyl groups, and polycaprolactone.

[0072] Blocking agents include alcohols such as methanol, ethanol, and benzyl alcohol; phenols such as phenol and crezone; lactams such as caprolactam and butyrolactam; and oximes such as cyclohexanone, oxime, and methyl ethyl ketoxime.

[0073] For example, specific examples of blocked isocyanates include isophorone diisocyanates blocked with ε-caprolactam (e.g., Vestagon B1530 from Evonik and Clélan UI from Bayer).

[0074] The isocyanate compound preferably has a softening point of 10 to 120°C, more preferably 40 to 100°C. If the softening point is below 10°C, the powder coating composition may harden or form granular clumps at room temperature. On the other hand, if the softening point exceeds 120°C, it becomes difficult to uniformly disperse the isocyanate compound in the powder coating composition when manufacturing it by melt kneading, which may impair the performance of the resulting coating film, such as smoothness, film strength, and moisture resistance.

[0075] The isocyanate compound preferably has an equivalent amount of isocyanate groups to hydroxyl groups in the resin of 0.05 to 1.5 equivalents, more preferably 0.8 to 1.2 equivalents. If the amount of isocyanate groups is less than 0.05 equivalents, the degree of curing of the powder coating composition may be insufficient, potentially resulting in poor coating performance such as adhesion, coating hardness, and chemical resistance. If the amount of isocyanate groups exceeds 1.5 equivalents, the coating film may become brittle, and its heat resistance, chemical resistance, and moisture resistance may be inferior. Furthermore, since blocked isocyanates are expensive, excessive use of blocked isocyanates tends to increase costs.

[0076] The resin (A1) constituting the resin-containing powder particles (A) preferably comprises one or more binder resins (A11) selected from the group consisting of fluororesins, polyester resins, and acrylic resins, and one or more curing agents (A12) selected from the group consisting of compounds having epoxy groups or polymers thereof, amide compounds, and isocyanate compounds.

[0077] The resin (A1) constituting the resin-containing powder particles (A) more preferably comprises one or more binder resins (A11) selected from the group consisting of fluororesins and polyester resins, and a curing agent (A12) consisting of an isocyanate compound.

[0078] The resin (A1) constituting the resin-containing powder particles (A) more preferably comprises a binder resin (A11) made of a polyester resin and a curing agent (A12) made of a compound having an epoxy group or a polymer thereof.

[0079] The resin (A1) constituting the resin-containing powder particles (A) more preferably comprises a binder resin (A11) made of polyester resin and a curing agent (A12) made of amide compound.

[0080] <Additive (A3)> Examples of additives (A3) include plasticizers, curing accelerators, crosslinking catalysts, surface modifiers, UV absorbers, light stabilizers, antioxidants, flow modifiers, anti-sagging agents, and defoamers, which are common additives for paints.

[0081] <Coloring pigment (A4)> Examples of coloring pigments (A4) include inorganic pigments such as titanium dioxide, yellow iron oxide, titanium yellow, red iron oxide, lithopone, and antimony oxide, as well as organic pigments such as Hansa Yellow 5G, Permanent Yellow FGL, phthalocyanine blue, indanthrene blue RS, permanent red F5RK, and brilliant first scarlet G.

[0082] As described above, the resin-containing powder particles (A) are prepared by, for example, melt-kneading a mixture containing at least a binder resin (A11) and a curing agent (A12), then cooling and pulverizing it to include resin (A1).

[0083] The resin-containing powder particles (A) may, if necessary, further contain components derived from additives (A2), coloring pigments (A3), etc., in addition to the resin (A1).

[0084] The resin-containing powder particles (A) have a 50% volume average particle size of, for example, 15 to 100 μm, preferably 20 to 70 μm, and more preferably 30 to 50 μm.

[0085] (Luminous pigment (B)) Examples of luminous pigments (B) include aluminum powder pigment, nickel powder pigment, stainless steel powder pigment, copper powder, bronze powder, gold powder, silver powder, mica pigment, graphite pigment, glass flake pigment, flaked plastic pigment, and flaky iron oxide pigment. For example, aluminum powder pigment can be made from flake-shaped aluminum pieces. It is preferable that the luminous pigment (B) be in the form of flake-shaped aluminum pieces because it exhibits high luminosity.

[0086] The luminous pigment (B) has a 50% volume average particle size of, for example, 3 to 100 μm, preferably 5 to 80 μm, and more preferably 15 to 60 μm.

[0087] The luminous pigment (B) has an aspect ratio of, for example, 2 to 60, preferably 3 to 40, and more preferably 5 to 25.

[0088] (Binding agent (C)) The binder (C) is a resin that bonds the resin-containing powder particles (A) and the luminous pigment (B). The binder (C) is used dissolved or dispersed in the solvent (D) to ensure fluidity during the bonding process between the resin-containing powder particles (A) and the luminous pigment (B).

[0089] The binder (C) constituting the powder coating composition according to the present invention is used together with a solvent (D) that does not dissolve the resin (A1) constituting the resin-containing powder particles (A) but dissolves or disperses the binder (C) when bonding the resin-containing powder particles (A) and the luminous pigment (B).

[0090] Specifically, the binder (C) is the specific central coordinate (δ) of the Hansen lysis sphere on the Hansen 3D graph. d , δ p , δ h The interaction distance R is the distance from (19.0, 7.0, 5.0) a The substance is dissolved or dispersed in a solvent (D) within a specific range, and the resulting resin has a Tg and weight-average molecular weight within a specific range.

[0091] More specifically, the binder (C) has a central coordinate (δ) in the Hansen lysis sphere that determines its solubility with the solvent being mixed. d , δ p , δ h When the interaction distance R is (19.0, 7.0, 5.0), a The material is dissolved or dispersed in solvent (D) having a value of 20 or higher, resulting in a resin with a Tg of 30°C or higher and a weight-average molecular weight of 1,000 to 100,000.

[0092] The above is a 3D graph of Hansen, showing the Hansen lysis sphere and its central coordinates (δ). d , δ p , δ h ), and interaction distance R a HSP(δ d , δ p , δ h These are formed and calculated based on the following. These concepts will be explained below with reference to the diagrams.

[0093] <Hansen Solubility Parameter (HSP)> Figure 1 shows HSP(δ d , δ p , δ h This figure illustrates a method for creating a Hansen lysis sphere with specific central coordinates and a specific interaction radius R0 on a Hansen 3D graph using ).

[0094] Hansen HSP(δ) of a certain substance X d , δ p , δ h ) is a parameter defined by the following equation (1).

[0095]

number

[0096] In this invention, the above substance X is defined as a virtual resin X that can be applied to many resins (A1) that constitute the resin-containing powder particles (A). Specifically, in this invention, this virtual resin X is defined as a specific central coordinate (δ) in the Hansen fusion sphere. d , δ p , δ h The resin was set to be located at (19.0, 7.0, 5.0). In this invention, the central coordinates of the Hansen molten sphere are set to a specific central coordinate (δ d , δ p , δ h By setting )=(19.0, 7.0, 5.0), it becomes possible to bond luminous pigments to various types of resin-containing powder particles.

[0097] As shown in Figure 1, HSP(δ d , δ p , δ h ) is δ d axis, δ p axis and δ h It is represented on Hansen's 3D graph G, which has three axes. On Hansen's 3D graph G, HSP(δ d , δ p , δ h ) is represented by point XC in Figure 1.

[0098] In this invention, point XC(δ) in Figure 1 d , δ p , δ h As a specific numerical value, the (δ) of the virtual resin X is as described above.d , δ p , δ h Using )=(19.0, 7.0, 5.0), this (δ d , δ p , δ h Set )=(19.0, 7.0, 5.0) as the center coordinates CC of the Hansen lysis sphere HSS.

[0099] In this invention, the (δ of the virtual resin X) d , δ p , δ h A Hansen solubility sphere HSS is created with center coordinates CC = (19.0, 7.0, 5.0). The Hansen solubility sphere HSS is the smallest sphere containing only the solvent that dissolves the virtual resin X. The smallest sphere is calculated as the smallest sphere containing only the solvent that dissolves the virtual resin X when testing or simulating whether or not the virtual resin X dissolves in various solvents.

[0100] The radius of the Hansen lysis sphere (HSS) is defined as the interaction radius R0. The interaction radius R0 is defined by the following equation (2) and is the distance from the center coordinate CC on Hansen's 3D graph G, which is the interaction distance R a Of these, the Hansen solubility sphere HSS is the radius of the smallest sphere containing only the solvent that dissolves the virtual resin X. In the following formula (2), component 1 is the virtual resin X and component 2 is the solvent. In this invention, from the results of "testing or simulating whether or not the virtual resin X dissolves in various solvents" as described above, it was found that the interaction radius R0 of the virtual resin X can be set to less than 20 (excluding 0).

[0101]

number

[0102] By the way, generally, Δδ defined by the following formula (3), that is, the solubility parameter HSP (δ d,1 , δ p,1 , δ h,1 ) on the Hansen's 3D graph G of Component 1 (Virtual Resin X) and the HSP (δ d,2 , δ p,2 , δ h,2 ) on the Hansen's 3D graph G of Component 2 (Solvent), the distance Δδ between them is an index indicating the solubility of Component 1 (Virtual Resin X) and Component 2 (Solvent). It can be said that the smaller Δδ is, the easier the two components dissolve, and the larger Δδ is, the more difficult the two components dissolve.

[0103] ) (Δδ: The distance between the solubility parameter HSP (δ d,1 , δ p,1 , δ h,1 ) on the Hansen's 3D graph G of Component 1 (Virtual Resin X) and the HSP (δ d,2 , δ p,2 , δ h,2 ) on the Hansen's 3D graph G of Component 2 (Solvent), δ d,1 : Dispersion force term of the HSP of Component 1 (Virtual Resin X), δ d,2 : Dispersion force term of the HSP of Component 2 (Solvent), δ p,1 : Dipole-dipole force term of the HSP of Component 1 (Virtual Resin X), δ p,2 : Dipole-dipole force term of the HSP of Component 2 (Solvent), δ h,1 : Hydrogen bonding term of the HSP of Component 1 (Virtual Resin X), δ h,2 : Hydrogen bonding term of the HSP of Component 2 (Solvent)

[0104] Figure 2 is a diagram showing a group of solvents that dissolve the resin (Virtual Resin X) used for forming a specific Hansen solubility sphere and a group of solvents that do not dissolve the resin (Virtual Resin X).

[0105] ​In FIG. 2, the solvent of the plot “○ (open circle)” is within the Hansen solubility sphere HSS with the center coordinates CC and the interaction radius R0, and dissolves the virtual resin X. Also, the solvent of the plot “□ (open square)” is outside the Hansen solubility sphere HSS and does not dissolve the virtual resin X.

[0106] FIG. 3 shows a group of solvents that dissolve the resin (virtual resin X) used for forming a specific Hansen solubility sphere, a group of solvents that do not dissolve the resin (virtual resin X), and a solvent located at the interaction distance R from the center coordinates CC of the specific Hansen solubility sphere. a and is a diagram showing the above.

[0107] In FIG. 3, the solvent of the plot ○ is within the Hansen solubility sphere HSS with the center coordinates CC and the interaction radius R0, and dissolves the virtual resin X. Also, the solvent of the plot □ is outside the Hansen solubility sphere HSS and does not dissolve the virtual resin X. Further, among the solvents of the plot □, the solvent of the plot DD is outside the Hansen solubility sphere HSS, and moreover, since the interaction distance R a is considerably larger than the interaction radius R0, it can be said that the virtual resin X is surely not dissolved.

[0108] The binder (C) is a resin that dissolves or disperses in a solvent (D) in which the interaction distance R a is 20 or more, preferably 25 or more, more preferably 30 or more. The solvent (D) will be described later.

[0109] The binder (C) has a Tg of 30° C. or higher, preferably 40° C. or higher, more preferably 45° C. or higher. When the Tg is less than 30° C., since the binder shows adhesiveness even after the solvent volatilizes, sufficient binding property between the resin-containing powder particles and the bright pigment cannot be obtained. Further, due to the binder remaining on the surface of the powder particles, the resin-containing powder particles (A) adhere to each other and the particle diameter of the resin-containing powder particles (A) increases.

[0110] The binder (C) has a weight-average molecular weight of 1,000 to 100,000, preferably 2,000 to 70,000, and more preferably 2,000 to 50,000. If the weight-average molecular weight of the binder (C) is less than 1,000, it is difficult to obtain sufficient binding between the resin-containing powder particles and the lustrous pigment. If the weight-average molecular weight of the binder (C) exceeds 100,000, its solubility or dispersibility in the solvent tends to deteriorate. While the dispersibility of the binder can be improved by further using emulsifiers or dispersants, in this case, the binding between the resin-containing powder particles and the lustrous pigment tends to decrease.

[0111] (Solvent (D)) Solvent (D) is a solvent that dissolves or disperses the binder (C). For example, one or more solvents selected from the group consisting of water, ethylene glycol, and methanol can be used as solvent (D). It is preferable that solvent (D) is a mixed solvent of water and a water-soluble organic solvent, because this allows the binder to easily wet the surface of the resin-containing powder particles while maintaining sufficient insolubility to the resin-containing powder particles.

[0112] (action) In the powder coating composition according to the present invention, a solution or dispersion is prepared in advance by dissolving or dispersing a binder (C) in a solvent (D), the obtained solution or dispersion is added to resin-containing powder particles (A) and mixed thoroughly, and then the solvent (D) is completely evaporated, thereby bonding the resin-containing powder particles (A) and the luminous pigment (B) with the binder (C).

[0113] Here, "a method of adding a solution or dispersion obtained by dissolving or dispersing a binder (C) in a solvent (D) to resin-containing powder particles (A) and mixing thoroughly" includes, for example, "a method of gradually dropping the solution or dispersion obtained by dissolving or dispersing a binder (C) in a solvent (D) at a specific rate while stirring the resin-containing powder particles (A)" or "a method of atomizing and spraying the solution or dispersion obtained by dissolving or dispersing a binder (C) in a solvent (D) using a spray nozzle or the like while stirring the resin-containing powder particles (A)".

[0114] Furthermore, a method using vacuum suction is preferred for completely volatilizing solvent (D). The temperature for volatilizing the solvent is preferably 0 to 80°C. When the temperature is within the range of 0 to 80°C, it is easier to obtain a powder coating composition with good bonding.

[0115] Furthermore, while solvent (D) dissolves or disperses the binder (C), it does not dissolve the resin-containing powder particles (A) or the resin (A1) that constitutes them. Therefore, even when solvent (D) is added, there is no risk of the resin-containing powder particles (A) binding together, increasing their particle size, reducing paintability, or degrading the appearance of the coating film.

[0116] Therefore, the powder coating composition according to the present invention is capable of forming a coating film that is glossy and has excellent brilliance, and moreover, it has excellent recoverability and reusability.

[0117] Furthermore, in the powder coating composition according to the present invention, a specific virtual resin X is set as a resin applicable to many resins (A1) constituting the resin-containing powder particles (A), and a specific central coordinate CC(δ) is set. d , δ p , δ h A specific Hansen dissolving sphere with values ​​of (19.0, 7.0, 5.0) is set. Therefore, by using a solvent (D) present outside this specific Hansen dissolving sphere as the solvent for the binder (C), the binder (C) can be dissolved or dispersed without dissolving much of the resin (A1) present inside the Hansen dissolving sphere. Thus, in this invention, it is possible to bond a luminous pigment to various types of resin-containing powder particles.

[0118] (effect) The powder coating composition according to the present invention provides a powder coating composition that can form a coating film having high brilliance and gloss and is excellent in terms of recovery and reuse.

[0119] [coating film] The coating film according to the present invention is formed using the powder coating composition according to the present invention. Methods for forming the coating film include, for example, electrostatic powder coating, corona charging, and tribo-charging powder coating.

[0120] The thickness of the coating film is not particularly limited, but is preferably 20 to 1000 μm, more preferably 20 to 500 μm, and even more preferably 20 to 300 μm. When the coating film is a coating film for components of high-rise buildings such as aluminum curtain walls, the thickness of the coating film is preferably 20 to 90 μm. When the coating film is a coating film for components with high weather resistance requirements, such as outdoor units of air conditioners installed along the coast, traffic signal poles, and signs, the thickness of the coating film is preferably 100 to 200 μm.

[0121] The method for forming the coating film is not particularly limited. For example, a method can be used in which the powder coating composition according to the present invention is applied to a substrate to form a molten film consisting of the molten powder coating composition, and then the molten film is cooled to form the coating film.

[0122] The molten film consisting of the molten powder coating composition described above can be obtained, for example, by a method that forms it simultaneously with the coating of the powder coating composition onto the substrate, or by a method that forms it by heating and melting the powder coating composition on the substrate after the powder coating composition has been attached to the substrate.

[0123] Furthermore, if the powder coating composition contains a curing agent, the curing reaction of the reactive components in the composition may begin almost simultaneously with the heating and melting of the powder coating composition. In this case, preferred methods for forming the coating film include heating and melting the powder coating composition and adhering it to the substrate almost simultaneously, or heating and melting the powder coating composition after it has been adhering to the substrate.

[0124] The heating temperature (hereinafter also referred to as the "baking temperature") and heating duration (hereinafter also referred to as the "baking time") for heating and melting the powder coating composition, and for maintaining this heated and melted state for a predetermined time, are appropriately set depending on the type and composition of the raw material components of the powder coating composition, the desired thickness of the coating film, etc.

[0125] If the powder coating composition does not contain a curing agent, the baking temperature is preferably 160 to 300°C. If the powder coating composition contains a curing agent, the baking temperature is preferably set according to the reaction temperature of the curing agent. When a curing agent is used, the baking temperature is preferably 120 to 240°C.

[0126] The reaction temperature of the curing agent can be determined by measuring the change in the elastic modulus of the powder coating composition. This change in elastic modulus can be measured using a rheometer, such as the ARES rheometer manufactured by T.A. Instruments Japan Co., Ltd.

[0127] The curing time is preferably 2 to 60 minutes. If the powder coating composition does not contain a curing agent, the curing time is more preferably 5 to 60 minutes, and even more preferably 10 to 50 minutes. If the powder coating composition contains a curing agent, the curing time is more preferably 2 to 50 minutes, and even more preferably 5 to 40 minutes.

[0128] Painting methods used in forming coating films include electrostatic painting, electrostatic spraying, electrostatic immersion, spraying, fluidized bed immersion, spraying, thermal spraying, and plasma spraying. Of these, electrostatic painting using a powder coating gun is preferred due to its excellent surface smoothness of the molten film. Examples of powder coating guns include corona-charged coating guns and triboelectric coating guns. Here, a corona-charged coating gun refers to a gun that sprays a powder coating composition after treating it with corona discharge. A triboelectric coating gun refers to a gun that sprays a powder coating composition after treating it with triboelectric charging.

[0129] The cooling temperature of the molten film is preferably 20 to 25°C. When the powder coating composition according to the present invention contains a curing agent, the formed coating film becomes a cured film. Cooling after baking can be either rapid cooling or slow cooling, but slow cooling is preferred because it prevents the coating film from peeling off the substrate.

[0130] (effect) The coating film according to the present invention can be formed using a powder coating composition that has high brilliance and gloss and is excellent in terms of recovery and reuse.

[0131] [Painted body] The coated body according to the present invention comprises a substrate and a coating film formed on the surface of the substrate using the powder coating composition according to the present invention.

[0132] (base material) Preferably, the base material used is made of metal (iron, stainless steel, aluminum, copper, titanium, brass, aluminum alloy, etc.), steel, cast iron, etc. As for steel, alloy steel, special steel, and carbon steel are used.

[0133] Examples of substrates made from aluminum alloy include building window frames and building panels. Examples of substrates made from carbon steel include railway bridges, road bridges, gas tanks, oil tanks, transmission towers, and springs.

[0134] The coated body according to the present invention is obtained by using the powder coating composition according to the present invention and carrying out the method for forming a coating film described in the section on coating films according to the present invention.

[0135] (effect) The coating according to the present invention allows for the formation of a coating film that is glossy and has excellent brilliance, and can be formed using a powder coating composition that also has excellent recoverability and reusability. [Examples]

[0136] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. In the descriptions of examples and comparative examples, "parts" and "%" are based on mass.

[0137] The following examples and comparative examples used the following raw materials.

[0138] <1. Raw materials for powder coating compositions> (1) Raw materials for resin-containing powder particles (A) (1-1) Binder resin (A11) • Fluororesin 1: Lumiflon LF710F, hydroxyl group-containing fluororesin (Hydroxyl value: 46 mg KOH / g, manufactured by AGC Inc.) • Polyester resin 1: Yupika Coat GV560, hydroxyl group-containing polyester resin (Hydroxyl value: 50 mg KOH / g, Acid value: 5 mg KOH / g, Softening point: 125°C, Manufactured by Nippon Yupika Co., Ltd.) • Polyester resin 2: Acrylic coat 1683-0, carboxylic acid-containing polyester resin (acid value: 50 mg KOH / g, manufactured by Daicel Ornex Co., Ltd.) • Polyester resin 3: Acrylic coat 2630-2, carboxylic acid-containing polyester resin (acid value: 33 mg KOH / g, manufactured by Daicel Ornex Co., Ltd.)

[0139] (1-2) Hardener (A12) • Hardener 1: ε-Caprolactam Block Isocyanate (manufactured by Evonik Degussa Co., Ltd., product name: Vestagon B1530) • Hardener 2: Bis-A type epoxy resin (manufactured by Mitsubishi Chemical Corporation, product name: jER(registered trademark) 1004) • Hardener 3: β-hydroxyalkylamide (manufactured by M-Scheme Co., Ltd., product name) (Primido XL-552)

[0140] (1-3) Additive (A3) • Additive 1: Silica-based surface modifier (manufactured by Big Chemie Co., Ltd., product name: BYK360P) Lubricant 1: Amorphous silicon dioxide (manufactured by Fuji Silysia Co., Ltd., product name: SYLYSIA 358)

[0141] (2) Luminous pigment (B) • Aluminum flake 1: PCF7620A (manufactured by Toyo Aluminum Co., Ltd.)

[0142] (3) Binding agent (C) • Binding agent 1: Joncryl JDX-C3000 (BASF, acrylic resin, 100% by mass of active ingredient, Tg 57℃, weight-average molecular weight 10000) • Binding agent 2: Pluscoat Z-730 (manufactured by Go-o Chemical Industry Co., Ltd., polyester resin aqueous solution, active ingredient 25% by mass, Tg 46℃, weight-average molecular weight 3000) • Binding agent 3: BURNOCK WD-551P (manufactured by DIC Corporation, aqueous hydroxyl group-containing acrylic resin dispersion, active ingredient 40% by mass, Tg 40℃, weight-average molecular weight 28000) • Binding agent 4: WATERSOL EFD-5580 (manufactured by DIC Corporation, water-based acrylic resin dispersion, active ingredient 40% by mass, Tg 15℃, weight-average molecular weight 70000) • Binding agent 5: JER 1001 (manufactured by Mitsubishi Chemical Corporation, epoxy resin, 100% by mass of active ingredient, Tg 64℃, weight-average molecular weight 3000) • Binding agent 6: HA 3509 (manufactured by Resonaq Holdings Co., Ltd., acrylic resin solution, active ingredient 55% by mass, Tg 50℃, weight-average molecular weight 7500) • Binding agent 7: YS Polystar TH130 (manufactured by Yasuhara Chemical Co., Ltd., terpene-phenol resin, active ingredient 100% by mass, Tg 130℃, weight-average molecular weight 1500)

[0143] (4) Solvent (D) • Solvent 1: Deionized water Solvent 2: A mixture of 75 wt% deionized water and 25 wt% methanol (manufactured by Kanto Chemical Co., Ltd.) Solvent 3: Mix 50 wt% deionized water and 50 wt% methanol (manufactured by Kanto Chemical Co., Ltd.) • Solvent 4: A mixture of 25 wt% deionized water and 75 wt% methanol (manufactured by Kanto Chemical Co., Ltd.) • Solvent 5: Methanol (manufactured by Kanto Chemical Co., Ltd.) • Solvent 6: Ethylene glycol (manufactured by Kanto Chemical Co., Ltd.) • Solvent 7: Xylene (manufactured by Kanto Chemical Co., Ltd.) • Solvent 8: n-heptane (manufactured by Kanto Chemical Co., Ltd.) Solvent 9: Perfluoromethylcyclohexane (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.)

[0144] Table 2 shows the NV (%), which is the ratio of the paint content after drying to the paint content before drying, the glass transition temperature Tg (°C), and the weight-average molecular weight Mw of the binder (C).

[0145] [Test Example 1] Using Hansen's solubility parameter calculation software "Hansen Solubility Parameters in Practice (HSPiP)", we calculated the HSP(δ) for each solvent (D). d , δ p , δ h The following was calculated. Note that the HSP for solvent (D) is (δ) in the above equations (2) and (3). d,2 , δ p,2 , δ h,2 ) However, in the test examples and the following examples and comparative examples, (δ d , δ p , δ h We will use the notation ) Furthermore, for each solvent (D), (δ on the 3D graph G) d , δ p , δ h The interaction distance R is the distance from a specific center coordinate CC of (19.0, 7.0, 5.0). a The result was calculated. HSP(δ d , δ p , δ h ) and interaction distance R a This is shown in Table 2.

[0146] [Table 1]

[0147] [Table 2]

[0148] [Test Example 2] (Solubility evaluation test) Each of the binders 1, 2, and 5-7 was measured out at 25°C and under reduced pressure of 760 mmHg (gauge pressure) to achieve a solid content of 100%, and then 0.01 g was measured out. Next, each of the measured binders 1, 2, and 5-7 was mixed with 10 ml each of solvents 1-9 and stirred at 25°C for 30 minutes. After stirring, the mixture was left to stand for 24 hours, and the state of the resulting material was visually evaluated. The evaluation results are shown in Table 3. The evaluation criteria are as follows. Note that binders 3 and 4 are in a state where the resin components are dispersed in water (solvent 1), and if the solid content is 100%, a film will form, making it impossible to determine the original solubility of the resin. Therefore, for binder 3, 0.04 g (solid content 0.01 g) was measured out, and methanol was added so that the water / methanol mixing ratio was equivalent to that of solvents 2 and 3, and the dispersion state was evaluated. For binder 4, 0.018 g (solid content 0.01 g) was measured out, and methanol was added so that the water / methanol mixing ratio was equivalent to that of solvents 2 and 3, and the dispersion state was evaluated.

[0149] <Rating> The evaluation was as follows: ◎(Excellent): It is a clear liquid and is dissolved. ○ (Good): The liquid is cloudy and dispersed (no precipitate forms). × (Poor): Precipitation is present from the time of stirring. -: Variance evaluation not performed.

[0150] [Table 3]

[0151] [Examples 1-36, Comparative Examples 1-15] (1. Preparation of powder coating composition) <1-1: Preparation of resin-containing powder particles (A)> (1) 1-1-1: Preparation of powder particles containing fluororesin and polyester resin Using the raw materials shown in Tables 1 and 2, the components were mixed to achieve the blending ratios shown in Tables 4 and 5 to obtain powder particles (A) containing fluororesin and polyester resin. Specifically, fluororesin, polyester resin, curing agent (block isocyanate), additives, and lubricant were placed in a high-speed mixer and mixed for 1 minute. Then, the mixture was kneaded using a single-screw mixer (manufactured by BUSS) with the temperature adjusted to 120°C, and the discharged mixture was cold-rolled with cooling rolls. After that, it was crushed using a pin mill and classified using a 150-mesh screen to obtain each powder particle (A) (50% volume average particle diameter: approximately 35 μm) that will be used as raw material for powder coating compositions (coatings 1 to 17).

[0152] (2) 1-1-2: Preparation of powder particles containing polyester resin and epoxy resin Using the raw materials shown in Tables 1 and 2, the components were mixed to achieve the blending ratios shown in Tables 6 and 7 to obtain powder particles (A) containing polyester resin and epoxy resin. Specifically, the polyester resin, epoxy resin, and additives were placed in a high-speed mixer and mixed for 1 minute. Then, the mixture was kneaded using a single-screw mixer (manufactured by BUSS Co., Ltd.) with the temperature adjusted to 120°C, and the discharged mixture was cold-rolled with a cooling roll. After that, it was crushed using a pin mill, classified with a 150-mesh screen, and a lubricant was added to obtain powder particles (A) (50% volume average particle diameter: approximately 35 μm) that would serve as raw materials for powder coating compositions (coatings 18-34).

[0153] (3) 1-1-3: Preparation of powder particles containing polyester resin and amide compound Using the raw materials shown in Tables 1 and 2, the components were mixed to achieve the blending ratios shown in Tables 8 and 9 to obtain powder particles (A) containing polyester resin and amide compounds. Specifically, the polyester resin, amide compound, additives, and lubricant were placed in a high-speed mixer and mixed for 1 minute. Then, the mixture was kneaded using a single-screw mixer (manufactured by BUSS Co., Ltd.) with the temperature adjusted to 120°C, and the discharged mixture was cold-rolled with cooling rolls. After that, it was crushed using a pin mill and classified using a 150-mesh screen to obtain each powder particle (A) (50% volume average particle diameter: approximately 35 μm) that will be used as raw material for powder coating compositions (coatings 35-51).

[0154] <1-2: Preparation of Binding Agent Solution> The binder and binder solvent were mixed to achieve the proportions shown in Tables 4 to 9, and binder solutions for use in the manufacture of powder coating compositions (coatings 1 to 51) were prepared.

[0155] <1-3: Preparation of powder coating compositions (coatings 1-51)> The powder particles (A) obtained by the method described above were mixed with a bright pigment (PCF7620A, manufactured by Toyo Aluminum Co., Ltd., average particle size 21 μm, resin-coated aluminum powder) in the proportions shown in Tables 4 to 9, and then mixed uniformly with a spatula. Next, the binder solution obtained by the method described above was added and the mixture was kneaded while being allowed to air dry for 1 hour. This was then packed into a 1-liter volumetric flask and vacuum-dried at room temperature for 20 minutes while rotating and mixing with an evaporator for 30 minutes. The powder obtained in this way was classified using a mesh with a mesh size of 100 μm to obtain powder coating compositions (coatings 1 to 51).

[0156] (2. Characteristic Evaluation) The obtained powder coating compositions (coatings 1 to 51) were subjected to characterization. The results of each evaluation test are shown in Tables 4 to 9. For the evaluation tests of gloss and surface smoothness, test specimens prepared as follows were used.

[0157] <2-1: Method for preparing test specimens> Each powder coating was electrostatically applied to one surface of a chromate-treated aluminum plate (substrate) using an electrostatic coating machine equipped with a powder coating gun (manufactured by Onoda Cement Co., Ltd., product name: GX3600C), and held in a 200°C atmosphere for 20 minutes. By leaving it to cool to room temperature, an aluminum plate (test specimen) with a coating film (cured film) of 55-65 μm thickness was obtained.

[0158] <2-2: Evaluation> Layer separation properties, luster, surface smoothness, and recyclability were measured and evaluated as follows.

[0159] (1) Layer separation property For the coating films of Examples 1-12 and Comparative Examples 1-5, the cross-section of the coating film was observed using a microscope (Keyence Corporation) to evaluate whether the interior of the coating film was separated into upper and lower layers. Similarly, the cross-section of the coating film was observed using a scanning electron microscope (Hitachi High-Technologies Corporation Ultra-High Resolution Analytical Scanning Electron Microscope SU-70), and the distribution of fluorine elements (fluororesin) in the cross-section of the coating film was confirmed by elemental analysis.

[0160] The evaluation was as follows: ○ (Good): Fluorine elements were unevenly distributed on the surface of the coating. × (Poor): No uneven distribution of fluorine elements was observed on the surface of the coating film.

[0161] (2) Brightness The evaluation was as follows: For each test specimen, the color unevenness of the coating was evaluated visually according to the following criteria. ○ (Good): Color unevenness occurs in less than 20% of the total surface area of ​​the test specimen. × (Defective): Color unevenness occurred in more than 20% of the total surface area of ​​the test specimen.

[0162] (3) Surface smoothness The evaluation was as follows: The condition of the coating surface after the test panels were prepared was visually evaluated. ◎ (Excellent): No abnormalities. ○ (Good): Orange skin × (Poor): Skin irritation

[0163] (4) Recoverability and reusability The evaluation was as follows: The paint that did not adhere during the first coat was reapplied, and the color unevenness of the paint film on each test piece was evaluated visually according to the following criteria. ○ (Good): Color unevenness occurs in less than 20% of the total surface area of ​​the test specimen. × (Defective): Color unevenness occurred in more than 20% of the total surface area of ​​the test specimen.

[0164] The results are shown in Tables 4 to 9.

[0165] [Table 4]

[0166] [Table 5]

[0167] [Table 6]

[0168] [Table 7]

[0169] [Table 8]

[0170] [Table 9]

[0171] From the examples and comparative examples, it was found that the powder coating compositions of the examples exhibited good gloss, surface smoothness, and recyclability. [Explanation of Symbols]

[0172] CC center coordinates G. Hansen's 3D Graph HSS Hansen's lysis sphere R0 interaction radius R a interaction distance

Claims

1. A powder coating composition containing resin-containing powder particles (A), a luminous pigment (B), and a binder (C), The aforementioned binder (C) is The central coordinate (δ) of the Hansen solubility sphere used to determine solubility with the solvent being mixed. ｄ , δ ｐ , δ ｈ When the interaction distance R is (19.0, 7.0, 5.0), ａ A water-soluble acrylic resin, water-soluble polyester resin, or resin that disperses in water, which is dissolved or dispersed in a solvent (D) having a ratio of 20 or higher, has a Tg of 30°C or higher, and has a weight-average molecular weight of 3,000 to 100,000. The powder coating composition is characterized in that the resin-containing powder particles (A) contain a resin (A1), the resin (A1) contains a binder resin (A11) containing a hydroxyl group-containing fluororesin and a hydroxyl group-containing polyester resin, and a curing agent (A12) containing an isocyanate compound, and is insoluble in the solvent (D).

2. The powder coating composition according to claim 1, characterized in that the resin dispersed in water is an acrylic resin dispersed in water.

3. The powder coating composition according to claim 1, characterized in that the binder (C) is a resin that dissolves or disperses in the solvent (D) having an interaction distance Ra of 30 or more.

4. The powder coating composition according to claim 1, characterized in that the binder (C) has a Tg of 40°C or higher.

5. The powder coating composition according to claim 1, characterized in that the solvent (D) is one or more solvents selected from the group consisting of water, ethylene glycol, and methanol.

6. The powder coating composition according to claim 1, characterized in that the solvent (D) is a mixed solvent of water and a water-soluble organic solvent.

7. The powder coating composition according to claim 1, characterized in that the luminous pigment (B) is a flake-shaped piece of aluminum.

8. A coating film formed using the powder coating composition according to any one of claims 1 to 7.

9. Substrate and A coated body having a coating film formed on the surface of the substrate using the powder coating composition described in any one of claims 1 to 7.

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