JPH10324823A - Production of thermosetting double-layer powder coating film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a coating film excellent in finish and film performances by electrocoating a substrate surface-treated with an onium salt compound with a mixed powder coating material being a combination of two of the three thermosetting acrylic resin, epoxy resin and polyester resin powder coating materials. SOLUTION: The surface of a substrate is treated with an onium salt compound and then electrocoated with a mixed powder coating material of formula I, II or III and heated to cure the film. (I) both a thermosetting acrylic resin powder coating A and a thermosetting epoxy resin powder coating material, (II) both A and a thermosetting polyester resin powder coating material C, and (III) both C and B. The mixing ratio between A and B, between A and C or between C and B in the coating material is desirably about 30 to 70 wt.%. In the three coating films, (I) A preponderates in the upper layer, while B preponderated in the lower layer; likewise, (II) A preponderates in the upper layer, while C preponderates in the lower layer, and (II) C preponderates in the upper layer, while B preponderates in the lower layer. The onium salt compound is desirably a phosphonium salt compound.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a thermosetting double-layer powder coating capable of providing a double-layer powder coating excellent in finished appearance and coating performance.

[0002]

2. Description of the Related Art Conventionally, thermosetting powder coatings have been used for home appliances,
It is widely used for outdoor or indoor applications in the field of industrial products such as automobiles, vehicles, office supplies, steel furniture, and building materials. As the above-mentioned thermosetting powder coating, acrylic resin-based powder coating, polyester resin-based powder coating, and epoxy resin-based powder coating are mainly used.

[0003] However, among the coating films formed from these powder coatings, acrylic resin powder coating films are often used in outdoor applications where the appearance of the coating film surface is emphasized because the coating film deteriorates little due to sunlight or the like. However, the epoxy resin-based powder coating has the disadvantage that it has excellent corrosion resistance but has poor weather resistance, contrary to the acrylic resin-based powder coating, and is mainly used for indoor applications. Has been used as In addition, coatings formed from polyester resin powder coatings can exhibit only intermediate performance between acrylic resin powder coatings and epoxy resin powder coatings, resulting in incomplete performance and limited applications. There were drawbacks.

[0004] As a powder coating for improving the disadvantages of such powder coating, for example, a mixture of an acrylic resin powder coating and an epoxy resin powder coating or a polyester resin powder coating is applied to a surface-treated steel sheet. After coating the body, heat-curing to form a multi-layer coating on the upper layer of an acrylic resin powder coating and the lower layer of an epoxy resin powder coating or polyester resin powder coating No. 54-105135).

[0005] However, the multilayer powder coating film formed therefrom still has disadvantages such as insufficient finished appearance and poor performance such as corrosion resistance.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a multilayer powder coating film having excellent finished appearance and coating film performance.

[0007]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, have found that a mixed powder coating of a specific thermosetting powder coating has been applied to a material which has been surface-treated with an onium salt compound. The inventors have found that a thermosetting coating film excellent in finished appearance and performance is formed by electrostatic powder coating, and the present invention has been completed.

That is, the present invention relates to the following: 1. The substrate surface is treated with an onium salt compound, and then a mixed powder coating of a thermosetting acrylic resin powder coating and a thermosetting epoxy resin powder coating is prepared. A method for forming a thermosetting double-layer powder coating film, which is characterized by coating with an electric powder and heat-curing. 2. Treating the substrate surface with an onium salt compound, and then thermosetting acrylic resin-based powder coating. A method for forming a thermosetting double-layer powder coating film, which comprises electrostatically powder coating a mixed powder coating of a thermosetting polyester resin powder coating and a thermosetting polyester resin-based powder coating; Is treated with an onium salt compound, then a mixed powder coating of a thermosetting polyester resin-based powder coating and a thermosetting epoxy resin-based powder coating is electrostatically powder-coated, and then heat-cured. Method for forming thermosetting multilayer powder coating film, 4. Onium 4. The method according to any one of the above 1 to 3, wherein the salt compound is a phosphonium salt compound.

The substrate used in the method of the present invention may be a substrate which is conventionally used for electrostatic powder coating, which is capable of electrostatic powder coating and does not cause deformation of the substrate upon heating. . Specific examples include metals such as steel, copper, stainless steel, alloy steel, aluminum and alloys thereof, zinc, galvanized steel, zinc alloy, tin-plated steel, zinc phosphate and iron phosphate-treated steel. The base material may be a plate, a processed product molded into a pipe, a box, or the like. Further, the surface of the base material may be subjected to primer coating or intermediate coating as needed.

As the onium salt compound for treating the above-mentioned substrate, a general formula [(R) 4Y] + X- or [(R) 3
Those represented by [S] + X− are preferable. In the formula, R is the same or different and is a hydrogen atom, a lower alkyl group (eg, methyl, ethyl, propyl, butyl, hexyl, etc.), a hydroxy lower alkyl group (eg, hydroxymethyl, hydroxyethyl, hydroxypropyl, hydroxybutyl, hydroxyhexyl, etc.) ), Halo-lower alkyl groups (eg, methyl bromide, ethyl bromide, etc.), lower alkoxy lower alkyl groups (eg, methoxymethyl, methoxyethyl, methoxypropyl, methoxybutyl, methoxyhexyl, etc.), cycloalkyl groups (eg, cyclohexyl, cyclohexyl) Organic groups such as methyl, cyclopentyl, etc.), aryl groups (eg, phenyl, toluyl, xylyl, etc.) and aralkyl groups (eg, benzyl group, etc.). Y is a nitrogen atom or a phosphorus atom. X represents a negative ion, for example, a halogen ion (eg, chlorine, bromine, fluorine, iodine, etc.), an inorganic acid group (eg, a sulfate group, a phosphate group, etc.), an organic acid group (eg, an acetate group, a benzylsulfonic acid group, water) Acid radicals). The above lower meaning means those having 6 or less carbon atoms. In the above-mentioned general formula, an ammonium or phosphonium salt compound in which R is a lower alkyl group, a phenyl group or a benzyl group and X is a halogen ion is particularly preferred.

Examples of the onium salt compound include tetramethylphosphonium chloride, tetraethylphosphonium chloride, tetrabutylphosphonium chloride, trimethylethylphosphonium chloride, triphenylbenzylphosphonium chloride, tetramethylphosphonium bromide, and triphenylbenzylphosphonium bromide. Phosphonium salt compounds such as; ammonium salt compounds such as tetramethylammonium chloride, tetraethylammonium chloride, tetrabutylammonium chloride, trimethylethylammonium chloride, triphenylbenzylammonium chloride, tetramethylammonium bromide, and triphenylbenzylammonium bromide ; Trimethylsulfonium chloride, tetraethylsulfonium chloride, tetrabutylsulfonium chloride, salt Trimethyl ethyl sulfonium,
And sulfonium salt compounds such as triphenylbenzylsulfonium chloride.

The thermosetting mixed powder coating used in the method of the present invention is a mixed powder coating of a thermosetting acrylic resin powder coating (A) and a thermosetting epoxy resin powder coating (B). I), a mixed powder coating of a thermosetting acrylic resin powder coating (A) and a thermosetting polyester resin powder coating (C) (II), a thermosetting polyester resin powder coating (C) And a thermosetting epoxy resin-based powder coating (B).

Mixed powder coating (I): As the thermosetting acrylic resin-based powder coating (A) used in the mixed powder coating (I), electrostatic powder coating can be performed by itself and heated. A conventionally known powder coating that cures, for example, an acid epoxy-curable acrylic resin-based powder coating (a), a blocked isocyanate-curable acrylic resin-based powder coating (b), and the like can be given.

Examples of the powder coating (a) include an epoxy group-containing radically polymerizable unsaturated monomer (eg, glycidyl (meth) acrylate, methyl glycidyl (meth) acrylate), and a hard acrylic monomer having a glass transition temperature of 40 ° C. or higher. (Eg, methyl methacrylate, ethyl methacrylate, iso-butyl methacrylate, ter-
Butyl methacrylate, ter-butyl acrylate, etc.) and, if necessary, a soft acrylic monomer having a glass transition temperature of less than 40 ° C. (eg, methyl acrylate, ethyl acrylate, n-butyl methacrylate, iso-
Butyl acrylate, 2 ethylhexyl (meth) acrylate, stearyl methacrylate, etc.), radical polymerizable unsaturated monomers other than acrylic monomers (eg, styrene, vinyltoluene, α-methylstyrene, (meth)
Acrylonitrile, (meth) acrylamide, etc.), functional group-containing radically polymerizable unsaturated monomer other than the epoxy group (for example, hydroxyethyl (meth) acrylate,
A polycarboxylic acid crosslinking agent (eg, adipic acid, azelaic acid, dodecane diacid, adipic anhydride, trimellitic anhydride, etc.) is added to an epoxy group-containing acrylic base resin obtained by a radical copolymerization reaction of hydroxypropyl (meth) acrylate or the like. ) Is blended.

The powder coating (b) may be a hydroxyl-containing radically polymerizable unsaturated monomer (eg, hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, etc.), or a hard acrylic having a glass transition temperature of 40 ° C. or higher. Monomers (eg, methyl methacrylate,
Ethyl methacrylate, iso-butyl methacrylate, ter-butyl methacrylate, ter-butyl acrylate, etc.) and, if necessary, a glass transition temperature of 40 ° C.
Less than a soft acrylic monomer (eg, methyl acrylate, ethyl acrylate, n-butyl methacrylate, iso-butyl acrylate, 2ethylhexyl (meth) acrylate, stearyl methacrylate, etc.), a radical polymerizable unsaturated monomer other than an acrylic monomer (eg, styrene, Vinyltoluene, α-methylstyrene, (meth) acrylonitrile, (meth) acrylamide, etc.), radical-polymerizable unsaturated monomers containing functional groups other than the above hydroxyl groups (eg, glycidyl (meth) acrylate, methylglycidyl (meth) acrylate, etc.)
To a hydroxyl group-containing acrylic base resin obtained by a radical copolymerization of Phenols, lactams, alcohols, oximes, etc.).

The mixing ratio of the base resin and the crosslinking agent is such that the crosslinking agent is mixed in the range of 10 to 100 parts by weight with respect to 100 parts by weight of the base resin.

As the powder coating (B) used by mixing with the above powder coating (A), a conventionally known powder coating which can be electrostatic powder coated by itself and is cured by heating, for example, bisphenol An epoxy resin such as epichlorohydrin type epoxy base resin (for example, trade name: Epicoat 1004, Epicoat 1007, manufactured by Yuka Shell Co., Ltd.), novolak type epoxy base resin, etc.
(Anhydride) Polycarboxylation such as trimellitic acid, cation polymerization catalyst of aromatic sulfonium salt such as benzyl-4-hydroxyphenylmethylsulfonium hexafluoroantimonate, amide compound such as dicyandiamide, carboxyl such as adipic dihydrazide A compound in which a crosslinking agent for epoxy such as an acid dihydrazide compound, imidazoline, imidazole or the like is blended can be used.

The mixing ratio of the base resin and the curing agent is in the range of about 0.01 to 10 parts by weight, preferably about 0.1 to 5 parts by weight in the case of a cationic polymerization catalyst per 100 parts by weight of the base resin. About 10 to 10 in cases other than polymerization catalyst
A range of 0 parts by weight, preferably about 15 to 80 parts by weight, is suitable.

The coating film obtained by heating the mixed powder coating material (I) is formed of a coating film containing a large amount of the powder coating material (A) in the upper layer and a coating film containing a large amount of the powder coating material (B) in the lower layer. .

Mixed powder coating (II): mixed powder coating (II) above
As the thermosetting acrylic resin-based powder coating (A) used in (1), the same ones as described above can be used. As the thermosetting polyester resin-based powder coating (C), a conventionally known powder coating which can be electrostatically powder-coated by itself and is cured by heating, for example, a blocked isocyanate-curing polyester resin-based powder coating (C) and the like.

Examples of the powder coating (c) include aromatic phthalic acid, isophthalic acid, terephthalic acid, dimethyl isophthalate, dimethyl terephthalate, hexahydro (anhydride) phthalic acid, and tetrahydro (anhydride) phthalic acid. Aliphatic or alicyclic dicarboxylic acids and dihydric alcohols such as (poly) ethylene glycol, (poly) propylene glycol, butylene glycol, butylene glycol, neopentyl glycol, 1,6-hexanediol, and dimethylpropionic acid, if necessary It is obtained by reacting with a monocarboxylic acid such as benzoic acid, a trivalent or more carboxylic acid such as (anhydride) trimellitic acid, and a trivalent or more alcohol such as trimethylolethane, trimethylolpropane, glycerin, and pentaerythritol. Hydroxyl value of about 20 to
A paint obtained by blending the above blocked polyisocyanate crosslinking agent with a hydroxyl group-containing polyester resin of 300 KOH mg / g can be used.

The mixing ratio of the base resin and the curing agent is preferably about 10 to 100 parts by weight, and more preferably about 15 to 80 parts by weight, per 100 parts by weight of the base resin.

The coating film obtained by heating the mixed powder coating material (II) is formed of a coating film containing a large amount of the powder coating material (A) in the upper layer and a coating film containing a large amount of the powder coating material (C) in the lower layer. .

Mixed powder paint (III): Mixed powder paint (II)
As the thermosetting polyester resin-based powder coating (C) and the thermosetting epoxy resin-based powder coating (B) used in I), the same ones as described above can be used.

The coating film obtained by heating the mixed powder coating material (III) is formed of a coating film containing a large amount of the powder coating material (C) in the upper layer and a coating film containing a large amount of the powder coating material (B) in the lower layer. .

In the mixed powder coating used in the method of the present invention, powder coatings (A) and (B), powder coatings (A) and (B),
The mixing ratio of the powder coatings (B) and (C) is about 30-
A range of 70% by weight, especially about 40-60% by weight, is preferred.

An antimicrobial agent can be added to the powder coating for forming the upper layer. Specifically, for example, an inorganic antibacterial agent particularly supporting silver ions can be blended. As the antibacterial agent, a conventionally known one can be used without any particular limitation as long as it is an inorganic compound carrying silver ions. Examples of the inorganic compound supporting silver ions include activated carbon, activated alumina, inorganic adsorbents such as silica gel, zeolite, hydroxyapatite, zirconium phosphate, titanium phosphate, potassium titanate, hydrated bismuth, hydrated zirconium, and the like. Can be

The method for supporting silver ions on these inorganic compounds is not particularly limited, and any conventionally known supporting method can be employed. For example, a method of supporting by physical adsorption or chemical adsorption, a method of supporting by ion exchange reaction,
A method in which a silver compound is supported by a binder, a method in which a silver compound is supported by being driven into an inorganic compound, and a method in which a thin layer of a silver compound is formed on the surface of the inorganic compound by a thin film forming method such as vapor deposition, dissolution deposition reaction, or sputtering. Method and the like. Among the above inorganic compounds, the inorganic ion exchanger is preferable because it can strongly support silver ions,
In particular, zeolite and zirconium phosphate can be preferably used.

Specific examples of the compound include "NOVALON AG-300" (manufactured by Toa Gosei Chemical Co., Ltd., zirconium phosphate carrying silver ion), and "ZEOMIC AW-10D".
Commercially available products such as (Sinanen-Ceramic Co., Ltd., silver ion-supporting zeolite) can also be used.

The average particle size of the inorganic antibacterial agent carrying silver ions is from 0.001 to 20 μm, preferably from 0.01 to 20 μm, depending on the finish after coating and the effective area of the antibacterial agent.
It is desirable that the fine particles have a particle size of 10 μm.

The mixing ratio of the inorganic antibacterial agent carrying silver ions is preferably 0.05 to 50 parts by weight, more preferably 0.5 to 10 parts by weight, per 100 parts by weight of the thermosetting resin.
A weight part is preferable from an antibacterial effect and economical efficiency.

In the thermosetting powder coating used in the present invention, zinc (bis (pyridine-2-thiol-1-oxide) zinc salt) may be added as needed, so-called zinc pyrithione. The average particle size of the bis (pyridine-2-thiol-1-oxide) zinc salt is 0.001 to 20 μm or less from the finish after coating and the effective area of the antibacterial agent.
Preferably, it is in the form of fine particles of 0.01 to 10 μm.

The mixing ratio of bis (pyridine-2-thiol-1-oxide) zinc salt is preferably 0.001 to 20 parts by weight, more preferably 0.05 to 100 parts by weight of the thermosetting resin. From 5 to 5 parts by weight is suitable from the viewpoint of antibacterial effect, discoloration preventing ability and economy.

It is preferable that an oil repellent, an ultraviolet stabilizer, and an ultraviolet absorber (such as a benzotriazole compound) are added to the powder coating material for forming the upper layer coating film, if necessary.

In the present invention, a rust preventive can be added to the powder coating for forming the lower layer coating film, if necessary.
Further, paint additives such as a colorant, a filler, a curing catalyst, a fluidity control agent, and an anti-cissing agent can be added to the powder coating material forming the upper layer and the lower layer, if necessary.

The mixed powder coating can be produced, for example, by mixing the above two powder coatings with a Henschel mixer or by dry mixing and dispersing with a pulverizer such as an atomizer or a jet mill.

The mixed powder coating has an average particle diameter of 5 to 100.
μm, preferably in the range of 10 to 80 μm. When the average particle diameter is less than 5 μm, the workability of the electrostatic powder coating decreases, while when the average particle diameter exceeds 100 μm, the coating efficiency, the appearance of the coating film, etc. decrease, which is not preferable.

In the method of the present invention, an aqueous treating agent obtained by dissolving or dispersing an onium salt compound in water is applied to the above-mentioned substrate, dried, and then the mixed powder coating is subjected to electrostatic powder coating and baked. Can be implemented. The onium salt compound itself is easily soluble in water, but may be mixed with an aqueous organic solvent (alcohols, ketones, esters) and the like, if necessary. The solid content of the aqueous treating agent is about 0.1.
The range of 01 to 30% by weight is preferred. The processing method is
It can be performed by means such as brush, roller, spray, immersion and the like. The treatment amount is preferably in the range of about 0.01 to 10 microns in dry film thickness. Drying can be performed at room temperature or by heating. When heating, it is preferable to carry out in the range of about 40 to 140 ° C. Electrostatic powder coating includes corona electrostatic coating and triboelectric powder coating. The powder thickness is preferably in the range of about 30-200 microns, preferably about 40-100 microns. The baking of the powder coating can be usually performed at about 120 to 200 ° C. for about 20 to 40 minutes.

[0039]

The present invention will be described below in detail with reference to examples. Parts and% indicate parts by weight and% by weight, respectively.

Production Example of Acrylic Resin Powder Coating (A) Glycidyl group-containing acrylic resin (glycidyl methacrylate / styrene / methyl methacrylate / n-butyl acrylate = 40/10/20/30 ") Weight ratio "average molecular weight 8000, softening point 85 ° C, average particle size about 35μ"
m) A mixture of 1000 parts by weight, 290 parts by weight of dodecanedioic acid and 500 parts by weight of titanium dioxide pigment is melt-kneaded with a twin-screw extruder, then cooled, pulverized and filtered to obtain a white powder having an average particle diameter of about 35 μm. (A) was manufactured.

Production Example of Epoxy Resin Powder Coating (B) Epicoat 1004 (trade name, manufactured by Yuka Shell Co., Ltd.)
After melt-kneading 1000 parts by weight, 500 parts by weight of adipic dihydrazide, and 200 parts by weight of red iron oxide with a biaxial extruder, the softening point is 97 to 103 ° C., the average molecular weight is about 1400, and the epoxy resin has the same meaning. , Cooling, crushing,
Filtration produced a reddish-colored powder coating (B) having an average particle size of about 30 μm.

Production Example of Polyester Resin Powder Coating (C) Ester ER-7200 (trade name, manufactured by Nippon Ester Co., Ltd., hydroxyl group-containing polyester resin, softening point 80 ° C.) 1
000 parts by weight, 105 parts by weight of ε-caprolactam block isophorone diisocyanate, 10 parts by weight of TK-1 (trade name, manufactured by Takeda Pharmaceutical Co., Ltd., tin-based catalyst) and 70 parts by weight of a Shanin blue coloring pigment The resulting mixture was melt-kneaded with a twin-screw extruder, cooled, pulverized, and filtered to produce a blue powder coating (C) having an average particle diameter of about 40 μm.

Example 1 500 parts of the powder coating (A) and 500 parts of the powder coating (B) were mixed with a Henschel mixer to obtain a mixed powder coating (I).
Was manufactured. A 1% benzyltetraphenylphosphonium chloride (solvent, water / propanol = 30/70 weight ratio) solution is brush-coated on a zinc phosphate-treated steel sheet so that a dry film thickness is about 0.5 μm, and then 80 ° C.
After drying for 10 minutes, electrostatic powder coating is performed on the mixed powder coating material (I) so that the film thickness becomes 80 μm.
Baking was performed at 180 ° C. for 20 minutes to form a multilayer powder coating. FIG. 1 shows a cross-sectional view of the coating film formed in Example 1. As is clear from FIG. 1, the powder coating (A) is separated into the upper layer and the powder coating (B) is separated into the lower layer.

Example 2 500 parts of the powder coating (A) and 500 parts of the powder coating (C) were mixed with a Henschel mixer to obtain a mixed powder coating (II).
Was manufactured.

Next, a multilayer powder coating film was formed in the same manner as in Example 1.

Example 3 500 parts of the powder coating (B) and 500 parts of the powder coating (C) were mixed with a Henschel mixer to obtain a mixed powder coating (II
I) was manufactured.

Next, a multilayer powder coating film was formed in the same manner as in Example 1.

Comparative Example 1 A multilayer powder coating film of Comparative Example 1 was obtained in the same manner as in Example 1 except that the zinc phosphate treated steel sheet was not treated with a 1% benzyltetraphenylphosphonium chloride solution. Was. A cross-sectional view of the coating film formed in Comparative Example 1 is shown in FIG.
As is clear from FIG. 2, the powder coatings (A) and (B) are not completely separated into an upper layer and a lower layer, and discontinuous coating films are formed.

Comparative Example 2 A multilayer powder coating film of Comparative Example 2 was obtained in the same manner as in Example 2 except that the zinc phosphate-treated steel sheet was not treated with a 1% benzyltetraphenylphosphonium chloride solution. Was.

Comparative Example 3 A multilayer powder coating film of Comparative Example 3 was obtained in the same manner as in Example 3 except that the zinc phosphate-treated steel sheet was not treated with a 1% benzyltetraphenylphosphonium chloride solution. Was.

Table 1 shows the coating film performance test results of the various powder coatings of Examples 1 to 3 and Comparative Examples 1 to 3.

[0052]

[Table 1]

In Table 1, the test was performed as follows.

Coating film performance test Preparation of coated plate: Zinc phosphate treated steel plate had a dry film thickness of about 6
Electrostatic powder coating was performed so that the thickness became 0 μm, and baking was performed at 180 ° C. for 30 minutes. In Table 1, finishability and coating film performance were tested by the following methods.

Coating film separability: After cutting the coated plate, the cross section was polished with abrasive paper No. 2000 to flatten the cross section of the coating film, and the coating film separability was evaluated. ○: good separation, Δ: separation but not vertical separation, ×: no separation and mottled pattern.

Coating appearance: The coating surface was visually observed and evaluated. ◎ indicates that there is no abnormality such as smoothness and shrinkage, ○ indicates that there is smoothness and shrinkage but there is no practical problem, Δ indicates that there is an abnormality such as smoothness and shrinkage, and x indicates smoothness and shrinkage. Those with remarkable abnormalities such as

Specular reflectance: 60 according to JIS K-5400
And 20 degrees of specular gloss.

Solvent resistance: Gauze impregnated with acetone on the surface of the coating film was rubbed with a finger for 10 times in a reciprocating manner, and then the coating film surface was observed. ○ indicates no abnormality, △ indicates glossiness,
×: matte.

Impact resistance: JIS K-5400
Performed according to 3.2. The test was conducted with an impact core diameter of 1/2 inch and a drop weight of 500 g. The height without cracking and peeling was measured.

[0060]

According to the present invention, it is possible to form a multi-layer powder coating film having excellent separability of the coating film and excellent coating film performance due to having the above constitution.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a multilayer powder coating film showing an example of the present invention.

FIG. 2 is a sectional view of a multilayer powder coating film showing a comparative example of the present invention.

[Explanation of symbols]

Reference Signs List 1 powder coating (A) 2 powder coating (B) 3 zinc phosphate treated steel sheet treated with 1% benzyltetraphenylphosphonium chloride on zinc phosphate treated steel sheet 4 zinc phosphate treated steel sheet

Claims (4)

[Claims] 1. A surface treatment of a base material with an onium salt compound, followed by electrostatic powder coating of a mixed powder coating of a thermosetting acrylic resin powder coating and a thermosetting epoxy resin powder coating,
A method for forming a thermosetting multi-layer powder coating film, wherein the method comprises heating and curing. 2. The surface of a base material is treated with an onium salt compound, and then a mixed powder coating of a thermosetting acrylic resin powder coating and a thermosetting polyester resin powder coating is electrostatically powder-coated. A method for forming a thermosetting multi-layer powder coating film, wherein the method comprises heating and curing. 3. A base material surface is treated with an onium salt compound, and then a mixed powder coating of a thermosetting polyester resin powder coating and a thermosetting epoxy resin powder coating is electrostatically powder-coated. A method for forming a thermosetting multi-layer powder coating film, wherein the method comprises heating and curing. 4. The method according to claim 1, wherein the onium salt compound is a phosphonium salt compound.