JPH10324824A - Thermosetting double-layer powder coating material and method for forming coating film therefrom - 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 thermosetting powder coating materials. SOLUTION: The thermosetting double-layer powder coating used is a mixed powder coating of I, II, II or IV. (I) both a thermosetting acrylic resin powder coating A and a polyester resin curing epoxy resin powder coating material (B), (II) both a polyester resin curing acrylic resin powder coating material (C) and a thermosetting epoxy resin powder coating material (D), (III) both C and B, and (IV) both a thermosetting polyester resin powder coating material (E) and component D. The mixing ratio between the respective components in each mixed powder coating material I, II, III or IV is desirably about 30 to 70 wt.%. In the coating films, (I) A preponderates in the upper layer, while B preponderates in the lower layer; (II) C preponderates in the upper layer, while D preponderates in the lower layer, (III) C preponderates in the upper layer, while B preponderates in the lower layer, and (IV) E preponderates in the upper layer, while D preponderates in the lower layer. The treatment is desirably performed with 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 thermosetting multilayer powder coating material capable of providing a multilayer powder coating film having excellent finished appearance and coating film performance, and a method for forming the coating film.

[0002]

[Prior 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 powder coating, polyester resin powder coating and epoxy resin 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, epoxy resin powder coatings are used mainly for indoor applications because of their drawbacks such as poor corrosion resistance and poor weather resistance, contrary to acrylic resin powder coatings. ing. Further, a coating film formed from a polyester resin powder coating has a drawback that corrosion resistance is inferior to an epoxy resin powder coating.

[0004] As a powder coating for improving the disadvantages of such a 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 powder-coated on a surface-treated steel plate. Then, heat-curing to form a multilayer coating film on the upper layer of an acrylic resin powder coating film and the lower layer of an epoxy resin powder coating film or a polyester resin powder coating (Japanese Patent Application Laid-Open No. 54-105135) Reference).

[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 present inventors have made 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 is applied to a material by electrostatic powder coating. As a result, it was found that a thermosetting coating film having excellent finished appearance and performance was formed, and the present invention was completed.

That is, the present invention provides: 1. A thermosetting resin composition comprising a mixed powder coating of a thermosetting acrylic resin powder coating (A) and a polyester resin curing type epoxy resin powder coating (B). A multi-layered powder coating (I), 2, a mixed powder coating of a polyester resin curing type acrylic resin powder coating (C) and a thermosetting epoxy resin powder coating (D). Curable multi-layer powder coating (II), 3. Mixed powder coating of polyester resin-curable acrylic resin powder coating (C) and polyester resin-curable epoxy resin powder coating (B) Thermosetting type multi-layer powder coating (III), 4, mixed powder coating of thermosetting polyester resin powder coating (E) and thermosetting epoxy resin powder coating (D) Thermosetting multilayer powder coating (IV), 5, groups A method for forming a thermosetting multilayer powder coating film, which comprises treating the surface with an onium salt compound, then applying a thermosetting multilayer powder coating material to an electrostatic powder, and curing by heating; The method for forming a thermosetting multilayer powder coating film, wherein the curable powder coating material is the mixed powder coating material described in any one of the above items 1 to 4, 7. The onium salt compound is a phosphonium salt compound 7. The method for forming a thermosetting multilayer powder coating film according to the above item 5 or 6, wherein

First, thermosetting double-layer powder coatings (I) to (I)
V) will be described.

Thermosetting double layer powder coating (I): The powder coating (I) is composed of a thermosetting acrylic resin powder coating (A) and a polyester resin curing epoxy resin powder coating (B). It is a mixed powder coating.

Powder coating (A) As the powder coating (A), a conventionally known powder coating which can be electrostatic powder coated by itself and is cured by heating, for example, an acid epoxy-curable acrylic resin powder Body paint (a) and blocked isocyanate-curable acrylic resin-based powder paint (b).

The powder coating (a) includes a radical polymerizable unsaturated monomer containing an epoxy group (eg, glycidyl (meth) acrylate, methyl glycidyl (meth) acrylate), 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 applied 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.), a hard acrylic resin 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.

Powder coating (B) As the powder coating (B), a conventionally known powder coating which can be applied by itself to electrostatic powder coating and is cured by heating, for example, bisphenol / epichlorohydrin type epoxy base resin (For example, Epicoat 1004, Epicoat 1007, manufactured by Yuka Shell Co., Ltd.), and epoxy resin such as novolak type epoxy base resin (for example) mixed with a high acid value polyester resin.

Examples of the high acid value polyester resin include aromatic resins such as (phthalic anhydride), isophthalic acid, terephthalic acid, dimethyl isophthalate, dimethyl terephthalate, hexahydro (anhydride) phthalic acid, and tetrahydro (anhydride) phthalic acid. Or an alicyclic dicarboxylic acid and a dihydric alcohol such as (poly) ethylene glycol, (poly) propylene glycol, butylene glycol, butylene glycol, neopentyl glycol, 1,6-hexanediol, dimethylpropionic acid, and, if necessary, benzoic acid It is obtained by reacting a monocarboxylic acid such as an acid, a trivalent or higher carboxylic acid such as (anhydride) trimellitic acid, and a trivalent or higher alcohol such as trimethylolethane, trimethylolpropane, glycerin, and pentaerythritol. Acid value about 20-3
A polyester resin of 00 KOH mg / g can be used.

The mixing ratio of the base resin and the high acid value polyester resin is such that the high acid value polyester resin is mixed in the range of 50 to 200 parts by weight with respect to 100 parts by weight of the base resin.

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. .

Thermosetting double layer powder coating (II): A mixed powder coating of a polyester resin curing type acrylic resin powder coating (C) and a thermosetting epoxy resin powder coating (D).

Powder coating (C) It is obtained by blending the epoxy group-containing acrylic resin described in (a) and the high acid value polyester resin described in (B).

Powder coating (D) Examples of the powder coating (D) include the above-mentioned bisphenol / epichlorohydrin type epoxy base resin and novolak type epoxy base resin, for example, adipic acid, (anhydrous)
Polycarboxylic acid compounds such as trimellitic acid, benzyl-
Formulated with a cationic polymerization catalyst for aromatic sulfonium salts such as 4-hydroxyphenylmethylsulfonium hexafluoroantimonate, amide compounds such as dicyandiamide, carboxylic acid dihydrazide compounds such as adipic dihydrazide, and epoxy crosslinking agents such as imidazoline and imidazole. 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 (II) 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 (D) in the lower layer. .

Thermosetting double layer powder coating (III): A mixed powder coating of the above powder coating (C) and the above powder coating (B). A 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 (C) in the upper layer and a coating film containing a large amount of the powder coating material (B) in the lower layer.

Thermosetting double layer powder coating (IV): a mixed powder coating of powder coating (E) and powder coating (D).

Powder coating (E) As the powder coating (E), a conventionally known powder coating which can be electrostatic powder coated by itself and is cured by heating, for example, a blocked isocyanate-curable polyester resin powder Body paint and the like.

Examples of the powder coating (E) include aromatic phthalic acid such as (phthalic anhydride), isophthalic acid, terephthalic acid, dimethyl isophthalate, dimethyl terephthalate, hexahydro (phthalic anhydride), and tetrahydro (phthalic anhydride). 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 monocarboxylic acid such as benzoic acid, trivalent or more carboxylic acid such as (anhydride) trimellitic acid, and 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.

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

In the powder coating of the present invention, an antibacterial agent can be added to the powder coating 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 Toagosei 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 particle size of the inorganic antibacterial agent carrying silver ions is from 0.001 to 20 μm, preferably from 0.01 to 20 μm, based 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 compounding 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.

Further, bis (pyridine-2) is added to the powder coating.
The so-called zinc pyrithione can be blended with the (thiol-1-oxide) zinc salt as needed. The particle size of the bis (pyridine-2-thiol-1-oxide) zinc salt is from 0.001 to 20 μm or less, preferably from 0.01 to 20 μm, from the finish after coating and the effective area of the antibacterial agent.
Desirably, it is in the form of fine particles of 10 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 to add an oil repellent, an ultraviolet stabilizer, and an ultraviolet absorber (such as a benzotriazole compound) to the powder coating for forming the upper layer coating film, if necessary.

In the powder coating of the present invention, a rust inhibitor can be added to the powder coating 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.

Powder coatings (A) to (E) used in the present invention
Can be produced by processes such as melt-kneading, pulverizing, and filtering (sieving).

The powder coatings (I) to (IV) of the present invention are produced, for example, by mixing the above two types of powder coatings with a Henschel mixer or by dry mixing and dispersing with a pulverizer such as an atomizer or a jet mill. be able to.

In powder coatings (I) to (IV), powder coatings (A) and (B), powder coatings (C) and (D), powder coatings (C) and (B) and powder coatings The mixing ratio of the paints (E) and (B) is about 30 to 70% by weight, especially about 40 to 60% by weight.
A range of weight% is preferred.

The powder coatings (I) to (IV) have an average particle diameter of 5 to 100 μm, preferably 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 and
It is not preferable because the appearance of the coating film is deteriorated.

Next, the coating film forming method of the present invention will be described.

The method for forming a powder coating film of the present invention is a method in which the surface of a substrate is treated with an onium salt compound, and then a thermosetting double-layer powder coating material is electrostatically powder-coated and cured by heating.

The substrate used in the method of the present invention may be any of those conventionally used for electrostatic powder coating, which can be applied with electrostatic powder and does not deform the substrate due to 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 method of the present invention is carried out by applying an aqueous treating agent obtained by dissolving or dispersing an onium salt compound in water to the above-mentioned substrate, followed by drying, followed by electrostatic powder coating of the powder coating and baking. it can. 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 0.01
The range is preferably from 30 to 30% by weight. The treatment 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. Powder film thickness is about 4
A range from 0 to 100 microns is preferred. The baking of the powder coating can be usually performed at about 120 to 200 ° C. for about 20 to 40 minutes.

[0049]

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 "by 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.

Example of Production of Polyester Resin-Curable Epoxy Resin Powder Coating (B) Yupika Coat GV-230 (trade name, acid value 53, high acid value polyester resin, manufactured by Nippon Yupika Co., Ltd.) 500 Parts by weight, Epicoat 1004 (manufactured by Yuka Shell Co., Ltd., softening point 97 to 103 ° C, average molecular weight of about 1400, epoxy resin, hereinafter the same meaning) 5
A mixture of 00 parts by weight and 200 parts by weight of a red stalk is melt-kneaded with a twin-screw extruder, then cooled, pulverized and filtered to produce a powder coating (B) having a red stalk color with an average particle diameter of about 30 μm. did.

Production Example of Polyester Resin-Curable Acrylic Resin Powder Coating (C) 700 parts by weight of Yupica Coat GV-230, glycidyl group-containing acrylic resin (same as the resin used in the above powder coating (A)) A mixture of 300 parts by weight and 500 parts by weight of titanium dioxide pigment was melt-kneaded with a twin-screw extruder, then cooled, pulverized and filtered to obtain an average particle diameter of about 30.
A μm white powder coating (C) was produced.

Production Example of Epoxy Resin Powder Coating (D) A mixture of 1000 parts by weight of Epicoat 1004, 500 parts by weight of adipic dihydrazide, and 200 parts by weight of a red stem was melt-kneaded with a twin-screw extruder. , Cooling, crushing,
Filtration was performed to produce a reddish-colored powder coating material (D) having an average particle size of about 30 μm.

Production Example of Polyester Resin Powder Coating (E) Ester ER-7200 (trade name, manufactured by Nippon Ester Co., Ltd.)
Hydroxyl-containing polyester resin, softening point 80 ° C) 1000
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 catalyst) and 500 parts by weight of a titanium dioxide pigment. The mixture was melt-kneaded with a twin-screw extruder, cooled, pulverized and filtered to produce a white powder coating (E) having an average particle size of about 40 μm.

Production Example of Polyester Resin Powder Coating (E ') Powder coating (E) except that in the production example of powder coating (E) above, 70 parts by weight of phthalocyanine blue pigment were used instead of titanium dioxide pigment. In the same manner as in the above, a blue powder coating material (E) was produced.

Example 1 A mixed powder coating was produced by mixing 600 parts of the powder coating (A) and 400 parts of the powder coating (B) with a Henschel mixer. FIG. 1 shows a cross-sectional view of the coating film formed in Example 1 (with surface treatment). 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 A mixed powder coating was produced in the same manner as in Example 1 with the composition shown in Table 1.

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

Example 3 A mixed powder coating was produced in the same manner as in Example 1 with the composition shown in Table 1.

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

Example 4 A mixed powder coating was produced in the same manner as in Example 1 with the composition shown in Table 1.

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

Comparative Example 1 A mixed powder coating was produced in the same manner as in Example 1 with the composition shown in Table 1.

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

FIG. 2 shows a cross-sectional view of the coating film formed in Comparative Example 1 (without surface treatment). As is clear from FIG. 2, the powder coatings (A) and (D) are not completely separated into an upper layer and a lower layer, and discontinuous coating films are formed.

Comparative Example 2 A mixed powder coating was produced in the same manner as in Example 1 with the composition shown in Table 1.

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

Table 1 shows the coating film performance test results of the various powder coatings of the examples and comparative examples.

[0069]

[Table 1]

In Table 1, the test was performed as follows.

Test of coating film performance Preparation of coated plate: no surface treatment; electrostatic powder coating on zinc phosphate treated steel plate so that dry film thickness is about 80 μm;
Baked for 30 minutes was used as a test.

With a surface treatment; a 1% benzyltetraphenylphosphonium chloride (solvent, water / propanol = 30/70 weight ratio) solution is applied to a zinc phosphate-treated steel sheet so that the dry film thickness becomes about 0.5 μm. Apply, then 80 ° C
A plate dried at 10 ° C. for 10 minutes was subjected to electrostatic powder coating so as to have a film thickness of about 60 μm, and baked at 180 ° C. for 30 minutes, and used as a test plate.

Coating separability: After cutting the coated plate, the cross section was polished with abrasive paper No. 2000 to smooth the coating cross section, and the coating 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: A gauze impregnated with acetone was soaked on the surface of the coating film ten times with a finger, and the surface of the coating film was observed. ○ indicates no abnormality, △ indicates glossiness,
×: matte.

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

Erichsen value: JIS K-5400
The test was performed according to 8.2.

The breaking distance (cm) at which the steel ball was extruded until the coating film cracked and peeled off was determined.

[0080]

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 powder coating (E) 4 zinc phosphate-treated steel sheet treated with 1% benzyltetraphenylphosphonium chloride on zinc phosphate-treated steel sheet 5 zinc phosphate Treated steel plate

Claims (7)

[Claims] 1. A thermosetting double-layer powder coating material which is a mixed powder coating of a thermosetting acrylic resin powder coating material (A) and a polyester resin curing type epoxy resin powder coating material (B). . 2. A thermosetting multi-layer powder coating material which is a mixed powder coating of a polyester resin curing type acrylic resin powder coating material (C) and a thermosetting epoxy resin powder coating material (D). . 3. A thermosetting double-layer powder, which is a mixed powder coating of a polyester resin-curable acrylic resin powder coating (C) and a polyester resin-curable epoxy resin powder coating (B). paint. 4. Thermosetting polyester resin powder coating (E)
And a thermosetting epoxy resin powder coating (D). 5. A thermosetting multi-layer powder coating film characterized by treating a substrate surface with an onium salt compound, then applying a thermosetting multi-layer powder coating material to an electrostatic powder, and heat-curing. Formation method. 6. A method for forming a thermosetting multilayer powder coating film, wherein the thermosetting powder coating material is the mixed powder coating material according to any one of claims 1 to 4. 7. The method for forming a thermosetting double-layer powder coating according to claim 5, wherein the onium salt compound is a phosphonium salt compound.