JPH11323202A - Epoxy resin-based powder coating composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject composition, giving thin coating films high in edge cover rate while keeping leveling and also good in preservation stability by including an epoxy resin, hardening agent, hardening accelerator, inorganic filler and thixotropic agent. SOLUTION: This composition contains (A) an epoxy resin, (B) hardening agent, (C) hardening accelerator, (D) inorganic filler and (E) thixotropic agent. The component E is preferably organic or inorganic. The organic thixotropic agent is preferably contained at 0.02 to 20 pts.wt. per 100 pts.wt. of the component A. The inorganic thixotropic agent is preferably of finely powdered inorganic compound having a primary particle diameter of 1 μm or less, attached to the powder coating composition surfaces while in use, and contained at 0.02 to 20 pts.wt. per 100 pts.wt. of the component A.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an epoxy resin-based powder coating composition which is excellent in electric insulation, edge coverage, and leveling property and can be applied to both thin film coating and thick film coating.

[0002]

2. Description of the Related Art Conventionally, bisphenol A has been used as a powder coating for electric insulation materials of electric and electronic parts such as motor iron cores, ceramic capacitors, film capacitors, resistance networks, coil products such as inductors, varistors, thermistors, and hybrid ICs. Resins such as epoxy resins, novolak epoxy resins, alicyclic epoxy resins, etc., curing agents such as acid anhydrides and polyamines, curing accelerators such as tertiary amines, imidazoles, triphenylphosphine, etc., fillers, etc. Powder coatings containing the above additives are well known.

[0003] These powder coatings are applied to motor iron cores and electric / electronic parts by a method such as a fluid immersion method or an electrostatic fluid immersion method.
It is widely used as an insulation coating method for electronic components. The thickness of the insulating coating at this time is usually 200 to 200
400 μm, and 200 to 500 μm for electric / electronic parts. However, in recent years, with the rapid progress and miniaturization of AV equipment such as video and CD players, and OA equipment such as computers, the size of motors has also been reduced, and as a result, a coating film having a thickness of 100 μm or less has been required. Despite being a small motor, a thin film having a thickness of 50 μm or less has been required in order to increase the linear area factor and obtain high output. Conventionally, a liquid paint has been used to obtain a thin film, and it has generally been applied by an electrodeposition coating or a spray coating method. However, these coating methods using liquid paints require 6 to 7 layers until a certain film thickness is obtained in order to impart insulation performance.
Since coating and drying (baking) must be repeated several times and several times, there is a problem in terms of cost, and since a solvent is used, there is a great problem of worker safety and a problem of environmental impact. Pollution-free to solve these problems,
Attention has been paid to powder coating, which is very cost-effective because only one coating is required. However, the conventional powder coating has a problem that the edge coverage is poor and an insulating layer is not formed on an edge portion when the coating film becomes thin, resulting in poor pressure resistance, and the average particle diameter of the powder coating is 60 μm or more. Therefore, when a thin film is formed, pinholes are apt to occur, which causes a failure in pressure resistance.

As a means for increasing the edge coverage, a method of increasing the filling amount of the filler to shorten the flowability of the powder coating to increase the edge coverage, or increasing the amount of the catalyst to shorten the gelation time to increase the edge coverage. A method of increasing the coverage is known, but in the former case, the edge coverage is high but the flowability is low, so that the yuzu skin is strong and a smooth coating surface is not formed, and when a thin film is formed, a pinhole is formed. Occurs. On the other hand, in the latter case, although the edge coverage is increased, there is a problem that the storage stability is deteriorated due to the large amount of the catalyst.

[0005]

There is a need for an epoxy resin-based powder coating composition which has a high edge coverage while maintaining leveling properties and which can be applied as a thin film with good storage stability.

[0006]

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 powder coating material which simultaneously satisfies the above performance can be obtained. That is, the present invention provides (1) an epoxy resin-based powder coating material containing an epoxy resin, a curing agent, a curing accelerator, an inorganic filler, and a thixotropy-imparting agent, and (2) an organic thixotropy-imparting agent. Alternatively, the epoxy resin-based powder coating composition of (1), which is an inorganic thixotropy-imparting agent, and the organic thixotropy-imparting agent of (3), containing 0.02 to 20 parts with respect to 100 parts of the epoxy resin (1) Or (2) the epoxy resin-based powder coating composition, (4) the inorganic thixotropy-imparting agent is an inorganic thixotropy-imparting agent having a primary particle diameter of 1 μm or less (1).
Or (3) an epoxy resin-based powder coating composition, (5)
The inorganic thixotropic agent is contained in an amount of 0.02 to 20 parts based on 100 parts of the epoxy resin (1) to (4).
(6) an epoxy resin-based powder coating composition having an inorganic thixotropy-imparting agent on the surface of the powder coating, (7) an epoxy resin-based powder coating composition, (1) The epoxy resin-based powder coating composition according to any one of (1) to (6), wherein the average particle diameter is 1 to 100 μm, and (8) the average particle diameter of the powder coating is 1 to 50 μm.
(1) An epoxy resin-based powder coating composition according to (6), (9) an article coated with the epoxy resin-based powder coating composition according to (1) to (8), 1
0) The article of (9), which is an electric / electronic part, (11) the article of (10), wherein the electric / electronic part is a motor iron core, (12)
(7) to (11) painted by the triboelectric spray method
The article according to any one of the above.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The epoxy resin used in the present invention includes a polyfunctional epoxy resin which is a glycidyl etherified product of a polyphenol compound, a polyfunctional epoxy resin which is a glycidyl etherified product of various novolak resins, an alicyclic epoxy resin, Examples include a crystalline epoxy resin, a heterocyclic epoxy resin, and an epoxy resin obtained by glycidylation of a halogenated phenol. The amount of epoxy resin in the powder coating is 30% by weight or more, preferably 35 to 95% by weight,
More preferably, it is 40 to 90% by weight.

Examples of polyfunctional epoxy resins which are glycidyl etherified polyphenol compounds include, for example, bisphenol A, bisphenol F, bisphenol S,
4,4'-biphenylphenol, 2,2'-methylene-bis (4-methyl-6-tert-butylphenol), 2,2'-methylene-bis (4-ethyl-6-t
tert-butylphenol), 4,4'-butylylene-
Bis (3-methyl-6-tert-butylphenol), 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenol), trishydroxyphenylmethane, pyrogallol, phenol having a diisopropylidene skeleton And phenols having a fluorene skeleton such as 1,1-di-4-hydroxyphenylfluorene, and polyfunctional epoxy resins which are glycidyl etherified products of polyphenol compounds such as phenolized polybutadiene.

Examples of polyfunctional epoxy resins which are glycidyl etherified compounds of various novolak resins include, for example, phenol, cresols, ethylphenols, butylphenols, octylphenols, bisphenol A,
Glycidyl etherified products of various novolak resins such as novolak resin, phenol novolak resin containing xylylene skeleton, phenol novolak resin containing dicyclopentadiene skeleton, and phenol novolak resin containing fluorene skeleton using various phenols such as bisphenol F, bisphenol S, and naphthols as raw materials Is mentioned.

Examples of the alicyclic epoxy resin include an alicyclic epoxy resin having an aliphatic skeleton such as cyclohexane. Crystalline epoxy resins include, for example, 2,5-di-tert-butyl-hydroquinone-di-
Glycidyl ether, bis (4-hydroxy-2-methyl-5-butylphenyl) thio-ether glycidyl ether, tetramethylbisphenol-diglycidyl ether, bis (1,2-epoxypropoxy-naphthyl) -methane, heterocyclic epoxy Examples of the resin include a heterocyclic epoxy resin having a heterocyclic ring such as an isocyanuric ring and a hydantoin ring, and epoxy resins obtained by glycidylating halogenated phenols include brominated bisphenol A, brominated bisphenol F, and brominated bisphenol S.
Epoxy resins obtained by glycidylation of halogenated phenols such as brominated phenol novolak, brominated cresol novolak, chlorinated bisphenol S, and chlorinated bisphenol A are exemplified.

Among these epoxy resins, preferred are various phenolic compounds such as bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, phenol, cresols, bisphenol A, bisphenol F, naphthols and the like. Glycidyl etherified compounds of various novolak resins, such as novolak resins, phenol novolak resins containing a xylylene skeleton, phenol novolak resins containing a dicyclopentadiene skeleton, phenol novolak resins containing a fluorene skeleton, and an alicyclic ring having an aliphatic skeleton such as cyclohexane. Formula epoxy resin, heterocyclic epoxy resin having an isocyanuric ring, brominated bisphenol A, brominated phenol novolak resin or brominated cresol novolak Glycidyl ethers of the resin can be mentioned, more preferably bisphenol A type epoxy resins, phenol novolak type epoxy resin, cresol novolak type epoxy resins, glycidyl ethers of brominated bisphenol A type epoxy resin or brominated phenolic novolak resin.

The curing agent used in the present invention includes, for example, acid anhydrides, amines, phenols, imidazoles and the like. Examples of the acid anhydride include phthalic anhydride, trimellitic anhydride, pyromellitic anhydride,
Benzophenone tetracarboxylic anhydride, ethylene glycol trimellitic anhydride, aromatic carboxylic anhydride such as biphenyltetracarboxylic anhydride, azelaic acid,
Alicyclic carboxylic acids such as aliphatic carboxylic acid anhydrides such as sebacic acid and dodecanedioic acid, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, nadic anhydride, hetanoic anhydride, and hymic anhydride. Anhydrides.

Examples of the amines include diaminodiphenylmethane, diaminodiphenylsulfone, and diaminodiphenylether. Examples of the phenols include bisphenol A, tetrabromobisphenol A, bisphenol F, bisphenol S, 4,
4′-biphenylphenol, 2,2′-methylene-bis (4-methyl-6-tert-butylphenol),
2,2'-methylene-bis (4-ethyl-6-tert
-Butylphenol), 4,4′-butylylene-bis (3-methyl-6-tert-butylphenol),
1,1,3-tris (2-methyl-4-hydroxy-5
-Tert-butylphenol), trishydroxyphenylmethane, pyrogallol, phenols having a diisopropylidene skeleton, phenols having a fluorene skeleton such as 1,1-di-4-hydroxyphenylfluorene, polyphenol compounds such as phenolized polybutadiene, Novolak resin using various phenolic compounds such as phenol, cresols, ethylphenols, butylphenols, octylphenols, bisphenol A, brominated bisphenol A, bisphenol F, bisphenol S, naphthols, and phenol novolak resin containing a xylylene skeleton And various novolak resins such as a phenol novolak resin containing a dicyclopentadiene skeleton and a phenol novolak resin containing a fluorene skeleton.

Examples of imidazoles include 2-methylimidazole, 2-phenylimidazole, 2-undecylimidazole, 2-heptadecylimidazole,
2-phenyl-4-methylimidazole, 1-benzyl-2-phenylimidazole, 1-benzyl-2-methylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2 -Undecyl imidazole,
2,4-diamino-6 (2′-methylimidazole (1 ′)) ethyl-s-triazine, 2,4-diamino-6 (2′-undecylimidazole (1 ′)) ethyl-s-triazine, , 4-Diamino-6 (2′-ethyl, 4-methylimidazole (1 ′)) ethyl-s-triazine, 2,4-diamino-6 (2′-methylimidazole (1 ′)) ethyl-s-triazine Isocyanuric acid adduct, 2-methylimidazole isocyanuric acid 2: 3 adduct, 2-phenylimidazole isocyanuric acid adduct, 2-phenyl-3,5-dihydroxymethylimidazole, 2-phenyl-4-hydroxymethyl-
Various imidazoles of 5-methylimidazole and 1-cyanoethyl-2-phenyl-3,5-dicyanoethoxymethylimidazole, and those imidazoles and phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, pyromellitic acid, naphthalene Salts with polycarboxylic acids such as dicarboxylic acid, maleic acid and oxalic acid are mentioned.

[0015] Of these curing agents, which curing agent is used is appropriately selected depending on the use, characteristics, and the like of the powder coating material, and is preferably an acid anhydride, a phenol novolak resin, or an imidazole. The amount of these curing agents used is in the range of 0.3 to 2.0, preferably 0.4 to 1.6, in the equivalent ratio of the curing agent to the epoxy group of the epoxy resin.
And more preferably in the range of 0.5 to 1.3. Further, two or more kinds of the above curing agents can be used as a mixture. Epoxy resin 1 for imidazoles
0.1 to 4 parts by weight, more preferably 0.3 to 3.5 parts by weight, and still more preferably 0.1 to 4 parts by weight, per 100 parts by weight.
About 5 to 3 parts by weight is preferable. Incidentally, the above imidazoles can also be used as a curing accelerator.

Examples of the curing accelerator that can be used in the present invention include the above-mentioned amides such as imidazoles and dicyandiamide, and 1,8-diaza-bicyclo (5.
4.0) diaza compounds such as undecene-7 and their phenols, salts with the polycarboxylic acids or phosphinic acids, phosphines such as triphenylphosphine and tetraphenylphosphonium tetraphenylborate, 2,4,6 And phenols such as trisaminomethylphenol. Which of these curing accelerators is used is appropriately selected depending on the curing speed, curing properties, and type of curing agent of the obtained powder coating. The mixing ratio of these accelerators is based on 100 parts by weight of the epoxy resin.
It is usually 0.01 to 5 parts by weight, preferably 0.05 to 3 parts by weight, more preferably 0.1 to 2 parts by weight.

The filler usable in the present invention includes fused silica, crystalline silica, silicon carbide, silicon nitride, boron nitride, calcium carbonate, magnesium carbonate, barium sulfate, calcium sulfate, mica, talc, clay, aluminum oxide, Magnesium oxide,
Zirconium oxide, aluminum hydroxide, magnesium hydroxide, calcium silicate, aluminum silicate, lithium aluminum silicate, zirconium silicate, barium titanate, glass fiber, carbon fiber, molybdenum disulfide, asbestos, etc., preferably fused silica, crystal silica,
Preferred are calcium carbonate, aluminum oxide, aluminum hydroxide and calcium silicate, and more preferred are fused silica, crystalline silica, calcium carbonate and aluminum oxide. The particle size of these fillers is 80% by weight when the particle size is 20 μm or less
Or more, preferably 85% by weight or more, more preferably 90% by weight or more.
% By weight or more. When the amount is less than 80% by weight, when the powder coating is used, the amount of the filler contained in the powder coating varies depending on the particle size of the powder coating. Cause a phenomenon. These fillers may be used alone or as a mixture of two or more kinds.
It is 5% by weight, preferably 30 to 60% by weight, more preferably 35 to 60% by weight.

The thixotropy-imparting agent which can be used in the present invention has a property of imparting thixotropy to a liquid composition, and is used as a thixotropy-imparting agent in a liquid paint and is preferably an organic thixotropy-imparting agent. And an inorganic thixotropic agent. Examples of the organic thixotropy-imparting agent include hydroxyethyl cellulose, methyl cellulose, carboxymethyl cellulose, sodium alginate, casein, xanthan gum, polyvinyl alcohol, modified polyether urethane, polyacrylic acid-acrylate,
Aluminum stearate, zinc stearate, aluminum octylate, castor oil with water, fatty acid amide,
Long chain fatty acid ester polymer, polyethylene oxide, dextrin fatty acid ester, dibenzylidene sorbitol,
Organic bentonite and vegetable oil-based polymerized oil. These thixotropy-imparting agents may be used alone or in a combination of two or more, and the amount used is 0.02 to 20 parts by weight, preferably 0.05 to 20 parts by weight, per 100 parts by weight of the epoxy resin.
15 parts by weight, more preferably 0.08 to 10 parts by weight,
Particularly preferably, it is 0.1 to 5 parts by weight. If the amount is less than 0.02 parts by weight, the effect of thixotropy is not obtained.
If the amount is more than 20 parts by weight, the cured physical properties are reduced.

The inorganic thixotropy-imparting agent is a fine powder of an inorganic compound having a primary particle diameter of 1 μm or less, preferably 500 nm or less, more preferably 100 nm or less, and particularly preferably 50 nm or less. It is also possible to use one that has been surface-treated with an agent or the like. When it is larger than 1 μm, the leveling property of the coating film is reduced. Examples of the inorganic compound-based fine powder include finely divided silica, finely divided aluminum oxide, and finely divided calcium carbonate. These thixotropic agents may be present in the powder coating composition, but are preferably used by adhering to the surface of the powder coating composition. These thixotropy-imparting agents may be used alone or in a combination of two or more, and the amount thereof is 0.02 to 20 parts by weight, preferably 0.1 to 20 parts by weight, per 100 parts by weight of the epoxy resin. 05 to 15 parts by weight, more preferably 0.08 to
It is 10 parts by weight, particularly preferably 0.1 to 5 parts by weight.
If the amount is less than 0.02 parts by weight, the effect of thixotropy is not obtained. If the amount is more than 20 parts by weight, the coating film becomes rough and pinholes are formed.

A flame retardant, a coloring agent, a coupling agent, a leveling agent, a lubricant and the like can be appropriately added to the powder coating of the present invention according to the purpose. Examples of the flame retardant include inorganic flame retardants such as antimony trioxide, antimony pentoxide, tin oxide, tin hydroxide, molybdenum oxide, zinc borate, barium metaborate, red phosphorus, aluminum hydroxide, magnesium hydroxide, and calcium aluminate; Bromobisphenol A,
Brominated flame retardants such as tetrabromophthalic anhydride, hexabromobenzene, decabromobiphenyl ether, brominated phenol novolak resin and brominated phenol novolak, and phosphoric flame retardants such as tris (tribromophenyl) phosphate. The coloring agent is not particularly limited, and various organic dyes such as phthalocyanine, azo, disazo, quinacridone, anthraquinone, flavanthrone, perinone, perylene, dioxazine, condensed azo, azomethine or methine, titanium oxide, lead sulfate, and oxidized Inorganic pigments such as zinc, chrome yellow, zinc yellow, chrome vermillion, red iron oxide, cobalt purple, navy blue, ultramarine, carbon black, chrome green, chromium oxide, and cobalt green.

As coupling agents, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 2- (3,4-epoxycyclohexyl) ethyl Trimethoxysilane, N- (2-
(Aminoethyl) 3-aminopropylmethyldimethoxysilane, N- (2-aminoethyl) 3-aminopropylmethyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, vinyltrimethoxysilane, N Silane-based cups such as-(2- (vinylbenzylamino) ethyl) 3-aminopropyltrimethoxysilane hydrochloride, 3-methacryloxypropyltrimethoxysilane, 3-chloropropylmethyldimethoxysilane, 3-chloropropyltrimethoxysilane Ringing agent, isopropyl (N-ethylaminoethylamino) titanate, isopropyl triisostearoyl titanate, titanium di (dioctyl pyrophosphate) oxyacetate, tetraisopropyl di (dioctyl phosphate) Aito) titanate, neoalkoxy tri (p-N- (β- aminoethyl) aminophenyl)
Titanium-based coupling agents such as titanate, Zr-acetylacetonate, Zr-methacrylate, Zr-propionate, neoalkoxy zirconate, neoalkoxytris neodecanoyl zirconate, neoalkoxytris (dodecanoyl) benzenesulfonyl zirconate, neoalkoxy Zirconium such as tris (ethylenediaminoethyl) zirconate, neoalkoxytris (m-aminophenyl) zirconate, ammonium zirconium carbonate, Al-acetylacetonate, Al-methacrylate, Al-propionate, or an aluminum-based coupling agent It is preferably a silicon-based coupling agent or a titanate-based coupling agent.

Examples of the leveling agent include acrylates such as ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, and the like.
000 oligomers, epoxidized soybean fatty acids, epoxidized aviethyl alcohol, titanium-based coupling agents, and the like. Examples of the lubricant include hydrocarbon lubricants such as paraffin wax, micro wax and polyethylene wax, higher fatty acid lubricants such as lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, and behenic acid, stearylamide, palmitylamide, oleyl. Higher fatty acid amide lubricants such as amide, methylene bis-stearamide, ethylene bis-stearamide, hydrogenated castor oil, butyl stearate, ethylene glycol monostearate, pentaerythritol (mono-, di-, tri-, or tetra-) Higher fatty acid ester lubricants such as stearate, cetyl alcohol, stearyl alcohol,
Alcohol-based lubricants such as polyethylene glycol and polyglycerol, and metals such as magnesium, calcium, cadmium, barium, zinc, and lead such as lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, ricinoleic acid, and naphthenic acid Examples include natural waxes such as salt metal soaps, carnauba wax, candelilla wax, beeswax and montan wax.

To prepare the epoxy resin-based powder coating composition of the present invention, for example, an epoxy resin, a curing agent, a curing accelerator, a filler, a coupling agent, a flame retardant, a colorant, a leveling agent, a lubricant After dry-mixing the ingredients such as with a Henschel mixer, the mixture is melt-mixed at, for example, 110 ° C. or less by a kneader or an extruder, and the mixture is cooled and solidified, finely pulverized, and then classified. Epoxy resin-based powder coating. The particle size of the obtained powder coating material is preferably smaller, for example, in order to obtain a film thickness of 50 μm, the average particle size is 100 μm or less, preferably 1 to 80 μm, more preferably 1 to 50 μm, further preferably 5 to 50 μm. ４０40 μm. If the average particle size is 100 μm or more, the result is conspicuous yuzu skin, resulting in poor appearance of the coating film.

The epoxy resin-based powder coating composition of the present invention can be prepared by a known flow immersion method, electrostatic flow immersion method, corona charging spray method, friction charging spray method, sprinkling method, rolling method, spraying method, fog box It is applied to the object to be coated by various coating methods such as the method.
It is appropriately selected depending on the shape, size, and thickness of the coating film. For example, in the case of a motor iron core of an OA device or the like, a triboelectric spray method is preferably used. In the case of the triboelectric spray method,
After the powder coating positively charged in the triboelectric charging gun is adhered to an object to be coated such as a motor iron core of an OA device or the like, the coated article of the present invention is melt-hardened by heating means such as high-frequency heating to obtain the coated article of the present invention. can get. The objects (articles) to be coated with the powder coating of the present invention include motor iron cores, motors for electrical equipment, and OA
Electrical and electronic parts such as motors for equipment, motors for AV equipment, motors for communication equipment, varistors, ceramic capacitors, film capacitors, etc., are preferred.
It is a motor iron core for A equipment.

[0025]

EXAMPLES The present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples. In the examples and comparative examples, "parts" means parts by weight.

Example 1 100 parts of bisphenol A type epoxy resin having an epoxy equivalent of 940, ethylene glycol anhydrous trimellitate 1
5.5 parts, phenol novolak resin (hydroxyl equivalent 10
5) 4.5 parts, 2.3 parts of 2MZ-A (manufactured by Shikoku Chemicals, imidazole-based curing agent), 72 parts of ordinary calcium carbonate, and 0.2 part of amide-based thixotropic agent were kneaded using a biaxial kneader. Thereafter, the mixture was cooled and solidified, pulverized and classified to obtain a powder coating having an average particle diameter of 1 to 100 μm. Measure the inclined flowability of the powder coating of the present invention,
Also, using a triboelectric charging gun (manufactured by Nordson), the diameter is 3 mm.
An 8 mmφ, 2 mm thick, 12 slot motor iron core was coated so as to have a coating thickness of 50 μm, baked with a high frequency heater, and the edge coverage of the motor iron core slot and the withstand voltage of 500 V were measured. Table 1 shows the measurement results.

Example 2 100 parts of bisphenol A type epoxy resin having an epoxy equivalent of 940, ethylene glycol anhydrous trimellitate 1
5.5 parts, phenol novolak resin (hydroxyl equivalent 10
5) 4.5 parts, 2.3 parts of 2MZ-A (manufactured by Shikoku Chemicals, imidazole-based hardener), 72 parts of ordinary calcium carbonate, 0.4 part of hydrogenated castor oil-based thixotropic agent using a biaxial kneader. After kneading, the mixture was cooled and solidified, pulverized and classified to obtain a powder coating material of the present invention having an average particle size of 1 to 100 μm. The gradient flowability of the powder coating of the present invention was measured, and using a triboelectric charging gun (manufactured by Nordson), a coating thickness of 50 μm was applied to a motor iron core having a diameter of 38 mmφ, a stack thickness of 2 mm, and 12 slots. After painting and baking with a high-frequency heater, the edge coverage of the motor iron core slot and the withstand voltage of 500 V were measured. Table 1 shows the measurement results.

Example 3 100 parts of bisphenol A type epoxy resin having an epoxy equivalent of 940, ethylene glycol anhydrous trimellitate 1
5.5 parts, phenol novolak resin (hydroxyl equivalent 10
5) 4.5 parts, 2.3 parts of 2MZ-A (manufactured by Shikoku Chemicals, imidazole-based curing agent), 72 parts of ordinary calcium carbonate, and a long-chain fatty acid ester polymer-based thixotropy-imparting agent 0.8
After kneading the parts using a biaxial kneader, the mixture was cooled and solidified, pulverized and classified to obtain a powder coating material of the present invention as a particle having an average particle diameter of 1 to 100 μm. The inclined flowability of the powder coating of the present invention was measured, and a triboelectric charging gun (manufactured by Nordson) was used.
Using a 38 mm diameter, 2 mm thick, 12-slot motor iron core with a coating thickness of 50 μm,
After baking with a high frequency heater, the edge coverage of the motor iron core slot and the withstand voltage of 500 V were measured. Table 1 shows the measurement results.

Example 4 100 parts of bisphenol A type epoxy resin having an epoxy equivalent of 940, ethylene glycol anhydrous trimellitate 1
5.5 parts, phenol novolak resin (hydroxyl equivalent 10
5) 4.5 parts, 2.3 parts of 2MZ-A (manufactured by Shikoku Chemicals, imidazole-based curing agent), and 72 parts of ordinary calcium carbonate
After kneading using a shaft kneader, the mixture is cooled and solidified,
After pulverization and classification, a powder having an average particle diameter of about 20 μm is obtained, and then 1.6 parts of a 20 nm primary particle aluminum oxide fine powder is added and adhered to the surface of the powder to obtain a powder coating of the present invention. Was. The gradient flowability of the powder coating of the present invention was measured, and using a triboelectric charging gun (manufactured by Nordson), a coating thickness of 50 μm was applied to a motor iron core having a diameter of 38 mmφ, a stack thickness of 2 mm, and 12 slots. After painting and baking with a high-frequency heater, the edge coverage of the motor iron core slot and the withstand voltage of 500 V were measured. Table 1 shows the measurement results.

Comparative Example 1 100 parts of bisphenol A type epoxy resin having an epoxy equivalent of 940, ethylene glycol anhydrous trimellitate 1
5.5 parts, phenol novolak resin (hydroxyl equivalent 10
5) 4.5 parts, 2.3 parts of 2MZ-A (manufactured by Shikoku Chemicals, imidazole-based curing agent), and 72 parts of ordinary calcium carbonate
After kneading using a shaft kneader, the mixture is cooled and solidified,
After pulverization and classification, the powder coating material of Comparative Example was obtained as a particle size having an average particle size of 1 to 100 μm. The inclined flowability of the powder coating material of the comparative example was measured, and a coating film thickness of 50 μm was applied to a motor iron core having a diameter of 38 mmφ, a stack thickness of 2 mm, and 12 slots by using a triboelectric gun (manufactured by Nordson). After painting and baking with a high-frequency heater, the edge coverage of the motor iron core slot and the withstand voltage of 500 V were measured. Table 1 shows the measurement results.

[0031]

[Table 1] Inclined flowability Average edge coverage 500 V pressure resistance test Example 1 14.5 mm 62% ○ Example 2 14.2 mm 55% ○ Example 3 14.0 mm 58% ○ Example 4 13.9 mm 60% ○ Comparative Example 1 14.3 mm 31% ×

Various evaluation methods will be described. <Gradient flow property> 0.5 g of powder coating is weighed, and the diameter is 10 m.
A tablet having a diameter of mφ was tableted, and the tablet was placed on an inclined plate having an inclination angle of 60 ° in an atmosphere of 150 ° C., and after 3 minutes, the distance over which the tablet melted and flowed was measured with a caliper. <Average edge coverage> The slot of the painted motor iron core is cut with a micro-cutting machine, and the cross section is photographed with a stereoscopic microscope. The end face film thickness, the slot film thickness, and the edge film thickness at the four corners of the cross section are measured. The edge coverage was calculated from the average film thickness of the film thickness at the edge portion / film thickness at the end surface and the film thickness at the slot portion. The average value of the edge cover rates at the four corners was defined as the average edge cover rate. <500v pressure resistance test> The inside of the slot of the painted motor iron core was traced with a 0.6 mmφ iron rod to which DC500v was applied, and the insulation of the coating film was examined. The evaluation criteria were evaluated as x for conducting, and ○ for insulating.

[0033]

By using an epoxy resin-based powder coating containing a thixotropic agent, for example, even in the case of a thin film having a coating thickness of about 50 μm, it has excellent electrical insulation properties and edge coverage, and a good melt flow. A thin film showing properties and giving excellent leveling properties was obtained. Therefore, the powder coating of the present invention is excellent in electrical insulation and edge coverage, and has excellent leveling properties, showing good melt flowability,
It is particularly useful as an epoxy resin powder coating for thin films.

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁶ Identification code FI H02K 3/30 H02K 3/30 (72) Inventor Akiki Niimoto 7-6-2-906 Suzuya, Yono City, Saitama Prefecture

Claims (12)

[Claims] 1. An epoxy resin-based powder coating composition comprising (a) an epoxy resin, (b) a curing agent, (c) a curing accelerator, (d) an inorganic filler, and (e) a thixotropy-imparting agent. 2. The epoxy resin powder coating composition according to claim 1, wherein the thixotropy-imparting agent is an organic thixotropy-imparting agent or an inorganic thixotropy-imparting agent. 3. The epoxy resin-based powder coating composition according to claim 1, wherein the organic thixotropy-imparting agent is contained in an amount of 0.02 to 20 parts based on 100 parts of the epoxy resin. 4. The epoxy resin powder coating composition according to claim 1, wherein the inorganic thixotropy-imparting agent is an inorganic thixotropy-imparting agent having a primary particle diameter of 1 μm or less. 5. The epoxy resin powder coating composition according to claim 1, wherein the composition contains 0.02 to 20 parts of an inorganic thixotropy-imparting agent based on 100 parts of the epoxy resin. 6. The epoxy resin powder coating composition according to claim 1, which has an inorganic thixotropy-imparting agent on the surface of the powder coating. 7. The epoxy resin powder coating composition according to claim 1, wherein the average particle size is 1 to 100 μm. 8. The epoxy resin-based powder coating composition according to claim 1, wherein the average particle size is 1 to 50 μm. 9. An article coated with the epoxy resin-based powder coating composition according to any one of claims 1 to 8. 10. The article according to claim 9, which is an electric / electronic component. 11. The article of claim 10, wherein the electrical and electronic component is a motor iron core. 12. The article according to claim 7, wherein the article is applied by a triboelectric spray method.