JP2000319580A - Composition for epoxy resin-based powder coating material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a composition for epoxy resin-based powder coating material capable of forming a coating film having the same water resistance, boiling water resistance, adhesiveness, etc., as those of a conventional biphenol type epoxy resin or more excellent without using a biphenol type epoxy resin. SOLUTION: This composition comprises a solid epoxy resin (A) which is obtained by epoxidizing a reaction product of 4,4'-isopropylidenebicyclohexanol with a polyfunctional carboxylic acid and has 400-2,000 g/eq epoxy equivalent and 60-120 deg.C softening point and a solid acid anhydride (B) having >=1.1 total acid anhydride groups of a single or mixed acid anhydride and 40-50 deg.C melting point in a formulating ratio of the epoxy resin (A) and the solid acid anhydride (B) of 1.0/0.3 to 1.5 on the basis of equivalent.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for producing a coating film formed of an epoxy resin powder coating, which is resistant to water and boiling.
And to provide a powder coating having excellent performance in adhesion.

[0002]

2. Description of the Related Art Epoxy resin powder coatings are disclosed in
No. 45365, which is disclosed and put to practical use.
This powder coating is useful as an anticorrosion coating for cast iron products, especially cast iron pipes, and is particularly excellent in water resistance, boiling water resistance, salt water resistance, impact resistance, abrasion resistance, flexibility, and smoothness. It has excellent performance and storage stability. Further, in order to improve the impact resistance and abrasion resistance of the coating film, a silica-based inorganic filler is blended in the coating material, and is produced and used by a melt-kneading method.

[0003] This epoxy resin-based powder coating is based on a bisphenol-type solid epoxy resin as a base material, and comprises amine and amine adduct, polyamide adduct, acid group-containing polyester, polycarboxylic acid or anhydride and modified product as curing agent, It is selected from dicyandiamide and its modified products, imidazoles and the like. By the bisphenol type epoxy resin skeleton, it has excellent corrosion resistance, chemical resistance and water resistance, and the hydroxyl group in the side chain in the resin skeleton forms a hydrogen bond with the metal surface, It is well known that a coating film having excellent adhesion to an object to be coated can be obtained. Utilizing such characteristics, it is customary to use, as a base material, most of conventional epoxy resin-based powder coating materials having a bisphenol-type epoxy resin skeleton.

[0004] In recent years, global environmental protection has been emphasized, and in using chemical substances including polymer compounds, environmental pollution,
It is becoming necessary to consider effects on the human body such as endocrine-like effects, reproductive toxicity, carcinogenicity, and chronic toxicity. Similar considerations have to be given to high molecular compounds, going back to the monomers used as raw materials. However, with respect to the epoxy resin for powder coating, excluding the bisphenol type epoxy resin, few epoxy resins exhibit high fluidity under kneading and mixing conditions and in a molten state of the coating and are in a solid form at room temperature. Only limited epoxy resins such as polyfunctional orthocresol novolak epoxy resin and heterocyclic triglycidyl isocyanate are only partially applied. Such multifunctional epoxy resin is not used alone,
At present, it is used in combination with or modified with a bisphenol-type epoxy resin. In addition, the heterocyclic epoxy resin is usually used in combination with an acid group-containing polyester, and is used for outdoor applications because of its excellent weather resistance, but there is a problem in terms of safety and health,
The reality is that it is not possible to obtain a coating film that is compatible with both adhesion and corrosion resistance. Therefore, the appearance of a new epoxy resin-based powder coating that does not use a bisphenol-type epoxy resin has been awaited.

[0005]

SUMMARY OF THE INVENTION The present invention provides an epoxy resin-based powder coating having a new resin skeleton instead of a bisphenol-type epoxy resin as described above. It is an object of the present invention to provide a composition for an epoxy resin-based powder coating material capable of forming an excellent coating film having higher corrosion resistance, boiling water resistance, and adhesion.

[0006]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, they have identified a solid epoxy resin obtained by using 4,4'-isopropylidenebiscyclohexanol as a raw material. Found that by combining a curing agent of the type, a coating performance equal to or higher than that of a conventional bisphenol-type epoxy resin can be expressed,
The present invention has been completed.

The 4,4′-isopropylidenebiscyclohexanol-based solid epoxy resin (A) used in the present invention is a terminal product which is a reaction product of 4,4′-isopropylidenebiscyclohexanol and a polycarboxylic acid. It is obtained by epoxidizing a carboxy polyester oligomer. The terminal carboxyl polyester oligomer is prepared by adding 1.5 to 2.0 moles of the carboxyl group of the polycarboxylic acid to 1 mole of the alcoholic hydroxyl group of 4,4′-isopropylidenebiscyclohexanol. Mix at 60-180 ° C
For 1 to 10 hours. Examples of polycarboxylic acids that can be used in the reaction include alicyclic and aromatic polycarboxylic acids such as methylhexahydrophthalic acid, hexahydrophthalic acid, phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, and anhydrides thereof. And saturated aliphatic dicarboxylic acids such as adipic acid, sebacic acid and azelaic acid, and among them, hexahydrophthalic anhydride is preferable.

As a method for epoxidizing a terminal carboxyl polyester oligomer, there are two methods, a direct synthesis method in which epihalohydrin is reacted, and an indirect synthesis method in which an epoxy resin is subjected to an addition polymerization reaction of a terminal carboxyl polyester oligomer. In a direct synthesis method, the terminal carboxyl polyester oligomer is reacted in the presence of a suitable catalyst using 0.6 to 40 moles of epihalohydrin per equivalent of carboxyl group,
Then, it can be obtained by dehydrohalogenation in the presence of sodium hydroxide. As the epihalohydrin, epichlorohydrin is usually used industrially.

As an indirect synthesis method, a terminal carboxyl polyester oligomer is subjected to an addition polymerization reaction with an epoxy resin obtained by a direct synthesis method of a terminal carboxyl polyester oligomer and / or a glycidyl ether of 4,4'-isopropylidenebiscyclohexanol. Obtainable. Particularly preferred are 4,4 '
-The above-mentioned carboxyl polyester oligomer having a carboxyl group at a terminal carboxyl group of 0.1 equivalent per 1 equivalent of the epoxy group of the glycidyl ether of isopropylidenebiscyclohexanol.
Mix at a ratio of 2 to 1.0 equivalent,
For 1 to 10 hours. In this reaction, polyisocyanates may be blended at a ratio of 0.01 to 0.5 equivalent of isocyanate group. Examples of the polyisocyanates that can be used include tolylene diisocyanate, xylylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 1,6-hexamethylene diisocyanate, isophorone diisocyanate, trimethylhexamethylene diisocyanate, hydrogenated tolylene diisocyanate, and hydrogenated xylylene. And hydrogenated xylylene diisocyanate.

The 4,4'-isopropylidenebiscyclohexanol-based solid epoxy resin (A) thus obtained has an average of 1.5 to 2.5 epoxy groups in the molecule. Epoxy equivalent is 400-2000
g / eq and the softening point must be in the range of 60 to 120 ° C. Epoxy equivalent of 400 g / eq, softening point of 6
If the temperature is 0 ° C. or lower, the blocking resistance is insufficient, and if the epoxy equivalent exceeds 2000 g / eq and the softening point exceeds 120 ° C., the smoothness of the coating film is deteriorated, which is not preferable.

As the solid acid anhydride (B) used in the present invention, known acid anhydrides used for epoxy resin-based powder coatings can be used. The mixed acid anhydride must be a polyfunctional acid anhydride having at least 1.1 or more total acid anhydride groups. The total number of acid anhydride groups referred to here is the number of acid anhydride groups per molecule when used alone, and indicates the number of acid anhydride groups per average molecule calculated from the mixing molar ratio when mixed acid anhydrides are used. . It is known that an epoxy resin containing an ester bond is easily hydrolyzed. However, when the epoxy resin (A) of the present invention is used alone as a solid acid anhydride (B) or in combination with a total acid anhydride group of 1.1 or more as a mixed acid anhydride, it is surprising that It has been found that a coating film having excellent boiling water resistance can be obtained without any abnormality occurring even if the sample is immersed in boiling water for 72 hours or more. That is, the present invention has been found for the first time by the present invention that, in a cured system of an epoxy resin containing an ester bond in a resin skeleton and an acid anhydride, by improving the cured crosslinking density, excellent boiling water resistance is developed. It was done. More preferably, it is a polyfunctional acid anhydride having a total acid anhydride group number of 1.4 or more as a single or mixed acid anhydride. When the total number of acid anhydride groups is less than 1.1 alone or as a mixed acid anhydride, a coating film can be formed but satisfactory coating film performance is not obtained. Aqueous cannot be obtained. Further, as the acid anhydride, an aromatic acid anhydride is effective. However, a mixture of an aromatic acid anhydride and an alicyclic acid anhydride and / or an aliphatic acid anhydride may be used.
It is desirable to be in the range of 50 ° C. Specific examples of the aromatic acid anhydride include phthalic anhydride, trimellitic anhydride, pyromellitic anhydride, benzophenonetetracarboxylic anhydride, ethylene glycol bis (anhydrotrimellitate), glycerol tris (anhydrotrimellitate) ). Examples of the alicyclic acid anhydride include hexahydrophthalic anhydride, tetrahydrophthalic anhydride, and methylcyclohexenedicarboxylic anhydride. Methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, methylhymic anhydride, etc., which are liquid alicyclic acid anhydrides at room temperature, cannot be used alone, but a mixture thereof in combination with a solid acid anhydride Melting point of 40 to 250
It can be used by adjusting it to the range of ° C. Examples of the aliphatic acid anhydride include polyadipic anhydride, polyazeleic anhydride, and polysebacic anhydride. Liquid aliphatic acid anhydrides such as dodecenyl succinic anhydride, poly (ethyl octadecane diacid) anhydride, and poly (phenylhexadecane diacid) anhydride are effective when used in combination with a solid acid anhydride. These may contain one kind or two or more kinds, and may be a eutectic mixture.

Further, the curing speed can be adjusted by using the solid acid anhydride (B) in combination with a known curing accelerator. Specific examples thereof include, but are not limited to, tertiary amines such as triethylamine and benzyldimethylamine, imidazoles such as 2-methylimidazole and 2-ethyl-4-methylimidazole, and precursors thereof. Certain imidazoline compounds, quaternary ammonium salts such as tetramethylammonium bromide and benzyltrimethylammonium bromide, phosphines such as triphenylphosphine and n-butyltriphenyl, and phosphonium salts include solid acid anhydrides (B ) Is selected according to the type.

The powder coating composition of the present invention contains, in addition to the epoxy resin (A) and the solid acid anhydride (B), conventionally known aromatic epoxy resins and alicyclic epoxy as long as the properties of the present invention are not impaired. Other epoxy resins such as resins can be blended. Further, a coloring pigment, an extender, an additive, and a catalyst can be added as needed. In each case, known materials can be used. Examples of the coloring pigment include titanium oxide, carbon black, and iron oxide. Practical examples of the extender include calcium carbonate, barium carbonate, barium sulfate, silica, mica, alumina, and talc. In addition, an acrylic oligomer (flow control agent), finely divided silica (powder fluidity improver), or the like can be used as an additive. Further, if necessary, known auxiliary materials such as a surface conditioning agent, an antifoaming agent, and a solid thermoplastic resin such as a petroleum resin can be added, but this does not impair the present invention.

The mixing ratio of the epoxy resin powder coating of the present invention is based on 1 equivalent of epoxy group of epoxy resin (A).
The acid anhydride equivalent of the solid acid anhydride (B) is 0.3 to 1.5.
Used in the equivalent range. When the acid anhydride equivalent is 0.3 or less, the crosslink density of the coating film is low and the boiling water resistance is reduced. Further, when the acid anhydride equivalent is used at 1.5 or more, the adhesion of the coating film is sharply reduced, which causes a practical problem. The preferred compounding amount is 0.4 to 1.2 equivalents. The amount of the curing accelerator varies depending on the type thereof, but is usually used in the range of 0.01 to 5 parts with respect to the solid acid anhydride (B). It is preferable that the addition amount of the extender and the coloring pigment is 0 to 150 parts by weight.

No particular process is required for the method for producing the powder coating of the present invention, and a general method for producing a powder coating can be applied. Although it can be produced by simply mixing the above-mentioned materials at room temperature, it is preferable to produce it by a commonly used melt mixing method. That is, after each raw material is premixed with a Henschel mixer or the like, it is melt-mixed at 80 to 130 ° C., and after pulverization, if it is necessary to adjust the particle size, classification can be performed to obtain a powder coating. Further, all or a part of the epoxy resin (A) and the solid acid anhydride (B) can be preliminarily kneaded.

[0016]

The powder coating of the present invention obtained as described above can be used by a coating method such as electrostatic coating, spray coating, fluid immersion coating, thermal spray coating, and sprinkling. The obtained powder coating is applied by the above-described coating method, and the baking-hardened coating film has surprisingly high adhesion and excellent boiling water resistance, and is an industrially useful anticorrosion powder coating. It turned out to be applicable. Conventionally, bisphenol-type epoxy resins such as bisphenol A and bisphenol F have an ether bond in the resin skeleton and a hydroxyl group in a side chain,
It is widely applied industrially because it shows high adhesion to metals and excellent water resistance. The present invention is completely different from these proven bisphenol-type epoxy resins and is based on a 4,4′-isopropylidenebiscyclohexanol-based epoxy resin having an aliphatic cyclic skeleton coexisting in the resin skeleton as a base material. And a powder coating in which the solid acid anhydride curing agent is combined. In the prior art, when an ester bond is present in the resin skeleton, the bonding point is easily hydrolyzed, and the water resistance and the boiling water resistance are inferior. Therefore, it is extremely difficult to apply the anticorrosion coating to a long-term reliable anticorrosive paint. . The effect of the present invention is to provide a powder coating which has not been considered in the past in that a coating film exhibiting high hydrolysis resistance while having an ester bond can be obtained. That is, in the present invention, by combining a specific epoxy resin (A) and a specific solid anhydride (B), and further optimally adjusting the number of functional groups of the epoxy resin and the number of functional groups of the solid acid anhydride, boiling water resistance is improved. Can be expressed. Compared with polyester powder coatings and polyester / epoxy hybrid powder coatings generally used in industry, it is possible to provide a powder coating which exhibits much better boiling water resistance and is industrially useful. As a result, it has been found that the method can be applied to the inner and outer surfaces of metal products requiring long-term anticorrosion, and to the coating of home electric appliances and outdoor products. Further, it has been found that it can be applied to a field requiring safety and health as a paint for coating the inner surface of a water pipe through which clean water flows. Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples. Unless otherwise specified, all "parts" in Examples are parts by weight. The hydrolysis resistance was evaluated based on the presence or absence of blister generation after the boiling test.

[Synthesis Example 1 of Epoxy Resin] ST-300
0 (glycidyl ether of 4,4′-isopropylidenebiscyclohexanol; epoxy equivalent 230 g / eq, manufactured by Toto Kasei Co., Ltd.), 460 parts, 240 parts of 4,4′-isopropylidenebiscyclohexanol and 260 parts of hexahydrophthalic anhydride. 250 parts of a carboxyl polyester oligomer having a carboxyl equivalent of 300 g / eq and solid at room temperature, obtained by reacting at 150 ° C. for 2 hours,
After adding 58 parts of hydrogenated xylylene diisocyanate and reacting at 160 ° C. for 4 hours, a 4,4′-isopropylidenebiscyclohexanol solid epoxy resin having a softening point of 92 ° C. and an epoxy equivalent of 700 g / eq (A-1) )
I got

[Synthesis Example 2 of Epoxy Resin]
A solid epoxy resin having a softening point of 105 ° C. and an epoxy equivalent of 950 g / eq (4-2′-isopropylidenebiscyclohexanol) (A-2) was prepared in the same manner except that the amount of hydrogenated xylylene diisocyanate was changed to 45 parts. I got

[Synthesis Example 3 of Epoxy Resin] Terminal carboxyl polyester oligomer 300 described in Synthesis Example 1
To this part, 200 parts of toluene and 74 parts of epichlorohydrin were added and dissolved. 10 parts of a 50% aqueous solution of tetramethylammonium chloride was added and reacted at 90 ° C. for 2 hours. Next, 160 parts of a 20% aqueous solution of caustic soda was added, and 9
The reaction was performed at 0 ° C. for 2 hours. After the reaction, 700 parts of toluene was added, and the mixture was washed three times with water. The toluene was recovered, and an epoxy equivalent of 980 g / eq and a softening point of 102,4 ° C.
An isopropylidenebiscyclohexanol-based solid epoxy resin (A-3) was obtained.

Example 1 100 parts of the solid epoxy resin (A-1) obtained in Synthesis Example 1 of epoxy resin, 15 parts of phthalic anhydride (phthalic anhydride, melting point: 130 ° C., manufactured by Mitsubishi Chemical Corporation), and ethylene glycol bistriene 10 parts of melitate (TMEG, melting point 68 ° C., manufactured by Nippon Rika Co., Ltd.), 1 part of imidazole (Curesol C11Z, manufactured by Shikoku Chemicals Co., Ltd.), 100 parts of titanium oxide, and a flow control agent (Acronal 4 manufactured by BASF Japan)
One part of F) was preliminarily mixed with a super mixer (manufactured by Kawata), and then melt-mixed with a co-kneader (manufactured by BUSS, Switzerland). After cooling, the mixture was pulverized and coarse powder was removed with a 100 mesh wire mesh. 1 was obtained. The proportions are shown in Table 1. The obtained powder coating is applied to JIS G 314
The cold-rolled steel sheet specified in No. 1 was coated with an electrostatic coating machine, and a coating film was formed under the curing conditions shown in Table 2. Further, the coating film properties shown in Table 2 were evaluated.

Example 2 Epoxy resin The solid epoxy resin (A) obtained in Synthesis Example 2
-2) and 13 parts of benzophenonetetracarboxylic anhydride (BTDA manufactured by ALCO, USA, melting point: 230 ° C.)
Part, 0.1 part of C11Z, 10 parts of titanium oxide, 50 parts of calcium carbonate (Whiteton B, manufactured by Shiraishi Industry Co., Ltd.), and 1 part of a flow control agent by the method described in Example 1 to obtain a powder coating No. 2 was obtained. The coating film characteristics were evaluated in the same manner as in Example 1.

Example 3 Epoxy Resin The solid epoxy resin obtained in Synthesis Example 3 (A
-3), 13 parts of ethylene glycol bistrimellitate (TMEG, melting point of 68 ° C., manufactured by Shin Nippon Rika Co., Ltd.), 0.05 part of Curesol C11Z, and titanium oxide 10
Part, 50 parts of silica (Crystalite A, manufactured by Tatsumori Co.) and 1 part of the flow control agent were prepared according to the method described in Example 1 to obtain powder coating No.
3 was obtained. The properties of the coating film were evaluated in the same manner as in Example 1.

Example 4 Epoxy Resin The solid epoxy resin (A) obtained in Synthesis Example 2
-2) and 100 parts of benzophenonetetracarboxylic anhydride and 12 parts of polyazeleic anhydride (Shin Nippon Rika Co., Ltd.)
AZ-90: 16 parts of a eutectic mixture having a softening point of 58 ° C. of 4 parts (melting point: 48 ° C.), 0.1 part of C11Z, and titanium oxide 10
Part, 70 parts of whiten B and 1 part of the flow control agent were prepared in the same manner as in Example 1 to obtain the powder coating No. 4 was obtained. The properties of the coating film were evaluated in the same manner as in Example 1.

Comparative Example 1 The solid epoxy resin (A
-2) and 100 parts of a terminal carboxyl group polyester (ER-8101 manufactured by Nippon Ester Co., Ltd., acid value 62 mg KO)
H / g, softening point 64 ° C.), 90 parts of C11Z, 0.1 part of C11Z, 80 parts of titanium oxide and 1 part of a flow control agent by the method described in Example 1 to obtain powder coating No. 5 was obtained. The properties of the coating film were evaluated in the same manner as in Example 1.

Comparative Example 2 YD-014 (bisphenol A type solid epoxy resin manufactured by Toto Kasei; epoxy equivalent: 950 g / eq, softening point: 96)
C), 100 parts of phthalic anhydride, 0.1 part of C11Z, 60 parts of titanium oxide, and 1 part of a flow control agent by the method described in Example 1 6 was obtained. The properties of the coating film were evaluated in the same manner as in Example 1.

Comparative Example 3 In Example 1, 15 parts of phthalic anhydride and TMEG10
Powder coating No. in the same manner as in Example 1 except that the phthalic anhydride was changed to 20 parts. 7 was obtained. The properties of the coating film were evaluated in the same manner as in Example 1.

Method for evaluating properties of coating film 1) The appearance of the coating film was visually determined. ；: Good ×;
Poor 2) JIS K 5400 8.4.
2 was measured. 3) The state of the coating film after the impact resistance was tested using a DuPont impact tester in accordance with JIS K 5400 8.3.2 was examined. ◎: 1/2 inch × 1 kg × 50 cm without any defects ○; 1/2 inch × 500 g × 50 cm without any defects △; 1/2 inch × 500 g × 25 cm without any defects ×; 1/2 inch × 500 g × 25 cm cracking 4) The Erichsen value was calculated according to JIS K 5400 8.2.2.
The extrusion distance until a crack was generated in the coating film was measured in accordance with the above. ◎; passed 6 mm or more △; 1 mm or more ○; passed 3 mm or more ×; 1 mm or less 5) Solvent resistance was rubbed lightly with gauze impregnated with MEK.
The number of reciprocations until an abnormality of the coating film occurred was measured. ◎: No abnormalities in 100 times △: No abnormalities in 20 times ○: No abnormalities in 50 times ×; 20 or less 6) The boiling water resistance is the number of days until an abnormality occurs in the coating film in accordance with JIS K 5400 8.20. Was measured. ◎: No abnormalities in one week △: No blisters generated in 3 days ○: No abnormalities in 3 days ×: Blister generated in 1 day 7) Salt spray resistance was 500 hours after the test time according to JIS K 5400 9.2. The tape peeling width from the cross cut portion was measured. ◎: Peeling width from the cross-cut portion is 1 mm or less 同: Same as above, 1 to 3 mm △; Same as above, 3 to 5 mm ×; Overall rust generation 8) Safety and hygiene are JWWA K 135 6.4.1
Perform test for dissolution water according to 3. ；: Pass ×: fail Note that the marks ◎ and の in the evaluation of each item are levels at which there is no practical problem.

[0028]

[Table 1]

[0029]

[Table 2]

[0030]

The powder coating obtained by combining the solid epoxy resin of the present invention with 4,4'-isopropylidenebiscyclohexanol as a raw material and a specific solid acid anhydride is shown in Table 2. In addition, it is possible to form a coating film which is excellent in water resistance, boiling water resistance, adhesion and the like and which has no problem in safety and hygiene.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroshi Nakanishi 10-1 Techno Park, Mita City, Hyogo Pref. Toto Resin Chemical Co., Ltd. Mita Plant (72) Inventor Masayoshi Hanabusa 3-17-14 Higashikasai, Edogawa-ku, Tokyo Tokyo Metropolitan Kasei Co., Ltd. Product Research Laboratory (72) Inventor Yasuyuki Takeda 3-17-14 Higashikasai, Edogawa-ku, Tokyo Tokyo Metropolitan Kasei Co., Ltd. Product Research Laboratory F-term (reference) 4J038 DB091 GA07 JA75 JB03 JB11 JB32 JC21 JC29 KA03 KA04 MA02 MA12 MA13 NA03 NA04 NA12 NA14 PA02

Claims (6)

[Claims] An epoxy resin powder coating composition comprising a 4,4'-isopropylidenebiscyclohexanol-based solid epoxy resin (A) and a solid acid anhydride (B). 2. A solid epoxy resin (A) obtained by epoxidizing a reaction product of 4,4′-isopropylidenebiscyclohexanol with a polycarboxylic acid, having an epoxy equivalent of 400 to 2000 g / eq. The powder coating composition according to claim 1, wherein the softening point is in the range of 60 to 120 ° C. 3. The solid acid anhydride (B) is an aromatic acid anhydride, having a total number of acid anhydride groups of 1.1 or more and a melting point in the range of 40 to 250 ° C., alone or as a mixture. The composition for a powder coating according to claim 1, wherein: 4. The solid acid anhydride (B) is a mixture of an aromatic acid anhydride and an alicyclic acid anhydride and / or an aliphatic acid anhydride, and has a total number of anhydride groups of 1.1 or more and a melting point of at least 1.1. Is 40 to 250
The powder coating composition according to claim 1, wherein the temperature is in the range of ° C. 5. The powder coating composition according to claim 1, wherein a curing accelerator is used in combination with the solid acid anhydride (B). 6. An epoxy resin (A) and a solid acid anhydride (B)
The composition for powder coating according to any one of claims 1, 2, 3, 4 and 5, wherein the compounding ratio of the same is from 1.0 / 0.3 to 1.5 on an equivalent basis.