JPH11116855A - Resin composition for powder coating material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a resin composition sufficiently kneadable in producing a powder coating material therefrom, ensuring the melt flowability of the coating film therefrom even during baked, thus affording a coating film of excellent physical properties, by using a specific epoxy group-bearing acrylic resin. SOLUTION: This resin composition comprises (A) an acrylic resin having at least two epoxy groups in one molecule, 100-2,000 in epoxy equivalent and 300-20,000 in average molecular weight, prepared by copolymerization between (1) an epoxy group-bearing acrylic acid-based derivative of formula I or formula II (R<1> to R<3> , R<8> to R<10> , and R<14> to R<17> are each H, phenyl or a 1-8C alkyl, wherein either one of R<14> to R<17> is 1,2-epoxymethyl or the like; R<11> is H, methyl or ethyl; X is methylene) and (2) a monomer copolymerizable with the component (1), and (B) a carboxyl bearing curing agent; wherein the equivalent ratio of the epoxy group in the component A to the carboxyl group in the component B is 0.5-2.0.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin composition for a powder coating material capable of forming a coating film having excellent coating appearance such as weather resistance, gloss and smoothness of the coating film, and physical properties of the coating film.

[0002]

2. Description of the Related Art Powder coatings comprising an acrylic resin containing an epoxy group and a curing agent having a carboxyl group are widely used due to their excellent weather resistance, gloss and the like. Conventionally, glycidyl methacrylate (hereinafter referred to as “GMA”) has been widely used for such an acrylic resin containing an epoxy group.

[0003]

SUMMARY OF THE INVENTION However, GMA
Is highly reactive, and when kneaded with a curing agent or pigment containing a carboxyl group to produce a powder coating, carboxyl groups and epoxy groups react with each other, so that kneading may not be possible. In addition, the melt fluidity at the time of baking was insufficient, and the smoothness of the coating film was sometimes insufficient.
Furthermore, when a carboxyl group-containing polyester is used as a curing agent having a carboxyl group, the compatibility between the carboxyl group-containing polyester and GMA is generally low, and the smoothness of the cured coating film may be significantly impaired or pinholes may occur. In some cases, it did not show sufficient coating physical properties.

[0004]

According to the present inventors, the use of a specific epoxy group-containing acrylic resin makes the reactivity between an epoxy group and a carboxyl group milder than the case where GMA is used. Can be sufficiently kneaded, and the melt fluidity of the coating film can be ensured even during baking.In addition, even if a carboxyl group-containing polyester is used as a curing agent, compatibility is improved and excellent coating film properties are obtained. It has been found that a coating film having the same can be obtained, and the present invention has been completed.

That is, the present invention provides an epoxy group-containing acrylic acid derivative represented by the following formula (1-1) or (1-2) and a polymerizable monomer copolymerizable with the derivative. An epoxy group-containing acrylic resin (A) having at least two epoxy groups in one molecule, an epoxy equivalent of 100 to 2,000 and an average molecular weight of 300 to 20,000, and a curing agent containing a carboxyl group (B), and an equivalent ratio (E) of the epoxy group of the epoxy group-containing acrylic resin (A) and the carboxyl group of the curing agent (B).
(POXY / -COOH) is from 0.5 to 2.0. Further, the curing agent (B) having a carboxyl group is a bifunctional or more carboxylic acid having a molecular weight of 500 or less, or has an acid value of 15 to 200 mgKOH / g and a softening point of 70 to 160.
The present invention provides the resin composition for a powder coating, wherein the resin composition is a carboxyl group-containing polyester in a temperature range of ° C. Hereinafter, the present invention will be described in detail.

[0006]

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[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The epoxy group-containing acrylic acid derivative represented by the formula (1-1) or (1-2) used in the present invention is an epoxy acrylate having an alicyclic skeleton. And methacrylic acid or ethacrylic acid, and a compound having an epoxy group and a vinyl group inside the alicyclic skeleton. Wherein R ^{1 to} R ³ , R
Examples of the alkyl group having 1 to 8 carbon atoms represented by ^{8 to} R ¹⁰ and R ^{14 to} R ¹⁷ include a methyl group, an ethyl group, a propyl group, an isopropyl group, and a butyl group. R ^{1 to} R ³ , R ⁸ to
R ¹⁰ and R ^{14 to} R ¹⁷ are preferably a hydrogen atom or a methyl group. Preferred compounds as the epoxy group-containing acrylic acid derivative of the present invention are the following compounds.

[0008]

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The epoxy group-containing acrylic acid derivatives used in the present invention are represented, for example, by the following formulas (2-1), (2-2; vinylcyclohexene monoepoxide) and (2-3; limonene monoepoxide). An epoxy group-containing alicyclic compound and acrylic acid or the like are bonded by a ring-opening addition reaction of an epoxy group, and then a vinyl group or 1-bonded to an alicyclic skeleton such as a cyclohexyl group or a bicyclohexyl group of the obtained compound. It can be produced by epoxidizing a double bond of a methylvinyl group. A reaction formula in the case of using vinylcyclohexene monoepoxide and acrylic acid is illustrated.

[0010]

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The above-mentioned addition reaction of the epoxy group-containing alicyclic compound with acrylic acid or the like is carried out in the presence or absence of a solvent at a reaction temperature of 60 to 140 ° C, particularly 70 to 120 ° C.
The reaction is preferably carried out. The solvent used in the reaction is not particularly limited, but hexane, cyclohexane, toluene, benzene, ethyl acetate, carbon tetrachloride, chloroform and the like can be used, and glycol ethers and glycol acetates can also be used.

At the time of the reaction, a catalyst can be used.
For example, phosphorus compounds such as triphenylphosphine, quaternary amine compounds such as diazabicycloundecene and tetraethylammonium, 2-methyl-imidazole and 2-
Imidazole compounds such as methyl-4-ethyl-imidazole can be used. Further, borate esters, Lewis acids, organic metal compounds, metal salts of organic acids, and the like can also be used. The use amount of these catalysts is preferably 0.03 to 5% by weight, particularly preferably 0.05 to 3% by weight, based on the total weight of the epoxy group-containing alicyclic compound and acrylic acid.

In the reaction, generally used polymerization inhibitors such as methoquinone (p-methoxyphenol), hydroquinone and phenothiazine can be used in order to prevent polymerization of acryloyl groups and the like. The amount of the polymerization inhibitor used is 0.03 to 5% by weight, particularly 0.05%, based on the total weight of acrylic acid or the like and the epoxy group-containing alicyclic compound.
It is preferably about 3% by weight.

Next, a double bond of a vinyl group or a 1-methylvinyl group bonded to a cyclohexyl group or a bicyclohexyl group of the obtained compound is epoxidized with an epoxidizing agent. As the epoxidizing agent, peracids and hydroperoxides can be used. Examples of the peracids include organic acids such as formic acid, peracetic acid, perbenzoic acid, and trifluoroperacetic acid, and examples of the hydroperoxides include hydrogen peroxide, tertiary butyl hydroperoxide, cumene peroxide, and the like. Can be exemplified.
Among them, it is particularly preferable to use peracetic acid. This is because peracetic acid is industrially available at low cost and has high stability. The amount of the epoxidizing agent can be appropriately selected depending on the particular epoxidizing agent used, the desired degree of epoxidation, the particular epoxidized compound used, and the like.

At the time of epoxidation, a catalyst can be used if necessary. For example, when a peracid is used as the epoxidizing agent, an alkali such as sodium carbonate or an acid such as sulfuric acid or an organic acid can be used as a catalyst. When hydroperoxide is used, a mixture of tungstic acid and caustic soda can be used. Specifically, a catalytic effect can be obtained by using an organic acid and hydrogen peroxide in combination with molybdenum hexacarbonyl and tertiary butyl hydroperoxide.

The molar ratio of the epoxidizing agent to be added is preferably equal to or more than 1 mol per 1 mol of the vinyl group or 1-methylvinyl group bonded to the cyclohexyl group. However, due to the problems of economy and side reactions described below,
It is usually disadvantageous to exceed the molar ratio, and when peracetic acid is used as the epoxidizing agent, it is preferable to use a molar ratio of 1 to 1.5.

The epoxidation reaction can use an inert solvent. As the inert solvent, the viscosity of the raw material decreases,
It can be used for the purpose of stabilization by dilution of an epoxidizing agent, and examples thereof include hexane, cyclohexane, toluene, benzene, ethyl acetate, carbon tetrachloride, and chloroform. More specifically, when peracetic acid is used as the epoxidizing agent, it is preferable to use aromatic compounds, ethers, esters, and the like.

The temperature of the epoxidation reaction is preferably from 0 to 70 ° C. when peracetic acid is used as the epoxidizing agent. If the temperature is 0 ° C. or lower, the reaction is slow, and if the temperature is 70 ° C., decomposition of peracetic acid may occur. In addition, when a tertiary butyl hydroperoxide / molybdenum dioxide diacetylacetonate-based compound, which is one example of hydroperoxide, is used, the temperature is increased to 20 ° C. for the same reason.
150 ° C. is preferred. Note that no special operation is required during the reaction, and the mixture may be stirred, for example, for 1 to 7 hours. Thereby, an epoxy group-containing acrylic acid derivative can be produced.

The acrylic acid derivative containing an epoxy group can be prepared by, for example, a method of precipitating from a reaction solution with a poor solvent, a method of pouring an epoxidized product into hot water with stirring, and removing the solvent by distillation, a direct desolvation method, and the like. Can be isolated.

The epoxy group-containing acrylic resin (A) used in the present invention contains at least one molecule obtained by copolymerizing the epoxy group-containing acrylic acid derivative and a polymerizable monomer copolymerizable with the derivative. It has two epoxy groups and has an epoxy equivalent of 100 to 2,000, preferably 15
It has an average molecular weight of 300 to 20,000, preferably 500 to 10,000. When the average molecular weight is lower than 300, the mechanical strength of the obtained coating film becomes insufficient, and when the average molecular weight exceeds 20,000, the flowability at the time of kneading the coating and baking of the coating becomes poor, and the sharpness of the coating, The smoothness also deteriorates. Further, when a carboxyl group-containing polyester is used as a curing agent, the compatibility is poor, the crosslinking reaction becomes insufficient, and the physical properties of the coating film may become insufficient.

Examples of the polymerizable monomer copolymerizable with the epoxy group-containing acrylic acid derivative include styrene and (meth)
Acrylic esters, fumaric diesters, acrylonitrile, acrylamide and the like can be exemplified. Among them, (meth) acrylic acid esters are preferable, and the use of methyl methacrylate is particularly preferable in terms of the glass transition temperature and weather resistance.

The epoxy group-containing acrylic resin (A) contains the epoxy group-containing acrylic acid derivative in an amount of 5 to less than 100% by weight, preferably 10 to 90% by weight, more preferably 10 to 90% by weight.
It is preferable to contain it as a structural unit in the range of 70 to 70% by weight. If the content is lower than 5% by weight, the kneading time cannot be extended as compared with the powder coating using glycidyl groups, the flowability of the coating film during coating baking is low, and a carboxylic acid-terminated polyester is used as a curing agent. This is because when used, the compatibility does not increase and no improvement in physical properties is observed.

The curing agent (B) used in the present invention is not particularly limited as long as it contains a carboxyl group and cures the epoxy group-containing acrylic resin. Preferably, the curing agent (B) is a carboxylic acid having a molecular weight of 500 or less, or a carboxylic acid. It is preferably a group-containing polyester. This is because such a curing agent (B) has excellent compatibility with the epoxy group-containing acrylic resin (A) used in the present invention, and can provide a coating film having excellent physical properties. As the carboxylic acid, R-
(COOH) n (R: a linear or branched alkylene group having 1 to 25 carbon atoms, an alicyclic alkyl group, an aromatic group or a heterocyclic ring, n: an integer of 2 to 5) preferable. For example, succinic acid, adipic acid, pimelic acid,
Suberic acid, azelaic acid, sebacic acid, decane dicarboxylic acid, brassic acid, phthalic acid, trimellitic acid, pyromellitic acid, benzophenonetetracarboxylic acid, ethylene glycol bis (trimellitate), glycerol tris (trimellitate), tetrahydrophthalic acid, methyl Examples thereof include tetrahydrophthalic acid, nadic acid, alkenyl succinic acid, hexahydrophthalic acid, methyl hexahydrophthalic acid, methylcyclohexenetetracarboxylic acid, dimer acid, and triscarboxyethyl isocyanurate. The carboxyl group-containing polyester has an acid value of 15 to 200 mgKOH / g and a softening point of 70 to 160 ° C, preferably 100 to 130 ° C.
C. is preferred. The number average molecular weight is 500
It is preferably from 20,000 to 20,000, particularly preferably from 1,000 to 15,000. The structure of the polyester may be a branched structure or a linear structure, but from the viewpoints of fluidity at the time of melting of the coating material, appearance and gloss of a coating film obtained after baking, and the like, it is preferable that the structure is close to a linear shape without many branch points. . In the present invention, the above curing agents (B) can be used alone or in combination of two or more.

The carboxyl group-containing polyester used as the curing agent (B) can be produced from a carboxylic acid and an alcohol such as a diol or a triol using a known esterification catalyst.

The carboxylic acids that can be used in the production of the carboxyl group-containing polyester include terephthalic acid, isophthalic acid, phthalic acid, methyl terephthalic acid,
Trimellitic acid, pyromellitic acid and its anhydride, adipic acid, sebacic acid, succinic acid, maleic acid, fumaric acid, tetrahydrophthalic acid, methyltetrahydrophthalic acid, hexahydrophthalic acid, methylhexahydrophthalic acid and its anhydride , Etc. can be exemplified. These may be used alone or in combination of two or more. Examples of the alcohol include ethylene glycol, propylene glycol, 1,3-butanediol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, hydrogenated bisphenol A, ethylene oxide adduct of hydrogenated bisphenol A, Propylene oxide adduct of hydrogenated bisphenol A, trimethylolpropane, trimethylolethane, glycerin, pentaerythritol,
In addition to 2,2,4-trimethylpentane-1,3-diol, α-olefin monoepoxide, Cardura E
Monoepoxides such as (glycidyl ether of versatic acid) can also be used. Furthermore, cyclic lactones can also be used. Such lactones include:
ε-caprolactone, 4-methylcaprolactone, 2-
Methylcaprolactone, δ-valerolactone, β-methyl-δ-valerolactone, β-propyrolactone, γ-
Butyrolactone and the like can be used alone or in combination of two or more.

The temperature of the esterification reaction is 130 to 240
° C, particularly preferably 140 to 230 ° C. During the reaction, by performing the reaction under a stream of an inert gas such as nitrogen gas, it is possible to suppress the oxidative deterioration of the polyester in the reaction process and to prevent the deterioration of the hue of the resin. When a polyester polyol is synthesized in advance and an excess carboxylic acid is reacted to synthesize the carboxyl group-containing polyester, an esterification catalyst can be used in the reaction with the polyester polyol and the subsequent carboxylic acid.

As the esterification catalyst, tin octylate, dibutyltin oxide, dibutyltin laurate,
Organotin compounds such as monobutyltin hydroxybutyloxide, tin compounds such as stannous oxide and stannous chloride, tetrabutyltin titanate, tetraethyl titanate and tetrapropyl titanate can be used. The amount of the catalyst used is 0.1 to 1,000 ppm, preferably 1 to 100 ppm. 1,000 pp catalyst
If it exceeds m, the coloring of the resin becomes intense, which may adversely affect the stability of the product. On the other hand, when the amount of catalyst used is 1p
If it is less than pm, the polymerization rate becomes extremely slow, which is not preferable.

In the resin composition for a powder coating of the present invention,
Epoxy group (E to carboxyl group (-COOH)
POXY), the equivalent ratio (EPOXY / -COOH) is
It is preferably in the range of 0.5 to 2.0, particularly 0.7 to 1.4. If the equivalent ratio is less than 0.5 or more than 2.0, the curing speed becomes extremely slow, and the cured coating film may not show sufficient properties.

The resin composition for a powder coating according to the present invention comprises, in addition to the epoxy group-containing acrylic resin (A) and the curing agent (B), a fluidity modifier such as a pigment, a silicon compound, and a 2-ethylhexyl acrylate polymer; A tertiary amine compound, a quaternary ammonium compound, an amine such as triphenylphosphine, a phosphonium salt, a phosphorus-based curing catalyst, and other additives are blended, and then kneaded using an extruder or the like, and then pulverized and classified to obtain a powder. It can be used as a paint, and a known coating method such as an electrostatic coating method or a flow immersion method can be used.

[0030]

EXAMPLES The present invention will now be described specifically with reference to examples, but the present invention is not limited to these examples. "Parts" means "parts by weight" unless otherwise specified.

Synthesis Example 1 (Synthesis of Epoxy Group-Containing Acrylic Acid Derivative) In a 1-liter jacketed flask, 144 g of vinylcyclohexene monoepoxide (molecular weight: 124), 1.36 g of triphenylphosphine, and 1.36 of methoquinone were added.
g, 275 g of propylene glycol monomethyl ether
Was charged, and while blowing air into the solution, the temperature in the reaction system was set to 80 ° C., and 83.5 g of acrylic acid was added dropwise over about 1 hour. After the completion of the dropwise addition, the temperature in the system was set to 100 ° C., and the reaction was further performed. The oxirane oxygen in the system is 0.3
The reaction was terminated when the percentage reached%. This reaction solution is
De-boiling at 10 ° C / 10mmHg, acrylate (1)
Was obtained in an amount of 208 g. ¹ H-NMR measurement of acrylate (1) confirmed that the presence of a vinyl group proton peak of δ 4.8 to 5 and the disappearance of the epoxy group proton peak of δ 3.2 ppm were almost eliminated. Further G
It was confirmed from C-MS that a component having a molecular weight of 196 was produced. The purity of GC was 99.1% in area%.
100 g of this acrylate (1) and 50 g of ethyl acetate were charged, the temperature in the reaction system was raised to 50 ° C. while blowing nitrogen into the gas phase, and 147.2 g of an ethyl acetate solution of peracetic acid (peracetic acid) was taken over about 1 hour. (Concentration: 29%) was added dropwise. After completion of the dropwise addition of peracetic acid, the mixture was aged at 50 ° C. for 5 hours to complete the reaction. Further, the reaction crude liquid was washed with water at 50 ° C.
Deboiling was performed at mmHg to obtain 94.7 g of an epoxy group-containing acrylic acid derivative (A). GC purity is area%
Was 99.0%. The epoxy group-containing acrylic acid derivative (A) has an oxirane oxygen of 6.87% and a viscosity of 15c.
P / 25 ° C. ^{When 1} H-NMR was measured, δ
A peak derived from a double bond near 4.5 to 5 almost disappeared, and a proton peak derived from an epoxy group near δ 2.9 to 3.3 was generated.

Synthesis Example 2 In a 1 liter jacketed flask, 144 g of limonene monoepoxide (molecular weight: 152), 1.25 g of diazabicycloundecene octylate, and 1.25 of methoquinone were added.
g, and 275 g of toluene was charged as a solvent. While blowing air into the liquid, the temperature in the reaction system was adjusted to 80 ° C., and 81.5 g of methacrylic acid (molecular weight: 86) was added dropwise over about 1 hour. After the completion of the dropwise addition, the temperature in the system was set to 110 ° C. to further react. The reaction was terminated when the oxirane oxygen in the system became 0.2%. This reaction solution is heated at 70 ° C./10 m
After de-boiling with mHg, 206 g of acrylate (2)
Obtained. According to ¹ H-NMR measurement of acrylate (2), δ
It was confirmed that there was a peak of 4.5 to 5.0 vinyl group protons, and the peak of δ 3.2 ppm of epoxy group protons almost disappeared. Furthermore, it was confirmed by GC-MS that a component having a molecular weight of 238 was generated. G
As a result of C, the purity was 98.6% in area%. 100 g of this acrylate (2) and 50 g of ethyl acetate were charged, and the temperature in the reaction system was adjusted to 5 while blowing nitrogen into the gas phase.
At 0 ° C., a solution of peracetic acid in ethyl acetate 1
32.1 g (peracetic acid concentration; 29%) was added dropwise. After completion of the dropwise addition of peracetic acid, the mixture was aged at 50 ° C. for 5 hours to complete the reaction. Further, the reaction crude liquid was washed with water at 50 ° C.
g, and the mixture was deboiled to obtain 96.8 g of an epoxy group-containing acrylic acid derivative (B). The epoxy group-containing acrylic acid derivative (B) has an oxirane oxygen of 5.98% and a viscosity of 3
It was 5 cP / 25 ° C. ^{When 1} H-NMR was measured, the peak derived from a double bond near δ 4.5 to 5 almost disappeared, and a peak of a proton derived from an epoxy group near δ 2.9 to 3.3 was generated. . According to the result of GC, the purity was 99.2% in area%.

Synthesis Example 3 A 0.5-liter jacketed flask was charged with 100 g of 5-vinylbicyclo [2.2.1] hept-2-ene (“VBH” manufactured by San Apro) and 50 g of ethyl acetate, and nitrogen was blown therein. The temperature inside the reaction system to 50 ° C
262.1 g of peracetic acid in ethyl acetate over about 1 hour
(Peracetic acid concentration: 29%) was added dropwise. After completion of the dropwise addition of peracetic acid, the reaction was aged at 50 ° C. for 4 hours to complete the reaction. further,
The reaction crude liquid was washed with water at 50 ° C., and deboiled at 70 ° C./10 mmHg to obtain 99.7 g of epoxidized VBH.
The epoxidized VBH has an oxirane oxygen concentration of 1
1.4%, viscosity 40 cP / 25 ° C., ¹ H-NMR
Was measured, the peak derived from an internal double bond at δ 5.3 to 5.6 ppm almost disappeared, and δ 2.9 to 3.2 p
A peak of a proton derived from the epoxy group was generated at pm. Into a 1 liter jacketed flask were charged 136 g of the epoxidized VBH (molecular weight 136), 1.25 g of triphenylphosphine, 1.25 g of methoquinone, and 275 g of toluene as a solvent. While blowing air into the liquid, the temperature in the reaction system was set to 80 ° C., and 86 g of methacrylic acid (molecular weight: 86) was added dropwise over about 1 hour. After completion of the dropwise addition, the temperature in the system was set to 100 ° C., and the reaction was further performed.
The reaction was terminated when the oxirane oxygen in the system became 0.2%. This reaction solution was deboiled at 70 ° C./10 mmHg to obtain 211 g of acrylate (3). According to ¹ H-NMR measurement of acrylate (3), δ 4.8 to
There is a peak of 5.0 ppm of the proton of the vinyl group,
It was confirmed that the peak of the proton of the epoxy group at δ 2.9 to 3.2 ppm almost disappeared. Further GC-M
It was confirmed that a component having a molecular weight of 222 was generated from S. The purity of GC was 99.2% in area%. 100 g of this acrylate (3) and 50 g of ethyl acetate were charged, and the temperature in the reaction system was lowered to 5 while blowing nitrogen into the gas phase.
At 0 ° C., a solution of peracetic acid in ethyl acetate 1
41.5 g (peracetic acid concentration; 29%) was added dropwise. After the addition of peracetic acid was completed, the reaction was aged at 50 ° C. for 4 hours to complete the reaction. Further, the reaction crude liquid was washed with water at 50 ° C.
g, and the mixture was deboiled to obtain 93.4 g of an epoxy group-containing acrylic acid derivative (C). The epoxy group-containing acrylic acid derivative (C) has an oxirane oxygen of 6.22% and a viscosity of 5%.
It was 5 cP / 25 ° C. ^{When 1} H-NMR was measured, a peak derived from a double bond near δ 4.8 to 5.0 almost disappeared, and a proton peak derived from an epoxy group near δ 2.9 to 3.3 was generated. Was. The purity of GC is
The area% was 98.9%.

Synthesis Example 4 (Synthesis of Epoxy Group-Containing Acrylic Resin) Epoxy group-containing acrylic acid derivative (A) (80 parts), methyl methacrylate (20 parts), t-butyl peroxybenzoate (Nippon Oil & Fats, "Perbutyl Z") ) Was dropped into 120 parts of xylene at 150 ° C, and after polymerization, the solvent was removed to obtain an epoxy group-containing acrylic resin (A-1) having a molecular weight of 2,000 and an epoxy equivalent of 310.

Synthesis Example 5 (Synthesis of Epoxy Group-Containing Acrylic Resin) 100 parts of epoxy group-containing acrylic acid derivative (B)
20 parts of methyl methacrylate and 1.5 parts of perbutyl Z (manufactured by NOF Corporation) were dropped into 120 parts of xylene at 150 ° C., polymerized, the solvent was removed, and an epoxy group-containing acrylic having a molecular weight of 2,000 and an epoxy equivalent of 365. Resin (B-1)
I got

Synthesis Example 6 (Synthesis of epoxy group-containing acrylic resin) 80 parts of epoxy group-containing acrylic acid derivative (C), 20 parts of methyl methacrylate, Perbutyl Z (manufactured by NOF Corporation)
1.5 parts was dropped into 120 parts of xylene at 150 ° C., and after polymerization, the solvent was removed. An epoxy group-containing acrylic resin having a molecular weight of 2,000 and an epoxy equivalent of 375 (C-1)
I got

Example 1 Epoxy group-containing acrylic resin (A-1) 50 of Synthesis Example 4
0 parts, 185 parts of dodecanedioic acid, 360 parts of titanium oxide and 1 part of a fluidity modifier "Modaflow" (manufactured by Monsanto Co.) are added and mixed.
A powder coating was obtained. Next, it was applied to a galvanized steel sheet by an electrostatic coating machine and baked at 180 ° C. for 20 minutes. The physical properties of the coating film were evaluated for coating film smoothness, gloss, impact resistance, pencil hardness, solvent resistance, and weather resistance. .

Examples 2 to 4 Coatings were prepared in the same manner as in Example 1 using the resin formulations shown in Table 1, and the physical properties of the coatings were evaluated. The results are shown in Table 1.

Comparative Examples 1-2 As Comparative Example 1, 500 parts of the epoxy group-containing acrylic resin (A-1) of Synthesis Example 4, 380 parts of dodecane diacid, 360 parts of titanium oxide, and a fluidity modifier "Modaflow" (Monsanto) Was added and mixed, and kneaded with an extruder, followed by cooling, pulverization, and classification to obtain a powder coating. Next, it was applied to a galvanized steel sheet by an electrostatic coating machine and baked at 180 ° C. for 20 minutes. The physical properties of the coating film were measured in the same manner as in Example 1. In Comparative Example 2, similarly to Comparative Example 1, coating films were produced at the compounding ratios shown in Table 1, and physical properties were measured. Table 1 shows these results.

The method of evaluating the coating film is as follows. (1) Smoothness of coating film: The smoothness of the cured coating film was visually judged. The evaluation criteria were。 good, △ slightly poor, and × bad. (2) Gloss (60 °): JIS K-5400-199
The reflectance (%) was measured when the incident angle and the light receiving angle were each 60 ° in accordance with the 17.6 60 ° mirror surface. (3) Pencil hardness: JIS K-5400-1991
A pencil scratch test specified in 8.4.2 was performed, and evaluation by scratches was performed. (4) Impact resistance test (cm): The test piece was placed in an atmosphere of 25 ° C., using a 1/2 inch diameter punch, with the coated surface of the test piece facing upward and a 1 kg weight changed in height. And dropped to find the highest height that would not cause destruction. (5) Adhesion: JIS K-5400-1991
5.2 After making a cut in accordance with the cross-cut test method (at 1 mm intervals), a cellophane adhesive tape was applied thereon, and then the tape was peeled off to evaluate the adhesion in a peeled state of the coating film. (6) Solvent resistance: xylene rubbing test (100 times)
And the state of the coating film was visually determined. The criteria are
○: good, Δ: slightly poor, ×: poor. (7) Weather resistance (retention rate of gloss 60 °): The gloss retention rate (%) of the coating film subjected to the test using a sunshine weatherometer until the irradiation time reached 2,000 hours was examined.

[0041]

[Table 1]

[0042]

According to the present invention, a coating film having excellent coating properties such as gloss, smoothness and the like, impact resistance, adhesion, solvent resistance, weather resistance and the like is formed. A resin composition for a powder coating is provided.

Claims (3)

[Claims] 1. One molecule obtained by copolymerizing an epoxy group-containing acrylic acid derivative represented by the formula (1-1) or (1-2) and a polymerizable monomer copolymerizable with the derivative. Has at least two epoxy groups and has an epoxy equivalent of 1
00 to 2,000 and an average molecular weight of 300 to 20,000
An epoxy group-containing acrylic resin (A) and a carboxyl group-containing curing agent (B), and an equivalent ratio of the epoxy group of the epoxy group-containing acrylic resin (A) to the carboxyl group of the curing agent (B). (EPOXY / -CO
OH) is 0.5 to 2.0. Embedded image 2. A curing agent having a carboxyl group (B)
Is a bifunctional or higher carboxylic acid having a molecular weight of 500 or less, or an acid value of 15 to 200 mgKOH / g and a softening point of 70 to
The resin composition for a powder coating according to claim 1, wherein the resin composition is a carboxyl group-containing polyester in a temperature range of 160 ° C. 3. An epoxy group-containing acrylic acid derivative (A) is one of the following compounds.
The resin composition for powder coating according to the above. Embedded image