JP2783363B2 - Resin composition for powder coating - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial application field) The present invention relates to the characteristics of a polyester resin coating film that is smooth, glossy, and excellent in strength, and to all of hardness, stain resistance, and weather resistance. The present invention relates to a resin composition for a powder coating material that can provide an ideal coating film having the excellent characteristics of an acrylic resin coating film.

(Prior Art) In order to cover the metal surface and to maintain the protection and aesthetics, which are the original philosophy of the paint, over a long period of time, two or more coating films are usually required in many cases. From such a viewpoint,
Adhesive and anti-corrosion resin is used as primer for weather resistance,
Resins with excellent stain resistance and hardness have been used in topcoats.

As a coating method, a shift to two coats and two bake, and further to two coats and one bake is progressing, and considering energy saving, one coat and one bake is ultimately an ideal method.

On the other hand, demand for powder coatings is steadily increasing from the viewpoint of performance and economy, but due to its single tank property, that is, single function, it is expanding to applications that match each performance. However, its demands have their own limits.

From such a viewpoint, research on a polyester-acrylic hybrid type powder coating resin composition having both the features of the resin composition for powder coatings composed of polyester resin and the features of the resin composition for powder coatings composed of acrylic resin has been conducted. It is actively performed (Japanese Patent Publication No. 55-1945).

(Problems to be Solved by the Invention) However, conventional resin compositions for polyester / acrylic / hybrid type powder coating materials are mainly blended simply of polyester resin and acrylic resin. In the case of blending both resins, a smooth coating surface is not obtained, and on the other hand, in the case of both resins that are easily compatible with each other in the blend, a coating film that shows an intermediate performance between the two resins is provided even in the most preferable case. You just get it.

The present inventors have found that the characteristics of a polyester resin coating film, which is smooth and glossy in one coating, and which have excellent strength, and those of an acrylic resin coating film, which are excellent in both hardness, stain resistance, and weather resistance. For the purpose of providing a resin composition for powder coatings capable of providing an ideal coating film having both of the above, Japanese Patent Application No. 62-272047 (Japanese Patent Application Laid-Open No. 1-115969)
We proposed a resin composition for powder coatings. However, even higher properties such as smoothness have been required, and it has been desired to develop a composition that satisfies such requirements.

SUMMARY OF THE INVENTION The present invention meets such a demand, and the object of the present invention is to provide a powder having both the characteristics of a polyester resin coating and the characteristics of an acrylic resin coating and capable of imparting a high degree of smoothness and toughness of the coating. An object of the present invention is to provide a resin composition for body paint.

(Means for Solving the Problems) In view of the current situation, the present inventors have conducted intensive studies to provide a resin composition for a polyester-acrylic-hybrid type powder coating material having no problems as described above. In the resin composition for powder coatings proposed in Japanese Patent Application No. 62-272047,
The present inventors have found that the above object can be achieved by blending a low-melting crystalline aliphatic polyester and / or a winding with a long-chain aliphatic polyhydric alcohol, and reached the present invention.

That is, the present invention provides a hydroxyl value having an average of 0.1 to 1.0 carboxyl groups per molecule, a hydroxyl value of 10 to 100, and a softening point of 50 to 100.
Polyester resin A at 150 ° C, hydroxyl value 10-400, melting point 50-1
Aliphatic polyester having a crystallinity at 20 ° C. and / or a long chain aliphatic polyhydric alcohol having a hydroxyl value of 10 to 400 and a melting point of 50 to 120 ° C. (compound B), on average 0.1 to 4.0 glycidyl per molecule Hydroxyl value 30-150, softening point 50-150 ℃
A resin composition E comprising a copolymer D obtained by reacting an acrylic resin C and a polyester resin A with an acrylic resin C, wherein A to D satisfy the following ratios. The gist of the present invention is a resin composition for powder coatings, which contains 5 to 50 parts by weight of a block polyisocyanate compound as a curing agent per part by weight.

Polyester resin A: 0 to 80% by weight Compound B: 1 to 20% by weight Acrylic resin C: 0 to 80% by weight Composition D: 99 to 1% by weight Hereinafter, the present invention will be described in detail.

The polyester resin A, which is a component of the resin composition E in the present invention, has an average of 0.1 carbonyl group in one molecule.
1 to 1.0, preferably 0.15 to 0.6, hydroxyl value 10 to 1
00, preferably 20-50, softening point 50-150 ° C, preferably 90
~ 140 ° C.

When the number of carboxyl groups is less than 0.1 in one molecule on average, the acrylic resin C
When the number exceeds 1.0, the molecular weight of the obtained copolymer becomes too high and not only does the smoothness of the coating film decrease, but also, for example, in the process of reacting the polyester resin A and the acrylic resin C. It is not preferable because it may gel. On the other hand, if the hydroxyl value is less than 10, a sufficient crosslinking effect cannot be obtained after painting and baking, and the strength of the resulting coating film is insufficient. Not only can a film not be obtained, but also the flexibility of the resulting coating film is impaired. If the softening point is less than 50 ° C, a powder coating with good storage stability cannot be obtained. If the softening point exceeds 150 ° C, the fluidity of the coating decreases and it is difficult to obtain a smooth coating film.

Such a polyester resin A is a hydroxyl-rich polyester resin having a predetermined amount of a carboxyl group at a terminal. For example, a method of adding an acid anhydride to a part of the hydroxyl groups of a hydroxyl group-containing polyester resin, or a polycondensation reaction It can be prepared by a method of controlling a reaction rate when producing a polyester resin.

In order to prepare the polyester resin A, for example, terephthalic acid, isophthalic acid, phthalic acid, 1,4-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 2,7
-An aromatic dicarboxylic acid such as naphthalenedicarboxylic acid, 4,4'-diphenyldicarboxylic acid or diphenic acid is used as a main acid component, and succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid in an amount of 20 mol% or less. , Azelaic acid, sebacic acid, 1,9-nonanedicarboxylic acid, 1,10-decanedicarboxylic acid, 1,12-dodecanedicarboxylic acid, 1,2-dodecanedicarboxylic acid, 1,2-octadecanedicarboxylic acid, eicosandicarboxylic acid Aliphatic dicarboxylic acids such as maleic acid, unsaturated dicarboxylic acids such as fumaric acid, alicyclic dicarboxylic acids such as hexahydroterephthalic acid, hexahydroisophthalic acid, hexahydrophthalic acid, trimellitic acid, pyromellitic acid, etc. Carboxylic acids or their lower alkyl esters and anhydrides, or malic acid, tartaric acid, 12-hydroxystearic acid It can be used hydroxycarboxylic acid such as p-hydroxybenzoic acid.

Examples of the alcohol component include ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propanediol, 1,3-propanediol,
1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,9-nonanediol, 1,10-decanediol, neopentyl glycol, spiroglycol, 1 1,4-cyclohexanedimethanol, 2,2,4-trimethylpentane-1,3-diol, trimethylolethane, trimethylolpropane, glycerin, pentaerythritol, hydrogenated bisphenol A, ethylene oxide addition of hydrogenated bisphenol A Or a propylene oxide adduct can be used.

Next, in the present invention, an aliphatic polyester resin and / or a long-chain aliphatic polyhydric alcohol (compound B) is used as one component of the resin composition E.

Examples of such aliphatic polyesters include succinic acid, adipic acid, suberic acid, sebacic acid, 1,10-decanedicarboxylic acid, 1,12-dodecanedicarboxylic acid, and SL-20 (a long-chain aliphatic dicarboxylic acid manufactured by Okamura Oil Co., Ltd.). Aliphatic dicarboxylic acids having an even number of carbon atoms, such as (trade name), are the main acid components, and ethylene glycol, 1,4-butanediol, 1,6-hexanediol, 1,8-octanediol, 1,10- Examples thereof include crystalline polyesters and polycaprolactones containing an aliphatic diol having an even number of carbon atoms such as decanediol as a main alcohol component. As other acid components, aromatic dicarboxylic acids such as terephthalic acid and isophthalic acid can be used in an amount of 20 mol% or less, but if the aromatic dicarboxylic acid exceeds 20 mol%, the crystallinity of the polyester decreases. Tend. As the other alcohol component, a branched diol such as 1,2-propanediol, 1,3-butanediol, or neopentyl glycol can be used in an amount of 20 mol% or less.

Examples of the aliphatic polyester having such crystallinity include polyethylene succinate, polyethylene adipate, polyethylene sebacate, poly-1,4-butylene sebacate, poly-1,6-hexylene sebacate, and the like.

In addition, as long-chain aliphatic polyhydric alcohol, SL-20-OH
(Trade names of long-chain aliphatic diols manufactured by Okamura Oil Co., Ltd.), and olefin waxes having an average of two or more hydroxyl groups in one molecule.

These compounds B have a melting point of 50 to 120 ° C. and a hydroxyl value of 10 to 400.

Among these crystalline aliphatic polyesters or crystalline long-chain aliphatic polyhydric alcohols, those having a hydroxyl value of 10 or less have a high molecular weight and tend to have reduced fluidity. It is not suitable for the purpose of further improving the properties. On the other hand, a low molecular weight compound having a hydroxyl value of 400 or more has good fluidity, but tends to decrease the blocking resistance of the powder coating. The melting points of crystalline aliphatic polyesters and crystalline long-chain aliphatic polyhydric alcohols are 50-1.
The temperature is preferably 20 ° C., and particularly those exhibiting a sharp melting behavior at 60 to 100 ° C. are preferable. If the melting point is lower than 50 ° C, the blocking resistance of the powder coating is reduced, while if it is higher than 120 ° C, the effect of improving the smoothness of the coating film is not sufficient.

The compounding ratio of the compound B is 1 to 20% by weight, preferably 2 to 10% by weight. If the compounding ratio of the compound B is less than 1% by weight, a sufficient effect cannot be obtained, while if it exceeds 20% by weight, the powder coating tends to block.

Next, the acrylic resin C which is one component of the composition E in the present invention has 0.1 to 4, preferably 0.3 to 2 glycidyl groups in one molecule on average, and has a hydroxyl value of 30 to 150,
Preferably 50-120, softening point 50-150 ° C, preferably 90-1
It is at 40 ° C.

When the number of glycidyl groups is less than 0.1 in one molecule on average, the glycidyl group does not sufficiently react with the polyester resin A, while
If the number exceeds the number, not only the smoothness of the coating film is liable to be lowered, but also, for example, gelling may occur during the reaction between the polyester resin A and the acrylic resin C, which is not preferable. On the other hand, if the hydroxyl value is less than 30, a sufficient crosslinking effect cannot be obtained and the coating strength is not sufficient, and if it exceeds 150, the curing reaction proceeds too much, making it difficult to obtain a smooth and glossy coating film. Also,
If the softening point is lower than 50 ° C, a powder coating with good storage stability cannot be obtained. If the softening point is higher than 150 ° C, the fluidity of the coating decreases and a sufficiently smooth coating film cannot be obtained.

Such an acrylic resin has a predetermined amount of a glycidyl group, and is one or two of hydroxyl group-containing monomers.
And at least one kind of glycidyl group-containing monomer and one or more kinds of other copolymerizable monomers, such as solution polymerization, suspension polymerization and bulk polymerization. It can be prepared by a polymerization method.

Examples of the hydroxyl group-containing monomer for preparing the acrylic resin include, for example, hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, hydroxybutyl methacrylate, 2-hydroxy-2-phenylethyl Acrylate, 2
-Hydroxy-2-phenylethyl methacrylate, allyl alcohol and the like can be used. Examples of the glycidyl group-containing monomer include glycidyl acrylate, glycidyl methacrylate, α-methyl glycidyl acrylate, α-methyl glycidyl methacrylate, β-methyl glycidyl acrylate, and β-methyl glycidyl methacrylate. Further, as other copolymer monomers, for example, acrylic acid, methacrylic acid, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, n-propyl acrylate, n-propyl methacrylate, isopropyl acrylate, isopropyl methacrylate, n- Butyl acrylate, n-butyl methacrylate, isobutyl acrylate, isobutyl methacrylate, tert-butyl acrylate, tert-butyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, octyl acrylate, octyl methacrylate, dodecyl acrylate, dodecyl methacrylate, benzyl acrylate, benzyl Methacrylate, dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate And methacrylic esters such as diethylaminoethyl acrylate and diethylaminoethyl methacrylate. Further, as other copolymerizable monomers, for example, dialkyl fumarate, dialkyl ester itacon, styrene, vinyltoluene, α-methylstyrene, acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, methylolacrylamide, methylol Methacrylamide, vinyl oxazoline, vinyl acetate, vinyl propionate, lauryl vinyl ether, halogen-containing vinyl monomers, silicon-containing vinyl monomers, and the like can be used.

Next, the composition D constituting the resin composition E of the present invention is:
It contains a copolymer obtained by reacting the polyester resin A and the acrylic resin C.

The amount of the copolymer of the polyester resin and the acrylic resin contained in the composition D varies depending on the weight ratio of the two resins and the distribution of the carboxyl groups in the polyester resin and the glycidyl groups in the acrylic resin. 20% by weight / weight of composition D is preferred, particularly preferably 2 to 10% by weight
/ Composition D. Therefore, when the content of the glycidyl group in the acrylic resin is small and when the blending amount of the acrylic resin is small, it is necessary to increase the reaction rate of the glycidyl group. On the other hand, when the content of the glycidyl group is large and when the amount of the acrylic resin is large, it is necessary to control the reaction rate of the glycidyl group and control the amount of the copolymer within a certain range. In particular, when more than one glycidyl group is contained in one molecule on average, the reaction rate of glycidyl groups is controlled so that the number of glycidyl groups involved in the reaction remains within one molecule on average. There is a need to.

Incidentally, it is difficult to isolate the copolymer of the polyester resin and the acrylic resin contained in the composition D. Therefore, the amount of such a copolymer is calculated by multiplying the reaction rate of the glycidyl group, assuming that the glycidyl group in the acrylic resin involved in the formation of the copolymer is included in every molecule of the acrylic resin. Value. In the present invention, the amount of the copolymer is calculated as described above and used as a rough guide.

Composition D can be prepared, for example, as follows. That is, the polyester resin A and the acrylic resin C are preferably used in a ratio of 10 to 90:90 to 10, more preferably 30 to 90:90.
7070: 70〜30, the polyester and acrylic resin are melted, and the carboxyl group of polyester resin A and the glycidyl group of acrylic resin C can be selectively reacted, for example, 120〜180. ° C, preferably 140-160
The carboxyl group of the polyester resin A and the glycidyl group of the acrylic resin C are selectively reacted at a temperature of 1 ° C. for 1 to 100 minutes, preferably 10 to 60 minutes, in a reaction vessel under melt stirring to form a copolymer of both. Can be prepared. In addition, a heating roll is used in place of the above reaction vessel,
It can also be prepared by selectively reacting the carboxyl group of the polyester resin A with the glycidyl group of the acrylic resin C under the same conditions as above using a kneader or the like to form a copolymer of both. If the above reaction is insufficient, favorable performance is hardly exhibited. In order to promptly advance this reaction, for example, a catalyst such as a metal salt of stearic acid, imidazole, or a phosphorus compound may be mixed in both resins or one of them.

The composition D in the resin composition E is used in an amount of 99 to 1% by weight, preferably 99 to 5% by weight. When the content of the composition D is less than 1% by weight, the compatibility between the polyester resin A and the acrylic resin C is not sufficient, and even when the coating film is formed after coating, the coating film has insufficient smoothness and the toughness of the coating film. Also inferior. On the other hand, if the content exceeds 99% by weight, the amount of compound B becomes 1 as a result.
% By weight, making it difficult to achieve the object of the present invention.

The copolymer obtained by reacting the carboxyl group of the polyester resin A with the glycidyl group of the acrylic resin C is preferably a block copolymer. The polyester-acrylic copolymer is formed by the reaction between the carboxyl group of the polyester resin A and the glycidyl group of the acrylic resin C. The degree of freedom of the combination of the two resins or
In consideration of the degree of freedom of blending, the number of groups involved in the reaction between the two resins is preferably 0.01 to 1.0, more preferably 0.1 to 0.9, per molecule on average.

As described above, the composition D contains a copolymer obtained by reacting the polyester resin A and the acrylic resin C, and the polyester resin and the acrylic resin contained in the composition D are the polyester resin. The resin A and the acrylic resin C are preferably the same, but may not be the same.

In the present invention, a block polyisocyanate compound is used as a curing agent.

As the block polyisocyanate compound, any one obtained by masking an isocyanate compound or a prepolymer having an isocyanate group with a blocking agent and reacting with a hydroxyl group of the resin composition E to participate in crosslinking and curing can be used. It is possible. More specifically, as the isocyanate compound, for example, isophorone diisocyanate, hexamethylene diisocyanate, hydrogenated xylylene diisocyanate, dicyclohexylmethane diisocyanate, or an isocyanate having a dimer or trimer of a uretdione ring and an isocyanuric ring Examples of the prepolymer include a prepolymer obtained by reacting the above isocyanate compound with ethylene glycol, diethylene glycol, trimethylolpropane, pentaerythritol and the like. Examples of the blocking agent include lactams, phenols, alcohols, oximes, malonic esters, and acetylacetone.

The amount of the block polyisocyanate compound to be used is 5 to 50 parts by weight, preferably 1 to 100 parts by weight of the resin composition E.
0 to 30 parts by weight. If the amount of the block polyisocyanate is less than 5 parts by weight, the composition does not cure sufficiently, and the strength of the resulting coating film is not sufficient. On the other hand, if the amount exceeds 50 parts by weight, the blocking resistance of the obtained paint decreases. , Not preferred.

The resin composition for powder coatings of the present invention may contain, for example, an epoxy resin for improving corrosion resistance, a benzoin for suppressing cracking of a coating film, and
Additives such as a curing catalyst, a pigment, a leveling agent, and an antistatic agent for accelerating the curing reaction can be blended.

The resin composition for powder coating of the present invention can be produced by a conventional method such as, for example, dry-blending the above components with a Henschel mixer, melt-blending with an extruder, and then cooling, pulverizing, and classifying. it can.

 The measuring method of each characteristic in the present invention is as follows.

Measurement of glycidyl group 5 g of a sample is dissolved in 100 ml of chloroform and measured using the tetraethylammonium bromide / perchloric acid method.

Measurement of hydroxyl value 3 g of sample was dissolved in 50 ml of pyridine, and acetic anhydride was added.
The hydroxyl group is blocked by adding 5 ml of a 12% by volume pyridine solution, and excess acetic anhydride and acetic acid are determined by titration with an alcoholic KOH solution.

Measurement of carboxyl group A 500 mg sample is dissolved in 50 ml of dioxane, and this is directly titrated with an alcoholic KOH solution.

Measurement of softening point The sample is pulverized to a fine powder, which is packed in a glass pillar (inner diameter 2.6 mmφ, outer diameter 5 mmφ) and placed in an oil bath at 1 ° C.
The temperature at which liquefaction starts is determined by the naked eye and read.

(Function) The resin composition for powder coating of the present invention is a polyester resin.
A, a composition D containing an acrylic resin C and a copolymer obtained from the polyester resin A and the acrylic resin C, a crystalline aliphatic polyester and / or a crystalline long-chain aliphatic polyhydric alcohol (compound B) In the baking of a powder coating made of such a resin composition, the compound B rapidly dissolves and flows at a temperature equal to or higher than its melting point during heating, and the flowability of the coating is improved. You. On the other hand, after the completion of baking, it reacts with the block polyisocyanate compound in the same manner as polyester resin A and is incorporated into the coating film, which contributes to the improvement of the toughness of the coating film due to its high flexibility. Presumed.

(Examples) Next, the present invention will be described specifically with reference to examples, but the present invention is not limited thereto.

 In the examples, “parts” means “parts by weight”.

In the following, each property such as the performance of the coating film was evaluated as follows.

 Smoothness Determine visually.

 ：: Extremely smooth, ○: Smooth, ×: No flow Gloss (60-degree specular reflectance) (%) Determine the 60-degree specular reflectance (%) according to JIS-K-5400.

 Erichsen strength (mm) Determined according to JIS-K-7777.

Impact resistance (cm) Du-Pont type impact resistance tester (diameter 1 / 2i according to JIS-K-5400)
n.φ 1kg load)

Flexibility (2mmφ bending) A bending test is performed at a bending diameter (curvature diameter) of 2mmφ according to JIS-K-5400.

○: passed, ×: failed Stain resistance Using a felt pen for writing impregnated with oil-based ink,
Apply oil-based ink, wipe off with methanol after standing for 24 hours, and determine residual contamination visually.

：: No trace, ×: Almost remaining Weather resistance (%) According to JIS-K-5400, light irradiation was performed for 500 hours using a sunshine weather meter to determine the gloss retention.

 Pencil hardness Calculated according to JIS-K-5400.

Acid value The amount of the carboxyl group is represented by KOHmg / g.

Reference Example 1 (Production Example of Polyester Resin) The following raw materials were charged into a reaction vessel, an esterification reaction was performed at 250 ° C. for 5 hours, a theoretical amount of water was removed from the system, and 0.5 part of antimony trioxide was added. At ℃, the reaction was carried out for 5 hours while controlling the degree of vacuum to 20 mmHg, and the hydroxyl value was 36 and the softening point was 1
A polyester resin A1 having an acid value of 1, a number average molecular weight of 4,200 at 15 ° C was obtained. This resin has an average of 0.08 parts of carboxyl groups per molecule.

Terephthalic acid 1162 parts Isophthalic acid 498 parts Ethylene glycol 186 parts Neopentyl glycol 1040 parts Trimetrol propane 67 parts Reference example 2 (Production example of polyester resin A) The following raw materials are charged into a reaction vessel and subjected to an esterification reaction at 250 ° C. After removing the theoretical amount of water from the system, 0.5 part of antimony trioxide was added, and the mixture was reacted at 270 ° C. for 4 hours under vacuum to prepare a polyester resin having a high polymerization degree of 100 to 150.
Next, the polyester resin having a high degree of polymerization was depolymerized using 54 parts of trimethylolpropane to obtain a hydroxyl value of 33 and a softening point of 1.
Polyester resin A2 with 25 ° C, acid value 1.6, number average molecular weight 2500
I got

This resin has an average of 0.15 carboxyl groups per molecule.

Terephthalic acid 1494 parts Adipic acid 146 parts Ethylene glycol 497 parts 1,4-cyclohexanedimethanol 721 parts Reference example 3 (Production example of polyester resin A) The following raw materials were charged into a reaction vessel, and the degree of polymerization was measured in the same manner as in Reference example 2. Polyester resins with a high degree of polymerization of 100-150 were prepared. Next, the polyester resin having a high degree of polymerization was depolymerized using 37 parts of glycerin to obtain a hydroxyl value of 36, a softening point of 110 ° C,
A polyester resin A3 having an acid value of 3, and a number average molecular weight of 4,700 was obtained.

This resin has an average of 0.25 carboxyl groups per molecule.

Terephthalic acid 1661 parts Neopentyl glycol 834 parts Ethylene glycol 372 parts 1,6-hexanediol 236 parts Reference example 4 (Production example of compound B) The following raw materials were charged into a reaction vessel, and esterification was carried out at 230 ° C. After removing the amount of water out of the system, add 0.7 parts of tetrabutyl titanate, and at 245 ° C under a reduced pressure of 0.5 mmHg.
A polyester resin having the same high degree of polymerization as in Reference Example 3 was prepared. Next, the polyester resin was depolymerized using 27 parts of trimethylolpropane, and the hydroxyl value was 20, the acid value was 2, and the melting point was 8.
Compound B1 having a number average molecular weight of 6700 at 7 ° C. was obtained.

SL-20 1710 parts 1,4-butanediol 675 parts Reference Example 5 (Production example of compound B) The following raw materials were charged into a reaction vessel and subjected to an esterification reaction at 230 ° C to remove the theoretical amount of water out of the system. Then, add 0.7 parts of tetrabutyl titanate, and at 245 ° C under a reduced pressure of 0.5 mmHg.
A polyester resin having the same high degree of polymerization as in Reference Example 4 was prepared. Next, this polyester resin was depolymerized using 12 parts of 1,6-hexanediol and 13 parts of trimethylolpropane, and had a hydroxyl value of 24, an acid value of 1, a melting point of 70 ° C, and a number average molecular weight of 530.
0 Compound B2 was obtained.

Sebacic acid 1010 parts 1,6-hexanediol 885 parts Reference example 6 (Example of compound B) SL-20-OH having a melting point of 88 ° C and a hydroxyl value of 357 (manufactured by Okamura Oil Co., Ltd.)
Long-chain aliphatic diol) is referred to as compound B3.

Reference Example 7 (Production example of acrylic resin) Xylene 30 was placed in a reactor equipped with a stirrer and a reflux condenser.
While adding 0 parts and heating and refluxing, a mixture composed of the following monomer, polymerization initiator and chain transfer regulator was added dropwise over 4 hours, and further maintained under reflux for 1 hour, and then cooled.
Add 5 parts of azoisobutyronitrile and remove the remaining monomers out of the system at 80 to 100 ° C to complete the polymerization. Further, remove the solvent under reduced pressure to obtain a hydroxyl value of 47, a softening point of 110 ° C, and a number average molecular weight. 4,700 glycidyl-free acrylic resin C1
I got

Methyl methacrylate 400 parts n-butyl methacrylate 284 parts Hydroxyethyl methacrylate 156 parts Styrene 291 parts Azobisisobutyronitrile 50 parts n-dodecylmercaptan 2 parts Reference Example 8 (Production example of acrylic resin C) Using the following monomers In the same manner as in Reference Example 7, a hydroxyl value of 77, a softening point of 105 ° C., a glycidyl equivalent of 5,800, and a number average molecular weight are used.
4,000 acrylic resins C2 were obtained.

This resin has an average of 0.7 glycidyl groups in one molecule.

Methyl methacrylate 600 parts n-butyl methacrylate 312 parts Hydroxypropyl methacrylate 230 parts Glycidyl methacrylate 25 parts Reference Example 9 (Production Example of Composition D) Polyester resin A2 and acrylic resin C2 are mixed at a weight ratio of 70:30, and 170 ° C. For 1 hour to obtain a composition D1. The glycidyl equivalent of the composition D1 was 33,700, and the conversion of the glycidyl group was 42.6%.

Reference Example 10 (Production Example of Composition D) A polyester resin A3 and an acrylic resin C2 were mixed at a weight ratio of 70:30 and reacted at 150 ° C. for 30 minutes to obtain a composition D2. The glycidyl equivalent of the composition D2 was 29,700, and the conversion of the glycidyl group was 34.8%.

Examples 1 to 5 and Comparative Examples 1 and 4 The compositions shown in Table 1, polyester resin A, compound B, acrylic resin C and block polyisocyanate [Adduct B-1530 (Hüls)] are shown in Table 1. 40 parts of rutile-type titanium oxide [JR600E (manufactured by Teikoku Chemicals Co., Ltd.)] as a pigment and a polyacrylate ester leveling agent (Acronal 4F;
1 part) and melt-kneaded at 120 ° C for 3 minutes using a heating roll. After cooling and solidifying, pulverize and classify to obtain a particle size.
A powder coating of 105 μm or less was obtained.

The resulting powder coating was applied to a 0.8 mm thick zinc phosphate treated steel sheet by electrostatic spraying to a thickness of about 50 μm.
Bake at 00 ° C for 20 minutes.

 Table 1 also shows the performance of the obtained coating films.

The resin composition for powder coating of Comparative Example 2 was difficult to pulverize, and could not be applied because the pulverized material was blocked.

As is clear from Table 1, the resin compositions for powder coatings of the present invention of Examples 1 to 5 have extremely high smoothness, and toughness and flexibility. It can be seen that it can be provided without sacrificing performance.

As in Comparative Examples 1 and 4, when the amount of Compound B is small or not contained at all, the flexibility of the coating film is not sufficient,
Smoothness is slightly inferior to the present invention. However, the blocking resistance of the paint may be sacrificed as in Comparative Example 2 in which the amount of the compound B is too large. Polyester resin A
As shown in Comparative Example 3, the resin composition for a powder coating material which does not contain the composition D containing the copolymer obtained by reacting the acrylic resin B with the acrylic resin B has extremely poor coating film smoothness and gloss. Not only that, but also the toughness of the coating film is lacking.

(Effect of the Invention) The resin composition for a powder coating of the present invention has the characteristics of a polyester resin coating film such as excellent hardness, stain resistance, and weather resistance, and the characteristics of an acrylic resin coating film. It is possible to provide a powder coating material that can be formed by applying once and baking an ideal coating film having smoothness and toughness.

Continuation of front page (58) Field surveyed (Int.Cl. ⁶ , DB name) C09D 5/03 C09D 175/04-175/16

Claims (1)

(57) [Claims] 1. A polyester resin (A) having an average of 0.1 to 1.0 carboxyl groups per molecule having a hydroxyl value of 10 to 100, a softening point of 50 to 150 ° C., a hydroxyl value of 10 to 400 and a melting point of 50 to 120.
Aliphatic polyester having a crystallinity of 10 ° C. and / or a long chain aliphatic polyhydric alcohol [compound (B)] having a hydroxyl value of 10 to 400 and a melting point of 50 to 120 ° C. Glycidyl group-containing hydroxyl value 30 to 150, softening point 50 to 150
A composition (D) containing a copolymer obtained by reacting an acrylic resin (C) and a polyester resin (A) with an acrylic resin (C) at a temperature of 10 ° C., wherein (A) to (D) have the following proportions: The resin composition (E) that satisfies
A resin composition for powder coatings comprising 5 to 50 parts by weight of a block polyisocyanate compound as a curing agent per part by weight. Polyester resin (A): 0 to 80% by weight Compound (B): 1 to 20% by weight Acrylic resin (C): 0 to 80% by weight Composition (D): 99 to 1% by weight