JPH09272822A - Resin composition for powder coating - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject composition containing a polyester resin having a specific hydroxyl group end and a curing agent, capable of providing cured coating film excellent in appearance of coating film, mechanical physical properties and interlayer adhesion and useful for coating of automobile. SOLUTION: This resin composition contains (A) a polyester resin obtained by using at least either one in (i) glycols having an alicyclic structural unit of formula I (the position of a substituent group is either one among ortho-, meta- and para-positions) and (ii) polybasic acids having an alicyclic structural unit of formula II as an essential raw material component and (iii) isophthalic acid as an essential raw material component and having 10-350mgKOH/g OH valence and 80-150 deg.C softening point by ring and ball softening point method and (B) a curing agent (preferably a blocked polyisocyanate compound) having a functional group capable of reacting with OH group of the component A as essential film-forming components.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a new and useful resin composition for powder coatings. More specifically, the present invention has a specific structural unit called an alicyclic structural unit,
Moreover, a hydroxyl-terminated polyester resin obtained by using also isophthalic acid and a curing agent having a functional group capable of reacting with the hydroxyl group are contained as essential film-forming components. (Hereinafter, it is also referred to as topcoat adhesiveness.) The present invention relates to a resin composition for powder coating having a very high practicality, which gives a coating film excellent in appearance and weather resistance.

[0002]

2. Description of the Related Art Powder coating is one form of coating that does not contain organic solvents, but in recent years, its low pollution has attracted attention from the viewpoint of environmental problems such as air pollution, and the amount used has been increasing year by year.
It has increased. Applications of such powder coatings include home appliances and
It has a wide variety of uses including coating metal products such as building materials, but it is also considered as a coating agent for automobiles due to the characteristic of powder coating that there is virtually no solvent that evaporates during coating. Is progressing.

At present, there are various types of resin compositions for powder coatings which are practically used. For example, a so-called acrylic powder coating material (hereinafter referred to as an acrylic powder coating material), which is composed of a glycidyl group-containing acrylic copolymer and an aliphatic dibasic acid, has a weather resistance of a coating film obtained from it. It is mainly used for outdoor use because of its good stain resistance.

Further, a composition obtained by combining a polyester resin mainly having a hydroxyl group and a block polyisocyanate compound has good appearance and mechanical properties, and is It is widely used for applications requiring flexibility, such as home appliances and building materials.

However, the resin composition for powder coatings (hereinafter referred to as polyester powder coating) in the form of containing the block polyisocyanate compound as a curing agent as described above is a coating film obtained. In particular, since the weather resistance is inferior to that of the coating film obtained from the above-mentioned acrylic powder coating, the weather resistance is highly required. However, it cannot be used and applied to various applications such as automotive top coatings and automotive intermediate coatings.

[0006] Here, a supplementary explanation will be given on the intermediate coating for automobiles. Usually, the intermediate coating is not usually required to have a high degree of weather resistance as required for the top coating for automobiles. . However, in the case where a so-called metallic coating is applied, if the weather resistance of the coating film obtained from the intermediate coating used for such coating is not sufficient, it is formed in the upper layer, aluminum powder, etc., respectively. The penetration of sunlight through the metallic base coating film layer containing the above and the transparent topcoat coating film layer formed on the uppermost layer causes deterioration of this intermediate coating film layer, and by extension, the interlayer of the coating film. It is also recognized that serious problems such as peeling occur.

From the viewpoint of appearance, mechanical properties and cost, the above polyester powder coating material is
Although it is desirable to use it as an intermediate coating paint, even in such a case, it has not been used because of the problem of delamination as described above.

[0008]

As described above, as long as the conventional technique is followed, it is inevitable that a coating film excellent in appearance and weather resistance can be obtained, and moreover, above all, the adhesion of the top coat, that is, the interlayer adhesion. It has been extremely difficult to provide a powder coating material having extremely high practicality that can give an excellent coating film to the above, and to provide a resin composition for the powder coating material therefor.

For this reason, the present inventor has diligently started research in order to eliminate various drawbacks in the conventional techniques. Therefore, the problem to be solved by the present invention is to provide a coating film which is excellent in appearance and weather resistance as well as in particular, particularly in interlayer adhesion such as topcoat adhesion. An object of the present invention is to provide a resin composition for a powder coating, which has an extremely high practicality and gives an excellent coating film.

[0010]

Therefore, in order to solve the various drawbacks and problems in the conventional technique as described above, the present inventor has additionally solved the problems to be solved by the invention as described above. As a result of intensive and careful study, the following alicyclic structural unit (1)

[0011]

Embedded image

(However, the position of the substituent in the above structural unit represents any position of the ortho position, the meta position and the para position.)

Further, as the acid component, a polyester resin obtained by using isophthalic acid as an essential raw material component and having a hydroxyl value in a specific range and a softening point by the ring and ball method in a specific range, and the polyester resin A curing agent having a functional group capable of reacting with the hydroxyl group of the resin,
When a resin composition for powder coatings, which is contained as an essential film-forming component, is found, and when a so-called multilayer coating film is formed by using it as an intermediate coating or as an undercoating coating, it is very good. It is of course possible to obtain a coating film having the following appearance, and the adhesiveness of the top coat is also good, as compared to the case where the conventional resin composition for powder coating is used for the intermediate coating,
The present invention has been completed here by discovering that it is remarkably improved.

That is, the present invention basically has a glycol (a-1) having a specific alicyclic structural unit as described above or a specific alicyclic structural unit as described above. It is obtained by using at least one of the polybasic acids (a-2) as an essential raw material component and also isophthalic acid as an acid component as an essential raw material component.
The hydroxyl value is 10 to 350 (mgKOH / g), and
A polyester resin [A] having a softening point of 80 to 150 ° C. by a ring and ball method and a curing agent [B] having a functional group capable of reacting with a hydroxyl group of the polyester resin [A] are contained as essential film forming components. The present invention is intended to provide a resin composition for powder coatings.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION To describe various means or means for solving the problems in the conventional techniques as described above, the present invention provides a glycol (a) having an alicyclic structural unit (1). -1) or at least one of the polybasic acids (a-2) having the alicyclic structural unit (1) as an essential component, and isophthalic acid as an acid component as an essential component, having a hydroxyl value of 10 350 (m
gKOH / g) and has a softening point of 80-
Powder coating comprising a polyester resin [A] at 150 ° C. and a curing agent [B] having a functional group capable of reacting with the hydroxyl groups of the polyester resin [A] as essential film forming components. Is to disclose a resin composition for

Further, the curing agent [B] having a functional group capable of reacting with the hydroxyl group of the polyester resin [A] is a block polyisocyanate compound or the following structural formula (2).

[0017]

[Chemical 6]

It also discloses a resin composition for powder coating, which is used alone or in combination with a so-called self-blocking polyisocyanate compound having a uretdione structure represented by in the molecule. It is a thing.

Further, the constitution of the resin composition for powder coating material according to the present invention will be described in detail below.

The above polyester resin [A], which is one of the essential constituents of the resin composition for powder coating according to the present invention, can be prepared by various known and conventional methods. Generally, the method of dehydration-condensing glycols and polybasic acids is the most convenient, and thus is particularly recommended.

The polyester resin [A], which is one of the essential constituents in the present invention, is a glycol (a-1) having a specific alicyclic structural unit (1) as described above or a specific oil as described above. It is obtained by using at least one of the polybasic acids (a-2) having the cyclic structural unit (1) as an essential raw material component, and further using isophthalic acid as an essential raw material component as the acid component. This refers to a resin of the form.

As only glycols (a-1) having an alicyclic structural unit which can be used as an essential raw material component, only typical ones are exemplified, 1,4-cyclohexanedimethanol or hydrogenated bisphenol A. Or various alicyclic glycols such as hydrogenated bisphenol A ethylene oxide adduct or hydrogenated bisphenol A propylene oxide adduct.

Similarly, only representative examples of the polybasic acids (a-2) having an alicyclic structural unit which can be used as an essential raw material component will be exemplified.
Examples thereof include alicyclic carboxylic acids such as 1,4-cyclohexanedicarboxylic acid and 1,3-cyclohexanedicarboxylic acid, and alicyclic acid anhydrides such as hexahydrophthalic anhydride. The glycols (a-1) or polybasic acids (a-2) having these alicyclic structural units may each be used alone,
Alternatively, of course, two or more kinds may be used in combination.

The polyester resin [A] is obtained by using isophthalic acid as one of the essential raw material components. Furthermore, in addition to these essential raw material components, the polyester resin Various glycols and polybasic acids used in the preparation can also be used.

Of these, only typical ones are exemplified, and ethylene glycol, propylene glycol, 1,3-butylene glycol, 1,6-hexanediol, diethylene glycol, dipropylene glycol, neopentyl glycol, Triethylene glycol, bisphenol A, ethylene oxide adduct of bisphenol A, propylene oxide adduct of bisphenol A, glycerin, trimethylolpropane, trishydroxymethylaminomethane, trishydroxyethyl isocyanurate, pentaerythritol or dipentaerythritol. .

Further, only typical polybasic acids are listed, for example, phthalic anhydride, terephthalic acid, succinic anhydride, adipic acid, azelaic acid, sebacic acid, tetrahydrophthalic anhydride, tetrabromophthalic anhydride. Acid, tetrachlorophthalic anhydride, het anhydride, and hymic acid anhydride ["Himimic acid" is a registered trademark of Hitachi Chemical Co., Ltd.]. ], Maleic anhydride, fumaric acid, itaconic acid, trimellitic anhydride, methylcyclohexene tricarboxylic acid anhydride or pyromellitic anhydride.

In addition to these polyhydric alcohols or polybasic acids, various monohydric alcohols such as methanol, propanol or butanol, benzyl alcohol, etc., benzoic acid or p-tert-butylbenzoic acid, etc. Various monobasic acids, various fatty acids such as castor oil fatty acid, coconut oil fatty acid or soybean oil fatty acid, and dimethylolpropionic acid or hydroxypivalyl pivalate, and hydroxyl group in one molecule. And various epoxy groups such as epoxy resin or “Cardura E10” (trade name of glycidyl ester of branched fatty acid manufactured by Shell Co., Netherlands) and the like. The compounds having can also be used.

Use of the specific glycols (a-1) or polybasic acids (a-2) having an alicyclic structural unit as described above, which are used when preparing the polyester resin [A]. The amount is preferably 3% by weight or more based on all raw materials used. When the amount of these specific glycols (a-1) or polybasic acids (a-2) having an alicyclic structural unit is less than 3% by weight,
Inevitably, the resulting coating film, in particular, becomes inferior in weather resistance and the like, so that delamination of the coating film is likely to occur, and thus the adhesion of the top coat is likely to be decreased, which is not preferable.

Among the acid components constituting the polyester resin [A], the amount of isophthalic acid used is 20 mol% or more, preferably 50 mol% or more, based on the total acid components used. .

When the amount of isophthalic acid used is less than 20 mol%, the resulting coating film is inevitably inferior in weather resistance and blocking resistance, which is not preferable.

The hydroxyl value of the polyester resin [A] is appropriately in the range of 10 to 350 (mgKOH / g), preferably 250 to 350 (mgKOH / g).

When the hydroxyl value is less than 10 (mgKOH / g), the appearance of the resulting coating film is inevitably deteriorated because the intermediate coating film, especially the solvent resistance, is insufficient. Delamination of the film is apt to occur, and when it is larger than 350, the resulting coating film tends to be inferior in smoothness and the like.
Either case is not preferred.

Further, of the polyester resin [A],
A suitable softening point by the ring and ball method is in the range of 80 to 150 ° C. If the softening point is lower than 80 ° C., the powder coating obtained will inevitably have inferior blocking resistance and the softening point will be 150 on the other hand.
If the temperature is higher than 0 ° C., the resulting coating film tends to have insufficient smoothness, which is not preferable in any case.

On the other hand, the curing agent [B] having a functional group capable of reacting with the hydroxyl group in the polyester resin [A] refers to a compound having a functional group capable of reacting with the hydroxyl group in the molecule. However, aminoplasts, polyisocyanate compounds, block polyisocyanate compounds, and the like can be cited as only specific examples of such compounds.

First, to list only particularly representative aminoplasts, various amino group-containing compounds such as melamine, urea, acetoguanamine, benzoguanamine, steroganamin or spiroguanamine, and formaldehyde, Condensates in the form obtained by reacting various aldehyde-based compound components such as paraformaldehyde, acetaldehyde or glyoxal by various conventionally known methods, or ethers of each of these condensates. Compounds in the form obtained by squeezing, etc., of course, any compound can be used as long as it is usually used for paints.

Among them, it is desirable to use a compound in which C ₁ -C ₄ alcohols are partially or completely etherified, and only typical aminoplasts are exemplified. If you keep
Hexamethyletherified methylolmelamine, hexabutyletherified methylolmelamine, methylbutyl mixed etherified methylolmelamine, methyletherified methylolmelamine, butyletherified methylolmelamine or isobutyletherified methylolmelamine, or condensates thereof.

Next, only specific examples of the above-mentioned polyisocyanate compounds will be exemplified. Various aliphatic diisocyanates such as hexamethylene diisocyanate or trimethylhexamethylene diisocyanate; xylylene diisocyanate or isophorone diisocyanate. Various cycloaliphatic diisocyanates such as;

In addition to organic diisocyanate compounds represented by various aromatic diisocyanates, such as tolylene diisocyanate or 4,4'-diphenylmethane diisocyanate, and further, these organic diisocyanate compounds and Polyhydric alcohols, low molecular weight polyester resins (polyester polyols), adducts with water, etc., or polymers of the organic diisocyanates mentioned above (including isocyanurate type polyisocyanate compounds) and isocyanates. -For example, a biuret body.

Further, only by exemplifying only typical examples of the above-mentioned block polyisocyanate compound, various polyisocyanate compounds such as those mentioned above can be used as ε-caprolactam, MEK oxime or monohydric alcohol. Compounds in the form which can be obtained by blocking with various known and commonly used blocking agents such as those mentioned above, and only typical commercial products as compounds of such a form will be exemplified. If

"VESTANAT B1358 / 10
0 ”,“ VESTAGON B1065 or B15
30 "(all are trade names of block polyisocyanate compounds manufactured by Huls in Germany)," Cleran UI or TPLS2151 "[trade name of block polyisocyanate compounds manufactured by Sumitomo Bayer Urethane Co., Ltd.], etc. Is.

As the polyisocyanate compound,
It is also possible to use a so-called self-block type compound having a uretdione bond represented by the structural formula (2) as described above in the molecule.

To exemplify only typical examples of such a self-blocking type polyisocyanate compound, "VESTAGON BF" will be given.
1540 or EP-BF1300 "(both are trade names of self-block type block polyisocyanate compounds having a uretdione bond manufactured by the above-mentioned company)," Clelan TPLS2147 "(manufactured by the above-mentioned company,
Examples include self-block type block polyisocyanate compounds having a uretdione bond).

A target powder coating material is prepared by using the resin composition for powder coating material according to the present invention, each of which is composed of the polyester resin [A] and the curing agent [B] described above. For this purpose, various known and conventional methods can be used and applied as they are.

That is, generally, the polyester resin [A] and the curing agent [B] are mixed with various additive components such as a pigment, a curing accelerator or a surface conditioner, if necessary. However, the so-called mechanical crushing method of melt kneading and then finely crushing is particularly convenient and is recommended.

The resin composition for powder coating material according to the present invention thus obtained, and the powder coating material obtained from the resin composition for powder coating material are coated on a substrate to be coated by various known methods. That is, by applying electrostatic powder coating, followed by baking, a target cured coating film is formed on the substrate to be coated.

Here, only representative examples of the above-mentioned substrate to be coated are exemplified, and various metal materials such as aluminum, stainless steel, chrome plating, galvanized iron plate or tin plate are used. Or metal products; or roof tiles; glass; or various inorganic building materials,

Concretely, such as automobile body or automobile (for) parts, two-wheeled vehicle or two-wheeled vehicle (for) parts, and various building materials such as gates or fences; aluminum sashes, etc. , Various building interior / exterior materials; various ferrous or non-ferrous metal materials such as aluminum foil, or various products.

[0048]

EXAMPLES Next, the present invention will be described more specifically with reference examples, examples and comparative examples. However, the present invention is by no means limited to only these illustrative examples. Absent. In the following, all parts and percentages are by weight unless otherwise specified.

Reference Example 1 [Preparation example of polyester resin [A] used in the present invention] In a reaction vessel equipped with a stirrer, a thermometer, a rectification column and a nitrogen gas inlet, 130 parts of ethylene glycol, 1, 4-
Charge 302 parts of cyclohexanedimethanol and 23 parts of trimethylolpropane, and in a nitrogen atmosphere,
While continuing stirring, the temperature was raised to 150 ° C.

Here, 348 parts of terephthalic acid, 348 parts of isophthalic acid and 0.5 parts of dibutyltin oxide.
Parts were added and the temperature was raised to 240 ° C. By continuing the dehydration condensation reaction at the same temperature, a polyester resin having a hydroxyl value of 30 mgKOH / g and a softening point of 106 ° C. according to the ring and ball method was obtained. Hereinafter, this is abbreviated as polyester resin [A-1].

Reference Example 2 (Same as above) A reaction vessel equipped with a stirrer, a thermometer, a rectification column and a nitrogen gas inlet was charged with 289 parts of neopentyl glycol and 120 parts of trimethylolpropane under a nitrogen atmosphere. Then, the temperature was raised to 150 ° C. while continuing stirring.

214 parts of terephthalic acid, 429 parts of isophthalic acid, 111 parts of 1,4-cyclohexanedicarboxylic acid and 0.5 part of dibutyltin oxide were added thereto, and the temperature was raised to 240 ° C. By allowing the dehydration condensation reaction to continue at the same temperature, the hydroxyl value becomes 1
00 mgKOH / g and softening point of 1 by ring and ball method
A polyester resin having a temperature of 10 ° C. was obtained. Hereinafter, this is abbreviated as polyester resin [A-2].

Reference Example 3 (Same as above) In a reaction vessel equipped with a stirrer, a thermometer, a rectification column and a nitrogen gas inlet, 125 parts of neopentyl glycol, 142 parts of hydrogenated bisphenol A and 340 parts of trimethylolpropane were placed. Was charged, and the temperature was raised to 150 ° C. under a nitrogen atmosphere while continuing stirring.

Here, 335 parts of isophthalic acid, 1,4
173 parts of cyclohexanedicarboxylic acid and 0.5 parts of dibutyltin oxide were added and the temperature was raised to 240 ° C. By continuing the dehydration condensation reaction at the same temperature, a polyester resin having a hydroxyl value of 290 mgKOH / g and a softening point of 110 ° C. according to the ring and ball method was obtained. Hereinafter, this is abbreviated as polyester resin [A-3].

Reference Example 4 [Preparation Example of Control Polyester Resin [A ']] In a reaction vessel equipped with a stirrer, a thermometer, a rectification column and a nitrogen gas inlet, 141 parts of ethylene glycol and neopentyl glycol were added. 236 parts and 30 parts of trimethylolpropane were charged, and the temperature was raised to 150 ° C. in a nitrogen atmosphere while continuing stirring.

757 parts of terephthalic acid and 0.5 parts of dibutyltin oxide were added thereto, and the temperature was raised to 240.degree. By allowing the dehydration condensation reaction to continue at the same temperature, the hydroxyl value is 35 (mgKOH / g).
A polyester resin for control having a softening point of 118 ° C. according to the ring and ball method was obtained. Hereinafter, this is abbreviated as polyester resin [A′-1].

Reference Example 5 (Same as above) In a reaction vessel equipped with a stirrer, a thermometer, a rectification column and a nitrogen gas inlet, 130 parts of ethylene glycol and 1,4-
Charge 301 parts of cyclohexanedimethanol and 25 parts of trimethylolpropane, and under a nitrogen atmosphere,
While continuing to stir, the temperature was raised to 150 ° C., 696 parts of terephthalic acid and 0.5 part of dibutyltin oxide were added, and the temperature was raised to 240 ° C. By allowing the dehydration condensation reaction to continue at the same temperature, the hydroxyl value becomes 3
A polyester resin of 0 (mgKOH / g) and having a softening point of 115 ° C. according to the ring and ball method was obtained. Hereinafter, this is abbreviated as polyester resin [A′-2].

Reference Example 6 (same as above) A reaction vessel equipped with a stirrer, a thermometer, a rectification column and a nitrogen gas inlet was charged with 431 parts of neopentyl glycol and 35 parts of trimethylol propane and placed under a nitrogen atmosphere. While continuing stirring, the temperature was raised to 150 ° C., 341 parts of terephthalic acid, 341 parts of isophthalic acid and 0.5 part of dibutyltin oxide were added, and the temperature was raised to 240 ° C.

By allowing the dehydration condensation reaction to continue at the same temperature, the hydroxyl value is 40 (mgKOH / g).
A polyester resin for control having a softening point of 112 ° C. according to the ring and ball method was obtained. Hereinafter, it is abbreviated as polyester resin [A′-3].

Reference Examples 7 to 13 [Preparation Example of Powder Coating] Each of the resin compositions for powder coating was blended in the proportions shown in Tables 1 and 2, and thus obtained. Each of the formulations was designated as "Co Kneader PR-4.
Type 6 "(trade name of uniaxial kneading machine manufactured by Buss in Switzerland) is used to melt-knead, finely pulverize, and further classify with a wire mesh of 150 mesh to obtain an average particle diameter. 30-40 micrometer, meter (μ
m) was prepared. Each of these powder coatings was tested for [P-1] as shown in Tables 1 and 2.
-[P-7] is abbreviated.

[0061]

[Table 1]

<< Footnotes in Table 1 >> 1) A block polyisocyanate compound in the form of "VESTAGON B1530", which is an isophorone diisocyanate nurate manufactured by Hüls, Germany, blocked with ε-caprolactam. Represents the product name of.

2) "VESTAGON BF154
The abbreviation "0" represents the trade name of a block polyisocyanate compound manufactured by the same company, in which isophorone diisocyanate is self-blocked by a uretdione bond.

3) manufactured by Dainippon Ink and Chemicals,
Trade name of polyglycidyl ether type epoxy resin of bisphenol A 4) Trade name of surface conditioner manufactured by BASF, Germany 5) Rutile manufactured by Ishihara Sangyo Co., Ltd. under the abbreviation “Taipec CR-90” Indicates the trade name of titanium oxide.

6) Trade name of carbon black manufactured by Mitsubishi Chemical Corporation

[0066]

[Table 2]

Reference Example 14 [Preparation Example of Transparent Paint Using Organic Solvent as Medium] 500 parts of xylene was charged in a reaction vessel equipped with a stirrer, a thermometer, a condenser and a nitrogen gas inlet, and the temperature was adjusted under stirring. Raised to 120 ° C. Then 100 parts of styrene, 200 parts of methyl methacrylate, 75 parts of n-butyl acrylate, 115 parts of 2-hydroxyethyl methacrylate, 10 parts of acrylic acid and te.
A mixture of 10 parts of rt-butyl peroctoate was added dropwise over 4 hours.

Even after the dropping is completed, the non-volatile content is kept at 50.2% by keeping the same temperature for 8 hours.
And the hydroxyl value of the solution base is 48 (mgKOH / g),
Moreover, the number average molecular weight in terms of polystyrene by GPC (gel permeation chromatography) is 5,
An organic solvent solution of a hydroxyl group-containing acrylic copolymer 300 was obtained.

Next, to 100 parts of this resin solution was added 35.7 parts of "Super Beckamine L-117-60" (trade name of butyl etherified melamine formaldehyde resin manufactured by Dainippon Ink and Chemicals, Inc.). In addition, "Solvesso 100" [manufactured by Exxon Chemical Co.,
Aromatic hydrocarbon solvent trade name] and isobutanol in a weight ratio of 70/30, and Ford Cup No. The desired transparent coating material was obtained by diluting the mixture according to 4 to a viscosity of 24 seconds. Hereinafter, this is abbreviated as transparent paint [X].

Examples 1 to 5 and Comparative Examples 1 to 3 Various coating films as shown in Tables 3 and 4 were prepared according to the coating film forming method as shown below, and then obtained as described above. A performance evaluation judgment test (coating performance test) was performed for each coating.

That is, the powder coatings [P-1] to [P-7] prepared in Reference Examples 7 to 13 and the transparent coating [X] prepared in Reference Example 14 were used to apply the following coatings. Various coating films were prepared according to the film forming method.

That is, first, the base material used as the article to be coated was of the form subjected to the following pretreatment. In other words, “Bondelite # 3030” [trade name of mild steel plate manufactured by Nippon Parkerizing Co., Ltd., which has been treated with a zinc phosphate-based treatment agent] is coated with an epoxy resin-based cationic electrodeposition coating by electrodeposition. I used one.

Next, powder coating [P-1] or the like was electrostatically powder coated on the above-mentioned substrate to be coated so that the film thickness after baking would be about 50 μm, and then 180 ° C. Baking was performed under the condition of / 20 minutes. Then, the electrostatic powder coated object to be coated was cooled to room temperature, and then the transparent top coat paint [X] was applied.

The coating in this case was carried out by an ordinary air spray coating method, and the baking condition was 140 ° C./20 minutes.

Each cured coating film thus obtained was evaluated for various properties. The results are summarized in Tables 3 and 4.

[0076]

[Table 3]

[0077]

[Table 4]

The outline of the evaluation judgment is as follows.

Smoothness ……………………………… Evaluation was judged by visual inspection. The criteria for evaluation judgment are as follows.

∘: very smooth and smooth coated surface ∘: large round is recognized x: fine dust skin is recognized

60 degree luster: Numerical evaluation judgment test by 60 degree specular reflectance (%).

DuPont impact: An evaluation judgment test (1/2 inch) by the DuPont impact tester. 50
The height (cm) at which the coating film was free from defects such as cracks when a load of 0 g was dropped was displayed. The larger this value is, the better the impact resistance is.

Erichsen value …………………… Evaluation judgment test by Erichsen tester. The larger this value, the better the flexibility of the coating film.

Interlayer adhesion ………………………………
It was immersed in warm water of 40 ° C. for 10 days, and 30 minutes after it was pulled up, a cross cut was put into the coating film with a cutter, and a peeling test with an adhesive tape was performed. The criteria for evaluation judgment are as follows.

O ... Between the interfaces of the coating layers or between the coating object and the coating layer,
When peeling is not observed at all: Δ ... between the interfaces of the coating layers or between the coating object and the coating layer
Partial peeling is observed. X ... Peeling is entirely observed at the interface of the coating layer.

Weather resistance ……………………………………………… ..
Gloss retention (%) after accelerated weathering test for 000 hours
Displayed with.

The higher this value, the better the weather resistance.

Adhesion between layers after weathering test ... After accelerated test weathering by a QUV tester, after 600 hours, the test plate was taken out, and a cross cut was put into the coating film with a cutter. A peeling test using an adhesive tape was performed.

The criteria for evaluation judgment are as follows.

O: Between the interfaces of the coating layers or between the article to be coated and the coating layer,
When peeling is not observed at all: Δ ... between the interfaces of the coating layers or between the coating object and the coating layer
Partial peeling is observed. X ... Peeling is entirely observed at the interface of the coating layer.

[0091]

As has already been clarified from the above description, the coating film obtained from the resin composition for powder coating material according to the present invention has a coating film appearance, It can be reasonably understood that it gives a cured coating film excellent in various physical properties such as mechanical properties and interlayer adhesion.

Therefore, it can be reasonably known that the resin composition for powder coating according to the present invention is extremely practical.

Claims (4)

[Claims] 1. The following alicyclic structural unit: (However, the position of the substituent in the above-mentioned structural unit represents any position of the ortho position, the meta position and the para position.).
1) or the following alicyclic structural unit: (However, the position of the substituent in the above structural unit represents any position of the ortho position, the meta position, and the para position.) Polybasic acids (a-2)
At least one of them is used as an essential raw material component, and isophthalic acid as an acid component is also used as an essential raw material component.
KOH / g) and the softening point by the ring and ball method is 80 to 1
Powder containing a polyester resin [A] at 50 ° C. and a curing agent [B] having a functional group capable of reacting with the hydroxyl groups of the polyester resin [A] as essential film-forming components. Resin composition for paints. 2. The composition according to claim 1, wherein the curing agent [B] having a functional group capable of reacting with the hydroxyl group of the polyester resin [A] is a block polyisocyanate compound. 3. The above-mentioned curing agent [B] having a functional group capable of reacting with the hydroxyl group of the polyester resin [A] has the following structural formula: Having a uretdione bond represented by
The composition according to claim 1 or 2, which is a so-called self-blocking polyisocyanate compound. 4. The above-mentioned curing agent [B] having a functional group capable of reacting with the hydroxyl group of the polyester resin [A] has the following structural formula: Having a uretdione bond represented by
The composition according to any one of claims 1 to 3, which is a mixture of a so-called self-blocked polyisocyanate compound and a blocked polyisocyanate compound.