JP2002241687A - Resin composition for powder coating - Google Patents

Abstract

(57) [Problem] To provide a composition for a powder coating material capable of obtaining a coating film having excellent appearance, mechanical properties, and weather resistance. SOLUTION: 50% by mole or more of the total acid component is composed of isophthalic acid or a derivative thereof, and is reactive with a hydroxyl group or a polyester resin (A) having an acid group and a hydroxyl group, a crystalline polyurethane resin (B), and an acid group. Provided is a resin composition for a powder coating, which comprises a curing agent (C) and a curing agent (D) reactive with a hydroxyl group.

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 powder coating used for building materials, metal products, parts of automobiles and the like.

[0002]

2. Description of the Related Art Thermosetting powder coatings are recognized as being non-polluting coatings, having excellent physical properties, and being relatively inexpensive compared with conventional solvent-based coatings. Demand for steel coatings, road materials, building materials, automotive parts, and decorative coatings is growing rapidly.
However, in order to obtain a polyester resin having excellent physical properties, and from the viewpoint of the stability of the coating material, it is necessary to increase Tg. Therefore, terephthalic acid is generally used as a main acid component. As a result, there has been a problem that weathering is inferior, for example, whitening and chalking occur in a very short time, and gloss is remarkably reduced.

As a method for solving this problem, Japanese Patent Application Laid-Open No. 9-71 has examined weather resistance from the viewpoint of the composition of polyester resin.
No. 738 has been proposed. However, in this method, although the weather resistance of the coating film is remarkably improved by using isophthalic acid as the acid component, the physical properties are reduced, so that it can be used only for specific applications that do not require flexibility. Problems have been pointed out.

In order to solve the above-mentioned problems, attempts have been made to achieve both weather resistance and physical properties by (1) using a combination of terephthalic acid and isophthalic acid, and (2) copolymerizing an aliphatic dicarboxylic acid or an aliphatic glycol. However, in the former, as the substitution amount of terephthalic acid to isophthalic acid increases, the physical properties such as flexibility decrease, and when the substitution amount is small, good weather resistance characteristic of isophthalic acid is not expressed, Further, in the latter case, it is not possible to obtain practically sufficient mechanical properties of the coating film.In the prior art, a polyester resin powder coating using isophthalic acid as a main acid component has good mechanical properties and weather resistance. It was difficult to obtain a coating.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a powder coating composition capable of obtaining a coating film having excellent appearance, mechanical properties and weather resistance. is there.

[0006]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, a specific amorphous polyester resin (A) and a crystalline polyurethane resin (B)
And a curing agent (C) having a reactivity with an acid group and a curing agent (D) having a reactivity with a hydroxyl group have excellent appearance, mechanical properties, and weather resistance. The present inventors have found that it is possible to provide a powder coating capable of obtaining a coating film having both of the above and completed the present invention.

That is, according to the present invention, a polyester resin (A) having a hydroxyl group or an acid group and a hydroxyl group, and a crystalline polyurethane resin, preferably an acid group and A crystalline polyurethane resin (B) having a hydroxyl value and a crystallization peak temperature of 30 to 150 ° C. and a curing agent reactive with an acid group, preferably a solid acrylic copolymer containing a glycidyl group (C) And a curing agent reactive with hydroxyl groups, preferably a blocked polyisocyanate compound (D).

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. First, 50% of the total acid component, which is an essential component of the present invention, is used.
The polyester resin (A) in which at least mol% is isophthalic acid or a derivative thereof and has a hydroxyl value or an acid group and a hydroxyl value will be described.

The polyester resin (A) is solid at ordinary temperature, and preferably has an acid value of 10 to 100 mg KOH /
g, hydroxyl value is 10 to 100 mgKOH / g. The Tg of the polyester resin (A) is preferably 50 ° C. or higher from the viewpoint of storage stability, and more preferably 60 ° C.
That is all.

The polyester resin (A) needs to contain isophthalic acid and its derivative as a main acid component in order to exhibit excellent weather resistance in a cured coating film comprising the composition of the present invention. Representative examples of isophthalic acid derivatives include 5-tert-butyl-isophthalic acid. Isophthalic acid and its derivative are used in an amount of 50 mol% or more, preferably 80 mol% or more, of all the acid components. The isophthalic acid and its derivatives in the present invention include those which react with an alcohol component such as an esterified product.

In addition to isophthalic acid, aromatic dicarboxylic acids such as terephthalic acid, naphthalenedicarboxylic acid and (phthalic anhydride); hexahydroisophthalic acid, hexahydroterephthalic acid, and the like, as long as the effects of the present invention are not impaired.
Hexahydrophthalic acid, tetrahydrophthalic acid, 1,4
Alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid and 1,3-cyclohexanedicarboxylic acid; aliphatic dibasic acids such as oxalic acid, succinic acid, adipic acid, azelaic acid, sebacic acid, dodecane diacid and eicosane diacid; Unsaturated dicarboxylic acids such as maleic acid, fumaric acid and itaconic acid; trivalent or higher carboxylic acids such as trimellitic acid, pyromellitic acid and trimesic acid can be used in combination. These acid components include those which react with alcohol components such as anhydrides and esterified products.

As the alcohol component, various polyol components can be used, and typical ones are neopentyl glycol, ethylene glycol, 1,3-
Propylene glycol, 1,2-propylene glycol, 2-methyl-1,3-propylene glycol, 1,
4-butylene glycol, 1,3-butylene glycol, 1,6-hexanediol, diethylene glycol, dipropylene glycol, triethylene glycol, 1,4-cyclohexanedimethanol, ethylene oxide adduct of bisphenol A, bisphenol A
Propylene oxide adduct, cyclohexanedimethanol, hydrogenated bisphenol A, hydrogenated bisphenol A
Ethylene oxide adduct, hydrogenated bisphenol A propylene oxide adduct, glycerin, trimethylolethane, trimethylolpropane, trishydroxymethylaminomethane, pentaerythritol, dipentaerythritol, sorbitol and the like. From the viewpoint, use of neopentyl glycol is preferred.

Next, the crystalline polyurethane resin (B) will be described. The crystalline polyurethane resin (B) is obtained by reacting a polyester polyol component (E) and / or a polyether polyol (F) with a chain extender (H) and, if necessary, a polyisocyanate compound (G). It has a group and / or a hydroxyl group.

As the polyester polyol (E),
Polycarboxylic acid (I) having 2 to 22 carbon atoms and 2 carbon atoms
Polyester polyol (E) and polyether polyol (F) preferably have an average molecular weight in the range of 500 to 10,000.

[0015] In addition, as long as the effect of the present composition is not impaired,
Acrylic polyols, epoxy polyols, carbonate polyols, caprolactone polyester polyols, butadiene polyols and the like can be used, but the use of crystalline polyester polyols is particularly preferred.

Typical examples of the polycarboxylic acid (I) having 2 to 22 carbon atoms include fatty acids such as oxalic acid, succinic acid, adipic acid, azelaic acid, sebacic acid, dodecane diacid, and eicosane diacid. Aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, phthalic acid and 2,6-naphthalenedicarboxylic acid; 1,4
Alicyclic dicarboxylic acids such as -cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, hexahydrophthalic anhydride and tetrahydrophthalic anhydride; and unsaturated dicarboxylic acids such as maleic acid, fumaric acid and itaconic acid. In addition, a small amount of a trivalent or higher carboxylic acid such as trimellitic acid or pyromellitic acid may be used in combination, or a small amount of a hydroxycarboxylic acid such as p-oxybenzoic acid or tartaric acid may be used in combination. Among them, the use of an even-numbered linear aliphatic dicarboxylic acid having 12 or less carbon atoms is preferable from the viewpoint of lowering the melt viscosity and controlling the crystallization peak temperature of the crystalline polyurethane resin. Particularly preferred are oxalic acid, succinic acid, and adipic acid. These acid components include those which react with alcohol components such as anhydrides and esterified products.

Representative examples of the polyol component (J) having 2 to 20 carbon atoms include ethylene glycol, 1,3-propylene glycol, 1,2-propylene glycol, and 2-methyl-1,3-propylene. Glycol, 1,4-butylene glycol, 1,3-butylene glycol, 1,6-hexanediol, diethylene glycol, dipropylene glycol, neopentyl glycol, triethylene glycol, 1,4-cyclohexanedimethanol, ethylene oxide of bisphenol A Adduct, bisphenol A propylene oxide adduct, cyclohexanedimethanol, hydrogenated bisphenol A, hydrogenated bisphenol A ethylene oxide adduct, hydrogenated bisphenol A propylene oxide adduct, glycerin Trimethylolethane, trimethylolpropane, trishydroxymethylaminomethane, pentaerythritol, dipentaerythritol,
There are sorbitol and the like, and among them, a linear aliphatic diol having an even number of carbon atoms is preferable. Particularly preferably, ethylene glycol, 1,4-butylene glycol, 1,
6 hexanediol.

Next, the polyisocyanate compound (G) will be described. Typical examples of the polyisocyanate compound (G) include polymethylene polyphenyl isocyanate, diphenylmethane diisocyanate, tolylene diisocyanate, triphenylmethane triisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, and isophorone diisocyanate. ,
Xylylene diisocyanate, lysine isocyanate and the like. Also, adducts of these diisocyanates and polyols, and nullates can be used.
Of these, diisocyanate compounds are preferred from the viewpoint of lowering the viscosity and the degree of crystallinity, and hexamethylene diisocyanate is particularly preferred.

The reaction between the polyisocyanate compound (G) and the polyol component (E) and / or (F) is carried out at 100 to 200 ° C.
And / or the ratio of the hydroxyl groups in (F) to the isocyanate groups in the polyisocyanate compound (G) is such that the hydroxyl groups are excessive. At that time, a reaction catalyst such as a tin compound can be used. At the time of this reaction, a chain extender (H) can be used in combination to increase the urethane group concentration and control the crystallinity.

Typical examples of the chain extender (H) include ethylene glycol, 1,3-propylene glycol, 1,2-propylene glycol, and 2-methyl-
1,3-propylene glycol, 1,4-butylene glycol, 1,3-butylene glycol, 1,6-hexanediol, diethylene glycol, dipropylene glycol, neopentyl glycol, triethylene glycol, 1,4-cyclohexanedimethanol, Bisphenol A ethylene oxide adduct, bisphenol A propylene oxide adduct, cyclohexane dimethanol, hydrogenated bisphenol A, hydrogenated bisphenol A ethylene oxide adduct, hydrogenated bisphenol A
Propylene oxide adducts, glycerin, trimethylolethane, trimethylolpropane, trishydroxymethylaminomethane, pentaerythritol, dipentaerythritol, low molecular weight polyols such as sorbitol, among which the number of carbon atoms is even The use of linear aliphatic diols is preferred. In addition, polyethers such as polytetramethylene glycol and diamines such as hexamethylene diamine can be mentioned.

Regarding the method for introducing a carboxylic acid group into the crystalline polyurethane resin (B), the polyester resin (E)
A method of leaving a carboxylic acid group at the time of adjustment, or a method of introducing a remaining hydroxyl group and an esterification reaction with a polycarboxylic acid after completion of the urethane reaction, or a ring-opening addition reaction using a carboxylic anhydride. Can be used.

The crystalline urethane resin (B) is a component that exhibits excellent mechanical properties in the coating film, but preferably has a crystallization peak temperature of 30 to 150 ° C. When the urethane resin has a crystallization peak temperature of 30 to 150 ° C., the storage stability of the powder coating is good and the melt-kneading at the time of coating is easy. The crystallization peak temperature is JIS K7121.
It can be determined from the peak temperature of the DSC (differential scanning calorimetry) curve described in the method for measuring the transition temperature of plastic.

The melt viscosity of the crystallized polyurethane resin (B) is required to be low at the curing temperature in order to obtain good smoothness.
s or less, more preferably 0.00
The pressure is preferably 5 to 1 Pa · s or less.

Further, the crystalline polyurethane resin (B) preferably has a curable functional group, and especially preferably has a carboxyl group and / or a hydroxyl group. Considering the reactivity with (C) and the effect of improving mechanical properties, the acid value is 5
It is preferable that the hydroxyl value is 5 to 100 mgKOH / g. More preferably, the crystalline polyurethane resin (B) has an acid group and a hydroxyl group, and the total of the acid value and the hydroxyl value is 50 mgKOH /
g or less.

The compounding weight ratio (A) / (B) of the polyester resin (A) and the crystalline polyurethane resin (B) may be any compounding ratio that achieves the effects of the present invention, and is preferably 9
9/1 to 70/30.

Next, as a curing agent reactive with an acid group ,
A curing agent capable of reacting with a carboxyl group is preferred, and a glycidyl group-containing acrylic polymer, triglycidyl isocyanurate, and hydroxyalkylamides are preferred. Examples of the glycidyl group-containing acrylic resin include a (methyl) glycidyl methacrylate copolymer obtained by copolymerizing (methyl) glycidyl methacrylate with another polymerizable monomer. On the market, "FINEDIC A-261" (Dainippon Ink & Chemicals, Inc.) as (methyl) glycidyl methacrylate copolymer and "Araldite PT-810" (Ciba Specialty Chemicals) as triglycidyl isocyanurate are commercially available. I have.
As hydroxylalkylamides, bis (N, N
-Dihydroxyalkyl) adipamide, "PRI
“MID XL552” (EMS) is commercially available.
Also, a diglycidyl ether type epoxy resin of bisphenol A can be used.

The glycidyl group-containing acrylic polymer refers to a vinyl copolymer which is solid at ordinary temperature and has a glycidyl group at the terminal or side chain of the molecule. At least one compound selected from the group consisting of glycidyl acrylate, glycidyl methacrylate, β-methyl glycidyl acrylate and β-methyl glycidyl methacrylate, can be used alone or in combination of two or more, or can be copolymerized with these compounds Copolymers obtained by copolymerizing other vinyl monomers in combination with the other vinyl monomers can be suitably used.

The amount of the (β-methyl) glycidyl (meth) acrylate used at that time is preferably in the range of about 10 to 100% by weight of the total monomers, more preferably A range of 15 to 90% by weight is appropriate. This use amount is preferable because the mechanical strength of the coating film becomes good.

The glycidyl group-containing acrylic polymer preferably has a number average molecular weight in the range of about 500 to about 15,000, more preferably 700 to 15,000.
5,000.

When the number average molecular weight of the copolymer is within the above range, the mechanical strength and the like are good, and the resulting coating film has excellent smoothness and the like.

Further, as other vinyl monomers which can be used in preparing the glycidyl group-containing acrylic polymer, only typical ones may be mentioned, such as methyl acrylate, ethyl acrylate and butyl. Various acrylates, such as acrylate or cyclohexyl acrylate; methyl methacrylate, ethyl methacrylate, n-, iso- or tert
Various methacrylates, such as butyl methacrylate, cyclohexyl methacrylate or benzyl methacrylate; (meth) acrylic acid, crotonic acid, itaconic acid, maleic acid or fumaric acid,
Various carboxyl group-containing monomers; mono- or of various polyvalent carboxyl group-containing monomers such as itaconic acid, maleic acid or fumaric acid, and monoalkyl alcohol having 1 to 18 carbon atoms. Diesters; 2-
Hydroxyethyl vinyl ether, 3-hydroxypropyl vinyl ether, 2-hydroxypropyl vinyl ether, 4-hydroxybutyl vinyl ether, 3-hydroxybutyl vinyl ether, 2-hydroxy-2-
Vinyl ethers having various hydroxyl groups such as methylpropyl vinyl ether, 5-hydroxypentyl vinyl ether or 6-hydroxyhexyl vinyl ether; or addition reaction products of various vinyl ethers as described above with ε-caprolactone object;
2-hydroxyethyl (meth) allyl ether, 3-hydroxypropyl (meth) allyl ether, 2-hydroxypropyl (meth) allyl ether, 4-hydroxybutyl (meth) allyl ether, 3-hydroxybutyl (meth) allyl ether, Various hydroxyl-containing allyl ethers, such as 2-hydroxy-2-methylpropyl (meth) allyl ether, 5-hydroxypentyl (meth) allyl ether or 6-hydroxyhexyl (meth) allyl ether; Addition reaction products of various allyl ethers as described above with ε-caprolactone; 2-hydroxyethyl (meth) acrylate,
2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 3-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth)
Various hydroxyl-containing (meth) acrylates such as acrylate, polyethylene glycol mono (meth) acrylate or polypropylene glycol mono (meth) acrylate; and various (meth) acrylates as described above, and ε- The main component of the addition reaction of caprolactone (the main component of the addition reaction product),

Various amino group-containing amides such as N-dimethylaminoethyl (meth) acrylamide, N-diethylaminoethyl (meth) acrylamide, N-dimethylaminopropyl (meth) acrylamide or N-diethylaminopropyl (meth) acrylamide Unsaturated monomers; various dialkylaminoalkyl (meth) acrylates such as dimethylaminoethyl (meth) acrylate or diethylaminoethyl (meth) acrylate; tert-butylaminoethyl (meth) acrylate, tert-butylaminopropyl ( Various amino group-containing monomers such as meth) acrylate, aziridinylethyl (meth) acrylate, pyrrolidinylethyl (meth) acrylate or piperidinylethyl (meth) acrylate Various α-olefins such as ethylene, propylene or butene-1; various halogenated olefins (halo olefins) such as vinyl chloride or vinylidene chloride except fluoroolefin; styrene, α-methylstyrene Or various aromatic vinyl monomers such as vinyltoluene; γ-
Various hydrolyzable silyl group-containing monomers such as (meth) acryloyloxypropyltrimethoxysilane, γ- (meth) acryloyloxypropyltriethoxysilane or γ- (meth) acryloyloxypropylmethyldimethoxysilane; vinyl acetate , vinyl propionate, vinyl butyrate, iso (an iso-) butyrate, vinyl caproate, vinyl caprylate, vinyl caprate, vinyl laurate, C ₉ becomes branched (branched) aliphatic carboxylic acid vinyl, C ₁₀ Various aliphatic carboxylic acids such as a branched aliphatic vinyl carboxylate, C ₁₁ branched aliphatic carboxylate or vinyl stearate; vinyl cyclohexanecarboxylate, vinyl methylcyclohexanecarboxylate, vinyl benzoate or p −
Various vinyl esters of a carboxylic acid having a cyclic structure such as vinyl tert-butyl benzoate.

The method for preparing the glycidyl group-containing acrylic polymer is not particularly limited, and various known and commonly used methods can be used and applied. In a solution, after a radical polymerization reaction, a method of obtaining a desired polymer by desolvation is particularly recommended in that the molecular weight can be easily adjusted, which is particularly recommended. I can do it.

The compounding amount of the curing agent (C) reactive with an acid group is equivalent to the acid group of the polyester resin (A) and, if necessary, the crystalline polyurethane resin (B) [｛(A) +
(B)｝ / (C)] is 1.3 / 1.0 to 1.0 / 1.3.
Is preferably within the range.

Next, a curing agent (D) reactive with a hydroxyl group
As for the above, polyisocyanate compounds and amino compounds are useful. Examples of the polyisocyanate compound include a polyisocyanate compound which is a raw material of a crystalline polyurethane resin, and a blocked isocyanate compound is preferable from the viewpoint of storage stability of the obtained powder coating.

Particularly typical examples of the blocked polyisocyanate compound include aliphatic diisocyanates such as hexamethylene diisocyanate and trimethylhexamethylene diisocyanate; cycloaliphatic diisocyanates such as xylylene diisocyanate and isophorone diisocyanate; tolylene diisocyanate Organic diisocyanates such as aromatic diisocyanates such as 4,4'-diphenylmethane diisocyanate, or adducts of these organic diisocyanates with polyhydric alcohols, low molecular weight polyester resins (polyester polyols), water and the like. Polymers of organic diisocyanates (including isocyanurate type polyisocyanate compounds) and isocyanate biuret as described above Various blocking agents conventionally known polyisocyanate compounds such as body, lactams, there are such as those obtained allowed blocking like oximes, by way of example of a commercially available product, VESTANAT B1358 /
100, BESTAGONB1065, B1530
(All are block polyisocyanates manufactured by Degussa-Hüls, Germany), Cleran UI, Cleran TPLS
2122 (block polyisocyanate manufactured by Sumitomo Bayer Urethane Co., Ltd.).

Further, as the polyisocyanate compound,
A so-called self-blocking type compound having a uretdione bond in the molecule can also be used. Examples of such self-block type polyisocyanates include VESTAGON BF1540 and EP-B.
F1300 (all self-block type block polyisocyanates having a uretdione bond manufactured by Degussa Huls, Germany) and Cleran TPLS214
7 (self-block type block polyisocyanate having a uretdione bond manufactured by Sumitomo Bayer Urethane Co., Ltd.)
G). It is particularly preferable to use a so-called self-blocking type compound having a uretdione bond in the molecule as long as the blocking agent does not volatilize during curing.

Examples of the amino compound include condensates obtained by reacting an amino group-containing compound such as melamine, urea and benzoguanamine with an aldehyde compound such as formaldehyde and glyoxal by a known method. Alternatively, etherified compounds obtained by etherifying these condensates with alcohols include, for example, hexamethoxymethylmelamine “CYMEL 303” (Mitsui Cytec),
Furthermore, "POWDERLINK PL-1174"
(American Cyanamid Co.) and the like.

The amount of the curing agent (D) reactive with hydroxyl groups is determined by the equivalent ratio [｛(A) + to the hydroxyl groups of the polyester resin (A) and the crystalline polyurethane resin (B).
(B)｝ / (C)] is 1.3 / 1.0 to 1.0 / 1.3.
Is preferably within the range.

The powder of the present invention comprising a polyester resin (A), a crystalline polyurethane resin (B), a curing agent (C) reactive with an acid group and a curing agent (D) reactive with a hydroxyl group. In order to adjust the target powder coating using the resin composition for body coating, for example, various known and commonly used methods can be used as they are.

That is, in general, a polyester resin (A) and a crystalline polyurethane resin (B) a curing agent (C) reactive with an acid group and a curing agent (D) reactive with a hydroxyl group, If necessary, epoxy resin, pigment,
A so-called mechanical method in which various additive components such as a curing accelerator, a surface conditioner, an anti-blocking agent, an ultraviolet absorber, and an antioxidant are mixed, melt-kneaded, and then finely pulverized. The pulverization method is recommended because it is particularly simple.

The resin composition for a powder coating according to the present invention thus obtained and the powder coating obtained from the resin composition for a powder coating are coated on a substrate to be coated by various known and common methods. By being painted and then baked, the intended cured coating film is formed on the substrate to be coated.

Here, as typical examples of the above-mentioned substrates to be coated, various metal materials such as iron, aluminum, stainless steel, chromium plating, galvanized sheet, and tin plate may be used. Or metal products; tiles; glass; various inorganic building materials; heat-resistant plastics, wood, etc., specifically, automobile bodies or automobile (for) parts; motorcycles or motorcycle (for) parts Various building materials such as gates or fences; Various materials for building interior and exterior such as aluminum sashes; Various iron or non-ferrous metal materials such as aluminum wheels or plastic products, and woodworking materials There are products. In addition, those subjected to surface treatment such as chemical conversion treatment, zinc phosphate treatment, and chromate treatment, and those subjected to electrodeposition coating are also included.

The coating film using the resin composition for powder coating of the present invention has a smoother coating film without impairing the storage stability as compared with the case of using the conventional polyester powder coating composition. Properties, mechanical properties, weather resistance, etc. are significantly improved.

[0045]

EXAMPLES Next, the present invention will be described more specifically with reference examples, examples and comparative examples, but the present invention is by no means limited to only these illustrative examples. . In the following, all parts and percentages are by weight unless otherwise specified. The characteristic values of Reference Examples were measured or evaluated by the following methods.

Hydroxyl value: A polyester resin and a crystalline polyurethane resin sample are dissolved in a mixed solution of acetic anhydride and pyridine, and the mixture is heated under reflux at 100 ° C. for 1 hour to acetylate the hydroxyl groups, and then ion-exchanged water is added to further acetylate the hydroxyl groups. After heating under reflux, the mixture was cooled and back titrated with a 0.5 N solution of potassium hydroxide in toluene / methanol. (unit:
mg KOH / g).

Acid value: (unit: mg KOH / g) Polyester resin (A): A polyester resin sample was dissolved in benzyl alcohol and titrated with a 0.1 N potassium hydroxide-methanol solution. Crystalline polyurethane resin (B): A crystalline polyurethane resin sample was dissolved in cyclohexanone and titrated with a 0.1 N potassium hydroxide-methanol solution.

Crystallization peak temperature: Measured according to JIS K7121 using a DSC-3100 Differential Thermal Scanning Calorimeter (manufactured by Mac Science). (unit:
° C) Glass transition temperature Tg: Differential scanning calorimetry can be used, and at a heating rate of 10 ° C per minute, the glass transition temperature Tg
Is obtained at the first inflection point. (Unit: ° C)

Melt viscosity: Cone-plate type viscometer CV-
Using 1S [Toa Kogyo Co., Ltd.], corn CP-
5, the rotation speed was set to 750 rpm, and the plate temperature was 18
The melt viscosity at 0 ° C. was measured. (Unit: Pa · s)

Softening point: Using a ring and ball type automatic softening point tester (Akimine Co., Ltd.), in a glycerin heating bath at 3 ° C. /
The temperature was raised at a rate of one minute, the sample began to soften, and the temperature when the sphere dropped was measured (unit: ° C)

Reference Examples 1 to 3 [Examples of Preparation of Polyester Resin (A)]

Reference Example 1 [Preparation of Polyester Resin [A-1]] In a reaction vessel equipped with a stirrer, a thermometer, a rectification tower and a nitrogen gas inlet, 206 parts of neopentyl glycol, 1,4
-285 parts of cyclohexanedimethanol are charged, and the mixture is heated to 150 ° C while stirring under a nitrogen atmosphere, and 616.4 parts of isophthalic acid, 28.6 parts of adipic acid and 0.5 part of dibutyltin oxide are further added. In addition, 240 ° C
Temperature. The dehydration condensation reaction is continued at the same temperature, the hydroxyl value is 20 mgKOH / g, and the acid value is 15 mg / KOH / g.
Thus, a polyester resin having a glass transition temperature (Tg) of 60 ° C. by differential scanning calorimetry was obtained. This is abbreviated as polyester resin [A-1].

Reference Example 2 (same as above) In a reaction vessel equipped with a stirrer, a thermometer, a rectification tower and a nitrogen gas inlet, 434.4 parts of neopentyl glycol and 7 parts of trimethylolpropane were charged, and the mixture was placed under a nitrogen atmosphere. The temperature was raised to 150 ° C. while stirring continuously, and terephthalic acid 2
11.5 parts, 493.6 parts of isophthalic acid and 0.5 part of dibutyltin oxide were further added, and the temperature was raised to 240 ° C. The dehydration condensation reaction is continued at the same temperature, and the hydroxyl value is 20 m
A polyester resin having a gKOH / g, an acid value of 20 mg / KOH / g and a Tg by differential scanning calorimetry of 63 ° C. was obtained. 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 tower, and a nitrogen gas inlet, 393.2 parts of neopentyl glycol and 34 parts of trimethylolethane were charged and placed under a nitrogen atmosphere. The temperature was raised to 150 ° C while stirring continuously, and isophthalic acid 7
19.1 parts and 0.5 part of dibutyltin oxide were further added, and the temperature was raised to 240 ° C. The dehydration condensation reaction was continued at the same temperature, and the hydroxyl value was 15 mgKOH / g and the acid value was 30.
mg / KOH / g, Tg of 5 by differential scanning calorimetry
A 7 ° C. polyester resin was obtained. This is abbreviated as polyester resin [A-3].

Preparation Example 1 of Crystalline Polyurethane Resin (B) 1: Preparation Example of Polyester Polyol (E) Reference Examples 4 to 5, Preparation of Polyester Resin (E)] J) and the polycarboxylic acid component (I) were charged in the amounts shown in Table 1 into a reaction vessel equipped with a stirrer, thermometer, rectification tower and nitrogen gas inlet, and stirring was continued in a nitrogen atmosphere. While 1
The temperature was raised to 50 ° C.

0.5 parts of dibutyltin oxide was added thereto, the temperature was raised to 240 ° C., and the dehydration condensation reaction was continued at the same temperature to obtain a hydroxyl group-containing polyester resin. Hereinafter, these will be referred to as polyester resins (E-
Abbreviated as 1) to (E-2).

[0057]

[Table 1]

<< Footnotes in Table 1 >> 1) 1,4BG: 1,4-butanediol 2) EG: ethylene glycol

Reference Examples 6 to 10 (Examples of Preparation of Crystalline Urethane Resin [B]) The polyol component and the polyester component were used in the amounts shown in Table 2 and a stirrer, thermometer, rectification tower and nitrogen gas inlet were used. The reaction vessel was charged and heated to 150 ° C. while stirring in a nitrogen atmosphere.

Here, if necessary, a chain extender [G] and dibutyltin dilaurate as a urethanizing catalyst are added.
The urethanization reaction was carried out at the same temperature for an additional time to obtain a crystalline urethane resin (B). further,
A carboxylic acid group was introduced by adding a carboxylic anhydride in an amount shown in Table 2 and performing a ring-opening addition reaction. Less than,
These are made of crystalline polyester urethane resin [B-1]
Abbreviated as [B-5].

[Table 2]

Reference Example 11 [Preparation Example of Glycidyl Group-Containing Acrylic Polymer (C) of the Present Invention] A reaction vessel equipped with a stirrer, a thermometer, a condenser and a nitrogen gas inlet was charged with 500 parts of xylene. The temperature was raised to 135 ° C. in a nitrogen atmosphere.

Here, 350 parts of methyl methacrylate and 150 parts of glycidyl methacrylate, 3 parts of azobisisobutyronitrile and 20 parts of tert-butyl peroxyoctoate (abbreviated as TBPO).
Of the mixture was added dropwise over 4 hours, and after completion of the addition, the mixture was kept at the same temperature for 10 hours.

After the completion of the polymerization reaction, the resin solution thus obtained is kept at 170 ° C. under a reduced pressure of about 30 Torr to distill off xylene. Softening point 110 ° C
As a result, an intended glycidyl group-containing acrylic polymer (C) having an epoxy equivalent of 550 and a number average molecular weight of 2,500 was obtained. Hereinafter, this is abbreviated as polymer (C-1).

Examples 1 to 5 and Comparative Examples 1 to 4 (Preparation of Powder Coating Compositions and Powder Coatings) The resin compositions were blended and the respective compositions thus obtained were melt-kneaded at 90 ° C. using “Co-kneader PR-46” (a single-axis kneader manufactured by Bus, Switzerland). Then, the mixture was finely pulverized and further classified with a 200-mesh wire net to have an average particle size of 30.
Various powder coatings of ４０40 μm were prepared. Each of these powder coatings is referred to as [P-1] to [P-10], [Q-1] to
Abbreviated as [Q-4].

[Table 3]

[0065]

[Table 4]

<< Footnotes of Tables 3 and 4 >> 1) B1530: "V" manufactured by Degussa-Hüls, Germany
Estagon B1530 ", a block polyisocyanate compound in which a nurate of isophorone diisocyanate is blocked with ε-caprolactam. 2) BF1540: “VESTAGON BF” manufactured by Dojo
1540 ", a block polyisocyanate compound in which isophorone diisocyanate is self-blocked with a uretdione bond. 3) Acronal 4F: a surface conditioner manufactured by BASF, Germany. 4) CR-90: Rutile-type titanium oxide "Taipe CR-90" manufactured by Ishihara Sangyo Co., Ltd.

Examples 1 to 5 and Comparative Examples 1 to 4 Various coating films as shown in Table 7 were prepared according to the following coating film forming method, and then the respective coating films thus obtained were prepared. Were subjected to a coating film performance test.

That is, the powder coatings [P-1] to [P-
5] and [Q-1] to [Q-4], various coating films were produced in accordance with the following coating film forming method.

The substrate used as a substrate to be coated may be 0.1 to 1 μm.
An 8 mm thick "Bondalite # 3030" [mild steel sheet treated with a zinc phosphate-based treating agent manufactured by Nippon Parkerizing Co., Ltd.] was used.

Powder coatings [P-1] to [P-5], [Q-
Each of [1] to [Q-4] was subjected to electrostatic powder coating so that the film thickness after baking was 50 μm, and then baking was performed at 200 ° C. for 20 minutes. An object to be coated having a coating film of a powder coating (hereinafter, abbreviated as a powder coating film) was obtained.

The thus obtained powder coating on the substrate was evaluated for smoothness, impact resistance, bending resistance and accelerated weather resistance. Tables 5 and 6 summarize the results.
Shown in the table.

[0072]

[Table 5]

[0073]

[Table 6]

The procedure of evaluation judgment is as follows. Gloss: A 60 ° gloss value was measured with a gloss meter. -Smoothness: Evaluation was visually determined. The evaluation criteria are as follows. ：: A very smooth smooth painted surface. Δ: Coated surface on which fine dust skin is observed.

Impact resistance: Du-po on the coating surface
500g on 1/2 inch diameter punch with nt impact tester
The impact was determined by the height (cm) at which the weight of the sample was dropped to cause cracking.

Bending resistance: Cracking of the coating film at the portion where the coating surface was bent at 90 ° with the coating surface up at 25 ° C. was judged. ：: No crack was observed at all. ×: Cracks are observed on part or all of the surface.

Accelerated weather resistance: The 60 ° gloss after a 1000-hour sunshine weatherometer was measured, and the gloss retention rate (%) of the initial gloss was evaluated.

[0078]

The resin composition for a powder coating according to the present invention comprises:
It has the characteristics of excellent smoothness, flexibility and weather resistance of the coating film,
Flexibility, weather resistance and the like are remarkably improved as compared with conventional powder coating compositions.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C09D 175/04 C09D 175/04 175/06 175/06 175/08 175/08 F-term (Reference) 4J034 BA03 BA07 BA08 CA03 CA04 CA05 CB03 CC03 CC05 CC08 CC26 CC52 CC61 CC62 CC65 DA01 DB03 DB04 DB07 DF14 DF15 DF16 DF17 DF20 DF21 DF22 DF27 DF29 DG16 GA55 HA06 HA07 HA08 HC03 HC12 HC22 HC35 HC46 HC61 HC64 HC67 HC71 HC73 Q42 KB03 CG142 CH172 DD041 DD051 DD061 DD081 DD121 DG042 DG112 DG132 DG302 GA03 GA06 GA07 GA08 KA03 MA02 NA03 NA09 PA02 PB02 PB04 PB05 PB07 PB09 PC02 PC03 PC05 PC08

Claims (12)

[Claims] (1) at least 50 mol% of the total acid component is composed of isophthalic acid or a derivative thereof, and has a reactivity with a hydroxyl group or a polyester resin (A) having an acid group and a hydroxyl group, a crystalline polyurethane resin (B) and an acid group. A resin composition for a powder coating, comprising a curing agent (C) and a curing agent (D) reactive with a hydroxyl group. 2. The resin composition for a powder coating according to claim 1, wherein the curing agent (C) reactive with an acid group is a glycidyl group-containing acrylic polymer. 3. The resin composition for a powder coating according to claim 1, wherein the curing agent (D) reactive with a hydroxyl group is a blocked polyisocyanate compound. 4. The resin composition for powder coatings according to claim 1, wherein the crystalline polyurethane resin (B) has an acid group and / or a hydroxyl group. 5. The resin composition for a powder coating according to claim 1, wherein the crystalline polyurethane resin (B) has a crystallization peak temperature of 30 to 150 ° C. 6. A crystalline polyurethane resin (B) comprising a polyester polyol (E) and / or a polyether polyol (F) and a polyisocyanate compound (G) as essential components, and optionally a chain extender (H). And a carboxyl group-containing polyurethane resin obtained by reacting a polycarboxylic acid compound or an acid anhydride thereof with the hydroxyl group-containing polyurethane resin. The resin composition for a powder coating according to any one of claims 1 to 5. 7. A polyester polyol (E) comprising a polycarboxylic acid (I) having 2 to 22 carbon atoms and a polycarboxylic acid (I) having 2 carbon atoms.
The resin composition for a powder coating according to claim 6, wherein the resin composition is a hydroxyl group-containing polyester resin obtained from the polyol (J). 8. The resin composition for a powder coating according to claim 1, wherein the crystalline polyurethane resin (B) has an acid value of 5 to 100 mgKOH / g. 9. The resin composition according to claim 1, wherein the crystalline polyurethane resin (B) has a hydroxyl value of 5 to 100 mgKOH / g. 10. The crystalline polyurethane resin (B) comprises 1
The resin composition for powder coating according to any one of claims 1 to 9, which is a crystalline polyurethane resin having a melt viscosity at 80 ° C of 10 Pa · s or less. 11. The composition according to claim 1, further comprising a curing agent (K).
0. The resin composition for a powder coating according to any one of 0. 12. The resin composition for a powder coating according to claim 11, wherein the curing agent (K) is a blocked polyisocyanate compound having a uretdione bond.