JPH0978010A - Thermosetting powder coating composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a thermosetting powder coating composition excellent in antiblocking property of the coating and acid and weather resistances, etc., of its coating film. SOLUTION: This thermosetting powder coating comprises, as essential ingredients, (A) an epoxy group-containing copolymer, having the glass transition temperature of 40-100 deg.C and the number average molecular weight of 1000-15000, produced by copolymerizing the following radical-polymerizable unsaturated monomers [(a) 25-50wt.% of an unsaturated monomer containing epoxy group, (b) 5-45wt.% of a styrene monomer, (c) 10-50wt.% of an isobornyl acrylate monomer and (d) 0-60wt.% of unsaturated radical-polymerizable monomers excluding the prescribed monomers] in an organic solvent then after the polymerization, removing the solvent and (B) a cross-linking agent.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a novel thermosetting powder coating composition.

[0002]

2. Description of the Related Art Conventionally, since powder coating compositions contain almost no volatile components such as organic solvents, they have attracted attention as coatings excellent in pollution prevention and global environment protection.

In general, articles used outdoors (for example,
Thermosetting powder coatings are applied to automobile outer panels, etc., and the coating film formed from itself is strongly required to have performances such as finished appearance, acid resistance, and weather resistance, as can be considered from its application. It

A method for improving the finished appearance of the powder coating composition can be achieved by lowering the glass transition temperature of the powder coating resin or lowering the molecular weight to lower the melt viscosity of the resin. Moreover, the blocking resistance of the powder coating was poor, and it was difficult to satisfy the performance of both.

As a method for solving the above-mentioned problems, a resin obtained by copolymerizing a monomer containing a polycyclic aliphatic hydrocarbon group such as isobornyl methacrylate is used as a resin for thermosetting powder coating (Japanese Patent Laid-Open No. 7-58200). No. 166103), the isobonyl ring is opened during the production of a powder resin by removing the solvent after carrying out a solution polymerization reaction of the isobonyl methacrylate, and the glass of the resin There is a drawback that the transition temperature is lowered, and thus the blocking resistance of the coating is deteriorated. Further, a powder coating composition using the resin has a problem that it turns yellow during baking and curing.

[0006]

Means for Solving the Problems As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that a specific amount of an epoxy group-containing unsaturated monomer and isobornyl acrylate monomer, respectively. -, A coating composition using a copolymer obtained by subjecting a styrene-based monomer to a radical copolymerization reaction in an organic solvent and then removing the solvent is used as a resin for a thermosetting powder coating, has a blocking resistance and a finished appearance. As a result, they have found that they are excellent, and have completed the present invention.

That is, the present invention comprises the following components (A) the following radical-polymerizable unsaturated monomer components (a) 25 to 50% by weight of an epoxy group-containing unsaturated monomer, and (b) 5 to 45% by weight of a styrene monomer. %, (C) 10 to 50% by weight of isobornyl acrylate monomer, and (d) 0 to 60% by weight of other radically polymerizable unsaturated monomer other than the above-mentioned radical copolymerization in an organic solvent. An epoxy group-containing copolymer having a glass transition temperature of 40 to 100 ° C. and a number average molecular weight of 1,000 to 15,000, which is obtained by removing the solvent after the reaction.
And (B) a thermosetting powder coating composition containing a crosslinking agent as an essential component.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The epoxy group-containing copolymer (A) used in the coating composition of the present invention comprises (a) an epoxy group-containing unsaturated monomer-25 to 50% by weight, and (b) a styrene-based monomer-5. ˜45% by weight, (c) 10 to 50% by weight of isobornyl acrylate monomer, and (d) 0 to 60% by weight of other radically polymerizable unsaturated monomer other than those mentioned above in an organic solvent. It is an epoxy group-containing copolymer having a glass transition temperature of 40 to 100 ° C. and a number average molecular weight of 1,000 to 15,000, which is obtained by desolvating after a radical copolymerization reaction.

Examples of the epoxy group-containing unsaturated monomer (a) include, for example, glycidyl (meth) acrylate, glycidyl allyl ether, 3,4-epoxycyclohexylmethyl (meth) acrylate, and β-methylglycidyl. (Meth) acrylate, allyl glycidyl ether and the like can be mentioned. These monomers can be used alone or in combination of two or more. Among these, glycidyl (meth) acrylate and β-methylglycidyl methacrylate are particularly preferable. The β-methylglycidyl methacrylate is excellent in blocking resistance and smoothness. Also,
Both can be used in combination, and the mixing ratio thereof is preferably in the range of about 5 to 100% by weight of β-methylglycidyl methacrylate in terms of the total amount of both.

Examples of the styrene-based monomer (b) include styrene and α-methylstyrene. These monomers can be used alone or in combination of two or more.

Other monomers (d) include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, iso. -Butyl (meth) acrylate, tert-butyl (meth) acrylate, octyl (meth) acrylate, lauryl (meth) acrylate, dodecyl (meth) acrylate, stearyl (meth) acrylate _C1-24 alkyl esters of (meth) acrylic acid such as; cycloaliphatic (meth) acrylate, alicyclic ring-containing (meth) acrylic acid esters such as tricyclodecanyl (meth) acrylate 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate , Hydroxybutyl (meth) acrylate, (poly) ethylene glycol mono (meth) acrylate, hydroxyethyl vinyl ether and other unsaturated monomers containing hydroxyl groups; nitrile compounds such as (meth) acrylonitrile Vinyl ethers such as ethyl vinyl ether, butyl vinyl ether, cyclohexyl vinyl ether; tetrafluoroethylene, trifluoroethylene, vinylidene difluoride, trifluoromonochloroethylene, fluorocarbons such as vinyl fluoride Perfluoroalkyl (meth) acrylates such as olefins and perfluorobutylethyl (meth) acrylate, perfluoroisononylethyl (meth) acrylate, perfluorooctylethyl (meth) acrylate And other fluorine-containing unsaturated monomers. These monomers can be used alone or in combination of two or more.

The blending ratios of the above-mentioned monomers (a) to (d) are as follows in terms of the total amount of the monomers.

Monomer (a): in the range of 25 to 50% by weight, preferably 36 to 50% by weight, if less than 25% by weight, the acid resistance and workability are deteriorated, while if it exceeds 50% by weight, the coating composition The storage stability and the finished appearance (smoothness, yellowing, etc.) of the coating film are deteriorated, which is not preferable.

Monomer (b): in the range of 5 to 45% by weight, preferably 10 to 20% by weight, if less than 5% by weight, the acid resistance deteriorates, and if more than 45% by weight, the storage stability of the coating composition However, the finished appearance (smoothness, gloss, etc.) of the coating film is deteriorated, which is not preferable.

Monomer (c): in the range of 10 to 50% by weight, preferably 15 to 45% by weight, if less than 10% by weight, the melt flowability is poor and the coating film has a finished appearance (smoothness etc.) and acid resistance. On the other hand, if it exceeds 50% by weight, weather resistance, scratch resistance and the like are deteriorated, which is not preferable.

Monomer (d): 0 to 60% by weight, preferably 10 to 50% by weight.

The epoxy group-containing copolymer (A) can be produced by radically polymerizing the mixture of the monomers (a) to (d) in an organic solvent in the presence of a polymerization initiator.

As the organic solvent, the above-mentioned monomer (a) is used.
~ (D) can be used without particular limitation as long as it is an inert organic solvent that does not substantially react, specifically, for example, aromatic compounds such as toluene and xylene, amyl acetate, propyl acetate, butyl acetate, acetic acid. Acetate ester system such as methoxybutyl, methyl acetoacetate, ethyl acetoacetate, methyl cellosolve acetate, cellosolve acetate, diethylene glycol monomethyl ether acetate, carbitol acetate, dioxane, ethylene glycol diethyl ether, ethylene glycol dibutyl ether Examples thereof include ethers such as ether and diethylene glycol diethyl ether, and ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone. These can be used alone or in combination of two or more. In the organic solvent, it is preferable to use an aromatic system as a main component (50% by weight or more), and to use it in combination with a solvent other than the aromatic solvent, if necessary.

As the polymerization initiator, conventionally known radical polymerization initiators can be used without particular limitation. Specifically, for example, benzoyl, di-tert-butyl hydroper oxide, tert-butyl hydroper oxide, cumylper oxide, cumene hydroper.
Oxide, diisopropylbenzan hydroperoxide, tert-butylperoxybenzoate, laurylperoxide, acetylperoxide, te
rt-butyl-2-ethylhexanoate, tert-
Amylpa-oxy-2-ethylhexanoate, 1,
Peroxides such as 1,3,3-tetramethylbutylperoxy-2-ethylhexanoate; 2 ', 2'-azobisisobutyronitrile, azobisdimethylvaleronitrile, azobiscyclohexanecarbo Azo-based compounds such as nitrile can be used. These can be used alone or in combination of two or more.

The conditions of the radical polymerization reaction are not particularly limited, but are, for example, about 50 to 200 ° C., preferably about 70 to.
About 150 hours at a temperature range of about 1 to 24 hours, preferably about 5 hours.
A range from 10 to 10 hours is preferred.

The organic solvent solution of the above-mentioned epoxy group-containing copolymer (A) is used as a powder resin containing substantially no organic solvent by removing the solvent from the solution by a method such as decompression. If necessary, a component other than the copolymer (for example, a crosslinking agent (B),
Other compounds) can be mixed.

The epoxy group-containing copolymer (A) is
Glass transition temperature 40 to 100 ° C, preferably 50 to 80
It has a range of ° C and a number average molecular weight of 1,000 to 15,000, preferably 3,000 to 10,000. When the glass transition temperature is lower than 40 ° C, the coating has poor blocking resistance. On the other hand, when the glass transition temperature is higher than 100 ° C, the finished appearance (smoothness and the like) of the coating film is not preferable. When the number average molecular weight is less than 1,000, the blocking resistance of the coating material and the weather resistance of the coating film are poor, while when it exceeds 15,000, the finished appearance of the coating film is poor, which is not preferable.

The above-mentioned glass transition temperature (Tg, ° C) is a value obtained by converting the temperature (° K) calculated by the following Fox equation into (° C).

100 / Tg = W ₁ / Tg ₁ + W ₂ / Tg ₂ +
W ₃ / Tg ₃ + W ₄ / Tg ₄ ... (In the formula, W ₁ , W ₂ , W ₃ and W _{4 respectively} represent the weight% of the monomer used in the copolymer. , Tg ₁ , Tg ₂ , Tg
₃ and Tg ₄ represent the glass transition temperature (° K) of the same polymer. ) The glass transition temperature of the polymer is Polymer H
andbook (Second Edition,
J, Brandrup E, H, Immergut
(Eds.) And the manufacturer's catalog values were used unless otherwise stated in the literature. For example, Tg of isobornyl acrylate (Hitachi Kasei "stock" catalog value) is 367 °.
K, tricyclodecanyl acrylate is 379 ° K, tricyclodecanyl methacrylate is 448 ° K, and methylglycidyl methacrylate is 332 ° K.

Crosslinking agent (B) used in the coating composition of the present invention
Any known cross-linking agent can be used without particular limitation as long as it is a cross-linking agent that reacts and cures with the epoxy group of the epoxy group-containing copolymer (A). Specifically, for example, adipic acid, sebacic acid, suberic acid, succinic acid, glutaric acid,
Maleic acid, fumaric acid, dodecanedioic acid, pimelic acid, azelaic acid, itaconic acid, citraconic acid and other aliphatic polycarboxylic acids and their (poly) anhydrides; terephthalic acid,
Aromatic polycarboxylic acids such as isophthalic acid, phthalic acid, trimellitic acid and pyromellitic acid and their anhydrides; alicyclic polycarboxylic acids such as hexahydrophthalic acid, hexahydroisophthalic acid and methylhexahydrophthalic acid and their (Anhydrous) polycarboxylic acid compounds such as anhydrides, and, for example, benzyl-4-hydroxyphenylmethylsulfonium hexafluoroantimonate, triphenylsulfonium boron tetrafluoride, triphenylsulfonium antimony hexafluoride, p- Sulfonium salts such as tert-butylbenzyl tetrahydrothiophenium antimony hexafluoride; N, N-dimethyl-N-benzylanilinium antimony hexafluoride, N, N-dimethyl-N-benzylanilinium boron tetrafluoride, N , N-
Dimethyl-N- (4-chlorobenzyl) anilinium antimony hexafluoride, N, N-dimethyl-N- (tert
-Phenylethyl) anilinium antimony hexafluoride and other anilinium salts; N-benzyl-4-dimethylaminopyridinium antimony hexafluoride, N-benzyl-4
-Diethylaminopyridinium trifluoromethanesulfonic acid, N, N-dimethyl-N- (4-methoxybenzyl) toluidinium antimony hexafluoride, N, N-diethyl-N- (4-methoxybenzyl) toluidinium Toluidinium such as antimony hexafluoride Salts: Potential cationic polymerization catalysts such as phosphonium salts such as ethyltriphenylphosphonium antimony hexafluoride and tetrabutylphosphonium antimony hexafluoride, and the like. These can be used alone or in combination of two or more.
Further, among the above, dodecanedioic acid has good performances such as blocking resistance of coating material, finished appearance of coating film, and acid resistance.

When the (anhydrous) polycarboxylic acid compound is used with respect to 100 parts by weight of the epoxy group-containing copolymer (B), the mixing ratio of the crosslinking agent (B) is preferably about 10 to 50 parts by weight, preferably A range of about 15-40 parts by weight is preferred. Further, when a latent cationic polymerization catalyst is used, the range of about 0.05 to 5 parts by weight, preferably about 0.2 to 2 parts by weight is suitable. Further, when used in combination, about 10 to 50 parts by weight of (anhydrous) polycarboxylic acid compound, relative to 100 parts by weight of the epoxy group-containing copolymer (B),
A range of about 15 to 40 parts by weight and a latent cationic polymerization catalyst of about 0.05 to 5 parts by weight, preferably about 0.2 to 2 parts by weight is suitable. If the blending amount is less than the above range, the acid resistance, processability, weather resistance and the like are inferior, while if it exceeds the above range, the finished appearance is inferior, which is not preferable.

In the coating composition of the present invention, in addition to the above-mentioned components, for example, color pigments, fillers, fluidity regulators, antiblocking agents, ultraviolet absorbers, ultraviolet stabilizers, surface regulators, anti-armpits agents, and oxidation agents. Other compounds such as an inhibitor, a charge control agent, a curing accelerator, and other resins can be compounded as necessary.

The coating composition of the present invention is produced, for example, by adding a mixture of the crosslinking agent (B) and, if necessary, other additives to the organic solvent solution of the epoxy group-containing copolymer (A). As a method for producing a powder coating material using a solvent, a solid powder resin composition can be obtained by removing the solvent, and then finely pulverized by a pulverizer to produce a powder coating material. When the polymer (A) is a single solid powder resin containing no cross-linking agent (B) and, if necessary, other additives, the powder resin, cross-linking agent (B) and, if necessary, other After blending the additive mixture, the mixture can be dry-blended with a mixer, then melt-kneaded by heating, cooled, and finely pulverized. The average particle size of powder coating is about 1
A range of 100 microns, preferably about 5-60 microns is suitable.

The coating composition of the present invention is powder-coated on an object to be coated and baked (for example, at a temperature of about 140 to 200 ° C. for about 2 minutes).
The cured coating film can be formed by (0 to 40 minutes). The powder coating can be carried out by a method known per se, for example, electrostatic powder coating (corona charging type, friction charging type, etc.), fluidized coating and the like.

The coating film thickness is not particularly limited, but is generally in the range of about 30 to 100 μm, preferably about 40 to 80 μm.

[0031]

EXAMPLES The present invention will be described in detail below with reference to examples. Unless otherwise specified, "part" and "%" are based on weight.

Production Example of Copolymer (a) A reactor equipped with a thermometer, thermostat, stirrer, reflux condenser and dropping device was charged with 85 parts of toluene and heated to 110 ° C. while blowing nitrogen gas. Upon heating, 15 parts of styrene, 37 parts of isobornyl acrylate, 3 parts of n-butyl methacrylate, iso-butyl methacrylate.
9 parts, glycidyl methacrylate 26 parts, methylglycidyl methacrylate 10 parts, 2,2′-azobis (2
A mixture of 3 parts of (methylbutyronitrile) was added dropwise over about 3 hours. After the dropping was completed, the reaction was terminated by leaving it at 110 ° C. for 2 hours. Then, toluene was removed by vacuum distillation, and the mixture was cooled to produce a copolymer (a).

Production Examples of Copolymers (b) to (p) Copolymers (b) to (p) were produced in the same manner as the production of copolymer (a) with the formulations shown in Table 1.

[0034]

[Table 1]

Example 1 100 parts of the copolymer (a) and 26 parts of dodecanedioic acid were dry blended with a Henschel mixer at room temperature, and then melt-kneaded with an extruder. Then, after cooling, it was finely pulverized with a pin desk mill and filtered through 150 mesh to obtain Example 1.
Powder coatings were produced.

Examples 2 to 10 Copolymers (b) to (j) were used in the same manner as in Example 1 to produce powder coating materials of Examples 2 to 10. The types of copolymers used in Examples 2 to 10 were the copolymers shown in Table 2.

Comparative Examples 1 to 6 Copolymers (k) to (p) were used to produce the same as in Example 1 to obtain powder coating materials of Comparative Examples 1 to 6.

The results are shown in Table 2.

[0039]

[Table 2]

In Table 2, the test was conducted as follows.

Blocking resistance of the coating material The powder coating material is placed in a cylindrical container having a bottom area of about 20 cm ² so that the height is 6 cm, and allowed to stand at 30 ° C. for 7 days. Then, the powder coating material was taken out and the state was observed. The evaluation is as follows. ◎ is good without any lumps, ○ is slightly lumps but can be easily loosened with fingers, △ is lumps that cannot be loosened without pressing firmly with fingers, × is lumps that can be loosened even with strong pressing with fingers None , coating film preparation conditions Paint and cured coating film were prepared using powder paint.

Thickness 0.8 mm after zinc phosphate conversion treatment
Epoxy cation electrodeposition paint was applied to the dull steel plate of No. 2 to give a dry coating film thickness of about 20 microns, and an automobile intermediate coat surfacer was dried on the baked electrodeposition coating film to a dry film thickness of about 20 microns. After baking as described above, the resultant was sanded with a # 400 sandpaper, drained and dried. Then, Magicron base coat HM-22 (Kansai Paint Co., Ltd., metallic paint, trade name) was applied so as to have a cured film thickness of about 15 microns, and baked and cured at 140 ° C. for 30 minutes in a dryer for testing. I used it as a material.

Then, powder coating is electrostatically coated on the surface of the material to a film thickness of about 70 μm, and dried by a drier to obtain 160
It was heat-cured at 30 ° C. for 30 minutes. The following test was performed on the obtained coated plate.

Appearance of Coating Film The finish appearance of the coating film was evaluated according to the following criteria from glossiness and smoothness. ⊚ is good, ◯ is slightly inferior in smoothness but good in gloss, Δ is slightly inferior, × is inferior, and the specular reflectance was measured at 60 ° gloss 60 °. It was measured according to JISK-5400.

0.4 cc of acid resistant 40% sulfuric acid water was dropped on the surface of the coating film, heated for 15 minutes on a hot plate heated to 85 ° C., washed with water, and the coating film was observed. evaluated. ⊚ is good with no change, ◯ is very good with a slight step difference at the interface between the drip part and the non-drip part, and Δ is inferior because there is a step difference at the interface between the drip part and the non-drop part No., X indicates that the coating film was whitened, yellow coating was applied to the test coated plate (metallic base coat) prepared under the conditions for forming the coating film, and Magicron clear coat (manufactured by Kansai Paint Co., Ltd., clear -Paint, trade name) was applied using an air spray gun so that the cured film thickness would be about 40 microns, and baked and cured at 140 ° C for 30 minutes in a dryer to obtain a coated plate for comparison test. The test coated plate and the comparative coated plate were visually evaluated for comparative yellowness. The evaluation criteria are as follows. ○: no abnormality, △: slightly yellowish compared to the comparative coated plate, ×: marked yellowish compared to the comparative coated plate, exposed to weather-resistant sunshine weatherometer for 1500 hours After that, the coating film was observed and evaluated according to the following criteria. ○: No abnormality, △: Blurred, small cracks occurred, ×: Significant blur, cracked,

[0046]

INDUSTRIAL APPLICABILITY The coating composition of the present invention can be used in the epoxy copolymer used in the coating composition, especially in styrene monomer-5.
A copolymerization amount of up to 45% by weight makes it possible to improve the acid resistance without lowering the weather resistance, and the isobonyl acrylate monomer is a stable copolymer in the powdering technique after solution polymerization. By further copolymerizing 10 to 50% by weight, the coating finish is improved without deteriorating the anti-blocking property of the coating, which is a contradictory performance.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Nobushige Numa 4-17-1, Higashi-Hachiman, Hiratsuka-shi, Kanagawa Kansai Paint Co., Ltd. (72) Naoto Adachi 4--17-1, Higashi-Hachiman, Hiratsuka, Kanagawa Kansai Paint Co., Ltd.

Claims (1)

[Claims] 1. The following component (A) the following radically polymerizable unsaturated monomer component (a) 25 to 50 wt% of an epoxy group-containing unsaturated monomer, (b) 5 to 45 wt% of a styrene monomer, c) Isobornyl acrylate monomer 10 to 50% by weight, and (d) Other radically polymerizable unsaturated monomer other than those described above 0 to 60% by weight were subjected to radical copolymerization reaction in an organic solvent. Then, an epoxy group-containing copolymer having a glass transition temperature of 40 to 100 ° C. and a number average molecular weight of 1,000 to 15,000, which is obtained by removing the solvent.
And a thermosetting powder coating composition comprising (B) a crosslinking agent as an essential component.