JP2000063705A - Thermosetting powder coating material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a thermosetting powder coating material capable of forming coating films excellent in finish and surface appearance, and useful as a top clear coating for automobiles, etc., by dissolving a specific resin in an organic solvent, grinding in a wet process, and then pulverizing into powder coating material. SOLUTION: This powder coating material is obtained by compounding (A) a resin mixture comprising the following three components: (i) a resin obtained by the radical polymerization of (a) a vinylic monomer having a sulfonic acid group and/or a sulfonate salt group in an amount of 0.1-20 pts.wt. with (b) another vinylic monomer having no functional group, (ii) a resin prepared by the radical polymerization of the component (a) in an amount of 0.1-520 pts.wt. and (c) a vinylic monomer having an epoxy group and/or a hydroxyl group in an amount of 15-50 pts.wt. with the component (b), and (iii) a resin made by the radical polymerization of the component (c) in an amount of 15-50 pts.wt. with the component (b), (B) a powdery hardener component which is solid at room temperature and can crosslink with a functional group of the component A, and (C) an organic solvent capable of dissolving the component A but incapable of dissolving the component B, then grinding the compounded materials in a wet process until the particle diameter becomes smaller than that of the powdery hardener composition, further removing the solvent to solidify, and finally more grinding.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Conventionally, thermosetting powder coating materials are applied to articles used outdoors (for example, automobile outer panels), and the coating film formed thereon has a finished appearance, acid resistance,
Must meet requirements such as weather resistance.

In particular, when it is used as a top coat clear for automobiles and the like, powder paints are generally inferior in finishability to solvent-based paints, so that improvement in finish appearance is strongly desired. Further, since the powder coating material cannot be filtered, dust mixed in the manufacturing process cannot be removed, which may cause a serious problem in appearance.

Conventionally, acrylic powder coating materials have been produced by melt-kneading an acrylic resin having a functional group and a curing agent capable of reacting with the functional group at a melting point of the curing agent or higher. In this step, since the resin and the curing agent are partially reacted with each other to have a high molecular weight because they are melt-kneaded at a high temperature, the finishability is deteriorated and a gelled product is generated, which causes a big problem in the appearance of the coating film. May be. Further, the particle diameter of the curing agent is also re-precipitated by melting and dispersing and then cooling to make the particle diameter finer, but the particle diameter is naturally limited. The smaller the particle diameter of the curing agent is, the better the improvement of the finishability is. However, it is difficult to further improve the finishability by the above method because there is a limit to making the particle diameter fine.

When the kneading agent is melt-kneaded at a temperature lower than the melting point, the increase in the molecular weight or the formation of a gel is suppressed, but the particle diameter of the hardening agent cannot be made finer than the above-mentioned method. However, there is a problem that the finished appearance of the coating film is deteriorated due to the poor dispersibility.

[0006] Further, in the method of wet-grinding and dispersing the curing agent in an organic solvent solution in which the resin is dissolved but the curing agent is not dissolved, a method of forming a coating material by removing the solvent can be filtered before drying under reduced pressure. Since dust and lumps that have been mixed up to that time can be removed, it is advantageous as a method for producing a clear powder coating in which such dust and lumps cannot be mixed.

However, in conventional powder coatings, the particle size of the curing agent does not become sufficiently small during wet pulverization, and the dispersibility and dispersion stability of the resin and the curing agent in an organic solvent solution or after desolvation, etc. However, there is a problem in that the finish of the powder coating film is poor.

The inventors of the present invention have conducted extensive studies to solve the above-mentioned problems, and as a result, in conventional thermosetting powder coatings, sulfonic acid or a salt thereof was used as a resin for dispersing a curing agent. By using a resin obtained by radically polymerizing a vinyl-based monomer having, by dissolving this in a specific organic solvent and wet pulverizing, and then forming a powder coating,
The inventors have found that a thermosetting powder coating material that forms a coating film with excellent finish and coating film appearance can be provided, and completed the present invention.

That is, the present invention comprises (A) 0.1 part by weight of at least one of the following resin components (1) (a) a vinyl-based monomer having a sulfonic acid group and / or its base.
20 parts by weight and at least one resin selected from radical-polymerized vinyl monomers having no other functional groups, and (b) vinyl monomers having a sulfonic acid group and / or a base thereof. Radical polymerization of 0.1 to 20 parts by weight, 15 to 50 parts by weight of a vinyl-based monomer having an epoxy group and / or a hydroxyl group, and a vinyl-based monomer having no other functional group. Resin and three-component resin of (c) resin obtained by radically polymerizing 15 to 50 parts by weight of a vinyl-based monomer having an epoxy group and / or a hydroxyl group and a vinyl-based monomer having no other functional group Mixture (A-1), (2)
Two-component mixed resin (A-2) with the resin (b) and the resin (c), (3) Two-component mixed resin (A-3) with the resin (a) and the resin (c) or ( 4) The above resin (b)
Resin (A-4), (B) crosslinks with the functional groups of the resin (A) at room temperature solid powdered curing agent component (C) dissolves the resin (A) component and dissolves the curing agent (B) component It is obtained by pulverizing with a wet method until it becomes finer than the particle size of the powdery curing agent component with an organic solvent solution for powder coating containing an organic solvent, then removing the solvent to solidify, and further pulverizing. The present invention relates to a thermosetting powder coating material.

Among the resins (A) used in the present invention, examples of the vinyl monomer having a sulfonic acid group which is copolymerized with the resin (a) or the resin (b) include styrenesulfonic acid and tert-butylacrylamidesulfone. Examples of the acid include salts with strong bases such as sodium salt and potassium salt, and salts with weak base such as triethylamine salt and dimethylethanolamine salt.

Among the resins (A) used in the present invention, the vinyl-based monomer having a sulfonic acid group or its base is the resin (A-1), (A-2), (A-3) or The unsaturated monomer component constituting (A-4) is preferably contained in the range of 0.005 to 3% by weight, particularly 0.01 to 1.5% by weight. The mixing ratio of the vinyl-based monomer having the sulfonic acid or its salt is 0.005.
If it is less than wt%, the particle size of the curing agent by wet pulverization will not be sufficiently small, and the dispersion stability of the curing agent-dispersed resin organic solvent solution will be poor, and the finish of the thermosetting powder coating film will be poor, On the other hand, the mixing ratio of the vinyl monomer is 3% by weight.
If it exceeds, there is a drawback that the water resistance of the coating film decreases, which is not preferable.

In the resin (A) used in the present invention, the vinyl monomer having an epoxy group and / or a hydroxyl group is an unsaturated monomer component constituting the resin (b) or (c). 15 to 50 parts by weight, especially 20 to 4
It is preferably contained in the range of 0 parts by weight. When the blending ratio of the vinyl-based monomer having an epoxy group and / or a hydroxyl group is less than 15% by weight, the curability is deteriorated, while 5
If it exceeds 0% by weight, there is a drawback that the weather resistance and water resistance of the coating film are deteriorated, which is not preferable.

Among the resins (A) used in the present invention, examples of the vinyl monomer having an epoxy group as a monomer component constituting the resin (b) or the resin (c) include glycidyl (meth) acrylate and glycidyl. Allyl ether, 3,4-epoxycyclohexylmethyl (meth) acrylate, 3,4-epoxycyclohexylethyl (meth) acrylate, β-methylglycidyl (meth)
Examples thereof include acrylate and allyl glycidyl ether. These monomers can be used alone or in combination of two or more. Glycidyl (meth) acrylate and β-methylglycidyl (meth) acrylate are particularly preferable. When the vinyl-based monomer having an epoxy group is used in combination with the vinyl-based monomer having a sulfonic acid, these monomers react with each other, and therefore it is preferable to avoid the combined use. Further, the vinyl-based monomer having a sulfonate can be used in combination because the vinyl-based monomer having an epoxy group does not have such a fear.

As the vinyl type monomer having a hydroxyl group,
For example, 2-hydroxyethyl (meth) acrylate,
2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, (poly) ethylene glycol mono (meth) acrylate and the like can be mentioned.

Examples of the radically polymerizable vinyl-based monomer having no functional group used in the resin (A) used in the present invention include, for example, styrene, α-methylstyrene, vinyltoluene and α-chlorostyrene. Vinyl aromatic compound; methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, i-butyl (meth) acrylate, t-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n
-Acrylic acid such as octyl (meth) acrylate, decyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, tricyclodecanyl (meth) acrylate or An alkyl ester of methacrylic acid having 1 to 24 carbon atoms or a cyclic alkyl ester can be copolymerized.

In the resin (A) used in the present invention,
The mixing ratio of the resins of (A-1) to (A-3) is in the above range of the vinyl monomer containing a sulfonic acid group and / or a base thereof and the vinyl monomer containing an epoxy group and / or a hydroxyl group. The mixture may be mixed so that
In 1), the resin (a) is 0.1 to 1 in terms of total measurement of three components.
0% by weight, preferably 0.5-2% by weight / resin (b)
0.1-50% by weight, preferably 0.2-30% by weight /
Resin (c) 40-99.8% by weight, preferably 65-9
In the case of (A-2), the resin (b) is 9.6% by weight.
0.1-50% by weight, preferably 0.2-30% by weight /
Resin (c) 50 to 99.9% by weight, preferably 70 to 9
9.8% by weight, and in (A-3), resin (a) 0.1
-10 wt%, preferably 0.2-5 wt% / resin (c) 90-99.9 wt%, preferably 95-99.
8% by weight.

Resins (A-1) to (A) used in the present invention
-4) has a glass transition temperature of 40 ° C to 80 ° C, preferably 45 ° C to 70 ° C, and a weight average molecular weight of 1,000.
˜15,000, preferably 2,000 to 10,000
It is preferably in the range of. Glass transition temperature is 40 ℃
If it is less than 80%, the blocking resistance of the paint is poor,
When the temperature exceeds ℃, the finish appearance (smoothness) of the coating film is deteriorated, which is not preferable. If the number average molecular weight is less than 1,000, the coating has poor blocking resistance and weather resistance, while
When it exceeds 00, the finished appearance (smoothness) of the coating film is deteriorated, which is not preferable.

The above glass transition temperature (Tg, ° C) is
Calculate as follows. That is, using a differential scanning calorimeter (DSC), about 10 mg of a sample was weighed in a sample pan, heated to 100 ° C., held for 10 minutes, and then rapidly cooled to −20 ° C. Then, the temperature is raised at a rate of 10 ° C./min to determine the glass transition temperature.

When an epoxy group is introduced as a functional group of the resin (A), the curing agent (B) used in the present invention includes, for example, adipic acid, sebacic acid, suberic acid,
Aliphatic polycarboxylic acids such as succinic acid, glutaric acid, maleic acid, fumaric acid, dodecanedioic acid, piperic acid, azelaic acid, itaconic acid, citraconic acid and the like (poly)
Acid anhydrides; aromatic polycarboxylic acids such as terephthalic acid, isophthalic acid, phthalic acid, trimellitic acid, pyromellitic acid and their (poly) acid anhydrides; hexahydrophthalic acid, hexahydroisophthalic acid, methylhexahydrophthalic acid (Anhydrous) polycarboxylic acid compounds such as alicyclic polycarboxylic acids such as acids and their anhydrides can be used. These can be used alone or in combination of two or more. Further, when a hydroxyl group is copolymerized as a functional group of the resin (A), for example, aliphatic or fat such as isophorone diisocyanate, hexamethylene diisocyanate, (water-added) xylylene diisocyanate, (water-added) tolylene diisocyanate, etc. Examples thereof include blocked isocyanate compounds such as those obtained by blocking a cyclic or aromatic polyisocyanate with a blocking agent such as phenols, caprolactones and alcohols. These can be used alone or in combination of two or more. Further, both of the above-mentioned curing agent types may be used in combination.

The melting point of the curing agent (B) used in the present invention is preferably in the range of 60 ° C to 150 ° C, preferably 70 ° C to 110 ° C. If the melting point is less than 60 ° C., the particle size will not be sufficiently small during wet dispersion, and the blocking resistance of the coating will be poor, such being undesirable. Also, 150
When the temperature is higher than 0 ° C, the coating film is not sufficiently melted at the time of curing, the curing becomes insufficient, and the finish property of the coating film is deteriorated, which is not preferable.

As the curing agent (B) before wet pulverization used in the present invention, a commercially available product or a product obtained by pulverizing it by mechanical pulverization (jet mill pulverization, atomizer pulverization, etc.) can be used. As such a curing agent,
For example, taking dodecanedioic acid as an example, a product having a small average particle diameter of about 15 μm is commercially available.

In the present invention, the above-mentioned curing agent (B)
Is wet pulverized to have a particle size of 50% and a cumulative particle size of 9
It is preferable that the thickness is in the range of μm or less, preferably 7 μm or less. If the particle size exceeds 9 μm, the curing reaction becomes non-uniform and the meltability is poor, so that the finished appearance, especially the smoothness is poor, which is not preferable.

As the organic solvent (C) used in the present invention, the solubility of the resin (A) in the curing agent (B) (20 ° C., the number of g of the curing agent dissolved in 1 g of the organic solvent) is 0.1.
02 or less and a boiling point of 70 to 170 ° C., especially 8
It is preferably in the range of 0 to 150 ° C. If the boiling point is lower than 70 ° C., the temperature cannot be raised during desolvation, the viscosity of the system increases, and desolvation cannot be performed sufficiently, which is not preferable. Further, when the temperature exceeds 170 ° C., the organic solvent cannot be sufficiently distilled off, and the organic solvent remains in the powder coating material, and the blocking resistance of the powder coating material (the powder coating material particles adhere to each other and solidify). It is not preferable because it is inferior or the coating film is cracked.

Further, an organic solvent which does not dissolve the resin or an organic solvent which can dissolve the curing agent may be mixed so that the resin dissolves and the curing agent has a predetermined solubility or less. When the organic solvent (C) dissolves the curing agent, when the solvent is removed, the amount of the organic solvent that dissolves the curing agent decreases and the curing agent precipitates as a crystal with a large particle size. It is not preferable because the finishability is deteriorated.

Examples of the organic solvent (C) include aromatic solvents such as xylene and toluene, acetic acid ester solvents such as butyl acetate and isobutyl acetate, methyl ethyl ketone,
A ketone solvent such as methyl isobutyl ketone is used.

In the present invention, the amount of the organic solvent used is not particularly limited, but for example, the nonvolatile content of the powder coating composition solution containing the organic solvent is preferably in the range of about 15 to 80% by weight. Further, from the viewpoint of handling the solution and performing the wet pulverization process, it is preferably about 20 to 70% by weight.

For the wet dispersion of the organic solvent solution for powder coating in the present invention, a disperser used for pigment dispersion such as an ordinary sand mill or ball mill may be used. Dispersion is carried out by preparing the organic solvent solution containing the resin (A), the curing agent (B) and the organic solvent (C), and then using the above-mentioned disperser.
The curing agent (B) is wet-dispersed to a predetermined particle size.

In the obtained organic solvent solution for powder coating, the resin (a), (b),
(C), organic solvents other than the above, organic solvents (C), additives, etc. may be added. Furthermore, the organic solvent solution,
If necessary, a surface conditioner, a curing accelerator (curing catalyst), an anti-armpit agent, an ultraviolet absorber, an antioxidant, a pigment, and a pigment dispersant may be used.

In the present invention, the organic solvent solution for powder coating material obtained as described above is desolvated and solidified.
The method of removing the solvent is not particularly limited, but as an apparatus for continuously heating and drying under reduced pressure, for example, an SCP series manufactured by Kurimoto Iron Works Co., Ltd. or a belt type continuous vacuum drying apparatus manufactured by Okawara Seisakusho Co., Ltd. Bellmax and the like can be mentioned as preferred methods. Further, in the present invention, a method in which the product obtained by heating and drying under reduced pressure is continuously cooled and taken out and pulverized is preferable. In addition, JP-A-9-1
As described in JP-A-24049, heating and depressurizing are batchwise performed using an Erich vacuum mixer or the like, water is added under reduced pressure, and the mixture is instantly cooled and solidified by latent heat of evaporation of water, and at the same time, by the power of the mixer. After pulverizing to obtain a solid, a step of evaporating water and pulverizing may be used if necessary. These manufacturing methods, especially heating temperature and time, the degree of reduced pressure, the functional group of the resin and the crosslinking agent hardly react, and
It is preferable to manufacture under the condition that the organic solvent in the paint is removed as completely as possible.

The powder coating material of the present invention can be applied to a powder coating method such as electrostatic powder coating, triboelectric powder coating or the like (non-) on the surface of a conductive substrate.
The surface of the electrically conductive substrate can be coated by a powder coating method such as fluidized dip coating. Primers for these substrates,
The intermediate coating, the base coat and the like may be applied alone or in combination. The film thickness of the powder coating film is not particularly limited and may be appropriately selected and determined according to the purpose and application,
Usually about 30 μm to 100 μm, especially about 40 μm to 80 μm
The range of μm is preferred. The baking temperature varies depending on the type of the curing agent, but is usually about 10 to 60 minutes, particularly about 20 to 60 in the baking temperature range of about 140 to 200 ° C.
A range of 40 minutes is preferred.

The powder coating composition of the present invention can be used without any particular limitation in the applications conventionally used as thermosetting powders. For example, it can be used as a top coat paint for applications such as vehicles, home appliances, building materials, and office work.

[0032]

EXAMPLES The present invention will be described in detail below with reference to examples. Unless otherwise specified, “part” or “%” represents the weight standard.

Production Example of Resin Solution 1 A reaction vessel equipped with a thermometer, a thermostat, a stirrer, a reflux condenser and a dropping device was charged with 80 parts of toluene and heated to 110 ° C. while blowing nitrogen gas to give 15 parts of styrene. Parts, 35 parts of methyl methacrylate, 15 parts of n-butyl methacrylate, 35 parts of glycidyl methacrylate,
A mixed solution of 4 parts of azobisisobutyronitrile was added dropwise over about 3 hours. After completion of dropping, the mixture was left standing at 110 ° C for 1 hour, then 0.5 parts of azobisdimethylvaleronitrile and 10 parts of toluene were added dropwise over 1 hour, and then 110 ° C.
After standing for 1 hour, the reaction was completed and a resin solution was prepared.

Production Example of Resin Solution 2 A reaction vessel equipped with a thermometer, a thermostat, a stirrer, a reflux condenser and a dropping device was charged with 60 parts of iso-butanol and heated to 105 ° C. while blowing nitrogen gas,
A mixture of 15 parts of styrene, 35 parts of methyl methacrylate, 14.5 parts of n-butyl methacrylate, 35 parts of glycidyl methacrylate, and 4.5 parts of azobisisobutyronitrile and 0.5 parts of tert-butylacrylamide sulfonic acid.
Parts, 10% sodium hydroxide aqueous solution 0.97 parts, iso-
A mixed solution of 15 parts of butanol was simultaneously added dropwise over about 3 hours. After dripping, leave at 105 ° C for 1 hour, then
0.5 part of azobisdimethylvaleronitrile and 10 parts of iso-butanol were added dropwise over 1 hour, and then 105 parts were added.
Allow to stand for 1 hour at ℃ to complete the reaction, then depressurize
After removing 30 parts of iso-butanol and water and diluting with 30 parts of toluene, a resin solution was prepared.

Production Example of Resin Solutions 3 and 4 Resin solutions 3 and 4 were produced in the same manner as in the resin solution 2 by mixing the monomers shown in Table 1.

Production Example of Resin Solution 5 A reaction vessel equipped with a thermometer, a thermostat, a stirrer, a reflux condenser and a dropping device was charged with 60 parts of iso-butanol and heated to 105 ° C. while blowing nitrogen gas,
A mixture of 15 parts of styrene, 35 parts of methyl methacrylate, 14.5 parts of n-butyl methacrylate, 35 parts of glycidyl methacrylate, and 4.5 parts of azobisisobutyronitrile and 0.5 parts of tert-butylacrylamide sulfonic acid.
Part, 15% dimethylethanolamine aqueous solution 1.43
Part, and a mixed solution of 15 parts of iso-butanol were simultaneously added dropwise over about 3 hours. After the dropping is completed, the mixture is left for 1 hour at 105 ° C., and then azobisdimethylvaleronitrile 0.5
Parts, iso-butanol 10 parts were added dropwise over 1 hour and then left at 105 ° C. for 1 hour to complete the reaction, and then 30 parts iso-butanol and water were desolvated by depressurization. A resin solution was prepared by diluting with toluene.

Production Example of Resin Solution 6 A resin solution 6 was produced in the same manner as in the resin solution 2 by blending the monomers shown in Table 1.

Production Example of Resin Solution 7 A reaction vessel equipped with a thermometer, a thermostat, a stirrer, a reflux condenser and a dropping device was charged with 60 parts of iso-butanol and heated to 105 ° C. while blowing nitrogen gas,
Mixture of 15 parts of styrene, 50 parts of methyl methacrylate, 31 parts of n-butyl methacrylate, 4.5 parts of azobisisobutyronitrile and 4 parts of tert-butylacrylamide sulfonic acid, 4 parts of water, 15 parts of iso-butanol. The solution was simultaneously added dropwise over about 3 hours. 105 after completion of dropping
The mixture was allowed to stand for 1 hour at 0 ° C, then 0.5 parts of azobisdimethylvaleronitrile and 10 parts of iso-butanol were added dropwise over 1 hour, and then left at 105 ° C for 1 hour to complete the reaction, and then the pressure was reduced. To iso-butanol and water 3 times
After removing 0 parts of the solvent, it was diluted with 30 parts of toluene to prepare a resin solution.

[0039]

[Table 1]

Example 1 155.6 parts of Resin Solution 1 and 38.2 parts of Resin Solution 2
25 parts of dodecanedioic acid and 206 parts of toluene were added, and a suspension obtained by crushing dodecanedioic acid using a sand mill can continuously remove the solvent SCP-100 (manufactured by Kurimoto Iron Works Co., Ltd., product Name) heat medium temperature 90 ℃, feed amount 12
It was treated at a reduced pressure of 60 Torr for kg / hour, the discharged melt was cooled, and the resulting dry solid was roughly crushed, then finely crushed with a pin disk, and filtered with a 150 mesh to obtain a powder coating material.

Examples 2 to 7 Example 1 except that the formulation of the resin solution was changed as shown in Table 2.
I went the same way.

Comparative Examples 1 and 2 Example 1 except that the composition of the resin solution was changed as shown in Table 2.
I went the same way.

Example 8 155.6 parts of Resin Solution 1 and 38.4 parts of Resin Solution 2
Dodecanedioic acid (100 parts) and toluene (306 parts) were added, and the suspension obtained by grinding dodecanedioic acid with a sand mill was further stirred with a disper while further adding resin solution 1 to 58 parts.
3.5 parts was gradually added to obtain a suspension. This suspension was treated with SCP-100 (manufactured by Kurimoto Iron Works Co., Ltd.), which can continuously remove the solvent, at a heat medium temperature of 90 ° C., a feed rate of 12 kg / hour, and a pressure reduction degree of 60 Torr. The dried solid obtained by cooling is coarsely pulverized and then finely pulverized with a pin disc to obtain 1
It was filtered through 50 mesh to obtain a powder coating material.

Comparative Example 3 The solvent was removed from the resin solution 1 by vacuum distillation to obtain a solid resin. 100 parts of this solid resin and 25 parts of dodecanedioic acid were dry blended at room temperature with a Henschel mixer, and then melt-kneaded with an extruder. Next, it was cooled, coarsely pulverized, then finely pulverized with a pin disk, and filtered with 150 mesh to obtain a powder coating material.

[0045]

[Table 2]

In Table 2, () indicates parts by weight of solid content.

[0047]

[Table 3]

The results are shown in Table 3.

The tests in Table 3 were conducted as follows.

Particle size of curing agent: A resin solution (suspension) of dodecanedioic acid was diluted with toluene, charged into a cell equipped with a stirrer, and a particle size distribution measuring device LS-920 was stirred.
The 50% cumulative particle size was measured using (manufactured by Horiba Ltd.).

Conditions for coating film formation: A 0.8 mm thick dull steel sheet which had been subjected to zinc phosphate chemical conversion treatment was electro-deposited with an epoxy-based cationic electrodeposition coating so that the dry film thickness was 20 microns, and then baked. An automobile intermediate coating surfacer was baked on the coating film so that the dry film thickness was 20 μm, then sanded with # 400 sandpaper, drained and dried. Next, Magiclon Base Coat H
M-22 (Kansai Paint Co., Ltd., metallic paint,
(Trade name) was applied so as to have a cured film thickness of about 15 μm, and baked and cured at 140 ° C. for 30 minutes in a dryer to prepare a test material.

Next, powder coating is electrostatically coated on the surface of the material to a film thickness of about 50 μm, and dried with a drier to 160
It was heat-cured at 30 ° C for 30 minutes. The following tests were performed on the obtained coated plate.

Appearance of coating film: The finished appearance of the coating film is glossy,
The smoothness was evaluated according to the following criteria. ◎ is good, ◯ is slightly inferior in smoothness but has a good gloss, △ is slightly inferior, × is inferior, Smoothness: Surface roughness meter (Surfcom, trade name, manufactured by Toyo Seimitsu Co., Ltd.) Was used to measure the center line surface roughness.

60 ° gloss: Specular reflectance at 60 ° is JI
It was measured according to SK-5400.

Water resistance: Each coated plate was dipped at 40 ° C. for 10 days, taken out, and left standing for 1 hour to visually evaluate the state of the coating film. (○ indicates no abnormality, × indicates bleaching).

Adhesiveness: Each coated plate was immersed at 40 ° C. for 10 days, taken out, and then the coating film was cross-cut to reach the substrate, and an adhesive cellophane tape was attached to the coated surface and strongly peeled off. The coating film surface was evaluated (◯ indicates no peeling, Δ indicates slight peeling, and x indicates significant peeling).

[0057]

Since the present invention has the above-mentioned structure, it exhibits the following remarkable effects.

(1) Conventionally, an acrylic powder coating material is produced by melt-kneading an acrylic resin having a functional group and a curing agent capable of reacting with the functional group at a melting point of the curing agent or higher. Since the invention does not include such a melt-kneading step, there is no possibility that the resin and the curing agent are partially reacted with each other to form a high molecular weight product or a gelled product is produced, so that the finished appearance of the coating film is excellent.

(2) The resin having a sulfonic acid group or its base used as a resin for powder coating is a powdered curing agent,
In particular, because the compatibility with a polycarboxylic acid curing agent such as dodecanedioic acid is excellent, the viscosity of the resin solution in which the curing agent is dispersed is unlikely to be higher than the viscosity of a resin solution that does not use this, so crushing the curing agent Since the properties and the dispersion stability of the pulverized product are improved, the appearance of the finished coating film and the coating performance are excellent.

(3) Since the powder coating material of the present invention uses an organic solvent, it is possible to remove dust, lumps and the like by filtration similar to the solution coating material, so that the finished appearance of the coating film is excellent.

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 4J038 CC031 CC032 CC081 CC082                       CC101 CC102 CG141 CG142                       CH031 CH032 CH051 CH052                       CH071 CH072 CH121 CH122                       CH262 CJ111 CJ112 GA03                       GA07 GA13 JA05 JA33 JA39                       JA41 JA42 JA56 JB18 KA03                       KA20 LA06 LA07 MA07 MA13                       NA01 PA02 PB05 PB06 PB07                       PC02 PC06

Claims (5)

[Claims] 1. (A) 0.1 part by weight of at least one of the following resin component (1) (a) a vinyl-based monomer having a sulfonic acid group and / or a base thereof:
20 parts by weight and a resin obtained by radically polymerizing a vinyl-based monomer having no other functional group, and (b) at least one of vinyl-based monomers having a sulfonic acid group and / or a base thereof. Radical polymerization of 0.1 to 20 parts by weight, 15 to 50 parts by weight of a vinyl-based monomer having an epoxy group and / or a hydroxyl group, and a vinyl-based monomer having no other functional group. Resin and three-component resin of (c) resin obtained by radically polymerizing 15 to 50 parts by weight of a vinyl-based monomer having an epoxy group and / or a hydroxyl group and a vinyl-based monomer having no other functional group Mixture (A-1), (2) Two-component mixed resin (A-2) with the above resin (b) and resin (c), (3) Two components with the above resin (a) and resin (c) Resin (A-3) or (4) Resin (A-4) of the above resin (b) (B) a powdery curing agent component (C) which is solid at room temperature and is crosslinkable with a functional group of the resin (A). The resin (A) component is dissolved, but an organic solvent which does not dissolve the curing agent (B) component is added. Thermosetting, characterized by being obtained by pulverizing by wet method until it becomes finer than the particle size of the powdery curing agent component mixed with the organic solvent solution for powder coating, then removing the solvent to solidify, and further pulverizing. Powder coating. 2. The vinyl-based monomer component having a sulfonic acid group and / or its base is the resin (A-1) or (A-
2), (A-3) or (A-4) is contained in an amount of 0.005 to 3% by weight as an unsaturated monomer component constituting (A-4). Powder coating. 3. The curing agent (B) component has a melting point of 60 ° C. to 15 ° C.
The thermosetting powder coating material according to claim 1, which is in the range of 0 ° C. 4. The thermosetting powder according to any one of claims 1 to 3, wherein the particle size of the powdery curing agent component after wet pulverization is 9 μm or less in 50% cumulative particle size. paint. 5. The organic solvent (C) component has a solubility in the curing agent (B) (20 ° C., g of the curing agent dissolved in 1 g of the organic solvent) of 0.02 or less and a boiling point of 70 ° C. to 17 ° C.
The thermosetting powder coating material according to claim 1, which is in the range of 0 ° C.