JP2003096398A - Coating method - Google Patents

Abstract

(57) [Summary] [Problem] Toning method for powder which is easy to toning, that is, 2
Using a thermosetting powder coating material having different hues of more than one kind, a coating film having a visually uniform hue can be formed, and a coating film of a thermosetting powder coating composition having excellent coating workability. To provide a forming method. SOLUTION: A hue obtained by spray-drying a powder coating material solution containing a thermosetting resin (B), a curing agent (C), a coloring agent (D), and an organic solvent (E) is obtained. A coating film forming method for forming a coating film on an object using a thermosetting powder coating composition obtained by dry mixing two or more different thermosetting powder coating materials (A).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a coating film using a novel and useful thermosetting powder coating material. More specifically, the present invention relates to a coating film forming method using a thermosetting powder coating composition containing two or more thermosetting powder coatings having different hues.

[0002]

2. Description of the Related Art Powder coatings are widely used in general metal coatings as environmentally friendly coatings that do not volatilize organic solvents into the atmosphere during coating. Among them, thermosetting powder coating materials have been recognized for their excellent coating film performance and have been applied to various applications.

Thermosetting powder coating materials are generally manufactured by mixing raw materials such as a resin, a curing agent, a pigment and an additive, melt-kneading them, and then cooling, pulverizing and classifying them.
The powder coating material manufactured in this manner has a broad particle size distribution and a non-uniform shape when it is attempted to reduce the particle size during the manufacturing process, so that the coating film is not uniform. Since the fluidity becomes non-uniform, it has different hues.
Even when coating was performed using a powder coating composition obtained by dry-mixing at least one kind of thermosetting powder coating, it was not possible to visually form a coating film having a uniform hue. In addition, there is a problem that the coating workability is significantly reduced.

Therefore, in order to form a coating film having a desired hue using a thermosetting powder coating material, in addition to the resin, the curing agent, the additive, etc., which are the raw materials of the powder coating material, the desired hue is provided. After mixing several color pigments in order to put out, melt kneading, then cooling, crushing, there is no choice but to manufacture by classifying, it is necessary to prepare a powder coating for each required hue, The reality is that the product lineup is huge.

Therefore, Japanese Patent Publication No. Hei 4-504431 discloses a method of mixing several kinds of colored powders preferably having a particle size of 10 μm or less and then aggregating them to form particles of 15 to 75 μm. . In addition, JP-A-7-18858
No. 6 discloses a method in which two or more primary color powder coating materials having an average particle diameter of 10 μm or less are dry-mixed to adjust the color.
A method of granulating to 0 μm, and JP-A-2001-19905.
Japanese Unexamined Patent Application Publication No. JP-A-2003-96242, a method of using two or more kinds of powder coatings having a 90% particle diameter of 20 μm or less, ΔL value between coating films formed independently of 30 or less, and ΔE value of 43 or less. Etc. are disclosed.

However, even if these methods are used,
It was difficult to obtain a coating film having a uniform hue depending on the hue, because the coating workability was significantly reduced due to the effect of reducing the particle size to 20 μm or less.

[0007]

DISCLOSURE OF THE INVENTION The present inventors solved the various problems in the above-mentioned prior art and started earnest research to obtain a highly practical coating method of thermosetting powder coating material. . The problem to be solved by the present invention is to provide a powder toning method that facilitates toning operation, in other words, a coating film having a visually uniform hue using two or more thermosetting powder coating materials having different hues. It is intended to provide a method for forming a coating film of a thermosetting powder coating composition which is capable of forming a coating composition and is excellent in coating workability.

[0008]

Means for Solving the Problems The present inventors have earnestly studied to solve the above-mentioned problems, and as a result, as a result, a thermosetting resin (B) and a curing agent (C), a coloring agent (D) have been obtained. , A powder coating material solution containing an organic solvent (E) as an essential component is spray-dried to dry mix two or more thermosetting powder coatings (A) having different hues. A powder coating composition obtained, wherein the thermosetting powder coating has a volume average particle size of 1 to 20 μm, a standard deviation of the particle size distribution of 20 or less, and an average circularity of 0.9 to 1. The coating film formed using the thermosetting powder coating composition of 0.0 is particularly excellent in coating film appearance and coating workability, and can form a coating film having a visually uniform hue. Etc., and came to complete the present invention.

That is, according to the present invention, a thermosetting powder coating composition obtained by dry-mixing two or more types of thermosetting powder coatings (A) having different hues is applied onto an object to be coated. A coating film forming method for forming a film, the thermosetting powder coating material (A)
Is obtained by spray drying a powder coating material solution containing a thermosetting resin (B), a curing agent (C), a coloring agent (D), and an organic solvent (E) as essential components. A method for forming a coating film, which is characterized by being

BEST MODE FOR CARRYING OUT THE INVENTION The details of the present invention will be specifically described below. The particle diameter of the powder coating material of the present invention is preferably 1 to 20 μm in volume average particle diameter. It is more preferably 15 μm or less in consideration of the uniformity of hue when a thin film is used. The above average particle diameter means the volume average median diameter,
For example, it can be measured with a laser diffraction particle size analyzer (SALD-2000) manufactured by Shimadzu Corporation. The standard deviation of the particle size distribution is preferably 20 or less, more preferably 15 or less. The smaller the standard deviation value, the higher the hue uniformity.

The standard deviation referred to herein can be obtained by the following equation using the data obtained by the particle size measuring device.

S = [Σ {(DX) ² F} / ΣF] ^1/2

In the formula, S represents the standard deviation of the particle size distribution, D is the particle size of individual particles, X is the volume average particle size, and F is the frequency of the particles.

The powder coating material of the present invention is essentially spherical and its average circularity must be 0.9 or more. By using a spherical powder coating material having a specific average particle diameter and a particle diameter distribution in a specific range, the hue uniformity is remarkably improved and the coating workability is remarkably improved. From this viewpoint, it is preferable that particles having a circularity of 0.9 or more have a frequency of 5.
It is suitable that the frequency is 0% or more, more preferably 70% or more.

The circularity and the average circularity referred to here are one of the particle shape indexes representing the unevenness of the particle surface,
It is expressed as the following equation.

Circularity = (perimeter of a circle having the same area as the projected area of particle) / (perimeter of projected image of particle)

Therefore, the circularity becomes 1 if the particle image is a perfect circle, and becomes smaller as the particle image deviates from the perfect circle and becomes elongated or uneven. The average circularity is calculated by dividing the sum of the circularity of each particle by the total number of particles. The shape and average circularity of the above powder coating material are determined by a flow type particle image analyzer (FPIA-
1000, manufactured by Toa Medical Electronics Co., Ltd. The shape of the powder coating material can also be confirmed by a scanning electron microscope.

Next, spray drying will be described. The powder coating material of the present invention comprises a powder coating material solution containing a thermosetting resin (B), a curing agent (C), a coloring agent (D) and an organic solvent (E) as essential constituents (hereinafter , Powder coating material solution). The apparatus used for spray drying may be one capable of removing the organic solvent from the sprayed powder coating material solution, for example, by contacting the sprayed powder coating material solution with a heat source gas to volatilize the organic solvent. A spray drying device or the like can be used. Since the organic solvent is volatilized, it is desirable that the device be explosion proof. Further, from the viewpoint of keeping the vapor content of the solvent in the heat source gas low, which is used for drying the sprayed powder coating material raw material solution, it is desirable to provide a solvent recovery device.

In the case of using the above-mentioned spray dryer for contacting the sprayed powder coating material solution with the heat source gas to volatilize the organic solvent, the method of contacting the powder coating material solution and the heat source gas is not particularly limited. Instead, any method such as a co-current type, a counter-current type, a co-current / counter-current mixed type, which is commonly used, may be used.

Regarding the spraying method of the powder coating material solution,
Any of known and conventional types such as a rotating disk type, a two-fluid nozzle type, and a pressure nozzle type can be used. Factors for controlling the particle size during spraying include the rotation speed of the disk in the rotary disk system, the discharge speed from the nozzle in the two-fluid nozzle system, and the compression used by mixing with the raw material solution. The mixing ratio of air and the raw material solution, and the pressure nozzle type include the discharge pressure and the like, but these values may be appropriately determined according to the target particle size.

The feed rate of the raw material solution and the flow rate of the heat source gas may be appropriately determined according to the target particle size, but if the feed rate of the raw material solution or the flow rate of the heat source gas changes during spray drying, Since the particle size, particle size distribution and non-volatile content of the obtained particles also change, it is desirable to keep it constant during spray drying.

Usually, the heat source gas containing particles obtained by spray drying is continuously introduced into a classifier represented by a cyclone, and particles are collected and classified. In order to adjust the particle size distribution of the powder coating material of the present invention, when it is necessary to perform classification for removing coarse particles and fine particles, a commercially available general classifier can be used.

An inert gas is desirable as the heat source gas. Above all, it is preferable to use nitrogen gas in terms of cost and the like. The temperature of the heat source gas is such that the thermosetting powder coating material solution of the powder coating material solution does not substantially undergo a curing reaction,
That is, it may be appropriately determined within a temperature range in which the performance of the powder coating material obtained as a coating material is not substantially impaired even if a partial curing reaction occurs. The lower limit of the temperature of the heat source gas is not particularly limited, but in order to evaporate the solvent efficiently, it is preferably 30 ° C. or higher, 40 ° C. or higher.
It is more preferable that the temperature is not lower than ° C. Usually, the temperature of the heat source gas is appropriately determined in the range of 30 to 160 ° C, preferably 40 to 130 ° C.

The flow rate of the heat source gas and the supply rate of the powder coating material solution may be appropriately adjusted according to the target particle diameter under the conditions that the nonvolatile content of the obtained particles is 99% by weight or more. . The pressure inside the apparatus is not particularly limited, and may be normal pressure, reduced pressure, or increased pressure.

Further, the non-volatile content concentration of the powder coating material solution at the time of performing the spray drying may be appropriately determined according to the specifications of the spray drying apparatus and the spray drying conditions.

Further, in order to evaporate the solvent more efficiently, the powder coating material raw material solution may be preheated before spray drying. At this time, the temperature for preheating is preferably 70 ° C. or lower in order to prevent gelation of the powder coating material raw material solution, and spray drying is preferably performed as soon as possible after preheating.

The powder coating material thus obtained can be used as it is as a powder coating material, but if necessary, it may be secondarily dried by another drying method such as vacuum drying. In that case, in order to prevent gelation of the powder coating material, it is desirable that the secondary drying be performed at a temperature of about 70 ° C. or lower.

The powder coating material solution used in the present invention is
It is preferable that the thermosetting resin (B) and the curing agent (C) are completely dissolved in the organic solvent. This is because when the pigment is completely dissolved, it is possible to obtain a powder coating material in which the pigments are more uniformly mixed, and particularly the hue uniformity of the coating film is significantly improved. A solvent that does not dissolve both the resin (B) and the curing agent can be used as long as it does not impair the storage stability of the powder coating material raw material solution.

Next, the organic solvent used in the present invention will be described. As the organic solvent, a solvent that dissolves the thermosetting resin (B) and the curing agent (C) can be used, and one kind or two or more kinds of solvents may be used in combination.

Further, it is also preferable that the organic solvent contains a high boiling point solvent having a boiling point of 150 to 300 ° C. under normal pressure. By using a high boiling point solvent as a part of the organic solvent, it is possible to obtain a powder coating material which forms a coating film without causing coating film defects such as armpits and pinholes. The high boiling point solvent may be a single component or a mixture of a plurality of components.

The boiling point of the high boiling point solvent at normal pressure is as follows:
Those having a temperature of 150 to 250 ° C. are preferably used. Further, it is particularly preferable that the boiling point at normal pressure is +5 to + 150 ° C. with respect to the temperature when baking and curing the powder coating material of the present invention.

The amount of the high boiling point solvent used is preferably 0.005 to 2 parts, more preferably 0.005 to 1 part, based on 100 parts of the solid content in the powder coating material solution.

When the boiling point of the high boiling point solvent at atmospheric pressure and the amount used are within the above-mentioned ranges, an appropriate amount of the high boiling point solvent remains in the powder coating material of the present invention, resulting in cracks and pinholes during baking and curing. It is possible to prevent the generation of coating film defects.

Specific examples of such high-boiling point solvents include, but are not limited to, alcohols such as n-hexanol, n-octanol, 2-ethylhexanol, cyclohexanol, and benzyl alcohol; ethylene glycol, propylene glycol, and glycerin. Such as polyhydric alcohols; butyl cellosolve, hexyl cellosolve, ethylene glycol dipropyl ether, ethylene glycol dibutyl ether, propylene glycol monobutyl ether, propylene glycol dipropyl ether, propylene glycol dibutyl ether, methyl carbitol, ethyl carbitol, diethylene glycol dimethyl ether, Diethylene glycol diethyl ether, diethylene glycol dipropyl ether, diethylene glycol Glycol ethers, such as dibutyl ether;

Aromatic hydrocarbons such as propylbenzene, butylbenzene, pentylbenzene, diethylbenzene, dipropylbenzene, dipentylbenzene, dodecylbenzene, cyclohexylbenzene; Solvesso 1
00, Solvesso 150, Solvesso 200 (all manufactured by Exxon, USA); mixed hydrocarbons containing aromatic hydrocarbons; Exxon Naphtha No. 3, Exxon naphtha No. 5, Exxon Naphtha No. 6, Exxon Solvent No. 7, Isopar G, Isopar H, Isopar L, Isopar M, Exol D40, Exol D90, Exol D110 (all manufactured by US Exxon Corporation), IP Solvent 1620, IP Solvent 202
Mixed hydrocarbons containing aliphatic hydrocarbons such as 8 (manufactured by Idemitsu Petrochemical Co., Ltd.), Merbeil 20, Merbeil 30, Merbeil 40 (manufactured by Showa Shell Sekiyu Co., Ltd.), and mineral spirits;

Glycerin alkyl ether, glycerin alkyl ester; ketones such as diisobutyl ketone, methyl amyl ketone, cyclohexanone, isophorone; cyclohexyl acetate, 2-ethylbutyl acetate, 2-ethylhexyl acetate, cyclohexyl acetate, isoamyl propionate, butyric acid alkyl ester Esters such as, stearic acid alkyl ester, benzoic acid alkyl ester, adipic acid dialkyl ester, phthalic acid dialkyl ester;

There are N-methylpyrrolidone, dimethylformamide, dimethylacetamide, ethylene carbonate and the like. Among the above-mentioned high-boiling solvents, the use of an aromatic solvent and / or an aliphatic solvent is preferably used because the effect of preventing the generation of coating film defects is more remarkable.

The method of adding the high boiling point solvent to the powder coating material solution is not particularly limited, but it is recommended to add the powder coating material solution immediately before spray drying, for example, because it is simple and convenient. It

As the organic solvent (C), in addition to the above-mentioned high boiling point solvent, a known and commonly used organic solvent can be used in consideration of the solubility in the resin.

As typical examples of such organic solvents, methanol, ethanol, n-
Alkyl alcohols such as propanol, isopropanol, n-butanol, isobutanol, sec-butanol, tert-butanol, n-pentanol, isopentanol;

Methyl cellosolve, ethyl cellosolve, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether,
Glycol ethers such as propylene glycol monopropyl ether, propylene glycol dimethyl ether, propylene glycol diethyl ether;

Aromatic hydrocarbons such as benzene, toluene, xylene, ethylbenzene; Exxon aromatic naphtha No. 2 (manufactured by Exxon, USA), such as mixed hydrocarbons containing aromatic hydrocarbons; n-pentane, n
-Aliphatic hydrocarbons such as hexane and n-octane;
Isopar C, Isopar E, Exor DSP100
/ 140, Exol D30 (all manufactured by Exxon, USA), IP Solvent 1016 (manufactured by Idemitsu Petrochemical Co., Ltd.), mixed hydrocarbons containing aliphatic hydrocarbons; cyclopentane, cyclohexane, methylcyclohexane,
Alicyclic hydrocarbons such as ethylcyclohexane;

Ethers such as tetrahydrofuran, dioxane, diisopropyl ether, di-n-butyl ether; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone; methyl acetate, ethyl acetate, n-propyl acetate, isopropyl acetate, acetic acid n -Butyl, isobutyl acetate, n-amyl acetate, isoamyl acetate, hexyl acetate, ethyl propionate, butyl propionate, and other esters;

From the viewpoint of improving the drying property of the paint particles during spray drying, the remaining solvent components of the organic solvent except the high boiling point solvent have a boiling point of 100 at normal pressure.
It is preferable that the solvent at a temperature of not more than 0 ° C. accounts for 65 to 100% by weight.

Next, the thermosetting resin (B) will be described.
As the thermosetting resin (B), any of an acrylic resin, a polyester resin, an epoxy resin and a urethane resin can be used, but among them, an acrylic resin and a polyester resin are preferable. Further, as the thermosetting resin (B), a resin having a glass transition point in the range of 50 to 100 ° C. is used because a powder coating having excellent storage stability during storage and excellent balance of coating film appearance can be obtained. Particularly preferred.

When the thermosetting resin (B) is an acrylic resin, known conventional methods can be applied to prepare the base acrylic resin, but various vinyl monomers are further copolymerized, if necessary. The method of polymerizing in an organic solvent using vinyl monomers containing a curing reactive group that is possible is recommended because it is the simplest method. As the polymerization initiator and solvent used at that time, known and conventional ones can be used as they are.

As the curing reactive group of the thermosetting resin (B), epoxy group, carboxyl group, hydroxyl group, amino group,
It is desirable to have at least one curing reactive group selected from the group consisting of an isocyanate group, a hydrolyzable silyl group, a blocked carboxyl group, a blocked amino group, and a blocked isocyanate group. Above all, it is more preferable that at least one of the curing reactive groups is an epoxy group because of excellent storage stability and appearance of the coating film.

As the monomers to be used when the thermosetting resin (B) is an acrylic resin, only typical examples are given, for example, methyl acrylate, ethyl acrylate, butyl acrylate, cyclohexyl acrylate. Various acrylic acid esters such as: methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, iso-butyl methacrylate, t
various methacrylic acid esters such as ert-butyl methacrylate, cyclohexyl methacrylate, benzyl methacrylate;

Various α-olefins such as ethylene, propylene and butene-1; various halogenated olefins (halo olefins) other than fluoroolefins such as vinyl chloride and vinylidene chloride; styrene and α
Various aromatic vinyl monomers such as methylstyrene, vinyltoluene;

Dimethyl fumarate, diethyl fumarate, dibutyl fumarate, dioctyl fumarate, dimethyl maleate, diethyl maleate, dibutyl maleate, dioctyl maleate, dimethyl itaconate, diethyl itaconate, dibutyl itaconate, dioctyl itaconate. Such as various unsaturated dicarboxylic acids with 1 to 18 carbon atoms
Diesters with monohydric alcohols;

Various amino group-containing amides such as N-dimethylaminoethyl (meth) acrylamide, N-diethylaminoethyl (meth) acrylamide, N-dimethylaminopropyl (meth) acrylamide, N-diethylaminopropyl (meth) acrylamide Unsaturated monomers; various dialkylaminoalkyl (meth) acrylates such as dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate;

Tert-Butylaminoethyl (meth) acrylate, tert-butylaminopropyl (meth)
Various amino group-containing monomers such as acrylate, aziridinylethyl (meth) acrylate, pyrrolidinylethyl (meth) acrylate, piperidinylethyl (meth) acrylate; maleic anhydride, itaconic anhydride,
Various acid anhydride group-containing monomers such as citraconic anhydride, anhydrous (meth) acrylic acid, and tetrahydrophthalic anhydride;

Diethyl-2- (meth) acryloyloxyethyl phosphate, dibutyl-2- (meth) acryloyloxybutyl phosphate, dioctyl-2
-(Phosphorus ester group-containing monomers such as meacryloyloxyethyl phosphate and diphenyl-2- (meth) acryloyloxyethyl phosphate);
Various hydrolyzable silyl group-containing monomers such as γ- (meth) acryloyloxypropyltrimethoxysilane, γ- (meth) acryloyloxypropyltriethoxysilane and γ- (meth) acryloyloxypropylmethyldimethoxysilane;

Vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl caproate, vinyl caprylate, vinyl caprate, vinyl laurate, branched (branched) aliphatic vinyl carboxylate having 9 carbon atoms. ,
Various aliphatic vinyl carboxylates such as branched aliphatic vinyl carboxylates having 10 carbon atoms, branched aliphatic vinyl carboxylates having 11 carbon atoms, and vinyl stearate;

Vinyl cyclohexanecarboxylate, vinyl methylcyclohexanecarboxylate, vinyl benzoate, p
There are various vinyl esters of carboxylic acids having a cyclic structure such as -tert-butyl vinyl benzoate.

To exemplify only typical vinyl monomers having a curing reactive group, first, when the curing reactive group is an epoxy group, for example, glycidyl (meth) acrylate, Various epoxy group-containing monomers such as β-methylglycidyl (meth) acrylate, glycidyl vinyl ether and allyl glycidyl ether; (2-oxo-1,3-oxolane) methyl (meth) acrylate, (2- Oxo-1,3-
Oxolane) group-containing vinyl monomers; 3,4-epoxycyclohexyl (meth) acrylate, 3,4-epoxycyclohexylmethyl (meth) acrylate, 3,4
There are various alicyclic epoxy group-containing vinyl monomers such as epoxycyclohexylethyl (meth) acrylate.

When the curing reactive group is a carboxyl group, various carboxyl group-containing monomers such as (meth) acrylic acid, crotonic acid, itaconic acid, maleic acid and fumaric acid; monomethyl fumarate; Monoethyl fumarate, monobutyl fumarate, monoisobutyl fumarate,
Monotert-butyl fumarate, monohexyl fumarate, monooctyl fumarate, mono-2-ethylhexyl fumarate, monomethyl maleate, monoethyl maleate, monobutyl maleate, monoisobutyl maleate, monotert-butyl maleate, monohexyl maleate. , Monooctyl maleate, mono 2 maleate
-Monoesters of various α, β-unsaturated dicarboxylic acids such as ethylhexyl and monohydric alcohols having 1 to 18 carbon atoms; monomethyl itaconate, monoethyl itaconate, monobutyl itaconate, monoisobutyl itaconate, There are monoalkyl esters of itaconic acid, such as monohexyl itaconic acid, monooctyl itaconic acid and mono-2-ethylhexyl itaconic acid.

When the curing-reactive group is a hydroxyl group, for example, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate. , 3-hydroxybutyl (meth)
Various hydroxyl group-containing (meth) acrylates such as acrylate, 4-hydroxybutyl (meth) acrylate, polyethylene glycol mono (meth) acrylate, polypropylene glycol mono (meth) acrylate;
Addition reaction products of various (meth) acrylates and ε-caprolactone as listed above;

2-hydroxyethyl vinyl ether, 3
-Hydroxypropyl vinyl ether, 2-hydroxypropyl vinyl ether, 4-hydroxybutyl vinyl ether, 3-hydroxybutyl vinyl ether, 2-
Hydroxy-2-methylpropyl vinyl ether, 5-
Various hydroxyl group-containing vinyl ethers such as hydroxypentyl vinyl ether and 6-hydroxyhexyl vinyl ether; various vinyl ethers as listed above,
addition reaction product with ε-caprolactone;

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, 2-hydroxy-2-methylpropyl (meth) allyl ether, 5-
Various hydroxyl group-containing allyl ethers such as hydroxypentyl (meth) allyl ether and 6-hydroxyhexyl (meth) allyl ether; addition reaction products of various allyl ethers listed above with ε-caprolactone .

The amount of various curing-reactive group-containing vinyl monomers as exemplified above is appropriately within the range of 0 to 50% by weight based on the total amount of vinyl monomers used.

The number average molecular weight of the thermosetting acrylic resin is preferably in the range of 1,000 to 20,000, and more preferably in the range of 1,500 to 15,000. . When the number average molecular weight of the thermosetting acrylic resin is within the above range, a coating film having excellent smoothness and mechanical properties can be obtained.

The preparation method for obtaining the polyester resin used as the thermosetting resin (B) is not particularly limited, and various known and conventional methods can be used, but a method of condensing a polyhydric alcohol and a polybasic acid. Manufactured by.
As the curing-reactive group, a carboxyl group and / or a hydroxyl group is preferably adopted because of easy preparation.

As the polyhydric alcohol and polybasic acid that can be used as a raw material for the polyester resin used as the thermosetting resin (B), various known and commonly used compounds can be used. Use of these polyhydric alcohol and polybasic acid A polyester resin having a carboxyl group and / or a hydroxyl group can be obtained by adjusting the amount.

First of all, only typical examples of the above-mentioned polyhydric alcohols will be given. Ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, 1,3-butanediol, 1,4-butanediol. , 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, triethylene glycol, bis-hydroxyethyl terephthalate, cyclohexanedimethanol, octanediol, diethylpropanediol, butylethylpropanediol, 2-methyl-1. , 3-propanediol, 2,2,4-trimethylpentanediol, hydrogenated bisphenol A, ethylene oxide adduct of hydrogenated bisphenol A, propylene oxide adduct of hydrogenated bisphenol A, Trimethylol ethane, trimethylol propane, glycerine, pentaerythritol, tris-hydroxyethyl isocyanurate, and the like hydroxypivalic valyl hydroxy pivalate.

On the other hand, if only representative ones of the above-mentioned polybasic acids are exemplified, terephthalic acid,
Isophthalic acid, phthalic acid, methylterephthalic acid, trimellitic acid, pyromellitic acid or their anhydrides; succinic acid, adipic acid, azelaic acid, sebacic acid or their anhydrides; maleic acid, itaconic acid or their anhydrides Fumaric acid, tetrahydrophthalic acid, methyltetrahydrophthalic acid, hexahydrophthalic acid, methylhexahydrophthalic acid or their anhydrides; cyclohexanedicarboxylic acid, 2,6-naphthalenedicarboxylic acid and the like.

Further, as a raw material of the polyester resin, a compound having both a carboxyl group and a hydroxyl group in one molecule such as dimethanolpropionic acid and hydroxypivalate; "Cadura E10" (branched by Shell Co., Netherlands) Monoepoxy compounds such as glycidyl ester of aliphatic carboxylic acid); such as methanol, propanol, butanol, benzyl alcohol,
Various monohydric alcohols; various monohydric basic acids such as benzoic acid and p-tert-butylbenzoic acid; various fatty acids such as castor oil fatty acid, coconut oil fatty acid, soybean oil fatty acid and the like can also be used. it can.

The polyester resin obtained by using various polyhydric alcohols, polybasic acids, other raw materials, etc. as described above has a total acid value and hydroxyl value of 1 to 1
It is preferably 250 (mgKOH / g; the same applies hereinafter) and also has a number average molecular weight of 500 to 30,000.

The structure of the polyester resin is not particularly limited as long as it is within the range of various characteristic values of the resin as described above, and may have a branched structure or a linear structure.

The epoxy resin which can be used as the thermosetting resin (B) is not particularly limited, and examples thereof include epoxy resins such as polyglycidyl ether of bisphenol-A.

Next, the curing agent (C) which reacts with the thermosetting resin (B) will be described. As the curing agent, those generally used for powder coatings are appropriately selected and used according to the type of curing reactive group of the thermosetting resin (B).

As such a curing agent, when the curing-reactive group of the thermosetting resin (B) is an epoxy group, only representative ones are exemplified. Succinic acid, glutaric acid, adipic acid, Pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, aicosandicarboxylic acid, maleic acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, trimellitic acid, pyromellitic acid, tetrahydrophthalic acid, hexahydrophthalic acid Acid, cyclohexene-1,2-dicarboxylic acid, trimellitic acid, pyromellitic acid, or acid anhydrides thereof, etc. Among them, aliphatic dibasic acid is preferable because of excellent coating film physical properties and storage stability. In particular, dodecanedicarboxylic acid is particularly preferable because it has excellent coating film properties.

Further, when the thermosetting resin (B) has a carboxyl group as the curing reactive group, various epoxy resins such as polyglycidyl ether of bisphenol A will be mentioned, if only representative examples are given. An epoxy group-containing acrylic resin such as a glycidyl group-containing acrylic resin;
1,6-hexanediol, trimethylolpropane,
Polyglycidyl ethers of various polyhydric alcohols such as trimethylolethane; phthalic acid, terephthalic acid,
Polyglycidyl esters of various polycarboxylic acids such as isophthalic acid, hexahydrophthalic acid, methylhexahydrophthalic acid, trimellitic acid, pyromellitic acid; bis (3,4-epoxycyclohexyl) methyl adipate, Various alicyclic epoxy group-containing compounds;
Examples thereof include triglycidyl isocyanurate and hydroxyamides such as β-hydroxyalkylamide.

When the curing-reactive group of the thermosetting resin (B) is a hydroxyl group, a polyblock isocyanate compound, aminoplast, or the like is suitable as a particularly representative curing agent.

As the polyblock polyisocyanate compound, only representative ones are exemplified. Various aliphatic diisocyanates such as hexamethylene diisocyanate and trimethylhexamethylene diisocyanate; xylylene diisocyanate and isophorone diisocyanate, Various cyclic aliphatic diisocyanates; organic diisocyanates such as various aromatic diisocyanates such as tolylene diisocyanate and 4,4′-diphenylmethane diisocyanate, or these organic diisocyanates, polyhydric alcohols, low molecular weight polyester resins ( (Polyester polyol) or an adduct with water or the like, which is well-known and commonly used,
Some are obtained by reacting with active hydrogen compounds such as oximes,

Further, the above-mentioned polymers of organic diisocyanates (including isocyanurate type polyisocyanate compounds) as well as various polyisocyanate compounds such as isocyanate biuret form a known and commonly used block. Examples thereof include those obtained by blocking with an agent, so-called self-blocked polyisocyanate compounds having a uretdione bond as a structural unit, and the like.

On the other hand, examples of aminoplasts include melamine, urea, acetoguanamine, benzoguanamine,
Various amino group-containing compounds such as steroganamin and spiroguanamine, and formaldehyde, paraformaldehyde, acetaldehyde and glyoxal,
Condensates in the form obtained by reacting various aldehyde compound components with various conventionally known methods, or compounds in the form obtained by etherifying these condensates with alcohols and so on.

Specific examples of such aminoplasts include only hexamethoxymethylolmelamine, hexabutyletherified methylolmelamine, methylbutyl mixed etherified methylolmelamine, methyletherified methylolmelamine, and n-butyletherified methylol. Melamine, isobutyl etherified methylol melamine, or their condensates; various bicyclic compounds such as hexamethoxyglycoluril, hexabutoxyglycoluril, tetramethoxymethylglycoluril; aliphatic dibasic acids and diethanolamine, etc. Various acid amides in the form of being obtained by condensation reaction with various alkanolamines; Polymerizable monomers such as butyl ether of N-methylolacrylamide Alone, or other such as obtained by copolymerizing possible Naru monomers and copolymerization reaction, and the like various polymer compounds.

The above-mentioned hexamethoxymethylol melamine is "Cymel 300, 301 or 303" (manufactured by Mitsui Cyanamid Co.); methylbutyl mixed etherified methylol melamine is "Cymel 238, 2".
32 or 266 "(manufactured by Mitsui Cyanamid); n-butyl etherified methylol melamine as" Super Beckamine L-164 "(manufactured by Dainippon Ink and Chemicals, Inc.); tetramethoxymethylglycoluril as" Powder Link " (POWDERLIN
K) 1174 ”(product of American Cyanamid Co., USA); acid amides are“ PRIMID (PRIMI)
D) XL-552 "," Primid (PRIMID)
QM-1260 "(manufactured by EMS), which is commercially available.

The above curing agents may be used alone or in combination of two or more. The curing reactive group of the thermosetting resin (B) and the curing agent are blended in such a manner that the equivalent ratio of the curing reactive group of the thermosetting resin (B) to the equivalent of the curing agent is 2.0 to 0.
It is preferably between 5 and 5.

Next, the colorant (D) will be described. As a typical example of the colorant, titanium oxide,
Benji, chrome titanium yellow, yellow iron oxide, various inorganic pigments of carbon black, phthalocyanine type such as phthalocyanine blue and phthalocyanine green, anthraquinone type such as induslen blue, dianthraquinonyl red, quinacridone type, lake red, fast yellow , Various azo pigments such as azo series such as disazo yellow and permanent red, nitro series such as naphthol yellow, nitroso series such as pigment green B and naphthol green, calcium carbonate, precipitated barium, talc, and oxidation. For example, various known conventional extender pigments such as zinc, aluminum hydroxide, magnesium hydroxide, talc, mica and silica, metallic pigments of respective colors, pearl pigments of respective colors, metal powders and surface-treated ones are given as examples. That.

The colorant (D) as described above is dispersed in a powder coating material solution and then spray-dried to obtain
The thermosetting powder coating material (A) can be prepared. As a method for dispersing the colorant (D) in the powder coating material solution, a method of mixing and stirring using a known conventional disperser such as a ball mill, a pebble mill, an attritor, a roll mill and a high speed impeller disperser can be used. . In addition, a curing catalyst, an antioxidant, a leveling agent,
You may add additives, such as a matting agent, a defoaming agent, and an ultraviolet absorber. It is also possible to prepare a colored powder coating material solution having a desired color by mixing a plurality of colored powder coating material solutions and spray-dry the solution.

As a method for dry-mixing two or more kinds of thermosetting powder coatings (A) having different hues, a known and common dry-mixing stirring method such as a Henschel mixer or a Nauta mixer can be used. For the coating method, an electrostatic spraying method or a triboelectrification coating method, a known conventional method such as fluidized dipping, is used to coat the base material to be coated,
Usually, the coated article thus obtained is about 120 to about 250.
It may be done by baking at a temperature of ℃,
In this way, a powder coated article can be obtained.

By the coating film forming method of the present invention, a single-layer or multi-layer coating film can be formed on an object to be coated, and it can be applied to an undercoat paint and a top coat paint.

Here, the article to be coated refers to a base material to which the coating material is applied, and more specifically, it is an unpainted metal material such as an unpainted steel plate or an untreated or chemically treated aluminum base material. Examples include base materials used for road vehicles such as automobile bodies and motorcycle bodies, base materials used for automobile parts such as aluminum wheels, and base materials used for beverage cans. Also included are base materials used for road vehicles such as automobile bodies that have been subjected to electrodeposition coating.

Furthermore, base materials used for home electric appliances, vending machines, steel furniture, etc., such as electrogalvanized steel sheets,
Hot-dip galvanized steel sheets and the like, roof tiles; glass; or various inorganic building materials; various building materials such as gates or fences; various building interior and exterior materials such as aluminum sashes; road marking boards, Road materials such as guardrails are also exemplified.

These base materials may be processed into a shape according to the end use, or a form to which the PCM (pre-coat metal) coating method is applied, that is, a roughly flat plate-like base material. However, after the coating film is formed by the method of the present invention, the coating film may be bent into a predetermined shape according to the purpose, or may be completely post-processed such as coil coating. It may be a base material used in a coating system.

As described above, the method for forming a coating film of the present invention comprises applying the thermosetting powder coating composition to the various base materials to be coated by the conventional method, Then, according to a conventional method, by baking and drying,
It is possible to provide a powder-coated product which is excellent in the coating film, in particular, in smoothness and hue uniformity.

[0088]

EXAMPLES Next, the present invention will be described more specifically by reference examples, examples and comparative examples, but it goes without saying that the present invention is not limited to these examples.
In the following, all "parts" mean "parts by weight" unless otherwise specified.

Example 1 (Preparation example of thermosetting powder coating material (X-1) used in the present invention) 84 parts of Finedick A-224S (a solid acrylic resin containing a glycidyl group manufactured by Dainippon Ink and Chemicals, Inc., epoxy equivalent: 525) 16 parts of dodecanedioic acid (produced by Ube Industries, aliphatic dibasic acid), 0.5 part of benzoin, 1 part of Modaflow (leveling agent manufactured by Monsanto Co.) were dissolved in 150 parts of methyl ethyl ketone and 100 parts of isobutanol by heating. Next, 40 parts of TYPAQUE CR-90 (titanium oxide manufactured by Ishihara Sangyo Co., Ltd.) was added, and the mixture was dispersed at 60 ° C. or lower for 1 hour using a sand mill filled with glass beads.

This organic solvent solution was spray-dried using an explosion-proof vertical descending cocurrent spray dryer equipped with a solvent recovery device, using a rotary disk system as the spray system. The rotation speed of the disk was 15,000 rpm, nitrogen gas was used as the heat source gas, and the raw material solution and the heat source gas were brought into contact with each other in a vertically descending cocurrent manner. The gas temperature was set to 120 ° C. The powder coating raw material solution preheated to 60 ° C. is sprayed into the spray drying device at a supply rate of 0.5 kg / hr, and the particles of the powder coating dried in the device are collected by a cyclone to heat cure. A powdery coating composition (X-1-1) was obtained.

The average particle size of the particles is 8 μm, and the standard deviation is 7.
2 The average circularity was 0.98. Then, a thermosetting powder coating material (X-1-2) was prepared in the same manner as in (X-1-1), except that 1 part of carbon black MA-100 (manufactured by Mitsubishi Chemical Co., Ltd.) was used instead of Typake CR-90. Obtained. The average particle size of the particles is 7 μm, the standard deviation is 9.7, and the average circularity is 0.97.
Met. 95 parts of (X-1-1) and 5 parts of (X-1-2) were dry-mixed with a Henschel mixer to obtain a thermosetting powder coating material (X-1).

Example 2 (Preparation example of thermosetting powder coating material (X-2) used in the present invention) FINEDIC M-8034 (manufactured by Dainippon Ink and Chemicals, Inc., hydroxyl group-containing solid polyester resin, hydroxyl value 30)
) 87 parts, Vestagon B-1530 (manufactured by Degussa)
13 parts of a blocked isocyanate compound, 0.5 part of benzoin, and 1 part of Modaflow (a leveling agent manufactured by Monsanto Co.) were dissolved by heating in 250 parts of methyl ethyl ketone. Then, 1 part of Fastgen Blue NK (copper phthalocyanine blue manufactured by Dainippon Ink and Chemicals, Inc.) was mixed and dispersed in the above resin solution with a sand mill in the same manner as in Reference Example 1, and this organic solvent solution was used in the same manner as in Reference Example 1. And spray dried. A thermosetting powder coating material (X-2-1) was obtained by collecting particles of the powder coating material dried in the apparatus with a cyclone.

The average particle size of the particles was 10 μm, and the standard deviation was 8.9. The average circularity was 0.98. Then, a thermosetting powder coating material (X-2-2) was obtained in the same manner as in (X-2-1) except that 1 part of Carmine 6B (manufactured by Sumitomo Chemical Co., Ltd.) was used instead of Fastgen Blue NK. . The average particle size of the particles is 9 μm, the standard deviation is 11.3, and the average circularity is 0.97.
Met. (X-2-1) 50 parts and (X-2-2) 50
Partial dry mixing was performed to obtain a thermosetting powder coating material (X-2).

Comparative Example 1 (Example of thermosetting powder coating material (Z-1) prepared by melt-kneading method) Finedic A-224S, 84 parts, dodecanedioic acid 16 parts, benzoin 0.5 part, Modaflow 1 Part 40 parts of Taipaque CR-90 is mixed with a Henschel mixer, and a Busunder Conider PR46 type single-screw kneader, 100 ° C
Melt kneading at 100 rpm for 100 minutes, cool and pulverize to 200
Classification with a mesh wire mesh and thermosetting powder coating (Z-1-
1) was obtained. Average particle size is 15 μm and average circularity is 0.81
Met. Then, a thermosetting powder coating (Z-1-1) was used in the same manner as in (Z-1-1) except that the TYPAKE CR-90 was replaced with 1 part of carbon black MA-100 (manufactured by Mitsubishi Chemical Corporation).
1-2) was obtained. The average particle size of the particles was 11 μm, and the standard deviation was 14.0. The average circularity was 0.82. (Z-1-
1) 95 parts and 5 parts of (Z-1-2) were dry-mixed with a Henschel mixer to obtain a thermosetting powder coating material (Z-1).

Comparative Example 2 (Example of Thermosetting Powder Coating (Z-1) Prepared by Melt Kneading Method) Finedic M-8034 (Dainippon Ink and Chemicals Incorporated Hydroxyl group-containing solid polyester resin Hydroxyl value 3)
0) 87 parts, Vestagon B-1530 (manufactured by Degussa,
Block isocyanate compound) 13 parts, benzoin 0.5 part, Modaflow (Monsanto leveling agent) 1 part Fastgen Blue NK (Dainippon Ink and Chemicals Co., Ltd. copper phthalocyanine blue) 1 part are mixed with a Henschel mixer, and Busder Conider A PR46 type uniaxial kneader was melt-kneaded at 100 ° C. for 100 rotations, cooled, finely pulverized, and classified with a 200-mesh wire net to obtain a thermosetting powder coating material (Z-2-1). Average particle size is 9μm and standard deviation is 2
The average circularity was 1.5 and the average circularity was 0.85. Then, a thermosetting powder coating material (Z-2-2) was obtained in the same manner as in (Z-2-1) except that 1 part of Carmine 6B (manufactured by Sumitomo Chemical Co., Ltd.) was used instead of Fastgen Blue NK. . The average particle size of the particles is 9 μm, the standard deviation is 24.8, and the average circularity is 0.88.
Met. (Z-2-1) 50 parts and (Z-2-2) 50
Partial dry mixing was performed to obtain a thermosetting powder coating material (Z-2).

Examples (X-1) to (X-2) and thermosetting powder coatings (Z-1) to (Z-2) for reference.
Was coated on a 0.8 mm-thick polished steel sheet treated with zinc phosphate with an electrostatic spray coating machine for powder coating, and then baked at 180 ° C. for 20 minutes,
Various test plates on which a cured coating film was formed were obtained. The evaluation and judgment results of these coating films are summarized in Table 1.

[0097]

[Table 1]

<< Procedure for Evaluation and Evaluation of Physical Properties of Paint and Coating Film >> Film thickness: Measured with an electromagnetic film thickness meter. Smoothness: Five-level evaluation and judgment were carried out by visual judgment. Evaluation "5"; Evaluation of very smooth and smooth coated surface "4"; Evaluation of small rounds "3"; Evaluation of large rounds "2"; Evaluation of large rounds and many fine dust skin When observed: Evaluation “1”; when there is a large round, the fine dust skin is remarkable, and the appearance of the coating film is significantly impaired.

Criteria for Evaluation of Uniformity of Hue: When an evaluator with a visual acuity of 1.5 observes at a distance of 20 cm to 2 m and 20 cm from the coating film Evaluation 5: Even at 20 cm, it looks uniform. Evaluation 4: It looks uneven at 20 cm, but 70c
It looks uniform at m. Evaluation 3: Although it looks uneven at 70 cm, 120
It looks uniform in cm. Evaluation 2: It looks uneven at 120 cm, but 17
It looks uniform at 0 cm. Evaluation 1: It looks uneven at 170 cm, but 22
It looks uniform at 0 cm.

Transportability of coating material: After coating the powder coating material from the fluidized bed through the injector with a hose continuously for 2 hours, the accumulation state of the powder coating material in the injector and the hose was visually judged. Evaluation ◎: Evaluation in which powder coating material was not deposited at all ○: Evaluation in which powder coating material was hardly deposited ×: Powder coating material was deposited and the injector or hose was almost blocked.

[0101]

As has been made clear by the detailed description above,
According to the present invention, a coating film having excellent smoothness and a uniform hue can be formed by using two or more kinds of thermosetting powder coating materials having different hues.

Continued front page    F-term (reference) 4D075 BB16X BB24X BB63X CA48                       DA06 DB02 DB07 DB12 DB13                       DC03 DC05 DC10 DC12 DC13                       DC18 DC38 DC42 EA02 EA19                       EB13 EB14 EB15 EB19 EB20                       EB22 EB32 EB33 EB35 EB37                       EB38 EB42 EB45 EB57 EC11                 4J038 CG001 DB001 DD001 DG001                       GA03 GA06 GA07 GA09 GA11                       GA15 KA03 KA06 KA08 KA20                       MA02 PA07 PA19

Claims (4)

[Claims] 1. A coating film is formed on an object to be coated using a thermosetting powder coating composition obtained by dry-mixing two or more thermosetting powder coatings (A) having different hues. The thermosetting powder coating (A) comprises a thermosetting resin (B), a curing agent (C), a coloring agent (D), and an organic solvent (E).
A method for forming a coating film, which is obtained by spray-drying a powder coating material raw material solution containing and as essential components. 2. The thermosetting powder coating material (A) has a volume average particle diameter of 1 to 20 μm, a standard deviation of its distribution of 20 or less, and an average circularity of 0.9 to 1.0. , Claim 1
The method for forming a coating film according to. 3. The thermosetting powder coating material (A) contains a resin having a curing reactive group selected from the group consisting of acrylic resin, polyester resin, epoxy resin and urethane resin. The method for forming a coating film according to 1 or 2. 4. A thermosetting powder coating (A) comprises an epoxy group, a carboxyl group, a hydroxyl group, an amino group, an isocyanate group, a hydrolyzable silyl group, a blocked carboxyl group, a blocked amino group, and a blocked isocyanate. The coating film forming method according to claim 1, 2 or 3, which has at least one curing reactive group selected from the group consisting of groups.