JP2003013005A - Powder coating manufacturing method - Google Patents

Abstract

(57) [Problem] To provide a method for producing a polyester powder coating which gives a coating appearance such as excellent smoothness and glossiness. At least (1) the number average molecular weight is 1000
-30000, a glass transition temperature of 30-100 ° C, and a hydroxyl group or a carboxyl group of the curable polyester resin (A) having a hydroxyl group and / or a carboxyl group at the terminal, and (2) a curable polyester resin (A). A curing agent (B) which is solid at room temperature and which can react, and (3) a solvent (C) having a boiling point of 50 to 130 ° C. at normal pressure.
A method for producing a powder coating, wherein a curable polyester resin (A), a curing agent (B), and a solvent (C) are continuously mixed such that at least 20% by weight of the curing agent (B) is dissolved. A method for producing a powder coating, comprising kneading the solvent (C) under reduced pressure and removing the solvent (C) under reduced pressure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a polyester powder coating material comprising a curable polyester resin.

[0002]

2. Description of the Related Art Powder coatings are widely used in place of solution coatings because they do not generate volatile organic substances during baking and do not cause environmental problems such as air pollution.

Such a powder coating material is a curable resin mixed with a curing agent. For example, as the curable resin,
Acrylic powder coating using curable acrylic resin having glycidyl group or hydroxyl group, polyester powder coating using curable polyester resin having hydroxyl group or carboxyl group, or epoxy powder coating using epoxy resin Are typical. Further, as a curing agent for acrylic powder coatings, aliphatic dibasic acids, blocked isocyanates, uretdiones, amino compounds and the like are known, and as curing agents for polyester powder coatings, blocked isocyanates, uretdiones, amino compounds. ,
Epoxy compounds, glycidyl compounds and the like are known, and dicyandiamide, acid anhydrides and the like are known as curing agents for epoxy powder coatings.

Conventionally, powder coatings are produced by dry-mixing a pigment and other coating additives in addition to a curable resin and a curing agent, kneading and dispersing with a melt-kneader, then pulverizing and classifying. Has been done.

However, in the above method, it is necessary to suppress the progress of the crosslinking reaction between the curable resin and the curing agent when the curable resin and the curing agent are heated and melted and kneaded.
Therefore, the kneading time is short and the kneading temperature must be set to a low temperature equal to or lower than the melting point or softening point of the curing agent, which makes it difficult to uniformly disperse the curing agent. there were. That is, in the powder coating material in which the curing agent is not uniformly dispersed, the formed coating film has a problem that the appearance, especially the smoothness is lacking. In addition, the dispersibility of the pigment is also poor, and such a powder coating material has image clarity, image clarity, and
There was a problem that a glossy coating film could not be obtained.

Therefore, as a method for solving such a problem, there is a method of mixing a curable resin and a raw material for powder coating such as a curing agent in a wet manner, that is, in a solvent.
531 (Gazette a), JP-A-10-53729 (JP-B), JP-A-11-302567 (JP-C), JP-A-11-349859 (JP-D), and JP-A-2000-034426. Publication (publication e), JP 20
No. 00-103866 (publication f) and the like. It is disclosed that these methods improve uniform dispersion of the curable resin and the curing agent.

However, the methods proposed in the above-mentioned gazettes a, d, and e are applied to acrylic powder paints, and cannot be applied to polyester powder paints. That is, since the polyester powder coating material uses a resin and a curing agent different from those of the acrylic powder coating material, the solvent used in these prior arts cannot be used as it is. Another reason is that the polyester powder coating material is basically different from the acrylic powder coating material in physical properties in terms of weather resistance and chipping resistance.

Further, although the types of powder coating materials are not particularly limited in the above publications b and c, only the acrylic powder coating material is specifically disclosed, and the polyester powder material is disclosed. There is no specific disclosure of paints. In particular, the above-mentioned publication b discloses the use of an acrylic resin solution and a curing agent solution, but since different solvents are used in each solution, when these solutions are mixed, In some cases, the curing agent may precipitate, and the solubility between the solutions is extremely low, which causes a problem in the uniform dispersibility of the curing agent. Further, the above publication c discloses an example in which a solvent in which the curing agent is not dissolved is used, and in this case also, there is a problem in the uniform dispersibility of the curing agent.

The above publication f relates to a method for producing acrylic powder coatings, polyester powder coatings and the like by spray drying, and uses a solvent that dissolves both a curable resin and a curing agent. Hardeners and pigments easily bleed out on the surface of the powder coating obtained by spray drying, and there are problems with the crosslinking density and the uniformity of additives, and a coating film with a high degree of finished appearance and physical properties is obtained. I can't.

Further, the various methods disclosed in the above-mentioned publications a to f are the large-scale devolatilization / collection for removing a large amount of solvent and a mixing device for mixing each solution of the coating material and the solution. Many problems still remain, such as the need for a device.

[0011]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems in the prior art and to provide a method for producing a polyester powder coating which gives a coating appearance such as excellent smoothness and gloss. To provide.

[0012]

Means for Solving the Problems As a result of intensive studies on a method for producing a polyester powder coating, the present inventors have found that a powder coating raw material containing at least a curable polyester resin and a curing agent, a solvent, and 20% of the curing agent used
The above is continuously kneaded so as to be dissolved in a solvent, and then by removing the solvent by devolatilization under reduced pressure, a coating film having excellent smoothness and uniformity of color tone can be obtained without using a large-scale manufacturing apparatus. The present invention has been achieved by finding that a powder coating to be given can be produced.

That is, according to the present invention, at least (1) a curable polyester resin (A) having a number average molecular weight of 1,000 to 30,000, a glass transition temperature of 30 to 100 ° C., and having a hydroxyl group and / or a carboxyl group at the terminal. , (2) a curing agent (B) which is solid at room temperature and can react with a hydroxyl group or a carboxyl group of the curable polyester resin (A), and (3) a boiling point at normal pressure of 50 to 1
A method for producing a powder coating material using a solvent (C) at 30 ° C., wherein a curable polyester resin (A), a curing agent (B) and a solvent (C) are heated at a temperature condition of 50 to 130 ° C. The present invention relates to a method for producing a powder coating material, which comprises continuously kneading so that 20% by weight or more of a curing agent (B) is dissolved, and then volatilizing and removing the solvent (C) under reduced pressure.

In the present invention, the solvent (C) is preferably used in an amount of 10 to 1000 parts by weight per 100 parts by weight of the curing agent (B). Further, in the present invention, the kneading step of the curable polyester resin (A), the curing agent (B) and the solvent (C) and the devolatilization removing step of the solvent (C) are carried out by one kneading and devolatilizing removal. It can be carried out continuously using the device. In this case, as the kneading / devolatilizing / removing device, a single-screw or twin-screw extruder or a kneader having at least one devolatilization port can be used.

Further, in the present invention, the apparatus used in the kneading step of the curable polyester resin (A), the curing agent (B) and the solvent (C) and the devolatilization removal step of the solvent (C) are used. Kneading and devolatilization removal can be continuously performed by connecting the apparatus in series. In this case, examples of the apparatus used in the kneading step include a single-screw or twin-screw extruder, a single-screw or twin-screw kneader, or an in-line mixer. Examples of the apparatus used in the devolatilization removal step include a single-screw or twin-screw extruder equipped with at least one devolatilization port, or a single-screw or twin-screw kneader.

In the present invention, the coating additive (D) can be further supplied to the kneading step of the curable polyester resin (A), the curing agent (B) and the solvent (C) to carry out the kneading. . Examples of the additive (D) for paint include a melt flow regulator, a defoaming agent, a pinhole inhibitor, an ultraviolet absorber,
At least one selected from an antioxidant, a curing catalyst, a plasticizer, a blocking resistance improver, a powder flow imparting agent, and a pigment can be used. According to the present invention, usually, the mixture of the curable polyester resin (A) and the curing agent (B) obtained by removing the solvent (C) by devolatilization is pulverized to obtain the target powder coating material. Obtainable.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION (I) Curable Polyester Resin (A): The curable polyester resin (A) used in the present invention has a hydroxyl group and / or a carboxyl group at the terminal. Terminal group (hereinafter,
(Also referred to as a reactive group), but a curing agent (B) described later
It reacts with and forms a cured product.

The curable polyester resin (A) is
It can be manufactured by a known method. That is, an oligomerization step of obtaining a low polymer by an esterification reaction or transesterification reaction of an acid component composed of a polybasic acid or its ester-forming derivative and an alcohol component composed of a polyhydric alcohol, and a desired polymer from the low polymer It is carried out by a two-step method including a step of increasing the molecular weight to obtain a polyester resin having a molecular weight. In addition, a three-step method including a depolymerization step to obtain a desired molecular weight after the step of increasing the molecular weight is also used depending on the case.

The above acid components include, but are not limited to, succinic acid, glutaric acid, adipic acid,
Pimelic acid, suberic acid, azelaic acid, sebacic acid,
Dodecanedicarboxylic acid, cyclohexanedicarboxylic acid,
Aliphatic dicarboxylic acids such as decacin dicarboxylic acid, norbornane dicarboxylic acid, tricyclodecane dicarboxylic acid, pentacyclododecane dicarboxylic acid; terephthalic acid, isophthalic acid, phthalic acid, 2-methylterephthalic acid, naphthalenedicarboxylic acid, biphenyldicarboxylic acid, Aromatic dicarboxylic acids such as tetralindicarboxylic acid; and ester-forming derivatives thereof (for example, acid anhydrides, acid chlorides, esters); oxycarboxylic acids such as paraoxybenzoic acid; and the like. They can be used alone or in combination of two or more.

The above-mentioned alcohol component, that is, the polyhydric alcohol is not particularly limited, but for example,
Ethylene glycol, diethylene glycol, 1,2-
Propanediol, 1,3-Propanediol, 2,2
-Dimethyl-1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 2-methyl-1,
3-butanediol, 2-methyl-1,4-butanediol, 2,3-dimethyl-1,4-butanediol,
1,5-pentanediol, 3-methyl-1,5-pentanediol, 2-methyl-1,3-pentanediol, 2-methyl-1,4-pentanediol, 2-methyl-1,5-pentanediol 1,6-hexanediol, 2-ethyl-1,3-hexanediol, neopentyl glycol, 1,8-octanediol, 1,1
0-decanediol, 1,12-dodecanediol,
1,4-cyclohexanediol, 2-butene-1,4
And aliphatic diols such as diols; aromatic diols such as hydroquinone resorcin.

As the polyhydric alcohol exemplified above, glycerin, 2-methyl-1,2,3-propanetriol, 2-methyl-1,2,3-butanetriol, 2-methyl-1,2,2. 4-butanetriol, 3-
Methyl-1,2,3-butanetriol, trimethylolpropane, trimethylolethane, 1,2,6-hexanetriol, pentaerythritol, polypropylene glycol, polytetramethylene ether glycol, polyoxyalkylene glycol, polymer polyol, polyester polyol , Polycaprolactone polyol, polycarbonate diol, polybutadiene polyol, acrylic polyol, epoxy polyol, polysaccharides and the like. The various polyhydric alcohols described above can be used alone or in combination of two or more.

The curable polyester resin (A) used in the present invention is mainly composed of a carboxyl group or a hydroxyl group at the terminal of the molecular chain. Therefore, in order to obtain a polyester resin having a carboxyl group as a main chain terminal (hereinafter, may be simply referred to as a polyester resin having a carboxyl group at the terminal), the above acid component is used in excess with respect to the alcohol component. To do. Further, in order to obtain a polyester resin having a hydroxyl group as a main chain terminal (hereinafter, may be simply referred to as a polyester resin having a hydroxyl group at the terminal), the above alcohol component is used in excess of the acid component. To do.

In the present invention, the curable polyester resin (A) has a glass transition temperature of 30 to 100 ° C., preferably 40 ° C. to 80 ° C., and a number average molecular weight of 1000 to
It is 30,000, preferably 2,000 to 10,000.
If the glass transition temperature is lower than the above range, particles of the powder coating material are fused to each other, resulting in poor blocking resistance. Further, when the glass transition temperature is higher than the above range, the melt viscosity at the time of baking becomes large, and not only the finishability is deteriorated, but also the miscibility of the resin, the curing agent, and the solvent at the time of kneading is decreased, resulting in a uniform The powder coating composition cannot be obtained. If the number average molecular weight is smaller than the above range, the powder coating obtained has poor blocking resistance, and if it is larger than the above range, it becomes difficult to obtain a smooth coating film appearance.

In the present invention, the number average molecular weight is measured by gel permeation chromatography (GPC) method. A sample is a tetrahydrofuran solution in which 0.3 part of resin is dissolved in 100 parts by weight of tetrahydrofuran, and this is measured by GPC, for example, 8020 type GPC device manufactured by Tosoh Corporation, and the number average molecular weight is calculated by polystyrene conversion. Also, glass transition temperature (℃)
Is a DSC method (differential scanning calorimetry, temperature rising rate 10 ° C. /
min) and the midpoint glass transition temperature (Tm
Let g) be the glass transition temperature (Tg).

In the present invention, the hydroxyl value of the curable polyester resin (A) having a hydroxyl group at the terminal is 1
0 to 130 mg KOH / g, especially 20 to 120 mg KO
The acid value of the curable polyester resin (A) having a carboxyl group at its terminal is preferably 10 to 10 H / g.
100 mg KOH / g, especially 20-80 mg KOH / g
It should be in the range of. When the hydroxyl value or the acid value is smaller than the above range, sufficient stain resistance of the coating film cannot be obtained, and when it is larger than the above range, sufficient weather resistance of the coating film cannot be obtained, which is not preferable.

(II) Curing agent (B): The curing agent (B) used in the present invention reacts with the terminal hydroxyl group or carboxyl group of the above-mentioned curable polyester resin (A). Therefore, an appropriate curing agent (B) is used depending on the type of terminal group of the polyester resin. For example, when the curable polyester resin (A) having a hydroxyl group at the terminal is used, the aliphatic, alicyclic or aromatic polyisocyanate is used as a phenol or caprolactam, but not limited thereto. ,
Blocked isocyanate compound blocked with a blocking agent such as alcohols; uretdione compound blocked by cyclizing isocyanato groups; amino compound represented by tetramethoxyglycolyl; 2,2-bis (4-cyanatephenyl) propane Representative cyanate compounds and the like are suitable as the curing agent (B), and these can be used alone or in combination of two or more kinds. Among these, preferred are blocked isocyanate compounds, uretdione compounds and amino compounds.

When the curable polyester resin (A) having a carboxyl group at its end is used, the triglycidyl isocyanurate, epichlorohydrin-bisphenol A type, novolac type, glycidyl group are not limited thereto. Epoxy compounds having epoxy groups such as ether type epoxy resins; glycidyl group- or methylglycidyl group-containing acrylic resins; amide compounds represented by β-hydroxyalkylamides; and the like are suitable as the curing agent (B), and Is alone 2
Combinations of more than one species can also be used.

The above-mentioned curing agent (B) is generally used in an amount of 0.7 to 1 per equivalent of the reactive group (that is, the terminal hydroxyl group or carboxyl group) in the curable polyester resin.
Used in an amount of 1.3 times equivalent.

(III) Paint additive (D): In the method for producing a powder paint of the present invention, in addition to the above-mentioned curable acrylic resin (A) and curing agent (B), a paint known per se. Additives such as melt flow regulators, pinhole inhibitors, UV absorbers, antioxidants, curing catalysts, plasticizers, blocking resistance improvers, powder fluidizers, defoamers, and pigments. , Can be used if necessary. For example,
Pigments include, but are not limited to, titanium oxide, phthalocyanine blue, phthalocyanine green, carbon black, iron oxide and the like. Such an additive (D) for paint is used in such an amount that a predetermined function is exerted without impairing the characteristics such as coating film forming ability of the powder paint. For example, the pigment is usually used in an amount of 200 parts by weight or less per 100 parts by weight of the curable polyester resin (A).

(IV) Solvent (C): The solvent (C) used in the method for producing the powder coating composition of the present invention is at least a curing agent used when continuously kneading at a temperature of 50 to 130 ° C. A material that can dissolve 20% by weight or more, preferably 30% by weight or more, more preferably 50% by weight or more, most preferably 70% by weight or more of (B), and then remove by volatilization by heating and reducing pressure is selected. In order to suppress the curing reaction between the curable polyester resin (A) and the curing agent (B) during the devolatilization removal treatment after kneading, the devolatilization removal treatment is carried out at the lowest possible temperature condition. Therefore, the solvent (C) used in the present invention has a boiling point in the range of 50 to 130 ° C. under normal pressure.

Examples of such a solvent (C) used in the present invention include aromatic hydrocarbons such as toluene and benzene; dichloromethane, chloroform, tetrachloromethane, 1,2-dichloroethane, 1,1,1. -Halogenated aliphatic hydrocarbons such as trichloroethane, 1,1,2-trichloroethane, trichloroethylene, tetrachloroethylene, 1,2-dichloropropane; methyl formate, ethyl formate, propyl formate, butyl formate, isobutyl formate, pentyl formate, methyl acetate , Ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, isobutyl acetate, sec-butyl acetate, methyl propionate, ethyl propionate, methyl butyrate, ethyl butyrate and other aliphatic carboxylic acid esters; dimethyl carbonate, diethyl carbonate and other carbonates Ester; geo Cyclic ethers such as sun, tetrahydrofuran, tetrahydropyran; ether alcohols such as 2-methoxyethanol, 2-ethoxyethanol, 1-methoxy-2-propanol; methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, iso Butanol, 2-butanol, tert-
Examples thereof include alcohols such as butanol, 2-pentanol, and 3-pentanol; aliphatic ketones such as acetone, methyl ethyl ketone, 2-pentanone, 3-pentanone, and methyl isobutyl ketone; and the like.
One kind may be used alone, or two or more kinds may be mixed and used.

By the way, the above-mentioned solvent (C) dissolves at least 20% by weight, preferably 30% by weight or more, more preferably 50% by weight or more, particularly preferably 70% by weight or more of the curing agent during kneading. Therefore, a proper one is selected according to the type of the curing agent used.

For example, when the hydroxyl group-terminated curable polyester resin (A) is used, a blocked isocyanate compound, a uretdione compound, an amino compound and a cyanate compound are used as the curing agent (B) as described above. However, as a suitable solvent having solubility in such a curing agent (B), among those exemplified above, for a blocked isocyanate compound, a uretdione compound, and an amino compound, an aromatic hydrocarbon, Halogenated aliphatic hydrocarbons, aliphatic carboxylic acid esters, carbonic acid esters, cyclic ethers, ether alcohols, alcohols, aliphatic ketones are particularly preferred;
For the cyanate compound, aromatic hydrocarbons, halogenated aliphatic hydrocarbons, aliphatic carboxylic acid esters, carbonic acid esters, cyclic ethers and aliphatic ketones are particularly suitable.

When the carboxyl group-terminated curable polyester resin (A) is used, an epoxy compound, a glycidyl group- or methylglycidyl group-containing acrylic resin and an amide compound are used as the curing agent (B). Examples of suitable solvents having solubility in the curing agent (B) include aromatic compounds, halogenated aliphatic hydrocarbons, and fats for epoxy compounds and acrylic resins, among those exemplified above. Group carboxylic esters, carbonates, cyclic ethers, aliphatic ketones are preferred; for amide compounds, alcohols are preferred.

The curable polyester resin (A) is
Although it does not necessarily have to be completely dissolved in the above-mentioned solvent (C), in order to uniformly disperse the curable polyester (A) and the curing agent (B) or the coating additive (D), a curable polyester It is most preferable to use the solvent (C) which exhibits good solubility in the resin (A). Examples of such a solvent (C) include aromatic hydrocarbons, halogenated aliphatic hydrocarbons, aliphatic carboxylic acid esters, cyclic ethers, and aliphatic ketones.

(V) Mixing-kneading: In the present invention, the above-mentioned curable polyester resin (A), the curing agent (B) and, if necessary, the coating additive (D) are present in the presence of the above-mentioned solvent (C). Wet-mixing (kneading) continuously underneath, and then the solvent is continuously devolatilized under reduced pressure. In order to suppress the curing reaction between the resin (A) and the curing agent (B), continuous kneading and solvent devolatilization are performed at 50 to 130 ° C.
It is done within the range of.

In the present invention, the curing agent (B) used is at least 20% by weight, preferably 3% by weight or more.
It is necessary to carry out the above kneading in a state in which 0% by weight or more, more preferably 50% by weight or more, and most preferably 70% by weight or more are dissolved. That is, the kneading is performed in a state where a certain amount or more of the curing agent (B) is dissolved, so that the dispersibility of the curing agent (B) in the resin (A) is improved. From the powder coating material thus obtained, the curing reaction proceeds uniformly to form a coating film, and a coating film excellent in surface smoothness, mechanical properties and the like can be obtained. Further, the dispersibility of components such as pigments that are not dissolved in a solvent is improved, and a coating film having excellent image clarity and gloss can be obtained.
Therefore, in the present invention, in order to dissolve a certain amount or more of the curing agent (B), the amount of the solvent (C) used is the amount of the curing agent (B) 1
10 to 1000 parts by weight, preferably 1 per 00 parts by weight
The amount is preferably 5 to 900 parts by weight, more preferably 20 to 800 parts by weight. When the amount of the solvent (C) used is less than the above range, it becomes difficult to dissolve a certain amount or more of the used curing agent (B), and the resin (A) and other components (particularly the curing agent (B There is a possibility that the miscibility with)) cannot be sufficiently improved. When the amount of the solvent (C) used is larger than the above range, the miscibility between the resin (A) and other components can be improved, but the load on the devolatilization of the solvent increases, It becomes economically disadvantageous because a long devolatilization device is required.

In the present invention, the continuous kneading step and the devolatilization removal (desolventization) step described above can be carried out in one stage using one continuous kneading-devolatilization removal apparatus, or continuous kneading is performed. A continuous kneading machine and a devolatilization remover for devolatilizing and removing the solvent volatilized under reduced pressure can be connected in series to carry out in two stages.

The curable polyester resin (A) used for continuous kneading, the curing agent (B), and the paint additive (D) used as necessary are separately added to the above continuous kneading-
It can be charged into a devolatilization remover or a continuous kneader, or can be charged after previously mixing them.
The mixing before charging is not limited to this, but can be performed using a Henschel mixer, a tumbler, or the like.

The solvent (C) can be directly side-fed into the continuous kneading-devolatilizer or the continuous kneader without mixing with the above-mentioned components, and the solvent (C) is used. It is also possible to prepare a solution of the curable polyester resin (A) and the curing agent (B) and side feed as such a solution. (In addition, the side feed means that a part of the components to be kneaded is supplied to the device used for kneading through a separate inlet located on the downstream side of the inlet connected to the main supply line. In addition, as described above, when the kneading and the devolatilization removal are performed in the second stage, the solvent (C) is transferred to the second stage devolatilization removal device as long as the devolatilization removal device has a kneading function. It can also be supplied.

Further, the additive (D) for coating, which is optionally used, can be mixed with the curable polyester resin (A) or the curing agent (B) and subjected to continuous kneading. It is also possible to dissolve or disperse it in the resin (A) solution or the curing agent (B) solution and use it for continuous kneading.

In the present invention, as the above-mentioned continuous kneading-devolatilizing / removing apparatus used when kneading and devolatilizing / removing are carried out in one step, a hopper capable of stably supplying each component into the apparatus and A device equipped with a quantitative feeder, a quantitative pump for supplying a solvent or a solution, and the like, which has a kneading function and a solvent devolatilization removal function under reduced pressure, such as a single-screw or twin-screw extruder or a kneader is used. It

As such a single screw extruder, for example,
The rotating shaft has a screw shape and is suitable for kneading.
ck) type, toped type, etc. having a high shearing shape, notch type, dullage type, etc., which are provided with a generally known kneading section can be used. As the twin-screw extruder, a twin-screw extruder having a pair of screw shafts having a kneading function that rotate in different directions or in the same direction can be used. Of course, it is necessary that all extruders have at least one devolatilizing port for devolatilizing and removing volatile matter, and the solvent (C) can be devolatilized under reduced pressure from this devolatilizing port. Done. In particular, an extruder having a plurality of devolatilizing ports preferably has a structure in which the degree of pressure reduction can be set separately in each devolatilizing zone (portion where the devolatilizing ports are provided). In the extruder having such a structure, it is possible to increase the degree of pressure reduction toward the downstream side in the extrusion direction, and since it generally has excellent devolatilization performance,
It is particularly suitable for the present invention. Further, in the case of having a plurality of devolatilization ports, the solvent or solution can be supplied to any kneading zone, for example, the solvent or solution can be supplied from one place, or the solvent or solution can be divided into two or more places. It is also possible to supply a solution. In the present invention, as an extruder that is particularly preferably used as the continuous kneading-devolatilization removing device, for example, "TEM-37BS" manufactured by Toshiba Machine Co., Ltd.
Can be illustrated.

The kneader which can be used as a continuous kneading-devolatilizing device has at least one devolatilizing port,
It is preferable to have a structure in which two stirring shafts are arranged side by side in a row in the barrel, and a screw and a paddle are incorporated in each shaft. That is, the screw and the paddle are rotated in the same direction, the raw material supplied from the upper end of one end of the barrel is fed into the kneading zone by the screw, and after kneading with the paddle in the kneading zone, the other end lower part of the barrel,
The kneaded material is continuously discharged from the side or the front.
Examples of the kneader having such a structure include "SC processor" and "KRC" manufactured by Kurimoto Iron Works Co., Ltd.
An example is “kneader”.

When a continuous kneader and a devolatilization remover are connected in series to carry out kneading and devolatilization removal in two stages, both such continuous mixers and devolatilization removers are used. The single-screw or twin-screw extruder or kneader described above can be used. A resin liquid in which a curable polyester resin (A) is dissolved or dispersed in a solvent (C), and a curing agent (B)
An in-line mixer can be used when mixing a curing agent solution obtained by dissolving or dispersing the above in a solvent (C). Of course, when the above-mentioned extruder, kneader or in-line mixer is used as a continuous mixer, no devolatilization port is required for these. Further, in this case, since the devolatilization removal device also has a kneading function, it is possible to feed at least a part of the solvent (C) described above into the devolatilization removal device.

As can be understood from the above description, continuous kneading and devolatilization removal can be carried out in various patterns depending on the apparatus used and the like. 1 to 4 show typical examples of these patterns. Incidentally, FIG.
4 shows an example of performing kneading and devolatilization removal in a single stage using a continuous kneading-devolatilization removal device, this continuous kneading-devolatilization removal device is a continuous kneading machine described above. It can also be replaced with a device in which the devolatilizer and the devolatilizer are connected in series.

In the pattern shown in FIG. 1, a resin liquid in which a curable polyester resin (A) is dissolved or dispersed in a solvent (C) and a curing agent in which a curing agent (B) is dissolved or dispersed in a solvent (C) are used. The liquid and the liquid are separately prepared and supplied to a continuous kneading-devolatilizing / removing apparatus to continuously perform the kneading and the removal of the solvent from the devolatilizing port. Each solution may be supplied from different supply ports, or these solutions may be mixed and supplied in advance with an in-line mixer such as a static mixer. Further, the curable polyester resin (A) and the curing agent (B) can be melted or dispersed in the solvent (C) using the same dissolution tank and supplied to the continuous kneading-devolatilization removing apparatus. However, as described above, at least 2 of the curing agent (B) used at the time of kneading.
The type and amount of the solvent (C) used are determined so that 0% by weight is dissolved. This is exactly the same for the patterns shown in FIGS. 2 to 4 below.

In the pattern of FIG. 2, the curable polyester resin (A) and the curing agent (B) are supplied to the continuous kneading-devolatilization / removal apparatus from the same supply port, and at the same time, the solvent is supplied from the other supply port. By side-feeding (C) to the continuous kneading-devolatilizing / removing apparatus, kneading is continuously performed in the presence of the solvent (C), and the solvent is further removed from the devolatilizing port.

In the pattern of FIG. 3, the curable polyester resin (A) is supplied to the continuous kneading-devolatilizing / removing apparatus, and the curing agent solution or dispersion containing the curing agent (B) and the solvent (C) is supplied. The continuous kneading-devolatilization removing device is side-fed from a supply port different from the supply port of the curable polyester resin (A) for continuous kneading, and then the solvent is removed from the devolatilizing port.

In the pattern of FIG. 4, a resin liquid prepared by dissolving or dispersing a curable polyester resin (A) in a solvent (C) is supplied to a continuous kneading-devolatilizing / removing device, and a curing agent (B) is added. By supplying from separate supply ports, kneading and removal of the solvent from the devolatilization port are continuously performed.

In any of the patterns shown in FIGS. 1 to 4 described above, the additives for paints such as pigments, which are used as necessary, are usually a curable polyester resin (A) or a curable polyester resin (A). It is supplied by being mixed with the solution or dispersion of (1) in advance, but can also be supplied after being dissolved or dispersed in the curing agent (B) or the solution of the curing agent (B).

The kneaded composition obtained as described above is pulverized, if necessary, and classified to have a predetermined particle size, and then used as a powder coating material.

In the polyester powder coating material thus obtained, the curing agent (B) and coating additives such as pigments used as necessary are uniformly dispersed in the curable polyester resin (A). In particular, the curing agent exists as fine particles. A coating film in which the curing reaction has proceeded uniformly is obtained from the powder coating material thus obtained, and a coating film excellent in surface smoothness, mechanical properties and the like is provided. Further, the use of the solvent (C) also improves the dispersibility of components such as pigments that are not soluble in the solvent, and a coating film having excellent image clarity and gloss can be obtained.

[0054]

EXAMPLES The present invention will be specifically described with reference to the following Reference Examples, Examples and Comparative Examples, but it goes without saying that the present invention is not limited to these Examples. Further, in these examples, the compounding amounts are all shown by weight. The physical properties of the powder coating material were evaluated as follows. 1) Nonvolatile content concentration (wt%): 2g of powder coating material at 140 ° C
After drying for 30 minutes, the weight retention rate (wt%) before and after drying was calculated. 2) Particle diameter (μm): The volume average particle diameter of the powder coating material was measured using a laser diffraction scattering type particle size distribution measuring device (manufactured by Horiba, Ltd., model: LA-910). 3) Blocking resistance: 30 g of the powder coating material was placed in a cylindrical container having a diameter of 2 cm and stored at 40 ° C. for 7 days, and the lump of the powder coating material was evaluated according to the following criteria. Good: No powder coating lumps and no agglomerates. Δ: Some lumps of the powder coating material are observed, but the cohesive force of the lumps is weak, so it cannot be picked up with a finger. ×: A lump of powder coating was observed, and the lump could not be picked up with a finger.

4) Appearance of coating film (smoothness): Powder coating is electrostatically coated on a zinc phosphate-treated steel sheet, and the coating is applied in an oven at 180 ° C. for 2 minutes.
The surface smoothness of the coating film obtained by curing for 0 minutes was visually evaluated. ◯: Good smoothness without any dents or irregularities. Δ: A slight dent and unevenness are recognized, and the smoothness is slightly inferior. X: Significant dents and irregularities are recognized, and the smoothness is poor. 5) Film thickness: The film thickness of the coating film after coating / curing is manufactured by Kett Scientific Research Co., Ltd., film thickness measuring instrument (model: LZ-300C ) Was used for the measurement. 6) Center line average roughness Ra: The surface of the coating film after coating / curing was quantified by averaging the unevenness using a SURFCOM stylus type surface roughness meter manufactured by Tokyo Seimitsu Co., Ltd. The cutoff is 0.8 mm, and the smaller the value, the smoother the coating film. 7) Gloss (60 °): The 60 ° specular reflectance (%) of the coating film surface after coating and curing was measured. JIS K5
According to 400 7.6. 8) Coating film clarity: The appearance of the coating film was visually evaluated. ◯: The color tone is uniform and the image clarity is excellent. Δ: The color tone is slightly uneven and the image clarity is slightly inferior ×: The image clarity is inferior.

Reference Example 1 (Synthesis of hydroxyl group-terminated curable polyester resin) 38 parts by weight of neopentyl glycol and trimethylol were placed in a reactor equipped with a thermometer, a stirrer, a reflux condenser, a nitrogen inlet and a bottom extraction tube. 1.5 parts by weight of propane was charged and heated to 150 ° C., and terephthalic acid 60.
5 parts by weight and 0.05 part by weight of dibutyltin oxide were added, stirred, and dehydrated and heated to 240 ° C. for 6 hours. Furthermore, by continuing the polycondensation reaction at the same temperature, the hydroxyl value is 34 mgKOH / g, the number average molecular weight is 3800,
A polyester resin having a glass transition temperature Tg of 59 ° C. was obtained. This polyester resin is further roughly crushed with a crusher,
It was used in the experimental examples described below.

Reference Example 2 (Synthesis of carboxyl group-terminated curable polyester resin) Neopentyl glycol 3 was placed in the same reactor as in Reference Example 1.
5.0 parts by weight, trimethylolpropane 1.9 parts by weight,
63.1 parts by weight of terephthalic acid was charged, then 0.05 part by weight of dibutyltin oxide was added, and the mixture was stirred and heated to 240 ° C. for 6 hours while dehydrating. further,
The polycondensation reaction was continued at the same temperature and the acid value was 35 mgKOH /
g, number average molecular weight is 3700, glass transition temperature Tg is 5
A 7 ° C. polyester resin was obtained. This polyester resin was further roughly crushed with a crusher and used in the experimental examples described later.

Reference Example 3 (Preparation of Auxiliary Material) Melt flow regulator (Modaflow powder 2 manufactured by Monsanto Co.)
000) 2.0 parts by weight, a defoaming agent (benzoin) 1.0 part by weight, and a pigment (titanium oxide) 97.0 parts by weight were added and dry blended to obtain an auxiliary raw material mixture for a polyester powder coating.

Example 1 28.2 parts by weight of the hydroxyl group-terminated polyester resin obtained in Reference Example 1, a curing agent (Vestagon B manufactured by Huls)
1530: Isophorone diisocyanate / adduct / ε
-Caprolactam block) 4.65 parts by weight, curing catalyst (di-n-octyltin maleate) 0.15 parts by weight, and auxiliary material 17.0 parts by weight of Reference Example 3 were dry blended to obtain a powder. It was a raw material mixture for paints. This raw material mixture for powder coating is supplied from a raw material hopper of a three-vent type twin-screw devolatilization extruder TEM-37BS (manufactured by Toshiba Machine Co., Ltd.) adjusted to a cylinder temperature of 110 ° C. and a screw rotation speed of 170 rpm to supply 50 kg / Extruded at a speed of h. At the same time, in the first kneading zone downstream of the raw material hopper,
While supplying the ethyl acetate (solvent) at a rate of 4 kg / h using a metering pump and continuously kneading the raw material for the powder coating, the volatile matter was further extracted at the first vent located at the downstream of 53 kPa. Partly removed. Furthermore, the second kneading zone,
The second vent (6.7 kPa), the third kneading zone, and the third vent (0.67 kPa) are used for kneading and devolatilization removal,
A kneaded composition was obtained. The kneaded composition was crushed using an impact crusher and then classified to obtain a powder coating having an average particle size of 25 μm. The obtained powder coating material was electrostatically coated on a zinc phosphate-treated steel sheet and cured in an oven at 180 ° C. for 20 minutes to obtain a coating film. The physical properties of the obtained coating film were evaluated, and the results are shown in Table 1. In the composition of the powder coating material and the solvent, it was confirmed that 100% by weight of the curing agent was dissolved.

Example 2 15.0 parts by weight of the auxiliary raw material of Reference Example 3 was added to 25.0 parts by weight of the hydroxyl group-terminated polyester resin obtained in Reference Example 1 and dry blended to obtain a resin raw material. Further, 3.98 parts by weight of acetone (solvent), 3.98 parts by weight of isophorone diisocyanate-adduct uretdione-bonded block (curing agent: Vestagon BF1540), and curing catalyst (di-n-octyltin maleate). 0.35 parts by weight was added and heated to prepare a curing agent solution at 56 ° C.
While the resin raw material prepared above was continuously extruded at a rate of 40 kg / h under the same conditions as in Example 1, the above curing agent solution was side-fed to the extruder at a rate of 8.3 kg / h. Then, kneading and devolatilization were continuously carried out to obtain a kneaded composition. This kneaded composition was treated in the same manner as in Example 1 to obtain a powder coating material. Table 1 shows the evaluation results of the physical properties of the powder coating material and the coating film. In the composition of the powder coating material and the solvent, it was confirmed that 100% by weight of the curing agent was dissolved.

Example 3 25.2 parts by weight of the hydroxyl group-terminated polyester resin obtained in Reference Example 1 and methyl ethyl ketone 1 as a solvent
0.8 parts by weight was mixed and heated to prepare a resin solution at 80 ° C. In addition, a curing agent (Vestagon B1530) 4.
18 parts by weight, 15.28 parts by weight of the auxiliary material of Reference Example 3 and 0.14 of a curing catalyst (di-n-octyltin maleate).
The curing agent raw material was adjusted by dry blending with parts by weight.
Under the same conditions as in Example 1 except that the temperature condition of the extruder was 120 ° C., the resin solution was supplied to the extruder at a rate of 36 kg / h by a metering pump, and the curing agent raw material was further fed into the screw type metering feeder. Then, the mixture was supplied to the extruder at a rate of 19.6 kg / h, and kneading and devolatilization were continuously performed. The obtained kneaded composition was treated in the same manner as in Example 1 to obtain a powder coating material. Table 1 shows the evaluation results of the physical properties of the powder coating material and the coating film. In the composition of the powder coating material and the solvent, it was confirmed that 100% by weight of the curing agent was dissolved.

Example 4 25.4 parts by weight of the hydroxyl-terminated polyester resin obtained in Reference Example 1, 10.9 parts by weight of acetone (solvent),
And 15.3 parts by weight of the auxiliary raw materials of Reference Example 3 were mixed and heated to prepare a resin-pigment mixed solution at 56 ° C. Further, 4.16 parts by weight of a curing agent (Vestagon B1530), 0.14 parts by weight of a curing catalyst (di-n-octyltin maleate) and 4.36 parts by weight of acetone were mixed and heated to 56 ° C. A solution was prepared. 52 kg of resin-pigment mixture
At a rate of h and at a rate of 8.6 kg / h, the curing agent solution was continuously fed to the extruder under the same conditions as in Example 1, and kneading and devolatilization were performed continuously to obtain a kneading composition. I got a thing.
This kneaded composition was treated in the same manner as in Example 1 to obtain a powder coating material. Table 1 shows the evaluation results of the physical properties of the powder coating material and the coating film. In the composition of the powder coating material and the solvent, it was confirmed that 100% by weight of the curing agent was dissolved.

Example 5 A powder coating material was produced by kneading and devolatilizing in the same manner as in Example 1 except that tetrahydrofuran was used as the solvent. Table 1 shows the evaluation results of the powder coating and the coating film. In the composition of the powder coating material and the solvent, it was confirmed that 100% by weight of the curing agent was dissolved.

Example 6 To 38.9 parts by weight of the carboxyl group-terminated polyester resin obtained in Reference Example 2, the auxiliary raw material 21.1 obtained in Reference Example 3 was added.
Parts by weight were added and dry blended to prepare a resin raw material. Also, β-hydroxyalkylamide (curing agent; E
MS-Chemie's Primid XL-522)
2.01 parts by weight was added to 6.03 parts by weight of methanol at 64 ° C. and substantially dissolved to prepare a curing agent solution. 60.0 k of the above resin raw material was continuously applied under the same conditions as in Example 2.
While supplying to the extruder at g / h and extruding, the above curing agent solution was side-fed to the extruder at 8.04 kg / h to continuously perform kneading and devolatilization to produce a powder coating. . The evaluation results of the powder coating material and the coating film are shown in Table 2.
In the composition of the powder coating material and the solvent, it was confirmed that 100% by weight of the curing agent was dissolved.

Example 7 24.8 parts by weight of the carboxyl group-terminated polyester resin obtained in Reference Example 2 and 11.7 parts by weight of an epoxy resin (curing agent; Epicoat # 1003F manufactured by Japan Epoxy Resins Co., Ltd., epoxy equivalent: 750 eq / g). Parts, a curing catalyst (Curazole C11Z manufactured by Shikoku Chemicals Co., Ltd.) 0.1 part by weight, and 13.4 parts by weight of the auxiliary material of Reference Example 3 are dry blended,
A raw material mixture for powder coating was prepared. Under the same conditions as in Example 1, this raw material mixture was fed into an extruder at 50 kg / h and extruded, while adding 20 kg / ethyl acetate (solvent).
Side feeding was carried out at h, kneading and devolatilization were continuously carried out, and a powder coating material was produced in the same manner as in Example 1. The evaluation results of the powder coating material and the coating film are shown in Table 2. In the composition of the powder coating material and the solvent, 100% of the curing agent was used.
It was confirmed that wt% was dissolved.

(Same Feed Composition as in Example 6 and Side-Feeding a Small Amount of Methanol) Example 8 38.9 parts by weight of the carboxyl group-terminated polyester resin obtained in Reference Example 2, a curing agent (curing agent; EMS-Chem)
2.01 parts by weight of Primid XL-522 manufactured by IE Co., Ltd. and 21.1 parts by weight of the auxiliary raw material of Reference Example 3 were dry-blended to obtain a raw material mixture for powder coating. This raw material mixture for powder coating material was supplied from a raw material hopper of a three-vent type twin-screw devolatilization extruder TEM-37BS (manufactured by Toshiba Machine Co., Ltd.) adjusted to a cylinder temperature of 110 ° C. and a screw rotation speed of 170 rpm to obtain 62 kg. Extruded at a speed of / h. At the same time, while supplying (methanol) at a rate of 1 kg / h to the first kneading zone, which is located downstream of the raw material hopper, at a rate of 1 kg / h, while continuously kneading the raw material for powder coating material, 53 kPa further downstream is provided. Part of the volatile matter was removed by the adjusted first vent. Furthermore, kneading and devolatilization removal were performed through the second kneading zone, the second vent (6.7 kPa), the third kneading zone, and the third vent (0.67 kPa) to obtain a kneading composition. This kneaded composition was treated in the same manner as in Example 1 to obtain a powder coating material. Table 2 shows the evaluation results of the physical properties of the powder coating material and the coating film. In the composition of the powder coating material and the solvent, it was confirmed that 33% by weight of the curing agent was dissolved.

Comparative Example 1 A powder coating material was produced and evaluated in the same manner as in Example 1 without using ethyl acetate. The results are shown in Table 3.
The coating film obtained from this powder coating was inferior in smoothness and physical properties.

Comparative Example 2 Side feed rate of ethyl acetate was 60 kg /
A powder coating material was produced in the same manner as in Example 1 except that the content was changed to h, the physical properties of the powder coating material and the coating film were evaluated, and the results are shown in Table 3. In this example, the solvent could not be completely removed by devolatilization in the extruder, resulting in poor blocking properties and coating film physical properties.

Comparative Example 3 Except that the solvent for side feeding was changed to hexane,
A powder coating material was produced in the same manner as in Example 1, the physical properties of the powder coating material and the coating film were evaluated, and the results are shown in Table 3. The coating film was inferior in smoothness and physical properties.

Comparative Example 4 A powder coating material was produced in the same manner as in Example 4 except that the solvent used was changed to xylene, and the physical properties of the powder coating material and the coating film were evaluated. The results are shown in Table 3. . In this example, the solvent could not be completely removed by devolatilization in the extruder, resulting in poor blocking properties and coating film physical properties.

Table 1 Example 1 Example 2 Example 3 Example 4 Example 5 Nonvolatile content concentration (wt%) 99.9 99.9 99.8 99.8 99.9 Average particle size (μm) 25 28 24 28 27 Blocking resistance ○ ○ ○ ○ ○ Film thickness (μm) 42 45 43 47 45 Coating image clarity ○ ○ ○ ○ ○ Gloss value (60 ℃) 93 94 93 94 94 Coating film appearance (smoothness) ○ ○ ○ ○ ○ Center line average roughness Ra (μm) 0.06 0.07 0.07 0.06 0.06

Table 2 Example 6 Example 7 Example 8 Nonvolatile content concentration (wt%) 99.9 99.8 99.9 Average particle size (μm) 27 28 28 Blocking resistance ○ ○ ○ Film thickness (μm) 44 45 46 Coating image clarity ○ ○ ○ Gloss value (60 ° C) 95 95 94 Coating film appearance (smoothness) ○ ○ ○ Center line average roughness Ra (μm) 0.06 0.07 0.08

Table 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Nonvolatile content concentration (wt%) 99.8 97.4 99.6 96.1 Average particle size (μm) 25 23 24 28 Blocking resistance ○ × ○ × Thickness (μm) 50 47 46 48 Coating sharpness × Δ Δ Δ Gloss value (60 ° C.) 89 88 90 89 89 Coating appearance (smoothness) Δ × × × Center line average roughness Ra (μm) ) 0.13 0.12 0.13 0.11

[Brief description of drawings]

FIG. 1 is a process in which a curable polyester resin and a solvent, a curing agent and a solvent are separately prepared and supplied to a continuous kneading-devolatilizing / removing apparatus to perform kneading and devolatilizing / removing.

FIG. 2 shows that the curable polyester resin and the curing agent are supplied from the same supply port to the continuous kneading-devolatilization / removal device, and the solvent is supplied from another supply port to continuously mix the mixture. And the process of removing the volatilization.

FIG. 3 is a process in which a curable polyester resin is supplied to a kneading-devolatilizing / removing device, and a mixture of a curing agent and a solvent is supplied from another supply port to perform kneading and devolatilization / removal. .

FIG. 4 is a process in which a mixture of a curable polyester resin and a solvent is supplied to a continuous kneading-devolatilizing device, and a curing agent is supplied from another supply port to perform kneading and devolatilization. .

[Explanation of symbols]

1-curable polyester resin 2 ... Hardener 3 ... solvent 4 ... volatile matter (recovered solvent) 5 ... Powder coating composition 11-Curable polyester resin-solvent storage tank 12 ... Curing agent-solvent storage tank 13 ... Solvent storage tank 14 ... Liquid delivery pump 15 ... Continuous kneading-devolatilization removal device 16 ... Venting port for volatilization

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Claims (20)

[Claims] 1. At least (1) a number average molecular weight of 100.
Curable polyester resin (A) having a glass transition temperature of 0 to 30,000, a glass transition temperature of 30 to 100 ° C. and having a hydroxyl group and / or a carboxyl group at the terminal, and (2) a hydroxyl group or a carboxyl group of the curable polyester resin (A). A solid curing agent (B) that can react with room temperature, and (3) a solvent (C) having a boiling point of 50 to 130 ° C. under normal pressure
A method for producing a powder coating composition using the method of claim 5, wherein the curable polyester resin (A), the curing agent (B), and the solvent (C) are mixed with each other.
20% by weight of the curing agent (B) under a temperature condition of 0 to 130 ° C.
A method for producing a powder coating material, characterized in that the above is continuously kneaded so as to be dissolved in the solvent (C), and then the solvent (C) is removed by devolatilization under reduced pressure. 2. The method for producing a powder coating material according to claim 1, wherein the curable polyester resin (A) has a number average molecular weight of 2,000 to 10,000 and a glass transition temperature of 40 ° C. to 80 ° C. 3. The curable polyester resin (A) is 10
The method for producing a powder coating according to claim 1, which has a hydroxyl value of 130 mgKOH / g. 4. The curable polyester resin (A) is 10
The method for producing a powder coating material according to claim 1, which has an acid value of -100 mgKOH / g. 5. The curing agent (B) is at least one selected from the group consisting of blocked isocyanate compounds, uretdione compounds, amino compounds, and cyanate compounds.
The method for producing a powder coating material according to claim 3, which is a seed and reacts with a hydroxyl group of the curable polyester resin (A). 6. The powder according to claim 4, wherein the curing agent (B) is at least one selected from the group consisting of an epoxy compound, an acrylic resin containing a glycidyl group or a methylglycidyl group, and an amide compound. Paint manufacturing method. 7. The curing agent (B) is used in an amount of 0.7 to 1.3 times equivalents per equivalent of hydroxyl groups and / or carboxyl groups in the curable polyester resin (A). The method for producing the powder coating material according to 1. 8. The method for producing a powder coating composition according to claim 1, wherein the solvent (C) is used in an amount of 10 to 1000 parts by weight with respect to 100 parts by weight of the curing agent (B). 9. At least one selected from the group consisting of uretdione compounds, amino compounds, and block cyanate compounds is used as the curing agent (B), and aromatic hydrocarbons and halogenated compounds are used as the solvent (C). The production of the powder coating material according to claim 5, wherein at least one selected from the group consisting of an aliphatic hydrocarbon, an aliphatic carboxylic acid ester, a carbonic acid ester, a cyclic ether, an ether alcohol, an alcohol and an aliphatic ketone is used. Method. 10. A cyanate compound is used as a curing agent (B), and an aromatic hydrocarbon is used as a solvent (C).
The method for producing a powder coating material according to claim 5, wherein at least one selected from the group consisting of halogenated aliphatic hydrocarbons, aliphatic carboxylic acid esters, carbonic acid esters, cyclic ethers, and aliphatic ketones is used. 11. At least one selected from the group consisting of an epoxy compound, an acrylic resin containing a glycidyl group or a methylglycidyl group as the curing agent (B).
Using a seed and as a solvent (C), an aromatic hydrocarbon,
The method for producing a powder coating material according to claim 6, wherein at least one selected from halogenated aliphatic hydrocarbons, aliphatic carboxylic acid esters, carbonic acid esters, cyclic ethers, and aliphatic ketones is used. 12. The method for producing a powder coating material according to claim 6, wherein an amide compound is used as the curing agent (B), and an alcohol is used as the solvent (C). 13. A kneading and devolatilizing apparatus is used for the kneading step of the curable polyester resin (A), the curing agent (B) and the solvent (C) and the devolatilizing and removing step of the solvent (C). The method for producing a powder coating material according to claim 1, which is carried out continuously. 14. The kneading / devolatilizing device is at least 1
The method for producing a powder coating material according to claim 13, which is a single-screw or twin-screw extruder or a single-screw or twin-screw kneader equipped with individual devolatilization ports. 15. An apparatus used in a kneading step of a curable polyester resin (A), a curing agent (B) and a solvent (C),
The method for producing a powder coating material according to claim 1, wherein kneading and devolatilization are continuously performed by connecting in series with an apparatus used in the devolatilizing and removing step of the solvent (C). 16. The apparatus used in the kneading step is a single-screw or twin-screw extruder, a single-screw or twin-screw kneader,
Or the manufacturing method of the powder coating material of Claim 15 which is an in-line mixer. 17. The apparatus used in the devolatilizing and removing step,
The method for producing a powder coating material according to claim 15, which is a single-screw or twin-screw extruder or a single-screw or twin-screw kneader having at least one devolatilization port. 18. The powder according to claim 1, wherein in the kneading step of the curable polyester resin (A), the curing agent (B) and the solvent (C), a coating additive (D) is further supplied for kneading. Body paint manufacturing method 19. As a coating additive (D), a melt flow regulator, a defoaming agent, a pinhole inhibitor, an ultraviolet absorber, an antioxidant, a curing catalyst, a plasticizer, a blocking resistance improver, and a powder. The method for producing the powder coating composition according to claim 18, which uses at least one selected from a fluidizing agent and a pigment. 20. The powder coating composition according to claim 1, wherein a mixture containing a curable polyester resin (A) obtained by devolatilizing and removing the solvent (C) and a curing agent (B) is pulverized to obtain a powder coating composition. Manufacturing method.