JP2005272723A - Powder coating and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a powder coating without inducing its curing reaction in its production and at the same time, capable of obtaining a coating film excellent in various performances such as curing property, film appearance, close adhesion, impact resistance, etc. <P>SOLUTION: This powder coating consists of a binder resin and a curing agent. The powder coating particles constituting the powder coating are aggregated particles having 10-40 μm volume-average particle diameter and formed by aggregation of fine particles consisting of the binder resin and fine particles consisting of the curing agent, the fine particles consisting of the binder resin do not contain the curing agent and the fine particles consisting of the curing agent do not contain the binder resin. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to a powder coating material and a manufacturing method thereof.

As a powder coating material, an epoxy resin, an acrylic resin, a polyester resin or the like as a binder resin and various curing agents are widely known. A coating film obtained from such a powder coating is excellent in curability, water resistance, and the like, and is used in many fields such as home appliances, automobiles, and building materials.

Usually, the powder coating is prepared by measuring raw materials such as a binder resin, a curing agent, a pigment, a curing catalyst, and other additives, and then preliminarily mixing these raw materials using a super mixer, a Henschel mixer, etc. The material is manufactured by melting and kneading the raw material using a kneader such as a kneader or an extruder, and then crushing it to the target particle size (for example, see Non-Patent Document 1). However, when the raw materials are mixed and melt-kneaded as described above, the binder resin and the curing agent and / or the curing catalyst come into contact with each other at a high temperature, so that a curing reaction may occur or the resin physical properties may decrease. there were. If the curing reaction proceeds during the production of powder coatings, it will gel during melt-kneading, making it impossible to produce coatings, making the coatings hard and difficult to grind, and increasing the viscosity to make uniform curing agents, pigments, additives, etc. Cannot be mixed, and the resulting coating film has reduced smoothness, gloss, appearance, such as the occurrence of blisters, and the curing reaction at the time of baking of the coating film is limited. Or the impact resistance and workability are reduced.

In addition, the powder coating obtained by mixing all raw materials individually and then mixing the resulting pulverized product does not melt and knead the binder resin and curing agent at the same time, so that a curing reaction occurs before coating. However, even when the coating film is melt-cured, the raw materials are not sufficiently uniformly mixed, so that the gloss and impact resistance of the coating film tend to be insufficient.
Therefore, it has been desired to develop a powder coating material that does not cause a curing reaction before coating and that has a good coating film performance.

"Easy technical review: Characters and functions of paints: Knowledge and application for the 21st century" Nihon Paint Co., Ltd., published by Paint Newspapers (1998) pages 148-149

In view of the above, the present invention is a powder coating that does not cause a curing reaction during production, and at the same time can obtain a coating film excellent in various properties such as curability, coating film appearance, adhesion, and impact resistance. Is intended to provide.

The present invention is a powder coating material comprising a binder resin and a curing agent, and the powder coating particle constituting the powder coating material is a volume formed by agglomerating fine particles comprising a binder resin and fine particles comprising a curing agent. It is an aggregated particle having an average particle size of 10 to 40 μm, the fine particles made of the binder resin do not contain a curing agent, and the fine particles made of the curing agent do not contain a binder resin. It is a characteristic powder paint.

The aggregated particles preferably further contain a pigment.
The mass ratio between the binder resin and the curing agent is preferably 60/1 to 1/1.
The binder resin and the curing agent are preferably those that cause a curing reaction at 160 ° C. or lower.

The present invention is a method for producing the above-described powder coating material, which is composed of a binder resin by separately pulverizing a binder resin and a curing agent and then mixing them, or mixing and pulverizing a binder resin and a curing agent. Step (I) for producing a mixture of microparticles comprising microparticles and a curing agent, and crushing and agglomerating the mixture of microparticles obtained in the step (I), so that the volume average particle diameter is 10 to 40 μm. It is also a method for producing a powder coating material comprising the step (II) of producing the aggregated particles.
The step (II) is preferably performed using a ball mill.
Hereinafter, the present invention will be described in detail.

The powder coating of the present invention is a powder coating composed of a binder resin and a curing agent, and the powder coating particles are in the form of aggregated particles in which fine particles composed of a binder resin and microparticles composed of a curing agent are aggregated. It is what you have. That is, since the powder coating particles are agglomerated fine particles made of the binder resin and fine particles made of the curing agent, the binder resin and the curing agent may be heated and melted in a mixed state during production. Therefore, problems caused by performing the melt-kneading process in the manufacturing process can be prevented. In addition, since the fine particles are agglomerated, the binder resin and the curing agent are easily and uniformly mixed by heating during the formation of the coating film, so that a uniform coating film is formed and the appearance of the coating film is abnormal. Will not occur. Moreover, since it does not go through a melt-kneading process in the manufacturing process, it can be a low-temperature curable powder coating that causes a curing reaction at 160 ° C. or lower.

The powder paint particles constituting the powder paint of the present invention have a volume average particle diameter in the range of a lower limit of 10 μm and an upper limit of 40 μm. When the volume average particle size is less than 10 μm, the fluidity of the coating is deteriorated and the coating workability is lowered, which is not preferable. When the volume average particle diameter exceeds 40 μm, the appearance of the resulting coating film such as a decrease in smoothness is deteriorated. The volume average particle size is, for example, a particle size caused by electromagnetic wave scattering such as a light scattering particle size distribution measuring machine manufactured by Seishin Enterprise, SK LASER MICRON SIZER PRO-700, or Microtrack-II manufactured by Reed and Northrop. It can be measured by a measuring device.

The powder coating particles preferably have a maximum particle size of 130 μm or less. When aggregated particles having a particle size exceeding 130 μm are present, a coating film having a high appearance cannot be obtained. Preferably, the largest particle size of the particles is 100 μm or less. It is more preferable that the aggregated particles have a maximum particle size of 100 μm or less among the particles and a minimum particle size of 1 μm or more among the particles. If particles having a particle size of less than 1 μm are present, the fluidity of the coating is deteriorated and the coating workability is lowered, which is not preferable.

The agglomeration is preferably not agglomerated by a binder. That is, it is preferable not to use a binder in the powder paint of the present invention. If the binder is used, it may affect the physical properties of the coating film. Therefore, it is important to adjust the type and blending amount even if it is used.

Among the fine particles forming the aggregated particles, the fine particles made of the binder resin are composed of the binder resin and other optional components used as necessary, and do not contain a curing agent. Here, the phrase “not containing a curing agent” includes a case where a very small amount of a curing agent is included so as not to affect the properties of the binder particles and the properties of the obtained powder coating material.

The binder resin is not particularly limited, and examples thereof include binder resins that are usually used in the powder coating field. Examples thereof include polyester resins, acrylic resins, epoxy resins, epoxy-polyester resins, and fluorine resins. it can.

It does not specifically limit as said polyester resin, The normal polyester resin which can be used in a coating material can be used. Examples of the polyester resin include a hydroxyl group-containing polyester resin and a carboxylic acid group-containing polyester resin. The hydroxyl group-containing polyester resin preferably has an OH number of 20 to 100 and a number average molecular weight of 3000 to 30000. The carboxylic acid group-containing polyester resin preferably has an acid value of 20 to 50 and a number average molecular weight of 3000 to 30000.

It does not specifically limit as said acrylic resin, The normal acrylic resin which can be used in a coating material can be used. Examples of the acrylic resin include a hydroxyl group-containing acrylic resin, a carboxylic acid group-containing acrylic resin, and a glycidyl group-containing acrylic resin. The acrylic resin may have two or more functional groups. The hydroxyl group-containing acrylic resin preferably has an OH number of 20 to 100 and a number average molecular weight of 3000 to 30000. The carboxylic acid group-containing acrylic resin preferably has an acid value of 20 to 50 and a number average molecular weight of 3000 to 30000. The glycidyl group-containing acrylic resin preferably has an epoxy equivalent of 100 to 200 and a number average molecular weight of 3000 to 30000.

Examples of the epoxy resin include bisphenol A type epoxy resin, bisphenol F type epoxy resin, novolac type epoxy resin, alicyclic epoxy resin, and linear aliphatic epoxy resin. Of these, bisphenol A type epoxy resins and bisphenol F type epoxy resins are preferred. The epoxy resin preferably has an epoxy equivalent of 600-2200. If it is less than 600, blocking may occur during storage of the paint, and if it exceeds 2200, the melting point of the epoxy resin becomes high and is not suitable for a low-temperature curing powder paint. More preferably, it is 670-1000, More preferably, it is 670-840.

Among the fine particles forming the aggregated particles, the fine particles made of a curing agent are composed of a curing agent and other optional components used as necessary, and do not contain a binder resin. Here, the phrase “not including a binder resin” includes a case where a very small amount of binder resin is included so as not to affect the properties of the curing agent and the properties of the obtained powder coating material.

It does not specifically limit as a hardening | curing agent used by this invention, Arbitrary arbitrary hardening | curing agents can be used according to the binder resin to be used, for example, (beta) -hydroxyalkyl acrylamide compound, a carbodiimide compound, an imidazole compound, uretonimine Compounds, block polyisocyanate compounds, epoxy compounds, oxazoline compounds, imidazoline compounds, polycarboxylic acid compounds, methylolated or alkyletherified amino resins, dicyandiamide compounds, 6-membered ring carbonate compounds, etc. It can be selected in consideration of the type of binder resin to be used.

The binder resin and the curing agent contained in the powder coating of the present invention are preferably a combination that causes a curing reaction at 160 ° C. or lower. Conventionally used powder coatings are required to be baked at a certain temperature or higher, usually 180 ° C. or higher. This is because it is necessary to prevent the curing reaction from progressing in the melt-kneading process because the melt-kneading process is performed in the manufacturing process. However, since the powder coating material of the present invention is obtained without kneading in a mixed state of the binder resin and the curing agent, it can be cured at a low temperature of 160 ° C. or lower. Low temperature curing powder coatings are preferred because they have good energy efficiency and can be cured by coating equipment used for solvent-type paints or water-based paints that cure under baking conditions of 130 to 160 ° C. . The binder resin and the curing agent are more preferably a combination that causes a curing reaction at 150 ° C. or lower.

The combination of the binder resin and the curing agent that cause a curing reaction at 160 ° C. or lower is not particularly limited, and examples thereof include a carboxylic acid group-containing polyester resin / β-hydroxyalkylamide compound, a carboxylic acid group-containing polyester resin / carbodiimide compound, and a carboxylic acid group. Acid group-containing polyacrylic resin / carbodiimide compound, carboxylic acid group-containing polyester resin / uretonimine compound, carboxylic acid group-containing polyacrylic resin / uretonimine compound, hydroxyl group-containing polyester resin / block polyisocyanate compound, carboxylic acid group-containing acrylic resin or polyester resin / Epoxy compounds, carboxylic acid group-containing acrylic resins or polyester resins / oxazoline compounds, epoxy resins / imidazoline compounds, glycidyl group-containing acrylic resins / carbo Acid compound, hydroxyl group-containing polyester resin or acrylic resin / carbodiimide compound, hydroxyl group-containing polyester resin or acrylic resin / uretonimine compound, hydroxyl group-containing polyester resin or acrylic resin / methylolated or alkyletherified amino resin, hydroxyl group-containing polyester resin or acrylic A combination of resin / cyclic carbonate compound and the like can be mentioned.

Also, combinations that cause a curing reaction at 150 ° C. or less include carboxylic acid group-containing polyester resin / carbodiimide compound, carboxylic acid group-containing polyacrylic resin / carbodiimide compound, carboxylic acid group-containing polyester resin / uretonimine compound, carboxylic acid group -Containing polyacrylic resin / uretonimine compound, hydroxyl group-containing polyester resin / block polyisocyanate compound, carboxylic acid group-containing acrylic resin or polyester resin / epoxy compound, carboxylic acid group-containing acrylic resin or polyester resin / oxazoline compound, glycidyl group-containing acrylic resin / A combination of a carboxylic acid compound, a hydroxyl group-containing polyester resin or an acrylic resin / methylolated or alkyletherified amino resin can be used.

In the powder coating material of the present invention, the mass ratio of the binder resin to the curing agent is preferably (binder resin) / (curing agent) = 60/1 to 1/1. There exists a possibility that the external appearance of the coating film obtained as the said mass ratio is less than 1/1 may fall. When the mass ratio exceeds 60/1, the effect of the curing agent is insufficient, which is not preferable. The mass ratio is more preferably 60/5 to 60/30.

The powder paint of the present invention may or may not contain a pigment. When the powder coating material contains a pigment, the pigment is preferably dispersed in the fine particles. The pigment may be dispersed in the microparticles made of the binder resin, may be dispersed in the microparticles made of the curing agent, or may be dispersed in both microparticles.

The pigment is not particularly limited. For example, iron oxide, lead oxide, carbon black, coal dust, titanium dioxide, talc, barium sulfate, cadmium yellow, cadmium red, chrome yellow, metal pigment (for example, aluminum flake) And organic pigments (for example, phthalocyanine blue, Shinkashi red, etc.), pearl mica, and the like. These may be used alone or in combination of two or more. The blending amount of the pigment is preferably in the range of a lower limit of 0.5% by mass and an upper limit of 40% by mass in the powder coating.

The powder coating material of the present invention is optionally added with a surface modifier, a plasticizer, an ultraviolet absorber, an antioxidant, an anti-waxing agent, a charge control agent, a curing catalyst, an antiblocking agent, and a flow modifier. An agent may be included. The additive is preferably present in the fine particles. The additive may be dispersed in the fine particles made of the binder resin, may be dispersed in the fine particles made of the curing agent, or may be dispersed in both fine particles.

As the surface conditioner, in particular, from the viewpoint of applicability to a coating line, methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate A number average molecular weight of 300 to 50000, preferably 1000 to 30000, and a glass transition temperature of less than 20 ° C., preferably 0 ° C. or less, obtained from an alkyl ester of (meth) acrylic acid such as What consists of a polymer is preferable. When the number average molecular weight is out of the above range, the surface adjustability cannot be sufficiently imparted, and there is a possibility that the prevention of appearance defects such as dents may be insufficient. Moreover, there exists a possibility that surface adjustability cannot fully be provided as glass transition temperature is 20 degreeC or more.

The surface conditioner is preferably blended in the powder paint in an amount of 0.01 to 5% by mass, more preferably 0.05 to 3% by mass, and still more preferably 0.1 to 2% by mass. If the amount is less than 0.01% by mass, the surface adjustability cannot be sufficiently imparted, and the probability of poor appearance may be increased. If the amount exceeds 5% by mass, the coating blocking property may be deteriorated. . Examples of commercially available products of the surface conditioner include Acronal 4F (manufactured by BASF), Polyflow S (manufactured by Kyoeisha Chemical Co., Ltd.), Regiflow LV (manufactured by ESTON CHEMICAL), and the like. Modaflow III (manufactured by Monsanto), Regiflow P67 (manufactured by ESTRON CHEMICAL) and the like can be suitably used.

The powder coating material of this invention is demonstrated along a manufacturing method below. In addition, the powder coating material of this invention is not limited to what was manufactured by the method illustrated below.
The powder coating material of the present invention comprises a step (I) of producing a mixture of fine particles composed of a binder resin and fine particles composed of a curing agent by pulverizing and mixing a binder resin and a curing agent, and the above steps By crushing and aggregating the microparticles obtained in (I), it can be obtained by the step (II) for producing aggregated particles having a volume average particle diameter of 10 to 40 μm.

In the step (I), the binder resin and the curing agent are separately pulverized to form fine particles and then mixed, and the mixture is then pulverized by mixing the binder resin and the curing agent. It may be a thing. Moreover, after coarsely pulverizing each separately, both may be mixed and further pulverized.

The pulverizing means in the step (I) is not particularly limited, and examples thereof include a known impact pulverizer such as a hammer mill and an airflow pulverizer such as a jet mill. The fine particles made of the binder resin and the fine particles made of the curing agent are preferably pulverized in the step (I) so that the volume average particle diameter is 5 to 40 μm. When the volume average particle size is less than 5 μm, it is not preferable because fine pulverization is difficult or the particles remain without agglomeration because the coating workability and the coating efficiency are lowered. When the volume average particle diameter exceeds 40 μm, the subsequent crushing and aggregation are not performed efficiently in the subsequent step (II), and the appearance of the coating film formed by the obtained powder coating material is deteriorated. In the step (I), the volume average particle diameter may be within the above range by sieving as necessary after pulverization.

When the powder paint of the present invention contains the pigment and / or additive, etc., these components are uniformly mixed by pre-melting and kneading with a binder resin or a curing agent from the viewpoint of dispersibility, and then pulverized. Thus, it is preferable to prepare fine particles containing necessary components, or to prepare a pigment dispersion composition by dry milling the pigment and the dispersing resin. In the above mixing, a binder resin and / or a curing agent, and a pigment and / or an additive are preliminarily mixed using a super mixer, a Henschel mixer, etc., and melt kneaded using a kneader such as a kneader or an extruder. Can be done. Next, the melt is cooled and solidified by a cooling roll, a cooling conveyor or the like, and is pulverized through coarse pulverization and fine pulverization steps as necessary.

When the pigment and / or the additive are used in combination, a master batch which is a fine particle containing these components at a high concentration is produced, and the master batch is composed of only the fine particle consisting of only the binder resin and the curing agent. The target powder coating material may be obtained by crushing and agglomerating three or more kinds of fine particles. When a powder coating is manufactured by such a method, when it is necessary to adjust the amount of the pigment or additive in the powder coating according to the application, by adjusting the mixing ratio of the fine particles, It is preferable at the point which can obtain the target powder coating material.

The powder coating material of the present invention can be obtained by crushing and agglomerating a mixture of the microparticles made of the binder resin and the microparticles made of the curing agent obtained in the step (I) (step II). In the step (II), the fine particles are crushed and aggregated simultaneously. The above-mentioned crushing and agglomeration is not only that the particles are made fine by crushing, but also the particles that are made fine by frictional force and shearing force applied during crushing, or each component diffuses from the particle surface of each raw material particle. By mixing and homogenizing, it means that the particles take a dense aggregate state.

Examples of the apparatus that can be used to perform the above step (II) include a ball mill, an attritor, a lycra machine, a CF mill, and a kryptron. A ball mill is preferred because it can be agglomerated. As the ball mill, for example, a centrifugal ball mill such as a rapid mill manufactured by MACCINE MACINA SMALTO can be suitably used.

In the step (II), it is preferable that various binders that are often used for granulation are not substantially used. That is, it is preferable to simultaneously perform crushing and aggregation by physical action. When using a binder, it is preferable to use it in a range that does not affect the performance of the coating film, with the type and amount used being limited.

When the treatment by the ball mill as described above is performed, in the initial stage of the treatment, the volume average particle size is decreased by performing the treatment, and when the treatment time is increased thereafter, the volume average particle size is gradually increased. In view of such a change state of the particle diameter, it is clear that crushing and agglomeration are proceeding simultaneously in the treatment by the step (II).
The method for producing a powder coating as described above is also one aspect of the present invention.

The powder paint of the present invention can be applied to an object to be coated and then heated to obtain a coating film. The material to be coated is not particularly limited, and specific examples include iron plates, plated steel plates, aluminum plates and the like, and surface treated products thereof. The formation of the coating film of the object to be coated has a good protective function even if it is a single layer made of the powder paint of the present invention, but it may form a multilayer. In this case, the powder coating material of the present invention may be directly applied to the article to be coated as an undercoating paint, that is, a primer to form an undercoating film, and an intermediate coating composition or an overcoating composition may be applied thereon. Moreover, undercoating etc. may already be given to the said to-be-coated object, the powder coating material of this invention may be apply | coated as an intermediate coating material or a top coating material on the undercoat coating film. In this case, as the undercoat paint for forming the undercoat, known materials such as an electrodeposition paint and a primer can be used.

The method for applying the powder coating material of the present invention is not particularly limited, and methods well known by those skilled in the art such as spray coating method, electrostatic powder coating method, fluidized dipping method and the like can be used. From the viewpoint of deposition efficiency, an electrostatic powder coating method is preferably used. Although the coating film thickness at the time of apply | coating the powder coating material of this invention is not specifically limited, It can set to 20-200 micrometers.

For example, the heating temperature is 100 to 230 ° C., preferably 120 to 200 ° C., although the heating condition after application of the powder coating of the present invention varies depending on the amount of functional groups involved in curing. In the case where the powder coating is a low-temperature curable coating composition, or in the case of an object to be coated that is weak against heat, a good cured coating film can be obtained by heating at about 100 to 160 ° C. The heating time can be appropriately set according to the heating temperature. The powder coating material of the present invention can be suitably used even for automotive parts such as aluminum wheels and plastic members that cannot be baked and cured at high temperatures.

The powder coating material of the present invention is a fine particle made of a binder resin and an agglomerated particle formed by agglomerating fine particles made of a curing agent, and is obtained without melting and kneading the binder resin and the curing agent. It is. That is, since the powder coating of the present invention does not undergo a curing reaction due to the binder resin and the curing agent at the time of manufacture, a coating film excellent in appearance, curability and the like can be obtained, and can be cured at a low temperature. It becomes possible.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. In the examples, “parts” means “parts by mass” unless otherwise specified. The average particle diameter means all volume average particle diameters.

Example 1
200 parts by mass of a curing agent (1,1,8,8-tetra (2-hydroxyethyl) adipamide, EMS-PRIMD, trade name: Primid XL552) was pulverized using an atomizer (Fuji Powder) After classification with a 150 mesh wire netting, the mixture was pulverized with a jet mill (manufactured by Seishin Enterprise Co., Ltd.) to obtain fine particles A made of a curing agent having an average particle diameter of 35 μm. Next, 600 parts by mass of a carboxylic acid group-containing polyester resin CC7617 (manufactured by Daicel UC Corporation, acid value 33), 300 parts by mass of titanium dioxide CR90 (manufactured by Ishihara Sangyo Co., Ltd.), 10 parts by mass of benzoin as an additive, Regisflow P67 (ESTRON) After mixing 10 parts by mass with a Henschel mixer, the mixture was melted and dispersed with Conyder PR-46 (manufactured by Busus), cooled, pulverized with an atomizer, and classified with a 150 mesh wire mesh. Further, it was pulverized by a jet mill to obtain fine particles B made of a binder resin having an average particle size of 36 μm. The fine particles were mixed at a mass ratio A: B = 3: 92. The average particle size of this mixture was 36 μm. 190 g of this mixture was pulverized and agglomerated for 40 minutes using a rapid mill (manufactured by MACCINE MACINA SMALTO), and classified with a 100 mesh wire netting to obtain a powder coating material having an average particle diameter of 38 μm.
This powder coating was applied to a zinc phosphate-treated steel plate (plate thickness 0.8 mm) by an electrostatic coating method using an electrostatic coating gun, and then baked at 160 ° C. for 20 minutes to obtain a coating film. The film thickness of the obtained coating film was 50-70 micrometers. The gloss, adhesion test and impact resistance test of this coating film were conducted. The results are shown in Table 1.

Examples 2-4
A powder coating material was prepared and the coating film was evaluated in the same manner as in Example 1 except that the average particle size of the fine particles was adjusted by variously changing the pulverization conditions in the jet mill and the rapid mill.

Example 5
200 parts by mass of a curing agent (1,1,8,8-tetra (2-hydroxyethyl) adipamide, EMS-PRIMD, trade name: Primid XL552) was pulverized using an atomizer (Fuji Powder) After classification with a 150 mesh wire netting, the mixture was pulverized with a jet mill to obtain fine particles A made of a curing agent having an average particle diameter of 36 μm. Next, 600 parts by mass of a carboxylic acid group-containing polyester resin CC7617 (manufactured by Daicel UC Corporation, acid value 33), 10 parts by mass of benzoin as an additive, and 10 parts by mass of Regiflow P67 were mixed with a Henschel mixer, and then with an atomizer After pulverizing and classifying with a 150-mesh wire mesh, the particles were pulverized with a jet mill to obtain fine particles C made of a binder resin having an average particle diameter of 34 μm. The fine particles were mixed at a mass ratio A: C = 3: 62. The average particle size of this mixture was 34 μm. 195 g of this mixture was pulverized and agglomerated for 40 minutes using a rapid mill, and classified with a 100-mesh wire mesh to obtain a powder coating having an average particle size of 39 μm. A coating film was prepared and evaluated in the same manner as in Example 1.

Example 6
Hardener B-1530 (Huls Japan Co., Ltd., ε-caprolactam block isocyanate) 200 parts by mass was pulverized using an atomizer (Fuji Powder Co., Ltd.), classified with a 150 mesh wire mesh, and pulverized with a jet mill. Thus, fine particles D made of a curing agent having an average particle diameter of 35 μm were obtained. Next, Finedick M8020 (Dainippon Ink Chemical Co., Ltd. hydroxyl group-containing polyester resin, hydroxyl value 30 ± 5) 600 parts by mass, titanium dioxide CR90 (Ishihara Sangyo Co., Ltd.) 300 parts by mass, benzoin 10 parts by mass as an additive, After mixing 10 parts by mass of Regiflow P67 with a Henschel mixer, melt and disperse with Conyder PR-46 (manufactured by Busus), cool, pulverize with an atomizer, classify with a 150 mesh wire mesh, and pulverize with a jet mill. Thus, microparticles E made of a binder resin having an average particle diameter of 35 μm were obtained. The fine particles were mixed at a mass ratio D: E = 10: 92. The average particle size of this mixture was 35 μm. 190 g of this mixture was crushed and agglomerated for 1 hour using a rapid mill, and classified with a 100-mesh wire mesh to obtain a powder coating having an average particle size of 37 μm. This powder coating was applied to a zinc phosphate-treated steel plate (plate thickness 0.8 mm) by an electrostatic coating method using an electrostatic coating gun, and then baked at 190 ° C. for 25 minutes to obtain a coating film. The film thickness of the obtained coating film was 50-70 micrometers. The coating film was evaluated in the same manner as in Example 1.

Example 7
A powder coating material was prepared in the same manner as in Example 6 except that the pulverizing conditions in the jet mill were changed, and a coating film was prepared and evaluated.

Example 8
Fined M8020 (Dainippon Ink & Chemicals, Inc. hydroxyl group-containing polyester resin, hydroxyl value 30 ± 5) 600 parts by mass, benzoin 10 parts by mass and 10 parts by mass of Resiflow P67 as an additive were mixed with a Henschel mixer, and then KONIDER PR -46 (manufactured by Busus Co., Ltd.) melted and dispersed, cooled, pulverized with an atomizer, classified with a 150 mesh wire mesh, and pulverized with a jet mill to produce fine particles F made of a binder resin having an average particle size of 35 μm. Obtained. The fine particles D obtained in Example 6 and the fine particles F were mixed at a mass ratio D: F = 10: 62. The average particle size of this mixture was 35 μm. 195 g of this mixture was crushed and agglomerated for 1 hour using a rapid mill, and classified with a 100-mesh wire mesh to obtain a powder coating having an average particle size of 40 μm. Furthermore, a coating film was prepared and evaluated in the same manner as in Example 6.

Example 9
Hardener B-1530 (Huls Japan Co., Ltd., ε-caprolactam block isocyanate) 200 parts by mass was pulverized using an atomizer (Fuji Powder Co., Ltd.), classified with a 150 mesh wire mesh, and pulverized with a jet mill. Thus, microparticles D made of a curing agent having an average particle diameter of 10 μm were obtained. Next, after mixing 600 parts by mass of Finedick M8020 (Dainippon Ink Chemical Co., Ltd. hydroxyl group-containing polyester resin, hydroxyl value 30 ± 5) and 300 parts by mass of titanium dioxide CR90 (Ishihara Sangyo Co., Ltd.) with a Henschel mixer, Conyder Fine particles comprising a binder resin having an average particle diameter of 9 μm, melt-dispersed with PR-46 (manufactured by Busus), cooled, pulverized with an atomizer, classified with a 150-mesh wire mesh, and further pulverized with a jet mill. G was obtained. Further, 100 parts by mass of benzoin and 100 parts by mass of regiflow P67 as an additive are mixed, pulverized with an atomizer, classified with a 150 mesh wire net, and then pulverized with a jet mill to obtain fine particles H having an average particle diameter of 10 μm. It was. The fine particles were mixed at a mass ratio D: G: H = 10: 90: 2. The average particle size of this mixture was 9 μm. 190 g of this mixture was crushed and agglomerated for 1 hour using a rapid mill, and classified with a 100-mesh wire mesh to obtain a powder coating having an average particle size of 13 μm. Furthermore, a coating film was prepared and evaluated in the same manner as in Example 6.

Example 10
A curing agent dodecanedioic acid (average particle diameter of about 1 μm) was prepared as fine particles I. Next, 1000 parts by mass of acrylic resin (glycidyl methacrylate / styrene / methyl methacrylate / n-butyl acrylate = 40/10/20/30 (mass ratio), average molecular weight 8000) and titanium dioxide CR90 (produced by Ishihara Sangyo Co., Ltd.) 300 After mixing a mass part with a Henschel mixer, it was melt-dispersed with a Conyder PR-46 (manufactured by Busus), cooled, ground with an atomizer, and classified with a 150-mesh wire mesh. Further, it was pulverized by a jet mill to obtain fine particles J made of a binder resin having an average particle size of 25 μm. The fine particles were mixed at a mass ratio of I: J = 45: 195. The average particle size of this mixture was 20 μm. 240 g of this mixture was crushed and agglomerated for 2 hours using a rapid mill, and classified with a 100-mesh wire mesh to obtain a powder coating having an average particle size of 27 μm. Further, a coating film was prepared and evaluated in the same manner as in Example 1.

Example 11
1000 parts by mass of an acrylic resin (glycidyl methacrylate / styrene / methyl methacrylate / n-butyl acrylate = 40/10/20/30 (mass ratio), average molecular weight 8000) was pulverized with an atomizer and classified with a 150 mesh wire mesh. . Further, the mixture was pulverized by a jet mill to obtain fine particles K made of a binder resin having an average particle diameter of 15 μm. Microparticles I and K were mixed at a mass ratio of I: K = 60: 200. The average particle size of this mixture was 10 μm. 240 g of this mixture was crushed and agglomerated for 1 hour using a rapid mill, and classified with a 100-mesh wire mesh to obtain a powder coating with an average particle size of 15 μm. A coating film was prepared and evaluated in the same manner as in Example 1 except that the baking condition at the time of preparing the coating film was 20 minutes at 140 ° C.

Comparative Example 1
In the same manner as in Example 1, fine particles A having an average particle diameter of 15 μm and fine particles B having an average particle diameter of 14 μm were prepared. The fine particles were mixed at a mass ratio A: B = 3: 92. The average particle size of this mixture was 14 μm. A coating film was prepared and evaluated in the same manner as in Example 1 using 190 g of this mixture as a powder coating material.

Comparative Example 2
In the same manner as in Example 1, fine particles A having an average particle diameter of 45 μm and fine particles B having an average particle diameter of 41 μm were prepared. The fine particles were mixed at a mass ratio A: B = 3: 92. The average particle size of this mixture was 41 μm. 190 g of this mixture was crushed and agglomerated for 40 minutes using a rapid mill, and classified with a 100 mesh wire netting to obtain a powder coating material having an average particle size of 42 μm. Further, a coating film was prepared and evaluated in the same manner as in Example 1.

The performances of the coating films obtained in Examples and Comparative Examples were evaluated for the following items. The results are shown in Tables 1 and 2.
(Evaluation methods)
<Gloss value>
Based on JIS K 5400 7.6, the specular reflectance at 60 degrees and 20 degrees was measured. Furthermore, the coating film surface was visually evaluated according to the following evaluation criteria.
A: Very good (high gloss value)
○: Good (pass level)
×: Bad in glossy condition

<Adhesion>
100 grids with an interval of 1 mm were prepared with a sharp cutter on the coating film, and an adhesive tape was applied and then peeled off. The remaining coating film was measured and evaluated.

<Impact resistance>
The highest condition in which a steel ball with a weight of 500 g and a diameter of 1 / 2φ is dropped from the height of 50 cm, 45 cm, 40 cm, 35 cm, 30 cm and 25 cm above the coating film by the Dupont formula, and no cracking or cracking of the coating film occurs. I investigated.

From Table 1 and 2, it was shown that the coating film obtained by the powder coating material of this invention has the outstanding performance in all the evaluation items. On the other hand, it was shown that the coating film obtained by the comparative example was inferior to the Example in glossiness and impact resistance.

Since the powder coating material of the present invention has a form of aggregated particles formed by agglomerating fine particles made of a binder resin and fine particles made of a curing agent, it does not cause a curing reaction at the time of manufacture, and at the same time, it is hardened, coated and coated. A coating film excellent in various performances such as film appearance, adhesion, and impact resistance can be obtained.

Claims (6)

A powder paint comprising a binder resin and a curing agent,
The powder coating particles constituting the powder coating are agglomerated particles having a volume average particle diameter of 10 to 40 μm formed by agglomerating microparticles made of a binder resin and microparticles made of a curing agent,
The fine particles made of the binder resin do not contain a curing agent,
The powder coating material, wherein the fine particles comprising the curing agent do not contain a binder resin. The powder coating material according to claim 1, wherein the aggregated particles further contain a pigment. The powder coating material according to claim 1 or 2, wherein a mass ratio of the binder resin and the curing agent is 60/1 to 1/1. The powder coating material according to claim 1, 2 or 3, wherein the binder resin and the curing agent cause a curing reaction at 160 ° C or lower. A method for producing a powder coating material according to claim 1, 2, 3 or 4,
A step of producing a mixture of microparticles made of binder resin and microparticles made of curing agent by mixing after pulverizing binder resin and curing agent separately, or by mixing and pulverizing binder resin and curing agent ( I) and
A powder coating material comprising the step (II) of producing aggregated particles having a volume average particle diameter of 10 to 40 μm by crushing and aggregating the mixture of fine particles obtained in the step (I) Production method. 6. The method for producing a powder coating material according to claim 5, wherein step (II) is performed using a ball mill.