WO2019074041A1 - Powder coating material composition and method for forming coating film - Google Patents

Abstract

This powder coating material composition can form a smooth coating film having an excellent appearance, and can form a coating film having excellent impact resistance and excellent abrasion resistance. A powder coating material composition including, as coating-film-forming resins, an acrylic resin (A) and a polyester resin (B), wherein the acrylic resin (A) has an epoxy group, has a solubility parameter SP(A) of 9.0 to 12.0, and has an average molecular weight of 500 to 4,000, the epoxy equivalent of the acrylic resin (A) is 200 g/eq to 500 g/eq, the polyester resin (B) has a carboxyl group and has a solubility parameter SP(B) of 9.0 to 11.0, and the absolute value |SP(A) – SP(B)| obtained by subtracting the solubility parameter SP(B) from the solubility parameter SP(A) is 0 to 2.

Description

Powder coating composition and method of forming coating film

The present disclosure relates to powder coating compositions. Furthermore, the present disclosure relates to a method of forming a coating.

There is a growing awareness of reducing environmental impact, and replacement with environmentally conscious products is required. In the coating composition, a powder coating composition that does not contain an organic solvent, is low in pollution and excellent in workability, and has a small impact on the environment has attracted attention.
Furthermore, the powder coating composition is relatively inexpensive, can recover and reuse the excess coating, can thicken the coating (cured product) by multilayer recoating, and can be used immediately after coating From the advantages such as that, the demand is high as a coating composition for forming a coating film on electronic parts, office automation equipment, home appliances, building materials, automobile parts and the like.

Various resin systems exist in powder coating compositions. For example, powder coating compositions of epoxy resin type, acrylic resin type, and polyester resin type are mainly used as powder coating compositions. Among these, polyester resin powder coating compositions can form a relatively well-balanced coating film in terms of coating film appearance and coating film physical properties.

For example, Patent Document 1 discloses a powder coating composition having a specific structure and containing a polyester resin which is suitably used as a raw material of the powder coating composition and a curing agent. The powder coating composition which concerns on patent document 1 can harden | cure in low temperature, and it aims at forming the coating film which is excellent in a weather resistance and smoothness.

As in the invention of Patent Document 1, the powder coating composition generally contains a curing agent (crosslinking agent) and the like in addition to the resin as the main ingredient.
For example, as a curing agent in a polyester resin powder coating composition, triglycidyl isocyanurate (hereinafter sometimes abbreviated as “TGIC”), blocked polyisocyanate, etc. are known.
TGIC has problems in its use in terms of skin irritation and environmental burden. In the blocked polyisocyanate, the blocking agent is a target substance for PRLR (Pollutant Release and Transfer Register), and further, there is a problem that the volatile organic compound (VOC) is generated when it is detached at the baking reaction of the coating film.

Further, Patent Document 1 proposes a β-hydroxyalkylamide-based curing agent as an alternative curing agent. The powder coating composition using the β-hydroxyalkylamide curing agent can be cured at a low temperature, has no generation of volatiles upon curing, and has a low environmental impact.
However, the powder coating composition using the β-hydroxyalkylamide-based curing agent has a problem that the adhesion between the coating film and the object to be coated (in particular, the adhesion after a water resistance test and a moisture resistance test) is poor.

Moreover, a powder coating composition can form a coating film by heating and fuse | melting. However, as compared with the solvent-based paint, the smoothness of the coating film was insufficient. In order to improve the smoothness of the coating film, it is generally performed to reduce the melt viscosity of the components contained in the powder coating, that is, the resin component, and to improve the flowability by heating and melting.
However, when a resin having a low melting point or a resin having a low molecular weight is used for the purpose of reducing the melt viscosity of the coating composition, although the smoothness of the resulting coating film is improved, the physical properties of the coating film, for example, impact resistance, etc. There is also a problem of becoming inadequate.

Furthermore, the curing temperature of the powder coating composition is often about 180 ° C., and a powder coating composition capable of forming a coating film at a lower temperature is also required from the viewpoint of environmental load reduction.

JP, 2015-129267, A

Thus, there is a need for a powder coating composition that can form a coating film having well-balanced physical properties such as high smoothness and excellent impact resistance, abrasion resistance and the like.

The present disclosure provides a powder coating composition which can form a coating film having high smoothness and can form a coating film having sufficient physical properties such as sufficient impact resistance in a well-balanced manner in view of the above-mentioned present situation. With the goal. Furthermore, a coating film having good scratch resistance can be formed.
Another object of the present invention is to provide a powder coating composition capable of forming a coating film at a lower temperature as compared with powder coating compositions generally used.
Furthermore, the present disclosure provides a method of forming a coating film using the above-described coating composition.

In order to solve the above-mentioned subject, this indication provides the following modes.
[1] In the present disclosure, the coating film-forming resin includes an acrylic resin (A) and a polyester resin (B),
The acrylic resin (A) has an epoxy group,
It has a solubility parameter SP (A) of not less than 9.0 and not more than 12.0,
It has a weight average molecular weight of 500 or more and 4,000 or less, and an epoxy equivalent in the acrylic resin (A) is 200 g / eq or more and 500 g / eq or less,
The polyester resin (B) has a carboxyl group, and has a solubility parameter SP (B) of 9.0 or more and 11.0 or less, and the solubility parameter SP (B) from the solubility parameter SP (A) A powder coating composition is provided, wherein the absolute value | SP (A) −SP (B) | after subtraction is 0 or more and 2 or less.

According to this aspect, the powder coating composition can form a coating film having well-balanced physical properties such as high smoothness and excellent impact resistance and scratch resistance.

[2] In one embodiment, the solubility parameter SP (A) of the acrylic resin (A) is 9.0 or more and 11.0 or less.
[3] In one embodiment, the solubility parameter SP (A) of the acrylic resin (A) is 10.0 or more and 11.0 or less.

According to these aspects, the powder coating composition can form a coating film having higher smoothness and physical properties such as superior impact resistance and scratch resistance in a well-balanced manner.

[4] In one embodiment, the epoxy equivalent of the acrylic resin (A) is 250 g / eq or more and 400 g / eq or less.
By such an embodiment, a coating film having more sufficient coating film hardness can be formed.

[5] In one embodiment, an absolute value | SP (A) −SP (B) | obtained by subtracting the solubility parameter SP (B) from the solubility parameter SP (A) is 0 or more and 1 or less.

According to this aspect, a good appearance and smoothness can be obtained, and a coating film having excellent physical properties such as cupping resistance, impact resistance, abrasion resistance and the like in a well-balanced manner can be formed.

[6] In one embodiment, the carboxyl group equivalent in the polyester resin (B) is 1,600 g / eq or more and 3,000 g / eq or less.

According to this aspect, it is possible to form a coating film having further excellent smoothness and being excellent in adhesion between the coating film and the object to be coated, for example, adhesion after water and moisture resistance treatment. Furthermore, it is possible to form a coating film having more excellent coating film properties such as impact resistance, cupping resistance and scratch resistance.

[7] In one embodiment, the polyester resin (B) has a weight average molecular weight of 5,000 or more and 100,000 or less.

This aspect can further improve the physical properties of the resulting coating film.

[8] In one embodiment, the polyester resin (B) has a weight average molecular weight of 5,000 or more and 20,000 or less.

This aspect can further improve the physical properties of the resulting coating film.

[9] In one embodiment, the solubility parameter SP (B) of the polyester resin (B) is 10.0 or more and 11.0 or less.

According to this aspect, it is possible to form a coating film having further excellent smoothness and being excellent in adhesion between the coating film and the object to be coated, for example, adhesion after water and moisture resistance treatment. Furthermore, it is possible to form a coating film having excellent coating film properties such as impact resistance, cupping resistance and scratch resistance.

[10] In one embodiment, the polyester resin (B) has a glass transition temperature (Tg _B ) of 40 ° C. or more and 70 ° C. or less.

According to this aspect, the smoothness of the appearance of the resulting coated film is further improved, and the baking temperature of the powder coating composition can be further lowered.

[11] In one embodiment, the minimum melt viscosity of the powder coating composition is 1 Pa · s or more and 200 Pa · s or less.

According to this aspect, the smoothness of the appearance of the resulting coated film is further improved, and the physical properties of the coated film can be further improved.

[12] In one embodiment, the glass transition temperature (Tg) of the acrylic resin (A) is 0 ° C. or more and 65 ° C. or less.

According to this aspect, the smoothness of the appearance of the resulting coated film is further improved, and the physical properties of the coated film can be further improved.

[13] In one embodiment, the powder coating composition is selected from an imidazole compound, an imidazoline compound and a metal salt complex thereof, a tertiary phosphine compound, a quaternary phosphonium salt compound and a quaternary ammonium salt compound. It further comprises a curing catalyst of a species.

According to this aspect, for example, the curing rate of the obtained powder coating composition can be controlled more effectively, and can be applied to various objects to be coated and coating and drying equipment.

[14] In one embodiment, the powder coating composition comprises from the group consisting of aliphatic polyamines, polyaminoamides, ketimines, alicyclic diamines, aromatic diamines, imidazoles, dicyandiamides, polyamides and β-hydroxyalkylamides (HAA) It further comprises at least one amine curing agent selected.

By this aspect, for example, the low temperature curability and the coating quality can be further improved.

[15] Another embodiment is a method for forming a coating film, wherein the powder coating composition is coated and heated to form a cured coating film,
The coating-film formation method which performs the said heating at the temperature of 140 to 200 degreeC of to-be-coated-article temperature is provided.

According to this aspect, it is possible to form a coating film having well-balanced physical properties such as high smoothness and excellent impact resistance and scratch resistance.

The powder coating composition of the present disclosure has an excellent appearance, can form a smooth coating film, and can form a coating film having excellent cupping resistance, impact resistance, and excellent abrasion resistance.
In addition, if it is a coating-film formation method using the coating composition which concerns on this indication, compared with the heating temperature of a general powder coating composition, it can heat at lower temperature.

First, the process leading to the invention according to the present disclosure will be described.
For example, powder coating compositions containing an acid group-containing polyester resin and an epoxy group-containing acrylic resin have been studied. However, it is still difficult to control the reaction, and improvements are still required to form a coating having a smooth coating and good coating properties.

Moreover, as a composition put into practical use as a powder coating composition, a combination of a hydroxyl group-containing polyester and a block isocyanate, a combination of an acid group-containing polyester and an epoxy compound, a combination of an acid group-containing polyester and triglycidyl isocyanurate And combinations of epoxy group-containing vinyl polymers and dibasic acids.
The baking conditions of such a thermosetting powder coating composition are generally about 180.degree.
In view of environmental load reduction, powder coating compositions that can be cured at lower temperatures are desirable.

Therefore, the present inventors have invented a powder coating composition that can form a coating film having a smooth coating film and good coating film properties, and can be cured at a lower temperature.
With the powder coating composition of the present disclosure, it is possible to form a coating film having excellent smoothness and excellent adhesion between the coating film and the object to be coated, for example, adhesion after water and moisture resistance treatment. Furthermore, it is possible to form a coating film having excellent coating film properties such as impact resistance, cupping resistance and scratch resistance. In addition, the powder coating composition of the present disclosure has less environmental impact. Furthermore, even when cured at a low temperature, it is possible to form a coating film having excellent smoothness and excellent coating film properties such as impact resistance, cupping resistance and scratch resistance.

The powder coating composition according to the present disclosure, which has such an effect,
A powder coating composition comprising an acrylic resin (A) and a polyester resin (B) as a coating film-forming resin,
The acrylic resin (A) has an epoxy group,
It has a solubility parameter SP (A) of not less than 9.0 and not more than 12.0,
It has a weight average molecular weight of 500 or more and 4,000 or less, and an epoxy equivalent in the acrylic resin (A) is 200 g / eq or more and 500 g / eq or less,
The polyester resin (B) has a carboxyl group, and has a solubility parameter SP (B) of 9.0 or more and 11.0 or less, and the solubility parameter SP (B) from the solubility parameter SP (A) The absolute value | SP (A) -SP (B) | obtained by subtraction is 2 or less.

Each component will be described below [ acrylic resin (A) ]
Acrylic resin (A) has an epoxy group,
It has a solubility parameter SP (A) of not less than 9.0 and not more than 12.0,
It has a weight average molecular weight of 500 or more and 4,000 or less, and an epoxy equivalent in the acrylic resin (A) is 200 g / eq or more and 500 g / eq or less.

Acrylic resin (A) has an epoxy group. An acrylic resin having an epoxy group is an acrylic resin, which is obtained, for example, by copolymerizing a monomer containing at least one epoxy group with another copolymerizable vinyl monomer. It is.
The epoxy equivalent in acrylic resin (A) is 200 g / eq or more and 500 g / eq or less. In one aspect, the epoxy equivalent in the acrylic resin (A) is 200 g / eq or more and 400 g / eq or less, for example, the epoxy equivalent is 250 g / eq or more and 400 g / eq or less, and in an aspect, the epoxy equivalent is It is 300 g / eq or more and 400 g / eq or less.
When the epoxy equivalent in an acrylic resin (A) is in the said range, the coating film which has sufficient coating film hardness can be formed.
In addition, the epoxy equivalent in this indication can be measured by the method based on JISK7236.

Acrylic resin (A) has solubility parameter SP (A) of 9.0 or more and 12.0 or less. In one aspect, the acrylic resin (A) has a solubility parameter SP (A) of 9.0 or more and 11.0 or less. In one embodiment, the acrylic resin (A) has a solubility parameter SP (A) of 9.5 or more and 11.0 or less, and for example, has a solubility parameter SP (A) of 10.0 or more and 11.0 or less.
Since acrylic resin (A) has SP (A) in such a range, it can show favorable compatibility with polyester resin (B) concerning this indication. Furthermore, reaction control can be easily performed as compared with conventional powder coating compositions.
Thereby, for example, it is possible to form a coating film having excellent coating film appearance (smoothness, gloss) and excellent adhesion between the coating film and the object to be coated, for example, adhesion after water resistance and moisture resistance treatment. Furthermore, it is possible to form a coating film having excellent coating film properties such as impact resistance, cupping resistance and scratch resistance.

The SP value is an abbreviation of solubility parameter (solubility parameter), and is a measure of solubility. As the SP value is larger, the polarity is higher, and conversely, the smaller the value is, the lower the polarity is.

For example, the SP value can be measured by the following method [References: SUH, CLARKE, J. Mol. P. S. A-1, 5, 1671-1681 (1967)].

As a sample, 0.5 g of an organic solvent is weighed in a 100 ml beaker, 10 ml of acetone is added using a whole pipet, and one dissolved by a magnetic stirrer is used. A poor solvent is dropped to this sample at a measurement temperature of 20 ° C. using a 50 ml burette, and the point at which turbidity occurs is defined as the dropped amount. As the poor solvent, the turbidity points are respectively measured using ion exchanged water as a high SP poor solvent and n-hexane as a low SP poor solvent. The SP value δ of the organic solvent is given by the following formula.
δ = (V _ml ^1/2 δ _ml + V _mh ^1/2 δ _mh ) / (V _ml ^1/2 + V _mh ^1/2 )
V _m = V ₁ V ₂ / (φ ₁ V ₂ + φ ₂ V ₁ )
δ _m = φ ₁ δ ₁ + φ ₂ δ ₂
Vi: Molecular volume of solvent (ml / mol)
φi: Volume fraction of each solvent at the cloud point δi: SP value of the solvent ml: low SP poor solvent mixed system mh: high SP poor solvent mixed system

In addition, when acrylic resin (A) contains multiple types of acrylic resin (A), SP value of acrylic resin (A) is in the acrylic resin (A) component using SP value of each monomer. It can obtain | require by calculating an average value based on solid content mass ratio.

Here, in the present disclosure, an absolute value obtained by subtracting the solubility parameter SP (B) according to the polyester resin (B) described later from the above-mentioned solubility parameter SP (A),
| SP (A) -SP (B) | is 0 or more and 2 or less.
In one aspect, an absolute value | SP (A) −SP (B) | obtained by subtracting the solubility parameter SP (B) from the solubility parameter SP (A) is 0 or more and 1.8 or less. In one aspect, the absolute value | SP (A) -SP (B) | is 0 or more and 1.5 or less, and for example, the absolute value | SP (A) -SP (B) | is 0 or more and 1 or less . In an aspect, the absolute value | SP (A) -SP (B) | is 0.01 or more, for example, 0.1 or more and 0.8 or less.
Since the absolute value which deducted solubility parameter SP (B) concerning polyester resin (B) from solubility parameter SP (A) is in such a range, the powder coating composition of this indication is excellent in smoothness. It is possible to form a coating film which is excellent in adhesion between the coating film and the object to be coated, for example, adhesion after water and moisture resistance treatment. Furthermore, it is possible to form a coating film having excellent coating film properties such as impact resistance, cupping resistance and scratch resistance. Furthermore, even when cured at a low temperature, it is possible to form a coating film having excellent smoothness and excellent coating film properties such as impact resistance, cupping resistance and scratch resistance.
Here, when an acrylic resin is used in combination in a conventional polyester resin powder coating composition, the appearance of the formed coating, for example, smoothness may be adversely affected. However, in the case of the powder coating composition of the present disclosure, by including the specific acrylic resin (A), a coating film having an excellent coating appearance (in addition to smoothness and gloss) can be formed.

The weight average molecular weight of the acrylic resin (A) having an epoxy group is 500 or more and 4,000 or less, and in one aspect, is 500 or more and 3,000 or less, for example, 500 or more and 2,000 or less.
When the molecular weight of the acrylic resin (A) is in such a range, the powder coating composition of the present disclosure can have an excellent coating film appearance (smoothness, gloss). Furthermore, it is possible to form a coating film having excellent coating film properties such as impact resistance, cupping resistance and scratch resistance.
Conventionally, a coating film is formed from a powder coating composition containing an acrylic resin (A) having an epoxy group, and furthermore, in order to obtain a coating film excellent in coating film physical properties, a high molecular weight acrylic resin (A) Had to be used. However, in the present application, the molecular weight of the acrylic resin (A) can lead to a remarkable effect although it is in the above range, that is, although it is a lower molecular weight acrylic resin (A).
In addition, the weight average molecular weight in this specification means the weight average molecular weight of styrene homopolymer conversion using gel permeation chromatography (GPC).

The glass transition temperature (Tg _A ) of the acrylic resin (A) is not particularly limited, but is 0 ° C. or more and 65 ° C. or less, and in one embodiment, 0 ° C. or more and 55 ° C. or less. When the glass transition temperature is in the above range, a coating film having excellent coating film properties can be formed.
The glass transition temperature can be measured using a differential scanning calorimeter (DSC) in accordance with JIS K 7121.

The amount of the acrylic resin (A) according to the present disclosure is determined by the blending ratio with the polyester resin (B) which is the powder coating composition. That is, the epoxy equivalent of the acrylic resin (A) is not less than 0.7 equivalent and not more than 1.5 equivalents with respect to one equivalent of the carboxyl group of the polyester resin (B). Or less, for example, not less than 1 equivalent but not more than 1.3 equivalents. When the amount of the acrylic resin (A) and the polyester resin (B) is within the above range, excellent mechanical strength, insulation property, flexibility, heat resistance can be obtained for the coating film formed from the powder coating composition Corrosion resistance, chemical resistance, etc. can be imparted.

By containing the acrylic resin (A) in such a range, the coating film formed from the powder coating composition has excellent mechanical strength, insulation property, flexibility, heat resistance, corrosion resistance, and chemical resistance. Etc. can be given.

An acrylic resin (A) having an epoxy group is an acrylic resin, which is obtained by copolymerizing a polymerizable monomer having at least one epoxy group with another vinyl monomer copolymerizable therewith. It is obtained.
The range of epoxy equivalent is as described above. Here, considering the relationship between the epoxy equivalent and the resin solid content of the powder coating composition, when the epoxy equivalent is less than 200 g / eq, curing of the acrylic resin (A) and the polyester resin (B) The reaction does not proceed sufficiently and the physical properties of the coating film are significantly reduced. On the other hand, when it exceeds 500 g / eq, there is a concern that the appearance of the obtained coating may be deteriorated.

The monomer having an epoxy group, for example, a polymerizable monomer having a glycidyl group is not particularly limited, and examples thereof include glycidyl (meth) acrylate and β-methyl glycidyl (meth) acrylate. Preferably, glycidyl (meth) acrylate etc. can be mentioned. One or more of these may be used.

The other vinyl monomers copolymerizable with the polymerizable monomer having an epoxy group are those having at least one unsaturated bond such as a vinyl group in the molecule, and acrylic acid and methacrylic acid. Derivatives of The vinyl-based monomer is not particularly limited. For example, ethylene-based monomers such as methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate and the like Unsaturated carboxylic acid alkyl ester monomers; cycloalkyl group-containing polymerizable monomers such as cyclopentyl (meth) acrylate and cyclohexyl (meth) acrylate; 2-hydroxyethyl (meth) acrylate, (meth) acrylate Hydroxyl-containing ethylenically unsaturated carboxylic acid alkyl ester monomers such as 2-hydroxypropyl, 4-hydroxybutyl (meth) acrylate, and a reaction product of 2-hydroxyethyl (meth) acrylate and ε-caprolactone; Acrylamide , Methacrylamide, N-methylol acrylamide, methoxybutyla Other amide group-containing ethylenically unsaturated carboxylic acid monomers such as lylamide and diacetone acrylamide; vinyl cyanide monomers such as (meth) acrylonitrile and α-chloroacrylonitrile; and saturation of vinyl acetate and vinyl propionate Aliphatic carboxylic acid vinyl ester monomers; styrene monomers such as styrene, α-methylstyrene, vinyl toluene and the like can be mentioned. These can be used 1 type or in mixture of 2 or more types. In the present specification, (meth) acrylic acid refers to acrylic acid or methacrylic acid.

As a method of preparing the acrylic resin (A) having an epoxy group, it is possible to copolymerize the above-mentioned monomer having at least one epoxy group with another vinyl-based monomer copolymerizable therewith. There is no particular restriction. For example, various known methods can be used, and for example, the above-mentioned various monomers are subjected to a radical polymerization reaction in a solution and then desolvated to obtain a target polymer. Is preferred in that it is easy to control molecular weight.

[ Polyester resin (B) ]
The polyester resin (B) has a carboxyl group and has a solubility parameter SP (B) of not less than 9.0 and not more than 11.0.
Furthermore, as described above, the absolute value | SP (A) −SP (B) | obtained by subtracting the solubility parameter SP (B) from the solubility parameter SP (A) is 0 or more and 2 or less.

The polyester resin (B) has a solubility parameter SP (B) of not less than 9.0 and not more than 11.0. In one aspect, the polyester resin (B) has a solubility parameter SP (B) of 9.5 or more and 11.0 or less, for example, a solubility parameter SP (B) of 10.0 or more and 11.0 or less.
Since polyester resin (B) has SP (B) in such a range, it can show favorable compatibility with acrylic resin (A) concerning this indication. Furthermore, reaction control can be easily performed as compared with conventional powder coating compositions.
By having solubility parameter SP (B) in the above range, for example, it has excellent smoothness, and a coating film which is excellent in adhesion between the coating film and the object to be coated, such as adhesion after water resistance and moisture resistance treatment Can be formed. Furthermore, it is possible to form a coating film having excellent coating film properties such as impact resistance, cupping resistance and scratch resistance.

In one embodiment, the polyester resin (B) has a lower limit of 1,000 g / eq and an upper limit of 6,000 g / eq, for example, an upper limit of 3,800 g / eq. And in certain embodiments, the upper limit is 3,000 g / eq. For example, the carboxyl group equivalent in the polyester resin (B) is 1,000 g / eq or more and 6,000 g / eq or less, for example, 1,000 g / eq or more and 3,800 g / eq or less. It is 600 g / eq or more and 3,000 g / eq or less, for example, 1,800 g / eq or more and 3,000 g / eq or less.
In another aspect, the polyester resin (B) may have a lower limit of carboxyl group equivalents of 1,100 g / eq and an upper limit of 2,800 g / eq.
When the carboxyl group equivalent is in the above range, it is possible to form a coating film having excellent smoothness and excellent adhesion between the coating film and the substrate, for example, adhesion after water resistance and moisture resistance treatment. Furthermore, it is possible to form a coating film having excellent coating film properties such as impact resistance, cupping resistance and scratch resistance.
In addition, the carboxyl group equivalent in this specification represents solid content carboxyl group equivalent, and it can measure and calculate according to the measuring method of the acid value described in JISK 0070.

The polyester resin (B) has, for example, a weight average molecular weight of 5,000 to 100,000, and in another embodiment, the polyester resin (B) has a weight average molecular weight of 5,000 to 50,000. For example, polyester resin (B) has a weight average molecular weight of 5,000 or more and 30,000 or less. In one aspect, the polyester resin (B) has a weight average molecular weight of 5,000 or more and 20,000 or less. When the weight average molecular weight of the polyester resin (B) is in the above range, the physical properties of the coating film can be improved.

The polyester resin (B) has, for example, a glass transition temperature (Tg _B ) of 40 ° C. or more and 70 ° C. or less. In one aspect, the polyester resin (B) has a glass transition temperature (Tg _B ) of 45 ° C. or more and 65 ° C. or less, and in another aspect, the polyester resin (B) is 50 ° C. or more and 65 ° C. or less It has a glass transition temperature (Tg _B ).
When the glass transition temperature (Tg _B ) is in the above range, a coated film having good smoothness can be obtained.
The glass transition temperature can be measured using a differential scanning calorimeter (DSC) in accordance with JIS K 7121.

The melt viscosity at 200 ° C. of the polyester resin (B) is 1 Pa · s or more and 15 Pa · s or less, preferably 1 Pa · s or more and 12 Pa · s or less, more preferably 1 Pa · s or more and 10 Pa · s or less It is. When the melt viscosity of the polyester resin (B) at 180 ° C. is within the above range, a coating film having excellent coating appearance, for example, smoothness, and coating film physical properties such as impact resistance can be formed.
The above-mentioned melt viscosity means the viscosity which chain polymer shows in the melt state, and it is the viscosity measured with a dynamic viscoelasticity measuring device, for example, Rheosol-G3000 (made by UBM) etc., and the measurement condition is , When the frequency is 2 Hz and the twist angle is 0.5 °.

Here, the compounding quantity of the polyester resin (B) in a powder coating composition is decided by the compounding ratio with the acrylic resin (A) which is a powder coating composition. That is, the epoxy equivalent of the acrylic resin (A) is not less than 0.7 equivalent and not more than 1.5 equivalents with respect to one equivalent of the carboxyl group of the polyester resin (B). Or less, for example, not less than 1 equivalent but not more than 1.3 equivalents. When the powder coating composition contains the polyester resin (B) in such a relationship, it is possible to form a coating film having excellent coating physical properties such as impact resistance, cupping resistance and scratch resistance.

The polyester resin (B) according to the present disclosure has a carboxyl group.
The polyester resin (B) can be obtained, for example, by condensation polymerization using an acid component containing polyvalent carboxylic acid as a main component and an alcohol component containing polyhydric alcohol as a main component according to a conventional method. Thereby, polyester resin (B) can have a carboxyl group.
By selecting each component and the conditions of condensation polymerization, it is possible to obtain the polyester resin (B) having the above-mentioned physical property values and special values.

The above-mentioned acid component is not particularly limited. For example, aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, and anhydrides thereof, tris Trivalent or higher aromatic polyvalent carboxylic acids such as melittic acid and anhydrides thereof, saturated aliphatic dicarboxylic acids such as succinic acid, adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid and the like And their anhydrides, lactones such as γ-butyrolactone and ε-caprolactone, and aromatic oxymonocarboxylic acids such as p-oxyethoxybenzoic acid, etc., preferably terephthalic acid and isophthalic acid etc. be able to. The said acid component can use 1 type, or 2 or more types.

In one embodiment, as the acid component, the proportion of the total of terephthalic acid and isophthalic acid in the total acid component is 70 mol% or more, preferably 75 mol% or more, more preferably 80 mol% or more. . It is preferable in the point of durability, physical properties, and a price that it is the range of the said total ratio. Here, the case where 70% by mole or more of the total proportion of terephthalic acid and isophthalic acid is used as the acid component means that these are particularly used as the main raw materials.
About the upper limit of the said terephthalic acid and isophthalic acid content, it is good also considering the whole quantity of the acid component used for preparation of a polyester resin as a terephthalic acid and / or isophthalic acid. When it is desired to particularly improve the weather resistance, the proportion of isophthalic acid in the total acid component is 70 mol% or more, preferably 80 mol% or more, more preferably 90 mol% or more. Here, using 70% by mole or more of the proportion of isophthalic acid in the total acid component means using isophthalic acid as the main raw material.

The alcohol component is not particularly limited. For example, ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol 1,2-pentanediol, 1,4-pentanediol, 1,5-pentanediol, 1,6-hexanediol, 2,3-pentanediol, 1,4-hexanediol, 1,5-hexanediol, 2,5-hexanediol, 3-methyl-1,5-pentanediol, neopentyl glycol, 1,2-dodecanediol, 1,2-octadecanediol, diethylene glycol, triethylene glycol, 1,4-cyclohexanediol, 1 , 4-Cyclohexanedimethanol, bisphenol A alkylene And linear or branched aliphatic glycols such as adducts of bisphenols and alkylene oxides of bisphenol S, and trivalent or higher polyhydric alcohols such as trimethylolpropane, glycerin and pentaerythritol. Preferably, ethylene glycol, neopentyl glycol, 1,6-hexanediol and the like can be mentioned. The alcohol component may be used alone or in combination of two or more.

In an aspect, the powder coating composition of the present disclosure may contain resin components other than the above-mentioned acrylic resin (A) and polyester resin (B), as long as the effects of the present disclosure are not impaired. As such a resin component, acrylic resins other than the said acrylic resin (A), polyester resins other than the said polyester resin (B), an epoxy resin etc. can be mentioned, for example. For coatings formed from the powder coating compositions of the present disclosure, additional benefits may be included, such as, for example, lower temperature cure and coating quality.

In one aspect, for example, at least one of a monomer having a carboxyl group and / or a monomer having a hydroxyl group, and another vinyl monomer copolymerizable with the monomer having the above epoxy group And an acrylic resin other than the above-mentioned acrylic resin (A) obtained by copolymerizing
Examples of the monomer having a carboxyl group include (meth) acrylic acid, and examples of the monomer having a hydroxyl group include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, Examples thereof include hydroxyl group-containing ethylenically unsaturated carboxylic acid alkyl ester monomers such as 4-hydroxybutyl (meth) acrylate and a reaction product of 2-hydroxyethyl (meth) acrylate and ε-caprolactone. The monomer which has the said functional group can be used combining 1 type, or 2 or more types.

In one aspect, for example, polyester resins having a carboxyl group and a hydroxyl group other than the above polyester resin (B) can be mentioned. Polyester resins other than the said polyester resin (B) which has these functional groups may have only 1 type, and may have 2 or more types.

In one embodiment, for example, an epoxy resin having two or more epoxy groups in one molecule is mentioned. Specifically, glycidyl ester resins; glycidyl ether type resins such as condensation products of bisphenol A and epichlorohydrin, condensation products of bisphenol F and epichlorohydrin, etc .; and alicyclic epoxy resins, straight chain A chain aliphatic epoxy resin, a brominated epoxy resin, a phenol novolac epoxy resin, a cresol novolac epoxy resin, and the like can be mentioned.

The amount of these resin components is 5 to 30 parts by mass, and in one aspect, 5 to 20 parts by mass with respect to a total of 100 parts by mass of the resin solid content of the powder coating composition.
In the present disclosure, the resin solid content of 100 parts by mass of the powder coating composition means that the total resin solid content of the acrylic resin (A) and the polyester resin (B) is 100 parts by mass. Also in the following, when it describes as 100 mass parts of resin solid content, it is the same unless there is particular notice.

[Hardener component]
In one aspect, the powder coating composition of the present disclosure may contain a curing agent component as long as the effects of the present disclosure are not impaired.
Examples of the curing agent component that may be contained in the powder coating composition of the present disclosure include aliphatic polyvalent carboxylic acids such as decanedicarboxylic acid, dodecanedicarboxylic acid and sebacic acid, acid anhydrides of polyvalent carboxylic acids, and acid groups Acid curing agents such as acrylic resins containing; blocked isocyanate curing agents obtained by blocking a nurate compound of an isocyanate compound such as hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate with a blocking agent such as ε-caprolactam, methyl ethyl ketone oxime, etc., molecular Self-block type isocyanate curing agent having uretdione bond inside; aliphatic polyamine, polyaminoamide, ketimine, alicyclic diamine, aromatic diamine, imidazole, dicyandiamide, polyamide, β-hydroxyalkylamide And amine curing agents such as (HAA); phenol resin curing agents; and the like.
For coatings formed from the powder coating composition of the present disclosure, the powder coating composition may comprise a hardener component to further enhance the effects, such as low temperature cure and coating quality. .
These curing agent components are 0.5 to 10 parts by mass with respect to 100 parts by mass of the resin solid content of the polyester resin (B), and in one embodiment 0.5 to 5 parts by mass, for example, 0 6 parts by mass to 3.5 parts by mass. In another aspect, the curing agent component is 0.7 parts by mass to 3 parts by mass with respect to 100 parts by mass of the resin solid content of the polyester resin (B).
The powder coating composition of the present disclosure can form a coating film having good gloss, adhesion and the like by containing the curing agent component in such a range, and further has good flexibility and the like. It can form a coating film.

[Curing catalyst]
The powder coating composition in the present disclosure may include a curing catalyst.
The gel time of the powder coating composition can be adjusted by including the curing catalyst. For example, the gel time at 160 ° C. can be 50 seconds or more and 100 seconds or less.
The gel time of the powder coating composition in the present specification is a value at 160 ° C. measured according to JIS K 5600-9-1 (Method for measuring gel time of thermosetting powder coating at a predetermined temperature). It is.

The amount of the curing catalyst according to the powder coating composition of the present disclosure is 0 parts by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the resin solid content of the powder coating composition The content is 15 parts by mass or less, for example, 0 parts by mass or more and 10 parts by mass or less.
By including the curing catalyst within such a range, the curing rate of the obtained powder coating composition can be controlled, and the composition can be applied to various objects to be coated and coating / drying equipment.

The curing catalyst can be appropriately selected depending on the purpose. For example, the curing catalyst is at least one curing catalyst selected from an imidazole compound, an imidazoline compound and a metal salt complex thereof, a tertiary phosphine compound, a quaternary phosphonium salt compound and a quaternary ammonium salt compound.

The imidazole compound is not particularly limited, and examples thereof include 2-ethyl-4-methylimidazole, 1-methylimidazole, 1,2-dimethylimidazole, 2-methylimidazole, 2-ethylimidazole, 2-undecylimidazole, and the like. Alkylimidazoles such as 2-heptadecylimidazole and 2-isopropylimidazole, carbamylalkyl-substituted imidazoles such as 1- (2-carbamylethyl) imidazole, and cyanoalkylsubstituted imidazoles such as 1-cyanoethyl-2-methylimidazole Aromatic substituted imidazoles such as 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, and alkenyl substituted imidazoles such as 1-vinyl-2-methylimidazole , There may be mentioned 1-allyl-2-ethyl-4-allyl-substituted imidazoles of methylimidazole and poly imidazole, preferably, alkyl imidazoles, aromatic-substituted imidazoles. Alternatively, commercially available products may be used. Commercially available products include, for example, 2MZ-H (2-methylimidazole), C11Z (2-undecylimidazole), C17Z (2-heptadecylimidazole), 1.2DMZ, which are cuazole series (manufactured by Shikoku Kasei Kogyo Co., Ltd.) (1,2-dimethylimidazole), 2E4MZ (2-ethyl-4-methylimidazole), 2P4MZ (2-phenyl-4-methylimidazole), 1B2MZ (1-benzyl-2-methylimidazole), 1B2PZ (1-benzyl) -2-phenylimidazole) and the like.

The imidazoline compound is not particularly limited, and examples thereof include 2-phenylimidazole, 2-methylimidazoline, 2-undecylimidazoline, 2-heptadecylimidazoline and the like. Alternatively, commercially available products may be used. Examples of commercially available products include Cuazole 2PZL-T (manufactured by Shikoku Kasei Kogyo Co., Ltd .; 2-phenylimidazoline).

As a metal salt complex, what combined the said imidazole compound or the said imidazoline compound with the metal salt can be illustrated. Such metal salts are not particularly limited, and examples thereof include copper, nickel, cobalt, calcium, zinc, zirconium, silver, chromium, manganese, tin, iron, titanium, antimony, metals such as aluminum, chloride, bromide and fluoride. And salts composed of sulfate, nitrate, acetate, malate, stearate, benzoate, methacrylate and the like.
The tertiary phosphine compounds are not particularly limited, and examples thereof include triphenyl phosphine and tritolyl phosphine.

The quaternary phosphonium salt compound is not particularly limited, and examples thereof include benzyl triphenyl phosphonium chloride, butyl triphenyl phosphonium bromide, ethyl triphenyl phosphonium iodide, ethyl triphenyl phosphonium bromide and the like.

The quaternary ammonium salt compound is not particularly limited, and examples thereof include tetraethyl ammonium chloride, tetraethyl ammonium bromide, benzyltrimethyl ammonium bromide and the like.

In one aspect, the curing catalyst is at least one of an imidazole compound and an imidazoline compound. The powder coating composition of the present disclosure can be cured at a lower temperature by including these curing catalysts.

[Other ingredients]
The powder coating composition contains, in addition to the acrylic resin (A), the polyester resin (B) and the optional curing catalyst, a coloring pigment as a coloring agent and an extender pigment having substantially no coloring power. It is also good. The extender pigment is effective for adjusting the specific gravity of the powder coating composition, and includes talc, silica, calcium carbonate, barium sulfate and the like.
Even if the powder coating composition is appropriately blended with known additives such as surface conditioners, UV absorbers, antioxidants, anti-slip agents, etc., which can be used for ordinary powder coating compositions. Good.

(Colorant)
In one aspect, the powder coating composition of the present disclosure may include a colorant as another component. Moreover, as a coloring agent contained in a powder coating composition, the known inorganic pigment and organic pigment which are normally used for a powder coating composition can be used.

Examples of colored inorganic pigments include red iron oxide, chromium titanium yellow, yellow iron oxide and the like, and examples of achromatic inorganic pigments include titanium oxide and carbon black. Examples of chromatic organic pigments include azo, perylene, condensed azo, nitro, nitroso, phthalocyanine, anthraquinone, quinacridone, and dioxane pigments, and more specifically, azo Pigments such as lake red, fast yellow, disazo yellow, permanent red etc., nitro pigments such as naphthol yellow etc., nitroso pigments pigment green B, naphthol green etc., phthalocyanine pigments such as phthalocyanine blue, phthalocyanine green etc. Anthraquinone pigments such as indaslen blue, dianthraquinonil red, etc., quinacridone pigments such as quinacridone red, quinacridone violet etc., and dioxane pigments such as carbazole dioxazine violet etc. And the like, respectively.

The content of the coloring agent in the powder coating composition varies depending on the type thereof, but in the inorganic pigment, 0.05 parts by mass or more and 60 parts by mass or less with respect to 100 parts by mass of the resin solid content of the powder coating composition The organic pigment is preferably 0.05 parts by mass or more and 20 parts by mass or less.

In one aspect, the powder coating composition according to the present disclosure further comprises an inorganic filler. Inorganic fillers may contribute to the blocking of corrosion factors to improve chemical resistance. Examples of the inorganic filler include extender pigments such as alumina, silica, precipitated barium sulfate, calcium carbonate, clay, talc and mica; and rust preventive pigments such as zinc phosphate and aluminum phosphate.
The amount of the inorganic filler is 5 parts by mass or more and 60 parts by mass or less, and in an embodiment, 5 parts by mass or more and 50 parts by mass or less, with respect to 100 parts by mass of the resin solid content of the powder coating composition 5 parts by mass or more and 35 parts by mass or less.

[Powder coating composition]
With the powder coating composition according to the present disclosure, it is possible to form a coating film having excellent smoothness and excellent adhesion between the coating film and the object to be coated, for example, adhesion after water and moisture resistance treatment. Furthermore, it is possible to form a coating film having excellent coating film properties such as impact resistance, cupping resistance and scratch resistance. In addition, the powder coating composition of the present disclosure has less environmental impact. Furthermore, even when cured at a low temperature, it is possible to form a coating film having excellent smoothness and excellent coating film properties such as impact resistance, cupping resistance and scratch resistance.

The average particle size of the powder coating composition of the present disclosure is not particularly limited. For example, a desirable range can be selected according to the coating method and the like.

In an embodiment, the average particle diameter of the powder coating composition is, for example, 15 μm or more and 50 μm or less when electrostatic coating is performed, and in an embodiment, 25 μm or more and 40 μm or less, for example, 25 μm or more and 35 μm or less is there.
In the case of electrostatic coating, by having such an average particle size, the formed coating can have excellent smoothness.

In another embodiment, the average particle diameter of the powder coating composition is, for example, 50 μm or more and 200 μm or less when fluid immersion coating is performed, and in one embodiment is 80 μm or more and 170 m or less, for example 100 μm or more 150 μm or less.
In the case of fluid immersion coating, by having such an average particle diameter, excellent smoothness can be obtained.

As described above, the powder coating composition of the present disclosure can be selected to have an average particle size depending on the coating method. In any of the embodiments, when the average particle diameter of the powder coating composition is in such a range, it is possible to form a coating film having excellent edge coverage and a uniform film thickness, and smoothness Excellent in impact resistance, cupping resistance and scratch resistance.

In the present specification, the average particle size means volume average particle size (D50) unless otherwise specified. The volume average particle diameter (D50) can be measured, for example, using a particle size measuring device such as a laser diffraction / scattering particle diameter distribution measuring device (Microtrac, manufactured by Nikkiso Co., Ltd.). Specifically, it refers to a value measured using "Microtrack MT3000II" (manufactured by Nikkiso Co., Ltd.) as a measuring device.
Here, in the present disclosure, the average particle size of the powder coating composition means the average particle size of the powder coating composition containing the acrylic resin (A) and the polyester resin (B).

For example, the minimum melt viscosity of the powder coating composition is 1 Pa · s or more and 200 Pa · s or less, and in one embodiment is 1 Pa · s or more and 100 Pa · s or less. By having a specific minimum melt viscosity at the specific temperature, the rate at which the coating composition melts can be controlled. Therefore, when the powder coating composition of the present disclosure is applied to a part having a complicated shape, for example, by a fluid immersion method or an electrostatic powder coating method, no uneven thickness or stringing occurs. Can form a coating film having a uniform film thickness. In the present specification, the minimum melt viscosity is the minimum viscosity when the temperature is raised from 110 ° C. to 160 ° C. at a temperature rising rate of 5 ° C./min, and, for example, a dynamic viscoelasticity measuring apparatus (Rheosol-G 3000; It can be measured by UBM company).

The glass transition temperature (Tg) of the coating film-forming resin in the powder coating composition is, for example, 40 ° C. or more and 70 ° C. or less. In one aspect, the glass transition temperature (Tg) of the film-forming resin is, for example, 40 ° C. or more and 65 ° C. or less.
When the glass transition temperature of the coating film-forming resin is in the above range, the coating film has excellent smoothness, and a coating film having excellent adhesion between the coating film and the object to be coated, for example, adhesion after water resistance and moisture resistance treatment Can be formed. Furthermore, a coating film having excellent coating film properties such as impact resistance and cupping resistance can be formed. In addition, the powder coating composition of the present disclosure has excellent smoothness even when cured at a lower temperature, and excellent coating physical properties such as impact resistance, cupping resistance and scratch resistance. Since the coating film can be formed, environmental impact can be reduced.

[Method of producing powder coating composition]
The powder coating composition in the present disclosure can be produced by known methods.
For example, in the powder coating composition of the present disclosure, after preparing the raw materials comprising the above-described components, the raw materials are preliminarily mixed using a super mixer, a Henschel mixer or the like, and then a co-kneader, an extruder, etc. The raw materials are melt-kneaded using a kneader.
Melt-kneading is performed at a temperature at which at least a part of the raw material is melted and the whole can be kneaded. The temperature at the time of melt-kneading is generally 80 ° C. or more and 130 ° C. or less, and in one aspect is 80 ° C. or more and 120 ° C. or less.
The obtained melt is cooled and solidified by a cooling roll, a cooling conveyor or the like, and is crushed to a desired particle size through coarse grinding and fine grinding steps. The pulverization can be performed by physical pulverization (coarse pulverization or pulverization), and can be performed using a pulverizer such as a hammer mill or a jet impact mill.
Then, classification is performed if desired. For example, it is possible to remove large particles and microparticles and adjust the particle size distribution. For classification, an air classifier, a vibrating sieve, an ultrasonic sieve, etc. are used.

[Coating method]
After the powder coating composition of the present disclosure is applied to a substrate, it can be baked by heating or the like to form a coating (cured coating).

(Coated object)
The substrate to which the powder coating composition of the present disclosure is applied is not particularly limited. It does not specifically limit as a to-be-coated thing, Specifically, an iron plate, a steel plate, an aluminum plate, a ceramic plate etc., those which surface-treated them, etc. are mentioned. The coating film formation on the object to be coated has a good protective function even if it is a single layer comprising the powder coating composition of the present disclosure, but the powder coating composition of the present disclosure is coated on the undercoat coating. It may be applied as a top coat. As the undercoat paint for forming the undercoat film, known coatings such as an electrodeposition paint and a primer can be used. Furthermore, the member etc. which processed these into complicated shape are mentioned.

For coating formation on a substrate, the powder coating composition of the present disclosure may be directly coated on an iron plate or the like, and for example, the powder coating composition of the present disclosure may be overcoated on a primer coating. It may be painted as As a primer coating which forms a primer coating, well-known things, such as an electrodeposition paint and a primer, can be used.

(Painting method)
The present disclosure further relates to a method for forming a coating film, wherein the powder coating composition is coated on a substrate and heated to form a cured coating, wherein the substrate temperature is 140 ° C. or higher. Provided is a method of forming a coating film, which is performed at a temperature of 200 ° C. or less.

The coating method of the powder coating composition is not particularly limited, and methods well known to those skilled in the art such as a spray coating method, an electrostatic powder coating method, a fluid immersion method and the like can be used. From the point of view, the electrostatic powder coating method is preferred.

Hereinafter, an example of the electrostatic powder coating method is shown.
For example, preheating of the substrate may be performed. Preheating of the object to be coated may be performed using a heating furnace such as an electric furnace or a gas furnace, or induction heating using an induction heater.
In this case, the preheating needs to be performed within a range capable of maintaining the temperature of the object to be coated at 150 ° C. or more and 250 ° C. or less in consideration of the heat storage amount according to the shape and thickness of the object to be coated . In general, the temperature is often set to about 10 to 30 ° C. higher than the coating temperature of the powder coating composition.

The coating film thickness at the time of coating the powder coating composition of the present disclosure is at least 20 μm or more from the viewpoint of preventing mottle and transparency of the coating film and preventing generation of bubbles on or in the surface of the coating film. , 150 μm or less. In one aspect, it is 40 μm or more and 90 μm or less, for example, 60 μm or more and 80 μm or less.
A coating film formed from the powder coating composition of the present disclosure can form a uniform coating film and has high smoothness.

For example, in the case of a powder coating composition according to the present disclosure, the film thickness can be adjusted according to the required conditions such as the coating film appearance, for example, the smoothness and the coating film physical properties. Can be performed more efficiently than in the past, and in addition, the excess powder coating composition can be reused.

The heating temperature, for example, the baking temperature and time, varies depending on the type and amount of curing agent used. The temperature is, for example, 140 ° C. or more and 200 ° C. or less, and in one embodiment, 140 ° C. or more and 190 ° C. or less, from the viewpoint of preventing the generation of bubbles on or in the coating film surface. In another embodiment, the temperature is 150 ° C. or more and 190 ° C. or less, for example, 160 ° C. or more and 190 ° C. or less, and in another embodiment, 160 ° C. or more and 180 ° C. or less. In one embodiment, the bake temperature is between 150 ° C and 170 ° C.
The baking time can be appropriately set according to the baking temperature. For example, with the above-mentioned baking temperature, the baking time may be 10 minutes to 40 minutes.

In one aspect, the powder coating composition of the present disclosure is applied onto a substrate and heated to form a cured coating film, whereby a building material, an electrical product, an office equipment, an automobile body, an exterior Plates and parts can be manufactured. With the powder coating composition of the present disclosure, the building material and the like can have a coating film having high smoothness, and excellent physical properties such as impact resistance and abrasion resistance in a well-balanced manner.

The present disclosure will be more specifically described by the following examples, but the present disclosure is not limited thereto. In the examples, "parts" and "%" are by mass unless otherwise indicated.

(Production Example A-1)
Production of acrylic resin (A-1) 15 parts by mass of butyl acetate and 30 parts by mass of S100 are charged into a reaction vessel equipped with a reflux condenser, a dropping funnel, a stirrer, a thermometer, a condenser, a nitrogen gas inlet and a pressure reducing device. The temperature was raised to 130 ° C. under an atmosphere. Further, 4 parts of styrene, 55 parts by mass of isobornyl acrylate, 11 parts by mass of lauryl methacrylate, 30 parts by mass of glycidyl methacrylate and Kayaester O (chemical agent manufactured by Akzo; t-butylperoxy-2-ethylhexa) A monomer solution consisting of 12 parts by mass was dropped at a constant speed over 3 hours through a dropping funnel, and stirring was further continued for 2 hours to obtain an acrylic resin containing a solvent. This is heated to 130 ° C. under reduced pressure, the solvent is completely distilled off, and acrylic resin (A-1) (SP (A): 9.0, weight average molecular weight: 2,500, Tg _A : 50) C., epoxy equivalent weight: 475 g / eq) was obtained.

(Production Examples A-2 to A-13)
Production of Acrylic Resins (A-2) to (A-13) Acrylic resins (A-2) to (A-13) were produced in the same manner as the acrylic resin (A-1). Various special values such as monomer composition and epoxy equivalent in each resin are shown in Table 1.
In addition, even if the preparation amounts of various monomers were the same, values such as weight average molecular weight were changed by appropriately adjusting the conditions such as the reaction temperature.

(Production Example B-1)
Production of polyester resin (B-1) 1.9 parts by mass of terephthalic acid, 19 parts by mass of isophthalic acid, Neo in a reaction vessel equipped with a reflux condenser, a stirrer, a thermometer, a condenser and a nitrogen gas inlet 78 parts by mass of pentyl glycol, 1 part by mass of trimethylolpropane and 0.1 parts of di-n-butyltin oxide are mixed, and the temperature is gradually raised to 240 ° C. in a nitrogen stream to distill off generated water. Polyester resin (B-1, SP (B): 9.0, weight average molecular weight: 15,000, Tg _B : 55 ° C., carboxyl group equivalent: 2,800 g / eq, melting) Viscosity: 8.2 Pa · s) was obtained. The melt viscosity of the polyester resin (B) was measured using Rheosol-G3000 (manufactured by UBM, measurement temperature: 200 ° C., frequency: 2 Hz, twist angle: 0.5 °).

(Production Examples B-2 to B-13)
Production of Polyester Resins (B-2) to (B-13) Polyester resins (B-2) to (B-13) were produced in the same manner as the polyester resin (B-1). Various special values such as monomer composition and carboxyl group equivalent in each resin are shown in Table 2.

Example 1
(Preparation of powder coating composition 1)
10 parts by mass of acrylic resin (A-3), 100 parts by mass of polyester resin (B-2), 15 parts by mass of Typek CR-50 (manufactured by Ishihara Sangyo Co., Ltd .; titanium oxide), Aerosil R 972 (manufactured by Nippon Aerosil Co., Ltd .; finely powdered silica 1) 1 part by mass was blended and mixed for 3 minutes using a super mixer (manufactured by Nippon Spindle Co., Ltd.). Next, the mixture was melt-kneaded at 110 ° C. in a co-kneader (manufactured by Buss Co.), and the obtained kneaded product was extruded, cooled, roughly crushed, and further crushed using cryptron. The obtained pulverized material was classified using a turbo classifier (manufactured by Nisshin Engineering Co., Ltd.) to obtain a powder coating composition 1 having an average particle diameter of 30 μm. The minimum melt viscosity of the powder coating composition 1 is raised from 110 ° C. to 160 ° C. at a heating rate of 5 ° C./min using a dynamic viscoelasticity measuring apparatus (Rheosol-G 3000; manufactured by UBM). The lowest viscosity was measured.

(Preparation of Coating Film 1 for Evaluation)
The powder coating composition 1 obtained as described above was applied to a zinc phosphate-treated JIS G 3141 (SPCC to SD) cold-rolled steel plate (75 x 150 x 0.8 mm) for powder coatings The coated film was applied to a dry film thickness of 80 μm using an electrostatic coater (applied voltage: −80 kV), and baked at 160 ° C. for 15 minutes to obtain a coating film 1.

(Examples 2 to 40, Comparative Examples 1 to 5)
A powder coating composition was prepared in the same manner as Example 1, except that the types and amounts of the respective components were changed as described in Tables 3A, 3B, 3C, 3D and 4 below. Details of the raw materials used are described below.
Further, various coated films were formed in the same manner as in Example 1 using the obtained powder coating composition.
The description of each component described in Tables 1 to 4 is as follows.
HAA: Primid XL-552 (manufactured by EMS-CHEMIE; β-hydroxyalkylamide, hydroxyl equivalent: 85 g / eq)
-Imidazole-based curing catalyst: Cuazole 2MZ-H (manufactured by Shikoku Kasei Kogyo Co., Ltd .; 2-methylimidazole)
-Imidazoline curing catalyst: Cuazole 2PZL-T (manufactured by Shikoku Kasei Kogyo; 2-phenylimidazoline)

The following evaluations were performed using the powder coating compositions and the coatings obtained in Examples 1 to 40 and Comparative Examples 1 to 5 above. The obtained evaluation results are shown in Tables 3A to 4 below.

(Coating film appearance)
The appearances of the coatings obtained in Examples and Comparative Examples were visually observed and evaluated according to the following criteria.
:: uniform overall and smooth △: very slight skin is seen but almost uniform as a whole :: some skin is visible x: noticeable dents are seen

(Glossiness)
Using a mirror gloss meter (micro-TRI-gloss; manufactured by BYK-Gardner), the 60 ° glossiness of the coating obtained in Examples and Comparative Examples was measured according to JIS K-5600-4-7 (mirror gloss) It measured according to). I passed 85 or more.

(Adhesive)
In the coating film of the test piece obtained in the example and the comparative example, make a cut of 11 vertical and horizontal at intervals of 1 mm with a cutter, apply Cellophane tape ^{(registered trademark)} (made by Nichiban Co., Ltd.) on it and peel off Of the 100 squares, the number of squares remaining was counted (cross-check test). 100/100 indicates the case where the peeling area of the coating is 0%, for example, 90/100 indicates the case where the peeling area of the coating is 10%, and 50/100 indicates the coating The case where the peeling area is 50% is shown. Passed 100/100.

(Pencil hardness)
The hardness of the coatings obtained in the examples and comparative examples was evaluated according to JIS K 5600-5-4 (scratch hardness (pencil method)). Passed H or higher.

(Flexibility) (Capping resistance test)
With respect to the test pieces (painted plates) obtained in Examples and Comparative Examples, flexibility (capping resistance) was evaluated according to JIS K 5600-5-2 (Capping resistance test).
From the back side of the coated surface of the test piece, extrusion processing was performed with a punch having a diameter of 20 mm using an automatic cupping tester HD-4525 (manufactured by Uejima Seisakusho Co., Ltd.). The extrusion height at which the coating film was cracked was evaluated as flexibility (resistance to cupping). In addition, "7 <" in the table indicates a case where no cracking occurs even if the extrusion height is 7 mm. It was judged as 7 <.

(Flexibility) (Impact resistance)
The weight drop resistance was evaluated according to JIS K 5600-5-3 (weight resistance drop resistance test) for the test pieces (coated plates) obtained in Examples and Comparative Examples.
Using a Dupont impact tester (shooting type 1/2 inch; manufactured by Uejima Mfg. Co., Ltd.), a weight of 500 g is dropped from a certain height, and the height at which a crack is generated is measured. Sex) was evaluated. In addition, "50 <" in the table indicates a case where no crack occurs even if the weight is dropped from a height of 50 cm. Passed 45 cm or more.

(Abrasion resistant)
The test pieces obtained in Examples and Comparative Examples were attached to an evaluation stand of a wear resistance tester IMC-155F (manufactured by Imoto Machinery Co., Ltd.) with an adhesive tape, and a scratch resistance test was performed. The measurement conditions were “cardboard A flute” as a wear material, load 1 kg, reciprocation speed 60 times / min, reciprocation distance 100 mm, reciprocation 150 times. The state of the coating after the test (the presence or absence of scratches) was visually observed and evaluated according to the following criteria. Pass 4 or more.
5: no scratches 4: 1 slight scratch 3: 2 or more and 4 or less slight scratches 2: 2 or more slight scratches 1: there is a clear scratch and gloss change

(Reference Example 1)
The powder coating composition containing the acrylic resin (A-2) was baked at 250 ° C. for 15 minutes to obtain a coating film according to Reference Example 1. Various physical properties were measured in the same manner as described above. Various physical property values and the like are shown in Table 4.

Thus, the powder coating composition according to the present disclosure can form a coating film having high smoothness and physical properties such as excellent impact resistance and scratch resistance in a well-balanced manner.
In addition, the coating film can be formed at a lower temperature than generally used powder coating compositions, and moreover, as described above, high smoothness, excellent impact resistance, scratch resistance, etc. It is possible to form a coating film having well-balanced physical properties of

On the other hand, in Comparative Example 1, the solubility parameter SP (B) of the polyester resin (B) falls below the lower limit value in the present invention. As a result, a coating film inferior in at least coating film appearance, coating film gloss and scratch resistance was obtained.
In Comparative Example 2, the weight average molecular weight of the acrylic resin (A) is below the lower limit of the present invention. As a result, at least a coating film inferior in impact resistance, cupping resistance and scratch resistance was obtained.
In Comparative Example 3, the acrylic resin (A) according to the present invention is not included. As a result, at least a coating film inferior in impact resistance and scratch resistance was obtained.
In Comparative Example 4, the absolute value | SP (A) −SP (B) | obtained by subtracting the solubility parameter SP (B) from the solubility parameter SP (A) is out of the scope of the present invention. As a result, a coating film inferior in coating film appearance, cupping resistance, impact resistance and scratch resistance was obtained.
In Comparative Example 5, the weight average molecular weight of the acrylic resin (A) exceeds the upper limit value of the present invention. A coating film inferior in at least coating film appearance, adhesion, cupping resistance and impact resistance was obtained.

The powder coating composition of the present disclosure has excellent smoothness, and can form a coating film excellent in the adhesion between the coating film and the object to be coated, for example, the adhesion after water resistance treatment and moisture resistance treatment. Furthermore, it is possible to form a coating film having excellent coating film properties such as impact resistance, cupping resistance and scratch resistance. In addition, the powder coating composition of the present disclosure can have the above technical effects even when cured at a low temperature, so that environmental impact can be reduced.

Claims (15)

1. A powder coating composition comprising an acrylic resin (A) and a polyester resin (B) as a coating film-forming resin,
   The acrylic resin (A) has an epoxy group,
   It has a solubility parameter SP (A) of not less than 9.0 and not more than 12.0,
   It has a weight average molecular weight of 500 or more and 4,000 or less, and an epoxy equivalent in the acrylic resin (A) is 200 g / eq or more and 500 g / eq or less,
   The polyester resin (B) has a carboxyl group, and has a solubility parameter SP (B) of 9.0 or more and 11.0 or less, and the solubility parameter SP (B) from the solubility parameter SP (A) A powder coating composition, wherein the absolute value | SP (A) -SP (B) | obtained by subtraction is 0 or more and 2 or less.
2. The powder coating composition according to claim 1, wherein the solubility parameter SP (A) of the acrylic resin (A) is 9.0 or more and 11.0 or less.
3. The powder coating composition according to claim 1 or 2, wherein the solubility parameter SP (A) of the acrylic resin (A) is 10.0 or more and 11.0 or less.
4. The powder coating composition according to any one of claims 1 to 3, wherein the epoxy equivalent in the acrylic resin (A) is 250 g / eq or more and 400 g / eq or less.
5. The powder according to any one of claims 1 to 4, wherein an absolute value | SP (A)-SP (B) | obtained by subtracting the solubility parameter SP (B) from the solubility parameter SP (A) is 0 or more and 1 or less. Body paint composition.
6. The powder coating composition according to any one of claims 1 to 5, wherein a carboxyl group equivalent in the polyester resin (B) is from 1,600 g / eq to 3,000 g / eq.
7. The powder coating composition according to any one of claims 1 to 6, wherein the polyester resin (B) has a weight average molecular weight of 5,000 or more and 100,000 or less.
8. The powder coating composition according to any one of claims 1 to 7, wherein the polyester resin (B) has a weight average molecular weight of 5,000 or more and 20,000 or less.
9. The powder coating composition according to any one of claims 1 to 7, wherein the solubility parameter SP (B) of the polyester resin (B) is 10.0 or more and 11.0 or less.
10. The powder coating composition according to any one of claims 1 to 9, wherein the polyester resin (B) has a glass transition temperature (Tg _B ) of 40 ° C to 70 ° C.
11. The powder coating composition according to any one of claims 1 to 10, wherein the minimum melt viscosity is 1 Pa · s or more and 200 Pa · s or less.
12. The glass transition temperature (Tg _A) is 65 ° C. or less 0 ℃ more acrylic resin (A), the powder coating composition according to any one of claims 1 to 11.
13. 13. The method according to claim 1, further comprising at least one curing catalyst selected from imidazole compounds, imidazoline compounds and metal salt complexes thereof, tertiary phosphine compounds, quaternary phosphonium salts compounds and quaternary ammonium salts compounds. The powder coating composition as described in any one.
14. Further comprising at least one amine curing agent component selected from the group consisting of aliphatic polyamines, polyaminoamides, ketimines, cycloaliphatic diamines, aromatic diamines, imidazoles, dicyandiamides, polyamides and β-hydroxyalkylamides (HAA) The powder coating composition according to any one of claims 1 to 13.
15. It is a coating-film formation method which coats the powder coating material composition in any one of Claims 1-14 on a to-be-coated-article, and it heats and forms a cured coating film,
    The coating-film formation method which performs the said heating at the temperature of 140 to 200 degreeC of to-be-coated-article temperature.