KR20220143944A - A resin composition for a powder coating material, a powder coating material, and an article having a coating film of the coating material - Google Patents

Abstract

(일반식(1) 중, R¹은 수소 원자 또는 메틸기를 나타내고, R²는 수소 원자, 또는 탄소 원자수 1~8의 분기 또는 비분기의 알킬기를 나타내고, R³은 탄소 원자수 1~8의 분기 또는 비분기의 알킬기를 나타낸다)를 이용한다.An acrylic monomer (a1) having an epoxy group, an acrylic monomer (a2) represented by the following general formula (1), and an unsaturated monomer (a3) other than the acrylic monomer (a1) and the acrylic monomer (a2) as essential raw materials It provides a resin composition for powder coatings characterized in that it contains an acrylic resin (A). This resin composition for powder coatings is suitably used for powder coatings from the viewpoint of obtaining a cured coating film excellent in appearance, flexibility, and filiform corrosion resistance.

(In the general formula (1), R ¹ represents a hydrogen atom or a methyl group, R ² represents a hydrogen atom or a branched or unbranched alkyl group having 1 to 8 carbon atoms, and R ³ represents 1 to 8 carbon atoms. represents a branched or unbranched alkyl group of ).

Description

A resin composition for a powder coating material, a powder coating material, and an article having a coating film of the coating material

The present invention relates to a resin composition for a powder coating material, a powder coating material, and an article having a coating film of the coating material.

In recent years, regulations on organic solvents have become stricter due to problems such as air pollution, and environmentally friendly paints are attracting attention. Among them, powder coatings are attracting attention from the viewpoint of environmental protection as solvent-free coatings. In particular, acrylic powder coatings are excellent in coating film performance such as weather resistance and stain resistance. It is attracting attention for its use. However, the powder coating material had a drawback in that the smoothness of the coating film was inferior compared with the solvent type coating material.

In contrast, a powder coating comprising an epoxy group-containing acrylic resin obtained by copolymerizing (meth)acrylic acid alkylester, an epoxy group-containing acrylic monomer, and other copolymerizable vinyl monomers, and a curing agent having a functional group capable of reacting with an epoxy group has been proposed ( For example, refer to patent document 1). However, although the smoothness of the cured coating film obtained from this powder coating material was improved, there existed a problem that filiform corrosion resistance was insufficient.

Japanese Patent Laid-Open No. 2002-69368

The problem to be solved by the present invention is to provide a resin composition for a powder coating material, a powder coating material, and an article having a coating film of the coating material, which can obtain a cured coating film excellent in smoothness, flexibility, and thread-like corrosion resistance.

As a result of intensive research to solve the above problems, the present inventors have obtained from a resin composition for powder coatings containing an acrylic monomer having an epoxy group, an acrylic monomer having a specific structure, and an acrylic resin having other unsaturated monomers as essential raw materials. It was found that the cured coating film was excellent in smoothness, flexibility, and resistance to thread-like corrosion, and the invention was completed.

That is, the present invention provides an acrylic monomer (a1) having an epoxy group, an acrylic monomer (a2) represented by the following general formula (1), an unsaturated monomer other than the acrylic monomer (a1) and the acrylic monomer (a2) ( A resin composition for a powder coating comprising an acrylic resin (A) containing a3) as an essential raw material. It relates to a powder coating and an article coated with the coating.

(In the general formula (1), R ¹ represents a hydrogen atom or a methyl group, R ² represents a hydrogen atom or a branched or unbranched alkyl group having 1 to 8 carbon atoms, and R ³ represents 1 to 8 carbon atoms. represents a branched or unbranched alkyl group of

The resin composition for a powder coating material of the present invention can form a cured coating film excellent in appearance, flexibility, and thread-like corrosion resistance, so that it can be suitably used as a coating material for coating articles such as aluminum wheels.

The resin composition for powder coating of the present invention comprises an acrylic monomer (a1) having an epoxy group, an acrylic monomer (a2) represented by the following general formula (1), and the acrylic monomer (a1) and the acrylic monomer (a2) other than It contains the acrylic resin (A) which uses as an essential raw material the unsaturated monomer (a3) of.

(In the general formula (1), R ¹ represents a hydrogen atom or a methyl group, R ² represents a hydrogen atom or a branched or unbranched alkyl group having 1 to 8 carbon atoms, and R ³ represents 1 to 8 carbon atoms. represents a branched or unbranched alkyl group of

First, the said acrylic resin (A) is demonstrated. Although the said acrylic resin (A) has an epoxy group, it is obtained by copolymerizing the said acrylic monomer (a1), the said acrylic monomer (a2), and the said unsaturated monomer (a3).

The acrylic monomer (a1) is an acrylic monomer having an epoxy group, for example, glycidyl (meth) acrylate, methyl glycidyl (meth) acrylate, (meth) allyl glycidyl ether, (meth) Although allylmethyl glycidyl ether, 3, 4- epoxycyclohexyl methyl (meth)acrylate, etc. are mentioned, Among these, glycidyl (meth)acrylate is preferable. Moreover, these acrylic monomers (a1) may be used independently and may use 2 or more types together.

In addition, in this invention, "(meth)acrylic acid" means one or both of methacrylic acid and acrylic acid, "(meth)acrylate" means one or both of methacrylate and acrylate, "( A "meth)acrylamide" means one or both of methacrylamide and acrylamide, and a "(meth)acryloyl group" means one or both of a methacryloyl group and an acryloyl group.

The said acrylic monomer (a2) is an acrylic monomer represented by the said General formula (1), For example, N-methyl (meth)acrylamide, N-ethyl (meth)acrylamide, N-isopropyl (meth) Acrylamide, N-t-butyl (meth)acrylamide, N-t-octyl (meth)acrylamide, N,N-dimethyl (meth)acrylamide, N,N-diethyl (meth)acrylamide, etc. are mentioned, but these Among them, N-isopropyl (meth)acrylamide, N,N-dimethyl (meth)acrylamide, and N,N-diethyl (meth)acrylamide are excellent in the balance between the flexibility of the coating film and the resistance to thread corrosion. desirable. Moreover, these acrylic monomers (a2) may be used independently and may use 2 or more types together.

The unsaturated monomer (a3) is an unsaturated monomer other than the acrylic monomers (a1) and (a2), for example, (meth)acrylic acid, methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, sec-butyl (meth) acrylate, n-pentyl (meth) acrylate, n -Hexyl (meth) acrylate, n-heptyl (meth) acrylate, n-octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, Dodecyl (meth) acrylate, cetyl (meth) acrylate, stearyl (meth) acrylate, behenyl (meth) acrylate, cyclohexyl (meth) acrylate, 4-tert-butylcyclohexyl (meth) acrylic Late, isobornyl (meth) acrylate, dicyclopentanyl (meth) acrylate, benzyl (meth) acrylate, (meth) acrylamide, (meth) acrylonitrile, N,N-dimethylaminoethyl (meth) acrylate, 3-(meth)acryloyloxypropyltrimethoxysilane, 3-(meth)acryloyloxypropyltriethoxysilane, 3-(meth)acryloyloxypropylmethyldimethoxysilane, styrene; α-methylstyrene, p-methylstyrene, p-methoxystyrene, 2-methoxyethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4 -Hydroxy-n-butyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxy-n-butyl (meth)acrylate, 3-hydroxy-n-butyl (meth)acryl Rate, 1,4-cyclohexanedimethanol mono(meth)acrylate, glycerin mono(meth)acrylate, polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, 2-hydroxy-3 Monofunctional monomers, such as phenoxypropyl (meth)acrylate, 2-(meth)acryloyloxyethyl-2-hydroxyethyl phthalate, and lactone-modified (meth)acrylate which has a hydroxyl group at the terminal; Ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, dipropylene glycol Di (meth) acrylate, tripropylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, 1,3-butanediol di (meth) acrylate, 1 ,4-Butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, hydroxypivalic acid ester neopentyl glycol di(meth)acrylate, bisphenol A-di(meth)acrylate, bisphenol bifunctional monomers such as A-EO modified di(meth)acrylate and isocyanuric acid EO modified diacrylate; Isocyanuric acid EO modified triacrylate, trimethylolpropane tri(meth)acrylate, trimethylolpropane EO modified tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, ditrimethylolpropane tetraacrylate, trifunctional or higher than trifunctional monomers such as dipentaerythritol hexa (meth) acrylate and dipentaerythritol penta (meth) acrylate. , styrene, and/or methyl methacrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, and isobornyl (meth) acrylate are preferably used. Moreover, these acrylic monomers (a3) may be used independently and may use 2 or more types together.

The amount of the acrylic monomer (a1) to be used is preferably 10 to 60 mass %, and 20 to 50 mass % among the monomer components that are the raw materials of the acrylic resin (A) from the viewpoint of improving the appearance and thread corrosion resistance of the coating film. % is more preferable. The amount of the acrylic monomer (a2) used is preferably 0.1 to 30% by mass, and 0.5 to 20% by mass among the monomer components serving as the raw material of the acrylic resin (A) from the viewpoint of improving the thread corrosion resistance of the coating film. more preferably. The amount of the acrylic monomer (a3) to be used is preferably 30 to 80% by mass, and preferably 40 to 80% by mass, among the monomer components that are the raw material of the acrylic resin (A), from the viewpoint of improving the flexibility and thread corrosion resistance of the coating film. % is more preferable.

Moreover, as for the glass transition temperature of the said acrylic resin (A), 20-120 degreeC is preferable at the point which the thread-like corrosion resistance of a coating film improves. More preferably, 40-100 degreeC is preferable.

In addition, in the present invention, the glass transition temperature is

Equation of FOX: 1/Tg=W1/Tg1+W2/Tg2+…

(Tg: desired glass transition temperature, W1: weight fraction of component 1, Tg1: glass transition temperature of homopolymer of component 1)

was calculated according to As the value of the glass transition temperature of the homopolymer of each component, the value described in the "Adhesive Technology Handbook" of the Ilgan Kogyo Shimbun or the "Polymer Handbook" of Wiley-Interscience shall be adopted. Hereinafter, the glass transition temperature by this calculation is abbreviated as "design Tg".

Further, the number average molecular weight of the acrylic resin (A) is preferably 1,000 to 10,000 from the viewpoint of excellent fluidity at the time of melting and resistance to thread-like corrosion. More preferably, 2,000 to 8,000 are preferable. Here, a number average molecular weight is the value which carried out polystyrene conversion based on the gel permeation chromatography (it abbreviates to "GPC" hereafter) measurement.

As a method of obtaining the acrylic resin (A), it can be carried out by a known polymerization method using the acrylic monomer (a1), the acrylic monomer (a2) and the unsaturated monomer (a3) as raw materials, but the solution radical polymerization method is the most It is preferable from the point of simplicity.

Said solution radical polymerization method is a method of melt|dissolving each monomer which is a raw material in a solvent, and performing a polymerization reaction in the presence of a polymerization initiator. Examples of the solvent that can be used at this time include hydrocarbon solvents such as toluene, xylene, cyclohexane, n-hexane and octane; Alcohol solvents such as methanol, ethanol, isopropanol, n-butanol, isobutanol and sec-butanol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol ether solvents such as dimethyl ether; ester solvents such as methyl acetate, ethyl acetate, n-butyl acetate, isobutyl acetate, and amyl acetate; Ketone solvents, such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone, etc. are mentioned. These solvents may be used independently and may use 2 or more types together.

Examples of the polymerization initiator include ketone peroxide compounds such as cyclohexanone peroxide, 3,3,5-trimethylcyclohexanone peroxide, and methylcyclohexanone peroxide; 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(tert-butylperoxy)cyclohexane, n-butyl-4,4-bis(tert- Butylperoxy)valerate, 2,2-bis(4,4-ditert-butylperoxycyclohexyl)propane, 2,2-bis(4,4-ditert-amylperoxycyclohexyl)propane, 2 ,2-bis(4,4-ditert-hexylperoxycyclohexyl)propane, 2,2-bis(4,4-ditert-octylperoxycyclohexyl)propane, 2,2-bis(4,4 -Peroxyketal compounds, such as dicumyl peroxycyclohexyl) propane; hydroperoxides such as cumene hydroperoxide and 2,5-dimethylhexane-2,5-dihydroperoxide; 1,3-bis(tert-butylperoxy-m-isopropyl)benzene, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, diisopropylbenzene peroxide, tert-butyl dialkyl peroxide compounds such as mil peroxide; diacyl peroxide compounds such as decanoyl peroxide, lauroyl peroxide, benzoyl peroxide and 2,4-dichlorobenzoyl peroxide; peroxycarbonate compounds such as bis(tert-butylcyclohexyl)peroxydicarbonate; organic peroxides such as peroxyester compounds such as tert-butylperoxy-2-ethylhexanoate, tert-butylperoxybenzoate, and 2,5-dimethyl-2,5-di(benzoylperoxy)hexane; and azo compounds such as 2,2'-azobisisobutyronitrile and 1,1'-azobis(cyclohexane-1-carbonitrile).

Although the resin composition for powder coating materials of this invention contains the said acrylic resin (A), it is preferable to contain the hardening|curing agent (B) which has a functional group which can react with an epoxy group from the point which the coating-film physical property improves more.

The curing agent (B) is a curing agent having a functional group capable of reacting with an epoxy group, for example, suberic acid, azelaic acid, 2,4-diethyl glutaric acid, sebacic acid, undecane dicarboxylic acid, dodecane dicarboxylic acid, bra Polyvalent carboxylic acid compounds such as silic acid, tetradecanedicarboxylic acid, pentadecanedicarboxylic acid, hexadecanedicarboxylic acid, heptadecanedicarboxylic acid, octadecanedicarboxylic acid, eicosanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, and butanetricarboxylic acid; The anhydride of polyhydric carboxylic acid, a polyhydric phenol compound, etc. are mentioned. Among these, an aliphatic polyhydric carboxylic acid compound and its anhydride are preferable at the point from which a high-strength coating film is obtained, and dodecane dicarboxylic acid is more preferable. In addition, these hardening|curing agents (B) may be used independently and may use 2 or more types together.

As a compounding amount of the said acrylic resin (A) and the said hardening|curing agent (B) in the resin composition for powder coating materials of this invention, since a high-strength coating film is obtained, the number of equivalents of the epoxy group in the said acrylic resin (A), and the said hardening|curing agent ( 0.5-1.5 are preferable and, as for the equivalent ratio (A/B) of the number of equivalents of the functional group which can react with the epoxy group in B), 0.8-1.2 are more preferable.

In the resin composition for powder coatings of the present invention, within the scope not impairing the effects of the present invention, organic or inorganic pigments, leveling agents, flow regulators, light stabilizers, ultraviolet absorbers, antioxidants, and other known and usual various types of antioxidants Additives may be added. Moreover, in order to accelerate|stimulate the hardening reaction at the time of baking, you may add a catalyst.

In the resin composition for powder coatings of the present invention, a hydrolyzable silane compound such as silica, an alkoxysilane, and a silane coupling agent is further added to the resin composition for a coating film, within a range that does not impair the effects of the present invention, in order to improve the thread corrosion resistance of the coating film. may include Moreover, these compounds may be used independently and may use 2 or more types together.

As an example of a suitable silane coupling agent, glycidyl alkoxysilane, aminoalkoxysilane, etc. are mentioned. Among these, glycidyl trialkoxysilane is preferable and glycidyl trimethoxysilane is more preferable at the point from which the coating film excellent in thread-like corrosion resistance is obtained.

As a compounding quantity of the said silane coupling agent, 0.01-3 mass % is preferable in the resin composition for powder coating materials at the point from which the coating film excellent in thread corrosion resistance is obtained, and 0.01-1 mass % is more preferable.

As a manufacturing method of the powder coating material of this invention, although various well-known and usual methods can be used, For example, the said acrylic resin (A), the said hardening|curing agent (B), and if necessary, various types of pigments, surface conditioning agents, etc. After mixing the additives and then melt-kneading them, a so-called mechanical pulverization method of finely pulverizing and classifying can be used.

The powder coating material of the present invention can be applied to exteriors, home appliances, automobile products, two-wheeled vehicle products, protective fences, etc. It is suitable for coating to metal members, such as an aluminum wheel alloy member, from the point obtained.

As a coating method of the powder coating material of this invention, various well-known and usual methods, such as an electrostatic powder coating method, are mentioned. In addition, as a method of forming a cured coating film after coating the powder coating material of the present invention, it can be appropriately selected depending on the type and purpose of the substrate, but from the viewpoint of obtaining a coating film excellent in thread corrosion resistance, water resistance and weather resistance, 120 to 250 ° C. In a temperature range, it is preferable to bake in the range for 5 to 30 minutes. Moreover, as for a coating film thickness, the range of 50-200 micrometers is preferable.

[Example]

Hereinafter, the present invention will be described in more detail with reference to specific examples. In addition, the epoxy equivalent and number average molecular weight of an acrylic resin are measured by the following method.

[Method for measuring epoxy equivalent]

It was measured by the hydrochloric acid-pyridine method. 25 ml of hydrochloric acid-pyridine solution was added to resin, and after heating and dissolving at 130 degreeC for 1 hour, it titrated with 0.1N- potassium hydroxide solution using phenolphthalein as an indicator. The epoxy equivalent was computed with the quantity of the consumed 0.1N- potassium hydroxide alcohol solution.

[Method for Measuring Number Average Molecular Weight]

Measured by GPC.

Measuring device: High-speed GPC device (“HLC-8220GPC” manufactured by Tosoh Corporation)

Column: The following columns manufactured by Tosoh Corporation were connected in series and used.

「TSKgel G5000」(7.8mmI.D.×30cm)×1

「TSKgel G4000」(7.8mmI.D.×30cm)×1

「TSKgel G3000」(7.8mmI.D.×30cm)×1

「TSKgel G2000」(7.8mmI.D.×30cm)×1

Detector: RI (Differential Refractometer)

Column temperature: 40°C

Eluent: tetrahydrofuran (THF)

Flow rate: 1.0ml/min

Injection volume: 100 μL (tetrahydrofuran solution with a sample concentration of 4 mg/mL)

Standard sample: A calibration curve was prepared using the following monodisperse polystyrene.

(monodisperse polystyrene)

"TSKgel standard polystyrene A-500" made by Tosoh Corporation

"TSKgel standard polystyrene A-1000" made by Tosoh Corporation

"TSKgel standard polystyrene A-2500" made by Tosoh Corporation

"TSKgel standard polystyrene A-5000" made by Tosoh Corporation

"TSKgel standard polystyrene F-1" made by Tosoh Corporation

"TSKgel standard polystyrene F-2" made by Tosoh Corporation

"TSKgel standard polystyrene F-4" made by Tosoh Corporation

"TSKgel standard polystyrene F-20" made by Tosoh Corporation

"TSKgel standard polystyrene F-40" made by Tosoh Corporation

"TSKgel standard polystyrene F-80" made by Tosoh Corporation

"TSKgel standard polystyrene F-128" made by Tosoh Corporation

"TSKgel standard polystyrene F-288" made by Tosoh Corporation

"TSKgel standard polystyrene F-550" made by Tosoh Corporation

(Synthesis Example 1: Synthesis of acrylic resin (A-1))

67 parts by mass of xylene was put into a reaction vessel equipped with a stirrer, a thermometer, a condenser, and a nitrogen gas inlet, and the temperature was raised to 135°C in a nitrogen atmosphere. There, 25 parts by mass of styrene (hereinafter abbreviated as "St"), 45 parts by mass of methyl methacrylate (hereinafter abbreviated as "MMA"), glycidyl methacrylate (hereinafter abbreviated as "GMA") A mixture consisting of 28 parts by mass, 2 parts by mass of N-isopropylacrylamide (hereinafter abbreviated as "NIPAM") and 6.0 parts by mass of t-butylperoxy2-ethylhexanoate is added dropwise over 6 hours, After completion of the dropwise addition, the polymerization reaction was carried out while maintaining the same temperature for 6 hours. After that, the solvent was removed at 160°C under a reduced pressure of 20 mmHg, and a solid acrylic resin having a number average molecular weight of 3,000, a glass transition temperature of 84°C, and an epoxy equivalent of 525 g/eq. (A-1) was obtained.

(Synthesis Example 2: Synthesis of acrylic resin (A-2))

The composition of the monomer is St 20 parts by mass, MMA 25 parts by mass, n-butyl acrylate (hereinafter abbreviated as "nBA") 17 parts by mass, isobornyl methacrylate (hereinafter abbreviated as "IBOMA") 5 By operating in the same manner as in Synthesis Example 1, except that it was changed to 5 parts by mass, 28 parts by mass of GMA, and 5 parts by mass of N-isopropylmethacrylamide (hereinafter abbreviated as “NIPMAA”), number average molecular weight 2,800, glass transition temperature 51°C , to obtain a solid acrylic resin (A-2) having an epoxy equivalent of 525 g/eq.

(Synthesis Example 3: Synthesis of acrylic resin (A-3))

The composition of the monomer is St 10 parts by mass, MMA 30 parts by mass, n-butyl methacrylate (hereinafter abbreviated as "nBMA") 13 parts by mass, GMA 45 parts by mass, N-t-octyl acrylamide (hereinafter "NOAA") (abbreviated to)) A solid acrylic resin (A-3) having a number average molecular weight of 3,000, a glass transition temperature of 60°C, and an epoxy equivalent of 340 g/eq was obtained by operating in the same manner as in Synthesis Example 1 except that it was changed to 2 parts by mass.

(Synthesis Example 4: Synthesis of acrylic resin (A-4))

67 parts by mass of xylene was put into a reaction vessel equipped with a stirrer, a thermometer, a condenser, and a nitrogen gas inlet, and the temperature was raised to 135°C in a nitrogen atmosphere. There, 30 parts by mass of St, 20 parts by mass of MMA, 20 parts by mass of GMA, 20 parts by mass of nBMA, 10 parts by mass of N,N-dimethylacrylamide (hereinafter abbreviated as “DMAA”) and 10 parts by mass of t-butylperoxy2 - A mixture consisting of 4.0 parts by mass of ethylhexanoate is added dropwise over 6 hours, and the polymerization reaction is carried out while maintaining the same temperature for 6 hours even after the completion of the dropping, and 0.5 parts by mass of 3-glycidoxypropyltrimethoxysilane is added , stirred and mixed for 30 minutes. Then, the solvent was removed under the reduced pressure of 20 mmHg at 160 degreeC, and the solid acrylic resin (A-4) which has a number average molecular weight of 5,000, a glass transition temperature of 72 degreeC, and an epoxy equivalent of 750 g/eq was obtained.

(Synthesis Example 5: Synthesis of acrylic resin (RA-1))

By operating in the same manner as in Synthesis Example 1 except that the composition of the monomer was changed to 20 parts by mass of St, 30 parts by mass of MMA, 22 parts by mass of IBOMA, and 28 parts by mass of GMA, number average molecular weight 3,000, glass transition temperature 94° C., epoxy equivalent 525 g/ A solid acrylic resin (RA-1) of eq was obtained.

(Synthesis Example 6: Synthesis of acrylic resin (RA-2))

By operating in the same manner as in Synthesis Example 1 except that the composition of the monomer was changed to 25 parts by mass of St, 30 parts by mass of MMA, 30 parts by mass of nBMA, and 15 parts by mass of GMA, number average molecular weight 3,000, glass transition temperature 65° C., epoxy equivalent 900 g/ A solid acrylic resin (RA-2) of eq was obtained.

(Synthesis Example 7: Synthesis of acrylic resin (RA-3))

By operating in the same manner as in Synthesis Example 1 except that the composition of the monomer was changed to 15 parts by mass of St, 15 parts by mass of MMA, 42 parts by mass of nBA, and 28 parts by mass of GMA, number average molecular weight 3,000, glass transition temperature 4 ° C., epoxy equivalent 525 g / A solid acrylic resin (RA-3) of eq was obtained.

The monomer compositions and property values of the acrylic resins (A-1) to (A-4) and (RA-1) to (RA-3) synthesized in Synthesis Examples 1 to 6 are shown in Tables 1 and 2.

[Table 1]

[Table 2]

(Example 1: Preparation and evaluation of powder coating material (1))

84 parts by mass of the acrylic resin (A-1) obtained in Synthesis Example 1, 16 parts by mass of dodecanedicarboxylic acid (hereinafter, abbreviated as "DDDA"), 5 parts by mass of benzoin, and a leveling agent ("Resiflow LF" manufactured by ESTRON) ) After melt-kneading the resin composition blended with 3 parts by mass using a twin-screw kneader (“APV Knitter MP-2015 Model” manufactured by Tsubako Yokohama Hanbai Co., Ltd.), finely pulverized, and further, 200 mesh Classification was carried out with a wire mesh to obtain a powder coating (1).

[Preparation of cured coating film for evaluation]

The powder coating obtained above was electrostatically powder coated on an untreated aluminum plate (A-1050P) (7 cm × 15 cm) so that the film thickness after baking was 80 to 120 μm, and then baked at 170° C. for 20 minutes to cure evaluation. made a coating.

[Smoothness test]

It judged using the standard plate for smoothness visual judgment of the powder coating film by PCI (Powder Coating Institute). A standard plate is 10 sheets of 1-10, and smoothness becomes favorable as a number becomes large. It was determined visually to which standard plate the smoothness of the created powder coating film corresponded. Based on the determined result, smoothness was determined as follows.

○: smoothness of 8 or more

△: smoothness of 6-7

×: smoothness of 5 or less

[Erichsen test]

The extrusion test was done for the coating film surface of the coating film for evaluation obtained above with an Eriksen testing machine ("ERICHSEN GMBH&CO. Model 200"), and the length which extruded when cracking generate|occur|produced was measured. Based on the extrusion length, the flexibility of the coating film was determined as follows.

○: Extrusion length exceeds 7.0 mm

△: the extrusion length is 5.0 to 7.0 mm

×: Extrusion length less than 5.0 mm

[Evaluation of thread-like corrosion resistance]

Two 13 cm straight scratches were put into the cured coating film for evaluation obtained above with a cutter knife to reach the base of the substrate, and the following test was performed with a CASS tester. Dissolve brine (2.6 g of copper(II) chloride hydrate, 10 cc of glacial acetic acid, and 500 g of normal salt) in 10 L of ion-exchanged water under the conditions of a temperature of 50° C., a spraying liquid volume of 1.2 to 1.8 cc/h, and a spraying pressure of 0.1 MPa. preparation) was sprayed for 6 hours, and Test 2 left to stand for 96 hours under conditions of a temperature of 60°C and a humidity of 85% was 1 cycle, and a total of 5 cycles were performed. After completion of the CASS test, filiform corrosion generated from scratches on the painted plate was visually confirmed, and the length of the longest-grown filiform corrosion was evaluated for filiform corrosion resistance. Based on the length of the longest-grown thread-like corrosion, the thread-like corrosion resistance of the coating film was determined as follows.

○: The longest length of thread-like corrosion is 2.0 mm or less

△: The longest length of the thread-like corrosion exceeds 2.0 mm, 3.0 mm or less

×: The longest length of thread-like corrosion exceeds 3.0 mm

(Examples 2 to 4: Preparation and evaluation of powder coatings (2) to (4))

Except having changed the acrylic resin (A-1) and DDDA blended in Example 1 to the composition shown in Table 3, it operated similarly to Example 1, manufacturing powder coating materials (2) - (4), and various properties were evaluated.

(Comparative Examples 1 to 3: Preparation and evaluation of powder coatings (R1) to (R3))

Except for changing the acrylic resin (A-1) and DDDA blended in Example 1 as shown in Table 4, by operating in the same manner as in Example 1, powder coatings (R1) to (R3) were manufactured, and various physical properties evaluated.

Tables 3 and 4 show the formulation compositions and evaluation results of the powder coating materials (1) to (4) obtained in Examples 1 to 4 and the powder coating materials (R1) to (R3) obtained in Comparative Examples 1 to 3 above.

[Table 3]

[Table 4]

It was confirmed that the cured coating films obtained from the resin compositions for powder coatings of the present invention of Examples 1 to 4 were excellent in smoothness, flexibility, and resistance to thread-like corrosion.

On the other hand, Comparative Examples 1 to 3 are examples in which the acrylic monomer (a2) represented by the general formula (1) is not used as a raw material of the acrylic resin (A), which is a component of the resin composition for a powder coating material of the present invention. It was not obtained that satisfies all of the smoothness, flexibility and resistance to thread-like corrosion of the coating film.

Claims (6)

An acrylic monomer (a1) having an epoxy group, an acrylic monomer (a2) represented by the following general formula (1), and an unsaturated monomer (a3) other than the acrylic monomer (a1) and the acrylic monomer (a2) as essential raw materials A resin composition for a powder coating comprising an acrylic resin (A).

(In the general formula (1), R ¹ represents a hydrogen atom or a methyl group, R ² represents a hydrogen atom or a branched or unbranched alkyl group having 1 to 8 carbon atoms, and R ³ represents 1 to 8 carbon atoms. represents a branched or unbranched alkyl group of The method of claim 1,
In the monomer component that is the raw material of the acrylic resin (A), the acrylic monomer (a1) is 10 to 60 mass%, the acrylic monomer (a2) is 0.1 to 30 mass%, and the acrylic monomer (a3) is 30 to 80 mass% The resin composition for a powder coating material which is mass %. 3. The method of claim 1 or 2,
Furthermore, the resin composition for powder coatings containing the hardening|curing agent (B) which has a functional group which can react with an epoxy group. 4. The method of claim 3,
The said hardening|curing agent (B) is an aliphatic polyhydric carboxylic acid and/or its anhydride, The resin composition for powder coatings. The powder coating material obtained from the resin composition for powder coating materials in any one of Claims 1-4. An article having a coating film of the powder coating material according to claim 5.