CN111492019A - Powder coating material and article having coating film of the same - Google Patents

Abstract

To provide a powder coating material comprising an acrylic resin (A) having an epoxy group and a curing agent (B) having a functional group capable of reacting with an epoxy group, the powder coating having The molecular morphology parameter α value in the Mark-Houwink-Sakurada diagram of the epoxy-based acrylic resin (A) is 0.3 to 0.5. Since this powder coating material can form a cured coating film excellent in filiform rust resistance, it can be suitably used as a coating material for coating various articles such as aluminum wheels.

Description

Powder coatings and articles having coating films of the same

technical field

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

Background technique

In recent years, due to air pollution and other issues, restrictions on organic solvents have become increasingly stringent, and environmentally friendly coatings have attracted attention. Among them, from the perspective of environmental protection, powder coatings are attracting attention as solvent-free coatings, especially acrylic powder coatings. It has attracted attention in the use of decoration and home appliances. However, powder coatings have the disadvantage of poor film appearance compared to solvent-based coatings.

In view of this point, a powder coating material comprising an epoxy group-containing acrylic resin and a curing agent having a functional group capable of reacting with the epoxy group has been proposed. (For example, refer to Patent Document 1.) obtained by copolymerizing an alkyl (meth)acrylate, an epoxy group-containing acrylic monomer, and other copolymerizable vinyl-based monomers. However, although the appearance of the cured coating film obtained from this powder coating material was improved, there was a problem that the filamentous rust resistance (Japanese: shichikoku property) was insufficient.

prior art literature

Patent Literature

Patent Document 1: Japanese Patent Laid-Open No. 2002-69368

SUMMARY OF THE INVENTION

The problem to be solved by the invention

The subject to be solved by this invention is to provide the powder coating material which can obtain the cured coating film excellent in filiform rust resistance, and the article which has the coating film of this coating material.

solutions to problems

The inventors of the present invention have conducted intensive studies in order to solve the above-mentioned problems, and as a result, they have found that a cured coating film obtained from a powder coating material comprising: a powder coating material having a specific The epoxy-based acrylic resin (A) and the curing agent (B) having a functional group capable of reacting with the epoxy group.

That is, the present invention relates to a powder coating material comprising an acrylic resin (A) having an epoxy group, and an epoxy The curing agent (B) of the functional group reacted with the epoxy group, the molecular morphology parameter α value in the Mark-Houwink-Sakurada (Mark-Houwink-Sakurada) diagram of the above-mentioned epoxy group-containing acrylic resin (A) is 0.3～ 0.5.

Invention effect

Since the powder coating material of the present invention can form a cured coating film excellent in filiform rust resistance, it can be suitably used as a coating material for coating articles such as aluminum wheels.

Detailed ways

The powder coating material of the present invention is a powder coating material containing an acrylic resin (A) having an epoxy group, and a curing agent (B) having a functional group capable of reacting with an epoxy group, and the above-mentioned acrylic resin having an epoxy group The molecular morphology parameter α in the Mark-Howink-Sakurada diagram of (A) is 0.3 to 0.5.

First, the acrylic resin (A) which has the said epoxy group is demonstrated. From the viewpoint of obtaining a coating film having excellent coating film physical properties such as filamentous rust resistance, the molecular morphology parameter α value in the Mark-Houwink-Sakurada diagram of the epoxy group-containing acrylic resin (A) is 0.3 ~0.5 is important.

In addition, the molecular morphology parameter α value in the Mark-Houwink-Sakurada diagram of the acrylic resin (A) in the present invention was determined by GPC-MALS-VISCO measurement. Log[η]=logK+αlogMw is derived from the Mark-Howink-Sakurada formula: [η]=K·Mw ^α . The absolute molecular weight Mw was obtained from MALS, the intrinsic viscosity [η] was obtained from VISCO, the log Mw was plotted on the horizontal axis, and the log [η] was plotted on the vertical axis, and the slope α was obtained.

The acrylic resin (A) which has the said epoxy group can be obtained by copolymerizing the acrylic monomer (a1) which has an epoxy group, and another unsaturated monomer (a2), for example.

Examples of the acrylic monomer (a1) having an epoxy group include glycidyl (meth)acrylate, methyl glycidyl (meth)acrylate, (meth)allyl glycidyl ether, ( Meth)allyl methyl glycidyl ether, 3,4-epoxycyclohexyl methyl (meth)acrylate, etc. Among these, glycidyl (meth)acrylate is preferable. In addition, these acrylic monomers (a1) may be used individually and may be used in combination of 2 or more types.

In addition, in the present invention, "(meth)acrylic acid" refers to one or both of methacrylic acid and acrylic acid, and "(meth)acrylate" refers to methacrylic acid ester and acrylic acid ester. Either or both, "(meth)acryloyl" refers to one or both of methacryloyl and acryloyl.

As said other unsaturated monomer (a2), (meth)acrylic acid, methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, (meth)acrylate, for example are mentioned. Isopropyl 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, (meth)acrylic acid Lauryl ester, cetyl (meth)acrylate, stearyl (meth)acrylate, behenyl (meth)acrylate, cyclohexyl (meth)acrylate, 4-tert. (meth)acrylate Butyl cyclohexyl, isobornyl (meth)acrylate, dicyclopentyl (meth)acrylate, benzyl (meth)acrylate, acrylamide, N,N-dimethyl (meth)acrylamide, (methyl) (meth)acrylonitrile, N,N-dimethylaminoethyl (meth)acrylate, 3-(meth)acryloyloxypropyltrimethoxysilane, 3-(meth)acryloyloxypropyl Triethoxysilane, 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, (meth)acrylate ) 2-hydroxypropyl acrylate, 2-hydroxy-n-butyl (meth)acrylate, 3-hydroxy-n-butyl (meth)acrylate, 1,4-cyclohexanedimethanol mono(meth)acrylate , Glycerol mono(meth)acrylate, polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate , 2-(meth)acryloyloxyethyl-2-hydroxyethyl phthalate, monofunctional monomers such as lactone-modified (meth)acrylates with hydroxyl groups at the end; (Meth)acrylate, Diethylene glycol di(meth)acrylate, Triethylene glycol di(meth)acrylate, Polyethylene glycol di(meth)acrylate, Propylene glycol di(meth)acrylic acid Esters, dipropylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,3-butanedi Alcohol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, hydroxypivalate neopentyl glycol di( Meth)acrylate (Japanese: ヒドロキシピバリンacid エステルネオペンチルグリコールジ (メタ)アクリレート), bisphenol A-di(meth)acrylate, bisphenol A-EO modified di(meth)acrylate, iso EO-modified diacrylate and other 2-functional monomers; EO-modified triacrylate of isocyanurate, trimethylolpropane tri(meth)acrylate, trimethylolpropane EO modified tri(meth)acrylate base) acrylate, Tri- or higher functional monomers such as pentaerythritol tetra(meth)acrylate, bis-trimethylolpropane tetraacrylate, dipentaerythritol hexa(meth)acrylate, dipentaerythritol penta(meth)acrylate, etc., preferably monofunctional Using a functional monomer and a multifunctional monomer in combination, it is preferable to use a monofunctional monomer and a bifunctional monomer from the viewpoint of the low possibility of gelation and the ease of obtaining an acrylic resin with a molecular morphology parameter α value of 0.3 to 0.5. used in combination. These other unsaturated monomers (a2) may be used alone or in combination of two or more. In addition, in the present invention, a monomer having one polymerizable double bond is referred to as a monofunctional monomer, a monomer having two polymerizable double bonds is referred to as a bifunctional monomer, and a monomer having three or more The monomer of a polymerizable double bond is described as a trifunctional or higher monomer.

About the usage-amount of the acrylic monomer (a1) which has the said epoxy group, from the viewpoint of further improving the filamentous rust resistance of the obtained coating film and the physical properties of the coating film, it can be used as the above-mentioned acrylic resin (A) The mass ratio in the monomer component of the raw material is preferably in the range of 10 to 70 mass %, and more preferably in the range of 20 to 50 mass %. The usage-amount of the said polyfunctional monomer is a mass ratio in the monomer component which is a raw material of the said acrylic resin (A) from the viewpoint of further improving the filamentous rust resistance of the obtained coating film, The range of 0.1-10 mass % is preferable, and the range of 0.1-5 mass % is more preferable.

The number average molecular weight of the above-mentioned acrylic resin (A) is preferably 1,000 to 5,000 from the viewpoint of further improving the filamentous rust resistance of the obtained coating film and the physical properties of the coating film. Here, the number-average molecular weight is a value measured by gel permeation chromatography (hereinafter, simply referred to as "GPC" in some cases) and converted into polystyrene.

The glass transition temperature of the above-mentioned acrylic resin (A) is preferably 30 to 80° C. from the viewpoint of further improving the filamentous rust resistance of the obtained coating film and the physical properties of the coating film.

As a method for obtaining the above-mentioned acrylic resin (A), the above-mentioned acrylic monomer (a1) and other unsaturated monomers (a2) can be used as raw materials by a known polymerization method, and the solution radical polymerization method is the most simple and convenient. Preferred.

The above-mentioned solution radical polymerization method is a method in which each monomer serving as a raw material is dissolved in a solvent and a polymerization reaction is performed in the presence of a polymerization initiator. Examples of solvents that can be used in this case include hydrocarbon solvents such as toluene, xylene, cyclohexane, n-hexane, and octane; methanol, ethanol, isopropanol, n-butanol, isobutanol, sec-butanol, and the like. Alcohol solvents; ether solvents such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, and diethylene glycol dimethyl ether; methyl acetate, ethyl acetate, N-butyl acetate, isobutyl acetate, amyl acetate and other ester solvents; acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone and other ketone solvents, etc. These solvents may be used alone or in combination of two or more.

As the above-mentioned polymerization initiator, a polyfunctional polymerization initiator is preferably used, and a trifunctional or more than trifunctional polymerization initiator is more preferably used from the viewpoint of easily obtaining an acrylic resin having a molecular morphology parameter α value of 0.3 to 0.5. Examples of the polyfunctional polymerization initiator include 2,2-bis-(4,4-di-tert-butylcyclohexylperoxide)propane, 2,2-tert-butyloctaneperoxide, 1,1-di- - tert-butylperoxy-3,3,5-trimethylcyclohexane, 1,3-bis-(tert-butylperoxyisopropyl)benzene, 2,5-dimethyl-2,5- (tert-butylperoxy)hexane, 2,5-dimethyl-2,5-di-(tert-butylperoxy)hexyne-3, tris-(tert-butylperoxy)triazine, 1, 1-Di-tert-butylcyclohexaneperoxide, 2,2-di-tert-butylbutane peroxide, n-butyl 4,4-di-tert-butylperoxyvalerate, hexahydroterephthalate peroxide Di-tert-butyl formate, di-tert-butyl peroxyazelaate, di-tert-butyl peroxytrimethyl adipate, 3,3',4,4'-tetrakis(tert-butyl carbonyl peroxide) diphenyl A substance having a functional group having a polymerization initiating function such as two or more peroxide groups in one molecule, such as ketone.

As the above-mentioned polymerization initiator, a monofunctional polymerization initiator may be used, or a polyfunctional polymerization initiator may be used in combination. Examples of the monofunctional 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, 4,4-bis(tert-butyl) n-butyl peroxy)valerate, 2,2-bis(4,4-di-tert-butylperoxycyclohexyl)propane, 2,2-bis(4,4-di-tert-amylperoxycyclohexyl) Propane, 2,2-bis(4,4-di-tert-hexylperoxycyclohexyl)propane, 2,2-bis(4,4-di-tert-octylperoxycyclohexyl)propane, 2,2-bis(4 ,4-Dicumylperoxycyclohexyl)propane, 1,1-bis(tert-amylperoxy)cyclohexane and other peroxide ketal compounds; cumene hydroperoxide, 2,5-dimethylhexane Hydrogen peroxide compounds such as alkane-2,5-dihydroperoxide and tert-amyl hydroperoxide; 1,3-bis(tert-butylperoxy-m-isopropyl)benzene, 2,5-dimethyl- Dialkyl peroxide compounds such as 2,5-di(tert-butylperoxy)hexane, dicumyl peroxide, tert-butylcumyl peroxide, di-tert-amyl peroxide; decanoyl peroxide , diacyl peroxide compounds such as lauroyl peroxide, benzoyl peroxide, 2,4-dichlorobenzoyl peroxide; bis(tert-butylcyclohexyl) peroxydicarbonate, tertiary isopropyl peroxide Peroxycarbonate compounds such as amyl ester, tert-amyl peroxide 2-ethylhexyl carbonate, tert-butyl peroxy-2-ethylhexanoate, tert-butyl peroxybenzoate, 2,5-dimethyl- 2,5-bis(benzoylperoxy)hexane, tert-amyl peroxyneodecanoate, tert-amyl peroxypivalate, tert-amyl peroxy-2-ethylhexanoate, peroxyn-octanoic acid Organic peroxides such as peroxyester compounds such as tert-amyl ester, tert-amyl peroxyacetate, tert-amyl peroxy isononanoate, tert-amyl peroxybenzoate, etc.; and, 2,2'-azobisisobutyl Nitriles, azo compounds such as 1,1'-azobis(cyclohexane-1-carbonitrile), and the like.

The usage-amount of the said polymerization initiator is preferable with respect to the monomer component which is the raw material of the said acrylic resin (A) from the viewpoint of further improving the filamentous rust resistance of the obtained coating film and the physical properties of the coating film. The range of 0.5-15 mass %, and the range of 2-10 mass % is more preferable.

Next, the said hardening|curing agent (B) is demonstrated. The said curing agent (B) is a curing agent having a functional group that can react with an epoxy group, and examples thereof include suberic acid, azelaic acid, 2,4-diethylglutaric acid, sebacic acid, and undecane. Diacid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, pentadecanedioic acid, hexadecanedioic acid, heptadecanedioic acid, octadecanedioic acid, eicosanedioic acid , 1,3-cyclohexanedicarboxylic acid, polybasic carboxylic acid compounds such as butanetricarboxylic acid, acid anhydrides of these polybasic carboxylic acids, polyhydric phenol compounds, and the like. Among these, from the viewpoint of obtaining a high-strength coating film, an aliphatic polyvalent carboxylic acid compound and its acid anhydride are preferable, and dodecanedicarboxylic acid is more preferable. In addition, these curing agents (B) may be used alone or in combination of two or more.

The powder coating material of the present invention contains the above-mentioned epoxy group-containing acrylic resin (A) and a curing agent (B) having a functional group capable of reacting with the epoxy group, and from the viewpoint of obtaining a high-strength coating film, these are The compounding amount is preferably the equivalent ratio [(EP)/(COOH)] of the equivalent number of epoxy groups (EP) in the above-mentioned acrylic resin (A) to the equivalent number of carboxyl groups (COOH) in the above-mentioned curing agent (B). It is the range of 0.5-1.5, More preferably, it is the range of 0.8-1.2.

To the powder coating material of the present invention, well-known and conventional ones such as flow conditioners represented by organic or inorganic pigments, light stabilizers, ultraviolet absorbers, and antioxidants can be added within the range that does not impair the effects of the present invention. various additives. In addition, in order to promote the curing reaction during baking, a catalyst may be added.

As the preparation method of the powder coating material of the present invention, various known and conventional methods can be used. For example, a so-called mechanical pulverization method can be used. The mechanical pulverization method means that the above acrylic resin (A), the above cured The agent (B) is mixed with various additives such as pigments and surface conditioners as needed, and these are melt-kneaded, and then finely pulverized and classified.

The powder coating material of the present invention can be coated on various articles such as outdoor equipment, household appliances, automobile articles, motorcycle articles, guardrails, etc., and obtains filamentous rust resistance, weather resistance, impact resistance, chipping resistance, From the viewpoint of a high-appearance coating film excellent in water resistance and the like, it is suitable for coating on metal members such as aluminum wheel alloy members.

As a coating method of the powder coating material of this invention, various well-known conventional methods, such as an electrostatic powder coating method, are mentioned. In addition, the method for forming a cured coating film after applying the powder coating material of the present invention can be appropriately selected according to the type and purpose of the substrate, from the viewpoint of obtaining a coating film excellent in filiform rust resistance, water resistance and weather resistance From the beginning, it is preferable to bake in the range of 5 to 30 minutes in the temperature range of 120-250 degreeC. Moreover, it is preferable that the coating film thickness is in the range of 50-150 micrometers.

Example

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

[Measurement method of epoxy equivalent]

Measured by the hydrochloric acid-pyridine method. 25 ml of a hydrochloric acid-pyridine solution was added to the resin, and after heating and dissolving at 130° C. for 1 hour, titration was performed with a 0.1N-potassium hydroxide alcohol solution using phenolphthalein as an indicator. The epoxy equivalent was calculated from the amount of 0.1N-KOH alcoholic solution consumed.

[Method for measuring glass transition temperature]

It was calculated|required by DSC method (differential scanning calorimetry).

Measuring apparatus: Differential scanning calorimeter ("DSCQ-100" manufactured by TA INSTRUMENTS Co., Ltd.)

Atmospheric conditions: under nitrogen atmosphere

Temperature range: -50～150℃

Heating rate: 5°C/min

[Method for Measuring Weight Average Molecular Weight]

Measured by GPC.

Measuring device: High-efficiency 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℃

Eluent: Tetrahydrofuran (THF)

Flow rate: 1.0mL/min

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

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

(monodisperse polystyrene)

Tosoh Corporation "TSKgel standard polystyrene A-500"

Tosoh Corporation "TSKgel standard polystyrene A-1000"

Tosoh Corporation "TSKgel standard polystyrene A-2500"

Tosoh Corporation "TSKgel standard polystyrene A-5000"

Tosoh Corporation "TSKgel standard polystyrene F-1"

Tosoh Corporation "TSKgel standard polystyrene F-2"

Tosoh Corporation "TSKgel standard polystyrene F-4"

Tosoh Corporation "TSKgel standard polystyrene F-10"

Tosoh Corporation "TSKgel standard polystyrene F-20"

Tosoh Corporation "TSKgel standard polystyrene F-40"

Tosoh Corporation "TSKgel standard polystyrene F-80"

Tosoh Corporation "TSKgel standard polystyrene F-128"

Tosoh Corporation "TSKgel standard polystyrene F-288"

Tosoh Corporation "TSKgel standard polystyrene F-550"

(Synthesis Example 1: Synthesis of Acrylic Resin (A-1))

76 parts by mass of xylene was put into a reaction container equipped with a stirrer, a thermometer, a condenser tube, and a nitrogen introduction tube, and the temperature was raised to 135° C. under a nitrogen atmosphere. Thereto, a mixture containing 18 parts by mass of styrene (hereinafter, simply referred to as "St" in some cases) and 42 mass parts of methyl methacrylate (hereinafter, simply referred to as "MMA" in some cases) was dropwise added thereto over 6 hours. parts, n-butyl methacrylate (hereinafter may be simply referred to as "nBMA".) 4 parts by mass, 2-ethylhexyl methacrylate (hereinafter may be abbreviated as "2EHMA".) 2 mass parts, methacrylic acid 32 parts by mass of glycidyl ester (hereinafter may be simply referred to as "GMA".), n-butyl acrylate (hereinafter may be simply referred to as "BA".) 2 mass parts, and 2,2-bis-(4,4-di - tert-butyl cyclohexyl peroxide) propane (hereinafter may be simply referred to as "P-TA".) 0.3 parts by mass, tert-butyl peroxide-2-ethylhexanoate (hereinafter may be simply referred to as "P-O") .) 5 parts by mass. After the completion of the dropwise addition, the polymerization reaction was carried out by keeping at the same temperature for 10 hours, and then the solvent was removed at 160°C under a reduced pressure of 20 mmHg to obtain a molecular morphology parameter of 0.47, a number average molecular weight of 2,200, a glass transition temperature of 52°C, Solid acrylic resin (A-1) with an epoxy equivalent of 460 g/eq.

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

The composition of the monomer and the polymerization initiator was changed to 20 parts by mass of St, 44 parts by mass of MMA, 6 parts by mass of nBMA, 3 parts by mass of isobutyl methacrylate (hereinafter, simply referred to as "iBMA".), and 24 parts by mass of GMA 3 parts by mass, ethyl acrylate (hereinafter sometimes simply referred to as "EA".) 3 parts by mass, and 5.3 parts by mass of P-TA, except that it was carried out in the same manner as in Synthesis Example 1 to obtain a molecular morphology parameter of 0.42 and a number average of 0.42. A solid acrylic resin (A-2) having a molecular weight of 2,100, a glass transition temperature of 52° C., and an epoxy equivalent of 600 g/eq.

(Synthesis Example 3: Synthesis of Acrylic Resin (A-3))

The composition of the monomer and the polymerization initiator was changed to 25 parts by mass of St, 38 parts by mass of MMA, 4 parts by mass of nBMA, 2 parts by mass of 2EHMA, 26 parts by mass of GMA, and isobutyl acrylate (hereinafter sometimes simply referred to as "iBA". ) 4 parts by mass, ethylene glycol dimethacrylate (hereinafter may be simply referred to as "EDMA".) 1 part by mass and 8 parts by mass of P—O, except that it was carried out in the same manner as in Synthesis Example 1 to obtain a molecule The morphological parameter was 0.46, the number average molecular weight was 1,700, the glass transition temperature was 41 degreeC, and the solid acrylic resin (A-3) whose epoxy equivalent was 570 g/eq.

(Synthesis Example 4: Synthesis of Acrylic Resin (A-4))

The composition of the monomer and polymerization initiator was changed to 18 parts by mass of St, 38 parts by mass of MMA, 8 parts by mass of nBMA, 30 parts by mass of GMA, 1 part by mass of nBA, 5 parts by mass of EDMA, and 5.3 parts by mass of P-O, except that Other than that, in the same manner as in Synthesis Example 1, a solid acrylic resin (A-4) having a molecular morphology parameter of 0.40, a number average molecular weight of 2,600, a glass transition temperature of 60° C., and an epoxy equivalent of 490 g/eq was obtained. .

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

The composition of the monomer and polymerization initiator was changed to 20 parts by mass of St, 30 parts by mass of MMA, 9 parts by mass of nBMA, 8 parts by mass of nBA, 28 parts by mass of GMA, 5 parts by mass of iBA, and 3.5 parts by mass of P-O, except that Other than that, in the same manner as in Synthesis Example 1, a solid acrylic resin (RA-1) having a molecular morphology parameter of 0.57, a number average molecular weight of 3,300, a glass transition temperature of 50°C, and an epoxy equivalent of 520 g/eq was obtained. .

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

The composition of the monomer and polymerization initiator was changed to 18 parts by mass of St, 43 parts by mass of MMA, 10 parts by mass of nBMA, 2 parts by mass of 2EHMA, 25 parts by mass of GMA, 2 parts by mass of iBA, and 5.3 parts by mass of P-O, except that Other than that, in the same manner as in Synthesis Example 1, a solid acrylic resin (RA-2) having a molecular morphology parameter of 0.52, a number average molecular weight of 2,200, a glass transition temperature of 50°C, and an epoxy equivalent of 580 g/eq was obtained. .

(Synthesis Example 7: Synthesis of Acrylic Resin (RA-3))

The composition of the monomer and polymerization initiator was changed to 25 parts by mass of St, 36 parts by mass of MMA, 7 parts by mass of iBMA, 1 part by mass of 2EHMA, 30 parts by mass of GMA, 1 part by mass of nBA, and 6 parts by mass of P-O, except that Other than that, in the same manner as in Synthesis Example 1, a solid acrylic resin (RA-3) having a molecular morphology parameter of 0.53, a number average molecular weight of 2,200, a glass transition temperature of 56°C, and an epoxy equivalent of 490 g/eq was obtained. .

The monomer and polymerization initiator compositions and property values of the acrylic resins (A-1) to (A-4) and (RA-1) to (RA-3) synthesized in the above synthesis examples 1 to 7 are shown in Table 1.

[Table 1]

(Example 1: Preparation of Powder Coating (1))

82 parts by mass of the acrylic resin (A-1) obtained in Synthesis Example 1, 18 parts by mass of dodecanedioic acid (hereinafter, simply referred to as "DDDA" in some cases), 0.5 part by mass of benzoin, and surface adjustment were blended. ("Resiflow LF" manufactured by ESTRON; hereinafter simply referred to as "surface conditioner (1)".) 1 part by mass of the compound was obtained using a twin-screw kneader ("APV·kneader MP-" manufactured by Tubako Yokohama Sales Co., Ltd. 2015 type") after melt-kneading, finely pulverized, and then classified with a 200-mesh metal mesh to obtain a powder coating (1).

(Example 2: Preparation of Powder Coating (2))

The same procedure as in Example 1 was carried out, except that 82 parts by mass of the acrylic resin (A-1) and 18 parts by mass of DDDA mixed in Example 1 were changed to 86 parts by mass of the acrylic resin (A-2) and 14 parts by mass of DDDA. The powder coating material (2) was obtained by this operation.

(Example 3: Preparation of Powder Coating (3))

The same procedure as in Example 1 was carried out, except that 82 parts by mass of acrylic resin (A-1) and 18 parts by mass of DDDA, which were blended in Example 1, were changed to 85 parts by mass of acrylic resin (A-3) and 15 parts by mass of DDDA. The powder coating material (3) was obtained thereby.

(Example 4: Preparation of Powder Coating (4))

The same procedure as in Example 1 was performed, except that 82 parts by mass of acrylic resin (A-1) and 18 parts by mass of DDDA were changed to 83 parts by mass of acrylic resin (A-4) and 17 parts by mass of DDDA. The powder coating material (4) was obtained by this operation.

(Comparative Example 1: Preparation of Powder Coating (R1))

The same procedure as in Example 1 was carried out, except that 82 parts by mass of acrylic resin (A-1) and 18 parts by mass of DDDA, which were blended in Example 1, were changed to 84 parts by mass of acrylic resin (RA-1) and 16 parts by mass of DDDA. By doing this, a powder coating material (R1) was obtained.

(Comparative Example 2: Preparation of Powder Coating (R2))

The same procedure as in Example 1 was carried out, except that 82 parts by mass of acrylic resin (A-1) and 18 parts by mass of DDDA were changed to 85 parts by mass of acrylic resin (RA-2) and 15 parts by mass of DDDA. The powder coating material (R2) was obtained by this operation.

(Comparative Example 3: Preparation of Powder Coating (R3))

The same procedure as in Example 1 was carried out, except that 82 parts by mass of acrylic resin (A-1) and 18 parts by mass of DDDA were changed to 83 parts by mass of acrylic resin (RA-3) and 17 parts by mass of DDDA. The powder coating material (R3) was obtained by this operation.

[Preparation of Cured Coating Film for Evaluation]

After the powder coating obtained above was electrostatically powder coated on an untreated aluminum plate (A-1050P) (7cm×15cm) so that the film thickness after baking was 80 to 120 μm, the process was carried out at 160° C. for 20 minutes. By baking, the cured coating film for evaluation was produced.

[Evaluation of filamentous rust resistance]

Two linear scratches of 13 cm were made on the cured coating film for evaluation obtained above with a dicing knife so as to reach the base of the base material, and the following test was carried out with a CASS tester. Salt water (2.6 g of copper chloride (II) hydrate, 10 cc of glacial acetic acid, and coarse salt (Japanese: 塩) will be sprayed under the conditions of a temperature of 50° C., a spray liquid volume of 1.2 to 1.8 cc/h, and a spray pressure of 0.1 MPa. 500 g were dissolved in 10 L of ion-exchanged water and prepared) for 6 hours in Test 1 and under conditions of 60° C. and 85% humidity for 96 hours as one cycle, and a total of 5 cycles were performed. After the completion of the CASS test, filiform rust generated from scratches on the coated sheet was visually confirmed, and the filiform rust resistance was evaluated according to the following criteria.

⊚: Filamentous rust is less than 1 mm in the direction perpendicular to the straight-line scratches.

○: Filamentous rust is 1 mm or more and less than 2 mm in the direction perpendicular to the straight-line scratches.

×: Filamentous rust is 2 mm or more in the direction perpendicular to the straight-line scratches.

The formulation compositions and evaluation results of the powder coatings (1) to (4) prepared in the above-mentioned Examples 1 to 4 and the powder coatings (R1) to (R3) prepared in Comparative Examples 1 to 3 are shown in Table 2. .

[Table 2]

From the evaluation results of Examples 1 to 4, it was confirmed that the coating films obtained from the powder coating materials of the present invention were excellent in the filamentous rust resistance.

On the other hand, Comparative Examples 1 to 3 are examples in which the molecular morphology parameter α value of the acrylic resin (A), which is a component of the powder coating material of the present invention, is 0.5 or more, and it was confirmed that the obtained coating films are resistant to filamentous rust. Bad sex.

Claims (5)

1. A powder coating material comprising: an acrylic resin A having an epoxy group and a curing agent B having a functional group capable of reacting with an epoxy group, the acrylic resin A having an epoxy group The molecular morphology parameter α in the Mark-Houwink-Sakurada diagram is in the range of 0.3 to 0.5. 2 . The powder coating material according to claim 1 , wherein the epoxy group-containing acrylic resin A uses a polyfunctional monomer as an essential raw material. 3 . 3 . The powder coating material according to claim 1 , wherein the epoxy group-containing acrylic resin A is a polymer using a polyfunctional polymerization initiator. 4 . 4 . The powder coating material according to claim 1 , wherein the curing agent B having a functional group capable of reacting with an epoxy group is an aliphatic polyvalent carboxylic acid and/or an acid anhydride thereof. 5 . 5 . An article having a coating film of the powder coating material according to claim 1 .