JP6674163B2 - Powder coating and article having a coating of the coating - Google Patents

Description

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

  In recent years, regulations on organic solvents have become stricter due to problems such as air pollution, and environmentally friendly paints have been receiving attention. Among them, powder coatings have been spotlighted from the viewpoint of environmental protection as solvent-free coatings, and acrylic powder coatings in particular have excellent coating performance such as weather resistance and stain resistance. Attention has been focused on the use of automotive parts, metal exteriors, and home appliances. However, the powder coating has a drawback in that the appearance of the coating is inferior to that of the solvent coating.

  On the other hand, epoxy group-containing acrylic resin obtained by copolymerizing (meth) acrylic acid alkyl ester, epoxy group-containing acrylic monomer, and other copolymerizable vinyl monomers can react with epoxy group. There has been proposed a powder coating comprising a curing agent having a functional group (for example, see Patent Document 1). However, although the cured coating film obtained from this powder coating has an improved appearance, it has a problem that the rust resistance is insufficient.

JP-A-2002-69368

  The problem to be solved by the present invention is to provide a powder coating material capable of obtaining a cured coating film having excellent yarn rust resistance, and an article having a coating film of the coating material.

  The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, they contain a specific epoxy group-containing acrylic resin (A) and a curing agent (B) having a functional group capable of reacting with the epoxy group. The inventors have found that a cured coating film obtained from a powder coating material has excellent yarn rust resistance and completed the invention.

  That is, the present invention relates to a powder coating containing an acrylic resin having an epoxy group (A) and a curing agent having a functional group capable of reacting with the epoxy group (B), wherein the acrylic resin having the epoxy group The present invention relates to a powder coating material having a molecular form parameter α value of 0.3 to 0.5 in a Mark-Houwink-Sakurada plot of (A) and an article having a coating film of the coating material.

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

  The powder coating of the present invention is a powder coating containing an acrylic resin having an epoxy group (A) and a curing agent having a functional group capable of reacting with the epoxy group (B), and having the epoxy group. The molecular form parameter α value in the Mark-Houwink-Sakurada plot of the acrylic resin (A) is 0.3 to 0.5.

  First, the acrylic resin (A) having an epoxy group will be described. The value of the molecular form parameter α in the Mark-Houwink-Sakurada plot of the acrylic resin (A) having an epoxy group is from 0.3 to 0, since a coating film having excellent coating properties such as yarn rust resistance is obtained. It is important that it is 5.

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

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

  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, and 3,4-epoxy. Examples thereof include cyclohexylmethyl (meth) acrylate, and among them, glycidyl (meth) acrylate is preferable. In addition, these acrylic monomers (a1) can be used alone or in combination of two or more.

  In the present invention, “(meth) acrylic acid” refers to one or both of methacrylic acid and acrylic acid, “(meth) acrylate” refers to one or both of methacrylate and acrylate, and “(meth) acrylic acid”. The term “) acryloyl group” means one or both of a methacryloyl group and an acryloyl group.

  Examples of the other unsaturated monomer (a2) include (meth) acrylic acid, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, and 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) acrylate, isobornyl (meth) acrylate, dicyclopentanyl (meth) acrylate, benzyl (meth) acrylate, acrylamide, N, N-dimethyl (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) acrylate, 1, 4-cyclohexanedimethanol mono (meth) acrylate, glycerin mono (meth) acrylate, polyethylene glycol mono (meth) acrylate, polypropylene glycol mono (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, 2- ( Monofunctional monomers such as (meth) acryloyloxyethyl-2-hydroxyethyl phthalate, lactone-modified (meth) acrylate having a hydroxyl group at a terminal; ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate; ) 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, hydroxy Pivalic acid ester neopentyl glycol di (meth) acrylate, bisphenol A-di (meth) acrylate, bisphenol A-EO modified di (meth) acrylate, isocyanuric acid EO Bifunctional monomers such as functional diacrylates; isocyanuric acid EO-modified triacrylate, trimethylolpropane tri (meth) acrylate, trimethylolpropane EO-modified tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, ditrimethylolpropane tetra Examples include trifunctional or higher functional monomers such as acrylate, dipentaerythritol hexa (meth) acrylate, and dipentaerythritol penta (meth) acrylate. Preferably, a monofunctional monomer and a bifunctional monomer are used in combination, since the possibility of gelation is low and an acrylic resin having a molecular form parameter α value of 0.3 to 0.5 can be easily obtained. preferable. These other unsaturated monomers (a2) can be used alone or in combination of two or more. In the present invention, a monomer having one polymerizable double bond is a monofunctional monomer, a monomer having two is a bifunctional monomer, and a monomer having three or more is a trifunctional or more monofunctional monomer. And a monomer.

  The amount of the acrylic monomer (a1) having an epoxy group to be used is such that the obtained coating film has improved filiform rust resistance and coating film properties, so that the monomer used as the raw material of the acrylic resin (A) can be used. The mass ratio in the component is preferably in the range of 10 to 70% by mass, and more preferably in the range of 20 to 50% by mass. The amount of the polyfunctional monomer used is 0.1% by mass in the monomer component, which is a raw material of the acrylic resin (A), since the obtained coating film has a further improved rust resistance. The range is preferably from 10 to 10% by mass, more preferably from 0.1 to 5% by mass.

  The number average molecular weight of the acrylic resin (A) is preferably from 1,000 to 5,000, since the resulting coating film has improved rust resistance and coating film properties. Here, the number average molecular weight is a value converted into polystyrene based on gel permeation chromatography (hereinafter abbreviated as “GPC”) measurement.

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

  The acrylic resin (A) can be obtained by a known polymerization method using the acrylic monomer (a1) and the other unsaturated monomer (a2) as raw materials. Legalization is preferred because it is the simplest.

  The solution radical polymerization method is a method in which each monomer as a raw material is dissolved in a solvent and a polymerization reaction is performed 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; and alcohol solvents such as methanol, ethanol, isopropanol, n-butanol, isobutanol, and sec-butanol. 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; ester solvents such as methyl acetate, ethyl acetate, n-butyl acetate, isobutyl acetate and amyl acetate; acetone And ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone. These solvents can be used alone or in combination of two or more.

  As the polymerization initiator, a polyfunctional polymerization initiator is preferably used because an acrylic resin having a molecular form parameter α value of 0.3 to 0.5 can be easily obtained, and a trifunctional or higher functional polymerization initiator is preferably used. It is more preferable to use The polyfunctional polymerization initiator includes, for example, 2,2-bis- (4,4-di-t-butylperoxycyclohexyl) propane, 2,2-t-butylperoxyoctane, 1,1-di- t-butylperoxy-3,3,5-trimethylcyclohexane, 1,3-bis- (t-butylperoxyisopropyl) benzene, 2,5-dimethyl-2,5- (t-butylperoxy) hexane, 2,5-dimethyl-2,5-di- (t-butylperoxy) hexyne-3, tris- (t-butylperoxy) triazine, 1,1-di-t-butylperoxycyclohexane, 2,2 -Di-t-butylperoxybutane, 4,4-di-t-butylperoxyvaleric acid-n-butyl ester, di-t-butylperoxyhexahydroterephthalate, di- Two or more peroxide groups in one molecule such as -butylperoxyazelate, di-t-butylperoxytrimethyladipate, 3,3 ', 4,4'-tetra (t-butylperoxycarbonyl) benzophenone And those having a functional group having a polymerization initiation function.

  As the 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 (t-butylperoxy) -3 , 3,5-trimethylcyclohexane, 1,1-bis (t-butylperoxy) cyclohexane, n-butyl-4,4-bis (t-butylperoxy) valerate, 2,2-bis (4,4- Di-t-butylperoxycyclohexyl) propane, 2,2-bis (4,4-di-t-amylperoxycyclohexyl) propane, 2,2-bis (4,4-di-t-hexylperoxycyclohexyl) propane, 2,2-bis (4,4-di-tert-octylperoxycyclohexyl) propane, 2,2 Peroxyketal compounds such as bis (4,4-dicumylperoxycyclohexyl) propane and 1,1-bis (t-amylperoxy) cyclohexane; cumene hydroperoxide, 2,5-dimethylhexane-2,5- Hydroperoxide compounds such as dihydroperoxide and t-amyl hydroperoxide; 1,3-bis (t-butylperoxy-m-isopropyl) benzene, 2,5-dimethyl-2,5-di (t- Butylperoxy) hexane, diisopropylbenzene peroxide, t-butylcumyl peroxide, di-t-amyl peroxide and other dialkyl peroxide compounds; decanoyl peroxide, lauroyl peroxide, benzoyl peroxide, 2,4-dichlorobenzoyl Paoki Diacyl peroxide compounds such as amides; peroxycarbonate compounds such as bis (t-butylcyclohexyl) peroxydicarbonate, t-amylperoxyisopropyl carbonate and t-amylperoxy 2-ethylhexyl carbonate; t-butylperoxy- 2-ethylhexanoate, t-butylperoxybenzoate, 2,5-dimethyl-2,5-di (benzoylperoxy) hexane, t-amylperoxyneodecanate, t-amylperoxypivalate, t -Peroxyester compounds such as amyl peroxy-2-ethylhexanoate, t-amyl peroxy normal octoate, t-amyl peroxy acetate, t-amyl peroxy isononanoate, t-amyl peroxy benzoate, etc. No And azo compounds such as 2,2'-azobisisobutyronitrile and 1,1'-azobis (cyclohexane-1-carbonitrile).

  The amount of the polymerization initiator to be used is from 0.5 to 0.5% with respect to the monomer component as a raw material of the acrylic resin (A), since the obtained coating film has improved filiform rust resistance and coating film properties are further improved. A range of 15% by mass is preferable, and a range of 2 to 10% by mass is more preferable.

  Next, the curing agent (B) will be described. The curing agent (B) is a curing agent having a functional group capable of reacting with an epoxy group, such as suberic acid, azelaic acid, 2,4-diethylglutaric acid, sebacic acid, undecanedicarboxylic acid, dodecanedicarboxylic acid, Polyvalent carboxylic acid compounds such as brassic acid, tetradecanedicarboxylic acid, pentadecanedicarboxylic acid, hexadecanedicarboxylic acid, heptadecanedicarboxylic acid, octadecanedicarboxylic acid, eicosandicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, and butanetricarboxylic acid; Examples thereof include anhydrides of polyvalent carboxylic acids and polyhydric phenol compounds. Among these, an aliphatic polycarboxylic acid compound and its anhydride are preferable, and dodecanedicarboxylic acid is more preferable, since a high-strength coating film can be obtained. These curing agents (B) can be used alone or in combination of two or more.

  The powder coating of the present invention contains the acrylic resin (A) having an epoxy group and a curing agent (B) having a functional group capable of reacting with the epoxy group. From the fact that they are obtained, the mixing ratio of the equivalent number of the equivalent number of epoxy groups (EP) in the acrylic resin (A) and the equivalent number of carboxyl groups (COOH) in the curing agent (B) is determined. [(EP) / (COOH)] is preferably in the range of 0.5 to 1.5, and more preferably in the range of 0.8 to 1.2.

  In the powder coating of the present invention, within the range not impairing the effects of the present invention, including organic or inorganic pigments, flow regulators, light stabilizers, ultraviolet absorbers, known and commonly used antioxidants and the like. Various additives can be added. Further, a catalyst may be added for the purpose of accelerating the curing reaction at the time of baking.

  As a method for preparing the powder coating material of the present invention, various known and common methods can be used. For example, the acrylic resin (A), the curing agent (B), and if necessary, a pigment A so-called mechanical pulverization method of mixing various additives such as a surface conditioner and the like, then melt-kneading them, and then pulverizing and classifying them can be used.

  The powder coating of the present invention can be applied to various articles such as exteriors, home appliances, automobiles, motorcycles, protective fences, etc., and has a high resistance to thread rust, weather resistance, impact resistance, and chipping resistance. It is suitable for coating metal members such as aluminum wheel alloy members since a high-appearance coating film having excellent water resistance and the like can be obtained.

  Examples of the coating method of the powder coating of the present invention include various known and commonly used methods such as an electrostatic powder coating method. Further, the method of forming a cured coating film after applying the powder coating of the present invention can be appropriately selected according to the type and purpose of the substrate, but is excellent in thread rust resistance, water resistance and weather resistance. From the viewpoint of obtaining a coating film, baking is preferably performed at a temperature in the range of 120 to 250 ° C. for 5 to 30 minutes. Further, the coating film thickness is preferably in the range of 50 to 150 μm.

Hereinafter, the present invention will be described in more detail with reference to specific examples. The epoxy equivalent, glass transition temperature, and number average molecular weight of the acrylic resin were measured by the following methods.
[Method of measuring epoxy equivalent]
It was measured by the hydrochloric acid-pyridine method. To the resin was added 25 ml of a hydrochloric acid-pyridine solution, and the mixture was heated and dissolved at 130 ° C. for 1 hour, and titrated with a 0.1 N potassium hydroxide alcohol solution using phenolphthalein as an indicator. The epoxy equivalent was calculated from the amount of the consumed 0.1 N potassium hydroxide alcohol solution.

[Measurement method of glass transition temperature]
It was determined by the DSC method (differential scanning calorimetry).
Measuring device: Differential scanning calorimeter ("DSC Q-100" manufactured by TA INSTRUMENTS Co., Ltd.)
Atmosphere conditions: Under nitrogen atmosphere Temperature range: -50 to 150 ° C
Heating rate: 5 ° C / min

[Method of measuring weight average molecular weight]
It was 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" (7.8 mm ID x 30 cm) x 1 "TSKgel G4000" (7.8 mm ID x 30 cm) x 1 "TSKgel G3000" (7.8 mm ID x 30 cm) x 1 Book “TSKgel G2000” (7.8 mm ID × 30 cm) × 1 Detector: RI (differential refractometer)
Column temperature: 40 ° C
Eluent: tetrahydrofuran (THF)
Flow rate: 1.0 mL / min Injection volume: 100 μL (sample concentration 4 mg / mL in tetrahydrofuran solution)
Standard sample: A calibration curve was prepared using the following monodisperse polystyrene.

(Monodisperse polystyrene)
"TSKgel Standard Polystyrene A-500" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene A-1000" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene A-2500" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene A-5000" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-1" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-2" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-4" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-10" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-20" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-40" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-80" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-128" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-288" manufactured by Tosoh Corporation
"TSKgel Standard Polystyrene F-550" manufactured by Tosoh Corporation

(Synthesis Example 1: Synthesis of acrylic resin (A-1))
76 parts by mass of xylene was charged into a reaction vessel equipped with a stirrer, a thermometer, a cooling pipe, and a nitrogen introduction pipe, and heated to 135 ° C. under a nitrogen atmosphere. There, 18 parts by mass of styrene (hereinafter abbreviated as "St"), 42 parts by mass of methyl methacrylate (hereinafter abbreviated as "MMA"), and n-butyl methacrylate (hereinafter abbreviated as "nBMA"). ) 4 parts by mass, 2-ethylhexyl methacrylate (hereinafter abbreviated as “2EHMA”) 2 parts by mass, glycidyl methacrylate (hereinafter abbreviated as “GMA”) 32 parts by mass, n-butyl acrylate (hereinafter “BA”) 2) and 0.3 parts by mass of 2,2-bis- (4,4-di-t-butylperoxycyclohexyl) propane (hereinafter abbreviated as “P-TA”). And 5 parts by mass of t-butylperoxy-2-ethylhexanoate (hereinafter abbreviated as “PO”) were added dropwise over 6 hours. After completion of the dropwise addition, the mixture was kept at the same temperature for 10 hours to carry out the polymerization reaction. After removing the solvent at 160 ° C. under a reduced pressure of 20 mmHg, the molecular form parameter was 0.47, the number average molecular weight was 2,200, and the glass transition temperature was 52. C., a solid acrylic resin (A-1) having an epoxy equivalent of 460 g / eq was obtained.

(Synthesis Example 2: Synthesis of acrylic resin (A-2))
The composition of the monomer and the polymerization initiator was 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 abbreviated as “iBMA”), 24 parts by mass of GMA, and ethyl acrylate. (Hereinafter, abbreviated as "EA".) The same procedure as in Synthesis Example 1 was carried out except that the amount was changed to 3 parts by mass and 5.3 parts by mass of P-TA, whereby a molecular form parameter 0.42 and a number average molecular weight were obtained. A solid acrylic resin (A-2) having a glass transition temperature of 2,100 and an epoxy equivalent of 600 g / eq was obtained.

(Synthesis Example 3: Synthesis of acrylic resin (A-3))
The composition of the monomer and the polymerization initiator was 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 abbreviated as “iBA”). The same procedure as in Synthesis Example 1 was carried out except that 4 parts by mass, 1 part by mass of ethylene glycol dimethacrylate (hereinafter abbreviated as "EDMA") and 8 parts by mass of P-O were used, whereby the molecular morphological parameter was changed to 0.1 part by mass. Thus, a solid acrylic resin (A-3) having a number average molecular weight of 1,700, a glass transition temperature of 41 ° C. and an epoxy equivalent of 570 g / eq was obtained.

(Synthesis Example 4: Synthesis of acrylic resin (A-4))
The composition of the monomer and the 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 PO. A solid acrylic resin (A-4) having a molecular form 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 by operating in the same manner as in Synthesis Example 1 except for the change. I got

(Synthesis Example 5: Synthesis of acrylic resin (RA-1))
The composition of the monomer and the 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 PO. A solid acrylic resin (RA-1) having a molecular form 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 by operating in the same manner as in Synthesis Example 1 except for the change. I got

(Synthesis Example 6: Synthesis of acrylic resin (RA-2))
The composition of the monomer and the polymerization initiator was adjusted 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 PO. A solid acrylic resin (RA-2) having a molecular form 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 by operating in the same manner as in Synthesis Example 1 except for the change. I got

(Synthesis Example 7: Synthesis of acrylic resin (RA-3))
The composition of the monomer and the polymerization initiator was changed to St 25 parts by mass, MMA 36 parts by mass, iBMA 7 parts by mass, 2EHMA 1 part by mass, GMA 30 parts by mass, nBA 1 part by mass and PO 6 parts by mass. A solid acrylic resin (RA-3) having a molecular form 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 by operating in the same manner as in Synthesis Example 1 except for the above. Was.

  Table 1 shows the monomer / polymerization initiator composition and properties of the acrylic resins (A-1) to (A-4) and (RA-1) to (RA-3) synthesized in Synthesis Examples 1 to 7 above. Shown in

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 dodecanedicarboxylic acid (hereinafter abbreviated as “DDDA”), 0.5 parts by mass of benzoin, and a surface conditioner (“ESTRON”) Resinflow LF "; hereinafter, abbreviated as" surface conditioner (1) ".) A mixture prepared by mixing 1 part by mass was mixed with a twin-screw kneader (" APV Kneader MP-2015 "manufactured by Tubaco Yokohama Sales Co., Ltd.). After melt-kneading using, the mixture was finely pulverized and further classified using a 200-mesh wire net to obtain a powder coating material (1).

(Example 2: Preparation of powder coating material (2))
Same as Example 1 except that 82 parts by mass of the acrylic resin (A-1) and 18 parts by mass of DDDA blended in Example 1 were changed to 86 parts by mass of the acrylic resin (A-2) and 14 parts by mass of DDDA. By operating, a powder coating (2) was obtained.

(Example 3: Preparation of powder coating material (3))
Same as Example 1 except that 82 parts by mass of the acrylic resin (A-1) and 18 parts by mass of DDDA blended in Example 1 were changed to 85 parts by mass of the acrylic resin (A-3) and 15 parts by mass of DDDA. By operation, a powder coating (3) was obtained.

(Example 4: Preparation of powder coating (4))
Same as Example 1 except that 82 parts by mass of the acrylic resin (A-1) and 18 parts by mass of DDDA blended in Example 1 were changed to 83 parts by mass of the acrylic resin (A-4) and 17 parts by mass of DDDA. By operation, powder coating (4) was obtained.

(Comparative Example 1: Preparation of powder coating (R1))
Same as Example 1 except that 82 parts by mass of the acrylic resin (A-1) and 18 parts by mass of DDDA blended in Example 1 were changed to 84 parts by mass of the acrylic resin (RA-1) and 16 parts by mass of DDDA. By operation, a powder coating (R1) was obtained.

(Comparative Example 2: Preparation of powder coating material (R2))
Same as Example 1 except that 82 parts by mass of the acrylic resin (A-1) and 18 parts by mass of DDDA blended in Example 1 were changed to 85 parts by mass of the acrylic resin (RA-2) and 15 parts by mass of DDDA. By operation, a powder coating (R2) was obtained.

(Comparative Example 3: Preparation of powder coating material (R3))
Same as Example 1 except that 82 parts by mass of the acrylic resin (A-1) and 18 parts by mass of DDDA blended in Example 1 were changed to 83 parts by mass of the acrylic resin (RA-3) and 17 parts by mass of DDDA. By operation, a powder coating (R3) was obtained.

[Production of cured coating film for evaluation]
The powder coating obtained above is applied to an untreated aluminum plate (A-1050P) (7 cm × 15 cm) by electrostatic powder coating so that the film thickness after baking becomes 80 to 120 μm. After baking for a minute, a cured coating film for evaluation was prepared.

[Evaluation of thread rust resistance]
Two 13-cm linear scratches were made on the cured coating film for evaluation obtained above with a cutter knife so as to reach the base material of the base material, and the following test was performed with a CASS tester. Under a condition of a temperature of 50 ° C., a spray liquid amount of 1.2 to 1.8 cc / h, and a spray pressure of 0.1 MPa, salt water (2.6 g of copper (II) chloride hydrate, 10 cc of glacial acetic acid, 500 g of normal salt in 10 L) was used. Test 1 in which spraying (prepared by dissolving in ion-exchanged water) was sprayed for 6 hours, and Test 2 in which the test was left for 96 hours at a temperature of 60 ° C. and a humidity of 85%, as one cycle, for a total of 5 cycles. After the completion of the CASS test, thread rust generated from scratches on the coated plate was visually confirmed, and the thread rust resistance was evaluated according to the following criteria.
：: Yarn rust is less than 1 mm in the vertical direction with respect to a scratch placed in a straight line
Good: Yarn rust is not less than 1 mm and less than 2 mm in the vertical direction with respect to a scratch placed in a straight line.
X: The thread rust is 2 mm or more in the vertical direction with respect to the scratch placed in a straight line.

  Table 2 shows the composition and evaluation results of the powder coatings (1) to (4) prepared in Examples 1 to 4 and the powder coatings (R1) to (R3) prepared in Comparative Examples 1 to 3. .

  From the evaluation results of Examples 1 to 4, it was confirmed that the coating film obtained from the powder coating material of the present invention had excellent rust resistance.

  On the other hand, Comparative Examples 1 to 3 are examples in which the molecular form parameter α value of the acrylic resin (A) which is a component of the powder coating of the present invention is 0.5 or more. Inferiority was confirmed.

Claims (5)

Resin containing an acrylic resin having an epoxy group (A) for a powder coating containing an acrylic resin having an epoxy group (A) and a curing agent having a functional group capable of reacting with the epoxy group (B) A composition, wherein the acrylic resin (A) having an epoxy group has a molecular morphological parameter α value in a range of 0.3 to 0.5 in a Mark-Houwink-Sakurada plot, and the acrylic resin having an epoxy group ( tree fat composition you characterized by a) is a polymer using a polyfunctional polymerization initiator. The acrylic resin having an epoxy group (A) is, tree fat composition according to claim 1, wherein in which the polyfunctional monomer as an essential raw material. And tree fat composition according to claim 1 or 2, wherein the curing agent having a functional group capable of reacting with epoxy group (B) and powder coating, characterized in that it contains.   The powder coating according to claim 3, wherein the curing agent (B) having a functional group capable of reacting with an epoxy group is an aliphatic polycarboxylic acid and / or an anhydride thereof.   An article having a coating film of the powder paint according to claim 3.