JP4923675B2 - Thermosetting powder coating resin composition and aluminum wheel powder coating resin composition - Google Patents

Description

  The present invention relates to a thermosetting powder coating resin composition suitable for obtaining a powder coating material that has high storage stability and can form a coating film having excellent coating film appearance, corrosion resistance, and water resistance. Furthermore, the present invention has high storage stability, and is suitable for obtaining a powder coating material that forms a coating film excellent in corrosion resistance and water resistance when coated on an aluminum wheel for automobiles as a single layer or a primer. The present invention relates to a resin composition for powder coatings for aluminum wheels, which has extremely high properties.

  In recent years, the issue of global warming has attracted more attention. As one of the countermeasures, the automobile industry is strongly required to reduce the amount of carbon dioxide emitted from automobiles and to save energy, and the importance of reducing the weight of automobile bodies for the purpose of improving fuel efficiency is increasing. . As a weight reduction technology, the application of aluminum materials to automobile parts is being considered as a very effective means, but among them, aluminum wheels are not only lighter in weight but also more resistant to corrosion, and diversifying the preferences of automobile users. Therefore, the mounting rate has increased dramatically.

  On the other hand, in the paint industry, restrictions on organic solvents have become strict due to problems such as air pollution, and the transition to environmentally friendly products is rapidly progressing. Powder coatings are attracting attention as an environmentally friendly product from the viewpoint of environmental protection, and are used in applications such as building materials, automotive parts, and automotive top clear coats. Under such circumstances, research on powder coatings for future aluminum components is also actively conducted, and powder coatings, which are environmentally friendly coatings, are used in place of current solvent-based coatings. If this is the case, it will be possible to significantly reduce the load on the global environment.

  Powder coating for aluminum wheels has started to be used as a substitute for solvent-based paints because it can be thickly applied at one time and has a feeling of fleshiness, and has a relatively low baking temperature and a high coating appearance (smoothness, Transparency), weather resistance, and scratch resistance are required, so acrylic powder coatings such as acrylic powder coatings composed of epoxy group-containing acrylic resins and polyvalent carboxylic acids and / or their anhydrides are mainly used. It's being used. However, such acrylic powder paints have insufficient corrosion resistance and water resistance against aluminum base materials compared to conventional solvent-based paints, and there are several proposals for improving corrosion resistance and water resistance. Has been made.

  For example, aluminum containing an acrylic phosphate group-containing acrylic copolymer as an essential component together with an epoxy group-containing acrylic resin can be used to improve the corrosion resistance and water resistance when an acrylic powder coating is used as an aluminum wheel paint. A powder primer for a wheel is disclosed (for example, see Patent Document 1). If the aluminum wheel powder primer is used, the substrate adhesion and corrosion resistance are improved, but the acid phosphate group reacts with the epoxy group, so the storage stability (solid phase resistance) is greatly reduced. There is still room for improvement.

JP 2002-138246 A

  The present invention is a thermosetting powder coating resin composition suitable for obtaining a powder coating material that can form a coating film having high storage stability and excellent coating film appearance, corrosion resistance, and water resistance. Resin composition for powder coatings for aluminum wheels that is highly practical and suitable for obtaining powder coatings that form coatings with excellent corrosion resistance and water resistance when coated on aluminum wheels as a single layer or primer. Is to provide.

  As a result of intensive studies to solve the above problems, the present inventors have found that for thermosetting powder coatings containing an epoxy group-containing vinyl resin and a polyvalent carboxylic acid and / or anhydride (C) thereof. In the resin composition, as the epoxy group-containing vinyl resin, an epoxy equivalent-containing vinyl resin (A) having an epoxy equivalent (EEW) of 180 to 560 g / equivalent and a weight average molecular weight of 4,000 to 15,000, and an epoxy equivalent ( EEW) 720 to 14,000 g / equivalent and an epoxy group-containing vinyl resin (B) having a weight average molecular weight of 25,000 to 120,000, and the difference in solubility parameters of these epoxy group-containing vinyl resins (SpA-SpB) ) Is 0 to 0.8 and the weight ratio (A / B) is 98/2 to 80/20. Built high stability, coating film appearance, corrosion resistance, to obtain a powder coating capable of forming a coating film excellent in water resistance found to be suitable, and have completed the present invention.

  That is, the present invention includes an epoxy equivalent-containing vinyl resin (A) having an epoxy equivalent (EEW) of 180 to 560 g / equivalent and a weight average molecular weight of 4,000 to 15,000, and an epoxy equivalent (EEW) of 720 to 14,000 g / equivalent. An epoxy group-containing vinyl resin (B) having an equivalent weight average molecular weight of 25,000 to 120,000, a polyvalent carboxylic acid and / or an anhydride thereof (C), and an epoxy group-containing vinyl system The difference (SpA-SpB) between the solubility parameter (SpA) of the resin (A) and the solubility parameter (SpB) of the epoxy group-containing vinyl resin (B) is 0 to 0.8, the epoxy group-containing vinyl resin (A And a weight ratio (A / B) of the epoxy group-containing vinyl resin (B) is 98/2 to 80/20, and a thermosetting powder coating resin composition is provided. It is.

  Moreover, this invention provides the resin composition for powder coating materials for aluminum wheels characterized by using the said thermosetting type resin composition for powder coating materials.

  The resin composition for powder coatings of the present invention is a resin composition suitable for obtaining a powder coating that has high storage stability and can form a coating film having excellent coating film appearance, corrosion resistance, and water resistance. Moreover, when the resin composition for powder coatings is used for powder coatings, a powder coating that can form a coating film excellent in coating film appearance, corrosion resistance, and water resistance can be easily obtained. When coated on a wheel as a single layer or as a primer, a coating film excellent in corrosion resistance and water resistance can be formed. Therefore, it is useful as a resin composition for powder coatings for aluminum wheels.

  First, the epoxy group-containing vinyl resins (A) and (B), which are essential components of the resin composition for powder coatings of the present invention, will be described.

  The epoxy group-containing vinyl-based resins (A) and (B) have two types of epoxy having at least one epoxy group in one molecule and having a specific epoxy equivalent and a specific weight average molecular weight as described below. A group-containing vinyl resin is designated.

  The epoxy equivalent (EEW) of the epoxy group-containing vinyl resin (A) used in the resin composition for thermosetting powder coatings of the present invention is essential to be 180 to 560 g / equivalent, preferably 300 to 560 g. / Equivalent. When the epoxy equivalent (EEW) is less than 180 g / equivalent, the storage stability deteriorates. When the epoxy equivalent (EEW) exceeds 560 g / equivalent, the solvent resistance and impact resistance of the resulting coating film are insufficient, and therefore all are preferable. Absent.

  The weight average molecular weight of the epoxy group-containing vinyl resin (A) is essentially 4,000 to 15,000, preferably 5,000 to 10,000. When the weight average molecular weight is less than 4,000, the storage stability is deteriorated, and when it exceeds 15,000, the appearance (smoothness) of the coating film is deteriorated.

Here, the epoxy equivalent (EEW) and the weight average molecular weight are determined by the following methods.
[Epoxy equivalent (EEW)]
A value obtained by dissolving a resin sample in a mixed solution of hydrochloric acid and pyridine, heating and refluxing at 130 ° C. for 1 hour, cooling to 25 ° C., and back titrating with an alcohol solution of potassium hydroxide.

(Weight average molecular weight)
Value obtained by molecular weight measurement in gel permeation chromatography of tetrahydrofuran solubles.

  Next, the epoxy equivalent (EEW) of the epoxy group-containing vinyl resin (B) is essential to be 720 to 14,000 g / equivalent, and preferably 1,000 to 7,000 g / equivalent. When the epoxy equivalent (EEW) is less than 720 g / equivalent or exceeds 14,000 g / equivalent, the corrosion resistance and water resistance of the coating film become insufficient.

  In addition, the weight average molecular weight of the epoxy group-containing vinyl resin (B) is necessarily 25,000 to 120,000, preferably 30,000 to 100,000, more preferably 40,000 to 100. , 000. When the weight average molecular weight is less than 25,000, the corrosion resistance and water resistance of the coating film are not sufficient, and when it exceeds 120,000, the appearance of the coating film is deteriorated.

  It is essential that the mixing ratio of the epoxy group-containing vinyl resins (A) and (B) is 98/2 to 80/20 by weight ratio (A / B), preferably 96/4 to 85 /. 15. When the weight ratio (A / B) exceeds 98/2 [when (B) is less than 2 parts by weight with respect to 100 parts by weight of (A) and (B) in total), the corrosion resistance and water resistance of the coating film In the case of less than 80/20 [when (B) exceeds 20 parts by weight relative to the total of 100 parts by weight of (A) and (B)], the appearance of the coating film (smoothness) deteriorates. However, neither is preferable.

  In addition, the epoxy group-containing vinyl resin (A) and the epoxy group-containing vinyl resin (B) can provide a powder coating having excellent corrosion resistance and water resistance, so that the epoxy equivalent of the epoxy group-containing vinyl resin (A) is obtained. The ratio [EEW (B) / EEW (A)] of the epoxy equivalent [EEW (B)] of the epoxy group-containing vinyl resin (B) to [EEW (A)] is preferably 2 or more, more preferably 3 or more, more preferably 3-20.

  Further, the epoxy group-containing vinyl resin (A) and the epoxy group-containing vinyl resin (B) are obtained from the solubility parameter (SpA) of the epoxy group-containing vinyl resin (A) and the epoxy group-containing vinyl resin (B). It is essential that the difference in solubility parameter (SpB) (SpA-SpB) is 0 to 0.8, preferably 0 to 0.5. This means that the epoxy group-containing vinyl resin (A) and the epoxy group-containing vinyl resin (B) are in a substantially compatible relationship, and the (SpA-SpB) is less than 0. If it is, the corrosion resistance and water resistance are not sufficient, and if it exceeds 0.8, the appearance of the coating film deteriorates.

The epoxy group-containing vinyl resin (A), the the solubility parameter (Sp value) of the resin (B) or the like, a parameter which represents the polarity of the resin, determined by the following method.

0.5 g of sample resin is weighed into a 100 ml Meyer flask and 10 ml of tetrahydrofuran (THF) is added to dissolve the resin. While the dissolved solution is kept at a liquid temperature of 25 ° C. and stirred with a magnetic stirrer, hexane is added dropwise using a 50 ml burette, and the dropping amount (v _h ) of the point at which the solution becomes turbid (turbid point) is determined. Ask.

Next, the dropping amount (v _d ) at the cloud point when deionized water is used instead of hexane is determined.

From v _h and v _d , the solubility parameter (Sp value) δ of the resin is Sue (SUH), Clarke (CLARKE) [J. Polym. Sci. A-1, Vol. 5, 1671-1681 (1967)] can be obtained as follows.
δ = [(V _mh ) ^(1/2) · δ _mh + (V _md ) ^(1/2) · δ _md ] / [(V _mh ) ^(1/2) + (V _md ) ^(1/2) ]
here,
V _mh = (V _h · V _t ) / (φ _h · V _t + φ _{h t} · V _h )
V _md = (V _d · V _t ) / (φ _d · V _t + φ _{d t} · V _d )
δ _mh = φ _h · δ _h + φ _{h t} · δ _t ,
δ _md = φ _d · δ _d + φ _{d t} · δ _t
φ _h , φ _{h t} ; volume fraction of hexane and THF at the cloud point when hexane is used as the titration solvent
φ _d , φ _dt ; volume fraction of deionized water and THF at the cloud point when using deionized water as the titration solvent [φ _h = v _h / (v _h +10), φ _ht = 10 / (v _h +10), φ _d = v _d / (v _d +10) , φ _dt = 10 / (v _d +10) ] [where 10 is the working volume of THF (10 ml). ]
δ _h , δ _d , δ _t ; Solubility parameters (Sp value ) of hexane, deionized water, and THF
V _h , V _d , V _t ; hexane, deionized water, THF molecular volume (ml / mol)

  The softening point of the epoxy group-containing vinyl resin (A) or (B) is not particularly limited, but a powder coating having excellent storage stability (blocking resistance) is obtained, and therefore, 90 ° C or higher is preferable. Further, the glass transition temperature (Tg) is preferably 40 ° C. or higher, and more preferably in the range of 50 to 90 ° C., because a powder coating having excellent storage stability (blocking resistance) can be obtained.

Here, the glass transition temperature (Tg) is determined by the following method.
The numerical value obtained by converting the glass transition temperature (Tg _K ) expressed in the absolute temperature (K) calculated by the following Fox equation into the Celsius temperature (° C.) is defined as the glass transition temperature (Tg) in the present invention.
100 / Tg _K = W ₁ / Tg ₁ + W ₂ / Tg ₂ + W ₃ / Tg ₃ + W ₄ / Tg ₄ ...
- _{wherein, W 1, W 2, W} 3, W 4 ··· denotes the weight fraction of the various components (wt%).
- _wherein indicates a _{Tg 1, Tg 2, Tg 3} , Tg 4 ··· glass transition temperature of the absolute temperature (K) Display of the homopolymer of each monomer component. Here, the glass transition temperatures (Tg ₁ , Tg ₂ , Tg ₃ , Tg ₄ ...) Indicated by the absolute temperature (K) of the homopolymer of each of the above monomer components are determined by Polymer Handbook (Second Edition, J, Brandrup E. , H, edited by Immergut).

  Further, the weight average molecular weights of the epoxy group-containing vinyl resins (A) and (B) may be any combination as long as they are within the above-mentioned ranges, and are not particularly limited, but the coating having excellent corrosion resistance and water resistance. Since a powder coating material that forms a film is obtained, the ratio (B / A) of the weight average molecular weight is preferably 2 or more, more preferably 4 or more, and further preferably 4 to 15.

  The epoxy group-containing vinyl resins (A) and (B) can be produced by various methods. The epoxy group-containing vinyl monomer and other vinyls copolymerizable with the monomer can be used. The monomers are used in combination so that the solubility parameter (Sp), the epoxy equivalent (EEW), and the weight average molecular weight are the desired values, and after polymerizing them in an organic solvent, the solvent is distilled off. It is preferable to solidify by making it simplest. At that time, various polymerization initiators can be used.

  Here, as a vinyl monomer which can be used when manufacturing the said epoxy group containing vinyl-type resin (A) and (B), an epoxy group containing vinyl monomer and other copolymerizable with the said monomer are used. These vinyl monomers can be used alone or in combination of two or more.

  Examples of the epoxy group-containing vinyl monomer that can be used when producing the epoxy group-containing vinyl resins (A) and (B) include glycidyl (meth) acrylate and β-methylglycidyl (meth) acrylate. Various epoxy group-containing monomers such as glycidyl vinyl ether and allyl glycidyl ether, and (2-oxo-1,3-oxolane) groups such as (meth) acrylic acid (2-oxo-1,3-oxolane) methyl Containing vinyl monomers, and further various (meth) acrylic acid 3,4-epoxycyclohexyl, (meth) acrylic acid 3,4-epoxycyclohexylmethyl, (meth) acrylic acid 3,4-epoxycyclohexylethyl, etc. And alicyclic epoxy group-containing vinyl monomers.

  As the other vinyl monomer copolymerizable with the epoxy group-containing vinyl monomer, various vinyl monomers such as (meth) acrylic acid ester can be used.

  Examples of the (meth) acrylic acid ester include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, and n-butyl (meth) acrylate. , Isobutyl (meth) acrylate, tert-butyl (meth) acrylate or n-hexyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate (Meth) such as, octyl (meth) acrylate, 2-ethyloctyl (meth) acrylate, dodecyl (meth) acrylate, isodecyl (meth) acrylate, lauryl (meth) acrylate or stearyl (meth) acrylate Acrylic acid alkyl ester;

Benzyl (meth) acrylate, phenyl (meth) acrylate, phenoxyethyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, isobornyl (meth) acrylate, dicyclopentanyl (meth) acrylate, (meta ) Dicyclopentenyl acrylate, dicyclopentenyloxyethyl (meth) acrylate; alkyl carbitol (meth) acrylate such as ethyl carbitol (meth) acrylate;

Hydroxyl group-containing (meth) acrylic esters such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate; Hydroxyl group-containing (meth) acrylic acid esters obtained by ring-opening reaction of these hydroxyl group-containing (meth) acrylic acid esters with ε-caprolactone; polyethylene glycol mono (meth) acrylate, polypropylene glycol mono (meth) acrylate, etc. .

  Furthermore, examples of the vinyl monomer other than the (meth) acrylic acid ester include γ- (meth) acryloyloxypropyltrimethoxysilane, γ- (meth) acryloyloxypropyltriethoxysilane, and γ- (meth) acryloyl. Hydrolyzable silyl group-containing monomer such as oxypropylmethyldimethoxysilane; Organosiloxane having one vinyl group in one molecule;

Vinyl fluoride, vinylidene fluoride, trifluoroethylene, tetrafluoroethylene, chlorotrifluoroethylene, bromotrifluoroethylene, pentafluoropropylene, hexafluoropropylene; trifluoromethyl trifluorovinyl ether, pentafluoroethyl trifluorovinyl ether, heptafluoro Fluorine-containing vinyl monomers such as fluoroalkyl-fluorovinyl ethers such as propyl trifluorovinyl ether or fluoroalkyl vinyl ethers (alkyl groups having a carbon number in the range of 1-18);

Various halogen-containing vinyl monomers other than the above-mentioned fluorine-containing vinyl monomers such as vinyl chloride and vinylidene chloride; α-olefins such as ethylene, propylene and butene-1; acidic properties such as mono [(meth) acryloyloxyethyl] phosphoric acid Phosphoric acid (meth) acrylic acid ester; phosphoric acid (meth) acrylic acid ester such as diphenyl-2- (meth) acryloyloxyethyl phosphate; containing two or more polyvalent carboxyl groups such as fumaric acid, maleic acid, itaconic acid Monoesters or diesters of a monoalkyl alcohol having 1 to 18 carbon atoms and an aromatic vinyl compound such as styrene, vinyltoluene, α-methylstyrene, p-tert-butylstyrene;

(Meth) acrylamide, N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, Nn-propyl (meth) acrylamide, N-iso-propyl (meth) acrylamide, Nn-butyl (meth) acrylamide N-iso-butyl (meth) acrylamide, N-tert-butyl (meth) acrylamide, N-amyl (meth) acrylamide, N- (meth) acrylamide, N-hexyl (meth) acrylamide, N-heptyl (meth) Acrylamide, N-2-ethylhexyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N-methylol (meth) acrylamide, N-methoxymethyl (meth) acrylamide, N -Ethoxymethyl (meth) Kurylamide, Nn-propoxymethyl (meth) acrylamide, N-iso-propoxymethyl (meth) acrylamide, Nn-butoxymethyl (meth) acrylamide, N-iso-butoxymethyl (meth) acrylamide, N-tert- Butoxymethyl (meth) acrylamide, N-amyloxymethyl acrylamide, N-hexyloxy (meth) acrylamide, N-heptyloxymethyl (meth) acrylamide, N-octyloxymethyl (meth) acrylamide, N-2-ethyl-hex Amide vinyl monomers such as siloxymethyl (meth) acrylamide and diacetone (meth) acrylamide;

(Meth) acrylic acid-tert-butylaminoethyl, (meth) acrylic acid-tert-butylaminoethyl, (meth) acrylic acid-tert-butylaminoethyl such as dimethylaminoethyl (meth) acrylate, diethylaminoethyl (meth) acrylate; Propyl, aziridinylethyl (meth) acrylate, pyrrolidinylethyl (meth) acrylate, piperidinylethyl (meth) acrylate, (meth) acryloylmorpholine, N-vinyl-2-pyrrolidone, N-vinyl Nitrogen-containing vinyl monomers such as caprolactam, N-vinyloxazoline, (meth) acrylonitrile; vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl caproate, vinyl caprylate, vinyl caprate, vinyl laurate, Branch having 9 to 11 carbon atoms Aliphatic carboxylic acid vinyl, aliphatic carboxylic acid vinyl esters of vinyl stearate and the like;

Vinyl esters of carboxylic acids having a cyclic structure such as vinyl cyclohexanecarboxylate, vinyl methylcyclohexanecarboxylate, vinyl benzoate, vinyl p-tert-butylbenzoate; ethyl vinyl ether, hydroxyethyl vinyl ether, hydroxy n-butyl vinyl ether, hydroxyisobutyl Examples thereof include alkyl vinyl ethers such as vinyl ether, cyclohexyl vinyl ether, and lauryl vinyl ether.

  When producing the epoxy group-containing vinyl resins (A) and (B), various known and commonly used radical polymerization initiators can be used.

  Examples of such radical polymerization initiators include 2,2′-azobisisobutyronitrile, 2,2′-azobis-methylbutyronitrile, 2,2′-azobis-2,4-dimethylvaleronitrile, , 1'-azobis-cyclohexanecarbonitrile, dimethyl-2,2'-azobisisobutyrate, 4,4'-azobis-4-cyanovaleric acid, 2,2'-azobis- (2-amidinopropene) 2 Hydrochloride, 2-tert-butylazo-2-cyanopropane, 2,2′-azobis (2-methyl-propionamide) dihydrate, 2,2′-azobis [2- (2-imidazolin-2-yl ) Propene], azo compounds such as 2,2′-azobis (2,2,4-trimethylpentane);

Benzoyl peroxide, methyl ethyl ketone peroxide, cumene hydroperoxide, potassium persulfate, tert-butyl peroxyneodecanoate, tert-butyl peroxypivalate, tert-butyl peroxy-2-ethylhexanoate, tert- Butyl peroxyisobutyrate, 1,1-bis-tert-butylperoxy-3,3,5-trimethylcyclohexane, tert-butyl peroxylaurate, tert-butyl peroxyisophthalate, tert-butyl peroxyacetate , Tert-butylperoxybenzoate, dicumyl peroxide, di-tert-butyl peroxide, and other ketone peroxides; peroxyketals; hydroperoxides; Oxides; diacyl peroxides like; peroxy esters; peroxydicarbonates like; hydrogen peroxide and the like.

  When the above-mentioned various vinyl monomers are copolymerized in an organic solvent to produce the epoxy group-containing vinyl resins (A) and (B), various organic solvents can be used.

  Examples of the organic solvent include alkyl alcohols such as methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, sec-butanol, tert-butanol, n-pentanol, and isopentanol;

Glycol ethers such as methyl cellosolve, ethyl cellosolve, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol dimethyl ether, propylene glycol diethyl ether;

Aromatic hydrocarbons such as benzene, toluene, xylene and ethylbenzene; Exon Aromatic Naphtha No. Mixed hydrocarbons containing aromatic hydrocarbons such as 2 (made by Exxon USA); aliphatic hydrocarbons such as n-pentane, n-hexane and n-octane; Isopar C, Isopar E, Exol DSP 100/140 , Exol D30 (all manufactured by Exxon, USA), IP hydrocarbon 1016 (produced by Idemitsu Petrochemical Co., Ltd.) and other mixed hydrocarbons containing aliphatic hydrocarbons; cyclopentane, cyclohexane, methylcyclohexane, ethylcyclohexane Group hydrocarbons;

Ethers such as tetrahydrofuran, dioxane, diisopropyl ether, di-n-butyl ether; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone; methyl acetate, ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate And esters such as n-amyl acetate, isoamyl acetate, hexyl acetate, ethyl propionate and butyl propionate.

  Moreover, when manufacturing the said epoxy-group containing vinyl-type resin (A) and (B), a chain transfer agent can also be used as needed, for example, a dodecyl mercaptan, a lauryl mercaptan, thioglycolic acid ester, Examples include mercaptoethanol and α-methylstyrene dimer.

  The epoxy group-containing vinyl resins (A) and (B) are produced by, for example, solidifying the resin solution obtained by polymerization by a method such as removing the solvent under reduced pressure or volatilizing the solvent by spray drying. However, the method for distilling off the solvent is not limited at all. In addition, each may be solidified individually, and each obtained resin solution is uniform in advance in the mixing ratio of the epoxy group-containing vinyl resins (A) and (B) when producing the powder coating material. You may solidify after mixing.

  Here, since the excellent corrosion resistance and water resistance of the coating film are further improved while maintaining the high storage stability of the thermosetting powder resin composition of the present invention, the epoxy group-containing vinyl It is desirable that the resin (B) is a vinyl resin (B1) containing a regular phosphoric acid triester group and / or a phosphite triester group and an epoxy group.

  The vinyl resin (B1) containing an orthophosphoric triester group and / or a phosphite triester group and an epoxy group has at least one, preferably two or more epoxy groups in one molecule. This refers to a vinyl-based resin in which an orthophosphoric acid triester and / or a phosphorous acid triester group is bonded to the chain.

  The production method of the vinyl resin (B1) containing the normal phosphoric acid triester group and / or phosphite triester group and the epoxy group is not limited at all. A method of copolymerization using an orthophosphoric acid triester and / or phosphite triester having one radical polymerizable group in one molecule and other vinyl monomers, 2) epoxy It can be produced by a method of adding a normal phosphoric acid diester and / or a phosphorous acid diester to a group-containing vinyl resin.

  As the orthophosphoric acid triester and / or phosphite triester having one radical polymerizable group in one molecule used in the method for producing the vinyl resin (B1) of 1), for example, in one molecule Trialkyl ester, trialkenyl ester or triaryl ester of orthophosphoric acid and / or phosphorous acid having one radical polymerizable group is exemplified, and specific examples thereof are dialkyl-2- (meth) acryloyl. Examples thereof include oxyethyl phosphate, diphenyl-2- (meth) acryloyloxyethyl phosphate, and compounds obtained by adding a normal phosphoric acid diester and / or phosphorous acid diesel to the above-described epoxy group-containing vinyl monomer. As a method of adding the orthophosphoric diester and / or the phosphite diester compound to the epoxy group-containing vinyl monomer, for example, heating to 80 to 180 ° C., the epoxy group in the epoxy group-containing vinyl monomer and The method of making it react is mentioned.

  Examples of the orthophosphoric diester and / or phosphite diester compound include dimethyl phosphate, dibutyl phosphate, dioctyl phosphate, di-2-ethylhexyl phosphate, dilauryl phosphate, diphenyl phosphate, dinaphthyl phosphate. , Diphosphoryl phosphate, di (nonylphenyl) phosphate, methyl octyl phosphate, cetyl phenyl phosphate, diisodecyl phosphate and other phosphoric acid diester compounds, dimethyl phosphite, dibutyl phosphite, dioctyl phosphite, di-2 -Phosphorous acid diester compounds such as ethylhexyl phosphite, dilauryl phosphite and diphenyl phosphite.

  In order to produce the vinyl resin (B1) by the production method of 2), for example, an orthophosphoric diester and / or phosphorous acid is added to a resin solution of an epoxy group-containing vinyl resin or a melt after removal of the solvent. An acid diester compound may be added, uniformly dispersed, heated to 80 to 180 ° C., and reacted with an epoxy group in the epoxy group-containing vinyl resin.

  In this case, as the normal phosphoric acid diester and / or phosphite diesel compound used, it is used for the production of a compound obtained by adding a normal phosphoric acid diester and / or phosphorous acid diesel to the above-mentioned epoxy group-containing vinyl monomer. Any of the orthophosphoric acid diesters and / or phosphite diester compounds exemplified as those to be used can be used.

  Since the vinyl resin (B1) can maintain the storage stability (solid phase resistance) of the resin composition for thermosetting powder coatings of the present invention, it is a normal phosphoric acid having 4 or more carbon atoms. It is preferably a dialkyl ester compound modified with dibutyl phosphate, di-2-ethylhexyl phosphate or the like.

  As the amount of modified orthophosphoric acid triester and / or phosphite diester of the vinyl resin (B1), the corrosion resistance and water resistance are improved while effectively suppressing the decrease in storage stability (solid phase resistance). Therefore, the range in which the content ratio of components derived from orthophosphoric acid triester and / or phosphite diester is 0.1 to 5% by weight is preferable, and more preferably 0.5 to 2% by weight. .

  At that time, the epoxy equivalent of the vinyl resin (B1) is preferably 600 to 14,000 g / equivalent, and more preferably 1,000 to 14,000 g / equivalent.

Next, the polyvalent carboxylic acid and / or anhydride (C) used in the present invention will be described.
As the polyvalent carboxylic acid and / or its anhydride (C), aliphatic (including cycloaliphatic) or aromatic polyvalent carboxylic acids and / or their anhydrides can be mainly used. For example, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, brassic acid, dodecanedioic acid, tetradecanoic acid, octadecanoic acid, hexadecanoic acid, eicosane diacid Tetraeicosane diacid, maleic acid, citraconic acid, itaconic acid or glutaconic acid;

Examples thereof include phthalic acid, isophthalic acid, trimellitic acid, pyromellitic acid, tetrahydrophthalic acid, hexahydrophthalic acid, cyclohexene-1,2-dicarboxylic acid, and acid anhydrides thereof. These polyvalent carboxylic acids and / or anhydrides (C) thereof may be used alone or in combination of two or more.

  Among them, aliphatic dibasic acids are preferable because of excellent coating film properties and storage stability, and dodecanedioic acid is particularly preferable because of excellent coating film properties.

  As a compounding ratio of the epoxy group-containing vinyl resin (A), the epoxy group-containing vinyl resin (B), and the polyvalent carboxylic acid and / or its anhydride (C) used in the present invention, an epoxy group-containing vinyl is used. Equivalent ratio [epoxy group / carboxyl] of epoxy group in resin (A) and (B) and carboxyl group (including carboxylic anhydride group) in polyvalent carboxylic acid and / or its anhydride (C) Group] is preferably in the range of 0.5 to 1.5, more preferably in the range of 0.6 to 1.0.

  The powder coating material comprising the resin composition for thermosetting powder coating material of the present invention and the powder coating material for aluminum wheel comprising the resin composition for powder coating material for aluminum wheel are within a range not departing from the object of the present invention. Within the range that does not impair the effects of the present invention, and further, various synthetic resins such as epoxy resin, polyester resin, urethane resin, polyamide resin, etc., curing catalyst, flow regulator, blocking Various additives for paints or pigments such as an inhibitor, an ultraviolet absorber, a light stabilizer, benzoin, an antistatic agent, and an antioxidant can be added and used as necessary.

  Among these additives, examples of the UV absorber include UV absorbers such as benzophenone, benzotriazole, salicylate, and nickel complexes, and examples of the light stabilizer include light such as various hindered amines. As stabilizers and antioxidants, for example, antioxidants such as phenols, phosphites and thioethers can be used.

  As the curing catalyst, for example, phosphine such as triphenylphosphine, imidazole such as 2-methylimidazole, ammonium salt such as tetrabutylammonium chloride, and the like can be used.

  Examples of the pigment include inorganic pigments such as titanium oxide, dial, chrome titanium yellow, yellow iron oxide, and carbon black; phthalocyanines such as phthalocyanine blue and phthalocyanine green; anthraquinones such as indanthrene blue and dianthraquinonyl red; Organic pigments such as quinacridone, lake red, first yellow, disazo yellow, permanent red, etc. azo, naphthol yellow, etc., nitroso, pigment green B, naphthol green etc., various body pigments; aluminum flakes Further, brilliant (metallic tone) pigments such as mica flakes can be used.

  As a manufacturing method of the resin composition for thermosetting powder coatings of this invention, epoxy group containing vinyl resin (A), epoxy group containing vinyl resin (B), polyhydric carboxylic acid, and / or its anhydride ( C) may be mixed, and the mixing method is not limited, but from the viewpoint of quality stability and stable mass productivity, the so-called melt-kneading method is optimal. That is, the above-mentioned various raw materials are mixed, melted and mixed sufficiently at 50 to 130 ° C. using a melt kneader such as a heating roll or an extruder, then cooled, pulverized and classified to obtain the desired powder. The method of obtaining the resin composition for body paints is mentioned.

  Moreover, the resin composition for powder coatings for aluminum wheels of the present invention is obtained using the above-described resin composition for thermosetting powder coatings of the present invention. Specifically, the resin composition for thermosetting powder coatings of the present invention can be used as it is as a resin composition for powder coatings for aluminum wheels, and the resin composition for thermosetting powder coatings of the present invention. Furthermore, various additives etc. can be mixed and used as a resin composition for powder coatings for aluminum wheels.

  The baking temperature and time of the substrate to be coated can be appropriately selected according to the type and purpose of the substrate to be coated, and are, for example, in the range of 5 to 50 minutes at 120 to 250 ° C.

  As described above, the thermosetting powder coating resin composition and the aluminum wheel powder coating resin composition of the present invention have high storage stability and are excellent in coating film appearance, corrosion resistance, water resistance, and the like. Forms an excellent coating film, and even when coated as a single layer or primer on an automotive aluminum wheel, forms a coating film with excellent corrosion resistance and water resistance without being affected by the pretreatment of the base material. Is.

  Next, the present invention will be described more specifically with reference examples, examples and comparative examples. In the following, “parts” means “parts by weight” unless otherwise specified.

Reference Example 1 [Preparation of Epoxy Group-Containing Vinyl Resin (A-1)]
In a reaction vessel equipped with a thermometer, a stirrer, a reflux condenser and a nitrogen inlet, 60 parts of xylene was placed and heated to 130 ° C. To this, 55 parts of glycidyl methacrylate, 10 parts of i-butyl methacrylate, 13 parts of methyl methacrylate and 22 parts of styrene as monomers, and tert-butyl peroxy 2-ethylhexanoate 4.0 as a polymerization initiator The mixture consisting of parts was added dropwise over 6 hours. After completion of the dropping, the polymerization reaction was continued for 10 hours at the same temperature to obtain a solution (A′-1) of the epoxy group-containing vinyl resin (A-1). Furthermore, 30 parts of the obtained resin solution (A′-1) was maintained at 170 ° C. under a reduced pressure of 20 Torr, and xylene was removed to obtain an epoxy group-containing vinyl resin (A-1). Table 1 shows the property values of the epoxy group-containing vinyl resin (A-1) and its solution (A′-1).

Reference Example 2 [Preparation of epoxy group-containing vinyl resin (A-2)]
The target epoxy group-containing vinyl resin (A-2) and its solution (A ′) were the same as in Reference Example 1 except that a mixture comprising the monomer and polymerization initiator shown in Table 1 below was used. -2) was obtained. Table 1 shows the property values of the epoxy group-containing vinyl resin (A-2) and its solution (A′-2).

Reference Example 3 [Preparation of Comparative Epoxy Group-Containing Vinyl Resin (A-3)]
The target epoxy group-containing vinyl resin (A-3) and its solution (A ′) were the same as in Reference Example 1 except that a mixture of the monomer and polymerization initiator shown in Table 1 below was used. -3) was obtained. Table 1 shows the property values of the epoxy group-containing vinyl resin (A-3) and its solution (A′-3).

  The glass transition temperature (° C.), weight average molecular weight, epoxy equivalent, and solubility parameter (Sp) in the table are values determined by the method described in detail in this specification.

Reference Example 4 [Preparation of epoxy group-containing vinyl resin (B-1)]
In a reaction vessel equipped with a thermometer, a stirrer, a reflux condenser and a nitrogen inlet, 60 parts of xylene was placed and heated to 100 ° C. To this, a mixture composed of the monomer and polymerization initiator shown in Table 2 (1) below was added dropwise over 6 hours. After completion of the dropping, the polymerization reaction was continued for 10 hours at the same temperature to obtain a solution (B′-1) of the epoxy group-containing vinyl resin (B-1). Furthermore, 30 parts of the obtained resin solution (B′-1) was maintained at 170 ° C. under a reduced pressure of 20 Torr, and xylene was removed to obtain an epoxy group-containing vinyl resin (B-1). The property values of the epoxy group-containing vinyl resin (B-1) and its solution (B′-1) are shown in Table 2 (1).

Reference Example 5 [Preparation of epoxy group-containing vinyl resin (B-2)]
The target epoxy group-containing vinyl resin (B-2) and its solution in the same manner as in Reference Example 4 except that a mixture consisting of a monomer and a polymerization initiator shown in Table 2 (1) below was used. (B′-2) was obtained. The property values of the epoxy group-containing vinyl resin (B-2) and its solution (B′-2) are shown in Table 2 (1).

Reference Example 6 [Preparation of epoxy group-containing vinyl resin (B-3)]
In a reaction vessel equipped with a thermometer, a stirrer, a reflux condenser and a nitrogen inlet, 60 parts of xylene was placed and heated to 100 ° C. To this, a mixture comprising the monomer and the polymerization initiator shown in Table 2 (1) was added dropwise over 6 hours. After completion of the dropwise addition, the polymerization reaction was continued for 10 hours at the same temperature to complete the polymerization reaction. Thereafter, 1 part of DBP (manufactured by Johoku Chemical Industry Co., Ltd .; dibutyl phosphate) was added at the same temperature, and the mixture was further reacted by heating for 2 hours to obtain a solution (B′-3) of an epoxy group-containing vinyl resin (B-3). Got. Further, 30 parts of the obtained resin solution (B′-3) was maintained at 170 ° C. under a reduced pressure of 20 Torr, and xylene was removed to obtain an epoxy group-containing vinyl resin (B-3). Table 2 (1) shows the property values of the epoxy group-containing vinyl resin (B-3) and the solution (B′-3) thereof.

Reference Examples 7 to 8 [Preparation of epoxy group-containing vinyl resins (B-4) to (B-5) for comparison]
The target epoxy group-containing vinyl-based resin (B-4) to (B) is used in the same manner as in Reference Example 4 except that a mixture of a monomer and a polymerization initiator shown in Table 2 (2) below is used. B-5) and its solutions (B′-4) to (B′-5) were obtained. Table 2 (2) shows the property values of the epoxy group-containing vinyl resins (B-4) to (B-5) and the solutions (B′-4) to (B′-5) thereof.

Reference Example 9 [Preparation of acidic phosphate group-containing acrylic copolymer (E-1) for comparison]
In a reaction vessel equipped with a thermometer, a stirrer, a reflux condenser and a nitrogen inlet, 60 parts of propylene glycol monomethyl ether was added and the temperature was raised to 100 ° C. To this, a mixture comprising the monomer and the polymerization initiator shown in Table 2 (2) was added dropwise over 6 hours. After completion of the dropwise addition, the polymerization reaction was continued for 10 hours at the same temperature to obtain a solution (E′-1) of an acidic phosphate group-containing acrylic copolymer (E-1). Further, the obtained copolymer solution (E′-1) was maintained at 170 ° C. under a reduced pressure of 20 Torr, and the propylene glycol monomethyl ether was removed to remove the acidic phosphate group-containing acrylic copolymer (E-1). ) The property values of the acidic phosphoric acid group-containing acrylic copolymer (E-1) and of the solution (E′-1) are shown in Table 2 (2).

Reference Examples 10 to 13 [Preparation of Mixture (S) of Epoxy Group-Containing Vinyl Resin (A) and (B)]
With the formulation shown in Table 3 (1) below, any one of the solutions (A′-1) to (A′-2) of the epoxy-containing vinyl resin (A) obtained in Reference Examples 1 and 2, and Any one of the solutions (B′-1) to (B′-3) of the epoxy-containing vinyl resin (B) obtained in Examples 4 to 6 was combined, charged into a container, and stirred and mixed. The mixture (S-1) to (S-4) having a non-volatile content of 99.7% by weight or more was obtained by removing xylene while maintaining a reduced pressure of 20 Torr.

Reference Examples 14 to 16 [Preparation of mixtures (S-5) to (S-7) of epoxy group-containing vinyl resins (A) and (B) for comparison]
With the compounding composition as shown in Table 3 (2) below, the epoxy-containing vinyl resin solutions (A′-2) to (A′-3) obtained in Reference Examples 2 to 3, Reference Example 5, and Using the epoxy group-containing vinyl copolymer solution (B′-2) and (B′-4) to (B′-5) obtained in 7 to 8 in the same manner as in Reference Example 10, Mixtures (S-5) to (S-7) of 99.7% by mass or more were obtained.

Examples 1-4 and Comparative Examples 1-5
The components shown in Table 4 (1) and (2) below are mixed with a “Henschel mixer” (mixer manufactured by Mitsui Miike Processing Co., Ltd.), and the mixture is mixed with ZSK-25WLE ”( Using a biaxial kneader manufactured by Werner & Frederer), each was melt-kneaded at a barrel temperature of 80 to 120 ° C. Subsequently, each kneaded product obtained was cooled, pulverized, and further classified to obtain a desired resin composition for powder coating (X-) having an average particle size of 15 to 35 micrometer (μm). 1) to (X-4) and comparative resin compositions for powder coatings (x-1) to (x-5) were prepared.

<< 註 in Table 4 (1), (2) >>
Epicron 3050: Epoxy resin manufactured by Dainippon Ink & Chemicals, Inc.
Benzoin: Reagent manufactured by Tokyo Chemical Industry Co., Ltd.
Troy 570FL …… Leveling agent made by Troy Chemical.

  Subsequently, the storage stability of the obtained powder coating resin compositions (X-1) to (X-4) and the comparative control powder coating resin compositions (x-1) to (x-5) These were used to prepare various coating films according to the following coating film forming method, and then a coating film performance test was performed on each coating film.

  Powder coating resin compositions (X-1) to (X-4) and comparative control powder coating resin compositions (x-1) to (x-5) were electrostatic sprayed for powder coating. 0.8 mm (thickness) x 70 mm x 150 mm aluminum untreated plate "A-1050P" (manufactured by Nippon Test Panel Co., Ltd.) so that the film thickness after baking on the substrate with a coating machine is 90 μm Various test plates on which a cured coating film was formed were obtained by painting on and then baking at 160 ° C. for 20 minutes. The evaluation judgment results of these coating films are summarized and shown in Tables 5 (1) and (2).

[Methods for evaluating physical properties of coating films]
[1] Appearance of coating film [1] -1 Smoothness: PCI [(powder coating institute), the spread of powder coatings representing the North American powder coating industry established in 1981, the powder coating industry A value determined using a standard plate for visual judgment of the smoothness of powder coating film by a non-profit organization (http://www.powdercoating.org/home.htm)] for the purpose of exchange. The standard plate is No. 1-No. There are 10 sheets up to 10. 1-No. The smoothness becomes good step by step. It was visually judged which standard plate the smoothness hits.
No. 1: poor smoothness 10: Good smoothness

[1] -2 Transparency: The finished appearance of the coating film was visually evaluated according to the following criteria from the gloss and transparency.
Evaluation “○” …… Good Evaluation “△” …… Slightly bad Evaluation “×” …… Bad

[2] Solvent resistance: The coating film was rubbed 30 times with absorbent cotton containing xylene and then visually judged according to the following criteria.
Evaluation “◯”: The coating film has a glossy appearance and there is no noticeable damage to the coating film.
Evaluation “Δ”: The coating film has gloss, but is etched with a solvent.
Evaluation “×”: The coating film was dissolved by the solvent and there was no gloss.

[3] Corrosion resistance: A test plate in which a cross-cut was made to reach the substrate base with a cutter knife on the coating film was sprayed for 240 hours with a cast tester under the condition of a temperature of 50 ± 2 ° C. Thereafter, it was washed with water, and the number of blisters and the maximum length (mm) of the one-side blister width of the crosscut were measured.
<Test solution>
After dissolving 0.26 g of copper (II) chloride dihydrate per 1 l of saline in 5 wt% saline, 1 ml of acetic acid was added per 1 l of saline and mixed well, and pH = 3 ± 0. 2 test solutions.

[4] Water resistance: After immersing the test plate in warm water at 40 ° C. for 5 days and pulling it up 1 hour later, a 25 mm cross-cut was made by putting a 2 mm wide crosscut into the coating film with a cutter. Then, a peel test using an adhesive tape was performed. The criterion for evaluation judgment was displayed by the remaining number in the 25 grids. The higher this value, the better the adhesion. Moreover, the presence or absence of the occurrence of swelling of the coating film was visually evaluated.
Evaluation “○” …… No bulge Evaluation “△” …… There is a little bulge Evaluation “×” …… There are many bulges

[5] Storage stability: Each resin composition for powder coatings was placed in a 50 CC sample bottle, left at 30 ° C. for 2 weeks, taken out, and evaluated for the presence or absence of solidification of each coating based on the following criteria.
Evaluation “◯”: Not blocked or solidified.
Evaluation “Δ”: Slightly blocking, but easily pulverized.
Evaluation “×”: Blocking and solidifying.

Claims (8)

  Epoxy equivalent (EEW) 180-560 g / equivalent, weight average molecular weight 4,000-15,000 epoxy group-containing vinyl resin (A), epoxy equivalent (EEW) 720-14,000 g / equivalent, weight average molecular weight 25 1 to 120,000 epoxy group-containing vinyl resin (B) and polyvalent carboxylic acid and / or anhydride (C) thereof, and dissolution of epoxy group-containing vinyl resin (A) Difference (SpA-SpB) between the solubility parameter (SpB) of the solubility parameter (SpA) and the epoxy group-containing vinyl resin (B) is 0 to 0.8, the epoxy group-containing vinyl resin (A) and the epoxy group-containing vinyl A resin composition for thermosetting powder coating material, wherein the weight ratio (A / B) of the resin based resin (B) is 98/2 to 80/20.   The thermosetting powder according to claim 1, wherein an epoxy equivalent ratio [EEW (B) / EEW (A)] of the epoxy group-containing vinyl resin (B) and the epoxy group-containing vinyl resin (A) is 2 or more. Resin composition for paint.   The thermosetting powder according to claim 1, wherein an epoxy equivalent ratio [EEW (B) / EEW (A)] of the epoxy group-containing vinyl resin (B) and the epoxy group-containing vinyl resin (A) is 3 or more. Resin composition for paint.   The epoxy group-containing vinyl resin (A) is an epoxy group-containing vinyl resin having an epoxy equivalent (EEW) of 300 to 560 g / equivalent and a weight average molecular weight of 5,000 to 10,000, and an epoxy group-containing vinyl resin ( The thermosetting type according to claim 1, 2 or 3, wherein B) is an epoxy group-containing vinyl resin having an epoxy equivalent (EEW) of 1,000 to 7,000 g / equivalent and a weight average molecular weight of 30,000 to 100,000. Resin composition for powder coatings.   The difference (SpA-SpB) between the solubility parameter (SpA) of the epoxy group-containing vinyl resin (A) and the solubility parameter (SpB) of the epoxy group-containing vinyl resin (B) is 0 to 0.5, and the epoxy group contains The resin composition for thermosetting powder coating materials according to claim 4, wherein the weight ratio (A / B) of the vinyl resin (A) and the epoxy group-containing vinyl resin (B) is 96/4 to 85/15. .   The epoxy group-containing vinyl resin (B) is a vinyl resin (B1) containing an orthophosphoric acid triester group and / or a phosphite triester group and an epoxy group. The resin composition for a thermosetting powder coating as described. A resin composition for powder coatings for aluminum wheels, wherein the resin composition for thermosetting powder coatings according to any one of claims 1 to 6 is used. The resin composition for powder coatings for aluminum wheels according to claim 7 , which is a primer for coating aluminum wheels.