JP6869753B2 - High solid content paint composition - Google Patents

Description

The present invention relates to a high solid content coating composition and a method for forming a multi-layer coating film using the coating composition.

In recent years, from the viewpoint of protecting the global environment, it has been required to reduce volatile organic compounds (VOCs) released from paints, and the replacement of solvent-based paints with water-based paints is rapidly progressing in each field.

In the past, a large amount of solvent-based paints were used in the painting of automobiles, and there was an urgent need to reduce the VOC emitted from those paints, but various paints used in the undercoating, intermediate coating and topcoating processes of automobiles. With regard to, the replacement of organic solvent-based paints with water-based paints has been promoted, and at present, painting with water-based paints is the mainstream.

However, the topcoat clear paint is particularly required to have a high level of coating film performance (scratch resistance, acid resistance, finished appearance, etc.) and finished appearance, and coating workability such as armpit resistance and sagging resistance. Due to the insufficient level of paint, solvent-based clear paints are still mainly applied.

As one of the VOC reduction methods that does not rely on making the clear paint water-based, high solid differentiation (increasing the solid content concentration) of the paint can be mentioned.

For example, Patent Document 1 describes a high solid content coating composition in which a polyisocyanate compound and a melamine resin are used in combination with a reaction product of a specific carboxyl group-containing compound and an epoxy group-containing compound, and further contains a specific hydroxyl group-containing resin. The thing is disclosed.

However, since this coating composition contains a reaction product of a carboxyl group-containing compound and an epoxy group-containing compound, which has a low molecular weight and a high hydroxyl group concentration, the pot life of the coating material becomes insufficient, or 2 coats 1 In the bake metallic coating specifications, low molecular weight components may erode the underlying metallic layer, resulting in a poor metallic appearance finish (so-called epoxide phenomenon).

Further, Patent Document 2 describes a topcoat coating composition containing a vinyl copolymer containing a side chain having a specific group (lactone-modified hydroxyl group), an alkoxymonomeric melamine, a blocked isocyanate, and a rheology control agent as essential components. Is disclosed.

However, in this topcoat coating composition, since the vinyl-based copolymer has a structure derived from a specific group (lactone-modified hydroxyl group), the scratch resistance is improved, but the acid resistance is insufficient. was there. Furthermore, since the specific group (lactone-modified hydroxyl group) of the vinyl-based copolymer is highly polar, the modli phenomenon is likely to occur as in the coating composition of Patent Document 1, and the metallic in the 2-coat 1-bake metallic coating specification. In some cases, the appearance was poor.

Further, Patent Document 3 discloses a clear coating material comprising a specific acrylic resin, a specific polyester resin, a specific melamine resin, a specific acid catalyst, and a blocked isocyanate.

However, this clear paint has a problem that high solid differentiation is difficult and that the acid resistance of the coating film is insufficient because the amount of melamine resin is relatively large.

JP-A-2002-201430 Japanese Unexamined Patent Publication No. 2002-02682 Japanese Unexamined Patent Publication No. 4-130168

An object of the present invention is a high solid content coating composition capable of obtaining a coating film having excellent pot life, scratch resistance, acid resistance, and a finished appearance, and a multi-layer coating using the coating composition. It is to provide a film forming method.

As a result of diligent studies to achieve the above object, the present inventors have found that (A) a secondary hydroxyl group-containing acrylic resin having a specific molecular weight range, (B) an aliphatic polyisocyanate compound and / or a derivative thereof, and ( C) The present invention has been found that the above object can be achieved by a coating composition containing an alkyl etherified melamine resin in a specific molecular weight range and the amount of the component (C) with respect to the component (B) within the specific range. It came to be completed.

That is, the present invention includes the following aspects.

Item 1, (A) Secondary hydroxyl group-containing acrylic resin having a weight average molecular weight of 3000 to 7000,
(B) Aliphatic polyisocyanate compound and / or its derivative,
A coating composition containing (C) an alkyl etherified melamine resin having a weight average molecular weight of 1000 or less, and (D) a sulfonic acid compound and / or a phosphoric acid compound.
A high solid content coating composition, wherein the amount of the component (C) is in the range of 1.5 to 20% by mass with respect to the total amount of the component (B).

Item 2. The high amount according to Item 1, wherein the secondary hydroxyl group-containing polymerizable unsaturated monomer (a) is 50 to 100% by mass in the total amount of the hydroxyl group-containing polymerizable unsaturated monomer which is a constituent component of the acrylic resin (A). Solid content coating composition.

Item 3. The high solid content coating composition according to Item 1 or 2, wherein the alkyl etherified melamine resin (C) has substantially no imino group.

Item 4. The high solid content coating composition according to any one of Items 1 to 3, further comprising an acylated hindered amine and / or an amino ether-based hindered amine.

An article having a coating film of the coating composition according to any one of Items 5 and 1 to 4.

Item 6, a method of forming a multi-layer coating film by sequentially coating at least one layer of a colored base coat paint and at least one layer of a clear coat paint on an object to be coated, and as the top layer clear coat paint, item 1. A method for forming a multi-layer coating film, which comprises coating the coating composition according to any one of No. 4 to 4.

The coating composition of the present invention contains a secondary hydroxyl group-containing acrylic resin in a specific weight average molecular weight range as a base resin, and an aliphatic polyisocyanate compound and / or a derivative thereof as a cross-linking agent in an alkyl etherified melamine resin in a specific weight average molecular weight range. The alkyl etherified melamine resin is contained in a specific amount range with respect to the total amount of the aliphatic polyisocyanate compound and / or its derivative, and further contains a sulfonic acid compound and / or a phosphoric acid compound. It is characterized by doing.

Since an aliphatic polyisocyanate compound and / or a derivative thereof is used as the main component of the cross-linking agent and an alkyl etherified melamine resin having a specific low molecular weight range is used as an auxiliary component, the coating film has excellent acid resistance and scratch resistance. Can be obtained.

In addition, since the acrylic resin, which is the substrate resin, contains a secondary hydroxyl group that has a milder reactivity than the primary hydroxyl group in the specific low molecular weight range, a coating film having excellent pot life and an excellent finished appearance can be obtained. Obtainable.

As described above, according to the coating composition of the present invention, due to these synergistic effects, it is possible to form a coating film having excellent scratch resistance, acid resistance, and finished appearance, and it has an excellent pot life. The effect that a solid content coating composition can be obtained can be obtained.

Hereinafter, the coating composition of the present invention (sometimes referred to as “the present coating material” in the present specification) and the coating film forming method will be described in more detail.

The coating composition of the present invention (hereinafter, may be abbreviated as "the present coating material") is
(A) Acrylic resin containing a secondary hydroxyl group having a weight average molecular weight of 3000 to 7000,
(B) Aliphatic polyisocyanate compound and / or its derivative,
A coating composition containing (C) an alkyl etherified melamine resin having a weight average molecular weight of 1000 or less, and (D) a sulfonic acid compound and / or a phosphoric acid compound.
A high solid content coating composition, wherein the amount of the component (C) is in the range of 1.5 to 20% by mass with respect to the total amount of the component (B).

<Secondary hydroxyl group-containing acrylic resin (A)>
The secondary hydroxyl group-containing acrylic resin (A) (may be referred to as “component (A)” in the present specification) is a secondary hydroxyl group-containing acrylic resin, and specifically, for example, (a). It can be synthesized by copolymerizing a monomer component composed of a secondary hydroxyl group-containing polymerizable unsaturated monomer and (b) another polymerizable unsaturated monomer by a conventional method.

The secondary hydroxyl group-containing polymerizable unsaturated monomer (a) is a compound having one secondary hydroxyl group and one polymerizable unsaturated bond in one molecule. The polymerizable unsaturated bond means an unsaturated bond capable of radical polymerization. Examples of such polymerizable unsaturated bonds include (meth) acryloyl group, acrylamide group, vinyl group, allyl group, (meth) acryloyloxy group, vinyl ether group and the like.

Examples of the secondary hydroxyl group-containing polymerizable unsaturated monomer (a) include 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, and 3-hydroxybutyl (meth) from the viewpoint of the finished appearance of the coating film. ) A polymerizable unsaturated monomer having a secondary hydroxyl group having 2 to 8 carbon atoms, particularly 3 to 6 carbon atoms, and particularly 3 or 4 alkyl groups in the ester portion of an ester such as acrylate; (meth) acrylic acid and an epoxy group-containing compound ( For example, an additive with Carjura E10 (trade name), manufactured by Hexion Specialty Chemical Co., Ltd., neodecanoic acid glycidyl ester) and the like can be mentioned. Of these, 2-hydroxypropyl (meth) acrylate is particularly preferable. The above-mentioned monomer (a) can be used alone or in combination of two or more.

As used herein, "(meth) acrylate" means "acrylate or methacrylate". "(Meta) acrylic acid" means "acrylic acid or methacrylic acid". In addition, "(meth) acryloyl" means "acryloyl or methacryloyl". "(Meta) acryloyl" means "acryloyl or methacryloyl".

The other polymerizable unsaturated monomer (b) is a monomer other than the above-mentioned secondary hydroxyl group-containing polymerizable unsaturated monomer (a), and specifically, has one polymerizable unsaturated bond in one molecule. Compounds can be mentioned. Specific examples of the unsaturated monomer (b) are listed in (1) to (8) below.

(1) Acid group-containing polymerizable unsaturated monomer The acid group-containing polymerizable unsaturated monomer is a compound having one acid group and one polymerizable unsaturated bond in one molecule. Examples of the monomer include carboxyl group-containing monomers such as (meth) acrylic acid, crotonic acid, itaconic acid, maleic acid and maleic anhydride; and sulfonic acid group-containing monomers such as vinyl sulfonic acid and sulfoethyl (meth) acrylate. Can be mentioned. These can be used alone or in combination of two or more. When an acid group-containing polymerizable unsaturated monomer is used, the acid value of the acrylic resin (A) is 1.0 to 15.0 mgKOH / g, particularly 3. The amount is preferably 0 to 8.0 mgKOH / g.

(2) Hydroxylable unsaturated monomer containing a hydroxyl group (excluding a secondary hydroxyl group) A compound having one hydroxyl group (excluding a secondary hydroxyl group) and one polymerizable unsaturated bond in one molecule. The hydroxyl group excluding the secondary hydroxyl group is a primary hydroxyl group or a tertiary hydroxyl group. Examples of the monomer include (meth) acrylic acid such as 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, and 4-hydroxybutyl (meth) acrylate, and a dihydric alcohol having 2 to 10 carbon atoms. (Excluding those having a secondary hydroxyl group); Hydroxyl-containing monomers modified by subjecting ε-caprolactone to a ring-open polymerization reaction (excluding those having a secondary hydroxyl group) and the like.

As the hydroxyl group-containing monomer modified by ring-opening polymerization reaction of ε-caprolactone, a commercially available product can be used, and examples of the commercially available product include "Plaxel FA-1", "Plaxel FA-2", and "Placel FA-2". Praxel FA-3 "," Praxel FA-4 "," Praxel FA-5 "," Praxel FM-1 "," Praxel FM-2 "," Praxel FM-3 "," Praxel FM-4 "," Praxel FM-5 ”(all of which are manufactured by Daicel Chemical Co., Ltd., trade names) and the like can be mentioned.

(3) Esteride of acrylic acid or methacrylic acid and a monovalent alcohol having 1 to 20 carbon atoms Specifically, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth). ) Acrylate, iso-butyl (meth) acrylate, tert-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, isomyristyl (meth) acrylate, stearyl (meth) acrylate, isostearyl acrylate ( Osaka Organic Chemical Industry Co., Ltd., trade name), lauryl (meth) acrylate, tridecyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, cyclohexyl (meth) acrylate, isobornyl (meth) acrylate and the like can be mentioned.

(4) Ekoxysilyl group-containing polymerizable unsaturated monomer Specifically, vinyltrimethoxysilane, vinyltriethoxysilane, acryloxyethyltrimethoxysilane, methacrylateethyltrimethoxysilane, acryloxipropyltrimethoxysilane, methaloxy. Examples thereof include propyltrimethoxysilane, acryloxipropyltriethoxysilane, methaloxypropyltriethoxysilane, vinyltris (β-methoxyethoxy) silane and the like. Among these, preferred alkoxysilyl group-containing polymerizable unsaturated monomers include vinyltrimethoxysilane, γ-acryloxypropyltrimethoxysilane, and γ-methacryloxypropyltrimethoxysilane.

By using an alkoxysilyl group-containing polymerizable unsaturated monomer as a constituent component, curability can be improved by forming a cross-linking bond by a condensation reaction between alkoxyryl groups and a reaction between an alkoxysilyl group and a hydroxyl group.

(5) Aromatic Vinyl Monomer Specific examples thereof include styrene, α-methylstyrene, vinyltoluene and the like.

By using an aromatic polymerizable unsaturated monomer as a constituent component, the glass transition temperature of the obtained resin rises, and a hydrophobic coating film having a high refractive index can be obtained, so that the gloss of the coating film is improved. The effect of improving the finished appearance can be obtained.

When the aromatic polymerizable unsaturated monomer is used as a constituent component, the blending ratio thereof is preferably in the range of 5 to 50% by mass, particularly 10 to 40% by mass, based on the total amount of the monomer components.

(6) Glycidyl group-containing polymerizable unsaturated monomer The glycidyl group-containing polymerizable unsaturated monomer is a compound having one glycidyl group and one polymerizable unsaturated bond in one molecule, and specifically, glycidyl acrylate. , Glycidyl methacrylate and the like.

(7) Polymerizable unsaturated bond-containing nitrogen atom-containing compound For example, acrylamide, methacrylamide, dimethylacrylamide, N, N-dimethylpropylacrylamide, N-butoxymethylacrylamide, N-methylolacrylamide, N-methylolmethacrylamide, diacetone Examples thereof include acrylamide, N, N-dimethylaminoethyl (meth) acrylate, vinylpyridine, vinylimidazole, acrylonitrile, and methacrylonitrile.

(8) Other Vinyl Compounds For example, vinyl acetate, vinyl propionate, vinyl chloride, vinyl versatic acid ester and the like can be mentioned. Examples of the versatic acid vinyl ester include commercially available products such as "Beova 9" and "Beova 10" (above, trade name, manufactured by Japan Epoxy Resin Co., Ltd.).

As the other polymerizable unsaturated monomer (b), the monomers represented by the above (1) to (8) can be used alone or in combination of two or more.

The weight average molecular weight of the acrylic resin (A) is 3000 to 7000 from the viewpoint of high solid differentiation and the finished appearance of the coating film, and is particularly preferably in the range of 3500 to 6500, and more particularly preferably 4000 to 6000. ..

In this specification, the average molecular weight is a value calculated from a chromatogram measured by a gel permeation chromatograph based on the molecular weight of standard polystyrene. As the gel permeation chromatograph, "HLC8120GPC" (manufactured by Tosoh Corporation) was used. Four columns, "TSKgel G-4000HXL", "TSKgel G-3000HXL", "TSKgel G-2500HXL", and "TSKgel G-2000HXL" (all manufactured by Tosoh Corporation, trade name) were used. Mobile phase; tetrahydrofuran, measurement temperature; 40 ° C., flow rate; 1 cc / min, detector; RI conditions.

The glass transition temperature of the acrylic resin (A) is preferably in the range of 10 to 50 ° C., particularly 20 to 45 ° C. from the viewpoint of the hardness of the coating film and the finished appearance.

In the present specification, the glass transition temperature (° C.) of the acrylic resin was calculated by the following formula.

1 / Tg (K) = (W1 / T1) + (W2 / T2) + ... (1)
Tg (° C.) = Tg (K) -273 (2)
In each formula, W1, W2, ... Represent the mass fraction of each of the monomers used in the copolymerization, and T1, T2, ... Represent the Tg (K) of the homopolymer of each monomer.

In addition, T1, T2, ... Are the values according to Polymer Hand Book (Second Edition, J.Brandup, E.H.Immergut ed.) III-139-179. When the Tg of the homopolymer of the monomer is not clear, the glass transition temperature (° C.) is set to the static glass transition temperature, and for example, a differential scanning calorimeter "DSC-220U" (manufactured by Seiko Instruments) is used. The sample is placed in a measuring cup, vacuum sucked to completely remove the solvent, and then the calorific value change is measured in the range of -20 ° C to + 200 ° C at a heating rate of 3 ° C / min, and the first baseline on the low temperature side. The change point was the static glass transition temperature.

The blending ratio of the secondary hydroxyl group-containing polymerizable unsaturated monomer (a) and the other polymerizable unsaturated monomer (b) is 20 to 20 to 20 to that of the secondary hydroxyl group-containing polymerizable unsaturated monomer (a) with respect to the total amount of the monomers. It is preferably in the range of 45% by mass, particularly 25-40% by mass, and the other unsaturated monomer (b) is in the range of 55-80% by mass, particularly 60-75% by mass. preferable. If the amount of the secondary hydroxyl group-containing polymerizable unsaturated monomer (a) is less than 20% by mass, the curability and the finished appearance of the cured coating film may be insufficient, and if it exceeds 45% by mass, it is cured. The finished appearance of the coating film may be insufficient.

From the viewpoint of improving the pot life and the finished appearance of the coating film, 50 to 100% by mass of the secondary hydroxyl group-containing polymerizable unsaturated monomer (a) is used in the total amount of the hydroxyl group-containing polymerizable unsaturated monomer in the acrylic resin (A). In particular, it preferably contains 75 to 100% by mass, and more particularly preferably 85 to 100% by mass.

The hydroxyl value of the acrylic resin (A) is preferably in the range of 70 to 200 mgKOH / g, particularly 80 to 185 mgKOH / g, and more particularly 100 to 170 mgKOH / g from the viewpoint of curability and scratch resistance. ..

The acid value of the acrylic resin (A) is in the range of 1.0 to 15.0 mgKOH / g, particularly 3.0 to 8.0 mgKOH / g, from the viewpoint of the pot life of the coating composition and the finished appearance. Is preferable.

The copolymerization method for copolymerizing the above-mentioned monomer mixture to obtain the secondary hydroxyl group-containing acrylic resin (A) is not particularly limited and can be carried out by a conventional method, but in particular, in an organic solvent. , A solution polymerization method in which polymerization is carried out in the presence of a polymerization initiator can be preferably used.

Examples of the organic solvent used in the above solution polymerization method include aromatic solvents such as toluene, xylene, and swazole 1000 (manufactured by Cosmo Petroleum Co., Ltd., trade name, high boiling petroleum solvent); ethyl acetate, butyl acetate, propyl. Ester solvents such as propionate, butyl propionate, methoxypropyl acetate, ethoxyethyl propionate, 3-methoxybutyl acetate, ethylene glycol ethyl ether acetate, propylene glycol methyl ether acetate; methyl ethyl ketone, methyl isobutyl ketone, methyl amyl Examples thereof include a ketone solvent such as ketone, an alcohol solvent such as isopropanol, n-butanol, iso-butanol, and 2-ethylhexanol.

These organic solvents can be used alone or in combination of two or more, but it is preferable to use an ester solvent or a ketone solvent from the viewpoint of the solubility of the acrylic resin. Further, it is also possible to use an aromatic solvent in a suitable combination.

Examples of the polymerization initiator that can be used in the copolymerization of the secondary hydroxyl group-containing acrylic resin (A) include 2,2'-azobisisobutyronitrile, benzoyl peroxide, di-t-butyl peroxide, and di-t. Known radical polymerization initiators such as −amyl peroxide, t-butylperoctate, 2,2′-azobis (2-methylbutyronitrile), 2,2′-azobis (2,4-dimethylvaleronitrile) Can be mentioned.

The secondary hydroxyl group-containing acrylic resin (A) can be used alone or in combination of two or more.

In the coating composition of the present invention, resins other than the secondary hydroxyl group-containing acrylic resin (A) can also be used in combination as needed. Specifically, for example, an acrylic resin other than the acrylic resin (A), a polyester resin, a polyurethane resin, a polyether resin and the like can be mentioned, and a hydroxyl group-containing polyester resin and a hydroxyl group-containing polyurethane resin can be preferably mentioned. it can.

The hydroxyl group-containing polyester resin can be produced by a conventional method, for example, by an esterification reaction of a polybasic acid and a polyvalent alcohol. The polybasic acid is a compound having two or more carboxyl groups in one molecule, and is, for example, phthalic acid, isophthalic acid, terephthalic acid, succinic acid, adipic acid, azelaic acid, sebacic acid, tetrahydrophthalic acid, hexa. Examples thereof include hydrophthalic acid, maleic acid, fumaric acid, itaconic acid, trimellitic acid, pyromellitic acid and anhydrides thereof, and the polyvalent alcohol has two or more hydroxyl groups in one molecule. Compounds having, for example, ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 2,2-diethyl-1,3. -Propanediol, neopentyl glycol, 1,9-nonanediol, 1,4-cyclohexanediol, neopentyl glycol hydroxypivalate, 2-butyl-2-ethyl-1,3-propanediol, 3-methyl-1 , 5-Pentanediol, 2,2,4-trimethylpentanediol, diols such as bisphenol A hydride, and trivalent or higher polyol components such as trimethylolpropane, trimethylolethane, glycerin, pentaerythritol, and 2 , 2-Dimethylolpropionic acid, 2,2-Dimethylolbutanoic acid, 2,2-Dimethylolpentanoic acid, 2,2-Dimethylolhexanoic acid, 2,2-Dimethyloloctanoic acid and other hydroxycarboxylic compounds. Be done.

Further, α-olefin epoxides such as propylene oxide and butylene oxide, monoepoxy compounds such as Cardura E10 (manufactured by Japan Epoxy Resin Co., Ltd., trade name, glycidyl este of synthetic highly branched saturated fatty acids) are reacted with an acid to react these The compound may be introduced into the polyester resin.

When introducing a carboxyl group into a polyester resin, for example, it can be introduced by adding anhydrous acid to a hydroxyl group-containing polyester and half-esterifying it.

The hydroxyl value of the hydroxyl group-containing polyester resin is preferably in the range of 100 to 250 mgKOH / g, more preferably 120 to 220 mgKOH / g. The weight average molecular weight of the hydroxyl group-containing polyester resin is preferably in the range of 500 to 3000, more preferably 500 to 2000.

Examples of the hydroxyl group-containing polyurethane resin include a hydroxyl group-containing polyurethane resin obtained by reacting a polyol with a polyisocyanate.

Examples of the polyol include dihydric alcohols such as ethylene glycol, diethylene glycol, propylene glycol, butylene glycol and hexamethylene glycol, and trihydric alcohols such as trimethylolpropane, glycerin and pentaerythritol. Can be done. Examples of the high molecular weight ones include polyether polyols, polyester polyols, acrylic polyols, epoxy polyols and the like. Examples of the polyether polyol include polyethylene glycol, polypropylene glycol, polytetramethylene glycol and the like. The polyester polyol includes the above-mentioned dihydric alcohol, dipropylene glycol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol and other alcohols, and dibasic acids such as adipic acid, azelaic acid and sebatic acid. Examples thereof include a polycondensate of the above, a lactone-based ring-opening polymer polyol such as polycaprolactone, and a polycarbonate diol. Further, for example, carboxyl group-containing polyols such as 2,2-dimethylolpropionic acid and 2,2-dimethylolbutanoic acid can also be used.

Examples of the polyisocyanate to be reacted with the above polyol include aliphatic polyisocyanates such as hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, dimerate diisocyanate, and lysine diisocyanate; and addition of these polyisocyanates to a burette type. Isocyanurate ring adduct; isophorone diisocyanate, 4,4'-methylenebis (cyclohexylisocyanate), methylcyclohexane-2,4- (or -2,6-) diisocyanate, 1,3- (or 1,4-) Alicyclic diisocyanates such as di (isocyanatomethyl) cyclohexane, 1,4-cyclohexanediisocyanate, 1,3-cyclopentanediisocyanate, 1,2-cyclohexanediisocyanate; and burette-type adducts of these polyisocyanates, isocyanate. Nurate ring adduct; xylylene diisocyanate, metaxylylene diisocyanate, tetramethylxylylene diisocyanate, tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 1,5-naphthalenedi isocyanate, 1,4-naphthalenedi isocyanate, 4,4- Truizin diisocyanate, 4,4'-diphenyl ether diisocyanate, (m- or p-) phenylenediisocyanate, 4,4'-biphenylenediisocyanate, 3,3'-dimethyl-4,4'-biphenylenediocyanate, bis (4-isocyanato) Aromatic diisocyanate compounds such as phenyl) sulfone, isopropyridenebis (4-phenylisocyanate); and burette-type adducts, isocyanurate ring adducts of these polyisocyanates; triphenylmethane-4,4', 4'' -One molecule of triisocyanate, 1,3,5-triisocyanatobenzene, 2,4,6-triisocyanatotoluene, 4,4'-dimethyldiphenylmethane-2,2', 5,5'-tetraisocyanate, etc. Polyisocyanates having three or more isocyanate groups; and burette-type adducts and isocyanurate ring adducts of these polyisocyanates; and the like can be mentioned.

The hydroxyl value of the hydroxyl group-containing polyurethane resin is preferably in the range of 100 to 250 mgKOH / g, more preferably 120 to 220 mgKOH / g. The weight average molecular weight of the hydroxyl group-containing polyurethane resin is preferably in the range of 1000 to 4000, more preferably 1000 to 2000.

When a resin other than the above secondary hydroxyl group-containing acrylic resin (A) (more specifically, polyester resin, polyurethane resin, polyether resin, etc.) is used in combination, a resin other than the secondary hydroxyl group-containing acrylic resin (A) is used. Is preferably in the range of 50% by mass or less, more preferably 0 to 20% by mass, based on the total solid content of the secondary hydroxyl group-containing acrylic resin (A).

<Aliphatic polyisocyanate compound and / or its derivative (B)>
The aliphatic polyisocyanate compound and / or its derivative (B) may be referred to as "component (B)" in the present specification.

Examples of the aliphatic polyisocyanate compound include aliphatic compounds having two or more isocyanate groups in one molecule known for producing polyurethane, such as ethylene diisocyanate, trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, and pentamethylene diisocyanate. Dodecamethylene diisocyanate, lysine diisocyanate, 1,2-propylene diisocyanate, 1,2-butylenediocyanate, 2,3-butylenediocyanate, 1,3-butylenediocyanate, 2,4,4- or 2,2,4-trimethylhexa Methylene diisocyanate, bis (2-isocyanatoethyl) fumarate, bis (2-isocyanatoethyl) carbonate, 2,6-diisocyanatomethyl caproate, 2-isocyanatoethyl-2,6-diisocyanatohexanoate And other aliphatic diisocyanates, such as lysine ester triisocyanate, 1,4,8-triisocyanatooctane, 1,6,11-triisocyanatoundecane, 1,8-diisocyanato-4-isocyanatomethyloctane, 1, Examples thereof include aliphatic triisocyanates such as 3,6-triisocyanatohexane and 2,5,7-trimethyl-1,8-diisocyanato-5-isocyanatomethyloctane.

Examples of the derivative of the above-mentioned aliphatic polyisocyanate compound include various derivatives of the above-mentioned aliphatic polyisocyanate compound such as dimer, trimmer, biuret, allophanate, carbodiimide, uretdione, uretoimine, isocyanurate and iminooxadiazinedione. Can be done.

Among the above aliphatic polyisocyanate compounds and derivatives thereof, aliphatic diisocyanates and their isocyanurates can be preferably used from the viewpoint of high solid differentiation and scratch resistance.

Among them, hexamethylene diisocyanate and its isocyanurate form can be particularly preferably used.

In addition, in this specification, "and / or" means "at least one of them". For example, "aliphatic polyisocyanate compound and / or its derivative" is at least one selected from the group consisting of "at least one of the aliphatic polyisocyanate compound and its derivative" or "aliphatic polyisocyanate compound and its derivative". It can be paraphrased as "one".

As the polyisocyanate compound, in addition to the above-mentioned aliphatic polyisocyanate compound and its derivative, those known for producing polyurethane, for example, alicyclic polyisocyanate, aromatic aliphatic polyisocyanate, aromatic polyisocyanate and derivatives of these polyisocyanates and the like. Can also be used in combination to the extent that the coating performance such as high solid differentiation of the coating composition and the scratch resistance of the obtained coating film is not impaired.

Examples of the alicyclic polyisocyanate include 1,3-cyclopentenediisocyanate, 1,4-cyclohexanediisocyanate, 1,3-cyclohexanediisocyanate, and 3-isocyanatomethyl-3,5,5-trimethylcyclohexylisocyanate (common name:: Isophorone diisocyanate), 4,4'-methylenebis (cyclohexylisocyanate), methyl-2,4-cyclohexanediisocyanate, methyl-2,6-cyclohexanediisocyanate, 1,3-bis (isocyanatomethyl) cyclohexane, 1,4-bis (Isocyanatomethyl) cyclohexane, norbornan diisocyanate, dicyclohexylmethane-4,4'-diisocyanate (hydrogenated MDI), cyclohexylene diisocyanate, methylcyclohexylene diisocyanate (hydrogenated TDI), bis (2-isocyanatoethyl) -4- Alicyclic diisocyanates such as cyclohexene-1,2-dicarboxylate, such as 1,3,5-triisocyanatocyclohexane, 1,3,5-trimethylisocyanatocyclohexane, 2- (3-isocyanatopropyl)- 2,5-di (isocyanatomethyl) -bicyclo (2.2.1) heptane, 2- (3-isocyanatopropyl) -2,6-di (isocyanatomethyl) -bicyclo (2.2.1) Heptane, 3- (3-isocyanatopropyl) -2,5-di (isocyanatomethyl) -bicyclo (2.2.1) heptane, 5- (2-isocyanatoethyl) -2-isocyanatomethyl-3 -(3-Isocyanatopropyl) -bicyclo (2.2.1) heptane, 6- (2-isocyanatoethyl) -2-isocyanatomethyl-3- (3-isocyanatopropyl) -bicyclo (2.2) .1) Heptane, 5- (2-isocyanatoethyl) -2-isocyanatomethyl-2- (3-isocyanatopropyl) -bicyclo (2.2.1) -heptane, 6- (2-isocyanatoethyl) ) -2-Isocyanatomethyl-2- (3-isocyanatopropyl) -bicyclo (2.2.1) Alicyclic triisocyanates such as heptane can be mentioned.

Examples of the aromatic aliphatic polyisocyanate include 1,3- or 1,4-xylylene diisocyanate or a mixture thereof, ω, ω'-diisocyanato-1,4-diethylbenzene, 1,3- or 1,4-bis (). Arophilic aliphatic diisocyanates such as 1-isocyanato-1-methylethyl) benzene (common name: tetramethylxylylene diisocyanate) or a mixture thereof, for example, aromatic aliphatic triisocyanates such as 1,3,5-triisocyanatomethylbenzene. And so on.

Examples of the aromatic polyisocyanate include m-phenylenediocyanate, p-phenylenediocyanate, 4,4'-diphenyldiisocyanate, 3,3'-dimethyl-4,4'-diisocyanatobiphenyl, and 3,3'-dimethyl. -4,4'-diisocyanatodiphenylmethane, 1,5-naphthalenediocyanate, 2,4'-or 4,4'-diphenylmethane diisocyanate (MDI) or a mixture thereof, 2,4- or 2,6-tolylene diisocyanate Or a mixture thereof, aromatic diisocyanates such as 4,4'-toluidin diisocyanate, 4,4'-diphenyl ether diisocyanate, m- and p-isocyanatophenylsulfonyl isocyanate, for example, triphenylmethane-4,4', 4''. Aromatic triisocyanates such as − triisocyanate, 1,3,5-triisocyanatobenzene, 2,4,6-triisocyanatotoluene, for example 4,4'-diphenylmethane-2,2', 5,5' -Aromatic tetraisocyanates such as tetraisocyanates can be mentioned.

Examples of the polyisocyanate derivative include various derivatives such as dimer, trimmer, biuret, allophanate, carbodiimide, uretdione, uretoimine, isocyanurate, and iminooxadiazinedione of the above-mentioned polyisocyanate compound.

These polyisocyanate compounds may be used alone or in combination of two or more.

The weight average molecular weight of the aliphatic polyisocyanate compound and / or its derivative (B) is 1000 or less, particularly 150 to 1000, and more particularly, from the viewpoint of high solid differentiation and the finished appearance and scratch resistance of the obtained coating film. It is preferably in the range of 400 to 950.

When a polyisocyanate compound other than the above-mentioned aliphatic polyisocyanate compound and / or its derivative (B) and its derivative are used in combination, the polyisocyanate compound other than the aliphatic polyisocyanate compound and / or its derivative (B) and its derivative thereof. Is preferably in the range of 50% by mass or less, more preferably 0 to 20% by mass, based on the total solid content of the aliphatic polyisocyanate compound and / or its derivative (B).

<Alkyl etherified melamine resin (C)>
The alkyl etherified melamine resin (C) (sometimes referred to as "component (C)" in the present specification) is obtained by subjecting melamine to an addition reaction or an addition condensation reaction of aldehydes such as formaldehyde, paraformaldehyde, acetaldehyde, and benzaldehyde. It can be synthesized by forming a methylolated melamine resin and further converting the methylol group portion with an alcohol to alkyl ether.

Examples of the alcohol used for etherification include methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, 2-ethylbutanol, 2-ethylhexanol and the like.

The alkyl etherified melamine resin is, for example, one in which the hydrogen atom of the hydroxyl group of the methylol group is substituted with an alkyl group, and the alkyl group includes a methyl group, an ethyl group, an n-butyl group, an isobutyl group and a 2-ethylbutyl group. , 2-Ethylhexyl group and the like.

The alkyl etherified melamine resin may be a condensate of the alkyl etherified melamine resin (a condensation reaction of the alkyl etherified melamine resin to increase the molecular weight).

Of these, a methyl and butyl mixed alkyl etherified melamine resin is particularly preferable.

The alkyl etherified melamine resin (C) has a weight average molecular weight of 1000 or less, and particularly preferably 950 or less, from the viewpoint of high solid differentiation and the finished appearance and scratch resistance of the obtained coating film. Can be done.

As the alkyl etherified melamine resin (C), a commercially available product can be used. Examples of commercially available products include Cymel 235, Cymel 238, Cymel 232, Cymel 325, Cymel 327, Cymel 350, Cymel 370, Cymel 212, Cymel 211, Regimin 745, and Regimin 747 manufactured by Ornex Japan. ..

From the viewpoint of improving the pot life, the alkyl etherified melamine resin (C) is preferably as having as few imino groups, and more preferably as having substantially no imino groups.

More specifically, each triazine nucleus has 5 or more, particularly 5.5 or more, and more preferably, all methylolated so that substantially no imino group remains, and has 6 methylol groups. An alkyl etherified melamine resin synthesized by alkyl etherifying the methylolated melamine resin thus synthesized is preferable.

Further, the alkyl etherified melamine resin (C) has a maximum of 6 alkyl ether groups per triazine nucleus, 4.0 or more, particularly 5.0 or more, and particularly 5.5 or more alkyl ether groups. The synthesized alkyl etherified melamine resin is preferable from the viewpoint of improving the pot life.

The alkyl etherified melamine resin (C) can be used alone or in combination of two or more.

In the coating composition of the present invention, the amount of the component (C) is in the range of 1.5 to 20% by mass with respect to the total amount of the component (B) from the viewpoint of the finished appearance and scratch resistance, particularly. It is preferably in the range of 1.5 to 15% by mass, and more preferably 1.5 to 10% by mass.

The amount of the secondary hydroxyl group-containing acrylic resin (A), the aliphatic polyisocyanate compound and / or its derivative (B), and the alkyl etherified melamine resin (C) in the present paint determines the finished appearance, the curability of the coating film, and the like. From the viewpoint, the secondary hydroxyl group-containing acrylic resin (A) is 45 to 80% by mass, particularly 50 to 70% by mass, and the fat is based on the total solid content of the components (A), (B) and (C). The group polyisocyanate compound and / or its derivative (B) is 20 to 50% by mass, particularly 25 to 40% by mass, and the alkyl etherified melamine resin (C) is 0.5 to 10% by mass, particularly 1 to 7% by mass. Further, it is particularly preferable that the content is in the range of 1 to 5% by mass.

<Sulfonic acid compound and / or phosphoric acid compound (D)>
In the coating composition of the present invention, from the viewpoint of imparting scratch resistance, a sulfonic acid compound and / or a phosphoric acid compound (D) (may be referred to as a component (D) in the present specification) is used as an acid catalyst. contains.

The sulfonic acid compound is a compound containing a sulfonic acid group, for example, a sulfonic acid compound such as paratoluene sulfonic acid, dodecylbenzene sulfonic acid, dinonylnaphthalene sulfonic acid; a neutralizing salt of these sulfonic acid compounds and an amine compound. And so on.

The phosphoric acid compound is a compound containing a phosphoric acid group, for example, phosphoric acid; mono-n-propyl phosphoric acid, monoisopropyl phosphoric acid, mono-n-butyl phosphoric acid, monoisobutyl phosphoric acid, mono-tert-butyl phosphoric acid. , Monoalkyl phosphoric acid such as monooctyl phosphoric acid, mono2-ethylhexyl phosphoric acid, monodecyl phosphoric acid; di-n-propyl phosphoric acid, diisopropyl phosphoric acid, di-n-butyl phosphoric acid, diisobutyl phosphoric acid, di-tert-butyl phosphorus Dialkyl phosphoric acid such as acid, dioctyl phosphoric acid, di2-ethylhexyl phosphoric acid, didecyl phosphoric acid; mono-n-propyl phosphoric acid, monoisopropyl phosphoric acid, mono-n-butyl phosphoric acid, monoisobutyl phosphoric acid , Mono-tert-butyl phosphoric acid, monooctyl phosphoric acid, monoalkyl phosphoric acid such as monodecyl phosphoric acid; di-n-propyl phosphoric acid, diisopropyl phosphoric acid, di-n-butyl phosphoric acid , Diisobutyl phosphoric acid, di-tert-butyl phosphoric acid, dioctyl phosphoric acid, didecyl phosphoric acid and other dialkyl phosphoric acid; phosphoric acid group-containing acrylic resin; neutralization of these phosphoric acid compounds and amine compounds Salt and the like can be mentioned.

The sulfonic acid compound and / or the phosphoric acid compound (D) can be used alone or in combination of two or more.

In the coating composition of the present invention, a sulfonic acid compound can be preferably used from the viewpoint of scratch resistance and pot life.

As the sulfonic acid, dodecylbenzenesulfonic acid and dinonylnaphthalenesulfonic acid are particularly preferable from the viewpoint of scratch resistance.

Further, as the amine compound as a neutralizing agent for the sulfonic acid compound and / or the phosphoric acid compound, a tertiary amine compound such as triethylamine can be preferably used from the viewpoint of the finished appearance.

The amount of the sulfonic acid compound and / or the phosphoric acid compound (D) is determined from the viewpoint of the finished appearance, that is, the secondary hydroxyl group-containing acrylic resin (A), the aliphatic polyisocyanate compound and / or its derivative (B), and the alkyl etherified melamine. It should be in the range of 1.5% by mass or less, particularly 0.1 to 1.0% by mass, and more particularly 0.3 to 0.8% by mass, based on the total solid content of the resin (C). preferable.

The coating material may further contain a coloring pigment, a bright pigment, a dye, etc., if necessary, and further, an extender pigment, a catalyst, an ultraviolet absorber, a light stabilizer, a defoaming agent, a thickener, etc. A rust preventive, a surface conditioner, an organic solvent and the like can be appropriately contained.

Examples of coloring pigments include titanium oxide, zinc flower, carbon black, cadmium red, molybdenum red, chromium yellow, chromium oxide, Prussian blue, cobalt blue, azo pigment, phthalocyanine pigment, quinacridone pigment, isoindoline pigment, and slene pigment. Perylene pigment and the like can be mentioned.

Examples of the bright pigment include aluminum powder, mica powder, mica powder coated with titanium oxide, and the like.

Examples of the extender pigment include talc, clay, kaolin, barita, barium sulfate, barium carbonate, calcium carbonate, alumina white and the like.

The pigments can be used alone or in combination of two or more.

When the coating composition of the present invention is used as a clear coating material and contains a pigment, the blending amount of the pigment is preferably an amount that does not impair the transparency of the obtained coating film, for example. It is usually in the range of 0.1 to 20% by mass, particularly 0.3 to 10% by mass, and more preferably 0.5 to 5% by mass with respect to the total amount of solids in the coating composition.

Further, when the coating composition of the present invention is used as a coloring coating material and contains a pigment, the blending amount of the pigment is usually 1 to 200% by mass with respect to the total solid content in the coating composition. In particular, it is preferably in the range of 2 to 100% by mass, and more particularly preferably in the range of 5 to 50% by mass.

As the ultraviolet absorber, conventionally known ones can be used, and examples thereof include ultraviolet absorbers such as benzotriazole-based absorbents, triazine-based absorbents, salicylic acid derivative-based absorbents, and benzophenone-based absorbents. it can. These can be used alone or in combination of two or more.

When the coating composition of the present invention contains an ultraviolet absorber, the blending amount of the ultraviolet absorber is usually 0.1 to 10% by mass, particularly 0.2 to 10% by mass, based on the total amount of solids in the coating composition. It is preferably in the range of 5% by mass, more particularly 0.3 to 2% by mass.

As the light stabilizer, conventionally known ones can be used, and examples thereof include hindered amine-based light stabilizers.

As the hindered amine-based light stabilizer, a hindered amine-based light stabilizer having low basicity can be preferably used from the viewpoint of pot life. Examples of such hindered amine-based light stabilizers include acylated hindered amines, amino ether-based hindered amines, and specifically, HOSTAVIN3058 (manufactured by Clariant), TINUVIN123 (manufactured by BASF), and the like.

When the coating composition of the present invention contains a light stabilizer (for example, acylated hindered amine, amino ether-based hindered amine), the blending amount of the light stabilizer is usually 0 with respect to the total solid content in the coating composition. It is preferably in the range of 1 to 10% by mass, particularly 0.2 to 5% by mass, and more preferably 0.3 to 2% by mass.

As the organic solvent, those usually used for paints can be used, and examples thereof include aromatic solvents, ester solvents, ketone solvents, alcohol solvents and the like that can be used in the above-mentioned solution polymerization method. Will be done. These organic solvents can be used alone or in combination of two or more.

In a preferred embodiment, the coating composition of the present invention is an organic solvent type coating composition in which the solvent is mainly an organic solvent.

In the present specification, the "high solid content coating composition" refers to a coating composition having a coating solid content concentration (solid content concentration at the time of coating; coating NV (nonvolatile content) value) higher than usual. For example, when the coating composition of the present invention is used as a clear coating material, a high solid content means a coating solid content concentration of about 50 to 55% by mass or more. The coating solid content concentration of the present coating material is usually 57 to 65% by mass, particularly preferably 58 to 63% by mass from the viewpoint of achieving both high solid differentiation and finished appearance.

The solid content can be determined as a heating residue, which is a mass fraction of the residue obtained by evaporation under predetermined conditions, as defined in JIS K5601.

Since this coating material usually contains an aliphatic polyisocyanate compound having a free (free) isocyanate group and / or a derivative thereof as a component (B) which is a cross-linking agent, it is a substrate resin at room temperature (A). Since the cross-linking reaction with the component) proceeds, a two-component type consisting of a main agent containing the components (A) and (C) and a curing agent containing the component (B) is used, and the main agent and the curing agent are used immediately before painting. It is preferable to mix and adjust the viscosity before use.

The object to be coated to which the coating composition of the present invention is applied is not particularly limited, but for example, the outer panel of an automobile body such as a passenger car, a truck, a motorcycle, or a bus; an automobile part; a mobile phone, an audio. Examples thereof include the outer panel portion of household electric products such as equipment, and among them, the outer panel portion of an automobile body and automobile parts are preferable.

The material of the object to be coated is not particularly limited, and for example, iron, aluminum, brass, copper, tin, stainless steel, zinc-plated steel, and alloyed zinc (Zn-Al, Zn-Ni, Zn-Fe, etc.) Metal materials such as plated steel; resins such as polyethylene resin, polypropylene resin, acrylonitrile-butadiene-styrene (ABS) resin, polyamide resin, acrylic resin, vinylidene chloride resin, polycarbonate resin, polyurethane resin, epoxy resin, etc. And various plastic materials such as FRP; inorganic materials such as glass, cement and concrete; wood; fiber materials (paper, cloth, etc.), etc. Among them, metal materials and plastic materials are preferable.

The object to be coated may be a metal surface such as the metal material or a vehicle body formed from the metal material, which has been subjected to surface treatment such as phosphate treatment, chromate treatment, or composite oxide treatment. Further, the object to be coated may be one in which an undercoat coating film such as various electrodeposition coating films is formed on the metal base material, the vehicle body or the like, and in particular, the undercoat coating film is formed by the cationic electrodeposition coating material. The car body is particularly suitable.

The coating method of this coating material is not particularly limited, and examples thereof include coating methods such as air spray coating, airless spray coating, rotary atomization coating, and curtain coat coating. Can be formed. In these coating methods, static electricity may be applied if necessary. Of these, air spray coating or rotary atomization coating is particularly preferable. The coating amount of the present paint is usually preferably an amount such that the cured film thickness is about 10 to 60 μm, particularly about 25 to 50 μm.

Further, in the case of performing air spray coating, airless spray coating and rotary atomization coating, the viscosity of this coating material is set to a viscosity range suitable for the coating, usually Ford Cup No. In the four viscometers, it is preferable to appropriately adjust the viscosity range at 20 ° C. for 15 to 60 seconds, particularly about 20 seconds to 40 seconds, using a solvent such as an organic solvent.

The wet coating film formed by coating the object to be coated with the present paint can be cured by heating, and the heating can be performed by a known heating means, for example, a hot air furnace, an electric furnace, or an infrared induction heating. A drying furnace such as a furnace can be used. The heating temperature is not particularly limited, and is preferably in the range of, for example, 60 to 160 ° C, preferably 80 to 140 ° C. The heating time is not particularly limited, and is preferably in the range of, for example, 10 to 60 minutes, preferably 15 to 30 minutes.

Since this paint is a high solid content paint composition that can form a coating film with excellent scratch resistance, acid resistance, and finished appearance and has an excellent pot life, it can be used as a topcoat top clear coat paint. It can be preferably used. This paint can be particularly suitably used as a paint for automobiles.

Multi-layer coating film forming method As a multi-layer coating film forming method in which this paint is applied as a top coat top clear coat paint, at least one layer of colored base coat paint and at least one layer of clear coat paint are sequentially applied to an object to be coated. This is a method for forming a multi-layer coating film, and examples thereof include a multi-layer coating film forming method including coating the coating composition of the present invention as a clear coat coating material for the uppermost layer.

Specifically, for example, a base coat paint is applied onto an object to be coated with electrodeposition coating and / or an intermediate coating, and a solvent in the base coat coating is required without curing the coating film. In order to promote the volatilization of, for example, preheating is performed at 40 to 90 ° C. for about 3 to 30 minutes, and this paint is applied as a clear coat paint on the uncured base coat coating material, and then the base coat coating material is applied. A two-coat, one-bake method of forming a multi-layer coating film in which the coating film and the clear coating coating film are cured together can be mentioned.

Further, this paint can also be suitably used as a top clear coat paint in the top coat coating of the 3-coat 2-bake method or the 3-coat 1-bake method.

As the base coat paint used above, a conventionally known heat-curable base coat paint can be used. Specifically, for example, a base resin such as an acrylic resin, a polyester resin, an alkyd resin, or a urethane resin. A coating material obtained by appropriately combining a cross-linking agent such as an amino resin, a polyisocyanate compound, or a blocked polyisocyanate compound with a reactive functional group contained in the base resin can be used.

Further, as the base coat paint, for example, a water-based paint, an organic solvent-based paint, or a powder paint can be used. Of these, water-based paints are preferable from the viewpoint of reducing the environmental load and the finished appearance of the coating film.

In the multi-layer coating film forming method, when two or more layers of clear coat are applied, a conventionally known thermosetting clear coat paint can be used as the clear coat paint other than the uppermost layer.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. However, the present invention is not limited to these examples. Both "part" and "%" are based on mass.

Production of secondary hydroxyl group-containing acrylic resin (A) In an acrylic resin reaction tank equipped with a stirrer, thermometer and reflux cooler, 27 parts of Swazole 1000 (Aromatic solvent manufactured by Cosmo Petroleum Co., Ltd.) and methoxy Add 5 parts of propyl acetate (KH Neochem Co., Ltd., ester solvent), heat and stir under nitrogen gas aeration, stop the nitrogen gas aeration after reaching 150 ° C, 20 parts of styrene, 2-hydroxypropyl. A monomer mixture having a composition of 32.5 parts of acrylate, 46.8 parts of isobornyl acrylate, 0.7 part of acrylic acid and 6.0 parts of ditersharia mill peroxide (polymerization initiator) was added dropwise over 4 hours. ..

Then, it was aged at 150 ° C. for 1 hour and then cooled, and 21 parts of isobutyl acetate was further added for dilution to obtain a hydroxyl group-containing acrylic resin (A1) having a solid content concentration of 65% by mass. The hydroxyl group-containing acrylic resin (A1) had a weight average molecular weight of 5500, a hydroxyl value of 139 mgKOH / g, an acid value of 5.5 mgKOH / g, and a glass transition temperature of 25 ° C.

Production Examples 2 to 10
In Production Example 1, a hydroxyl group is contained in the same manner as in Production Example 1 (the amount of the polymerization initiator is adjusted to a desired weight average molecular weight) except that the monomer mixture is a monomer mixture having the composition shown in Table 1. Acrylic resins (A2) to (A10) were obtained. Table 1 also shows the glass transition temperature (Tg (° C.)) calculated from the weight average molecular weight, hydroxyl value, acid value, and monomer composition.

The hydroxyl group-containing acrylic resins (A8) to (A10) are acrylic resins for comparative examples.

<Manufacturing of paint composition>
Example 1
93.8 parts (solid content 61 parts) of the hydroxyl group-containing acrylic resin (A1) solution obtained in Production Example 1, melamine resin (C1) (trade name, Cymel 350, manufactured by Ornex Japan, methyl etherified melamine resin, weight) Average molecular weight 550, virtually 0 imino groups, methylol group: 1.3 parts per triazine nucleus) 5.15 parts (5 parts solids), sulfonic acid compound (D1) (NACURE 5523: trade name, KING INDUSTRIES Amine salt of dodecylbenzene sulfonic acid, active ingredient solid content 35%) 2.14 parts (solid content 0.75 part), HOSTAVIN3058 (trade name, manufactured by CLARIANT, hindered amine-based light stabilizer, acylated hindered amine, 1.0 part of active ingredient), TINUVIN400 (trade name, manufactured by BASF, benzotriazole-based ultraviolet absorber, 100% active ingredient), 3 parts and BYK-300 (trade name, Big Chemie) , Surface conditioner, active ingredient 52%) 0.4 parts (solid content 0.2 parts) of the main agent
Polyisocyanate compound (B1) which is a curing agent (crosslinking agent) (Sumijour N3300, trade name, manufactured by Sumika Covestro Urethane Co., Ltd., isocyanurate of hexamethylene diisocyanate, solid content 100%) 34 parts (solid content 34 parts) ) Is uniformly mixed immediately before coating, and butyl acetate is further added to obtain Ford Cup No. 2 at 20 ° C. Adjusting the viscosity according to No. 4 to 30 seconds, the coating composition No. I got 1.

Examples 2-14 and Comparative Examples 1-5
In the same manner as in Example 1, with the paint formulations shown in Table 2 below, Ford Cup No. 1 at 20 ° C. Each coating composition No. 4 having a viscosity of 30 seconds according to No. 4 2 to 19 were obtained. Paint composition No. Reference numerals 15 to 19 are for comparative examples.

In addition, each coating composition No. of Table 2 The paint formulations 1 to 19 are solid content formulations.

Table 2 (* 1) to (* 4) are as follows.
(* 1) Melamine resin (C2): Cymel 250, trade name, methylbutyl mixed etherified melamine resin, manufactured by Ornex Japan, weight average molecular weight 2700
(* 2) Phosphoric acid compound (D2): NACURE4167, trade name, triethylamine salt of alkylphosphoric acid, manufactured by KING INDUSTRIES, active ingredient solid content 25%
(* 3) TINUVIN123: Product name, B.I. A. S. F. Hindered amine light stabilizer, 100% active ingredient
(* 4) Polyisocyanate compound (B2): XP2679, trade name, hexamethylene diisocyanate allophanate, manufactured by Sumika Bayer Urethane, solid content 80%
<Preparation of test plate>
(Preparation of test object)
Eleklon GT-10 (trade name, manufactured by Kansai Paint Co., Ltd., cationic electrodeposition paint) is electrodeposited on a cold-rolled steel sheet that has been subjected to zinc phosphate chemical conversion treatment so that the dry film thickness is 20 μm, and the temperature is 170 ° C. for 30 minutes. After heating and curing, "WP-306T" (trade name, manufactured by Kansai Paint Co., Ltd., polyester melamine resin-based water-based intermediate coating paint) is applied onto the electrodeposited coating film using a rotary atomization type electrostatic coating machine. Then, electrostatic coating was performed so that the cured film thickness was 30 μm, left for 5 minutes, preheated at 80 ° C. for 3 minutes, and then heated at 140 ° C. for 30 minutes to form an intermediate coating film to be coated for testing. I made it a thing.

(Preparation of test plate)
"WBC-713T No. 1F7" (trade name, manufactured by Kansai Paint Co., Ltd., acrylic melamine resin-based water-based base coat paint, silver coating color) was applied to the test object to be coated using a rotary atomization type electrostatic coating machine. Then, it was electrostatically coated so as to have a cured film thickness of 15 μm, left for 5 minutes, and then preheated at 80 ° C. for 3 minutes.

Next, on the uncured base coat coating film, the coating composition No. 1 obtained in Example 1 was applied. 1 was electrostatically coated using a rotary atomization type electrostatic coating machine so as to have a dry film thickness of 40 μm to form a clear coat coating film, and left for 7 minutes. Next, the coating composition No. 1 was heated by heating at 140 ° C. for 30 minutes (keeping time) to heat-cure the base coat coating film and the clear coat coating film. The test plate of No. 1 was prepared.

The above paint composition No. In the preparation of the test plate of No. 1, the coating composition No. 1 was prepared. 1 is the paint composition No. 1 respectively. No. 2 to 19 except that the coating composition No. The coating composition No. 1 was prepared in the same manner as in the preparation of the test plate of 1. 2 to 19 test plates were prepared respectively.

Each of the test plates obtained above was evaluated by the following test method. The evaluation results are shown in Table 2 together with the coating composition.

Further, the coating solid content concentration of each coating composition (paint solid content concentration at the time of coating (solid content mass% of the coating material adjusted to a viscosity of 30 seconds by Ford Cup No. 4 at 20 ° C.; "painting NV" in the table) Pot life (viscosity% after mixing the main agent and hardener to adjust the viscosity by Ford Cup No. 4 at 20 ° C to 30 seconds and allowing it to stand at 20 ° C for 4 hours; Rate) ”) is also shown.

(Test method)
Finished appearance: The finished appearance was evaluated based on the Long Wave (LW) value and the Short Wave (SW) value measured by Wave Scan (trade name, manufactured by BYK Gardener).

LW: An index of smoothness, and the smaller the LW value, the higher the smoothness of the coated surface.

SW: An index of vividness, and the smaller the SW value, the higher the vividness of the coated surface.

Flip-flop property (FF property): Using a multi-angle spectrophotometer MA-68 (trade name, manufactured by X-Rite), the L value (brightness) of a light receiving angle of 15 ° and a light receiving angle of 110 ° is measured. The FF value was calculated by the following formula.
FF value = L value with a light receiving angle of 15 ° -L value with a light receiving angle of 110 °.
The larger the FF value, the larger the change in the L value (brightness) depending on the observation angle (light receiving angle), indicating that the flip-flop property is excellent.

Scratch resistance: Using an Atlas Clock Meter, double rub 10 times with a 3M281Q polishing sheet (manufactured by Sumitomo 3M Ltd.), rub the test plate, and then wipe with a mineral spirit. The test plate was cleaned.

The 20-degree specular reflectance (20 ° gloss value) of the test plate after the test was measured, and the scratch resistance was evaluated by the gloss retention rate (%) with respect to the 20 ° gloss value before the test. The higher the gloss retention rate (%), the better the scratch resistance.

Tucon hardness: After leaving the test plate in a constant temperature room at 20 ° C for 4 hours, TUKON (American)
"Two-con hardness" was measured with a micro hardness tester (manufactured by Chain & Cable Company). The Knoop hardness test method, the two-con hardness, is a numerical value measured by the TUKON micro hardness tester manufactured by the American Chain & Cable Company. The two-con hardness, also known as Knoop Hardness Number (KHN), is a constant test load on a square pyramid diamond indenter. It is the hardness of the coating film that can be read from the size of the diamond-shaped depression that is formed by pushing it into the test surface of the material. The larger the value, the harder it is.

Acid resistance: Each test plate was half immersed in a 10% sulfuric acid solution, left at 50 ° C. for 5 hours, washed with water, and the coated surface was observed and evaluated according to the following criteria.

S: No change is observed.

A: There is no abnormality on the coated surface, but a slight step is observed at the boundary between the immersed portion and the non-immersed portion.

B: The coated surface is swollen or whitened.

NSR Adhesiveness (Non-Sandricot Adhesiveness): Paint Composition No. A test plate prepared at a heat curing temperature of 160 ° C. in the preparation of the test plate of 1 was separately prepared for each coating composition.

The coating composition No. In the same manner as in the preparation of the test plate of No. 1, the base coat coating film and the clear coat coating film are formed again and recoated (the same coating composition as the base coat paint and the clear coat paint is applied again), and the temperature is 130 ° C. Each recoat test plate was prepared by heating the base coat coating film and the clear coat coating film by heating for 30 minutes (keeping time).

The test was carried out by the adhesive cellophane tape peeling test (100 goban stitches having a size of 2 mm × 2 mm) described in JIS K5600, and the evaluation was made according to the following criteria.

S: 100 Goban eyes remain, and no edge chips are found in each Goban eye.

A: 100 Goban eyes remain, but edge chips are observed in the Goban eyes.

B: The number of remaining Goban eyes is 99 or less.

Claims (6)

(A) Acrylic resin containing a secondary hydroxyl group having a weight average molecular weight of 3000 to 7000,
(B) Aliphatic polyisocyanate compound and / or its derivative,
A coating composition containing (C) an alkyl etherified melamine resin having a weight average molecular weight of 1000 or less, and (D) a sulfonic acid compound and / or a phosphoric acid compound.
(C) the amount of components based on the total amount of component (B) state, and are within the scope of 1.5 to 20 wt%, high for paint solid concentration and wherein 57-65% by mass Rukoto Solid paint composition. The high solid content according to claim 1, wherein the secondary hydroxyl group-containing polymerizable unsaturated monomer (a) is 50 to 100% by mass in the total amount of the hydroxyl group-containing polymerizable unsaturated monomer which is a constituent component of the acrylic resin (A). Paint composition. The high solid content coating composition according to claim 1 or 2, wherein the alkyl etherified melamine resin (C) has substantially no imino group. The high solid content coating composition according to any one of claims 1 to 3, further containing an acylated hindered amine and / or an amino ether-based hindered amine. An article having a coating film of the coating composition according to any one of claims 1 to 4. A method of forming a multi-layer coating film by sequentially coating at least one layer of a colored base coat paint and at least one layer of a clear coat paint on an object to be coated, wherein the top layer of the clear coat paint is claimed 1 to 4. A method for forming a multi-layer coating film, which comprises coating the coating composition according to any one of the above items.