JPH10231454A - Thermosetting water-base coating composition and method for applying the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermosetting water-base coating compsn. improved in smoothness and resistances to foaming and sagging by dissolving or dispersing a specific film-forming resin, a polyester polyol, and a curative in a water-base medium contg. a neutralizing base. SOLUTION: A polymer obtd. by the ring-opening addition reaction of a trifunctional or higher polyhydric alcohol, a 4-7C lactone, and a polycarboxylic anhydride in the presence of a catalyst (e.g. dibutyltin dilaurate) is reacted with a 6C or higher monoepoxide compd. to give a polyester polyol (B) having an acid value of 40 or lower, a hydroxyl value of 50-250, and a number average mol.wt. of 500-2,000, 50-80wt.% film-forming resin (A) having an acid value of 10-100, a hydroxyl value of 20-300, and a number average mol.wt. of 2,000-50,000, 3-50wt.% ingredient B, and 20-50wt.% curative (C) for ingredient B are dissolved or dispersed in a water-base medium contg. a neutralizing base in an amt. enough to neutralize ingredient A to a degree of neutralization of 50-120%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water-based coating composition which has a good coating workability (abrasion resistance and sagging resistance) and provides a high-appearance coating film excellent in smoothness.

[0002]

2. Description of the Related Art Water-based coating compositions are used as intermediate coatings and top coatings for automobiles. Conventionally, organic solvent-based paints have been mainly used as automotive paints, but there is a strong demand for a shift to water-based paints from the viewpoints of safety during painting, reduction of environmental pollution, and resource saving.

As an aqueous intermediate coating composition, for example, an aqueous intermediate coating containing a carboxylic acid group-containing resin, a urethane bond-containing diol and resin fine particles as main components (Japanese Patent Laid-Open Publication No.
No. 52973), and a thermosetting water-based paint containing a polycarboxylic acid resin, an amino resin, a linear low-molecular polyester diol and benzoin as main components (JP-A-4-9337).
No. 4) are known, but there are various problems when these are used as an intermediate coating.

[0004] That is, the above-mentioned water-based paint does not have sufficient smoothness of the coating film itself and the sharpness of the top coat, and furthermore, when compared with the conventional organic solvent-based paint, the appearance abnormality caused by bumping of water at the time of film curing is caused. "Waki" is easy to occur. This phenomenon is 20 ~
It is recognized even at a film thickness of 40 μm, which causes a reduction in the finished appearance. Furthermore, the water resistance of the coating film containing the linear low molecular weight polyester diol is not sufficient.

[0005] On the other hand, a metallic base paint containing a metallic pigment is applied as a top coat on a coated plate which has been subjected to undercoat and intermediate coat in automotive coating, and then the clear paint is applied by wet-on-wet coating without curing the coat. And a two-coat one-bake method in which the metallic base and the clear paint are combined and cured. In the metallic base paint used in this method, an excellent coating film appearance can be obtained by satisfactorily orienting a scaly glittering pigment such as aluminum.

Particularly for such uses, an aqueous metallic base coating composition containing a water dispersion of an amide group-containing organic resin and a hydrophilic group-containing polyurethane resin as a main component (JP-A-4-25582) is known. However, this paint is also not always sufficient because it tends to cause an abnormal appearance when heated and cured after applying the clear paint.

[0007]

SUMMARY OF THE INVENTION The present invention relates to an aqueous intermediate coating composition comprising a carboxylic acid group-containing resin, a hydrophilic group-carrying polyurethane resin and resin fine particles as main components.
Alternatively, it further improves the coating workability (waxability) of an aqueous metallic base paint containing an amide group-containing aqueous acrylic resin and a hydrophilic group-carrying polyurethane resin as a main component, and further improves the smoothness and water resistance of the obtained coating film. It is an object of the present invention to provide a water-based coating composition.

[0008] The occurrence of wrinkles is related to the non-volatile content of the paint at the time of painting. That is, when the paint is diluted with a volatile component such as water in order to reduce the viscosity to such a level that the paint can be applied, coating is caused by bumping of water in the coating film. Therefore, by reducing the water content, adding a component having a relatively low molecular weight and reacting with a curing agent to be incorporated in the cured coating film to the coating material, the nonvolatile content can be increased, and the occurrence of wrinkles can be suppressed. However, the addition of such components should not adversely affect other performances, especially sagging properties, water resistance, and the like. In this regard, such components proposed hitherto have not been satisfactory.

[0009]

Accordingly, the present invention uses a polyfunctional polyester polyol containing a ring-opened polymerized lactone chain as a reactive component capable of increasing the non-volatile content without increasing the viscosity. Solved the above problem.

[0010] Against this background, the present invention provides:
(A) a film-forming resin having an acid value of 10 to 100, a hydroxyl value of 20 to 300, and a number average molecular weight of 2,000 to 50,000; and (B) a trihydric or higher functional polyhydric alcohol and a C4 to C6 polyhydric alcohol. The lactone is obtained by reacting a monoepoxide compound having 6 or more carbon atoms with a ring-opening addition polymer of a lactone and a polycarboxylic acid anhydride, and has an acid value of less than 40 and a hydroxyl value of 50 to 2
50, a polyester polyol having a number average molecular weight of 500 to 2,000, and (C) a thermosetting aqueous solution obtained by dissolving or dispersing the curing agent of the component (A) and the component (B) in an aqueous medium containing a neutralizing base. A coating composition is provided.

The coating composition according to the invention is suitable, for example, as an intermediate coating for use in the finishing of automobile bodies or as a topcoat. When used in such applications, the coating compositions of the present invention can, of course, contain conventional additives, including pigments suitable for each application.

[0012] The present invention also provides a method of using the coating composition as an intermediate coating or a topcoat basecoat, for example, to form a composite coating on an automobile body.

Hereinafter, preferred embodiments of the present invention will be described in detail.

Component (A) The film-forming resin used in the aqueous coating composition must have at least an acid group corresponding to a resin acid value of 10 in order to be soluble or dispersible in an aqueous medium containing a neutralizing base. No. The resin must also have the necessary functional group density and molecular weight to provide a robust coating with sufficient crosslink density. Therefore, the film-forming resin (A)
Has an acid value of 10 to 100, preferably 30 to 80, a hydroxyl value of 20 to 300, preferably 50 to 200, and a number average molecular weight of 1,000 to 50,000, preferably 2,000.
It must be in the range of ~ 30,000. Resins that meet these requirements are well known in the coatings field,
Further, it has been conventionally used as a vehicle resin for water-based paint. Typical examples are acrylic resins and polyester resins (including alkyd resins).

The acrylic resin having an acid group and a hydroxyl group can be obtained by copolymerizing an acid group-containing ethylenic monomer, a hydroxyl group-containing ethylenic monomer, and another ethylenic monomer by a conventional method. For use in a base coating for a top coat, it is preferable to use an amide-containing ethylenic monomer as at least a part of another ethylenic monomer.

Preferred acrylic resins are 5 to 40% by weight of an amide group-containing ethylenic monomer, 3 to 15% by weight of an acidic group-containing ethylenic monomer, 10 to 40% by weight of a hydroxyl group-containing ethylenic monomer, and the remaining amount of other ethylenic monomers. Is a copolymer of

Examples of amide group-containing ethylenic monomers include acrylamide, methacrylamide, N, N-dimethylacrylamide, N, N-dimethylmethacrylamide, N, N-dibutylacrylamide, N, N-dibutylmethacrylamide, N , N-dioctylacrylamide, N, N-dioctylmethacrylamide, N-monobutylacrylamide, N-monobutylmethacrylamide, N-monooctylacrylamide, N-monooctylmethacrylamide and the like.

Examples of the acidic group of the acidic group-containing ethylenic monomer include a carboxyl group and a sulfonic group. Examples of the carboxyl group-containing monomer include a styrene derivative (eg, 3-vinylsalicylic acid, 3-vinylacetylsalicylic acid, etc.); an acrylic acid derivative (eg,
Acrylic acid, methacrylic acid, crotonic acid, isocrotonic acid and the like). Examples of the sulfonic acid group-containing ethylenic monomer include p-vinylbenzenesulfonic acid and 2-acrylamidopropanesulfonic acid.

The acidic group-containing ethylenic monomer may be a half ester, half amide or half thioester of a dibasic acid monomer. Examples of such are the half esters, half amides and half thioesters of maleic acid, fumaric acid and itaconic acid. The alcohol forming the ester includes one having 1 to 12 carbon atoms, such as methanol, ethanol, propanol, butanol, methyl cellosolve, ethyl cellosolve, dimethylaminoethanol, diethylaminoethanol, acetol, allyl alcohol, and propargyl alcohol. Preferred are butanol, dimethylaminoethanol, diethylaminoethanol, acetol, allyl alcohol, and propargyl alcohol. As a mercaptan forming a half thioester, a mercaptan having 1 to 12 carbon atoms
Such as ethyl mercaptan, propyl mercaptan and butyl mercaptan. Examples of the amine forming the half amide include those having 1 to 12 carbon atoms, such as ethylamine, diethylamine, butylamine, dibutylamine, cyclohexylamine, aniline, and naphthylamine. Among them, the half thioester has a problem in terms of odor, and half esters and half amides are preferably used. The half-esterification, half-thioesterification or half-amidation reaction is carried out according to a conventional method, at a temperature from room temperature to 120 ° C., and optionally using a tertiary amine as a catalyst.

Examples of the hydroxyl group-containing ethylenic monomer include 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate,
-Hydroxybutyl acrylate, 2,4-dihydroxy-4'-vinylbenzophenone, N- (2-hydroxyethyl) acrylamide, N- (2-hydroxyethyl) methacrylamide Praxel FA-1 and FM-
1 (manufactured by Daicel Chemical Industries, Ltd.).

Other ethylenic monomers are ethylenic monomers having no reactive functional group, such as styrenes (eg, styrene, α-methylstyrene) and acrylates (eg, methyl acrylate). , Ethyl acrylate, butyl acrylate or 2-ethylhexyl acrylate), methacrylates (eg, methyl methacrylate, ethyl methacrylate, butyl methacrylate, isobutyl methacrylate, p-butyl methacrylate), nitriles (eg, , Acrylonitrile), olefins (eg, ethylene, propylene) and the like. Based on the total weight of all the monomers, the proportion of the amide group-containing ethylenic monomer is 5 to 40%, preferably 8 to 30%, and the proportion of the acid group-containing monomer is 3 to 15%.
%, Preferably 5 to 13%, and the proportion of the hydroxyl group-containing monomer is 10 to 40%, preferably 13 to 30%. By using these monomers in the proportions described above, an acrylic resin having the above-mentioned acid value and hydroxyl value can be obtained. However, if the proportion of the hydrophilic monomer is too large, the water resistance of the coating film is adversely affected.

As is well known, a polyester resin is produced by polycondensing a polyhydric carboxylic acid and a polyhydric alcohol as essential components. As other reaction components, a small proportion of monocarboxylic acid, hydroxycarboxylic acid,
It can include lactones and the like, and the alkyd resins include drying or semi-drying oils and their resin acids.

Examples of the acid component include aromatic polyvalent carboxylic acids such as phthalic anhydride, isophthalic acid, terephthalic acid, trimellitic anhydride, tetrabromophthalic anhydride, tetrachlorophthalic anhydride, and pyromellitic anhydride; Stuff;
Hexhydrophthalic anhydride, tetrahydrophthalic anhydride,
Alicyclic polycarboxylic acids and acid anhydrides such as 1,4- and 1,3-cyclohexanedicarboxylic acid; aliphatic polyhydric acids such as maleic anhydride, fumaric acid, succinic anhydride, adipic acid, sebacic acid and azelaic acid There are polycarboxylic acids and anhydrides. It may contain small proportions of hydroxybenzoic acid, hydroxypivalic acid, 12-hydroxystearic acid and the like, and monocarboxylic acids such as benzoic acid, t-butylbenzoic acid and the like.

Examples of the polyhydric alcohol component include ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, and 2,2-diethyl-diol. 1,3-propanediol, neopentyl glycol, 1,9-nonanediol, 1,4-cyclohexanedimethanol, neopentyl glycol hydroxypivalate, 2-butyl-2-ethyl-1,3-propanediol, Diols such as -methyl-1,5-pentanediol, 2,2,4-trimethylpentanediol, hydrogenated bisphenol A, and trivalent or higher polyols such as trimethylolpropane, trimethylolethane, glycerin, and pentaerythritol There is.

In the case of alkyd resins, up to 30%, preferably up to 25%, in particular 10 to 10% of the total weight of all the reactants.
It must contain 20% of fatty acids having 6 or more carbon atoms or fats and oils containing the same. Examples of these fat components are castor oil, linseed oil, dehydrated castor oil, tung oil, safflower oil, soybean oil, tall oil, coconut oil, palm kernel oil and their fatty acids. Palm oil and palm kernel oil are preferred.

When a polyester resin is used for the intermediate coating, a part of the polyhydric alcohol component may include a hydroxyl-terminated polyalkadiene diol alone, a hydrogenated product thereof alone, or a mixture thereof. These diols are derived from conjugated alkadiene oligomers or polymers having a degree of polymerization of 5 to 50. The number average molecular weight is 1,
It is preferably in the range of 000 to 4,000, especially 1,500 to 3,000. Preferred are 1,4-polyisoprenediol, 1,4- and 1,2-polybutadiene diol, and their hydrogenated products. As a commercial product, Epol (hydrogenated polyisoprene diol, molecular weight 186)
0, average degree of polymerization 26, manufactured by Idemitsu Petrochemical Co., Ltd.), PIP
(Polyisoprene diol, molecular weight 2,200, average degree of polymerization 34, manufactured by Idemitsu Petrochemical Co., Ltd.), Polytail HA
(Hydrogenated polybutadiene diol, molecular weight 2,200,
Average polymerization degree 39, manufactured by Mitsubishi Chemical Corporation, polytail H (hydrogenated polybutadiene diol, molecular weight 2,350, average polymerization degree 42, manufactured by Mitsubishi Chemical Corporation), R-45HT (polybutadiene diol, molecular weight 2,270, Average degree of polymerization 4
2, Idemitsu Petrochemical Co., Ltd.). By using these diols as part of the polyhydric alcohol component, a high molecular weight polyester resin which gives a relatively low viscosity at a high degree of neutralization can be obtained. However, if too much is used, the water dispersibility decreases, and a satisfactory coating film hardness cannot be obtained.

When a polyester resin is used for the intermediate coating, the synthesized oil-free polyester may be mixed with a polyisocyanate, especially a diisocyanate compound (hereinafter referred to as (C)).
When the urethane-modified polyester resin obtained by reacting the component (as will be described later in connection with the component) with an NCO / OH equivalent ratio of less than 1 is used as at least a part of the component (A), the storage stability and the abrasion resistance are improved. , Sharpness and chipping resistance are improved.

The synthesis of the polyester is carried out by a conventional method in a nitrogen stream, for example, at 150 to 250 ° C. for 4 to 1 hour.
It can be carried out by heating for 0 hour and condensing. In this case, a known catalyst such as dibutyltin oxide, antimony trioxide, zinc acetate, manganese acetate, cobalt acetate, calcium acetate, lead acetate, tetrabutyl titanate, and tetraisopropyl titanate can be used. The reaction components may be added all at once, or may be added in several portions.

The molar ratio of the reaction components and the reaction conditions should be adjusted so that the acid value, hydroxyl value and number average molecular weight of the obtained polyester resin reach the above-mentioned ranges.

The component (A) of the present invention can be dissolved or dispersed in an aqueous medium containing 0.3 to 1.2 equivalents, preferably 0.5 to 1.0 equivalent, of a base relative to the resin acid value. it can. As the base, an inorganic base such as an alkali metal hydroxide and aqueous ammonia, and methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, isopropylamine, diisopropylamine, diethylenetriamine, triethylenetetramine, monoethanolamine, Diethanolamine, 2-amino-2-methylpropanol, morpholine, N-methylmorpholine, N-ethylmorpholine,
There are amines such as piperazine, dimethylethanolamine, diethylethanolamine and dimethyldodecylamine. Triethylamine, dimethylethanolamine,
Diethylethanolamine is preferred.

(B) Component Ring-opening addition (polymerization) of a cyclic lactone using an active hydrogen compound as an initiator is well known. The polyester polyol used as the component (B) in the present invention includes:
This reaction can be used to produce a precursor having an acid group from a trihydric or higher-functional polyhydric alcohol, a lactone, and a polycarboxylic anhydride, and then reacting it with a monoepoxide compound. it can.

There are two ways to prepare a precursor having an acid group. In the first method, a lactone is subjected to a ring-opening addition (polymerization) reaction using a polyhydric alcohol as an initiator. A carboxyl group is introduced by reaction with a carboxylic anhydride. In the second method, an acid group is first introduced into a polyhydric alcohol by reaction with an acid anhydride, and then the product is used as an initiator to carry out a ring-opening addition reaction of a lactone.

When the thus obtained precursor is reacted with a monoepoxide, the epoxy group is opened by a reaction with a carbosyl group to obtain a desired polyester polyol having a secondary alcoholic hydroxyl group.

All of the above-mentioned reactions do not involve the formation of reaction by-products such as water or alcohol. Therefore, the molecular weight distribution of the product is narrow (eg, Mw / Mn <1.
8) Since it does not contain unnecessary low molecular weight components, it does not adversely affect the water resistance of the coating film. Further, by changing the number of moles of the reaction components, the content and hydrophobicity of the soft segment can be changed as desired.

Examples of trihydric or higher polyhydric alcohols used as starting materials include glycerin, trimethylolpropane, ditrimethylolpropane, pentaerythritol, dipentaerythritol and the like. Carbon number 4-7
Examples of lactones include ε-caprolactone, γ-valerolactone, δ-valerolactone, γ-butyrolactone, and the like. ε-caprolactone, γ-valerolactone and γ-butyrolactone are preferred. Examples of polycarboxylic anhydrides include hexahydrophthalic anhydride, succinic anhydride, maleic anhydride and the like, with alicyclic and aliphatic dicarboxylic anhydrides being preferred.

As is well known, the lactone ring-opening addition reaction requires a catalyst such as dibutyltin oxide or tetrabutyl titanate.

The monoepoxide compounds having 6 or more carbon atoms to be reacted with the precursor are AOEX24 and AOEX68.
(All are mixtures of α-olefin monoepoxides manufactured by Daicel Chemical Industries), α-olefin monoepoxides having 6 or more carbon atoms such as styrene oxide; butyl glycidyl ether, phenyl glycidyl ether, decyl glycidyl ether, cresyl glycidyl ether, nonyl Glydyl ethers such as phenyl glycidyl ether and 2-ethylhexyl glycidyl ether; Cardura E5, Cardura E10, PESID (all manufactured by Shell Chemical)
Glycidyl esters such as; 1,2-epoxyhexanol, 1,2-epoxyoctanol, 1,2-
Monoepoxide compounds having a hydroxyl group such as epoxydecanol, hydroxybutyl glycidyl ether, hydroxyoctyl glycidyl ether, hydroxyphenyl glycidyl ether, and hydroxycyclohexyl glycidyl ether. The Cardura E series is preferred.

The polyester polyol which can be used as the component (B) has an acid value of 40 or less, preferably 5 to 30, and a hydroxyl value of 50 to 250, preferably 70 to 220. The acid value and the hydroxyl value are related to the hydrophilicity and the crosslink density, respectively, and if too large, the water resistance of the coating film is adversely affected. The number average molecular weight is in the range of 500 to 2,000. If the molecular weight is too large, the effect of increasing the nonvolatile matter without increasing the coating viscosity is not exhibited.

The curing agent for the component (C) polyester resin is well known in the coatings field. One of them is an amino resin, specifically, di-,
Tree, tetra-, penta-, hexa-methylolmelamine and their alkyl etherified products (alkyl is methyl, ethyl, propyl, isopropyl, butyl, isobutyl, etc.), urea-formaldehyde condensate, urea
Melamine co-condensates and the like can be mentioned.

Of the above, melamine resins are preferred, and specifically, the following are suitable. Mitsui Cytec's Mycoat 212, Cymel 254, Cymel 202, Cymel 303, Cymel 325, Cymel 1156, etc.
Mitsui Toatsu Chemical Co., Ltd. U-Van 20N, U-Van 20SB,
Sumitomo M-50 manufactured by Sumitomo Chemical Co., Ltd.
W, Sumimar M-40N, Sumimar M-30W and the like. When using an amino resin as a curing agent, para-toluenesulfonic acid, dodecylbenzenesulfonic acid,
Sulfonic acids, such as dinonylnaphthalenesulfonic acid, and salts of these sulfonic acids with amines that dissociate at the baking temperature of the coating can be used as catalysts.

A blocked polyisocyanate compound obtained by blocking a polyisocyanate compound with a blocking agent may be used as a curing agent.

Examples of the polyisocyanate compound include aliphatic diisocyanates such as hexamethylene diisocyanate (HMDI) and trimethylhexamethylene diisocyanate, alicyclic diisocyanates such as isophorone diisocyanate (IPDI), and aromatic compounds such as xylylene diisocyanate (XDI). Aliphatic diisocyanate, tolylene diisocyanate (TDI), 4,4'-
Examples include aromatic diisocyanates such as diphenylmethane diisocyanate (MDI), dimers and trimers of these diisocyanate compounds, adducts with polyhydric alcohols such as trimethylolpropane, and water.

Examples of the blocking agent include oximes such as methyl ethyl ketoxime, acetoxime, cyclohexanone oxime, acetophenone oxime and benzophenone oxime, phenols such as m-cresol and xylenol, methanol, ethanol, butanol,
Alcohols such as ethylhexanol, cyclohexanol, ethylene glycol monoethyl ether, ε-
There are lactams such as caprolactam, diketones such as malonic acid diester and acetoacetic ester, and mercaptans such as thiophenol. Polyisocyanate compounds blocked with diketones (active methylene compounds) are preferred. When a blocked polyisocyanate compound is used, a tin compound such as dibutyltin dilaurate is added as a catalyst.

Coating Composition The coating composition of the present invention is prepared by dissolving or dispersing the polyester resin of the component (A) in an aqueous medium containing a neutralizing base to produce an aqueous varnish, and then adding the polyester polyol of the component (B) to the aqueous varnish. And by adding and dispersing the curing agent of component (C). At this time, the neutralizing base is used to neutralize the polyester resin in a degree of neutralization of 50 to 120%, preferably 70 to 100%.
% Used to neutralize.

[0045] The coating compositions of the present invention can contain conventional pigments. Examples thereof include titanium dioxide, zinc white, carbon black, yellow iron oxide, various lake pigments, aluminum flakes, coloring pigments such as titanium mica, glitter pigments, and extenders such as calcium carbonate, barium sulfate, and clay. When the coating composition is used as a base coat coating, a coloring pigment and / or a bright pigment are added. When used as an intermediate coating, barium sulfate,
An extender pigment such as calcium carbonate or clay is used in combination with the coloring pigment. The pigment is prepared by using the component (A) alone or a part of the aqueous varnish of the components (A) and (B) to form a pigment paste, which is added to the remaining aqueous varnish together with other components. Of course, other conventional additives such as an antifoaming agent, a dispersant, and a surface conditioner may be added.

The proportion of the component (A), the component (B) and the component (C) in the paint is such that the component (A) is 35 to 75%, preferably 40 to 6%, based on the total weight of the solid content thereof.
0% by weight, component (B) is 5 to 50%, preferably 10 to 10%.
35% by weight, component (C) is 10 to 40% by weight, preferably 20 to 30%. In each case, component (A) is the main component, and component (B) is the auxiliary component.
The component (A) must be contained more than the component (B).

The coating compositions of the present invention are particularly suitable for use in basecoats used, for example, for painting and finishing automotive bodies. In this coating method, the metallic or solid color base paint of the present invention is applied to the surface on which the electrodeposition coating layer and the intermediate coat are applied, and an aqueous or powder clear coat paint is applied thereon by wet-on-wet, Both can be baked and finished simultaneously. In this case, since the base paint is minimized in wrinkles, for example, there is no unevenness in the orientation of the metallic pigment, and a coating film having a high quality appearance can be obtained.

In the following production examples and examples,
“Parts” and “%” are based on weight unless otherwise specified.

Production Example 1 (aqueous polyester resin) 20.51 parts by weight of ethylene glycol, 12.91 parts by weight of trimethylolpropane, and phthalic anhydride
After adding 71 parts by weight and performing an esterification reaction at 160 to 220 ° C. for 5 hours, 14.88 of trimellitic anhydride is further added.
Parts by weight and reacted at 180 ° C. for 1 hour to give an acid value of 5
A polyester resin having 0, a hydroxyl value of 60 and a number average molecular weight of 2,000 was obtained.

The melamine resin Cymel 254 manufactured by Mitsui Cytec Co., Ltd.
70/30 (all in a non-volatile content ratio). After stirring at 60 ° C. for 1 hour, triethylamine was added to the mixture so as to have a neutralization rate of 100%. After stirring at 60 ° C. for another 15 minutes, the non-volatile
% Ion-exchanged water was added over 1 hour.
Thus, an aqueous varnish (I) was obtained.

Production Example 2 0.2 parts by weight of dibutyltin oxide was added to 14.67 parts by weight of coconut oil fatty acid and 27.31 parts by weight of trimethylolpropane, followed by stirring at 200 ° C. for 30 minutes. After cooling to 80 ° C., 30.72 parts by weight of 1,4-dicyclohexyldicarboxylic acid, 16.5 parts by weight of adipic acid, 10.0 parts by weight of dimethylolpropionic acid, 7.82 parts by weight of neopentyl glycol, Epol (Idemitsu Petrochemical)
5.67 parts by weight was added and reacted at 150 to 220 ° C. for 4 hours. After cooling this to 80 ° C, Plaxel FM-
1 (manufactured by Daicel Chemical Industries, Ltd.) and 9.23 parts by weight
The reaction was carried out at 50 ° C. for 1 hour to obtain an alkyd resin having a number average molecular weight of 4,500 and an acid value of 50.

The melamine resin Mycoat 212 manufactured by Mitsui Cytec Co., Ltd.
70/30 (all in a non-volatile content ratio). This was stirred at 100 ° C. for 1 hour and then cooled to 50 ° C. N, N-dimethylethanolamine was added to the mixture so that the neutralization ratio became 100%. 15 more at 60 ° C
After stirring for 1 minute, ion-exchanged water was added over 1 hour so that the nonvolatile content became 40% while maintaining the temperature. Thus, an aqueous varnish (II) was obtained.

Production Example 3 (Aqueous alkyd resin) 14.67 parts by weight of coconut oil fatty acid and 27.31 parts by weight of trimethylolpropane were added, and the mixture was heated and stirred at 210 ° C. for 1 hour. After cooling to 80 ° C., 30.72 parts by weight of 1,4-cyclohexanedicarboxylic acid and 16.5 parts of adipic acid were used.
3 parts by weight, 1.30 parts by weight of neopentyl glycol and 22.23 parts by weight of phthalic anhydride were added.
After reacting at 0 ° C. for 5 hours, 19.2 parts by weight of trimellitic anhydride was further added and reacted at 180 ° C. for 1 hour to obtain an alkyd resin having an acid value of 60, a hydroxyl value of 80 and a number average molecular weight of 4500. Obtained. N, N-dimethylethanolamine was added to the mixture so that the neutralization rate became 100%. 6
After stirring at 0 ° C. for further 15 minutes, ion-exchanged water was added over 1 hour while maintaining the temperature so that the nonvolatile content became 40%, to obtain an aqueous varnish (III).

Production Example 4 (Aqueous amide group-containing acrylic resin) Ethylene glycol monomethyl ether 76 was added to a reaction vessel.
A part by weight was charged and heated to 100 ° C. 15 parts by weight of styrene, 30 parts by weight of acrylamide, 63 parts by weight of methyl methacrylate, 48 parts by weight of 2-hydroxyethyl methacrylate, 117 parts by weight of n-butyl acrylate, 27 parts by weight of methacrylic acid, 3 parts by weight of azobisisobutyronitrile 243 parts by weight of a monomer mixture consisting of
The reaction was continued at the same temperature for 1 hour, and the acid value was 58, the hydroxyl value was 70, and the number average molecular weight was 1200.
0 acrylic resin was obtained.

Then, N, N are adjusted so that the neutralization ratio becomes 80%.
-Add dimethylethanolamine and add another 1 at 60 ° C.
After stirring for 5 minutes, ion exchange was added over 1 hour so that the volatile content was 40% while maintaining the temperature, to obtain an aqueous acrylic resin varnish (IV).

Production Example 5 (Polyester polyol) Trimethylolpropane (TMP) was added to 201 parts by weight of ε-
669.15 parts by weight of caprolactone and 1.22 parts by weight of dibutyltin oxide were added, and the mixture was stirred at 130 ° C. for 3 hours. To this, 163.95 parts by weight of hexahydrophthalic anhydride was added and stirred at 100 ° C. for 3 hours. Further, 76.00 parts by weight of Cardura E10 (aliphatic monoepoxide manufactured by Shell Chemicals) was added thereto, and the mixture was stirred at 150 ° C. for 3 hours. Number average molecular weight 900, hydroxyl value 190mgK
Polyester polyol (I) having an OH / g and an acid value of 30 mgKOH / g was obtained.

Production Examples 6 to 8 (Polyester Polyol) Polyester polyols (II) to (IV) were synthesized under the same reaction conditions as in Production Example 5 by changing the blending of the raw materials as follows.

Production Example {Raw Material (Mole) 5 6 7 8} ─ ──── ──── ──── Trimethylolpropane 1.0 ── ── 1.0 Ditrimethylolpropane ── 1.0 ── ペ ン タ Pentaerythritol ── ── 1.0 ── ε-Caprolactone 4.0 ── ── 4.0 γ-valerolactone ── 4.5 ── γ γ-butyrolactone ── 4.8 ── hexahydrophthalic anhydride 0.71 ── 1.52 コ succinic anhydride ── 0.936 ── マ maleic anhydride ── ── ── 0.71 Cardula E10 0.30 0.40 0.91 0.71 ポ リ エ ス テ ル Polyester polyol (I) (II) (III) (IV) Acid value 30 70 5 30 Hydroxyl value 190 150 190 190 Number average molecular weight 900 1000 1500 1750 ───────────────────────────────────

Pigment pace for intermediate coat / white base paint
Against DOO creation aqueous varnish (I) ~ (IV) each having a nonvolatile 100 parts, was added pigment formulation shown in Table 1. Glass beads were further added to the mixture, and a high shear was applied with a paint conditioner. The glass beads were filtered and removed to obtain a pigment dispersion paste.

The pigment dispersion paste for silver metallic
An aluminum pigment paste was added to each of the prepared aqueous varnishes (I) to (IV) in an amount shown in Table 1 to 100 parts of the nonvolatile components. This was sufficiently stirred with a lab disper to obtain a pigment dispersion paste.

[0061]

[Table 1]

Aqueous Intermediate Coating Compositions Examples 1 to 6 and Comparative Examples 1 and 3 The total pigment weight / non-volatile resin weight = 24% and the ratio of main resin / hardener to the pigment dispersion paste are shown in Table 2. Aqueous varnish, a melamine resin or a blocked isocyanate resin was added so as to obtain an aqueous intermediate coating composition. Example 7 and Comparative Example 2 An aqueous varnish (II) was added to the above pigment dispersion paste so that the total pigment weight / the resin non-volatile content = 24% and the ratio of the main resin / hardener was the value shown in Table 2. Thus, an aqueous intermediate coating was obtained.

Aqueous White Base Coating Composition Examples 8 to 9, 11 and Comparative Examples 4, 6 In the above pigment dispersion paste, the total pigment weight / resin non-volatile content weight = 18%, and the ratio of main resin / curing agent is shown in Table 3. An aqueous varnish, a melamine resin or a blocked isocyanate resin was added to obtain the indicated value to obtain an aqueous white base paint.

Example 10 and Comparative Example 5 An aqueous varnish (II) was added to the above-mentioned pigment-dispersed paste so that the total pigment weight / the resin non-volatile content = 18% and the ratio of the main resin / hardener was as shown in Table 3. ) Was added to obtain an aqueous white base paint.

Preparation of Water-based Aluminum Metallic Base Coating Example 12 The pigment dispersion paste was mixed with a water-based material so that the total pigment weight / resin non-volatile content = 5% and the ratio of main resin / hardener to the values shown in Table 3. Varnish (II) was added to obtain a water-based aluminum metallic base paint.

Examples 13 to 14 and Comparative Example 6 An aqueous varnish was added to the above-mentioned pigment-dispersed paste so that the total pigment weight / resin nonvolatile weight = 5% and the ratio of main resin / hardener to the values shown in Table 3. And a melamine resin or a blocked isocyanate resin were added to obtain an aqueous aluminum metallic base paint.

Coating Method (Part 1) Each of the coating compositions of Examples 1 to 7 and Comparative Examples 1 to 3 4, diluted with ion-exchanged water to 60 seconds / 20 ° C., sprayed onto a commercially available test plate coated with an electrodeposition coating film so as to have a dry film thickness of 20 μm, and set for about 7 minutes. After preheating at 80 to 120 ° C for 10 minutes, baking was performed at 130 to 160 ° C for 25 minutes to obtain an intermediate coating film.

Performance Evaluation Each intermediate coating composition was evaluated for the limit film thickness and sagging limit. The coating film smoothness was evaluated after applying a clear coating on the intermediate coating film and baking.
Table 2 shows the results.

[0069]

[Table 2]

Evaluation Method Waxy limit film thickness: The waki limit film thickness was shown as the maximum film thickness without a coating film defect on a coated plate which was coated at 15 μm in the thin film portion and 70 μm in the thick film portion. Sagging limit film thickness: The sagging limit film thickness was determined at a maximum film thickness without a coating film defect of sagging on a coated plate which was coated at 15 μm in the thin film portion and 70 μm in the thick film portion. Coating smoothness: visually evaluated according to the following criteria. ○ ・ ・ ・ ・ Good smoothness △ ・ ・ ・ ・ Slightly poor smoothness (with rounds) × ・ ・ ・ ・ ・ Smoothness poor (skin rough, orange peel)

Production Example 9 (Acrylic resin for clear powder coating) 63 parts of xylene was charged into a reaction vessel equipped with a thermometer, a stirrer, a cooling pipe, a nitrogen introduction pipe, and a dropping funnel.
Heated to ° C. Using a dropping funnel, a mixed solution of 45 parts of glycidyl methacrylate, 20 parts of styrene, 27 parts of methyl methacrylate, 8 parts of isobutyl methacrylate, 6.5 parts of t-butyl peroctoate, and 6 parts of xylene was added to this container. The solution was dropped at a constant speed in 3 hours. After the completion of the dropping, 0.1 part of t-butyl peroctoate and 7 parts of xylene were dropped at a constant speed for 30 minutes using a dropping funnel. After completion of the dropwise addition, the mixture was kept at 130 ° C. for 1 hour, and then xylene was distilled off under reduced pressure to obtain an acrylic resin.

Production Example 10 (Surface modifier for powder coating) 90 parts by weight of xylene was charged into a reaction vessel equipped with a thermometer, a stirrer, a cooling pipe, a nitrogen introduction pipe, and a dropping funnel.
Heated to 20 ° C. Ethyl acrylate 50 parts by weight, n-butyl acrylate 50
Parts by weight and 3 parts by weight of t-butylperoxy-2-ethylhexanoate were dropped at a constant rate over 3 hours. After the completion of the dropwise addition, the mixture was held for 30 minutes, and then 0.3 parts by weight of t-butylperoxy-2-ethylhexanoate and 10 parts by weight of xylene were added dropwise at a constant rate over 30 minutes using a dropping funnel. After completion of the dropwise addition, the mixture was further kept at 120 ° C. for 2 hours, and then xylene was removed by distillation under reduced pressure to obtain a surface conditioner.

Production Example 11 (clear powder coating) 100 parts of the epoxy group-containing acrylic resin of Production Example 9, 27.3 parts of decanedicarboxylic acid, 2,6-di-t-butyl-
A mixture obtained after mixing 1.27 parts of 4-methylphenol, 2.54 parts of tris (4-t-butylphenyl) phosphite, 0.76 parts of the surface conditioner of Preparation Example 10, and 0.64 parts of benzoin. Was melt-kneaded using a Busconida (manufactured by Buss Corp.), extruded, and cooled to obtain a solid coating composition. This was ultracentrifugally crushed using an “Ultracentrifugal crusher” manufactured by Mitamura Riken Kogyo Co., Ltd., classified (150 mesh), and 0.2 part of Aerosil R- manufactured by Nippon Aerosil Co., Ltd. was added to 100 parts of the classified paint. 974 was added and mixed well to obtain a powder coating composition having an average particle diameter of 25 μm.

Coating Method (Part 2) Coatings of Examples 8 to 10, 13 to 14 and Comparative Examples 4 to 5 were applied to commercially available water-polished test plates coated with an electrodeposition coating and an intermediate coating, respectively. Was applied by air spraying so that the thickness of the dried coating film was about 16 μm, and the mixture was set for about 7 minutes to form a base coating film. This was pre-heated at 80 to 120 ° C. for 10 minutes, and then Mac O-37 was further added.
A clear paint of 0 or O-150 (both made by Nippon Paint Co., Ltd.) was sprayed by air so that the thickness of the dried coating film was about 40 μm. After setting this for about 7 minutes, it was baked at 130 to 160 ° C. for 25 minutes to obtain a coating film.

Coating Method (Part 3) The coatings of Examples 11 to 12 and Comparative Example 6 were applied to a commercially available water-polished test plate to which an electrodeposition coating film and an intermediate coating film were applied, respectively. The base coating film was formed by air spray coating so that the thickness became about 16 μm and setting for about 7 minutes. This was preheated at 80 to 120 ° C. for 10 minutes, and then the powder coating composition of Production Example 11 was electrostatically coated to a film thickness of 60 μm by wet-on-wet and baked at 150 ° C. for 25 minutes. A painted plate was obtained.

Method for Forming Coating Film (Part 4) Example 15 The paint of Example 1 was applied to a commercially available test plate coated with an electrodeposition coating film by air spraying so that the thickness of the dried coating film became 20 μm. For about 7 minutes to form an intermediate coating film. This was preheated at 80-120 ° C for 10 minutes. Ford Cup No. 60 seconds / 2 using 4
The aqueous white base paint of Example 8 diluted with ion-exchanged water to 0 ° C. was applied by air spray coating so that the film thickness after drying became 20 μm, and set for about 7 minutes. This was preheated again at 80-120 ° C for 10 minutes. A clear paint of Mac O-150 (manufactured by Nippon Paint Co., Ltd.) was sprayed thereon so that the thickness of the dried coating film became about 40 μm. After setting this for about 7 minutes,
Baking was performed at 60 ° C. for 25 minutes to obtain a cured coating film. In the same procedure, the paints of Example 16 and Comparative Examples 4 to 5 were applied to a commercially available test plate coated with an electrodeposition coating film in the combination of the paints shown in Table 4 and baked under the same conditions. A cured coating was obtained.

Evaluation of Performance The intermediate coating and the base coating were evaluated for the limit film thickness and the critical film thickness for sagging, and the clear coat on the base coat was evaluated for smoothness and water resistance. The results are shown in Tables 3 and 4.

[0078]

[Table 3]

[0079]

[Table 4]

Evaluation method Waki limit film thickness: The waki limit film thickness was shown as a maximum film thickness without any coating film defects on a coated plate which was coated at 15 μm in the thin film portion and 70 μm in the thick film portion. Sagging limit film thickness: The sagging limit film thickness was determined at a maximum film thickness without a coating film defect of sagging on a coated plate which was coated at 15 μm in the thin film portion and 70 μm in the thick film portion. Coating smoothness: Visually evaluated according to the following criteria. ○ ・ ・ ・ ・ Good smoothness △ ・ ・ ・ ・ Slightly poor smoothness (with rounds) × ・ ・ ・ ・ ・ Smoothness poor (skin rough, orange peel) Water resistance: hot water at 40 ° C overcoated steel sheet For 240 hours, and then allowed to stand at 20 ° C. and a temperature of 75% for 24 hours, and then subjected to a tape peel test (100 pieces of 1 × 1 mm) to evaluate the residual ratio of the coating film. ○ ・ ・ ・ ・ ・ ・ ・ 100/100 (no peeling) × ・ ・ ・ ・ ・ 99/100 or less

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁶ Identification code FI C09D 133/00 C09D 133/00 161/20 161/20 163/00 163/00 175/04 175/04 201/06 201/06

Claims (13)

[Claims] (A) an acid value of 10 to 100 and a hydroxyl value of 20 to
(B) a ring-opening addition polymerization of a polyhydric alcohol having 3 or more functional groups, a lactone having 4 to 7 carbon atoms, and a polycarboxylic acid anhydride. Polyester polyol having an acid value of less than 40, a hydroxyl value of 50 to 250, and a number average molecular weight of 500 to 2,000, which is obtained by reacting a product with a monoepoxide compound having 6 or more carbon atoms; (C) the component (A) and (B) A thermosetting aqueous coating composition obtained by dissolving or dispersing a component curing agent in an aqueous medium containing a neutralizing base. 2. The composition according to claim 1, wherein said component (A) and said component (B) are non-volatile components.
(A) based on the total weight of component (C) and component (C)
2. The thermosetting aqueous coating composition according to claim 1, comprising 50 to 80% of the component, 3 to 50% of the component (B), and 20 to 50% of the component (C). 3. The composition according to claim 1, wherein said component (A) is an acrylic resin, a polyester resin, or a mixture of both.
Thermosetting coating composition. 4. The acrylic resin has a monomer composition of 5 to 40% by weight of an amide group-containing ethylenic monomer,
4. The thermosetting aqueous coating composition according to claim 3, comprising 3 to 15% by weight of an acid group-containing ethylenic monomer, 10 to 40% by weight of a hydroxyl group-containing ethylenic monomer, and the remaining other ethylenic monomers. 5. The thermosetting aqueous coating composition according to claim 3, wherein said polyester resin is an oil-free polyester resin or an alkyd resin. 6. The component (B) comprises, before the reaction with the monoepoxide compound, (i) a polyhydric alcohol selected from the group consisting of trimethylolpropane, ditrimethylolpropane and pentaerythritol; A lactone selected from the group consisting of caprolactone, γ-valerolactone and γ-butyrolactone, and (iii) an acid anhydride selected from the group consisting of hexahydrophthalic anhydride, succinic anhydride and maleic anhydride, (i) is first reacted (ii) and then (iii) stepwise, or (i) is first reacted (iii) and then (i)
3. The thermosetting aqueous coating composition according to claim 1, which is produced by reacting i) stepwise. 7. The component (C) comprises a melamine resin and / or
3. The thermosetting aqueous coating composition according to claim 1, which is a blocked polyisocyanate. 8. A thermosetting aqueous coating composition according to claim 1, which comprises a pigment and a conventional coating additive. 9. A thermosetting aqueous coating composition according to claim 8, which is applied as a base coat on the surface of the substrate on which the electrodeposition coating film and the intermediate coating film are applied, and a clear coat coating material is wetted before curing. A method for forming a composite coating film, wherein the coating is performed on-wet and the base coat and the clear coat are simultaneously baked and cured. 10. The method according to claim 9, wherein the clearcoat paint is an acrylic / melamine or acid / epoxy paint. 11. The method according to claim 9, wherein the clearcoat paint is a powder paint. 12. The thermosetting coating composition according to claim 8, which is applied as an intermediate coating on the surface of the substrate to which the electrodeposition has been applied,
A method for forming a composite coating film, further comprising applying a coloring paint as a top coat. 13. A thermosetting coating composition according to claim 8, which is applied as an intermediate coating on the surface of the substrate to which the electrodeposition has been applied,
Before curing, the thermosetting aqueous coating composition according to claim 8 is applied as a base coat, and before the curing, a clear coat paint is applied, and the intermediate coat, the base coat and the clear coat are baked simultaneously. To form a composite coating film.