WO2010143032A1

WO2010143032A1 - Coating compositions, a process for finish coating, and coated articles

Info

Publication number: WO2010143032A1
Application number: PCT/IB2010/000908
Authority: WO
Inventors: Tetsu Konishi; Rui Niimi; Takaaki Kawai
Original assignee: Basf Coatings Japan Ltd.
Priority date: 2009-06-11
Filing date: 2010-04-19
Publication date: 2010-12-16
Also published as: JP2010285549A; JP5456381B2

Abstract

To provide coating compositions which can form coated films with excellent clear-on-clear adhesive properties, recoating properties, water resistance, acid resistance, external appearance, coated film hardness and scratch resistance, and which have adequate stability as 1-component coating materials. [The Means of Solution] Coating compositions, characterized in that they contain, as essential components: (A) polyester resins, containing 2 or more carboxyl groups in 1 molecule (B) radical copolymers containing 2 or more carboxyl groups in 1 molecule (C) radical copolymers containing 2 or more epoxy groups in 1 molecule (D) crosslinking agents which react with hydroxyl groups and characterized in that: the solubility parameters (SP values) of all of (A), (B) and (C) are 9.5 to 11.2 (cal/cm3)^1/2; the ratios of the numbers of epoxy groups in component (C) versus the total number of carboxyl groups in component (A) and component (B) are from 0.7 to 1.3 as ratios of equivalents; and the percentage content of component (D) is from 1 to 15% by mass in the total solid resin fraction.

Description

Coating compositions, a process for finish coating, and coated articles.

[Technical Field] [0001]

The present invention relates to new coating compositions, a process for finish coating, and coated articles. Described in further detail, it relates to coating compositions, a process for finish coating, and coated articles which may be obtained by this means, where, in the field of automobile coatings, coatings may be formed with high recoating properties and excellent clear-on-clear adhesive properties, water resistance, acid resistance, external appearance, coated film hardness and scratch resistance; and it is similarly also possible to form overcoats on clear coatings, having satisfactory stability as a 1- component paint.

[0002]

There have recently been demands in the field of automobile coatings for obtaining coated films which have, in top coats, high weather resistance and acid resistance, and an excellent external appearance.

Known techniques which use acid/epoxy cross-linking are, as clear coating compositions, liquid coating compositions containing 0.01 to 3.0 parts by weight of an onium salt per 100 parts of: (a) compounds which have at least 2 carboxyl groups; (b) compounds which have at least 2 epoxy groups; and (c) a solid resin fraction (cf., for example, Patent Reference 1). However, the water resistance and clear-on-clear adhesive properties are inadequate.

[0003]

Known resin compositions for thermosetting coatings which can form coated films having good storage stability and also excellent low temperature hardening properties, acid resistance, scratch resistance, and the like, are resin compositions for coatings, having: (A) copolymers containing half ester groups, wherein the weight average molecular weights are in the range 1,500 to 10,000, formed by copolymerizing: (a) polymerizable unsaturated monomers, formed by half- esterification of polymerizable unsaturated compounds containing acid anhydride groups with monoalcohols, (b) polymerizable unsaturated monomers, containing carboxyl groups with 9 to 24 carbon atoms, which are half esters of polymerizable unsaturated monomers containing hydroxyl groups and compounds containing acid anhydride groups, and (c) other copolymerizable monomers; (B) polyesters, containing carboxyl groups, of number average molecular weights 800 to 5,000, formed by half esterification of polyester polyols and compounds containing acid anhydride groups; and (C) copolymers of epoxy equivalents, 200 to 800, alkoxysilyl equivalents, 300 to 10,000, and weight average molecular weights 1,500 to 10,000 (cf., for example, Patent Reference 2). However, the water resistance and clear-on-clear adhesive properties in these coating compositions are inadequate .

[0004]

Further known techniques for increasing the solid fractions of curable resins having acid groups and epoxy groups, together with raising cross-linking density, are thermosetting resin compositions characterized in that there are: (a) 10 to 70% by mass of acrylic-based polycarboxylic acids having carboxyl groups and carboxylic acid ester groups, obtained by the reaction of (i) (1) copolymers obtained by copolymerization of ethylenic unsaturated monomers containing acid anhydride groups and (2) ethylenic unsaturated monomers having no acid anhydride groups and (ii) monoalcohols having 1 to 12 carbon atoms; (b) 10 to 70% by mass of polyester carboxylic acids, obtained from multifunctional polyols, lactone compounds and acid anhydride; and (c) 10 to 80% by mass of acrylic-based polyepoxides having hydroxyl groups and epoxy groups, and wherein the branching in the abovementioned polyester polycarboxylic acids (b) is 70% or more, (cf., for example, Patent Reference 3). However, the water resistance and clear-on-clear - A -

adhesive properties in these coating compositions are inadequate .

[0005] Further known coating compositions, as coating compositions whereby coated films may be obtained having, in top coat coatings, high weather resistance and acid resistance, and an excellent external appearance, and wherein sufficient storage stability may be obtained to be able to withstand use in circulation, contain, as essential components, (A) resins containing 2 or more epoxy groups in 1 molecule, with acid values of 100 to 300 mg KOH/g and weight average molecular weights of 2,000 to 30,000, obtained by copolymerization of radical polymerizable monomers containing carboxyl groups and other radical polymerizable monomers, and resins containing carboxyl groups, containing 5 to 50% by weight of structural units based on lactone compounds in resin solid fractions; (B) resins containing epoxy groups, which contain 2 or more epoxy groups in 1 molecule; (C) ultraviolet absorbents; and (D) photostabilizers having a basicity (pKb) of 9 or more; the ratios of the carboxyl groups of component (A) to the epoxy groups of component (B) are the molar ratios in the range 75:25 to 25:75. (cf., for example, Patent Reference 4). However, the clear-on-clear adhesive properties in these coating compositions are inadequate. [ 0006 ]

The use of polyester resins is known, which have hydroxyl values in the range 10 to 300 mg KOH/g, acid values in the range 10 to 100 mg KOH/g and number average molecular weights in the range 400 to 6,000 and which are aqueous coating compositions forming coated films with excellent finishes, such as coated film performance and metallic appearance, which may be obtained by the reaction of: (a) polyhydric alcohols, (b) polycarboxylic acids and/or polycarboxylic acid anhydrides, and (c) monoepoxide compounds having long chain hydrocarbon groups; or they may be obtained by the reaction of: (d) polycarboxylic acid and/or polycarboxylic acid anhydrides and/or (e) polyisocyanate compounds with polyester polyols having hydroxyl values in the range 50 to 600 mg KOH/g and number average molecular weights in the range 300 to 3,000 (cf. Patent Reference 5). However, when these are used for clear coatings, their water resistance is inadequate, since they are aqueous and highly polar.

[REFERENCES TO PRIOR ART]

[Patent References] [0007]

[Patent Reference 1] International Patent Application

Publication (in Japanese) 9-509696

[Patent Reference 2] Japanese Unexamined Patent Application 2002-060672

[Patent Reference 3] Japanese Unexamined Patent

Application 2007-238896

[Patent Reference 4] Japanese unexamined Patent Application 2007-177216

[Patent Reference 5] Republication (in Japanese) of PCT International Application WO 2005-121209

[ SUMMARY OF THE INVENTION] [ Problems to be Solved by the Invention] [ 0008 ]

An obj ect of the present invention is to provide coating compositions , a process for finish coating, and coated articles , whereby coated films may be formed which are excellent in recoating properties , clear-on- clear adhesive properties , water resistance , acid resistance , external appearance , coated film hardness and scratch resistance , and which have adequate stability as 1-component paints .

Here, "recoating properties" signifies adhesive properties of multilayer coated films, which may be obtained from a surface coated film, which may be obtained by coating, by means of a coating and finishing process which is, for example, a 3-coat 2- bake, or 3-coat 1-bake process, which uses at least a colored base coat coating and a clear coating, and baking; and coating for a second time the same colored base coat coating as the first coating onto the clear coated film of a multilayer coated film, which is a clear coated film where a clear coating material has been coated, further coating and baking the same clear coating as the unchanged non-cross-linked first coating.

"Clear-on-clear adhesive properties" signifies the adhesive properties of multi-layer coatings, obtained by an overcoat finish coating process wherein the same clear coating material as the first coating is coated onto a clear coated film, which is a multilayer coated film where a clear coating material has been coated, and baked, with the surface coated film being obtained by coating, by means of a process, such as 3-coat 2- bake, or 3-coat 1-bake, using at least a colored base coat coating material and a clear coating material.

[The Means of Solving the Problems] [0009] The present inventors, as a result of a series of diligent investigations in order to solve the abovementioned problems, discovered that the object of the present invention may be attained by using coating compositions, wherein cross-linking agents are essential components, which react: with, for example, polyester resins, with specified SP values, and preferably specified acid values, and contain 2 or more carboxyl groups in 1 molecule, having a specified weight average molecular weight, and with radical copolymers containing 2 or more carboxyl groups in 1 molecule; and also used with radical copolymers having specified SP values, and preferably specified epoxy values, and containing 2 or more epoxy groups in 1 molecule, having a specified weight average molecular weight; and used with hydroxyl groups, and the present invention was achieved on the basis of this information.

[0010]

That is, the present invention provides coating compositions characterized in that they contain, as essential components, (A) polyester resins containing 2 or more carboxyl groups in 1 molecule; (B) radical copolymers containing 2 or more carboxyl groups in 1 molecule; (C) radical copolymers containing 2 or more epoxy groups in 1 molecule; (D) crosslinking agents which react with hydroxyl groups, and characterized in that the solubility parameters (SP values) of component (A) , component (B) and component C are all 9.5 to 11.2 (cal/cm³) ^1/2; and the ratios of the number of epoxy groups in component (C) versus the total number of carboxyl groups in component (A) and component (B) is 0.7 to 1.3 as ratios of equivalents; and the percentage content of component (D) is 1 to 15% by mass in the total solid resin fraction. [0011]

The present invention also provides coating compositions, wherein, in the abovementioned compositions, component (A) is a polyester resin, obtained by a condensation reaction of a fatty acid of 6 or more carbons, with a polyol with a weight average molecular weight of 300 to 3,700 and a hydroxyl value of 210 to 1,200 mg KOH/g and thereafter, or simultaneously with the said condensation reaction, carrying out an addition reaction of an acid anhydride; and/or a polyester resin, obtained by the further addition reaction of a glycidyl ether and/or glycidyl ester of 6 or more carbons to an adduct of a polyol, with a weight average molecular weight of 300 to 3,700, and a hydroxyl value of 210 to 1,200 mg KOH/g, and an acid anhydride, with the weight average molecular weight of the polyester resin being 1,000 to 12,000 and its acid value being 110 to 220 mg KOH/g. The present invention further provides coating compositions wherein, in the abovementioned compositions, component (B) has an acid value of 80 to 200 mg KOH/g, the weight average molecular weight of component (B) is 2,000 to 15,000, the percentage content of component (B) is 1% or more by mass to less than 50% by mass per total content of component (A) and component (B) , as the solid resin fraction mass ratio.

[0012] The present invention further provides coating compositions wherein, in the abovementioned compositions, the weight average molecular weight of component (C) is 2,000 to 15,000 and the epoxy value is 120 to 250 mg KOH/g.

The present invention further provides coating compositions wherein, in the abovementioned compositions, component (D) is a cross-linking agent, selected from tris (alkoxycarbonylamino) triazines, blocked isocyanate compounds, or melamine resins.

The present invention further provides a finish coating process whereby the abovementioned coating compositions are coated, and coated articles which have been coated by the finish coating process.

[Effects of the Invention]

[0013]

The coating compositions according to the present invention can form coated films with excellent recoating properties, clear-on-clear adhesive properties, water resistance, acid resistance, external appearance, coated film hardness and scratch resistance, and they have sufficient stability as 1- component paints.

[Mode of Carrying out the Invention]

[0014]

The component (A) polyester resins used according to - li ¬

the present invention are polyester resins having 2 or more carboxyl groups in 1 molecule, preferably having 4 or more carboxyl groups in 1 molecule, particularly preferably having 5 or more carboxyl groups in 1 molecule. When the carboxyl groups contained in the component (A) polyester resins have fewer than 2 carboxyl groups in 1 molecule, the coated film hardness falls, and the acid resistance and water resistance of coated films are reduced.

The component (A) polyester resins preferably have weight average molecular weights of 1,000 to 12,000, more preferably 1,200 to 10,000, particularly preferably 1,400 to 8,000. With a weight average molecular weight of less than 1,000 of a component (A) polyester resin, there is a fall in water resistance, and if it exceeds 12,000 compatibility with other resins is reduced and the external appearance is poor.

The acid values of the component (A) polyester resins are preferably 110 to 220 mg KOH/g, more preferably 120 to 190 mg KOH/g, particularly preferably 130 to 180 mg KOH/g. With an acid value of less than 110 mg KOH/g of a component (A) polyester resin, there is a fall in coating hardness, and if 220 mg KOH/g is exceeded the stability is decreased.

[0015] The component (A) polyester resins are preferably manufactured using polyols of weight average molecular weights from 300 to 3,700, and hydroxyl values from 210 to 1,200 mg KOH/g.

The weight average molecular weights of the polyols used for the manufacture of component (A) polyesters are more preferably 350 to 3,000, particularly preferably 400 to 2,500. When the weight average molecular weight of a polyol is less than 300, there is a fall in the coating hardness, and if it exceeds 3,700 the compatibility with other resins is decreased, and the external appearance is poor.

The hydroxyl values (OHV) of the polyols are preferably 210 to 1,200 mg KOH/g, particularly preferably 400 to 1,000 mg KOH/g. When the hydroxy value of a polyol is less than 210 mg KOH/g, there is a fall in the coated film hardness, and if it exceeds 1,200 mg KOH/g there is a decrease in water resistance.

[0016]

The polyols which may be used for the manufacture of component (A) polyesters are polyhydric alcohols containing several hydroxyl groups in 1 molecule; examples thereof which may be used are: polyester polyols where polyhydric alcohols and polybasic acids have reacted, and polyurethane polyols where polyhydric alcohols and isocyanates have reacted.

Examples of the polyhydric alcohols which may be used for the abovementioned polyols which may be given are: diols, such as ethylene glycol, propylene glycol, diethylene glycol, butanediol, neopentyl glycol, 1,4- hexanediol, 1, 6-hexanediol, cyclohexane dimethanol; glycerine; trimethylolethane; trimethylolpropane; pentaerythritol; dipentaerythritol; and various commercial dendrimers, such as Boltorn H30 and Boltorn

PlOOO (both manufactured by the Perstorp company) .

[0017]

When the polyol is a polyester polyol, a normal polyester resin synthesis process may be used.

When the polyester resin synthesis process is a direct esterification process, using polycondensation of a polycarboxylic acid and a polyhydric alcohol, examples of the polycarboxylic acids which may be given are: dibasic acids, such as phthalic acid, isophthalic acid, terephthalic acid, succinic acid, adipic acid, sebacic acid, maleic acid, fumaric acid, tetrahydrophthalic acid, hexahydrophthalic acid, and anhydrides thereof; and tribasic acids, such as trimellitic acid and pyromellitic acid, and anhydrides thereof. Examples of the polyhydric alcohols which may be given are: diols such as ethylene glycol, propylene glycol, diethylene glycol, butanediol, neopentyl glycol, 1, 4-hexanediol, 1, 6-hexanediol and cyclohexane dimethanol; and tri- hydric alcohols such as glycerine, trimethylolethane, trimethylolpropane and pentaerythritol.

[0018]

Examples of the polyester synthesis processes which may be used are a polycondensation process using transesterification of a lower alkyl ester of a polycarboxylic acid and a polyhydric alcohol, and a ring-opening polymerization process of lactones such as β-propiolactone, δ-valerolactone and ε-caprolactone.

[0019] When a polyol is a polyurethane polyol it may be obtained by reaction of an abovementioned polyhydric alcohol and an isocyanate compound. Specific embodiment examples of the isocyanate compounds which may be given are: compounds termed "isocyanate monomers", such as hexamethylene diisocyanate, isophorone diisocyanate, tolylene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate and dicyclohexylmethane-4, 4' - diisocyanate; and polyisocyanate derivatives, such as biuret, isocyanurate and trimethylolpropane adducts of these isocyanates.

[0020]

The component (A) polyester resins are preferably from addition reactions of acid anhydrides to condensation products of the abovementioned polyols and fatty acids with 6 or more carbons, preferably 6 to 25 carbons, more preferably fatty acids with 7 to 18 carbons.

The reason for using fatty acids is for the control of SP values, and also because when the number of carbons of a fatty acid is fewer than 6 control of SP values is difficult.

Examples of the fatty acids with 6 or more carbons which may be given are: caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, neodecanoic acid, lauric acid, myristic acid, pentadecylic acid, palmitic acid, margaric acid and stearic acid.

[0021] An addition reaction of a polyol and an acid anhydride may be used for a component (A) polyester resin, or to carry out the reaction with an acid anhydride by completing the reaction of a polyol and a fatty acid of 6 or more carbons, and thereafter charging the acid anhydride to the reaction system, and it is best to carry out the condensation reaction and the addition reaction simultaneously by charging the acid anhydride and the fatty acid with 6 or more carbons together. Examples of the acid anhydrides which may be given are: phthalic anhydride, 4-methylhexahydrophthalic acid anhydride, hexahydrophthalic acid anhydride and naphthalene-1, 8 : 4, 5-tetracarboxylic acid dianhydride; 4-methylhexahydrophthalic acid anhydride and hexahydrophthalic acid anhydride particularly preferred.

[0022] The component (A) polyester resins may use glycidyl ethers or glycidyl esters of 6 or more carbons, instead of the abovementioned fatty acids of 6 or more carbons.

The reason for using glycidyl ethers or glycidyl esters is to control SP values, and, in relation to the numbers of carbons of the glycidyl ethers or glycidyl esters, when the number of carbons is fewer than 6, control of SP values is difficult.

Examples of glycidyl ethers with 6 or more carbons which may be given are: 2-ethylhexyl glycidyl ether, 2- methyloctyl glycidyl ether, and various commercial alpha-olefin oxides, such as AOE X24 (manufactured by Daiseru Kagaku Kogyo-sha) .

Examples of glycidyl esters with 6 or more carbons which may be given are: various commercial aliphatic carboxylic acid glycidyl esters such as Cardura ElO (manufactured by the Hexion Speciality Chemicals company) .

[0023] When the component (A) polyester resins are synthesized, the addition reactions of the abovementioned polyols and the abovementioned acid anhydrides are carried out in advance, and thereafter an addition reaction of a glycidyl ether or a glycidyl ester of 6 or more carbons with a carboxyl group in a polyol, or a carboxyl group from ring opening of an acid anhydride, may be carried out.

The conditions for the synthesis of component (A) polyester resins which may be used are: for the condensation reaction, reaction at 140° to 250⁰C for 1 to 20 hours; and for the addition reaction, 100° to 200⁰C for 1 to 20 hours.

[0024]

The component (B) radical copolymers used according to the present invention are resins containing 2 or more carboxyl groups in 1 molecule. There is preferably contained 3 or more carboxyl groups, more preferably 4 or more carboxyl groups, in 1 molecule. When component (B) radical copolymers contain less than 2 carboxyl groups in 1 molecule, the coated film hardness is decreased. The component (B) radical copolymers are different from the component (A) polyester resins: no component (A) is contained in a component (B) .

[0025]

The component (B) radical copolymers preferably have weight average molecular weights from 2,000 to 15,000, more preferably 2,500 to 10,000, particularly preferably 3,000 to 6,000. With component (B) radical copolymers with weight average molecular weights of less than 2,000 there is a fall in the water resistance, and if they exceed 15,000 the compatibility with other resins is decreased and the external appearance is poor.

The component (B) radical copolymers preferably have acid values from 80 to 200 mg KOH/g, more preferably 100 to 180 mg KOH/g, particularly preferably from 120 to 160 mg KOH/g. With acid values of component (B) radical copolymers of less than 80 mg KOH/g, the coated film hardness falls, and, if they exceed 200 mg KOH/g, the stability is decreased.

[0026]

The component (B) radical copolymers are copolymer resins containing 2 or more carboxyl groups in 1 molecule, which may be obtained by copolymerization of radical copolymerizable monomers containing carboxyl groups and other radical copolymerizable monomers.

Specific embodiment examples of the radical copolymerizable monomers containing carboxyl groups which may be used for the manufacture of component (B) radical copolymers which may be given are: acrylic acid, methacrylic acid, maleic acid, fumaric acid, citraconic acid and itaconic acid. These radical polymerizable monomers containing carboxyl groups may be used singly, or as combinations of 2 or more thereof.

[0027] Specific embodiment examples of the other radical polymerizable monomers which may be used for the manufacture of component (B) radical copolymers which may be given are: methyl acrylate, ethyl acrylate, n- propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, secondary-butyl acrylate, hexyl acrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, lauryl acrylate, stearyl acrylate, methyl methacrylate, ethyl methacrylate, n-propyl meth- acrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, secondary-butyl methacrylate, hexyl methacrylate, cyclohexyl methacrylate, 2-ethylhexyl methacrylate, octyl methacrylate, lauryl methacrylate, stearyl methacrylate, styrene, acrylonitrile, methacrylonitrile, acrylamide and methacrylamide. These radical polymerizable monomers may be used singly, or as combinations of 2 or more thereof.

[0028]

The radical copolymerizations for the manufacture of component (B) radical copolymers may be carried out by means of known radical copolymerization processes. Normal radical polymerization initiators may be used for the radical copolymerizations. Examples of the radical polymerization initiators which may be given are: azo compounds such as 2, 2' -azobisisobutyronitrile, 2,2' -azobis-2, 4-dimethylvaleronitrile, 4,4' -azobis (4- cyanovaleric acid), 1, 1-azobis-l-cyclohexanecarbo- nitrile, dimethyl 2, 2' -azobisisobutyrate; and organic peroxides such as methyl ethyl ketone peroxide, cyclohexanone peroxide, 3, 5, 5-trimethylhexanone peroxide, 1, 1-bis ( tertiary-butylperoxy) 3,3, 5-trimethyl- cyclohexanone, 1, 1-bis ( tertiary-butylperoxy) cyclo- hexane, 2, 2-bis ( tertiary-butylperoxy) octane, tertiary- butylhydroperoxide, diisopropylbenzene hydroperoxide, dicumyl peroxide, tertiary-butylcumyl peroxide, isobutyl peroxide, lauroyl peroxide, benzoyl peroxide, diisopropyl peroxycarbonate, tertiary-butylperoxy 2- ethylhexanoate, tertiary-butylperoxy neodecanate, tertiary-butylperoxy laurate, tertiary-butylperoxy benzoate and tertiary-butylperoxy isopropylcarbonate. [ 0029 ]

The radical polymerization initiators may be used singly, or they may be used as combinations of 2 or more thereof. The quantities to use of the radical polymerization initiators are not particularly restricted, but there is preferably from 0.01 to 20% by mass, per total quantity of radical polymerizable monomers .

Combinations of reducing agents such as: dimethyl- aniline; ferrous salts, like ferrous sulfate, ferrous chloride and ferrous acetate; sodium bisulfite, sodium thiosulfate and Rongalite, may also be permitted, as required, in these radical polymerization initiator systems, but they need to be selected by taking care that the polymerization temperature is not lowered too much.

[0030] The organic solvents used for the manufacture of component (B) radical polymers are preferably those having no functional groups which would react with carboxyl groups. Examples of suitable organic solvents which may be given are: alicyclic hydrocarbons such as cyclohexane and ethylcyclohexane; aromatic hydrocarbon- based solvents such as toluene, xylene, ethylbenzene and aromatic naphtha; ketone-based solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone and isophorone; ester-based solvents such as ethyl acetate, n-butyl acetate, isobutyl acetate, 3- methoxybutyl acetate and bis (2-ethylhexyl) adipate; ether-based solvents such as dibutyl ether, tetrahydrofuran, 1,4-dioxan and 1, 3, 5-trioxane; nitrogen-containing solvents such as acetonitrile, valeronitrile, N,N-dimethylformamide and N, N- diethylformamide . The organic solvents may be used singly, or as mixtures of 2 or more thereof.

[0031]

The concentrations of the solid resin fractions of the component (B) radical copolymers may be optionally chosen from within a range in which the dispersion stabilities of the resins are not lost, but the solid resin fraction concentrations are normally from 10 to 70% by mass.

The percentage contents of the component (B) radical polymers are, as proportions by mass of the solid resin fractions, 1% by mass or more, preferably less than 50% by mass, more preferably 5 to 40% by mass, particularly preferably 10 to 30% by mass per total quantities of components (A) and components (B) .

With a content of component (B) versus the total quantity of a component (A) and component (B) of less than 1% by mass, the water resistance falls and, if there is more than 50% by mass, the coated film hardness is decreased.

[0032] The component (C) radical copolymers which may be used according to the present invention are resins containing 2 or more epoxy groups in 1 molecule. They preferably contain 3 or more epoxy groups, and they particularly preferably contain 4 or more epoxy groups in 1 molecule. When there are fewer than 2 epoxy groups in 1 molecule of a component (C) radical copolymer, the coated film hardness is decreased. The component (C) radical polymers are different from the component (B) radical copolymers: no component (B) is contained in component (C) .

The component (C) radical copolymers preferably have weight average molecular weights from 2,000 to 15,000, more preferably from 2,500 to 14,000, particularly preferably from 3,000 to 13,000. With a weight average molecular weight of a component (C) radical copolymer of less than 2,000 the coated film hardness falls, and if it exceeds 15,000 the compatibility with other resins is reduced, and the external appearance deteriorates.

The component (C) radical polymers preferably have epoxy values from 120 to 250 mg KOH/g, more preferably from 130 to 240 mg KOH/g, particularly preferably from 140 to 230 mg KOH/g. With an epoxy equivalent of a component (C) radical copolymer of less than 120 mg KOH/g the coated film hardness falls, and if it exceeds 250 mg KOH/g the stability is decreased.

[0033]

The component (C) radical copolymers are copolymer resins containing 2 or more epoxy groups in 1 molecule, which are obtained by copolymerization of radical polymerizable monomers containing epoxy groups and other radical polymerizable monomers. Specific embodiment examples of the radical polymerizable monomers containing epoxy groups which may be given are: glycidyl acrylate, glycidyl methacrylate, 3,4- epoxycyclohexylmethyl acrylate and 3, 4-epoxycyclohexyl- methyl methacrylate; these monomers may be used singly, or as combinations of 2 or more thereof. Examples of the other radical polymerizable monomers which may be given are the aforementioned other radical polymerizable monomers which are used for the manufacture of component (B) . The other radical polymerizable monomers may be used singly, or as combinations of 2 or more thereof. [0034]

According to the present invention, the solubility parameters (SP values) of the resins which are component (A) , component (B) and component (C) are all 9. 5 to 11 . 2 ( cal/cm³) ^1/2.

The more preferred SP values of component (A) , component (B) and component (C) are in the range 9.5 to 11.0 (cal/cm³)^1/2. When each of the SP values of the components is less than 9.5 (cal/cm³) ^1/2, the recoating properties and clear-on-clear adhesive properties deteriorate and, when 11.2 (cal/cm³) ^1/2 is exceeded, the water resistance is decreased. The solubility parameters (SP values) according to the present invention are values determined by turbidi- metric titrations of acetone - hexane and acetone - water, on the basis of the method of the reference literature (K. W. Suh et al . , Journal of Polymer Science: Part A-I, 5, 1671 - 1681, 1967).

[0035]

To be specific, a sample (0.5 g) and acetone (50 g) are placed in a conical flask and the sample is dissolved; hexane is added dropwise, with stirring, and the quantity of hexane to reach the turbidimetric point is measured. The SPl value (low polarity SP value) is then calculated, using the respective SP values (literature values) of each of the solvents, according to the ratio of the molar volumes of the solvents at the turbidi- metric point. Similarly, deionized water is added dropwise to a solution of a sample (0.5 g) in acetone (5 g) , the quantity of deionized water when the turbidimetric point has been reached is measured, and the SP2 value (high polarity SP value) is obtained. The SP value of a sample may be obtained by calculating the mean of the SPl and SP2 values which were obtained.

The literature values of the solvents used are as hereunder.

(Reference Literature: Polymer Handbook, Third Edition, pages 526 to 544, A Wiley-Interscience publication) [0036] [Table 1]

[0037]

According to the present invention, the ratio of the number of epoxy groups in component (C) to the total number of carboxyl groups in component (A) and component (B) is a ratio of equivalent weights from 0.7 to 1.3.

When the ratio of the number of epoxy groups in component (C) to the total number of carboxyl groups in component (A) and component (B) is a ratio of equivalent weights less than 0.7 and, when it exceeds 1.3, since unreacted functional groups remain in coated films, the water resistance is poor. [ 0038 ]

The component (D) cross-linking agents used according to the present invention may have at least 1 functional group in 1 molecule, which will react with a hydroxyl group; examples thereof which may be given are: resins for cross-linking having functional groups such as isocyanate groups and blocked isocyanate groups; and tris (alkoxycarbonylamino) triazine and melamine resins; these may be used singly, or as combinations of 2 or more thereof. The number of functional groups which react with hydroxyl groups in the cross-linking agents are preferably 2 or more, preferably 3 or more, in 1 molecule. The upper limit of the number of functional groups which react with hydroxyl groups is not particularly restricted, but it is preferable to have 30 or fewer.

[0039]

The percentage contents of the component (D) cross- linking agents are 1 to 15% by mass, preferably 3 to 10% by mass per total solid resin fraction. With a percentage of cross-linking agent of less than 1% by mass, per total solid resin fraction, the cross-linking density falls and scratch resistance is poor and, when 15% by mass is exceeded, the strain on hardening is increased, and the external appearance of coated films deteriorates . The "total solid resin fraction" signifies the total quantity of component (A) , component (B) , component (C) and component (D) , when the resin components of the coating compositions comprise component (A) , component (B) , component (C) and component (D) .

Specific embodiment examples of the compounds containing isocyanate groups which may be given are polyisocyanates containing 2 or more isocyanate groups in 1 molecule such as hexamethylene diisocyanate, phenylene diisocyanate, xylylene diisocyanate and isophorone diisocyanate.

[0040]

Specific embodiment examples of the compounds containing blocked isocyanates which may be given are polyisocyanates having 2 or more isocyanate groups in 1 molecule such as polyisocyanates, for instance, hexamethylene diisocyanate, phenylene diisocyanate, xylylene diisocyanate and isophorone diisocyanate; these isocyanate compounds are blocked with blocking agents, such as pyrazole-based, active methylene-based and oxime-based blocking agents.

Specific embodiment examples of the preferred tris(al- koxycarbonylamino) triazines which may be given are tris (methoxycarbonylamino) triazine and tris (butoxycar- bonylamino) triazine. [ 0041 ]

Examples of the melamine resins which may be given are melamine resins fully alkylated with different reactive groups, methylol melamine resins, imino group-contain- ing melamine resins, and mixtures of these resin types; imino group-containing melamine resins are particularly preferred.

The fully alkylated melamine resins are preferably fully methylated melamine resins; the imino group- containing melamine resins are preferably imino group- containing methylated resins, imino group-containing butylated melamine resins and mixed methylated/ butylated resins.

[0042]

Examples of commercial fully alkylated melamine resin products which may be given are: Luwipal LO66 (manufactured by the BASF company) ; and Cymel 300, Cymel 301, Cymel 303 and Cymel 350 [manufactured by the above Nihon Saitekku Indasutorizu (K K) ].

Examples of commercial imino group-containing methylated melamine resins which may be given are Cymel 325 and Cymel 327 [manufactured by the above Nihon Saitekku Indasutorizu (KK) ] .

An example of a commercial imino group-containing butylated melamine resin which may be given is Yuban 220 [manufactured by Mitsui Kagaku (KK) .

An example of a commercial imino group-containing methylated melamine resin which may be given is Cymel

254 [manufactured by the above Nihon Saitekku Indasutorizu (KK) ] .

The component (D) crosslinking agents may be used singly, or they may be used as combinations of 2 or more thereof.

[0043]

The coating compositions according to the present invention may be used as they are, or, as required, with the addition of organic solvents and of 1, 2 or more of various additives, for example, surfactants, surface control agents, hardening reaction catalysts, antistatic agents, aromas, dehydrating agents, and also rheology control agents such as polyethylene wax, polyamide wax and internally crosslinked resin microparticles . The coating compositions according to the present invention may ideally be used as 1- component coating materials and have excellent storage stabilities.

The coating compositions according to the present invention may be used as clear coating materials, and they may also be used as colored coating materials, by compounding in colorants, such as dyes and pigments, but they are preferably used as finish coating compositions .

[0044]

The coating processes for the coating compositions according to the present invention are not particularly restricted, examples thereof which may be given are: a process wherein a colored base coat is coated, onto a base material whereon intermediate coating has been carried out, and 3-coat 2-bake coating is carried out, with a coating composition according to the present invention being coated as a non-crosslinked finish coating material; a process wherein an intermediate coating material is applied onto a base material, a non-crosslinked colored base coat is applied, and 3- coat 1-bake coating is carried out, with a coating composition according to the present invention being coated as a non-crosslinked finish coating; and a process wherein coating is carried out by means of a finish coating process such as 3-coat 2-bake or 3-coat 1-bake, and, after baking, a coating composition according to the present invention is applied as an overcoat material and the overcoat is finished when it is baked. [ 0045 ]

The aforementioned colored base coat coating materials, intermediate coating materials, finish coating materials, overcoating materials and first coating materials may be adjusted to the desired viscosities by heating, or by adding organic solvents or reactive diluents, as required, and thereafter carrying out coating employing, for example, a coating machine which is normally used, in the form of, for instance, an air spray, electrostatic air spray, roll coater, flow coater or dipping, or a paint brush, bar coater or applicator. Of these, spray coating is preferred.

[0046] The quantities applied of the coating compositions according to the present invention are normally such that dried film thicknesses are from 10 to 100 μm. It is normally preferable to bake the coated films obtained by applying the coating compositions according to the present invention. It is normally best to appropriately select baking temperatures in the range from 120° to 180⁰C. It is normally best to appropriately select baking times in the range from 10 to 60 minutes. Examples of the base materials which may be coated by the coating compositions according to the present invention which may be given are: organic and inorganic materials such as wood, glass, metals, cloth, plastics, foamed materials, elastic materials, paper, ceramics, concrete and plaster. These materials may have pretreatment of the surfaces, or coated films may be preformed on the surfaces. Specific embodiment examples have been given up to this point, but the finish coating processes according to the present invention are not restricted in any way by these examples .

[0047] Examples of the coated products obtained by means of the coating compositions according to the present invention which may be given are: structural materials, wooden products, metal products, plastic products, rubber products, coated paper, ceramic products and glass products. To be more specific, examples which, may be given are: automobiles; parts for automobiles (parts such as bodies, bumpers, spoilers, mirrors, wheels and interior materials, and materials with various properties) ; metal sheet, such as steel sheet; parts for two-wheeled vehicles; materials for roads (such as guard rails, road signs and soundproof walls) ; materials for tunnels (such as side wall plates) , ships, railroad vehicles, aircraft, furniture, musical instruments, home electric appliances, building materials, containers, office equipment and supplies, sports equipment and toys. [Examples]

[0048]

The present invention will next be described more concretely by means of Examples of its execution, but the present invention will not be limited in any way by these Examples . The performance of coatings obtained from the clear coating compositions according to the present invention was obtained as follows.

[0049]

«Test Procedure»

Preparation of Test Pieces and Investigation of Coated

Film Performance

A cationic electrodeposition paint Cathoguard 500 [trade name, manufactured by BASF Coatings (company) ] was applied by electrodeposition such that the dried film thickness was 20 μm and baked for at 175⁰C for 25 minutes; an intermediate coating Hi-Epico Number 560 [trade name, manufactured by BASF Coatings (company) ] was applied by air spray, such that the dried film thickness was 30 μm and baked at 140⁰C for 30 minutes. Test pieces were produced by applying Belcoat Number 6000 Black [trade name, manufactured by BASF Coatings Japan (K K) ; paint color, black] with an air spray and setting it at 20⁰C for 3 minutes, such that the dried coated film thickness was 15 μm, ; thereafter the clear paints obtained in the undermentioned Examples were diluted to the painting viscosity (Ford cup Number 4, 25 seconds at 2O⁰C) with Sorbesso 100 [trade name, aromatic naphtha-based solvent, manufactured by Exxon (company) ] and applied with an air spray by a wet-on- wet method, such that each of the dry coated film thicknesses was 40 μm, and baked at 140⁰C for 30 minutes .

[0050]

External Appearance

Assessments were made according to the following criteria by means of visual inspection.

[0051]

Coated Film Hardness

The coated film hardness was determined in conformity with the Japanese Industrial Standard (JIS) K5600-5-

4(1999) scratch hardness test method (pencil method). A good coated film hardness was HB or harder.

[0052]

Storage Stability

Clear coating materials were diluted to the painting viscosity (Ford cup Number 4, 25 seconds at 20°C) with Sorbesso 100 [trade name, aromatic petroleum naphtha- based solvent, manufactured by Exxon (company) ] and changes in viscosity were checked after storage at 30°C for 10 days.

G _• Viscosity change, less than 5 seconds

O Viscosity change, more than 5 seconds to less than 10 seconds

Δ • Viscosity change, more than 10 seconds to less than 15 seconds

X _: Viscosity change, more than 15 seconds

[0053]

Water Resistance A test plate where a coated film had been formed on the surface was exposed outdoors for 3 months, in conformity with the JIS K-5400 9.9(1990) weather resistance test method; thereafter the color of the unwashed surface of the coated film was determined in conformity with the JIS K5400 (1990) 7.4.2 measurement method; the ΔL* value was calculated by subtracting the L* value before the test from the L* value after immersing the test piece in warm water at 40⁰C for 240 hours, and bleaching of the coated film was assessed by means of the undermentioned criteria.

Θ • Less than 1.0

O • More than 1.0 to less than 2. 0

Δ More than 2.0 to less than 3. 0

X More than 3.0

[0054] Recoating Properties

Recoated test pieces were produced by applying, as a base coat, to the clear coated film surfaces of the test pieces obtained by the abovementioned method for producing test pieces, Belcoat Number 6000 Black [trade name, manufactured by BASF Coatings Japan (K K) ; paint color, black] with an air spray and setting it at 20°C for 3 minutes, such that the dried coated film thickness was 15 μm, ; thereafter, as non-crosslinked finish coat coating materials, the clear coating materials according to the invention, which were used in the production of the test pieces, and which were diluted to the painting viscosity (Ford cup Number 4, 25 seconds at 20⁰C) with Sorbesso 100 [trade name, aromatic naphtha-based solvent, manufactured by Exxon (company) ] were applied by a wet-on-wet method, such that the dried coated film thicknesses were 40 μm, and baked at 140⁰C for 30 minutes. Square checkerboard intersections were made with a cutter knife at 2 mm intervals of 11 parallel lines length and width, which reached the base material, on the coated films of the recoated samples; approximately 30 mm cellophane tape was adhered, and peeled off upwards in a single movement, and the number of checkerboard lines remaining on the coated film, which had not peeled off, and the number which had peeled off were obtained. The results were appraised by the undermentioned criteria.

O No peeling

Δ . Less than 10% of the total square area peeled off

X _: More than 10% of the total square area peeled off

[0055]

Clear-on-Clear Adhesive Properties

Clear-on-clear adhesive property test pieces were produced by applying, with an air spray, as an over- clear coating material, to the surfaces of clear coated films of test pieces obtained by the abovementioned method for producing test pieces, the clear coating materials according to the present invention, which were used in the production of test pieces, and which were diluted to the painting viscosity (Ford cup Number 4, 25 seconds at 20⁰C) with Sorbesso 100 [trade name, aromatic naphtha-based solvent, manufactured by Exxon (company) ] and baking at 140°C for 30 minutes, so that the dried film thickness was 40 μm. Square checkerboard intersections were made with a cutter knife at 2 mm intervals of 11 parallel lines length and width, which reached the base material, on the coated films of the clear-on-clear adhesion test samples, approximately 30 mm cellophane tape was adhered, and peeled off upwards in a single movement, and the number of checkerboard lines remaining on the coated film which had not peeled off and the number which had peeled off were obtained. The results were appraised by the undermentioned criteria.

O No peeling

Δ _*> Less than 10% of the total square area peeled off

X More than 10% of the total square area peeled off [0056]

(7) Acid Resistance

0.2 ml spots of 40% sulfuric acid were placed on test plates, thereafter heated at 60⁰C for 15 minutes, subsequently washed and the degree of production of marks was assessed visually.

O • Almost no visible change in the coated film.

Δ Slight water stain marks visible.

X Marked water stain marks visible.

[0057]

(8) Scratch Resistance

Car wash resistance both good; muddy water (JIS Z-8901- 84 a 10:99:1 mixture of type 8 dust : water : neutral detergent) was applied with a brush to a test sheet; thereafter it was cleaned with a car-wash brush rotating at 150 rpm for 10 seconds in an automatic car- wash machine and the test sheet was rinsed with flowing water. The above procedure was repeated twice; thereafter the extent of scratching of the test sheet surface was determined by measuring the L* value with a color difference meter [CR-331, manufactured by Minolta Camera (K K) ]. The ΔL* values were calculated from the following equation and the scratch resistances were appraised from these values.

ΔL* value = L* value after testing - L* value before testing

O ΔL* value less than 20

Δ • ΔL* value more than 20 to less than 30

X _: ΔL* value more than 30

[0058] Manufacturing Example>

<Manufacture of a Polyester Polyol (PE-I) > Adipic acid (50.3 parts by mass), trimethylolpropane (30.9 parts by mass) and pentaerythritol (31.3 parts by mass) were charged to a 4-neck flask fitted with a thermometer, Dean and Stark apparatus, reflux condenser, nitrogen inlet tube and stirrer, stirred and heated from 160° to 200°C, and condensation polymerization was carried out until 12.5 parts by mass of water had been removed. A polyester polyol (PE-I) of weight average molecular weight 1,740 was obtained. [ 0059 ]

Manufacture of PE2 to 7>

PE2 to PE7 were obtained by compounding the substances listed in Table 2, by similar processes to that of

Manufacturing Example PE-I.

[0060] [Table 2]

[0061]

<Manufacture of Polyurethane Polyol (PU-I) > Hexamethylene diisocyanate (47.4 parts by mass), trimethylolpropane (26.2 parts by mass) and pentaerythritol (26.5 parts by mass) were charged to a 4-neck flask fitted with a thermometer, reflux condenser, nitrogen inlet tube and stirrer, stirred and heated at 80⁰C and reaction was carried out until the absorption of the isocyanate group (2270 cm^"1) in the infrared (IR) spectrum had disappeared. Polyurethane polyol PU-I of weight average molecular weight 2,100 was obtained. Manufacture of Polyester Resin A-I Containing Carboxyl Groups> Polyester polyol PE-I (24.9 parts by mass) and neodecanoic acids (9.8 parts by mass) were charged to a 4-neck flask fitted with a thermometer, Dean and Stark apparatus, reflux condenser, nitrogen inlet tube and stirrer, stirred and heated from 160° to 200⁰C, and condensation polymerization was carried out until 1.1 parts by mass of water had been removed. Cooling to 140⁰C was then carried out, then hexahydrophthalic anhydride (26.4 parts by mass) was added and stirred for 2 hours; thereafter Sorbesso 100 (40 parts by mass) was added. Polyester A-I, of resin acid value 160 and weight average molecular weight 4200 was obtained.

[0062]

Manufacture of A-2 to A-19>

A-2 to A-19 were obtained by compounding the substances listed in Table 3 to Table 5, by similar processes to that of Manufacturing Example A-I.

[0063]

[Table 3]

[0064]

[Table 4]

[0065] [Table 5]

[0066]

«Explanation of Symbols in Table 3 to Table 5»

[0067]

Manufacture of Radical Copolymer B-I Containing

Carboxyl Groups> Sorbesso 100 [trade name, aromatic naphtha-based solvent, manufactured by Exxon (company) ; 35 parts by mass) ] was charged to a 4-neck flask fitted with a thermometer, reflux condenser, stirrer and dropping funnel, heated with stirring in a current of nitrogen, and maintained at 140⁰C. A mixture of butyl methacrylate (13.2 parts by mass), styrene (6.0 parts by mass), ethyl hexylmethacrylate (30.0 parts by mass), acrylic acid (10.8 parts by mass) and tertiary- butylperoxy-2-ethyl hexanoate (4.0 parts by mass) was added dropwise from the dropping funnel at a uniform rate over 2 hours. After the reaction had finished, the temperature was maintained at 140⁰C for 1 hour, and thereafter a mixture of tertiary-butyl peroxybenzoate (0.5% by mass) and Sorbesso 100 (0.5% by mass) was added dropwise, and the reaction was finished when a temperature of 140⁰C had been maintained for a further 2 hours. Radical copolymer B-I was obtained, with a resin acid value of 140 and a weight average molecular weight of 4900.

[0068]

Manufacture of B-2 to B-9>

Resins B-2 to B-9 were obtained by compounding the substances listed in Table 6, by similar processes to that of Manufacturing Example B-I

[0069] [Table 6]

[0070]

Manufacture of Radical Copolymer Resin Solution C-I

Containing Epoxy Groups>

Sorbesso 100 (35 parts by mass) was charged to a 4-neck flask fitted with a thermometer, reflux condenser, stirrer and dropping funnel, heated with stirring in a current of nitrogen, and maintained at 140⁰C. Next, at the temperature of 140⁰C, a mixture of butyl methacrylate (21.9 parts by mass), ethyl hexylacrylate (4.8 parts by mass), glycidyl methacrylate (27.3 parts by mass) 2-hydroxypropyl methacrylate (6.0 parts by mass) and tertiary-butylperoxy 2-ethylhexanoate

(4.0 parts by mass) was added dropwise, as a dropping component, at a uniform rate from the dropping funnel over 2 hours. After dropping in had finished, the temperature of 140° was maintained for 1 hour; thereafter a mixture of tertiary-butylperoxy benzoate (0.5 parts by mass) and Sorbesso 100 (0.5 parts by mass) was added dropwise and the reaction was completed when a temperature of 140⁰C had been maintained for 2 hours. Radical copolymer C-I of weight average molecular weight 5000 was obtained.

[0071]

Manufacture of C-2 to C-13>

C-2 to C-13 were obtained by compounding the substances listed in Table 7 and Table 8, by similar processes to that of Manufacturing Example C-I.

[0072] [Table 7]

[0073] [Table 8]

[0074]

(Examples 1 to 40)

Manufacture of Clear Coating Materials CC-I to CC-40>

The raw materials listed in Table 9 to Table 12 were mixed in order and stirred until they became uniform, whereupon clear coatings CC-I to CC-40 were obtained.

(Comparative Examples 1 to 14)

Manufacture of Clear Coating Materials CC-41 to CC-54>

The raw materials in listed in Table 13 and Table 14 were mixed in order and stirred until they became uniform, whereupon clear coatings CC-41 to CC-54 were obtained.

In Table 9 to Table 14, the ratio of equivalents (epoxy value/acid groups) signifies that the ratio of the number of epoxy groups in a component (C) to the total number of carboxyl groups in a component (A) and a component (B) represents a ratio of equivalents. [0075]

[Table 9]

[0076]

[Table 10]

[0077]

[0078]

[0079]

[0080]

[0081]

«Explanation of Symbols in Table 9 to Table 14»

1) Desmodur VPLS2253: 75% by mass blocked polyiso- cyanate solution, manufactured by the Sumika Bayer Urethane company.

2) Larotact LR9018: 50% by mass solution of tris(al- koxycarbonylamino) triazine, manufactured by BASF Aktiengesellschaft company.

3) Cymel 327: 90% by mass solution of methylated melamine resin, manufactured by the Nihon Cytec Industries company. 4) Ultraviolet Absorbent: 85% by mass solution, manufactured by the Ciba Specialty Chemicals company. 5) Photostabilizer: 100% by mass solution, manufactured by the Ciba Specialty Chemicals company. 6) Surface control agent: 10% by mass solution, manufactured by the Kusumoto Chemicals company.

[Potential for Industrial Use] [0082]

The coating compositions according to the present invention may be used as coating compositions for various purposes; in particular, they are useful as coating compositions for automobiles.

Claims

Patent Claims

[1] Coating compositions, characterized in that they contain, as essential components: (A) polyester resins containing 2 or more carboxyl groups in 1 molecule

(B) radical copolymers containing 2 or more carboxyl groups in 1 molecule

(C) radical copolymers containing 2 or more epoxy groups in 1 molecule

(D) crosslinking agents which react with hydroxyl groups and characterized in that: the solubility parameters (SP values) of (A), (B) and (C) are all 9.5 to 11.2 (cal/cm³) ^**; the ratios of the numbers of epoxy groups in component (C) versus the total number of carboxyl groups in component (A) and component (B) are from 0.7 to 1.3 as ratios of equivalents; and the percentage content of component (D) is from 1 to 15% by mass in the total solid resin fraction.

[2] The coating compositions, as claimed in claim 1, wherein component (A) is: a polyester resin obtained by the condensation reaction of a fatty acid of 6 or more carbons with a polyol of weight average molecular weight 300 to 3,700 and a hydroxyl value of 210 to 1,200 mg KOH/g, and thereafter, or simultaneously with the said condensation reaction, carrying out an addition reaction of an acid anhydride; and/or a polyester obtained by the further addition reaction of a glycidyl ether and/or glycidyl ester of 6 or more carbons to an adduct of a polyol with a weight average molecular weight 300 to 3,700, and hydroxyl value of 210 to 1,200 mg KOH/g, with the weight average molecular weight of the polyester resin being 1,000 to 12,000, and its acid value being 110 to 220 mg KOH/g.

[3] The coating compositions as claimed in claim 1, wherein, in the abovementioned compositions, component (B) has an acid value of 80 to 200 mg KOH/g, the weight average molecular weight of component (B) is 2,000 to 15,000, the percentage content of component (B) is 1% or more by mass to less than 50% by mass per total content of component (A) and component (B) , as the solid resin fraction mass ratio.

[4] The coating compositions as claimed in claim 1, wherein the weight average molecular weight of component (C) is from 2,000 to 15,000, and the epoxy value of component (C) is from 120 to 250 mg KOH/g.

[5] The coating compositions as claimed in claim 1, wherein component (D) is a crosslinking agent, selected from tris (alkoxycarbonylamino) triazines, blocked isocyanate compounds and melamine resins.

[6] A finish coating process, characterized in that the coating compositions as claimed in any of claims 1 to 5 are applied.

[7] The coated articles which are coated by the finish coating process as claimed in claim 6.