JP2001026747A - Organic solvent-based coating composition and method of forming coating film using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an organic solvent-based coating composition capable of forming coating films excellent in acid resistance and resistance to scuffing, and to provide a method of forming multilayer coating films using the above composition. SOLUTION: This organic solvent-based coating composition is such one as to contain (A) a hydroxyl group-containing resin, (B) colloidal fine particles of an inorganic oxide and (C) a (blocked) polyisocyanate compound, and have an acid value of 0.1 to 50 mg KOH/g based on the total solids in the coating composition. The other objective method of forming a multilayer coating film comprises coating at least one kind of color coating material and at least one kind of clear coating material; wherein a clear coating material to be coated on the uppermost layer is the above coating composition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic solvent-based coating composition for forming a coating film having excellent acid resistance and scratch resistance, and a method for forming a multilayer coating film using the same.

[0002]

2. Description of the Related Art It has been demanded that an overcoat film of an automobile outer panel or the like be free from etching or stain-like stains due to acid rain or the like, and be free from scratches caused by a car washer. The acid resistance of the coating is improved by introducing a cross-linking system that is resistant to acids, while
It is thought that the anti-scratch resistance is improved by increasing the crosslink density, but in reality, a coating composition satisfying both of these properties has not yet been proposed.

For example, it has been proposed that a coating film obtained by heat-curing an acrylic resin having a high hydroxyl value and a monomeric melamine resin in the presence of an acid catalyst has an increased crosslink density and improved abrasion resistance (Japanese Unexamined Patent Application Publication No. Hei. -222,753)
However, since a melamine resin is used as a cross-linking agent, the coating film is easily decomposed by an acid and has poor acid resistance.

In addition, a combination of a carboxyl group / epoxy group / hydroxyl group / melamine resin is used in combination with a melamine resin cross-linking system and an acid-resistant cross-linking system to achieve both acid resistance and scratch resistance. Crosslinking system (JP-A-2-2472)
No. 64) or a complex crosslinking system of a hydroxyl group / alkoxysilyl group / melamine resin (JP-A-4-816383).
And the like have been proposed, but none of them have sufficient acid resistance because a melamine resin is used.

On the other hand, as a cross-linking system not using a melamine resin, a cross-linking system comprising a carboxyl group / epoxy group or a carboxyl group / epoxy group / hydroxyl group (JP-A-62-8)
No. 7288, JP-A-2-45577, JP-A-3-287650, etc. have also been proposed, and these have good acid resistance, but have a drawback of insufficient scratch resistance.

[0006] A coating composition comprising a thermosetting resin mixed with colloidal silica has also been proposed (JP-A-10-2).
No. 98460), when an isocyanate compound is used as a crosslinking agent in this paint, the coating film hardness is not sufficient,
It has a defect of poor scratch resistance.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above circumstances, and has as its object to develop an organic solvent-based coating composition which forms a coating film having both excellent acid resistance and scratch resistance. .

The present inventors have conducted intensive studies in order to achieve this object and found that (A) a hydroxyl group-containing resin and (B)
It contains colloidal fine particles of an inorganic oxide and (C) a polyisocyanate compound which may be blocked, and has an acid value of 0.1 to 50 m based on the total solid content in the coating composition.
The present inventors have found that an organic solvent-based coating composition of gKOH / g achieves the object and completed the present invention.

Thus, according to the present invention, there is provided a coating composition containing (A) a hydroxyl group-containing resin, (B) colloidal fine particles of an inorganic oxide, and (C) a polyisocyanate compound which may be blocked. An organic solvent-based coating composition (hereinafter, referred to as the present composition), characterized in that the acid value based on the total solid content in the product is 0.1 to 50 mgKOH / g.

Hereinafter, the present composition will be described in detail.

Component (A): Hydroxyl-containing resin This resin skeleton is preferably a vinyl resin or a polyester resin, and the component (A) is obtained by introducing a hydroxyl group into the resin skeleton.

The hydroxyl group content in the component (A) is, based on the hydroxyl value, from 10 to 260 mgKOH / g, and particularly preferably 5 to 260 mgKOH / g.
It is preferably in the range of 0 to 200 mgKOH / g, and the number average molecular weight is more preferably 1000 to 60000, particularly 2000 to 2000 KOH / g.
A range of 20,000 is suitable.

The hydroxyl group-containing vinyl resin can be prepared, for example, by using a hydroxyl group-containing vinyl monomer in combination with another vinyl monomer and copolymerizing the same with a conventional method.

The hydroxyl group-containing vinyl monomer is a compound having at least one hydroxyl group and at least one polymerizable unsaturated bond in one molecule. For example, 2-hydroxyethyl (meth)
Acrylate, hydroxypropyl (meth) acrylate
And monoesters of (meth) acrylic acid such as 4-hydroxybutyl (meth) acrylate and glycols having 2 to 10 carbon atoms. Further, esterified products of these hydroxyl group-containing vinyl monomers and lactones can also be used as hydroxyl group-containing vinyl monomers. As the other vinyl monomers, compounds having one or more polymerizable unsaturated bonds in one molecule other than the hydroxyl group-containing vinyl monomer can be used. For example, carboxyl group-containing vinyl monomers such as (meth) acrylic acid; methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, n- (meth) acrylate Butyl, isobutyl (meth) acrylate, tert-butyl (meth) acrylate, (meth)
Hexyl acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, decyl (meth) acrylate, stearyl (meth) acrylate, lauryl (meth) acrylate, cyclohexyl (meth) acrylate, etc. C1-C24 alkyl esters or cycloalkyl esters of (meth) acrylic acid; (meth) acrylic acids such as methoxybutyl (meth) acrylate, methoxyethyl (meth) acrylate, and ethoxybutyl (meth) acrylate C2-C18 alkoxyalkyl esters; aromatic monomers such as styrene and vinyltoluene; vinyl ethers; olefins; nitrogen-containing vinyl monomers; and acid anhydrides (eg, hexahydrophthalic anhydride, succinic anhydride , Tetrahydrosuccinic anhydride, methylhexahydroanhydride Half-esterified vinyl monomer of succinic acid, etc.) and hydroxyl group-containing vinyl monomer; polymerizable acid anhydride monomer such as maleic anhydride, itaconic anhydride, hymic anhydride; polymerizable acid anhydride and non-polymerizable monoalcohol Half-esterified vinyl monomer with phenol (e.g., methanol, ethanol); glycidyl (meth) acrylate, methyl glycidyl (meth) acrylate, 3,4-epoxycyclohexylmethyl (meth)
Epoxy group-containing vinyl monomers such as acrylate and allyl glycidyl ether; fluorine-containing olefins such as vinyl fluoride, vinylidene fluoride, trifluoroethylene, tetrafluoroethylene, and chlorotrifluoroethylene; vinyl acetate, vinyl octylate And vinyl esters such as isopropenyl acetate and isopropenyl octylate; ω- (meth) acryloyl (oxy) alkyl acid phosphate, ω- (meth) acryloyl (oxy) alkyl acid phosphate and alcohol And reaction products, and hetero element oxygen-containing vinyl monomers such as terminal sulfonic acid type (meth) acryloyl.

In preparing the hydroxyl group-containing vinyl resin, the ratio of the hydroxyl group-containing vinyl monomer to the other vinyl monomer is preferably such that the hydroxyl value of the obtained vinyl resin is within the above range.

Further, the hydroxyl group-containing polyester resin is
A polyvalent alcohol having two or more hydroxyl groups in the molecule;
It can be obtained by subjecting a polybasic acid having two or more carboxyl groups in a molecule to an ester reaction in an alcohol excess in a known manner. Examples of the polyhydric alcohol include ethylene glycol, propylene glycol, butylene glycol, hexanediol, diethylene glycol, dipropylene glycol, and neopentyl glycol.
, Triethylene glycol, hydrogenated bisphenol A, glycerin, trimethylolethane, trimethylol
Such as phthalic anhydride, isophthalic acid, terephthalic acid, succinic acid, adipic acid, azelaic acid, sebacic acid, tetrahydrophthalic acid, hexahydrophthalic acid, heptic acid, hemic acid, and maleic acid as polybasic acids Acids, fumaric acid, itaconic acid, trimellitic acid and anhydrides thereof.

The hydroxyl group-containing resin as the component (A) includes:
Further, those having an alkoxysilyl group introduced as required are also included. .

The alkoxysilyl group has the formula (1) -Si
(OR ₁ ) _{3 -k} . This equation (1)
Wherein R ₁ is an alkyl group having 1 to 10 carbon atoms, an alkoxyalkyl group, an acetyl group, and _k is 0 or 1. Examples of the alkyl group or alkoxyalkyl group having 1 to 10 carbon atoms for R ₁ include a methyl group, an ethyl group, a 2-methoxyethyl group, a 2-ethoxyethyl group, and a 2-butoxyethyl group. The content of the alkoxysilyl group in the component (A) is preferably 3.3 mmol / g or less.

The introduction of an alkoxysilyl group into a vinyl resin (resin skeleton) is carried out, for example, by copolymerizing the above-mentioned vinyl monomer with an alkoxysilyl group-containing vinyl monomer.

Alkoxysilyl group-containing vinyl monomer
Is a compound having at least one alkoxysilyl group and at least one polymerizable unsaturated bond in one molecule, for example, vinyltrimethoxysilane, vinyltriethoxysilane,
Vinyltris (methoxyethoxy) silane, γ- (meth) acryloylpropyltrimethoxysilane, γ-
(Meth) acryloylpropyltriethoxysilane, γ
-(Meth) acryloylpropylmethyldimethoxysilane, γ- (meth) acryloylpropylmethyldiethoxysilane and the like.

The alkoxysilyl group can also be introduced by urethane-forming an alkoxysilane compound having an isocyanate group at the terminal to a vinyl resin or a polyester resin having a hydroxyl group.

As the alkoxysilane compound having an isocyanate group at a terminal, for example, a compound represented by the following formula (2) is preferably used.

Formula (2) {OCN- (CH ₂ ) _j } -R ₂ kSi (OR ₁ ) _{3 -k} (wherein R ₁ is an alkyl group having 1 to 10 carbon atoms, an alkoxyalkyl group, acetyl A group, R ₂ is a methyl group or a phenyl group, and _k is 0 or 1.) Examples of the alkyl group having 1 to 10 carbon atoms and the alkoxyalkyl group of R ₁ include a methyl group, an ethyl group, and 2-methoxyethyl. Group, 2-ethoxyethyl group, 2-butoxyethyl group and the like.

This urethanization reaction can be carried out by a urethanization reaction known per se, and the ratio of both components is such that the content of alkoxysilyl groups in the resin obtained by this reaction is 3.3 mmol / g or less. It is preferred that

Component (B): Colloidal fine particles of inorganic oxide
The component (B) includes colloidal inorganic oxide fine particles themselves, colloid particles obtained by reacting an alkoxysilane compound on the surface of the fine particles, and the like. Examples of the colloidal inorganic oxide fine particles themselves include colloidal silica (SiO ₂ ) and colloidal titania (TiO ₂ ).
₂ ), colloidal zirconia (ZrO ₂ ), colloidal alumina (Al ₂ O ₃ ) and the like.
It is preferably from 200 to 200 nm, particularly preferably from 5 to 100 nm.

It is preferable that these colloidal inorganic oxide fine particles are usually used by dispersing them in an organic solvent. Examples of the organic solvent include alcohol solvents such as methanol, isopropanol, ethylene glycol and ethylene glycol monopropyl ether; hexane, heptane, xylene, toluene, cyclohexane, and the like.
Hydrocarbon solvents such as naphtha; ketone solvents such as methyl isobutyl ketone, methyl ethyl ketone, isophorone and acetophenone; amide solvents such as dimethylacetamide and methylpyrrolidone; ethyl acetate, isobutyl acetate, octyl acetate, ethylene glycol monomethyl ether , Diethylene glycol monomethyl acetate
And ester solvents such as ter. These can be used alone or in combination of two or more.
The content of the colloidal inorganic oxide fine particles dispersed in the organic solvent is usually in the range of 1 to 60% by weight, particularly 5 to 40% by weight.

The organic solvent dispersion of colloidal inorganic oxide fine particles can be obtained by converting the commercially available aqueous dispersion into an organic solvent by a known method as an organic solvent dispersion as component (B). Can be used. Examples of commercially available aqueous dispersions of colloidal inorganic oxide fine particles include, for example, “Methanol Silica Sol”, “MA-ST-M”, “IPA-ST”, and “EG” manufactured by Nissan Chemical Industries, Ltd.
-ST "," EG-ST-ZL "," NPC-ST ",
"DMAC-ST", "MEK-ST", "XBA-S
T "and" MIBK-ST "(all are trade names).

Examples of the alkoxysilane compound which reacts with the colloidal inorganic oxide fine particles include a compound represented by the following formula (3).

Formula (3) R _{5 m} R _{6 n} Si (OR ₇ ) _{4 -m-n wherein} R ₅ is an alkyl group having 12 or less carbon atoms, an alkenyl group, an epoxyalkyl group, an aminoalkyl group, (Meth) acryloyloxyalkyl group, ureidoalkyl group, R ₆ is a methyl group, phenyl group, and R ₇ has 1 to 1 carbon atoms.
10 alkyl groups, alkoxyalkyl groups, acetyl groups, _m and _n are 0 or 1.) In the formula (3), the alkyl group having 1 to 10 carbon atoms of R ₇ and the alkoxyalkyl group include, for example, a methyl group , Ethyl group, 2-methoxyethyl group, 2-ethoxyethyl group, 2
-Butoxyethyl group and the like.

The reaction between the colloidal inorganic oxide fine particles and the alkoxysilane compound is carried out by mixing both components with an organic solvent and stirring the mixture at a temperature of 20 to 150 ° C. for one to several hours. In this reaction, the ratio of the alkoxysilane compound is 50 parts by weight or less per 100 parts by weight of the colloidal inorganic oxide fine particles in a solid content ratio,
Particularly, 30 parts by weight or less is suitable. The storage stability of the present composition is improved by using colloidal inorganic oxide fine particles reacted with an alkoxysilane compound.

The particle diameter of a product obtained by reacting an alkoxysilane compound with colloidal inorganic oxide fine particles is 3 to 200 n.
m, particularly preferably 5 to 100 nm.

Component (C): Possibly Blocked
A polyisocyanate compound having two or more isocyanate groups in one molecule of a lysocyanate compound, a block polyisocyanate compound in which all of the isocyanate groups are blocked, and the like can be used. This reacts with the component (A) and the component (B) to act as a cross-linking agent for forming a three-dimensionally cured coating film.

Examples of the polyisocyanate compound include aromatic diisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate and naphthalenedi isocyanate; tetramethylene diisocyanate; Aliphatic diisocyanates such as isocyanate, hexamethylene diisocyanate, dimer diisocyanate, lysine diisocyanate, 2-isocyanate ethyl-2,6-diisocyanate tocaproate; Methylene bis (cyclohexyl isocyanate-
G), isophorone diisocyanate, methylcyclohexane diisocyanate, cyclohexane diisocyanate
Alicyclic diisocyanates such as cyclopentane diisocyanate; buret type adducts and isocyanuric ring type adducts of these polyisocyanates; low molecular weight or high molecular weight activities of these polyisocyanates and polyisocyanates An isocyanate group-containing prepolymer obtained by reacting a hydrogen-containing compound with an isocyanate group in excess. The number average molecular weight of these polyisocyanate compounds is suitably in the range of 200 to 5,000.

The block polyisocyanate compound is obtained by converting the isocyanate group of these polyisocyanate compounds to phenols, oximes, active methylenes, lactams, alcohols, mercaptans, acid amides. Kind,
Those blocked with a blocking agent such as imides, amides, imidazoles, ureas, carbamic acids, and imines can be used.

The content of unblocked isocyanate groups in the polyisocyanate compound and the block polyisocyanate compound is 1.0 to 16.0 mmol / mol.
g is preferred.

The component ratio of the components (A), (B) and (C) can be arbitrarily selected according to the purpose, but the component (B) is composed of the components (A), (B) and (B). C)
1 to 60% by weight, especially 2 to 60% by weight based on the total solid content of the components
50% by weight is suitable. The component (C) has an isocyanate group / hydroxyl group ratio of the component (A) of 0.6 to 1.3 /
1, particularly preferably in the range of 0.9 to 1.1 / 1 (molar ratio).

As a characteristic of the present composition, in addition to including the above-mentioned components (A), (B) and (C) as essential components, the total solid content of all the components constituting the present composition is further reduced. 0.1 to 50 mgKOH /
g, preferably 0.5 to 40 mg KOH / g. This acid value is 0.1
If the amount is less than mgKOH / g, the hardness and the abrasion resistance of the coating film decrease. On the other hand, if it exceeds 50 mgKOH / g, the storage stability of the present composition decreases.

Here, the acid value refers to the content of an acidic functional group such as a carboxyl group, a sulfonic acid group and a phosphoric acid group, and the “total solid content” refers to the component (A), (B) ) Component, component (C), and various pigments and other resin components that can be further blended as necessary, and all other solid components that form a coating film.

In the present composition, by introducing these acid values, the hardness of the cured coating film of the present composition can be increased and the scratch resistance can be improved. Although the reason is unknown, it is presumed that these acidic functional groups promote the condensation reaction of the component (A), the component (B) and the component (C) to improve the crosslink density. . Even if these acid values are introduced, it is difficult to improve the hardness and the scratch resistance unless the component (B) is present.

The introduction of the acid value in the present composition is, for example,
An acidic functional group is introduced into the component (A) together with a hydroxyl group, or other components (D) having these acidic functional groups are blended together with the components (A), (B) and (C). It can be done by doing.

As a method for introducing an acidic functional group together with a hydroxyl group into the component (A), for example, a hydroxyl group-containing vinyl monomer may be used.
In addition, among the other vinyl monomers described above, a carboxyl group-containing vinyl monomer such as (meth) acrylic acid, a half-esterified vinyl monomer of an acid anhydride and a hydroxyl group-containing vinyl monomer, maleic anhydride, itaconic anhydride, and anhydride. Polymerizable acid anhydride monomer such as hymic acid, and a mixture of polymerizable acid anhydride and non-polymerizable monoalcohol.
Esterified vinyl monomer, ω- (meth) acryloyl (oxy) alkyl acid phosphate, reaction product of ω- (meth) acryloyl (oxy) alkyl acid phosphate with alcohol, terminal sulfonic acid type It can be carried out by copolymerizing a hetero element oxygen-containing vinyl monomer such as (meth) acryloyl.

Examples of the other component (D) having an acidic functional group include the following compounds.

A): Carboxyl group-containing vinyl resin. The resin preferably has an acid value of 0.5 to 250 mgKOH / g and a number average molecular weight of 1,000 to 60,000.

B) Carboxyl group-containing polyester resin. It is preferable that this has an acid value of 10 to 250 mgKOH / g and a number average molecular weight of 1500 to 4000.

C) alkylsulfonic acid, arylsulfonic acid, (poly) phosphoric acid compound, polycarboxylic acid compound,
Proton acid-containing compounds such as polysulfonic acid compounds.

Of these components (D), a) and b)
The amount of the component is 0.0% per 10 parts by weight of the component (B).
A range of 4 to 800 parts by weight, especially 0.1 to 600 parts by weight, is suitable. The amount of the component (c) is 0.04 to 50 parts by weight, particularly 0.1 to 10 parts by weight of the component (B).
A range of ４０40 parts by weight is suitable.

In order to accelerate the crosslinking reaction of the coating film, the composition further comprises an oxonium salt of a halide ion, an organic zinc compound, an organic boron compound, an organic aluminum compound, an organic titanium compound, an organic zirconium compound. It is also possible to mix a catalyst such as a compound or an organotin compound. The mixing ratio of this catalyst is as follows: 100 parts by weight of the total solid content of the component (A), the component (B) and the component (C).
A range of 0.1 to 10 parts by weight, especially 0.3 to 5 parts by weight, is suitable.

The present composition can be prepared by mixing the above components in an organic solvent and dissolving or dispersing the same. If necessary, a coloring pigment (solid color pigment, metallic pigment, optical pigment, Interference pigments, etc.), anti-settling agents, flow inhibitors, ultraviolet stabilizers, flame retardants, antifouling agents and the like can be appropriately compounded.

The coating film of the present composition can be cured by leaving it at room temperature or by heating it at a temperature of 200 ° C. or lower for 10 to 60 minutes.

The present composition is used as a clear paint for forming a transparent coating film, a solid color paint containing a solid color pigment, a metallic paint containing a metallic pigment, a light interference paint containing a light interference pigment, and the like. can do. In particular, the cured coating film of the present composition is hard and has excellent scratch resistance and the like. It is preferable to use the present composition as a clear paint for coating.

Specific examples of the use of the present composition for forming an overcoat film on an automobile outer panel are as follows.

Coating method A: Solid color using this composition
Finish with a single top coat of paint. Coating method B: one or more colored paints and one or more clear paints
In applying the paint sequentially to form a multi-layer top coat,
The composition is used as the top clear coating to form a multi-layer topcoat.

As a specific example of this coating method B, for example,
(B-1) In a two-coat finish in which a colored paint and a clear paint are sequentially applied, the present composition is used as the clear paint. (B-2) A colored paint, a first clear paint, and a second clear paint -In a three-coat finish in which the paint is applied sequentially, the composition is used in the second clear paint, (B-
3) In the three-coat finish in which the first colored paint, the second colored paint, and the clear paint are sequentially applied, the present composition is used as the clear paint.

In this coating method, “colored paint” means
One type selected from solid color paints, metallic paints and interference pattern paints.

In the coating method A, for example, an undercoat paint or an intermediate paint (optional) such as a cationic electrodeposition paint is applied directly to a metal or plastic object to be applied to an automobile,
After curing, the viscosity is 10 to 25 seconds (Food cup #
4/20 ° C.), and a solid color coating composition of the present composition adjusted to a solid content of 20 to 60% by weight is applied to an airless spray, an air spray, an electrostatic coating or the like to form a cured coating film having a thickness of about 20. To about 80 μm and left at room temperature or about 200 ° C. or less, preferably about 60 to about 1 μm.
It is carried out by heating at 70 ° C. for about 10 to about 60 minutes for crosslinking and curing.

The coating method (B-1) is, for example, applied directly to a metal or plastic object to be applied to an automobile, or to an undercoat or intermediate coat such as a cationic electrodeposition paint (can be omitted).
After coating and curing, the colored paint is applied by airless spray, air spray, electrostatic coating or the like so that the thickness of the cured coating film is about 10 to about 50 μm, and about 100 to about 1 μm.
After heating at a temperature of 80 ° C. for cross-linking or curing, or after leaving it at room temperature for several minutes without curing, the viscosity is 10 to 25 seconds (for ford cup # 4/20 ° C.), the solid content is 20 to 20 seconds.
A clear coating of the present composition adjusted to 60% by weight is applied in a similar manner so that the thickness of the cured coating is about 20 to about 70 μm, and left at room temperature or at about 200 ° C.
Below, preferably, about 10 to about 60 at about 60 to about 170 ° C.
A two-coat one-bake system (2C1B) or a two-coat two-bake system (2C2B), which is performed by heating for a minute to carry out crosslinking and curing, is suitable.

The color paints used in the coating method (B-1) include solid color paints, metallic paints, and light interference paints, and are known thermal paints containing a resin component, a color pigment and a solvent as main components. Curable coatings are suitable. Specifically, the resin component is a crosslinkable functional group (for example, a hydroxyl group, an epoxy group, a carboxyl group, an alkoxysilane base, etc.)
Having one or more base resins selected from acrylic resins, vinyl resins, polyester resins, alkyd resins, urethane resins, and the like, and alkyletherified melamine resins, urea resins, guanamine resins for crosslinking and curing these; It comprises at least one crosslinking agent component selected from a polyisocyanate compound which may be blocked, an epoxy compound, a carboxyl group-containing compound and the like, and the base resin accounts for 50 to 90% based on the total weight of both components. It is preferable that the crosslinking agent component is used in combination at a ratio of 50 to 10%. Color pigments include solid color pigments, metallic pigments and light interference pattern pigments, and these can be used alone or in combination of two or more. As a solvent, an organic solvent is suitable, but an aqueous solvent may be used.

As the colored paint used in the coating method (B-2), the colored paint described in the coating method (B-1) can be used, and the first clear paint is a transparent coating film forming paint. A coating obtained by removing most or all of the coloring pigment from the coloring coating or the present composition can be used. The composition is used as a second clear coating. In the coating method (B-2), specifically, an undercoat or an intermediate paint (optional) such as a cationic electrodeposition paint is applied directly to a metal or plastic object to be applied to an automobile, and then cured. After that, apply the colored paint by airless spray, air spray, electrostatic coating, etc. so that the film thickness becomes about 10 to about 50 μm with a cured coating film, and heat at about 100 to about 180 ° C to crosslink. After curing, or leaving at room temperature for several minutes without curing, the first clear coating is applied to the coated surface in a similar manner to a thickness of about 10 to about 50
μm and heated at about 100 to about 180 ° C. for cross-linking and curing, or left uncured at room temperature for several minutes, and then viscosity for 10 to 25 seconds (Ford cup # 4 / 20 ° C.), and a second clear coating of the present composition adjusted to a solid content of 20 to 60% by weight in a similar manner so that the cured coating has a thickness of about 10 to about 50 μm. A 3-coat 1-bake method (3C1B), which is carried out by leaving at room temperature or by heating at about 200 ° C. or lower, preferably about 60 ° C. to about 170 ° C. for about 10 to about 60 minutes for crosslinking and curing. 3 coat 2 bake method (3C2B)
Alternatively, a three-coat three-bake system (3C3B) is suitable.

As the first colored paint used in the coating method (B-3), the colored paint described in the coating method (B-1) can be used, and among these, a paint capable of concealing a base material is preferable. . Further, as the second colored paint, a coating method (B
Of the color paints exemplified in -1), a paint that forms a colored transparent coating film having a weak concealing property enough to allow the substrate (that is, the first colored paint coated surface) to be seen through can be used. Viscosity of 10 to 25 seconds (Food cup # 4/20 ° C) as 1 clear paint, solid content 20 to 20
A clear paint of the present composition adjusted to 60% by weight is used.

The coating method (B-3) is, specifically, applied directly to a metal or plastic object to be applied to an automobile, or to an undercoat or intermediate coating such as a cationic electrodeposition coating (optional). After coating and curing, the first colored paint is applied by airless spray, air spray, electrostatic coating or the like so that the film thickness becomes about 10 to about 50 μm in a cured coating film,
After heating at about 100 to about 180 ° C to crosslink and cure,
Alternatively, after being left at room temperature for several minutes without curing, the second colored paint is applied to the coated surface in a similar manner to a thickness of about 10
About 100 to about 180
And then left at room temperature for a few minutes at room temperature without curing, and then apply the clear coating composition in a similar manner to a cured coating film thickness of about 10 to about 50 μm.
Paint and leave at room temperature or about 200
C. or lower, preferably from about 60 to about 170.degree.
Performed by heating and crosslinking for 0 minutes, 3
C1B, 3C2B or 3C3B are suitable.

[0061]

Advantages of the Invention The cured coating film formed by the present composition has the same or better weather resistance and finished appearance as compared to organic solvent-based coatings containing a hydroxyl group-containing acrylic resin and a melamine resin as main components, and furthermore, has stain resistance, Scratch resistance is remarkably excellent.

[0062] 2. The acid resistance, weather resistance and finished appearance of the cured coating film formed by the present composition are equal to or higher than those of the acid epoxy type coating material, and the stain resistance is remarkably excellent.

3. Since the cured coating film formed by the present composition is hard, even if contaminants such as bird droppings, pollen, dead insects, and exhaust soot adhere to the coating film, it hardly penetrates into the coating film and easily. It can be wiped off, and the gloss and clarity of the portion are not reduced.

4. The cured coating film of the present composition did not cause iron powder, sand mud, etc. to adhere or sink into the coating film.

5. We have developed a new organic solvent-based paint that forms a good coating such as finished appearance such as weather resistance, gloss and sharpness, acid resistance and stain resistance.

[0066]

The present invention will be described below more specifically with reference to examples and comparative examples. Parts and percentages are based on weight, and the thickness of the coating is for a cured coating.

1. Production Example 1) Component (A) (hydroxyl-containing resin) a): 18 parts of butyl acrylate, 36 parts of cyclohexyl methacrylate, 6 parts of 2-ethylhexyl methacrylate, 10 parts of 2-hydroxyethyl acrylate , 2-
A mixture of 30 parts of hydroxyethyl methacrylate and 9 parts of 2,2'-azobis (2-methylbutyronitrile) was mixed with 50 parts of xylene heated to 125 ° C and butanol.
And a hydroxyl value of about 175
A 65% solution of a hydroxyl-containing resin a) having a mg KOH / g and a number average molecular weight of about 3000 was obtained.

B): 20 parts of isobutyl acrylate, 38 parts of cyclohexyl methacrylate, 6 parts of 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate
9 parts, 2-hydroxyethyl methacrylate 27 parts,
A mixture consisting of 8 parts of 2,2′-azobis (2-methylbutyronitrile) was mixed with xylene 50 heated to 125 ° C.
In a mixed solvent of 6 parts of butanol and 6 parts of butanol, a hydroxyl value of about 158 mgKOH / g and a number average molecular weight of about 3000.
A 65% solution b) of a hydroxyl group-containing resin was obtained.

2) Component (B) (colloidal fine particles of inorganic oxide) a): Colloidal silica having a solid content of 30% dispersed in a mixed solvent of butanol / xylene = 30/70 (weight ratio). Fine particle dispersion. Particle size 10-20 nm.

3) Component (C) (Blocked polyisocyanate compound) a) 50 parts of 2-isocyanate-ethyl-2,6-diisocyanate-tocaproate and 50 parts of methyl ethyl ketone oxime are reacted in butyl acetate. A solution of an isocyanate compound obtained by blocking a hydroxy group; Equivalent to 40% solids in isocyanate compound.

4) Component (D) (Resin having an acidic functional group) a) 13 parts of butyl acrylate, 37 parts of cyclohexyl methacrylate, and 6 parts of 2-ethylhexyl methacrylate 6
Part, 2-hydroxyethyl acrylate 10 parts, 2-hydroxyethyl methacrylate 30 parts, acrylic acid 5
Part, 2,2'-azobis (2-methylbutyronitrile)
A mixture of 9 parts is copolymerized in a mixed solvent of 50 parts of xylene and 6 parts of butanol heated to 125 ° C., and has a hydroxyl value of about 175 mgKOH / g and an acid value of 31 mgK.
An acidic functional group-containing resin having OH / g and a number average molecular weight of about 3000.

2. Examples and Comparative Examples Using the samples obtained in the above Production Examples, these were mixed at the ratio (solid content) shown in Table 1 to obtain an organic solvent-based coating composition.

[0073]

[Table 1]

(Note 1) to (Note 3) in Table 1 are as follows.

(Note 1): Dibutyltin laurate (Note 2): Paratoluenesulfonic acid (Note 3): Acid value (mgKOH / g) Coating performance test result Acrylic resin / melamine resin organic solvent-based metallic paint is applied to a metal plate that has been coated with a cationic electrodeposition paint and an intermediate paint and then heat-cured (film thickness: 20 μm) and left at room temperature for 3 minutes. After that, an organic solvent-based thermosetting coating composition (clear coating) prepared based on the composition shown in Table 1 was coated to a film thickness of 40.
It was coated to a thickness of μm and heated at 140 ° C. for 30 minutes to simultaneously cure the metallic coating and the clear coating.

Using the coated metal plate thus obtained, a performance test of this multilayer coating film was performed. The results are shown in Table 2.

[0077]

[Table 2]

The coating film performance test method in Table 2 is as follows.

Coating appearance: It is the result of visual evaluation. ○
Indicates that the gloss and smoothness are good, Δ indicates that the gloss and smoothness are slightly inferior, and X indicates that the gloss and smoothness are very poor.

Stain resistance: Pigeon droppings collected in the field were mixed with deionized water to a concentration of 30%, the mixture was stirred with a disper for 30 minutes and filtered through a gauze to obtain a test solution. (40 ° C.) for 24 hours, pulled up, washed with water, and observed the coated surface. ○ indicates that no contamination is observed, △ indicates that some stains, blisters and cloud are recognized, and x indicates that many stains, blisters and cloud are recognized.

Hardness: Tween hardness at 20 ° C.

Scratch resistance: Polished powder ("Dalmac Cleanser", trade name, manufactured by Dalmac Cleanser Honpo) was kneaded with water, placed on a coated surface, and further weighed 0.5K.
The coated surface was observed after rubbing the coated surface by reciprocating 40 times while applying a load of g. ○ indicates that the gloss of the coated surface is hardly changed compared to that before the test, Δ indicates that the gloss of the coated surface is slightly lower than before the test, and x indicates that the gloss of the coated surface is slightly lower than before the test. Indicates that you have done.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Kazuhiro Kato 4-171-1, Higashiyawata, Hiratsuka-shi, Kanagawa Prefecture Inside Kansai Paint Co., Ltd. (72) Inventor Hiroshi Igarashi 4-171-1, Higashi-Yawata, Hiratsuka-shi, Kanagawa F term (reference) in Kansai Paint Co., Ltd. 4D075 CA02 CA32 DA06 DB02 DC12 EA12 EB35 EB38 EB55 EB56 EB57 4J038 DG262 DG302 EA011 GA03 KA06 KA20 MA07 MA14 PA07 PB07

Claims (7)

[Claims] 1. A coating composition comprising (A) a hydroxyl group-containing resin, (B) colloidal fine particles of an inorganic oxide, and (C) a polyisocyanate compound which may be blocked, and The base acid value is 0.1 to 50 mgKOH /
g, an organic solvent-based coating composition. 2. Component (A) having a hydroxyl value of 10 to 260 mg.
The organic solvent-based coating composition according to claim 1, which is a hydroxyl group-containing resin having a KOH / g and a number average molecular weight of 1,000 to 60,000. 3. The organic solvent-based coating composition according to claim 1, wherein the component (B) has a particle size of 3 to 200 nm. 4. The composition according to claim 1, wherein the content of the component (B) is:
Based on the total solid content of component (B) and component (C), 1 to
The organic solvent-based coating composition according to claim 1, which is 60% by weight. 5. The organic solvent-based coating composition according to claim 1, wherein the content of component (C) as an unblocked isocyanate group is 1.0 to 16.0 mmol / g. 6. A clear paint applied to the uppermost layer in forming a multi-layer coating by sequentially applying at least one kind of colored paint and at least one kind of clear paint to an object to be coated. A method for forming a multilayer coating film, which is the organic solvent-based coating composition according to any one of the preceding claims. 7. The method according to claim 6, wherein the object to be coated is an automobile outer panel.