JPH0994523A - Multi-layer film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve resistances to acid, chipping and wet-on-wet properties by forming a base coating material and a clear coating material by using of acrylic polymers of specified compositions, respectively. SOLUTION: A carboxyl containing monomer represented by formula I or II of 0.2-20wt.%, a (meth)acrylamide monomer represented by formula III of 3-40wt.%, a (meth)acrylate containing hydroxyl of 5-60wt.%, a (meth)acrylate represented by formula IV of 20-80wt.% and a vinyl monomer of 0-50wt.% are copolymerized, and an acrylic copolymer having the hydroxyl value of 30-120mgKOH/g, the acid value of 0.1-40mgKOH/g and weight average molecular weight of 3000-100000 is formed. A base coating material is prepared by the above acrylic copolymer of 50-95wt.%, a curing agent of 5-50wt.% and other resin of 0-40wt.%. A clear coating material is prepared by an acrylic polymer containing carboxyl and an acrylic polymer containing epoxy. In the formulae, R<1> -R<6> represent respectively prescribed hydrocarbon substituent groups.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-layer coating film which is required to have cosmetic properties such as automobiles and long-term weather resistance. More specifically, the present invention relates to a metallic powder, a glittering material such as mica and / or a coloring material. The present invention relates to a two-coat, one-bake multi-layer coating film using a base coat paint containing a pigment and a clear coat paint.

[0002]

2. Description of the Related Art Acrylic-melamine resins are often used as top-coat paints for automobiles because they have excellent weather resistance and beauty. However, in the clear coat paint, the acrylic-melamine-based resin has a low acid resistance because the melamine resin is used as a curing agent, and has the drawback that acid stains cause rain stains on the coating film to deteriorate the appearance. ing.

In order to solve this problem, a clear coat paint having a novel curing system in place of melamine has been demanded, and various curing systems utilizing a crosslinking reaction between an acid group and an epoxy group have been proposed.

For example, Japanese Patent Application Laid-Open No. 1-196553 discloses a thermosetting solvent type coating composition comprising an acrylic copolymer having an acid group and an acrylic polymer having an epoxy group, and Japanese Patent Application Laid-Open No. 2-19653. Japanese Patent No. 45577 discloses a thermosetting composition containing a copolymer obtained by half-esterifying an acid anhydride group as an acid group and a compound having a hydroxyl group and an epoxy group.

However, although the above clear coat paints have good acid resistance, the polarities of the paints are high because the resin contains many functional groups such as acid groups and epoxy groups. When coating by the wet-on-wet method, the base coat and the clear coat are mixed at the interface, and there is a problem that the finished appearance such as gloss and smoothness is deteriorated.

On the other hand, chipping resistance is also required for automotive top coatings. Chipping is a phenomenon in which pebbles and the like that are flipped up while a vehicle is running collide with the vehicle body and the coating film is momentarily peeled off. When the damage extends to the metal substrate, not only the aesthetic appearance is deteriorated but also corrosion progresses.

Usually, the coating system of an automobile is composed of each process of chemical conversion treatment, electrodeposition coating, intermediate coating and top coating, and in order to improve chipping resistance, energy generated by impact is It is necessary to absorb it in the coating film and prevent it from being transmitted to the metal substrate.

Therefore, for example, Japanese Patent Laid-Open No. 63-593 is used.
No. 75, a method for imparting flexibility to an intermediate coating film,
JP-A-6-322059 proposes a method of adding a highly flexible coating film called a chipping primer to a laminated coating film, but the top coating film has a coating film performance such as weather resistance and a cosmetic property. Since it is intended to impart the chipping property, it is difficult to achieve compatibility with imparting the chipping resistance.

[0009]

SUMMARY OF THE INVENTION The object of the present invention is to improve the original glossiness of acrylic thermosetting resins, coating film performance, and cosmetic properties in the case of containing a glittering material such as metallic powder or mica and a coloring pigment. An object of the present invention is to provide a multilayer coating film which is excellent in acid resistance, chipping resistance and wet-on-wet property without deteriorating.

[0010]

[Means for Solving the Problems] That is, according to the present invention, a base coat paint containing a luster colorant and / or a coloring pigment is applied, and a clear coat paint is overcoated without heating, followed by heat curing. In a 1-bake multi-layer coating film, the base coat coating comprises (1) (a) 0.2 to 10% by weight of a carboxyl group-containing monomer represented by the following general formula (I) or (II):

Embedded image

[Chemical 6] (B) 3 to 40% by weight of a (meth) acrylamide-based monomer represented by the following general formula (III),

[Chemical 7] (C) Hydroxyl group-containing (meth) acrylic acid ester 5 to 60
% By weight, (d) represented by the following general formula (IV) (meta)
Acrylic ester 20 to 80% by weight,

Embedded image (E) A hydroxyl value of 30 to 120 mgKOH / g and an acid value of 0.1 obtained by copolymerizing 0 to 50% by weight of another vinyl monomer copolymerizable with the above components (a) to (d). 40 mg
KOH / g, and weight average molecular weight of 3000-100
Acrylic copolymer (A) of 50 to 95% by weight, a curing agent (B) of 5 to 50% by weight, and another resin (C) of 0 to 40% by weight, and a clear paint comprising ) Acrylic polymer (D) having a carboxyl group
And an acrylic polymer (E) having an epoxy group.

[0011]

DETAILED DESCRIPTION OF THE INVENTION A detailed description will be given below. The acrylic polymer (A) used in the base coat paint of the present invention has a specific monomer (a) to (e) having the above specific structure (however, the use of the monomer (e) is optional). It is obtained by copolymerizing at a ratio.

The carboxyl group-containing monomer (a) represented by the above general formulas (I) and (II) is a component exhibiting a remarkable effect in improving the wet-on-wet property of the 2-coat 1-bake system. The amount of the monomer (a) used is 0.2
It is used in the range of 10 to 10% by weight. If it is less than 0.2% by weight, the effect of improving the wet-on-wet property is not sufficient, and if it exceeds 10% by weight, the viscosity of the resin solution becomes high and the solid content of the coating becomes low, and the pigment and the curing agent are hardened. The storage stability of the base coat paint containing the composition becomes poor.

Specific examples of the carboxyl group-containing monomer (a) represented by the above general formula (I) or (II) include:
Examples thereof include fumaric acid, fumaric acid monomethyl ester, fumaric acid monobutyl ester, maleic acid, maleic acid monomethyl ester, maleic acid monobutyl ester, itaconic acid, itaconic acid monomethyl ester, and itaconic acid monobutyl ester. These can be used alone or in combination of two or more.

The (meth) acrylamide monomer (b) represented by the general formula (III) is used in the range of 3 to 40% by weight. If it is less than 3% by weight, the effect of improving chipping resistance and impact resistance is not sufficient, and if it exceeds 40% by weight, the water resistance and gloss of the coating film are deteriorated.

Specific examples of the (meth) acrylamide-based monomer (b) represented by the above general formula (III) include N-methylol (meth) acrylamide, N-methoxymethyl (meth) acrylamide and N-ethoxymethyl. (Meta)
Examples thereof include acrylamide, N-butoxymethyl (meth) acrylamide, N-isobutoxymethyl (meth) acrylamide, N-hexyloxymethyl (meth) acrylamide and the like. These can be used alone or in combination of two or more.

The hydroxyl group-containing (meth) acrylic acid ester (c) is used in the range of 5 to 60% by weight. If it is less than 5% by weight, the cross-link density of the cured coating film is lowered, so that the hardness, water resistance, solvent resistance, weather resistance, etc. are lowered, and if it exceeds 60% by weight, the cured coating film becomes brittle and flexible. As well as water resistance and moisture resistance.

Specific examples of the hydroxyl group-containing (meth) acrylic acid ester (c) include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, and 4-hydroxybutyl (meth) acrylate. .

Further, 1 mol addition product, 2 mol addition product, 3 mol addition product or 4 mol addition product of γ-butyrolactone to 2-hydroxyethyl (meth) acrylate, or 2-
Ring-opening addition products of organic lactones to hydroxyl group-containing (meth) acrylates such as 1 mol addition product, 2 mol addition product, 3 mol addition product or 4 mol addition product of ε-caprolactone to hydroxyethyl (meth) acrylate Is mentioned.
These compounds can be synthesized by a known addition reaction using a transition metal.

Further, ring-opening adducts of ethylene oxide and propylene oxide with methacrylic acid or acrylic acid, and dimers and trimers of 2-hydroxyethyl (meth) acrylate or 2-hydroxypropyl (meth) acrylate. It also includes a quantity. These can be used alone or in combination of two or more.

The (meth) acrylic acid ester (d) represented by the above general formula (IV) contributes to imparting a metallic feeling and a glossy feeling, and at the same time, the water resistance, solvent resistance, chemical resistance and weather resistance of the coating film. It also has the property of improving the property such as 20 to 8
Used in the range of 0% by weight. If it is less than 20% by weight, the above effect is insufficient, and if it exceeds 80% by weight, the cross-linking density of the cured coating film is lowered and water resistance, moisture resistance and the like are lowered.

Specific examples of the (meth) acrylic acid ester (d) include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, and n.
-Butyl (meth) acrylate, i-butyl (meth) acrylate, sec-butyl (meth) acrylate, t
-Butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, cyclohexyl (meth) acrylate, phenyl (meth) acrylate, benzyl (meth )
Acrylate and the like. These can be used alone or in combination of two or more.

The other vinyl monomer (e) copolymerizable with the above-mentioned components (a) to (d) is used in the automotive paint, which is the main use of the present invention, for quality performance such as weather resistance, cosmetics, Since it affects chemical resistance, solvent resistance, water resistance, flexibility, adhesion, etc., it is appropriately selected and used within a range not impairing these performances. The usage range of the monomer (e) is 0
It is ˜50% by weight, preferably 40% by weight or less.

Specific examples of the other copolymerizable vinyl monomer (e) include styrene derivatives such as styrene, α-methylstyrene and vinyltoluene; polymerizable unsaturated nitriles such as acrylonitrile and methacrylonitrile; Vinyl esters such as vinyl acetate; epoxy group-containing monomers such as glycidyl (meth) acrylate and (meth) acrylglycidyl ether; basic monomers such as dimethylaminoethyl (meth) acrylate and diethylaminoethyl (meth) acrylate Etc.

Examples of the carboxyl group-containing monomer other than the carboxyl group-containing monomer (a) represented by the general formulas (I) and (II) include acrylic acid and methacrylic acid. These can be used alone or in combination of two or more.

The hydroxyl value of the acrylic copolymer (A) of the present invention is preferably in the range of 30 to 120 mgKOH / g. If the hydroxyl value is less than 30 mgKOH / g, the curability is insufficient and the solvent resistance and weather resistance are reduced, and the interlayer adhesion to the clear coating film is also reduced. If it exceeds 120 mgKOH / g, the water resistance of the coating film is reduced. Sex will be reduced.

The acid value of the acrylic copolymer (A) is preferably in the range of 1-40 mgKOH / g. When the acid value is less than 1 mgKOH / g, the curability is insufficient and the solvent resistance and weather resistance are lowered, and when it exceeds 40 mgKOH / g, the water resistance of the coating film is lowered.

The weight average molecular weight of the acrylic copolymer (A) is preferably in the range of 3,000 to 100,000. When the weight average molecular weight is less than 3,000, solvent resistance and weather resistance are deteriorated. When the weight average molecular weight is more than 100,000, the viscosity of the resin solution is increased, so that the solid content of the coating is lowered and the appearance of the coating film is also deteriorated. Become.

The polymerization method of the acrylic copolymer (A) of the present invention may be any known polymerization method such as solution polymerization method, bulk polymerization method and emulsion polymerization method, but in general, the solution polymerization method is used. preferable.

In the case of the solution polymerization method, the mixture of the above monomers is copolymerized in the presence of an organic solvent and a polymerization initiator. As the organic solvent, isopropyl alcohol, n
-Generally used organic solvents such as butanol, toluene and xylene can be used. As the polymerization initiator, a commonly used polymerization initiator such as azobisisobutyronitrile, benzoyl peroxide and cumene hydroperoxide can be used. Furthermore, if necessary, a chain transfer agent such as 2-mercaptoethanol, n-octylmercaptan, n-dodecylmercaptan, α-methylstyrene dimer or the like can be used.

The acrylic polymer (A) used in the base coat paint of the present invention is used in the range of 50 to 95% by weight. If it is less than 50%, the effect of improving the wet-on-wet property and chipping resistance of the two-coat one-bake system in the automotive coating which is the main application of the present invention is not sufficient, and if it exceeds 95%, a cured coating film is obtained. The cross-linking density becomes low and the water resistance becomes low.

The curing agent (B) used in the base coat paint of the present invention is used in the range of 5 to 50% by weight. 5
When it is less than wt%, the cross-linking density of the cured coating film becomes low,
The hardness and water resistance are lowered, and when it exceeds 50% by weight, the cured coating film becomes brittle and flexibility is lowered, and the physical performance and the chemical performance are deteriorated.

As the curing agent (B), amino resins, polyisocyanate compounds, etc. are used. Amino resins include amino compounds such as aminotriazine, urea, benzoguanamine and acetoguanamine, and formaldehyde,
Amino resins obtained by further alkyl-etherifying a condensation product with an aldehyde compound such as acetaldehyde with an alkanol having 1 to 6 carbon atoms,
Methyl etherified melamine resin and butyl etherified melamine resin obtained from aminotriazine are particularly preferable.

Specific examples of the polyisocyanate compound include aliphatic or alicyclic diisocyanates such as tetramethylene diisocyanate, hexamethylene diisocyanate and isophorone diisocyanate, burettes, dimers and trimers thereof, or these. Examples of the polyisocyanate include ethylene glycol, propylene glycol, and polyhydric alcohol adducts such as trimethylolpropane. Further, the isocyanate group is blocked with a known blocking agent such as alcohols, amides, imides, and oximes. There are things.

In the base coat paint of the present invention, in addition to the acrylic copolymer (A) and the curing agent (B), water resistance,
Other resins (C), for example, known resins such as polyester resins, acrylic resins, and epoxy resins can be used for the purpose of improving the pigment dispersibility and the adhesion to the intermediate coating film. The amount of these resins used is 40% by weight or less. If it exceeds 40% by weight, the wet-on-wet property with the clear coating, the chipping resistance, and the weather resistance, which are the objects of the present invention, may be deteriorated.

In the base coat paint of the present invention, bright materials such as aluminum paste, metallic powder, mica, and scaly iron oxide, which are conventionally known when used as paints; titanium oxide, carbon black, quinacridone, cyanine blue, etc. Coloring pigments; resins such as fibrous resins; external catalysts for amino resins such as paratoluene sulfonic acid, dodecylbenzene sulfonic acid or their neutralized amines; surface conditioners, UV absorbers, antioxidants, pigment settling inhibitors Additives such as thixotropic agents can be used as necessary.

The acrylic polymer (D) used in the clear coat paint of the present invention is obtained by copolymerizing a polymerizable monomer mixture containing a monomer having a carboxyl group.

Examples of the carboxyl group-containing monomer used in the acrylic polymer (D) include acrylic acid,
Methacrylic acid, fumaric acid, fumaric acid monomethyl ester, fumaric acid monobutyl ester, maleic acid, maleic acid monomethyl ester, maleic acid monobutyl ester, itaconic acid, itaconic acid monomethyl ester,
Itaconic acid monobutyl ester, itaconic anhydride, maleic anhydride, citraconic anhydride, and the like.In addition, itaconic anhydride, maleic anhydride, citraconic anhydride and other acid anhydride groups are subjected to ring-opening esterification with an alkanol after polymerization. Examples thereof include those having the α, β-dicarboxylic acid monoester obtained as a structural unit. These can be used alone or in combination of two or more.

The amount of these carboxyl group-containing monomers used is such that the acrylic copolymer (D) has an acid value of 30 to 200.
The range is preferably mgKOH / g, for example, 5 to 40% by weight.

Other polymerizable monomers used in the acrylic polymer (D) include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth). Acrylate, i-butyl (meth) acrylate, sec-butyl (meth) acrylate, t-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, lauryl (meth) acrylate, stearyl ( (Meth) acrylate ester monomers having a hydrocarbon substituent such as (meth) acrylate, cyclohexyl (meth) acrylate, phenyl (meth) acrylate, benzyl (meth) acrylate; styrene, α-methylstyrene, vinyltoluene, etc. Styrene derivative; acryloni Polymerizable unsaturated nitriles such as ril and methacrylonitrile; acrylamide monomers such as N-methylol (meth) acrylamide, N-methoxymethyl (meth) acrylamide, N-butoxymethyl (meth) acrylamide; 2-hydroxy Ethyl (meta)
Acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate,
Γ-Butyrolactone ring-opening adduct of 2-hydroxyethyl (meth) acrylate, 2-hydroxyethyl (meth)
Ε-caprolactone ring-opening adduct of acrylate, ring-opening adduct of ethylene oxide or propylene oxide to 2-hydroxyethyl (meth) acrylate or 2-hydroxypropyl (meth) acrylate, 2
A hydroxyl group-containing (meth) acrylic acid ester monomer such as a dimer or trimer of hydroxyethyl (meth) acrylate or 2-hydroxypropyl (meth) acrylate;
Vinyl esters such as vinyl acetate; glycidyl (meth)
Epoxy group-containing monomers such as acrylate and (meth) acrylic glycidyl ether; and basic monomers such as dimethylaminoethyl (meth) acrylate and diethylaminoethyl (meth) acrylate. These can be used alone or in combination of two or more.

The acid value of the acrylic copolymer (D) of the present invention is preferably in the range of 30 to 200 mgKOH / g. If the acid value is less than 30 mg KOH / g, the curability is insufficient, the hardness of the coating film and the solvent resistance are reduced, and 200 mg.
If it exceeds KOH / g, the viscosity of the resin solution will increase significantly,
Further, the weather resistance and water resistance of the coating film will be reduced.

The weight average molecular weight of the acrylic copolymer (D) is preferably in the range of 5,000 to 50,000. If the weight average molecular weight is less than 5,000, the solvent resistance and weather resistance of the coating film will deteriorate, and if it exceeds 50,000, the viscosity of the resin solution will remarkably increase, the solid content of the coating composition will decrease, and the appearance of the coating film will also decrease. Will start to decline.

The acrylic polymer (E) in the clear coat paint of the present invention is obtained by copolymerizing a polymerizable monomer mixture containing a monomer having an epoxy group.

Examples of the epoxy group-containing monomer used in the acrylic polymer (E) include glycidyl (meth) acrylate, methylglycidyl (meth) acrylate and 3,4-epoxycyclohexylmethyl (meth).
Examples thereof include acrylate and allyl glycidyl ether. These can be used alone or in combination of two or more.

The amount of these epoxy group-containing monomers used is
The epoxy equivalent of the acrylic copolymer (E) is 200 to
It is preferably in the range of 1500 g / eq, for example, in the range of 10 to 60% by weight.

As the other polymerizable monomer used in the acrylic polymer (E), all of those exemplified as the copolymerizable polymerizable monomer described in the acrylic polymer (D) can be used. Can be used alone or in combination of two or more.

The epoxy equivalent of the acrylic copolymer (E) of the present invention is preferably in the range of 200 to 1500 g / eq. If the epoxy equivalent exceeds 1500 g / eq, the curability is insufficient and the solvent resistance and weather resistance are reduced.
If it is less than g / eq, the resin solution tends to thicken or gel.

The weight average molecular weight of the acrylic copolymer (E) is preferably in the range of 1,000 to 20,000. If the weight average molecular weight is less than 1000, solvent resistance and weather resistance are deteriorated, and if it exceeds 20,000, the viscosity of the resin solution is remarkably increased, the solid content of the coating is lowered, and the appearance of the coating film is also deteriorated. become.

The acrylic polymers (D) and (E) in the clear coat paint of the present invention can be polymerized by a conventional method similarly to the acrylic polymer (A) in the base coat paint. The polymerization method described in the combination (A), an organic solvent, a polymerization initiator and, if necessary, a chain transfer agent can be used.

The molar ratio of the carboxyl group of the acrylic polymer (D) and the epoxy group of the acrylic polymer (E) in the clear coat coating composition of the present invention is 1 / 2≤carboxyl group / epoxy group≤1 / 0. A range of 0.5 is preferred. Outside this range, the water resistance and weather resistance of the coating film will decrease due to unreacted functional groups.

The clear coat paint of the present invention may contain a catalyst to accelerate curing. The curing catalyst may be a known one used in the esterification reaction of an acid group and an ester group, and for example, a quaternary ammonium salt or a phosphonium salt is preferable. Specific examples thereof include benzyltrimethylammonium chloride, benzyltrimethylammonium bromide, benzyltributylammonium chloride, benzyltributylammonium bromide, tetrabutylammonium chloride and tetrabutylammonium bromide.

The clear coat paint of the present invention contains
If necessary, an amino resin or an isocyanate compound can be added as an auxiliary curing agent in order to increase the crosslink density.

In order to improve the stability, if necessary, an acid represented by sulfonic acid such as paratoluenesulfonic acid and dodecylbenzenesulfonic acid, or phosphoric acid such as monoalkylphosphoric acid and dialkylphosphoric acid. Compounds can be added.

Further, known resins such as polyester resin, acrylic resin and epoxy resin; rheology control agents such as organic benton, polyamide, microgel and fibrin resin; surface conditioner, ultraviolet absorber, light stabilizer, oxidation Additives such as inhibitors can be used if necessary. The multilayer coating film of the present invention is formed by applying a base coat coating composition and a clear coating coating composition in which the above-mentioned components are compounded by a general compounding method, and then heating and curing.

The following method can be exemplified as a typical forming method. First, the base coat paint was diluted with Ford Cup No. The viscosity at 20 ° C according to 4 is 10 to 2
It was adjusted to be within the range of 0 second, and the dry film thickness was adjusted to 10 to 30 with respect to the base material on which the primer coating film was previously formed.
Paint so that the thickness becomes μm. Then, after leaving it at room temperature for several minutes, the clear coat paint was diluted with a Ford cup No. 4. The viscosity at 20 ° C. according to No. 4 was adjusted to be within the range of 15 to 40 seconds, and this was overcoated on the base coat coating film so that the dry film thickness was 20 to 60 μm.
Leave at room temperature for a few minutes. After that, 100 ℃ ~ 180 ℃
It is cured in the temperature range of 10 to 40 minutes. In this way, it is possible to form a two-coat one-bake multi-layer coating film having excellent acid resistance, chipping resistance and wet-on-wet resistance.

[0055]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to examples, but the present invention is not limited to these examples. All parts and percentages in the examples are by weight.

Acrylic polymer B-for base coat paint
Examples of Synthesis of 1 to B-10 The solvent shown in Table 1 was added to a container equipped with a stirrer, a temperature controller, and a cooling tube, and heated to 100 ° C while stirring. Thereafter, a mixture of the monomer and the polymerization initiator having the composition shown in Table 1 was added dropwise over 4 hours, and the mixture was further polymerized at the same temperature for 3 hours to increase the conversion rate to a resin, and thus the acrylic polymer for base coat paint B-1. .About.B-10 were synthesized.

[0057]

[Table 1]

Acrylic polymer C for clear coat paint
Synthesis Example of -1 After purging nitrogen into a container equipped with a stirrer, a temperature controller, a cooling pipe, and a nitrogen introducing pipe, the solvent shown in Table 2 was added,
Heat to 100 ° C. with stirring. After that, a mixture of the monomer and the polymerization initiator having the composition shown in Table 2 was added dropwise over 4 hours, and the mixture was further polymerized at the same temperature for 3 hours to increase the conversion rate into a resin, and thus the acrylic polymer C- for clear coat paint.
1 was synthesized.

Acrylic polymer C for clear coat paint
-2, C-3 Synthesis Example After purging nitrogen into a container equipped with a stirrer, a temperature control device, a cooling pipe, and a nitrogen introducing pipe, the solvents shown in Table 2 were added,
Heated to 130 ° C. with stirring. After that, a mixture of the monomer and the polymerization initiator having the composition shown in Table 2 was added dropwise over 4 hours, and the mixture was further polymerized at the same temperature for 3 hours to increase the conversion rate into a resin, and thus the acrylic polymer C- for clear coat paint.
2, C-3 was synthesized.

[0060]

[Table 2]

Preparation of Base Coat Paints BP-1 to BP-14 The base coat paints (BP
-1 to BP-14) were obtained. In addition, BP-11 to BP-
For No. 13, using a known disperser, the red pigment was
It was confirmed that the particles were pulverized to a size of μm or less. Apply this basecoat paint to ethyl acetate / toluene / Solvesso # 1
50 (Esso Co., aromatic hydrocarbon) = 40/30/3
Ford cup No. No. 4 was adjusted to 13 seconds / 20 ° C.

[0062]

[Table 3]

Preparation of clear coat paint CP-1 The following components were blended to obtain a clear coat paint (CP-1). Acrylic polymer (C-1) 100 parts Acrylic polymer (C-2) 80 parts Benzyltributylammonium chloride 1.8 parts Tinuvin 328 (UV absorber made by Ciba Geigy) 1.3 parts Sanol LS-440 (Sankyo) Light stabilizer manufactured by Co., Ltd. 1.3 parts Modaflow (leveling agent manufactured by Monsanto Co.) 0.2 parts Next, this clear coat paint (CP-1) was applied to Solvesso # 100 / cellosolve acetate = 50/50.
Diluted with a mixed solvent consisting of (% by weight), and Ford Cup No. It was prepared so as to be 25 seconds / 20 ° C.

Preparation of clear coat paint CP-2 The following components were blended to obtain a clear coat paint (CP-2). Acrylic polymer (C-3) 120 parts U-Van 20SE-60 50 parts Tinuvin 328 1.3 parts Sanol LS-440 1.3 parts Modaflow 0.2 parts Then, this clear coat paint was applied to Solvesso # 10.
Dilute with a mixed solvent consisting of 0 / Solvesso # 150 = 2/1 (weight ratio), and Ford Cup No. 28 seconds / 2 in 4
The temperature was adjusted to 0 ° C.

[0065]

Examples 1 to 7 and Comparative Examples 1 to 8 A zinc phosphate-treated steel sheet (0.8 mm × 300 mm × 900 mm) was coated with a cationic electrodeposition paint for automobiles, baked at 180 ° C. for 30 minutes, and further subjected to amino treatment. An alkyd resin-based intermediate coating material was applied and baked at 160 ° C. for 30 minutes, and then the coating film was water-polished to obtain a test piece. First, the base coat paint (BP-1 to BP-14) was applied on the test piece so that the dry film thickness was 15 μm, and after leaving it for 5 minutes, the clear coat paint (CP-1 to CP-2) was dried. Film thickness is 3
The wet-on-wet method was repeatedly applied so as to have a thickness of 5 μm, and the coating was left at room temperature for 15 minutes and then baked at 140 ° C. for 30 minutes to form a multi-layer coating film by a two-coat one-bake method.
The coating performance of the resulting multilayer coating is shown in Table 4.

[0066]

[Table 4]

As is clear from Table 4, the multilayer coating films of the present invention (Examples 1 to 7) were superior to the multilayer coating films (Comparative Examples 1 to 8) which did not satisfy the conditions specified by the present invention. It can be seen that it has good gloss due to wet-on-wet property, coating film appearance and excellent acid resistance and chipping resistance, and is also excellent in other coating film performance.

[0068]

The multi-layer coating film of the present invention is excellent in acid resistance, chipping resistance and wet-on-wet property without impairing glossiness, coating film performance and cosmetic properties, and is particularly useful as a vehicle body coating film. Extremely useful.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display location C09D 133/06 PFY C09D 133/06 PPHY 133/14 133/14 133/26 PFW 133/26 PFW

Claims (1)

[Claims] 1. A two-coat, one-bake multi-layer coating comprising coating a base coat paint containing a brightening material and / or a coloring pigment, applying the clear coat paint repeatedly without heating, and then curing by heating. The base coat coating comprises (1) (a) 0.2 to 10% by weight of a carboxyl group-containing monomer represented by the following general formula (I) or (II): Embedded image (B) 3 to 40% by weight of a (meth) acrylamide-based monomer represented by the following general formula (III): (C) Hydroxyl group-containing (meth) acrylic acid ester 5 to 60
% By weight, (d) represented by the following general formula (IV) (meta)
Acrylic ester 20-80% by weight, (E) A hydroxyl value of 30 to 120 mgKOH / g and an acid value of 0.1 obtained by copolymerizing 0 to 50% by weight of another vinyl monomer copolymerizable with the above components (a) to (d). 40 mg
KOH / g, and weight average molecular weight of 3000-100
The acrylic coating composition (A) of 50 to 95% by weight, the curing agent (B) of 5 to 50% by weight, and the other resin (C) of 0 to 40% by weight, 2) Acrylic polymer (D) having a carboxyl group
And an acrylic polymer (E) having an epoxy group.