JP2001300416A - Coating film forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for forming a laminated coating film having excellent chipping resistance by controlling the affinity or reversal at the interface of an intercoat coating film and a topcoat coating film when both coating films are applied successively by a wet-on-wet method. SOLUTION: In the method for forming the coating film by successively forming the intercoat coating film, a base coating film and a clear coating film on a base material by a wet-on-wet method, an intercoat paint for forming the intercoat coating film and a base paint for forming the base coat film contain a coating film forming resin consisting of an amide group-containing acrylic resin and other coating film forming resin and a curing agent and the content of the curing agent in the respective paints is 20-100% by weight of the coating film forming resin on a solid basis.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a laminated coating film formed on an automobile body and the like, and a laminated coating film obtained by the method.

[0002]

2. Description of the Related Art A laminated coating film for automobiles includes a method of baking and curing each time each coating film is formed, and a method of simultaneously curing a plurality of laminated coating films. For example, the formation of a metallic coating film by two coats and one bake is a commonly used method, and further disclosed in JP-A-11-114489.
As disclosed in Japanese Patent Application Laid-Open Publication No. H11-115, in order to enhance the design properties of the top coat, a color base coat, a metallic base coat, and a clear coat are sequentially formed, and a coat forming method of baking and curing at the same time has already been proposed. .

On the other hand, when a vehicle travels, pebbles are flipped up and collide with the coating film, that is, so-called chipping may cause peeling of the coating film. In the conventional method of forming a coating film, after the intermediate coating film is formed, a step of once curing the intermediate coating film alone is provided.Therefore, a special intermediate coating film having chipping resistance can be provided or a top coating film can be provided. It was possible to take measures such as matching the brightness with the coating film and providing an intermediate coating film with less noticeable chipping.

However, the above-mentioned paint for forming an intermediate coating film is formed by wet-on-wet coating of two or three layers of an intermediate coating film and a top coating film. If the method is applied to a method having no curing step, problems such as adaptation and inversion occur, and the appearance as a laminated coating film is not established.

When the above-mentioned two-layer or three-layer coating film is formed on a wet-on-wet basis, a baking / drying furnace for intermediate coating can be omitted, and a great effect can be expected from the viewpoint of economy and environment. However, when it comes to painting a car body with many irregularities by wet-on-wet, appearance defects such as armpits and familiarity occur depending on parts,
There was a problem.

Further, in the conventional process of forming a laminated coating film, the intermediate coating film is baked once only with the intermediate coating film, and further baked after forming the top coating film. However, in the above method of forming a coating film on a wet-on-wet basis, the intermediate coating film is baked only once, so that the physical properties of the coating film cannot be sufficiently exhibited. In some cases, peeling of the coating film occurred from the film or the surface of the steel sheet, and defects such as rust occurred.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method comprising:
When the intermediate coating film and the top coating film are sequentially applied on a wet-on-wet basis, it controls the adaptation and reversal at the interface between each coating layer, and the size of the peeling and peeling area on the electrodeposition coating surface caused by chipping. It is an object of the present invention to provide a method for forming a laminated coating film that reduces the thickness.

[0008]

According to the present invention, there is provided a method of forming an intermediate coating film, a base coating film and a clear coating film on a substrate in order by wet-on-wet. The base coat forming the base coat and the base coat forming the base coat contains a coat forming resin composed of an amide group-containing acrylic resin and another coat forming resin and a curing agent, Wherein the weight ratio of solid content between the amide group-containing acrylic resin and the other film-forming resin is 30/70 to 80/20, and the amide group-containing acrylic resin and the other film-forming resin in the base paint Is 30/70 to 90/10, and the content of the curing agent in each paint is 20 to 10 with respect to the solid weight of the film-forming resin.
It is intended to provide a method for forming a coating film characterized by being 0% by weight.

Further, the present invention provides a laminated coating film formed by the above method. Hereinafter, the present invention will be described in more detail.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Intermediate Coating In the method for forming a coating according to the present invention, an intermediate coating is used for forming the intermediate coating, and the intermediate coating is composed of an amide group-containing acrylic resin and other coatings. The intermediate coating composition has a solid content weight ratio of the amide group-containing acrylic resin to the other film-forming resin of from 30/70 to 80 / 20 and
The content of the curing agent in the paint is 20 to 100% by weight based on the solid content of the film-forming resin.
Further, it may contain various organic or inorganic coloring pigments and extenders.

The amide group-containing acrylic resin obtained by radical polymerization of the amide group-containing ethylenically unsaturated monomer and another ethylenically unsaturated monomer preferably has a number average molecular weight of 5,000 to 30,000. Preferably it is 7000-25000. If it is smaller than 5,000, workability and curability are not sufficient, and
If the ratio exceeds, the non-volatile content at the time of coating becomes too low, and the workability is rather deteriorated. In the present specification, the molecular weight is determined by a GPC method using a styrene polymer as a standard.

[0012] The amide group-containing acrylic resin is 20 to
It preferably has a hydroxyl value of 180, more preferably 30 to 160. Exceeding the upper limit lowers the water resistance of the coating film, while lowering the lower limit lowers the curability of the coating film. Further, it preferably has an acid value of 2 to 30 mgKOH / g, and more preferably 3 to 25 mgKOH / g.
Exceeding the upper limit lowers the water resistance of the coating film, while lowering the lower limit lowers the curability of the coating film.

The amide group-containing acrylic resin is obtained by radical polymerization of an amide group-containing ethylenically unsaturated monomer and another ethylenically unsaturated monomer. The amide group-containing ethylenically unsaturated monomer is contained in an amount of 1 to 20% by weight, preferably 2 to 20% by weight, based on the total amount of the ethylenically unsaturated monomer used for producing the resin.
15% by weight, 99% of other ethylenically unsaturated monomers
８０80% by weight, preferably 98-85% by weight. When the content of the amide group-containing ethylenically unsaturated monomer is 1
When the amount is less than the weight%, the viscosity controllability and the chipping resistance decrease. If it exceeds 20% by weight, the water resistance of the resulting coating film will be reduced.

Examples of the amide group-containing ethylenically unsaturated monomer include (meth) acrylamide, N-methylol (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N, N-dibutyl (meth) acrylamide, N, N-dioctyl (meth) acrylamide, N-monobutyl (meth) acrylamide and N-
Monooctyl (meth) acrylamide and the like can be mentioned.
Preferred amide group-containing ethylenically unsaturated monomers are acrylamide, methacrylamide, N-monobutylacrylamide and N-monobutylmethacrylamide.

The above-mentioned other ethylenically unsaturated monomers are not particularly limited, but examples thereof include a hydroxyl group-containing ethylenically unsaturated monomer. Specifically, 2-hydroxyethyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate,
Examples include hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, allyl alcohol and methacryl alcohol, and adducts of 2-hydroxyethyl (meth) acrylate with ε-caprolactone. Among them, it is preferable to use a long-chain hydroxyl group-containing monomer as the hydroxyl group-containing monomer from the viewpoint of improving chipping resistance. Examples include 4-hydroxybutyl (meth) acrylate, adducts of 2-hydroxyethyl (meth) acrylate and ε-caprolactone, and the like.

Next, there may be mentioned ethylenically unsaturated monomers having a carboxyl group. Examples thereof include (meth) acrylic acid derivatives (for example, acrylic acid,
Α-hydro-ω-((1-oxo-2-propenyl) oxy) poly (oxy (1-oxo) obtained by adding ε-caprolactone to methacrylic acid, crotonic acid, isocrotonic acid, acrylic acid dimer and acrylic acid And unsaturated dibasic acids, their half esters, half amides and half thioesters (eg, maleic acid, fumaric acid, itaconic acid, their half esters, half amides and half thioesters) ).

Further, examples other than the above monomers include:
(Meth) acrylate ester monomers (eg, methyl (meth) acrylate, ethyl (meth) acrylate,
n-butyl (meth) acrylate, isobutyl acrylate, t-butyl acrylate, 2-ethylhexyl (meth) acrylate, lauryl methacrylate, phenyl acrylate, isobornyl (meth) acrylate, cyclohexyl methacrylate, t-butyl cyclohexyl (meth) acrylate, di-butyl Cyclopentadienyl (meth) acrylate and dihydrodicyclopentadienyl (meth) acrylate, and the like, polymerizable aromatic compounds (such as styrene, α-methylstyrene, vinyl ketone, t-butylstyrene, parachlorostyrene, and vinylnaphthalene) ), Polymerizable nitriles (eg, acrylonitrile and methacrylonitrile), α-olefins (eg, ethylene and propylene), vinyl esters (eg, vinyl acetate) And diene (such as butadiene and isoprene). Such other ethylenically unsaturated monomers can be used alone or in combination of two or more.

An amide group-containing acrylic resin can be obtained by radical copolymerization of each of the above ethylenically unsaturated monomers. As the polymerization method, an ordinary method described in known literature such as solution radical polymerization can be used. For example, a method in which an appropriate radical polymerization initiator and a monomer mixed solution are added dropwise to an appropriate solvent over a period of 2 to 10 hours at a polymerization temperature of 60 to 160 ° C. and agitated while stirring. The radical polymerization initiator that can be used here is not particularly limited as long as it is usually used at the time of polymerization, and examples thereof include azo compounds and peroxides. The solvent that can be used here is not particularly limited as long as it does not adversely affect the reaction, and examples thereof include alcohols, ketones, and hydrocarbon solvents. Further, in order to adjust the molecular weight, a mercaptan such as lauryl mercaptan and a chain transfer agent such as α-methylstyrene dimer may be used as needed.

The above-mentioned other film-forming resins are not particularly limited, and preferred are film-forming resins such as acrylic resins, polyester resins, alkyd resins, epoxy resins and urethane resins. ,
One or more of them can be used in combination.

The solid content weight ratio of the amide group-containing acrylic resin to the other film-forming resin in the film-forming resin component is 30/70 to 80/20, preferably 50/50 to 70/20. 30. When the amide group-containing acrylic resin falls below the lower limit, the suppression of sagging and the appearance are reduced,
If it exceeds the upper limit, the film-forming properties deteriorate.

Preferred examples of the curing agent include amino resins, blocked isocyanate resins, epoxy compounds, aziridine compounds, carbodiimide compounds, and oxazoline compounds. An amino resin and / or a blocked isocyanate resin are particularly preferably used in view of various properties and cost of the obtained coating film.

The content of the curing agent is 20 to 100% by weight based on the total solid content of the film-forming resin including the amide group-containing acrylic resin and other film-forming resins. If the content is less than 20% by weight, the curability becomes insufficient and
If it exceeds 00% by weight, the cured film becomes too hard and brittle.

The amino resin as the curing agent includes:
Not particularly limited, methylated melamine resin,
Butylated melamine resin or a mixed melamine resin of methyl and butyl can be used. For example, "Symer-303", "Symel 254", "Uban 20N60" commercially available from Mitsui Toatsu Co., Ltd., and "Sumimar Series" commercially available from Sumitomo Chemical Co., Ltd. are exemplified.

The content of the above amino resin is 20 to the solid content of the amide group-containing acrylic resin and the film-forming resin.
The content is preferably from 100 to 100% by weight, more preferably from 30 to 100% by weight. If the content is less than 20% by weight, the curability becomes insufficient, and if it exceeds 100% by weight, the cured film becomes too hard and brittle.

Further, the blocked isocyanate resin is obtained by adding a blocking agent having active hydrogen to polyisocyanate, and the blocking agent is dissociated by heating to generate an isocyanate group. One that reacts and cures.

The above-mentioned blocked isocyanate resin is not particularly limited, and typical polyisocyanates include:
Aliphatic isocyanates such as trimethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, and trimethylhexamethylene diisocyanate;
Cyclopentane diisocyanate, 1,4-cyclohexane diisocyanate, aliphatic cyclic isocyanate such as 1,2-cyclohexane diisocyanate, xylylene diisocyanate, 2,4-tolylene diisocyanate, aromatic isocyanate such as 2,6-tolylene diisocyanate, Alicyclic isocyanates such as isophorone diisocyanate and norbornane diisocyanate methyl,
Multimers and mixtures of these nurate compounds can be used.

Examples of the blocking agent include aliphatic, aromatic and heterocyclic compounds such as halogenated hydrocarbons, methanol, ethanol, n-propanol, isopropanol, furfuryl alcohol, alkyl-substituted furfuryl alcohol and benzyl alcohol. Oximes such as alcohol, methyl ethyl ketone oxime, methyl isobutyl ketone oxime, acetone oxime and cyclohexane oxime, and caprolactam and the like can be mentioned.

Of these, preferred are oximes,
Alcohols. Further, a catalyst for dissociating the blocking agent can be used.

The amount of the above blocked isocyanate is as follows:
It is preferably 20 to 100% by weight based on 100% by weight of the total solid content of the film-forming resin in the paint, and 40 to 100% by weight.
More preferably, it is 100% by weight. Outside the above range, curing is insufficient.

Examples of the coloring pigment include organic azo chelate pigments, insoluble azo pigments, condensed azo pigments, phthalocyanine pigments, indigo pigments, perinone pigments, perylene pigments, dioxane pigments, quinacridone pigments, Examples include isoindolinone-based pigments and metal complex pigments, and examples of inorganic-based pigments include graphite, yellow iron oxide, red iron oxide, carbon black, and titanium dioxide. Also,
As the extender, calcium carbonate, barium sulfate, clay, talc and the like are used. In addition, aluminum powder,
A flat pigment such as mica powder may be added.

As a standard, a gray pigment having carbon black and titanium dioxide as main pigments is used.
Further, a combination of a hue with the top coat and a combination of various coloring pigments can also be used.

Further, a viscosity controlling agent can be added to the above intermediate coating material in order to prevent adaptation to the top coating film and ensure coating workability. As the viscosity control agent, those which generally show thixotropic properties can be contained, for example, swelling dispersions of fatty acid amides, amide-based fatty acids, and polyamide-based ones such as long-chain polyaminoamide phosphates,
Polyethylene-based materials such as colloidal swelling dispersion of polyethylene oxide, organic acid smectite clay, organic bentonite-based materials such as montmorillonite, aluminum silicate,
Examples of the viscosity control agent include inorganic pigments such as barium sulfate, flat pigments exhibiting viscosity depending on the shape of the pigment, and crosslinked or non-crosslinked resin particles.

The total solid content of the intermediate coating used in the present invention is 30 to 80% by weight, preferably 3 to 80% by weight.
5 to 65% by weight. Outside this range, the paint stability decreases. On the other hand, if the upper limit is exceeded, the viscosity is too high and the appearance of the coating film deteriorates, and if it is lower than the lower limit, the viscosity is too low and poor appearance such as adaptability and unevenness occurs.

The intermediate coating used in the present invention may contain, in addition to the above components, additives usually added to the coating, such as a surface conditioner, an antioxidant and an antifoaming agent. These amounts are within the range known to those skilled in the art.

The method for producing the coating composition used in the present invention is not particularly limited, including those described below, and those skilled in the art such as kneading and dispersing a compound such as a pigment using a kneader or a roll. All known methods can be used.

Base Coating In the coating forming method of the present invention, the base coating constitutes a top coating together with the clear coating. This base coating is formed from a base paint. The base paint contains a film-forming resin, a curing agent, a coloring pigment, and, if necessary, a glittering pigment.

The base coating material for forming the base coating film contains a film-forming resin composed of an amide group-containing acrylic resin and another film-forming resin, and a curing agent. The solid content weight ratio of the contained acrylic resin to the other film-forming resin is 30/70 to 9
0/10, and the content of the curing agent in the paint is 20 to 100% by weight based on the solid content of the film-forming resin.

As the amide group-containing acrylic resin,
The acrylic resin containing an amide group shown in the description of the intermediate coating material can be given. By containing this resin, the appearance of the coating film and the chipping resistance can be improved.

The above-mentioned other film-forming resins are not particularly restricted but include acrylic resins, polyester resins, alkyd resins, epoxy resins, urethane resins and the like.
More than one species can be used in combination.

The weight ratio of the solid content of the amide group-containing acrylic resin to the other film-forming resin in the above-mentioned film-forming resin component is 30/70 to 90/10, preferably 5/90.
0/50 to 80/20. If the amide group-containing acrylic resin is below the lower limit, sagging is suppressed and the appearance is reduced, and if it exceeds the upper limit, the film forming property is deteriorated.

The content of the amide group-containing acrylic resin in the film-forming resin component contained in the intermediate coating and the base coating and the content of the curing agent in each of the coatings are brought close to each other so that the respective coatings can be formed. Curing distortion can be reduced, and chipping resistance is improved, which is particularly preferable.

To approximate the content of the amide group-containing acrylic resin in the film-forming resin component contained in the intermediate coating and the base coating means that the difference in the content of the amide group-containing acrylic resin in each coating is determined by: That is, it is 20 or less, and more preferably 10 or less.

The above-mentioned film-forming resin can be used in combination with the curing agent mentioned in the description of the above-mentioned intermediate coating. However, from the viewpoint of various properties and cost of the obtained coating film, amino resin and / or Blocked isocyanate resins are used as preferred.

The content of the curing agent is preferably 20 to 100% by weight based on the total solid content of the film-forming resin including the amide group-containing acrylic resin and other film-forming resins. More preferably, it is 30 to 100% by weight. If the content is less than 20% by weight, the curability becomes insufficient, and if it exceeds 100% by weight, the cured film becomes too hard and brittle.

The above-mentioned coloring pigments may include, for example, those mentioned in the description of the intermediate coating.

The glitter pigment optionally contained in the base paint is not particularly limited in its shape, and may be further colored. For example, the glitter pigment may have an average particle size (D ₅₀ ) of 2-5.
It is preferable that the thickness is 0 μm and the thickness is 0.1 to 5 μm. Those having an average particle size in the range of 10 to 35 μm are excellent in glitter and are more preferably used.

The pigment concentration (PW) of the bright pigment in the paint
C) is generally at most 20.0%. If it exceeds the upper limit, the appearance of the coating film will be reduced. Preferably, 0.01% to 1%
8.0%, and more preferably 0.1% to 15.0.
%. When the content of the glittering agent exceeds 20.0% by weight, the appearance of the coating film deteriorates.

The glitter pigment includes aluminum,
Non-colored or colored metal glitters such as metals or alloys such as copper, zinc, iron, nickel, tin and aluminum oxide, and mixtures thereof. Further, interference mica pigments, white mica pigments, graphite pigments, and other colored or colored flat pigments may be used in combination.

The total pigment concentration (PWC) in the paint, including the above-mentioned brilliant pigments and all other pigments, is 0.
1% to 50%, preferably 0.5% to 40%, more preferably 1.0% to 30%. If it exceeds the upper limit, the appearance of the coating film will be reduced.

Further, it is preferable to add a viscosity controlling agent to the base paint, in order to ensure the workability of the coating, similarly to the above-mentioned intermediate paint. The viscosity controlling agent is used for favorably forming a coating film without unevenness and sagging, and generally contains a material having thixotropic properties.
As such a material, for example, those described in the description of the intermediate coating material can be contained.

In the base coating material used in the present invention, in addition to the above-mentioned components, additives usually added to the coating material, for example, a surface conditioner, a thickener, an antioxidant, an ultraviolet inhibitor, an antifoaming agent and the like. May be blended. These amounts are within the range known to those skilled in the art.

The total solid content of the base paint used in the present invention at the time of coating is 10 to 60% by weight, preferably 1 to 60% by weight.
5 to 50% by weight. Exceeding the upper and lower limits lowers the paint stability. If the upper limit is exceeded, the viscosity is too high and the appearance of the coating film is reduced, and if it is lower than the lower limit, the viscosity is too low and poor appearance such as adaptability and unevenness occurs.

[0053] clear coating is used to form the clear coating the clear coating film. The clear paint is not particularly limited, and a paint containing a film-forming thermosetting resin, a curing agent, and the like can be used. Examples of the form of the clear coating include a solvent type, an aqueous type and a powder type.

Preferred examples of the solvent-type clear paint include a combination of an acrylic resin and / or a polyester resin and an amino resin, or an acrylic resin having a carboxylic acid / epoxy curing system in terms of transparency or acid etching resistance. Resins and / or polyester resins.

Examples of the water-based clear paint include a resin obtained by neutralizing a film-forming resin contained in the above-mentioned solvent-based clear paint with a base to form an aqueous solution. Things can be mentioned. This neutralization can be carried out before or after the polymerization by adding a tertiary amine such as dimethylethanolamine and triethylamine.

On the other hand, as the powder type clear coating material, an ordinary powder coating material such as a thermoplastic and thermosetting powder coating material can be used. A thermosetting powder coating is preferred because a coating film having good physical properties can be obtained. Specific examples of the thermosetting powder coating include epoxy, acrylic, and polyester powder clear coatings, and the like.
An acrylic powder clear coating having good weather resistance is particularly preferred.

As the powder type clear paint used in the present invention, there is no volatile matter at the time of curing, a good appearance is obtained, and there is little yellowing.
Powder coatings based on polycarboxylic acids are particularly preferred.

Further, it is preferable that a viscosity control agent is added to the clear paint in order to ensure the workability of the coating, similarly to the above-mentioned intermediate paint. The viscosity controlling agent can generally contain one exhibiting thixotropic properties. As such a material, for example, those described in the description of the intermediate coating material can be contained. If necessary, a curing catalyst, a surface conditioner and the like can be included.

Substrates The coating film forming method of the present invention can be advantageously used for various substrates, for example, metals, plastics, foams, etc., particularly metal surfaces and castings. Can be particularly preferably used.

The metal products include, for example, iron, copper,
Aluminum, tin, zinc, and the like, and alloys containing these metals are included. Specific examples include automobile bodies and parts such as passenger cars, trucks, motorcycles, and buses. It is particularly preferable that these metals have been previously subjected to a chemical conversion treatment with a phosphate, a chromate or the like.

Further, the base material used in the method for forming a metallic coating film of the present invention may have an electrodeposition coating film formed on a chemically treated steel sheet. As an electrodeposition paint for forming an electrodeposition coating film, a cationic type and an anionic type can be used,
The cationic electrodeposition coating composition is preferable because it gives a laminated coating film having excellent corrosion protection.

[0062] In the coating film formation method of a coating film forming method of the present invention, on a substrate, the primer film by the intermediate coating, the clear coating film by base coating film and a clear paint by the base paint, sequentially wet-on-wet Form.

When the intermediate coating is applied to an automobile body according to the present invention, in order to enhance the appearance, multi-stage coating by air electrostatic spray coating, preferably two-stage coating, or air electrostatic spray coating is used. And commonly known as "μ
The coating film can be formed by a coating method or the like in combination with a rotary atomizing electrostatic coating machine called "μ (micro-micro) bell", "μ (micro) bell", or "meta bell".

In the present invention, the thickness of the dried coating film of the intermediate coating varies depending on the desired use.
0-60 μm is useful. If the upper limit is exceeded, the sharpness may deteriorate, or problems such as unevenness or flow may occur at the time of coating. If the lower limit is not reached, the base material cannot be concealed and the film is cut.

In the method for forming a coating film of the present invention, a base coating material and a clear coating material are further applied on an uncured intermediate coating film by wet-on-wet to form a base coating film and a clear coating film.

The base paint used for forming the base coating film in the method of the present invention is the same as the above-mentioned intermediate paint,
The coating can be performed by air electrostatic spray coating or a rotary atomizing electrostatic coating machine such as μμ bell, μ bell, etc., and the dry film thickness of the coating film can be set to 5 to 35 μm, preferably 7 μm. ２５25 μm. When the thickness of the base coating film is more than 35 μm, the sharpness may be deteriorated or unevenness or flow may occur in the coating film. Both are not preferable because the film may be discontinuous).

In the method of forming a coating film according to the present invention, the clear coating film formed after the formation of the above-mentioned base coating film smoothes out irregularities caused by the above-mentioned base coating film, and flickers and the like which occur when a bright pigment is contained. Formed for protection. Specifically, as a coating method, it is preferable to form a coating film by using a rotary atomizing electrostatic coating machine such as a μμ bell or μ bell described above.

The dry film thickness of the clear coating film formed by the clear coating is generally preferably about 10 to 80 μm, more preferably about 20 to 60 μm. If the upper limit is exceeded, problems such as splashes or sagging may occur during coating. If the lower limit is not reached, irregularities on the base cannot be concealed.

The laminated coating film obtained as described above is simultaneously cured to form a coating film by so-called three-coat one-bake. In this case, the baking / drying furnace can be omitted, which is preferable in terms of economy and environment.

The curing temperature for curing the laminated coating film is 80
By setting the temperature to 180 ° C, preferably 120 ° C to 160 ° C, a cured coating film having a high degree of crosslinking can be obtained. When the amount exceeds the upper limit, the coating film becomes hard and brittle, and when the amount is less than the lower limit, curing is not sufficient. The curing time varies depending on the curing temperature.
A temperature of 160 ° C. for 10 to 30 minutes is appropriate.

The thickness of the laminated coating film formed in the present invention is in most cases 30 to 300 μm, preferably 50 to 2 μm.
50 μm. If it exceeds the upper limit, the physical properties of the film such as a thermal cycle decrease, and if it falls below the lower limit, the strength of the film itself decreases.

[0072]

EXAMPLES The present invention will be described in detail with reference to specific examples, but the present invention is not limited to the following examples. In the following, “parts” means “parts by weight”.

Production Example Production of Amide Group-Containing Acrylic Resin 1 A 1-L reaction vessel equipped with a nitrogen inlet tube, a stirrer, a temperature controller, a dropping funnel and a cooling tube equipped with a decanter was charged with 80 parts of xylene and 20 parts of butyl acetate. And the temperature was adjusted to 120 ° C. Next, 5 parts of styrene, 30 parts of methyl methacrylate, 10.4 parts of 2-hydroxyethyl methacrylate, 39.4 parts of ethyl acrylate, 7 parts of ethyl methacrylate, 2.3 parts of methacrylic acid, 5 parts of methacrylamide and 5 parts of a polymerization initiator 2.5 parts of t-butylperoxy-2-ethylhexanoate was charged into a dropping funnel to prepare a monomer solution. The monomer solution was added dropwise over 3 hours while maintaining the inside of the reaction vessel at 120 ° C. After the dropwise addition, the temperature was kept at 120 ° C. for another hour. Number average molecular weight 1
4000, hydroxyl value 45 and acid value 15 mgKOH / g
The amide group-containing acrylic resin 1 was obtained.

Production of Amide Group-Containing Acrylic Resin 80 parts of xylene and 20 parts of butyl acetate were charged into a 1 L reaction vessel equipped with a nitrogen inlet tube, a stirrer, a temperature controller, a dropping funnel and a cooling tube equipped with a decanter. And the temperature was 120 ° C. Next, 5 parts of styrene, 30 parts of methyl methacrylate, 4-hydroxybutyl acrylate 1
1.5 parts, 38.3 parts of ethyl acrylate, 7 parts of ethyl methacrylate, 2.3 parts of methacrylic acid, 5 parts of acrylamide, and t-butyl peroxy-2 as a polymerization initiator
-2.5 parts of ethylhexanoate was charged into a dropping funnel to prepare a monomer solution. The monomer solution was added dropwise over 3 hours while maintaining the inside of the reaction vessel at 120 ° C. After the dropwise addition, the temperature was kept at 120 ° C. for another hour. Number average molecular weight 140
Thus, an amide group-containing acrylic resin 2 having a hydroxyl value of 45 and an acid value of 15 mgKOH / g was obtained.

Production of Film-Forming Resin 80 parts of xylene and 20 parts of butyl acetate were charged into a 1 L reaction vessel equipped with a nitrogen inlet tube, a stirrer, a temperature controller, a dropping funnel and a cooling tube. And 5 parts of styrene, 30 parts of methyl methacrylate, 10.4 parts of 2-hydroxyethyl methacrylate, 44.4 parts of ethyl acrylate, 7 parts of ethyl methacrylate, 2.3 parts of methacrylic acid and 2 parts of t-butylperoxy-2-hexanoate A monomer solution was separately prepared by mixing. This monomer solution was added to the reaction vessel over 3 hours with stirring, and then stirring was continued for 1 hour. Number average molecular weight 21000, hydroxyl value 45 and acid value 15 mg KOH
/ G of acrylic resin 3 was obtained.

Production of Crosslinkable Resin Particles In a reaction vessel equipped with a stirring and heating device, a thermometer, a nitrogen inlet tube, a cooling tube and a decanter, 213 parts by weight of bishydroxyethyltaurine, 208 parts by weight of neopentyl glycol, 296 parts by weight of phthalic anhydride Parts by weight, 376 parts by weight of azelaic acid and 30 parts by weight of xylene were charged and heated to the reflux temperature. Here, water generated by the reaction was removed by azeotropic distillation with xylene.

The temperature in the reaction system was raised to 210 over about 3 hours from the start of reflux, and the reaction was carried out with stirring and dehydration until the acid value corresponding to carboxylic acid in the resin solids reached 135 mgKOH / g.

After the temperature in the reaction system was cooled to 140 ° C., 500 parts by weight of “Kajura E10” (trade name, glycidyl versatate) manufactured by Shell Co., Ltd. were added to 30 parts by weight.
Dropped over minutes. Then, after stirring for about 2 hours, the reaction was terminated. Thereby, the acid value of the resin solid content is 55 m
gKOH / g and a hydroxyl number of 91 mgKOH / g
g, and a zwitterionic group-containing polyester resin having a number average molecular weight of 1250 was obtained.

10 parts by weight of the obtained amphoteric group-containing polyester resin, 140 parts by weight of deionized water, 1 part by weight of dimethylethanolamine, 50 parts by weight of styrene and 50 parts by weight of ethylene glycol dimethacrylate were placed in a stainless steel beaker. A monomer suspension was prepared by vigorous stirring. Also, by mixing 0.5 parts by weight of azobiscyanovaleric acid, 40 parts by weight of deionized water and 0.32 parts by weight of dimethylethanolamine,
An aqueous initiator solution was prepared separately.

A reaction vessel equipped with a stirring and heating device, a thermometer, a nitrogen inlet tube, and a cooling tube was charged with 5 parts by weight of an amphoteric group-containing polyester resin, 280 parts by weight of deionized water, and 0.5 part by weight of dimethylethanolamine. At 80 ℃
Temperature. Here, the previously prepared monomer suspension 2
51 parts by weight and 40.82 parts by weight of an aqueous initiator solution were simultaneously added dropwise over 60 minutes, and the reaction was continued for further 60 minutes. Then, the reaction was terminated to obtain a crosslinkable resin particle emulsion.

The average particle size of the crosslinked resin particle emulsion was 55 nm as measured by a dynamic light scattering method. Xylene was added to this crosslinkable resin particle emulsion, and azeotropic distillation was performed under reduced pressure to remove water and replace the medium with xylene. Thus, a xylene solution of crosslinkable resin particles having a resin solid content of 20% by weight, which can function as a structural viscosity imparting agent, was obtained.

Example 1 Intermediate coating 1 42 parts of the amide group-containing acrylic resin 1 obtained in the preparation 1 of the amide group-containing acrylic resin, and 39.5 parts of titanium oxide.
Part, carbon part 0.4 part, scaly talc 4.4 part and S-100 (exxon aromatic solvent) 2
2.8 parts were charged in a 1000 mL stainless steel container, and mixed and dispersed at room temperature for 45 minutes using a paint conditioner to obtain a gray pigment paste.

To this, 28 parts of the acrylic resin 3 obtained in the above-mentioned production of the film-forming resin and 28 parts of Euban 20N6
0 (butylated melamine resin manufactured by Mitsui Toatsu Co., Ltd.) was added, and the mixture was further stirred and mixed with a laboratory mixer for 30 minutes to obtain a gray intermediate coating material 1. In addition, the compounding amount (part) was shown by solid content.

Metallic base paint 1 Aluminum pigment paste "Alpaste 7160N"
(Toyo Aluminum, aluminum content 65%) 1
In 0 parts, 42 parts of the amide group-containing acrylic resin 1 obtained in the above production example, 28 parts of the acrylic resin 3,
0N60 "(butylated melamine resin manufactured by Mitsui Toatsu) 30
Parts were added and mixed homogeneously. Further, 10 parts of the crosslinkable resin particles produced in the above Production Example were added and further uniformly dispersed to obtain a metallic base paint 1. In addition, the compounding amount (part) was shown by solid content.

[0085] After the zinc coating film forming method phosphoric acid treatment, the cationic electrodeposition paint "Power Top V-6" (manufactured by Nippon Paint Co., Ltd.), a dry film thickness of 20μ
m, and then coated on a coated plate baked at 160 ° C. for 30 minutes, using the diluted paint thinner composed of ethyl acetate / ethylethoxypropanol = 6/4 in advance. What was diluted for 19 seconds (measured at 20 ° C. using a No. 4 Ford cup) was coated with a “microbell” (rotary atomizing electrostatic coating machine) to a dry film thickness of 20 μm. An interval of 5 minutes was taken after application, and setting was performed.

Next, the metallic base paint 1 of the above-mentioned production example was treated with a diluent thinner consisting of toluene / ethyl acetate / ethylethoxypropanol = 5/2/3 to obtain 18.
Seconds (measured at 20 ° C using No. 3 Ford Cup)
The two-stage coating was performed using “Microbell” and “Metabell” so as to have a dry film thickness of 20 μm. 2
An interval of 1.5 minutes was performed between each application.
After the second application, setting was performed for 8 minutes.

Next, MAC O-380 clear (acid epoxy curing type solvent clear paint manufactured by Nippon Paint Co., Ltd.)
One-stage coating was performed with a “microbell” so as to have a dry film thickness of 40 μm, and setting was performed for 7 minutes. Next, the obtained coated plate was baked in a dryer at 140 ° C. for 30 minutes.

The obtained coated plate was visually evaluated for the appearance of the coating film, particularly the glossiness, according to the following evaluation criteria. <Glossy criterion>5; Very glossy 4; Glossy 3; Glossy 2; Slightly glossy 1;

Further, the chipping resistance of the obtained coated plate was evaluated as follows. Using a Gravello tester (manufactured by Suga Test Instruments Co., Ltd.), 100 g of No. 7 crushed stone was injected at a rate of 50 g / s from a distance of 35 cm to 3.0 kg / cm ^2.
At an angle of 30 ° against the coating film cooled to -20 ° C. After washing and drying, a peeling test was performed using an industrial gum tape manufactured by Nichiban Co., Ltd., and then the degree of peeling of the coating film was visually observed and evaluated according to the following criteria. At the same time, the peel interface was visually checked. <Criterion of chipping resistance>5; Peeling area is small and frequency is very small 4; Peeling area is small and frequency is low 3; Peeling area is small but frequency is somewhat high 2: Peeling area is large, The frequency is low 1; the peeled area is large and the frequency is high Table 1 shows the above results.

Examples 2 and 3 The coating components (indicated by solid content) shown in Table 1 were previously blended.
In the same manner as in Example 1, an intermediate coating, a metallic base coating, and a clear coating were combined to prepare a laminated coating film, which was evaluated. In Example 2, DISMODULE BL-3 was used as a blocked isocyanate instead of the melamine resin.
175 (HDI Nurate, manufactured by Sumitomo Bayer Urethane Co., Ltd.)
Was blended in 30 parts.

Comparative Example 1 Each of the intermediate coatings and the metallic base were prepared in the same manner as in Example 1 except that the amide group-containing acrylic resin was not used and the coating components (indicated by solid content) shown in Table 1 were blended. Combine paint and clear paint to produce a laminated coating,
evaluated. Table 1 shows the evaluation results of the above Examples and Comparative Examples.

[0092]

[Table 1]

In the examples of the present invention, even when the intermediate coating film, the base coating film, and the clear coating film were sequentially formed by wet-on-wet, a laminated coating film excellent in glossiness could be obtained. Further, the intermediate coating film containing the amide group-containing acrylic resin has a small appearance peeling area and a low peeling frequency even when chipped. Furthermore, it was found that a fatal defect that peeling occurred at the coating interface between the base material or the undercoating film and the intermediate coating film as in the comparative example, causing rust and deterioration of the undercoating film, could be prevented. Was.

[0094]

As shown in the examples of the present invention, the mixing ratio of the amide group-containing acrylic resin, other film-forming resin and the curing agent contained in the intermediate coating material, and the metallic base coating film are contained. The amide group-containing acrylic resin, other film-forming resins, and the mixing ratio with the curing agent interact with each other in a specific quantitative ratio to reduce curing distortion between each film and optimize chipping resistance. It is thought that various physical properties appear.

According to the method of the present invention, when the intermediate coating film and the metallic coating film are successively applied, adaptation and inversion at the interface between the coating layers can be controlled, and the coating film has excellent physical properties. It has become possible to industrially provide a laminated coating film having an appearance.

Continued on the front page F term (reference) 4D075 AE06 CA04 CA48 DA06 DB02 DC12 EA05 EA43 EB22 EB45 EB56 4J038 CA021 CA022 CB061 CB062 CB091 CB092 CC011 CC012 CC061 CC062 CC071 CC072 CC081 CC082 CC101 CC102 CG1 CE2 CG061 CG062 CG071 CG072 CG121 CG122 CG141 CG142 CG161 CG162 CH031 CH032 CH041 CH042 CH071 CH072 CH121 CH122 CJ131 CJ132 DB001 DB002 DD001 DD002 DD121 DD122 DG001 DG002 GA09 KA03 NA12 NA23 PB07 PC02 PC08

Claims (2)

[Claims] In a method of forming an intermediate coating film, a base coating film and a clear coating film on a base material sequentially in a wet-on-wet manner, the intermediate coating material for forming the intermediate coating film and The base paint for forming the base coating film contains a film-forming resin and a curing agent composed of an amide group-containing acrylic resin and other film-forming resins, and the amide group-containing acrylic resin in the intermediate coating. The solid content weight ratio with the other film-forming resin is 30/70 to 80/20.
Wherein the weight ratio of the solid content between the amide group-containing acrylic resin and the other film-forming resin in the base paint is 3
0/70 to 90/10, and the content of the curing agent in each paint is 20 to 100% by weight based on the solid content of the film-forming resin. Forming method. 2. A laminated coating film formed by the method according to claim 1.