JPH08220B2 - How to paint metal materials - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a coating method for forming a coating film excellent in chipping resistance, corrosion resistance and physical performance on a metal material, particularly an automobile outer plate.

In the field of automobile industry, problems such as durability of the coating film, particularly deterioration of coating film appearance due to impact peeling and acceleration of corrosion of metal material are being emphasized. In particular, in an automobile running on a road, rock salt particles and pebbles that are bounced up by wheels collide with the surface of the coating film on the outer surface of the vehicle, and the impact causes the coating film to locally peel off entirely from the vehicle body. It often causes "chipping". Due to this phenomenon, the metal surface of the impacted portion on the outer surface of the vehicle body is exposed, promptly rusts, and corrosion progresses. Usually, peeling of the coating film due to chipping is common on the bottom of the vehicle body and around the feet,
It is known that local corrosion occurs considerably in about half a year to one year after it reaches the hood and roof.

In order to prevent the chipping and the progress of corrosion caused by the chipping, various studies have been conventionally conducted on the chemical conversion treatment of the outer metal substrate surface of the vehicle body, and the electrodeposition coating, the intermediate coating and the top coating. For example, in chemical conversion treatment, the use of iron phosphate-based coatings and zinc phosphate-based coatings with different crystal forms was examined, but it is difficult to sufficiently improve the adhesion of the coating on the impacted area by such chemical conversion treatment. is there. In addition, various studies have been conducted on resins and / or pigments contained in the electrocoating paints, intermediate coatings, and topcoating paints, but those having a sufficient adhesion improving effect that can withstand chipping have been hitherto found. It has not been found yet.

Therefore, the present inventors have sought to improve the above-mentioned problems.
For forming a coating film that has at least the same finished appearance as that obtained by the coating system of steel plates consisting of ordinary electrodeposition paint, intermediate paint and topcoat paint, and that is excellent in chipping resistance, physical properties and corrosion resistance. As a result of intensive studies aimed at providing a coating method, the present invention has been completed.

That is, according to the present invention, a metal material is coated with an electrodeposition coating composition and an intermediate coating composition, and then the intermediate coating surface has a static glass transition temperature of the formed coating film of 0 to −75 ° C. There is provided a method for coating a metal material, which comprises coating an object and then applying a top coating.

In the present invention, a coating composition which forms a coating film having the above characteristic values is abbreviated as "barrier coat".

A feature of the present invention is that a barrier coat having specific physical properties is applied in the step of sequentially coating an electrodeposition coating composition, an intermediate coating composition and a top coating composition on a metal material, after applying the intermediate coating composition, and before applying the top coating composition. The middle coated surface is in the place where it is painted in advance. As a result, chipping resistance, corrosion resistance,
It has been found that it is possible to form a coating film having remarkably excellent physical properties.

That is, the via coat coating film having a static glass transition temperature adjusted to 0 to −75 ° C. is more flexible than the intermediate coating film for the purpose of improving the chipping resistance and has such physical properties. Even if a strong impact force due to collision of rock salt or pebbles is applied to the surface of the overcoat film formed through the barrier coat film, most or all of the impact energy is absorbed in the barrier coat film and the lower layer It was found that the electrodeposition coating film of No. 1 did not reach the electrodeposition coating film, and the top coating film was hardly physically damaged. In other words, the barrier coating film layer exhibits a buffering effect against impact force from the outside to remarkably improve the chipping resistance, and can prevent the metal material from rusting and corroding due to chipping. The deterioration of the top coating film due to such collisions could be eliminated.

Hereinafter, the coating method of the present invention will be described more specifically.

Metal Material: The metal material coated by the method of the present invention is not limited in kind as long as it is a conductive object to be coated and has a metal surface capable of electrodeposition coating. Examples include iron, copper, aluminum, tin, zinc and alloys containing these metals, and materials such as these metals, plating or vapor deposition products of the alloys, and specifically, passenger cars using these materials, Car bodies, parts and electrical products such as trucks, subaru cars, and motorcycles,
There are building materials. The metal material is preferably subjected to a chemical conversion treatment with a phosphate or chromate in advance prior to applying the electrodeposition coating.

Electrodeposition paint: The electrodeposition paint for coating the above-mentioned metal material may be either a cation type or anion type known per se.

First of all, the cationic electrocoating paint includes a cathodic deposition type thermosetting electrocoating paint based on a resin having a basic amino group, which is neutralized with an acid and solubilized (water dispersed). This is coated with the metal material (object to be coated) as a cathode. The resin having a basic amino group is, for example, a bisphenol type epoxy resin, an epoxy resin containing an epoxy group (or a glycidyl group), a glycidyl ether of an alkylene glycol, an epoxylated polybutadiene, and an epoxy group-containing resin such as an epoxy compound of a novolac phenol resin. Addition of amine to epoxy group (oxirane ring); Polymerization using an unsaturated compound having a basic amino group (eg, dimethylaminoethyl methacrylate, N-vinylpyrazole, N-diethylaminoethyl acrylate) as a monomer; A glycol containing a tertiary amino group (for example,
N-methyldiethanolamine) as a glycol component and a polyisocyanate compound react with each other; an amino group is introduced into a resin by the reaction of an acid anhydride with a diamine to produce an iminoamine. The amine that can be used in the reaction is a basic amine, and is an aliphatic, alicyclic or aromatic-alicyclic primary amine, secondary amine, tertiary amine salt and quaternary ammonium salt. In addition, secondary sulfide salts and tertiary phosphine salts can also be used.

Then, the resin having the basic amino group is neutralized,
Examples of the neutralizing agent for water solubilization (dispersion in water) include:
Acetic acid, hydroxyl acetic acid, propionic acid, butyric acid, lactic acid,
Organic acids such as glycine; inorganic acids such as sulfuric acid, hydrochloric acid and phosphoric acid can be used. The content of the neutralizing agent is appropriately in the range of neutralization equivalent of about 0.1 to 0.4 with respect to the base number (about 20 to 200) of the resin.

Further, as a cross-linking agent of the cationic electrodeposition coating, it is common to use a blocked polyisocyanate compound, and when the coating film is heated (about 140 ° C. or higher), the blocking agent dissociates to regenerate the isocyanate group, It is cross-linked with the hydroxyl group in the cationic resin as described above to be cured. Further, the cationic electrodeposition coating composition includes pigments (coloring pigments, extender pigments, rust-preventive pigments, etc. The amount of pigment can be less than 150 parts by weight per 100 parts by weight of resin solids), hydrophilic solvent, Water, additives and the like are blended as necessary, diluted with deionized water or the like so that the solid content concentration is about 5 to 40% by weight, and the pH is adjusted within the range of 5.5 to 8.0. Cationic electrodeposition coating using the thus-prepared cationic electrodeposition coating can usually be carried out using the object to be coated as a cathode under the conditions of a bath temperature of 15 to 35 ° C and a load voltage of 100 to 400V. The electrodeposition coating film thickness is not particularly limited, but it is 10 to 40 based on the cured coating film.
The range of μ is preferred. The baking temperature of the coating film is generally 100.
A range of ~ 200 ° C is suitable.

On the other hand, the anion-type electrodeposition coating is an anodic deposition type electrodeposition coating mainly composed of a resin having a carboxyl group, neutralized with a basic compound, and solubilized (water-dispersed). It is painted using the (object to be coated) as an anode.

Resins with carboxyl groups are drying oils (linseed oil,
Maleated oil resin obtained by adding maleic anhydride to dehydrated castor oil, tung oil, etc .; Maleated polybutadiene obtained by adding maleic anhydride to polybutadiene (1,2 type, 1,4 type, etc.); Unsaturated fatty acid ester of epoxy resin Resin with maleic anhydride added; polybasic acid (trimellitic anhydride, maleic acid) in high molecular weight polyhydric alcohol (molecular weight of about 1000 or more, including partial ester of epoxy resin and styrene / allyl alcohol copolymer) Resins obtained by adding fatty acids, maleated oils, etc .; carboxyl group-containing polyester resins (including those modified with fatty acids); carboxyl group-containing acrylic resins; polymerizable unsaturated monomers containing glycidyl groups or hydroxyl groups and unsaturated Anhydrous maleic acid was added to the polymer or copolymer formed using the reaction product with fatty acid. Examples thereof include resins to which an acid or the like is added, and those having a carboxyl group content of generally about 30 to 200 based on the acid value are suitable. Then, as a neutralizing agent for neutralizing the carboxyl groups in these carboxyl group-containing resins and making the resin in a water bath (dispersion), for example, alkanolamines such as monoethanolamine, diethanolamine and dimethylaminoethanol; diethylamine , Alkylamines such as triethylamine; potassium hydroxide,
An inorganic alkali such as sodium hydroxide can be used. The amount of these neutralizing agents used is about 0.1 to 1.0 times the theoretical neutralization equivalent to the acid value of the resin (preferably 0.4 to 0.8).
The range of (double equivalent) is suitable.

Further, as a cross-linking agent for the above resin, a low molecular weight melamine resin such as hexakis methoxymethyl melamine, butoxylated methyl melamine, ethoxylated methyl melamine can be used if necessary.

Furthermore, the anionic electrocoating paint contains a pigment (coloring pigment,
Extender pigment, rust preventive pigment, etc. The pigment content is 10 resin solids.
(It can be less than 150 parts by weight per 0 parts by weight), a hydrophilic solvent, water, additives, etc. are blended as necessary, and the solid content concentration is adjusted to about 5 to 40% by weight with deionized water or the like. , PH
It can be used for anion electrodeposition coating while maintaining the range of 7 to 9. The anion electrodeposition coating can be carried out according to a conventional method, and for example, the object to be coated can be used as an anode under the conditions of a bath temperature of 15 to 35 ° C. and a load voltage of 100 to 350V. Although the coating film thickness is not particularly limited, it is usually based on the cured coating film.
It is preferably in the range of 10 to 40μ.

The anion electrodeposition coating film can be cured by heating in the range of 100 to 200 ° C, preferably 140 to 200 ° C in principle, but it is dried at room temperature when a resin modified with an electrodrying unsaturated fatty acid is used. You can also let it.

Intermediate coating: As the intermediate coating applied to the above electrodeposition coated surface, an intermediate coating known per se that has excellent adhesion, smoothness, sharpness, overbaking resistance, weather resistance, etc. is used. To be done.
Specifically, an organic solution type thermosetting intermediate coating composition containing a short oil or ultrashort oil alkyd resin having an oil length of 30% or less or an oil-free polyester resin and an amino resin as a vehicle main component can be mentioned. These alkyd resins and polyester resins have a hydroxyl value of 60 to 140 and an acid value of 5 to 20,
Moreover, unsaturated oil (or unsaturated fatty acid) as modified oil
Is preferable, and as the amino resin, an alkyl (preferably having 1 to 5 carbon atoms) etherified melamine resin, a urea resin benzoguanamine resin, and the like are suitable. The blending ratio of these two resins is based on the solid content weight of alkyd resin and / or oil-free polyester resin 65-85%, especially 70-80%, amino resin 35-15
%, Particularly preferably 30 to 20%. Furthermore, at least a part of the amino resin may be replaced with a polyisocyanate compound or a blocked polyisocyanate compound.

The form of the intermediate coating is most preferably an organic solution type, but may be a non-aqueous dispersion type using the vehicle component, a high solid type, an aqueous solution type, an aqueous dispersion type, or the like. In the present invention, the hardness (pencil hardness) of the intermediate coating film is generally preferably in the range of 3B to 2H. Further, an extender pigment, a coloring pigment, and other additives for paints can be added to the intermediate coating paint, if necessary.

In the present invention, the method of applying the intermediate coating composition to the electrodeposition coating surface is not particularly limited, and for example, spray coating, brush coating, dip coating, electrostatic coating, etc. can be used,
The coating film thickness is preferably in the range of 10 to 50μ based on the coating film after curing, the curing temperature of the coating film is different depending on the vehicle component, 80 ~ 170 ℃ when heat curing, particularly 120 ~ 15
It is preferable to heat at a temperature in the range of 0 ° C.

Barrier coat: The barrier coat is a coating composition for coating on the above-mentioned intermediate coating surface, and in the present invention, particularly, water having a static glass transition temperature of the formed coating film of 0 to −75 ° C. and ( Or)
A composition using an organic solvent as a solvent or a dispersion medium is used.

The composition is mainly composed of a vehicle and a solvent or a dispersion medium, and if necessary, a viscosity imparting agent, an organic solvent,
Coloring pigments, extender pigments, anticorrosion pigments and the like can be appropriately contained.

The vehicle is preferably a thermoplastic resin having excellent adhesion to the intermediate coating film and the after-mentioned top coating film, and having a static glass transfer temperature within the range of the static glass transition temperature, specifically There are things.

Modified polyolefin resin: For example, propylene-ethylene copolymer (in molar ratio,
40 to 80:60 to 20 is preferable) to 1 to 60% by weight of chlorinated polyolefin (for example, polypropylene having a chlorination rate of about 1 to 60% by weight).
50 parts by weight, preferably 10 to 20 parts by weight (all per 100 parts by weight of the copolymer); or a mixture of maleic acid or maleic anhydride 0.1 to 100 parts by weight per 100 parts by weight of the propylene-ethylene copolymer. A graft polymer obtained by graft-polymerizing 50 parts by weight, preferably 0.3 to 20 parts by weight, may be used. The number average molecular weights of these copolymers, chlorinated polyolefins and graft polymers are generally preferably in the range of about 5000 to about 3030,000. It can be dissolved or dispersed by an organic solvent of the above components, and examples of the organic solvent include aromatic hydrocarbons such as benzene, toluene and xylene, aliphatic hydrocarbons such as hexane, heptane, octane and decane, and trichlor. Examples thereof include chlorinated hydrocarbons such as ethylene, perchlorethylene, dichloroethylene, dichloroethane and dichlorobenzene.

Upon watering the modified polyolefin resin, the propylene-ethylene copolymer can be watered by anionic, cationic or nonionic emulsion polymerization known per se, and the graft polymer has an intermediate carboxyl group. The chlorinated polyolefin can be water-dispersed or water-dispersed by mixing, and the chlorinated polyolefin can be water-dispersed in the presence of, for example, an emulsifier.

Styrene-butadiene copolymer: The content of styrene is about 1 to 80% by weight, preferably 10 to
An aqueous dispersion of the copolymer is obtained by copolymerizing 40% by weight of styrene and butadiene in the presence of a polymerization regulator, a catalyst, soap and water. The polymerization temperature is preferably 100 ° C or lower. The number average molecular weight of the copolymer is preferably in the range of about 10,000 to about 1,000,000.

Further, the above copolymer can be dissolved or dispersed by using an ordinary organic solvent for coating material.

Butadiene resin: An organic solvent-based or water-based composition obtained by polymerizing without using styrene.

Acrylonitrile-butadiene copolymer: A copolymer having an acrylonitrile content of 1 to 50% by weight, preferably 10 to 40% by weight, and acrylonitrile and butadiene having functional groups such as acrylic acid and methacrylic acid as necessary. It is obtained by adding an organic monomer and carrying out emulsion polymerization in water in the presence of a polymerization catalyst, a molecular weight modifier, a surfactant, or the like, or by polymerizing in an organic solvent. The polymerization temperature is preferably 100 ° C or lower. Suitably the copolymer has a number average molecular weight in the range of from about 10,000 to about 1,000,000.

Polybutene: Isobutene is the main component, normal butylene is mixed if necessary, and polybutene obtained by low-temperature polymerization is heated to 50 to 70 ° C in the presence of an emulsifier and water is added to stir it evenly. It can be obtained by dissolving or dispersing the polybutene in an organic solvent for paint.
The number average molecular weight of the resin is preferably in the range of about 1000 to about 500000.

Acrylic resin: Acrylic ester and / or methacrylic acid ester as the main component, and if necessary, acrylic acid,
Emulsion polymerization of a vinyl monomer component prepared by mixing a functional monomer such as methacrylic acid, hydroxyethyl acrylate, and hydroxypropyl methacrylate and / or other polymerizable unsaturated monomer into an aqueous dispersion: or solution polymerization After that, it can be obtained by dissolving it in an organic solvent for coating as it is, or changing it to an aqueous solution or an aqueous dispersion. Examples of the acrylic acid ester include ethyl acrylate, propyl acrylate, n
-Butyl acrylate, iso-butyl acrylate, 3
-Pentyl acrylate, hexyl acrylate, 2-
Heptyl acrylate, octyl acrylate, 2-octyl acrylate, nonyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, 2-ethylbutyl acrylate and the like are particularly suitable, and examples of the methacrylic acid ester include pentyl methacrylate, hexyl methacrylate and 2-ethylhexyl. Methacrylate, decyl methacrylate, lauryl methacrylate, stearyl methacrylate and the like are particularly preferable. The homopolymers derived from these acrylic acid esters and methacrylic acid esters exemplified here have a static glass transition temperature of 0 ° C. or less, and one or more acrylics selected from these monomers. Acid esters and methacrylic acid esters are suitable as monomers for forming the acrylic resin. The acrylic resin has a number average molecular weight of about 5,000 to 1,000,00.
It is preferably in the range of 0.

In addition to these, natural rubber latex, methyl methacrylate-butadiene copolymer emulsion, polychloroprene emulsion, polyvinylidene chloride emulsion and the like can also be used as the vehicle.

The coating film formed by the barrier coat has a static glass transition temperature (Tg) of 0 to -75 ° C, preferably -30 to -60.
℃, particularly preferably in the range of -40 ~ -55 ℃, Tg higher than 0 ℃, the multilayer coating film does not improve the chipping resistance, corrosion resistance, physical performance, etc. 75
When the temperature is lower than 0 ° C, the water resistance and adhesion of the multilayer coating film are deteriorated, which is not preferable.

In the present invention, if these vehicles themselves have a static glass transition temperature within the above range, they can be used as a barrier coat by themselves. When it is desired to finely adjust the objective glass transition temperature, a viscosity-imparting agent can be added as necessary. As the viscosity-imparting agent, a resin having good compatibility with the above-mentioned vehicle, for example, rosin, petroleum resin (coumarone resin), ester gum, epoxy modified polybutadiene, low molecular weight aliphatic epoxy resin, low molecular weight aliphatic bisphenol type Epoxy resin, polyoxytetramethylene glycol, vinyl acetate-modified polyethylene and the like can be mentioned, and the compounding amount thereof is preferably in the range of 1 to 50 parts by weight (as solid content) per 100 parts by weight of the vehicle (solid content).

Further, the barrier coat has an extender pigment, a coloring pigment,
It does not matter if anticorrosive pigments are added. The amount of these pigments is 1 to 1 per 100 parts by weight of the vehicle (solid content).
A range of 50 parts by weight is preferred.

In the present invention, with respect to the coating film forming the barrier coat, it is essential that the static glass transition temperature is included in the above range, and further, the tensile breaking strength elongation rate of the coating film itself is -20. If the tensile speed is adjusted to 200 to 1000%, especially 300 to 700% in an atmosphere of ℃ at a tensile speed of 20 mm / min, the final coating film can be further improved in chipping resistance and corrosion resistance.

The "static glass transition temperature" of the coating film forming the barrier coat used in the present invention is a value measured by a differential scanning calorimeter (DSC-10 type manufactured by Daini Seikosha Co., Ltd.), and "tensile rupture strength elongation rate". "Is a value measured using a universal tensile tester with a thermostat (Shimadzu Corporation Autograph SD type) at a sample length of 20 mm and a pulling speed of 20 mm / min. The samples used for these measurements were based on the coating forming the barrier coat.
It was coated on a tin plate so that it had a thickness of μ, baked at 120 ° C. for 30 minutes, and then isolated by the mercury amalgam method.

In the present invention, the barrier coat can be applied either after heat curing the coating film or in an uncured state, and the coating film is 1 to 20 based on the formed coating film.
It is preferable that the thickness is μ, particularly 5 to 10 μ.

It is preferable to bake the via coat in advance when the top coat is applied to the coating film of the barrier coat, but the top coat may be applied wet-on-wet without baking. Generally, a baking temperature in the range of 80 to 200 ° C is suitable.

Topcoat paint The above-mentioned barrier coat is applied on the coated surface and imparts beauty to the article to be coated. Specifically, the finished appearance (vividness, smoothness, gloss, etc.), weather resistance (gloss retention,
(Color retention, chalkiness resistance, etc.), chemical resistance, water resistance, moisture resistance, a coating material known per se which forms an excellent coating film such as curability can be used, and examples thereof include amino-acrylic resins,
Examples of the coating material include an amino-alkyd resin, an amino-polyester resin, etc. as a vehicle main component. The form of these paints is not particularly limited, and any form such as an organic solution type, a non-aqueous dispersion type, an aqueous (dispersion) liquid type, a powder type and a high solid type can be used. The coating film is dried or cured by room temperature drying, heat drying, active energy ray irradiation, or the like. In the present invention, it is desirable that the formed coating film of these top-coat paints generally has a pencil hardness in the range of 2B to 3H.

The top coating used in the present invention is a metallic pigment and / or the above-mentioned vehicle-based coating.
It may be either an enamel paint containing a coloring pigment or a clear paint containing no or little of these pigments. Then, examples of the method for forming an overcoat film using these paints include the following methods: Metallic paint prepared by mixing a metallic pigment and, if necessary, a coloring pigment, or a coloring pigment Method of applying solid color paint and heating and curing (1
(Coat 1 bake method with metallic or solid color finish).

A method in which a metallic paint or a solid color paint is applied, heat-cured, and then a clear paint is applied, and then heat-cured again (metallic or solid color finish by a two-coat two-bake method).

A method in which a metallic paint or a solid color paint is applied, a clear paint is subsequently applied, and then both the paint films are simultaneously cured by heating (metallic or solid color finish by a two-coat one-bake method).

It is preferable to apply these top coats by spray coating, electrostatic coating, or the like. Further, the coating film thickness is preferably in the range of 25 to 40μ in the above, in the above and in the range of 10 to 30μ for the metallic paint and the solid color paint, and in the range of 25 to 50 for the clear paint, based on the dry coating film. . The heating conditions can be arbitrarily selected depending on the vehicle component, but generally 80 to 170 ° C, particularly 120 to 150 ° C
It is preferable to heat for 0 to 40 minutes.

The "pencil hardness" of the above-mentioned middle coat and top coat was 20 on a test plate coated on a glass plate and cured (cured film thickness 30μ).
Hold the pencil at a temperature of ℃, flatten the tip of the thin, sharpen the sharpened pencil (Mitsubishi drawing pencil "Uni") at an angle of 45 degrees, and press it about 1 cm while pressing it against the coated surface so strongly that the thin does not break.
(3 seconds / cm) This is a value when evaluated by the hardness of the hardest pencil that does not leave a locus of scratches by a pencil after being moved.

According to the method of the present invention described above, electrodeposition coating on a metal material-
The performance of the multi-layer coating film formed by intermediate coating-barrier coat coating-top coating is better than that of the coating formed by omitting the barrier coat coating (for example, smoothness, gloss, sharpness, etc.). ), Water resistance, weather resistance, etc. are at least equivalent, but there is a feature that chipping resistance, corrosion resistance, physical properties, etc. are remarkably improved.

Next, the present invention will be further described with reference to Examples and Comparative Examples.

I Preparation of sample (1) Metal material: Bonderite # 3030 (Nippon Parker Rising Co., Ltd.)
Made, zinc phosphate-based) steel sheet (300 x 9 in size)
0 x 0.8 mm).

(2) Electrodeposition coating: (A) Cationic type electrodeposition coating: Electron # 9200 (Kansai Paint Co., Ltd., epoxy polyamide type cationic electrodeposition coating, gray color).

(B) Anion type electrodeposition coating: Electron # 7200 (Kansai Paint Co., Ltd., polybutadiene type anion type electrodeposition coating).

(3) Intermediate coating: Amylak N-2 Sealer (manufactured by Kansai Paint Co., Ltd.,
Amino polyester resin-based intermediate coating).

(4) Barrier coat: (A): Propylene / ethylene copolymer (weight ratio: 70/3
0, number average molecular weight: about 200,000) 10 parts by weight of maleic acid per 100 parts by weight of an organic solvent solution of a resin graft-polymerized (static glass transition temperature: −41 ° C., tensile breaking strength at -20 ° C. Elongation rate: 400 %).

(B): An aqueous dispersion obtained by emulsification polymerization of a component consisting of 30% by weight of styrene and 70% by weight of butadiene according to a conventional method (static glass transition temperature: 48 ° C, tensile breaking strength elongation at -20 ° C) : 450%).

(C): Organic solvent liquid of a copolymer consisting of 30% by weight of acrylonitrile, 67% by weight of butadiene and 3% by weight of acrylic acid (static glass transition temperature: -50 ° C, tensile elongation at break at -20 ° C: 500 %).

(D): Emulsion water dispersion of a copolymer composed of isobutylene and normal butylene (static glass transition temperature: -55 ° C,
Tensile breaking strength elongation at -20 ° C: 600%).

(E): Organic solution of a copolymer consisting of 60% by weight of nonyl acrylate, 20% by weight of 2-ethylhexyl acrylate, 15 parts by weight of methyl acrylate and 5 parts by weight of hydroxyethyl acrylate (static glass transition temperature: -48 ° C,
Tensile breaking strength elongation at -20 ° C: 370%).

(F): Hexadecyl acrylate 60% by weight, 2-ethylhexyl acrylate 20% by weight, methyl acrylate
15% by weight and hydroxyethyl acrylate 5% by weight
Solvent solution of copolymer consisting of (Static glass transition temperature: + 4 ° C) (5) Topcoat paint: (A): Amylak White (manufactured by Kansai Paint Co., Ltd.,
Amino-alkyd resin-based top coating, white coating for 1 coat / bake, pencil hardness H (20 ° C)).

(B): Magiclon Silver (manufactured by Kansai Paint Co., Ltd.,
Amino acrylic resin-based topcoat paint, 2 coats / one bake silver metallic paint, pencil hardness H (20 ° C)).

(C): Magiclon Clear (manufactured by Kansai Paint Co., Ltd.,
Amino acrylic resin topcoat, 2 coats / bake clear paint, pencil hardness H (20 ° C)).

II Example Comparative Example Using the above sample, an electrocoating paint, an intermediate coat paint, a barrier coat and a top coat paint were applied to a steel material according to the steps shown in Table 1 below.

In Table 1, cationic electrodeposition coating conditions: bath solid content concentration 19% by weight, bath temperature 28 ° C, PH6.5, load voltage about 250V, energization for 180 seconds.

Anion electrodeposition coating conditions: Bath solid concentration 12% by weight, bath temperature 30 ° C, PH 7.8, load voltage about 200V, electricity for 180 seconds.

In any of the above cases, the electrodeposition coating was followed by washing with water and baking at 170 ° C. for 30 minutes to cure the coating film. The coating thickness is 20μ based on the cured coating.

The barrier coat was coated with an air sprayer so as to have a thickness of 6 μm based on the dry coating film, and baked at 120 ° C. for 30 minutes.

Both the middle coat and the top coat were spray-coated with an electrostatic coater, and the thickness of the middle coat was 25μ based on the cured coating film and baked at 140 ° C for 30 minutes.

In the top coating, "1C1B" is a coating system in which the top coating A is coated to a thickness of 35μ based on the cured coating and baked at 140 ° C for 30 minutes. "2C1B" is the top coating B based on the cured coating. Is a system in which a top coat paint C is applied by wet-on-wet to a thickness of 35 μm based on the cured coating film, and both coating films are baked at 140 ° C. for 30 minutes to cure.

III Performance Test Results A coating film performance test was performed using the coated plates coated in the above Examples and Comparative Examples. The results are also shown in Table 1.

〔Test method〕

(* 1) Chipping resistance: Test equipment: QGR Gravelometer (product of Q panel company) Stone to be sprayed: Crushed stone with a diameter of about 15 to 20 m / m Capacity of stone to be sprayed: about 500 ml Sprayed Air pressure: About 4Kg / cm ² Temperature at the time of test: About 20 ℃ After mounting the test piece on the test piece holder, after blowing about 500ml of crushed stone to the test piece with the blowing air pressure of about 4Kg / cm ² , The coating state and salt spray resistance were evaluated. The state of the coated surface is visually observed and evaluated according to the following criteria. The salt spray resistance is tested by JIS Z 2371 for 960 hours for the salt spray test, and then the adhesive cellophane tape is attached to the coated surface.
Presence or absence of rust from the impacted part after abrupt peeling, corrosion state, coating peeling, etc.Coating surface condition ◎ (Good): Only a slight scratch on the top coating film is recognized due to impact, No peeling of the electrodeposition coating film was observed.

Δ (Slightly bad): Many scratches due to impact were observed on the top coat and the intermediate coat, and peeling of the electrodeposition coating was scattered.

X (Poor): Most of the top coat and intermediate coat are peeled off, and the electrodeposited coat on the impacted part and its surroundings is peeled off.

 Salt water spray resistance ⊚: No rust, corrosion, coating peeling, etc.

◯: Slight rust, corrosion and coating peeling are observed.

Δ: Rust, corrosion and coating peeling are slightly observed.

X: Rust, corrosion, and coating peeling occurred remarkably.

(* 2) Impact resistance: Performed in an atmosphere of 0 ° C according to JIS K5400-1979 6.13.3B method. A 500 g weight is dropped from a height of 50 cm to inspect the coating for damage.

(* 3) Adhesion: In accordance with JIS K5400-1979 6.15, make a rugged pattern on the coating film, attach an adhesive cellophane tape on the surface, and evaluate the coated surface after it is rapidly peeled off.

(* 4) Water resistance: Evaluate the coated surface after immersion in water at 40 ° C for 10 days.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Ichiro Tabuchi 4-17-1, Higashi-Hachiman, Hiratsuka-shi, Kanagawa Kansai Paint Co., Ltd. (72) Inventor Masafumi 4--17, Higashi-Hachiman, Hiratsuka, Kanagawa Nishi Paint Co., Ltd. (72) Inventor Takashi Udagawa 4-17-1, Higashi-Hachiman, Hiratsuka-shi, Kanagawa Kansai Paint Co., Ltd. (72) Inventor Kouji Matsui 4-1-1, Higashi-Hachiman, Hiratsuka-shi, Kanagawa Kansai Paint Incorporated (72) Inventor Yasuhiro Fujii 4-17-1, Higashi-Hachiman, Hiratsuka-shi, Kanagawa Kansai Paint Co., Ltd. Inspector Hiroyuki Oguro

Claims (1)

[Claims] 1. A metal material is coated with an electrodeposition coating composition and an intermediate coating composition, and then the intermediate coating surface is coated with a coating composition having a static glass transition temperature of the formed coating film of 0 to −75 ° C. After that, a method of coating a metal material, which comprises applying a top coat paint.