JPS6274474A - Method for coating steel plate - Google Patents

Abstract

PURPOSE:To enhance the corrosion resistance and chipping resistance of an end surface part still more, by preliminarily applying barrier coat having a specific composition and specific physical properties to the surface of an anionic electrodeposition film containing pigment at high concn. before applying intermediate coat and top coat. CONSTITUTION:Anionic electrodepostion paint, which was prepared by compounding 40-150pts.wt. of known colored pigment, extender pigment and rust inhibiting pigment, etc. with 100pts.wt. of the resin solid of the paint at high concn., is thickly applied to a desired steel plate such as the outer panel of a car to which chemical forming treatment was applied. Next, barrier coat based on a modified polyolefin resin forming a film with static glass transition temp. of -30--60 deg.C and an org. solvent is applied to the surface of the electro deposition paint film to enhance the smoothness and sharpness of the film still more in addition to rust-proofness and chipping resistance. Known intermediate coat and top coat are successively applied to the surface of a barrier coat film to form a composite film excellent in weatherability and finish appearance.

Description

[Detailed Description of the Invention] The present invention forms a composite coating film with excellent corrosion resistance, anti-corrosion properties on end faces, and physical performance on steel plates, in particular steel plate parts of automobile bodies. This is related to the subject Q method for .

A composite consisting of the anidine electrodeposited film, intermediate coating film, and Kamigori coating film on the outer panel of my M1 car! The problem of the durability of the I3 film, especially the problem of the decrease in corrosion resistance of the coating film due to impact peeling and the progress of corrosion of the steel plate, is becoming more important. In particular, in order to prevent the road surface of Satsuki Expressway from freezing in the cold regions of Europe and the United States, gravel is often ground into relatively coarse particles and mixed with a large amount of rock salt. Rock salt particles and pebbles thrown up by the wheels of a running car collide with the coating surface on the outer surface of the vehicle, and the impact causes the entire composite coating film to locally spread from the top of the vehicle. #A knock-off phenomenon, so-called 1-chip/I-ping, often occurs. As a result of this phenomenon, the metal surface of the impacted portion of the outer surface of the vehicle body is exposed, and rust immediately develops and corrosion progresses. Peeling of composite paint films due to chipping usually occurs at the bottom of the car body and around the suspension.
It is known that localized pilferage occurs on the hood and roof, and becomes noticeable in about six months to a year.

In order to prevent this chapping and the progress of corrosion caused by it, various studies have been made regarding chemical conversion treatments on the surface of the external metal base of the car body, as well as anionic electrodeposition additives, intermediate coatings, and top coatings. For example, in chemical conversion treatments, the use of iron phosphate coatings and zinc phosphate coatings with different crystal forms has been considered, but it is difficult to sufficiently improve the adhesion of coatings on impact areas with such chemical conversion treatments. be. Various studies have been conducted on the resins and/or pigments contained in paints, anionic electrodeposition paints, and topcoats, but there are currently only a few that have sufficient adhesion-improving effects to withstand chipping. I have not yet discovered it.

In addition, an inorganic foil-like pigment is contained in the intermediate coating, thereby achieving mitigation and/or dispersion of the impact force caused by shear within the intermediate coating layer, or within the intermediate coating Ig8 layer or between the electrodeposited surface and the intermediate coating. The aim is to cause localized peeling only at the interface with the paint film, thus preventing damage to the electrodeposited paint film and ensuring that this scratch-free paint film maintains its anti-rust function. However, the impact force applied to the outer surface of the car body is not constant and can be quite large, and these methods can reduce the amount of impact caused by shearing within the intermediate coating layer. In Vt1, the impact force could not be stopped at the intermediate coating layer, and the affected area affected the composite coating including the electrodeposited coating, and the entire composite coating peeled off from the metal substrate surface, and as a result, the area immediately developed. The disadvantage is that it rusts and corrodes.

Furthermore, there are many acute angle parts and Q-face parts in steel plates such as automobile bodies (for example, 7 Asia, fender, etc.).
, door spring I, panel hood, panel roof, etc., lower end, back surface), this part has a sharp shape unlike the other flat part 2. These acute angles and end surfaces (hereinafter referred to as "end surfaces J") are difficult to coat with paint, and moreover, they are more likely to melt and flow during heat curing, resulting in a thinner coating film than on flat areas. It was inevitable that the coating film Vi would become extremely thin on the edges.As a result, the corrosion resistance of the f @ faces, including acute angles, was significantly inferior to that of the flat parts, and rust easily occurred from the edges. A trend has been observed, and improvements in this regard are strongly desired.

Therefore, the inventors of the present invention aimed to improve the above-mentioned problems.
The composite coating film obtained by a composite coating system for steel plates consisting of a conventional anionic electrocoating paint, intermediate coating paint, and top coating paint has excellent chipping resistance and physical properties without degrading the finished appearance, and also provides corrosion protection for end surfaces, etc. With the aim of developing a method for forming a composite coating film with good properties, the present invention was completed as a result of repeated Eikura experiments.

That is, according to the present invention, a copper plate is blended with a polishing agent at a high concentration. An anionic electronic paint is applied, and then an organic solvent-based paint is formed on the painted surface, the static glass transition temperature of which is -30 to -60°C and whose main component is a modified polyurethane resin. A method for coating a steel plate is provided, which comprises applying a coat and then sequentially applying an intermediate coat and a top coat.

Although the term "barrier foot" is not commonly used, in the present invention, a solvent-based paint having a specific composition that forms a coating film having the above-mentioned physical properties is referred to as a "barrier coat."

In the process of sequentially applying anion-type electrostatic potting material, intermediate coating paint, and top coat 1 to a steel plate, Kinoe (7) has a special feature: anion-type box; Using an anionic electrocoating ladle containing a high concentration of A-lees, and applying the electrocoating paint before applying the intermediate coating, an organic solvent-based barrier coat with a specific composition and physical properties is applied. It is located in the area where the electric coating surface is pre-painted. As a result, chipping resistance, corrosion resistance on end surfaces, etc., and physical +! *It was possible to form a composite coating film with significantly improved performance.

The pigment content in conventional anionic type IV' paints is practically no more than 35 parts by weight per 100 g of resin solids, and if more is added than this, the smoothness of the paint film will be affected.
It is rarely used because it reduces the sharpness of overcoating.

On the other hand, the present inventors investigated the possibility of forming thick anionic electrodeposition paint on the end surfaces of steel materials to improve corrosion resistance, and found that anionic electrodeposition paint with a high concentration of pigment was used. When painted, a thick coating film was formed on the end surfaces, etc., and it was found that the corrosion resistance and chipping resistance of the flat parts and the end surfaces S etc. tended to improve, but this was not sufficient.
On the contrary, a decrease in the smoothness and sharpness of the finished coating film was observed. Therefore, the present inventors continued to conduct research in order to further improve the corrosion resistance and chipping resistance of the end surfaces, etc., and to improve the smoothness and sharpness of the finished coating film. These defects can be completely eliminated by applying a barrier coat with a specific composition and physical properties to the surface of the anionic electrodeposition coating containing a high concentration of pigment (7), then applying an intermediate coat and a top coat. Ta.

That is, the glass transition temperature of the formed coating film is -30 to -60
The coating film of the barrier coat adjusted to ℃ is more flexible than the intermediate coating film aimed at improving chipping resistance,
Furthermore, it has a unique viscoelasticity due to the modified polyolefin resin. However, if a barrier coat with such physical properties is applied to the surface of the anionic electrodeposition coating film containing a large amount of pigment, which is poor in smoothness and finish sharpness, it will cause damage to the edges, etc. After sufficient coating, the barrier coat penetrated into the uneven parts of the surface of the 'riL coated film, preventing the suction of the intermediate coat and improving smoothness, sharpness of the topcoat, corrosion resistance of the edge, etc. It is presumed that this is the case. In addition, regarding chipping resistance, even if a strong impact force is applied to the surface of the composite coating film formed on the barrier coat film surface, consisting of a sub-intermediate coat and a topcoat, the impact will not be affected. Almost all of the energy is absorbed within the barrier coat film, so there is almost no impact peeling of the electrodeposited film, and the occurrence of physical damage to the top coat film can be almost completely eliminated. It was possible to prevent peeling of both the top coat and intermediate coat due to chipping, as well as flaking and corrosion on metal parts.

The coating method of the present invention will be specifically explained below.

There are no restrictions on the steel plate as long as it is a material to be coated by the method of the present invention and has a metal surface that can be coated with anion electrodeposition. For example, iron, copper,
Aluminum, tin, zinc, alloys containing these metals, and plating or vapor deposition products of these metals and alloys, etc. Specifically, vehicle bodies such as passenger cars, trucks, safari cars, autopilots, etc. using these metals and alloys. There is. In addition, it is preferable that these steel sheets be chemically treated with phosphate or chromate before coating with anionic electrocoating paint. This is the next type of electrocoating coating that is applied to steel sheets, and it is an anionic electrocoating coating that contains pigments in a higher concentration than the commonly used anionic electrocoating coating.

Anionic electrodeposition paint is an anode-deposition type electrodeposition paint made by using a resin mainly having a carboxyl group as a paste, which is neutralized with a basic compound and made water-soluble (water-dispersed).
The above steel material (subject to be coated) is used as an anode for coating.
Oil, dehydrated castor oil, tung oil, etc.) K maleic anhydride is added to maleic anhydride;
2ffJ, 1.4 type, etc.) with maleic anhydride> acid added; ■Resin with maleic anhydride added to an unsaturated fatty acid ester of epoxy resin; (4)
Polybasic acids (trimellitic anhydride, maleated fatty acids, maleic oil, etc.) are added to high molecular weight polyhydric alcohols (with a molecular weight of about 1000 or more, including partial esters of epoxy resins and styrene/allylic alcohol copolymers). Resin obtained by addition; ■ Carboxyl group-containing polyester resin (including those modified with fatty acids); ■ Carboxyl group-containing acrylic resin; ■ Reaction of a polymerizable unsaturated monomer containing a glycidyl group or a hydroxyl group with an unsaturated fatty acid Polymers formed using the product and resins made by adding maleic anhydride to a copolymer; etc., and the content of carboxyl groups is generally about 3 based on the acid value.
A range of 0 to 200 is suitable. And Ko? l
I-) As a neutralizing agent for neutralizing the carboxyl group in the carboxyl group-containing resin and making the resin water-soluble (dispersed), for example, an alkanolytic agent such as monoethanolamine, jetanolamine, dimethylaminoethanol, etc. ! Rareamines: Alkyl-reamins such as diethylamine and triethyl-reamine; inorganic alkalis such as potassium hydroxide and sodium hydroxide can be used. The amount of these neutralizing agents used is approximately 1 to 1.0 times the theoretical neutralization equivalent to the acid value of the resin.
~0.8 times the same class) are appropriate.

i ft. As a crosslinking agent for the above resin, a low molecular weight melamine resin such as Hegisakis methoxymethyl melamine, butoxylated methyl melamine, or ethoxylated methyl melamine can be used as necessary. The amount of compounded sea bream of Compound 1) in the anionic type paint used in Step 1 is larger than usual, and specifically, 40 to 150
The amount is preferably 55 to 100 parts by weight, and preferably 60 to 85 parts by weight. The anion pear electrodeposition m? +
Pigments that can be blended with the pigments are not particularly limited, and include coloring pigments, extender pigments, and antirust pigments that are known per se. Examples include zinc white, antimoji white, basic acid lead, basic lead carbonate, titanium white, Litopone, lead silicate, dichloromethane oxide, carbon flake, graphite, black iron oxide, aniline black, cuprous oxide, cadmium resin, chromium vermilion,
Red Garla, Big Dame> Tread, Pigment Violet, Pigment Orange, Basal Lead Chromate, Yellow Lead, Ochre, Cadmium Yellow, Strositicum Chromate, Titanium Yellow, Lissage, Hydrangea Yellow, Pigment Green, Zinc Edge, Chromium Green, chromium oxide, phthalocyanine green, ultramarine, navy blue, phthalocyanide blue,
pigment blue, cobalt purple, pigment violet,
Zinc powder, zinc oxide, red lead, lead cyanamide, calcicum lead acid, zinc yellow, silicon carbide, aluminum powder, aspestici, alumina, sauce 1 limestone, slaked lime, limestone, melk, #acid baricum, sedimentation Examples include lucium carbonate, lucium carbonate, precipitated chlorine, paricum acid, pallite, bentonite, white carbon, and glass peas, and these can be used alone or in combination of two or more.

Furthermore, the anionic electrodeposition coating is blended with a wood-philic solvent, water, additives, etc. as necessary, and the solid content concentration is approximately 5 to 4.
It can be adjusted to 0% by weight and then applied to an anionic electrodeposition coating film at a pH of 7 to 9. Anion heavy @ painting can be done according to the usual method, for example, bath temperature 15-35
℃ and a load voltage of 100 to 350 V, the object to be coated can be used as an anode. The coating film thickness is not particularly limited, but it is usually preferably in the range of 10 to 40 μ based on the cured coating side. .

As a general rule, the anionic electrodeposition coating film should be heated at 100 to 200℃, preferably 1.
It is hardened by applying heat in the range of 140-200C, but is an air-drying unsaturated fat @-7'! In the case of using a cured resin, it can also be dried at room temperature.

Barrier coat: A composition to be applied to an anionic electrodeposited film, the static glass transition temperature of the formed film being -30 to -6.
It is a paint whose main components are a modified polyolefin resin and an organic solvent at a temperature of 0°C, preferably -40 to -50°C.

In other words, modified polyolefin resins, for example,
Propylene-ethylene copolymer (molar ratio, approximately 40 to 8
゜: preferably about 60 to 20%) and 1 to 50 parts by weight, preferably 10 to 20 parts by weight of chlorinated polyolefin (chlorination rate of about 1 to 60%) (in each case 100 parts by weight of the copolymer) ) or the above-mentioned propylene-ethylene co-It&CE1o.

0 maleic acid or maleic anhydride acid per part by weight
．． Examples include resins grafted with 1 to 50 parts by weight, preferably 0.3 to 20 parts by weight.

In the present invention, if these modified polyolefin resins themselves have a static glass transition temperature within the above range, they and an organic solvent can be used as a barrier coat. However, if it is desired to finely adjust the static glass transition temperature, a viscosity imparting agent can be added if necessary.

Examples of the viscosity imparting agent include rosin, Kumaro, etc., which have good compatibility with the modified polyolefin resin.
), ester film, polybutadiene epoxy modified polybutadiene, low molecular weight fd aliphatic epoxy E/+M [i
, the molecular mark aliphatic bisphenol type epoxy mt
J, polyoxytetramethylene glycol, vinyl acetate or polyethylene, etc., and the blending amount thereof is 1 to 100 parts per 100 parts of the above-mentioned modified polyolefin resin.
50 parts by weight is preferred.

The organic solvent for the barrier coat is preferably an organic solvent that dissolves or disperses the above components, such as aromatic hydrocarbons such as hexane, tonolenine, and xylenato, and aliphatic hydrocarbons such as hexane, heptane, octane, and decane. Hydrocarbons, chlorinated hydrocarbons such as trichlorethylene, perchlorethylene, dichloroethylene, dichloroethane, dichloroethylene, ketones such as methyl ethyl ketone and diacetodialcohol, alcohols such as ethanol, chlornol, butanol, butyl cellosolve, etc. Examples include cellosolve-based solvents.

In the present invention, the barrier coat formed coating film Kr! A
It is essential that the AL and static glass transition temperature be within the above range, but furthermore, the tensile strength elongation at break of the coating film should be 200 to 1000% in an atmosphere of -20°C, especially 3
It is preferable that it is 00-700%. If the static glass transition temperature of the formed coating film is higher than -30°C, the above object of the present invention cannot be achieved, and if it is lower than -60°C, the performance of the coating film, especially water resistance, adhesion, etc. will deteriorate, so it is preferable. It's not more than 1. Furthermore, the barrier coat includes a conditioning agent and a color @I.
It is okay to mix P+ (7'?, excluding anti-corrosion paint), etc. y+, -,. The blending amount of these components is preferably 1 to 150 parts by weight per 100 parts by weight of the modified polyolefin resin.

In the present invention, these barrier coats are applied to the anionic electrical sign coating surface, but the coating method is not limited, and examples include spray coating, I/K coating, dipping coating, melt coating, electrostatic coating, etc. Generally, the coating film thickness is preferably 1 to 20 microns, especially 5 to 10 microns, even for a dry coating film.

Note that the static glass transition temperature of the formed coating film of the barrier coat used in the present invention was determined using a differential scanning calorimeter (Daini Seikokin DS).
C-10 model), and the tensile strength elongation at break is a ratio value measured using a universal tensile tester equipped with a constant temperature bath (Dosha Seisakusho Autograph Model S-D). The test was carried out at a tensile speed of 201111 and a tensile speed of 20 min/min. The samples used for these measurements were coated on a tin plate to a thickness of 25 μm with the barrier coat added to the formed coating film.
After baking at 120° C. for 30 minutes, the sample was isolated by the mercury amalgam method and used.

It is preferable to bake the barrier coat before applying the intermediate coat on the surface of the barrier coat, but it is also possible to apply the intermediate coat without baking. A suitable baking temperature for the barrier foot is 80 to 160°C, particularly 80 to 130°C.

Intermediate Coat and Coating H/2 A paint to be applied to the above-mentioned barrier coated surface, which has excellent adhesion, smoothness, sharpness, overpaint resistance, weather resistance, etc., and any known intermediate paint can be used. . Specifically, examples include thermosetting intermediate coatings with an oil length of 30% or less and a super-furnace alkyd resin, and a thermosetting intermediate coating whose vehicle is mainly composed of an oil-free polyester resin and an amino resin. Alkyd resin and polyester resin have a hydroxyl value of 60 to 140 and an acid value of 5 to 2.
00, and it is preferable to use unsaturated oil or unsaturated fatty acid as the modified oil, and suitable amino resins include alkyl (1 to 5 carbon atoms) etherified submelamine side fat, urea resin, benzoguanamine resin, etc. . These compounding ratios are based on the solid content weight, and the alkyd resin and (
1-117t) Oil-free polyester ~80%, amino tree% 35-15%, especially 30-20
% is preferable. Furthermore, at least a portion of the above amino resin can 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
It is also possible to use the above vehicle components in a non-aqueous dispersion, a high solid type, an aqueous solution type, an aqueous dispersion type, etc. In the present invention, the hardness (pencil hardness) of the medium coating film is preferably in the range of 3B or more (at 20°C). Furthermore, extender pigments, coloring pigments, additives for extension paints, and the like may be blended into the intermediate coating paint, if necessary.

In the present invention, the intermediate coating paint can be applied to the barrier coat surface in the same manner as the barrier coat, and the coating thickness is preferably in the range of 10 to 50 μm even for a cured coating film. The curing temperature varies depending on the vehicle components, and in the case of heat curing, it is 80 to 170°C.
It is preferable to heat at a temperature of C120 to 150°C.

Top coat! +2 A paint to be applied to the intermediate coated surface, which imparts cosmetic properties to the object to be coated.

Specifically, the finished appearance (sharpness, smoothness, gloss, etc.)
There are many well-known paints that form a coating film with properties such as , weather resistance (glossy retention, color retention, chalking resistance, etc.), chemical resistance, water resistance, moisture resistance, hardening properties, etc. Examples include amino acrylic resin, amino alkyd resin,
Examples include paints whose vehicle main component is amino polyester resin thread, etc. The form of these paints is not particularly limited, and includes liquid solution type, non-water #y, liquid liquid type, water-soluble (dispersed) wave type, and powder. It can be used in 卆, high solid type, etc.

Drying φ curing of the coating film is carried out by drying at room temperature, heating drying, irradiation with active energy rays, etc. In the present invention,
The paint film formed by these top coats has a pencil hardness of 2B to 3.
It is preferable that H(2(11:)) be within the range.

The top coating used in the present invention is classified into enamel paints that use the above-mentioned vehicle as a main component and contain metallic pigments and/or coloring pigments, and clear paints that do not contain any of these pigments at all. Examples of methods for forming topcoat films using these paints include the following methods.

■Metallic paint made by blending metallic pigments and colored pigments if necessary.A method of applying solid color paints blending colored pigments and curing them by heating (1 coat 1 coat).
Metallic ``solid color finish'' by Beta method).

■ A method in which metallic paint or solid color paint is applied, heated and cured, and then a clear paint is applied and then heated and cured again (metallic meditation using the 2-coat 2-beam method is a solid color bhikkhuge).

G. Apply metallic paint or solid color paint, then apply clear paint, then heat to cure both coatings at the same time (metallic overlay solid color finish using 2-coat 1-bake method) ).

These top coat paints are preferably applied by spray painting, electrostatic painting, etc. In addition, based on the paint film *U and dry paint film, the above (■) is 25 to 40μ, and the above (■) and (■) are 10μ for metallic paints and solid color paints.
~3-0μ and clear paint preferably have a thickness of 25-50μ. Heating conditions can be arbitrarily selected depending on the vehicle components, but heating at 80 to 170°C, particularly 120 to 150°C is preferred.

The "pencil hardness" of the intermediate and top coats above was determined by coating these paints on a glass plate and curing them (cured film thickness: 3
0 μ) Hold the test plate at 20°C, sharpen the tip of the tip flat, sharpen the angle, hold a pencil (Mitsubishi drafting pencil "Uni#") at a 45 degree angle, and apply the coating firmly to the extent that the tip does not break. The hardness of the pencil was evaluated by moving it about 1 leap (3 seconds/...) while pressing it against the surface, and using the hardness of the hardest pencil that leaves no trace of scratches caused by the pencil.

As described above, the composite coating film is formed on a steel plate by coating with high pigment concentration anion electrodeposition paint - barrier coating - intermediate coating - top coating. It has excellent properties such as photoresistance, water resistance, weather resistance, etc., and in particular, chipping resistance, corrosion resistance of steel end faces, etc., and physical quality have been significantly improved.

Next, examples and comparative examples related to the present invention will be described.

■ Sample (1) Steel plate: One end of a steel plate (size 300 x 90 x 0.8 + AS +) chemically treated with Bonderite #3030 (manufactured by Nippon Parkerizing ■, zinc phosphate system) was bent 180' with an old V in the center. ^.

(2) Anionic electrodeposition paint: (5) 325 parts by weight of Epon #10 ('+1 (manufactured by Shell Chemical Co., Ltd., epoxy resin), 52,525 parts by weight of oil fatty acid and 17,575 parts by weight of dehydrated castor oil fatty acid were reacted with A1. 140 parts by weight of 1.2 polybutadiene carboxylic acid, 40 parts by weight of 1.4 polybutadiene and 75 parts by weight of maleic anhydride acid were added to the epoxy ester 27 o weight ff1ff, and reacted at 200°C. After ring-opening the acid anhydride groups and neutralizing Tokuten Yokozai (total acid value 85) with caustic potash, hexakismethoxymethylmelamine (crosslinking agent) was added to the total solid weight of both components to give 25%. Add weight% and mix.

Next, the solid content of the mixture of this resin and crosslinking agent was 100 parts by weight, 30 parts by weight of Akuri, Chita White, 33 parts by weight of clay, and 2 parts by weight of carbon black, and water was added to obtain the solid content. A coating material coated with an anionic type having a concentration of 20% by weight was obtained.

(8) Linseed oil fatty acid modified epoxy resin is reacted with anhydrous marin powder, the acid value after ring opening is 90, then neutralized with triethylamine, and this is added with part number butoxymethylmelamine (crosslinking agent). ) to the total weight of both components, then 2
Add 5% by weight, mix and make a hole.

Next, the solid content of the mixture of this resin and crosslinking agent was 100 parts by weight, 40 parts by weight of titanium white, 38 parts by weight of clay, and 2 parts by weight of carbon black, and then water was added to make the solid content. An anionic electrodeposition paint with a concentration of 20% by weight was obtained.

(O above (2) 1! The amount of @ken in the eyebrow paint,
Anion type IL made by changing 10 parts by weight of titanium white, 5 parts by weight of clay, and 0.5 parts by weight of carbon black.
! Seating fee.

(3) Barrier coat (A) near-ropyrene-ethylene copolymer (mole ratio, 6
0:40) 10,000 parts by weight and 11 parts by weight of maleic acid were graft-polymerized. fc8) Fatty organic liquid (static glass transition temperature -43°C, tensile strength elongation at -20°C: 410%).

(8: proviso ethylene copolymer (molar ratio 60:4
0) A liquid composition containing 100 parts by weight of a chlorinated polyolefin (chlorination rate 30%) (static glass transition temperature -48°C, tensile rupture at -2°C (1°C)) Strength elongation rate: 650%).

(0: A fatty organic liquid obtained by graft polymerizing maleic acid to a probi-receiving ethylene copolymer (static glass transition temperature +5°C).

(4) Intermediate coating! +Near Miraku N-2 Sealer (
(Manufactured by Kansai Paint, amino polyester resin intermediate coating) (5) Top coat (4) Near Miracle White (manufactured by Kansai Paint, amino alkyd resin top coating, white paint for 1 coat, 1 coat, pencil hardness H ) (9: Magikron Silver (manufactured by Kansai Paint ■, amino acrylic resin topcoat paint, 2-coat silver metallic paint for 1 coat, pencil hardness H) (0: Magikron Clear (manufactured by Kansai Paint ■, amino acrylic resin system) Top coat, 2-coat, 1-bake clear paint, pencil hardness H) 1 *Example, Comparative Example Using the above sample, apply anionic electrodeposition paint, barrier coat, intermediate coat and top coat to a steel plate as shown in Table 1. I painted it carefully.

For anionic electrodeposition coating, the bath temperature of the electrodeposition bath is 30℃ and P
Adjust to H7 or 8, use a steel plate as an anode, and apply a negative voltage.

This was carried out by applying electricity at a voltage of approximately 200V for 180 seconds. After electrocoating, wash with water and bake at 170℃ for 30 minutes. The coating thickness is also the same as the cured coating.

The barrier foot was painted with an air spray machine and was baked at 120℃ for 30 minutes. The film thickness is 6 μm based on the dry coating. Both the intermediate coat and top coat were spray-painted using an electrostatic coating machine, and the film thickness of the intermediate coat is based on the cured coating. It is 25μ.

In the top coating system, "ICIB" is the next coating system where the top coat paint A is applied and then baked at 140℃ for 30 minutes, and r2clBJ is the next coating system where the top coat paints B and C are coated with Couette Ocyque 7 and then coated with 140℃. This is a system in which both coatings are cured by baking at ℃ for 30 minutes.

■Performance test results A coating film performance test was conducted using the coated plates painted in the above examples and comparative examples. The results are shown in Table 2.

Test method (*1) Chipping resistance: (1) Test equipment: Q-G-R gravelometer (Q
Panel company product) (2) Stone to be sprayed: Crushed stone with a diameter of approximately 15-20% (3) Volume of stone to be sprayed: approximately 500-(4) Sprayed using air pressure crab approximately 4-cA (5) Temperature during test:
Approximately 20℃ Attach the test piece to the test piece holder and heat at approximately 4 Kq/a
In the spraying step d, approximately 500-sized crushed stone particles were shot onto the test piece using air pressure, and then the coated surface condition and salt water spray resistance were evaluated.

The condition of the painted surface was visually observed and evaluated using the following criteria. The salt water sprayability was determined by subjecting the test piece to JIS Z2371.
Conduct a salt spray test for 0 hours (just to be sure, stick adhesive cellophane tape on the painted surface, peel it off rapidly, and observe the presence or absence of rust from the impacted area, peeling of the paint film, and corrosion status.1) .Ta.

■ Condition of coated surface: ): Some scratches due to impact were observed on some parts of the stop coated coating, but no peeling of the electrodeposited coating was observed at all.

F: There are not many scratches caused by impact on the top coat and intermediate coat, and there are some peelings of the electrodeposition film.

×: Most of the top coat and intermediate coat peeled off, and the electrodeposited coating on the next impact area including the impact area and its surrounding area peeled off.

(2) Salt spray resistance O: Almost no rusting, corrosion, peeling of the paint film, etc. are observed.

○: 7. Slight flaking of the top coat or intermediate coat is observed.

Δ: Slightly more rust, corrosion, and peeling of the paint film are observed.

x: lI, corrosion and paint peeling occurred significantly.

(*2) Impact resistance: Partially conducted in an atmosphere at 10°C in accordance with JIS K5400-1979 6.13.3B method. Weight 500
Drop the weight from step 2 from a height of 50 cm to check for damage to the paint film.

((...: No cracks or peeling at all times ×: Significant cracks or peeling (*3) Adhesiveness: JIS K54oO-19796, 15 VC 1$ ]00
A piece is made, an adhesive cellophane tape is attached to the surface, and the number of remaining rough coating films after sudden Vζφl L fc is examined.

(i;' 4) Itt＊ SE'2: 40℃
Evaluate the painted surface after immersing it in water for 1 day (2?5)'' + - Smoothness: 1 Ne A, judgment ('-), +: Good △: Some small irregularities were observed on ? Ranel.

×: Significant minute irregularities are observed.

(*6) Edge corrosion resistance: A salt water spray test was conducted for 480 hours in the same manner as in 1 (*1) above, and the condition of the coated surface at the edge of the steel plate (bending portion) was visually determined. The judgment criteria are also the same as ■ in (*1).

(Bottle 7) Thread rust resistance: Cut the coating film in two diagonal lines to reach the substrate with a cutter, place it in a salt spray tester according to JIS Z2371 for 48 hours, and then clean the coating surface with deionized water. After cleaning, store in a constant temperature room box (temperature 40±2℃, humidity 85±2℃)
%), the occurrence of yarn rust after being placed in the yarn for 480 hours was investigated.

Record the average thread rust length and density, cut length 1
0 No more than 2 to 3 thread rust within the bud F 5 to 6 inside and outside of the wood M 10 or more threads D Evaluate as a guide (*8) Scapping resistance = Soaked in warm water at 40℃ for 120 hours, then 20℃ Dry for 4 hours and use Tomochi No. 6 crushed stone 300
9 was chipped at 4 K9/ca (straight cut was also used), [5% saline solution (3 (1℃)
Soak for 2 hours in water → leave open for 1 hour at -20°C → expose outdoors for 45 hours] three times a week, and consider this as one cycle.
Conducted an O-psy test to check the condition of the paint surface (especially regarding rust, blisters, etc.) C.

Claims (1)

[Claims] A steel plate is coated with an anionic electrodeposition paint containing a high concentration of pigment, and then formed on the coated surface.The main component is a modified polyolefin resin whose static glass transition temperature is -30 to -60°C. After applying an organic solvent barrier coat,
A steel plate coating method characterized by applying an intermediate coat and a top coat.