JP2001334207A - Method for coating automotive body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a new method for coating an automotive body by which it is possible to finish the metal part and the plastic part of the automotive body made up of these parts, with a coat of an approximate or the same color tone. SOLUTION: The method for coating an automotive body is characterized in that a colored coating material (A) containing a resin which contains a hydroxyl group, a melamine resin and a colored pigment is applied to the metal part and a colored coating material (B) obtained by adding a polyisocyanate compound to the colored coating material (A) is applied to the plastic part, when the colored coating materials (A), (B) are applied to the automotive body made up of the metal part and the plastic part. 2. The method for coating the automotive body is characterized in that the colored coating material (A) and a clear coating material (C) are applied to the metal part by a two-coat one-bake process and the colored coating material (B) and a clear coating material (D) are applied to the plastic part by the two-coat one-bake process, when the colored coating materials (A), (B) are applied to the automotive body made up of the metal part and the plastic part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel method of coating a vehicle body in which both parts of a vehicle body in which a metal part and a plastic part coexist can be painted with similar or the same color.

[0002]

2. Description of the Related Art A part of an outer panel of an automobile body,
For example, plastic parts such as polypropylene and polyurethane are often used for bumpers, fenders and the like instead of conventional metals.
It seems to be due to the light weight of the body and the ease of molding. And paint is applied to both parts for aesthetics and protection, the plastic part is softer than the metal part, the heat softening temperature is low, and the adhesion with the coating film is not enough, The paint for the plastic part is different from the paint for the metal part.

[0003] For example, a thermosetting coloring paint using a melamine resin that can be cured at a high temperature of 140 ° C. or more as a curing agent is applied to a metal portion, and a polyisocyanate compound that cures at a low temperature of 100 ° C. or less is used as a curing agent to a plastic portion. Each of the two-component type coloring paints is applied. However, among these paints, the coloring paints used for coating plastic parts are of a two-pack type, so that the pot life is short, and the paint is mixed so that the curing agent is mixed quickly and does not remain. And there is a defect that the operation for that is complicated. In addition, it has a defect that it is difficult to approximate or match the color tone of the metal part colored paint applied to the same object.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned deficiencies. As a result of intensive studies, when applying a colored paint to an automobile body in which a metal part and a plastic part coexist, particularly, a plastic material is used. The present inventors have found that the above-mentioned object can be achieved by using a paint obtained by adding a polyisocyanate compound to a metal part paint containing a hydroxyl group-containing resin, a melamine resin and a coloring pigment as a part paint, and completed the present invention. I came to. Thus, according to the present invention, when coating a colored paint on an automobile body where a metal part and a plastic part coexist, the metal part is coated with a colored paint (A) containing a hydroxyl group-containing resin, a melamine resin and a color pigment. The plastic part is coated with a coloring paint (B) obtained by adding a polyisocyanate compound to the coloring paint (A) (hereinafter referred to as "the present method 1"). Provided.

Further, according to the present invention, when a colored paint is applied to an automobile body in which a metal part and a plastic part coexist, the colored paint (A) and the clear paint (C) are applied to the metal part by a two-coat one-bake method. In addition, a coating method for an automobile body (hereinafter, referred to as "the present method 2"), characterized in that the plastic part is coated with the colored paint (B) and the clear paint (D) in a two-coat one-bake system, is also provided. You.

Hereinafter, a method of coating an automobile body according to the present invention will be described. This method 1 is for applying a colored paint to an automobile body where a metal part and a plastic part coexist.
The metal part is coated with a color paint (A) containing a hydroxyl group-containing resin, a melamine resin and a color pigment, and the plastic part is coated with a color paint (B) obtained by adding a polyisocyanate compound to the color paint (A). The present invention relates to a method for painting an automobile body characterized by painting.

Examples of the automobile include various passenger cars, mini cars, buses, and the like. These automobiles include panel hoods, fenders, door panels, panel trunk lids, pillars, rear quarters, sill outers, bumpers, aprons, radiator grills, and protection malls. It is exemplified as a vehicle body. Of these, the fenders, silouters, bumpers, aprons, radiator grills, and protection malls are often made of plastic.
As a material of the plastic part, a polyolefin resin such as polypropylene, a polyurethane resin, or the like is often used.

[0008] In carrying out the present method 1, it is preferable that the metal parts are previously coated with a known cationic electrodeposition coating and intermediate coating, and the coating is cured. It is preferable to perform a surface treatment or the like in advance by a method known per se. The colored paint (A) used in the present method 1 is a paint applied to a metal part of an automobile body where a metal part and a plastic part coexist, and is a paint containing a hydroxyl group-containing resin, a melamine resin, and a coloring pigment.

As the hydroxyl group-containing resin, for example, at least one selected from known polyester resins, alkyd resins, acrylic resins and the like for paints having two or more hydroxyl groups in one molecule can be used. The hydroxyl value is 20
The number average molecular weight is preferably in the range of 1,000 to 100,000.

As the melamine resin, an alkyl etherified melamine resin obtained by etherifying a part or all of the methylol group of the condensate of melamine and formaldehyde with a monoalcohol having 1 to 10 carbon atoms can be preferably used. The composition ratio of the hydroxyl group-containing resin and the melamine resin is, for example, 50 to 90% by weight, particularly 60 to 80% by weight, based on the total solid weight of both components.
The latter is suitably in the range from 50 to 10% by weight, especially from 40 to 20% by weight.

Color pigments include solid color pigments for ordinary paints, aluminum flakes, vapor-deposited aluminum powder, metallic pigments such as aluminum oxide, mica flakes, and light interference coated with iron oxide and / or titanium oxide. Pigments are included, and one or more selected from these can be used. The mixing ratio of these coloring pigments is 10% of the total solid content of the hydroxyl group-containing resin and the melamine resin.
The range of 1 to 200 parts by weight per 0 parts by weight is suitable.

The colored paint (A) is a paint containing these hydroxyl-containing resin, melamine resin and color pigment,
Further, it is prepared by adding an extender, an ultraviolet absorber, a coating surface adjuster and the like as needed, mixing these with an organic solvent, and dissolving or dispersing them. And the viscosity is 1
0-25 seconds / Ford cup # 4/20 ° C, adjusted by air spray, airless spray, electrostatic coating, etc.
10 to 40μ based on the cured coating on the metal part of the car body
It is preferable to apply a coating thickness of m. This coating is 12
The composition can be cured by heating at 0 to 180 ° C, particularly 130 to 160 ° C, for 10 to 40 minutes.

The color paint (B) used in the present method 1 is a paint to be applied to a plastic part of an automobile body where a metal part and a plastic part coexist, and the above-mentioned color paint (A)
Is a coating composition further containing a polyisocyanate compound. That is, the paint (A) and the paint (B) are painted on the same automobile body, and the paint (B)
Is a paint which is applied to a plastic part and is obtained by additionally mixing a polyisocyanate compound with the paint (A) used for coating a metal part. Therefore, paint (A)
And the color tone of the coating film (B) are the same or very similar, and little or no difference in color tone between the two coating films is observed. When the paint (A) and the paint (B) are applied to an automobile body in which a metal part and a plastic part coexist, little or no difference in color tone is recognized between the two parts.

The coloring paint (B) is obtained by adding a polyisocyanate compound to a coloring paint (A) containing a hydroxyl group-containing resin, a melamine resin and a coloring pigment, which is used for coating the same object (automobile body). A hydroxyl group-containing resin,
As the melamine resin and the color pigment, those described above can be suitably used. The polyisocyanate compound used in the paint (B) is a compound having two or more free isocyanate groups in one molecule, and specifically, for example, hexamethylene diisocyanate, trimethylene diisocyanate, tetramethylene diisocyanate Polyisocyanate compounds such as dimer acid diisocyanate and lysine diisocyanate; alicyclic polyisocyanate compounds such as isophorone diisocyanate, methylene bis (cyclohexyl isocyanate) and cyclohexane diisocyanate; xylylene diisocyanate, meta-xylylene diisocyanate, tolylene diisocyanate, diphenylmethane diisocyanate , Aromatic polyisocyanate compounds such as naphthalene diisocyanate; Dimer bets compounds, trimers, etc. polyol and isocyanate excess urethane products of these polyisocyanate compounds such as ethylene glycol or trimethylol propane.

[0015] In the colored coating (B), the compounding amount of the polyisocyanate compound is 5 to 30 parts by weight, particularly 10 to 20 parts by weight, per 100 parts by weight of the total of the hydroxyl group-containing resin and the melamine resin in terms of solid content. Are suitable. This polyisocyanate compound may react with the hydroxyl group-containing resin during storage, but it hardly gels during storage because it is in a small amount.

The color paint (B) is a paint containing the above-mentioned hydroxyl group-containing resin, melamine resin, polyisocyanate compound and color pigment, and further contains an extender pigment, an ultraviolet absorber, a coating surface adjuster and the like, if necessary. They may be added, and they are prepared by mixing these in an organic solvent and dissolving or dispersing them. Then, the viscosity of the colored paint (B) was adjusted to 10 to 15 seconds / Ford Cup # 4/2.
It is preferable that the temperature is adjusted to 0 ° C. and the plastic part of the vehicle body is painted by air spray, airless spray, electrostatic painting or the like. The film thickness is 1 based on the cured coating film.
A range of 0 to 30 μm is suitable. This coating is 50 ~
The composition can be cured by heating at 120 ° C., particularly 70 to 90 ° C., for 30 to 60 minutes.

It is preferable that the coating film of the coating material (A) and the coating material (B) is colored and concealed so that the color tone of the surface to be coated cannot be seen through. In the first method, the metal parts and the plastic parts are separated in advance, and the metal parts are colored paint (A), and the plastic parts are colored paint (B).
, Respectively, and after the coating film is cured, the two members can be combined and assembled to form an automobile body. In the method 2, as described above, the colored paint (A) is applied to the metal part and the colored paint (B) is applied to the plastic part, and the coated surface is coated with the clear paint without curing the coated film. After the two coating films are cured, the two members are combined and assembled to form an automobile body.

As the clear paint, a known paint which forms a colorless transparent or colored transparent coating film can be used.
That is, in the metal part, a base resin such as an acrylic resin or a polyester resin having a crosslinkable functional group such as a hydroxyl group, a carboxyl group, or an epoxy group, a melamine resin, a (block) polyisocyanate compound, a carboxyl group-containing compound or a resin, A thermosetting clear paint (C) containing a crosslinking agent such as an epoxy group-containing compound or a resin can be suitably used. This clear paint (C) has a viscosity of 10 to 30.
Seconds / Ford cup # 4/20 ° C, adjusted by air spray, airless spray, electrostatic coating, etc. to the uncoated color paint (A) coated as described above, based on the cured coating Paint to a film thickness of 20-80 μm;
It is carried out by heating at 20 to 180 ° C. for 10 to 40 minutes to simultaneously cure both coating films.

On the other hand, a two-pack clear paint (D) containing a base resin such as an acrylic resin or a polyester resin having a crosslinkable functional group such as a hydroxyl group and a crosslinker such as a polyisocyanate compound is preferably used for the plastic part. Can be used. This clear coating material (D) is adjusted to a viscosity of 10 to 30 seconds / Ford cup # 4/20 ° C., and is coated with an uncured color coating material (as described above) by air spray, airless spray, electrostatic coating, or the like. On the coated surface of B), apply a film thickness of 20 to 80 μm based on the cured coating film, and
It is carried out by heating at 0 ° C. for 30 to 60 minutes to simultaneously cure both coatings. In this method 2, the metal part and the plastic part are separated in advance, and the metal part is coated with the colored paint (A) and the clear paint (C), and the plastic part is coated with the colored paint (B) and the clear paint (D), respectively. 2
This is achieved by applying a coat 1 bake method, curing the coating film, and combining and assembling the two members to form an automobile body.

[0020]

Advantages of the Invention The colored paint (B) is a paint applied to a plastic part of an automobile body in which a metal part and a plastic part coexist. The colored paint (A) applied to a metal part contains a polyisocyanate compound. The color tone of the coating film of the colored paint (A) and that of the coating material (B) are the same or very similar, and little or no difference in the color tone between the two coating films is observed. 2. Since the colored paint (B) is a paint obtained by simply adding a polyisocyanate compound to the colored paint (A),
Toning work can be omitted, product types can be integrated, production costs can be reduced, and processes can be shortened. 3. After coating and curing the colored paint (B) and the clear paint (D) on the plastic part of the automobile body in a two-coat one-bake system, the repaired part is polished as necessary in the repair line, and these parts are colored paint. (B) and the cured coating obtained by repair-coating the clear coating with a two-coat one-bake method had good interlayer adhesion. 4. The storage stability of the colored coating (B) containing the polyisocyanate compound was good. 5. When the colored paint (A) for metal parts is applied to the plastic part as it is, the color consistency of both parts is good, but since the coating film is thermosetting, the low temperature of 100 ° C or less for the plastic part is used. Is not cured, it is difficult to form a practical coating film, but in the present invention,
A color paint (B) which contains a polyisocyanate compound in a color paint (A), and is applied to a plastic part to be cured into a sufficiently practical coating film without impairing color consistency. Is now possible. 6. Since the colored paint (A) for metal members, particularly the metallic paint, has a better orientation of the metallic pigment than the metallic paint for the plastic part, in the present invention, it can be applied to the plastic member. Therefore, the metallic feeling in the plastic part was improved.

[0021]

EXAMPLES Examples and comparative examples according to the present invention will be described below. All parts and percentages are on a weight basis and the thickness of the coating is for the cured coating. The invention is not limited to only these examples. Example 1 A hydroxyl-containing acrylic resin (hydroxyl number 80, number average molecular weight 12000) was applied to a metal coated object (metal member) obtained by applying a cationic electrodeposition coating and an intermediate coating and curing the coating.
70 parts, 30 parts of butyl etherified melamine resin, 30 parts of aluminum flake pigment, and 1 part of carbon black were mixed with an organic solvent (toluene), and the viscosity was 10 to 25 seconds /
Ford cup # 4 / Apply a metallic paint (colored paint A) adjusted to 20 ° C to a film thickness of 15 µm, leave it at room temperature for 3 minutes, and then “Magiclon clearer”
(Clear paint for forming an acrylic melamine resin-based transparent coating film, manufactured by Kansai Paint Co., Ltd.) was applied to a thickness of 40 μm, and was heated at 140 ° C. for 30 minutes to cure both coating films.

On the other hand, 70 parts of hydroxyl-containing acrylic resin (hydroxyl value 80, number average molecular weight 12000), 30 parts of butyl etherified melamine resin, 10 parts of hexamethylene diisocyanate, 30 parts of aluminum flake pigment were added to a degreased and washed polypropylene plate (plastic member). Then, one part of carbon black was mixed with an organic solvent (toluene), and the viscosity was adjusted to 10 to 25 seconds / Ford cup # 4/20 ° C. to form a metallic paint (colored paint B) having a thickness of 15 μm.
And soaked at room temperature for 3 minutes, and then "SOFLEX 5200" (trade name, manufactured by Kansai Paint Co., Ltd., a two-part clear paint for forming an acrylic polyisocyanate-based transparent coating film) having a film thickness of 40 μm. It was then coated and heated at 80 ° C. for 30 minutes to cure both coatings.

Since the colored paint (B) is a paint obtained by simply adding a polyisocyanate compound to the paint (A), the toning work can be omitted, and product integration can be achieved.
The production cost has been reduced and the process can be shortened. Moreover, when comparing the metal member and the plastic member coated in this way, no difference in color tone was recognized.

 ──────────────────────────────────────────────────続 き Continuing on the front page F term (reference) 4D075 AE06 BB26Z CA47 CB05 CB06 CB13 CB14 DA23 DB01 DB36 DB50 DC12 EA07 EA43 EB22 EB32 EB33 EB35 EB36 EB38 EB45 EC11 4J038 CG141 CH121 DA161 DD001 DD121 GA 181151 GA HA066 HA216 HA546 KA08 NA01 NA12 NA25 NA27 PA19 PB07 PC02 PC08

Claims (3)

[Claims] When a colored paint is applied to an automobile body where a metal part and a plastic part coexist, a colored paint (A) containing a hydroxyl group-containing resin, a melamine resin and a colored pigment is applied to the metal part, and the plastic part is coated. A method for coating an automobile body, which comprises applying a colored paint (B) obtained by adding a polyisocyanate compound to the colored paint (A). 2. When applying a colored paint to an automobile body having both a metal part and a plastic part, the metal part is coated with the colored paint (A) and the clear paint (C) by a two-coat one-bake method. Is the above colored paint (B)
And coating the clear paint (D) with a two-coat one-bake method. 3. The coating method for an automobile body according to claim 1, wherein the colored paint (A) and the colorant (B) are a solid color paint, a metallic paint or a light interference paint.