JPH05185031A - Topcoating film for automobile - Google Patents

Abstract

PURPOSE:To enhance the weatherability of topcoating film by using a color dye in the topcoating to impart high clearity and transparency. CONSTITUTION:A base coat 4 contg. at least a color dye is formed on primary coats 1, 2 and 3, a first clear topcoat 5 is formed on the undried base coat, a clear base coat 6 is formed on the first clear topcoat, and a second clear topcoat 7 is formed on the undried clear base coat. At this time the first clear topcoat contains 0-5 pts.wt. of a UV absorbent, the clear base coat contains 0-3 pts.wt. of the absorbent, the second clear topcoat contains 0-5 pts.wt. of the absorbent, and the total amt. of the absorbent contained in the first clear topcoat, clear base coat and second clear topcoat is controlled to >=6 pts.wt.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a topcoat coating system in which a coloring dye is mixed in a topcoat paint in order to impart high freshness and high transparency, and in particular, the weather resistance of a coating film using the color dye is improved. It is a thing.

[0002]

2. Description of the Related Art Solid color coating films, metallic color coating films, and pearl color coating films are known as conventional top coating films for automobiles. Among them, the solid color coating film is a top-coating coating film having a predetermined color with a coloring pigment, whereas the metallic coating film is composed of a metallic base layer containing a coloring pigment and aluminum pieces and a transparent clear layer. It is a coating film composed of layers. Also,
In order to improve the weather resistance of such a conventional coating film, a two-coat one-bake type solid color coating film has also been developed (for example, Japanese Patent Publication No. 61-54,063).

A method for forming a metallic color coating film is shown in FIG.
As shown in FIG. 1, first, a steel plate 10 which is an object to be coated is subjected to electrodeposition coating, and an electrodeposition coating film 11 is formed by baking this, and then an intermediate coating material is applied and baked to form an intermediate coating film 12 To form. A metallic base paint 14 containing a coloring pigment and aluminum pieces 13 is applied to the intermediate coating film, a clear paint 15 is applied wet-on-wet, and finally, the metallic base and clear are baked at the same time. The metallic color coating film thus obtained has a so-called "glittering" design because the color of the metallic base coating film 14 is combined with the irregular reflection of light by the aluminum pieces 13.

On the other hand, a pearl color coating is one in which the depth of the metallic color coating described above is improved. As shown in FIG. 4, the pearl color coating film is formed by first coating the intermediate coating film 12 with a color base coating material containing a color pigment and baking the coating.
6 is formed. Then, on this color base coating film, a transparent (no color pigment-containing) mica base paint 18 containing pearl pieces or mica pieces 17 was applied, and a clear paint 19 was applied wet-on-wet, and finally, Bake these mica base and clear at the same time. This pearl color coating is also called interference coating, and clear coating 1
Part of the light that has passed through 9 is reflected by the mica pieces 17 in the mica base coating film 18, and the remaining light also passes through this mica base coating film 18 and is reflected by the color base coating film 16. Therefore, the light reflected by the mica-based coating film and the light reflected by the color-based coating film combine to give a sense of depth in addition to the "glittering feeling" in the metallic color coating film. Moreover, there is a feature that the depth feeling varies depending on the viewing angle.

[0005]

The solid color coating film, the metallic color coating film, and the pearl color coating film described above each provide a unique design property, but use a coloring dye in view of freshness and transparency. It was inferior to the paint I had. In order to further enhance the commercial value of automobiles, it is effective to realize a high freshness and highly transparent top coat, but paints using colored dyes have problems with weather resistance,
In particular, it could not be applied to the top coating of an automobile that is left outdoors for a long time.

The present invention has been made in view of the above problems of the prior art, and uses a coloring dye in the topcoat paint to impart high freshness and high transparency, and the weatherability of the topcoat film. The purpose is to improve sex.

[0007]

The present invention for achieving the above object comprises a base coat layer formed on an underlayer and containing at least a coloring dye, and formed on the base coat layer without interposing a drying step. A first top coat clear layer, a base coat clear layer formed on the first top coat clear layer, and a second top coat clear layer formed on the base coat clear layer without interposing a drying step. It is a top coating film for automobiles characterized by the above.

At this time, 0 to 5 parts by weight of the ultraviolet absorber is contained in the first top coat clear coating constituting the first top coat clear layer, and 0 to 5 parts by weight of the ultraviolet absorber is contained in the base coat clear coating constituting the base coat clear layer. To 3 parts by weight, the second topcoat clear coating material constituting the second topcoat clear layer contains 0 to 5 parts by weight of an ultraviolet absorber, and the first topcoat clear coating material, the basecoat clear coating material and the first topcoat clear coating material. 2 It is preferable that the total amount of the ultraviolet absorber contained in the top coat clear paint is 6 parts by weight or more.

[0009]

[Function] A coloring dye that provides high freshness and high transparency is mixed in the base coat layer, and the first top coat clear layer, the base coat clear layer, and the second top coat clear layer are formed on the base coat layer. The first top coat clear layer, the base coat clear layer, and the second top coat clear layer are each mixed with an ultraviolet absorber in an amount of 0 to 5 parts by weight, 0 to 3 parts by weight, and 0 to 5 parts by weight, and further, Since the total amount of ultraviolet absorbers contained in the three layers is 6 parts by weight or more, the amount of ultraviolet rays incident on the base coat layer can be suppressed, and a top coat film having excellent weather resistance can be obtained.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view of a coating film showing a top coating film according to an embodiment of the present invention, and FIG. 2 is a process diagram showing a coating process of the embodiment.

The top coat film of this embodiment is formed on the base 1 of a vehicle body or a part such as a bumper. The base layer according to this embodiment is a general electrodeposition layer 2 and intermediate coating layer 3.
The following is a detailed description of the forming method. That is, the body (object to be coated) that has been conveyed from the vehicle body welding process before coating has the rust preventive oil applied during the pressing process in the cleaning process and the dust and the like attached to the body during vehicle body welding. This washing process is 40-50
It consists of steps such as hot water washing at ℃, degreasing, chemical conversion treatment, etc., and its main purpose is to remove dust and to form a chemical conversion coating that enhances the adhesion between the electrodeposition coating and the steel sheet. The body that has undergone the cleaning and chemical conversion treatment steps is then dried and conveyed to the undercoating step. In the undercoating process, in a passenger car, electrodeposition coating is generally performed with a coating material made of epoxy resin, but electrostatic coating is also possible. In this electrodeposition coating, a full-dip coating is used that completely sinks the body into the electrodeposition tank containing the electrodeposition coating, and a cationic electrodeposition method is used in which the coating side is applied to the anode and the body side is applied to the cathode. It can be said that the adoption is preferable in terms of rust prevention performance. Next, the body on which the electrodeposition coating is performed is heated and dried at a high temperature of about 200 ° C. to form an electrodeposition coating film 2 having a dry film thickness of 10 to 25 μm. The body on which the electrodeposition coating film 2 was formed was conveyed to an intermediate coating booth and had a dry film thickness of 15 to 30 μm.
Is formed. The intermediate coating material is a thermosetting coating material containing a polyester-melamine resin as a main component, and it is preferable that the intermediate coating material has excellent weather resistance of the coating film and excellent adhesion to the top coating film. It is also possible to employ a so-called inner plate color paint which uses an inorganic pigment or an organic pigment as a color pigment of the intermediate coating paint and provides a color similar to the outer plate color. Although the underlayer of this embodiment is formed in this manner, the present invention is not limited to the above-mentioned embodiments.

Next, the base coat layer 4 is formed on the intermediate coating layer 3. The base coat paint according to this embodiment contains a paint resin as a main component, contains at least a coloring dye, and may further contain a coloring pigment, a coloring pearl pigment, and a metallic powder. The coloring dye is one that imparts higher freshness and a higher transparency to the color of the base coat, and the coloring pigment is one that imparts a desired color to the base coat and is particularly limited as long as it is a coloring pigment that can be used in an automotive topcoat paint It can be used without being processed. The colored pearl pigment imparts a pearl luster to the base coat, and a powder obtained by coating mica powder with titanium oxide, iron oxide or the like can be used. The metallic powder imparts a metallic luster to the base coat, and metal powder such as aluminum powder and stainless powder is used. Further, the coating resin is a resin for forming a continuous coating film when applied to an object to be coated, and a polyester resin, an acrylic resin, a polyurethane resin or the like can be used. Such a base coat paint is applied onto the intermediate coating layer 4 by air spray coating or the like so that the dry film thickness is about 15 μm.

Next, the first top coat clear paint is applied on the base coat layer 4 formed by applying the base coat paint without a drying step, that is, wet-on-wet. It is preferable that the first top coat clear coating composition according to the present embodiment contains acrylic resin, polyester resin, polyurethane resin and the like as main components, and contains 0 to 5 parts by weight of an ultraviolet absorber. If the content of the ultraviolet absorber is more than 5 parts by weight, the bleeding phenomenon of the ultraviolet absorber that occurs during baking hinders the curing of the base coat clear coating material applied next and causes poor adhesion, which is not preferable. Then, this first top coat clear coating material is applied by air spray coating or the like so that the dry film thickness becomes about 30 μm, and the first top coat clear coating layer 5 and the base coating layer described above are applied to about 14
Bake by heating at a temperature of 0 ° C. for about 30 minutes.

Further, the first is formed by baking and curing.
A base coat clear paint is applied on the top coat clear layer 5. The base coat clear paint according to the present embodiment,
It is preferable to contain an acrylic resin, a polyester resin, a polyurethane resin or the like as a main component and an ultraviolet absorber in an amount of 0 to 3 parts by weight. If the amount is more than 3 parts by weight, the ultraviolet absorber will hinder the curing of the coating film when baking the second top coat clear which is applied by wet-on-wet, and cause poor adhesion, which is not preferable. The base coat clear paint is applied by air spray coating or the like so that the dry film thickness is about 15 μm.

Next, the second top coat clear paint is applied on the base coat clear layer 6 formed by applying this base coat clear paint without a drying step, that is, wet-on-wet. The second top coat clear paint according to the present embodiment is an acrylic resin,
Mainly made of polyester resin, polyurethane resin, etc.,
It is preferable to contain 0 to 5 parts by weight of the ultraviolet absorber. If the content of this ultraviolet absorber is more than 5 parts by weight,
Prolonged outdoor exposure causes the bleeding phenomenon of the ultraviolet absorber and causes so-called "cloudiness" on the coating film surface, which is not preferable. Then, this second top coat clear coating material is applied by air spray coating or the like so that the dry film thickness becomes about 30 μm, and the second top coat clear layer 7 together with the above base coat clear layer 6 is heated at a temperature of about 140 ° C. Heat and bake for 30 minutes.

The total amount of ultraviolet absorbers contained in the first top coat clear paint, the base coat clear paint and the second top coat clear paint is preferably 6 parts by weight or more. When the total amount of the ultraviolet absorber contained in the coating material constituting the three layers is less than 6 parts by weight,
Long-term outdoor exposure causes discoloration, which is not practical as a topcoat for automobiles.

Further, in this embodiment, the base coat clear layer 6 is formed between the first top coat clear layer 5 and the second top coat clear layer 7, which is a conventional general topcoat coating process. This is because the two-coat one-bake type paint has been designed so that it can be used as it is. Therefore, the base coat clear layer can be formed without changing the top coat coating process, and the top coat film having excellent weather resistance can be provided. Further, when the base coat clear layer 6 is formed between the first top coat clear layer 5 and the second top coat clear layer 7, the adhesion with the first top coat clear layer 5 is also improved.

Next, the present invention will be described in more detail, but this embodiment does not limit the present invention.

Production of Acrylic Resin A The following components were mixed in a reactor equipped with a stirrer, a thermometer, a reflux condenser and a monomer mixture dropping tank.

Xylene 10.5 parts by weight Butyl acetate 10.5 parts by weight These are heated to 140 ° C. with stirring so that the contents are in a gentle reflux state, and the following monomer is added to a dropping tank of the monomer mixture. The mixture was added and dropped into the solvent at a uniform rate over about 3 hours.

Methyl methacrylate 19.0 parts by weight 2-Ethylhexyl acrylate 4.7 parts by weight Methacrylate 0.5 parts by weight Tertiary butyl 1.5 parts by weight Butyl methacrylate 6.0 parts by weight 2-hydroxyethyl 16.3 parts by weight Acrylic Acid 2.0 parts by weight Perbenzoate 0.5 parts by weight After completing the feeding of this monomer, an additional 2
The reaction was continued for a time, cooled, and then diluted with the following solvent.

Butyl acetate 23.5 parts by weight Butyl alcohol 5.0 parts by weight In this way, a transparent acrylic resin solution having a nonvolatile content of 50% was obtained.

Manufacture of Acrylic Resin B The following components were mixed in the same reactor used for the manufacture of acrylic resin A described above.

Xylene 10.5 parts by weight Solvesso 100 (Note 1) 10.5 parts by weight Note 1) Product name, manufactured by Esso Petrochemical Co., Ltd. These are heated to 140 ° C. with stirring to loosen the contents. The following monomer mixture was put into the dropping tank for the monomer mixture and added dropwise into the solvent at a uniform rate over about 3 hours.

Styrene 19.0 parts by weight Butyl methacrylate 8.0 parts by weight Methacrylate 0.5 parts by weight Tertiary butyl 1.5 parts by weight 2-Ethylhexyl acrylate 11.0 parts by weight 2-Hydroxyethyl 8.0 parts by weight Acrylic acid 2.0 parts by weight Perbenzoate 0.5 parts by weight After completing the feeding of this monomer, an additional 2
The reaction was continued for a time, cooled, and then diluted with the following solvent.

Solvesso 100 23.5 parts by weight Butyl alcohol 5.0 parts by weight In this way, a transparent acrylic resin solution having a nonvolatile content of 50% was obtained.

Preparation of Red Base Coat The following ingredients were placed in the vessel of a ball mill disperser and
It was dispersed for 2 hours to obtain a red paste.

Acrylic resin A 28.0 parts by weight Chrome phthal red A3B (Note 2) 4.0 parts by weight Ethylene glycol monoethyl ether acetate 3.0 parts by weight Xylene 3.0 parts by weight Note 2) Red pigment, trade name, Ciba Geigy Co., Ltd. A red metallic base coat was prepared by adding the following components to this red paste.

Acrylic resin A 38.5 parts by weight Super Beckamine J820-60 (Note 3) 14.0 parts by weight SAP 561 EA (Note 4) 1.0 parts by weight Indanthrene-Red 5GK Dye 2.0 parts by weight Iriodin 210 Red Pearl (Note 5) 1.0 parts by weight Sandbar 3206 (Note 6) 0.5 parts by weight CAB 381-0.5 (Note 7) 1.0 parts by weight Ethylene glycol monoethyl ether acetate 2.0 parts by weight Ethyl acetate 2.0 parts by weight Note 3) 60% solution of butylated melamine resin, trade name, manufactured by Dainippon Ink and Chemicals, Inc. Note 4) Non-leafing type aluminum pigment, trade name, manufactured by Showa Aluminum Powder Co., Ltd. Note 5) Red pearl pigment, trade name, Note 6) ultraviolet absorber manufactured by Merck Japan Co., Ltd., product name, sand Co., Ltd. Note 7) cellulose resin, product name, Eastman Chemical Co., Ltd. base coat clear The following ingredients in addition to the adjustment acrylic resin A 66.5 parts by weight,
Adjusted the base coat clear.

Super Beckamine J820-60 14.0 parts by weight Ethylene glycol monoethyl ether acetate 10.0 parts by weight Ethyl acetate 9.5 parts by weight Adjustment of top coat Acrylic resin B 56.0 parts by weight The following components were added. ,
The top coat was adjusted.

Superbeckamine J820-60 20.0 parts by weight Solvesso 100 10.0 parts by weight xylene 7.0 parts by weight Butanol 7.0 parts by weight Example 1 The red base coat described above was mixed with xylene / isobutyl acetate / ethylene glycol mono. The mixture was diluted with a mixed solvent having a butyl ether ratio of 72/20/8 so that the viscosity was 13 seconds (Ford cup No. 4 viscometer, 20 ° C.). This base coat paint 4 was air-spray coated on a test plate on which an intermediate coating film was formed so that the dry film thickness was 15 μm, and in this state, it was set at room temperature for 5 minutes.

To 97.0 parts by weight of the above-mentioned top coat clear, 1.0 part by weight of TINUVIN 144 (UV absorber, trade name, manufactured by Ciba-Geigy Co., Ltd.) and 900 parts of TINUVIN.
(UV absorber, trade name, manufactured by Ciba Geigy)
After adding 2.0 parts by weight, the viscosity becomes 25 seconds (Ford cup No. 4 viscometer, 20 ° C.) in a mixed solvent having a ratio of Solvesso 100 / butanol / isobutyl acetate of 70/15/15. So diluted. The first top coat clear coating composition 5 is air-spray coated onto the red base coating layer 4 so that the dry film thickness is 30 μm, and is heated at 140 ° C. for 30 minutes to cure, and the temperature of the test plate is room temperature. Cooled down.

97.0 parts by weight of the above base coat clear, 1.0 parts by weight of tinuvin 144 and 900 parts by weight of tinuvin 900
2.0 parts by weight was added, and a mixed solvent having a ratio of xylene / isobutyl acetate / ethylene glycol monobutyl ether of 72/20/8, a viscosity of 13 seconds (Ford cup No. 4 viscometer, 20 ° C.) It was diluted so that The base coat clear coating material 6 was air-spray coated on the test plate on which the red base coat layer 4 and the first top coat clear layer 5 were formed so that the dry film thickness was 15 μm, and set at room temperature for 5 minutes.

97.0 parts by weight of the above-mentioned top coat clear and 1.0 parts by weight of tinuvin 144 and 900 parts by weight of tinuvin.
2.0 parts by weight was added, and the viscosity was 25 seconds (Ford cup No. 4 in a mixed solvent having a ratio of Solvesso 100 / butanol / isobutyl acetate of 70/15/15).
Viscometer, 20 ° C.). The second top coat clear paint 7 was air-spray coated on the test plate on which the base coat clear layer 6 was formed so that the dry film thickness was 30 μm, and heated at 140 ° C. for 30 minutes to cure.

The coating film thus obtained was exposed outdoors in Okinawa for 24 months and tested for weather resistance. The results are shown in Table 1. The color difference ΔE from before exposure is 1.8 NBS.
As a result, a color change was small, and the result of a cross-cut eye adhesion test showed that the coating film did not peel off.

Example 2 The addition amount of the ultraviolet absorber added to 98.0 parts by weight of the first top coat clear was 0.67 parts by weight of tinuvin 144 and 1.33 parts by weight of tinuvin 900, and 98.0 parts by weight of clear base coat. The amount of UV absorber added to TINUVIN 144 0.67 parts by weight and TINUVIN 900
The amount of the ultraviolet absorber added to 1.32 parts by weight and 98.0 parts by weight of the second top coat clear is 1440.67 parts by weight of tinuvin and 1.33 of tinuvin 900.
A coating film was formed in the same manner as in Example 1 except that parts by weight were used.

The results of weathering tests conducted by exposing this coating film to outdoor weather in Okinawa for 24 months are shown in Table 1. The color difference ΔE from that before exposure is 2.6 NBS, and there is little change in color. As a result of conducting a grid adhesion test on a cross board, no coating film peeling occurred.

Example 3 The amount of ultraviolet absorber added to 95.0 parts by weight of the first top coat clear was 1.67 parts by weight of tinuvin 144 and 3.33 parts by weight of tinuvin 900, and 98.0 parts by weight of clear base coat. The amount of UV absorber added to TINUVIN 144 0.67 parts by weight and TINUVIN 900
1.33 parts by weight, and the addition amount of the ultraviolet absorber added to 95.0 parts by weight of the second top coat clear was 1441.17 parts by weight of tinuvin and 3.33 of tinuvin 900.
A coating film was formed in the same manner as in Example 1 except that parts by weight were used.

The results of weathering tests conducted by exposing this coating film to the outdoors in Okinawa for 24 months are shown in Table 1. The color difference ΔE from that before exposure is 1.2 NBS, and there is little change in color. As a result of conducting a grid adhesion test on a cross board, no coating film peeling occurred.

Example 4 No ultraviolet absorber was added to the first top coat clear, and the amount of the ultraviolet absorber added to 99.0 parts by weight of the clear base coat was 0.33 parts by weight of tinuvin 144 and 0.67 of tinuvin 900 0.67. The weight of the UV absorber added to 95.0 parts by weight of the second top coat clear is 1.67 parts by weight of TINUVIN 144 and 900% by weight of TINUVIN.
A coating film was formed in the same manner as in Example 1 except that 3.33 parts by weight was used.

The results of weathering tests conducted by exposing this coating film to the outdoors for 24 months in Okinawa are shown in Table 1. The color difference ΔE from that before exposure is 2.3 NBS, and there is little change in color. As a result of conducting a grid adhesion test on a cross board, no coating film peeling occurred.

Example 5 The addition amount of the ultraviolet absorber added to 97.0 parts by weight of the first top coat clear was 1.04 parts by weight of Tinuvin 144 and 2.0 parts by weight of Tinuvin 900, and the ultraviolet absorber was used for the clear base coat. In addition, the addition amount of the ultraviolet absorber added to 97.0 parts by weight of the second top coat clear is 1.0% by weight of TINUVIN 144 and 900% by weight of TINUVIN.
A coating film was formed in the same manner as in Example 1 except that the amount was 2.0 parts by weight.

The results of weathering tests conducted by exposing this coating film to outdoor weather in Okinawa for 24 months are shown in Table 1. The color difference ΔE from that before exposure is 2.7 NBS, and there is little change in color. As a result of conducting a grid adhesion test on a cross board, no coating film peeling occurred.

Example 6 The amount of the ultraviolet absorber added to 97.0 parts by weight of the first top coat clear was 1.0 parts by weight of tinuvin 144 and 2.0 parts by weight of tinuvin 900, and 97.0 parts by weight of clear base coat. The amount of UV absorber added to the product is 1441.0 parts by weight of TINUVIN and 900 2.0 of TINUVIN.
A coating film was formed in the same manner as in Example 1 except that the amount was parts by weight and no ultraviolet absorber was added to the second top coat clear.

The results of weathering tests conducted by exposing this coating film to the outdoors for 24 months in Okinawa are shown in Table 1. The color difference ΔE from that before exposure is 3.1 NBS, and there is little change in color. As a result of conducting a grid adhesion test on a cross board, no coating film peeling occurred.

Comparative Example 1 The amount of UV absorber added to 97.0 parts by weight of the first top coat clear was 1.0 parts by weight of TINUVIN 144 and 2.0 parts by weight of TINUVIN 900, and the UV absorber was added to the clear base coat. Is added to the second top coat clear 98.0 parts by weight, and the addition amount of the UV absorber is 0.67 parts by weight of TINUVIN 144 and 90% by weight of TINUVIN.
A coating film was formed in the same manner as in Example 1 except that the amount was 1.33 parts by weight.

The results of weathering tests conducted by exposing this coating film to outdoor weather in Okinawa for 24 months are shown in Table 1. The color difference ΔE from that before exposure is 5.7 NBS, showing a large change in color. As a result of conducting a grid adhesion test on a cross board, no coating film peeling occurred.

Comparative Example 2 The addition amount of the ultraviolet absorber added to 97.0 parts by weight of the first top coat clear was 1.04 parts by weight of tinuvin 144 and 2.0 parts by weight of tinuvin 900, and 96.0 parts by weight of clear base coat. The amount of the ultraviolet absorber added to the above was added to Tinuvin 1441.33 parts by weight and Tinuvin 900 2.
67 parts by weight, and second top coat clear 9
Add the amount of UV absorber added to 7.0 parts by weight to Tinuvin.
A coating film was formed in the same manner as in Example 1 except that the amount was 144 1.0 parts by weight and Tinuvin 900 2.0 parts by weight.

The results of weathering tests conducted by exposing this coating film to the outdoors for 24 months in Okinawa are shown in Table 1. The color difference ΔE from that before exposure is 1.8 NBS, and there is little change in color. As a result of conducting a grid cross-contact test, peeling of the coating film occurred.

Comparative Example 3 The addition amount of the ultraviolet absorber added to 97.0 parts by weight of the first top coat clear was 1.04 parts by weight of tinuvin 144 and 2.0 parts by weight of tinuvin 900, and 97.0 parts by weight of clear base coat. The amount of UV absorber added to the product is 1441.0 parts by weight of TINUVIN and 900 2.0 of TINUVIN.
2 parts top coat clear 94.0
Add the amount of UV absorber added to parts by weight to Tinuvin 144
A coating film was formed in the same manner as in Example 1 except that 2.0 parts by weight and Tinuvin 900 4.0 parts by weight were used.

Table 1 shows the weather resistance test results of this coating film exposed outdoors in Okinawa for 24 months. The color difference ΔE from that before exposure was 2.1 NBS, and there was little change in color. As a result of conducting a cross-contact test on a cross board, no peeling of the coating film occurred, but clouding occurred on the surface of the coating film.

Comparative Example 4 The amount of the ultraviolet absorber added to 94.0 parts by weight of the first top coat clear was 2.0 parts by weight of tinuvin 144 and 4.0 parts by weight of tinuvin 900, and 97.0 parts by weight of clear base coat. The amount of UV absorber added to the product is 1441.0 parts by weight of TINUVIN and 900 2.0 of TINUVIN.
2 parts of top coat clear 97.0
Add the amount of UV absorber added to parts by weight to Tinuvin 144
A coating film was formed in the same manner as in Example 1 except that 1.0 part by weight and 2.0 parts by weight of Tinuvin 900 were used.

The results of weathering tests conducted by exposing this coating film to the outdoors for 24 months in Okinawa are shown in Table 1. The color difference ΔE from that before exposure is 1.8 NBS, which shows little change in color. In addition, as a result of conducting a grid adhesion test, the coating film peeled.

Comparative Example 5 The above red base coat was mixed with a mixed solvent having a ratio of xylene / isobutyl acetate / ethylene glycol monobutyl ether of 72/20/8 for a viscosity of 13 seconds (Ford cup No. 4 viscometer, 20 (° C) was diluted. This base coat paint 4 was air-spray coated on a test plate on which an intermediate coating film was formed so that the dry film thickness was 15 μm, and in this state, it was set at room temperature for 5 minutes.

To 97.0 parts by weight of the above-mentioned top coat clear, 1.0 part by weight of TINUVIN 144 (UV absorber, trade name, manufactured by Ciba-Geigy Co., Ltd.) and 900 parts of TINUVIN.
(UV absorber, trade name, manufactured by Ciba Geigy)
After adding 2.0 parts by weight, the viscosity becomes 25 seconds (Ford cup No. 4 viscometer, 20 ° C.) in a mixed solvent having a ratio of Solvesso 100 / butanol / isobutyl acetate of 70/15/15. So diluted. The first top coat clear coating composition 5 was air-spray coated onto the red base coating layer 4 so that the dry film thickness was 30 μm, and heated at 140 ° C. for 30 minutes to be cured.

The results of weathering tests conducted by exposing this coating film to the outdoors for 24 months in Okinawa are shown in Table 1. The color difference ΔE from that before exposure is 6.8 NBS, and the color change is large. As a result of conducting a cross-contact test on a cross board, no peeling of the coating film occurred, but clouding occurred on the surface of the coating film.

[0057]

[Table 1]

[0058]

As described above, according to the present invention, a first top coat clear layer formed without interposing a drying step on a base coat layer formed on an underlayer and containing at least a coloring dye, Since the base coat clear layer formed on the first top coat clear layer and the second top coat clear layer formed on the base coat clear layer without the drying step interposed therebetween, the weather resistance of the top coating film is improved. It is possible to provide a top coat film having a high freshness and a high transparency while increasing the transparency.

[Brief description of drawings]

FIG. 1 is a sectional view of a coating film showing a top coating film according to an embodiment of the present invention.

FIG. 2 is a process drawing showing a coating process of the same embodiment.

FIG. 3 is a coating cross-sectional view showing a conventional solid color coating film.

FIG. 4 is a sectional view of a coating film showing a conventional metallic color coating film.

[Explanation of symbols]

1 ... Steel plate, 2 ... Electrodeposition layer, 3
... Intermediate coating layer, 4 ... Base coat layer, 5 ... First top coat clear layer, 6 ... Base coat clear layer, 7 ... Second top coat clear layer.

Claims (2)

[Claims] 1. A base coat layer formed on an underlayer and containing at least a coloring dye, a first top coat clear layer formed on the base coat layer without interposing a drying step, and the first top coat clear layer. A topcoat coating film for an automobile, comprising: a base coat clear layer formed on the layer; and a second top coat clear layer formed on the base coat clear layer without interposing a drying step. 2. The first topcoat clear coating material constituting the first topcoat clear layer contains 0 to 5 parts by weight of an ultraviolet absorber, and the basecoat clear coating material constituting the basecoat clear layer contains no ultraviolet absorber. To 3 parts by weight,
The second top coat clear coating material forming the second top coat clear coating layer contains 0 to 5 parts by weight of an ultraviolet absorber, and the first top coat clear coating material, the base coat clear coating material and the second top coat clear coating material. The top coating film for an automobile according to claim 1, wherein the total amount of the ultraviolet absorber contained in is 6 parts by weight or more.