JP3035367B2 - Painting method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a coating method, and more particularly to a method for coating a surface of an object to be coated with a partially different color.

[0002]

2. Description of the Related Art In general, for example, an outer body plate of an automobile includes:
An undercoat for the purpose of rust prevention, a middle coat for the purpose of surface adjustment for improving the finished appearance, and an overcoat for the purpose of finished appearance and durability are provided.

[0003] By the way, parts such as sashes and center pillars of automobile doors are partially coated with a black paint having a different color from the top coat after the top coat due to design requirements. As described above, the following method has conventionally been adopted as a method of partially coating the surface of the object to be coated with a different color.

<Conventional Example I> First, as shown in FIG. 2 (a), an undercoat is applied to the surface of an object to be coated a to form an undercoat layer b.
To form Next, as shown in FIG. 2B, for example, a gray intermediate paint is applied on the undercoat layer b to form an intermediate coat c. Thereafter, as shown in FIG. 2 (c), a black paint having a different color from the top coat is partially applied in a wet-on-wet manner (in a state where the middle coat is not dried) on a required portion on the intermediate coat c. To form a different color layer d. Thereafter, as shown in FIG. 2D, a top coat is applied on the middle coat c while the different color layer d is masked with the masking paper e to form a top coat f.

<Conventional Example II> First, as shown in FIG. 3 (a), an undercoat is applied to the surface of an object to be coated a to form an undercoat layer b.
To form Next, as shown in FIG. 3B, for example, a gray intermediate paint is applied on the undercoat layer b to form an intermediate coat c. Thereafter, as shown in FIG. 3 (c), a top coat is applied on the intermediate coat c to form a top coat f. Thereafter, as shown in FIG.
After sanding a required portion on the overcoat layer f, the surrounding area is masked with a masking paper e, and the sanding portion is partially painted with a natural drying type black paint having a different color from the overcoat paint to obtain a different color layer d. To form

<Conventional Example III> First, as shown in FIG. 4 (a), an undercoat is applied to the surface of an object a to form an undercoat layer b. Next, as shown in FIG. 4B, for example, a gray intermediate paint is applied on the undercoat layer b to form an intermediate coat c. Thereafter, as shown in FIG. 4C, a top coat is applied on the intermediate coat c to form a top coat f. Thereafter, as shown in FIG.
In a state in which the required area on the top coat f is masked with the masking paper e, a black paint of a heat-drying type (baking type) having a different color from the top coat is partially applied to the required area to form a different color layer d. To form

[0007]

However, in the above-mentioned conventional coating method I, the black paint is applied on the gray intermediate coat c by wet-on-wet, so that the boundary between the two is blurred and unclear. Therefore, when the top coat has low concealment properties, the boundary between the intermediate coat c and the different color layer d can be seen through, so that a low concealment paint cannot be adopted as the top coat.

In the coating method of the prior art II, the disadvantage of the conventional example I can be solved because it is not a wet-on-wet method, but a required portion on the overcoat layer f has to be sanded, which is troublesome. There is such a problem. As described above, sanding of a required portion on the overcoat layer f is performed because the surface of the overcoat layer f is inactive because physical properties such as weather resistance are required. This is because the mold paint does not easily adhere to the overcoat layer f. In addition, when the shape of the sanding portion is complicated, the sanding cannot be sufficiently performed, and the different color layer d
, The adhesion reliability of the air-drying paint which constitutes the above is reduced. It is known that the adhesion of the air-drying paint to the intermediate coating layer c is good, and the sanding does not have to be performed like the top coating layer f.

Further, in the coating method of Conventional Example III, since a heat-drying type (baking type) paint is used as a coating material for forming the different color layer d, unlike the air-drying type paint of Conventional Example II, the inside of the drying furnace is coated after coating. There is a problem that the production efficiency must be reduced due to having to pass through.

The present invention has been made in view of the above-mentioned points, and an object of the present invention is to adopt a low concealing paint as a top coat by changing a coating procedure and components of an intermediate coat, Another object of the present invention is to eliminate sanding, improve the adhesion reliability of air-drying paint, and improve production efficiency.

[0011]

Means for Solving the Problems To achieve the above object, the solution of the present invention according to claim 1 is a method for coating the surface of the object to be coated with a partially different color. An undercoat is applied to the surface of the coating to form an undercoat layer. Next, an epoxy resin of 8 to 8
An intermediate coating containing 12 wt% and an ultraviolet absorber of 1 to 3 wt% is applied to form an intermediate coating layer. Thereafter, a top coat is applied to the intermediate coat layer in a state where the required portions are masked to form a top coat layer. Thereafter, in a state where the overcoat layer is masked, a natural drying type paint having a color different from that of the overcoat paint is applied to the masking corresponding portion of the intermediate coat layer to form a different color layer.

[0012] Further, in the above-mentioned solution, in the above case, the naturally drying type paint is specified as a two-pack polyurethane resin paint, and the content of the epoxy resin in the intermediate paint is 6%. １２12 wt%.

[0013]

According to the above construction, in the method according to the first aspect of the present invention, after an intermediate coat layer is formed on the undercoat layer on the surface of the object to be coated, the required portion is masked on the intermediate coat layer. An overcoat layer is formed, and then, in a state where the overcoat layer is masked, a natural drying type paint having a color different from that of the overcoat paint is applied to a portion corresponding to the masking of the intermediate coat layer.

Accordingly, the air-drying type paint is applied on the intermediate coating layer, and has better adhesion than the case where it is applied on the inert coating layer, so that sanding such as the upper coating layer is not required. Since the epoxy resin is contained in the intermediate coating material in an amount of 8 to 12% by weight,
Due to the properties of the epoxy resin, the adhesion reliability of the air-drying paint to the intermediate coating layer is improved.

Further, since the natural drying type paint is applied on a dry intermediate coating layer instead of wet-on-wet, the boundary between the two does not blur and become unclear.
It is possible to adopt a low concealment material as the top coating,
Moreover, the UV-absorber is contained in the intermediate coating in an amount of 1 to 3% by weight.
Since it is contained, when the overcoating material has a low concealing property, the adverse effect on the epoxy resin due to the ultraviolet light passing through the overcoating layer is suppressed by the characteristics of the ultraviolet absorber, and the adhesion reliability of the air-drying paint is suppressed. Nature is secured.

Further, as described above, since a natural drying type paint is used instead of a heat drying type (baking type) paint as a coating material for forming a different color layer, it is not necessary to pass through a drying furnace after coating, and only that amount is required. Production efficiency is improved.

Further, in the method of the present invention according to claim 2, in the above case, when an air-drying two-pack polyurethane resin coating is used as the coating constituting the different color layer, the epoxy resin is contained in the intermediate coating. Since the amount is set to 6 to 12 wt%, the same operation and effect as in the above case can be obtained.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A coating method according to an embodiment of the present invention will be described below with reference to the drawings.

FIGS. 1A to 1D show a painting process. This embodiment is, for example, an undercoat for the purpose of rust prevention on an object to be coated such as a car body outer panel, an intermediate coat for the purpose of surface adjustment for improving the finished appearance, and an overcoat for the purpose of the finished appearance and durability. The present invention relates to a method of partially painting a door sash, a center pillar, or the like in a color different from the top coat according to design requirements or the like.

To explain the procedure of the coating, first, FIG.
As shown in (a), the undercoat layer 3 is formed by, for example, electrodepositing an undercoat paint on the surface of the workpiece 1 which has been subjected to pretreatment such as degreasing and film formation.

Next, as shown in FIG. 1 (b), on the undercoat layer 3, an intermediate paint containing 8 to 12 wt% or 6 to 12 wt% of an epoxy resin and 1 to 3 wt% of an ultraviolet absorber. Is applied, for example, by electrostatic coating to form an intermediate coating layer 5 through a baking process. 8 to 12 wt% or 6 to 12 wt% of epoxy resin in the intermediate coating
The reason why the two types are set is that the lower limit is set to 8 wt% or 6 wt% in order to properly use them according to the type of the natural drying type paint that forms the different color layer 13 described later.
If the content is less than 8 wt% or less than 6 wt%, the adhesion reliability of the air-drying paint to the intermediate coating layer 5 is reduced. On the other hand, the upper limit is set to 12 wt%
%, The weather resistance of the intermediate coating layer 5 decreases. Further, the content of the ultraviolet absorbent in the intermediate coating paint is 1 to
The reason why the content is set to 3 wt% is that the intermediate coating layer 5
This is because the effect of improving the weather resistance is lost, but if it exceeds 3 wt%, the effect of improving the weather resistance in proportion to the content cannot be expected. As described above, the combined use of the epoxy resin and the ultraviolet absorber can improve the adhesion reliability of the air-drying paint to the intermediate coating layer 5 with the epoxy resin, but the epoxy resin is easily deteriorated by the ultraviolet light. It is intended to suppress a decrease in weather resistance due to the addition with an ultraviolet absorber.

Thereafter, as shown in FIG. 1 (c), a top coat is electrostatically applied to the intermediate coat layer 5 with a required portion thereof being masked with a masking paper 7, for example, by an electrostatic coating, followed by a baking step. 9 is formed.

Thereafter, as shown in FIG. 1D, after the masking paper 7 is removed, the overcoat layer 9 is masked with another masking paper 11 and the intermediate coating layer 5 is masked. An air-drying paint having a color different from that of the top coat paint is applied to the portion, for example, by spray coating to form a different-color layer 13 by natural drying, and the surface of the article to be coated 1 is partially painted in a different color. Examples of the natural drying type paint constituting the different color layer 13 include an acrylic lacquer and a two-pack polyurethane resin paint. When the natural drying type paint is an acrylic lacquer, the content of the epoxy resin in the intermediate coating is reduced. In the case of a two-component polyurethane resin paint, the content of the epoxy resin contained in the intermediate coating paint is set to 8 to 12 wt%, and the content of the epoxy resin is set to 6 to 12 wt%.

Next, a test of the adhesion reliability of the air-drying type paint to the intermediate coating layer 5 in the above example was performed. The test data obtained are shown in Table 1, and the paint composition and test plate used in obtaining the test data are shown in Table 1. Preparation procedures and test procedures are shown below. However, no UV absorber was added to the intermediate coating.

<Coating composition (unit: wt%)> [Intermediate coating (color: gray)] Oil-free polyester resin 60.2 to 70 Butylated melamine resin 25.8 to 30 Bisphenol A epoxy resin 0 to 14 rutile type Titanium white 70 Carbon black 0.3 Barium sulfate 20 [Top coat (color: white)] Alkyd resin 70 Butylated melamine resin 30 Rutile type titanium white 80 Carbon black 0.05 [Two-component polyurethane resin paint (color: black)] Acrylic resin 100 Carbon black 3.5 Polyisocyanate 20 [Acrylic lacquer (color: black)] Acrylic lacquer resin 100 Carbon black 3.2 <Procedure for preparing test plate> (A): Paint intermediate coating on surface of object to be coated And 140 ° C
After obtaining a middle coat layer having a thickness of 23 μm under baking conditions of × 25 minutes, a top coat was applied, and a top coat layer of 40 μm was obtained under baking conditions of 140 ° C. × 25 minutes.

(B): An intermediate coating is applied on the surface of the object to be coated, and a 23 μm-thick intermediate coating layer is obtained under a baking condition of 140 ° C. × 25 minutes, and then a two-component polyurethane resin coating is applied. The mixture was naturally dried at 20 ° C. for 2 hours to obtain a 20 μm two-pack polyurethane resin layer.

(C): An intermediate coating is applied to the surface of the object to be coated, and a 23 μm-thick intermediate coating layer is obtained under the conditions of baking at 140 ° C. × 25 minutes.
It was air dried for 2 hours to obtain an acrylic lacquer layer of 20 μm.

Incidentally, (A), (B) and (C) correspond to those in the column of “paint combination” in Table 1.

<Test Procedures> Water adhesion test: After immersion in warm water at 40 ° C. for 10 days,
Judgment was made based on the number of cellophane tapes peeled off by the cellophane tape. In Table 1, a circle indicates that the remaining number is 90 or more out of 100 Goban eyes, and a cross indicates that the remaining number is 89.
The following are indicated respectively.

[0030]

[Table 1]

According to this, in the case of (a) in which the top coat 9 was formed on the middle coat 5, adhesion reliability was obtained when the content of the epoxy resin in the middle coat was 2 wt% or more. . In the case of (B) in which a different-color layer 13 of a two-pack polyurethane resin paint as a natural drying type paint was formed on the intermediate coat 5, the content of the epoxy resin in the intermediate paint was 6 wt.
% Or more, adhesion reliability was obtained. In the case of (C) in which the different color layer 13 of the acrylic lacquer as the air-drying type coating was formed on the intermediate coating 5 (C), the content of the epoxy resin in the intermediate coating was 8 wt% or more and the adhesion reliability was low. Obtained.

Further, the weather resistance test of the intermediate coating layer 5 in the above example was carried out, and the obtained test data is shown in Table 3. The paint composition, test plate preparation procedure and test procedure used in obtaining the test data are as follows. Shown in

<Coating composition (unit: wt%)> [Intermediate coating (color: gray)] Oil-free polyester resin 60.2-66.5 Butylated melamine resin 25.8-28.5 Bisphenol A epoxy resin 6 -14 Benzotriazole 0-4 Rutile titanium white 70 Carbon black 0.3 Barium sulfate 20 [Top coating (color: blue)] Alkyd resin 70 Butylated melamine resin 30 Slen blue

[0034]

[Table 2]

In Table 2, “〜” corresponds to those in the column “Light transmittance of overcoat” in Table 3.

<Procedure for preparing test plate> A cationic undercoat is electrodeposited on the surface of the object to be coated, and an undercoat layer having a thickness of 20 μm is obtained under a baking condition of 175 ° C. × 25 minutes. Painted, thickness 3 under baking conditions of 140 ° C x 25 minutes
Obtain an intermediate coating layer of 0 μm, then apply a top coating,
Under a baking condition of 140 ° C. × 25 minutes, a 30 μm-thick overcoat layer was obtained.

<Test Procedures> After exposing for 240 hours with a sunshine weather meter, immersion in warm water at 40 ° C. for 24 hours was repeated 10 times to examine the adhesion of the overcoat layer. In Table 3, the mark ○ indicates that the epoxy resin in the intermediate coating layer was not deteriorated by ultraviolet rays and the top coat layer was firmly adhered to the intermediate coating layer and had good adhesion. The mark × indicates the epoxy in the intermediate coating layer. It indicates that the resin is deteriorated or powdered by ultraviolet rays, the upper coating layer is peeled off, and the adhesiveness is deteriorated.

[0038]

[Table 3]

The test data in Table 3 shows that the light transmittance of the low concealment paint is generally 2 at a wavelength of 360 to 420 nm.
Judging comprehensively from 0 to 60%, the content of the epoxy resin in the intermediate coating is 6 to 12 wt%,
And when the content of the ultraviolet absorber was 1 to 4% by weight, the adhesion of the overcoat layer was improved. Since the content of the ultraviolet absorber is the same at 3 wt% and 4 wt%, it is more economical to use a smaller amount.

As described above, in this embodiment, after the required portion is masked by the masking paper 7 on the intermediate coating layer 5 to form the overcoat layer 9, the overcoat layer 9 is masked by another masking paper 11. In this state, a natural drying type paint having a different color from the top coating is applied to the masking corresponding portion of the intermediate coating layer 5 to form the different color layer 13, so that the natural drying type paint is applied on the intermediate coating layer 5. ,
Adhesion can be improved as compared with the case where the inert overcoat layer 9 is applied. Therefore, the sanding like the top coat 9 is not required, and the epoxy resin is added to the intermediate coat in an amount of 8 to 12 wt%, so that the air-drying paint adheres to the intermediate coat 5 depending on the properties of the epoxy resin. Reliability can be improved.

Further, in the above embodiment, since the air-drying paint is applied on the dry intermediate coating layer instead of wet-on-wet, it is possible to prevent unclearness due to bleeding of the boundary between the two, and to provide a low concealing property as a top coating. Things can be adopted. Moreover, an ultraviolet absorber is contained in the intermediate coating paint.
Since 3 wt% is added, when the top coat is of a low concealment property, the adverse effect on the epoxy resin due to the ultraviolet light passing through the top coat 9 can be suppressed by the characteristics of the ultraviolet absorber, and the natural drying type Adhesion reliability can be ensured.

Further, in the above embodiment, as described above, a natural drying type paint is used as the paint constituting the different color layer 13 instead of the heat drying type (baking type) paint. And the production efficiency can be improved accordingly.

When a two-component polyurethane resin paint of a natural drying type is used as a paint for forming the different color layer 13,
The content of epoxy resin in the intermediate coating is 6 to 12 wt%
, The same operation and effect as in the above case can be obtained.

[0044]

As described above, according to the method of the present invention, required portions of the intermediate coating layer containing 8 to 12% by weight of an epoxy resin and 1 to 3% by weight of an ultraviolet absorber are masked. After forming the overcoat layer in a state where the overcoat layer is masked, since a different color layer composed of a natural drying type paint of a different color from the overcoat paint is formed on the masking corresponding portion of the intermediate coat layer in a state where the overcoat layer is masked, no sanding is required. In addition, even if the top coat has low concealment properties, the adhesion reliability of the air-drying paint can be improved by the properties of the epoxy resin and the ultraviolet absorber. Furthermore, since the different color layer is formed by a natural drying type paint,
It is not necessary to go through a baking process, and the production efficiency can be improved accordingly.

According to the second aspect of the present invention, in the above case, when a two-component polyurethane resin paint of a natural drying type is used as a paint constituting the different color layer,
The content of epoxy resin in the intermediate coating is 6 to 12 wt%
, The same operation and effect as in the above case can be obtained.

[Brief description of the drawings]

FIG. 1 is a drawing showing a coating process of this embodiment. (A) is an undercoat layer formation process drawing. (B) is an intermediate layer forming process diagram. (C) is an overcoat layer forming step diagram. (D) is a step diagram of the different color layer formation.

FIG. 2 is a drawing showing a coating process of Conventional Example I. (A) is an undercoat layer formation process drawing. (B) is an intermediate layer forming process diagram. (C) is a drawing of a different color layer forming step. (D) is an overcoat layer forming step diagram.

FIG. 3 is a coating process diagram of Conventional Example II. (A) is an undercoat layer formation process drawing. (B) is an intermediate layer forming process diagram. (C) is an overcoat layer forming step diagram. (D) is a step diagram of the different color layer formation.

FIG. 4 is a drawing showing a coating process of Conventional Example III. (A) is an undercoat layer formation process drawing. (B) is an intermediate layer forming process diagram. (C) is an overcoat layer forming step diagram. (D) is a step diagram of the different color layer formation.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Coated object 3 ... Undercoat layer 5 ... Intermediate layer 9 ... Overcoat layer 13 ... Different color layer

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁷ Identification code FI B05D 7/24 302 B05D 7/24 302T 302U

Claims (2)

(57) [Claims] 1. A method of coating a surface of an object to be coated with a partially different color, wherein an undercoat is applied to the surface of the object to form an undercoat layer. 8 to 12 wt% epoxy resin and 1 ultraviolet absorber
An intermediate coating containing 3 wt% to 3 wt% each is applied to form an intermediate coating layer, and then a topcoat is applied on the intermediate coating in a state where required portions are masked to form an uppercoat. A coating method characterized by forming a different-color layer by applying a natural-drying paint having a different color from that of the overcoat layer to a portion of the intermediate coat layer corresponding to the mask while the overcoat layer is masked. 2. A method of coating the surface of an object to be coated with a partially different color, wherein an undercoat is applied to the surface of the object to form an undercoat layer, and 6 to 12 wt% epoxy resin and 1 ultraviolet absorber
An intermediate coating containing 3 wt% to 3 wt% each is applied to form an intermediate coating layer, and then a topcoat is applied on the intermediate coating in a state where required portions are masked to form an uppercoat. After that, in a state where the topcoat layer is masked, a two-component polyurethane resin paint of a natural drying type having a color different from that of the topcoat paint is applied to a portion corresponding to the masking of the intermediate coat layer to form a different color layer. .