JPH0824886B2 - Car top coating method - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating method, and more particularly to a coating method for an automobile having an improved color design.

2. Description of the Related Art Conventionally, from an optical standpoint, two color systems called solid color and metallic color are used for automobile paints.

As a coating method using these paints, for example, Japanese Patent Application Laid-Open No. 60-248266 discloses a technique of coating paints having different hiding power by coating, and Japanese Patent Application Laid-Open No. 58-98167 discloses metallic coatings. Means for eliminating coating defects associated with the coating (for example, means for improving gloss image clarity, smoothness and chipping property) are disclosed, and JP-A-60-248262 discloses a two-tone finishing method. Etc. are disclosed.

However, such a method does not satisfy the needs of customers, and a new color that is clear and excellent in design that these coating films do not have is demanded.

From such a new viewpoint, JP-A 61-37423 proposes a coating system in which a paint containing a mica pigment is applied over an intermediate coating film having a specific color tone, and JP-A-60-
It is proposed in Japanese Patent No. 238183 that it is necessary to consider the coating thickness of mica paint, coating voltage, coating machine, coating distance and the like.

Also, as a coating mica to be mixed with a mica-based paint to be applied on top of a color intermediate coating, it is possible to secure dichroism with a color intermediate coating, and to facilitate paint production and coating workability, it has been conventionally used. , Relatively large particle size eg
Those having a thickness of 40 to 60 μm have been exclusively used. However, since the particle size is large, it is very difficult to maintain a stable and uniform state in the paint, and color unevenness is likely to occur even during painting. Further, when the amount of coating mica in the paint is increased, there are problems that the gloss is lowered and the filter is clogged.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention and Means for Solving the Problems Therefore, in order to meet the customer's needs described above, the present invention provides an unprecedented composite color of an intermediate color paint and a mica base paint without impairing continuous productivity. , Aims to develop a coating method that can be easily obtained.

DESCRIPTION OF THE CONSTRUCTION OF THE INVENTION AND ITS OPERATION That is, according to the present invention, on an electrodeposition coating film applied by ordinary electrodeposition coating in an automobile manufacturing process, first, an intermediate coating with a brightness of Munsell value N1 to N6. The coating film is formed as a base (hereinafter, color intermediate coating) coating film by a general method.

Next, the surface of this color intermediate coating film is adjusted by water polishing, etc., and a mica base paint containing 1 to 30% by weight of coated mica with a particle size of 0.1 to 30 μm is further air-fogged on the color intermediate coating film. A two-stage, one-bake method is used to form a coating film by applying it in two stages with a chemical type electrostatic coating machine, and while the mica base paint is uncured, the clear paint is applied wet-on-wet and baked. .
In the present invention, "Munsell value is JIS-
Of the hue, brightness, and saturation shown in Z-8721 “Color Display Method According to Three Attributes”, a relatively bright color gamut of N1 to 6 on the brightness axis is targeted.

In the method of the present invention, the electrodeposition coating composition to be first coated on the article to be coated such as an automobile may be any of the conventionally known anion type and cation type coatings, and these are coated by a conventional electrodeposition coating method. The film thickness of this electrodeposition coating film is not particularly limited, but usually it is 15 to 20 μm as a dry film thickness, but if it is thicker than this, there is no particular problem except economy.

The color intermediate coating used in the present invention is a color intermediate coating having a Munsell value of N1 to N6 as described above, which is a known thermosetting resin and its curing agent, colorant, solvent, etc. As the thermosetting resin, one or more kinds of alkyd resin, oil-free alkyd resin, acrylic resin and the like can be used. Also, as a curing agent for thermosetting resin, melamine resin, free NCO
A general one such as a polyisocyanate having a group can be used, and pigments, solvents and the like are used in ordinary thermosetting paints such as titanium, colored organic pigments, aliphatic hydrocarbons, aromatic hydrocarbons and ketones. , Ester and the like can be used. The blending amount of these raw materials is not particularly limited as compared with the conventional one, but generally, the ratio of the resin and the curing agent is 85/15 to 60/40 and the pigment concentration (PWC) is 5 to 55. % Is preferable. The Munsell value of the color intermediate coating can be adjusted by increasing or decreasing the color pigments such as titanium and carbon to be used, and if this value is out of the above range, unevenness or no complex color occurs. Occurs, which is not preferable in terms of design.

The coating thickness of the color intermediate coating composition is not particularly limited, but it is generally 15 to 65 μm as a dry film thickness, preferably 30
Apply to ~ 40μm, bake and dry under specified conditions to make a colored base. The intermediate coating film may be water-polished with, for example, # 600 sandpaper to improve smoothness.

According to the present invention, 1 to 30% by weight of coating mica is blended in the mica base paint to be coated on the color intermediate coating film, and as such a coating mica, conventionally, a relatively large particle size of 40 to 60 μm is used. Have been used exclusively. Therefore, it is very difficult to keep it stable and uniform in the paint, and there is a drawback that color unevenness is likely to occur even at the time of coating. Furthermore, increasing the content in the paint lowers the gloss and There were also problems such as clogging.

However, according to the present invention, mica having a particle size of 0.1 to 30 μm is used as the mica to be added to the mica base paint.
The smaller the particle size of mica, the more uniform and stable the paint,
Color unevenness is improved, but the glittering feeling peculiar to mica paint is eliminated, so that a particle size of 0.1 μm or less is not suitable. It was also found that the use of mica with a small particle size does not reduce gloss and durability even if the content in the paint is increased, and the clogging of the filter, which has been a problem in the past, does not occur.
However, if the blending amount is 30% by weight or more, gloss and durability are deteriorated, which is not preferable. Furthermore, they have found that by reducing the particle size of mica, it is possible to obtain a more precise and calm glittering feeling than conventional mica paints, and to obtain an interesting new color that is unprecedented in terms of hue. Further, the conventional mica paint has a strong so-called directionality, in which the color changes greatly depending on the viewing direction, but the mica paint used in the present invention has this directionality largely relieved. The present inventors have found that this direction tends to disappear as the particle size of the mica pigment decreases.

The types of mica pigments used in the present invention include:
Examples include pearl white mica coated with a thin layer of titanium mica, interference mica in which the titanium coating layer emits a relatively thick interference color, and coated mica such as colored mica coated with iron oxide. Is 1 to 30% by weight, preferably 5 to 20% by weight, and when the amount of the compounded in the mica base coating is more than 30% by weight, the light transmittance is deteriorated and a composite color cannot be obtained. On the other hand, if it is less than 1% by weight, the color of the base is too strong to give a complex color.

The resin used for the mica-based paint is the same acrylic resin as the color intermediate paint, polyester resin, etc.,
A thermosetting resin can be used in combination with the curing agent.

Next, a very important feature point in the present invention will be explained with respect to a method for coating a mica-based paint. Mica-based paint has already been applied to automobiles, but if the same coating method as that of the solid or metallic paint is used, uneven coating is likely to occur and the commercial value is significantly impaired.

Therefore, the inventors of the present invention have conducted intensive studies on a coating method in which uneven coating is less likely to occur, and as a result, have found that if a coating is applied under the following conditions, a clean and uniform coating film can be continuously produced industrially.

That is, an air atomization type electrostatic coating machine (for example, REA gun manufactured by Nihon Ransberg Co., Ltd.) is used as a coating machine, and finishing is performed in two stages. Color unevenness is conspicuous because uniform coating is difficult in the first stage, but color unevenness is improved to the extent that it does not become a problem if the coating is performed in the following two preferable conditions. If the number of stages is further increased, more uniform coating will be possible, but the cost will increase. In addition,
This "two-stage" painting is divided into two
It means that the coating is repeated while taking a predetermined flash-off time between the processes, and the coating of the first stage and the coating of the second stage mean that the coating is repeated with a flash-off time of about 1 to 3 minutes. To do.

Coating viscosity of # 4 Ford cup is 10 to 20 seconds / 20 ° C (10 to 15 seconds / 20 ° C is more preferable for obtaining a smooth coating film), applied voltage -30 to -90KV (atomization, leaking property) From the relationship of -50 to -70 KV), conveyor speed 2 to 10 m / min (more preferably 3.5 to 6 m / min), air atomization pressure 3 to 10 kg / cm ² (more preferably 4 to 6 kg / cm) ² , 4 kg or less, poor atomization is likely to cause color unevenness, and the higher the air pressure is, the better atomization is, but if it is 6 kg / cm ² or more, the pressure resistance problem will occur in the current equipment) The distance between the objects to be coated is 20 to 60 cm (more preferably 30 to 40 cm, color unevenness tends to occur even if it is too short or too long), stroke number 15 to 40 times / minute (more preferably 20 ~ 30 times / minute), the interval between stages is 30 seconds to 5 minutes (more preferably 50)
Second to 2 minutes, discharge rate 150 to 1000cc / minute (more preferably 30)
0 to 500 cc / min), number of guns 1 to 2 (in order to apply a large area uniformly at once, it is better to have more guns, but at present, more than 2 multi-headed guns are not in practical use) It is preferable to use coating conditions.

If coating is performed in a form that satisfies all of these preferable conditions, a coating method capable of continuous industrial production without color unevenness is suitably achieved.

The film thickness of the mica-based paint coating film applied in the present invention is not particularly limited, but in general, the dry film thickness is 10
-40 μm, preferably 15-25 μm.

In the present invention, the clear coating which is applied on the mica base coating film to form the top layer is a thermosetting resin of the same kind as the color intermediate coating composition and its curing agent as a main component and a general composition excluding the pigment component. Clear paints can be used. The thickness of the clear paint is also not particularly limited,
Generally, the dry film thickness is 15 to 50 μm, preferably 25 to
40 μm.

The lightness described above is the Munsell value of N1 to N6 intermediate paint,
The mica base paint containing 1 to 30% by weight of coated mica and the clear paint as the top layer are preferably applied by a wet-on-wet method. According to the present invention, the mica base paint can be coated with an electrostatic dew spray gun in two stages to obtain a composite color of the color intermediate coating and the mica base paint.

Examples The present invention will be described in more detail based on the following examples, but it goes without saying that the scope of the present invention is not limited to these examples.

Example 1 A steel plate test piece (0.8 mm × 300 mm × 500 mm) was pretreated with Granodine SD5000 (a phosphate coating chemical conversion treatment manufactured by Nippon Paint Co., Ltd.), and then Nippon Paint (a cationic electrodeposition paint) Power Top U-30 manufactured by Co., Ltd. was used to apply a dry film thickness (hereinafter referred to as film thickness) of 20 μm.
Baking for 20 minutes at 0 ° C.

Next, on this electrodeposition coating film, an Olga P-2 black paint (manufactured by Nippon Paint Co., Ltd.) (N
-1) was applied to a film thickness of 35 μm and baked at 140 ° C. for 20 minutes.
On the obtained color intermediate coating film, 7 weights of Superlac M-12 (manufactured by Nippon Paint Co., Ltd.) and Exterior Marlin Fine Pearl (white mica manufactured by Marl Co., Ltd., maximum particle size 20 μm) as a mica base paint The coating composition containing 10% was applied under the following conditions.

Mica base paint coating conditions Spray gun: REA cap No. 6 Coating viscosity: 13 seconds / # 4 Ford cup 20 ° C Discharge rate: 300cc / min Film thickness: approx. 15μ Coating stage: 1st stage (1 minute flash off) → 1st 2 stages Conveyor speed: 4m / min Spray gun stroke number: 25 reciprocations / min Gun distance: 30cm Pattern width: 30cm Number of guns: 2 Air pressure: 4.5kg / cm ² Applied voltage: -60KV With the mica base paint under the above conditions After painting, another 2 minutes of flash-off time is applied, and Nippon Paint Co., Ltd.
Super rack 0-28M (clear paint) made by 35μ film thickness
m was wet-on-wet and baked at 140 ° C for 20 minutes.

 The results are as shown in Table 1.

Example 2 Coating was carried out in the same manner as in Example 1 except that the type of mica pigment of the mica base paint used in Example 1 was changed to Exterior Marine Bright Wright (Marl).

 The results are as shown in Table 1.

Example 3 Coating was performed in the same manner as in Example 1 except that the concentration of the mica pigment in the mica-based paint used in Example 1 was changed to 20%.

 The results are as shown in Table 1.

Example 4 Coating was performed in the same manner as in Example 1 except that the mica pigment concentration of the mica base coating used in Example 2 was changed to 20% by weight.

 The results are as shown in Table 1.

Example 5 The type of color intermediate coating material used in Example 1 was changed to Olga P.
-2 Gray (manufactured by Nippon Paint Co., Ltd., N-5) was applied in the same manner as in Example 1 except that it was changed to gray.

 The results are as shown in Table 1.

Comparative Example 1 Coating was carried out in the same manner as in Example 1 except that the discharge rate under the coating conditions of Example 1 was 500 ml / min and the coating stage was once.

 The results are as shown in Table 1.

Test method Gloss: JIS K-5400 6.7 Accelerated weather resistance: JIS K-5400 6.17 Gloss retention rate after 400 hours Dark and light color unevenness: Visual judgment Impact resistance: JIS K-5400 6.12

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Keisaku Ueda Nakayoshi Nitta No.2, 3rd, Yoshiyoshi-cho, Takahama-shi, Aichi Nihon Paint Co., Ltd. Aichi Works (56) References JP-A-61-37423 (JP, A) )

Claims (1)

[Claims] 1. A mica base paint containing 1 to 30% by weight of coating mica having a particle size of 0.1 to 30 μm is air-atomized on an undercoating film consisting of an intermediate coating film having a Munsell value of N1 to N6. -Type electrostatic coating equipment is used to coat on two or more stages.
And while this mica base paint is uncured, on it,
A coating method characterized by applying clear paint wet on wet.