JP2515336B2 - Top coating method for automobiles - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a coating method, and more particularly to an automobile top coating method having an improved color design.

[Prior art]

From an optical standpoint, conventionally, two color-based paints called solid color and metallic color have been used for coating automobiles.

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. A means for eliminating coating film defects associated with the coating film (for example, a means for improving gloss image clarity, smoothness, and chipping property) is disclosed. Further, JP-A-60-248262 discloses a two-tone finishing method. Etc. are disclosed.
However, these methods have not yet solved the uneven coating, which was a problem of conventional mica coating,
New colors that are clear and have excellent designs that are not found in these coating films are required.

From such a new viewpoint, JP-A-61-37423 proposes a coating system in which a coating material containing a mica pigment is applied over an intermediate coating film having a specific color tone, and JP-A-60-2
It is proposed in Japanese Patent No. 38183 that it is necessary to consider the coating thickness of mica paint, coating voltage, coating machine, coating distance and the like. However, although these techniques are general improvements to mica coating, it has been difficult to form a sufficiently uniform composite color in the coating of automobiles having horizontal portions, one-bent portions, vertical portions and the like.

[Problems to be Solved by the Invention and Means for Solving the Problems]

Therefore, the present invention is an excellent coating that solves the above-mentioned problems of the prior art and can easily obtain a composite color of a low-brightness color intermediate coating and a mica-based coating without impairing continuous productivity. The purpose is to develop a method.

[Explanation of the structure of the invention and its operation]

That is, according to the present invention, the object is to coat a mica-based paint containing 0.1 to 10% by weight of coating mica in the paint solid content on a color intermediate coating having a Munsell value of N1 to N6. Is coated on the flat surface portion and side surface portion by the rotary atomization type electrostatic coating method (A), the front and rear correction portions are coated by the rotary atomization type electrostatic coating method (B), and then this mica base is coated. It can be solved by an automotive topcoat application method, in which the clear paint is applied wet-on-wet while the paint is uncured.

That is, according to the present invention, first, an intermediate coating film having a Munsell value of lightness N1 to N6 as a base (hereinafter referred to as a color intermediate coating) is formed on an electrodeposition coating film applied by ordinary electrodeposition coating in an automobile manufacturing process. The coating film is formed by a general method.

Next, the surface of this color intermediate coating film is adjusted by water polishing, etc., and then on this color intermediate coating film having a Munsell value of N1 to N6 with a brightness of 0.1 to 1 in the coating solid content of the coating mica.
A mica-based paint containing 0% by weight (excluding the combined use of coated mica and aluminum foil) with a rotary atomization type electrostatic sprayer with a diameter of the atomization disk of 5-10 cm on the flat surface and side surface of the object. Disk rotation speed 10,000 to 50,000 using a coating machine
Rotation / min, applied voltage -30 to -100 kV, shaving air pressure 0.5 to 5 kg / cm ² and discharge rate 100 to 700 ml / min are applied by the rotary atomization type electrostatic coating method (A). Rotation atomization type electrostatic coating machine with atomization disc diameter of 2-5 cm is used for the correction unit, and the rotation number of the disc is 5,000-40,000 revolutions / minute.
Applied voltage −30 to −90 kV, shaving air pressure 0.5 to 5 kg
/ m ² and discharge rate 10-300ml / min, the rotary atomization type electrostatic coating method (B) is applied, and then the clear paint is wet-on on this mica base paint while it is not cured. Apply wet. Incidentally, the "lightness" of the Munsell value defined in the present invention, JIS-Z-8721 "hue shown in the display method of the color by the three attributes, the lightness of the lightness and saturation" (ie Hue, Chroma, Value of V value), and in the present invention, a low to medium lightness gamut of N1 to N6 is targeted.

In the method of the present invention, any of the cationic types may be first used for the article to be coated such as automobiles, and these are coated by a usual 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. In addition,
If the film thickness of the electrodeposition coating film is too thin, the smoothness of the coating film becomes insufficient and the corrosion resistance decreases, which is not preferable.

As described above, the color intermediate coating used in the present invention is a color intermediate coating having a lightness of Munsell value of N1 to N6, which is a known thermosetting resin and its curing material, a coloring agent, a 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 the pigment, the solvent, etc. are colored inorganic pigments such as titanium used in usual thermosetting paints, colored organic pigments, aliphatic hydrocarbons, aromatics. Group hydrocarbons, ketones, esters and the like can be used. The amount of these raw materials to be compounded is not particularly limited as compared with the conventional one, but generally, the ratio of the resin to the curing agent is 85/15 to 60/40 and the pigment concentration (PW
The coating composition is preferably such that C) is 5 to 55%. The Munsell value of the color intermediate coating composition can be adjusted by increasing or decreasing the color pigment such as titanium or carbon black to be used, and if this value is out of the above range, unevenness or a composite color is difficult to obtain. It is not preferable.

The thickness of the color intermediate coating composition is not particularly limited, but is generally 10 to 50 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 the smoothness.

According to the present invention, as the type of the coating mica compounded in the mica base paint to be coated on the intermediate coating film, pearl white mica in which mica is coated with a thin layer of titanium, the titanium coating layer is relatively thick. An interference mica that emits an interference color, a coated mica such as a colored mica coated with iron oxide, and the like can be used.

Furthermore, the mica base paint used in the present invention includes
In addition to the above-mentioned mica, other pigments currently used for automobiles can be blended as required, and examples of such pigments include titanium, transparent iron oxide red, transparent iron oxide yellow, and heavy metal firing. Inorganic pigments such as pigments (oxides of Co, Ni, Sn, Cr, etc.), phthalocyanine blue, phthalocyanine green, quinacridone red, quinacridone violet, perylene red, perylene maroon, benzimidazolone yellow, orange, slen blue,
Examples thereof include organic pigments such as Anzanthuron orange, flavanthuron yellow, isoindoline yellow, and isoindolinone yellow.

The mica pigment is 0.1 to 10% by weight, preferably 0.5 to 10% by weight, and if this value is out of the above range, problems such as "unevenness" and no complex color occur, which is not preferable in terms of design.

The resin used for the mica base is not particularly limited as long as it has been conventionally used for automobiles, but a combination of a thermosetting resin and a curing agent thereof is preferable. Examples of such thermosetting resins include short oil alkyd resins, oil-free polyester resins and acrylic resins, and examples of curing agents include melamine resins and polyisocyanates having free NCO groups. These thermosetting resins and curing agents can be used alone or as an arbitrary mixture.

As the solvent used for the mica-based paint, any solvent usually used for paints, for example, aliphatic, aromatic, ester, alcohol, ketone or other solvent can be used without particular limitation. Further, if necessary, it is possible to mix any additives commonly used for coating materials such as a leveling agent and an ultraviolet absorber.

The clear coating which becomes the top layer in the coating method according to the present invention can be used, for example, in the same composition as that of the mica-based coating except that the curing agent and the curing agent thereof are mainly excluded from the pigment component.

The mica-based paint and the clear paint to be the top layer are preferably applied by the wet-on-wet method, but the so-called 2-coat 2-bake method also causes no problem.

On the other hand, regarding the coating method of the mica-based paint which is the point of the present invention, if the mica-based paint is applied using the same coating method as the solid paint or the metallic paint currently applied to automobiles, etc., uneven coating is likely to occur. It is not preferable because the value is significantly lost. Therefore, as a result of diligent research on a coating method in which uneven coating is less likely to occur, the inventors have found that if a coating is applied under the following conditions, it is possible to industrially continuously produce a clean coated film without unevenness.
That is, the flat surface portion and the side surface portion of the automobile are coated by the rotary atomization type electrostatic coating method (A) as the coating method, and the front and rear correction portions are coated by the rotary atomization type electrostatic coating method (B). Finish on stage. If there is no correction for the front and rear parts, it is difficult to apply a uniform coating on one curved part, vertical part, etc., resulting in color unevenness or unpainted parts. Rotation atomization electrostatic coating method (B)
It was improved to the extent that color unevenness does not become a problem if it is painted with. If the number of stages is further increased, more uniform coating is possible, but there is a problem that the cost becomes high.

Also, if the front and rear compensators are painted by a method other than the rotary atomizing electrostatic coating method (B), the orientation of mica particles will be uneven with the flat and side surfaces, and overdust due to a wide pattern width, etc. This is not preferable because it causes color unevenness or causes problems such as not being able to obtain a satisfactory finished skin.

The rotary atomization type electrostatic coating method (A) is as follows. For example, the coating viscosity is # 4 Ford cup for 10-20 seconds / 20 ℃.
(10 to 15 seconds / 20 ° C is preferable to obtain smooth skin)
Atomizing the paint of 5 to 10 cm in diameter of the disk, the rotation speed of the disk is 10,000 to 50,000 rotations / minute (if the rotation speed is low, the atomization of the paint will be poor, and if it is too high, it is not economical 3
It is preferably about 0,000 to 40,000 rotations / minute). The applied voltage is -30Kv to -100Kv (approx. -80Kv is preferable because the coating efficiency becomes poor when the voltage is low, and the risk of leakage increases when it is too high), and the shaving air pressure is 0.5 to 5Kv.
kg / cm ² , discharge rate 100-700 ml / min (usually 200-400
(ml / min is preferable).

That is, according to the present invention, the flat surface portion and the side surface portion of the object to be coated are coated by the rotary atomization type electrostatic coating method (A) and finished in one stage. If the number of stages is further increased, more uniform coating will be possible, but the cost will increase.

Next, regarding the coating conditions of the rotary atomization type electrostatic coating method (B) for coating the front and rear correction parts of the automobile, the present inventors have found that it is necessary to coat under the following conditions. That is, it is preferable that the diameter of the microbell disc is 2 to 5 cm. If the diameter is smaller than 2 cm, it becomes difficult to make a coating machine, and if the diameter is larger than 5 cm, the pattern becomes too large, which is intended. There is a possibility that it will be painted to the places where it is not present and that dust will be added unnecessarily, causing color unevenness. The rotation speed is usually 5,000 to 40,000 rotations / minute, preferably about 15,000 rotations / minute, because if the rotation speed is low, the atomization of the paint is deteriorated, and if it is too high, it is not economical. -30Kv~-90Kv as the applied voltage (coating efficiency and low voltage is deteriorated, is preferably about -60Kv because the risk of leakage increases Beyond Matataka), as a shaving air pressure 0.5 to 5 kg / cm ² , The discharge amount is 10-30
0 ml / min (usually 60 to 70 ml / min is preferable),
If coating is performed under such conditions, a desired finish can be obtained, and continuous industrial production becomes possible.

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 clear coating film is also not particularly limited,
Generally, the dry film thickness is 10 to 50 μm, preferably 20 to
40 μm.

As described above, the flat surface portion and the side surface portion of the automobile are coated by the rotary atomization type electrostatic coating method (A), and the front and rear correction portions are coated by the rotary atomization type electrostatic coating method (B). By doing so, it has become possible to industrially continuously produce the mica coating, which was conventionally finished with 3 coats, with the 2 coats of the mica base and the clear layer without causing color unevenness.

〔Example〕

Hereinafter, the present invention will be further described based on Examples, but it goes without saying that the technical scope of the present invention is not limited to these Examples. In the following examples, "%" means% by weight unless otherwise specified.

Example 1 An automobile body was first subjected to a pretreatment, a cationic electrodeposition coating and an intermediate coating under the following conditions, and then a mica base coating was applied to the flat surface portion and the side surface portion thereof.

1) Substrate: Automotive body 2) Pretreatment: Granodine SD5000 (Nippon Paint Co., Ltd. phosphate film chemical conversion treatment agent) 3) Cationic electrodeposition paint: Power Top U-30 (Nippon Paint Co., Ltd.) Dry film thickness (hereinafter referred to as film thickness) 20 μm is applied,
180 ℃ x 20 minutes baking 4) Intermediate coating: Olga P-2 intermediate coating paint (Nippon Paint Co., Ltd.) (N-1) is applied to a film thickness of 35μm, 140 ° C x 20 minutes baking 5) Mica base coating: Super LAC M-12 (Nippon Paint Co., Ltd.) is blended with exterior bright (White Mica manufactured by Marl Co., Ltd.) at 5.7% 6) Mica base paint coating conditions Spray gun: Minibell (Ransburg Japan Co., Ltd.) Coating viscosity: 14 seconds / # 4 Ford Cup 20 ℃ Discharge rate: 500cc / min Film thickness: Approximately 15μm Conveyor speed: 4m / min Revolution: 40,000 revolutions / min Gun distance: 30cm Pattern width: 50cm Shaving air pressure: 3kg / cm ² Applied voltage: − 90Kv Under the above conditions, the mica base paint was applied to the flat and side parts of the automobile body, and then the same mica base paint was applied to the front and rear correction parts under the following conditions.

Spray gun: Microbell Coating viscosity: 13 seconds / # 4 Ford cup 20 ° C Discharge rate: 80cc / min Film thickness: about 15μm Conveyor speed: 4m / min Rotation speed: 20,000 revolutions / min Applied voltage: -60Kv Shaving air pressure: 3kg / cm ² Spray gun Stroke rate: 25 reciprocations / minute After applying the mica base paint under the above conditions, a flash-off time of 2 minutes is set, and then Nippon Paint Co., Ltd. Superlac 0-28M clear paint is applied. Wet-on-wet coating was applied to 35 μm and baked at 140 ° C for 20 minutes.

Comparative Example 1 An automobile body was painted in the same manner as in Example 1 except that the front and rear correction parts were not painted.

Comparative Example 2 An automobile body was coated in the same manner as in Example 1 except that the front and rear correction parts were coated with an air atomization type electrostatic coating machine under the following conditions.

Spray gun: Ransburg Japan REA gun Coating viscosity: 13 seconds / # 4 Ford cup 20 ° C Discharge rate: 300cc / min Film thickness: 15μm Conveyor speed: 4m / min Spray gun stroke: 25 reciprocations / min Gun distance: 30 cm Pattern width: 30 cm Air pressure: 4.5 kg / cm ² Applied voltage: -60 Kv Table 1 shows the test results obtained in Example 1 and Comparative Examples 1 and 2.

(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: naked eye judgment Gobang eye test: JIS K-5400 6.15 Impact resistance: JIS K-5400 6.12 (Evaluation) ◎: good, ○: good, ×: bad

Front page continuation (72) Inventor Fumichi Matsuda 2-3 Nakayoshi Nitta, Yoshihama-cho, Takahama City Japan Paint Co., Ltd. Aichi Works (72) Masamichi Arima 2-3 Nakayoshida, Yoshihama-cho, Takahama City Japan Paint Co., Ltd. Aichi Works (56) Reference JP-A-58-11068 (JP, A) JP-A-61-37423 (JP, A) JP-A-63-205177 (JP, A)

Claims (1)

(57) [Claims] 1. A mica base paint containing 0.1 to 10% by weight of coating mica in the solid content of the paint on a color intermediate coating film having a lightness of Munsell value N1 to N6 (excluding the combination of coating mica and aluminum foil). ), The rotation speed of the disk is 10,000 to 50,000 rotations / minute, and the applied voltage is −30 using a rotary atomization type electrostatic coating machine having a diameter of the atomization disk of 5 to 10 cm on the flat surface portion and the side surface portion of the coated object. ~ -100kV, shaving air pressure
Painted by the rotary atomization type electrostatic coating method (A) under the conditions of 0.5 to ⁵ kg / cm ² and discharge rate of 100 to 700 ml / min, and the diameter of the atomizing disc is 2 to 5 cm on the front and rear compensator. Rotation speed of the disk is 5,000 to 40,000 rpm, applied voltage is -30 to -90 kV, and shaving air pressure is 0.5 to 5 kg / cm ² using an atomization type electrostatic coating machine.
And the spray atomization type electrostatic coating method (B) under the condition that the discharge rate is 10 to 300 ml / min. Then, while this mica base paint is uncured, the clear paint is wet-on on it.
A top coating method for automobiles, which is characterized in that the coating is wet.