JP2515335B2 - 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.

[Conventional technology]

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 met the needs of customers, and they have not solved the coating unevenness that has been a problem of conventional metallic coatings. There is a need for excellent new colors and effective methods for forming coating films.

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 problems of the prior art described above and can easily obtain a composite color of a low-brightness color intermediate coating and a metallic base 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 lightness Munsell value N1 ~ N6 on the color intermediate coating film, aluminum foil, bronze foil, tin foil,
At least one foil-like pigment selected from the group of gold foil, silver foil, titanium metal foil, stainless steel foil, nickel foil, copper foil and alloy foils thereof, metal foil coated with plastic, foil phthalocyanine blue and coating mica ( (Except for combined use of coating mica and aluminum foil) Metallic paint containing 0.05 to 8% by weight, the atomizing disk diameter is 5 to 10
Rotation speed of the disk 1 using a rotary atomization type electrostatic coating machine of cm
0,000 to 50,000 revolutions / minute, applied voltage −30 to −100 kV, shaving air pressure 0.5 to 5 kg / cm ^2, and discharge rate 100 to 700 ml / m
Painted by the rotary atomization type electrostatic coating method (A) under the condition of in, and rotating the disc by using the rotary atomization type electrostatic coating machine with a diameter of the atomization disc of 2 to 5 cm in the front and rear correction parts. Number 5,000-40,00
It is applied by the rotary atomization type electrostatic coating method (B) under the conditions of 0 revolutions / minute, applied voltage −30 to −90 kV, shaving air pressure 0.5 to 5 kg / cm ² and discharge rate 10 to 300 ml / min. A method of overcoating an automobile is provided which comprises applying a clear paint wet-on-wet on the metallic paint while it is uncured.

According to the present invention, according to the present invention, on the electrodeposition coating film which is applied by the usual electrodeposition coating in the automobile manufacturing process, first the lightness in Munsell value
An intermediate coating film from N1 to N6 is formed by a general method as a base (hereinafter referred to as color intermediate coating) coating film.

Next, the color intermediate coating film is surface-adjusted by water polishing or the like, and next, on the color intermediate coating film whose brightness is Munsell value N1 to N6, the foil-like pigment described below is added to the coating solid content. Medium 0.
The metallic base paint containing 05 to 8% by weight is applied to the flat surface and the side surface of the article by the rotary atomization type electrostatic coating method (A), and the front and rear compensating parts are coated with the rotary atomization type static paint. The electrocoating method (B) is applied, and then the clear paint is applied wet-on-wet while the mica base paint is uncured. 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 three attributes, the lightness of the lightness and saturation"
(That is, V value of Hue, Chroma, Value), and N1 in the present invention.
Targets the low-to-medium color gamut of ~ N6.

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.

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, etc. are colored inorganic pigments such as titanium used in usual thermosetting paints, colored organic pigments, resin group 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, the metallic paint applied on the color intermediate coating film, aluminum foil, bronze foil, tin foil, gold foil, silver foil, titanium metal foil, stainless steel foil, alloy foil such as Ni-Cu, Foil-shaped pigments such as metal foil coated with plastic, foil-shaped phthalocyanine blue, and coated mica are mixed. As such a pigment,
For example, commercially available aluminum foil, bronze foil, tin foil, gold foil, silver foil, titanium metal foil, stainless steel foil, alloy foil such as Ni-Cu, plastic coated metal from Toyo Aluminum, Asahi Kasei, Furukawa Aluminum, Silver Line, Eckart, etc. Foil [for example, Astroflakes (Fukuda Metal)], foil-shaped phthalocyanine blue, coating mica and the like can be used, and the compounding amount thereof is 0.05 to 8% by weight in the metallic paint, and the preferable range is 0.1 for aluminum foil. ~ 2.5
% By weight. Since the metal foils other than the aluminum foil have different densities, the preferable range can be calculated by the following density conversion formula.

Preferred amount = [(density of metal) / (density of aluminum)] ×
Appropriate amount of aluminum (% by weight) If the amount of the foil-like pigment compounded in the metallic paint used in the present invention is too large, it is not preferable because the base color is too concealed and a composite color is difficult to obtain. It is not preferable because the metallic feeling is lowered, the base color is conspicuous, and the design effect becomes poor.

The thickness of the metallic paint coating film applied in the present invention is not particularly limited, but generally 10 to 40 as a dry film thickness.
μm, preferably 15 to 25 μm.

The resin blended as a vehicle component in the metallic paint used in the present invention 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 metallic base 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.

In the clear coating which forms the top layer in the coating method according to the present invention, for example, a thermosetting resin of the same type as the metallic base coating and its curing agent can be used in a composition mainly excluding the pigment component.

Wet-on-wet coating is suitable for coating the mica-based paint and the clear coating that forms the top layer, but the so-called 2-coat 2-bake method does not cause any problems.

On the other hand, regarding the coating method of the metallic base paint which is the point of the present invention, if the metallic base paint is applied using the same coating method as the solid paint currently applied to automobiles etc., coating unevenness easily occurs and the commercial value is remarkable. It is not preferable because it is damaged. 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 electrostatic coating method (A) as the coating method, and the front and rear correction portions are coated by the rotary atomization 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. The correction of the front and rear parts was improved by the rotary atomization type electrostatic coating method (B) to such an extent that uneven color was not a problem. If the number of stages is further increased, more uniform coating is possible, but there is a problem that the cost becomes high.

Further, when the front and rear correction parts are coated by a method other than the rotary atomization type electrostatic coating method (B), the orientation of the metallic particles is flat,
It is not preferable because it causes unevenness with the side surface portion, uneven color due to overdust due to a wide pattern width, and the like that a satisfactory finished skin cannot be obtained.

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 -30 kv to -100 kv (if the voltage is low, the coating efficiency will be poor, and if it is too high, the risk of leakage will increase.
kv is preferable), and the shaping air pressure is 0.
5 to 5 kg / cm ² , discharge rate 100 to 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 disk of the microbell is 2 to 5 cm, and if this diameter is smaller than 2 cm, it becomes difficult to make a coating machine, and if it is larger than 5 cm, the pattern tends to be too large. As a result, unintended areas may be painted, and dust may be applied 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. The applied voltage is -30kv to -90kv (if the voltage is low, the coating efficiency is poor, and if it is too high, the risk of leakage increases, so -60kv is preferable), and the shaping air pressure is 0.5 to 5kg / c.
m ² , discharge rate 10-300 ml / min (usually 60-70 ml / min
Is preferable), and a desired finish can be obtained by coating under such conditions, and continuous industrial production becomes possible.

The film thickness of the metallic base coating film applied in the present invention is not particularly limited, but is generally 10 to 40 μm, preferably 15 to 25 μm as a dry film thickness.

In the present invention, the clear coating which is applied on the metallic 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 content. Clear paints can be used. The coating film of clear paint is also not particularly limited, but in general, 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 a metallic coating, which was conventionally finished with 3 coats, with the 2 coats of the metallic 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,
Bake at 180 ℃ for 20 minutes.

4) Intermediate coating: Olga P-2 intermediate coating (manufactured by Nippon Paint Co., Ltd.) (N-1) is applied at a film thickness of 35 μm, and baked at 140 ° C. for 20 minutes.

5) Metallic base paint: Super Bright M-12 (manufactured by Nippon Paint Co., Ltd.) with 7% of exterior bright (white mica manufactured by Marl) 6) Painting conditions for metallic base paint Spray gun: Minibell (manufactured by Randsburg Japan) ) Coating viscosity: 14 seconds / # 4 Ford cup 20 ° C Discharge rate: 500cc / min Film thickness: Approximately 15μm Conveyor speed: 4m / min Rotation speed: 40,000 revolutions / min Gun distance: 30cm Pattern width: 50cm Shaping air pressure: 3kg / cm ² Applied voltage: −90 kv After the metallic base paint was applied to the flat surface and the side surface of the automobile body under the above conditions, the same metallic 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: Approximately 15μm Conveyor speed: 4m / min Rotation speed: 20,000 revolutions / min Applied voltage: -60kv Shaping 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.

Example 2 Coating was carried out in the same manner as in Example 1 except that Olga P-2 Gray (N-3) was used as the color intermediate coating.

Example 3 All were coated in the same manner as in Example 1 except that Olga P-2 Gray (N-6) was used as the color intermediate coating.

Comparative Example 1 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: REA gun made by Japan Ransburg Co., Ltd. Painting viscosity: 13 seconds / # 4 Ford cup 20 ° C Discharge rate: 300cc / min Film thickness: 15μm Conveyor speed: 4m / min Spray gun stroke number: 25 reciprocations / min Gun distance: 30 cm Pattern width: 30 cm Air pressure: 4.5 kg / cm ² Applied voltage: -60 kv The test results obtained are shown in Table 1 below.

Test method Light and shade unevenness: Visual judgment PGD value: Evaluated by PGD-4 type manufactured by Japan Color Research Institute * 1 Accelerated weathering resistance: JIS K-5400 6.17 Gloss retention rate after 400 hours * 2 Goggles: JIS K -5400 6.15 Remaining number * 3 Impact resistance: JIS K-5400 6.13 500g [Effect of the invention] As described above, the present invention is based on the idea of aluminum concentration based on the idea of productivity in the automobile manufacturing process. It is an epoch-making method that can form a composite color of a color intermediate coating and a metallic paint without causing unevenness.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Bunichi Matsuda 2-3 Nakayoshi Nitta, Yoshihama-cho, Takahama City Japan Paint Co., Ltd. Aichi Works (72) Masamichi Arima 2nd Nakayoshida, Yoshihama-cho, Takahama-shi 3 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. An aluminum foil, a bronze foil, a tin foil, a gold foil, a silver foil, on a color intermediate coating film whose brightness is Munsell value N1 to N6,
At least one foil pigment selected from the group of titanium metal foil, stainless steel foil, nickel foil, copper foil and alloy foils thereof, metal foil coated with plastic, foil phthalocyanine blue and coating mica (however,
(Excluding combined use of coated mica and aluminum foil) 0.05 ~
Metallic paint containing 8% by weight was applied to the flat surface and the side surface of the object to be coated using a rotary atomization type electrostatic coating machine having a diameter of the atomizing disk of 5 to 10 cm. 0
It is coated by the rotary atomization type electrostatic coating method (A) under the conditions of 00 revolutions / minute, applied voltage −30 to −100 kV, shaving air pressure 0.5 to 5 kg / cm ^2, and discharge rate 100 to 700 ml / min. The rotating part of the atomizing type electrostatic coating machine with the diameter of the atomizing disc is 2 to 5 cm is used for the correction part of
Minute, applied voltage −30 to −90 kV, shaving air pressure 0.5
~ 5kg / cm ² and discharge rate of 10 ~ 300ml / min are applied by rotary atomization type electrostatic coating method (B), then, while this metallic paint is not cured, a clear paint is wet on it.
A top coating method for automobiles, which is characterized by coating on wet.