JP2000140748A - Coating of wheel for vehicle with plating tone appearance and wheel for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for coating for forming a coating film with a brilliant appearance being a match for metal plating and with excellent interlaminar adhesiveness on a wheel for a vehicle, and the wheel for the vehicle. SOLUTION: After a powder coating material which can form a coating film with a luster is applied as an undercoat on a base material for a wheel for a vehicle, a coating compsn. as an intermediate coating material contg. an ultrathin scale-like aluminum with a thickness of 0.01-0.1 μm and a diameter of 1-60 μm is applied as an intermediate coating so as to make the film thickness after drying to be 0.1-3 μm and in addition, a colored or a non-colored powder clear coating material is applied as a topcoat.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating method for forming a coating film having a glossy plating appearance on a wheel base material for a vehicle, and a coating method applied by the coating method. The present invention relates to a vehicle wheel.

[0002]

2. Description of the Related Art Conventionally, there has been a method of plating a metal (for example, Cr or the like) or vacuum-depositing aluminum in order to make the surface of a metal material such as a wheel have a brilliant appearance having a metallic luster. However, each of these methods requires a large-scale apparatus and is expensive.

[0003] For this reason, various studies have been made to obtain a brilliant appearance using a coating composition. This is a so-called metallic coating using a resin coating mixed with non-leafing type aluminum. In such a conventional metallic coating, a metallic feeling is obtained by using a paint mixed with scale-like aluminum having a thickness of more than 0.1 μm and making the coating film 10 μm or more in thickness. If the metallic paint is used to form a thin film in order to obtain a plating-like appearance, even a metallic feeling is lost, instead of obtaining a plating-like appearance. Therefore, a coating composition capable of forming a coating film having a plating appearance that can solve these problems has been desired.

On the other hand, in the automotive field, powder coatings are often used as coatings having low VOC (volatile organic compounds) and low environmental pollution. Recently, the appearance of metal-plated wheels has been demanded even for vehicle wheels, but when a thin film of an intermediate coating that can provide a plating-like appearance is used, powder coatings are generally solvent-based coatings. Since the coating is applied to a thicker film, the interlayer adhesion between the intermediate coating layer of the thin film and other layers is poor due to the influence of internal stress, and a practical coating film has not been obtained.

[0005]

Therefore, in the present invention,
An object of the present invention is to provide a coating method and a vehicle wheel for forming a coating film having a glittering appearance comparable to that of metal plating and having excellent interlayer adhesion on a vehicle wheel.

[0006]

SUMMARY OF THE INVENTION According to the present invention, a base material for a vehicle wheel is coated with a powder coating material capable of forming a glossy coating film. 1μ
m, the thickness of the intermediate coating composition containing ultra-thin flaky aluminum having a diameter of 1 to 60 μm after drying is 0.1 to 3 μm.
m, and then a top coat of a colored or non-colored powder clear paint is applied to the vehicle wheel having a plating appearance.

[0007] It is preferable that the coating film formed by the intermediate coating composition is discontinuous. This is because the interlayer adhesion is improved. In particular, when the coating film formation rate indicating the ratio of the area where this coating film covers the undercoat layer is 15 to 85%,
It is possible to form a multilayer coating film having a beautiful plating appearance and excellent interlayer adhesion.

[0008] It is also preferable to perform the overcoating in a state where the coating film formed by the undercoating is not completely cured in order to improve the interlayer adhesion.

The intermediate coating composition contains 1 to 3 parts by weight of a binder resin based on 1 part by weight of ultra-thin flake aluminum, and 1 part by weight of ultra-thin flake aluminum contains a solvent. Is a preferred embodiment of the method of the present invention.

The present invention also includes a vehicle wheel having a plating appearance, which is coated by the above-mentioned coating method.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The method of the present invention is based on the finding that a coating method capable of securing good adhesion to a powder coating using an intermediate coating composition containing an ultra-thin flaky aluminum. There is. By this coating method, a vehicle wheel having an extremely excellent plating-like appearance as if a metal is plated was successfully obtained. Hereinafter, the present invention will be described in detail. The term “plating-like appearance” or “plating feeling” used in the present invention means:
It is much glossier than the "metallic feeling" conventionally used, and has a beautiful appearance as if it is metal-plated.

The coating method of the present invention is applied to a vehicle wheel. Various metals and alloys such as aluminum alloys, magnesium alloys, and steels are appropriately selected as the base material of the vehicle wheel. Corrosion resistance treatment such as chemical conversion treatment,
A substrate subjected to a known surface treatment may be used.

According to the coating method of the present invention, first, a powder coating for undercoating capable of forming a glossy coating film is applied to a wheel base material by a known coating method. As described below, if there is a portion where the intermediate coating film is formed and a portion where the intermediate coating film is not formed, excellent interlayer adhesion is obtained. At this time, since the undercoat film is exposed in the portion where the intermediate coat film is not formed, the glitter of the undercoat film is also reflected in the final coat appearance, so that the undercoat film has a gloss. It is necessary to form a coating film having the same. As a powder coating for undercoat,
Any known powder coating can be used as long as it is capable of forming a glossy coating film, and may be a type containing a coloring pigment. Specifically, epoxy powder coating, glycidyl acrylic (epoxy acrylate)
Powder coating, polyamide powder coating, acrylic powder coating and the like.

Undercoating receives a thermal history due to heating during intermediate coating and topcoating. Since this heat history may adversely affect the adhesion between layers, it is preferable that the coating film formed by the undercoating is not completely cured when performing the overcoating. As a result, the undercoat layer is completely cured by heating during the overcoating, and good interlayer adhesion is obtained.

As an indication of whether or not the undercoat layer is completely cured, it is determined whether or not the insoluble content when the coating film is dissolved in acetone, that is, whether or not the gel fraction is 95% by weight or less. If the curing of the undercoat layer is too incomplete, the undercoat layer cannot be completely cured at the time of coating the overcoat layer. Therefore, the gel fraction is preferably set to 80% by weight or more.

In order to make the undercoat layer incompletely cured at the time of coating the overcoat layer, the reaction speed of the undercoat powder coating is made slower than that of the overcoat powder coating.

The crosslink density of the undercoat powder coating is made lower than that of the top coating powder coating.

The undercoat powder coating contains an uncured component compatible with the top coating powder coating. And the like. The above can be adjusted by controlling the amounts of the crosslinking agent and the curing accelerator, and the non-curable component that can be used in the above includes a hydroxyl-modified acrylic resin.

In the case where the intermediate coating layer is discontinuous, there is a portion where the undercoat is exposed, and the undercoat and the overcoat are directly adhered to this portion. Increasing the properties is also effective for improving the interlayer adhesion. For example, a component that crosslinks with the undercoat powder coating may be contained in the overcoat powder coating, and the two may be chemically reacted during heating of the overcoat. As such a crosslinking component, a blocked isocyanate or the like is suitably used.

After the undercoating, the intermediate coating composition is applied as an intermediate layer by a known method. At this time, the film thickness after drying is adjusted to be 0.1 to 3 μm. If the thickness of the intermediate coating layer is too small, a feeling of plating is hardly obtained. If the thickness is too large, a metallic feeling is obtained but the plating appearance is not reached. When the thickness is too large, the adhesion between the undercoat layer and the middle coat layer or between the middle coat layer and the top coat layer may be poor. A more preferred thickness of the intermediate coating layer is 0.5 to 2 μm.

Further, a thin coating film (approximately 0.1 to 3 μm) is prepared with a coating composition prepared in a preferable amount of a binder resin described below (1 to 3 parts by weight of binder resin based on 1 part by weight of ultra-thin flake aluminum). When formed and observed by taking a micrograph of the coating film, it was found that the coating film containing ultra-thin flaky aluminum was discontinuously scattered. That is, a portion where the coating film is formed and the undercoat layer is covered is mixed with a portion where the coating film is not formed and the undercoat layer is visible. And since the coating film exhibiting this plating appearance is scattered, a place where the undercoat layer and the overcoat layer are in direct contact with each other is created.
It has also been found that the interlayer adhesion of the multilayer coating is significantly improved. That is, since the intermediate coating film having ultra-thin flake aluminum does not have good adhesion to the undercoat layer or the top coating layer, the interlayer adhesion becomes poor when this coating film is formed on the entire surface of the undercoat layer. Inferior. On the other hand, the undercoat layer and the overcoat layer are usually formed of the same type of paint or high-affinity paints, so that the interlayer adhesion is good. For this reason, the undercoat layer and the topcoat layer directly adhere to the portion where the intermediate coating film is not formed, and exhibit good interlayer adhesion as a whole.

However, if there are too many portions where the intermediate coating film exhibiting the plating appearance is not formed, a good plating appearance cannot be obtained, so that the intermediate coating film is formed and the undercoat layer is not covered. Is the area ratio (for convenience,
15% or more is required.
However, when the coating film formation ratio exceeds 85%, the interlayer adhesion tends to be inferior as described above. A more preferable coating film formation rate is 25% or more and 65% or less.

An overcoat is applied on the intermediate coat. This is because it is preferable to provide an overcoat layer as a protective layer in order to protect the plating appearance while maintaining a beautiful appearance. The overcoat layer is colored in a range that does not impair the luster of the undercoat layer or the plating feeling of the middle coat layer, or is formed by applying a non-colored powder clear paint. The type of the powder clear coating is the same as the powder coating for undercoat.

In order to impart a beautiful plating-like appearance to a vehicle wheel, the coating composition for intermediate coating contains, as an essential component,
Ultra-thin flaky aluminum having a thickness of 0.01 to 0.1 μm and a diameter of 1 to 60 μm must be contained.
If the thickness of the ultra-thin flaky aluminum is less than 0.01 μm, it is easily broken, and a beautiful plating appearance cannot be obtained. When the thickness is more than 0.1 μm, a metallic film can be obtained when the coating film is made thick, but a plating-like appearance cannot be obtained, and even when a thin film is formed, a beautiful plating-like appearance cannot be obtained. More preferred thickness of ultra-thin flake aluminum,
0.02 to 0.04 μm. The diameter of the ultra-thin flake aluminum is 1 to 60 μm. The lower limit is the value of the minor axis of the ultra-thin flake aluminum, and the upper limit is the value of the major axis. If the ultra-thin flaky aluminum is too small or too large, good plating appearance cannot be obtained. A more preferable size range is 10 to 20 μm in diameter.
It is.

The coating composition for intermediate coating preferably contains a binder resin together with the ultra-thin flaky aluminum. As the binder resin, resins commonly used in the field of coatings such as alkyd resins, acrylic resins, epoxy resins, and aliphatic hydrocarbon resins can be used, and among them, those having an acid value of 1 or less are preferable. If the acid value is more than 1, the shine of the ultra-thin flake aluminum may be adversely affected.

In order to obtain an excellent plating appearance, it is important to balance the binder resin and the ultra-thin flake aluminum. One to three parts by weight of the binder resin is added to 1 part by weight of the ultra-thin flake aluminum. Part (solid content)
It is preferable that If the amount of the binder resin is less than 1 part by weight, the orientation of the ultra-thin flaky aluminum in the coating film is impaired, and the glitter may be inferior.
If the amount is more than the weight part, the reflected light is attenuated and the gloss may be inferior.

It is preferable that the intermediate coating composition contains a solvent. This is because a uniform coating film can be obtained. The solvent is not particularly limited as long as it can dissolve the binder resin, and ester-based, ketone-based, and other known solvents that are commonly used in coating compositions can be used. The amount of the solvent used is preferably 50 to 400 parts by weight based on 1 part by weight of the ultra-thin flake aluminum. If the amount is less than 50 parts by weight, the smoothness of the coating film becomes poor, and a good plating appearance may not be obtained. 4
Exceeding 00 parts by weight is not preferable because problems such as sagging occur during coating.

The coating composition for intermediate coating can be produced by appropriately mixing ultra-thin flaky aluminum, a binder resin and a solvent by a known method. In the coating composition, various additives conventionally used in coatings, for example,
Additives such as curing accelerators, crosslinking agents, wetting agents, viscosity modifiers, thickeners, modifiers, pigments, colorants, antioxidants, UV absorbers, UV stabilizers, etc. It is also possible to add in a range that does not inhibit.

[0029]

The present invention will be described in detail with reference to the following examples, but the scope of the present invention is not limited to these examples. Unless otherwise specified, “%” indicates “% by weight” and “parts” indicates “parts by weight”.

Examples 1 to 5 and Reference Example 1 As a base material, an aluminum plate (75 mm × 150 mm × 2 mm thick) specified by JIS H 5020 was chromated using “Alchrome AM-713” (manufactured by Nippon Parkerizing Co., Ltd.). The treated one was used. The undercoating powder coating and the topcoating powder coating used had the composition shown in Table 1, and were heated for 20 minutes under the baking conditions shown in Table 1 so as to be 80 to 100 μm.

The intermediate coating material is an ultra-thin flaky aluminum (average thickness 0.03 μm, average diameter 13 μm;
A mixture of 1 part by weight of "VD-20" (Showa Aluminum Powder Co., Ltd.), 1 part by weight of "Alcon P-125" (aliphatic hydrocarbon resin; Arakawa Chemical Industries, Ltd.) and 50 parts by weight of butyl acetate. It was used and heated at 130 ° C. for 20 minutes to form a 0.8 to 1.0 μm intermediate coating layer.

In Table 1, the contents of each component are as follows. Armatex PD-7310: a thermosetting glycidyl acrylic resin manufactured by Mitsui Chemicals, Inc. (epoxy equivalent: 52
0-550) Finedick A-233S: thermosetting glycidyl acrylic resin (600-640 as epoxy equivalent) manufactured by Dainippon Ink and Chemicals, Inc. Araldite AER-6071: epoxy resin (epoxy equivalent 450-500; manufactured by Ciba Geigy) Fine Dick A-751: a hydroxyl-modified acrylic resin manufactured by Dainippon Ink and Chemicals, Inc.
105) Acronal 4F: polyacrylic acid-based viscosity modifier manufactured by BASF Co., Ltd. Carbon black MA-100: calcigros GU manufactured by Mitsubishi Carbon Co., Ltd. Calcium carbonate Vestagon B-1530 manufactured by OMYA Co .: Block isocyanate manufactured by Huls Co. NCO equivalent 275-285) The coating film properties of the obtained coated aluminum plate were evaluated by the following evaluation methods, and the results are shown in Table 1.

[Adhesion-1] The adhesion test of the coating film of the coated aluminum plate after standing at room temperature was performed according to JIS K54.
According to the cross-cut tape method specified in 8.5.2 of No. 00, cross-cuts with a clearance interval of 2 mm were formed and evaluated by the evaluation score method.

[Adhesion-2] The adhesion test of the coating film of the coated aluminum plate after immersion in hot water at 60 ° C. for 72 hours was evaluated in the same manner as in the case of Adhesion-1.

[Appearance] The appearance of the obtained coated aluminum plate was visually compared with a metal Cr-plated product and evaluated according to the following criteria. ：: Plating appearance equivalent to that of metal plating △: Plating appearance was not achieved, but sufficient metallic feeling ×: Almost no metallic feeling

[0036]

[Table 1]

Example 1 of the present invention is an example in which the baking temperature of the undercoat is lowered to an incompletely cured state, and the interlayer adhesion is improved by completely curing in the overcoating step.
The coating film formation rates of Examples 1 to 5 and Reference Example 1 were 55
%Met. In Example 2, the reaction rate of the undercoat layer was reduced by adjusting the amounts of decanedicarboxylic acid and dibutyltin dilaurate. Example 3 is an example in which the amount of resin, the amount of decanedicarboxylic acid, and the amount of dibutyltin dilaurate were adjusted to increase the crosslink density of the overcoat layer (as a result, the crosslink density of the undercoat layer was lower than that of the overcoat layer). is there. Example 4 is an example in which a hydroxyl-modified acrylic resin was added as a resin component having excellent compatibility with the overcoat layer. Example 5 is an example in which a block isocyanate was further added to the overcoat layer to the composition of Example 4 to crosslink the overcoat layer and the undercoat layer. All show good interlayer adhesion and plating feeling.

Reference Example 1 is an example in which undercoating, intermediate coating, and topcoating were performed under the same printing conditions as in the prior art. Since the undercoat layer has undergone thermal history, the result was poor interlayer adhesion.

[0039]

The method of the present invention is constituted as described above. The multilayer film of the upper and lower powder coating layers and the thin film intermediate coating layer has good interlayer adhesion and has an appearance like metal plating. Could be painted to give. Therefore, it was possible to form a coating film having a plating-like appearance on a vehicle wheel as if it were plated with metal. Therefore, a vehicle wheel having a very beautiful appearance can be manufactured at a low cost by using a powder coating material with less environmental pollution.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Eiji Ikeda 3-15-27 Nishi-Awaji, Higashi-Yodogawa-ku, Osaka-shi, Osaka Inside Kubo Paint Co., Ltd. Nissan Motor Co., Ltd. (72) Osamu Hidekawa, Inventor 2 Takaracho, Kanagawa-ku, Yokohama, Kanagawa Prefecture Nissan Motor Co., Ltd. ) Inventor Ryoji Shimizu F-term (reference) 4D075 AE06 CB13 DA23 DB01 DC13 EA02 EA43 EB22 EC10 EC23 EC35 EC53 EC54

Claims (7)

[Claims] 1. An undercoating of a powder coating material capable of forming a glossy coating film on a vehicle wheel base material, followed by a thickness of 0.01 to 0.1 μm and a diameter of 1 to 60 μm. The intermediate coating composition containing the thin film flaky aluminum is subjected to intermediate coating so that the film thickness after drying is 0.1 to 3 μm, and further, a colored or non-colored powder clear coating is overcoated. A method for coating a vehicle wheel having a plating appearance. 2. The coating method according to claim 1, wherein the coating film formed by the intermediate coating composition is discontinuous. 3. The coating method according to claim 2, wherein the coating film formation ratio, which indicates the ratio of the area where the coating film formed by the intermediate coating composition covers the undercoat layer, is 15 to 85%. 4. The coating method according to claim 1, wherein the top coat is applied in a state where the coating film formed by the undercoat is not completely cured. 5. The coating method according to claim 1, wherein the intermediate coating composition contains 1 to 3 parts by weight of a binder resin based on 1 part by weight of ultra-thin flake aluminum. 6. The coating method according to claim 1, wherein the coating composition for intermediate coating contains 50 to 400 parts by weight of a solvent based on 1 part by weight of ultra-thin flake aluminum. 7. A vehicle wheel having a plating-like appearance coated by the coating method according to any one of claims 1 to 6.