JPS6377576A - Coating method - Google Patents

Abstract

PURPOSE:To prevent the generation of troubles such as pinholes and sag by incorporating a flaky filler into a 1st coated film directly formed on the surface of a material to be coated so that the coated film thicker than heretofore can be formed by 2 times of baking and drying stages like in the conventional method. CONSTITUTION:The 1st paint prepd. by using an acrylic resin and melamine resin as a vehicle and incorporating 1-100pts.wt. flaky filler such as glass flake to 100pts.wt. acrylic resin is coated on the surface of the material to be coated such as Al stock. The material to be coated is baked and dried to form the 1st coated film. The 2nd paint prepd. by using the acrylic resin and melamine resin as the vehicle and incorporating a coloring material therein is then coated on at least part of the surface of the 1st coated film. The clear paint prepd. by using the acrylic resin and melamine resin as the vehicle is coated on the surface of the 2nd paint and the surface of the 1st coated film. Such material to be coated is baked and dried to form the 2nd coated film consisting of the 2nd paint and the 3rd coated film consisting of the clear paint on the surface of the 1st coated film.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention applies fIQ to a coating method. The coating method of the present invention includes:
For example, it is used when painting aluminum wheels of automobiles, and is suitable for coating coatings with excellent corrosion resistance.

[Prior Art] Conventionally, aluminum wheels of automobiles are often painted for the purpose of surface protection and rust prevention.

The paint used to paint these aluminum wheels is generally an acrylic baking paint containing an acrylic resin and a melamine resin as a vehicle, and is baked and dried to form a coating film. From a design point of view, there are parts that are painted only with clear paint to take advantage of the metallic luster of the aluminum material, and 21i!, which is a colored paint containing a coloring agent and a clear coat. It is often divided into a part formed from one coating film. To paint separately in this way, first mask off the areas where the aluminum material will be used, apply the colored paint, and let it dry. Then apply clear paint to the whole thing,
It is formed by baking. That is, in this case, the area is divided into a 2-coat, 2-bake coating area of colored paint and clear paint, and a 1-coat, 1-base coating area of clear paint only.

[Problems to be Solved by the Invention] In the conventional aluminum wheel painting described above, the coating thickness is thin in the area where only the clear coat is applied, so the rust prevention ability is inferior to that in the 2-coat, 2-baked area. There was a problem. To improve this rust prevention ability, it is possible to make the coating thicker, but with the 2-coat, 2-bake method, there is a limit to how thickly the clear coating can be applied, and if the limit is exceeded, wrinkles, sagging, etc. will occur. There is a problem with doing so.

The present invention has been made in view of the above-mentioned problems, and provides a coating method that can achieve a thicker film than before by using two baking and drying processes, and solves problems such as wrinkles and sagging. This is what we provide.

[Means for Solving the Problems] The coating method of the present invention uses a first coating method in which a vehicle is made of an acrylic resin and a melamine resin, and a scale-like filler is contained in 1 to 100 parts by weight per 100 parts by weight of the acrylic resin. a first coating step of applying a paint to the surface of the object to be coated; a first drying step of baking and drying the object to be coated with the first paint to form a first coating film; and a first drying step of applying the first paint to the surface of the object. a second coating step of applying a second paint containing a colorant as a vehicle to at least a portion of the surface of the first coating film; and a second coating step of applying a clear paint containing an acrylic resin and a melamine resin as a vehicle to at least a portion of the surface of the first coating film. a third painting step of applying the applied second paint surface and the first paint film surface; and baking and drying the object coated with the 21i material and the clear paint to form the first paint film. A second drying step of forming a second coating film made of the second paint and a third coating film made of the clear paint on the surface is performed in sequence.

The most distinctive feature of the present invention is that the first coating step is performed. The first paint applied in the first painting process uses an acrylic resin and a melamine resin as a vehicle, and the acrylic resin 10
The scale-like filler is contained in an amount of 1 to 100 parts by weight based on 0 parts by weight. Here, as the acrylic resin, the same acrylic resin for baking paints as in the past, which is polymerized from known monomers, can be used. Generally, those having a 1ffi average molecular weight of about 20,000 to 50,000 are used. Further, the same melamine resin as conventional ones can be used, and methylated melamine resin, butylated melamine resin, etc. having an Iuffi average molecular weight of 1000 to 5000 can be used. Note that melamine may be co-condensed with benzoguanamine, urea, or the like.

The blending ratio of acrylic resin and melamine resin is generally 20 to 50 parts by weight of melamine resin per 101 parts by weight of acrylic resin solids.

Outside this range, problems will occur in the elongation properties of the cured coating, such as poor curing and poor water resistance.

Note that other resins such as epoxy resin and cellulose acetate butyrate may be blended and used as the vehicle.

As the scaly filler, glass flakes, aluminum flakes, mica, mica-like iron oxide, etc. can be used. For example, if glass flakes are used, the first paint becomes a clear paint with excellent transparency, and the metallic luster of the aluminum material can be fully utilized. The scale-like filler is contained in an amount of 1 to 100 parts by weight per 100 parts by weight of the acrylic resin. If it is less than 1 layer, the rust prevention performance will not be sufficient, and 10
If the amount exceeds 0 parts by weight, the smoothness of the coating film will be impaired by vA.

Note that a range of 10 to 30 parts by weight is particularly desirable.

In addition, the scale-like filler has a thickness of 1 to 10 μm and a length of 5 to 10 μm.
It is desirable to have a shape of 50 μm and an aspect ratio of 5 to 10. Thickness exceeds 10μm or length exceeds 50μm
If it exceeds this, the surface condition of the coating film will deteriorate and the appearance quality will deteriorate. Also, if the aspect ratio is smaller than 5 and it is powdery,
The target rust prevention performance cannot be secured.

In this first coating step, the entire surface of the object is generally coated.

The coating is conventionally used air spray coating,
Various coating methods such as airless coating and electrostatic coating can be employed.

The object to be coated with the first paint is baked and dried in a first drying step to form a first paint film. This first drying step
It is desirable to bake dry at ~120°C for 5 to 20 minutes.

If the temperature is lower than 90° C. or the baking time is short, masking, which will be described later, may become impossible, and wrinkles, sagging, etc. may occur in subsequent steps. Furthermore, if the temperature is too high or the time is too long, the adhesion between the first coating film and the second coating film may deteriorate, resulting in problems such as peeling. Note that the first coating film is preferably applied so that the film thickness after drying is 20 to 30 μm. If it is thicker than 20μ, the rust prevention performance will be insufficient, and if it is thicker than 30μ, problems such as wrinkles and sagging may occur.

After the first drying process, masking is applied if necessary, and the second
A painting process is performed. In this second coating step, a second paint containing a colorant using an acrylic resin and a melamine resin as a vehicle is applied to at least a portion of the surface of the first paint film. The acrylic resin and melamine resin used here can be the same as those for the first paint. Note that the acrylic resin has a slightly higher molecular weight than the acrylic resin of the first coating material.The term "coloring material" is a concept that includes not only organic coloring pigments, inorganic coloring pigments, and dyes, but also aluminum powder. These colorants may be used alone or in combination.

This second painting step can also employ the same painting means as the first painting step. Further, the film thickness of the second paint to be applied is generally about 10 to 50 μm in dry film thickness as in the past, but is not particularly limited.

After the second painting process is completed, if masking was applied after the first drying process, the masking is removed and a third painting process is performed. The paint used in this third painting process is acrylic a
It is a clear paint that uses IIrf and melamine resin as a vehicle. The acrylic resin and melamine resin used can be the same as those for the first paint.

In this third coating step, a clear coating is applied to the first coating surface and the second coating surface coated on at least a portion of the surface. In addition, the parts where the second paint was painted are wet.
On-wet painting. Further, the film is coated to a dry film thickness of generally about 20 to 50 μm. If it is more than 20μ, problems such as rust prevention performance may occur, and if it is more than 50μ, problems such as wrinkles and sagging may occur. As this coating means, various coating means can be adopted as described above.

Next, a second drying step is performed. In this second drying step, the second paint and the clear paint are dried and hardened to form a second paint film made of the second paint and a third paint film made of the clear paint, respectively. In this second drying step, the same baking drying conditions as conventional ones can be applied, for example, baking drying is carried out at 120 to 130 to 140° C. for 20 minutes.

Here, the second coating film is not formed in the area that was masked during the first drying step, and has a two-layer structure of the first coating film and the third coating film. Also, the parts that were not masked are the first
It has a three-layer structure: a coating film, a second coating film, and a third coating film.

Note that there is no problem in adding various additives for paints that are commonly used in the past to the first paint, the second paint, and the clear paint.

[Operations and Effects of the Invention] In the coating method of the present invention, two coats and two bakes are applied as a whole, and at least partially, three coats and two coats are applied. The first coating film formed directly on the surface of the object to be coated contains a scaly filler. This scale-like filler is oriented in a layered manner, reduces the permeation of ions, moisture, etc., and contributes to improving rust prevention (corrosion resistance, water resistance).

Therefore, according to the coating method of the present invention, the rust prevention performance is improved by the scale-like filler compared to the conventional one, and even the thinnest part is coated with two coats and two bakes, which is better than the conventional one. A thicker bite can be achieved. Therefore, the rust prevention performance is further improved.

In addition, if glass flakes are used as the scaly filler, the transparency will not be impaired, so the first coating will be clear, and the second coating will be clear.
The two-layer structure part of the bake is entirely coated with clear coating, so
Just like before, you can take advantage of the metallic luster of the aluminum material.

[Example] The present invention will be specifically explained below using Examples. All parts mentioned below mean parts by weight.

(Example 1) (1) First coating step Acrylic resin (Acridic 44-179, manufactured by Dainippon Ink & Chemicals Co., Ltd.) 100 parts solids, melamine resin (
Kneepan 20SE-60, manufactured by Mitsui Toatsu Co., Ltd.) Solid content: 20
and glass flakes (micro glass flakes C
Mix 20 parts of EF-325 (manufactured by Nippon Sheet Glass Co., Ltd.), 10 parts of xylene, and Swazol 1000 (manufactured by Marukubi Sekiyu Co., Ltd. >2
Add 30 parts of an organic solvent consisting of 0 parts and stir well.
Paint 11 is 19. This first paint was prepared with a first thinner (50 parts of xylene, 50 parts of Swasol 100°) to a viscosity of 15 seconds (Ford Cup No., 4.20°C), and air sprayed onto the entire surface of an aluminum test plate to obtain a dry film thickness. is 20
It was applied so that it was μ.

(2) First Drying Step The test plate coated with the first paint described above was left at room temperature for 5 minutes, and then baked and dried at 110° C. for 10 minutes.

(3) Masking step Approximately half of the first coating film was masked with masking tape.

(4) Second coating process Acrylic resin (Acridic 47-712, manufactured by Dainippon Ink & Chemicals Co., Ltd.) 100 parts solids, melamine resin (
Knee pan 208E-60, manufactured by Mitsui Toatsu) Solid content: 20
and 70 parts of titanium oxide were mixed and dispersed using a sand mill, and an anti-settling agent (Disbaron 6900-20X
A white paint (second paint) was prepared by adding 20 parts of an organic solvent consisting of 10 parts of xylene and 10 parts of butyl acetate. The viscosity was reduced to 25 seconds (Ford Cup No. 4, 2) with a second thinner (20 parts of xylene, 30 parts of toluene, 50 parts of butyl acetate).
0° C.), and the surface of the test plate on which the first coating film had been formed and masked was coated with air spray so that the dry film thickness was 30 μm.

(5) Third painting process Next, leave it at room temperature for 5 minutes as a flash time, remove the masking tape, and then apply acrylic resin Wt (Acridic 44-179, manufactured by Dainippon Ink and Chemicals) at a solid content of 100 parts. Melamine resin (knee pants 20SE-60
, manufactured by Mitsui Toatsu Co., Ltd.) solid content: 20 parts, ultraviolet absorber (Tinuvin 328, Ciba Geigy Co., Ltd.) 1 part, and xylene 1 part.
Organic solvent 2 consisting of 0 parts and 1000 parts of sufuzol
Add the clear paint mixed with 0 parts to the first thinner for viscosity 25 seconds (Ford cup l'L 0.4.20°C)
It was prepared and coated with air spray to a dry film thickness of 20 μm.

(6) Second Drying Step The test panel coated as described above was left at room temperature for 5 minutes and then dried at 140° C. for 20 minutes, completing the coating method of this example.

(7) Test 1Q The test pieces were tested for salt spray resistance, water resistance, and water resistant adhesion, and the results are shown in the table. The salt water spray resistance was determined by spraying 5% saline solution onto the surface of the test piece for 1000 hours in a tank maintained at 35°C, and measuring the width of swelling from the cross-cut portion. Water resistance was determined by immersion in pure water at 40'C for 480 hours, and the diameter and number of blisters were determined by ASTM D7.
Evaluation was made based on No. 14-56. Water resistant adhesion was measured for samples immersed in pure water at 40°C for 480 hours as described above.
I cut 100 squares on the base with a knife, attached cellophane tape, then peeled it off and counted the number of squares remaining.

(Example 2) Same as the second paint of Eggplant Example 1 except that 10 parts of aluminum flakes (<779ON, manufactured by Toyo Aluminum Co., Ltd.) are added to the second coating used in the second coating process instead of titanium oxide. A test piece was prepared by carrying out each step in the same manner as in Actual Example 1, except that the metallic paint was applied to give a dry film thickness of 1915 μm. The 1r test piece was subjected to the same test as in Example 1, and the results are shown in the table.

(Example 3) Each step was carried out in the same manner as in Example 2 except that the blended solidity of aluminum flakes was 20 parts, and the results were similarly tested and shown in the table.

(Comparative Example 1) Not performing the first painting process and the first drying process, and the second painter 8! A test piece was prepared using the coating method of Comparative Example 1 by performing each step in the same manner as in Example 1 except that baking drying was performed afterwards and masking was performed thereafter. (
The obtained test pieces were subjected to the same test as in Example 1, and the results are shown in the table.

(Comparative Example 2) First! 'Do not perform the second loading process and the first drying process,
A test piece was prepared using the coating method of Comparative Example 2 by performing each step in the same manner as in Example 2, except that baking drying was performed after the second coating step and masking was performed thereafter.

The prepared test pieces were subjected to a test in the same manner as in Example 1, and the results are shown in the table.

(Comparative Example 3) Each process was performed in the same manner as in Example 3, except that the first painting process and the first drying process were not performed, and baking drying was performed after the second painting process, followed by masking. A test piece was prepared using the coating method of Example 3. The obtained test piece was subjected to the same test as in Example 1, and the results are shown in the table.

(The following is a blank space) (Evaluation) It is clear from the table that the test pieces of each Example exhibit better antirust performance than the corresponding Comparative Examples. Furthermore, when comparing the masked area of each example and the non-masked area of each comparative example, the example shows a better result (1) despite the fact that each film is a 2-coat, 2-bake coating. It is clear that this is due to the effect of incorporating the scaly filler into the first coating film.

Claims (7)

[Claims] (1) Acrylic resin and melamine resin are used as a vehicle, and 1 to 10 parts by weight of the scaly filler are added to 100 parts by weight of the acrylic resin.
a first coating step of applying a first paint containing 100 parts by weight to the surface of the object to be coated; and a first drying step of baking and drying the object coated with the first paint to form a first coating film. a second coating step of applying a second paint containing a colorant using an acrylic resin and a melamine resin as a vehicle to at least a portion of the surface of the first coating film; a third painting step of applying a clear paint to the second paint surface and the first paint film surface on which at least a portion of the surface has been applied; and baking the object to be coated with the second paint and the clear paint; When dried, a second coating material made of the second coating material is applied to the surface of the first coating film.
A coating method characterized by sequentially carrying out a coating film and a second drying step of forming a third coating film made of the clear paint. (2) The coating method according to claim 1, wherein the scale-like filler is contained in an amount of 10 to 30 parts by weight per 100 parts by weight of the acrylic resin. (3) The coating method according to claim 1, wherein the first drying step is performed by baking at 90 to 120°C for 5 to 20 minutes. (4) The coating method according to claim 1, wherein the second drying step is performed by baking at 120 to 150°C for 20 minutes. (5) The coating method according to claim 1, wherein the object to be coated is an aluminum material. (6) The coating method according to claim 1, wherein the scaly filler is glass flakes. (7) The scale-like filler has a thickness of 1 to 10 μm and a length of 5 μm.
The coating method according to claim 1, wherein the coating has a shape of 50 μm and an aspect ratio of 5 to 10.