JPS612768A - Coating material composition for aluminum - Google Patents

Abstract

PURPOSE:The titled composition, obtained by incorporating a specific benzotriazole derivative with a base material coating material, and having improved anticorrosive properties. CONSTITUTION:A coating material composition for aluminum obtained by adding a benzotriazole derivative expressed by the formula (R2 is H or CH3 when R1 is H; R2 is CH3 when R1 is K) to a base material coating material. The compounding ratio is preferably 0.2-2.0pts.wt. based on 100pts.wt. base material coating material solid.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a coating for aluminum, and provides a coating composition for aluminum that has particularly excellent anticorrosion performance.

(Prior Art) Conventionally, when painting aluminum, the aluminum surface is first subjected to a chemical conversion treatment in order to further strengthen anticorrosion performance, and then painted. There are methods for this chemical conversion treatment, such as anodic oxidation treatment, phosphate treatment, and oxidation treatment.Although anodization treatment and chromate treatment have strong anticorrosive properties, they may cause the aluminum surface to lose its luster or become discolored. A charcoal effect occurred, making it unsuitable for use as a clear coat finish. In particular, in the case of automobile aluminum wheels, unlike many other aluminum products, the beauty of the aluminum base metal on the ground surface is required as a design, so after grinding, it is degreased,
After phosphate-based chemical conversion treatment, an acrylic resin-based transparent paint is applied. This greatly improves the design. However, in the market, there is a problem that corrosion starts early, especially in areas where snow-melting salt is sprayed, which impairs the design of aluminum wheels and sometimes the function of the wheels. development was desired.

(Object of the Invention) Benzotriazole has conventionally been known as a preservative for copper alloys and silver, and has been used as a preservative in antifreeze solutions, full oil extraction hydraulic fluids, hydraulic fluids, and the like.

This is because benzotriazole chelates copper, forming a chelate layer on the copper surface to prevent corrosion. The present inventor took note of this point and discovered that by incorporating a benzotriazole derivative into a paint for aluminum, the anticorrosion performance of the paint was improved, and the present invention was completed. That is, the present invention satisfies the above-mentioned conventional needs, and aims to provide a coating composition for aluminum that provides a coating film with excellent anticorrosion performance when applied to aluminum and aluminum alloys.

[Summary of the invention]

The present invention provides a coating composition for aluminum characterized by containing a benzotriazole derivative represented by:

That is, the benzotriazole derivative has RI -H%
Benzotriazole which is Rt -H, R1-H,R
tolyltriazole which is z-CH3 and 1R to R+-
The solid content of the coating composition for aluminum is selected from tolyltriazole potassium salts where t = Cf-13, and the solid content is 100! 0.2 to 2.1 parts. Oil! 11
The present invention provides a coating composition for aluminum, characterized in that the composition contains:

[Detailed explanation of the structure of the invention]

In the aluminum coating composition of the present invention, the base coating to which the above benzotriazole derivative is added includes conventional thermoplastic resin coatings such as acrylic resin coatings, phthalic acid resin coatings, and vinyl resin coatings, and thermosetting resin coatings. Paint can be used. For example, in the case of an acrylic resin paint, it may be mixed with a melamine resin to form a baking paint, or a cellulose derivative such as nitrocellulose or cellulose acetate butyrate may be blended to form an acrylic lacquer. The above-mentioned paint may be a colorless and transparent rear paint, or a colored paint containing colored pigments or dyes. It may also be an undercoat or intermediate coating containing a rust preventive pigment such as zinc chromate and an extender pigment. A preferred method is to mix a small amount of epoxy resin into the base paint to improve adhesion.

Another method is to add it to a type of anti-corrosion agent such as wash primer. Depending on the purpose, additives such as ultraviolet absorbers, curing accelerators, leveling agents, thickeners, antifoaming agents, etc. can be used.

In addition, as for the form of the paint, a solution type paint dissolved in an organic solvent is preferable.

The benzotriazole derivative used in the present invention is selected from benzotriazole, tolyltriazole and tolyltriazole potassium salt. Benzotriazole derivatives and azole derivatives other than those mentioned above have no effect on improving anticorrosion performance. The above benzotriazole derivatives may be used alone, or two or more types of benzotriazole derivatives may be used in combination. In particular, it is desirable to use at least benzotriazole, since it exhibits a particularly excellent effect.

The benzotriazole derivative conductor is blended in an amount ranging from 0.2 to 2.0% by weight based on 100 parts by weight of the solid content of the base coating. If the blending ratio is less than 0.2% by weight, the anticorrosion performance will not be exhibited and there will be no effect. If the blending ratio exceeds 2.0% by weight, curing failure occurs in baking paint systems for aluminum made of acrylic resins and amino resins, and it also causes a decrease in water resistance in other paint systems, which is not preferable. In the range of 0.2 to 2.0j11%, anticorrosion performance can be improved without deteriorating other functions.

The coating composition for aluminum of the present invention exhibits the best effects when applied to objects made of aluminum and aluminum alloys. Note that there are no restrictions on the shape of the object to be coated. In addition, the coated objects made of aluminum and aluminum alloys may or may not be chemically treated, but they must be previously subjected to chemical conversion treatment such as anodizing treatment, phosphate treatment, chromate treatment, etc. is desirable.

The benzotriazole derivative in the present invention is.

It is well known to chelate copper and copper alloys to prevent corrosion. For this purpose, antifreeze, lubricating oil, hydraulic fluid,
Although it is added to hydraulic fluids, etc., it has never been used as a rust preventive agent in paints. The present invention was completed based on the discovery that when the benzotriazole derivative was added to a paint for aluminum, the anticorrosion performance against aluminum was improved. It is not yet clear why benzotriazole is effective in preventing corrosion of aluminum, but it is possible that benzotriazole chelates aluminum in the same way as copper.
Or a benzotriazole derivative incorporates the same ion,
It is inferred that a local battery is formed between the copper and aluminum, or that one or both of these effects prevent corrosion of the aluminum.

The benzotriazole derivative of the present invention is easily dissolved in most organic solvents such as alcohol solvents and aromatic hydrocarbon solvents. Therefore, when blending into a base paint containing an organic solvent, there is no need for steps such as heating or mechanical dispersion, and the mixture can be easily mixed. Furthermore, since it has excellent compatibility with most paint vehicles, the benzotriazole derivative does not precipitate and become cloudy after the coating film is formed, and a transparent coating film can be obtained. In particular, when blended with acrylic resin paints used for painting aluminum wheels for automobiles, which require high quality aluminum, it forms a coating film with excellent anti-corrosion performance without compromising its transparency. , beauty can be maintained for a long time.

〔Example〕

The composition and synthesis method of the acrylic resin used as the base resin in Examples and Comparative Examples will be explained below.

Add 50 parts by weight of xylene and 50 parts by weight toluene to a 1 liter fourth flask, and add 10 parts by weight while flowing nitrogen gas.
Heat to 0-130°C and start stirring. Next, 40 parts by weight of styrene, 30 parts by weight of ethyl acrylate, 20 parts by weight of n-butyl methacrylate, 9 parts by weight of 2-human O-oxyethyl acrylate, and 1 part by weight of acrylic acid were added with 2.2-azobisisobutylene. 1.91 parts of lonitrile is dissolved, and this solution is added dropwise over 2 hours to the flask containing the above solvent. One hour after the completion of the dropwise addition, 0.95 parts by weight of 2.2'-7zobisisobutyronitrile was added dropwise over a period of 4 hours, and after the completion of the dropwise addition, heating and stirring were continued for an additional hour, followed by cooling and filtration. A transparent acrylic base resin was obtained. This acrylic resin had a nonvolatile content of 50% and a weight average molecular weight of 20,700.

140 parts by weight of the acrylic resin obtained above and n-
Butylated melamine resin (Mitsui Toatsu Chemical (a) tfj-1
-Bread 20SE) 6Of! m part, hisphenol type epoxy resin (Shell Chemical Co., Ltd. class Epicote 1001) 1
43,111 parts were blended to form a base paint. Take 100 parts by weight of this base paint, add benzotriazole (Sumitomo Chemical
Co., Ltd. S tablnol BTZ-R) was blended in an amount of 0.5, 1.0, and 2.0% by weight, respectively, based on the solid content of the base coating to obtain the aluminum coating composition of the example. Ta. Here, the epoxy resin was blended for the purpose of improving adhesion.

The obtained coating composition was adjusted to a viscosity of 1124 seconds (Ford Cup #4) with thinner, and applied by air spray to an automotive aluminum wheel that had been previously subjected to alkaline degreasing and zirconium phosphate chemical conversion treatment, and then applied for 5 minutes. This was baked at 140° C. for 30 minutes with a setting time of 100° C. to form a transparent coating film with a thickness of 25 μm.

Comparative Example A transparent coating film having a thickness of 25 μm was formed by blending, adjusting, painting and baking in the same manner as in the example except that benzotriazole was not blended.

Test Example The aluminum wheels obtained in the above examples and comparative examples were
A cross cut with a length of 5 cm was made using a cutter knife, and the coating was subjected to a salt spray test and a beach exposure test to test the corrosion resistance of the coating film.

Each test method is as follows. 5% for salt spray test
This test method involves spraying a saline solution for 2000 hours to accelerate rust. The beach exposure test is a test method in which the specimen is left facing south at an angle of 45 degrees for 6 months on the Pacific coast of Aichi Prefecture. The evaluation of these test results was carried out during the rust, and the rust IJ was measured from the cross-cut portion 3 as shown in the figure.

The test results are shown in the table. According to the results in the table, there was no noticeable difference in the rusting of the paint film formed in this example compared to the comparative example in the salt spray test, but in the seashore exposure test which is a practical test. It was extremely good, being 1/10 or less. It is clear that this is an effect of the benzotriazole used in the example. In other words, the aluminum paint of the example to which benzotriazole was added was compared to the conventional aluminum paint of the comparative example without benzotriazole. , has extremely excellent anticorrosion performance from a practical standpoint.

[BRIEF DESCRIPTION OF THE DRAWINGS] The figure is a schematic explanatory diagram of a method for measuring rust from a cross-cut area. 1... Part of the aluminum wheel 2... Rust 3... Cross cut = 538- 1 Part of the aluminum wheel 3 Cross or sod 2 Rust

Claims (3)

[Claims] (1) A coating composition for aluminum, characterized in that it contains a benzotriazole derivative represented by the general formula ▲numerical formula, chemical formula, table, etc.▼ as a constituent component. (2) Benzotriazole derivatives are R_1=H, R_2
=H, benzotriazole, R_1=H, R_2=
Tolyltriazole which is CH_3 and R_1=K, R
The coating composition for aluminum according to claim 1, which is selected from tolyltriazole potassium salts in which _2=CH_3. (3) The benzotriazole derivative is contained in an amount of 0.2 to 2.0 parts by weight based on 100 parts by weight of the solid content of the coating composition for aluminum.
Coating composition for aluminum as described in .