JPH01272672A - Coating composition - Google Patents

Abstract

PURPOSE:To obtain the coating composition for protective coating of illuminator component, etc., containing a coloring substance and capable of forming colorless and transparent coating film after coating and checking film thickness by a shade of color of coating composition on a product to be coated. CONSTITUTION:The aimed composition, e. g., obtained by adding (B) an acid- base indicator (e.g., pentamethoxy red) capable of coloring in acidity and (C) an acidic reagent (e. g., hydrochloric acid) to (A) coating composition, capable of readily providing an uniform transparent protection film, because of being able to carry out coating while controlling film thickness of coating film and usable for various raw materials to be coated such as metal, paper, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to a coating composition that forms a transparent coating film.

[Conventional technology]

Conventionally, plated parts (eg, flanges, arms, etc.), reflectors, and the like used for decoration of lighting equipment have been coated with a protective coat to impart corrosion resistance. Generally, a transparent paint is used for this protective coat so as not to affect the optical properties of the object to be coated, so that a transparent coating film is formed.

[Problem to be solved by the invention]

However, since the protective coating paint is transparent, it is not easy to form a uniform coating on the plated parts, reflectors, etc. (and requires a high level of skill from the painter. If the thickness of the protective coat were to become non-uniform, this would be undesirable because it could lead to discoloration of the plated parts and a decrease in the reflectance of the reflector.

One possible way to control the film thickness of the protective coat is to perform contact measurement using a film thickness meter (eddy current method, ultrasonic method, etc.), but it is not practical due to the following problems. Not the point.

■ Since it is necessary to measure the whole part one by one, it is very time-consuming and there are problems with the detection accuracy and measurement efficiency of defective parts.

■ The thickness of the paint film can only be measured after the paint film has hardened, and it is not possible to check for variations in film thickness at the time of painting.

In view of the above circumstances, the present invention is a coating composition that forms a transparent coating film, but because it is colored at the time of coating, it is difficult to check the film thickness by visual inspection or the like.

An object of the present invention is to provide a new coating composition that can be painted while maintaining the same properties.

[Failure to solve the problem]

In order to solve the above-mentioned problems, the present invention provides a coating composition that contains a colored substance and is colored at the time of coating. It is designed to form a film.

[For production]

Since the coating composition according to the present invention is colored and contains a coloring substance, it is possible to apply the coating while checking the film thickness by checking the color shading of the coating composition on the object to be coated. can. In step 2, this colored substance turns colorless or disappears from the coating film after painting, so that a colorless and transparent coating film is ultimately formed.

〔Example〕

First, the coloring substance contained in the coating composition according to the present invention will be explained. This colored substance is not particularly limited as long as it ultimately turns colorless or disappears from the coating film after coating, and is capable of forming a transparent coating film. For example, specifically, it can be classified into the following types.

(A) A substance that is colored at room temperature, but turns colorless and transparent at high temperatures (the temperature at which paint bakes), and then remains that way even when the temperature returns to room temperature (an irreversible change). Or something that changes irreversibly from colored to colorless over time.

(Bl) When the paint film is cured after painting, it decomposes, evaporates (volatizes), or evaporates, and disappears from the cured paint film.

(0) Something that becomes colorless and transparent due to oxidation or reduction reactions.

(D) Low boiling point colored solvent.

Each of the above types will be explained in more detail below. First, the above (N type) includes, for example, a combination of an indicator that develops color under acidity and an acidic reagent (such as hydrochloric acid) that evaporates when heated. This indicator is an acid-base indicator that has a color change region in the acidic region. and
Acidic colors are colored.

Near neutrality, it is colorless (for example, pentamethoxy red, hexano[xy red, etc.). If both of the above are added to a paint, an acidic colored paint is prepared, and the acidic color of the indicator is abraded during painting, resulting in coloring. but,
When the acidic reagent is evaporated by heating or the like, the acidic color of the indicator disappears and a colorless neutral color is formed, so that the finished coating film becomes colorless and transparent. Conversely, it is also possible to use an indicator that develops color under alkalinity in combination with an alkaline reagent (for example, aqueous ammonia).

In this case, the basic color of the indicator is colored.

It is an acid-base indicator that is colorless as a neutral color and has a color change region in an alkaline region (for example, phenolphthalein, O-cresol phthalein, thymol phthalein, etc.).

Next, the above (9) Ri-ib is a colored compound that is stable at room temperature, such as carminic acid, 1,2-naphthoquinone, and O-benzoquinone, but decomposes at high temperatures and becomes colorless and transparent. There are several things that can be mentioned. Alternatively, it may be a colored compound that decomposes over time without being affected by temperature changes.

The above (type a includes, for example, oxidation (or reduction)
Examples include a combination of an indicator that becomes colorless (oxidation-reduction indicator) when heated, and a reagent that becomes an oxidizing agent (or reducing agent) when heated or the like. When both are added to the paint, the color of the indicator disappears due to the action of the oxidizing agent or reducing agent during baking. Such indicators include tris(dipyridyl)fi(II) chloride 2 methylene blue;
Examples include diphenylamine.

Furthermore, examples of the above type include 2-aminothiophene (boiling point: 62°C), N-nitroso-N-methylurethane (boiling point: 65 to 65.5°C), and the like. If these colored low boiling point solvents are added, they will evaporate after coating and a transparent coating film will be obtained.

Note that the colored substances used in this invention include the above (2) to
It goes without saying that it is not limited to ■). for example,
Colored complexes, double salts, molecular compounds, etc. are formed in paints, but after painting, decomposition and dissociation occur over time or by means of heating, cooling, etc. It may be a compound that becomes colorless and transparent due to a change in the electronic configuration of the metal ion, and it is also possible to use a metal indicator.Also, the concept of coloration includes the degree to which the presence of the substance causes 6gLH. This includes those that are cloudy.

There are no particular limitations on the amount of the above-mentioned coloring substances added, but coloring substances that remain in the paint film even after the paint is baked (
For example, in the case of (2) and (a) above, it is preferable to keep the addition amount to a minimum enough to control the film thickness during coating. The resin component) and the solvent are not particularly limited, and any type can be used. For example, there are coatings in which thermosetting, thermoplastic, photocuring, or oxidation-curing resins are the main elements for forming coatings, and various additives and/or solvents are added as necessary. , which can take any form such as organic solvent type, water dispersion type, aqueous solution type, high solid type, powder type, etc., depending on the method of use. Furthermore, the coating composition according to the present invention can be used on objects to be coated made of any materials such as metal, plastic, paper, and wood.

Next, more detailed examples will be explained in "Examples" together with comparative examples.

Example and Comparative Example - 1 Lid L Mouth color Oval) The coating composition of the example was coated with the following 0 in a predetermined amount (see Table 1).
Any one of No. 1 to C3 was added, and no addition was made to the comparative example.

C1: N-Nitroso-N-methylurethane (manufactured by Hanui Chemical ■, special grade) C2: Carminic acid (manufactured by H, same as above, special grade) C3: Bentamethoxyrefed (manufactured by Tokyo Kasei Kogyo ■, special grade) ■ Koryo Sarajitsu Using commercially available paints P1 or P2 below, each was made into a net as follows.

Pl: Epoxy resin paint (Fastite 14ON manufactured by Daiyo Kagaku Kogyo ■) * Diluted with special thinner, 10 to 13
The viscosity was adjusted so that it was within seconds. Thereafter, the coloring agents shown in Table 1 were added and thoroughly stirred to obtain a coating composition.

P2: Organic silicate paint (Glaska 90-A and -B manufactured by Japan Synthetic Rubber) *2
Because it is a liquid paint, the glass force is 90-A and the glass force is 90
-B was mixed at a ratio of 3:1 and left for 4 hours. Thereafter, the colorant shown in Table 1 was added and stirred to form a coating composition. However, if the colorant is the above C3 (benchmethoxylenod), after adding C3, add hydrochloric acid. pl(
Adjusted to 3.

■ A coated board was made by plating a steel plate (300+ m in length and width, 2 m in thickness) with copper, and then plating it with nickel.

■ Use a spray gun to apply one coat of the above paint to a film thickness of 10
It was coated on the above substrate so that the thickness was .mu.m. At this time, the applied weight of the paint was measured by a gravimetric method, and the coating was performed while checking the coating film thickness.

(2) Baking (NJ firing) was performed using a far-infrared furnace at 150°C for 20 minutes when the paint was Pi (Fastite), and at 180°C for 20 minutes when the paint was P2 (Glass Power).

A painted board (300 m in length and width) was divided into 25 square sections of the same size, 60 m in length and width, and the film thickness of each section was measured with an electromagnetic film thickness meter (5M-100 manufactured by Sancora Electronic Research Institute), and the average value was determined. and the standard deviation was calculated.

(a) After applying a predetermined weight of the paint composition to the substrate,
The coloring state of the coating film was evaluated visually.

(tsu) 1 meal L (t3 linit (2qλ2zshiru)
Colored state of the paint film after baking under specified conditions.

was visually evaluated.

The above results are also shown in Table 1.

As shown in Table 1, in the coating compositions of Examples in which colorants 01 to C3 were added, it was possible to control the film thickness by visual observation at the time of coating. As a result, it was possible to apply a uniform coating without any unevenness, and the film thickness measurement results after actual baking confirmed that a uniform coating film was obtained with little variation in film thickness. .

〔Effect of the invention〕

The coating composition according to the present invention is characterized in that although it forms a transparent coating film, it is colored at the time of coating, so coating can be performed while controlling the thickness of the coating film, making it more A uniform transparent coating will be formed. Therefore, when this coating composition is used to protect lighting equipment parts, for example, it becomes possible to easily form a uniform transparent protective film without impairing the properties of those products.

Agent: Patent Attorney Takehiko Matsumoto

Claims (1)

[Claims] 1. A coating composition that forms a transparent coating film, which contains a colored substance that is colored at the time of coating, and that the colored substance turns colorless or disappears from the coating film after coating.
A coating composition characterized in that it forms a transparent coating film.