JPS63128082A - Coating composition - Google Patents

Abstract

PURPOSE:To provide the titled composition composed of a mixture of an acidic aqueous colloidal silica and a non-aqueous colloidal silica, a specific organohydroxysilane and a mixed solvent comprising water and a lower alcohol, etc., and capable of giving a protecting coating film having excellent heat- resistance and weather-resistance. CONSTITUTION:The objective composition having a pH of 3 and a solid content of 5-30wt% is composed of (A) a mixture of (i) an acidic aqueous colloidal silica and (ii) a non-aqueous colloidal silica, (B) a solid component consisting of an organohydroxysilane (or its partial condensate) of formula II produced by hydrolyzing an organoalkoxysilane of formula I (R<1> is 1-3C alkyl, vinyl, etc.; R<2> is 1-3C alkyl or aryl) in a dispersion of the component A and (C) a mixed solvent comprising water and a lower aliphatic alcohol and/or glycol derivative. The amounts of the components A and B are 40-70% and 30-60%, respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a coating composition, and in particular, it can be applied to base materials such as metal and glass to improve heat resistance, corrosion resistance,
The present invention relates to a coating composition that provides a transparent coating with excellent hardness, weather resistance, etc., and is useful for protecting these substrates.

[Prior art and problems] In recent years, there has been a demand for heat-resistant transparent coating materials, especially in the electrical appliance and electronics industries. Covering materials include: In addition to heat resistance, these coating materials are required to have corrosion resistance, scratch resistance, weather resistance, and other properties.

In order to meet the requirements mentioned in Section L, organic paints such as silicone resins and fluororesins, and inorganic paints such as alkali metal silicate materials have been considered, but none have yet fully met the required performance. In other words, the former has shortcomings in heat resistance, weather resistance, corrosion resistance, and scratch resistance, and the latter has defects in the coating as the alkali remaining in the coating reacts with carbon dioxide gas in the air over time and turns into carbonate. It has the drawbacks of a so-called efflorescence phenomenon that precipitates on the surface and poor painting workability.

In addition, silica-organosilane-based wear-resistant coating compositions are being studied mainly as coating materials for plastic surfaces.

The purpose of these coating materials is to increase the hardness of the plastic surface and improve its scratch resistance, but their performance is not sufficient as a heat-resistant coating.For example, if these coating materials are applied to metal, etc. When heated at a temperature of 100 mL, the coating tends to crack, and its heat resistance is problematic. In addition, these coating materials have drawbacks such as poor storage stability and poor painting workability, and although various studies have been conducted to improve these drawbacks, a sufficient coating material has not yet been developed. is the current situation.

For example, Japanese Patent Publication No. 52-39691, Japanese Patent Publication No. 54-
Silica-organosilane-based wear-resistant coating compositions are disclosed in JP-A No. 87736 and Japanese Patent Application Laid-Open No. 55-94971. However, the heat resistance of the coatings obtained from these compositions is not sufficient, and the coatings tend to crack when heated, and since the compositions contain a large amount of water derived from aqueous colloidal silica, they are difficult to coat. It had the drawbacks of poor workability and poor storage stability.

In addition, Japanese Patent Application Laid-Open No. 1989-1999 was developed with the aim of eliminating these drawbacks.
In Japanese Patent No. 9-68377, an attempt has been made to adjust the water content by azeotropic distillation of the water in the composition with alcohol or the like to improve coating workability. The heat resistance of the coating and the storage stability of the composition are still insufficient.

In particular, the use of kM-based colloidal silica reduces the storage stability of the composition and the heat resistance of the coating.

[Means for Solving the Problems] The purpose of the present invention is to eliminate the above-mentioned drawbacks, and to provide a product that has excellent storage stability and painting workability, and is transparent and has excellent heat resistance, corrosion resistance, scratch resistance, and weather resistance. An object of the present invention is to provide a coating composition having the following properties.

That is, according to the present invention.

(A) A mixture of acidic aqueous colloidal silica and non-aqueous colloidal silica.

(B) Formula R1Si(OR2)3 (wherein R1 is an alkyl group having 1 to 3 carbon atoms, a vinyl group, a phenyl group, 3.4
- Represents a group selected from the group consisting of epoxycyclohexylethyl group, γ-glycidoxypropyl group, γ-methacryloxypropyl group, γ-mercaptopropyl group, and γ-chloropropyl group, and R2 has 1 carbon atom. Formula R1Si(OH)3 obtained by hydrolyzing an organoalkoxysilane represented by ) representing ~3 alkyl or aryl groups in a mixed dispersion of acidic aqueous colloidal silica and non-aqueous colloidal silica A solid content consisting of an organohydroxysilane or a partial condensate thereof represented by

(C) consists of a mixed solvent of at least one selected from the group consisting of lower aliphatic alcohols and glycol derivatives and water, has a pH of 3 to 6, a solid content of 5 to 30% by weight, and has a solid content composition (A) 40-70% by weight, (B) 30-6
A coating composition is provided, characterized in that it contains 0% by weight.

The coating composition of the present invention is prepared by hydrolyzing an organoalkoxysilane represented by the formula R1Si(OR2)3 or a mixture of these organoalkoxysilanes in a mixed dispersion of acidic aqueous colloidal silica and non-aqueous colloidal silica. Manufactured by.

The colloidal silica as component (A) used in the present invention is used as a mixed dispersion of aqueous colloidal silica and non-aqueous colloidal silica. The composition of the mixed dispersion is 10
~80% by weight of aqueous colloidal silica and 20-90% by weight of non-aqueous colloidal silica are preferred; if the composition of aqueous colloidal silica is less than 10% by weight, coating properties will be poor; if it exceeds 80% by weight, The storage stability of the coating composition deteriorates. As a result of various studies on the coating workability and storage stability of silica-organosilane coating compositions, the inventors have found that the water content in the composition is the problem. We found that this is a related factor. That is, when the water content in the composition exceeded about 40% by weight, the coating workability and storage stability of the composition decreased. Therefore, in the present invention, the water content in the composition is adjusted to less than 40% by weight by using aqueous colloidal silica and non-aqueous colloidal silica together.

The average particle size of colloidal silica as component (A) is 5 to 150.
It is preferably mg, more preferably 5 to 30 mg.
mg. If the average particle size of silica is less than 5 tags, it has little practical meaning, while if it exceeds 150 mIL, a transparent and heat-resistant coating cannot be obtained.

The pH of the colloidal silica dispersion as component (A) should be 2.
It is preferable to have an acidity of 4 to 4.

In addition, the silica content in the colloidal silica dispersion is 10 to
Preferably it is 50% by weight.

The above-mentioned colloidal silica dispersions are well known in the art and are commercially available as aqueous colloidal silica in which high molecular weight silicic acid anhydride is dispersed in water and non-aqueous colloidal silica in which alcoholic solvent is dispersed. be.

The organohydroxysilane represented by the formula R1Si(OH)3 or a partial condensate thereof, which is the CB) component of the present invention, is
Corresponding formula R1Si(OR2) (wherein R1 is an alkyl group having 1 to 3 carbon atoms, a vinyl group, a phenyl group, 3
．． 4-! Ho + dicyclohexylethyl group, γ-crisitoxypropyl group, γ-methacryloxypropyl group,
Represents a group selected from the group consisting of γ-mercaptopropyl group and γ-chloropropyl group, and R2 has 1 to 1 carbon atoms.
It is produced by hydrolyzing an organoalkoxysilane (representing three alkyl or aryl groups) in an acidic colloidal silica dispersion. Methyltrihydroxysilane is most preferred in view of the heat resistance, hardness, and economical efficiency of the coating, but other organoalkoxysilanes may be mixed in small amounts.

In the present invention, the organoalkoxysilane described above is hydrolyzed in an acidic colloidal silica dispersion containing a mixture of aqueous colloidal silica and non-aqueous colloidal silica, and substantially R'5i (OHh and its partial condensate) is dissolved. A uniform dispersion of colloidal silica is obtained, and the method for obtaining the coating composition of the present invention will be described in more detail.First, aqueous colloidal silica and non-aqueous colloidal silica are placed in a reaction vessel equipped with a stirrer. Next, the organoalkoxysilane is added, the temperature of the mixture is maintained at 10-80°C for about 1-5 hours, and the reaction is allowed to proceed under stirring. A portion of the non-aqueous colloidal silica may also be added after the reaction is complete. Also, when hydrolyzing organoalkoxysilane, a small amount of acid may or may not be added as a catalyst.

The dispersion obtained as a result of the reaction contains RIJi(OH)3 or its partial condensate and colloidal silica as solid contents, but the content ratio of each is R1Si(OH)3 or its partial condensate and colloidal silica.
Preferably, h or a partial condensate thereof is 30 to 60% by weight of the total, and colloidal silica is 40 to 70% by weight. If the content of colloidal silica is less than 40% by weight, a heat-resistant coating cannot be obtained. However, if it exceeds 70% by weight, coating properties will deteriorate.

(C) for adjusting the solids content of the coating composition of the present invention;
At least one component selected from the group consisting of lower aliphatic alcohols and glycol derivatives is added to the reaction mixture. These solvents may be added in advance before the reaction or may be added after the reaction. Examples of lower aliphatic alcohols used in the present invention include methanol, ethanol, propatool, inpropatool, n-
Butanol and t-butanol, etc., and glycol derivatives include ethylene glycol, propylene glycol, butylene gellicol, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, acetic acid ethylene glycol monoethyl ether, etc.0 The coating of the present invention The solid content of the composition for use is adjusted to 5 to 30% by weight by adding the above-mentioned solvent. If the solid content is less than 5% by weight or more than 30% by weight, it will be difficult to control the film thickness and the coating workability will be poor. The addition of these solvents not only adjusts the solid content and widens the range of coating workability, but also
This improves the storage stability of the coating composition.

The pH of the coating composition of the present invention is preferably 3-6, more preferably 4-5. When the pH is less than 3 and more than 6, the storage stability of the coating composition deteriorates, and
The heat resistance of the coating decreases.

The coating composition of the present invention has a storage stability of about 6 months or more at room temperature. The storage stability of the silica-organosilane coating compositions studied so far is about one month at room temperature, and the storage stability has been significantly improved by the present invention.

The coating composition of the present invention may further contain additives such as a smoothing agent, thickener, and antifoaming agent, and coloring agents such as pigments and dyes, as required. The coating composition of the present invention can be applied onto a substrate and cured by the following methods. First, as a coating method, ordinary coating methods such as spray coating, dipping, and flow coating can be employed.

The film thickness is preferably 1 to 20 g, more preferably 2 to 1 g.
It is 0p. Next, by heating at 100 to 200° C. for 10 to 30 minutes, a film with good adhesion to the substrate can be obtained. As described above, the coating composition of the present invention has extremely good coating workability, and coating methods for general organic paints can be used as is. The coating of silica-organosilane coating compositions that have been studied so far requires adjustment of the coating atmosphere, that is, the room temperature and humidity of the coating room, and the curing time of the coating is long, approximately 1 to 4 hours. Although there was a drawback that painting workability was poor, the painting workability was improved by the present invention.

The most suitable substrates to which the coating composition of the present invention can be applied are metal materials such as iron, stainless steel, aluminum, copper, and brass, and inorganic materials such as glass and ceramics. It has extremely good properties, and does not require any primer treatment on the surface of the substrate, and its adhesion to the substrate is superior to that of general organic paints. Furthermore, it is possible to coat vapor deposited films such as metals and ceramics, metal plating films, and even organic materials such as plastics, and the range of substrates to which the coating composition of the present invention can be applied is extremely wide.

[Effects of the Invention] As is clear from the Examples shown below, the coating composition of the present invention has excellent storage stability and coating workability, and the film thereof has excellent performance. The film is transparent and has heat resistance of about 200 to 500℃ or more, and does not generate smoke, which is a problem with organic paints.It also has excellent performance other than heat resistance, especially weather resistance, corrosion resistance, scratch resistance, It has excellent solvent resistance and is suitable for surface protection coating of substrates made of various materials.

[Examples] In order to enable a more concrete understanding of the practice of the present invention, examples are shown below as illustrations.

It should be noted that the following examples do not limit the present invention as described in the claims.

Example 1 250 g of an acidic aqueous colloidal silica dispersion (average particle size lO~20 rtrJL, solids content 20%) and 333 g of a methanolic colloidal silica dispersion (average particle size lO
After mixing 145 g of methyltrimethoxysilane (145 g of methyltrimethoxysilane) and stirring at room temperature for about 5 hours to complete hydrolysis. The resulting product was approximately aθ% solids, and isopropyl alcohol was added to obtain coating composition No. 1 with a solids content of 20% and pi(5).

Example 2 Coating composition No. 2 with a solid content of 20% and a pH of 5 was obtained in the same manner as in Example 1 except for using 375 g of an acidic aqueous colloidal silica dispersion and 250 g of a methanolic colloidal silica dispersion. Ta.

Comparative Example 1 Acidic aqueous colloidal silica dispersion (average particle size lO~2
0 rsg, solid content 20%) While cooling 750 g to 10° C. or lower, 145 g of methyltrimethoxysilane to which 5 g of glacial acetic acid had been added was added, and hydrolysis was completed in 5 days. The resulting product was approximately 25% solids with addition of isopropyl alcohol to 20% solids.

A coating composition N083 having a pH of 2 to 3 was obtained.

Comparative Example 2 Basic aqueous colloidal silica dispersion (average particle size lO~2
While cooling 5QOg to 10° C. or lower, 145 g of methyltrimethoxysilane to which 3.6 g of glacial acetic acid had been added was added, and the hydrolysis was completed in 5 days. Acetic acid was added to the obtained product to adjust pi (5), and isopropyl alcohol was further added to obtain coating composition N014 with a solid content of 20%.

Evaluation method: The coating composition, which had been stored in a sealed container at 25°C, was spray coated on an aluminum plate every 10 days at 160°C.

After heating for 20 minutes, film-forming properties were examined.

Spray coat the coating composition on an aluminum plate,
Heated at 60℃ for 20 minutes to obtain a film thickness of approximately 8 tiles.
The film was allowed to stand at 0°C, 300°C, and 500°C, and changes in the appearance of the film were observed after 24 hours.

A film was prepared in the same manner as in 181 Heat Resistance, and after being left at 500°C for 24 hours, it was poured into water at 20°C, and changes in the appearance of the film were observed.

Examples 1-2. The evaluation results of Comparative Examples 1 and 2 are shown in Table 1. In addition, the coating film performance test (JIS
K 5400, etc.) The results are shown in Table 2.

(Margin below)

Claims (4)

[Claims] (1) (A) A mixture of acidic aqueous colloidal silica and non-aqueous colloidal silica, (B) Formula R^1Si(OR^2)_3 (wherein R^1 is an alkyl group having 1 to 3 carbon atoms) group, vinyl group, phenyl group, 3,4-epoxycyclohexylethyl group, γ-glycidoxypropyl group, γ-methacryloxypropyl group, γ-mercaptopropyl group, γ-chloropropyl group R^2 represents an alkyl group or an aryl group having 1 to 3 carbon atoms) in a mixed dispersion of acidic aqueous colloidal silica and non-aqueous colloidal silica. A solid content consisting of an organohydroxysilane represented by the formula R^1Si(OH)_3 obtained by hydrolysis or a partial condensate thereof, and (C) at least one selected from the group consisting of lower aliphatic alcohols and glycol derivatives. It consists of a mixed solvent of seeds and water, has a pH of 3 to 6, a solid content of 5 to 30% by weight, and a solid content of (A) 40 to 70% by weight and (B) 30 to 60% by weight. A coating composition characterized in that: (2) The coating according to claim 1, wherein the composition of component (A) is 10 to 80% by weight of aqueous colloidal silica and 20 to 90% by weight of non-aqueous colloidal silica. Composition. (3) The coating composition according to claim 1, wherein the component (A) is acidic with a pH of 2 to 4. (4) The coating composition according to claim 1, wherein the organohydroxysilane or partial condensate thereof as component (B) is methyltrihydroxysilane or a partial condensate thereof.