JP2584216B2 - Coating composition - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a coating composition, and particularly to a composition such as a metal and a glass, which is applied to a heat-resistant, corrosion-resistant, hardness and weather-resistant material. The present invention relates to a coating composition which provides an excellent and transparent coating and is useful for protecting those bases.

[Related Art and Problems] In recent years, a transparent coating material having heat resistance has been demanded particularly in the electric appliance and electronics industries. For example, there is a transparent covering material used for protecting a reflection plate used in heat equipment such as lighting equipment. These coating materials are required to have properties such as corrosion resistance, scratch resistance, and weather resistance in addition to heat resistance.

In response to the above-mentioned demands, organic paints such as silicone resin and fluororesin and inorganic paints such as alkali metal silicate have been studied, but they have not yet sufficiently satisfied the required performance. In other words, the former has drawbacks in heat resistance, weather resistance, corrosion resistance, and abrasion resistance, and the latter has a problem in that the alkali remaining in the coating reacts with carbon dioxide gas in the air with time to form a carbonate, which precipitates on the coating surface. And there is a disadvantage that the coating workability is poor.

Further, silica-organosilane-based abrasion-resistant coating compositions have been studied mainly as coating materials for plastic surfaces. The purpose of these coating materials is to increase the hardness of the plastic surface and to improve the scratch resistance, and their performance is not sufficient as a heat-resistant coating material. For example, when these coating materials are applied to a metal or the like and heated at a temperature of 200 ° C. or more, cracks are easily generated in the coating, and there is a problem in its heat resistance. Further, these coating materials have drawbacks such as poor storage stability and poor coating workability, and various studies have been made to improve these drawbacks, but a sufficient coating material has not yet been developed. is the current situation.

For example, JP-B-52-39691, JP-A-54-87736
And JP-A-55-94971 disclose silica-organosilane-based abrasion-resistant coating compositions. However, the heat resistance of the coatings obtained from these compositions is not sufficient, and the coatings are easily cracked by heating, and the coating contains a large amount of water derived from aqueous colloidal silica. It had the drawback that the properties were poor and the storage stability was poor.

In addition, Japanese Patent Application Laid-open No.
In JP-A-59-68377, studies have been made to improve the coating workability by adjusting the amount of water by azeotropically distilling off the water in the composition with alcohol or the like, but it is obtained from the composition. The heat resistance of the coating and the storage stability of the composition are not yet sufficient. In particular, the use of basic colloidal silica reduces the storage stability of the composition and the heat resistance of its coating.

[Means for Solving the Problems] An object of the present invention is to solve the above-mentioned drawbacks, to provide excellent storage stability and coating workability, and to provide excellent heat resistance, corrosion resistance, scratch resistance and weather resistance with transparency. An object of the present invention is to provide a coating composition having:

That is, according to the present invention, there is provided (A) a dispersion having a pH of 2 to 4 containing 10 to 50% by weight of silica having an average particle size of 5 to 150 mμ and a solid component composition of 10 to 50%.
A mixed dispersion consisting of 80% by weight of aqueous colloidal silica and 20 to 90% by weight of non-aqueous colloidal silica, (B) a formula CH ₃ Si (OR) _{3 wherein} R is 1 to 3 carbon atoms A methyltrihydroxysilane [CH ₃ S] obtained by hydrolyzing a methylalkoxysilane represented by the formula (A) in the mixed dispersion of the above (A).
i (OH) ₃ ] or a solid condensate thereof; and (C) a mixed solvent of water and at least one selected from the group consisting of lower aliphatic alcohols and glycol derivatives, and having a pH of 3 to 6. The water content is less than 40% by weight, the solid content is 5 to 30% by weight, and the composition of the solid content is (A) 40 to 70% by weight;
(B) A coating composition characterized by being 30 to 60% by weight.

The coating composition of the present invention is prepared by hydrolyzing a methylalkoxysilane represented by the formula CH ₃ Si (OR) ₃ or a mixture of these methylalkoxysilanes in a mixed dispersion of acidic aqueous colloidal silica and non-aqueous colloidal silica. Manufactured by decomposition.

The colloidal silica (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
8080% by weight aqueous colloidal silica and 20-90% by weight non-aqueous colloidal silica. If the composition of the aqueous colloidal silica is less than 10% by weight, the coating properties will be poor, and if it exceeds 80% by weight, the storage stability of the coating composition will be poor. The present inventors have conducted various studies on the coating workability and storage stability of the silica-organosilane-based coating composition, and as a result, have found that the water content in the composition is a factor related to these problems. That is, when the water content in the composition exceeds about 40% by weight, the coating workability and the storage stability of the composition deteriorated. Therefore, in the present invention, the water content in the composition was adjusted to be less than 40% by weight by using both aqueous colloidal silica and non-aqueous colloidal silica.

The average particle size of the colloidal silica of the component (A) is 5 to 150 m.
μ, more preferably 5 to 30 μm. When the average particle size of the silica is less than 5 mμ, the meaning is practically poor. On the other hand, when the average particle size exceeds 150 μm, a transparent and heat-resistant coating cannot be obtained.

If the pH of the colloidal silica dispersion of the component (A) is basic, the storage stability of the coating composition deteriorates,
~ 4 acidic. The silica content in the colloidal silica dispersion is 10 to 50% by weight.

The above-mentioned colloidal silica dispersion is well known in the art, and is commercially available as aqueous colloidal silica in which high molecular weight silicic anhydride is dispersed in water and non-aqueous colloidal silica in which alcoholic solvents are dispersed. is there.

Component (B) is methyl trihydroxy silane [CH ₃ Si (OH) _3] or a partial condensate of the present invention, the corresponding formula CH ₃ Si (OR) (wherein R 1 to 3 carbon atoms Is produced by hydrolyzing a methylalkoxysilane represented by the formula (1) in an acidic colloidal silica dispersion. In the present invention,
By using methyltrihydroxysilane as the component (B), a coating composition excellent in heat resistance, hardness and economy of the coating film can be obtained.

The present invention hydrolyzes the above-mentioned methylalkoxysilane in an acidic colloidal silica dispersion obtained by mixing aqueous colloidal silica and non-aqueous colloidal silica, and substantially comprises
A method for obtaining a uniform dispersion of CH ₃ Si (OH) ₃ and its partial condensate and colloidal silica, and a method for obtaining the coating composition of the present invention will be described in more detail. First, an aqueous colloidal silica and a non-aqueous colloidal silica are charged to a reaction vessel with a stirrer, and then methylalkoxysilane is added. The temperature of the mixture is maintained at 10 to 80 ° C. for about 1 to 5 hours, and the mixture is stirred. Let react. Incidentally, a part of the non-aqueous colloidal silica may be added after the completion of the reaction.

The dispersion obtained as a result of the reaction contains CH ₃ Si (OH) ₃ or a condensate of the portion and colloidal silica as solid components, and the content of each is CH ₃ Si (OH) _3.
Alternatively, 30 to 60% by weight of the partial condensate thereof and 40 to 70% by weight of the colloidal silica. When the content of the colloidal silica is less than 40% by weight, a heat-resistant coating cannot be obtained, and when the content exceeds 70% by weight, the coating properties deteriorate.

In order to adjust the solid content of the coating composition of the present invention, at least one selected from the group consisting of a lower aliphatic alcohol and a glycol derivative as the component (C) is added to the reaction mixture. These solvents may be added before the reaction or before the reaction. The lower aliphatic alcohol used in the present invention includes methanol, ethanol, propanol, isopropanol, n-butanol and t-butanol, and the glycol derivatives include ethylene glycol, propylene glycol, butylene glycol, and ethylene glycol monoethyl ether. , Ethylene glycol monobutyl ether, and ethylene glycol monoethyl ether acetate. The solid content of the coating composition of the present invention 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 is difficult to control the film thickness, and the coating workability deteriorates. The addition of these solvents controls the solid content to broaden the range of coating workability and improves the storage stability of the coating composition.

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

The storage stability of the coating composition of the present invention is at least about 6 months at room temperature. The storage stability of the silica-organosilane-based coating composition studied so far is about one month at room temperature, and the storage stability was greatly improved by the present invention.

The coating composition of the present invention further optionally a leveling agent,
It is possible to add additives such as thickeners and defoamers, and coloring agents such as pigments and dyes. The coating composition of the present invention is applied to a substrate and cured as described below. First, as a coating method, a normal coating method such as spray coating, dipping, and flow coating can be employed. The film thickness is preferably from 1 to 20 µ, more preferably from 2 to 10 µ. Then, by heating at 100 to 200 ° C. for 10 to 30 minutes, a coating having good adhesion to the substrate can be obtained. As described above, the coating workability of the coating composition of the present invention is extremely good, and a general method for coating an organic paint can be used as it is.
In the coating of the silica-organosilane coating composition studied so far, the coating atmosphere, that is, the room temperature and humidity of the coating room must be adjusted, and the curing time of the coating is also about 1 to 4 times.
There was a drawback that the coating workability was poor such as long time, but the present invention improved the coating workability.

As a substrate on which the coating composition of the present invention can be applied, metal materials such as iron, stainless steel, aluminum, copper and brass and inorganic materials such as glass and ceramics are most suitable. Is very good, and no primer treatment or the like is required on the surface of the substrate, and the adhesion of the substrate is superior to that of a general organic paint. In addition, it is also possible to apply a coating film of a metal or ceramics, or a metal plating film, or an organic material such as a plastic, 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 following examples, the coating composition of the present invention has excellent storage stability and coating workability, and the coating has excellent performance. The coating is transparent, has a heat resistance of about 200 to 500 ° C. or higher, and has no smoke emission which is a problem with organic paints. Furthermore, it has excellent properties other than heat resistance, and particularly has excellent weather resistance, corrosion resistance, scratch resistance, solvent resistance, and the like, and is suitable for substrates made of various materials and for surface protective coating.

[Examples] In order to more specifically understand the practice of the present invention, examples will be described below as examples. It should be noted that the following examples do not limit the present invention described in the claims.

Example 1 250 g of an acidic aqueous colloidal silica dispersion (average particle size of 10
~ 20mμ, solid content 20%) and 333g of methanolic colloidal silica dispersion (average particle size 10-20mμ, solid content 30%), then add 145g of methyltrimethoxysilane and stir at room temperature for about 5 hours. To complete the hydrolysis. The obtained product had a solid content of about 30%, and isopropyl alcohol was added to obtain a coating composition No. 1 having a solid content of 20% and a pH of 5.

Example 2 Example 1 except that 375 g of an acidic aqueous colloidal silica dispersion and 250 g of a methanolic colloidal silica dispersion were used.
In the same manner as in the above, a coating composition No. 2 having a solid content of 20% and a pH of 5 was obtained.

Comparative Example 1 Acidic aqueous colloidal silica dispersion (average particle size of 10 to 20)
While cooling 750 g of m.mu., solid content 20%) to 10 DEG C. or lower, 145 g of methyltrimethoxysilane to which 5 g of glacial acetic acid was added was added, and the hydrolysis was completed in 5 days. The obtained product had a solid content of about 25%, and isopropyl alcohol was added to obtain a coating composition No. 3 having a solid content of 20% and a pH of 2 to 3.

Comparative Example 2 Basic aqueous colloidal silica dispersion (average particle size of 10 to 20)
mμ, solid content 30%)
145 g of methyltrimethoxysilane to which g of glacial acetic acid was added was added, and the hydrolysis was completed in 5 days. Acetic acid was added to the obtained product to adjust the pH to 5, and isopropyl alcohol was further added to obtain a coating composition No. 4 having a solid content of 20%.

<Evaluation method> Storage stability The coating composition sealed and stored at 25 ° C was spray-coated on an aluminum plate every 10 days, heated at 160 ° C for 20 minutes, and examined for film forming properties.

Spray coat the heat-resistant coating composition on an aluminum plate,
Heated at 160 ° C for 20 minutes to a film thickness of about 8μ
The film was allowed to stand at 0 ° C. and 500 ° C., and changes in the appearance of the film after 24 hours were observed.

Thermal shock resistance Adjust the coating in the same way as heat resistance, and leave it at 500 ° C for 24 hours for 20 hours.
After throwing in water at ℃, the appearance change of the coating was observed.

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

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical indication location C09D 183/06 C09D 183/06 (56) References JP-A-51-2736 (JP, A) Kaisho 53-111336 (JP, A)

Claims (1)

(57) [Claims] (A) silica having an average particle diameter of 5 to 150 mμ
A dispersion having a pH of 2 to 4 containing 50% by weight and having a solid component composition of 10 to 80% by weight of aqueous colloidal silica and 20 to 90% by weight.
(B) a mixed dispersion comprising non-aqueous colloidal silica by weight, represented by the formula: CH ₃ Si (OR) ₃ , wherein R represents an alkyl group or an aryl group having 1 to 3 carbon atoms. Methyl trihydroxysilane [CH ₃ S] obtained by hydrolyzing methyl alkoxysilane in the mixed dispersion of the above (A)
i (OH) ₃ ] or a solid condensate thereof; and (C) a mixed solvent of water and at least one selected from the group consisting of lower aliphatic alcohols and glycol derivatives, and having a pH of 3 to 6. The water content is less than 40% by weight, the solid content is 5 to 30% by weight, and the composition of the solid content is (A) 40 to 70% by weight;
(B) 30 to 60% by weight of a coating composition.