JPH0791110B2 - Method for forming inorganic coating - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming an electrically insulating, corrosion-resistant, chemical-resistant, heat-resistant, and wear-resistant inorganic black or white coating on a heat-resistant substrate.

The inorganic coating according to the present invention is formed by coating, drying and heat treating a heat resistant substrate such as a metal such as stainless steel or iron, or a ceramic such as brick, slate or alumina substrate, and is black or white and dense. Gives a good film. Therefore, the substrate having a coating film obtained by the method of the present invention is extremely useful as a material for roofing materials having a heavy feeling, building materials such as fences, household products such as bath tubs, and electric devices such as microwave ovens. .

[0003]

2. Description of the Related Art Conventionally, an inorganic coating composition containing a hydrolysis / polycondensation reaction product of a silane compound as a main component is applied to a heat-resistant base material, dried, and then heat-treated at room temperature to several hundreds of degrees Celsius to perform inorganic treatment. It is known to use a system coating.

Further, conventionally, in a film using an inorganic coating composition containing a hydrolysis / polycondensation reaction product of a silane compound as a main component, a colored film is obtained by dispersing a coloring pigment in the inorganic coating composition. Although a method has been adopted, when the inorganic coating is a micron-order thin film, a glossy colored coating is obtained because the particle size of the coloring pigment is too large and it is difficult to disperse even if it is small. I couldn't.

[0005]

Therefore, the inventors of the present invention have earnestly studied to provide a method for forming a colored and glossy inorganic coating film without using a coloring pigment, and as a result, hydrolysis and polycondensation of a silane compound have been carried out. After applying an inorganic coating composition containing a reactant as a main component to a heat resistant substrate and drying the composition,
Inorganic coating obtained by heat treatment under specific heat treatment conditions,
The present invention has been completed by finding that it forms an electrically insulating black or white inorganic coating having excellent corrosion resistance, chemical resistance, heat resistance, and abrasion resistance as compared with those obtained by conventional techniques. It is a thing.

[0006]

Means for Solving the Problems That is, the method for forming an inorganic coating of the present invention is a method for hydrolyzing and polycondensing a specific silane compound using a specific acid as a catalyst. It is a gist to apply an inorganic coating composition containing a polycondensate as a main component to a heat resistant substrate, dry it, and then heat-treat it under specific heat treatment conditions.

Many silane compounds are commercially available, but at least two kinds of silane compounds selected from γ-glycidoxypropyltrialkoxysilane, dimethyldialkoxysilane and methyltrialkoxysilane are used. Preferably there is.

That is, γ-glycidoxypropyltrialkoxysilane gives an inorganic coating excellent in adhesion to a substrate and air-drying (natural drying), but the coating has sufficient resistance to boiling water. Although it does not have it, when dimethyldialkoxysilane is blended with it, the water resistance is improved and it becomes sufficiently resistant to boiling water, and methyltrialkoxysilane imparts hardness to the film.

Methoxysilane and ethoxysilane are used as the alkoxy. If these methoxysilanes and ethoxysilanes are the main constituents, silane compounds other than the methoxysilanes and ethoxysilanes can be added. Furthermore, by using phosphoric acid as a hydrolysis / polycondensation catalyst in a mixed solution of silane compounds,
The obtained reaction product has high transparency, and the hardness and boiling water resistance of the coating are improved.

Chemically pure 85% phosphoric acid is preferable as phosphoric acid, but 75%, 89%, 100% phosphoric acid, or 105% to 116% polyphosphoric acid or polyphosphoric acid can also be used. The use of these polyphosphoric acid or diphosphoric acid is also included in the present invention. The ratio of phosphoric acid to the silane compound is 1 to 20 parts by weight, preferably 5 to 15 parts by weight, based on 100 parts by weight of the silane compound.

An inorganic coating composition containing a hydrolysis / polycondensation reaction product of a silane compound as a main component is usually prepared by uniformly mixing a mixture of silane compounds and dissolving water and a catalyst required for hydrolysis . It is obtained by adding to an alcohol solution and reacting at around room temperature. In this case, isopropyl alcohol is preferable as the alcohol.

A heat-resistant substrate is dipped in the inorganic coating composition thus obtained, or the composition is applied to the heat-resistant substrate by a method such as spraying, spin coating or brush coating to obtain 80 to 150. After removing the solvent by drying at ℃, heat treatment at about 400 ℃ or less, preferably 300 ~ 400 ℃ to cure the coating film, then about 600 ℃ or more 1
By heat treatment at 500 ° C. or less, a dense black inorganic coating film is formed.

The principle that a black inorganic coating film is formed is that the phosphoric acid component is incorporated into the network structure of silicon by heat treatment of the above inorganic coating composition at about 400 ° C. or lower, preferably 300 to 400 ° C., For example It becomes a dense hardened film with a bond like that, and the organic component such as -OCH ₃ trapped in this film is carbonized by heat treatment at about 600 ° C or more and 1500 ° C or less, so to speak, in glass. It is considered that the black inorganic coating film is formed in a form in which carbon particles are uniformly dispersed and enclosed. This dense black inorganic coating has a very high heat resistance, and according to experiments, it remains black even when heated up to around 1450 ° C.

However, the black coating is applied at about 1500.degree.
When heated to the above temperature, the phosphoric acid portion decomposes to release oxygen, so that the carbon, which is a black element, is oxidized to become white silica (quartz). This white coating also has corrosion resistance, chemical resistance,
It is a dense inorganic coating that has excellent heat resistance and abrasion resistance, and is electrically insulating, and is extremely useful industrially.

The base material used in the present invention must be a heat-resistant base material that can withstand the above film forming conditions.
For example, stainless steel, metal such as iron, brick,
Examples include ceramics such as slate, alumina substrate, and unglazed.

[0016]

According to the present invention, there is provided a method for forming an electrically insulating, corrosion-resistant, chemical-resistant, heat-resistant, and abrasion-resistant inorganic black or white coating on a heat-resistant substrate. The inorganic coating according to the present invention is formed on a heat resistant substrate such as stainless steel, metal such as iron, brick, slate, ceramics such as alumina substrate by drying, heat treatment to form a black or white dense coating. Since it gives, roof materials with a solid feeling, building materials such as fences,
It is extremely useful as a material for household items such as bath tubs and electrical equipment such as microwave ovens.

[0017]

EXAMPLES The present invention will be described below with reference to examples.
The invention is not limited to the examples.

Example 1 γ-glycidoxypropyltrimethoxysilane 340
g, 330 g of methyltrimethoxysilane and 330 g of dimethyldimethoxysilane were prepared and added to 890 g of isopropyl alcohol in which 50 g of orthophosphoric acid and 60 g of pure water were dissolved, and the mixture was allowed to stand at room temperature for 24 hours to prepare an inorganic coating composition. Got This is applied to SUS430 by dip coating, dried at 80 ° C for 30 minutes, and then at 150 ° C for 30 minutes.
Min, heat treatment was performed at 300 ° C. for 10 minutes and further at 750 ° C. for 5 minutes to form an inorganic black coating film having a thickness of about 1 micron. The obtained coating film was a glossy black coating film, and did not peel off even when the substrate was bent or punched, and showed excellent adhesion. In addition, no change was observed in the coating even after standing in boiling water for 48 hours.

Comparative Example 1 The inorganic coating composition obtained by the same procedure as in Example 1 was similarly dip-coated on SUS430, and then at 3 ° C. at 80 ° C.
After drying for 0 minutes, the temperature is continuously raised to 750 ° C (heating rate 1
0 ° C./minute), leave it at 750 ° C. for 10 minutes, and then
Cooled to form an inorganic black coating. Although this coating was black, it had poor gloss and had poor adhesion to the substrate.

Example 2 500 g of γ-glycidoxypropyltrimethoxysilane
And 500 g of methyltrimethoxysilane were prepared and added to 1000 g of isopropyl alcohol in which 50 g of dephosphoric acid and 50 g of pure water were dissolved.
The mixture was left at room temperature for 24 hours to obtain an inorganic coating composition. Spray this onto a slate plate and apply 6 at 100 ° C.
After drying for 0 minutes, heat treatment was performed at 350 ° C. for 30 minutes, and then the slate plate was red-heated (600 ° C. or higher) with a burner for about 5 minutes to form an inorganic black coating film. The obtained coating film was a glossy black coating film, which was fused and bonded to the base material and showed excellent adhesion without mechanical peeling. Also,
No change was observed in the coating even after standing in boiling water for 24 hours.

Example 3 γ-glycidoxypropyltrimethoxysilane 450
g, methyltrimethoxysilane 450 g, and dimethyldimethoxysilane 100 g were prepared and added to 1000 g of isopropyl alcohol in which 50 g of orthophosphoric acid and 60 g of pure water were dissolved, and the mixture was allowed to stand at room temperature for 24 hours to prepare an inorganic coating composition. Got

After dip-coating this on a unglazed plate, 80 ° C
30 minutes at 150 ° C, 10 minutes at 300 ° C, 750
Heat treatment was performed at 10 ° C. for 10 minutes and at 1650 ° C. for 10 minutes to form an inorganic coating film having a thickness of about 1 micron. The resulting coating was a glossy white coating that strongly bonded to the unglazed substrate, smoothed the unglazed surface and was found useful, for example, as a heat resistant furnace material.

[0023]

Industrial Applicability According to the present invention, there can be provided a method for forming an electrically insulating, corrosion-resistant, chemical-resistant, heat-resistant and abrasion-resistant inorganic black or white coating on a heat-resistant substrate.

According to the present invention, a black or white dense film is formed on a heat resistant substrate such as a metal such as stainless steel or iron, a brick, a slate, or a ceramic such as an alumina substrate by coating, drying or heat treatment. , It is extremely useful as a material for roofing materials with a solid feeling, building materials such as fences, household products such as bath tubs, and electric devices such as microwave ovens.

The black coating can be easily obtained by applying the inorganic coating composition to a heat resistant substrate, drying it, and then heat treating it at about 400 ° C. or lower, and then at about 600 ° C. or higher and lower than 1500 ° C.

The white coating is formed by applying the inorganic coating composition to a heat resistant substrate such as ceramics and drying it.
This is also easily formed by heat treatment at about 600 ° C. or more and less than 1500 ° C., and further final heat treatment at about 1500 ° C. or more, which is particularly useful for modifying and protecting the surface of refractory.

Claims (2)

[Claims] 1. γ-Glycidoxypropyl trialkoxy
Silane, dimethyl dialkoxy silane and methyl tri
At least two silanes selected from alkoxysilanes
Phosphoric acid is used as a catalyst for hydrolysis and polycondensation.
An inorganic coating composition containing a condensate obtained by hydrolysis and polycondensation as a main component is applied to a heat resistant substrate and dried, and then heat treated at about 400 ° C or lower, and then about 600 ° C. A method for forming an inorganic coating film, which comprises performing heat treatment at a temperature of less than 1500 ° C. 2. γ-Glycidoxypropyltrialkoxy
Silane, dimethyl dialkoxy silane and methyl tri
At least two silanes selected from alkoxysilanes
Phosphoric acid is used as a catalyst for hydrolysis and polycondensation.
An inorganic coating composition containing a condensate obtained by hydrolysis and polycondensation as a main component is applied to a heat resistant substrate and dried, and then heat treated at about 400 ° C or lower, and then about 600 ° C. A method for forming an inorganic coating film, which comprises performing heat treatment at a temperature of less than 1500 ° C. and further heat treatment at a temperature of about 1500 ° C. or more.