JPS5914109B2 - Manufacturing method for products with glassy coating - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to a method of manufacturing a product having a vitreous coating.

Products with vitreous coatings have hitherto been manufactured in the following manner.

That is, they were manufactured by applying an aqueous alkali silicate solution to the surface of the material, drying it, and baking it to form a glassy film based on the alkali silicate on the surface of the material. The vitrified coating of the product made from the glassy coating obtained in this manner has high hardness, and also has high water resistance, acid resistance, and alkali resistance when subjected to sufficient heat treatment. However, in this glassy film, the alkali metals in the film react with carbon dioxide gas and sulfuric acid gas in the atmosphere over time, become water-soluble components, migrate to the surface, dry, and precipitate as crystals5. Therefore, effloretscens (
There was a problem with the occurrence of efflorescence. In order to avoid this, after forming a glassy film on the material,
A method of immersing the film in a dilute aqueous solution of nitric acid, sulfuric acid, phosphoric acid, etc. for a short period of time to completely remove the alkali metal in the film10 has been carried out. In this case, in order to effectively prevent the occurrence of efflorescence, it is necessary to increase the concentration of the aqueous solution of these acids, raise the temperature of the solution, and immerse the material with the glassy film therein for a relatively long time. There is. However, when the vitreous film was heated in this way, the glassy film itself was dissolved in the acid aqueous solution, resulting in a problem that the strength of the glassy film was reduced. This invention was made in view of these circumstances, and involves applying an aqueous alkali silicate solution to the surface of the material, drying it for 20 minutes to form an alkali silicate film, and baking this alkali silicate film onto the material surface. A method for producing a product having a vitreous film by forming a vitreous film, wherein the material at the stage where the vitreous film is formed is moistened with a moisture-rich material containing at least one of carbon dioxide gas and 25 nitrogen dioxide gas. The gist of this method is to leave it in a hot atmosphere and then wash it with water.

That is, the present invention allows a material in which an alkali silicate film has been formed or a material in which a glassy film has been formed 30 to be left in a humid atmosphere containing carbon dioxide gas and nitrogen dioxide gas. , the alkali metal in the film is reacted with the above gas, and the reaction products (nitrates, carbonates, etc.) are transferred to the film by moisture to forcibly generate Efroretz sense, which is then removed by washing with water. By this, the alkali metals in the film are removed and the generation of efflorescence due to aging of the glassy film is effectively prevented.
This is to prevent A-cooling.

In this way, since the present invention does not use a conventional acid aqueous solution for treatment, there is no decrease in the strength of the glassy coating. Next, this invention will be explained in detail. This invention uses an aqueous alkali silicate solution for film formation.

Examples of the alkali silicate include sodium silicate, hydrium silicate, and lithium silicate. Among them, sodium silicate is often used. Sodium silicate is commonly called water glass and has the general formula Na, O.
It has 1 NSiO2 and can be divided into the following depending on the number of n. N2 (No. 1 water glass), n-2.5 (No. 2 water glass), n=3 (No. 3 water glass), n=4 (No. 4 water glass). In addition, lithium silicate has the general formula 1,120-N
Having SiO2, potassium silicate has the general formula K2O-N
It has siO2. Examples of materials to which the aqueous alkali silicate solution is applied include, but are not limited to, metal plates such as aluminum plates, glass plates, cement plates, and plastic plates. Any material may be used as long as it can withstand the heat during heat treatment. An aqueous alkali silicate solution is applied to such materials.

The method of application does not matter. The material may be immersed in an aqueous alkali silicate solution, or the aqueous alkali silicate solution may be sprayed onto the material. In this case, the concentration of the aqueous alkali silicic acid solution is adjusted according to the required thickness of the vitreous film, but in general, if the concentration is higher than 30% by weight (hereinafter abbreviated as "%"), it will not be possible to immerse it. As a result, the thickness of the resulting film becomes too large, causing foaming or clutching during drying and baking, making it difficult to form a good glassy film.
A thick glassy film is not necessary to ensure corrosion resistance, chemical resistance, etc. Generally, a film thickness of about 5 microns or less is sufficient, preferably from 0.5 to 2 microns. If such a glassy film is to be formed by one immersion, the concentration of the aqueous alkali silicate solution may be adjusted to 15% or less. However, it is more preferable to further dilute this, immerse it once, dry it, and then immerse it another time, because the occurrence of pinholes, etc. can be significantly reduced. After the aqueous alkali silicate solution is applied to the material in this way, it is dried.

The purpose of this drying is to evaporate the moisture in the aqueous alkali silicate solution and form an alkali silicate film on the surface of the material, and it is preferably carried out slowly at a temperature of about 150 to 160°C. This drying forms an alkali silicate film on the surface of the material. Next, this is baked.

This baking process is usually performed at a temperature higher than the drying temperature.
This process is carried out at a temperature of up to 00°C, thereby evaporating a small amount of water in the alkali silicate film, vitrifying the alkali silicate film, and baking it onto the material as a glass film to create a product with a glass film. This is the process of In the present invention, the material on which the glassy film has been formed is left in a humid atmosphere containing carbon dioxide gas, nitrogen dioxide gas alone or in a mixture, and an alkali metal carbonate is formed on the film. The alkali metals in the film are removed by forcibly generating efflorescence consisting of nitrates and washing away the efflorescence products with water.

In this case, the gas concentration is 0.01 to 5%, and the temperature is room temperature to 5%.
0℃, humidity is 800t) RH or higher, standing time is 1 to 10
From the viewpoint of effectiveness, it is most preferable to set the time. It is up to you whether to perform the above-mentioned dealkali metal treatment on the material at the stage where the glassy film has been formed, but in terms of effectiveness, it is more effective to perform the dealkali metal treatment on the former than on the latter. be.

When the material on which the alkali silicate film has been formed is subjected to dealkali metal treatment, it is subsequently subjected to baking treatment. In the product having a glassy film obtained in this manner, the alkali metal that causes efflorescence is removed from the film, so that the occurrence of efflorescence over time is prevented.

Next, examples will be described together with comparative examples.

Example 1 Temporary aluminum was prepared as the material.

This aluminum plate is a high-purity aluminum plate specified by JIS (manufactured by Sumitomo Light Metal Co., Ltd., AlO7OP, Ae purity of 97% or more, plate thickness 1?), hub-polished, dealkalized with a neutral detergent, and chemically polished. Bath (phosphoric acid 80% by volume,
5% by volume of acetic acid, 15% by volume of nitric acid, liquid temperature 100'C)
It was immersed for 5 seconds, washed with 10 volume 0/) HNO3, washed with water, and dried to form a mirror surface. This mirror surface is extremely active and requires immediate application of an aqueous alkali silicate solution. Next, we put this aluminum plate into water glass No. 3 (
The sample was immersed in a modified sodium silicate aqueous solution prepared by dissolving 0.99% sodium pyrophosphate in 15% aqueous solution 1009 (manufactured by Nihon Kagaku Kogyo Co., Ltd.). Finally, heat this at 90-95°C for 30 minutes.
After drying at 130-14°C for 10 minutes, the film was baked at 260-280°C for 20 minutes. This is 25
It was placed in a sealed box filled with saturated steam at ~30°C, and carbon dioxide was introduced so that the carbon dioxide concentration in the box was 0.5%. After turning on the gas and leaving it for 5 hours, remove the aluminum plate from the box and heat it for 80 minutes.
~ 9 'C was dried in an open oven, and the white crystals precipitated on the surface were removed by washing with water. This is designated as sample (4). Comparative Example 1 An aluminum plate treated with water glass and dried in the same manner as in Example 1 was immersed in an aqueous nitric acid solution with a concentration of 10% at a temperature of 60° C. for 1 minute to perform dealkali metal treatment.

This is designated as sample (8). These samples (A), (B)
A forced efflorescence test was conducted on the sample, with one cycle of leaving it in a 500PF1 sulfur dioxide gas atmosphere for one day and leaving it in an open air at 50°C for one hour.

The results are as follows. Sample (IX): Almost no efflorescence observed even after 10 cycles Sample (B): White after 2 cycles? Note that these (A) and 03) had good acid resistance and alkali resistance.

That is, 100 tons of hydrochloric acid and 10% caustic soda aqueous solution were dropped onto the surface of the sample, the sample was covered and left for 30 minutes, and then washed with water and examined for residue, but no abnormalities were found. Example 2 Diameter 10? of copper pipe with potassium silicate (K2O.3
1 at 80-90℃ by immersing it in a 15% aqueous solution of Si02).
After drying for 15 minutes at 130-140 C for 5 minutes,
Furthermore, it was immersed in a 5% potassium silicate (K2O.3Si02) aqueous solution for 15 minutes at 80 to 90°C for 130 to 14 minutes.
It was dried at 0°C for 15 minutes and baked at 280-290°C for 10 minutes.

Then, this product was subjected to dealkali metal treatment in the same manner as in Example 1 using nitrogen dioxide gas instead of carbon dioxide gas. This is designated as sample (C). Comparative example 2 Example 2
In the same manner as above, copper' Mipe treated with an aqueous potassium silicate solution and dried was immersed in sulfuric acid having a concentration of 15(f) at a temperature of 50° C. for 1 minute to carry out dealkali metal treatment.

This is the sample (self). These samples (C), (D)
When a forced efflorescence test similar to that in Example 1 was conducted for Sample (C), precipitation of cloudy efflorescence was observed in the 3rd cycle, but in Sample (C) after 15 cycles. There were no abnormalities until then.

Claims (1)

[Claims] 1. Apply an aqueous alkali silicate solution to the surface of the material and dry it to form an alkali silicate film, and then bake this alkali silicate film onto the material to form a vitreous film on the material surface to create a product with a vitreous film. A method for producing a vitreous material, the method comprising: leaving a material on which a vitreous film has been formed in a humid atmosphere containing at least one of carbon dioxide gas and nitrogen dioxide gas, and then washing the material with water. A method for manufacturing products with a film.