JPS5913589B2 - Manufacturing method for products with siliceous film - Google Patents

Description

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

Products with highly transparent siliceous films have been manufactured by applying an aqueous solution of silicates such as lithium silicate, potassium silicate, and sodium silicate to the surface of metal or glass substrates. It was manufactured by coating and drying to form a coating film, which was then baked to form a siliceous film based on silicate on the surface of the substrate.

The siliceous film of the product thus obtained has high hardness, and when subjected to sufficient heat treatment, has high water resistance, acid resistance, and alkali resistance. However, this siliceous film has a large number of small holes (pinholes) formed in a distributed manner. This is due to the fact that the behavior of free water in silicate during heat treatment and the dehydration reaction of silicate are not fully understood, and therefore, appropriate measures cannot be taken. In this way, conventional products with siliceous coatings have a large number of small pores distributed in the siliceous coating, so during long-term use, the base material in the pores may be eroded or the small pores may erode. As a result, the transparency of the film was impaired. In addition, the alkali metals in the siliceous film gradually react with carbon dioxide and nitrite gas in the atmosphere, becoming water-soluble components and migrating to the surface, where they dry and crystallize, causing efflorescence (whitening). It was happening. In order to avoid the occurrence of this efflorescence, after forming a siliceous film on the base material, this is immersed for a short time in a dilute aqueous solution of nitric acid, sulfuric acid, hydrochloric acid, phosphoric acid, etc., and the alkali metal in the film is removed. is being removed. 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 product with the siliceous film in it for a relatively long time. There is. However, in this case, the siliceous film itself dissolves in the acid aqueous solution, resulting in a problem that the strength of the siliceous film decreases. Furthermore, when acids are used, the working environment deteriorates due to odors and the like, and problems such as pollution arise, so a huge amount of equipment is required to deal with these problems. In order to solve this problem, the inventors conducted detailed research on the behavior of free water in silicate during heat treatment, and found that the temperature of 100℃ prior to the baking treatment of silicate at high temperature. It has been found that pre-drying at a temperature of less than 100 mL causes the free water in the silicate, which causes the formation of pores, to be removed, thereby significantly reducing the formation of pores in the siliceous coating.

As a result of further research, we decided to use two types of silicates, namely sodium silicate and lithium silicate, and formed a first silicate film on the base material using sodium silicate. By forming a second siliceous film using lithium silicate on it, the occurrence of efflorescence can be effectively prevented without performing alkalization treatment, and the siliceous film as a whole has excellent properties. It has been found that chemical resistance, impact resistance, etc. are improved. As a result of further research, the inventors found that at least one of the first siliceous film and the second siliceous film is free from acid oxidation when dissolved in aqueous acid solution and water. It has been discovered that when dealkalization treatment is performed with one or both of the salts exhibiting the above, the generation of efflorescens can be further prevented, and even if the resulting product is used under harsh conditions, no efflorescens will occur at all. completed. That is, this invention has the following general formula (1) (1) Na2O-XSlO2.
An aqueous solution of sodium silicate represented by YH2O (where X is a positive number of 0.5 or more, and Y is O or a positive number) is applied to the surface of the substrate, pre-dried at a temperature of less than 100°C, and then heated to a higher temperature. A first siliceous film is formed by baking, and the following general formula (
)() Ll2O-XSiO2・YH2O (where X and Y are the same as in general formula (1)) is coated with an aqueous solution of lithium silicate, pre-dried at a temperature below 100°C, and then baked at a higher temperature. The first gist is to perform a treatment to form a second siliceous film, and the formation The second aspect of the present invention is to perform a dealkalization treatment on the siliceous hard coating using at least one of an aqueous solution of an acid and an aqueous solution of a salt that exhibits acidity when dissolved in the aqueous solution.

Next, this invention will be explained in detail.

First, the raw materials used in this invention will be explained.

Examples of the base material used in this invention include metal plates such as aluminum plates, glass plates, and cement plates.

However, the material is not limited to this, and any material may be used as long as it can withstand the heat during heat treatment. In particular, when an aluminum reflector is used as a base material and a highly transparent siliceous film is formed on it by the method of the present invention5, the mirror surface of the reflector is maintained for a long period of time and the durability is increased. This is extremely useful as it provides a significant improvement. In other words, aluminum has traditionally been used as a reflector for lighting equipment such as floodlights and shades, but this material can be easily polished to a Q surface gloss (high reflectance), is lightweight, and can be molded easily. This is because it is also easy to use. In this case, the reflective surface was subjected to chemical polishing and electrolytic polishing, and then alumite treatment to maintain the mirror surface to impart corrosion resistance and weather resistance. However, the mirror surface was still susceptible to attack. However, when a silicate film is formed on an aluminum reflector, the mirror surface of the reflector is maintained semi-permanently by the film. This is thought to be due to the fact that, unlike other metals, aluminum reacts with silicates, so that the siliceous film and the aluminum reflector are in close contact with each other. The sodium silicate to be applied and baked on the above base material has the following general formula Na2O-XslO2・YH2O (where X is a positive number of 0.5 or more, and Y is O or a positive number).
Examples include sodium silicate represented by the formula, which is used in the form of an aqueous solution.

Sodium silicate has extremely good film-forming properties, especially
The values of about 0.5 to 3.2 are remarkable. The film formed from sodium silicate and thorium silicate, up to a thickness of about 1 to 2 microns, is not susceptible to mechanical shock even when subjected to considerable thermal shock (rapid cooling from 350 to 25 degrees Celsius). It is an excellent product that does not cause any cracks. However, no matter how strongly the film is baked or dealkalized, efflorescence is likely to occur and the film lacks chemical resistance, particularly alkali resistance. Also,
As lithium silicate, the following general formula Ll2O-XS
iO2・YH2O (X is a positive number of 0.5 or more, Y
Lithium silicate is represented by O or a positive number) and is used in the form of an aqueous solution.

Although lithium silicate lacks film-forming properties compared to sodium silicate, those with an X value of about 0.5 to 3.5 can sufficiently form a film with a thickness of 1 to 2 μm. However, when the value of As described above, although lithium silicate has somewhat less film-forming properties than sodium silicate, the film formed with it has extremely high chemical resistance. In other words, the film formed by baking for 0.5 minutes or more at a temperature of 200°C or higher has acid resistance (60 minutes at room temperature in 10% HCl) and alkali resistance (10% NaOH) even if it has a thickness of about 1 μm. 60 minutes at medium room temperature). Furthermore, the film formed with lithium silicate has extremely low occurrence of efflorescence, and the film formed through baking at 200°C or higher can release carbon dioxide and sulfur dioxide even without dealkalization treatment. It does not change in a gas atmosphere. Thus, although the film formed from lithium silicate has high chemical resistance and efflorescence resistance, its impact resistance is not as good as that of sodium silicate. Therefore, in order to mutually compensate for the drawbacks of sodium silicate and lithium silicate, the present invention first developed an aqueous solution of sodium silicate that can form a film with rich film-forming property and high impact resistance. It is applied to a material and baked to form a film, and then an aqueous solution of lithium silicate, which can form a film with high chemical and effrochemical resistance, is applied and baked.

An aqueous solution of sodium merate and lithium silicate is
It is preferable that the concentration of each is selected in the range of 1 to 30% by weight (hereinafter abbreviated as "?").

That is, if the concentration exceeds 30%, the viscosity becomes high, which makes coating work difficult, and the resulting film becomes thicker, making it more likely to crack or foam during baking. In particular, when the base material is made of aluminum, corrosion of the base material is likely to occur. On the other hand, if the concentration is less than 1%, it will be difficult to fully exhibit the effect. Next, an example of manufacturing a product having a siliceous film by the method of the present invention using the above raw materials will be described. First, an aqueous solution of sodium silicate is applied to the substrate. The method of application is not limited. For example, spraying
Brushing or dipping the substrate into an aqueous solution of sodium silicate is performed. Next, the substrate coated with the aqueous solution of sodium silicate is air-dried and then pre-dried at a temperature below 100°C. This pre-drying is performed to remove free water in the sodium silicate coating and to prevent foaming during subsequent baking at high temperatures. Usually, this preliminary drying is performed for 0.5 to 30 minutes within a temperature range of 50°C or higher and lower than 100°C. Next, the sodium silicate coating is baked at a high temperature to form a first siliceous coating.

In this case, the baking is divided into two stages and is performed at a relatively low temperature (100
-200℃), followed by high temperature baking (200℃).
If the secondary baking is carried out at a temperature exceeding 400°C or less, the formation of small pores in the siliceous film can be further prevented. In other words, as a result of repeated polishing, the inventors found that the cause of the formation of a large number of small pores in a siliceous film was that the cause was incomplete removal of free water in the silicate during drying, They discovered that the problem lies in the fact that the dehydration reaction of silicate during heat treatment was not fully understood and the heat treatment was performed under inappropriate conditions.

Therefore, the inventors investigated the dehydration reaction of silicate during heat treatment using differential thermal analysis (DTA) and thermogravimetric analysis (
As a result of detailed research by TGA), 100-2
Because the reaction that causes the formation of pinholes in the siliceous film (probably a dehydration reaction) occurs violently between 00℃ and 00℃, the silicate is heat-treated (primary baking) in this temperature range.
We found that the formation of small pores in the siliceous film was significantly reduced when the temperature was further increased to a temperature exceeding 200°C and below 400°C (secondary baking). be. This primary baking is 0.5
From the viewpoint of effectiveness, it is preferable to carry out the treatment for about 30 minutes. The secondary baking performed after the first baking is at a temperature exceeding 200℃ and 400℃.
It is preferable to carry out the reaction at the following temperature.

This secondary baking is performed for the purpose of strengthening the silica film, and the baking time is usually selected from 0.5 to 30 minutes in consideration of economical efficiency and the like. Next, an aqueous solution of lithium silicate is applied on the first silicate film thus formed, and a series of treatments from application of the aqueous sodium silicate solution to baking treatment are performed. A second siliceous film is formed.

In addition, from the viewpoint of effectiveness, it is preferable that the thicknesses of the first and second siliceous films are each set to 0.1 to 2 .mu.m. In this way, a siliceous film that does not require dealkalization treatment, is highly transparent, has no pinholes, and is highly resistant to efflorescence, chemicals, and impact. This results in a product having the following characteristics. That is, the siliceous coating of this product is pre-dried at a temperature below 100°C (to remove the free water in the silicate that causes pore formation) prior to the high-temperature dawning process.
This prevents the formation of small pore distribution. The siliceous film has two layers, and the surface side is a second siliceous film (with lithium silicate that is rich in chemical resistance and efflorescence resistance (slightly lacking in impact resistance and thermal shock resistance)). The base material side is made of a first siliceous film (formed by sodium silicate) which is highly impact resistant and thermal shock resistant (lacking chemical and efflorescence resistance). Therefore, the shortcomings of the first and second siliceous films are compensated for each other, and the siliceous film as a whole has excellent chemical resistance, efflorescence resistance, impact bending resistance, and thermal shock resistance. , there is no need to improve the efflorescence resistance of the film by dealkalization treatment as in the past.
If particularly necessary, the above series of steps may be repeated. In addition, in order to further prevent the occurrence of efflorescence in the siliceous film, the first
At least one of the siliceous coating and the second siliceous coating is subjected to dealkalization treatment, that is, when dealkalization treatment is performed, the first siliceous coating is dealkalized. and/or subjecting the second siliceous film to a dealkalization treatment.
things are done. In this dealkalization treatment, an aqueous solution of an acid, an aqueous solution of a salt that exhibits an acid periphery when dissolved in water, or a mixed aqueous solution of both is used. The acids used at this time include HNO3, H3PO4, H2SO4, HCl, I]
Examples include 3B03, H2C03 and organic acids. From the viewpoint of effectiveness, it is preferable to use HNO3. Salts that exhibit acidity when dissolved in water include aluminum nitrate, magnesium nitrate, calcium nitrate, zinc nitrate,
Nitrates such as barium nitrate, sulfates such as aluminum sulfate, magnesium sulfate, calcium sulfate, zinc sulfate, monobasic aluminum phosphate, monobasic calcium phosphate, monobasic magnesium phosphate, monobasic iron phosphate, monobasic copper phosphate, Examples include phosphates such as zinc monophosphate, and hydrochlorides such as calcium chloride, aluminum chloride, magnesium chloride, ammonium chloride, and zinc chloride. From the viewpoint of effectiveness, it is preferable to use nitrates, and it is particularly preferable to use aluminum nitrate. This dealkalization treatment is carried out by spraying the siliceous film with an aqueous solution of the above acid, an aqueous solution of the above salt, or a mixed aqueous solution of both, or by immersing the product having the siliceous film in the above aqueous solution. It will be done. In this case, the concentration of the above aqueous solution is preferably set to 1 to 20%, although it varies depending on the type of processing agent. Although the treatment time varies depending on the type of treatment agent and the concentration of the aqueous solution, it is preferably set to 0.5 to 30 minutes. In particular, it is more preferable to dealkalize using an aqueous solution of a salt that exhibits acid 1 when dissolved in water than to dealkalize using an aqueous acid solution. This is due to the following reason. In other words, whether using an aqueous acid solution or an aqueous salt solution, the alkali metal is eluted from the siliceous film by dealkalization, and a trace of the elution is formed. When treated, as elution traces are formed, cations such as metal ions of the salt enter from the aqueous salt solution and fill in the elution traces, so that the surface condition of the siliceous film is less likely to be damaged. After performing such a dealkalization treatment, washing with water is usually performed to prevent the dealkalization treatment agent from remaining in the film. By performing such a dealkalization treatment, the generation of efflorescence is further prevented, so that even if the obtained product is used under harsh conditions, no efflorescence will occur at all. Next, examples will be described together with comparative examples.

Examples, comparative examples An aluminum base material was prepared as a base material.

This aluminum base material is a high-purity aluminum plate specified by JIS (manufactured by Sumitomo Light Metal Co., Ltd., AlO7OPlAl purity of 97% or more, 100 x 100 x 1 mm), which is hub-polished and then chemically polished by dealkalization treatment with a neutral detergent. After immersing in a bath (phosphoric acid 80 volumes, acetic acid 5 volumes, nitric acid 15 volumes, liquid temperature 100°C) for 30 seconds, and then rinsing with water,
It was immersed in 0% by volume HNO3 and then washed with water to give it a mirror finish. Using this base material, as shown in Table 1 below, apply the silicate aqueous solution shown in the same manner to the surface of the base material in the amount shown in the same table, heat treat as shown in the same table, and then apply as necessary. A product with a siliceous film was obtained by dealkalization treatment. Next, the performance of the siliceous coating of the product having the siliceous coating obtained as described above was investigated.

The results were as shown in Table 2. As is clear from Table 2, the performance of the siliceous film of the product obtained in Example 7 was as follows, except that the siliceous film of Example 7 showed slight erosion in the pinhole area in the chemical resistance test. It can be seen that the results are extremely good. On the other hand, the siliceous film of the product obtained in the comparative example caused efflorescence and
It can be seen that the chemical resistance is poor and the small pores are distributed, both of which are unsatisfactory. The performance evaluation method shown in Table 2 was performed as follows. (1) Appearance: The presence or absence of cracks was checked using a microscope (×100).

Color was visually observed. (2) Chemical resistance; 10% CI and 10% NaOH aqueous solutions with filter paper (10mm
Three sheets of X10 Dragon) were soaked in layers, placed on the surface of the test item, covered with a watch glass, left for 30 minutes at room temperature, washed with water, and observed with a magnifying glass (x25) for discoloration and corrosion.
(3) SO2 gas test; 1c1n at the bottom of the desiccator
Fill the desiccator with water to a depth of , filled with a mixture of saturated steam and 4,000 PP [11(7) SO2 gas] at room temperature.

After that, take out the test item and test it at 100-130. After putting it into the open chamber and drying it, it was examined with a magnifying glass (X25) for the presence or absence of white matter (efflorescens). (
4) Salt water spray test and weather-o-meter test The salt-water spray test was conducted for 10 cycles and the weather-o-meter test was conducted for 150 hours according to the method based on JIS.

(5) Film thickness measurement: Measured with Permascope EWD8 (manufactured by Fissia Ichigo Co., Ltd. (West Germany)).

Claims (1)

[Claims] 1 An aqueous solution of sodium silicate represented by the following general formula (I) (I) Na_2O・XSiO_2・YH_2O (wherein, X is a positive number of 0.5 or more, and Y is 0 or a positive number) is applied to the surface of the base material and pre-dried at a temperature of less than 100°C, and then baked at a higher temperature to form a first siliceous film, and the following general coating is applied on this first siliceous film. Formula (II) (II) Li
An aqueous solution of lithium silicate represented by _2O. 1. A method for producing a product having a siliceous film, the method comprising: forming a second siliceous film. 2 The high-temperature baking treatment performed during the formation of the first and second siliceous films was performed at a temperature of 100°C to 200°C.
A method for manufacturing a product having a siliceous film according to claim 1, which is performed by performing secondary baking and then secondary baking at a temperature of more than 200°C and less than 400°C. 3 The time required for preliminary drying is selected within the range of 0.5 to 30 minutes, and the time required for primary baking and secondary baking are each selected within the range of 0.5 to 30 minutes. A method for manufacturing a product having a siliceous film according to Scope 2. 4. According to any one of claims 1 to 3, the base material is an aluminum substrate that has been degreased and then subjected to chemical polishing or electrolytic polishing to form a mirror surface with a reflectance of 85% or more. A method for producing a product with a siliceous film. 5 An aqueous solution of sodium silicate represented by the following general formula (I) (I) Na_2O・XSiO_2・YH_2O (where X is a positive number of 0.5 or more, Y is 0 or a positive number) is applied to the surface of the base material. After coating and pre-drying at a temperature of less than 100°C, a baking treatment is performed at a higher temperature to form a first siliceous film, and on this first siliceous film, the following general formula (II) (II) is applied. )Li
An aqueous solution of lithium silicate represented by 2_O・XSiO_2・YH_2O (where X and Y are the same as in general formula (I)) is applied, pre-dried at a temperature below 100°C, and then baked at a higher temperature. A method for producing a product having a siliceous film by forming a second siliceous film, the method comprising: after the formation of the first siliceous film; and at least one of the formed image of the second siliceous film. A method for producing a product having a siliceous film, characterized in that the formed siliceous film is subjected to dealkalization treatment with at least one of an aqueous acid solution and an aqueous solution of a salt that exhibits acidity when dissolved in water. 6 The high-temperature baking treatment performed during the formation of the first and second siliceous films includes primary baking at a temperature of 100°C to 200°C, followed by secondary baking at a temperature exceeding 200°C and below 400°C. Claim No. 5 carried out by baking
A method for manufacturing a product having a siliceous film as described in Section 1. 7 The time required for pre-drying is selected within the range of 0.5 to 30 minutes, and the time required for primary baking and secondary baking are each selected within the range of 0.5 to 30 minutes. A method for manufacturing a product having a siliceous film as described in Scope 6. 8. According to any one of claims 5 to 7, the base material is an aluminum substrate that has been degreased and then subjected to chemical polishing or electrolytic polishing to form a mirror surface with a reflectance of 85% or more. A method for producing a product with a siliceous film. 9. The siliceous material according to any one of claims 5 to 8, wherein the aqueous solution of acid for dealkalization treatment is an aqueous solution of nitric acid, and the aqueous solution of a salt that becomes acidic when dissolved in water is an aqueous solution of nitrate. A method for manufacturing products with a film.