JPS60264378A - Method of coating ceramic on calcium silicate board - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a method of forming a hard (and hard) ceramic coating on the surface of a xonotrite calcium silicate plate.

<Prior art> When forming a vitreous coating on a calcium silicate plate, various conditions such as the relationship between the vitrification temperature of the glaze and the heat resistance temperature of the calcium silicate plate and the difference in the coefficient of thermal expansion of the vitreous coating and the calcium silicate plate are required. must be taken into account.

Therefore, a conventional method is known in which the surface of a cementitious molded body is treated in advance with an aqueous solution of lithium silicate, heated to form an intermediate layer, coated with a glaze in the treated direction, and fired.

However, in the conventional coating method described above, the ALC board is used as a lacquer coating, and A
LC board is generally about 50% tobermorite calcium silicate.
, C8H, so there is a problem in that a ceramic coating with a high melting point cannot be formed.

That is, the firing limit of a calcium silicate plate made of 100% tobermorite is 650° C., and the crystal composition collapses when heated above this temperature. Therefore, the firing temperature of the glassy coating is limited to a maximum temperature of 4000 ℃, and if heated above this temperature, the plate itself will deteriorate. Furthermore, since the ALC plate contains about 50% of C8H'e, a hydrate whose crystal water evaporates at a lower temperature than the above-mentioned tobermorite calcium silicate, the firing temperature of the glassy coating is suppressed to 300° C. or lower.

On the other hand, glass coatings that are fired at higher temperatures are stronger and have better physical and chemical properties. For this reason, there is a limit to the properties of the vitreous coating in low-temperature firing where the firing temperature is at the limit of 400 C'i-. Furthermore, glazes fired at low temperatures generally have a large coefficient of thermal expansion, which exceeds that of the plate itself, so there is the problem that cracks are likely to occur in the vitreous glaze.

Similarly, when heating a xonotrite calcium silicate plate, gas generation from inside cannot be avoided, and it is necessary to eliminate this influence. However, in the above conventional method, this gas generation is
-cT4; 9a blue.

<Means for Solving Problems> The present invention eliminates the influence of gas generation by forming a coating that chemically bonds with xonotrite in advance when forming a ceramic silicate coating on a calcium silicate plate containing dinotrite as a main component, and It is an object of the present invention to provide a method for forming a high-strength ceramic coating with high adhesion. The structure of the present invention that achieves the above object is to apply a primary phosphate to the surface of a xonotrite calcium silicate molded body, heat it to around the firing temperature of the glaze, degas it, apply the glaze, and fire it. It is characterized by the meeting.

Furthermore, a preferred embodiment is characterized in that phosphoric acid is used in combination when applying the primary phosphate.

Generally, when firing a glaze, it is necessary to perform the firing at a temperature below which does not cause deterioration of the calcium silicate plate.

When the calcium silicate plate is heated for 7 hours above the temperature at which most of the crystallized water of xonotlite is volatilized and the crystalline structure undergoes a transition (hereinafter referred to as the total limit temperature), the calcium silicate plate contracts, cracks occur, and the strength decreases. let The critical temperature of the zonotrite siliceous calcium plate is about 750℃, and the operating temperature of M Karasu is 1.
It is 00Oc. In the present invention, the surface of such a xonotlite calcium silicate plate is treated with primary phosphate prior to glazing. In this case, the zonotlite-based calcium silicate molded body is a xonotlite-based calcium silicate plate produced by a hydrothermal synthesis reaction. Calcium silicate molded bodies as product components, including calcium silicate alone and molded bodies made of a mixture of calcium silicate and inorganic fiber or inorganic powder (hereinafter simply referred to as calcium silicate molded bodies) 7] 11
When heated, even if the temperature is below the above-mentioned limit temperature, the generation of gases originating from internal crystallized water, adsorbed water, carbonates, or mixed crystal water, adsorbed water, carbonates, etc. cannot be avoided.

For this reason, if you apply glaze directly to the calcium silicate plate and fire it,
Most of these volatile gases pass through the glaze coating and volatilize in the early stages of firing, but as the glaze progresses to vitrification and its viscosity increases, the volatile gases become trapped inside the coating and cause a roaring explosion. The coating is pushed up from below and peeled off from the calcium silicate plate, which remains as an unattached portion of the coating after firing.

Furthermore, depending on the type of glaze and the timing of gas generation, gas may be trapped in the glassy coating and cause pinholes. In order to remove the shadow V of gas generation, the calcium silicate plate is heated in advance to volatilize the gas, but a mere heat treatment does not provide a sufficient degassing effect and the above problem cannot be solved. Incidentally, a total of 700 calcium silicate plates
C Gas generation is observed even after heating for 18 hours or more. However, in the present invention, prior to firing the glaze, the effect of gas generation is eliminated by coating the surface of the glaze in advance with primary phosphate and heating it to around the firing temperature of the glaze (hereinafter this process is referred to as degassing treatment). ). That is, by applying the primary phosphate, gas generation in this area is promoted, and as the gas volatilizes, the surface layer of the calcium silicate plate and the primary phosphate undergo a chemical reaction, forming a phosphate film. Ru. This coating blocks the passage of gas generated from the inside, so when a ceramic coating is formed on the ruptured membrane, a strong coating can be fused without being affected by the gas generation. Furthermore, the VC phosphate film moderates the difference in coefficient of thermal expansion between the calcium silicate plate and the broken ceramic film, and greatly contributes to improving the fusing strength between the two.

As the primary phosphate, primary aluminum phosphate, primary phosphate/acid of an alkali metal, primary phosphate of an alkaline earth metal can be used.

However, if a silicate solution is used instead of a single phosphate, a large number of cracks will occur in the ceramic coating, making it impossible to achieve the full effect of the pretreatment. Conventionally, silicate solution k A
Examples of its use in LC plates are known, but since the silicate solution is alkaline, it does not react with xonotlitic calcium silicate plates at all and has no degassing effect. On the other hand, the primary phosphate is acidic, so it reacts strongly with the xonotrite calcium silicate plate, has a remarkable degassing effect, and generates a stable reactant.

Next, in order to enhance the degassing effect of the xonotlitic calcium silicate plate, it is recommended to apply phosphoric acid together with primary phosphate. By using phosphoric acid in combination, the primary phosphate salt and phosphoric acid penetrate into the interior of the xonotrite calcium silicate plate and have the effect of expelling gas, thereby further enhancing the gas volatilization effect. As specific conditions for the above-mentioned degassing treatment, heating is preferably performed at a temperature of about 100C for 5 to 10 minutes.

After the degassing treatment, it is glazed, dried and fired to form a ceramic coating. As for the composition of the glaze, a commercially available borosilicate composition can be used.

<Examples and Comparative Examples> Surface of calcium silicate plate containing Dinotolytra as the main component [
A 25% solution of phosphorus v is evenly applied, and then a 15% solution of monobasic aluminum phosphate is evenly applied 7-. This was placed in a heating furnace, heated at 700C for 10 minutes, and then slowly cooled after fc. Next, a borosilicate glaze was uniformly applied, dried at 45°C for 2 hours, heated at 700°C for 3 minutes, and slowly cooled.

As a result, a glossy and beautiful coating without inclusions was obtained on the surface of the calcium silicate plate. Furthermore, due to the formation of this coating, the surface of the p-calcium silicate plate becomes impermeable to water, and the surface hardness is 1
, an improvement of five times.

Comparative Example 1 The calcium silicate plate of Example 1 was heated at 700° C. for 30 minutes without any surface treatment, and then slowly cooled. Next, the same borosilicate glaze as above was applied to the entire surface, dried at 45C for 2 hours, and then fired at 700C for 3 hours. Many pinholes were observed in the coating on the surface of the obtained calcium silicate plate, and some unfused areas were observed.

Comparative example 2゜ Sodium silicate solution on the calcium silicate plate of Example 1 8- The solution was applied, heated at 700C for 10 minutes, and then slowly cooled.

The formed film was easily peeled off and it was difficult to form a sufficient film layer. Furthermore, the same borosilicate glaze as in Example 1 was applied to the areas that did not peel off, and after drying at 45C for 2 hours, the ceramic coating was formed by vigorously heating at 700C for 3 minutes.

However, many pinholes were generated in the slowly cooled ceramic coating, and a beautiful coating could not be obtained.

<Effects of the Invention> As explained above, according to the grade coating forming method of the present invention, gas volatilization from the surface of the xonotrite calcium silicate molded body is sufficiently promoted, and phosphate M[ is formed to block internal gas permeation, so the influence of gas generation can be completely suppressed, and the ceramic coating can be completely adhered to the surface of the molded body. Furthermore, since the influence of the difference in thermal expansion coefficient between the ceramic coating and the calcium silicate molded body is alleviated by the phosphate coating, the fusion properties between the two are further improved, and a high-strength ceramic coating can be formed.

Patent applicant: Onoda Chemical Industry Co., Ltd. Agent: Patent attorney: Shibu Mitsuishi (1 other person) 11- 442-

Claims (1)

[Claims] (1) The surface of the xonotrite calcium silicate molded body is completely coated with primary phosphate, heated to around the firing temperature of the glaze to degas it, then glazed and fired to form a ceramic coating on the surface of the molded body. A method for forming a ceramic coating on a calcium silicate plate by forming a t% mold. (2. A method for forming a ceramic coating on a calcium silicate plate according to claim 1, characterized in that when applying the primary phosphate, phosphoric acid is used in combination.