JPH01215775A - Production of glazed cement product - Google Patents

Abstract

PURPOSE:To provide the title production process so designed that when the title product is to be manufactured, the temperature decrease after the calcination is first made at the glazed layer side before that at the cement substrate side, thereby preventing the warpage of the product or the intrusion of the glazed layer. CONSTITUTION:When the objective product A is to be manufactured by glazing 2 on a cement substrate 1 followed by calcination, the temperature decrease is first made at the glazed layer 2 side before that at the cement substrate 1 side. The calcination temperature and the melting temperature of the glazing agent are pref. <=900 deg.C, respectively. Thus, even if a glazing agent with low melting point and high shrinkage is used, the difference in the shrinkage between the cement substrate 1 and glazing agent 2 is small from the point at which the adhesive force between the substrate 1 and the glazed layer 2 begins to develop by starting solidification of the molten glazing agent to the point at which the temperature of the system is normal, the ensuring the warpage or intrusion 3 to be prevented.

Description

[Detailed description of the invention]

1. Field of Industrial Application The present invention relates to a technique for preventing warpage of glazed cement products and penetration of the glaze layer.

[Conventional technology]

Glazed cement products have traditionally been manufactured by glazing a cement substrate and then firing it. Firing is carried out by raising the ambient temperature to melt the glaze, and then lowering the temperature.

[Problem to be solved by the invention]

In the conventional glazed cement product A', warpage and penetration 3 occurred in the glaze layer 2. Warpage and penetration of glazed cement products occur when the glaze solidifies during firing and shrinks until it reaches room temperature! (thermal expansion coefficient). That is, if the shrinkage amount of the glaze is larger than the cement base [1], the product A' as shown in FIG.
becomes a convex warp ((a) in the same figure), and a penetration 3 is made in the glaze layer 2 ((b) in the same figure).In the opposite case, as shown in Fig. 5, the product A' becomes warped by 6 ( (a) in the same figure, the glaze layer 2 peels off ((b) in the same figure). Therefore, it is ideal for the glaze and the cement substrate to have the same amount of shrinkage, but in order to increase the strength of glazed cement products, water is absorbed after firing and the cement undergoes the water-recycling reaction again, so the cement substrate absorbs water. It is preferable to design the material so that the amount of contraction of the cement substrate is slightly larger than the amount of contraction of the glaze to the extent that it can absorb the force even if it expands.On the other hand, the hydration reaction of cement is caused by firing at too high a temperature. In general, if the firing temperature exceeds 900℃, the hydration reaction will not proceed much even after water is absorbed, and a high-strength product will not be obtained.Therefore, for cement substrates, temperatures below 800℃ However, when it comes to glazes, the type that melts at a lower temperature tends to shrink more when the temperature cools down, and traditional methods result in products that are warped in all four parts and have penetration into the glaze layer. The present invention was made in view of the above circumstances, and its purpose is to provide a method for manufacturing a glazed cement board that does not cause warping or penetration into the glaze layer. 1. Means for Solving the Problems] The method for manufacturing a glazed cement board of the present invention includes a cement substrate 1
In a method of manufacturing a glazed cement product by applying glaze to a cement substrate and firing it, the glaze layer 2 is larger than the cement substrate 1gA when the temperature is lowered during firing.
This feature is characterized by lowering the temperature on the side first, and this configuration achieves the above object.

[Effect 1] During firing, the temperature on the glaze layer 2 side is lowered earlier than on the cement substrate 1 side, so even if a glaze with a low melting temperature and a large shrinkage amount is used, the molten glaze begins to solidify and the cement substrate 1 There is no significant difference in the amount of shrinkage between the cement substrate 1 and the glaze from the time when bonding force begins to appear until the temperature reaches room temperature, and the occurrence of warping, penetration, etc. can be prevented. [Example 1] The cement substrate 1 used in the present invention is not particularly limited. For example, ordinary Portland cement,
Silica sand, shelben or 7
It is manufactured by blending a compound that is stable during firing, such as lye ash, and adding other admixture materials, paper-molding or extrusion molding, and curing the resulting cement molded product. A glaze is applied to the surface of this cement substrate 1 and fired. The glaze is preferably one that melts at a temperature of about 800°C to promote the hydration reaction of the cement after firing. For example, such a glaze has a composition (%) of 5iOz:2
4.1/PbO: 41.81/LitO: 2,38/N
aaO:9. F1/J:8.72/TiO2:9.5
7, 5i02:2F/PbO:51.5/BtOs:3
/NatO:8/TiO2:0.5/Zr0z:2.0
, SiOx:33/PbO:48.0/BzOs:3/
Examples include those having a melting temperature of 600 to 650°C, such as Na1O:8. Of course, it is not limited to these, but low-temperature faces that melt at 600°C or less have weather resistance,
Desired performance in terms of wear resistance, chemical resistance, etc. may not be expected in some cases, and moreover, it is generally expensive, so it is not preferable. Next, the cement substrate 1 coated with glaze is placed in a firing furnace and fired by applying a uniform temperature to the top and bottom surfaces. Firing consists of an external temperature step UP%, a granule melting step MP, and a temperature lowering step DP, in which the temperature is gradually raised as shown in Figure 1, and the thickener such as hydroxypropyl methylcellulose in the cement substrate 1 and water are decomposed. While removing gas components, raise the temperature to the point where the glaze melts. Then, the temperature at which the glaze is melted is maintained for a certain period of time, and the gas components of the cement substrate 1 are sufficiently removed (and the glaze is evenly leveled. After this, the temperature lowering step DP is started, but the temperature is lower than that of the lower surface, that is, the cement substrate 11M. , lower the temperature of the upper surface, that is, the glaze layer 2 side first. Figure VI2 shows the relationship between the shrinkage amount (thermal linear expansion coefficient) of the cement substrate 1 and the glaze layer 2 and the temperature, and when the temperature is lowered, the glaze solidifies. At the beginning, when the bonding force with the cement substrate 1 starts to appear and becomes viscous, the temperature of the upper surface is T2, the temperature of the lower surface is T,
Then, the amount of shrinkage of the cement substrate 1 and glaze layer 2 from that temperature to room temperature is A1, A2, and A+>A.
Compression can be applied to the cement substrate 1 with glaze at t,
Glazed cement product A that does not penetrate the glaze layer 2 due to convex warping
is obtained. In addition, it absorbs water after firing! - At the same time, the hydration reaction of the cement proceeds to increase its strength (. By the way, the temperature T of the cement substrate 1 gA and the glaze layer 2 @
When the temperature T2 is the same, the shrinkage amounts of the cement substrate 1 and the glaze N2 from T2 to room temperature are As and A, respectively
x, and when A2>1, the amount of shrinkage of the glaze layer 2 is large, so the obtained product becomes concavely warped, and a penetration phenomenon occurs in the glaze layer 2. Effects of the Invention In the method of manufacturing glazed cement products by coating and firing a cement substrate, the present invention lowers the temperature on the glaze layer side earlier than the cement substrate side during firing, so the melting temperature is low. Even if a glaze with a large amount of shrinkage is used, there is no significant difference in the amount of shrinkage between the cement substrate and glaze from the time when the molten glaze begins to solidify and develop bonding force with the cement substrate until it reaches room temperature, and there is no possibility of warpage or glaze shrinkage. This prevents the occurrence of layer penetration, and since a glaze with a low melting temperature has excellent fluidity, pinholes and the like are less likely to occur in the glaze layer, and a smooth finished surface can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a graph showing the relationship between firing time and ambient temperature in one embodiment of the present invention, Fig. 2 is a graph showing the relationship between temperature and shrinkage amount, and Fig. 3 is a glazed cement product obtained by the above method. 4(a)(b) and FIG. 5(a)(b) are cross-sectional views showing applied cement products manufactured by conventional methods, where A is an applied cement product, 1
2 is a cement substrate, and 2 is a glaze layer. Agent Patent Attorney Ishi 1) Chief Shichiman 13 2v3 Blind 3 Agony

Claims (3)

[Claims] (1) A method for manufacturing a glazed cement product by applying a glaze to a cement substrate and firing it, which is characterized in that the temperature on the glaze layer side is lowered earlier than on the cement substrate side when the temperature is lowered during firing. (2) The method for producing a glazed cement product according to claim 1, characterized in that the firing temperature is 900°C or less. (3) The method for producing a glazed cement product according to claim 1, characterized in that the melting temperature of the glaze is 900° C. or lower.