JPH0339033B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a cement molded body, and more particularly, to a method for manufacturing a highly durable cement molded body whose surface is decorated with a silicate paint.

A kneaded mixture of cement, water, aggregates, fibers, etc. is pressure-molded, and the surface of the resulting molded product is coated with paint, baked, and then rehydrated to create a surface-coated cement. Methods for producing molded bodies are already known. However, in this conventional method, in order to facilitate the initial shapeability by molding and to improve the shape retention of the resulting molded product during firing, the cement kneaded material is high-pressure molded to form the molded product. As a result, the rehydration rate after firing is slow,
Therefore, there is a problem that the curing period becomes long.

The present invention was made in order to solve the above-mentioned problems, and it provides a cement kneaded product with good initial shapeability and subsequent shape retention, as well as a fast rehydration rate after firing. An object of the present invention is to provide a method for manufacturing a surface-decorated cement molded body that can quickly obtain a cement molded body with a required strength.

The method for producing a cement molded body of the present invention involves forming a cement mixture containing Portland cement, alumina cement, gypsum, lime, and water into a desired shape under heat and pressure, and then coating the surface with a silicate-based paint. It is characterized by being heated, fired, and then rehydrated in a heated atmosphere.

In the method of the present invention, in order to improve the initial shapeability of the cement mixture into a desired shape, a heating hardening agent consisting of a mixture of alumina cement, gypsum and lime is mixed with Portland cement, and water is poured into the cement mixture. to prepare a cement mixture.
The blending amount of the heat curing agent is preferably 5 to 40 parts by weight per 100 parts by weight of Portland cement.
The amount of water to be poured is preferably 5 to 30 parts by weight per 100 parts by weight of Portland cement. Further, this kneaded product preferably contains 0.5 to 10 parts by weight of an organic carboxylic acid salt such as sodium gluconate or sodium citrate as a hardening modifier per 100 parts by weight of the heat hardening agent. still,
The cement mixture may contain fine aggregate such as fly ash and silica sand, and reinforcing fibers such as asbestos and glass fiber, as required.

In the method of the present invention, the cement mixture as described above is molded into a desired shape under heat and pressure.
The temperature at that time is 60 to 95℃, and the pressure is 5 to 100Kg/cm ²
is preferable, and in this way a molded product with excellent shape retention can be obtained. Next, a silicate-based paint is applied to the surface of this molded product, and usually
The paint is baked at a temperature of 150-400℃.

In the present invention, a high-strength molded body can be obtained by rehydrating this fired product in a heated atmosphere. The ambient temperature is preferably 60 to 95°C, and therefore rehydration, for example in hot water or saturated steam, is preferred.

As described above, according to the method of the present invention, the cement kneaded material contains the above-mentioned heat hardening agent, and this forms an ettrin guide by molding under heat and pressure, thereby forming the initial shape of the kneaded material. It improves the properties and maintains good shape retention until firing. Then, by firing the molded product, the above-mentioned Etrin guide does not lose crystallization water, and the Etrin guide is quickly formed again by subsequent rehydration, and in this way, the rehydration As a result, the curing speed increases and a high-strength cement molded body can be obtained.

Examples of the present invention are listed below. In each example, the bending strength of the sheet molded product obtained was JIS
Measurements were made according to the bending test method for architectural boards according to A1408.

Example 1 To 100 parts by weight of Portland cement, parts by weight of alumina cement, 8 parts by weight of burnt lime, and 5 parts by weight of slaked lime were added and mixed, and 25 parts by weight of water and 0.5 parts by weight of sodium citrate were mixed thereto to form cement. A kneaded product was prepared. This is done at a temperature of 80℃ and a pressure of 30Kg/cm ²
Press molding was performed to obtain a fully cured sheet measuring 10 mm in length and width and 1 cm in thickness.

After applying a silicate-based paint to the surface of this sheet, it was held and baked at 250℃ for 60 minutes, then cooled to room temperature, rehydrated in warm water at 75℃ for 24 hours, and further submerged in water. A molded article was obtained after curing for 3 days.
The bending strength of this molded body was 280 Kg/cm ² .

Example 2 14 parts by weight of alumina cement, 9 parts by weight of burnt lime and 7 parts by weight of slaked lime were added and mixed to 100 parts by weight of Portland cement, and 22 parts by weight of water and 0.7 parts by weight of sodium gluconate were mixed thereto to make cement. A kneaded product was prepared. This is heated at a temperature of 80℃ and a pressure of 25Kg/
A sufficiently cured sheet was obtained by press molding at cm ² .

After applying a silicate-based paint to the surface of this sheet, it was held and fired at 250℃ for 60 minutes, then cooled to room temperature, rehydrated in saturated steam at 95℃ for 12 hours, and further submerged in water. After curing for 3 days, a molded body was obtained. The bending strength of this molded body was 250 Kg/cm ² .

Example 3 10 parts by weight of alumina cement, 6 parts by weight of burnt lime, 4 parts by weight of slaked lime, and 5 parts by weight of asbestos fiber were added to 100 parts by weight of Portland cement, and water was added to the mixture.
A cement kneaded product was prepared by mixing 25 parts by weight and 0.2 parts by weight of sodium citrate. This was press-molded in the same manner as in Example 1 to obtain a fully cured sheet.

After applying a silicate-based paint to the surface of this sheet, it was held and fired at 180°C for 60 minutes, then cooled to room temperature, rehydrated in saturated steam at 90°C for 12 hours, and further submerged in water. After curing for 3 days, a molded body was obtained. The bending strength of this molded body was 350 Kg/cm ² .

Comparative Example 1 A cement kneaded product was prepared by mixing 100 parts by weight of Portland cement with 25 parts by weight of water. this
It was molded into a sheet at a pressure of 30 kg/cm ² . Next, a silicate-based paint is applied to the surface of this sheet and heated to 250°C.
The mixture was held and fired for 60 minutes, then cooled to room temperature, and then rehydrated in water for two weeks to obtain a molded body. The bending strength of this molded body was 150 Kg/cm ² .

Comparative Example 2 A sheet was obtained using the same cement mixture as in Example 1 under the same conditions, and after applying a silicate-based paint to the surface of the sheet, it was incubated in water for 3 days or 2 weeks without heat curing. I took care of myself. The bending strength of the sheet molded product thus obtained was 75 Kg/cm ² when cured in water for 3 days, and 200 Kg/cm ² even when cured for 2 weeks.

Claims (1)

[Claims] 1 Portland cement, alumina cement,
After a cement mixture containing gypsum, lime and water is molded into a desired shape under heat and pressure, a silicate-based paint is applied to the surface, fired, and then rehydrated in a heated atmosphere. Characteristic method for producing cement molded bodies.