JPS5920628B2 - Manufacturing method of inorganic board - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing an inorganic plate that is lightweight and has excellent bending strength using fly ash as a main raw material.

Fly ash is a collection of fine particles of ash contained in the waste gas of pulverized coal-fired boilers.It is generated at thermal power plants, and in the current situation where soaring oil prices are forcing the use of lime. , it is expected that fly ash will be produced in large quantities and its cost will be reduced, and its effective use is attracting attention.

By the way, fly ash is S+02 pond Al2O3
Since it contains a large amount of C3H(I)(1
,0~1.5CaO,5i02゜xH2O) and Etrin guide (3CaO2A1203゜3CaS04,32
It is known that it produces insoluble calcium salts such as H20) and is useful as a raw material for inorganic board materials.

For this purpose, fly ash and cement are made by forming slaked lime or a water-containing mixture of cement and slaked lime into a plate shape.
This molded body is cured with high-temperature steam to obtain an inorganic plate.

However, fly ash contains a large amount of Al2O (approximately 26%), and due to the excess alumina, the formation of hydrogarnet is unavoidable, and since this hydrogarnet is coarse crystals, the above-mentioned hardening This has the disadvantage that it causes expansion and destruction of the body, and the strength of the inorganic plate is forced to decrease.

By the way, the present inventors have found that if a certain amount of magnesium hydroxide is added to a reaction system of fly ash and slaked lime or cement, the bending strength of the resulting hardened product can be significantly increased.

If 5i02 and Mg(OH)2 are subjected to a hydrothermal reaction using high-temperature, high-pressure steam at a pressure of 10 kg/i or higher, water-insoluble, high-strength amorphous or crystalline magnesium silicate crystals are produced. The above-mentioned strength-improving effect occurs even under low-pressure water vapor.

Therefore, although the cause of the strength improvement effect is not clear, M
It is presumed that g(OH)2 acts as an inhibitor of hydrogarnet formation.

Based on the above findings, the method for manufacturing an inorganic board according to the present invention attempts to improve the strength of the inorganic board by adding a certain amount of magnesium hydroxide to the hardening reaction system of fly ash and cement or slaked lime. This is a method in which a composition is prepared by adding 2 to 20% by weight of magnesium hydroxide and a predetermined amount of pulp, asbestos, etc. to a water-reactive material consisting of at least one of cement or slaked lime and fly ash in the presence of water. This method is characterized by molding into a plate shape and curing and curing the molded body.

In the present invention, the blending ratio of fly ash and cement or slaked lime is a well-known ratio determined from the production reaction of calcium salt (C8H(I), Etrin guide), and the weight of fly ash/(cement + slaked lime) The blending ratio is 70/30 to 50,150.

In this case, the weight mixing ratio of cement/slaked lime is 1001
It is 0 to 25/75.

The reason why the amount of magnesium hydroxide added is limited to 2 to 20% by weight is that if it is less than 2% by weight, the above-mentioned strength improvement effect cannot be achieved sufficiently, and if it is more than 20% by weight, the strength will decrease as magnesium hydroxide is added. This is because it will lead to this.

The desirable amount of magnesium hydroxide added is 4 to 15% by weight.
It is.

The reason for blending asbestos or pulp is to ensure the efficiency of slurry papermaking and the sawing and nailing properties required for building boards, and the blending amount is usually 10 to 20 Weight%.

As for the curing conditions in the present invention, steam curing at a relatively low pressure is sufficient, and curing for 8 hours or more in steam at 60°C or higher or at a pressure of 4 to 8 kg/cr? An autoflave curing of about 8 hours with 500 t of saturated steam can be used.

Hereinafter, the present invention will be explained with reference to Examples and comparison with Comparative Examples.

Examples 1 to 3 A slurry having a solid content of fly ash, magnesium hydroxide, slaked lime, cement, asbestos, and pulp in the blending ratio (wt%, same below) as shown in the table was prepared to a thickness of 10 mm.
To form the plate material, the molding pressure is 100ky/cI? L),
This molded body was cured by autoclaving in saturated steam at a pressure of 4 kg/cya for 8 hours.

Comparative Example 1 As shown in the table, the same procedure as in Example was carried out except that a formulation without addition of magnesium hydroxide was used as the solid content of the slurry.

Comparative Example 2 As shown in the table, the same procedure as in Example was carried out except that the amount of magnesium hydroxide added was 25% by weight, which is outside the range of the present invention, and the blend was used as the solid content of the slurry.

The bending strength and absolute dry specific gravity of the example product and the comparative example product were measured as shown in the table. It is also 1.1 to 1.2 and is lightweight.

As is clear from the above description, according to the present invention, it is possible to obtain an inorganic building material of fly ash-calcium hydroxide-cement-magnesium hydroxide hardening system that has excellent bending strength and is sufficiently lightweight.

Claims (1)

[Claims] 1 A composition prepared by adding 2 to 20% by weight of magnesium hydroxide and a predetermined amount of pulp, asbestos, etc. to a hydration-reactive material consisting of at least fallen cement or slaked lime and fly ash is shaped into a plate in the presence of water. 1. A method for manufacturing an inorganic board, which comprises molding the molded body into a shape, and curing and hardening the molded body.