JPH07108802B2 - Manufacturing method of fiber reinforced cement board - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a fiber-reinforced cement board.

[Conventional technology]

Conventionally, as a method for producing a fiber-reinforced cement board, cement, silica, reinforcing fibers, fine aggregates, and the like are uniformly mixed on a molding belt conveyor that is run as a method for producing a fiber-mixed powder, and the powder-like mixed raw material is sprayed and supplied in layers, and water is appropriately sprayed and rolled. A so-called dry method of forming into a plate shape compressed by is widely known.

Since this dry method is continuously produced on a traveling belt conveyor, it has an advantage that it is very advantageous as a means for producing building materials, such as roofing materials and wall boards, which are consumed in large quantities at one time.

[Problems of conventional technology]

By the way, the productivity improvement in the manufacturing method by the dry method is to improve the traveling speed of the molding belt conveyor.

However, when water is added to the surface of the cement raw material layer on the belt conveyor, water tends not to be absorbed uniformly and rapidly over the entire powder raw material layer, but tends to stay in the surface layer portion.

Therefore, when the speed of the belt conveyor is increased in order to change the productivity, a phenomenon in which only the surface layer portion is pushed back by the roll when passing through the compression roll due to the difference in the thickness direction of the cement layer due to water, and this phenomenon Since it increases with the passage of time, there is a problem that if the molding is continued while the speed of the conveyor is increased, the above raw material eventually accumulates in the compression roll portion and blowback occurs.

Therefore, there is a problem that the speed of the belt conveyor is limited to increase the productivity.

[Problems to be Solved by the Invention]

In view of the above problems, the present invention has an object to provide a method for producing a fiber-reinforced cement board with improved molding speed without lowering physical properties, particularly when producing a thin board by a dry method. It was made.

[Technology that has solved the problem]

That is, the method for producing a fiber-reinforced cement board according to the present invention is based on 95-60% by weight of a cement composition (A) composed of cement, silica, reinforcing fibers, fine aggregates and the like, and reinforcing fibers other than cement, silica and asbestos. And 5 to 40% by weight of a powdery composition (B) obtained by pulverizing a molded product obtained by naturally mixing and curing a composition comprising fine aggregate and water into a plate, and then crushing it with a crusher to a particle size of 8 mesh or less. Add and mix evenly with a mixing and dispersing machine, then spray the layers in layers on a molding belt conveyor whose surface has been moistened with water, compress with a roll into a plate, then spray water with the surface, and then compression-mold by rolls. After that, the molded body is taken out from the belt conveyor and cured by an autoclave.

[Action]

Usually, the cement composition (A) has water absorbency, but when water droplets are dropped on a powdery material in a dry state, it is difficult to uniformly mix the water-powdered material due to the influence of the surface tension of the water droplets. .

This is presumably because, as a result of the powdery substance being attracted to the periphery of the water droplets, this powdery substance becomes a barrier layer and blocks the powdery substance on the outer periphery thereof.

Therefore, according to the present invention, the powdery composition (B) which easily absorbs water and does not easily form a barrier layer as described above is added to the cement composition (A), and the mixture is uniformly mixed so that the entire cement layer can be rapidly added. It allows water to penetrate.

As the composition that easily absorbs water and does not easily form the barrier layer as described above, a powdery composition (B) obtained by crushing a curing-cured plate-like body made of a cement mixture that does not use asbestos is used. To do.

Since this powdery composition (B) is obtained by crushing a cement molded product that has been once cured and cured, it has a very good water absorption property due to the minute voids contained in the matrix. The dispersion significantly improves the overall water permeability.

The particle size of the powdery composition (B) is limited to 8 mesh or less in order to prevent the powdery composition from penetrating the plate thickness.

Further, as a molding condition of the powdery composition (B), curing is performed only by natural curing. That is, when the cement molded article molded by adding the powdery composition (B) is cured by autoclave, the powdery composition (B This is for obtaining the bonding strength of the cement matrix that has caused the bonding reaction to).

Further, the powder composition (B) is added to the cement composition (A) in an amount of 5
-40% by weight is mixed because if it is less than 5% by weight, the water permeability is insufficient and the molding speed cannot be increased sufficiently, and if it is more than 40% by weight, the strength of the molded product decreases. Is.

〔Example〕

 Next, an embodiment of the present invention will be described.

FIG. 1 is a side view of an essential part of an apparatus for carrying out the method of the present invention.

Dry defibrated pulp 5% by weight, ordinary Portland cement
57% by weight, crystalline silica with a plain value of 6000 to 15000 cm ² / g
38% by weight was sequentially charged into a mixing and dispersing machine equipped with a high-speed stirring device, and then this mixed raw material was supplied to the dry manufacturing apparatus shown in Fig. 1 to form a plate material, which was naturally cured for 2 days to cure. Then, this molded body was crushed by a leet crusher.

The particle size distribution of the ground product obtained at this time is as shown in the table below.

A finely pulverized product finer than 8 mesh among the pulverized products obtained above was used as a blend B.

Next, dry defibrated pulp 3% by weight, asbestos 5% by weight, ordinary Portland cement 55.2% by weight, Blaine value 6000 to 1500
Formulation B was mixed with 100 parts of Formulation A consisting of 36.8% by weight of 0 cm ² / g of crystalline silica in the proportions shown in Table 1.

Next, the following tests were carried out in order to know the water permeability and permeability of the powders having the formulations shown in Table 1.

Test 1. Permeability of water Put the composition shown in Table 1 into a cylindrical mold a with an inner diameter of 25 mm shown in Fig. 3 (a), and then press rod as shown in Fig. 3 (b). In the same state as when the back roll is pressed with b
After pressurizing with 10kg / cm ² and pulling out the press rod b, 3rd
As shown in the figure (c), water is contained in the dropper c at 15% by weight of the powder.
Was added dropwise. Then FIG. 3 as shown in (d), FIG. 3 Remove again breath rod b to the same 30kg / cm ² and compression pressure of the middle roll is pressurized, the mold (E)
As shown in, the height L of the sample and the height lω of the water penetration part are set to 3
Measured within minutes.

The water penetration depth lω and the pulverized material addition ratio measured in the order of the formulations 1, 2, and 3 shown in Table 1 are as shown in FIG.

Test 2. Air permeability The test was conducted by replacing water with air.

3.0 gr of the sample having the composition shown in Table 1 was introduced into each cell, and a certain amount of air was introduced into the cell using a brane device, and the time for passing through the sample was measured.

The number of seconds of passage of each sample and the pulverized material addition ratio are as shown in FIG.

Example 1 The ingredients shown in Table 1 in Table 1 were put into a mixing / dispersing machine equipped with a high-speed stirrer and mixed, and the mixture was fed in layers on a belt conveyor 1 whose surface was previously wetted with water as shown in FIG. After uniformizing with a roll (not shown), it is compressed with a back roll 2 and sprinkled with water from a water box 3 to wet it to a water content of 5 to 15%. It was compressed by the front roll 5 and then by the pressure rolls 6 and 6 at a linear pressure of 600 kg / cm to 1000 kg / cm.

The cut product of this compression molded product is finally carried into an autoclave and cured by steam under high temperature and pressure, and a plate thickness of 6.0 mm,
A sample having a width of 27 cm and a span of 58 was obtained.

Example 2 The same as Example 1 except that the compounding ingredient 2 in Table 1 was used.

Comparative Example A sample was obtained in the same manner as in Example 1 except that Table 3 in which no finely pulverized product was mixed was used for comparison.

The test results of the products obtained by changing the molding speeds of Example 1, Example 2 and Comparative Example are as shown in Table 2.

In Table 2, blowback refers to a phenomenon in which the raw material stays on the front surface of the roll as shown in FIG.

Table 2 ○: No blowback p at all △: Little blowback p ×: Large blowback p cannot be manufactured.

Molding speed 30 using the formulations of Examples 1 and 2 in Table 2
The relationship between the added amount of the pulverized product (B) of the product molded at m / min and the strength (kg / cm ² ) and the deflection (mm) is as shown in FIGS. 6 and 7.

〔effect〕

As described above, according to the present invention, the cement molded product is naturally cured and pulverized to have a particle size of 8 mesh or more, and by mixing it into the cement mixture, the water permeability and permeability of the mixture are improved. Therefore, the blowback phenomenon on the front surface of the compression roll can be effectively prevented, and therefore, the molding belt conveyor speed can be increased, and the molding speed is 30 m / min to 60 m / min for a thin plate having a thickness of 4.5 mm to 7.0 mm. The production rate can be doubled, and the so-called dry method can significantly improve the productivity.

In addition, the finely pulverized material that has been mixed reacts with the cement and silica during curing in the autoclave, so that it does not cause an interface with additives and does not impair the physical properties of the molded product.

[Brief description of drawings]

FIG. 1 is a side view of an essential part of an apparatus for carrying out the method of the present invention,
FIG. 2 is an explanatory view of the state of blowback, and FIG.
(E) is an explanatory view of a water permeation test, FIGS. 4 and 5 are graphs showing the amount of pulverized material B added and the permeability of water and air, respectively, and FIGS. 6 and 7 are pulverized materials. Each strength of B addition amount,
3 is a graph showing the relationship between the deflection and the deflection.

Claims (1)

[Claims] 1. A cement composition (A) composed of cement, silica, reinforcing fibers, fine aggregates and the like, relative to 95 to 60% by weight,
A powdered composition in which a molded body obtained by hydrolyzing a composition composed of cement, silica, a reinforcing fiber other than asbestos and fine aggregate, and plate-forming it, and then naturally curing it, was crushed with a crusher to a particle size of 8 mesh or less. (B) is added in an amount of 5 to 40% by weight and uniformly mixed by a mixing / dispersing machine, and then sprayed in layers on a molding belt conveyor whose surface has been previously moistened with water, compressed by a plate into rolls, and then sprayed with water on the surface. A method for producing a fiber-reinforced cement board, which comprises compressing and molding with a roll, and then removing the molded body from a belt conveyor and curing it by an autoclave.