JPS6112767B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a method for producing fiber-reinforced inorganic boards, and is particularly useful for producing asbestos-cement boards.

When manufacturing asbestos cement boards, a papermaking method may be used. In this paper-making method, asbestos-cement slurry that has been sufficiently stirred in a chisel is fed into a wet machine, and a thin film of asbestos-cement is excessively dehydrated and removed by the paper-making cylinder of the wet machine. The thin film is transferred to a blanket-like belt, and the thin film on the blanket-like belt is compressed and wound to a predetermined thickness by a rotating making roll in contact with the blanket-like belt, and when the predetermined winding thickness is reached. It is incised and then stretched flat.

In the above, when the wound thin film is cut open and stretched flat, the wound body is deformed from its rolled shape, which is circular, to a flat shape, so that shear stress is generated between the wound layers of the thin film. However, conventionally, in order to prevent delamination of the thin film due to this shear stress, the above-mentioned squeezing pressure of the making roll is set to a considerably high pressure to ensure the cohesion between the films. However, with this method, the thin film material is compressed more than necessary, making it difficult to obtain a lightweight plate material.

By the way, when the above-mentioned wound thin film is deformed into a flat plate shape, tension acts on the upper half and compression acts on the lower half. The Young's modulus of the thin film in tension is large because the asbestos fibers act as tension members, but the Young's modulus in compression is small because the asbestos fibers do not act as tension members. Therefore, the shear stress between the thin film layers on the tension side is larger than that on the compression side, and the shear stress becomes smaller as the distance between the thin film layers approaches the bending neutral line.

As described above, since the shear stress generated between the thin film layers when the wound thin film is stretched from a circular shape to a flat shape is not uniform, the releasability between the thin film layers is also not the same.
Therefore, if the same squeezing pressure is applied between all the thin film layers by a making roll as in the past, it means that more pressure than necessary is applied between certain thin film layers, and this excess pressure causes the above-mentioned This will be disadvantageous in reducing the weight of the plate material.

The method for manufacturing a fiber-reinforced inorganic board according to the present invention is a method invented in view of the above-mentioned points, and is a method for manufacturing a fiber-reinforced inorganic board, in which a thin film is formed by cutting a slurry of a fiber-mixed hydraulic inorganic material using a paper-making cylinder and transferring it onto a belt. This method is characterized in that when winding a predetermined number of sheets with a making roll, the thin film pressing force of the making roll is gradually reduced from the beginning of winding to the end of winding.

The present invention will be explained below with reference to the drawings.

In FIG. 1, 1 is a vat, which is filled with asbestos cement slurry. 2 is a paper-making cylinder, and 3 is a blanket-like belt rotating in contact with the paper-making cylinder 2. Asbestos cement in the slurry is removed into a thin film by the paper-making cylinder 2, and this thin film is transferred onto the belt 3. A making roll 4 is rotating in contact with the blanket-like belt, and the thin film on the belt 3 is wound around the making roll 4 until it reaches a predetermined thickness. The pressure applied to the thin film by the making roll 4 is gradually reduced from the beginning of winding to the end of winding. When the thickness of the thin film wound on the making roll 4 reaches a predetermined thickness, the rolled body is cut open and expanded from a circular shape to a flat shape, and this is transferred onto a take-up conveyor 5.

In this case, as described above, a greater shear force acts between the thin film layers on the upper surface of the flat body P, that is, closer to the surface of the making roll during winding of the making roll, and a greater shear force acts on the thin film layers that are farther away from the upper surface of the flat body. Shear stress decreases. Therefore, even if the pressurizing force of the making roll 4 is gradually reduced over time as described above, and the interlayer bonding force becomes smaller as the thin film layers are spaced apart from the making roll surface, the above-mentioned bonding force during flat development will correspond accordingly. Since the interlayer shear force is small, delamination during flat development can be sufficiently prevented. In this way, the compression densification of the thin film can be reduced by the amount of the gradually reduced pressure of the making roll 4, and a lightweight plate material without delamination can be obtained.

In the above, the thin film formed by the paper-making cylinder becomes richer in fibers toward the surface due to the excessive action of the cylinder, and therefore the thin film wound on the making roll also becomes richer in fibers toward the surface. At the time of winding, as shown in 6 in Figure 1, the slurry from which the fibers have been removed is sprinkled onto the thin film to replenish the lack of solids to the fiber-rich portions, thereby increasing the thickness of the thin film. It is desirable to homogenize the material. In this case, the amount of slurry to be sprayed is usually an amount that can replenish 0.5 to 5% of the solid content of one layer of raw material constituent solid content.

Instead of spraying the slurry, it is also possible to spray dry powder, which is the solid content of the slurry.

As shown in Fig. 2, the slurry or dry powder is spread by a gutter 7 of equal width at the lower end of the making roll 4.
It is also possible to carry out the process by making the powder flow further down, and especially in the case of dry powder, it is desirable to attach a vibrator to the gutter 7.

Example A slurry with a solid content of diatomaceous earth: 35% (weight %), lime: 30%, cement: 20%, asbestos: 10%, pulp: 5% is made into a paper, and the produced thin film is rolled up on a making roll. Initial pressure: 50Kg/cm, pressure at end of winding: 15Kg/cm, then winding 10 times, cutting it open, rolling it out flat, and final dehydration with press pressure: 100Kg/ ^cm2 . It was cured for 10 hours in an autoclave with saturated steam at a vapor pressure of 8 Kg/cm ² . The plate material thus obtained had a specific gravity of 0.92 and an interlayer peel strength of 10 to 11 Kg/cm ² .

Comparative example: Making roll pressure is always constant at 50Kg/cm
The same as in the example except that. The specific gravity of the plate thus obtained was 1:1, which was higher than that of the example product. In addition, the peeling resistance between layers is 10 to 11.
Kg/cm ² , and there was almost no difference between the comparative example product and the example product.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing a manufacturing device used in the present invention, and FIG. 2 is an explanatory diagram showing a solid dispersion device for a rolled thin film in the present invention. In the figure, 2 is a papermaking cylinder, 3 is a belt, and 4 is a making roll.

Claims (1)

[Scope of Claims] 1. When winding a predetermined number of sheets of paper-made thin film, which is extracted from a slurry of fiber-mixed hydraulic inorganic material using a paper-making cylinder and transferred onto a belt, using a making roll,
A method for manufacturing a fiber-reinforced inorganic board, characterized in that the thin film pressing force of a making roll is gradually reduced from the beginning of winding to the end of winding. 2. A method for manufacturing a fiber-reinforced inorganic board according to claim 1, characterized in that a hydraulic inorganic material is sprinkled on the thin film at the time of winding the thin film.