JPS6027561B2 - Manufacturing method of fiber reinforced cement board - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing fiber-reinforced cement boards, particularly asbestos fiber-reinforced cement boards, and is capable of reducing the amount of fiber used without substantially reducing the strength of the board during use. .

A typical fiber-reinforced cement board used as a building material is asbestos fiber-reinforced cement board.

However, most of the demand for asbestos fibers in Japan is met through recycling, and in recent years, asbestos fibers have become more expensive and difficult to obtain due to the depletion of asbestos resources worldwide.

For this reason, the practical use of fibers to replace asbestos fibers is being considered.

The present inventors should consider reducing the amount of fiber in asbestos fiber-reinforced cement temporary from the internal structure of the board, that is, the internal organization. A wide variety of plates with fiber-free upper layer a were fabricated as prototypes with various lower layer thicknesses b, and the bending strength of each plate was measured by applying a load from the upper surface c side.

As a result, the upper layer thickness is 0 to 0. I learned that the bending strength of each plate material is almost the same as long as it is within the range of the needle sound.
The composition of the asbestos fiber mixed cement used in the trial production of this plate material was 1% by weight of asbestos, 1% by weight of pulp, 25% by weight of powdered silica sand, and the balance was cement.
This is a formulation with asbestos removed from the above composition.

The thickness of the prototype boards was all 6 ribs, and the ratio of the non-fiber cement layer to the total thickness of the board was 0% for sample 1.
, 10% for sample 2, 20% for sample 3, 3 for sample 4
0%, 40% for sample 5, 50% for sample 6, 60% for sample 7, 70% for sample 8, 80% for sample 9, 100% for sample 10 (i.e., the entire board is fiber-free cement composition) It is.

The above bending test results for each of these samples are as shown in Figure 2. If it is 100% to 40%, the bending strength is almost constant.

Furthermore, the present inventors have developed a board sample 1 that is entirely made of asbestos fiber cement, the upper layer is made of a fiber-free cement composition, the lower layer is made of asbestos fiber cement, and the thickness ratio of the upper layer and the lower layer is 1:1. The above-mentioned bending test was conducted on board sample D by gradually increasing the amount of asbestos fiber mixed in. The test results are shown in Figure 3. Similarly to the former sample, the bending strength of the sample effectively increases as the amount of asbestos mixed increases.

From the above test results, even if the upper layer is fiber-free, asbestos fiber-reinforced cement boards have the strength against bending loads from above as long as the thickness of the upper layer is within the range of 0 to 60% of the total thickness of the board. It is clear that there is no substantial decrease in

Normally, in a laminate of different materials, if the thickness ratio of each laminate changes, the bending stress distribution will change and the bending strength will change.

However, in the asbestos fiber reinforced cement board, even if the thickness ratio of the fiber-free layer and the fiber mixed layer is changed as described above, the bending strength does not change within a certain thickness ratio range.

The reason for this is thought to be that, despite the change in the thickness ratio, there is no change in the bending stress distribution.

Now, as shown in FIG. 4, it is assumed that the bending neutral line nn of the asbestos fiber reinforced cement material with respect to the load W is located at a thickness ratio of 0.6 from the upper surface.

In this case, the compression zone is the upper layer, denoted Co, and the tensile zone is the lower layer, denoted Pu. Therefore, the compressive strength of the cement layer is greater than the tensile strength of the asbestos fiber-reinforced cement layer, regardless of the presence or absence of asbestos fibers, and the Young's modulus of the cement layer against compression is greater than the tensile strength of the asbestos fiber reinforced cement layer, regardless of the presence or absence of asbestos fibers. Assuming that they are the same, the bending stress distribution will not change even if the entire or part of the upper layer is made of a fiber-free cement layer, and the bending stress distribution will be lower than that of the lower layer (asbestos cement layer). This will occur at the point of action). The Young's modulus of the cement layer under compression is constant regardless of the presence or absence of fibers, and the compressive strength of the cement layer with aggregate is greater than the tensile strength of the fiber-reinforced cement layer.

Therefore, the experimental results described above can be understood based on the reasons discussed using FIG. In Figure 4, the assumption that the position of the bending neutral plane n-n of the asbestos fiber-reinforced cement board is shifted from the center of thickness also applies to the Young's modulus in tension in the tension region and the compression in the compression region. This can be confirmed from the difference between Young's modulus and Young's modulus.

The fiber-reinforced cement board manufactured in the present invention has the bending properties of the asbestos cement reinforced board material with a fiber-free upper layer, which was revealed by the above experimental results, that is, the fiber-free upper layer has a bending property of 0 to 0.
When the thickness ratio of Efforts are being made to reduce the amount of fiber used in reinforced cement boards.

In other words, in architectural boards, external forces are applied from the outside surface,
If it can withstand this external force, there will be no problem in use.

The present invention focuses on the fact that in asbestos fiber-reinforced cement boards, even if the upper layer within a certain range is not mixed with fibers, there is virtually no decrease in strength against external forces from the upper layer side,
It is assumed that this upper layer fiber-free asbestos-reinforced cement board is used with the upper layer surface facing outward. The present invention is a method that can produce a board material having the same strength as a conventional fiber-reinforced cement board with a small amount of reinforcing fibers.

That is, the method for manufacturing a fiber-reinforced cement board according to the present invention includes a first vat filled with a cement slurry containing no asbestos, and a second vat filled with an asbestos cement slurry containing 5 to 25% by weight of asbestos. Place it on the wet machine, first,
The paper-forming cylinder of the first vat is brought into contact with the paper-forming belt of the wet machine, and the film formed from the slurry of the first vat is wound onto the making roll of the wet machine until it reaches a predetermined thickness. The paper-making cylinder of the vat and the sand-making belt are made non-contact, and the paper-making cylinder of the second vat is brought into contact with the paper-making belt,
This method is characterized in that the film formed from the slurry in the second vat is wound around the above-mentioned making roll to a thickness that is 2.3 to 0.7 times the thickness of the above-mentioned film.

FIG. 5 shows a manufacturing apparatus used in the present invention.

In FIG. 5, 1 is a first vat, which is filled with hydraulic cement slurry without or with a small amount of fiber added.

This cement slurry is made by dispersing a solid raw material consisting of 1 to 2% by weight of pulp, 20 to 25% by weight of silica sand, and the balance cement with approximately 13% water (weight ratio).
The solid raw material of this cement slurry contains 1 to 10% asbestos fiber.
It can also be added in an amount of 5% by weight. lb is the second vat, filled with fiber mixed cement slurry.

The solid raw materials for this fiber mixed cement slurry include 5.0 to 25% by weight of asbestos fiber, 0 to 7% by weight of pulp, and 20% by weight of silica sand.
~25% by weight, the balance consisting of cement is used. 2a and 2b are paper-making cylinders in each vat la and lb.

3 is a papermaking belt of a wet machine, and 4 is a making roll.

5 is a belt conveyor.

In order to manufacture a fiber-reinforced cement board according to the present invention, first, the papermaking cylinder 2a of the first batt la is connected to the papermaking belt 3.
A thin film of cement slurry is brought into contact with the paper-making cylinder 2a and is wound onto a making roll 4 via a sand-making belt 3. When the winding thickness reaches about 3 skins, the papermaking cylinder 2a of the first vat la and the papermaking belt 3 are brought into contact with each other, and the papermaking cylinder 2b of the second vat lb is brought into contact with the papermaking belt 3. At this stage, a thin film (approximately 0.5 membrane thickness) of cement slurry remains on the papermaking belt 3. When the paper-making cylinder 2b of the second vat lb comes into contact with the paper-making belt 3, a thin film of the fiber-mixed cement slurry extracted by the cylinder 2b is transferred to the paper-making belt 3, and this thin film is transferred to the paper-making belt 3. Following the residual cement thin film, it is transferred and wound onto a making roll 4. When the thickness of the fiber-reinforced cement thin film reaches 0.7 to 2.3 times the thickness of the non-fiber cement thin film, the entire rolled thin film is incised and the cut body is placed on the belt conveyor 5. , transfer the fiber-free cement thin film surface to the top surface.

Thereafter, this cut body is cut into a predetermined size using a roll cutter on the belt conveyor 5, and the raw cut material is pressed and cured according to a conventional method.

In the above, the reason why the winding thickness of the fiber-mixed cement membrane is limited to 2.3 to 0.7 times the winding thickness of the fiber-free cement membrane is that if it is 0.7 times or less, the thickness of the fiber-mixed cement layer It is not possible to make the thickness ratio 0.4 or more with respect to the total plate thickness,
In this case, as is clear from the experimental results shown in FIG. 2, the bending strength is lower than that when the entire thickness of the board is made of asbestos-mixed cement.

Further, if the thickness is 2.3 times or more, the thickness of the asbestos-mixed cement layer reaches 0.7 times or more the total thickness of the board, and the amount of asbestos cannot be effectively reduced. Furthermore, the reason why the amount of asbestos in the asbestos-mixed cement layer is limited to 5.0 to 25% by weight is 5. This is because, as is clear from the experimental results shown in Figure 3 above, at weight % or less, the strength decreases due to the provision of a fiber-free cement layer compared to when the entire board is made of asbestos-mixed cement. . If it exceeds 25% by weight, the strength will be higher than that required as a construction board material, and it will be of no practical use.

The reason why a small amount of fiber is mixed into the fiber-free cement layer as needed is to prevent the occurrence of cracks when the raw original plate is taken out from the belt conveyor.

As mentioned above, the present invention provides a board material in which a part of the upper layer of an asbestos cement board is substantially free of fiber additives, and the thickness of the upper layer is regulated based on the above experimental results within a range that does not cause a decrease in the strength of the board material. This is a manufacturing method.

Therefore, according to the present invention, a board material having the same strength as a conventional fiber-reinforced cement board can be obtained with a small amount of fibers, and the amount of asbestos fibers used can be reduced.

Further, in the present invention, the order of contact between the papermaking cylinder of the first vat and the papermaking belt, and the contacting order of the papermaking cylinder and the papermaking belt of the first vat is selected such that the uncured board is transferred with the substantially non-fibrous surface facing upward. Therefore, it is possible to pattern the non-fiber surface by embossing molding advantageously in terms of the process, and since there are no fibers in this patterning, the emboss pattern can be engraved deeply and clearly.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram showing a sample of asbestos-reinforced cement board prototyped by the present inventors, Figures 2 and 3 are explanatory diagrams showing the bending strength measurement results of the above sample, and Figure 4 is an explanatory diagram showing the asbestos cement board sample. The drawing used to explain the bending state, FIG. 5, is an explanatory diagram showing the manufacturing apparatus used in the present invention. In the figure, la is the first bat, lb is the second bat, 2
A and 2b are paper-making cylinders, 3 is a paper-making belt, and 4 is a making roll. Power' legs? 2 style gummy diagram 74 diagram rich to

Claims (1)

[Claims] 1 Place the first vat filled with asbestos-free cement slurry and the second vat filled with asbestos cement slurry containing 5 to 5% asbestos by weight in a wet machine, and then
The papermaking cylinder of the vat is brought into contact with the papermaking belt of the wet machine, and the film formed from the slurry of the first vat is wound around the making roll of the wet machine until it reaches a predetermined thickness. The membrane formed from the slurry in the second vat is placed on the above-mentioned making roll and rolled to the above-mentioned thickness. A method for manufacturing a fiber-reinforced cement board, characterized by winding it up to a thickness of 2.3 to 0.7 times.