JPS584605B2 - 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 domestic demand for asbestos fibers is met by imports, 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.

In order to examine the reduction in the amount of fiber in asbestos fiber-reinforced cement boards from the internal structure of the board, that is, the internal organization, the present inventors developed an asbestos cement board in which asbestos fibers are mixed throughout, as shown in Figure 1. A wide variety of plates with fiber-free upper layer a were fabricated as prototypes with various large 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, it was found that if the thickness of the upper layer was within the range of 0 to 0.6 times that of the plate material, the bending strength of each plate material was approximately the same.

The composition of the asbestos fiber mixed cement used for this board prototype was 10% by weight of asbestos, 10% by weight of crushed stone, 25% by weight of powdered silica sand, and the balance was cement.The fiber-free cement composition was made by removing asbestos from the above composition. be.

The thickness of the prototype boards was all 6 mm, and the ratio of the fiber-free cement layer to the total thickness of the board was 0 for sample 1.
%, 10% for sample 2, 20% for sample 3, 30% for sample 4, 40% for sample 5, 50% for sample 6, sample 7
In this case, it is 60%, Sample 8 is 70%, Sample 9 is 80%, and Sample 10 is 100% (that is, the entire board is made of fiber-free cement composition).

The above bending test results of each of these samples are as shown in Figure 2, and the fiber-free cement composition layer, that is, the upper layer, is in the range of 0 to 60% of the total board thickness, that is, the lower layer of fiber reinforced cement is 100% of the total board thickness. ~40%, the bending strength is approximately constant.

Furthermore, the present inventors have developed a board sample 1 which is entirely made of asbestos fiber cement, a board material in which 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. For sample (2), the above bending test was conducted while gradually increasing the amount of asbestos fiber mixed.

The test results are shown in Figure 3, and the amount of asbestos mixed is 5.
．． At 0% by weight or more, the bending strength of the latter sample effectively increases as the amount of asbestos mixed increases, similar to the former sample.

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

Normally, in a laminate made 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 asbestos fiber-reinforced cement boards, even if the thickness ratio of the fiber-free layer and the fiber-mixed layer is changed as described above, there is no change in bending strength within a certain thickness ratio range. .

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

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 is located at a thickness ratio of 0.6 from the upper surface.

In this case, the compression zone is the upper layer section, denoted Co, and the tensile zone is the 7 layer section, 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 cotton fibers, and the Young's modulus of the cement layer against compression is greater than that of the asbestos fiber reinforced cement layer, regardless of the presence or absence of asbestos fibers. Assuming that it is the same regardless, even if the entire or part of the above upper layer is made of fiber-free cement layer, the bending stress distribution will not change, and the bending fracture will occur at the lowest position (maximum tensile stress) of the lower layer (asbestos cement wisteria). This will occur at the location where it is used.

: The Young's modulus of the cement layer under compression is almost constant regardless of the presence or absence of fibers, and the compressive strength of the aggregate-containing cement layer 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 is also based on 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.
Utilizing the property that when the thickness ratio is 6, the bending strength against the top surface bending load is substantially the same as the strength when the entire board is a fiber mixed layer, in relation to the usage state of the board,
Efforts are being made to reduce the amount of fiber used in asbestos-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 relates to asbestos fiber. In reinforced cement boards, even if the upper layer within a certain range is not mixed with fibers, in effect... Focusing on the fact that there is 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 side facing the outer surface.

Conventionally, as a manufacturing method of glass fiber reinforced cement board, Japanese Patent Publication No. 48-16691. No. 2, No. 2003-11-113 discloses alternately laminating glass fibers and cement, moistening the laminated layers with water, and integrating them by curing, but this method does not achieve any savings in reinforcing fibers.

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, in the method for manufacturing a fiber reinforced cement board according to the present invention, cement mixed with a large amount of reinforcing fibers is spread on a running belt conveyor, this spread layer is passed through a picker roll, and immediately after passing, Add cement mixed with a small amount of reinforcing fiber as needed to the above-mentioned sprinkled layer at a rate of 1.5 to 0.
．． Spraying at a thickness ratio of 4, then supplying water from above the sprayed layer, press-forming the sprayed layer, cutting it, taking it out from the belt conveyor, and curing the taken out raw original board. This method is characterized by the following.

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

In FIG. 5, 1 is a belt conveyor.

2 is a container for asbestos cement raw material, and asbestos cement raw material A is spread from this container 2 onto the belt conveyor 1 that is running.

Water is dripped onto the belt conveyor 1 before the raw material A is spread.

The composition of this raw material is 5.0 to 25% by weight of asbestos fiber, 20 to 30% by weight of crushed stone, 7 to 15% by weight of powdered silica sand, and the balance is cement.

3 is a pizka roll (hair opening machine roll), and when the above-mentioned sprinkled layer A' passes through this pizka roll 3, the sprinkled layer A'
The top of the is leveled and the excess material is thrown back.

This picker roll 3 has a large number of needles, and the surface of the sprayed layer is scratched by the needles to form dimple marks.

4 is a container for cement raw material, and water is dropped onto the surface of the sprayed layer A' that has passed through the picker roll 3, and then the cement raw material B is sprinkled thereon.

A small amount of asbestos fibers and synthetic fibers can be mixed with this raw material for the purpose described later, and the amount of the mixed asbestos fibers is 2% by weight or less in the case of asbestos fibers.

The thickness of this cement raw material is 1.5 to 0.4 times the thickness of the sprinkled layer of the above-mentioned asbestos cement raw material.

Reference numeral 5 denotes a hollow roller having a large number of air vent holes, which evens out the above-mentioned scattering layer B' and discharges the air in the scattering layer.

6 is a water dripping container, and the laminated raw material formed as described above is completely wetted by the dripping water from this container 6.

7 is a pressure roll, and 8 is a roll cutter. The above-mentioned water-wet raw material layer is pressed by the pressure roll 7, and further cut into a predetermined length by the roll cutter 8.

This cut piece, ie, the raw original plate, is taken out from the belt conveyor and then cured according to a conventional method.

In the above, the reason why the thickness of the cement dispersion layer is limited to 15 to 0.4 times the thickness of the asbestos cement layer is as follows:
．． 5 or more, it is not possible to make the thickness of the fiber-mixed cement layer 0.4 or more with respect to the total board thickness, and in this case, as is clear from the above experimental results, the entire thickness of the board is covered with asbestos. This is because the bending strength is lower than that of cement.

Further, if the thickness is less than 0.4, the thickness of the asbestos cement layer reaches 0.7 times or more of the total thickness of the board, and the reduction in the amount of asbestos cannot be effectively achieved.

Furthermore, the amount of asbestos in the asbestos cement raw material is reduced to 5.0 to 25% by weight.
The reason why it is limited to 5.0% by weight or less is that if it is less than 5.0% by weight,
This is because, as is clear from the experimental results shown in the figure, the provision of the fiber-free cement layer reduces the strength compared to when the entire board is made of asbestos cement.

If it exceeds 25% by weight, the strength will be higher than that required as a construction board material, and it will have no practical meaning.

The reason why a small amount of fiber is mixed into the non-fiber cement layer as necessary is to prevent cracks from occurring when the raw original plate is taken out from the belt conveyor due to elongation due to roll pressure.

As described above, the present invention provides a method for manufacturing an asbestos-cement board in which part of the upper layer is fiber-free, and the thickness of the upper layer is regulated within a range that does not reduce the strength of the board based on the experimental results. It is.

In particular, since the upper cement layer is sprinkled on the upper surface of the lower layer, which has needle scratch marks on the surface, immediately after the lower asbestos cement layer has passed through the Pitzkarol, the upper layer is formed after smoothing the upper surface of the lower layer with a roll. Compared to the case of spraying, it is possible to improve the bonding strength between the upper and lower layers.

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.

In addition, since the upper layer is fiber-free or contains only a very small amount of fiber, a pattern can be engraved by embossing or the like without any resistance from the fibers.

Another advantage is that a plate material with a smooth surface can be obtained.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram showing an asbestos-reinforced cement board sample prototyped by the present inventors, Figures 2 and 3 are diagrams showing the bending strength measurement results of the above sample, and Figure 4 is the bending state of the asbestos cement board. FIG. 5 is an explanatory diagram showing the manufacturing apparatus used in the present invention. In the figure, 1 is a belt conveyor, 2 is a raw material container for dispersing the asbestos-cement mixture, 3 is Pitzkarol, and 4
6 is a container for dispersing cement raw materials, 6 is a water dripping container, 7 is a pressure roller, and 8 is a roll cutter.

Claims (1)

[Claims] 1 Spread cement mixed with 5.0 to 25% by weight of asbestos fibers on a running belt conveyor, pass this spread layer through Pitzkarol, and immediately after passing through, add 2% by weight of asbestos fibers as necessary. The following mixed cement is sprinkled on the above-mentioned spread layer at a thickness ratio of 1.5 to 0.4, then water is supplied from above this spread layer, and the above-mentioned spread layer is pressure-molded, and then A method for producing a fiber-reinforced cement board, which comprises cutting the board, taking it out from a belt conveyor, and curing the taken-out raw board.