JPH0735288B2 - Method for manufacturing fiber cement board - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a fiber cement board used as a building board such as a flat roof material and an outer wall material.

BACKGROUND ART A fiber cement board is manufactured, for example, as shown in FIG. That is, from the raw material tank 1, cement, filler,
Asbestos, other pulp as a papermaking auxiliary agent, and mixed water are put into the chest 2 and stirred and mixed to prepare a fiber cement slurry 3. The fiber cement slurry 3 thus prepared is supplied to the papermaking vat 4,
The fiber cement slurry 3 is made into an endless papermaking felt 6 by the papermaking cylinder 5 and transferred as a wet mat 7. Further, the wet mat 7 is wound around the making roll 8 as the papermaking felt 6 moves, and the wet mat 7 is wound around the making roll 8 until a predetermined thickness is obtained. When it reaches a predetermined thickness, it is cut out from the making roll 8 as a green sheet 9 and flatly developed, and then press dehydration is performed to perform primary curing by wet heat curing and secondary curing by indoor storage, and finish processing to obtain fiber cement. It is obtained as a plate.

A problem with such wet papermaking is that fibers such as asbestos are oriented in the papermaking direction. When the fibers are oriented in the papermaking direction in this manner, in the manufactured fiber cement board 10, the papermaking direction between the papermaking direction indicated by the arrow a and the papermaking orthogonal direction indicated by the arrow b in FIG. The dimensional change rate is different, Fig. 3 (b)
As shown in (3), the fiber cement board 10 is likely to be largely warped. When curing is performed by autoclave curing, such a difference in dimensional change rate can be reduced, but since autoclave curing has problems in equipment and workability, curing is generally performed by wet heat curing. In the wet heat curing, the difference in the dimensional change rate is 2-3 times larger than that in the autoclave curing, and the occurrence of warpage becomes a problem.

Therefore, various attempts have been made to reduce the difference in the dimensional change rate in the papermaking direction by wet heat curing, and it is considered to increase the amount of filler such as silica sand and to mix it. However, since silica sand has a granular shape, the effect of reducing the difference in dimensional change rate is insufficient, and the effect of reducing warpage is small.

[Object of the Invention] The present invention has been made in view of the above points, and it is possible to reduce the difference in the dimensional change rate in the papermaking direction and reduce the warp of the fiber cement board. It is intended to provide a method for manufacturing a cement board.

DISCLOSURE OF THE INVENTION However, in the method for producing a fiber cement board according to the present invention, the fiber component mainly composed of asbestos in the cement and the aspect ratio are
A slurry 3 containing mica containing 70% or more and having a flake diameter of 211 μm or more and 75% or more is sequentially made into a papermaking felt 6 by a plurality of papermaking cylinders 5 and transferred as a wet mat 7, and the wet mat 7 is formed. The wet mat 7 laminated to a predetermined thickness is wound up to a predetermined thickness, then the wet mat 7 laminated to the predetermined thickness is cut out from the making roll 8 and spread flat to form a green sheet 9, and the green sheet 9 is dehydrated. After that, the present invention is characterized by being cured, and the present invention will be described in detail below.

The slurry is prepared by mixing a cement with a fiber component mainly composed of asbestos and a filler such as silica sand, and dispersing and kneading this in water. Here, as the fiber component, in addition to asbestos, reinforcing fibers such as carbon fiber, polypropylene fiber, and piniron fiber are blended as necessary. As the cement, ordinary Portland cement, blast furnace cement, fly ash cement and the like can be used.

In the present invention, mica is further added to the slurry. Mica is formulated as a partial replacement for asbestos, and is used as the amount of asbestos required for fiber cement boards.
15 to 50% by weight is blended. Therefore, the amount of asbestos blended will be reduced with the blending of mica. If the amount of mica is less than this, the effect of mica may not be sufficiently obtained, and if the amount of mica is greater than this, the amount of asbestos becomes relatively small, and The strength tends to decrease. Mica has a chemical composition of K ₂ Al ₄ (Si ₃ Al) ₂ O ₂₀ (OH) ₄ muscovite (white) and K ₂ Mg ₆ (Si ₃ Al) ₂ O ₂₀ (OH) ₄ flocovite (gold). Any of these can be used. Also, 75% of mica has a weight-average aspect ratio of 70 or more and a flake diameter distribution of 211 μm or more.
The one including the above is used. If the aspect ratio is smaller than this, the effect of reinforcement by mica cannot be sufficiently obtained, and consequently the effect of reducing the difference in dimensional change rate in the intended papermaking direction cannot be obtained. If the flake diameter of mica is smaller than this and the ratio of fine particles increases, the effect of using a mica with a high aspect ratio cannot be fully utilized.

Then, the green sheet is prepared by wet-making the slurry obtained as described above, for example, using an apparatus as shown in FIG. That is, the slurry 3 is supplied to the papermaking vat 4, the slurry 3 is sequentially made up by a plurality of papermaking cylinders 5 to an endless papermaking felt 6 and transferred as a wet mat 7, and the wetmat 7 is moved as the papermaking felt 6 moves. 7 is wound on a making roll 8 and wound on the making roll 8 until it has a predetermined thickness, and then the wet mat 7 laminated to have a predetermined thickness is cut out from the making roll 8 and spread flat to form a green sheet 9. create. At this time, the fiber components such as asbestos are oriented so that the longitudinal direction thereof is parallel to the papermaking direction. At the same time, as shown in FIG. 2 (a), the mica 11 in the green sheet 9 is also oriented so that its scaly surfaces are parallel to the papermaking direction. Since there is no direction of paper making in the dry manufacturing method, the orientation of mica 11 is irregular as shown in Fig. 2 (b), but in the wet paper making method there is direction of paper making, so mica 11 is regular. It will be oriented. Thus, the mica is oriented in the papermaking direction in the green sheet, but since the mica is scaly, there is no particular longitudinal direction like asbestos, and the mica has a papermaking direction and a direction perpendicular to the papermaking direction. Since it will be evenly oriented in both directions, it can be reinforced evenly in both the papermaking direction and the direction perpendicular to the papermaking direction by using mica. It can be reduced.

Then, the green sheet thus prepared is pressed and dehydrated, and primary curing by wet heat curing and secondary curing by indoor storage are performed to finish as a fiber cement board. In the fiber cement plate thus obtained, it is possible to reduce the dimensional change rate between the papermaking direction and the direction perpendicular to the papermaking direction by the orientation of mica, and the warpage due to repeated water absorption and drying. Occurrence can be reduced. Further, although the amount of asbestos blended will be reduced by blending mica, since the mica itself has a reinforcing effect, it is possible to prevent the strength of the fiber cement board from being lowered.

The invention will now be illustrated by the examples.

Example, Comparative Example, Conventional Example A slurry was prepared by adding a mixture according to the formulation shown in Table 1 to mixed water and mixing and dispersing. Using this slurry, papermaking was carried out by the apparatus shown in FIG. 1, and dehydration was carried out by pressing at 85 Kg / cm ² for 1.5 seconds, and then at 55 ° C., 80
% RH, primary curing was performed for 6 hours, and secondary curing was performed indoors for 7 days. After that, a fiber cement board was obtained by applying an acrylic emulsion paint on the surface. still,
As the mica in Table 1, a flake distribution having a weight average aspect ratio of 90, 100% of flake diameters of 188 to 211 μm and 80% of flake diameters of 211 μm or more was used.

The physical properties of the fiber cement board thus obtained were measured, and the results are shown in Table 2. In Table 2, "lateral bending fracture load" is the strength along the papermaking direction measured at a span of 15 cm for a fiber cement board having a size of 20 cm x 20 cm. The "500 span bending fracture load" was measured by measuring the strength in the direction perpendicular to the papermaking direction with a span of 500 mm. "Dimensional change rate"
Is the papermaking direction is vertical and the direction perpendicular to the papermaking direction is horizontal.
The dimensional change was measured on a fiber cement board with a size of cm × 3 cm. At this time, the rate of dimensional change is 70
It is shown as the value obtained by dividing the difference in the dry state dried at ° C by the air-dry size and multiplying this by 100. "Infrared warp" is the roof tile edge of each roof tile after heating with an infrared lamp with nine fiber cement boards manufactured as roof tiles installed on the roof tile construction surface and heating the surface temperature to 73 ° C. This was done by measuring three points on the exposed part of the part. "3H fluctuation" in "infrared warp" is the total dimension of the bounce deformation in the working state after heating for 3 hours, and "cooling variation" is the total dimension of the bounce deformation in the working state after 1 hour of heating stop Are shown respectively. "Single item infrared warp" is a tile plate and a fixed plate produced by warp deformation by heating one fiber cement plate manufactured as a roof tile in a saturated state on a plate and heating it with an infrared lamp. Was measured, and the difference between the average size of the gap after 3 hours of heating and the average size of the gap before heating was measured.

As shown in Table 2, even if the amount of silica sand is increased as shown in the comparative example, the warpage is hardly reduced, but as shown in the example, the papermaking direction and the papermaking direction are changed by substituting a part of the mica for the asbestos. It is confirmed that the occurrence of warpage can be reduced by reducing the difference in dimensional change rate in the perpendicular direction. It is also confirmed that in the example in which mica is replaced with a part of asbestos as compared with the conventional example, the strength is hardly reduced.

[Effects of the Invention] As described above, according to the present invention, a slurry is prepared by mixing cement with a fiber component mainly composed of asbestos and a mica containing 75% or more of an aspect ratio of 70 or more and a flake diameter of 211 μm or more. The sheets are sequentially made up on a papermaking felt by a plurality of papermaking cylinders and transferred as a wet mat, and the wet mat is wound around a making roll until a predetermined thickness is obtained, and then the wet mat laminated to the predetermined thickness is cut out from the making roll. Since it was developed flat to create a green sheet, it is possible to stack multiple layers of wet mats when creating a green sheet by the above-mentioned wet papermaking, so that the mica contained in the green sheet is the thickness of the green sheet. Direction and the scale surface should be oriented so that they are parallel to the papermaking direction. Therefore, the fiber cement board formed by dehydration curing of the green sheet with mica can be uniformly reinforced in both the papermaking direction and the direction perpendicular to the papermaking direction, and the dimension in the papermaking direction and the direction perpendicular to the papermaking direction. The difference in the rate of change can be reduced and warpage can be prevented.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an example of the production of a fiber cement board, FIGS. 2 (a) and 2 (b) are schematic views showing the arrangement of mica, and FIGS. 3 (a) and 3 (b) are the warp of the fiber cement board. It is a front view and a perspective view shown. 3 is a slurry, 5 is a papermaking cylinder, 6 is a papermaking felt, 7 is a wet mat, 8 is a making roll, 9 is a green sheet, 10 is a fiber cement board, and 11 is a mica.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display area // (C04B 28/16 14:40 14:20) A

Claims (1)

[Claims] 1. A slurry prepared by mixing a cement with a fiber component mainly composed of asbestos and a mica containing 75% or more of an aspect ratio of 70 or more and a flake diameter of 211 μm or more is sequentially formed into a papermaking felt by a plurality of papermaking cylinders. Transfer it as a wet mat, wrap it around a making roll to a specified thickness, then cut the wet mat laminated to the specified thickness from the making roll and spread it flat to create a green sheet. Then, the method for producing a fiber cement board is characterized in that the green sheet is dehydrated and then cured.