JPH0461770B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field] The present invention relates to a method for producing asbestos-cement construction boards used as roofing materials and the like. [Background Art] Asbestos-cement construction boards used as roofing materials have conventionally been produced in the following manner. That is, a slurry is prepared by defrosting asbestos and dispersing it in 5 to 10 times the volume of water together with fillers such as cement and silica powder, and papermaking aids such as pulp, and this asbestos-cement slurry is then subjected to circular mesh papermaking. The wet pine is made onto the felt by papering it with a cylinder or the like and transferring it onto the felt.The wet pine is then wrapped around a making roll several times to form a green sheet, and this green sheet is made into an appropriate thickness. Once the material has thickened, it is separated from the making roll, pressed and dehydrated, and if necessary, it is wavy or textured, and after curing, it is finished and manufactured into a product. In this case, the strength of the construction boards is reinforced by asbestos, but asbestos causes pollution and deterioration of the working environment due to its dust, and furthermore, the price of asbestos is rising due to resource depletion. Due to concerns, there are calls to reduce the amount of asbestos used. That is, currently, asbestos cement slurry contains about 15% by weight of asbestos based on the solid content, but there is a need to reduce this to about 10% by weight or less. When reducing the amount of asbestos in this way, it is possible to use organic fibers such as vinylon as a substitute for the reduced amount of asbestos in order to prevent a decrease in strength due to the reduced amount of asbestos. However, in this case, the following problem occurs. In other words, 5.5 mm thick, specific gravity manufactured using asbestos cement slurry containing 15% by weight of asbestos.
Table 1 shows a comparison of the strength of construction board A with a weight of 1.75 and construction board B manufactured using an asbestos-cement slurry containing 9% by weight of asbestos and 0.5% by weight of vinylon as an organic fiber. become.

[Purpose of the invention]

The present invention has been made in view of the above points, and it is possible to reduce the amount of asbestos used without significantly reducing bending strength, and improve impact resistance with organic fibers that have less directionality depending on the papermaking direction. It is an object of the present invention to provide a method for manufacturing an asbestos-cement construction board, which can yield a construction board with low warpage and dimensional change rate. [Disclosure of the Invention] However, the method for manufacturing an asbestos-cement construction board according to the present invention involves preparing an asbestos-cement slurry 1 containing asbestos and wollastonite and transferring it onto a felt 3 as a wet mat 2. A reinforcing cement slurry 4 containing organic fibers is sprinkled on the wet mat 2 as a reinforcing layer 5, and the wet mat 2 is wound around a making roll 6 several times, and then a plurality of wet mat 2 and reinforcing layers 5 are laminated. The green sheet 7 is cut out from the making roll 6, and the green sheet 7 is press-cured.Wollastonite is blended into the asbestos-cement slurry 1, and organic fibers are blended. The above object is achieved by using the reinforcing cement slurry 4 by spreading it, and the present invention will be described in detail below. FIG. 1 shows an example of the apparatus used in the present invention, in which the felt 3 is formed into an endless strip and the roll 10 is
It is driven to travel by. In addition, the asbestos cement slurry 1 is constantly supplied and filled in the papermaking vats 11, and a plurality of papermaking vats 11 are provided below the felt 3, and each papermaking vat 11 is filled with asbestos cement slurry 1. A cylinder 12 is rotatably provided. Further, a making roll 6 is provided which is driven to rotate while contacting a part of the felt 3. A spraying device 9 is disposed above the felt 3. The sprinkling device 9 is composed of a sprinkling vat 13 filled with reinforcing cement slurry 4 in which reinforcing organic fibers are dispersed, and a sprinkling brush roll 14 that can be rotated. Asbestos cement slurry 1 contains 70 to 85% by weight of cement such as boltland cement, blast furnace cement, and fly ash cement, and 5 to 15% by weight of filler such as fine silica and silica hume.
In addition, the amount of asbestos is set to 10% by weight or less, and 3 to 10% by weight of wollastonite (silica lime; an inorganic acicular substance made of cyclosilicate of calcium (CaSiO ₃ )) is added. 5 solids
It is prepared by dispersing it in ~10 times the amount of water. The asbestos cement slurry 1 is then drawn up by a papermaking cylinder 12 and transferred onto the surface of the felt 3. The wet mat 2 thus formed on the surface of the felt 3 is wound around the outer periphery of the making roll 6 by the running of the felt 3 and the rotation of the making roll 6. The wet mat 2 is generally wound around a 3 to 10 ply (3 ply to 10 ply) making roll 6, but the wet mat 2 wound around the making roll 6 has organic fibers dispersed therein for reinforcement by a scattering device 9. Reinforcing cement slurry 4 is spread. Here, the reinforcing organic fibers include vinylon, polyacrylonitrile,
It uses nylon, polypropylene, etc.
0.5 to 2.0% by weight of organic fiber is blended with 70 to 95% by weight of Portland cement, blast furnace cement, flyash cement, etc., and asbestos or crushed asbestos cement board waste is blended as a dispersant (in the case of asbestos, The reinforcing cement slurry 4 is prepared by dispersing these solid contents in 2 to 4 times the amount of water. In this way, cement slurry for reinforcement 4
When the wet mats 2, which have been sprinkled as reinforcement warehouses, are wound around the making roll 6, the second
As shown in the figure, the reinforcing layer 5 is laminated between the wet mats 2. When the wet mat 2 is wound around the making roll 6 to an appropriate thickness, it is cut out from the making roll 6 as a green sheet 7, and this green sheet 7 is pressed to dehydrate it and, if necessary, is given corrugations or uneven patterns. The final product is then further cured and finished.As shown in Fig. 3, the construction board thus obtained has a substrate layer 8 and a reinforcing layer 5 alternately laminated by wet mat 2. structure. At this time, as shown in FIG.
If the reinforcing cement slurry 4 is colored by adding a pigment so that it appears on the surface, the reinforcing layer 5 can serve as a surface decorative layer. Regarding the construction board obtained as above,
The asbestos-cement slurry 1 that forms the substrate layer 8, which can also be called the main body of the construction board, does not contain organic fibers and its specific gravity does not decrease, so the structure does not become poor, and there is no significant water absorption or drying, resulting in dimensional changes. Even if the amount of asbestos blended in asbestos-cement slurry 1 is reduced, since asbestos-cement slurry 1 is blended with wollastonite, this wollastonite It is possible to suppress a decrease in the bending strength of a construction board, and also to suppress the occurrence of warpage. In addition, since the organic fibers used to improve impact strength are mixed into the reinforcing cement slurry 4 and dispersed, the organic fibers are oriented in random directions and have no orientation. This means that the directionality of impact strength can be reduced. Next, the present invention will be specifically explained using examples. Example 1 Asbestos cement slurry was prepared by dispersing the formulation shown in Table 2 in water, and this asbestos cement slurry was made into paper using the apparatus shown in FIG. On the other hand, the second
A reinforcing fiber dispersed cement slurry prepared according to the formulation shown in the table was spread in the apparatus shown in FIG. In this way, a 6-ply green sheet was produced,
Cut the green sheet from the making roll and press it at 80Kg/cm ² for 1.5 seconds at 60℃ and 95℃.
After first curing under the conditions of %RH and 10 hours, the plate was cured indoors for a second time, and the board thickness was 5.4 mm and the thickness of the reinforcing layer was
A 0.15 mm asbestos-cement construction board was obtained. Example 2 An asbestos-cement building with a plate thickness of 5.4 mm and a reinforcing layer thickness of 0.15 mm was produced in the same manner as in Example 1, except that asbestos-cement slurry and reinforcing cement slurry having the compositions shown in Table 2 were used. I got a board. Comparative Example 1 An asbestos-cement building board with a thickness of 5.5 mm was obtained in the same manner as in Example 1, except that asbestos-cement slurry having the composition shown in Table 2 was used and no reinforcing cement slurry was used. Ta. Comparative Example 2 Asbestos cement slurry having the composition shown in Table 2 was used, no reinforcing cement slurry was used,
The rest was carried out in the same manner as in Example 1 to obtain an asbestos-cement construction board having a thickness of 5.3 mm.

[Table] Physical property tests were conducted on the asbestos-cement building boards obtained in Examples 1 and 2 and Comparative Examples 1 and 2, which were 10 days old. The results are shown in Table 3. still,
The bending strength was measured using a 20 cm x 20 cm test piece with a span of 15 cm, and the Charpy impact strength was measured using a 1.5 cm x 9 cm test piece. To measure infrared heating warpage, a 15 cm x 20 cm sample is irradiated with an infrared lamp from a distance of 50 cm, heated for 2 hours at a surface temperature of 80°C, and the intersection of diagonals of the sample 16 before and after heating is measured using a micro gauge 15. Measurements were made as shown in Figure 5, and the difference between the readings of Micro Gauge 1 before and after heating was calculated.

【table】

[Effect of idea]

As mentioned above, in the present invention, the asbestos-cement slurry that forms the substrate layer, which can also be called the main body of the building board, does not contain organic fibers, so the specific gravity does not decrease and the structure does not become poor. First, it does not cause large water absorption or drying, and dimensional changes can be kept to a small level.Also, even if the amount of asbestos mixed in the asbestos-cement slurry is reduced, wollastonite is still mixed in the asbestos-cement slurry. Therefore, this wollastonite can suppress a decrease in the bending strength of the architectural board, and can suppress the occurrence of warping. In addition, the organic fibers used to improve impact strength are mixed into cement slurry for reinforcement and used by scattering, so the organic fibers are oriented in random directions and the orientation of the organic fibers is It has no properties and can reduce the directionality of impact strength.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram showing an example of the device used in the present invention, Fig. 2 is an enlarged view of a part of the above-mentioned making roll portion, and Figs. 3 and 4 are enlarged sectional views of an asbestos-cement construction board. , FIG. 5 is a schematic diagram showing a method for measuring warpage. 1 is an asbestos cement slurry, 2 is a wet mat, 3 is a felt, 4 is a reinforcing cement slurry, 5 is a reinforcing layer, 6 is a making roll, and 7 is a green sheet.

Claims (1)

[Claims] 1. Asbestos-cement slurry containing asbestos and wollastonite is extracted and transferred onto felt as a wet mat, and a reinforcing cement slurry containing organic fibers is sprinkled on top of the wet mat as a reinforcing layer. is wound around a making roll several times, a green sheet in which wet mats and reinforcing layers are laminated in multiple layers is cut from the making roll, and this green sheet is press-cured. Law.