JPS6278175A - Manufacture of asbestos cement board - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field 1] The present invention relates to a method for manufacturing asbestos cement boards used as building boards such as flat roofing materials and exterior wall materials.

[Background Art] It is well known that asbestos cement boards tend to lose strength when manufactured in the summer. This is mainly due to the fact that the water temperature of the slurry during papermaking is high due to the high air temperature in the summer, and the initial hydration reaction in the cement is too continuous, which severely inhibits the subsequent development of strength. This results in a lack of product strength.

Therefore, in order to prevent the strength from decreasing in summer, it is being considered to add SO1 component to Portland cement I in cement, and to ease the initial water use by increasing the SO1 component.
The current situation is that it is not possible to obtain a satisfactory effect just by increasing one component.

[Object of the Invention J The present invention has been made in view of the above points, and is
It is an object of the present invention to provide a method for producing an asbestos cement board that can effectively prevent a decrease in strength in summer by increasing the amount of one component.

[Disclosure of the Invention] The method for manufacturing an asbestos cement board according to the present invention is as follows: - Making a green sheet by making a slurry in which cement is blended with an A41 component and a Soco component, which are mainly composed of asbestos;
This green sheet is placed on a saturated water-containing sheet, pressed, dehydrated, and then cured.The present invention will be described in detail below.

Slurry is prepared by blending cement with a fiber component mainly composed of asbestos, and dispersing and kneading this in water.

As fiber components, in addition to asbestos, reinforcing a-fibers such as carbon fibers, polypropylene fibers, and vinylon fibers are blended as necessary, and fine grains of silica sand and the like are blended in the slurry as necessary. As the cement, ordinary Portland cement, blast furnace cement, 7 Liat cement, etc. can be used, and a slurry is prepared by adding an SO2 component equivalent to 1 to 5% of Portland cement.

As a source of the SO1 component, any source containing gypsum components such as calcined gypsum, neutralized phosphate gypsum, dihydrate, hemihydrate, and anhydrous salt of heptatogypsum can be used, or any of these gypsum A powder containing the component, for example, Denka Σ1000 (trade name) manufactured by Denki Kagaku Kogyo Co., Ltd. can be used. This Denka Σ1000 contains 80-90% anhydrite.
It contains 12 to 22% silica. In addition, those containing these gypsum components have a powder degree (specific surface area) of 50
It is desirable to use it as one that has been adjusted to 00cm"/g or higher. By the way, Denka Σ1000 has a specific gravity of 2.5
Above, the specific surface area is 5000cm27g or more.

The asbestos-cement slurry prepared as described above is formed into a green sheet using a paper-forming device such as a Hachinik method. The green sheet is then pressed and dehydrated and then cured, but the added SO3
The initial hydration of the cement components is alleviated by increasing the amount of the components. In other words, Figure 1 shows a graph of the heat generation curve obtained by measuring the heat generation characteristics of green sheets using a condensation calorimeter. A green sheet made from the prepared slurry, and a solid line show a green sheet made from a slurry in which Denka Σ1000 was further added to the SO3 component in an amount of 4% of ordinary Portland cement.

In Fig. 1, the time A' until the start of heat generation is 114 minutes and the time B' until the maximum heat generation is 258 minutes in the case of the dashed line without the SO3 component added, whereas in the case of the solid line with the SO3 component added. The time A until the start of heat generation is 126 minutes, and the time B until the maximum heat generation is 318 minutes, confirming that the time to start heat generation and the time until maximum heat generation are delayed by increasing the amount of SO3.

Furthermore, the maximum heat generation amount c, c' corresponding to the heat generation rate is SO5
108.0 cal/h for the dashed line with no added ingredients
In contrast, the solid line with the SO3 component added was 92.2 cal/h, confirming that heat generation is suppressed by increasing the amount of the SO5 component.

In this way, the fact that the heat generation time is delayed and the heat generation is suppressed by increasing the amount of SO3 component means that the initial hydration of the cement component is alleviated.
-1+ Color, Year Fog L -To 1- Δ) Cape 1 Table!
The influence of S Os component in cement is C y
A (3CaO” A I203) and C, AF (4CaO”
O・A1□0.・S03 component reacts with FezOz) to form ethrine sheet (3CaO・ALO*
' 3 CaSO-, 3 2 H2O), but since ettringite is produced containing a large amount of crystal water, water must be present in order to complete the ettringite reaction. management becomes important.

That is, green sheets are subjected to curing after press dehydration, but the water content of the green sheets due to press dehydration is insufficient for complete formation of ettringite. Therefore, attempts are being made to supply sufficient moisture by blowing steam during the primary curing of the green sheets, but the green sheets are loaded on plywood plates during the curing process. If steam blowing is carried out in this way, rust will form on the plywood plate and rust will adhere to the sheet, causing problems in subsequent processes.
)-M-Rere 4-mine ult report; 入ノﾾ91neefr2-し端C71时, the curing reaction can be carried out only by the moisture contained in the green sheet in the press-dehydrated state. In this way, if the curing reaction is carried out using only the water contained in the green sheet, the water content will be insufficient and the ethrin production reaction will be insufficient, and the initial hydration mitigation effect due to the increased amount of SO3 component will not be sufficient. Therefore, the effect of improving strength is small and the variation in strength improvement becomes large. In particular, due to the high temperature of gas, the moisture in the green sheet is quickly absorbed by the cement, making the lack of moisture even more pronounced.

Therefore, in the present invention, a water-containing sheet such as felt is spread on a carrier plate formed of a plywood plate, etc., and the water-containing sheet is uniformly saturated with water by spraying water or the like. The green sheet is placed on the water-containing sheet, and in this state, the green sheet is dehydrated by pressing. This is stacked in many stages and cured in this state. Furthermore, by pressing the green sheet with the green sheet placed on the water-containing sheet in a slightly saturated water state, it is possible to leave some water remaining on the water-containing sheet even after pressing. The water remaining in the water-containing sheet can be used to replenish the lack of water in the green sheet, and it is possible for ethrin to fully carry out the reaction to produce ion without the need to supply water by blowing steam. It is what it is. Curing can be carried out by conventional methods such as primary curing using heat or secondary curing by leaving it indoors.

Further, it is preferable to use a carrier plate with holes so that water can be drained from the water-containing sheet. Note that, as shown in FIG.
When the green sheet 2 is conveyed by a roller conveyor 4 or the like, water may be sprayed from a nozzle 5 onto the green sheet 2 and then subjected to press dewatering. Green sheet 2 by spraying water
This means that by increasing the water content of ethrin, it is possible to more fully produce ito.

The invention will now be illustrated by examples.

A slurry was prepared by dispersing the formulations shown in Table 1 in water. At this time, a slurry was prepared by blending Denka Σ1000 so that the SO1 component was 4% by weight based on ordinary Portland cement.

A green sheet created by paper-making this slurry is pressed and dehydrated while being placed on water-saturated felt placed on a carrier plate at rx, and then the green sheet is placed on a carrier plate via the felt. Asbestos cement boards were obtained by performing primary curing using heat and secondary curing by leaving them indoors.

Village μj mouth = ! An asbestos cement board was obtained in the same manner as in the example except that the slurry was prepared without adding Denka Σ1000 as shown in Table @1, and the green sheet was press dehydrated without using saturated felt. Ta.

As shown in Table 1, a slurry was prepared without adding Denka Σtoooo, and asbestos cement boards were obtained in the same manner as in the examples.

"Yorido" - #S1 As shown in Table S1, slurry was prepared by blending Denka Σ1000 in the same manner as in the example, and the green sheet was press-dehydrated without using saturated felt. An asbestos cement board was obtained in the same manner as in the example.

In the above Examples and Comparative Examples 1 to 3, the water content of the green sheets after press dehydration could be increased by 1% or more by using saturated felt. In addition, the bending strength of the asbestos cement boards prepared in Examples and Comparative Examples 1 to 3 was measured at 8 days old, and the results are shown in Table IjS2. In Table 2, the span 50C111 is 60,6
The bending strength of an asbestos cement board made as a roofing material with a size of cm x 44 ca+ was measured at a span of 50CI6, and for one with a span of 15cm, the bending strength was measured at a span of 50CI6.
1 for a test piece formed into a size of 0cm x 20cm
The bending strength was measured over a span of 5 cm. The test was conducted using 32 materials, and the average value is shown as ma, and the variation is shown as σn.

The results in Table 2 confirm that by adding Denka Σ1000 to increase the amount of SO1, the strength of the asbestos cement F board can be improved as in the example.

However, even if the amount of SO is increased in this manner, it is confirmed that in cases where water is not supplied to the green sheet as in Comparative Example 3, the degree of improvement in strength is low, and furthermore, variations in strength occur. This confirms that when sufficient water is supplied to the green sheet, the generation of ethrin and ionite by increasing the amount of SO1 component is carried out well.

[Effects of the Invention] As described above, in the present invention, a green sheet is created by making a slurry in which cement is mixed with a fiber component mainly composed of asbestos and SO and a components, and this green sheet is saturated with water. Since the material was placed on a water-containing sheet and then pressed and dehydrated before curing, the SO7 component was increased, and the amount of SO1 component was increased by replenishing water from the water-containing sheet. Ettringite can be produced well, and the initial hydration of cement can be suppressed during the summer season, thereby preventing poor strength and variations in strength.

[Brief explanation of drawings]

Figure 1 is a graph showing the relationship between the elapse of time and the calorific value per hour with and without the addition of the S Os component.
The figure is a schematic diagram showing the state of water supply to the green sheet. 1 is a water-containing sheet, and 2 is a green sheet.

Claims (1)

[Claims] (1) Cement contains fiber components mainly composed of asbestos and SO_
Asbestos characterized in that a green sheet is created by paper-making a slurry containing three components, and this green sheet is placed on a saturated water-containing sheet and pressed to dehydrate it, and then cured. Method of manufacturing cement board.