JPH02275784A - Production of fiber cement board - Google Patents

Abstract

PURPOSE:To improve resistance to frost damage by molding green sheet from fiber cement slurry, dehydrating and cutting to form cement raw board, then subjecting to primary curing, impregnating with microgel emulsion and subjecting to secondary curing. CONSTITUTION:Green sheet is molded by sifting of fiber cement slurry and dehydrated, then cut to a fixed dimension to form cement raw board. Said cement raw board is subjected to primary curing at 40 to 60 deg.C in >=70% RH for 6 to 10 hour. Then, said raw board is impregnated with an aqueous solution of acrylate-based crosslinked microgel emulsion having about 0.03mum average particle diameter and 0.05 to 50wt.% solid concentration for >=3sec to obtain 1 to 5wt.% impregnating fraction and subjected to secondary natural curing for about 5 day to afford a fiber cement board. Besides, cement raw board after the primary curing is impregnated with aqueous solution of microgel emulsion and cured in autoclave, then a fiber cement board is obtained, too.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a method for manufacturing #& fiber cement board by forming fiber cement slurry.

[Conventional technology]

Fiber cement boards have been widely used for tiles, exterior materials, etc. M&fiber cement board A is l! as shown in FIG. ! be left behind. That is, first, fiber cement slurry I No. 1 is formed into a green sheet 3 using a beech-nick type wet machine 2, and after being wound up using a making roll 4, it is placed on a carrier plate 5, and the green sheet 3 is pressed! Steps 5 and 6 compress and dehydrate the cement and cut it into a predetermined size and shape to produce green cement board 7 (Fig. 1 (a)
(b)(c)(cl)). Next, the green cement boards 7 are loaded and cured under heat within the curing angle 8. Heat curing is usually 40-60°C, humidity 7
The test was carried out for 6 to 10 hours at 0% R8 or higher. After this second curing, a second curing is performed. For example, as shown in Fig. 2, the secondary curing is carried out by
are loaded on a pallet 9, covered with a sheet 10 on the top shelf, and left to naturally cure for about 5 days. When the fiber cement board A manufactured in this manner is used as a roof tile, the surface thereof is coated and the product is made into a product. In addition, if the product is to be painted after autoclave curing, as shown in Figure 3, pre-autoclave painting is done with acrylic paint or other synthetic resin paint before the secondary curing (Figure 3 (a)). After preventing efflorescence, autoclave curing is performed in autoclave 11, and the product is painted and manufactured.

[Problem to be solved by the invention]

In the past, there was a problem in that during secondary curing, water evaporated from the end faces of the loaded green cement boards and the small end faces in the vicinity and dried, resulting in insufficient water utilization reaction of the cement. In other words, in the secondary curing, only the top layer of the stacked green cement boards is covered with a sheet, so the evaporation of moisture from the outer edge of the stacked green cement boards that is not covered with the sheet is reduced. Inevitably, there will be a considerable difference in dryness between the center and the outer periphery of the fiber cement board. For this reason, the hydration reaction at the outer peripheral edge is not sufficient, and as it dries, a large number of voids are formed, resulting in a problem of reduced frost damage resistance. The present invention has been made to solve the above-mentioned problems, and has the following objectives: 1. It is possible to sufficiently advance the water utilization reaction at the outer peripheral edge of green cement boards, and to fill the voids. An object of the present invention is to provide a method for manufacturing a fiber cement board that can improve frost damage resistance.

[Means for Solving the Problems 1] The method for manufacturing a fiber cement board of the present invention involves forming a green sheet by making fiber cement slurry, dewatering the green sheet, and cutting it into predetermined dimensions to produce a green cement board. In the manufacturing method of M/L fiber cement board in which green cement board is first cured and then second cured, the green cement board is impregnated with microdel emulsion at the time of second curing. This configuration solves the above problems. [In action, since the green cement board is impregnated with Microdel emulsion before secondary curing, water evaporation from the outer edge of the green cement board can be avoided during the secondary curing, and the hydration reaction can be sufficiently carried out. Furthermore, the microdel emulsion can be used to fill voids and improve frost damage resistance. As the cement used in the present invention, any of plain Portland cement such as ordinary Portland cement, early strength Portland cement, and medium Portland cement, special cement such as mixed Portland cement, alumina cement, and magnesia cement can be used. This cement contains olastonite, mica, silica,
Inorganic aggregates such as Seviolite, reinforcing fibers such as asbestos, pulp, organic materials such as vinylon, water repellents such as lignin sulfonic acid, formalin condensates, and other admixtures are mixed as required, and an appropriate amount of water is added. A fiber cement slurry is prepared. This fiber cement slurry is prepared in the same way as before, for example.
The paper is made using a Hatchik-style wet machine. In the present invention, it is an essential component to impregnate the green cement board with the microdel emulsion before the primary curing and/or the secondary curing after forming. As the microdel emulsion, for example, acrylic acid ester-based pre-crosslinked Ni fine particle emulnotan can be mentioned, the average particle size is 0.03μ, and the Tg is -23°.
C. MFT (film forming temperature) is 0° C., elongation is 400%, and it is preferable that it is flexible and easy to handle. Microdel emulsion is made by immersing a green cement board in its water/H solution or impregnating it under reduced pressure. The solid content concentration of the microdel emulsion used is 0.05 to 50% by weight, and the ratio of impregnation into the green cement board is 1 to 5% by weight. If it is less than 1% by weight, the waterproofing effect will be poor and the effect of improving frost damage resistance will be small, and if it exceeds 5% by weight, there is a risk of failing the nonflammability test. The impregnation rate is determined by the formula [(weight of fiber cement board impregnated with microdel emulsion - bone dry weight of fiber cement board)/# & bone dry weight of fiber cement board x 10
Calculated from 0 (weight %) 1. For example, in the case of moist heat curing or natural curing, m-fiber cement slurry is made into paper to form a green cement board, this green cement board is impregnated with an aqueous solution of Microdel emulsion, and then multiple sheets are stacked at 40 to 60°. Primary curing is performed for 6-10 hours at C170%RH or above. Thereafter, the green cement board is impregnated with an aqueous solution of Microdel emulsion, and after a second natural curing, painting is applied to produce a fiber cement board. In the case of autoclave curing, fiber cement slurry is made into a paper to form a green cement board, this green cement board is impregnated with an aqueous solution of Microdel emulsion, then multiple sheets are loaded, and heated at 40 to 60°C and 170% RH or higher for 6 to 60 minutes. Primary curing takes 10 hours. Thereafter, the raw cement board is impregnated with an aqueous solution of Microdel emulsion and subjected to secondary natural curing for 24 hours or more. Then, the temperature was raised for 1 hour and held at 120℃ or higher for 3 hours.
After curing in an autoclave under the conditions of 1 hour and temperature drop of 1 hour, a #& fiber cement board is manufactured by painting. Next, the present invention will be explained in detail. (Example 1) A green sheet was formed from fiber cement slurry by a conventional method, and the green sheet was dehydrated and cut into a predetermined size to form a green cement board. Before secondary natural curing, the loaded green cement boards were immersed for 30 minutes in an aqueous microdel emulsion (solid content concentration 30% by weight) consisting of an acrylic acid ester-based low-crosslinked ultrafine particle emulsion (average particle size 0.03μ) ( Impregnation rate 2.
2% by weight) and then naturally cured for 5 days to produce a fiber cement board. Pore distribution ratio and swelling rate (freeze damage test A) of this fiber cement board
STMC-666A method (swelling rate of 200 c/s) and water absorption rate were measured. The results are shown in Table 1. (Example 2) The impregnation rate of the microgel emulsion was set at 3.6% by weight,
A fiber cement board was manufactured in the same manner as in Example 1 except that autoclave curing was performed. The pore distribution ratio, swelling ratio, and water absorption rate of this fiber cement board were measured. The results are shown in Table 1. (Example 3) A fiber cement board was manufactured in the same manner as in Example 1 except that the impregnation rate of the microdel emulsion was 0.4% by weight. The pore distribution ratio, swelling ratio, and water absorption rate of this fiber cement board were measured. The results are shown in the mi table. (Comparative Example 1) A fiber cement board was manufactured in the same manner as in Example 1 except that it was not impregnated with the microgel emulsion. The pore distribution ratio, swelling ratio, and water absorption rate of this fiber cement board were measured. The results are shown in table fjS1. (Comparative Example 2) A fiber cement board was manufactured in the same manner as in Example 2 except that it was not impregnated with the microgel emulsion. The pore distribution ratio, swelling ratio, and water absorption rate of this fiber cement board were measured. The results are shown in Table 1. Table 1 Examples Comparative Examples Pore diameter volume of 0.1 to 1μ (cm/g) 0.0247 0,0189 0
,0501 0.0652 0,0771 Total pore volume (cm/g) 0,0634 0,0413 0
．． 2292 0.2420 0.2692 Pore distribution ratio (%), 39.0 45.8 30.1. 2
6.9 28.6 Swelling rate (%) 0.81 0.72 3.65 4.0
8 4,86 Water absorption rate 6.2 4,7 16,1 18,5 19.
6 From the results in Table 1, it is understood that the pore distribution ratio of the examples of the present invention is larger than that of the comparative example, and the swelling ratio and water absorption rate are smaller than those of the comparative example. Effects of the Invention The present invention involves forming fiber cement slurry into a green sheet, dewatering the green sheet, cutting it into predetermined dimensions to form a green cement board, and then subjecting the green cement board to primary curing. In the manufacturing method of fiber cement board, which performs secondary curing after the second curing, the green cement board is impregnated with microgel emulsion before the second curing, so that water from the outer edge of the green cement board is absorbed during the second curing. It is possible to avoid evaporation, therefore, the hydration reaction can proceed sufficiently, and moreover, the voids can be filled with the microgel emalnotane to improve frost damage resistance.

[Brief explanation of drawings]

Figures 1 (a), (b), (c), (d), (e) and (f) are explanatory diagrams showing the manufacturing process up to the primary curing of fiber cement boards;
Figures (, ) and (b) are explanatory diagrams showing the process of secondary curing by natural curing of fiber cement boards, and Figure 3) (b) and (c) are explanatory diagrams showing the process of secondary curing of fiber cement boards by autoclave curing. 1 is a fiber cement board, 1 is a fiber cement slurry, 2 is a beech-nick type wet machine, 3 is a green sheet, 6 is a press machine, 7 is a raw cement board, 8 is a curing can, 1o is a sheet, 11 is an autoclave.

Claims (3)

[Claims] (1) Paper-making fiber cement slurry to form a green sheet, dewatering the green sheet, and cutting it into predetermined dimensions to form a green cement board.The green cement board is then subjected to primary curing, followed by secondary curing. A method for producing a fiber cement board comprising: impregnating a green cement board with a microgel emulsion before performing secondary curing. (2) The solid content concentration of the microgel emulsion is 0.05
The method for manufacturing a fiber cement board according to claim 1, characterized in that the content is 50% by weight. (3) A method for producing a fiber cement board, which comprises immersing a green cement board in a microgel emulsion for 3 seconds or more.