JPH05148002A - Production of fiber-reinforced cement board - Google Patents

Abstract

PURPOSE:To improve the bonding of pulp fibers so as to impart excellence in the heat resistance and chemical resistance to a cement matrix. CONSTITUTION:The production method comprises wet-fibrillating pulp fibers, adding silica powder to the fibrillated pulp for refining, drying the fibrillated pulp fibers, grinding the fibers into a prescribed size, adding the ground pulp to a cement composition comprising a cement and silica and subsequently molding the mixture on a molding belt by a drying method.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a fiber-reinforced cement board, and more particularly to an improvement of a method for producing a fiber-reinforced cement board by using a pulp fiber as a reinforcing fiber by a so-called dry method.

[0002]

2. Description of the Related Art Conventionally, as a means for producing a cement board, a powder material, which is a mixture of dry cement, silica, and reinforcing fibers, is supplied in layers on a molding belt, compression molding is carried out by means of rolls, and necessary moisture content is obtained. There is known a dry manufacturing method in which the compound is spray-supplied and cured and cured by an autoclave. In this dry method, high temperature and high pressure steam curing by an autoclave is indispensable because the hydration reaction of cement is carried out with the minimum necessary amount of water, and addition of reinforcing fiber is also indispensable for improving product strength.

[0003]

[Problems of the prior art] By the way, in the dry manufacturing method,
Asbestos fiber has been traditionally used as a reinforcing fiber to be added, but as asbestos causes pollution, it is strongly required to restrict its use or abolish it, and the necessity of adopting a substitute fiber for it has become very high. There is. However, since the autoclave is an indispensable step in the dry manufacturing method as described above, the alternative fiber must have heat resistance and alkali resistance, and therefore, the organic synthetic fiber and the like have heat resistance. Further, glass fibers are insufficient in terms of alkali resistance, and for the time being, pulp fibers without such difficulties have been used as promising in terms of cost. However, there is a problem in that the pulp fiber has a fairly smooth surface and has poor bonding properties with cement particles and does not have the adhesiveness of asbestos, so that the reinforcing effect commensurate with the addition cannot be obtained.

[0004]

In view of the above problems, the present invention provides a method for producing a stronger fiber-reinforced cement board by improving the bondability of pulp fibers having excellent heat resistance and chemical resistance to the cement matrix. It was made for the purpose of providing.

[0005]

Means for Solving the Problems That is, the method for producing a fiber-reinforced cement board according to the present invention is such that after pulp fibers are wet defibrated, silica fine powder is added to the defibrated pulp to carry out a refiner, The defibrated pulp fibers are dried and then crushed to a predetermined size, and the crushed pulp is added to a cement mixture composed of cement and silica and mixed, and molded by a dry method on a molding belt. is there.

[0006]

FUNCTION If the parf fiber as the reinforcing fiber added in the production of the fiber reinforced cement plate is as it is as described above, the surface is smooth and the bondability to the cement matrix is poor. When the pulp fiber is wet defibrated and refined, the surface becomes considerably bulged, which improves the bondability with the cement matrix, but in the case of the dry manufacturing method, it is necessary to dry the defibrated fiber again. However, during this drying, the fluffing of the bent fibers returns to the original state, and eventually it becomes impossible to obtain sufficient bondability with the cement matrix.

Therefore, in the present invention, after the pulp fibers are wet defibrated, silica fine powder is added to the defibrated pulp to perform a refiner. Since the pulp fiber is wet, the fine silica powder adheres very well, and since refining occurs in this state, silica particles enter between the fluffy pulp fibers, and if the pulp fiber is dried in this state, it rises. Is dried as it is. Therefore, when it is added to the cement formulation and dry mixed, the physical integrity of the pulp fiber and cement matrix is improved. Further, the pulp fiber incorporating the silica fine powder has a good chemical bondability with the cement particles and contributes to sufficient strength development.

[0008]

Embodiments of the present invention will be described below. When defibrating commercially available sheet pulp, the defibration of the pulp was performed using a wet defibrating machine. Then, when the wet defibrated pulp is applied to a refiner to make it stand up, a Blaine value of 10,0
Refinement was performed by adding the same amount of silica finely pulverized to 00 cm ² / g as the pulp. Next, after drying this pulp fiber, it is crushed by a crusher to an average fiber length of 2.0 mm, cement 56-58 wt%, silica (fine silica sand)
The cement mixture was prepared by adding 3 to 6% by weight of the pulverized pulp fiber to 36 to 38% by weight and dry-mixing with a mixer. Next, this cement mixture was fed in layers on a molding belt, and the dry method was used to obtain a thickness of 5.0 mm, a width of 45 cm, and a length of 90 cm.
A cm-shaped plate was formed. Next, the plate-shaped molded body was naturally cured for 3 days, and then autoclaved at 180 ° C. for 10 hours.

As a comparative example, a pulp of the same size was molded in the same manner as in Example except that the refined pulp was used without adding the fine silica powder at the time of refining, and curing was performed under the same conditions. Let When the bending strength test, specific gravity measurement and water absorption test were conducted on the plate materials obtained in Examples and Comparative Examples, the results shown in Table 1 were obtained.

[0010]

[Table 1]

As is clear from Table 1, there was no difference in specific gravity and water absorption, but in terms of flexural strength, it was 10 to 15%.
It was confirmed that the strength was improved.

[0012]

As described above, according to the present invention, silica fine powder is forcibly mixed and refined to intervene between fluff fibers when refining pulp fibers. Is maintained as it is, so that the bondability with the cement matrix is improved and the strength can be improved.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display location C04B 28/18 8618-4G 40/00 7351-4G // (C04B 28/18 16:02 Z 2102 -4G 20:02) Z 2102-4G

Claims (1)

[Claims] 1. After wet defibrating pulp fibers, silica fine powder is added to the defibrated pulp for refining, and then the defibrated pulp fibers are dried and then crushed to a predetermined size,
A method for producing a fiber-reinforced cement board, which comprises adding the crushed pulp to a cement mixture composed of cement and silica, mixing and molding the mixture on a molding belt by a dry method.