JPS58222809A - Manufacture of fiber reinforced 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] This invention relates to a method for manufacturing fiber-reinforced cement boards, which does not use asbestos at all, taking into consideration the limited resources of asbestos that has traditionally been used and the legal regulations regarding its use. ,
A method for easily manufacturing asbestos-free cement boards that have excellent physical properties and do not require significant improvements to the circular mesh papermaking machine that has been used to manufacture asbestos-cement boards. The purpose is to provide

Legal regulations regarding the use of asbestos are now international. In Japan, it has been designated as a specially controlled substance since 1976.

Against this background, attempts have been made to develop products and manufacturing methods that do not use asbestos or use a reduced amount of asbestos.

However, despite past efforts, no product has been developed that approaches the characteristics of asbestos-cement boards.

The reason for this is thought to be as follows.

■ As an asbestos alternative fiber, it has many disadvantages in terms of characteristics, price, and manufacturing method.

■ It costs money to modify existing equipment.

■ Weak need for asbestos-free products.

However, it is an almost certain fact that asbestos is becoming depleted in terms of resources, and it must therefore be said that there is still an urgent need to develop products and manufacturing methods that do not use asbestos.

Under the above circumstances, the inventors of the present invention have arrived at the present invention as a result of research into a method for manufacturing an asbestos-free cement board that is as inexpensive as possible and can be expected to have sufficient quality. In other words, they were able to invent a method for manufacturing fiber-reinforced cement boards that minimized the modifications to existing circular mesh paper machines and improved performance (particularly high initial and long-term strength) and cost. This will be explained in detail below.

The present invention provides a method for manufacturing fiber-reinforced cement boards using a papermaking method, in which a mat (meaning a thin sheet-like uncured cement sheet formed by papermaking on felt, hereinafter the same) is prepared from a hydraulic cement slurry. When forming a green sheet by winding a predetermined number of layers around a making roll, a reinforcing material is sprinkled on the mat corresponding to the first layer formed on the felt, and then one layer is applied from the final layer. It is characterized in that it includes a step of dispersing a reinforcing material similar to that described above on the felt before the layer. Although reinforcing fibers are usually blended into the hydraulic cement slurry, here, a slurry containing reinforcing fibers with a relatively short fiber length is used. For example, a hydraulic cement slurry containing short organic fibers with a fiber length not exceeding 31 as the main reinforcing fiber component (hereinafter referred to as short fibers) is prepared, and if necessary other additives, such as cement Hardening modifier, polymer flocculant or silica sand (No. 8 silica sand is often used), silica powder,
It is preferable to use a slurry to which an inorganic filler such as calcium carbonate is added. This slurry must be capable of being made into paper using a conventionally used circular mesh paper making machine.
The short fiber is 1.0 per solid weight of this slurry.
The content is preferably 5.0% by weight (hereinafter abbreviated as %). As short fibers, pulp is particularly preferred, although it is not intended to be set at +4. The concentration of the slurry used is most preferably 5.0 to 15.0%. The composition is 1 to 15% filler and the remainder is Portland cement.

The above-mentioned papermaking slurry is made into paper using a circular mesh papermaking machine, and a cloak is formed on endless felt. Here, the thickness is preferably 0.5 to 1.0 mm, although this is not intended to be limiting. This kind of man-nod is then wound onto a making roll.

In a fiber-reinforced cement board, when stress is applied to the board surface, cracks occur on the opposite surface. In fiber-reinforced cement boards, the fibers near the surface layer serve to suppress the occurrence of cracks. The internal fibers play a role in suppressing the propagation of this crack. However, in reality, once a crack occurs on the surface, it has already lost its commercial value, so preventing the propagation of the crack is of little value. Therefore, it is considered important to prevent the occurrence of scratches in the surface layer. In this invention, this problem is solved by dispersing a reinforcing material, that is, reinforcing fibers, on the first layer of the cloak and on the layers before the final layer and the IN layer.

5-4- The reinforcing fibers here are preferably longer fibers than the reinforcing fibers in the cement slurry.

This long fiber reinforcing material is a monofilament or a strand-like material made by physically or chemically assembling fibers with a fiber length of preferably 3 inches or more, or a paper-like cloak made of such fibers. , sheets, cloth, and other reinforcing fibers. In addition, the material is charcoal S.
One or more of fibers such as polypropylene fibers, vinylon fibers (trademark), aramid fibers (kepler (trademark)), polyacrylonitrile fibers, metal fibers, etc. are used. Among these, fibers with particularly good alkali resistance are recommended.

The long fiber reinforcing material is arranged in the above predetermined position as follows.

゛ That is, the length equivalent to the first layer of a cloak made using the above slurry and formed on felt (1st N refers to the layer that is wound around the making roll for the first time, and the length equivalent to one turn of the making roll) Scatter or spread the long fiber reinforcing material as evenly as possible on top of

In this case, the spraying method may be a dry method, or a mixture with a thin cement milk or the like may be sprayed.

A cement paste-like material may be spread after dry spreading.

The preferred composition of the long fiber mixed cement slurry is 1 to 15% of long fibers, 1 to 15% of inorganic filler, and the remainder is Portland cement. In addition,
Here, the blending amount of water is preferably 40 to 6% of the solid content.
It is 0%.

Next, the same long fiber reinforcing material as described above is sprinkled on the mat one layer before the final layer. For example, reinforcing fibers are sprinkled on the mat surface of the first layer, then the 3rd to 6th layers of the cloak are wound up on a making roll, the same reinforcing fibers are sprinkled on the 7Nth mat, and then the final He is winding up the eighth layer of his cloak.

Of course, during this time, dehydration is carried out by passing a burr through the felt as necessary.

After the mat is rolled a predetermined number of times with a making roll, it is spread out into a flat shape by cutting, and if necessary, it is pressurized to an appropriate pressure to cure and harden.

After spreading the long fiber reinforcement material, a cement paste-like material, which is spread as necessary, is spread on the fibers that were previously supplied on the mantle, and the gaps between the fibers are filled in the section head (filling). It is preferable that the composition and viscosity be such that the area around the fibers is covered with this cement paste-like material, and usually this cement paste-like material is blended with water in a range of 25 to 70% based on the solid content of hydraulic cement. The above effect can be achieved most efficiently if the paste is made of a paste.

Note that the degree of dehydration through the felt is not particularly limited. The purpose of this dewatering process is to remove excess water from the multiple layers of cementitious mantle formed just before the making roll, or to remove excess water from the making roll, which has a high moisture content and adheres to its surface, resulting in poor mold release properties. This is to prevent this from happening. Therefore, the amount of water removed may vary depending on other manufacturing conditions and the condition of the felt.

However, if this dehydration is done too much, it will harden.
11" l=8-, the adhesive strength between the eyebrows is weakened, which has a particularly negative effect on frost resistance.

The green sheet obtained through the making roll section is
Thereafter, if necessary, it may be pressed and pressurized, and a high specific gravity material or an embossed pattern etc. may be added to the surface.

As for the curing conditions, all the conditions normally used for cement products can be used.

As explained above, the present invention is a method for producing fiber-reinforced cement boards using a circular net-type paper machine, in which a green sheet is produced by drawing up a mat from hydraulic cement slurry and winding a predetermined number of layers around a making roll. When forming the felt, the reinforcing material was sprinkled on the mantle corresponding to the first layer formed on the felt, and the reinforcing material similar to the above was further sprayed on the felt layer one layer before the final layer. Because of this feature, it was possible to manufacture a fiber-reinforced cement board with excellent initial and long-term strength without using Ashest M fibers and with a reduced amount of reinforcing fibers.

91 Example A cement slurry for papermaking containing short fibers having the following composition was used.

71. , Pu 5% No. 8 silica sand 5% Portland cement 90% Slurry solid content concentration 85% Using the above papermaking slurry, papermaking was carried out using a circular mesh papermaking machine, and a mat of 0.5 to 1 dragon was made on felt. was formed.

The following materials were used as long fiber reinforcing materials.

A Carbon fiber: Monofilament 2Qm chair, manufactured by Kureha Chemical B Polypropylene fiber: C Vinylon fiber: Manufactured by Kuraray ■, trademark, 13 Rycho.

D Kevlar fiber: DuPont (manufactured by T1, trademark, 10 crane length) E Polyacrylonitrile fiber: The following two methods were used for spraying.

-10- a Dry spraying b Spraying as long fiber mixed cement slurry. However, the slurry composition is the amount of long fiber reinforcing material: 10% No. 8 silica sand 5% Portland cement 85% Water 55% The structure of the plate obtained is schematically shown in FIG. 2. In this figure, 1 is a storage tank for cement slurry containing short fibers, 2 is a transport pipe, 3 is a bar, 4 is white water, 5 is a sieve cylinder, 5a is a cloak, 6 is an endless felt, and 7 is a long fiber reinforcement material. 8 is a suction box, 9 is a making roll, 10.11 is a conveying roll, 12 is a cement layer containing short fibers, and 13 is a layer containing a long fiber reinforcing material i. When the above-described apparatus is used, a slurry having a predetermined composition is stored in the slurry tank 1. Then, it is made and raised by the sheave cylinder 5, and the felt 6
A mat 5a-11- is formed on the mat 5a-11-. Next, the long fiber reinforcing material is spread by the long fiber reinforcing material spreading device 7. Spreading of long fiber reinforcement is 1
The length can be kept equal to the length of the layer. This mat 5a is dehydrated by a suction 8 and wound onto a making roll 9. Next, at a stage one layer before the scheduled number of winding layers, the long fiber reinforcing material is again dispersed in one layer. When a predetermined layer is completed on the making roll 9, it is cut by a cutting device and transferred to the next process. The following is cured (conditions are 60° C. for 124 hours) and hardened in a conventional manner. As can be seen in Figure 2, the resulting board has a layer 13 containing long fiber reinforcing material located one layer below the surface layer, and the rest is short fiber-containing cement! 12 shows a layered structure in which 12 are overlapped. In this example, a plate having eight layers including both layers was manufactured.

The physical properties of the cured plates obtained above were measured and shown in Table 1.

even more 19- Table 1 13- −　l　t　−

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a paper making machine used in this invention, and FIG. 2 is a sectional view of a plate obtained by this invention. ■Storage tank 2 for slurry containing short fibers Transport pipe 3 Batt 4 White water 5 Sieve cylinder 5a Matro Endless felt 7 Long fiber reinforcement spreading device 8 Suction box 9 Making roll 10111 is conveyance The roll 1''2 is a cement layer containing short fibers 13 is a layer containing a long fiber reinforcing material.Patent applicant: Matsushita Electric Works Co., Ltd. Representative patent attorney: Toshimaru Takemoto (2) 14-

Claims (1)

[Claims] (1) In the manufacturing method of fiber-reinforced cement board using a circular net-type paper machine, when forming a green sheet by cutting a mantle from hydraulic cement slurry and winding it around a making roll for a predetermined number of layers, A fiber-reinforced fiber reinforced material comprising the steps of: scattering a reinforcing material on the mat corresponding to the first layer formed in the first layer, and further scattering the same reinforcing material on the felt layer one layer before the final layer. Manufacturing method of cement board. −