JPH0890536A - Method and apparatus for manufacturing fiber-reinforced cement plate - Google Patents

Abstract

PURPOSE: To uniformly supply cement slurry having low water content and high concentration and to obtain uniform orientation without considerably disordering the orientation of fiber in a method and an apparatus for manufacturing a fiber-reinforced cement plate having the steps of supplying the slurry in a layer state to a molding belt, sucking and dehydrating excess water, and manufacturing a plate. CONSTITUTION: This method for manufacturing a fiber-reinforced cement plate comprises the steps of supplying cement slurry S in a layer state on a molding belt 3, dehydrating from the rear of the belt 3 by a sucking and dehydrating unit 4 to remove the moisture, then manufacturing a plate, cutting the uncured cement plate, curing and hardening it. Accordingly, the slurry S is supplied from a discharge port 2B reduced in the aspect ratio of the section of the opening via a supply tube 2 reduced toward the port 2B of the belt 3 side in the aspect ratio of the section, and the material supply pressure to a supply port 2A is held constant by the weight of the slurry S held at the position higher than the port 2B constantly.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a fiber-reinforced cement board and an apparatus therefor, and more particularly to a method for manufacturing a fiber-reinforced cement board in so-called flow-on molding and an improvement in the apparatus.

[0002]

2. Description of the Related Art Conventionally, as a method for producing a fiber reinforced cement board, cement slurry B is fed in layers on a molded dehydration belt A from a flow box or an extrusion feeder C as shown in FIG. There is known a method for producing a fiber-reinforced cement board in which the water content of the cement slurry C is dehydrated by a suction dehydrator D while the plate-like body G is formed. The manufacturing method of these fiber-reinforced cement boards is called a papermaking method or a flow-on molding method among so-called wet manufacturing methods, and is well known as an industrial means for continuously mass-producing plate-shaped cement products.

By the way, as a means for supplying the cement slurry by this flow-on molding method, in addition to the above-mentioned flow box, a forced supply means by a screw cylinder, and a forced supply means by a dovetail nozzle previously proposed by the applicant of the present invention ( For example, Japanese Patent Application No. 5-219080 or Japanese Patent Application No. 5-219081
No. specification and drawings).

[0004]

However, when a flow box is used for supplying the cement slurry C onto the molded dewatering belt A, the solid content concentration relative to the water content of the cement slurry C is too high in order to secure the fluidity of the cement slurry C. Therefore, there is a problem that the dehydration load on the forming belt increases. In addition, since the flow rate may be different between both ends and the central part of the overflow weir of the flow box due to natural flow, it is difficult to make the supply amount uniform, and the alignment of the reinforcing fibers contained in the cement slurry is also difficult. However, there was a problem that the reinforcing effect of the reinforcing fibers could not be exerted effectively.

When an extrusion supply device is used instead of this flow box, the cement slurry is forcibly extruded and supplied, so that it is possible to raise the solid content concentration relative to the water content of the cement slurry to some extent. Therefore, the dehydration load on the molding belt is considerably reduced as compared with the flow box system, and specifically, there is an advantage that the scale of the molding dehydration belt can be reduced.

Besides, since the arranging property of the reinforcing fibers can be regulated to some extent by providing a flow regulating weir at the discharge port of the extrusion supply device, there is an advantage that a fiber-reinforced cement board having excellent strength can be formed. However, the structure of the extrusion feeding device is considerably more complicated than that of the flow box, and since cement hardens over time, maintenance and inspection of the device are indispensable, which increases the cost of the entire equipment and makes maintenance difficult. there were.

On the other hand, when the cement slurry is forcedly supplied by the dovetail nozzle proposed by the applicant of the present invention, that is, when the cement slurry is supplied, the cement slurry is inclined upward from the lower surface of the belt to the upper surface of the belt, and flattened toward the upper surface of the belt. The means for supplying from the expanding dovetail nozzle requires a separate means for supplying the cement slurry under pressure, but the supplied slurry smoothly spreads to the shape of the dovetail nozzle discharge port due to the supply pressure, just like extrusion molding. Molding ability is obtained.

Therefore, even a slurry having a low water content can be easily supplied, and the dehydration load on the forming belt can be considerably reduced. Further, since the pressurizing means can utilize the self-weight of the slurry whose water level is kept high on the supply side without using an extrusion device in particular, the molding capacity similar to that of the above-mentioned extrusion supply can be obtained while the facility is simplified. Although it has an advantage and is superior to the former two in this respect, it reduces the cross-sectional area of the slurry supply channel, but the width of the cross-section of the supply channel widens rapidly as it approaches the discharge port. Due to this spread, a turbulent flow is generated at both ends in the width direction of the discharge port, and due to this, the orientation of the reinforcing fibers is not constant and the orientation of the fibers is closer to both ends in the width direction of the plate-shaped molded body that requires the highest strength. Problems such as disorder were discovered.

[0009]

In view of the above problems, the present invention provides a method for producing a fiber-reinforced cement plate as described above, which can uniformly supply even a cement slurry having a low water content and a high concentration, and further, a fiber The purpose of the present invention is to provide a method for producing a fiber-reinforced cement board and an apparatus for the same, in which the orientation of the sheet is not disturbed so much.

[0010]

That is, the method for producing a fiber-reinforced cement board according to claim 1 is that the cement slurry is supplied in layers on a molding belt and dehydrated from the back surface of the molding belt by a suction dehydrator. In the method for producing a fiber-reinforced cement plate in which moisture is removed and after plate-making, the uncured cement plate is cut and cured to be cured, cement slurry is used as the vertical and horizontal dimensions of the cross section approach the discharge port on the molding belt side. Through the reduced supply pipe, the discharge port having the smallest vertical and horizontal dimensions of the opening cross-section is supplied onto the forming belt, and the material supply pressure to the supply port of the supply pipe is fixed at a position higher than the discharge port. It is characterized in that it is kept constant by the weight of the cement slurry kept at.

Further, in the apparatus for producing a fiber-reinforced cement plate according to a second aspect, a discharge port for molding and discharging the cement slurry into a plate shape is provided at one end, and the cross-sectional area of the supply pipe connected to the discharge port is: As the vertical and horizontal dimensions of the cross section are both closer to the discharge port from the supply side, the rate of change is reduced smoothly, and the supply side of the supply pipe is made higher than the horizontal position of the discharge port, and the increased supply side is kneaded with water. It is characterized by being used as a supply tank for the fiber-reinforced cement compound slurry.

Further, the invention according to claim 3 is such that, in the apparatus according to claim 2, the supply pipe from the supply tank of the fiber-reinforced cement mixture slurry to the discharge port is once located at a position lower than the discharge port. It is characterized by being smoothly curved downward.

[0013]

The method for producing a fiber-reinforced cement board according to the present invention is, as described above, a method of papermaking or a flow method in the so-called wet method in which cement slurry is supplied in layers on a forming dewatering belt and dehydrated to make a board. The on-molding method is assumed.

In the method for producing the fiber-reinforced cement plate according to the first aspect, as a means for supplying the cement slurry, the cement slurry is passed through a supply pipe whose cross-sectional length and width are both reduced as it approaches the discharge port on the molding belt side. , Is supplied onto the molding belt from the discharge port having the smallest vertical and horizontal dimensions of the opening cross section.

Therefore, the cement slurry always flows while being compressed from the vertical and horizontal sides until it reaches the discharge port. Like the dovetail nozzle, the cement slurry is vertically compressed but diffuses in the width direction. Therefore, non-uniform pressure change does not occur. Therefore, the slurry flows in the supply pipe and is discharged from the discharge port in a state where turbulent flow such as vortex is unlikely to occur. Therefore,
The internal texture state of the layered cement slurry discharged from the discharge port is almost uniform in the entire cross-sectional area, the phenomenon that the fiber orientation state is different between the center and both ends in the width direction is avoided, and the product strength is also uniform as a whole. It becomes possible.

An apparatus for producing a fiber-reinforced cement board according to a second aspect is an apparatus for carrying out the method according to the first aspect, wherein the cross-sectional area of the cement slurry supply pipe is such that both the vertical and horizontal dimensions of the cross-section are from the supply side. The closer to the ejection port, the smaller the rate of change is. That is, the cross-sectional area of the supply pipe along the path from the supply side to the discharge port has a cross-sectional shape in which both the vertical dimension and the horizontal dimension are reduced. Therefore, the cement slurry flowing in this supply pipe reaches the discharge port,
Lateral pressure is always applied from both the vertical and horizontal directions.

Since the supply side of the supply pipe is higher than the horizontal position of the discharge port, the supply pressure and the discharge pressure to the supply pipe can be obtained by this head pressure without using an extruder or the like.

According to a third aspect of the apparatus for manufacturing a fiber-reinforced cement plate, the supply pipe according to the second aspect is smoothly curved downward so that it is once lower than the discharge port.
This smooth curved portion improves the orientation of the reinforcing fibers contained in the cement slurry.

That is, the flow of the slurry is fast on the outside of the curved portion of the supply pipe and slow on the inside. Therefore, the reinforcing fibers mixed in the cement slurry in the longitudinal direction change their postures along the flow direction of the slurry due to the difference in the flow, and thereby the orientation of the fibers in the flow direction is increased to some extent. It will be improved. Therefore,
The fibers contained in the cement slurry discharged from the discharge port are highly likely to be in a posture along the flow direction, whereby the orientation of the fibers is maintained and the bending strength can be improved.

[0020]

Embodiments of the present invention will be described below. 1 is a side view of an apparatus for carrying out the method of the present invention, FIG. 2 is a front view of an apparatus for carrying out the method of the present invention, and FIG. 3 is a side view of another apparatus.

[Example 1] As shown in FIGS. 1 and 2, an opening 2A having a length H = 300 mm and a width B = 1200 mm is provided on the lower surface of a hopper-shaped cement slurry S supply tank 1. The length H and width B both decrease smoothly, and there is a discharge port 2B of length H = 45 mm and width B = 530 mm at the end of the length 10
A 00 mm supply pipe 2 was attached to form a slurry supply section. Next, as a raw material for the cement slurry S, 45% by weight of cement, 45% by weight of silica sand powder, 5% by weight of pulp fiber, lightweight aggregate
5% by weight was prepared, and water was added to this cement formulation to prepare cement slurries S having a slurry concentration of 15%, 20% and 25%. The head h is maintained at 1000 mm in the supply tank 1, the cement slurry S is supplied in layers from the discharge port 2B to a thickness of 40 mm and a width of 450 mm on the molding belt 3, and suction dewatering is performed by the suction dewatering box 4 to obtain the thickness. The 12 mm plate was cut to a length of 2700 mm and a width of 45 cm, transferred to a pallet (not shown), and cured by autoclave curing to obtain a test plate.

[Embodiment 2] As shown in FIG.
In place of the supply pipe 2 in the above, as the supply pipe reaching the discharge port 2B, the outer surface 2C is 240 mm from the lower edge of the discharge port 2B and the inner surface 2D is
A test plate was obtained in the same manner as in Example 1 using the supply pipe 2 that was smoothly curved as shown so that the level was lowered by 40 mm.

[Comparative Example 1] The same cement formulation as in Example was used, and the amount of water added was varied to prepare cement slurries having slurry concentrations of 15%, 20% and 25%. As shown in FIG. 4, each of these cement slurries S was supplied to a conventional flow box, supplied onto a forming belt, and similarly plate-formed.

[Comparative Example 2] As shown in FIGS. 5 and 6, a cement slurry supply pipe 2 having an inner diameter of 80 mm, a terminal width B of 450 mm, a height H of 40 mm, and a length L in the flow direction of 450 m.
The dovetail-shaped nozzle 6A set to m is arranged so that the discharge port 6B of the dovetail-shaped nozzle 6A opens to the forming belt 3 with an upward inclination angle of θ = 45 ° from the supply pipe 2 portion. Then, the cement slurry having the same concentration as in Example 1 is discharged in layers on the molding belt 3 to form a layer having a thickness of 40 mm and a width of 45 mm.
A 0 mm plate G was formed. After that, the plate was made and cured in the same manner as in Example 1.

When the ejection states of the plate-like bodies were observed in Examples 1 and 2 and Comparative Examples 1 and 2, Examples 1 and 2 were obtained.
In both Comparative Example 2 and Comparative Example 2, smooth molding was possible, but in Comparative Example 1, when the cement slurry concentration was 20%, uneven supply occurred, and when it was 25%, almost uniform thickness could not be supplied.

Next, a width of 450 mm obtained in Examples and Comparative Examples,
A plate-like body G having a length of 2700 mm was cut into pieces each having a length of 900 mm to form a test plate, and the bending strength was measured. Next, for Examples 1 and 2 and Comparative Example S with a slurry concentration of 25%, the same test plate was vertically divided into three strips of left, center and right with a width of 150 mm, and the fibers of these plates were divided. When the bending strength due to the orientation was measured, the results shown in Table 2 were obtained.

[0027]

[Table 1]

[0028]

[Table 2]

[0029]

As is apparent from Tables 1 and 2, when the plate-like body is formed by the method of the invention of claim 1, it is possible to form a uniform plate-like body even if the concentration of the cement slurry is high. Moreover, since there is almost no turbulent flow of the slurry in the supply path, it is possible to form a plate-shaped body having a uniform structure in the width direction and reduce the dehydration load on the forming belt. Also has an excellent effect.
The invention of claim 2 has a simple structure, and when the cement slurry is supplied, the density of the slurry is made uniform by utilizing the weight of the slurry. Therefore, a special device for that purpose, such as an extrusion supply device, is not required, and the invention is simple. It becomes possible to manufacture a fiber reinforced cement board with various devices. The invention of claim 3 has various effects such as being able to form a plate-like body having particularly excellent bending strength, since the fibers contained in the invention can be oriented as much as possible.

[Brief description of drawings]

FIG. 1 is a side sectional view of an apparatus for carrying out the method of the present invention.

FIG. 2 is a front sectional view of an apparatus for carrying out the method of the present invention.

FIG. 3 is a side sectional view of a device of another invention.

FIG. 4 is a side view of a conventional example.

FIG. 5 is a side view of a comparative example device.

FIG. 6 is a plan view of a comparative device.

[Explanation of symbols]

 S ... Cement slurry 1 ... Supply tank 2A ... Opening 2B ... Discharge port 2 ... Supply pipe 3 ... On molding belt 4 ... Suction dehydration box

Claims (3)

[Claims] 1. A cement slurry is supplied in layers on a molding belt, and water is removed from the back surface of the molding belt by a suction dehydrator to remove water, and after plate making, the uncured cement plate is cut and cured by curing. In the method for producing a fiber reinforced cement plate, the cement slurry is passed through a supply pipe in which the vertical and horizontal dimensions of the cross section are both reduced as they approach the discharge port on the molding belt side,
Along with supplying from the discharge port having the smallest vertical and horizontal dimensions of the opening cross-section onto the molding belt, the material supply pressure to the supply port of the supply pipe is kept constant at a position higher than the discharge port, and the weight of the cement slurry is kept constant. A method for producing a fiber-reinforced cement board, characterized in that it is kept constant. 2. A discharge port for molding and discharging cement slurry in a plate shape is provided at one end, and the cross-sectional area of a supply pipe connected to the discharge port is such that the vertical and horizontal dimensions of the cross section are closer to the discharge port from the supply side. , A smooth rate of change, and the supply side of the supply pipe is higher than the horizontal position of the discharge port, and the raised supply side is a supply tank for the fiber-reinforced cement mixture slurry. Equipment for manufacturing fiber-reinforced cement boards. 3. The supply pipe from the supply tank of the fiber-reinforced cement mixture slurry to the discharge port is smoothly curved downward so as to be located at a position once lower than the discharge port. Equipment for manufacturing fiber-reinforced cement boards.