JPH1199512A - Manufacture of fiber reinforced cement plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize the stronger plane tensile strength of a surface layer and, at the same time, heighten the working strength after its primary curing by easily giving a deep-engraved uneven pattern to the surface of a cement plate by a method wherein a micro-bubble-containing surface layer is provided. SOLUTION: In a single layer flow-on molding method, in which a plate is produced by laminarly feeding a cement slurry mixed with a suction dehydrating device and, after being suction-dehydrated, embossably pressed, 2-10 wt.% of silica fume or crystalline silica having the specified surface area of cement by blaine of 8,000 cm<2> /g or finer is added to the cement slurry prepared by mixing micro-bubbles. Instead, a process, in which 75-200 g of a silica fume aqueous solution per the square meters of the surface of the cement slurry layer mixed with micro-bubbles before pressing is sprayed on the surface of the cement slurry and then embossably pressed, is prepared.

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 more particularly, to a flow-on molding method, in which a cement slurry layer containing fine air bubbles is provided on a plate-making belt, and the surface thereof is pressed. The present invention relates to an improvement in a method of manufacturing a fiber reinforced cement board having a deeply carved uneven pattern.

[0002]

2. Description of the Related Art A flow-on molding method is known as a method for producing a fiber-reinforced cement board. This flow-on molding method is a kind of papermaking method in a method of producing a fiber-reinforced cement board, in which a cement slurry composed of a fiber-reinforced cement is supplied in a layer form on a felt belt equipped with a suction dewatering device, and a predetermined moisture content is obtained. It is transported and dehydrated until it becomes a plate shape, and then cut at predetermined lengths at the end of the felt belt,
It refers to a process consisting of a step of pressing to form an uneven pattern on the surface and curing and curing.

[0003] By the way, many fiber-reinforced cement boards are provided with an uneven pattern on the surface to impart a design, and the uneven pattern is usually formed by pressing, but by a papermaking method such as a flow-on molding method. The produced fiber reinforced cement board has a problem that it is relatively difficult to clearly impart a deep uneven pattern.

[0004] When a sheet is formed by a papermaking method including a flow-on molding method, the moisture content of the plate material is considerably reduced due to suction dehydration on a plate-making belt, and the fluidity of the cement layer surface is reduced at the time of pressing. It is considered that the cause is.

[0005] The applicant of the present invention has proposed that at least the surface layer of the cement layer formed in the flow-on molding method is a layer made of cement slurry containing fine bubbles,
A method was proposed in which the friction between particles was reduced by fine bubbles contained therein, and even when the water content was small, a deeply carved uneven pattern was formed by pressing without causing defects such as cracks.

[0006]

By the above method, it is possible to easily form a deeply carved uneven pattern, especially a deep carved uneven pattern having a large shaping angle, even if the surface layer has a small water content. However, the surface layer had a porous structure due to microbubbles, so the final product lacked in plane tensile strength and frost resistance, and even during the manufacturing process, the surface layer had resistance after primary curing and before final curing. There was a problem that the impact strength was insufficient, and the surface layer was easily cracked or chipped by the impact due to contact with other objects during transportation.

[0007] However, such a problem during the production is considered to increase the curing temperature during the primary curing and promote the hydration reaction of the uncured plate to increase the bonding strength of the cement matrix.

However, since ordinary siliceous substances cause a pozzolanic reaction only at 100 ° C. or higher, if primary curing is performed at a high temperature of 100 ° C. or higher, a hydration reaction to be generated during autoclave curing occurs during primary curing.

If the hydration reaction proceeds as described above, the curing reaction due to the pozzolanic reaction during the subsequent autoclave curing is inhibited, even if the surface hardness after the primary curing can be increased. As a result, the fiber reinforced cement board having sufficient impact strength cannot be finally obtained.

As another means, it is conceivable to add reinforcing fibers such as pulp fibers to the surface layer. However, when a deeply carved uneven pattern with a large shaping angle is applied, the pulp fibers pressed at the convex corners pull the surrounding cement slurry, so that the corners may not be clear or cracks may occur. For example, there is a problem that the design is deteriorated.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has been developed by providing a cement slurry layer containing fine bubbles on the surface of a fiber-reinforced cement board manufactured by papermaking. Provided is a method for producing a fiber-reinforced cement board in which, when a carved uneven pattern is provided, the plane tensile strength of a surface layer thereof is increased, and thus the frost damage resistance is excellent, and the impact strength after primary curing is sufficient. It is done for the purpose of.

[0012]

According to a first aspect of the present invention, there is provided a method of manufacturing a fiber reinforced cement board, wherein a cement slurry containing fine air bubbles is supplied in a layered manner on a felt belt provided with a suction dewatering device, and suction dewatering is performed. Then, in a one-layer flow-on molding method in which a plate is formed by pressing the plate with irregularities, 2 to 10% by weight of silica fume is added to the cement slurry containing the fine bubbles.

That is, by adding silica fume to a layer having a reduced surface tensile strength due to the incorporation of microbubbles, the bonding strength of the cement matrix is increased, the plane strength is improved, and the frost damage resistance is improved.

The addition amount of silica fume is 2 to 10% by weight.
The reason is that if it is less than 2% by weight, there is no effect of addition and sufficient plane strength cannot be obtained, and if it is more than 10% by weight, there is no improvement in plane strength commensurate with the addition, and it is wasteful. Because. The cement composition of the cement slurry mixed with the fine bubbles has no particular characteristics, and a composition generally used conventionally is used. As means for mixing fine bubbles into the cement slurry, A
In addition to the air entrainment using the E agent, there is a method of mixing the bubbles into the slurry by forcibly stirring the slurry. In short, any means can be used as long as fine bubbles are uniformly mixed in the slurry.

According to a second aspect of the present invention, there is provided a method of manufacturing a fiber reinforced cement board, comprising: supplying a cement slurry in a layered manner by a conventional method onto a felt belt provided with a suction dehydrator; As a base layer, a cement slurry mixed with fine bubbles is further supplied in a layered form, laminated and pressed to form an uneven pattern on the upper layer surface, and thereafter cured and cured according to a conventional method. 2 to 10 in cement slurry containing air bubbles
It is characterized in that silica fume is added by weight%.

That is, with respect to a cement layer formed by a conventional method as a base layer and a layer containing microbubbles as a surface layer, the plane tensile strength of the surface layer is improved. It is desirable that pulp fibers having a long fiber length be used as the reinforcing fibers added to the cement composition of the base layer.

The reason why the amount of silica fume added to the surface layer is set to 2 to 10% by weight is the same as in claim 1. The cementing of the surface layer, the air mixing means, etc. are also the same as those in the first aspect.

Therefore, the strength of the entire sheet material is exhibited by the base layer, and the surface layer having the deeply carved uneven pattern exhibits a plane tensile strength by the addition of silica fume, thereby improving the frost damage resistance of the sheet material surface.

[0019] According to a third aspect of the present invention, there is provided the method for producing a fiber reinforced cement board according to the first or second aspect, wherein the cement slurry containing fine bubbles contains 2 to 10% by weight. Instead of adding silica fume, 75-200 g of silica fume aqueous solution is applied to the surface of the cement slurry layer containing fine bubbles before pressing.
/ M ² , followed by pressing with irregularities.

The bonding strength of the cement matrix on the surface of the layer is increased by spraying the aqueous solution of silica fume, and the surface strength is efficiently increased. The method for producing a fiber-reinforced cement board according to claim 4 is the method for producing a fiber-reinforced cement board according to claim 1 or 2, wherein a Brain value is used instead of silica fume added to a cement slurry containing fine bubbles. It is characterized by using crystalline silica of 8000 cm ² / g or more.

Crystalline silica having a Blaine value of 8000 cm ² / g or more is a fine particle mainly composed of silicic acid and, unlike ordinary siliceous materials such as silica sand, causes a pozzolanic reaction even at 40 to 60 ° C. The silica fumes according to claims 1 and 2 have a similar effect, but the pozzolanic reaction is not limited to this, but has a Blaine value of 80.
It can be obtained even with crystalline silica of not less than 00 cm ² / g.

Accordingly, sufficient strength can be imparted to the plate material even at a curing temperature of 100 ° C. or less at which the pozzolanic reaction due to the siliceous material of the silica sand does not occur, and chipping during handling after the primary curing can be effectively prevented.

Further, at the time of autoclave curing performed as final curing thereafter, the pozzolanic reaction by the siliceous material of the silica sand originally blended in the surface layer occurs for the first time, so that the strength of the final product is improved.

According to a fifth aspect of the present invention, there is provided a method for producing a fiber reinforced cement board according to the second, third or fourth aspect, wherein the cement slurry containing fine bubbles contains a CSF of 400 mL or less. It is characterized by blending beaten pulp.

The pulp fiber has a good ability to capture raw material particles and has an effect of preventing cracks. Therefore, high beating pulp with a short fiber length of 400 mL or less of CSF is added so as not to hinder press molding, and the surface strength is increased.

As the pulp fiber, hardwood pulp having a short fiber length is preferably used, and when softwood pulp is used, pulp which has been beaten to a high degree of freeness as described above is used.

[0027]

Next, an embodiment of the present invention will be described.
40% by weight of cement, 40% by weight of silica sand, 10% by weight of pearlite, fiber length 2 as pulp fiber
A commonly used cement formulation of 10% by weight of 3 mm pulp fiber was prepared. These blended materials were put into a mixing tank together with water and uniformly mixed to prepare a cement slurry. [Example 1] 0-15% by weight of silica fume was added to this slurry, and an air entraining agent ("A" manufactured by Kao Corporation)
E-03 ") was added at an outer rate of 0.1% by weight, and the mixture was stirred at a high speed to mix microbubbles to obtain a slurry A having a slurry concentration of 25%.

The amount of silica fume added was increased by reducing the amount of silica sand to balance the total amount. This slurry A is coated on an endless felt belt 2 provided with a suction dehydrator 1 as shown in FIG.
And then transported while suction dewatering was performed. When the surface was dehydrated to such an extent that free water on the surface disappeared, a single-layer molded plate was cut by the cutter 4.

The cut formed plate 5 was transferred to a press platen 6 and pressed at a pressing speed of 3.5 mm / s using a mold having a depth d = 5 mm and a shaping angle θ = 60 ° as shown in FIG. After pressing, the molded plate 5 was naturally cured for 24 hours, and then autoclaved at 170 ° C. for 15 hours to obtain a product.

The planar tensile strength of the plate-like product obtained as described above was measured. The results are shown in Table 1 and FIG. In addition, the column of silica fume addition amount 0 in Table 1 means no addition.

[Example 2] As a cement composition, the above-mentioned cement 40% by weight, silica sand 40% by weight, perlite 10% by weight,
A raw material having a general basic composition of 10% by weight of pulp fiber was charged into a mixing tank together with water and uniformly mixed to prepare a base layer cement slurry B having a slurry concentration of 25%.

As shown in FIG. 2, this cement slurry B is supplied in a layer 10 having a thickness of 10 to 13 mm on an endless felt belt 2 provided with a suction dewatering device 1 and conveyed while being suctioned and dewatered. When dehydrated to the extent that disappears,
The same slurry A containing silica fume as shown in Example 1 was supplied to a layer 11 having a thickness of 5 mm on the cement layer 10 as the base layer composed of the cement slurry B to form a multilayer, and immediately thereafter, the slurry 4 was mixed by the cutter 4. The layer formed plate was cut.

The cut molded plate 8 was transferred to the press platen 6 and pressed with the same mold as in Example 1. The molded plate 8 was naturally cured for 24 hours, and then subjected to autoclave curing at 170 ° C. × 15 hours to obtain a product. did.

When the planar tensile strength of the surface of the plate-like product obtained as described above was measured, the results shown in Table 1 and FIG. 3 were obtained. In Table 1, 0 in the column of silica fume addition amount indicates a case where silica fume was not added.

[0035]

[Table 1]

As is clear from Table 1 and FIG. 3, the surface strength increases as the amount of added silica fume becomes 2% by weight, and the effect commensurate with the addition even when the amount of addition is increased from about 10% by weight. Was not obtained.

In Table 1, when the plane strength is 1 Mpa or more, it is determined that the frost resistance is acceptable. Therefore, it was found that the lower limit should be 2% by weight or more in the case of adding silica fume, and the upper limit should be 10% by weight in consideration of efficiency.

Example 3 40% by weight of cement, 40% by weight of silica sand, 10% by weight of pearlite, fiber length 2 to 2 as pulp fiber
0.1% by weight of an air entraining agent ("KA-03", "AE-03") is added to a slurry containing 10% by weight of 3 mm pulp fiber and 10% by weight of a cement commonly used as a basic cement, and the mixture is stirred at high speed. Air bubbles were mixed in to obtain a slurry A having a slurry concentration of 25%.

As shown in FIG. 1, this microbubble-mixed slurry A is supplied onto an endless felt belt 2 provided with a suction dewatering device 1 in a layer 3 having a thickness of 10 to 13 mm, and is conveyed while being suction-dewatered. When the water is dehydrated to the extent that free water disappears,
A silica fume aqueous solution having a concentration of 15% was sprayed on the surface by spraying at a spraying amount of 0 to 200 g / m ² , and then a single-layer molded plate was cut with a cutter 4.

The cut formed plate 5 is transferred to a press platen 6 and a pressing speed is set using a mold having a depth d = 5 mm and a shaping angle θ = 60 °.
Pressed at 3.5 mm / s. After pressing, the molded plate 5 was naturally cured for 24 hours, and then autoclaved at 170 ° C. for 15 hours to obtain a product.

The planar tensile strength of the plate-like product obtained as described above was measured. The results were as shown in Table 2 and FIG. In Table 2, the column of the silica fume aqueous solution application amount of 0 means that the application was not performed.

[Example 6] As the cement composition, the above-mentioned cement 40% by weight, silica sand 40% by weight, perlite 10% by weight,
A raw material having a general basic composition of 10% by weight of pulp fiber was charged into a mixing tank together with water and uniformly mixed to prepare a base layer cement slurry B having a slurry concentration of 25%.

As shown in FIG. 2, this cement slurry B is supplied in a layer 10 having a thickness of 10 to 13 mm on an endless felt belt 5 provided with a suction dewatering device 4, and is conveyed while being suctioned and dewatered. When dehydrated to the extent that disappears,
The same slurry A containing fine bubbles as shown in Example 5 is supplied to a layer 11 having a thickness of 5 mm on the cement layer 10 as the base layer composed of the cement slurry B to form a multilayer, and free water on the surface disappears. When dehydrated to a degree, the surface
Spray a 5% aqueous solution of silica fume from 0 to 2
It was sprayed at a spraying rate of 00 g / m ² , and then the formed plate was cut with a cutter 4.

The cut molded plate material 8 was transferred to a press board 9 and pressed in the same manner as in Example 3. After pressing, the molded plate 8
The product was naturally cured for 24 hours and then autoclaved at 170 ° C. for 15 hours to obtain a product.

When the planar tensile strength of the surface of the plate-like product obtained as described above was measured, the results shown in Table 2 and FIG. 4 were obtained. In Table 2, the plane strength is 1 Mpa
If it is above, it is judged as freezing resistance.

Therefore, the spray amount of the silica fume aqueous solution was 7
It was confirmed that the spray amount should be 5 g / m ² or more. As is clear from Table 2 and FIG. 4, even if the silica fume aqueous solution was sprayed at more than 200 g / m ^2, no improvement in the planar strength corresponding to the increase in the spraying was observed and no further increase in the spraying amount was wasted. It was also found that.

[0047]

[Table 2]

Example 5 An uncured single-layer plate-like product was obtained in the same manner as in Example 1 except that crystalline silica having a Blaine value of 8000 cm ² / g was used instead of the silica fume in Example 1. Then, after curing at 80 ° C. for 12 hours under moist temperature, the product was subjected to autoclave curing at 170 ° C. for 15 hours to obtain a product.

Example 6 An uncured multi-layer plate product was obtained in the same manner as in Example 2 except that crystalline silica having a Blaine value of 8000 cm ² / g was used instead of the silica fume in Example 2. Then, after curing at 80 ° C. for 12 hours under moist temperature, the product was subjected to autoclave curing at 170 ° C. for 15 hours to obtain a product.

The bending strength of the plate-like product obtained as described above after primary curing and after curing in an autoclave was measured. The results shown in Table 3 were obtained. The bending strength was measured in accordance with the JIS No. 5 bending test method for cement boards.

[0051]

[Table 3]

As is clear from Table 3, the addition amount was 5% by weight.
It was found that the effect of improving the strength was seen from around, and when the addition amount exceeded 10% by weight, the effect of improving the strength in proportion to the added amount could not be obtained any more.

The strength after the primary curing and after the curing in the autoclave was also improved in the examples in which the amount of addition exceeds 5% by weight as compared with the case where no additives were added, and especially the handling after the primary curing. It was confirmed that the property was improved. [Example 7] In Examples 2, 4 and 6 in which a cement layer containing microbubbles was laminated on a normal cement layer, hardwood and softwood pulp having a CSF of 400 mL or less was added to the surface layer to carry out each operation. A plate-like product was manufactured in the same manner as in the example, and a bending strength test was performed by the same test method as in Example 6. As a result, a 15 to 20% improvement in strength was observed for each example.

[0054]

As described above, according to the first aspect of the present invention, even in the case of a fine-bubble mixed fiber reinforced cement board having a concave-convex pattern of a deep-engraving press with good reproducibility, silica fume is added. Thereby, the plane tensile strength is strong and the frost damage resistance is excellent.

According to the second aspect of the present invention, the structure of the fiber reinforced cement board is multi-layered, and the base layer is a board material strength, and the upper layer is a layer in which an uneven pattern is easily formed. The overall strength is increased, and the surface strength is improved by the addition of silica fume, which has the effect of being excellent in frost damage resistance.

According to the third aspect of the present invention, since it is only necessary to spray the aqueous solution of silica fume, the step of adding and mixing silica fume is not required, and the effect of improving the plane strength close to that of adding silica fume can be obtained. Has the effect of being easy.

According to the fourth aspect of the present invention, since the surface layer exhibits sufficient strength even at low temperature and humidity curing, accidental cracking of the surface layer during handling can be effectively prevented even after primary curing. It has the effect of not adversely affecting the strength of the sheet material after the subsequent autoclave curing.

According to the fifth aspect of the present invention, the cement matrix is reinforced by the ability of the surface layer to capture pulp fibers. Further, since the fiber length is very short, there is little adverse effect on the reproducibility of the uneven press.

Accordingly, in addition to the improvement of the bonding strength by the silica fume or the like, there is an effect that the plane tensile strength and the bending strength of the surface layer are further improved.

[Brief description of the drawings]

FIG. 1 is a side view of an apparatus for performing a method according to the first and third aspects of the present invention.

FIG. 2 is a side view of an apparatus for performing the method according to the second and third aspects of the present invention.

FIG. 3 is a graph showing the correlation between the amount of added silica fume and the plane tensile strength.

FIG. 4 is a graph showing a correlation between a spray amount of a silica fume aqueous solution and a plane tensile strength.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Suction dehydration apparatus 2 Endless felt belt 3 Cement layer 4 Cutter 5 Cut formed plate material 6 Press machine

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C04B 14:18 22:06 16:02) 111: 20 (72) Inventor Atsushi Uematsu 1-1-1 Hama, Amagasaki-shi, Hyogo Shares Company Kubota Technology Development Laboratory

Claims (5)

[Claims] 1. A one-layer flow-on molding method in which a cement slurry containing microbubbles is supplied in a layered form onto a felt belt equipped with a suction dewatering device, suction-dewatered, and then pressed by uneven pressing to make a plate. A method for producing a fiber-reinforced cement board, comprising adding 2 to 10% by weight of silica fume to a cement slurry containing fine bubbles. 2. A cement slurry containing a blended cement slurry by a conventional method is supplied in a layered form onto a felt belt equipped with a suction dewatering device, and the plate is formed by suction dehydration. Is further supplied in a layered form, laminated and pressed to form an uneven pattern on the upper layer surface, and then cured and cured in a conventional manner in a method for producing a fiber-reinforced cement board. A method for producing a fiber-reinforced cement board, comprising adding silica fume of 10 to 10% by weight. 3. The method for producing a fiber-reinforced cement board according to claim 1 or 2, wherein 2 to 10% by weight of silica fume is added to the cement slurry containing fine bubbles before pressing. Of silica fume aqueous solution on the surface of the cement slurry layer
A method for producing a fiber-reinforced cement board, which comprises spraying at a rate of 200 g / m ² and then pressing unevenly. 4. The method for producing a fiber reinforced cement board according to claim 1 or 2, wherein the silica fume added to the cement slurry containing fine bubbles is replaced with a crystal having a Blaine value of 8000 cm ² / g or more. A method for producing a fiber-reinforced cement board, comprising using silica. 5. The method for producing a fiber-reinforced cement board according to claim 2, wherein high-beaten pulp having a CSF of 400 mL or less is mixed with a cement slurry containing fine bubbles. Of producing fiber reinforced cement boards.