JPH0976217A - Dehydrate press molded form and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dehydrated press molded form, having sufficient and necessary resistance to fire, strength and workability when the molded form is employed for architectual material, and the manufacturing method thereof. SOLUTION: A dehydrated press molded form is produced by dehydrating press molding of slurry consisted of 30-50 pts.wt. of cement, 35-60 pts.wt. of slag, 5-15 pts.wt. of lightweight aggregate, 4-10 pts.wt. of plaster, 3-6 pts.wt. of pulp, 1.5-8 pts.wt. of mica and 0.4-1.5 pts.wt. of reinforcing fibers.

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dewatering press-molded article and a method for producing the same, and more specifically, a dewatering press-molded article having necessary and sufficient fire resistance, strength and workability when used as a building material and civil engineering material. And a method for producing a dehydration press-molded body capable of easily producing such a dehydration press-molded body.

[0001]

BACKGROUND OF THE INVENTION Asbestos cement boards are usually prepared by adding cement, asbestos, pulp as a papermaking auxiliary agent to water, stirring and mixing the mixture to prepare a slurry, and making this slurry into papermaking. It is obtained by post-press dehydration, curing and curing.

However, since asbestos is a natural product, the quality of the asbestos varies greatly. Therefore, the quality of the obtained asbestos cement board, especially the strength, often varies. Further, since the asbestos fibers contained in the produced asbestos cement board are oriented in the papermaking direction, the produced asbestos cement board has a dimensional change rate during water absorption and drying in the papermaking direction and the direction perpendicular to the papermaking direction. Differently, there is a problem that warpage is likely to occur after manufacturing.

In order to solve the above problems, silica flour, wollastonite, sepiolite, etc. are used as a substitute material for asbestos in the production of asbestos cement, and as an asbestos substitute fiber, alkali-resistant glass fiber, vinylon fiber, Attempts have been made to use rock wool fibers and the like. However, the conditions of the method for producing an asbestos cement plate when using the above materials or the like as an alternative material of asbestos or an alternative fiber, particularly the slurry concentration at the time of press molding, the press temperature, etc. are not described in the literature. It is the actual situation.

When an asbestos-cement board is produced by using the above-mentioned asbestos-substituting material or asbestos-substituting fiber, for example, when silica flour is used, the asbestos-cement board of the obtained asbestos-cement board is obtained by raising the amount to a certain amount. The dimensional stability and strength are improved to some extent, but if the amount used is further increased, the obtained asbestos cement board becomes dense and cracks occur after curing and drying, resulting in significant deterioration of strength.

Regarding the press molding conditions, when the asbestos cement board is produced using the above-mentioned asbestos substitute material or asbestos substitute fiber, if the slurry concentration is too low, it takes a long time for dehydration, and if it is too high, the slurry concentration becomes high. Poor production and forming result in defective products. Regarding the temperature of press molding, if the temperature is raised, the viscosity becomes low, and it becomes easy to add the slurry, but if it is too high, the hydration reaction of the cement is promoted and gel hydrate is generated, and the viscosity However, there is a problem that the fluidity of the slurry is lost and the strength is lowered.

Therefore, an object of the present invention is to provide a dewatering press-molded article having necessary and sufficient fireproofness, strength and workability when used as a building material and a civil engineering material, and a method for producing the same.

[0007]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that a slurry having a specific composition consisting of cement, slag, lightweight aggregate, gypsum, pulp, mica and reinforcing fibers (hereinafter simply referred to as slurry). It was found that a dehydration press-molded product obtained by subjecting (1) to (1) can achieve the above object.

The present invention has been made on the basis of the above-mentioned findings, and is 30 to 50 parts by weight of cement, 35 to 60 parts by weight of slag, 5 to 15 parts by weight of lightweight aggregate, 4 to 10 parts by weight of gypsum,
The present invention provides a dewatering press-molded product obtained by dewatering press-molding a slurry comprising 3 to 6 parts by weight of pulp, 1.5 to 8 parts by weight of mica, and 0.4 to 1.5 parts by weight of reinforcing fibers.

Further, according to the present invention, 30 to 50 parts by weight of cement, 35 to 60 parts by weight of slag, 5 to 15 parts by weight of lightweight aggregate, 4 to 10 parts by weight of gypsum, 3 to 6 parts by weight of pulp, and 1.5 of mica are used. ~ 8 parts by weight and 0.4-1.5 parts by weight of reinforcing fibers are made into a slurry having a solid content concentration of 25 to 35%, and the slurry is dehydrated and pressed at a temperature of 35 to 50 ° C. The above object has been achieved by providing a method for producing a dehydrated press molded body.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION First, the dewatering press-molded article of the present invention will be described in detail. The dewatering press-molded product of the present invention comprises 35 to 60 parts by weight of slag, 30 to 50 parts by weight of cement, 5 to 15 parts by weight of lightweight aggregate, 4 to 10 parts by weight of gypsum, 3 to 6 parts by weight of pulp, and 1.5 of mica. -8 parts by weight and 0.4 to 1.5 parts by weight of reinforcing fibers are dehydrated and press-molded.

The cement used in the present invention includes, for example, ordinary Portland cement, early strength Portland cement, super early strength Portland cement, sulfate resistant Portland cement, moderate Portland cement, white Portland cement, ultrafast Portland cement and the like. Components, expanded cement, acidic phosphate cement, white hardened cement, lime slag cement, blast furnace cement, high sulfate slag cement, fly ash cement, keens cement, pozzolan cement, alumina cement, calcium aluminate and the like.
In the present invention, the above cements can be used alone or in combination of two or more.

Examples of the slag used in the present invention include granulated blast furnace slag. The slag preferably has a Blaine value of 3500 to 9000 cm ² / g, more preferably 4000 to 8000 cm ² / g. Brain value is 350
If it is 0cm less than ² / g, has a low reactivity, hardly strength dewatering press molded body obtained is expressed, 9000 cm ²
If it exceeds / g, the obtained dehydrated press-molded product will be densified, and cracks and breakage are likely to occur during processing. Therefore, it is preferably within the above range. The above-mentioned Blaine value is JIS R5
It is the value measured by 201 (physical test method of cement).

The mixing ratio of the cement and the slag in the slurry is 35 to 60 parts by weight of the slag with respect to 30 to 50 parts by weight of the cement, and preferably 35 to 40 parts by weight of the cement. Slag 4
0 to 50 parts by weight. If the blending ratio of the slag is less than 35 parts by weight, the dimensional change rate, especially the shrinkage rate becomes large, and if it exceeds 60 parts by weight, the strength development is slow and the desired strength cannot be obtained.

Examples of the lightweight aggregate used in the present invention include perlite, shirasu balloon, diatomaceous earth, expanded polystyrene, expanded polypropylene, xonotlite, tobermorite and incinerated ash. In the present invention, the above lightweight aggregates may be used alone or in combination of two or more kinds.

The mixing ratio of the cement and the lightweight aggregate in the slurry is 5 to 15 parts by weight, preferably 30 to 50 parts by weight of the cement, with respect to 30 to 50 parts by weight of the cement. On the other hand, it is 7 to 10 parts by weight of the above lightweight aggregate. Mixing ratio of the above lightweight aggregate is 5
When the amount is less than the weight part, it is difficult to reduce the weight for the original purpose, and it becomes hard and brittle. When the amount exceeds 15 parts by weight, the material separation in the slurry is likely to occur and the strength is lowered.

The gypsum used in the present invention includes:
Examples thereof include natural gypsum, flue gas desulfurization gypsum, calcined gypsum, phosphate gypsum, and titanium gypsum. In the present invention, the above-mentioned gypsum can be used alone or in combination of two or more kinds.

The mixing ratio of the cement and the gypsum in the slurry is 4 to 10 parts by weight of the gypsum to 30 to 50 parts by weight of the cement, preferably 30 to 50 parts by weight of the cement. It is 5 to 7 parts by weight of gypsum. If the compounding ratio of the above-mentioned gypsum is less than 4 parts by weight, the desired strength cannot be obtained, and if it exceeds 10 parts by weight, the expansion rate becomes large.

The pulp used in the present invention includes, for example, newspaper waste paper, sulfite pulp, kraft pulp, groundwood pulp, semi-chemical pulp and synthetic pulp. In the present invention, the above pulps may be used alone or in combination of two or more.

The mixing ratio of the cement and the pulp in the slurry is 3 to 6 parts by weight of the pulp to 30 to 50 parts by weight of the cement, preferably 30 to 50 parts by weight of the cement. Pulp 4-5
Parts by weight. If the blending ratio of the pulp is less than 3 parts by weight, the materials in the slurry are likely to be separated, resulting in variation in quality, and if it exceeds 6 parts by weight, the shrinkage rate becomes large.

As mica used in the present invention
Has, for example, a chemical composition of K₂Al_Four(Si_ThreeAl) ₂O₂₀(OH)_FourThe trout
Cobite (white mica), K₂Mg₆(Si_ThreeAl)₂O₂₀(OH)_FourThe flow
Cobite (gold mica) and the like. As the above mica
Has a width and a thickness of 10 to 100 μm and a long length, respectively.
With an aspect ratio of 150 μm to 4 mm (aspect ratio is
1.5 to 400) is preferable, and the width and the thickness are each 3
0 to 80 μm and a length of 300 μm to 3 mm
(Aspect ratio of 3.8 to 38) is more preferably used.
Can be Asbestos with width, thickness and length less than the above range
Reinforcement with mica as an alternative material, dimensional stability, dewatering filter
Transparency, freeze-thaw resistance and impact resistance are improved.
It is difficult to stir the slurry and pump pressure above the above range.
As it breaks during transmission and does not exist stably,
It is preferably within the above range. In the present invention, the above
Mica can be used alone or in combination of two or more.
Can also be used.

The mixing ratio of the cement and the mica in the slurry is 30 to 50 parts by weight of the cement and 1.5 to 8 parts by weight of the mica, and preferably 30 to 50 parts by weight of the cement. , The above mica 2
~ 7 parts by weight. If the blending ratio of the mica is less than 1.5 parts by weight, it is difficult to obtain the effect as an asbestos substitute material like the above, and if it exceeds 8 parts by weight, the cost is increased and the effect equivalent to the excess is not obtained.

Examples of the reinforcing fiber used in the present invention include acrylic fiber, vinylon fiber, polypropylene fiber, polyethylene fiber, polyamide fiber (nylon fiber), alkali resistant glass fiber and carbon fiber. As the fibers, acrylic fibers having a diameter of 8 to 12 μm and a length of 3 to 18 mm are preferable,
Those having a diameter of 8 to 10 μm and a length of 6 to 12 mm are more preferably used. If the diameter or length is less than the above range, the adhesion area with the hardened material such as cement is small,
Since there is no restraint force and the strength is lowered, and if it exceeds the above range, the fluidity of the slurry is remarkably lost and stable forming cannot be obtained. Therefore, it is preferably within the above range. In the present invention, the above reinforcing fibers may be used alone or in combination of two or more.

The mixing ratio of the cement and the reinforcing fiber in the slurry is 0.4 to 1.5 parts by weight of the reinforcing fiber with respect to 30 to 50 parts by weight of the cement,
The amount of the reinforcing fiber is preferably 0.6 to 1.0 parts by weight with respect to 30 to 50 parts by weight of the cement. If the blending ratio of the reinforcing fiber is less than 0.4 parts by weight, excellent dimensional stability and impact resistance cannot be obtained, and the material becomes hard and brittle.
If it exceeds the weight part, the fluidity of the slurry is remarkably lost, and stable forming cannot be obtained.

If desired, additives such as a fluidizing agent, a water reducing agent, a polymer flocculant, and a thermoplastic resin may be added to the molding press-molded product of the present invention. The mixing ratio of these additives is preferably 0.01 to 0.5 parts by weight with respect to 30 to 50 parts by weight of the cement.

The method for producing the above-mentioned "dehydration press molded body" will be described later.

The thickness of the dewatering press molding of the present invention is generally preferably 8 to 50 mm, and 10 to 24 mm.
Is more preferable. Further, the specific gravity of the dehydration press-molded product of the present invention is generally preferably 0.85 to 1.40, more preferably 0.9 to 1.1.

The dewatering press-molded product of the present invention is excellent in fire resistance, strength and workability, and is used as an interior / exterior material for houses and non-houses.
It can be used as a soundproof wall material for highways and tunnels, as a construction material for revetment work and as a substitute for precast products, and as a civil engineering material.

Next, a method for producing the dehydration press molded article of the present invention, which is a preferred method for producing the dehydration press molded article of the present invention, will be described. The method for producing a dehydration press-molded article of the present invention comprises 30 to 50 parts by weight of cement, 35 to 60 parts by weight of slag, 5 to 15 parts by weight of lightweight aggregate, 4 to 10 parts by weight of gypsum,
A slurry raw material composed of 3 to 6 parts by weight of pulp, 1.5 to 8 parts by weight of mica, and 0.4 to 1.5 parts by weight of reinforcing fiber is made into a slurry having a concentration of 25 to 35%, and the slurry is used in an amount of 35 to 5%.
It consists of dewatering pressing at a temperature of 0 ° C.

In the method for producing a dehydration press-molded product of the present invention, in order to produce a dehydration press-molded product, first, the concentration is set to 2
Make a 5-35% slurry. If the concentration is less than 25%, the pressing force can be increased during dewatering press molding, but the pressing time must be lengthened, and if the pressing time is the same, the slurry will blow out, and the surface and thickness will be increased. Badness occurs. On the other hand, if it exceeds 35%, the fluidity of the slurry is lost, it becomes difficult to add the slurry to the mold and form it, and it becomes necessary to add a fluidizing agent to the slurry. The concentration of the above slurry is
It is preferably 28 to 32%. As the composition of the above-mentioned slurry, the slurry in the dehydration press molded body of the present invention described above is used.

Next, the above slurry adjusted to a temperature of 35 to 50 ° C. is put into a mold and then dehydrated by a dehydration press to obtain a molded body. As the mold, those conventionally used for producing dehydration press molding can be used without limitation. Also, as a method for dewatering press, a conventionally known method can be used without limitation. The dewatering press molded article of the present invention is obtained by dewatering pressing a slurry at 35 to 50 ° C. If the temperature is lower than 35 ° C., the hydration reaction of cement and slag will proceed slowly, and the curing time will be longer. On the other hand, when the temperature exceeds 50 ° C., the fluidity of the slurry is lost, making it difficult to put the slurry in the mold and forming it, and it becomes necessary to add a fluidizing agent to the slurry, so the above range is set. The temperature is 38 to 45
C. is preferred. Slurry temperature 35-50
Although there is no limitation on the method for controlling the temperature, for example, a slurry is produced by using heated water, live steam is added to water or the slurry, a stirring time of the slurry is set to 90 minutes or less, and a heat of hydration of the cement is set. And the like.

The dewatering press is preferably 20-60.
kgf / cm ² , more preferably 25-40 kgf / c
It is carried out under a pressure of m ² . The dehydration time is preferably 8 to 35 seconds. The above pressure is 20 kgf / cm ²
If it is less than 60 kgf / cm ² , the surface of the press-molded product is soft and may be dented or broken during loading. If it exceeds 60 kgf / cm ² , the release from the embossing mold may be poor and the cost may increase. . Also, the dehydration time is 8
If it is less than 2 seconds, the slurry will be blown out at the time of the dewatering press, and the moving time of the slurry will be too short to obtain the expected design, so the range is set to the above range. The concentration of the slurry thus dehydrated is preferably 55 to 75%.

Next, the dehydrated slurry is cured and hardened by a known method to obtain a dehydrated press molded body.

The above-mentioned curing can be carried out by a known method, but a method of performing steam curing at a temperature of 70 to 90 ° C. for 14 to 16 hours or more and drying the dehydrated and pressed slurry is preferable. If the temperature is lower than 70 ° C., steam curing time is required for 24 hours or longer, and if it exceeds 90 ° C., gel hydrate of the cement is accelerated and final strength is hardly obtained. Further, if the above time is less than 14 hours, the strength does not appear, so the content is within the above range. A more preferable curing temperature is 75 to 85 ° C. Furthermore, autoclave curing (temperature increase 1 hour, 130 to 18 to reduce the dimensional change rate)
It may be kept at 0 ° C. for 6 to 10 hours and reduced pressure for 1.5 hours.

[0034]

The present invention will be described in more detail with reference to the following examples. It goes without saying that the scope of the present invention is not limited to the examples.

[Examples 1 to 3 and Comparative Examples 1 to 5] Cement, slag, lightweight aggregate, gypsum, pulp, mica, and reinforcing fibers shown below are slurries each having the composition shown in [Table 1]. Was molded according to the production method described below to obtain a dehydrated press molded body.

Cement; Ordinary Portland cement 43 parts by weight Slag; Granulated blast furnace slag (Blaine value; 4000 cm ² / g) 35 parts by weight Light weight aggregate: Perlite 10 parts by weight Gypsum; Phosphate gypsum 5 parts by weight Pulp; Kraft pulp 4 Weight part Mica; Muscovite (width and thickness; 70 μm, length; 1 mm) 2 parts by weight Reinforcing fiber; Acrylic fiber (diameter; 8 μm, length 12 mm) 1 part by weight

The raw materials of the slurry having the composition shown in [Table 1] were added to a pulper whose water temperature was 40 ° C. in advance and the concentration was 30%.
Of the slurry. Then, the temperature of this slurry is adjusted to 40
The slurry was stirred for 30 minutes while maintaining the temperature at 0 ° C., the slurry was put into a mold, and pressed under a pressure of 30 kgf / cm ² for 8 seconds to have a thickness of 11.0 mm. Then, the dehydrated slurry is aged at a temperature of 80 ° C. for 16 hours to obtain 200
It was dried at a temperature of ° C for 17 minutes to obtain a dehydrated press molded body.
Each of the obtained dehydrated press-molded products was evaluated according to the following [Evaluation criteria for dehydrated press-molded products]. The evaluation results are shown in [Table 1].

[Evaluation Criteria for Dewatered Press Molded Articles] (1) Bulk Specific Gravity: Measured according to JIS A5422 (ceramic siding). (2) Bending strength; JIS A 1408 (No. 4 test piece)
It measured according to. (3) Dimensional change rate: Measured according to JIS A5422 (ceramic siding). (4) Young's modulus: Measured according to JIS A1408 (No. 4 test body).

(5) Phase-determining workability: Sumitomo Forestry Co., Ltd. machine cutting was performed and judged according to the following evaluation criteria. ⊚: No defects or cracks. ○: Defects and cracks are present only at the end in the lengthwise direction. Δ: Defects and cracks are within 30 mm in length. X: Defects and cracks are remarkable. (6) Impact resistance test: Measured according to JIS A5422 (ceramic siding), and evaluated according to the following evaluation criteria. ⊚: No cracks penetrated. X: There is a crack that penetrates.

(7) Freeze-thaw resistance test; JIS A542
2 (ceramic system siding) was measured and judged according to the following evaluation criteria. ⊚: The peeled area of the surface is 2% or less, there is no significant delamination, and the thickness change rate is 10% or less. X: The peeled area of the surface exceeds 2%, there is significant delamination, or the thickness change rate exceeds 10%. (8) Nonflammability test: Measured according to JIS A5422 (ceramic siding), and evaluated according to the following evaluation criteria. ⊚: No harmful deformation or melting for fire prevention, smoke coefficient and exhaust temperature curve are within the range. ×: There is harmful deformation or melting for fire prevention, or smoke coefficient or exhaust temperature curve is out of range.

[0041]

[Table 1]

As is clear from Table 1, Examples 1 to 1
The dehydrated press molded body of 3 was excellent in all test items. On the other hand, the dehydration press molded articles of Comparative Examples 1 to 5 were inferior in bending strength, impact resistance, fire resistance and the like.

Example 4 A dewatering press-molded product was obtained in the same manner as in Example 1 except that a fine Blaine value (8000 cm ² / g) was used as the slag. The bulk specific gravity, bending strength, and freeze-thaw resistance of the thus obtained dehydrated press-molded product were evaluated according to the above [Evaluation criteria for dehydrated press-molded product]. In addition, the forming property and the surface condition were evaluated by the following methods. The respective results are shown in [Table 2].

<Forming property> The height and concentration of the slurry were measured with a level meter, and the concentration was measured by sampling the slurry.
It was dried at 0 ° C. for 24 hours, calculated, and evaluated according to the following evaluation criteria. A: Height is within ± 5 mm and concentration is within ± 1.5%. ◯: Height is within ± 5 mm and concentration is within ± 2.0%. X: Height exceeds ± 5 mm or concentration exceeds ± 2.0%.

<Surface condition> Based on the embossed plate, the shape of the surface is compared, and unevenness other than the purpose is observed from a distance of 3 m to determine whether it is harmful in use such as cracking or peeling. The judgment was made according to the following evaluation criteria. ⊚: There are no noticeable irregularities and no harmful cracks. X: There are conspicuous irregularities or harmful cracks.

[Comparative Example 6] A dewatering press-molded product was obtained in the same manner as in Example 1 except that the temperature of the slurry was 25 ° C and the thickness was 11.5 mm. The dehydration press molded body thus obtained was evaluated in the same manner as in Example 4. The results are shown in [Table 2].

[Comparative Example 7] A dewatering press-molded product was obtained in the same manner as in Example 1 except that the temperature of the slurry was 60 ° C and the thickness was 11.6 mm. The dehydration press molded body thus obtained was evaluated in the same manner as in Example 4. The results are shown in [Table 2].

Comparative Example 8 A dewatering press-molded product was obtained in the same manner as in Example 1 except that the slurry concentration was 20% and the thickness was 12.0 mm. The dehydration press molded body thus obtained was evaluated in the same manner as in Example 4. The results are shown in [Table 2].

[Comparative Example 9] A dewatering press-molded product was obtained in the same manner as in Example 1 except that the slurry concentration was 40%, and the thickness was 10.8 mm. The dehydration press molded body thus obtained was evaluated in the same manner as in Example 4. The results are shown in [Table 2].

[Comparative Example 10] A dehydration press-molded article thus obtained was obtained in the same manner as in Example 1 except that the temperature of the slurry was 25 ° C and the thickness was 11.0 mm. Evaluation of the dehydrated press molded body was performed in the same manner as in Example 4. The results are shown in [Table 2].

[0051]

[Table 2]

As is clear from [Table 2], the dewatering press-molded articles of Examples 1 and 4 were excellent in all test items, but the dewatering press-molded articles of Comparative Examples 6 to 10 were excellent in forming property, It was inferior in surface condition and freeze-thaw resistance.

[0053]

The dewatering press-molded product of the present invention has necessary and sufficient fire resistance, strength and workability when used as a building material and civil engineering material. Further, according to the method for producing a dehydration press molded article of the present invention, it is possible to easily produce a dehydration press molded article having necessary and sufficient fire resistance, strength and processability when used as a building material and a civil engineering material. .

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Claims (7)

[Claims] 1. Cement 30 to 50 parts by weight, slag 35
-60 parts by weight, lightweight aggregate 5-15 parts by weight, gypsum 4-10
A dewatering press-molded body obtained by dewatering press-molding a slurry comprising 3 parts by weight of pulp, 3 to 6 parts by weight of pulp, 1.5 to 8 parts by weight of mica, and 0.4 to 1.5 parts by weight of reinforcing fibers. 2. The Blaine value of the slag (JIS R5
201: cement physical test method) is 3500 to 90
The dehydrated press-molded product according to claim 1, which has a volume of 00 cm ² / g. 3. The mica has a width and a thickness of 1 respectively.
The dewatering press-molded article according to claim 1 or 2, which has a length of 0 to 100 µm and a length of 150 µm to 4 mm. 4. The reinforcing fiber is an acrylic fiber having a diameter of 8 to 12 μm and a length of 3 to 18 mm.
The dehydrated press molded body according to any one of 1. 5. Cement 30 to 50 parts by weight, slag 35
-60 parts by weight, lightweight aggregate 5-15 parts by weight, gypsum 4-10
By weight, a slurry comprising 3 to 6 parts by weight of pulp, 1.5 to 8 parts by weight of mica, and 0.4 to 1.5 parts by weight of reinforcing fibers is used as a slurry having a solid content concentration of 25 to 35%, and the slurry is A method for producing a dehydration press-molded product, comprising performing dehydration press at a temperature of -50 ° C. 6. The dewatering press has a pressing force of 20 to 60 kg.
The method for producing a dehydration press-molded product according to claim 5, which is performed at f / cm ² and a dehydration time of 8 to 35 seconds. 7. A dehydrated press molded article according to claim 5, wherein after the dehydration press, the dehydrated press slurry is steam-cured at a temperature of 70 to 90 ° C. for 14 to 16 hours or more to be dried. Method. [0001]