JP2001316162A - Method for manufacturing calcium silicate board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for efficiently and inexpensively manufacturing a calcium silicate board for a wall material with improved strength and for a ceiling whose curing time in an autoclave is decreased. SOLUTION: Development of strength of the calcium silicate board is improved by a process where a mixture of a base material of the board and an acidic solution of a chitin and a chitosan is cured in the autoclave at 150-220 deg.C and for 6-15 hr. Practical strength for the wall and the ceiling is obtained even by shorter curing in the autoclave owing to the improved development of strength.

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 an asbestos-free calcium silicate plate, which is widely used as a base material for building interior materials and decorative boards.

[0002]

2. Description of the Related Art Conventionally, ceramic moldings used as interior and exterior materials for construction use 5-20 asbestos such as amosite and chrysotile as process fibers and reinforcing fibers.
% By mass. However, in recent years, there has been concern about the effects of asbestos fibers on the human body, and movements to minimize damage due to asbestos exposure have been widespread. This is no exception in the field of ceramic materials, and at present, most ceramic moldings are manufactured using wood-based cellulose fibers as asbestos substitute fibers.

[0003] For example, a cement board mainly used as an exterior material is obtained by beating wood-based cellulose pulp with a beater beater, a disc refiner, or the like, and cement, aggregate, filler, and the like with a water amount suitable for each production method. Mix,
For example, in the paper making method, a slurry adjusted to a solid content concentration of 2 to 5% is made by a round mesh type paper making machine in accordance with a conventional method, and the molded body is produced by curing cement by natural curing or steam curing. I have. In addition, calcium silicate plates, which are mainly used as interior materials, are obtained by beating wood-based cellulose pulp with a beater beater, disc refiner, etc., and mixing calcareous raw materials, siliceous raw materials, fillers, etc. with the appropriate amount of water for each production method. For example, in a press molding method, a slurry adjusted to a solid content concentration of 1 to 20% is poured into a mold and then pressed to be subjected to dehydration molding, and the obtained molded body is subjected to a hydrothermal reaction in an autoclave for 15 hours or more. It is manufactured by.

[0004] However, although the reinforcement effect of wood-based pulp is increased by beating treatment, the strength development of ceramic-based molded articles is lower than that of asbestos, and the reduction in strength due to non-asbestos conversion is inevitable. Although it has practically sufficient strength for applications such as ceiling panels that are difficult to receive, it has a problem that it is more susceptible to damage as compared to asbestos-containing products for inner and outer walls, and higher strength has been desired.

On the other hand, Japanese Patent Application Laid-Open (JP-A) No. 52-22026 discloses that a cement board is mixed with an acidic aqueous solution in which chitosan is dissolved and a basic hydraulic inorganic substance to make the entire system basic and increase the strength. A method is disclosed in which chitosan is insolubilized (released) in a cement slurry to form a fiber, and a reinforcing effect is obtained by curing at room temperature. Japanese Patent Application Laid-Open No. 08-217522 discloses a method for producing a solidified calcium carbonate that can be used as artificial marble in various building materials, decorative materials, and the like. Acid, protein and a natural polysaccharide are added, and a production method for crystal transformation is disclosed.However, when a solidification aid is added as it is to a raw material of a calcium silicate molded product, it cannot be molded by separating from a slurry component. Even if the molding can be performed, the interlayer strength is reduced.

Further, the time required for the autoclave curing step, which is indispensable for the production of calcium silicate plates, can be as long as about 15 hours, which is a major factor in lowering production efficiency and increasing equipment costs. Was desired.

[0007]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-mentioned problems and at the same time to increase the strength of a conventional asbestos-free calcium silicate plate and use it as an interior, exterior or decorative base material. It is an object of the present invention to provide a method for manufacturing a calcium silicate plate which is hard to be damaged even when it is performed. Another object of the present invention is to provide a method for producing a calcium silicate plate efficiently at a lower cost by shortening the autoclave curing time.

[0008]

Means for Solving the Problems As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that an acidic solution in which chitin or chitosan is dissolved as an additive for a calcium silicate plate has a solid content of 2%. It has been found that the above problem can be solved by adding and mixing -10% by mass, and the present invention has been completed.

That is, a siliceous material (30 to 40% by mass), a calcareous material (25 to 40% by mass), and a filler (15% by mass)
-25% by mass), a reinforcing fiber (2-10% by mass), an additive (2-10% by mass), and a mixed raw material slurry composed of water,
A method for producing a calcium silicate plate, which is formed into a plate shape, further press-molded as necessary, and cured by autoclaving, wherein the additive is obtained by dissolving an acidic solution in which chitin or chitosan is dissolved in a solid content of 2 to 2. It is intended to provide a method for producing a calcium silicate plate characterized by being 10% by mass. The addition of an acidic solution in which chitin and chitosan are dissolved promotes a hydrothermal reaction between a calcareous raw material and a siliceous raw material in autoclave curing. At the same time, the curing time of the autoclave can be shortened. The method for producing a calcium silicate plate as described above, wherein the molecular weight of chitin and chitosan is 100,000 to 300,000.

At this time, the siliceous raw material is a combination of either silica stone or silica sand and at least one selected from fly ash, diatomaceous earth and silica fume, and the calcareous raw material is selected from slaked lime, quicklime or cement. Characterized in that it is at least one kind, and furthermore, the autoclave curing temperature is 150 to 220 ° C., preferably 180 to 220 ° C.
An object of the present invention is to provide a method for producing the above-mentioned calcium silicate plate, which is characterized by being at 200 ° C., and to efficiently obtain a high-strength calcium silicate plate without impairing productivity.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention promotes the hydrothermal reaction between a calcareous raw material and a siliceous raw material in autoclave curing, and further increases the strength of an asbestos-free calcium silicate plate.
This is a method for producing a calcium silicate plate, characterized in that it is hardly damaged even when used as an inner or outer material. Also,
This is a method for producing a calcium silicate plate, characterized in that the autoclave curing time is shortened, the production efficiency is improved, and the cost is reduced. Chitin and chitosan used in the present invention are a kind of polysaccharide composed of amino acids and are naturally occurring biopolymers. Generally, chitin is obtained by using the cuticle (hard surface part) of crustaceans such as shrimp and crab as a raw material and chemically treating it to remove proteins, lipids, pigments, etc. Acetylation gives chitosan.

According to the present invention, a siliceous material (30 to 40% by mass), a calcareous material (25 to 40% by mass), a filler (15% by mass) are used.
-25% by mass), a reinforcing fiber (2-10% by mass), an additive (2-10% by mass), and a mixed raw material slurry composed of water,
It is a calcium silicate plate formed into a plate shape and obtained by a hydrothermal reaction, characterized by adding 2 to 10% by mass in terms of solid content of an acidic aqueous solution in which the above-mentioned chitin and chitosan are dissolved. The acidic solution referred to here is an aqueous solution having a pH of 5 or less in which chitin and chitosan are dissolved by an acid described below. This acidic solution is prepared by dissolving chitin and chitosan having a molecular weight of 100,000 to 300,000. The adjustment method is as follows. The above-mentioned chitin and chitosan are dispersed in water to obtain a solid content of 0.3 to 1.0%. The turbid solution adjusted to the above can be dissolved by adding a desired acid while stirring. At this time, an acidic aqueous solution obtained by adjusting the pH to preferably in the range of pH 1 to pH 5 is used. If the pH exceeds 5, the solubility of chitin or chitosan becomes extremely small, and the effect of improving strength and promoting hydrothermal curing cannot be obtained. Conversely, if the pH is less than 1, the solubility is saturated, and the acid is further added to lower the pH. However, the effect is saturated in terms of the strength and the promotion of hydrothermal curing, and only the raw material cost is wasted. After dissolution, if necessary, water can be added as a dilution water up to several times the amount.
However, chitosan has a different molecular weight depending on the degree of deacetylation. When a chitosan having a molecular weight of less than 100,000 (a high deacetylation rate has a low molecular weight) is used, if a chitosan and a siliceous raw material in the autoclave curing are used. Hydrothermal reaction is not promoted, so that the strength of the calcium silicate plate cannot be increased, and it is difficult to shorten the autoclave curing time and obtain a calcium silicate plate efficiently. That is, the preferred molecular weight of the chitosan used is 1
It is between 10,000 and 300,000. In addition, when chitin and chitosan are not dissolved in the acid and added as they are, the hydrothermal reaction between the calcareous raw material and the siliceous raw material in the autoclave curing is not promoted as described above, and the strength of the calcium silicate plate cannot be increased. .

When chitin or chitosan having a molecular weight of more than 300,000 is used, or when the solid concentration in the chitosan turbid solution exceeds 1%, a significant increase in viscosity occurs when an acid is added, The acidic solution cannot be uniformly dispersed in the raw material slurry, and the effect of increasing the bending strength is impaired, and the dewatering property of the slurry is significantly reduced.For example, in the papermaking method, clogging of the felt and softening of the green sheet are performed. Is generated. In the press molding method, dehydration moldability of a press and handling of a raw plate become difficult. The acid used in the above-mentioned acid treatment can be an inorganic acid such as hydrochloric acid or sulfuric acid, or an organic acid such as formic acid, acetic acid or oxalic acid, and gluconic acid, lactic acid or oxyacid such as tartaric acid. Although not restricted, it is preferable to use inexpensive hydrochloric acid or sulfuric acid from the industrial viewpoint.

In the present invention, an acidic aqueous solution in which chitin and chitosan are dissolved in this way can be used without being subjected to a neutralization treatment as disclosed in JP-A-52-22026.
The acidic solution is mixed with a raw material slurry obtained by mixing a siliceous raw material, a calcareous raw material, a filler and a woody cellulose fiber in an amount of water suitable for each production method, in terms of a solid content of chitin and chitosan in 2 parts.
-10 to 10% by mass, and the molded body obtained by each production method is cured under a saturated steam pressure of 150 to 220 ° C, preferably 180 to 200 ° C, preferably for 6 to 15 hours, more preferably for 6 to 12 hours. Thereby, the hydrothermal reaction between the calcareous raw material and the siliceous raw material is promoted, and it is possible to increase the strength of the calcium silicate plate. As a method of adding and mixing an acidic solution in which chitin or chitosan is dissolved, for example, a siliceous raw material, a calcareous raw material, a filler, a reinforcing fiber, and a raw material excluding an additive of water are preferably supplied while being supplied to a stirring mixer. Thereafter, an acidic solution of chitin or chitosan prepared in advance is added, and the mixture is stirred and mixed to obtain a raw material slurry. Alternatively, the raw materials excluding the siliceous raw materials, calcareous raw materials, fillers, reinforcing fibers, and water additives are mixed and stirred in a stirrer or after premixing, and then a previously prepared acidic solution of chitin or chitosan is prepared. This is a method in which a raw material slurry is obtained by adding and stirring and mixing.

However, if the addition amount of the acidic solution in which chitin and chitosan are dissolved is less than 2% by mass in terms of the solid content of chitin and chitosan based on the total solid content of the raw material, the hydrothermal reaction of the calcareous raw material and the siliceous raw material The reaction is not accelerated, and if added in an amount exceeding 10% by mass, the viscosity is remarkable, the dispersibility decreases, and the hydrothermal reaction between the calcareous material and the siliceous material becomes non-uniform, thereby increasing the bending strength. Is impaired. When the hydrothermal reaction temperature in the autoclave curing is lower than 150 ° C., the hydrothermal reaction between the calcareous raw material and the siliceous raw material is not sufficiently performed, and the strength of the formed body is reduced. When the temperature exceeds 200 ° C., the formed body is fragile. And the strength varies. Furthermore, when the autoclave curing time exceeds 15 hours, the production efficiency is not reduced and does not adversely affect the finally obtained calcium silicate plate, but if it is less than 6 hours, the effect of increasing the bending strength is impaired, The strength of the calcium silicate plate cannot be increased.

However, the bending strength of the calcium silicate plate obtained by the hydrothermal reaction for 3 to 6 hours is not at all inferior to that of the conventional product produced by hardening by the hydrothermal reaction for more than 15 hours. According to the present invention, wherein an acidic solution in which chitosan is dissolved is added to a calcium silicate plate,
The autoclave curing time can be shortened, and a calcium silicate plate for a ceiling plate or the like can be efficiently manufactured at a lower cost. However, if the curing time is less than 3 hours, the strength development is impaired, and the bending strength equivalent to that of the conventional product cannot be maintained.

As described above, in the autoclave curing,
If the hydrothermal reaction temperature is below 150 ° C,
The hydrothermal reaction of the siliceous raw material is not sufficiently performed, and the strength of the compact is low.
When the temperature exceeds 220 ° C., the compact becomes brittle,
Variations in strength occur. Used in the present invention
The siliceous raw material is either fly stone or quartz sand and fly up.
From ash, diatomaceous earth, silica fume and white carbon
One or more selected combinations. Silica or silica
Sand is crystalline and may be used together, but is it from the viewpoint of manufacturing control?
It is preferable to select any one of them. Also, hula
Iash, diatomaceous earth, silica fume, white carb
Since calcium is an amorphous and bulky material, calcium silicate
It is effective in reducing the bulk density of the
It is preferable to use in combination with amorphous siliceous raw materials.
New Also, as calcareous raw materials, slaked lime, quick lime or
Use one or more types selected from cement, and use siliceous raw materials
And the ratio of calcareous raw material is CaO / (SiO₂+ Al
₂O ₃) In a molar ratio of 0.4 to 1.2, more preferably
It is necessary to be in the range of 0.6 to 1.0. CaO / (S
iO₂+ Al₂O₃1.) a molar ratio of less than 0.4, or
If it exceeds 2, the final calcium silicate plate
Flexural strength is impaired. The cement used in this application
Portland is Portland cement, usually Portland
Cement, early-strength Portland cement, etc.
Cement, silica cement, fly ash cement, etc.
Compound cement can be used. Particularly preferred combination
In combination, siliceous raw materials include silica stone or silica sand.
Diatomaceous earth and slaked lime or quicklime as calcareous material
is there.

The filler used in the present invention includes wollastonite, mica, calcium carbonate, talc, perlite, bentonite, sepiolite and the like, and these also function as fillers or dimension stabilizers. be able to. Further, the reinforcing fiber used in the present invention is obtained by beating wood-based pulp with a beater beater, a disc refiner, or the like to obtain JIS P8121.
1 freeness according to the Canadian standard freeness test method specified in
What adjusted to 00-350 ml can be used. For example, in the case of manufacturing a calcium silicate plate in a papermaking method, if the freeness exceeds 350 ml, the product after autoclaving will cause a decrease in delamination strength, and if the freeness is less than 100 ml, the freeness of the raw slurry will significantly decrease. And the paper formability decreases.

The amount of the cellulose fibers beaten in this manner differs depending on the molding method. For example, in the case of a papermaking method or a press molding method, it must be 2 to 10% by mass of the whole raw material of the calcium silicate plate. If less than 2% by mass, a sufficient reinforcing effect cannot be exhibited, and
When the ratio exceeds the above, it is not preferable from the viewpoint of fire resistance and nonflammability. As other reinforcing fibers, besides wood-based cellulose fibers, glass fibers, carbon fibers, polypropylene, rayon, and acrylic organic synthetic fibers can be used. As a method for forming the calcium silicate plate of the present invention, a conventionally used method can be used, and examples thereof include a press forming method, a paper forming method, a casting method, and the like, and forming with a slurry concentration suitable for each forming method. be able to.

Hereinafter, embodiments of the present invention will be described. (Example) Chitin or chitosan having a molecular weight of 100,000 to 300,000 was previously dispersed in water to obtain a solid content of 1% or 1.2%.
% Of the turbid solution was stirred, and formic acid or hydrochloric acid was added until the liquid layer reached pH 5. Then, an acidic solution having a solid content concentration of chitin or chitosan of 0.8 to 1.1% was obtained. The acidic solution and the other raw materials were weighed at the ratios shown in Tables 1 and 2, and dispersed in water to adjust the solid content concentration to 10%.
m and a molded body having a thickness of 6 mm were obtained. The obtained molded body was subjected to autoclave curing at the temperature and time shown in Tables 1 and 2 to obtain a calcium silicate plate.

JIS A for this calcium silicate plate
In accordance with 1408, the size of the specimen was set to 3 (50 × 4
0 cm) and the bending strength was measured. The test specimen is 60 ° C
There were two levels of constant weight and saturated state. As can be seen from Tables 1 and 2, the bending strength of the calcium silicate plate obtained by performing the autoclave curing at 180 ° C. for 6 to 15 hours was remarkably increased as compared with that of the comparative example. Even when the autoclave curing time is 3 to 6 hours, 15
A flexural strength equivalent to or higher than that of the comparative example obtained by curing by autoclave curing for a long time was obtained, and the present technology made it possible to significantly shorten the autoclave curing time. In addition, in the above-mentioned acid treatment, when the solid concentration in the chitosan turbid solution was set to 1.2%, the test piece having a constant weight of 60 ° C. did not show a remarkable tendency to increase the bending strength. In the test specimen, the bending strength tended to be slightly increased as compared with the chitin and chitosan-free products shown in the comparative examples.

(Comparative Example) As a comparative example, a turbid solution in which the solid content of chitosan having a molecular weight of 300,000 was adjusted to 1% was stirred, hydrochloric acid or formic acid was added until the liquid layer reached pH 5, and then the chitosan solid content was adjusted. An acidic solution with a concentration of 0.8% was obtained. This acidic solution and other raw materials are weighed at the ratio shown in Table 3,
180cm in length, 90cm in width by the papermaking method as in the example,
A molded product having a thickness of 6 mm was obtained. The obtained molded body was subjected to autoclave curing at the temperature and time shown in Table 3 to obtain a calcium silicate plate, and the bending strength was measured in the same manner as in the example. As shown in the results shown in Table 3, the product without chitosan had a lower flexural strength due to a shorter autoclave curing time. When the amount of chitin or chitosan added was less than 2% or exceeded 10%, no effect of increasing bending strength was observed.

[0023]

As described above, using an acidic solution in which chitin or chitosan is dissolved, at 150 to 220 ° C. and 6 to
By performing the autoclave curing for 15 hours, the strength development of the calcium silicate plate is improved.
It has become possible to prevent breakage that has occurred when used as an exterior material. For calcium silicate boards for applications such as ceiling boards, which are less susceptible to external stress, the autoclave curing time has been shortened, and it has become possible to manufacture efficiently and at lower cost.

[0024]

[Table 1]

[0025]

[Table 2]

[0026]

[Table 3]

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Zenritsu Takamiya 6-1, Kashiwabara, Ishioka City, Ibaraki Prefecture Inside the Building Materials Techno Laboratory (72) Inventor Kazuo Sakamoto 6-1, Kashiwara, Ishioka City, Ibaraki Prefecture Building material techno research laboratory F term (reference) 4G012 PA04 PA05 PA07 PA16 PA22 PB03 PB39 RA05

Claims (5)

[Claims] 1. A calcium silicate plate formed by shaping a slurry comprising a siliceous raw material, a calcareous raw material, a filler, a reinforcing fiber, an additive, and water into a plate shape, further press-forming as required, and curing by autoclave curing. The method for producing a calcium silicate plate, wherein the additive is 2 to 10% by mass in terms of solid content of an acidic solution in which chitin or chitosan is dissolved. 2. The molecular weight of chitin and chitosan is from 100,000 to 3
The method for producing a calcium silicate plate according to claim 1, wherein the number is 10,000. 3. The siliceous raw material is a combination of at least one selected from the group consisting of silica stone and silica sand and fly ash, diatomaceous earth, and silica fume, and the calcareous raw material is one selected from slaked lime, quicklime or cement. The method for producing a calcium silicate plate according to claim 1 or 2, wherein: 4. An autoclave curing temperature of 150 to 22.
The method for producing a calcium silicate plate according to any one of claims 1 to 3, wherein the temperature is 0 ° C. 5. The autoclave curing temperature is from 180 to 20.
The method for producing a calcium silicate plate according to any one of claims 1 to 3, wherein the temperature is 0 ° C.