JPH11147712A - Humidity-controlling gypsum, its production and hardened body of gypsum - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a humidity-controlling gypsum excellent in humidity- controlling properties, produced by an uncomplicated process and capable of being readily and cheaply obtained, and further to provide a production method thereof and a hardened body of the gypsum. SOLUTION: This humidity-controlling gypsum is obtained by adding sulfuric acid to a calcium silicate-based raw material to react the calcium silicate-based raw material with the sulfuric acid in a non-slurry state having substantially no fluidity. The humidity-controlling gypsum obtained by reacting the calcium silicate-based raw material with the sulfuric acid is constituted of >=35 wt.% hydrated gypsum and has 0.3-1.2 light burden volume weight and hardenable properties. The hardened body of the gypsum is obtained by blending and mixing the humidity-controlling gypsum with water and hardening the obtained mixture.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a humidity-controlling gypsum, a method for producing the same and a gypsum cured product, and more particularly, to an excellent humidity-controlling performance and a simple production process.
The present invention relates to a moisture-controllable gypsum that can be easily and inexpensively obtained, a method for producing the same, and a cured gypsum.

[0002]

2. Description of the Related Art In recent years, there has been a strong demand for safety and energy saving in order to secure a comfortable living space, and the building materials (building materials) used are increasingly non-flammable and heat-insulating. It has come to be desired. For this reason, airtight sashes and the like have come to be widely used, and the interior of a modern building has an environment in which moisture tends to accumulate. The moisture easily causes dew condensation on walls, windows, and the like due to a temperature difference between a room and the outside or a temperature change due to cooling and heating. The formation of dew reduces the durability of building materials, promotes the growth of molds and mites, and is a serious problem as a cause of health problems due to asthma and allergies. From this, we remove accumulated moisture,
There is an urgent need to develop measures to prevent the formation of condensation.

[0003] For this reason, wooden materials excellent in moisture absorption / release performance have been frequently used in Japanese buildings in the past. However, wood has a variety of quality, and at the same time, there are many problems such as corrosion and pest generation, and non-combustibility and lack of dimensional stability. In order to solve such a problem, a calcium silicate building material (Japanese Patent Application Laid-Open No. 2-90919, Japanese Patent Publication No.
-46), zeolite-based building materials (Japanese Unexamined Patent Publication No. 3-109)
No. 244) has been proposed.

[0004] Two types of calcium silicate-based building materials are known: zonotolite-based materials and tobermorite-based materials. In general, zonotolite-based materials have the advantage of a high rate of moisture absorption / desorption, but require a small amount of moisture absorption / desorption. It is a drawback. on the other hand,
Tobermorite is generally known as a drawback in that it has a large amount of moisture absorption and desorption but has a low moisture absorption and desorption rate, and both zonotolite and tobermorite have sufficient moisture control performance compared to wood materials. Is hard to say.
In addition, the production of these calcium silicate-based building materials requires hydrothermal synthesis using an autoclave, which increases equipment costs and increases production costs due to their productivity. The product price is not the target.

[0005] In addition, zeolite-based building materials have a high specific surface area and thus have excellent moisture absorption performance, but have a disadvantage that they have insufficient moisture release performance due to a small pore diameter of 3 to 8 mm. Furthermore, since the raw material of the zeolite itself is expensive, and when manufacturing zeolite-based building materials, the firing of the raw material and press molding of the fired product are essential steps, the process becomes complicated, and as a result, the product price is increased. At present, it is not yet widely used as a general-purpose humidity control interior material.

On the other hand, a gypsum board is a typical interior building material having excellent versatility. This gypsum board uses a cast molding method excellent in productivity, and is offered to the market at low cost. However, gypsum board generally has low humidity control performance, and has a low effect of preventing the occurrence of dew condensation, which is a problem in modern architecture. For this reason, some techniques for improving the humidity control of gypsum board have been proposed.
For example, Japanese Patent Application Laid-Open No. 9-59052 discloses a technique in which silica gel is mixed with gypsum to improve the humidity control performance of the gypsum board obtained. However, if the specific surface area is large and bulky silica gel is blended in gypsum, a large amount of water is required for kneading the materials, so the specific gravity of the resulting gypsum board is low, resulting in extremely low strength. There was a problem that it would. For this reason, in order to ensure practical strength, the amount of silica gel must be limited, and as a result, it has been difficult to sufficiently improve the humidity control performance.

[0007] In view of the above, there has been a strong demand for the development of a humidity-control building material that is inexpensive, such as a gypsum board, and has outstanding humidity control performance.

[0008]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a moisture-regulating gypsum which is excellent in moisture-regulating performance and whose production process is not complicated, can be easily and inexpensively obtained, its production method and gypsum curing. Is to provide the body.

[0009]

The inventors of the present invention have made intensive studies and have found that a calcium silicate-based raw material and sulfuric acid are substantially free of flowing water, in other words, a dry or semi-dry non-slurry state. The moisture-regulating gypsum obtained by reacting with gypsum is particularly advantageously obtained as a humidity conditioning material, and the gypsum material obtained by reacting a calcium silicate-based raw material with sulfuric acid contains a specific hydratable gypsum. It has been found that when both the amount and the specific light weight are provided, a gypsum cured product excellent in strength and cost is obtained, and the present invention has been completed.

That is, the present invention provides a moisture-regulating gypsum obtained by adding sulfuric acid to a calcium silicate-based raw material and reacting the calcium silicate-based raw material with sulfuric acid in a non-slurry state having substantially no fluidity. Things.

The present invention also provides a method for producing a moisture-controlling gypsum, which comprises adding sulfuric acid to a calcium silicate-based raw material and reacting the calcium silicate-based raw material with sulfuric acid in a non-slurry state having substantially no fluidity. It provides a method.

Further, the present invention provides a moisture-regulating gypsum obtained by reacting a calcium silicate-based raw material with sulfuric acid, wherein at least 35% by weight of the moisture-regulating gypsum is composed of hydrating gypsum, and An object of the present invention is to provide a moisture-controlling gypsum having curability, characterized in that the light weight is in the range of 0.3 to 1.2.

Furthermore, the present invention provides a method for producing a curable, moisture-controlling gypsum comprising a step of reacting a calcium silicate-based raw material with sulfuric acid, wherein the reaction between the calcium silicate-based raw material and sulfuric acid substantially occurs. It is carried out in a non-slurry state without fluidity, the content of the hydratable gypsum contained in the humidity control gypsum is adjusted to 35% by weight or more, and the light weight of the humidity control gypsum is 0.3 to 1.2. An object of the present invention is to provide a method for producing a moisture-controlling gypsum characterized by being adjusted to a range.

[0014] The present invention also provides a cured gypsum obtained by mixing water, kneading and curing the moisture-controlling gypsum.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. The calcium silicate raw material used in the present invention is:
CaO-SiO ₂ or a CaO-SiO ₂ -H calcium silicate compound consisting of ₂ O, for example silicic acid tricalcium silicate dicalcium, calcium silicate does not contain crystal water such as wollastonite compound or tobermorite, xonotlite, gyro Light And calcium silicate hydrates such as CSH gels. In addition, building materials such as lightweight cellular concrete (ALC), a heat insulating material, a fire-resistant coating material and the like containing these calcium silicate compounds as main components can also be used as the calcium silicate-based raw material specified in the present invention.

Further, calcium silicate-based materials generated in the manufacturing process of these building materials, such as cutting chips and cutting chips generated in the ALC manufacturing process, and polishing debris generated during surface finishing of defective products and heat insulating materials, are also used. It can be used as a raw material. In addition, waste of the above-mentioned building materials from the construction site or the demolition site of a building can also be used as the calcium silicate-based raw material. Utilization of these wastes is a raw material that is advantageous not only in pursuing inexpensiveness but also in view of environmental issues.

As the calcium silicate raw material, the various materials described above can be used. The humidity control performance of the humidity control gypsum of the present invention depends on how much silica gel is produced by the reaction between the siliceous material and the sulfuric acid in the calcium silicate raw material. The humidity control performance increases as the amount of produced silica gel increases, so that when a high humidity control performance is desired, the higher the content of the calcium silicate compound in the raw material, the better. In particular, when using building material waste, there is a high possibility that components other than the calcium silicate compound will be mixed in, so that consideration on its purity is important.

Subsequently, gypsum and silica gel are produced by reacting the calcium silicate-based raw material with sulfuric acid. The humidity-controlling gypsum of the present invention can be obtained by adding sulfuric acid to a calcium silicate-based raw material and reacting the calcium silicate-based raw material with sulfuric acid in a non-slurry state having substantially no fluidity (hereinafter, this gypsum can be obtained). The reaction is sometimes simply referred to as "sulfation."

The non-slurry state having substantially no fluidity is not a wet state in which a slurry is formed, but a dry state or a semi-dry state in general. The main reason to avoid the wet state is to omit filtration, drying, or filtrate treatment in the step after the sulfation treatment. In particular, when a calcium silicate-based raw material is sulfated to obtain gypsum and silica gel, the resulting silica gel has a large specific surface area and is very fine, so its filterability is extremely poor. Then, it is difficult to perform sufficient and efficient filtration. Even if filtration is possible, the silica gel adsorbs a large amount of water, so that the water content of the filter cake is increased, and the drying energy consumed for removing water becomes enormous. Further, the filtrate requires some neutralization treatment, residue treatment, and the like, and such a step also becomes a major cause of complicating the production process. For this reason, it is necessary to perform the sulfation treatment in a non-slurry state having substantially no fluidity.

The method of performing the sulfation treatment in a non-slurry state having substantially no fluidity varies depending on the form and shape of the raw materials. For example, there is a method of mixing using a mixer. As the mixer, any mixer capable of performing high-precision mixing in a dry or semi-dry state can be used without particular limitation. Further, a method of performing a sulfation treatment while also performing pulverization in a ball mill without using such a mixer can also be recommended. In any case, it goes without saying that these sulfation methods should be appropriately selected in accordance with the desired form and properties of the humidity-controlling gypsum.

As the sulfuric acid used for the sulfation treatment, not only commercially available sulfuric acid solution but also waste sulfuric acid generated from the metal refining and acid manufacturing industries can be used. In any case, the concentration of the sulfuric acid aqueous solution is low. If it is too much, the amount of the sulfuric acid aqueous solution to be added increases as a result, and it becomes difficult to perform the sulfation treatment in a non-slurry state, which is an essential element of the present invention, which is not preferable.

The amount of water to be added must be appropriately set within a range in which a non-slurry state having substantially no fluidity is maintained and depending on the calorific value. For example, the amount of water is based on 100 parts by weight of the calcium silicate raw material. And about 20 to 100 parts by weight of water.

In addition, in the case where the curable gypsum is imparted with curability and is later formed into a gypsum cured product, it is also important to increase the purity of the gypsum itself in order to secure the mechanical strength of the cured gypsum product. In a state where a large amount of unreacted calcium silicate remains or an excessive amount of sulfuric acid is present, sufficient mechanical strength cannot be obtained. The purity of the gypsum greatly depends on the amount of sulfuric acid to be added, and specifically, it can be said that the addition amount of sulfuric acid of 70 to 100 mol% of CaO in the calcium silicate-based raw material is preferable.

The form of gypsum produced by the above-mentioned sulfate treatment is gypsum dihydrate, gypsum hemihydrate, type III anhydrous gypsum, II
It becomes at least one or more types of anhydrous gypsum, and this form varies depending on the conditions of the sulfation treatment. The form of these gypsums may be appropriately selected according to the purpose of use. For example, if the form of gypsum is predominantly dihydrate gypsum, the resulting moisture-regulating gypsum will not have curability. Such moisture-regulating gypsum contains fine silica gel that is excellent in moisture absorption and desorption performance, so if it is in a powder state, it can be made into various moisture conditioning materials by packaging with a breathable material, Alternatively, if it is in the form of pellets, it can be used as it is or packaged, and used as a humidity control material inside the house or under the floor. Further, powders and granules can be pressed and used as tiles, blocks, or plates.

In order to impart curability to the moisture-regulating gypsum, gypsum dihydrate and type-II anhydrous gypsum do not have hydration activity, so that the content is desirably as low as possible. In addition,
When an aqueous solution of sulfuric acid is added so that the water content becomes as small as possible, the dehydration reaction from gypsum to hemihydrate gypsum or type III anhydrous gypsum is promoted by the heat generated by the sulfation reaction, and type II anhydrous gypsum is produced. On the other hand, it is preferable because the remaining amount of dihydrate gypsum having no hydration activity also decreases.
However, if the water content is too low, an excessively exothermic reaction occurs, and a type II anhydrous gypsum having no hydration activity is generated, which is not preferable. Since the appropriate amount of water can vary greatly depending on the properties of the calcium silicate raw material used, it is needless to say that the properties need to be properly grasped and understood.

In the case where the curable gypsum is imparted with curability and is later converted into a gypsum cured product, it is essential that the moisture-regulated gypsum simultaneously satisfies the following two conditions. That is:

[0027] 35% by weight or more of the humidity control gypsum is composed of hydratable gypsum; and the light weight of the humidity control gypsum is in the range of 0.3 to 1.2. In addition, the light loading capacity in the present invention is JIS R61.
In accordance with No. 26, the ratio of the weight (for example, g) to a certain volume (for example, 1 cc) is used. For example, when filling a container having a certain volume with a material, the pressure applied to the material is only the weight of the material.

Preferably, 40 to 70% by weight of the humidity control gypsum is composed of hydratable gypsum, and the light weight of the humidity control gypsum is in the range of 0.5 to 1.0. .

In the present invention, the moisture-controlling gypsum obtained by the sulfation treatment is further subjected to a calcination treatment to promote the dehydration reaction of gypsum dihydrate, thereby increasing the proportion of hemihydrate gypsum and type III anhydrous gypsum. You can also. The baking treatment is preferably performed when the amount of hydratable gypsum to be formed is difficult to control for some reason or when it is desired to intentionally increase the amount of hydratable gypsum. The firing treatment is performed, for example, at a temperature of 100 to 2.
The temperature is 50 ° C. and the time is about 30 to 120 minutes. Excessive firing
Since there is a possibility of producing type II anhydrous gypsum, sufficient consideration must be given to the setting of the firing conditions. Further, in the present invention, a humidity-controlling gypsum that has not been calcined if necessary,
It is also possible to use in combination with the moisture-controlling gypsum subjected to the baking treatment.

Here, the amount of hydratable gypsum formed was 35% by weight.
The reason for defining the above is to secure the mechanical strength of the gypsum cured product finally obtained, and when the amount of hydratable gypsum is less than 35% by weight, the mechanical strength that can be used as a cured product is used. Is not obtained, which is not preferable. If necessary, hydratable gypsum can be separately added to adjust the hydratable gypsum in the humidity control gypsum.

The reason why the light weight is set in the range of 0.3 to 1.2 is also to secure the mechanical strength of the hardened gypsum body. That is, it is important to reduce the amount of kneading water in order to increase the mechanical strength. For this purpose, a raw material having a large light loading capacity is preferable. However, if the light weight is too large, the hardness of the powder increases, and the dispersibility in water deteriorates. Therefore, the hydration reaction does not proceed sufficiently, and as a result, the strength of the cured product decreases. For this reason, the light loading capacity must be in the range of 0.3 to 1.2. The adjustment of the light weight can be easily performed by pulverizing the humidity-controlling gypsum using a hammer mill, a ball mill or the like. When the baking treatment is performed, the light weight may be adjusted before or after the baking, but it is preferable to pulverize after the baking in order to increase the baking efficiency.

The curable moisture-controlling gypsum thus obtained is kneaded with water, hydrated and cured to obtain a cured gypsum of a desired shape. The type of the gypsum cured body includes a block, a board, a tile, and the like, which may be appropriately selected according to the purpose of use. However, when used as an interior building material, a board is preferable in view of ease of construction and the like. Known methods such as a casting method and a press molding method can be used for the production method of the gypsum cured body, but in the present invention, since the main purpose is to provide an inexpensive gypsum cured body, in order to achieve this object, Cast molding is the most recommended molding method. The adjustment of the gypsum cured body by the casting method can be performed by flowing a slurry obtained by mixing a moisture-controlling gypsum and water on a base paper of a production line, making the slurry have a desired thickness, and then curing.

In order to further improve the strength of the cured gypsum, addition of inorganic fibers such as glass fiber and metal fiber and organic fibers such as pulp fiber, polypropylene fiber, nylon fiber and vinylon fiber, properties of slurry and physical properties of the cured gypsum As an improvement, it is possible to add an admixture such as a water reducing agent, a sizing agent and a setting retarder.

Furthermore, the pH of the gypsum cured product can be adjusted according to the application. This adjustment can be easily performed by introducing sulfuric acid in an amount adjusted to the CaO content in the calcium silicate-based raw material or by introducing a pH adjuster, preferably an alkali calcium salt. The body can be adjusted to, for example, pH 4-8.

The cured gypsum body of the present invention is excellent in strength, easy to manufacture, and inexpensive, so that it can be sufficiently applied to various building materials.

[0036]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

1. Sulfation treatment method Raw materials used in Examples and Comparative Examples are shown below. Calcium silicate-based raw material: Light-weight cellular concrete (hereinafter abbreviated as ALC) manufactured by Onoda ALC Co., Ltd. was ground to 2 mm under, dried and used. According to still chemical analysis CaO content 25.2 wt%, SiO ₂
The content was 54.7% by weight. Minerally, it was a calcium silicate compound composed mainly of tobermorite and silica stone. Sulfuric acid: Kanto Chemical Co., Ltd. reagent first class (purity: 95% by weight)
And diluted with tap water to a predetermined sulfuric acid concentration to prepare a sulfuric acid aqueous solution. The sulfation treatment was performed as follows. 2000 g of the pulverized ALC is put into a 20-liter Henschel mixer (manufactured by Mitsui Miike Kakoki Co., Ltd.) and the stirring speed is 7
40r. p. m. While stirring with a predetermined sulfuric acid / CaO
An aqueous solution of sulfuric acid in an amount of mol% was added to perform a sulfation treatment.

2. Production method of hardened gypsum (1) Raw materials The following sulfated products and sulfated baked products were used as raw materials. The above 1. The sulfated product described in 1 above. The sulphated product was calcined at 150 ° C. for 15 hours and cured at 20 ° C. and a relative humidity of 60% for 24 hours. (2) Method for Producing a Hardened Gypsum First, the above-mentioned sulfated product and the above-mentioned sulfated and calcined product were kneaded by adding water to each of them alone or a mixture of both, to obtain a slurry. The slurry that had been subjected to the predetermined kneading was filled into a pipe cone of φ = 5 cm and h = 5 cm, and was gently pulled up. The water ratio at which the flow value at this time was 12 cm was determined. Thereafter, the slurry kneaded at this water ratio was poured into a 2 × 2 × 8 (cm) mold, hydrated and hardened, and dried at 45 ° C. to obtain a gypsum hardened body.

3. Evaluation method The humidity control gypsum and the cured gypsum obtained were evaluated by the following methods. The evaluation of the comparative example was also performed in the same manner. (1) Composition identification: X-ray diffractometer RINT1000
(Manufactured by Rigaku Co., Ltd.) using a powder diffraction method.
The mineral composition of gypsum in the sulfated product dried at ℃ and the sulfated calcined product was identified. (2) Content of hydratable gypsum: X-ray diffraction analysis of a sulfated product or a sulfated calcined product, the contained hemihydrate gypsum and
It was calculated from the peak intensity of type III anhydrous gypsum by extrapolation. (3) Light loading weight: The light loading weight of the sulfated and calcined product is 39.
The measurement was performed using a 7.5 cc stainless steel cup. (4) Flexural strength: Shimadzu Autograph AGS-1000B
(Shimadzu Corporation), the span was set to 6 cm, and the bending strength of the cured product was measured. (5) Moisture absorption: The moisture-controllable gypsum or the gypsum cured product dried at 45 ° C. was allowed to stand in an atmosphere of 20 ° C. and a relative humidity of 93% until equilibrium, and the moisture absorption was calculated from the change in weight. (6) Moisture absorption: Calculated by multiplying the moisture absorption determined by the method of (5) by the specific gravity of the cured product.

[Examples 1 and 2 and Comparative Examples 1 and 2] Sulfurization treatment was carried out according to the formulation shown in Table 1 below (Examples were in a non-slurry state, Comparative Examples were in a slurry state). Identification of mineral composition of gypsum in hydrolyzate, measurement of moisture absorption,
The shape of the sulfated product was observed. Here, the amount of the aqueous sulfuric acid solution was set to sulfuric acid / CaO 2 in both the examples and comparative examples so that unreacted substances (calcium silicate raw material) did not remain.
It adjusted so that mol% might be set to 100%. Table 1 also shows the obtained results.

[0041]

[Table 1]

First, the moisture-controlling gypsum in Examples 1 and 2 was subjected to a sulfation treatment in a non-slurry state, and as a result, the treated product appeared to be a dried powder in appearance. For this reason, this processed product could be used as a humidity control material by packaging it with a breathable material without performing any drying operation. Note that no gypsum phase and silica gel phase were separated in the treated product, and the composition was visually judged to be homogeneous. On the other hand, in Comparative Examples 1 and 2, as a result of performing the sulfation treatment in the slurry state, the treated product contains a large amount of water,
Filtration and drying were required to collect the solids. In addition, the actual filtration took a considerably long time in spite of employing vacuum filtration having high filtration efficiency. This was thought to be because the silica gel in the processed product was very fine. In addition, the drying took a considerably long time, and the dried product was in a state in which gypsum and silica gel were separated, and were visually nonuniform. As described above, according to the present invention, since the sulfation treatment is performed in a non-slurry state having substantially no fluidity, a homogeneous and economically useful moisture-controlling gypsum is provided.

[Examples 3 and 4 and Comparative Examples 3 and 4] Analysis of gypsum, measurement of light loading capacity and preparation of sulfated and calcined products after sulphation treatment with the composition shown in Table 2 below were carried out. The properties of the cured product were evaluated. The measurement of the light loading capacity and the production of the cured product were performed using a sulfated and calcined product which was pulverized to 2 mm under with a hammer mill. Table 2 also shows the obtained results.

[0044]

[Table 2]

In Examples 3 and 4, the sulphation treatment and the calcination treatment were performed so that the hydratable gypsum was contained in an amount of 35% by weight or more.
On the other hand, in Comparative Example 3, unreacted calcium silicate remained, and in Comparative Example 4, sulfuric acid was used as a condition that the content of hydratable gypsum was less than 35% by weight after baking treatment after sulfation treatment. Sulfation was performed under excessive conditions.
From these results, it can be seen that the cured gypsum body of the present invention is excellent in humidity control and has extremely high bending strength. on the other hand,
In Comparative Examples 3 and 4, since the amount of hydratable gypsum was small and the strength of the moisture-controllable gypsum cured product was low, it was determined to be inappropriate for use as a building material. Thus, in the gypsum cured product according to the present invention, sufficient mechanical strength is ensured by including 35% by weight or more of hydratable gypsum, and a cured product having humidity control can be provided.

[Examples 5 to 6 and Comparative Examples 5 to 6] Analysis of gypsum in sulfated and calcined products which had been subjected to sulfation treatment with the composition shown in Table 3 below, and calcined and cured, and measured and prepared for light weight. The properties of the cured product were evaluated. Next, with respect to the sulfated and calcined products, the light loading weight was changed to prepare a gypsum cured product. Table 3 also shows the obtained results.

[0047]

[Table 3]

First, Example 5 was crushed by a hammer mill to 1 mm under to make the light weight 0.46, and Example 6 was crushed by a hammer mill to 2.5 mm under and the light weight to 0.92. A cured product was prepared using each of the above. Comparative Example 5 was a hammer mill of 0.5 m.
A cured product was prepared by using a material having a light loading capacity of 0.19 by pulverizing the powder to m-under, and using a material having a light loading capacity of 1.34 without performing pulverization in Comparative Example 6. As can be seen from the results in Table 3, even in the sulfated and calcined product obtained under the same treatment conditions, when the light loading capacity changes, the amount of water necessary for kneading also changes, and the strength of the cured product also depends on this. . Particularly, as in the case of the fifth and sixth embodiments, the light loading capacity is 0.3 to
By setting the ratio in the range of 1.2, kneading was possible with a small amount of water, and a cured product having high strength was obtained. On the other hand, in Comparative Example 5 in which the light weight was less than 0.3, the amount of water required for kneading was large, and the strength of the cured product was small. Comparative Example 6, which has a larger light weight, has a high powder hardness, poor dispersibility in water, and does not proceed with a sufficient hydration reaction.
The bending strength of the cured product was reduced. from these things,
In the present invention, it has been confirmed that by specifying the light loading capacity, it is possible to provide a cured gypsum body having excellent humidity control performance and strength properties.

[0049]

According to the present invention, there is provided a moisture-regulating gypsum which is excellent in humidity control performance, can be easily and inexpensively obtained without a complicated production process, a method for producing the same, and a cured gypsum product. .

 ──────────────────────────────────────────────────の Continuing from the front page (72) Inventor Norifumi Nagata 2-4-2-4 Daisaku, Sakura City, Chiba Pref.

Claims (8)

[Claims] 1. A method for adding sulfuric acid to a calcium silicate-based raw material,
A moisture-controlling gypsum obtained by reacting the calcium silicate-based raw material with sulfuric acid in a non-slurry state having substantially no fluidity. 2. Addition of sulfuric acid to a calcium silicate-based raw material,
A method for producing a moisture-controlling gypsum, comprising reacting the calcium silicate-based raw material with sulfuric acid in a non-slurry state having substantially no fluidity. 3. A moisture-controlling gypsum obtained by reacting a calcium silicate-based raw material with sulfuric acid, wherein
A moisture-controlling gypsum having curability, characterized in that 5% by weight or more is composed of hydratable gypsum, and the light weight of the humidity-controlling gypsum is in the range of 0.3 to 1.2. 4. A method for producing a curable, moisture-controlling gypsum comprising a step of reacting a calcium silicate-based raw material with sulfuric acid, wherein the reaction between the calcium silicate-based raw material and sulfuric acid has substantially no fluidity. It is carried out in a non-slurry state, and the content of hydratable gypsum contained in the humidity control gypsum is 35% by weight.
Adjusted as described above, and the light weight of the humidity control gypsum is 0.
A method for producing a humidity-controlling gypsum, which is adjusted to a range of 3 to 1.2. 5. The production method according to claim 4, wherein the content of the hydratable gypsum contained in the humidity control gypsum is adjusted by a baking treatment of the humidity control gypsum. 6. A gypsum cured product obtained by mixing, kneading and curing water with the moisture-regulating gypsum according to claim 3. 7. The gypsum cured product according to claim 6, wherein the pH of the cured product is between 4 and 8. 8. A building material using the gypsum cured product according to claim 6 or 7.