JPH10245250A - Moisture-absorbing and releasing hardened plaster - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain hardened plaster that can absorb and release moisture better than natural timber does by using a reaction product containing plaster and silica gel prepared by subjecting a calcium silicate material or its waste material to sulfurization treatment. SOLUTION: The calcium silicate material means an inorganic compound mainly comprising calcium silicate, for example, CSH gel, tobermorite, xonotlite and the like. They are preferably adjusted in their particle size and shape so that they becomes suitable for sulfurization treatment. For example, lumps of about 5cm particle sizes to powder of less than 3mm particle sizes may be appropriately used. As a sulfurization material, are used at least one selected from sulfuric acid and aluminum sulfate. In addition to the commercially available products, waste sulfuric acid or sludge of high content of aluminum sulfate produced in metal refining or acid production may be used. The weight ratio of the calcium silicate material to the sulfurization material is suitably set to >=0.1 (SO4 <2-> /Ca<2+> ) so that plaster may be formed more and silica gel may be formed properly.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cured gypsum body having excellent moisture absorption and desorption properties. More specifically, the present invention relates to a hardened gypsum cured product having a high hygroscopic property, which can use a reaction product containing silica gel and gypsum obtained by performing a sulfation reaction of various calcium silicate materials or building waste mainly containing the same.

[0002]

2. Description of the Related Art In recent years, houses have been required to have heat insulation from the viewpoint of energy saving, and the airtightness of the housing space has become extremely high. In addition, various temperature control devices such as a heating device and a cooler have been introduced for the purpose of realizing the comfort of a living space. However, the temperature distribution in each part of the room has rather large variations, and specifically, dew condensation frequently occurs in poorly ventilated areas such as closets, behind chests, window frames and ceilings. Seen in For this reason, it has become an environment in which microorganisms such as molds can easily propagate, and these situations are beginning to be regarded as problems as factors that impair health such as asthma and allergic diseases.

[0003] Wood and wood-based building materials processed from wood have been widely used as building materials since ancient times. However, wood-based building materials generally have a large moisture absorption capacity. Exhibits moisture function. For example, even if the moisture temporarily stays in the space, the moisture can be stored in the base material, and when the humidity of the atmosphere decreases due to a ventilation operation, the moisture is quickly released. Therefore, the indoor humidity can be kept at an appropriate level.

[0004] As described above, the wood-based building material has excellent functions such as the ability to prevent the generation of dew condensation water in a living space by its moisture absorbing and releasing performance. However,
Due to the recent decrease in timber resources, it has become difficult to obtain good-quality wood-based building materials, and prices are constantly rising. On the other hand, wood-based building materials are flammable and have drawbacks such as generation of pests and corrosion, and inorganic materials are excellent from the viewpoint of ensuring safety in living spaces.

[0005] From such a point, gypsum boards employing a so-called cast molding method are widely used especially as interior building materials. This gypsum board is inexpensive and nonflammable, and has many features such as excellent dimensional stability.However, it is inferior to wood-based building materials in terms of moisture absorption and release performance.
It is also seen as one of the factors contributing to the condensation in the living space in recent years.

In order to compensate for such a defect, a material mainly composed of calcium silicate has been developed (JP-A-57-147).
No. 424, Japanese Patent Publication No. 2-46, Japanese Unexamined Patent Publication No. 2-90919). These calcium silicate-based materials are materials mainly composed of inorganic silicate minerals such as zonotolite and tobermorite,
It is nonflammable and has some moisture absorption / release properties. However, the amount of moisture absorbed and released by conventional calcium silicate-based materials is far from the performance of wood, and the production cost is high due to the need for complicated hydrothermal synthesis equipment during the production process, and it is a general-purpose building material. It is considerably more expensive than gypsum board.

On the other hand, the disposal method of construction waste has become a major social problem in recent years. In particular, calcium silicate-based building materials waste is enormous and has a low bulk specific gravity.
Even when reclaiming land, it is extremely difficult to secure a disposal site. Therefore, at present, landfill disposal and the like are performed by performing compression processing and the like.

Thus, there has been a strong demand for the development of a low-cost inorganic building material having excellent moisture absorption / desorption performance and effective use of calcium silicate waste material. The present invention has solved the above-mentioned conventional problems, and is an inorganic cured material excellent in moisture absorption and desorption mainly composed of gypsum, and can be manufactured using a calcium silicate-based waste material as a raw material, so that the cost is low and the waste material is reduced. An object of the present invention is to provide a moisture-absorbing and desorbing gypsum cured product that can be effectively used.

[0009]

The hardened gypsum of the present invention comprises:
It combines excellent moisture absorption / desorption performance comparable to wood-based building materials, non-flammability and stability of gypsum board and calcium silicate-based materials, which are inorganic materials, and aims to effectively use calcium silicate-based waste materials. By using calcium-based materials or the reaction products containing gypsum and silica gel obtained by sulfated waste materials, inorganic materials with moisture absorption and desorption performance comparable to wood-based building materials while achieving effective use of resources Material obtained.

That is, the present invention firstly comprises a gypsum obtained by subjecting a calcium silicate-based material to a sulfation reaction with a sulfated material, and a reaction product containing silica gel as a main component, and a moisture-absorbing and desorbing gypsum hardening material. It provides the body. Secondly, the present invention provides a moisture-absorbing and desorbing gypsum cured product in which the sulfated material is one or more of sulfuric acid or aluminum sulfate. Furthermore, the present invention provides, thirdly, a moisture-absorbing and desorbing gypsum cured product, which is a construction waste material in which the calcium silicate-based material contains one or more of CSH gel, tobermorite, or zonotolite.
Further, the present invention fourthly provides a cured hygroscopic gypsum cured product in which the calcium silicate-based material contains one or more of organic fibers, inorganic fibers, pulp fibers or glass fibers.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. The cured product of the present invention is a highly hygroscopic gypsum cured product mainly composed of a gypsum obtained by subjecting a calcium silicate-based material to a sulfation reaction with a sulfated material and a reaction product containing silica gel.

As the sulfated material, one or more of sulfuric acid and aluminum sulfate can be used.
In addition to commercially available sulfuric acid solutions and aluminum sulfate aqueous solutions, waste sulfuric acid produced from metal refining and acid production industries, sludge containing a large amount of aluminum sulfate, and mixtures thereof can be used. As the sulfated material, other than these, an acidic water-soluble sulfate such as iron sulfate can be used. A sulfated material is a material for reacting with a calcium silicate-based material to sulfate it to form a homogeneous mixture containing calcium sulfate (gypsum) and silica gel. That is, the present invention is to obtain a cured gypsum body which is more homogeneous and excellent in moisture absorption / desorption properties than a simple mixture of silica gel and gypsum by utilizing a homogeneous reaction called a sulfation reaction.

Accordingly, the ratio of the calcium silicate-based material to the sulfated material is not particularly limited as long as the gypsum and the silica gel are formed, but preferably the gypsum is formed most in the sulfation reaction, The amount ratio of the calcium silicate-based material to the sulfated material may be adjusted so that an appropriate amount of silica gel is generated. As an example, the molar ratio of sulfuric acid to calcium silicate (SO ₄ ²⁻ / Ca ²⁺ ) is suitably 0.1 or more. If it is less than 0.1 mol, the hygroscopicity decreases.

As described above, the hardened gypsum of the present invention contains silica gel produced by a sulfation reaction together with gypsum.
The content of silica gel is preferably adjusted according to the desired moisture absorption / release performance. The maximum content of silica gel depends on the calcium silicate-based material. For example, when tobermorite is used, a cured gypsum body containing silica gel at a maximum of about 40% by weight can be obtained. When zonotolite is used, a gypsum cured product containing up to about 36% by weight of silica gel can be obtained. This silica gel is present in the gypsum matrix voids. When aluminum sulfate is used as the sulfated material, the calcium silicate-based material reacts with aluminum sulfate to produce gypsum, alumina sol and / or alumina gel together with silica gel, and these gypsum were present in the voids of the gypsum matrix together with the silica gel. A cured product is obtained.

The calcium silicate-based material as another raw material of the gypsum cured product according to the present invention refers to an inorganic compound material mainly composed of calcium silicate. This calcium silicate-based material includes CSH gel, tobermorite, zonotlite, etc.
Or what consists of these mixtures is known.
As the calcium silicate-based material, a building waste material containing this as a main component can be used. Building materials mainly composed of calcium silicate-based materials are lightweight cellular concrete
(ALC), heat insulating materials, artificial wood, fire-resistant coated boards and the like are generally commercially available. In the present invention, in addition to these materials themselves, offcuts and defective products generated at the production stage, building construction sites, Waste generated from dismantling sites and the like can be used as a raw material. In recent years, building materials mainly composed of calcium silicate-based materials have been produced and consumed in large quantities, and accordingly, the amount of generated waste materials has become enormous. The present invention has realized a low-cost gypsum cured product having excellent moisture absorption / release properties by effectively utilizing this waste material.

The form of the calcium silicate material used is
It is not particularly limited as long as a uniform moisture-absorbing and releasing gypsum cured product can be obtained by the sulfation reaction. The moisture absorption / desorption characteristics of the gypsum cured product differ depending on the purity of the calcium silicate-based material to be used, and the higher the purity, the better the moisture absorption / desorption performance. The purity of the raw material calcium silicate-based material may be appropriately selected and used according to the properties desired for the body. In addition, these calcium silicate-based materials are suitable for sulfation treatment,
It is preferable to adjust the fineness and shape. For example, particle size 5
It can be suitably used from a lump having a size of about cm to a powder having a particle size of 3 mm or less.

Although various additives are used in the calcium silicate-based material used as a building material, a material containing a fibrous material is particularly preferable as a raw material of the gypsum cured product according to the present invention. By using a calcium silicate-based material containing a fiber material, the fiber material can be introduced in a form homogeneously dispersed in a cured product generated by a sulfation reaction, and the strength characteristics of the cured product can be improved. here,
As the fiber material, those generally blended with calcium silicate-based building materials can be used, for example, inorganic fibers such as wollastonite, rock wool, asbestos, and glass fibers, pulp fibers, polypropylene fibers, nylon fibers, and acrylic fibers. Organic fibers such as fiber and hemp fiber can be used.

The compounding ratio of the fiber material varies depending on the form, mineral composition, and type of fiber of the calcium silicate-based material used, and is appropriately determined in consideration of these. Specifically, for example, when a calcium silicate-based material containing an organic fiber is used, in order to achieve the flame retardant performance in accordance with the Japanese Industrial Standards (JIS standard), 7 g of the organic fiber is contained in the cured gypsum obtained. The amount ratio between the calcium silicate-based material and the sulfated material is adjusted so as to be not more than the weight%.

As described above, the moisture-absorbing and desorbing gypsum cured product of the present invention can actively recycle the reinforcing fiber blended in the calcium silicate-based building material as a reinforcing material for the gypsum cured product. When building material waste or the like is used as a raw material, these reinforcing fibers do not need to be removed and can be easily reused.

[0020]

Embodiments of the present invention will be described below. The raw materials used in the examples and comparative examples are shown in Table 1. The components of the composition were measured by a powder diffraction method using an X-ray diffractometer (Rigaku Corporation: RINT1000), and the specific surface area was measured by nitrogen adsorption (Shimadzu Micrometorics Flow Sorb II 2300). . The obtained cured product was evaluated by the following method. The evaluation of the comparative example was performed in the same manner as the evaluation of the cured product. (1) Specific gravity: A specific gravity was calculated from a weight and a measured size of a sample (2 × 2 × 8 cm) of a cured product. (2) Flexural strength: Measurement was performed using an Instron universal testing machine with a span of 6 cm. (3) Change in Moisture Absorption with Relative Humidity of 53% to 75% A sample of the cured product was weighed at 20 ° C. in a saturated aqueous solution of calcium nitrate (relative humidity of 53%) to determine the moisture absorption. Next, the weight of the cured product sample having a constant weight at a relative humidity of 53% was measured at 20 ° C. in a saturated aqueous solution of sodium chloride (relative humidity: 75%), the weight was measured, and the moisture absorption was determined. The difference between the moisture absorption at 75% relative humidity and the moisture absorption at 53% was determined as the change in moisture absorption. (4) Moisture absorption with respect to relative humidity of 53% to 75% The change in the moisture absorption obtained in the above (3) multiplied by the specific gravity was determined as the moisture absorption.

Example 1 Calcium hydroxide and silica were dry-mixed so that the molar ratio of CaO and SiO ₂ became 0.8, and 1000 parts by weight of water was added to 100 parts by weight of this mixture to prepare a raw material slurry. Obtained. Thereafter, the raw material slurry was reacted with stirring under hydrothermal conditions of 10 kgf / cm ² and 180 ° C. for 6 hours to obtain a calcium silicate slurry. The solid content was separated by filtration from the calcium silicate slurry, and the dried product was qualitatively analyzed by X-ray diffraction. As a result, it was a calcium silicate material mainly composed of tobermorite. Next, 330 parts by weight of a 3.7 N aqueous sulfuric acid solution was gradually added to 100 parts by weight of the solid content in the calcium silicate-based slurry, and the mixture was slowly stirred for 15 minutes to obtain a sulfated slurry. Thereafter, this slurry was inserted into a dryer at 150 ° C. for 24 hours to evaporate water, thereby obtaining a sulfated solid. The specific surface area of this sulfated solid by a nitrogen adsorption method was 145 m ² / g. Next, 100 parts by weight of the sulfated solid and 100 parts by weight of water were mixed, and the resulting slurry was mixed with three metal molds (2 × 2
× 8 cm), and the molded product after curing was dried at 45 ° C. to obtain a cured product of the present invention.
The cured product was confirmed by X-ray diffraction and chemical analysis to be a composition mainly composed of tobermorite, gypsum dihydrate and silica gel. The above test was performed on the cured gypsum body, and the measurement results are shown in Table 2.

Example 2 A gypsum cured product of the present invention was produced using a commercially available ALC as a typical calcium silicate-based material. First, commercial ALC
500 parts by weight of water was added to 100 parts by weight to obtain a calcium silicate slurry. 70 parts by weight of a 7N aqueous sulfuric acid solution was gradually added to 100 parts by weight of ALC, which is a solid content in the calcium silicate-based slurry, and stirred to obtain a sulfated slurry. Then, in the same manner as in Example 1,
A sulfated solid was obtained. The specific surface area of this sulfated solid is 5
It was 6 m ² / g. A slurry obtained by adding 100 parts by weight of water to 100 parts by weight of the sulfated solid was poured into a mold in the same manner as in Example 1 and molded to obtain a cured hygroscopic gypsum cured product of the present invention. This cured product was confirmed by X-ray diffraction and chemical analysis to be a composition mainly composed of tobermorite, quartz, gypsum and silica gel. The above test was performed on the cured gypsum, and the measurement results are shown in Table 2.
It was shown to.

Example 3 The moisture-absorbing and desorbing gypsum according to the present invention was cured in the same manner as in Example 2, except that 90 parts by weight of a 7N aqueous sulfuric acid solution was used per 100 parts by weight of the ALC solids in the calcium silicate slurry. I got a body. The specific surface area of the sulfated solid was 70 m ² / g. The cured product was confirmed by X-ray diffraction and chemical analysis to be a composition mainly composed of tobermorite, quartz, gypsum and silica gel. The above test was performed on the cured gypsum body, and the measurement results are shown in Table 2.

Example 4 2,000 parts by weight of water was added to 100 parts by weight of ALC waste generated in a manufacturing plant to obtain a calcium silicate slurry. With respect to 100 parts by weight of the ALC solid content in this calcium silicate slurry, 3.7N aqueous sulfuric acid solution 140
A part by weight was gradually added and stirred to obtain a sulfated slurry.
Thereafter, in the same manner as in Example 1, a moisture-absorbing and dehydrated gypsum cured product of the present invention was obtained. The specific surface area of the sulfated solid was 116 m ² / g. The cured product was confirmed by X-ray diffraction and chemical analysis to be a composition mainly composed of quartz, gypsum and silica gel. The above test was performed on the cured gypsum body, and the measurement results are shown in Table 2.

Example 5 Tobermorite-based heat insulating material (manufactured by Asahi Silicic Industry Co., Ltd.) 100
670 parts by weight of water was added to parts by weight to obtain a calcium silicate slurry. To 100 parts by weight of the solid content of the heat insulating material in the calcium silicate slurry, 300 parts by weight of a 3.7 N aqueous sulfuric acid solution was gradually added and stirred to obtain a sulfated slurry. Thereafter, a sulfated solid was obtained in the same manner as in Example 1. The specific surface area of this sulfated solid was 140 m ² / g. A slurry obtained by adding 300 parts by weight of water to 100 parts by weight of this sulfated solid was poured into a mold in the same manner as in Example 1 and molded to obtain a moisture-absorbing and desorbing gypsum cured product of the present invention.
The cured product was confirmed by X-ray diffraction and chemical analysis to be a composition mainly composed of gypsum dihydrate and silica gel. Perform the above test on this gypsum cured body,
Table 2 shows the measurement results.

Example 6 A calcium silicate slurry was obtained in the same manner as in Example 5, except that a zonotolite-based heat insulating material (manufactured by Asahi Silicic Acid Industry Co., Ltd.) was used. To 100 parts by weight of the solid content of the heat insulating material in the calcium silicate slurry, 320 parts by weight of a 3.7 N aqueous sulfuric acid solution was gradually added and stirred to obtain a sulfated slurry. Thereafter, a sulfated solid was obtained in the same manner as in Example 1. The specific surface area of this sulfated solid was 102 m ² / g. A slurry obtained by adding 350 parts by weight of water to 100 parts by weight of the sulfated solid was poured into a mold in the same manner as in Example 1 and molded to obtain a cured hygroscopic gypsum body of the present invention. The cured product was confirmed by X-ray diffraction and chemical analysis to be a composition mainly composed of gypsum dihydrate and silica gel.
The above test was performed on the cured gypsum body, and the measurement results are shown in Table 2.

Example 7 100 parts by weight of commercially available "plaster of Paris" was mixed with 100 parts by weight of the sulfated solid obtained in Example 4, and 1 part by weight of this mixture was added.
The slurry obtained by adding 00 parts by weight of water was poured into a mold in the same manner as in Example 1 and molded to obtain a hygroscopic plaster of the present invention. The above test was performed on the cured gypsum body, and the measurement results are shown in Table 2.

Comparative Example 1 Gypsum hemihydrate was obtained by inserting commercially available gypsum into a dryer at 150 ° C. for 24 hours. A slurry obtained from 100 parts by weight of water with respect to 100 parts by weight of this hemihydrate gypsum was prepared in Example 1.
In the same manner as in the above, the mixture was cast into a mold to obtain a cured gypsum body. The above test was performed on the cured gypsum body, and the measurement results are shown in Table 2.

Comparative Example 2 As a commercially available calcium silicate-based humidity control material, Chichibu Onoda Co., Ltd.
Table 2 shows the measurement results of the above test for Oslite (Comparative Example 2).

Comparative Example 3 Table 2 shows the measurement results of the above test for natural wood (trade name: Spruce).

[0031]

[0032]

As shown in Table 2, the gypsum cured product according to the present invention has a moisture absorption exceeding that of natural wood, and the change in the moisture absorption shows a change almost equal to that of natural wood. Has moisture release properties. In addition, although the strength of the cured product is lower than that of plain gypsum, most of it is a commercially available calcium silicate-based humidity control material.
(Comparative Example 2) Higher in practical strength.

[0034]

According to the present invention, it is possible to obtain a cured gypsum body which is comparable to natural wood and, in some cases, has superior moisture absorption and desorption properties over natural wood. In addition, since the hardened gypsum body of the present invention can be manufactured using calcium silicate-based building waste material as a raw material, the manufacturing cost is low, and moreover, a large amount of building waste material can be reused.

Continued on the front page (51) Int.Cl. ⁶ Identification code FI C04B 22:06) (72) Inventor Shinkichi Tanabe 2-4-2, Osaku, Sakura-shi, Chiba Pref. Noriyuki Nagata 2-4-2, Osaku, Sakura City, Chiba Prefecture Inside the Building Materials Techno Research Institute (72) Inventor Yoshiho Nishino 928 Takamatsu, Kawagoe-cho, Mie-gun, Mie Prefecture Inside Chiyoda Ute Co., Ltd. (72) Junichi Haneda 928 Takamatsu, Kawagoe-cho, Mie-gun, Mie Prefecture Chiyoda Ute Co., Ltd.

Claims (4)

[Claims] 1. A moisture-absorbing and desorbing gypsum cured product mainly composed of a reaction product containing gypsum obtained by subjecting a calcium silicate-based material to a sulfation reaction with a sulfated material and silica gel. 2. The moisture-absorbing and desorbing gypsum cured product according to claim 1, wherein the sulfated material is one or more of sulfuric acid and aluminum sulfate. 3. The calcium silicate-based material is CSH gel,
The hygroscopic gypsum cured product according to claim 1 or 2, which is a construction waste material containing one or more of tobermorite and zonotolite. 4. The moisture-absorbing and desorbing gypsum cured product according to claim 1, wherein the calcium silicate-based material contains one or more of organic fibers, inorganic fibers, pulp fibers and glass fibers.