JPS61127656A - Gypsum hardened body - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a hardened gypsum body used as a gypsum board, a gypsum block, or the like.

[Conventional technology]

Currently, chemical gypsum, which is a by-product from phosphoric acid factories, thermal power plants, etc., is mainly used as a raw material for gypsum board.

2. Gypsum board is manufactured by power-calcining plaster, such as the chemical plaster mentioned above, to make calcined plaster, mixing this with water, hydrating, curing, demolding, and drying. The process is carried out on an assembly line.

[Problem that the invention seeks to solve]

Currently, production of chemical gypsum, which is the raw material for gypsum board, is decreasing year by year due to reduced production of phosphoric acid, use of low-sulfur oil, etc., and to make up for the shortage, we rely on gypsum imported from countries such as South Korea. The reality is that Japan is struggling to ensure stability.

Furthermore, in the conventional method of manufacturing gypsum board, there is a problem in that approximately 40% of the production cost is required for drying excess water.

Therefore, an object of the present invention is to provide a hardened gypsum product equivalent to conventional products by using stably available raw materials and reducing production costs.

[Means for solving problems]

The present inventors used sulfuric acid, which is a by-product in large quantities from iron and metal factories, and lime, which is the most stable resource in Japan, as starting materials, and added a specific compound to them to cause a reaction. Then, the reaction product hardens to the point where it can be demolded in a short time, and a gypsum board can be obtained by the same assembly process as the conventional method, and the obtained gypsum board has the same strength as the conventional product. It has been found that virtually no drying step is required.

That is, the present invention was made based on the above-mentioned findings, and involves casting a kneaded mixture of a lime compound, sulfuric acid, and at least one compound selected from the group consisting of alum, aluminum sulfate, and sodium oxalate, and hardening the mixture. The purpose is to provide a hardened gypsum body made of

The hardened gypsum body of the present invention will be explained in detail below.

Examples of the lime compound used to produce the hardened gypsum body of the present invention include calcium carbonate, calcium hydroxide, calcium oxide, and slag, which may be used alone or in combination of two or more.

The hardened gypsum body of the present invention is manufactured as follows.

First, the lime compound, sulfuric acid, and at least one compound selected from the group consisting of alum, aluminum sulfate, and sodium oxalate are kneaded to obtain a kneaded product.

The above-mentioned sulfuric acid preferably has a concentration of 40 to 70%, and the preferred amount used is approximately equivalent to 100 parts by weight of the lime compound when converted to a concentration of 1.0%.

Further, it is preferable that alum is added and kneaded in the form of being dissolved in the above sulfuric acid in advance, and the preferable amount used is as follows:
1 to 30 parts by weight, especially 1 to 100 parts by weight of lime compound
~10 parts by weight.

Further, it is preferable that aluminum sulfate is added and kneaded in the form of being dissolved in the sulfuric acid in advance, and the preferable amount used is 1 to 30 parts by weight per 100 parts by weight of the lime compound.
In particular, it is 1 to 10 parts by weight.

In addition, sodium oxalate is preferably added to the lime compound and sulfuric acid after kneading, and the preferred amount used is 0.1 to 5 parts by weight per 100 parts by weight of the lime compound.
．． 0 parts by weight, especially 0.5 to 1.0 parts by weight.

In addition, when adding three of alum, aluminum sulfate, and sodium oxalate, it is preferable to first add sodium oxalate to a mixture of lime compound and sulfuric acid to which alum and aluminum sulfate have been added. ,
The total amount used is 0 per 100 parts by weight of lime compound.
．． The amount is preferably 1 to 5.0 parts by weight.

Next, the above kneaded material was immediately added (1 to 5 minutes after the start of the reaction).
, poured into a mold, formed into a desired shape such as a flat plate (board) shape, block shape, etc., hardened, and demolded to obtain a hardened gypsum body of the present invention.

The kneaded product may be shaped in the same manner as in the conventional method using calcined gypsum as a raw material, and when a gypsum board is obtained as a molded product, paper is adhered to both sides of the board during shaping.

The molded kneaded product is preferably cured in an atmosphere of around 60% RH at room temperature, and the curing time is, for example, in the case of a kneaded product in which 1 to 6 parts by weight of alum is added to 100 parts by weight of the lime compound 1 to 10 minutes after casting.

The hardened gypsum body of the present invention obtained as described above does not require drying because it has a moisture content of about 2 to 5% at the time of demolding, and is similar to gypsum obtained by the conventional method using calcined gypsum as a raw material. It has approximately the same physical properties as the cured product.

In addition, when calcium carbonate is used as the lime compound,
Since the CO2 generated by the reaction between calcium carbonate and sulfuric acid foams and creates fine pores, it is possible to reduce the weight and heat insulation of the hardened gypsum body.

In addition, in the present invention, when kneading the lime compound, sulfuric acid, alum, aluminum sulfate and/or sodium oxalate, a reactive silicate such as soluble silica, slag, fly ash, etc. is added to 100 parts by weight of the lime compound. The reactive silicate can be added in an amount of 1 to 50 parts by weight, and the water resistance, which is a disadvantage of hardened gypsum, can be significantly improved.

Next, the reaction mechanism in producing the hardened gypsum body of the present invention is as follows.
To explain the case where calcium carbonate is used as the lime compound, by kneading the lime compound, sulfuric acid, and alum, aluminum sulfate and/or sodium oxalate, the lime compound and sulfuric acid react to produce gypsum, and at that time, Due to the reaction heat generated, the temperature of the kneaded material is 70~
The temperature reaches 100℃, and using this reaction heat, hemihydrate gypsum and ■
Type anhydrite is produced. This reaction product is then hydrated by the water in the sulfuric acid and the water produced from the reaction and immediately cures. At this time, it is presumed that alum, aluminum sulfate, and sodium oxalate contribute to accelerating the curing rate and developing strength of the cured product. In addition, water resistance can be improved by adding reactive silicates by utilizing the heat of reaction between lime compounds and sulfuric acid.
For example, it is assumed that this is because tobermorite) is produced.

The present invention will be explained in more detail by showing Examples and Reference Examples below.

Example 1 50 parts by weight of slaked lime was added to 100 parts by weight of calcium carbonate to form a mixture. To this mixture, add 240 sulfuric acid (concentration 60%) and 1 w of sodium oxalate dissolved in 6 parts by weight of alum.
Add a certain amount and mix and stir for 1 minute to obtain a kneaded product. Next, this kneaded product was immediately poured into a mold, and heated at 20°C and 60% R1.
Cured and cured in the atmosphere of 1 for 5 minutes, removed from the mold, and
A gypsum board of the present invention measuring 910 mm x 1820 mm was obtained.

Example 2 The same kneaded material obtained in Example 1 was poured into a mold, with gypsum board paper adhered to both sides of the mold, and heated at 20°C.
The gypsum board of the present invention having the same size as that obtained in Example 1 was obtained by curing, hardening and demolding in an atmosphere of 60% R11 for 5 minutes.

Example 3 50 parts by weight of slaked lime was added to 100 parts by weight of calcium carbonate to form a mixture. To this mixture, 240 parts by weight of sulfuric acid (concentration 60%) in which 6 parts by weight of alum was dissolved were added and mixed and stirred for 3 minutes to obtain a kneaded product.

Next, this kneaded material was immediately poured into a mold and heated at 20°C for 6
The gypsum board of the present invention having the same size as that obtained in Example 1 was obtained by curing, hardening, and demolding in an atmosphere of 0% RH for 5 minutes.

Reference Example 1 50 parts by weight of slaked lime was added to 100 parts by weight of calcium carbonate to form a mixture. Add 240 sulfuric acid (concentration 60%) to this mixture.
After adding parts by weight and mixing and stirring for 1 minute, the kneaded mixture was immediately poured into a mold, cured in an atmosphere of 20°C and 60% RH for 30 minutes, and then removed from the mold. Got plasterboard.

Reference Example 2 Immediately pour the same kneaded material as that obtained in Reference Example 1 into a mold, and at that time, adhere gypsum board paper to both sides of the mold.
After curing and curing in an atmosphere of 0° C. and 60% RH for 30 minutes, the mold was removed to obtain a gypsum board of the present invention having the same size as that obtained in Example 1.

In addition, in Reference Examples 1 and 2, curing was insufficient after 5 minutes of curing and demolding was impossible.

Various physical property measurements were performed on the gypsum boards obtained in Examples 1 and 2.3 and Reference Example 1.2. The results were as shown in the table below.

〔Effect of the invention〕

The hardened gypsum of the present invention is produced by using a lime compound and sulfuric acid, adding and kneading at least one compound selected from the group consisting of alum, aluminum sulfate, and sodium oxalate, and molding and hardening the kneaded product. This material has approximately the same physical properties as a hardened gypsum obtained by a conventional method using calcined gypsum as a raw material. Furthermore, the raw material for the hardened gypsum body of the present invention can be easily and stably secured, and during its production, the kneaded material can be hardened in a manner that allows it to be removed from the mold within 1 to 10 minutes after pouring, so there is no problem with assembly work. The gypsum board manufacturing equipment used in the conventional method can be used as is, and since no drying process is required, production costs can be significantly reduced.The kneaded product also has extremely good adhesion to gypsum board paper. . Furthermore, in the present invention, if calcium carbonate is used as the lime compound, it is also possible to arbitrarily adjust the bulk specific gravity of the resulting hardened gypsum product to reduce its weight by controlling the reaction between calcium carbonate and sulfuric acid. .

Claims (2)

[Claims] (1) pouring and molding a kneaded product of a lime compound, sulfuric acid, and at least one compound selected from the group consisting of alum, aluminum sulfate, and sodium oxalate;
A hardened gypsum body made by hardening. (2) The hardened gypsum body according to claim (1), wherein the kneaded material is formed into a flat plate, and paper is adhered to both sides of the flat plate.