JPS586697B2 - Lightweight gypsum hardened body - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a lightweight hardened gypsum body mainly made of spherical gypsum.

The gypsum hardened material is water-cured by adding water to α-type hemihydrate acicular gypsum obtained by hydrothermal dehydration reaction of ordinary dihydrate gypsum or anhydrous acicular gypsum obtained by firing the acicular gypsum. Light-weight cured products are known which can be obtained by removing free water or by adding a specific binder during water-curing.

However, this cured product has a fatal drawback of low strength and there is a limit to its weight reduction, so its uses have been limited.

The present inventors first developed a spherical gypsum with an extremely low bulk density and a method for producing the same, but in the subsequent research process, the use of the spherical gypsum as a material made it extremely lightweight and hardened with sufficient strength. The present invention was completed based on the discovery that it is possible to obtain the desired results.

The present invention has a diameter of 2 mm or less and a scraping density of 0.3 g/
Water is added to spherical gypsum formed by intertwining fibrous gypsum, a mixture of the spherical gypsum and fibrous gypsum, or a mixture of the spherical gypsum and fibrous gypsum, or a mixture of the spherical gypsum and fibrous gypsum with a size of 3 cm3 or less, or a mixture in which a binder is added. The present invention provides a lightweight hardened gypsum body having a specific gravity of 0.1 to 0.8.

The spherical gypsum used in the present invention is spherical α-type hemihydrate gypsum obtained by hydrothermal reaction of dihydrate gypsum or a mixture of dihydrate gypsum and hemihydrate gypsum, or spherical α-type hemihydrate gypsum obtained by firing the hemihydrate gypsum. It is anhydrous gypsum.

An example of the manufacturing conditions for such spherical gypsum is as follows.

The desired spherical gypsum is obtained by heating and stirring 0.5 to 40% by weight of dihydrate gypsum or a mixture of dihydrate gypsum and hemihydrate gypsum in an acidic solution, based on the weight of the acidic solution.
Obtained by hydrothermal reaction.

The gypsum used as a raw material for this reaction is made into a slurry at a ratio of 0.5 to 40% by weight, preferably 2 to 30% by weight, based on the weight of the acidic solution described later.

Further, specific examples of the acid component in the acidic solution used in the present invention include organic acids such as formic acid, acetic acid, tartaric acid, and malic acid, and inorganic acids such as phosphoric acid, hydrochloric acid, nitric acid, and sulfuric acid.

The acidic solution used is an aqueous solution containing an acid component at a ratio of 0.1 to 80% by volume.

The hydrothermal reaction is carried out at a temperature of 100 to 180°C for a reaction time of several minutes to several hours.

The spherical gypsum thus obtained is essentially formed by intertwining fibrous α-type hemihydrate gypsum, and microscopic observation has confirmed that it has a burr-like or marimo-like shape. It was done.

Regarding the formation mechanism of spherical gypsum, it is thought that short fibrous gypsum is first formed, and as stirring continues, the fibrous gypsum becomes entangled to form spherical bodies.

In the present invention, the spherical α-type hemihydrate gypsum slurry after completion of the hydrothermal reaction may be used as it is as the raw material, or the wet α-type hemihydrate gypsum cake after solid-liquid separation may be used. Later dried spherical α-type hemihydrate gypsum,
Spherical anhydrous gypsum obtained by firing this or a mixture of these spherical gypsum and fibrous gypsum can also be used as the material.

The drying process may be carried out at a temperature of 50 to 80°C for 1 to 8 hours, and the drying process may be carried out at a temperature of 200 to 1000°C.
Anhydrous gypsum can be obtained by carrying out the process for 1 to 3 hours.

Spheroidal gypsum usually has a diameter of 2 mm or less, with an average diameter of 0.3 mm.
The bulk density is 0.3g/cm3 or less, and the average is 0.
．． It is about 0.079/cm3.

The amount of water added to the spherical gypsum should be at least the theoretical amount of water required to convert hemihydrate gypsum or anhydrous gypsum to dihydrate gypsum, and the mixture can be compressed, extruded, poured, formed into a paper, etc.
It is molded using a molding method such as spraying and hardened using water.

After water hardening, free water is removed by drying or other means.

At this time, if the conditions are such that dihydrate gypsum does not transfer to hemihydrate gypsum, water utilization hardening and drying can be performed at the same time.

In addition, by adding a binder during water-curing, it is possible to strengthen the bond between the gypsum and further improve the strength.

Examples of such binders include water-soluble organic polymers such as polyvinyl alcohol, carboxymethyl cellulose, hydroxyethyl cellulose, polyacrylamide, polyacrylic acid, polyethylene oxide, water-dispersible organic polymers such as vinyl acetate emulsions, acrylic resin emulsions, etc. These include polymers, water glass, water-soluble inorganic compounds such as sodium silicate, water-dispersed colloid-forming inorganic compounds such as alumina sol and silica sol, hydraulic compounds such as cement and gypsum, and mixtures thereof.

These binders are 0.01% by weight per 100 weight of spherical gypsum.
It may be added in a range of 100 parts by weight.

Furthermore, a hardening accelerator, reinforcing material, lightweight aggregate, etc. can be added as appropriate.

Examples of hardening accelerators include magnesium sulfate, calcium chloride, potassium sulfate, potassium nitrate, copper sulfate, etc., reinforcing materials include glass fiber, asbestos, etc., and lightweight aggregates include perlite, shirasu balloon, and hiru. There are stones etc.

Note that when a mixture of spherical gypsum and fibrous gypsum is used as the material, the fibrous gypsum also acts as a reinforcing material.

When a gypsum material is molded and hardened using water, since the material used in the present invention is spherical, crystal breakage is extremely less compared to fibrous materials.

If conventional fibrous gypsum was used as a material, it would be easily damaged during each work process, but by using spherical gypsum as a material, such concerns are eliminated and workability is extremely high.

Moreover, the gypsum hardened body obtained by the present invention has a specific gravity of 0.
．． It is lightweight with a weight of 1 to 0.8, and has sufficient strength, particularly in bending strength.

In addition, the insulation property is 0.04-0.08Kcal/m-hr
-deg, which is very good.

Furthermore, the strength of products obtained by water-curing with a binder added is superior to that of products without the binder added.

Therefore, the product of the present invention can be effectively used as lightweight aggregate, heat insulating material, heat insulating material, sound absorbing material, core material, etc.

Next, the present invention will be explained in detail with reference to examples.

Example 1 (1) Production of lightweight spherical gypsum 12 kg of dihydrate gypsum and β-type hemihydrate gypsum 6001 as seed crystals were added to 0.5% by volume acetic acid aqueous solution 601 and mixed to prepare a slurry.

This slurry was heated to 120°C.

A hydrothermal reaction was carried out at 120° C. for about 30 minutes under a saturated vapor pressure of 2 kg/crAm 2 and stirring using a propeller-type stirring blade.

After the completion of the hydrothermal reaction, the solid product obtained by separating solid and liquid with a centrifuge during heating is dried at 60℃ for about 8 hours using a hot air dryer, and the weight is reduced by removing attached water and solvent. Spherical α-type hemihydrate gypsum was obtained.

In addition, a part of this A-type hemihydrate gypsum was heated to 50% by using an electric furnace.
Anhydrous gypsum was obtained by firing at 0°C for 3 hours.

When the obtained lightweight spherical gypsum was observed under a microscope, it was found to be marimo-shaped.

This gypsum had an average diameter of about 250 μm for both α-type hemihydrate and anhydrous gypsum, and a bulk density of 0.10 g/cm 3 .

(2) Production of hardened body Dried α-type semi-water lightweight spherical gypsum obtained in (1) above 4
1800 ml of water was added to 56 g to form a slurry.

This suspension was poured into a papermaking form with a papermaking surface of 30cm x 30cm and a 40-mesh wire mesh, and was molded by papermaking compression.
After water-curing, the mold was demolded and dried in a hot air dryer at 60°C to obtain a plate-shaped cured product.

In addition, plate-shaped hardened bodies with different specific gravities were obtained by the same operation while changing the amounts of spherical gypsum and water.

Furthermore, plate-shaped hardened bodies were also produced using glass fiber or asbestos as a reinforcing material, type 2 anhydrous gypsum as the spherical gypsum, and magnesium sulfate as a hardening accelerator.

Table 1 shows the physical property values measured for these cured products.

The bending strength test was conducted under the following conditions.

(According to JISA-1408.) Test piece 2X
2×10 cm Distance between spans 8 cm Test speed 1 mm/min Comparative Example 1 The same operation as in Example 1 was performed except that α-type hemihydrous fibrous gypsum was used instead of the spherical gypsum used in Example 1.

The results are shown in Table 2. Example 2 Gypsum mixture 60 obtained by mixing α-type hemihydrate spherical gypsum obtained in Example 1 (1) with a predetermined amount of α-type hemihydrate fibrous gypsum.
2400 ml of water was added to Example 1 to form a slurry, and the same operations as in Example 1 were performed to obtain a cured product.

Similarly, a cured product was obtained using a gypsum mixture in which H-type anhydrous fibrous gypsum was mixed instead of α-type hemihydrate fibrous gypsum.

Table 3 shows the physical properties of these cured products.

Example 3 A part of the α-type semi-hydrospheric gypsum thermal slurry immediately after the hydrothermal reaction in (1) of Example 1 was directly poured into a 30 x 30 cm paper-making mold, and subjected to compression and dewatering paper-forming mold for water-curing. .

After demolding, remove excess adhering water using a hot air dryer at 60°C.
A plate-shaped cured body having a specific gravity of 0.5 was obtained.

The bending strength of this cured product was 12 kg/cm2.

Example 4 426 g of α-type hemihydrate spherical gypsum consisting essentially of entangled α-type hemihydrate fibrous (acicular) gypsum was added with a polymerization degree of 1700.
, 1,800 ml of a 2% by weight aqueous solution of polyvinyl alcohol with a degree of saponification of 97% was added, the suspension was made into a slurry, and the suspension was poured into a paper-forming mold with a 40-mesh wire mesh with a paper-making surface of 30 crrL x 30 cfrL, and subjected to paper-compression molding. After curing, the mold was demolded and excess free water was removed using a hot air dryer at 60°C to obtain a plate-shaped cured product.

Table 4 shows the measured physical properties of this cured product.

Note that the conditions for the bending strength test were the same as in Example 1.

Examples 5 to 9 The same operations as in Example 4 were performed except that the types and amounts of the lightweight spherical gypsum used in Example 4, the water-soluble binder added thereto, water, and filler and the amounts used were changed.

The results are shown in Table 5. Examples 10 to 13 Using the lightweight spherical gypsum used in Example 4, commercially available β-type hemihydrate gypsum was used as the hydraulic substance added to it, water was added to the mixture to form a slurry, and a 10×4 ×
The molded product was poured into a 2 cm molding frame, molded and cured by hydration, and then dried in a hot air dryer at 60° C. to obtain a cured product.

The results are shown in Table 6.

Examples 14 to 16 The lightweight spherical gypsum used in Example 4 was used, and commercially available α-type and β-type hemihydrate gypsum were used as hydraulic substances added to it. Water was added to the mixture to form a slurry, and this suspension was The suspension was poured into a paper molding mold having a wire mesh of 40 mesh with a paper size of 10×IO cm, and the rest of the procedure was carried out in the same manner as in Example 4.

The results are shown in Table 7.

Comparative Examples 2 to 4 The same operation as in Example 4 except that fibrous α-type hemihydrate gypsum was used instead of the lightweight spherical α-type hemihydrate gypsum in Example 4, and the amount of the binder aqueous solution was changed. I did this.

The results are shown in Table 8. Example 17 The α-type hemihydrate spherical gypsum used in Example 4 was fired at 500° C. for 3 hours to obtain a ■-type anhydrous spherical gypsum.

The same operation as in Example 4 was carried out except that 2400 ml of a 2% by weight polyvinyl alcohol aqueous solution in which 30 g of magnesium sulfate heptahydrate was dissolved was added to 570 g of this spherical anhydrous gypsum.

The results are shown in Table 9.

Example 18 550 g of α-type hemihydrate spherical gypsum and 6 α-type hemihydrate fibrous gypsum
The same operation as in Example 4 was carried out, except that 0 g was mixed and 2400 ml of a 2% by weight aqueous polyvinyl alcohol solution was added thereto to form a slurry.

Claims (1)

[Claims] 1. The diameter is 2 mm or less, and the scraping density is 0.3 g/c.
Spherical gypsum formed by substantially intertwining fibrous gypsum or a mixture of the spherical gypsum and fibrous gypsum with a size of 3 m3 or less is formed by adding water, and is made to harden using water, and has a specific gravity of 0.1 to 0. .8 lightweight gypsum hardened body. 2 Diameter is 2mm or less and bulk density is 0.3g/c
A specific gravity obtained by adding water to a mixture of spherical gypsum formed by substantially intertwining fibrous gypsum or a binder with a mixture of spherical gypsum and fibrous gypsum having a size of 3 m3 or less, molding the mixture, and curing with water. A lightweight gypsum hardened body with a value of 01 to 0.8.