JPS5918335B2 - hardened gypsum - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to a cured gypsum product with improved water resistance and strength.

Gypsum has been used in large quantities in recent years, especially as a building material such as various wall materials and flooring materials, because it is nonflammable, chemically very stable material, and the price of the material is relatively low. There is.

However, it is known that this gypsum generally has low water resistance and that its strength significantly decreases when it absorbs water or moisture.

A method of mixing cement into gypsum has been proposed to compensate for these drawbacks, but this method still suffers from the drawback that gypsum loses its rapid setting properties, such as the fact that it usually takes one week or more for cement to set.

Next, a method has been proposed in which a water-soluble polymer such as urea resin, melamine resin, or polyvinyl alcohol, or a synthetic resin such as acrylic resin emulsion is added to the plaster together with water and the plaster is cured.

However, in this case, the amount of resin added is 10 to 10% relative to the plaster.
It is a relatively large amount of 30 parts by weight, and in some cases, it is necessary to heat the resin to harden, which increases the amount of work, which causes high costs. It has the disadvantage of reducing its nonflammability.

The inventors hereby maintain the material properties of such gypsum.
As a result of intensive study to solve the above-mentioned problems such as water resistance and cost, we added magnesium slag to gypsum.
They discovered that it is effective to cure this in the presence of water and have completed this invention.

That is, the present invention is a cured gypsum product which is mainly composed of hydraulic gypsum and magnesium smelting slag, and is made by adding water to these and curing them.

The hydraulic gypsum used in this invention is α-hemihydrate gypsum, β-hemihydrate gypsum, and hydraulic anhydrite. All by-product gypsum such as gypsum is also used.

Next, what is the magnesium smelting slag used in this invention?
It is slag that is produced as a by-product when producing metallic magnesium from magnesium ore, that is, it contains 2CaO-8iO2 (dicalcium silicate) of 80% or more, and also contains magnesium oxide, iron oxide, aluminum oxide, etc. An example of its composition is shown below under the trade name Furukawa Daical (manufactured by Furukawa Magnesium Company).

2CaO・SiO It can be selected as appropriate depending on the purpose.

The magnesium slag is preferably mixed in an amount of 2 to 100 parts by weight, particularly preferably 5 to 50 parts by weight, per 100 parts by weight of gypsum.

If the amount of magnesium smelting slag is less than the lower limit, the above-mentioned water resistance will not be improved, and if it is more than the upper limit, the strength of the cured product will actually decrease, which is not preferable.

Next, for the purpose of improving various properties of the gypsum cured product, known curing retarders, water reducing agents, surfactants, slurry viscosity modifiers, etc. may be appropriately mixed.

It is also effective to use a foaming agent for weight reduction, glass fiber, asbestos, and rock wool for reinforcement, as well as the above-mentioned urea resin, polyvinyl alcohol, and the like.

There is no particular limitation on the amount of these used, but 1 gypsum
It is desirable that the amount is 40 parts by weight or less relative to 00 parts by weight.

In particular, the combined use of synthetic resins such as urea resin and polyvinyl alcohol is preferably 10 parts by weight or less.

In this invention, the method for shaping the cured product should be appropriately selected from extrusion, casting, pressing, etc. depending on its shape and use, and extrusion is particularly preferred for mass production.

When drying with high moisture content and forced drying,
It must be dried at a temperature lower than the temperature at which water of crystallization is removed from gypsum trihydrate.

As will be clear from the examples below, this invention significantly improves the water absorption and strength of conventional cured gypsum products, and the effect of solving the above problems is industrially significant.

The present invention will be specifically explained below with reference to Examples.

Examples 1 to 5 Furukawa Daikal powder (
7.20, 40, 50° and 80 parts by weight (Examples 1 to 5) of the product name (trade name, above) were added, and 70 parts by weight of water was further added to each of them to form a slurry.

This gypsum slurry was poured into a metal mold with dimensions of 20x20x8071711 and allowed to harden.

After drying the obtained cured product, its bending strength and compressive strength were measured using a tensile tester according to JISB 1771, and the water absorption rate was measured after immersing the cured product in hot water at 60°C for 100 hours. The request is shown in the postscript.

Furthermore, the measured values of the setting time according to JIS R5201-64 are also shown.

Comparative Example 1 As Comparative Example 1, a similar cured product was obtained using only the β-hemihydrate gypsum, and the same test as above was conducted. The results are shown in the same table.

Comparative Example 2 A solution prepared by dissolving 15 parts by weight of polyvinyl alcohol in 70 parts by weight of water was added to 100 parts by weight of β-hemihydrate gypsum to prepare a slurry.

A cured gypsum product was obtained in the same manner as in Example 1, and its physical properties were measured.

The results are shown in the same table. Comparative Examples 3 and 4 15 parts by weight of dimethylol urea and 0.2 parts by weight of ammonium chloride were added to 100 parts by weight of β-hemihydrate gypsum, and further 70 parts by weight of water were added to form a slurry.

Physical property values were measured for each of a cured product obtained in the same manner as in Example 1 (Comparative Example 3) and a product obtained by polymerizing this at 60° C. or higher (Comparative Example 4).

The results are shown in the table.

Curing at 60°C for 24 hours was required to obtain a certain level of strength.

Comparative Example 5 A mixture of 60 parts by weight of β-hemihydrate gypsum and 40 parts by weight of Portland cement was prepared, and 70 parts by weight of water was added thereto to form a slurry.

The setting time for obtaining a cured product was measured in the same manner as in Example 1, and the result was 150 minutes, which was significantly longer than in the Example.

Upper surface width meter 1: According to JIS R5201-64 cement physical test method.

According to the results shown in the table above, it was clear that the properties of the example products were significantly superior to those of the comparative examples, that is, gypsum itself or a cured product obtained by mixing gypsum with other resins.

Claims (1)

[Claims] 1. A hardened gypsum product whose main components are hydraulic gypsum and magnesium smelting slag, which are hardened by adding water.