JP2596994B2 - Method for producing hardened gypsum - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a marble-like architectural hardening by press-molding dihydrate gypsum powder such as natural gypsum or waste plaster produced as a by-product in flue gas desulfurization equipment. It relates to a method of producing the body.

[Conventional technology]

The method of producing a hardened gypsum body is well known, and is widely used in the production of gypsum boards and models for buildings. However, since gypsum has no hydration-hardening property, it is heated once and then heat-treated. A method has been adopted in which water gypsum or anhydrous gypsum is manufactured, and water is added thereto to form a cured product. A method of directly curing gypsum has not been put to practical use.

[Problems to be solved by the invention]

When producing a gypsum cured product, conventionally, such as calcined gypsum,
Utilizing the hydration-hardening reaction of the heat-treated product, the equipment cost and operating cost of the heating process increase. Moisture prevention measures are required for the transport and storage of calcined gypsum. Kneading equipment is required to mold the hydrated cured product. Certain problems such as the inability to create a hardened architectural body with a marble-like pattern.

The present invention has been made in view of the above technical level, and aims to provide a method for producing a marble-like hardened building material by directly pressing and molding dihydrate gypsum powder typified by waste gypsum.

[Means for solving the problem]

The present invention is a method for producing a gypsum cured product, which comprises press-molding gypsum dihydrate powder at a pressure of 1000 kg / cm ² or more.

That is, the present invention obtains a gypsum cured product by enclosing dihydrate gypsum powder in a pressure molding device such as a cold isostatic press (CIP) and pressing at 1000 kg / cm ² or more. is there.

In addition, a suitable amount, preferably 0.1 to 5% by weight, of a colored metal oxide, mineral, coal ash, plastic, etc. is added to dihydrate gypsum powder and mixed, and the mixture is pressure-molded with a pressure molding machine at 1000 kg / cm ² or more. ,
The object is to obtain a marble-like cured product having various colors and patterns.

[Action]

2 The mechanism by which gypsum becomes a marble-like cured product when pressed at a pressure of 1000 kg / cm ² or more is not clear, but a marble-like cured product can be obtained by press-molding a powder of hemihydrate gypsum or anhydrous gypsum. It is considered that the water of crystallization plays an important role in hardening because the water is not brittle and becomes brittle. Dissolved each ion of Ca and SO ₄ by the strong pressure connexion crystal water is liberated in the crystallization water, to recrystallization when returned to atmospheric pressure, which presumably would strong cured product.

The reason why the cured product exhibits a marble-like color pattern is considered that water of crystallization liberated upon pressurization acts on a trace component exhibiting a color tone.

As the raw material gypsum, waste gypsum and phosphate gypsum are mainly produced in Japan, but these gypsums are made of silicon,
It contains iron, magnesium, aluminum, manganese, phosphorus, sodium, copper, fluorine, chlorine, nickel, lead, zinc, vanadium, chromium, and titanium as trace components, which are linked to the marble-like pattern. Therefore, by adding and mixing metal oxides, minerals, coal ash, plastics, and the like to dihydrate gypsum, the color and pattern of the press-molded cured product can be freely changed.

A description will be given of the properties of dihydrate gypsum in the case where waste gypsum produced, for example, 1.8 million tons per year in Japan is used as dihydrate gypsum as a raw material.

Boiler exhaust gas from a thermal power plant is generally treated by a wet lime / gypsum method flue gas desulfurization unit. The exhaust gas is washed with a slurry containing calcium carbonate obtained by pulverizing limestone as a desulfurizing agent, and SO ₂ is discharged into two water streams. Collect as gypsum. This waste gypsum is derived from unreacted residual calcium carbonate and impurities originally contained in limestone (typically containing Mg, Fe, Al, Si, Mn, P, Zn compounds) and exhaust gas Duct (typical is coal ash, which is Si, Fe, Al, Ca, Na, Mg,
Contains K, Cl, F, Pb, Ti compounds, and heavy oil ducts are N, V, Ni, C
r, and Cu).

Further, the discharged gypsum has 10 to 3% by weight of adhering water because it is collected by centrifuging a water slurry of gypsum gypsum crystals having an average particle size of about 20 to 100. The adhesion water Cl ^-, F
_{^{-, S 2 O 6 2-,}} NO 3 -, Ca 2+, Mg 2+, Na +, and contains a soluble compound of BO ₃ ^3- traces, even these compounds with water adhered to the exhaust de-gypsum Will be included. If the discharged gypsum (gypsum plaster) cake is directly molded under pressure, the adhered water seeps out, and it is necessary to remove it. In the pressure molding of 1000 kg / cm ² or more, the passage of the adhered water remains in the cured cured product and causes a crack. Therefore, it is necessary to sufficiently dry the adhered water before the pressure molding in order to blow off the adhered water. It is important not to lose the water of crystallization when drying the adhering water.
It must be kept at 40-50 ° C.

The crystallization water starts to fly when it is heated to 60 ° C or higher, but losing the crystallization water leads to the loss of the strength and the marble-like pattern of the pressure-cured cured product. It is.

In order to produce a gypsum cured product, adhesion water is unnecessary and crystallization water is indispensable, and the present invention has been achieved based on the new finding that water is indispensable.However, a method for eliminating adhesion water is not limited to drying. Without mixing, for example, hemihydrate gypsum that combines with adherent water,
Of course, pressure molding is also possible. In such a case, the hydration reaction of hemihydrate gypsum into dihydrate should be terminated until the pressure molding is completed, and free water should not exude by pressurization of 1,000 kg / cm ² or more. This is very important.

 Specific embodiments of the present invention will be described below.

Example 1 Exhaust gypsum produced as a by-product from flue gas desulfurization equipment was dried at 50 ° C. for about 24 hours, and about 420 g of completely removed adhering water was CI.
P (Cold Isorated Press)
A cured product of 4 cm x 4 cm height x 13 cm length was made. The pressing force at this time was 3000 kg / cm ² .

The obtained cured product was free from cracks and had sufficient strength. This cured product was cut into 4 cm × 4 cm × 1 cm with an electric saw, and the surface was polished with a fine-grained paper file. A beautiful marble-like pattern was exposed on the surface.

[Example 2] A cured product was obtained in the same manner as in Example 1 except that about 20 g of nickel oxide powder was added to about 400 g of drained gypsum dried in the same manner as in Example 1. This cured product was prepared in Example 1.
It has a beautiful surface with a marble-like pattern and a green pattern of nickel oxide.

[Example 3] A cured product was obtained in the same manner as in Example 1 except that about 20 g of ferric oxide powder was added to about 400 g of gypsum-free gypsum dried in the same manner as in Example 1. . This cured product had a beautiful surface in which the brown pattern of ferric oxide was added to the marble-like pattern of Example 1.

Example 4 A cured product was obtained by the same method as in Example 1 except that about 20 g of red dye powder (methyl red) was added to about 400 g of the discharged gypsum dried in the same manner as in Example 1. Was. The cured product had a beautiful surface in which the red pattern of the dye was added to the marble-like pattern of Example 1.

[Example 5] Approximately 400 g of drained gypsum dried in the same manner as in Example 1
A cured product was obtained in the same manner as in Example 1 except that about 10 g of a blue plastic pellet (colored vinyl chloride pellet) having a particle size of about 3 mm was added thereto. This cured product is
The surface was aesthetically pleasing with the marble-like pattern of Example 1 plus a blue blue pattern.

In addition, when the cured body was made in the same manner as in Example 1 without drying 420 g of the drained gypsum cake without drying, it had a lot of cracks, and when it was cut with an electric saw, the mold was broken and the strength was weak. .

As described above, after the drained gypsum is dried to remove the adhering moisture, it is molded under pressure to obtain a hardened body having a marble-like aesthetic pattern. In addition, by adding powder or granules of Ni, Fe oxide, other metal compounds, dyes, plastics and the like of this embodiment to the dried waste gypsum, the marble-like appearance can be obtained. A cured product having a color pattern peculiar to the additive can be produced.
Furthermore, upon using the above-mentioned additive powder or granules,
Various color patterns can be freely created depending on the size, shape, amount of addition of the powder and the mixing condition with the discharged gypsum.

〔The invention's effect〕

As described above, the present invention produces a marble-like architectural hardened body by directly pressing and molding dihydrate gypsum powder typified by waste gypsum. It is effective in the following points different from the method. Equipment costs and operating costs for the heat treatment of gypsum are reduced. There is no need to prevent moisture during transportation and storage as with plaster of Paris. No kneading equipment is required to produce the cured product. A hardened architectural body with a marble-like pattern is created.

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Koji Igawa 4-62-22 Kannonshinmachi, Nishi-ku, Hiroshima-shi, Hiroshima Inside Ryomei Giken Co., Ltd. (56) References JP-A-52-141835 (JP, A) JP-A-56-113407 (JP, A)

Claims (2)

(57) [Claims] 1. A method for producing a hardened gypsum, wherein a gypsum powder is molded under pressure at a pressure of 1000 kg / cm ² or more. 2. The method for producing a hardened gypsum according to claim 1, wherein the dihydrate gypsum powder is obtained by adding coal ash, metal oxides, various minerals, plastics and the like.