JPH0124604B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for manufacturing a gypsum molded body used for arts and crafts, decorative wall materials, etc.

(Prior art) Conventionally, gypsum molded bodies used for wall materials, arts and crafts, etc. have been formed by injecting gypsum slurry, which is a mixture of hemihydrate gypsum powder and water, into a mold, or by using natural gypsum raw stone. It is manufactured by cutting and then polishing.

(Problem to be solved by the invention) However, when using the former method, it is impossible to make the skin surface of the natural pattern appear, and when using the latter method, it is impossible to make the skin surface of the natural pattern appear. Although it was possible to reveal the skin, there was a problem in that it was time-consuming and expensive to manufacture.

(Means for Solving the Problems) The present invention eliminates the above-mentioned problems and makes it possible to easily produce gypsum molded bodies of various shapes with natural patterned surfaces for use in arts and crafts, wall materials, etc. This method was developed for the purpose of manufacturing a gypsum molded body that can be made by heating natural crystalline gypsum in its lump form, and then crushing a large number of pieces of calcined gypsum, which are obtained by heating the natural crystalline gypsum in its lump form. filled with water in a mold,
It is characterized in that it is pressure-molded using a press and then directly subjected to a hydration reaction of calcined gypsum to harden it.

In the present invention, first, natural crystalline gypsum, which is a raw stone that is naturally produced as an ore, is heated in an autoclave or in the atmosphere in a lump form to form a lump of calcined gypsum,
Next, this calcined gypsum lump is mechanically crushed to produce calcined gypsum pieces with a diameter of 10 mm or more, and a large number of them are soaked with enough water to convert the calcined gypsum into dihydrate gypsum. If this is packed into a specified mold and pressurized by a press, the water exerts a lubricating effect because the many pieces of calcined gypsum contain enough water to turn them into dihydrate gypsum. This causes slippage between the irregularly shaped pieces and between the calcined gypsum particles, and at the same time, the hydrated water also penetrates evenly between the calcined gypsum particles, causing some collapse due to pressure. It will easily undergo plastic deformation within the round mold. Therefore, if the hydration reaction is carried out using water that is hydrated as it is,
Since calcined gypsum is obtained by a wet method by heating natural crystalline gypsum in the form of a lump, it expands slightly in volume and precipitates needle-shaped crystals of dihydrate, creating a hardened molded product with great strength. All that's left to do is to remove the mold.

In the present invention, natural crystalline gypsum is heated in the form of a lump to form a calcined gypsum lump, and this calcined gypsum lump is mechanically crushed to form a large number of irregularly shaped pieces of calcined gypsum in a state of being hydrated with water to make dihydrate. After being filled into a mold and pressure-formed, the plaster is cured by the hydration reaction of the calcined gypsum, so that the hardened gypsum molded body brings together the natural patterns of the natural crystalline gypsum raw stone. Furthermore, the precipitation of acicular crystals of dihydrate gypsum that accompanies the hardening of calcined gypsum by the wet method described above progresses properly in the molded state, making it hard and resistant to impact. The material is strong enough not to be easily damaged, and the skin surface is elegant with a slight luster. In addition, when a large number of pieces of calcined gypsum are kept in a hydrated state, the surface hardness can be reduced by dissolving a few percent of salts such as iron sulfate, aluminum sulfate, borax, alum, zinc sulfate, and alkali sulfate in water. This can be further improved.

(Example) Example 1 An amorphous raw stone of natural crystalline gypsum from Madagascar that is naturally produced as an ore (one piece weighs approximately 1 to 2
100 kg) are heated in an autoclave with 30 kg of water in the form of a lump, and held at 133°C with an internal pressure of 3 kg/cm ² for about 5 hours to form a lump of calcined gypsum in the same shape, and this lump of calcined gypsum is attached. After removing moisture, it shall be mechanically crushed into fragments with a diameter of 10 mm or more. Next, the first
As shown in the figure, a large number of pieces of calcined gypsum 1 are sprinkled with water to absorb enough water to form dihydrate gypsum, and then placed in a mold 2 of 60 cm wide x 45 cm deep in a single layer. Then, a second layer impregnated with moisture in the same manner as above was packed in order so as to close the gap between each calcined gypsum piece 1 from above, and this was pressurized with a 10-ton press to form it, The molded product was then removed from the mold after waiting for it to harden as a molded product through the hydration reaction of the calcined gypsum. The plate-shaped gypsum molded product thus obtained had an elegant striped pattern on its surface, which was a collection of the natural patterns of the natural crystalline gypsum raw stone, and had a hard, slightly glossy surface. Incidentally, one side of this plate-shaped gypsum molded body was lightly polished to form a wall board 3 as shown in FIG. 2.

Example 2 A large number of small pieces of calcined gypsum 1, which were crushed during the heat treatment in the autoclave in Example 1, were molded into a pair of upper and lower molds 2 for molding a nude figure, as shown in FIG. The same method as in Example 1 was carried out in a hydrated state, which was then pressure-molded using a press machine, cured, and removed from the mold.The natural pattern of natural crystalline gypsum rough appeared on the surface in the form of a suminagashi pattern, and was slightly glossy. A statue 4 of a nude woman with a certain hard skin was obtained.

(Effects of the Invention) As described above, the present invention heats natural crystalline gypsum in its lump form to form a calcined gypsum lump, and converts a large number of pieces of calcined gypsum obtained from this calcined gypsum lump into dihydrate gypsum in a mold. Because it is packed in a hydrated state and pressure-formed, and hardened by the hydration reaction of the calcined gypsum, the hardened gypsum molded product will have a striped pattern on its surface that is a combination of the natural patterns of the natural crystalline gypsum raw stone. It has a beautiful appearance and is hard and has a glossy surface, and is industrially useful as a product that can easily produce beautiful plaster moldings of various shapes that can be used for arts and crafts, wall materials, etc. The value is extremely great.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway front view showing the mold part of the device used in Example 1 of the present invention, in which crushed pieces of calcined gypsum are housed in two layers in a mold, and FIG. Embodiment 2 of the present invention, in which a nude female figure was molded using a pair of upper and lower molds; FIG.
FIG. 3 is a partially cutaway front view showing a molded state. 1: Plaster piece, 2: Mold.

Claims (1)

[Claims] 1. A large number of pieces of calcined gypsum obtained by heating natural crystalline gypsum in its lump form are crushed into pieces of calcined gypsum, which are filled with enough water to make dihydrate gypsum into a mold, and then put into a mold using a press machine. 1. A method for producing a gypsum molded body, which is characterized in that the molded gypsum is pressure-molded and then directly subjected to a hydration reaction of calcined gypsum to harden it.