JPS643819B2 - - Google Patents

Description

[Detailed description of the invention]

(Field of Industrial Application) The present invention relates to a disintegrating gypsum composition that can extremely quickly disintegrate a gypsum mold for casting and various other types of gypsum molded objects after molding. (Prior art) Plaster molds used for casting molds etc. need to be removed as soon as possible after the product is formed, but the removal of conventional plaster molds is mainly done manually. This is not only inefficient but can also damage the product, and is particularly difficult for complex shapes, deep groove types that get caught, and reverse taper types.Therefore, a solution to this problem is strongly desired. Ta. As a solution to this problem,
As shown in No. 35369, a swelling agent such as starch is mixed into calcined gypsum, kneaded with water, molded, and then immersed in water to collapse the plaster mold using the swelling of the swelling agent. method is known. However, with this method, the disintegration time of the plaster mold is slow, and to speed up the disintegration, a large amount of swelling agent is mixed in, or a large amount of water is mixed during molding of the plaster mold, which reduces the strength of the mold. It was too weak to be used. Another method has been proposed in which the plaster mold is mixed with another substance in advance and the plaster mold is collapsed by soaking it in a solution that dissolves this substance, but it takes a very long time for the plaster mold to disintegrate. It takes a long time and is only useful for small plaster molds, making it impractical. (Problems to be Solved by the Invention) The problem to be solved by the present invention is to eliminate the above-mentioned drawbacks, to be able to knead and mold by adding ordinary water, and to be able to disintegrate in an extremely short time after use. The purpose of this method is to simplify the casting process using a plaster mold. (Means for Solving the Problems) The present invention is characterized in that starch and an appropriate amount of carbonate, which is insoluble or sparingly soluble in water and soluble in carbonate ion-containing hot water, are added and mixed to calcined gypsum. be. (Function) If such a disintegrated gypsum composition is kneaded and molded by adding an appropriate amount of water in the same way as conventional disintegrated gypsum compositions, the carbonate contained in the disintegrated gypsum composition is insoluble or poorly soluble in water. Therefore, a molded gypsum containing carbonate can be obtained without dissolving, but if you want to disintegrate this molded gypsum,
Prepared by dissolving sodium bicarbonate, potassium bicarbonate, ammonium carbonate, etc. in hot water.
If the gypsum molded body is directly immersed in hot water containing carbonate ions at a temperature of 70°C or higher, preferably 80°C or higher, the carbonate in the gypsum molded body will begin to dissolve, which will help the penetration of the hot water, and at the same time it will dissolve into the disintegrated gypsum composition. The blended starch swells, and the synergistic action of the two rapidly embrittles the interlaced composition of the gypsum crystals, and the disintegration of the gypsum molding rapidly progresses. Note that the starch used in the present invention is not particularly limited as long as it swells by alphaning at the temperature of hot water, but potato starch is most preferable, and the blending ratio of starch to calcined gypsum is not particularly limited. However, it is desirable to use 60 to 75 parts by weight of plaster of Paris and 25 to 40 parts by weight of potato starch. This is because if the amount of potato starch is less than 25 parts by weight, the disintegration properties are not very good, and if it exceeds 40 parts by weight, the strength of the gypsum molded product becomes weak and its uses are limited. In addition, as carbonates that are insoluble or sparingly soluble in water and soluble in carbonate ion-containing hot water, inexpensive calcium carbonate, magnesium carbonate, etc. may be used, and the blending ratio thereof is not particularly limited. The amount is about 3 to 10 parts by weight per 100 parts by weight of the total amount of calcined gypsum and hot water that is insoluble or sparingly soluble in water and contains carbonate ions. Furthermore, as carbonate ion-containing hot water, we use hot water with a temperature of 70°C or higher with sodium bicarbonate, potassium bicarbonate, ammonium carbonate, etc. , potassium carbonate, ammonium carbonate, etc., or carbon dioxide gas may be supplied by blowing from a cylinder. (Example) Next, in order to compare the disintegration speed of the composition of the present invention and that of the conventional composition, cylindrical cured bodies with a diameter of 60 mm and a length of 60 mm were made with the following compositions and amounts of water mixed, and undried. The samples were immersed in hot water at 80°C containing 3% sodium hydrogen carbonate, and taken out after a certain period of time from the start of immersion, and the disintegration rates were compared. The results are shown in the table below. Example calcined gypsum 70 parts by weight Potato starch 30 parts by weight Calcium carbonate 5 parts by weight Water mixed 76 parts by weight Comparative example 1 Calcined gypsum 95 parts by weight Calcium carbonate 5 parts by weight Water mixed 73 parts by weight Comparative example 2 Calcined gypsum 70 parts by weight Potato starch 30 parts by weight Amount of water mixed 73 parts by weight The disintegration rate shown in the table below was determined by the following formula. (Initial weight - uncollapsed weight) / (Initial weight) x 10
0 = Collapse rate%

[Table] (Effects of the Invention) As is clear from the above description, in the present invention, in order to form a gypsum molded article, it is sufficient to add water and knead it into a desired shape, similar to the conventional disintegrated gypsum composition. Also, when disintegrating it, it can be easily disintegrated in a short time by simply immersing it in hot water containing carbonate ions, which can be obtained at low cost. As a disintegrating gypsum composition that has a wide range of uses, such as molding plaster molds for casting of various shapes, it has greatly contributed to the development of the industry.

Claims (1)

[Claims] 1. A disintegrating gypsum composition comprising calcined gypsum mixed with starch and an appropriate amount of a carbonate that is insoluble or sparingly soluble in water and soluble in carbonate ion-containing hot water.