JPH0231021B2 - HAKUSHOKUTAKOSHITSUZAIRYONOSEIZOHO - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD This invention relates to a method for producing a highly white porous material using naturally produced Cristobal rock as a raw material. Prior Art and Problems Cristobal rock is a naturally occurring material containing 80 to 90% silicic acid and 1.4 to 1.7% iron oxide, with cristobalite as the main constituent mineral. It has countless micropores of 20 to 200 Å inside.
Although the specific surface area is 50 to 80 m ² /g, which is more than three times that of natural zeolite, the material has a whiteness of about 40 (Hunter whiteness) due to a small amount of impurities such as iron and organic matter contained therein. Conventionally, Cristobal rock has been used in products for various purposes by taking advantage of its properties such as porosity, adsorption, and ion exchange properties, but it is also used as filler for inorganic paper, filler for plastics, and boards for building materials. When using it, it is difficult to simply crush the raw stone into powder because the whiteness is low. That is, when the above products are manufactured using crushed Cristobal rock as a raw material, a product with high whiteness cannot be obtained and the colorability is poor, and when a plastic film is used, the transparency is poor. The present inventors have conducted various studies on methods for improving the whiteness of Cristobal Rock while maintaining its porosity. In other words, we considered the removal of iron and organic matter mentioned above, but treatment with hydrochloric acid or other acids, which is generally used as a deferrous treatment method for nitrogenous raw materials, can reduce the iron content in Cristobal rock, but white You can't get it high enough.

【table】

[Table] However, as shown in Table 1, it has been found that if Cristobal rock is treated with hydrochloric acid and then heated and calcined, the whiteness can be improved while maintaining the porosity. Means for solving the problems and their effects The present invention is based on these findings,
Cristobal rock is treated with inorganic acid and then washed with water.
This is a method for producing a white porous material characterized by firing the Cristobal rock at a temperature of 800 to 1,100°C. As mentioned above, the cristobal rock used in the present invention is a naturally occurring material whose main constituent mineral is cristobalite, with a silicic acid content of 80 to 90% and an iron oxide content.
It is a porous substance containing 1.4 to 1.7%, has numerous micropores of 20 to 200 Å inside, and has a specific surface area of 50 to 80 m ² /g. In the present invention, the Cristobal rock is treated with an inorganic acid in order to remove the small amount of iron contained in it. At this time, the raw material is crushed as necessary to prepare particles with a certain particle size or less. It is desirable to do so. Further, as the inorganic acid, hydrochloric acid, sulfuric acid, and nitric acid can be used. The method of treatment with an inorganic acid includes immersing the crushed Cristobal rock in an acid solution and stirring it. Cristobal rock treated with inorganic acids needs to be washed with water after thorough solid-liquid separation. This is because if an inorganic acid component remains in the above-mentioned pulverized granules, the material becomes unsuitable as a porous material for the purpose of the present invention. Next, the washed Cristobal rock is fired.
The temperature is preferably 800-1100°C. This is because a porous material with a whiteness of 75 or higher cannot be obtained at temperatures below 800°C. This is clear from the results in Table 1. Although whiteness can be increased by firing at temperatures above 1100°C, the pores inside the particles begin to melt and break down, reducing the specific surface area and maintaining porosity. Can not do it. Therefore, a porous material with high whiteness can be obtained when the firing temperature is in the range of 800 to 1100°C. Although the present invention is as described above, the desired whiteness can also be obtained by a method in which Cristobal rock is fired at a high temperature and then treated with an inorganic acid. Example Cristobal rock having the chemical composition shown in Table 2 was crushed and the particle size was adjusted to 2 to 20 mm.

[Table] After immersing this in concentrated hydrochloric acid at 60°C for 6 hours, the Cristobal rock and the hydrochloric acid solution were separated, and the Cristobal rock was thoroughly washed with water. Next, this was fired in a rotary kieln under the conditions of a maximum temperature of the firing zone of 1020℃, a residence time in the furnace of 90 minutes, and an O ₂ content of 7.5% in the exhaust gas at the bottom of the furnace.
A white porous material shown in Table 3 was obtained.

[Table] Effects of the Invention According to the present invention, a white porous material with a high degree of whiteness and a large specific surface area can be obtained, so that the uses of Cristobal rock can be expanded.

Claims (1)

[Claims] 1. A method for producing a white porous material, which comprises treating Cristobal rock with an inorganic acid, washing it with water, and firing the Cristobal rock at 800 to 1100°C.