JPS61204033A - Granulating method for powder of inorganic raw material - Google Patents

Abstract

PURPOSE:To form the spherical granulated grains excellent in fluidity by dissolving or dispersing a metal alkoxide in the oil emulsified with water, preparing an oily slurry contg. a spherical structural material of the reaction product and thereafter removing the oil therefrom. CONSTITUTION:One and more kinds of metal alkoxides are dissolved or dis persed in the oil emulsified with water and an oily slurry contg. a spherical structural material of the following reaction product is prepared. The reaction product is obtained by hydrolyzing the metal alkoxides with water. Then the oil is removed form this slurry and the powder of an inorganic raw material is granulated. By this method, since the grains are spherical and excellent in the fluidity and also breakable, the dense product can be obtained by increasing the packing density in the press molding. Still more an organic solvent hard- soluble in water such as higher alcohol, ketone and turpentine oil other than gas oil can be used as the oil.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a method for granulating raw material powder that has excellent workability in pressing operations during the manufacturing process of various inorganic material sintered bodies.

"Prior Art" As a method for granulating this type of raw material powder, a spray drying method is widely used in which raw material powder, which has been made into a slurry, is granulated into granules by spray drying.

"Problem to be solved by the invention" The granules granulated by the above spray drying have a spherical shape,
Although the fluidity in the mold is high and the packing density is high, since the granules are formed by agglomeration of primary particles by an organic binder during drying, they are essentially hard and difficult to crush during press molding.

"Means for solving the problem" One or more metal alkoxides are added to oil that has been emulsified with water, and this is subjected to a hydrolysis reaction with the above water, and then the reaction product is separated from the oil and taken out. .

[Function] The metal alkoxides in the oil-based slurry emulsified with water undergo hydrolysis at the oil-water interface and form spherical reaction products due to the surface tension of water, which is higher than that of oil. By removing the oil from the slurry of the system, the spherical reaction products described above can be removed.

"Effects of the Invention" As described above, the present invention is to granulate a spherical reaction product by hydrolysis of a metal alkoxide. Unlike the hard granules obtained by hardening, they have a spherical shape with good fluidity and are easily crushed, so they can increase the packing density in press molding and produce dense products.

"Example" 500 mΩ of light oil and 1.51 mΩ of water dissolved in polyvinyl alcohol as an organic binder were mixed, stirred with a magnetic stirrer at 1800 RPM, and emulsified and dispersed to form a W10 emulsion.

The average particle size of the emulsified water particles was 20μ.

The agitation of the magnetic stirrer was reduced to 60 ORPM, and aluminum alkoxide (
Aluminum isopropoxide [A1 (OC3 minister) 3
]・Reagent) 144F and silicon alkoxide (tetramethoxysilane・[5i(OCH3)4]・Reagent) 3
61 is dissolved and dispersed.

AI(OH)s due to the hydrolysis reaction of alkoxides generated at the oil-water interface by stirring for about 80 minutes
An oil-based slurry containing water-containing spherical structures with a particle size of 30 μm was obtained from a mixture of S i (CH)4 and S i (CH)4.

The obtained oil-based slurry is frozen by freezing the above-mentioned water-containing spherical structure in a freezer at about 15 degrees Celsius below zero, where the light oil remains liquid without freezing, and then passing the light oil through a 350-mesh sieve and freezing it. The spherical structure was taken out and freeze-dried for about 1 hour (equipment: Tokyo Rikakikai Co., Ltd., vacuum degree 0.2).
mmH? ) to evaporate and volatilize the internal moisture to obtain a granular raw material powder with a mullite composition that maintains a spherical structure with a particle size of 25 μm and is easily crushed and has a high filling property.

Next, alumina (RC-H
P-DBM/Reynolds) 86 (l and average particle size 0
．． 8μ, approximately 99.2% purity silicic anhydride (SP-8, Snow Brand) 140F, organic binder polyvinyl alcohol 1.
51 and mixed with water soomn, 15mφ alumina ball 2
Put it together with the chest in a ball mill with an internal volume of 2ρ, 84 RPM,
Mix and grind for 48 hours, and the resulting slurry at a gas temperature of 1
70℃, atomizer diameter 110wφ, 7200RPM
, Spray drying was carried out under the conditions of 5 mfl/sec, and the average particle size was 5.
It was granulated into 0μ conventional granules.

The two types of granular raw material powders granulated in this way were
18.5X5.5X by mold press of 00~/d
The results (average values) are shown in which five 54 mm plate-like bodies were manufactured and the properties of samples fired in an electric furnace were compared.

From the table above, the samples using the raw material powder granulated according to the present invention have a significantly lower sintering temperature than the samples using the raw material powder granulated by conventional spray drying, and have lower density and resistance. It has been revealed that it greatly increases the strength and strength.

In the above example, AI and Si alkoxides were used for the raw material powder having a mullite composition, but Ca 1Mg
r Zr r Sr r Using alkoxides such as Be, forsterite composition 2Mg0-8io2 or 8-component cordierite composition 2Mg
It is effective for 0.2A1203.5SiO2, etc., and also for high-purity alumina porcelain containing extremely small amounts of mineralizing agents.

Next, in the above example, when producing the first W10 emulsion, the water in which the organic binder was dissolved was directly mixed with light oil and stirred, but the organic binder was not necessarily necessary, and HL to emulsify water in oil
It is preferable to mix a small amount of an emulsifier with a B value of 6 or less, or a solid emulsifier such as talcum powder, in the case of the former liquid, 8% or less based on the oil, and in the case of the latter solid, 5% or less, and metal alkoxides Although it was added to the W10 emulsion produced above, it may be dissolved or dispersed in light oil in advance, and the oil referred to in the present invention is not limited to light oil, but also includes higher alcohols, ketones, turpentine, etc. that are poorly soluble in water. It refers to an organic solvent.

In addition, as a means of extracting the product of hydrolysis of metal alkoxide, the product is frozen to give it mechanical strength. It is also possible to pass the oil through a sieve at room temperature, and when the dispersed product contains an organic binder, freeze-drying is preferred because it does not increase the bond strength between fine particles and increases the press-molding density. The drying method is not limited to this.

Therefore, among the essential components in the present invention, water is used in an amount necessary to hydrolyze the metal alkoxide, for example, a minimum of 3 molty per 17 mol of aluminum improxide in the example, and 1 mol of tetramethoxysilane. It is calculated from their chemical formulas that the minimum amount is 4 mol, and in order for water (including metal alkoxides) to be completely emulsified in oil, the volume ratio needs to be 70 mol or less of oil.

Claims (1)

[Claims] One or more metal alkoxides are dissolved or dispersed in an oil emulsified with water to form an oil-based slurry containing spherical structures of reaction products obtained by hydrolyzing the metal alkoxides with the water. , a method for granulating inorganic raw material powder, characterized by removing oil from the slurry.