JPS58166926A - Method for granulating inorganic powder - Google Patents

Abstract

PURPOSE:To improve the yield of granules and packing density by adding a solvent which differs from water and hardly dissolves water soluble polymer materials to water and making powder of inorg. raw materials and polymer binder materials into a slurry. CONSTITUTION:Polymer materials which are soluble in water or disperse uniformly in water are compounded together with a granular binder into water added with a solvent which is compatible with water and hardly dissolves said polymer materials and the mixture thereof is made into a slurry, whereafter the slurry of the powder of the inorg. raw materials is sprayed, dried and granulated. 3-Methyl 3-methoxy butanol, ethylene glycol, n-butanol, etc. are suitably usable for the above-described solvent which is compatible with water and hardly dissolves said polymer materials. The mixing ratio of said solvent and water is made preferably 30-90% water and 70-10% solvent based on weight.

Description

[Detailed description of the invention] A sintered body of cermet, cemented carbide, etc. should have as few internal pinholes as possible, which greatly affect its U characteristics, and be made as thin as possible. Therefore, it is necessary to increase the roundness of granules made of inorganic raw material powder (hereinafter simply referred to as raw material powder) used for press molding of the element body, thereby increasing the packing density.

Granulation by spray drying is generally used to produce granules with the above-mentioned high roundness, but when turning the raw material powder into a slurry for spray drying, the raw material powder is mixed with water. It is necessary to add a water-soluble or monomolecular material (hereinafter simply referred to as a polymeric binder) that binds and forms granules (hereinafter simply referred to as a polymeric binder). It covers the periphery of the slurry droplets ejected into the drying chamber and prevents the passage of water vapor inside, increasing the internal pressure, causing abnormal expansion of the slurry droplets, or causing them to break before they become granules, thereby reducing the yield rate. There was some dissatisfaction with this aspect.

Although some improvement in the above-mentioned granule abnormality and destruction was seen by reducing the rapid drying of the slurry, no substantial solution could be expected.

In the present invention, when a water-soluble or uniformly dispersible Emulsion Suntaig polymer binder is added to raw material powder together with water to form a slurry, the present invention is compatible with water and dissolves in the polymer binder. The above-mentioned dissatisfaction is resolved by adding a solvent that is difficult to dissolve, and the yield rate of granules with uniform particle size and high roundness is improved, and the sintered body is densified, as represented by transverse rupture strength. It has succeeded in greatly improving mechanical and mechanical properties as well as other M properties.

In the present invention, when the above-mentioned raw material powder is turned into a slurry, the raw material powder is mixed with water, and (ii) a 116 molecule binder and a solvent that is difficult to dissolve are added. In the process of drying the slurry consisting of the body, polymeric binder, water, and solvent by hot air,
First, the liquid phase of water and the solvent is evaporated, and as the temperature rises, the degree of droplet concentration of the liquid phase is increased to rapidly lower the solubility of the polymeric binder in the slurry droplets. This is intended to suppress the increase in internal pressure during drying of slurry droplets, and will be explained by referring to the vapor-liquid equilibrium in the drawing.

The drawing shows the case where J methyl J methoxybutanol is dissolved in water as a solvent. For example, when water is 70 TLjk'A and solvent is 70 wt -, the boiling point at point P is about 10/C, and the vapor at that time is The water inside evaporates from the slurry droplet at about P' point, but the solvent component that evaporates at the same time is just a copy of the point P'. Subsequently, as the temperature of the slurry droplet rises above the liquidus line, the m* solvent component increases, but 12
Even if the temperature is raised to 0°C, the water content in the steam remains at about 77-1 and the solvent component remains at about 77-1%, as indicated by the P' point. The drying process is completed by increasing the directivity and precipitating the coexisting polymer binder inward to envelop the raw material powder.

Aluminium (Showa light metal worker-/J) P4θV
Anhydrous silicon # (Hayashi Junyaku/M) /If translated calcium (Katayama Chemical 1st grade) 34F Magnesium oxide (Katayama Chemical 1st grade) Coy is the raw material powder, and the lubricant polyethylene/oxide is added to it. (M Iron Chemical PE0-/)jf, anti-scattering agent Methylcell p-z (Dow Chemical A-IM) J9. Along with polymer binder polyvinyl alcohol (Denka B-oj) toy, water 6J
Add OCAQ and 70ct of J Methyl J Methoxybutanol (Kuraray, Trufit) selected as a solvent.
A ball mill with an internal volume of Jt was used to mix and crush the mixture for a period of time to form a slurry, and the slurry was heated with a gas cylinder [tto℃,
The granules according to the present invention obtained by spray drying under the conditions of 10 ac per second with a disk diameter of l 0 - 141-100 R, P, h41, and the same granules obtained by spray drying at 700 esc of water except for the 3 methyl J methoxybutanol in the S medium. Table 7 shows the results of comparison with soft granules produced by conventional methods.

#i l Table However, step*b is the target ≦0~Jλ in all dry powder! Items within the range of metshu are shown in terms of weight and weight, and the full and horizontal writing quality is
A stainless steel vessel with an inner diameter of 10 cm and a depth of 11111 m was filled naturally, and the filled weight was measured.

It was revealed that the granules obtained by the present invention exhibited higher values of both yield 9 and packing density than conventional products.

Next, using the above two types of granules, /Jx≦0■, thickness tu
The square plate element is produced by pressing.

This is in the hot atmosphere of an electric furnace! The results of comparing sintered bodies obtained by firing at ti'c/time 't#
! - Shown in Table 2.

From Table 2, the products of the present invention have molding pressures of joo and 1ooo.
.

In both cases of 1zoox and 7aa, both the base body and the baked crystals clearly showed even higher density than the comparative product, and in terms of anti-disease power, the noodles of the present invention were significantly higher than the comparative product. The first effect of the present invention is that the water content of the steam released during the drying of slurry grains is reduced by 11 ili more than the solvent component. (Thus, since it is determined by what can be obtained, the liquid phase is good, and the gas phase is positive, so the #I & degree of water becomes even higher - k
A water-bath solution of a solvent is preferred, and a solvent with a high boiling point is preferred.For these reasons, in addition to 3-methyl J methoxybutanol shown in the example, ethylene glycol has a similar effect, n-tutanol, acetic acid However, the former J-methyl-3-methoxybutanol and ethylene glyco-λ are preferred from the viewpoint of toxicity and unpleasant odor.

Therefore, the combined ratio of these solvents, water, and Oa is expressed as water 3
Within the range of 0 to 0% by weight, solvent 70-103,
When the amount of solvent is less than the lower limit of to11, the organic binder oozes out to the outer periphery of the slurry droplets, and when it exceeds the upper limit of 70, the water in the slurry naturally decreases and the polymer binder is absorbed. # If the solution k is small, the required amount of polymeric binder cannot be completely digested, and if water is increased to compensate for this, the til1 degree of the slurry will become thinner, making spray drying difficult. It is necessary to limit it within the range.

[Brief explanation of the drawing]

The drawing is a diagram showing the structure of an aqueous solution of a solvent to illustrate the present invention.

Claims (1)

[Claims] (1) Aquatic Maku is an inorganic material (DIIIL material) made of a slurry using a polymeric material that is uniformly dispersed in water as a particle binder (DIIIL material), which is compatible with water and has the above-mentioned high 9. A method for granulating inorganic IX material powder, characterized by adding an illumination agent that is difficult to dissolve the molecular material to water to turn the inorganic 0IIA material and the binding material of the molecules into a slurry. 9) Claims The solvent that is compatible with water and difficult to dissolve the polymeric material described in IK is J methyl J methoxybutanol, ethylene glycol, n-butanol, or acetic acid, and the mixing ratio of the solvent and water is 9. A method for granulating inorganic powder, characterized in that the weight ratio of water is J0 to 0-1 to 70 to 10.