JPS5983931A - Composite alumina particle and its preparation - Google Patents

Abstract

PURPOSE:To prepare composite alumina particle having desired hardness and particle diameter and suitable as an abrasion material, a filler, etc., easily, by bonding fin particles of hydrated alumina firmly to the surface of a particle composed of alpha-alumina crystal. CONSTITUTION:The objective composite alumina particle can be prepared by mixing (A) 100pts.wt. of particles of alpha-alumina crystal having an average particle diameter of 0.2-5mum with (B) >=1pt.wt. of hydrated alumina particles having an average particle diameter of <=0.05mum, using a vibration mill, etc. under the condition to achieve an impact level of >1G, thereby bonding the hydrated alumina particles firmly to the surface of the alpha-alumina crystal particles. Composite alumina particles having desired average particle diameter can be obtained by selecting the average particle diameter of the alpha-alumina crystal used as the starting raw material, and the hardness of the resultant composite alumina particle can be controlled by controlling the amount of the hydrated alumina particles to be bonded with the alpha-alumina crystal.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to composite alumina particles and a method for producing the same.

More specifically, the present invention relates to composite alumina particles having a desired hardness and a desired particle size, and a method for producing the same.

Alumina particles have been widely used as fillers, abrasives, electrical insulating materials, and the like.

A number of methods are known for producing alumina particles, such as a sodium aluminate solution hydrolysis method, Meikan's thermal decomposition method, and an organic aluminum hydrolysis method.

In order to apply alumina particles to a wide range of applications, efforts are being made to improve their properties for each application.

For example, when alumina particles are used as an abrasive, both particle size and hardness are important factors, and as is well known, the hardness of alumina particles can be expressed as 3 on the Mohs scale by changing the degree of sintering. However, since the particle size is fixed to a certain extent depending on the type of raw material alumina and particle size, it is difficult to produce alumina particles with desired hardness and particle size. It is. In particular, it is inherently difficult to produce alumina particles having a relatively small hardness (Mohs hardness of about 3 to 8) and a suitably large particle size (about 0.2 to 5 μm).

In view of the above circumstances, the present invention provides a method for producing alumina particles suitable as an abrasive, a filler, etc.

That is, composite alumina particles are formed by firmly bonding alumina hydrate particles having an average particle size of 0.05 μm or less to the surface of particles substantially consisting of α-alumina crystals, and composite alumina particles substantially consisting of α-alumina crystals. 100 parts by weight of particles and 1 part by weight or more of alumina hydrate particles having an average particle diameter of 0.05 μm or less are mixed under conditions such that the impact value is greater than IG. The present invention provides a method for producing composite alumina particles in which alumina hydrate particles are firmly bonded.

The present invention will be explained in detail below.

The composite alumina particles of the present invention are characterized by fine T-
It has a composite structure formed by firmly bonding alumina hydrate particles such as alumina, boehmite, and gibbsite.

Normally, in order to increase the particle size, the degree of calcination must be increased, but increasing the degree of calcination also increases the hardness. However, if the degree of calcination is reduced, the particle size will not increase, making it difficult to produce alumina having the desired hardness and particle size. The alumina particles of the present invention have a particle size imparting portion serving as a core formed of particles consisting essentially of α-alumina crystals, on which alumina hydrate with low hardness and possibly a small particle size is bonded. Therefore, it has the advantage that it is possible to manufacture products with completely arbitrary combinations of hardness and particle size.

The alumina particles of the present invention, which are substantially composed of alumina crystals, generally have an average particle diameter of 0.1 μm or more, particularly 0.2 μm or more.
α-alumina particles of ~5 μm are used.

Although it is not impossible to produce α-alumina particles with an average particle size smaller than 0.1, it is not economical. The shape of the α-alumina particles is preferably as close to a spherical shape as possible in the form of a product.

The alumina hydrate used for bonding to the particle surface of the present invention consisting essentially of σ-alumina crystals has an average particle diameter of 0.05 μm or less, particularly 0.05 to 0.001 μm. used. Average particle size is 0.05
If the diameter is larger than the μ groove, the bond of alumina hydrate to the α-alumina particle surface becomes weak against external force, which is not preferable.

As the alumina hydrate, T-alumina, boehmite, gibbsite, etc. are generally used.

The surface of the α-alumina particles contains 91 parts by weight or more of alumina hydrate per 100 parts by weight of the α-alumina particles, preferably 5 to 5 parts by weight.
Combine 100 parts by weight.

If the binding ratio of alumina hydrate decreases by 1 part by weight, the area of the area covered by alumina hydrate on the surface of the α-alumina particles becomes small and the hardness of the surface of the α-alumina particles cannot be controlled, which is preferable. do not have.

Next, a method for producing composite alumina particles of the present invention will be explained.

The alumina particles of the present invention can be produced by mixing particles substantially consisting of α-alumina crystals and alumina hydrate particles as described above under conditions where the impact value is greater than IG, preferably 3 to 15G. It can be manufactured by

When the impact value during mixing is less than IG, the bonding force between the σ-alumina particles and the alumina hydrate particles becomes weak υ, and the external force causes them to peel off easily, making it difficult to achieve the objective. become unable.

Such mixing conditions can usually be achieved by grinding or mixing means such as a vibratory mill.

The grinding or mixing time varies depending on the type of raw materials used, but generally it can be done for 1 minute to 10 hours. α-alumina produced by any method may be used as long as it gives a particle size. It is desirable that the shape and particle size distribution of the α-alumina particles be uniform when the product of the present invention is used as an abrasive, a filler, etc., which is the main purpose of the product.

The particle size of the particles varies depending on the purpose and use, but the particle size of the final product is essentially determined by the α-alumina particles, so selection is important.

In addition, the alumina hydrate particles used in the production of composite alumina particles according to the method of the present invention may be of any type, as long as they have the particle size as described above, or can give such a particle size as a result. Alumina hydrate particles produced according to Production Method 1 can also be used. In particular, T-alumina is preferably used.

The reason why the composite alumina particles in the method of the present invention are tightly entangled is not clear.

Although the particle size of both raw material components may become smaller during mixing, the respective constituent components of the resulting composite alumina particles, σ
- It is desirable that the alumina particles and alumina hydrate particles have the above-mentioned particle size.

In addition to the alumina hydrate, other additives may be added to the production of the composite alumina particles of the present invention, depending on the purpose of use, within a range that does not impair the function of the present invention.

The composite alumina particles of the present invention have the advantage that alumina particles having any desired particle size and hardness can be manufactured because they can be designed with no difference in particle size and hardness.

The composite alumina particles of the present invention are particularly suitable as fillers and additives for abrasive materials and plastics for electronic parts that require wear resistance and thermal conductivity.

The composite alumina particles of the present invention will be explained in more detail with reference to examples below, but the present invention is not limited to the following examples as long as they do not go beyond the gist of the invention.

Example 1 α-alumina particles 1002 having an average primary particle size of 0.6 pm and T-alumina particles 2Of having an average primary particle size of 0.01 μm were 31! The mixture was placed in a vibrating mill (impact value = 6G) having an internal volume of 1, and pulverized and mixed for 20 minutes.

Next, the obtained composite alumina particles were observed using a scanning electron microscope, and the results showed that the T-alumina particles were evenly attached to the surface of the α-alumina particles and that the particle size of the α-alumina particles was not substantially changed. It turned out that.

In addition, 5v of the obtained composite alumina particles were added to 100cc of water.
And Beaker Ichibanko preparation, 200 r, p, m.

After stirring for 1 hour at a stirring speed of , the mixture was allowed to settle. After drying the precipitate, it was observed again using a scanning electron microscope. As a result, it was found that the T-alumina particles were attached to the surface of the Nobiichi alumina particles before treatment.

For comparison, the above raw materials were mixed for 30 minutes using a type 2 mixer.

As a result, after drying the precipitate, observation using a scanning electron microscope revealed that substantially T was present on the surface of the α-alumina particles.
- No alumina particles were attached.

From the above experimental examples, it can be understood that the composite alumina particles of the present invention have α-alumina particles and alumina hydrate firmly attached to them.

Example 2 α-alumina particles 10 having an average particle size of 2 μm
T with an average particle size of 0i and 0.011IWL
- Alumina particles 5F were charged into the same vibrating mill (impact value = 6G) used in Example 1, and pulverized and mixed for 20 minutes.

The obtained composite alumina particles were observed using a scanning electron microscope in the same manner as in Example 1. As a result, the state in which the T-alumina particles were attached to the surface of the expanded alumina particles before the treatment was similar to that after the treatment.

Example 3 α-alumina particles 100F having an average particle size of 0.4 cotton and T-alumina particles 20F having an average particle size of 0.005 μm were prepared in the same vibratory mill as used in Example 1 ( Impact value -3G) and pulverized and mixed for 20 minutes.

The obtained composite alumina particles were observed using a scanning electron microscope in the same manner as in Example 1. As a result, the state in which the T-alumina particles were attached to the surface of the expanded alumina particles before the treatment was similar to that after the treatment.

Comparative Example 1 α-Alumina particles 1002 having an average particle size of 0.6 μm and T having an average particle size of 0.01 μm
- Alumina particles of 0.2F were charged into the same vibrating mill (impact value = 6G) used in Example 1 and pulverized and mixed for 20 minutes.

Observation of the obtained composite alumina particles using a scanning electron microscope revealed that the surfaces of the α-alumina particles were hardly coated with T-alumina particles.

Procedural amendment (voluntary) Commissioner of the Patent Office Kazuo Wakasugi 1. Indication of the case 1982 Patent application No. 192889 2. Name of the invention Composite alumina particles and method for producing the same 3. Relationship with the person making the amendment m+= Patent Applicant Address: 5-15 Kitahama, Higashi-ku, Osaka Name (20
9) Hijikata, Representative of Sumitomo Chemical Industries, Ltd.
Take 4 Agent Address: 5-15-I, Kitahama, Higashi-ku, Osaka, “Claims” and “Detailed Description of the Invention” of the specification subject to amendment
Column, Contents of amendment (1) The scope of claims is corrected as shown in the attached sheet.

(2) On page 6, line 15 of the specification, the phrase ``haraai'' is corrected to read ``1 compound''.

Claims 1-1) Composite alumina particles comprising alumina hydrate particles having an average particle diameter of 0.05 μm or more firmly bonded to the particle surface consisting essentially of α-alumina crystals.

2) The α-alumina crystal has an average diagonal diameter of 0.2 to 5
Composite alumina particles according to claim 1, characterized in that they are α-alumina crystals of μmn.

3) The alumina hydrate particles have an average diameter of -17 or 0.0
The composite aluminum particles according to claim 1 or 2, which are alumina hydrate particles having a diameter of 5 to 0.001 μm.

4) The composite alumina particles according to claim 1.2 or 8, wherein the alumina hydrate particles are γ-alumina.

Claims (1)

[Claims] 1) On the surface of particles consisting of substantially 1 σ-alumina crystal,
Composite alumina particles made by firmly bonding alumina hydrate particles with an average particle diameter of 0.05 μm or less.
12) The composite alumina particles according to claim 1, wherein the α-alumina crystals are α-alumina crystals having an average particle diameter of 0.2 to 5 μm. 3) Alumina hydrate particles have an average particle diameter of 0.05 to 0.
．． Composite 2 alumina particles according to claim 1 or 2, characterized in that they are alumina hydrate particles having a particle size of 0.001μ. 4) The composite alumina particles according to claim 1.2 or 3, wherein the alumina hydrate particles are α-alumina. 5) Mixing 100 parts by weight of particles consisting essentially of α-alumina crystals with 1 part by weight or more of alumina hydrate particles having an average particle diameter of 0005 μm or less under conditions such that the impact value is greater than IG. A method for producing composite alumina particles by firmly bonding alumina hydrate particles to the surface of α-alumina crystal particles.