JPH07330499A - Granular aggregate of aluminum borate whisker - Google Patents

Abstract

PURPOSE:To obtain granular aggregates of aluminum borate whiskers not causing scattering at the time of handling and easy to disperse at the time of mixing with a matrix. CONSTITUTION:Flocculated particles of a mixture of aluminum oxide or an aluminum compd. convertible into aluminum oxide by heating in air with boron oxide or a boron compd. convertible into boron oxide by heating in air are heated in air at a temp. at which aluminum borate whiskers are formed to obtain the objective granular aggregates of aluminum borate whiskers.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to mechanical properties, heat resistance,
The present invention relates to a granular aggregate of aluminum borate whiskers which is excellent in corrosion resistance, heat insulation, electric insulation, etc. and is useful as a reinforcing material for various plastics, metals, ceramics, cement and the like.

[0002]

2. Description of the Related Art Reinforcing materials such as plastic, metal, ceramics and cement include whiskers, fibers and particulate aggregates. Among these reinforcing materials, aluminum borate whiskers are mechanical properties, heat resistance, corrosion resistance,
Excellent heat insulation and electrical insulation. This aluminum borate whisker is a vapor phase method in which vapor of aluminum halide and vapor of boron oxide are subjected to vapor phase reaction in the presence of water vapor, a hydrothermal method of heating aluminum borate gel, or aluminum oxide and boron oxide. And a melt method in which whiskers are grown from a melt added with a melting agent.

For example, U.S. Patent No. 3,350,166 describes a _{4Al 2 O 3 · B 2 O} 3 whiskers method of manufacturing by a vapor phase method, xAl ₂ O ₃ · by hydrothermal method in U.S. Patent No. 4,789,422 yB ₂ O ₃ (x = 4 to 9, y
= 2-5) A method for manufacturing whiskers is described. Further, in US Pat. No. 3,080,242, a method for producing 3Al ₂ O ₃ .B ₂ O ₃ whiskers by gradually cooling a melt of boron oxide to which 1 to 25% by weight of aluminum oxide is added, and a method for obtaining the same are obtained. ₃ Al ₂ O ₃ · B ₂ O _{3
9Al 2 O 3 · B 2 O} 3 whiskers method of manufacturing a whisker as a raw material are described. Furthermore, Japanese Patent Fair 4-2
No. 1640, Japanese Patent Publication No. 4-76954, Japanese Patent Publication No. 4-76
No. 955, Japanese Patent Publication No. 5-15679, and Japanese Patent Laid-Open No. 5-2.
No. 01800 discloses a method for producing 9Al ₂ O ₃ .2B ₂ O ₃ whiskers by a method using an alkali metal sulfate, an alkali metal carbonate, an alkali metal chloride or the like as a melting agent. There is.

[0004]

However, the vapor phase method can synthesize only whiskers of aluminum borate having a low melting point, and the growth rate is slow, so that mass production is difficult.
Further, in the case of the hydrothermal method, a pressure vessel that can withstand a pressure of several tens to several hundreds of atmospheric pressure is required, and it is difficult to control the shape of the whiskers.

On the other hand, in the method of growing whiskers from a melt of boron oxide to which aluminum oxide is added, it takes a long time to cool the melt and a much larger amount of boron oxide is used as compared with the composition of the whiskers. Material yield is poor. Moreover, since the whiskers of the reaction product after cooling are also surrounded by the matrix of boron oxide, the operation of separating the whiskers is troublesome. Also, in the case of the method of using alkali metal sulfate, alkali metal carbonate, alkali metal chloride, etc. as the melting agent, the molar ratio of alkali metal to aluminum is 1 to 1.
Since the amount of the melting agent required is 10 times (usually 2 to 3 times), the material yield is low, and the reaction product after cooling is also in a state where the whiskers are surrounded by the matrix of the melting agent. Therefore, it is troublesome to separate the whiskers.

On the other hand, from a practical point of view, whiskers are apt to scatter, and in addition to the problem that the worker inhales when handling them, there is a problem of affecting the living body, and mixing with various plastics, metals, ceramics, matrixes such as cement, etc. At times, a granular aggregate is desired so that it can be easily dispersed in the matrix. However, when trying to obtain those granular aggregates using the above-mentioned conventional method for producing aluminum borate whiskers, a step of aggregating the whiskers with each other is required after the formation of the whiskers, which causes a high cost, and the particle size is controlled. Therefore, it is technically difficult to obtain a granular aggregate of whiskers which maintains a granular morphology.

The present invention has been made in view of the above problems, and a main object of the present invention is to provide an aluminum borate whisker granular aggregate which does not scatter during handling and is easily dispersed when mixed with a matrix. I am trying.

[0008]

In order to achieve the above object, the aluminum borate whisker granular aggregate of the present invention comprises aluminum oxide or a compound of aluminum which becomes aluminum oxide by heating in air and boron oxide or It is characterized in that agglomerated particles composed of a mixture with a compound of boron which becomes boron oxide by heating in air are produced by heating at high temperature in air. In addition, aluminum oxide or an aluminum compound that becomes aluminum oxide when heated in air, boron oxide or a boron compound that becomes boron oxide when heated in air, and iron oxide or iron oxide when heated in air. It is characterized by being produced by heating agglomerated particles composed of a mixture with an iron compound in air at a high temperature.

The aluminum oxide is Al ₂ O ₃
However, examples of the aluminum compound which becomes aluminum oxide by heating in the air include aluminum hydroxide, aluminum sulfate, aluminum nitrate, aluminum chloride, etc., and oxidation which is highly reactive by heating in the air. It becomes aluminum and reacts with boron oxide at high temperatures to form aluminum borate whiskers. These compounds may be used alone or in combination of two or more.

The boron oxide is B ₂ O ₃ , and the boron compound which becomes boron oxide by heating in the air is, for example, H ₃ BO ₃ , H ₂ B ₄ O ₇ , HBO ₂ ,
Examples thereof include sodium borate, potassium borate, and boric acid alkoxide. These may be used alone or in combination of two or more.

Examples of the iron oxide include Fe ₂ O ₃ and Fe ₃ O
₄ , examples of the iron compound that becomes iron oxide by heating in the air include iron chloride, iron sulfate, iron nitrate, iron oxalate, and the like, and these may be used alone, You may mix and use 2 or more types.

The aluminum borate whisker granular aggregate according to the present invention comprises aluminum oxide or an aluminum compound which becomes aluminum oxide by heating in air, and boron oxide or a boron compound which becomes boron oxide by heating in air. By mixing to form agglomerated particles, or by further mixing the agglomerated particles with iron oxide or a compound of iron that becomes iron oxide by heating in air, and heating in air at the formation temperature of aluminum borate whiskers. can get. This heat treatment is performed at normal temperature and time,
For example, it is performed at 1200 to 1600 ° C. for about 1 to 10 hours.

The particle size of the agglomerated particles is 30 to 1000 μm.
m is preferable, and when it is 30 μm or less, it is difficult to obtain aluminum borate whiskers having a high aspect ratio. On the other hand, when the thickness is 1000 μm or more, the obtained aluminum borate whisker aggregates are plastic or metal,
Uniform mixing becomes difficult when mixed with a matrix such as ceramics or cement.

Further, the agglomerated particles have a molar ratio of aluminum to boron of 9: 2.5 to 1: 1 and aluminum oxide or a compound of aluminum which becomes aluminum oxide by heating in air and boron oxide. or by mixing a compound of boron to be boron oxide by heating in air, 9Al ₂ O ₃ · 2B ₂ having excellent high-temperature characteristics
Aluminum borate whisker granular aggregates having a composition of O ₃ can be obtained.

Further, when the aluminum borate whisker granular aggregate according to the present invention is mixed with a matrix of plastic, metal, ceramics, cement or the like, the granular morphology is broken and separated into individual whiskers and dispersed in the matrix. To be done. Therefore, it is preferable that the whiskers have a large aspect ratio and a uniform shape in terms of the mechanical strength of the matrix. In the present invention, a mixture of aluminum oxide or an aluminum compound that becomes aluminum oxide by heating in air and a mixture of boron oxide or a boron compound that becomes boron oxide by heating in air is further added in an amount of 0.1 to 10 wt. % Iron oxide or an iron borate whisker having a high aspect ratio by adding an iron compound that becomes iron oxide by heating in air in an amount of 0.1 to 10% by weight converted to iron oxide to form agglomerated particles. A granular aggregate consisting of can be obtained. The addition amount of the iron oxide or the iron compound which becomes iron oxide by heating in air is most preferably 2 to 4% by weight.

In producing the aluminum borate whisker granular aggregate of the present invention, alkali metal sulfates, alkali metal nitrates, and alkali metal alkali metal sulfates are produced within a range in which the produced granular aggregates do not fuse with each other. It is also possible to add a melting agent such as chloride. In this case, it is appropriate that the amount of the melting agent added is 10% by weight or less. Also,
The obtained aggregates of whiskers are washed with hot water, hot hydrochloric acid, hot sulfuric acid, etc. to remove excess boron oxide, etc. The degree of opening when dispersed in the matrix depends on the degree of this washing. Can be controlled.

[0017]

[Operation] Since the aluminum borate whisker granular aggregate of the present invention produces a small amount of liquid phase during heating in the manufacturing process, the aggregated particles do not fuse with each other during heating and maintain the shape of the aggregated particles. Whiskers grow in the state to form granular whisker aggregates. Therefore, in addition to preventing scattering during handling, excellent dispersibility is obtained when mixed in a matrix of plastic, metal, ceramics, cement or the like. Moreover,
Aluminum borate whisker granular aggregates to which iron oxides or iron compounds that become iron oxides by oxidation in air are added further improve the mechanical strength of the matrix because the individual whiskers have a high aspect ratio. be able to.

[0018]

EXAMPLES The following examples can clarify the aluminum borate whisker granular aggregate according to the present invention.

Example 1 10 g of aluminum hydroxide (Al (OH) ₃ ) and 3.5 g of orthoboric acid (H ₃ BO ₃ ) (molar ratio of aluminum and boron of 9: 4) were thoroughly mixed in an automatic mortar, Sieving,
Agglomerated particles having a particle size of 100 to 200 μm were prepared, which were placed in an alumina crucible and heated at 1400 ° C. for 3 hours. After completion of heating, the reaction product is cooled, excess boron oxide is removed with hot water, and dried to obtain 7.2 g of 9Al ₂ O ₃ .2B ₂ O ₃
A granular aggregate of whiskers was obtained. The yield was 96%. The particle size of the obtained whisker granular aggregate was 50.
The diameter of the whiskers constituting the aggregate was 1 μm, and the length was 5 to 10 μm.

Example 2 Aluminum hydroxide (Al (OH) ₃ ) 10 g, orthoboric acid (H ₃ BO ₃ ) 4 g (aluminum-boron molar ratio 9: 4.5) and iron oxide (Fe ₂ O ₃ ). After thoroughly mixing 0.3 g with an automatic mortar, sift it to obtain a particle size of 100-500 μ.
m as agglomerated particles, put this in an alumina crucible, and
Heated at 0 ° C. for 6 hours. After heating, the same treatment as in Example 1 was performed to obtain 7.4 g of 9Al ₂ O ₃ .2.
A granular aggregate of B ₂ O ₃ whiskers was obtained. The yield is 97
%Met. The particle diameter of the obtained whisker granular aggregate was 50 to 400 μm, the diameter of the whiskers constituting the aggregate was 0.8 μm, and the length was 20 to 30 μm. An electron micrograph of the obtained whisker aggregate is shown in FIG.

Example 3 22 g of aluminum sulfate (Al ₂ (SO ₄ ) ₃ ), 2.3 g of boron oxide (B ₂ O ₃ ) and sodium tetraborate (Na ₂
B ₂ O ₇ ) 0.5 g (molar ratio of aluminum to boron 9:
4.8) was thoroughly mixed in an automatic mortar and then sieved to form agglomerated particles having a particle size of 50 to 500 μm, which were placed in an aluminum alumina crucible and heated at 1250 ° C. for 6 hours. After the heating is completed, the same treatment as in Example 1 is performed to obtain 6.
It was obtained _{9Al 2 O 3 · 2B 2 O} 3 whisker particulate aggregate of 8 g. The yield was 90%. The particle diameter of the obtained whisker granular aggregate is 30 to 400 μm,
The diameter of the whiskers forming the aggregate was 0.4 μm, and the length was 10 to 20 μm.

[0022]

As described above, in the aluminum borate whisker granular aggregate according to the present invention, since the liquid phase generated during heating in the manufacturing process is small, the agglomerated particles are fused to each other during heating. However, it is obtained by growing whiskers while maintaining the shape of aggregated particles. Further, the aluminum borate whisker granular aggregate according to the present invention does not scatter during handling, and has good dispersibility when mixed with a matrix such as plastic, metal, ceramics, or cement. Moreover, the aluminum borate whisker granular aggregate to which iron oxide or an iron compound that becomes iron oxide by oxidation in air is added, the individual whiskers have a high aspect ratio, so that the mechanical strength of the matrix is improved. Can be improved.

[Brief description of drawings]

1 is an electron micrograph showing an aluminum borate whisker granular aggregate of Example 2. FIG.

Claims (4)

[Claims] 1. Agglomerated particles comprising a mixture of aluminum oxide or a compound of aluminum which becomes aluminum oxide when heated in air and boron oxide or a compound of boron which becomes boron oxide when heated in air are prepared in air. An aluminum borate whisker granular aggregate, which is produced by heating at a high temperature in the aluminum borate. 2. A compound of aluminum which becomes aluminum oxide by heating in aluminum oxide or air, a compound of boron which becomes boron oxide by heating in boron oxide or air, and a compound of iron oxide or by heating in air An aluminum borate whisker granular aggregate, which is produced by heating agglomerated particles composed of a mixture with an iron compound that becomes iron oxide in air at a high temperature. 3. A molar ratio of aluminum and boron of aluminum oxide or a compound of aluminum which becomes aluminum oxide by heating in air and boron oxide or a compound of boron which becomes boron oxide by heating in air is 9: 1. : 2.5 to 1: 1 and further 0.1
10% by weight of iron oxide or 0.1 to iron oxide
Aluminum borate whisker granular aggregate produced by heating agglomerated particles comprising a mixture of an iron compound which becomes iron oxide by heating in air at 10% by weight at high temperature in air . 4. The particle size of agglomerated particles of the mixture is
The aluminum borate whisker granular aggregate according to any one of claims 1 to 4, which has a diameter of 30 to 1000 µm.