JPH04114999A - Production of fibrous aluminum borate - Google Patents

Abstract

PURPOSE:To obtain a fibrous aluminum borate having uniform fiber diameter and fiber length, being a long fiber, having high aspect ratio and having high compatibility as a reinforcing material by spraying and drying a solution or homogeneous dispersion of an aluminum compound, a boron compound and an alkali metal salt and then heating and burning the dried mixture. CONSTITUTION:A solution or homogeneous dispersion of (1) and aluminum compound capable of giving a metal oxide by heating and burning, (2) boron compound and (3) alkali metal salt is sprayed and dried and heated and burned at 600-1200 deg.C. When a liquid obtained by uniformly suspending fine grains of oxide or hydroxide of aluminum and/or boron into the solution or homogeneous dispersion of the above-mentioned components (1) to (3) is sprayed and dried and then heated and burned at 600--1200 deg.C, a fibrous aluminum borate having longer fiber is preferably obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for producing fibrous aluminum borate.

Conventional technologies and their problems In recent years, with the advancement and rapid progress of high-tech technology, various research and development of composite materials have been conducted as advanced materials. Performance such as high strength, high rigidity, and abrasion resistance has come to be required, and whisker-shaped single crystal fibers that meet these requirements are attracting attention. Aluminum borate whiskers have also attracted attention as a reinforcing material with excellent heat insulation, heat resistance, chemical resistance, etc., and various methods for synthesizing them have been proposed.

Japanese Unexamined Patent Publication No. 63-319298, 6331, 929
Publication No. 9 states that the shape of aluminum borate whiskers is preferably about 0.05 to 5 μm in fiber diameter and 2 to 50 μm in fiber length, and that when the fiber diameter is 5 μm or more, single crystals aggregate on the fiber axis. It is disclosed that the crystal becomes polycrystalline, and furthermore, the defective portions of the crystal increase and the mechanical strength decreases. In recent years, needs have been diversifying and becoming more sophisticated, so no matter how excellent the functionality of aluminum borate whiskers is, if their fiber diameters and fiber lengths are uneven, they will not be suitable for industrial use. It is clear that this will result in a lack of usability.

Most of the currently known methods for synthesizing aluminum borate whiskers involve simply mixing an aluminum source, a boron source, and, if necessary, a flux, followed by heating and baking. For example, in U.S. Patent Nos. 3,755,536, 3,350,166, 3,080,242, 4,789,422, etc.
3 ・B203, (A/203) 3 to, +
・B203 (0<n≦2), XA/203 ・y
B203 (4≦X≦9.2≦y≦5), etc., has been proposed, but it is difficult to control the fiber shape by any of these methods, It is impossible to produce aluminum borate whiskers of a desired shape with uniform diameter and fiber length.

Furthermore, there is a desire today to develop fibrous aluminum borate having uniform fiber diameters and fiber lengths, long fibers, and a high aspect ratio.

Problems to be Solved by the Invention The purpose of the present invention is to provide a method for producing fibrous aluminum borate, which has uniform fiber diameter and fiber length, is long fiber, and has a high aspect ratio, and is highly compatible with needs as a reinforcing material. It is about providing.

Another object of the present invention is to provide a fibrous boron which has excellent heat insulating properties, heat resistance, chemical resistance, etc. and is useful as a filler for reinforcing plastics, cement, and metal products, as well as heat insulating materials, heat resistant materials, and heat insulating paints. An object of the present invention is to provide a method for producing aluminum acid.

Means for solving the problems, that is, the present invention, consists of a solution or homogeneous dispersion of (1) an aluminum compound that becomes a metal oxide by heating and baking, (2) a boron compound, and (3) an alkali metal salt. Spray dry and then apply this to 6
The present invention relates to a method for producing fibrous aluminum borate, which is characterized by heating and firing at a temperature of 00 to 1200°C.

In the present invention, as the aluminum compound used as component (1), which becomes a metal oxide by heating and baking, conventionally known aluminum compounds are widely used unless the aluminum content is low or causes a rapid hydrolysis reaction. For example, organoaluminum compounds such as aluminum alcolade; aluminum hydroxides such as aluminum hydroxide, aluminum oxide, sodium aluminum oxide,
Aluminum oxides such as aluminate, aluminum sulfates such as aluminum sulfate, aluminum potassium sulfate, ammonium aluminum sulfate, aluminum nitrates such as aluminum nitrate, aluminum halides such as aluminum chloride, and their hydrates. Examples include inorganic aluminum compounds. In the present invention, these may be used alone or in combination of two or more.

As the boron compound used as component (2) in the present invention, a wide variety of conventionally known ones can be used, such as boron oxide; orthoboric acid, tetraboric acid, metaboric acid, sodium tetraborate, sodium pyroborate, pyroboric acid. Oxygen acids of boron such as potassium, metaborate, lithium, etc., and oxides of boron such as alkali metal salts such as these are mentioned.

In the present invention, these may be used alone or in combination of two or more.

The alkali metal salt used as component (3) in the present invention acts as a melting agent, and a wide variety of conventionally known salts can be used. Specifically, sodium chloride,
Alkali metal halides such as potassium chloride, sodium bromide, potassium bromide, sodium fluoride, and potassium fluoride; alkali metal sulfates such as sodium sulfate and potassium sulfate; sodium carbonate, potassium carbonate, sodium bicarbonate, carbonic acid Carbonates of alkali metals such as double salts such as potassium hydrogen and the like; nitrates of alkali metals such as sodium nitrate and potassium nitrate; hydroxides of alkali metals such as sodium hydroxide and potassium hydroxide. In the present invention, these may be used alone or in combination of two or more.

In the present invention, the solvent for dissolving or dispersing the components (1) to (3) above is not particularly limited, and water, an organic solvent, or a mixture thereof can be used.

Examples of the organic solvent used here include lower alcohols such as methanol and ethanol.

In the present invention, the components (1) to (3) above are not limited to those shown above, but include organic and inorganic substances as long as they can be dissolved or homogeneously dispersed in water or an organic solvent. Although a wide range of conventionally known compounds can be used, from an industrial perspective, it is preferable to select and use compounds that are easy to handle and are soluble in or easily dispersed in water for environmental and disaster prevention purposes. is desirable.

In the present invention, when dissolving or dispersing the components (1) to (3) above in water or an organic solvent, there is no need for a special fuze method, and the desired solution or A uniform dispersion may be used.

For example, when an alkali salt of aluminum or boron is used as a raw material, the system becomes alkaline, and when sulfate, nitrate or chloride is used, the system becomes acidic, and each becomes a homogeneous solution system. In addition, in an organic solvent system, when organic aluminum, organic boron, or alkali metal Alcohol-1 is used as a raw material, a homogeneous solution system is obtained.

In order to obtain a homogeneous dispersion, it is convenient to homogeneously mix aqueous solutions of the various compounds mentioned above under stirring and use a slurry to precipitate fine insoluble components. It is also possible to add a dispersing agent. As such a dispersant, a surfactant such as a polyalkylene ether nonionic surfactant can be advantageously used.

In the present invention, it is desirable to further homogeneously suspend fine particles of aluminum and/or boron oxide or hydroxide in the solution or homogeneous dispersion. It becomes possible to produce aluminum acid.

In the above, the aluminum oxide is aluminum oxide, the aluminum hydroxide is aluminum hydroxide, the boron oxide is boric oxide, and the boron hydroxide is orthoboric acid, etc. For example, aluminum borate can also be used.

Furthermore, the fine particles described in "1" have a particle diameter of 0.1. nm～
It is about 10 μm, preferably about 1 nm to 1 μm,
It is desirable that the particle size is uniform. As such fine particles, for example, an aqueous alumina sol solution can be suitably used.

At this time, a slurry obtained by dispersing or precipitating a classified product of pulverized alumina by a wet reaction can be used as it is. The amount of the fine particles used is usually about 0.01 to i-Ow t%, preferably 0.
．． 01. The content is preferably about 1 wt%.

In the present invention, a solution or homogeneous dispersion of the components (1) to (3) above, or a liquid in which fine particles of aluminum and/or boron oxide or hydroxide are homogeneously suspended, is spray-dried. let For spray drying, a wide variety of conventionally known methods can be used, including, for example, a spray dry method.

The solid content concentration of the solution or homogeneous dispersion of the above components (1) to (3) to be spray-dried, or the liquid in which the above-mentioned fine particles are suspended, should be determined in consideration of workability during spray drying. , usually about 5 to 80 wt%, preferably 20 to 5
It is preferable to set it to about 0 wt%.

Further, the ratio of aluminum component to boron component in these liquids may be appropriately selected from a wide range depending on the composition of the target fibrous aluminum borate, but AI/B=
The range of 1/1 to 1-0/1 (molar ratio) is preferable, and AA
The range of /B=2/1 to 5/1 is more preferable. The alkali metal salt is usually 1-0 to 95 wt%, preferably 20 to 70 wt% of the total weight of the dry product obtained by spray drying.
It is preferable that the content is %.

In the present invention, a carbon material or the like as a cavitation agent that aids fiber growth may be mixed prior to spray drying.

In the present invention, the dried product obtained by spray drying is then heated and baked. The heating and firing temperature is usually 600 to 1200°C,
Preferably, 1000 to 1100'C is appropriate. Moreover, the heating and baking time is usually 30 minutes to 10 hours.

Any conventionally known method can be applied to isolate the fibrous aluminum borate produced by the heating and baking process. For example, hot water or hot hydrochloric acid at about IN level,
After treating with an acid such as hot sulfuric acid or hot nitric acid to dissolve the melting agent and other water-soluble components, it is separated in a furnace, washed with water, dried, and further classified if necessary to remove water and dilute acid insolubles.

Effects of the Invention According to the present invention, a homogeneous raw material composition can be prepared by spray-drying a solution or a homogeneous dispersion of the components (1) to (3) above, and each of these components can be homogeneously and densely distributed. Since they are in contact with each other, the melting reaction progresses homogeneously in the raw material composition during heating and firing, so the product aluminum borate has a homogeneous composition and a uniform fiber shape, eliminating crystal defects and polycrystalline formation. It is possible to obtain aluminum borate whiskers with little loss of strength even with long fibers.

Furthermore, according to the present invention, since the raw material composition obtained by spray drying is obtained as a granular material with a uniform particle size, it is heated evenly without unevenness during heating and firing, so that the melting reaction progresses homogeneously and Since the method has excellent thermal efficiency and the raw material composition is homogeneous, it is possible to obtain homogeneous aluminum borate whiskers that have not been obtained conventionally.

The fibrous aluminum borate whiskers obtained by the present invention have uniform fiber diameters and fiber lengths, are long fibers, and have a high aspect ratio. Therefore, they are highly compatible with needs as a reinforcing material, and have excellent heat insulation properties. Since it has excellent heat resistance and chemical resistance, it can be suitably used as a heat insulating material, a heat resistant material, a heat insulating paint, and as a filler for reinforcing plastics, cement, and metal products.

EXAMPLES The present invention will be further clarified with reference to Examples and Comparative Examples below.

Example 1 To 1.00 g of a 1-5% aqueous solution of potassium chloride, 30 g of a 5% aqueous solution of potassium tetraborate hydrate (K2B4O7.5H20) and sodium aluminum sulfate hydrate (N
a40% aqueous solution 1 of Al(SO4)2 ・12H20)
．． 27 g were mixed under stirring and fed to a spray dryer [manufactured by Itamoto Giken Co., Ltd.] under stirring to obtain 67 g of white granules with an average particle diameter of about 1 mm. Furthermore, the AI included in this thing is 4.
−． 45 wt%, B was 0.3 wt%, and the elemental molar ratio was Al17B6.0.

Filling 67g of the above white granules into a mold with a diameter of 50mm, 1
The pressure-molded material to 0 kgl/cm2 was transferred to a platinum board, reacted in a Matsufuru furnace at 900°C for 2 hours, cooled slowly to room temperature, boiled with 200 ytll of IN hydrochloric acid, and then washed with water. By drying, 4.7g of white powder
I got it.

This material was identified as 9AA203/2B203 by X-ray diffraction and elemental analysis, and the fiber diameter was approximately 0.5 μm.
It was a fibrous aluminum borate with a high aspect ratio and a uniform fiber shape with a fiber length of 25 to 30 μm. Yield: 9
6% Comparative Example 1 - Same raw materials and composition as used in Example 1, namely 15 g of potassium chloride, 1 potassium tetraborate hydrate (K2 B
40v ・5 H20) 1. 5 g and sodium aluminum sulfate hydrate (NaAA (SO4)2 .], 2H20) 50.8
g [both reagents manufactured by Nacalai Tesque ■] at 200 rI
After dissolving in 1 liter of water, the water was evaporated to dryness using a rotary evaporator, and 67 g was used and treated in the same manner as in Example 1 to obtain 2.9 g of white powder.

From X-ray diffraction and elemental analysis, this material was found to be 9A1203/2B203 as in Example 1, but the fiber diameter was 0.
The fiber shape was irregular, with a fiber length of 1 μm and a fiber length of 5 to 1-0 μm, and the yield was as low as 60%.

Example 2 5% of potassium tetraborate hydrate (K2 B407 ・5H20) was added to 100 g of a 1.5% aqueous solution of potassium chloride.
49 g of aqueous solution and sodium aluminum sulfate hydrate (
40 of NaAIl(SO4)2 ・]-2T-I20)
% aqueous solution was mixed under stirring and fed to a spray dryer [manufactured by Itamoto Giken Co., Ltd.] under stirring to obtain 52 g of white granules with an average particle diameter of 1 mm.

Fill a mold with a diameter of 50 mm with 67 g of the above white granules, 5
0 kg [7 cm2] was reacted in a Matsufuru furnace at 1100°C for 3 hours, slowly cooled, and then I
4.2 g of white powder was obtained by boiling in 200 ml of N-hydrochloric acid, washing with water, heating in a furnace for 1.5 hours, and drying.

This material was determined to be 9AA'203/2B203 by X-ray diffraction and elemental analysis, and the fiber diameter was approximately 0.5
It was a fibrous aluminum borate with a fiber length of 25 to 30 μm, a uniform fiber shape, and a high aspect ratio. Yield: 94% Example 3 Add 95 g of a 20% aqueous solution of aluminum sulfate (A12 (SO4)3) to 100 g of a 20% aqueous solution of sodium chloride.
Using 23 g of a 5% aqueous solution of orthoboric acid (H2PO4), 40 g of white granules with an average particle size of 0.8 mm were obtained by spray drying in the same manner as in Example. Furthermore, A/ contained in this material is 7.46 wt%, and B is 0.5 wt%.
wt%, and the elemental molar ratio was Al/B-6.

39 g of the above white substance was filled into a mold with a diameter of 30 mm, and the following Example 1. After reacting at 900°C for 2 hours in the same manner as above, 4.7 g of white powder was obtained by pickling, water washing, oven separation, and drying.
I got it.

This material was identified as 9A1203/2B203 by X-ray diffraction and elemental analysis, and the fiber diameter was approximately 0.4.
It was a fibrous aluminum borate having a uniform fiber shape, long fibers, and a high aspect I ratio. Yield: 96% Example 4 Al2 was added to the homogeneous solution consisting of potassium chloride, potassium tetraborate and aluminum sulfate prepared in Example 1-.
0.6 g of alumina sol [manufactured by Nissan Chemical Co., Ltd.] whose O3 concentration was adjusted to 5% was added under stirring, and the same procedure as in Example 1 was carried out to obtain 4.6 g of white powder.

This product was found to be 9A1203/2B203 by X-ray diffraction and elemental analysis, and was a fibrous aluminum borate with a uniform fiber shape of about 1 μm in fiber diameter and 50 to 60 μm in fiber length, long fibers, and high aspect ratio. Yield: 94% Example 5 The whiskers made of 9A1203 2B203 obtained in Example 1 above were ground in an alumina mortar, and the powder passed through a 300 mesh sieve was stirred into the raw material mixture prepared in Example 1. 0.2g of the above mixture was added and homogeneously dispersed, and then treated in the same manner as in Example 1 to obtain 4.7g of white powder.

This material was determined to be 9AI203.2B2o3 by X-ray diffraction and elemental analysis, and the fiber diameter was approximately 1.5 μm.
It was a fibrous aluminum borate having a uniform fiber shape with a fiber length of around 70 μm, long fibers, and a high aspect ratio. Yield, 92% Test Example 1 Example 1-1 The ratio of fibrous aluminum borate obtained in Example 2 and Comparative Example 1 to thermoplastic polyurethane [manufactured by Takeda Pharmaceutical Co., Ltd.] was 30/70. When the bending strength was measured using a homogeneous mixture of the two materials, it was found that the bending strength of each of Example 1 and Example 2 was 600 kgl.
The strength of Comparative Example 1 was only 4.50 kgf/cm2.

This shows that the fibrous aluminum borate obtained by the method of the present invention has excellent reinforcing properties.

Test Example 2 The ratio of fibrous aluminum borate obtained in Examples 3 to 5 and thermoplastic polyurethane [manufactured by Takeda Pharmaceutical Company Ltd.] was 30
When the bending strength of Example 3 was measured using a homogeneous mixture of 70% and 700%
kgl/cm2, 750 kgf/ in Example 4
cm2, and the letter of Example 5 has a strength of 750 kgl/cm2.

In addition, in the whisker of Comparative Example 1, even if the amount added was increased, the bending strength did not increase but on the contrary showed a tendency to decrease.

Claims (1)

[Scope of Claims] [1] A solution or homogeneous dispersion of (1) an aluminum compound that becomes a metal oxide by heating and baking, (2) a boron compound, and (3) an alkali metal salt is spray-dried, and then This is 6
A method for producing fibrous aluminum borate, which comprises heating and firing at a temperature of 00 to 1200°C. [2] Add a solution or homogeneous dispersion of the above components (1), (2) and (3) to a solution in which fine particles of aluminum and/or boron oxide or hydroxide are homogeneously suspended. A method for producing fibrous aluminum borate, which comprises spray drying and then heating and baking the product at a temperature of 600 to 1200°C.