JP3105622B2 - Aluminum borate-based whisker aggregate and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum borate whisker aggregate and a method for producing the same. Aluminum borate whiskers are excellent in mechanical strength, chemical resistance, heat insulation, heat resistance, neutron absorption ability and electrical insulation.In addition to heat insulation, heat resistance, corrosion resistance, especially thermoplastic resin,
It is useful as a reinforcing material for organic materials such as thermosetting resins, inorganic materials such as cement, glass and various ceramics, and metal materials such as aluminum alloys, magnesium alloys and titanium alloys.

[0002]

2. Description of the Related Art Ceramic whiskers having excellent thermal and mechanical properties are roughly classified into non-oxide whiskers and oxide whiskers. Non-oxide materials generally have a high melting point (1900 ° C. or higher) and excellent heat resistance, but require adjustment of the atmosphere during production, which increases equipment and raw material costs and limits their use. Examples of non-oxide whiskers include silicon carbide and silicon nitride. On the other hand, oxides such as calcium sulfate, calcium titanate, magnesium borate and aluminum borate (JP-A-63-319)
298 and JP-A-63-319299). These oxide-based whiskers have a lower melting point than non-oxide-based whiskers (1000 to 1600 ° C.), and therefore have poor heat resistance. Raw material costs have low characteristics. Among oxide-based whiskers, aluminum borate has been shown to exhibit mechanical strength comparable to non-oxide-based whiskers when used as a reinforcing material for aluminum (Katsuaki Suganuma: New Ceramics, No. 5, p
63-69 (1990)).

[0003] Methods for producing aluminum borate whiskers having excellent mechanical strength and chemical resistance can be roughly classified into a gas phase method and a flux method using a melting agent. As a gas phase method, by passing water vapor through gaseous aluminum fluoride and boron oxide at 1000 to 1400 ° C., 4Al ₂ O ₃ .B
It is known that whiskers having a composition of ₂ O ₃ can be obtained (US Pat. No. 3,350,166).

[0004] As the other hand flux method, by 1400 ° C. heat treatment of the mixture of aluminum hydroxide with an excess of boron oxide, whiskers composition of _{3Al 2 O 3 · B 2 O} 3 and _{9Al 2 O 3 · B 2 O} 3 (US Pat. No. 3,080,242) is known. According to a report from the U.S. Department of Home Affairs Mining Bureau, a mixture of aluminum oxide, sodium tetraborate and lithium chloride was heated at 1200 ° C. to produce 2.5Al ₂ O ₃
· Whisker having a composition of B ₂ O ₃ is obtained, also by heating aluminum oxide, a mixture of sodium tetraborate and boron oxide to 1400 ° C., having the composition _{4.8Al 2 O 3 · B 2 O} 3 It is known that whiskers can be obtained (Bureau of Mines Report of Investigati)
on 6575 "(1965)).

[0005] In Japan, 9Al ₂ O ₃ · 2B whiskers and a manufacturing method thereof having a composition of ₂ O ₃ (JP 63-319298) and 2A
Whiskers having a composition of l ₂ O ₃ · B ₂ O ₃ and a method for producing the whiskers (JP-A-63-319299) are known. Further, a method of mixing a trialkali aluminum trisulfate and a boric anhydride supply component and heat-treating the mixture at 700 to 1200 ° C.
7600), a method in which aluminum sulfate as an aluminum supply component and boric anhydride supply component are heat-treated at 1000 to 1200 ° C. in the presence of an alkali metal sulfate and an alkali metal carbonate (JP-A-2-164797). Oxides, hydroxides and oxyhydroxides of at least one and aluminum sulfate, a mixture of boric anhydride supply component and alkali metal sulfate 900-1200
Heat treatment at ℃ (JP-A-2-164798), as an aluminum supply component, at least one of aluminum oxide and hydroxide, a boric anhydride supply component, at least one of alkali metal sulfates and chlorides, and sulfuric acid Heat-treating the mixture at 900 to 1200 ° C. (Japanese Patent Laid-Open No. 3-13160)
0).

[0006]

However, conventional whiskers have a simple shape, and when used as a reinforcing material for a composite material, the whisker cannot be said to have a sufficient bonding strength with the mother phase. The present inventors have conducted intensive studies on aluminum borate-based whiskers having a complicated shape, and as a result, have found an aluminum borate-based whisker aggregate having an aggregated portion of needle-like crystals that have grown radially and a method for producing the same. .

[0007]

That is, the present invention provides an aluminum borate-based whisker aggregate characterized by having an aggregate of needle-like crystals grown radially, and a whisker aggregate grown substantially symmetrically in both directions. An aluminum borate-based whisker aggregate characterized by being composed of needle-like crystals and a method for producing these.

Hereinafter, the present invention will be described in more detail. An aluminum borate-based whisker aggregate characterized by having an aggregate portion of radially grown needle-like crystals according to the present invention and needle-like crystals grown radially substantially symmetrically in both directions. The typical shape of the aluminum borate-based whisker aggregate described above is as shown in FIG. An aluminum borate-based whisker aggregate comprising a collection of radially grown needle-like crystals according to claim 1 in FIG. 1 and substantially bidirectional in both directions according to claim 2. An aluminum borate-based whisker aggregate characterized by being composed of symmetrically grown needle-like crystals is seen. The former includes an aggregate obtained by dividing the latter at the center. The antimony component-containing additive is formed as a solid solution or another structure in the aluminum borate whisker aggregate in an integrated or adhered state.

The third invention relates to a method for producing the above-mentioned aluminum borate-based whisker aggregate, which will be described in further detail below. Examples of the aluminum component-containing raw material according to the present invention include aluminum oxides such as α-type aluminum oxide, γ-type aluminum oxide and aluminum hydroxide, such as aluminum hydroxide and aluminum sulfate, such as aluminum sulfate and aluminum sulfate.
14-18 hydrates, ammonium aluminum sulfate, ammonium aluminum sulfate dodecahydrate and aluminum and alkali metal sulfates, such as potassium aluminum sulfate,
Aluminum potassium sulfate 12 hydrate, aluminum sodium sulfate, sodium aluminum sulfate 12 hydrate and aluminum nitrate such as aluminum nitrate, aluminum nitrate 9 hydrate and aluminum chloride such as aluminum chloride and aluminum chloride hexahydrate Alternatively, known salts such as aluminum oxyhydroxides, for example, boehmite, diaspore, todite, and the like, may be used alone, or two or more of them may be mixed.

[0010] Next, as a raw material containing a boron component, oxides of boron, for example, boron oxide and oxygen acids of boron, for example, orthoboronic acid (H ₃ BO ₃ ), tetraboric acid (H ₂ B ₄ O ₇ ), metaborough Known salts such as acids (HBO ₂ ) or alkali metal salts thereof such as sodium tetraborate, potassium tetraborate, sodium metaborate and alkoxide compounds of boron such as boron ethoxide (B (OC ₂ H ₅ ) ₃ ) These may be used alone or in combination of two or more.

As examples of the melting agent, alkali metal sulfates and chlorides are preferred. Specifically, lithium sulfate, sodium sulfate, potassium sulfate, lithium chloride, sodium chloride, potassium chloride and hydrates thereof may be used alone or in combination of two or more. .

The mixing ratio of the raw material containing the aluminum component, the raw material containing the boron component and the melting agent varies depending on the desired composition of the aluminum borate whisker. For example,
In the case of whiskers in which the molar ratio of Al ₂ O ₃ and B ₂ O _{3 in} the whiskers is 2: 1, the mixing ratio of the aluminum component-containing material and the boron component-containing material is determined by the ratio of aluminum to boron contained in the aluminum component-containing material. Is preferably in the range of 1: 9 to 6: 4, and the melting agent is preferably in the range of 10 to 95% by weight based on the total weight. Also, Al ₂ O ₃ and B ₂ O ₃
In the case of a whisker having a molar ratio of 9: 2, the mixing ratio of the aluminum component-containing material and the boron component-containing material is such that the molar ratio of aluminum to boron contained in the aluminum component-containing material is 1: 4 to 9: 1. Preferably, the melting agent is in the range of 10 to 95% by weight of the total weight.

The additive containing an antimony component is not particularly limited as long as it contains antimony, and examples thereof include simple metals, various compounds, solid solutions and composite compounds. Specifically, organic acid salts such as oxides, hydroxides, carbonates, chlorides, nitrates, sulfates, phosphates and oxalates, formates, acetates, and tartaric acids containing these components and Alkoxides, sulfides and the like can be mentioned. Examples include metal antimony, oxides such as Sb ₂ O ₃ , chlorides such as SbCl ₃ and SbCl ₅ , sulfides such as Sb ₂ S _{3 and the} like.

The amount of the antimony component-containing additive varies depending on the desired composition of the whisker, and is not particularly limited. However, it is preferable to add the additive in an amount of 50 mol% or less based on the total number of moles of the constituent B and Al components. . This is because the addition effect does not improve even if it exceeds 50 mol%. Here, the number of moles of the additive component is expressed in terms of metal.For example, when Sb ₂ O ₃ is used as an additive material for the S b component, 1 mole of Sb ₂ O ₃ is used as an additive component for 2 moles. Converted.

The method of mixing the raw material containing the aluminum component, the raw material containing the boron component, the melting agent and the additive containing the antimony component can be carried out using a usual mixer, ball mill, vibration mill or the like. It is preferable to uniformly mix in any method.

The heat treatment temperature varies depending on the desired composition of the aluminum borate whisker. For example, 2Al ₂ O ₃
· B In ₂ O ₃ composition whisker, temperature 600 ° C. to 1000 ° C. is preferred. This temperature is insufficient reaction is less than 600 ° C., also in whiskers that generated it exceeds 1000 ° C. B ₂
This is not preferable because a decomposition reaction occurs in which the O ₃ component is gradually eliminated. Whisker with 9Al ₂ O ₃・ 2B ₂ O ₃ composition, temperature 900 ℃
~ 1200 ° C is preferred. This is 2A for temperatures below 900 ° C
This is because whiskers with l ₂ O ₃ and B ₂ O ₃ compositions are preferentially generated or raw materials remain unreacted.
Exceeding the temperature is not preferable because a decomposition reaction occurs in which the B ₂ O ₃ component in the whisker formed gradually desorbs. 4.8Al ₂ O ₃・
The whiskers of the amount of B ₂ O ₃ less composition, such as B ₂ O ₃ and _{9Al 2 O 3 · B 2 O} 3, is preferably a high temperature of about 1400 ° C..

In order to isolate aluminum borate-based whiskers from a reaction product containing a melting agent, several tens of hot hydrochloric acid, hot sulfuric acid, hot nitric acid or a mixture thereof, hot caustic soda or hot water is used. After removing the melting agent and other water-soluble substances, wash thoroughly with water. If there is a water-insoluble by-product, the whisker may be separated from the residue by a treatment such as decantation and then sufficiently washed with water. In addition, when the obtained antimony component-containing additive used when the obtained aluminum borate-based whisker aggregate is applied as a reinforcing material for a composite material, which is one of the applications, has a good effect in the composite material, for example, the plastics When the antimony compound has a flame retardant effect and an ultraviolet ray shielding effect, it is preferable to remove only the melting agent by washing only with hot water in order to positively leave the additive component.

[0018]

Embodiments of the present invention will be specifically described below. [Examples 1 to 5] As shown in Table 1, an aluminum component-containing raw material (aluminum sulfate powder: Al ₂ (SO ₄ ) ₃ ), a boron component-containing raw material (orthoboric acid powder: H ₃ BO ₃ ), and a melting agent (sulfuric acid) Potassium powder: K ₂ SO ₄ ) and an antimony component-containing additive (antimony oxide powder: Sb ₂ O ₃ ) were weighed.
The mol% of the antimony component shown in Table 1 is based on the total number of moles of the B and Al components constituting the whisker.
The amount added in the antimony component-containing additive is shown in terms of mol% of antimony in terms of metal. After weighing each raw material, they were mixed for 20 hours using a ball mill. The mixture was put into an alumina crucible and heat-treated in air at 1120 ° C. for 3 hours. The reaction product was cooled, hydrochloric acid was added and the mixture was boiled. After removing the melting agent and other water-soluble substances, the reaction product was sufficiently washed with water and dried.

[0019]

[Table 1]

The whisker aggregates obtained in Examples 1 to 5 are all white, and the crystal structure analysis by X-ray diffraction reveals that the Al ₁₈ B ₄ O ₃₃ (9Al ₂ O ₃ .2B ₂ O ₃ ) crystal structure is identified. Was done. In addition, a small amount of AlSbO ₄ was identified. The composition of the obtained whisker aggregate was analyzed by ICP emission spectroscopy (using ICPA-575 manufactured by Nippon Jarrell-Ash Co.). Its analysis limit is about 1 to 10 ppm. The composition analysis results are expressed by the value in terms of Al ₂ O ₃ and B ₂ O ₃ Al ₂ O ₃ and B ₂
The total amount of O ₃ is shown to be 100 mol%. In addition, mol% of the analysis value of the antimony component in the additive is Al ₂ O ₃ and B
_{Based on} the total number of moles of the B and Al components calculated based on the analysis value of ₂ O _3, the results are shown in terms of mole% of the antimony component in terms of metal. Table 1 shows the size (length in the long axis direction) of the whisker aggregate measured by scanning electron microscope observation. FIG. 1 shows a scanning electron micrograph of the whisker aggregate obtained in Example 2. The whisker aggregates obtained in the other examples were substantially similar in shape to those shown in FIG. 1 and differed only in size (length in the long axis direction).

[Comparative Example] A treatment was performed under the same conditions as in Example 1 except that antimony was not added. The obtained whiskers were white, and as a result of crystal structure analysis by X-ray diffraction, an Al ₁₈ B ₄ O ₃₃ (9Al ₂ O ₃ .2B ₂ O ₃ ) crystal structure was identified. As a result of observation by a scanning electron microscope, the whiskers were 0.5 to 1 μm in thickness and 3 to 20 μm in length, and were in the form of ordinary independent needles. No whisker aggregates were found and no whisker aggregates composed of needle-like crystals that grew radially substantially symmetrically in both directions.

[0022]

The present invention is characterized in that it has an aggregate of radially grown needle-like crystals or is composed of radially grown needle-like crystals substantially symmetrically in both directions. Aluminum borate-based whisker aggregates with a new shape.Since it is a complex shape, it has the characteristic of being excellent in bonding with the base material as a reinforcing material for composite materials, and manufacturing new composite materials as a new reinforcing material It is also applied to
Further, according to the method of the present invention, the aluminum borate-based whisker aggregate can be produced with high production efficiency by using a specific additive.

[Brief description of the drawings]

FIG . 1 is a photograph (particle structure is shown) instead of a drawing.
2 ) is a scanning electron micrograph of the whiskers obtained in Example 2. Note that the portion on the underlying powder is a carbon paste used when preparing an electron microscope sample.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-5-201798 (JP, A) JP-A-3-54200 (JP, A) JP-A-63-319299 (JP, A) (58) Survey Field (Int. Cl. ⁷ , DB name) C30B 1/00-35/00 CA (STN) JICST file (JOIS)

Claims (3)

(57) [Claims] 1. An aluminum borate-based whisker aggregate comprising an aggregate of radially grown needle-like crystals. 2. An aluminum borate-based whisker aggregate comprising needle-like crystals grown radially substantially symmetrically in both directions. 3. The aluminum borate whisker according to claim 1, wherein a mixture of the aluminum component-containing raw material, the boron component-containing raw material, the melting agent and the antimony component-containing additive is heat-treated. Manufacturing method of aggregate.