JP2791460B2 - Potassium aluminate titanate whisker 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 a potassium aluminate whisker and a method for producing the same.

The whisker of the present invention is excellent in reinforcing property, heat resistance, heat insulating property and chemical resistance, and is used for reinforcing material such as thermosetting resin, thermoplastic resin, cement, metal, ceramics, heat resistant material and heat insulating material. In addition, it is useful as a corrosion resistant material.

[0003]

2. Description of the Related Art In recent years, with the advancement and rapid progress of high-tech technology, various types of composite materials as new materials have been researched and developed as advanced materials. Whisker is known as a material that meets the required characteristics because of the demand for wear resistance and the like. It is said that the whisker is usually made of a fine single crystal and has almost no transition, no defect or the like in the crystal. Therefore, it is said that the mechanical strength of the whisker reaches tens to hundreds of times as compared with a polycrystal having the same composition. One of these whiskers is potassium titanate fiber, which has chemical resistance, heat resistance, heat insulation,
It is known as a whisker that is relatively excellent in friction resistance and can be manufactured at low cost.

The treatment of alkali titanate fibers with hydrated aluminum is disclosed in JP-B-43-8936.
And reported by the publication No.
The alkali titanate fiber is stabilized against shrinkage at 0 to 1200 ° C.

On the other hand, the existence of potassium aluminate titanate has been clarified. For example, powders of potassium carbonate, aluminum oxide and titanium oxide are ground and mixed, and 1200
Calcination for 3 hours at room temperature, followed by grinding and mixing again.
For about 20 hours to obtain K _2.0 Al _2.0 Ti ₆
A powdery potassium aluminate titanate having a composition of O _{16 to} K _2.4 Al _2.4 Ti _5.6 O ₁₆ has been produced (Japanese Patent Publication No. 62-41176). Further, starting from a raw material of potassium carbonate, aluminum oxide and titanium oxide and a mixed powder of potassium molybdate and molybdenum oxide as a flux raw material, the mixture is calcined at 1300 ° C. for about 4 hours and then gradually cooled to around 800 ° C. Maximum diameter 1m
m, 10 mm long K _2-x Al _2-x Ti _6-x O ₁₆ (0 <
x ≦ 1), and columnar single crystal potassium aluminate titanate has been produced (Japanese Patent Publication No. 58-12236).
No.). Further, a phase diagram of potassium aluminate under normal pressure has already been reported, and the relationship between the composition ratio of potassium aluminate and the lattice constant obtained by X-ray diffraction has been shown [H. Ohsato, J.Cer
am. Soc. Jpn, 100 [2] 148-151 (1992)].

However, to date, no attempt has been made to synthesize whiskers of potassium aluminate and whiskers having pores therein.

[0007]

Problems to be Solved by the Invention Chemical resistance, heat resistance,
Potassium titanate fiber, which has relatively excellent heat insulation and friction resistance, often elutes an alkali component. Particularly, when the potassium titanate fiber is heated to a high temperature, desorption of the potassium component and generation of titanium oxide occur. Inevitable.
The elution or elimination of the potassium component and the formation of titanium oxide not only cause the contamination of the matrix with impurities, but also cause the decomposition of the matrix component, the formation of by-products, and the unevenness of the potassium titanate surface. Further, desorption of the potassium component at a high temperature causes deterioration of the fiber shape, and as a result, it is impossible to exhibit sufficient reinforcing properties.

To date, powdery crystals and columnar single crystals of potassium aluminate have been obtained, but potassium aluminate whiskers and whiskers having pores therein have not been obtained. A whisker is defined as a single crystal having a cross-sectional area of 7.9 × 10 ⁻⁵ in ² or less and a length of 10 times or more the average diameter of the cross-section. Whiskers are needle-shaped single crystals with a high aspect ratio.Because they are small crystals, there are almost no transitions or defects in the crystals, and their mechanical strength is several tens to several hundred times higher than that of polycrystals of the same composition. The feature is to reach. However, it is a well-known fact that an increase in the shape of the whiskers causes an increase in the number of transitions and defects in the crystal, and the mechanical strength decreases accordingly.

Accordingly, an object of the present invention is to provide a potassium aluminate whisker excellent in heat resistance, heat insulation and chemical resistance, having a fine fiber diameter and excellent reinforcement, and a method for producing the same.

[0010]

Means for Solving the Problems In view of such circumstances, the present inventors have conducted intensive studies, and as a result, have found that an aluminum compound as an aluminum supply component is changed to a potassium supply component and potassium titanate as a titanium supply component. It has been found that the above object can be achieved by coating the surface of the fiber and reacting at a predetermined temperature in the presence of a melting agent.

That is, according to the present invention, the general formula K _x Al
_A potassium aluminate whisker having a composition represented by _x Ti _8-x O ₁₆ (0.8 ≦ x ≦ 2.5) and having 0 to 70% by volume of pores inside the fiber is provided.

Further, according to the present invention, an aluminum compound is coated on the surface of a potassium titanate fiber, and is heated to 900 ° C. to 1300 ° C. in the presence of at least one kind of a flux selected from alkali metal chlorides and alkali metal sulfates. A method for producing a potassium aluminate whisker, characterized in that the whisker is heated to a temperature of ° C. and reacted and grown.

Hereinafter, the present invention will be described in detail.

The potassium aluminate titanate whisker of the present invention is obtained by reacting an aluminum supply component, a potassium supply component and a titanium supply component in the presence of a melting agent. One feature is that the components are supplied by potassium titanate fibers coated with an aluminum compound. As a result, the aluminum compound coated on the surface of the potassium titanate fiber reacts in a state where each component is present in the closest vicinity, is converted into active aluminum oxide at the time of growing, and the low-reactivity potassium titanate fiber and It has the effect of forming a whisker shape at a relatively low firing temperature without any problem of remaining reactive alumina.

One of the features of the present invention is that the reaction is carried out in the presence of a melting agent, thereby preventing the potassium component in the potassium titanate fiber from being eliminated. An isolated potassium aluminate titanate whisker containing no polycrystalline fibers is formed.

In the present invention, the composition of the potassium supply component and the potassium titanate fiber serving as the titanium supply component are not particularly limited, and for example, the general formula aK _{2
O · TiO 2 · mH 2 O} (0 <a ≦ 1,0 ≦ m ≦ 1
And potassium titanate whiskers represented by 0). The shape of the potassium titanate whisker has a fiber diameter of 0.01 to 5 μm and a fiber length of 3 to 300 μm, preferably a fiber diameter of 0.1 to 3 μm, and a fiber length of 5 to 200 μm. Ten or more can be used. In a potassium titanate fiber having a fiber diameter of 0.01 μm or less and a fiber length of 3 μm or less, its cohesiveness is large,
The disadvantage is that the product, potassium aluminate titanate, is synthesized in the form of aggregates that cannot be isolated. Further, since potassium titanate fibers having a fiber diameter of 5 μm or more and a fiber length of 300 μm or more have low surface activity and are not uniformly coated with an aluminum compound, aluminum oxide and potassium titanate are present as unreacted substances in the synthetic powder. May be mixed.

The potassium titanate fiber whose surface is coated with an aluminum compound is, for example, at least one selected from the group consisting of aluminum sulfates, halides, nitrates, hydroxides and alcoholates, and potassium titanate. Or at least one selected from the group consisting of aluminum sulfates, halides, nitrates, hydroxides and alcoholates with an alkali metal hydroxide, an alkali metal carbonate, and an alkali metal aluminate It is obtained by, for example, reacting with at least one selected from the group consisting of a salt, an ammonium carbonate and an ammonium hydroxide to deposit on a potassium titanate fiber surface.

The aluminum sulfate used here includes, for example, monoaluminum sulfate. In this case, if necessary, at least one of aluminum halides, nitrates, hydroxides, and alcoholates may be used in combination. Examples of the aluminum halides, nitrates, hydroxides, and alcoholates include, for example, aluminum chloride, aluminum nitrate, aluminum hydroxide, and aluminum alcoholate, and are not particularly limited as long as they are water-soluble. .

Further, as the hydroxide of aluminum,
For example, aluminum hydroxide and the like can be mentioned. Examples of the alkali metal hydroxide include sodium hydroxide and potassium hydroxide. Examples of the alkali metal carbonate include sodium carbonate, sodium hydrogen carbonate, potassium carbonate and the like. Examples of the alkali metal aluminate include sodium aluminate and potassium aluminate. Examples of the ammonium carbonate include ammonium carbonate and ammonium bicarbonate. Examples of the ammonium hydroxide include ammonium hydroxide. In the present invention, even those other than the above can be used without particular limitation as long as they are water-soluble.

In the present invention, it is preferred that the aluminum compound is coated on potassium titanate fibers dispersed in water. At this time, it is preferable to coat the titanium oxide of the potassium titanate fiber with aluminum oxide in a molar ratio of 1: 3 to 1:18 in a molar ratio. The above reaction conditions are usually 5
~ 80 ° C, preferably 1-5 at a temperature of 10-50 ° C
About an hour. By this reaction, a coating of an aluminum compound is obtained on the surface of the potassium titanate fiber. Next, this is washed with water or the like as necessary, and then dried to obtain a potassium titanate fiber whose surface is coated with an aluminum compound.

Examples of the melting agent include alkali metal chlorides such as potassium chloride and sodium chloride and alkali metal sulfates such as potassium sulfate and sodium sulfate. These may be used alone or as a mixture of two or more. Is also good. The melting agent may be added after the particle size is reduced by a pulverizer such as a jet mill if necessary. Alternatively, the aluminum compound may be dissolved when coated on the surface of the potassium titanate fiber and dispersed in an aqueous solution.

According to the method of the present invention, the above-mentioned potassium supply component and potassium titanate fiber which is a titanium supply component,
An aluminum compound as an aluminum supply component is mixed in a molar ratio of aluminum oxide to titanium oxide of 1: 3 to 1:18.
, And the flux is further added in an amount of 50 to 9 based on the total weight.
By adding in an amount of 0% by weight and reacting at a temperature in the range of 900 to 1300 ° C. for 10 minutes to 10 hours, potassium aluminate titanate whiskers can be produced. At this time, if the heating temperature is lower than 900 ° C., the raw material remains unreacted, so that it is difficult to obtain a whisker of potassium aluminate titanate single phase. If it exceeds 1300 ° C., fusion between whiskers, polycrystallization and a decrease in aspect ratio tend to occur, which is not preferable.

When a potassium aluminate titanate whisker having pores in the crystal is produced, the whisker is allowed to react and grow at a predetermined temperature, and is then cooled to about 800 ° C. at a cooling rate of 10 ° C./min or more. Or natural cooling or rapid cooling by water cooling or the like. In this case, the volume ratio of the pores in the crystal can be controlled by the firing temperature and the cooling rate.
Further, when generating potassium aluminate titanate whiskers containing no pores in the crystal, the reaction is carried out at a predetermined temperature.
After the growth, it may be gradually cooled to around 800 ° C. at a cooling rate of 10 ° C./min or less.

In isolating the potassium aluminate titanate whiskers produced by heating and calcining, the water-soluble components are first dissolved in hot water, warm water or the like, or, if necessary, diluted with an aqueous acid solution, and separated by filtration. It is preferable to wash, dry, and classify as necessary, thus obtaining fine potassium titanate aluminate whiskers having a uniform fiber shape.

The potassium aluminate titanate isolated as described above has a fiber diameter of 0.1 to 10 μm, and a fiber diameter of 5 to 30 μm.
It is a needle-shaped single crystal having a fiber length of 0 μm and an aspect ratio of 10 to 100, and has excellent reinforcing properties, heat resistance, heat insulation properties, and chemical resistance, thermosetting resin, thermoplastic resin, cement, metal, It can be suitably used as a corrosion-resistant material in addition to a reinforcing material such as ceramics, a heat-resistant material, and a heat-insulating material.

[0026]

The present invention will be specifically described below with reference to examples.

Example 1 Potassium hexatitanate fiber (TISM, manufactured by Otsuka Chemical Co., Ltd.)
After dispersing 200 g of (O-N) in 2.5 liters of water, 228.4 g of ammonium bicarbonate was added, and 188.5 g of aluminum chloride hexahydrate was dissolved in water to make 400 ml. In addition, it was reacted. During this time, the reaction was continued for 3 hours while maintaining the reaction temperature at 30 to 40 ° C. After the completion of the reaction, the pH of the reaction solution was 7.4. Next, the reaction product was filtered, washed with water to remove impurities, and dried at 80 ° C. to obtain 263.0 g of a reaction dry product. As a result of analyzing the dried product, potassium hexatitanate was coated with an aluminum hydroxide compound containing 15.1% in terms of aluminum oxide, 0.003% as a sulfate, and 8.09% in ignition loss. Was.

Further, potassium sulfate (K ₂ SO ₄ ) as a flux raw material was sufficiently mixed with the potassium hexatitanate fiber coated with the aluminum hydroxide compound at a weight ratio of 1: 4 in a mortar, followed by pressure molding. Then, it was baked at 1100 ° C. for 3 hours. After the firing, the product was cooled to a temperature of 800 ° C. at a rate of 1 ° C./minute, and then cooled to room temperature by furnace cooling to obtain a fired product. The fired product was boiled in water, washed with water, separated by filtration, and dried to obtain a pale yellow powder. This was found to be K _2.0 Al _2.0 Ti _6.0 O ₁₆ from X-ray diffraction and elemental analysis.
A potassium titanate whisker having a fiber diameter of 1.0 μm and a fiber length of 20 μm was obtained. FIG. 1 shows a transmission image of the potassium aluminate whisker obtained as described above taken by a transmission electron microscope.

Further, the above-mentioned cooling after firing is performed under the same conditions except that it is taken out of the furnace and quenched in cold water.
A pale yellow powder was obtained. This was found to be K _2.0 Al _2.0 Ti _6.0 O ₁₆ by X-ray diffraction and elemental analysis, and had a fiber diameter of 1.0 μm.
m, fiber length 20μm, about 50% by volume in crystal relative to total volume
Thus, a potassium titanate whisker having the following pores was obtained. FIGS. 2 and 3 show a transmission image of the potassium aluminate titanate whisker having pores obtained as described above taken by a transmission electron microscope and a diffraction peak by a powder X-ray diffractometer.

Example 2 Potassium 8-titanate fiber (TISM, manufactured by Otsuka Chemical Co., Ltd.)
(OD) After dispersing 200 g of water in 2.5 liters of water, 47.3 g of aluminum sulfate 18 hydrate was dissolved in water to obtain 1
10 ml of the solution and sodium aluminate (Na ₂
O.Al ₂ O ₃ ) 16.6 g and sodium hydroxide 5.2
While stirring the solution prepared by dissolving g in a volume of 100 ml at a temperature of 20 to 30 ° C., the two solutions were slowly added so that the reaction solution showed a neutral range of pH 7 to 9, and the reaction was carried out for 5 hours. After the completion of the reaction, the pH of the reaction solution was 7.2. Next, the reaction product was filtered, washed with water to remove impurities, and dried at 90 ° C. to obtain 238.8 g of a reaction dry product. As a result of analyzing the dried product, potassium octitanate was coated with a basic aluminum sulfate compound containing 7.36% in terms of aluminum oxide, 3.31% as a sulfate, and a loss on ignition of 5.19%. I was

Furthermore the sodium sulfate as a flux material in 8 potassium titanate fibers coated with a basic aluminum sulphate compounds (Na ₂ SO ₄₎ and potassium sulfate (K ₂ SO ₄₎ in a molar ratio of 1: added at 3 The mixed powder thus obtained was sufficiently mixed in a mortar at a weight ratio of 1: 9, and then molded under pressure and baked at 1200 ° C. for 3 hours. After the firing, the product was cooled to a temperature of 800 ° C. at a rate of 1 ° C./minute, and then cooled to room temperature by furnace cooling to obtain a fired product. The fired product was boiled in water, washed with water, separated by filtration, and dried to obtain a pale yellow powder. It was found to be K _1.0 Al _{1.0 by} X-ray diffraction and elemental analysis.
Ti _7.0 O ₁₆ , fiber diameter 1.5 μm, fiber length 30 μ
m of potassium aluminate whisker was obtained.

Example 3 Potassium tetratitanate monohydrate fiber (manufactured by Otsuka Chemical Co., Ltd., T
(ISMO-L) 200 g was dispersed in 2.5 liters of water, and a solution obtained by dissolving 237.2 g of aluminum sulfate 18 hydrate in water to make 650 ml was slowly added with stirring to obtain a reaction mixture. During this time, the reaction temperature was set to 10 to 20.
The reaction is carried out for 3 hours while maintaining the temperature. After completion of the reaction, p
H was 4.2. Take a part from the above reaction solution,
The solution was filtered, washed with water to remove impurities, dried at 80 ° C., and analyzed. As a result, potassium tetratitanate monohydrate fiber was converted to aluminum oxide at 16.84% and sulfate as 5.74%. And an aluminum sulfate compound containing a loss on ignition of 7.68%. Further, potassium chloride (K) used as a flux raw material is added to the above reaction mixture.
Cl) at a weight ratio of 1: 2 to the dried product and wet-mixing. The combined solution is dried by a spray-dry method, and potassium tetratitanate monohydrate 1 coated with an aluminum sulfate compound and containing potassium chloride as a mixture.
266 g were obtained.

This mixture was molded under pressure and baked at 950 ° C. for 5 hours. After the firing, the product was cooled to a temperature of 800 ° C. at a rate of 1 ° C./minute, and then cooled to room temperature by furnace cooling to obtain a fired product.

The fired product was boiled in water, washed with water, separated by filtration, and dried to obtain a pale yellow powder. This was found to be K _2.4 Al _2.4 Ti _5.6 O ₁₆ by X-ray diffraction and elemental analysis, and a potassium aluminate whisker having a fiber diameter of 1.0 μm and a fiber length of 25 μm was obtained.

Example 4 200 g of potassium hexatitanate long fiber (manufactured by Otsuka Chemical Co., Ltd., fiber diameter 1.5 μm, fiber length 200 μm), 200 g of potassium hexatitanate short fiber (manufactured by Otsuka Chemical Co., Ltd., fiber diameter 0.1 mm) 1 μm
200 g of each fiber (3 μm in fiber length) was dispersed in 2.5 liters of water, and then 114.9 g of aluminum sulfate 18 hydrate.
Was dissolved in water to make 320 ml.
Add slowly with stirring at a temperature of ３０30 ° C. Further, sodium aluminate (Na ₂ O · Al ₂ O ₃ ) 3
A solution prepared by dissolving 8.4 g and sodium hydroxide 11.8 g in water to make a volume of 255 ml was slowly added to each at a temperature of 20 to 30 ° C. while stirring, and the reaction was carried out for 2 hours. After the completion of the reaction, the pH of the reaction solution was 7.6 and 7.
It was 5. Next, the reaction product was filtered, washed with water to remove impurities, and dried at 80 ° C. to obtain 274.1 g and 274.9 g of a reaction dry product, respectively. As a result of analyzing the dried product, potassium hexatitanate long fiber and short fiber were 15.10% and 1%, respectively, as aluminum oxide.
It was coated with a basic aluminum sulfate compound containing 5.11%, 6.15% and 6.26% as sulfates, and 5.48% and 5.79% of loss on ignition.

Further, potassium hexatitanate long fiber or potassium hexatitanate short fiber coated with the basic aluminum sulfate compound is used as a flux material in advance by a jet pulverizer to adjust the particle size of potassium sulfate (K ₂ ) to 30 μm or less. SO ₄ ) were further mixed in a mortar at a weight ratio of 1: 4, then molded under pressure and baked at 1100 ° C. for 3 hours. After firing, the product was cooled to a temperature of 800 ° C. at a rate of 100 ° C./min, and then cooled to room temperature by furnace cooling to obtain two types of fired products. The fired product is boiled in water, washed with water, separated by filtration,
By drying, a pale yellow powder was obtained. This is X
From line diffraction and elemental analysis, K _2.0 Al _2.0 Ti _6.0 O
₁₆ for each total volume of 2.0 μm, 0.2 μm, 300 μm, and 6 μm in fiber diameter.
A potassium titanate aluminate whisker having 0% by volume of pores was obtained.

Comparative Example Each powder of potassium carbonate, aluminum oxide and titanium oxide was mixed at a molar ratio of 4: 4: 6. Further, powders of potassium molybdate and molybdenum oxide were mixed at a molar ratio of 1: 0.5 as flux raw materials. These two powders are (K ₂ CO ₃ ) _4. (Al ₂ O ₃ ) in mol%.
₄・ (TiO ₂ ) ₆ : (K ₂ MoO ₄ ) ₁・ (Mo
O ₃ ) _{0.5 was} mixed at a ratio of 20:80 to obtain a starting material. This mixed powder was filled in a platinum crucible and heated and reacted at 1300 ° C. for 4 hours, and then gradually cooled at a rate of 4 ° C./hour to around 800 ° C., then taken out of the electric furnace and allowed to cool to room temperature. The fired product was boiled in water, washed with water, separated by filtration, and dried to obtain a pale yellow powder. This is X-ray diffraction,
From elemental analysis, it was K _2.6 Al _2.6 Ti _5.4 O ₁₆ , and was columnar crystals of potassium aluminate titanate having a fiber diameter of 0.3 to 1 mm and a fiber length of 5 to 10 mm.

[Brief description of the drawings]

FIG. 1 is a transmission image of a potassium aluminate whisker obtained in Example 1 taken with a transmission electron microscope.

FIG. 2 is a transmission image of a potassium aluminate titanate whisker having pores obtained in Example 1 taken by a transmission electron microscope.

FIG. 3 is a diffraction peak of the potassium aluminate titanate whisker having pores obtained in Example 1 measured by a powder X-ray diffractometer.

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Toshihiro Kamewa 202 Maehama, Kokuwajima, Nadu-cho, Naruto City, Tokushima Prefecture Reference JP-A-63-210026 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C30B 1/00-35/00

Claims (4)

(57) [Claims] 1. The compound of the general formula K _x Al _x Ti _8-x O ₁₆ (0.
8 ≦ x ≦ 2.5) A potassium titanate whisker having a composition represented by the formula: 2. Fiber diameter of 0.1 to 10 μm, 5 to 300
The whisker of claim 1 having a fiber length of μm and an aspect ratio of 10-100. 3. The whisker according to claim 1, which has 0 to 70% by volume of pores inside the fiber. 4. The method of claim 1, wherein the potassium titanate fiber whose surface is coated with an aluminum compound is heated at 900 to 1300 ° C. in the presence of at least one kind of a flux selected from alkali metal chlorides and alkali metal sulfates. A method for producing a potassium titanate whisker, comprising reacting and growing by heating to a temperature.