JPH0522650B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing potassium titanate fibers by a melting method.

[Conventional technology]

Potassium hexatitanate (K ₂ O・6TiO ₂ ) fiber,
Potassium titanate fibers, typified by potassium tetratitanate (K ₂ O.4TiO ₂ ) fibers, are synthetic inorganic fibers with excellent heat resistance, abrasion resistance, reinforcing properties, and the like.

A typical manufacturing method is known as the melting method (Japanese Patent Publication No. 54-19239,
58-158688). In the melting method, a titanium compound that becomes titanium dioxide (TiO ₂ ) when heated and a potassium compound that becomes potassium oxide (K ₂ O) when heated are mixed so that the molar ratio of TiO ₂ /K ₂ O is approximately 2. The process of heating and melting the raw material mixture using the mixed mixture as a raw material, pouring the heated melt into a cooling mold and solidifying it in one direction at a constant cooling rate, produces a crystalline material with a layered structure as a primary phase fiber. A cooling solidification step to obtain a fiber mass, which is an aggregate of potassium dititanate (K ₂ O.2TiO ₂ ) fibers, followed by washing the fiber mass with water and injecting K ⁺ until the molar ratio of TiO ₂ /K ₂ O becomes approximately 6. Water washing to elute ions (dealkalization)
The method includes a step of drying and heat-treating the hydrated potassium titanate fibers recovered through a water-washing step, and a step of further performing potassium removal treatment and heat treatment if desired.

[Problem that the invention seeks to solve]

The conventional production method described above requires a step of washing the primary phase fiber mass with water to elute K ⁺ ions until the TiO ₂ /K ₂ O molar ratio becomes approximately 6, resulting in loss of potassium content and The yield decreases accordingly.

In addition, the obtained potassium titanate fibers generally have a large fiber diameter of about 10 to 30 μm, and the fiber morphology (thickness and length) is irregular and lacks homogeneity. This is made by unidirectionally solidifying the heated melt in a cooling mold to form the primary phase potassium dititanate fiber (K ₂ O.
The cooling rate when generating 2TiO ₂ ) differs between the parts that are in contact with the inside of the mold and the parts that are not.
This is because the morphology of the initial phase fibers becomes irregular, and the variation in the morphology of the initial phase fibers has a strong influence on the morphology of the product fibers (potassium tetratitanate fiber, potassium hexatitanate fiber, etc.) obtained thereafter. Therefore, in order to obtain potassium titanate fibers with a small fiber diameter and excellent homogeneity, it is necessary to precisely control the cooling rate in the step of cooling and solidifying the heated melt. However, it is extremely difficult to precisely control the cooling rate of heated molten material in mass production and continuous production.

The present invention aims to provide an improved manufacturing method to solve the problems in the conventional methods described above.

Means and effects for solving the problems] The method for producing potassium titanate fibers according to the present invention includes: a titanium compound that becomes titanium dioxide (TiO ₂ ) when heated; and a potassium compound that becomes potassium oxide (K ₂ O) when heated. and the molar ratio of TiO ₂ /K ₂ O is
A heated melt of a mixture blended so that the ratio is 1.5 to 2.5 is rapidly cooled to obtain an amorphous solidified product, and titanium dioxide is added to the amorphous solidified product.
The method is characterized in that TiO ₂ /K ₂ O is added at a molar ratio of 3 to 6 to form a uniform powder mixture, and then the powder mixture is subjected to a firing treatment to grow potassium titanate fibers.

In the method of the present invention, TiO ₂ /K ₂ O in the raw material mixture
The molar ratio of 1.5 to 2.5 is the same as that of the conventional method.
While adjusting the TiO 2 /K 2 O molar ratio to a low value, by adding titanium dioxide to the solidified product obtained by rapidly cooling the melt, the value of the TiO ₂ /K ₂ O molar ratio can be adjusted to a value suitable for the formation of potassium titanate fibers. By increasing the amount of potassium to the required level, the loss of potassium content and the resulting decrease in yield, which was required in the conventional method where the molar ratio was adjusted by depotassium treatment, was eliminated, and the theoretical yield of fibers was reduced. be enhanced.

In addition, as another method to avoid the loss of potassium content due to the depotassium treatment, it is possible to increase the molar ratio of TiO ₂ /K ₂ O in the starting material mixture to the level required for fiber formation. ₂ /
If the molar ratio of K ₂ O is increased to such a high value, the melting point will rise to about 1250℃ or higher, which will lead to significant melting damage in the melting furnace, which will not only greatly reduce the durability of the melting furnace, but also cause melting Since the furnace material mixes into the melt and contaminates the melt, the quality of the obtained potassium titanate fibers deteriorates. In the present invention, the starting materials are
Since the molar ratio of TiO ₂ /K ₂ O is adjusted low,
Melting can be carried out at a heating temperature of about 950 to 1100°C, so there is no increase in the amount of melt damage to the furnace material or the contamination of the melt.

Furthermore, the method of the present invention differs from the conventional method in which potassium dititanate fibers are immediately produced from the melt by unidirectional solidification of the melt, by rapidly cooling the melt and once turning it into an amorphous solidified product. We decided to add titanium dioxide to this mixture to make a mixture, and then grow fibers from the pulverized product.
Compared to conventional methods, fibers with finer diameter, longer length, and greater homogeneity can be obtained. The fiber diameter and fiber length are
Although it varies slightly depending on the molar ratio of TiO ₂ /K ₂ O in the starting material, the fiber diameter is generally 0.2 to 1.0 μm and the fiber length is 1 to 20 μm.

According to the method of the present invention, the TiO ₂ /
Depending on the molar ratio of K ₂ O, potassium titanate fibers with different compositions and structures can be obtained, and if desired, the fibers can be subjected to a secondary treatment consisting of depotassium treatment and calcination treatment, thereby producing potassium titanate fibers with different compositions and structures. Can be converted into potassium titanate fiber.

Hereinafter, the method of the present invention will be explained in order of steps.

As the titanium compound that becomes titanium dioxide by heating, highly purified titanium oxide, synthetic rutin, titanium slag, natural rutile sand, natural anatase sand, etc. are used. The potassium compound added to the above titanium compound is typically potassium carbonate (K ₂ CO ₃ ), and in addition, hydroxide,
Nitrates and the like can also be used.

The mixing ratio of titanium compound and potassium compound is
The molar ratio of TiO ₂ /K ₂ O is suitably in the range of 1.5 to 2.5, and the heating and melting can be performed at a temperature of about 950 to 1100°C.

The above mixture is heated and melted in a melting furnace to produce a molten material, and then the molten material is subjected to a rapid cooling treatment (e.g.
By subjecting it to a cooling rate of 10 ⁶ °C/sec or more,
Preventing the formation of potassium dititanate crystals and obtaining an amorphous solidified product. The quenching treatment is performed, for example, by a twin roll method. A foil-like amorphous solidified material can be efficiently obtained by flowing the melt into the gap between the twin rolls while rotating the metal twin rolls at high speed.

After obtaining an amorphous solidified product by the above rapid cooling treatment,
This is mixed with titanium dioxide (eg, highly purified titanium oxide powder). At this time, the mixture
The mixing ratio of the amorphous solidified material and titanium dioxide is adjusted so that the molar ratio of TiO ₂ /K ₂ O is 3 to 6. By setting the above molar ratio to 3 to 6, it becomes possible to produce fibers with different compositions and structures, such as potassium tetratitanate fibers, potassium hexatitanate fibers, or mixed fibers thereof.

The amorphous solidified material and titanium dioxide are mixed and made into a uniform powder mixture by a pulverizing means such as a disk mill, and then the powder mixture is subjected to a firing treatment. Although the particle size of the powder is not particularly limited, the finer the particle, the better in order to increase the yield of fibers and grow fine and long fibers. The preferred particle size is
It is 10μm or less. The calcination treatment is achieved by holding the powder mixture at 800 to 1200° C. for an appropriate period of time (for example, 30 minutes). In this firing process, solid solution of titanium dioxide into the amorphous solidified particles and generation and growth of fibers from the solid solution occur.

The type (composition and structure) of potassium titanate fibers obtained by the firing process differs depending on the molar ratio of TiO ₂ /K ₂ O in the amorphous solidified material and titanium dioxide powder mixture prepared in the previous step. That is, when the TiO ₂ /K ₂ O molar ratio in the powder mixture is adjusted to a low value of 3.5 or less within the range of 3 to 6, potassium tetratitanate fibers are obtained; Mixed fibers of potassium tetratitanate and potassium hexatitanate are obtained when the mixture is adjusted to a medium value of 5.5 or less, and from a mixture whose molar ratio is adjusted to a high value of over 5.5. Potassium hexatitanate fibers are obtained.

When the above-mentioned fibers obtained by firing a powder mixture are left as they are, some of the fibers adhere to each other and exhibit a bundle-like aggregated state. By performing fiber treatment, it is possible to recover individual fibers as separate fibers.

If the fiber obtained through the above process is potassium tetratitanate fiber, it can be converted into potassium hexatitanate fiber by subjecting it to a secondary step consisting of a potassium removal treatment and a firing treatment, if desired. can. In addition, even when the fiber obtained through the above process is a mixed fiber of potassium tetratitanate and potassium hexatitanate, potassium hexatitanate can be converted into single-phase fibers.

The depotassium treatment can be carried out using water or an acid aqueous solution, preferably an acid aqueous solution (for example, a 0.5-2% sulfuric acid aqueous solution) as a washing liquid. In this depotassium treatment, the potassium content is eluted from potassium tetratitanate until it has a composition equivalent to potassium hexatitanate.

The chemical composition of the fiber after depotassium treatment corresponds to that of potassium hexatitanate, but the crystal structure retains the traces of the original layered structure of potassium tetratitanate, so it is necessary to dehydrate it.・After drying, it is subjected to firing treatment to convert the layered structure of potassium tetratitanate to the tunnel structure of potassium hexatitanate. The firing process preferably includes:
This is achieved by heating and holding at 400 to 900°C for an appropriate period of time (for example, 30 minutes).

〔Example〕

Example 1 (Production of potassium tetratitanate fiber) [] Raw material preparation (1) Titanium compound: Natural rutile sand (purity 95.6
%, produced in Australia) (2) Potassium compound: Potassium carbonate (purity 99.5
%) (3) TiO ₂ /K ₂ O (molar ratio): 2.0 [] Heat melting Place the raw material mixed powder in a platinum crucible and heat at 1100℃ x 40
Heat for a minute.

[] Rapid cooling process The molten material flows down onto twin metal rolls rotating at high speed to obtain a solidified product in the form of flakes.

The solidified product was confirmed to be amorphous by X-ray diffraction.

[] Firing treatment Titanium dioxide powder (highly purified titanium oxide, purity 99%) was added to the above amorphous solidified material in TiO ₂ /K ₂ O
were mixed so that the molar ratio of
5 μm), and then the powder mixture was charged into an alumina crucible and heated and held at 1000° C. for 0.5 hour.

[] Defibration treatment The above-mentioned fired product was poured into 10 times the volume (weight ratio) of water, defibrated in a mixer for 15 minutes, and then dehydrated and dried.

The above process was carried out to obtain potassium tetratitanate fibers.

Fiber morphology: diameter 0.2-1 μm, length: 5-20 μm.

Example 2 (Production of mixed fiber of potassium tetratitanate and potassium hexatitanate) Amorphous solidified material and titanium dioxide were mixed into TiO ₂ /
They were mixed so that the molar ratio of K ₂ O was 4.0, and fibers were obtained under the same conditions as in Example 1.

The obtained fiber is a mixed fiber of potassium tetratitanate and potassium hexatitanate.

Fiber form: diameter 0.2-1μm, length: 5-15μm
(acicular crystals) (scanning electron microscope).

Example 3 (Manufacture of potassium hexatitanate fiber) Amorphous solidified material and titanium dioxide were mixed into TiO ₂ /
The mixture was mixed so that the molar ratio of K ₂ O was 6.0, and fibers were obtained under the same conditions as in Example 1.

X-ray diffraction shows that the obtained fibers are potassium hexatitanate fibers.

Fiber morphology: diameter 0.1-0.5 μm, length 2-5 μm (acicular crystals) (scanning electron microscope).

Example 4 (Manufacture of potassium hexatitanate fiber) The potassium tetratitanium fiber obtained in Example 1 is subjected to a potassium removal treatment and a heat treatment to obtain a potassium hexatitanate fiber.

[] Depotassium treatment The fibers are immersed in a sulfuric acid aqueous solution (2%) as a washing liquid (1 g of fiber/10 c.c. of washing liquid), and it takes about 60 minutes.
Elute K ⁺ ions.

[] Heat treatment After the depotassium-treated fibers are washed and dried, they are placed in an alumina crucible and placed in a furnace set at 400℃, and the firing process is completed in about 0.5 hours.

X-ray diffraction shows that the obtained fibers are potassium hexatitanate fibers. Yield from starting material (weight of obtained fiber/weight of raw material x 100) is 73.9%
It is. The fiber morphology is almost the same as that obtained in Example 1 above.

Example 5 (Manufacture of potassium hexatitanate fibers) The mixed fibers obtained in Example 2 are subjected to a potassium removal treatment and a firing treatment to obtain potassium hexatitanate fibers.

[] Depotassium treatment The mixed fibers are immersed in an aqueous sulfuric acid solution (1%) as a washing liquid (1 g of fiber/10 c.c. of washing liquid), and K ⁺ ions are eluted over about 60 minutes.

[] Firing treatment After the depotassium-treated fibers are washed and dried, they are placed in an alumina crucible and placed in a furnace set at 400°C, and the firing process is completed in about 0.5 hours.

X-ray diffraction shows that the obtained fibers are potassium hexatitanate single phase. The yield from the starting material is
It is 81.2%. The fiber morphology is almost the same as that of the mixed fiber obtained in Example 1 above.

Comparative Example Potassium hexatitanate fibers are obtained by conventional melting methods.

[] Raw material preparation... Same as Example 1 [] Heat melting... Same as Example 1 [] Cooling treatment (unidirectional solidification) The molten material is poured into a metal cooling dish and cooled from the bottom, and the primary phase, 2 A lump of potassium titanate fibers is obtained.

[] Water washing treatment The lumps are immersed in 100 times the volume (weight ratio) of water for 24 hours.
By depotassium treatment which takes a long time, the composition is converted to hydrated potassium titanate having a composition equivalent to potassium hexatitanate. The fibers are plate-like crystals with a diameter of 10-30 μm and a length of 50-200 μm (scanning electron microscopy).

[] Firing treatment After washing with water, the fibers were dehydrated and dried, and kept in a furnace at 1050°C for 3 hours to transform the structure, thereby obtaining potassium hexatitanate fibers. Yield 62.8%. Fiber diameter is 10~
30μm, length is 50-200μm, coarse and irregular.

〔Effect of the invention〕

According to the method of the present invention, potassium titanate fibers can be produced with a higher yield than conventional methods, and the fibers are smaller in diameter, longer, and more homogeneous than those obtained by conventional methods. Because of its high properties, it can be used in a wide variety of applications, such as heat-resistant materials, heat insulating materials, friction materials, filtering materials, reinforcing materials, etc., and is especially suitable as filling reinforcing materials for plastics.

Claims (1)

[Claims] 1. A titanium compound that becomes titanium dioxide (TiO ₂ ) when heated and a potassium compound that becomes potassium oxide (K ₂ O) when heated, with a TiO ₂ /K ₂ O molar ratio of 1.5 to 2.5. A heated melt of the mixture blended so that
TiO ₂ /K ₂ O is added at a molar ratio of 3 to 6 to form a uniform powder mixture, and then the powder mixture is subjected to a firing treatment to grow potassium titanate fibers. Method for producing acid potassium fiber. 2 The above, wherein the molar ratio of TiO ₂ /K ₂ O in the powder mixture of the amorphous solidified material and titanium dioxide is 3 to 3.5, and the fiber obtained by firing the powder mixture is potassium tetratitanate fiber. The method for producing potassium titanate fiber according to item 1. 3 The molar ratio of TiO ₂ /K ₂ O in the powder mixture of the amorphous solidified material and titanium dioxide is more than 3.5 and less than 5.5, and the fibers obtained by firing the powder mixture are potassium tetratitanate and The method for producing potassium titanate fiber according to item 1 above, which is a mixed fiber of potassium hexatitanate. 4. The TiO ₂ /K ₂ O molar ratio of the powder mixture of the amorphous solidified material and titanium dioxide exceeds 5.5 and is 6 or less, and the fiber obtained by firing the powder mixture is potassium hexatitanate fiber. A method for producing a potassium titanate fiber according to item 1 above. 5. Production of potassium titanate fibers according to item 2 above, characterized in that potassium tetratitanate fibers are depotassium-treated to convert into potassium hexatitanate, and then subjected to firing treatment to obtain potassium hexatitanate. Method. 6. Potassium hexatitanate fibers are obtained by depotassiuming a mixed fiber of potassium tetratitanate and potassium hexatitanate to convert potassium tetratitanate into potassium hexatitanate, and then performing a firing treatment. The method for producing potassium titanate fiber according to item 3 above.