JPS63256526A - Production of potassium titanate fiber - Google Patents

Abstract

PURPOSE:To obtain titled fibers which are adequate particularly as a reinforcing material to be filled in plastics and have a small diameter and long size as well as excellent homogeneity by subjecting a mixture composed of prescribed ratios of a Ti compd. and K compd. to quick cooling after heating and melting to obtain an amorphous solid material, adding TiO2 thereto, and subjecting the powder mixture obtd. in such a manner to a calcination treatment. CONSTITUTION:The mixture prepd. by compounding (A) the Ti compd. such as natural rutile sand which is converted to TiO2 by heating and (b) the K compd. such as K2CO3 which is converted to K2O by heating is melted by heating at 950-1,100 deg.C and the melt is subjected to the quick cooling treatment by a twin roll method, etc., at, for example, >=10<6> deg.C/sec cooling rate, by which the amorphous solid material (A) is obtd. (B) TiO2 is then added to the component A so as to attain 3-6 molar ratio of TiO2/K2O and the mixture is ground by a disk mill, or the like, to form the powder mixture having <=10mu grain size; thereafter, the mixture is subjected to the calcination treatment by holding the same for a suitable time (e.g.: about 30min) at 800-1,200 deg.C to grow the potassium tetratitanate fibers and/or potassium hexatitanate fibers.

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 titanate fibers, such as potassium hexatitanate (CKtO・6TiO2) fibers and potassium tetratitanate (K2O・4TiO2) fibers, are synthetic inorganic fibers with excellent heat resistance, abrasion resistance, reinforcing properties, etc. .

As a typical manufacturing method, a method called the melting method is known (Japanese Patent Publication No. 54-19239, Japanese Unexamined Patent Publication No. 58-1
No. 58688). The melting method involves heating titanium dioxide (
TiO□/
A process of heating and melting the raw material mixture using a mixture in which the molar ratio of 20 to 20 is about 2, and pouring the heated melt into a cooling mold and solidifying it in one direction at a constant cooling rate. A cooling solidification step is performed to obtain a fiber mass, which is an aggregate of crystalline potassium dititanate (K2O.2TiO2) fibers having a layered structure as primary silk fibers.Then, the fiber mass is washed with water, and a molar ratio of 20 to TiO□/ is obtained. A water washing (dealkalization) step in which the ions are eluted until the value reaches approximately 6;
The process includes a step of drying and heat-treating the hydrated potassium titanate fibers recovered through the water-washing step, and a step of further performing potassium removal treatment and heat treatment if desired.

[Problem that the invention seeks to solve]

In the conventional manufacturing method described above, the primary phase fiber mass is washed with water and Ti
Since a step of eluting ions is required until the O2/K2O molar ratio reaches about 6, potassium content is lost and the yield is reduced accordingly.

Further, 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 poor in homogeneity. This means that when the heated melt is unidirectionally solidified in the cooling mold to generate primary phase potassium dititanate fibers (K2O 2TiOg), the cooling rate differs between the parts that are in contact with the inside of the mold and the parts that are not. As a result, the morphology of the primary silk fibers becomes irregular, and the variation in the morphology of the primary silk fibers has a strong influence on the morphology of the product fibers (potassium tetratitanate fiber, potassium hexatitanate fiber, etc.) that are subsequently obtained. By leaving . 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 cooling and solidification process of 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 comprises: a titanium compound that becomes titanium dioxide (TiO□) when heated; a potassium compound that becomes potassium oxide (K2O) when heated; , the molar ratio of TiO□/K t O is 1.5
A heated melt of a mixture blended so as to be 2.5 to 2.5% is rapidly cooled to obtain an amorphous solidified material, and titanium dioxide is added to the amorphous solidified material with TiOz/
The method is characterized in that a homogeneous powder mixture is prepared by adding 20 to 20 at a molar ratio of 3 to 6, and then the powder mixture is subjected to a firing treatment to grow potassium titanate fibers.

In the method of the present invention, the molar ratio of TiO2/K2O in the raw material formulation is adjusted to a low value of 1.5 to 2.5, similar to that of the conventional method, and the melt is rapidly cooled to obtain a solidified material. By adding titanium dioxide to the material, TiO
Since we decided to increase the value of the molar ratio of □/to20 to the level necessary for the formation of potassium titanate fibers, we avoided the loss of potassium content unlike the conventional method in which the molar ratio was adjusted by depotassium treatment. , the resulting decrease in yield is eliminated, and the theoretical yield of fibers is increased.

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□/20 to the level necessary for forming fibers in the starting material formulation, but Ti If the molar ratio of 20 to Oz/Oz/20 is increased to such a high value, the melting point will rise to about 1250°C or higher, which will cause significant melting damage in the melting furnace, which will not only greatly reduce the durability of the melting furnace, but also cause melting damage. This furnace material mixes into the melt and contaminates the melt, resulting in poor quality of the potassium titanate fibers obtained. In the present invention, since the starting material has a low (controlled) molar ratio of TiO2/K2O,
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 nititanate fibers are immediately produced from the melt by solidifying the melt in one direction. By adding titanium dioxide to the mixture to form a mixture, and then growing fibers from the pulverized product, it is possible to obtain fibers with a finer diameter, longer length, and greater homogeneity than those obtained by conventional methods. The fiber diameter and fiber length are
Although it varies slightly depending on the molar ratio of T i Oz / K 20 in the starting material, the fiber diameter is generally 0.2 to 1.0.
μm1 fiber length is 1 to 20 μm.

According to the method of the present invention, potassium titanate fibers having different compositions and structures can be obtained depending on the molar ratio of TiO□/2O in the mixture of the amorphous solidified material and titanium dioxide added thereto, and further, If desired, the fibers can be converted into potassium titanate fibers having a different composition and structure by subjecting them to an LLS treatment consisting of a depotassium treatment and a calcination treatment.

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

Titanium compounds that become titanium dioxide when heated include:
Highly purified titanium oxide, synthetic rutile, titanium slag, natural rutile sand, natural anatase sand, etc. are used. The potassium compound blended into the titanium compound is typically potassium carbonate (K z CO *),
In addition, hydroxides, nitrates, etc. can also be used.

The mixing ratio of titanium compound and potassium compound is TiO□
A suitable molar ratio of / to 20 is in the range of 1.5 to 2.5, and the heat melting can be carried out 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 rapid cooling treatment (for example, at a cooling rate of 10"C/sec or more) to prevent the formation of potassium nititanate crystals. Then, an amorphous solidified product is obtained.The quenching treatment is carried out, for example, by the twin roll method.By rotating the metal twin rolls at high speed and letting the melt flow down into the gap between the twin rolls, a foil-like amorphous solidified product is obtained. compounds can be obtained efficiently.

After obtaining an amorphous solidified material by the above-mentioned rapid cooling treatment, this is mixed with titanium dioxide (for example, highly purified titanium oxide powder). At this time, the mixing ratio of the amorphous solidified material and titanium dioxide is adjusted so that the molar ratio of 2O to TiO□/ of the mixture 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.

After mixing the amorphous solidified material and titanium dioxide and making it into a uniform powder mixture by pulverizing means such as a disk mill,
The powder mixture is subjected to a calcination 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 1011 m 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.

Types of potassium titanate fibers obtained by firing treatment (
composition and structure) of TiO2/K2O in the amorphous solidified and titanium dioxide powder mixture prepared in the previous step.
Varies depending on the molar ratio of That is, when the T i Oz / Kz 0 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, and the molar ratio 3.
If the mixture is adjusted to a medium value higher than 5 and lower than 5.5, a mixed fiber of potassium tetratitanate and potassium hexatitanate will be obtained, and if the molar ratio is adjusted to a high value exceeding 5.5. Potassium hexatitanate fibers are obtained from the mixture adjusted to .

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 aggregation 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, potassium tetratitanate is eluted with potassium content 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 treatment is preferably performed at 400 to 900°C for an appropriate time (for example, 30 minutes).
This is achieved by heating and holding.

〔Example〕

Example 1 (Production of potassium tetratitanate fiber) (1) Raw material preparation (1) Titanium compound: Natural rutile sand (purity 95.6
%, produced in Australia) (2) Potassium compound: Potassium carbonate (purity 99.5%)
) (3) T i Oz / K t O (mo) Lt ratio): 2.0 (If) The heated melted raw material mixed powder was placed in a platinum crucible and heated at 1100° C. for 40 minutes.

(II [) Quenching process The molten material flows down onto twin metal rolls rotating at high speed to obtain a solidified material in the form of flakes.

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

(IV) Firing treatment Titanium dioxide powder (highly purified titanium oxide, purity 99%) is mixed with the above amorphous solidified material so that the molar ratio of TiO2/K2O is 3.0, and the mixture is pulverized with a disk mill. to make a uniform powder mixture (average particle size: 5 μm), then the powder mixture was charged into an aluminum crucible and heated to 1000
The mixture was heated and held at 0.5°C for 0.5 hours.

(V) Defibration treatment The above fired product was poured into 10 times the amount (weight ratio) of water,
It takes 15 minutes to defibrate in a mixer, then dehydrate and dry.

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

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

The amorphous solidified material and titanium dioxide are TiO2/Kz
They were mixed so that the molar ratio of 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 0.2-1 μm, length = 5-15 μm (
needle-shaped crystals) (scanning electron microscopy).

Process 3 (Manufacture of potassium hexatitanate fiber) The amorphous solidified material and titanium dioxide were mixed at a molar ratio of 20 to Ti1t/6.
The fibers were obtained under the same conditions as in Example 1.

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

Fiber form: diameter 0.1-0.5 μm, length 2-5 μm (
needle-shaped crystals) (scanning electron microscopy).

Example 4 (Production of potassium hexatitanium fiber) The potassium tetratitanium fiber obtained in Example 1 was subjected to depotassium treatment and heat treatment to obtain potassium hexatitanate fiber.

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

(II) Heat treatment After washing and drying the depotassium treated fibers, they are placed in an aluminum crucible and charged into 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 fibers. The yield from the starting material (weight of obtained fiber/weight of raw material xloo) is 73.9%. The fiber morphology is almost the same as that obtained in Example 1 above.

5 (Lj Notification of Potassium Hexatitanate °) The mixed fiber obtained in Example 2 was subjected to a potassium removal treatment and a firing treatment to obtain potassium hexatitanate fiber.

CI) Depotassium treatment The mixed fibers are immersed in a sulfuric acid aqueous solution (1%) as a washing liquid (1 g of fiber/10 cc of washing liquid), and it takes about 60 minutes to remove K.
“Elute ions.

(II) Firing treatment After washing and drying the depotassium-treated fibers, they are placed in an aluminum crucible and charged into a furnace set at 400°C, and the firing process is completed in about 0.5 hours. do.

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

Le comparison■ Potassium hexatitanate fibers are obtained by conventional melting methods.

CI) Raw material preparation: Same as Example 1 (II) Heat melting: Same as Example 1 (II [) Cooling treatment (unidirectional solidification) Put the molten material into a metal cooling dish. It is poured and cooled from the bottom to obtain a lump of potassium nititanate fibers, which is the primary phase.

(IV) The water-washed mass is immersed in 100 times the volume (weight ratio) of water and subjected to depotassium treatment for 24 hours to convert the composition into hydrated potassium titanate having a composition equivalent to potassium hexatitanate. . The fibers have a diameter of 10 to 30 μm and a length of 50 to 200 μm.
It is a plate-like crystal (scanning electron microscope).

[V] Calcining treatment After washing with water, it was dehydrated and dried, and kept in a furnace at 1050° C. for 3 hours to undergo structural transformation, thereby obtaining potassium hexatitanate fibers. Yield 62.8%. Fiber diameter is 10-30μm,
The length is 50 to 200 μm, which is 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 have smaller diameters and longer dimensions than those obtained by conventional methods.
Because it is highly homogeneous, it can be used for a variety of purposes.
For example, it is suitable as a heat-resistant material, a heat insulating material, a friction material, a filter material, a reinforcing material, etc., and especially as a filling reinforcing material for plastics.

Claims (6)

[Claims] (1) A mixture of a titanium compound that becomes titanium dioxide (TiO_2) when heated and a potassium compound that becomes potassium oxide (K_2O) when heated so that the molar ratio of TiO_2/K_2O is 1.5 to 2.5. The heated melt is rapidly cooled to obtain an amorphous solidified material, and titanium dioxide is added to the amorphous solidified material to form TiO_2/K.
Production of potassium titanate fibers, characterized by adding _2O in a molar ratio of 3 to 6 to form a uniform powder mixture, and then subjecting the powder mixture to a firing treatment to grow potassium titanate fibers. Method. (2) T of powder mixture of amorphous solidified material and titanium dioxide
The method for producing potassium titanate fibers according to item 1 above, wherein the molar ratio of iO_2/K_2O is 3 to 3.5, and the fibers obtained by firing the powder mixture are potassium tetratitanate fibers. (3) T of powder mixture of amorphous solidified material and titanium dioxide
Item 1 above, wherein the molar ratio of iO_2/K_2O is more than 3.5 and less than 5.5, and the fiber obtained by firing the powder mixture is a mixed fiber of potassium tetratitanate and potassium hexatitanate. The method for producing potassium titanate fibers described in . (4) T of powder mixture of amorphous solidified material and titanium dioxide
The method for producing potassium titanate fibers according to item 1 above, wherein the iO_2/K_2O molar ratio is more than 5.5 and less than or equal to 6, and the fibers obtained by firing the powder mixture are potassium hexatitanate fibers. . (5) The potassium titanate fiber according to item 2 above, wherein the potassium tetratitanate fiber is depotassium-treated to convert it into potassium hexatitanate, and then subjected to a firing treatment to obtain potassium hexatitanate. manufacturing method. (6) Potassium hexatitanate fibers are obtained by depotassiuming the mixed fibers of potassium tetratitanate and potassium hexatitanate to convert potassium tetratitanate into potassium hexatitanate, and then firing the mixture. The method for producing potassium titanate fiber according to the above item 3.