JPS6379799A - Production of potassium titanate fiber - Google Patents

Abstract

PURPOSE:To economically obtain the title potassium titanate fiber having fine fiber diameter and excellent homogeneity by mixing a mixture of a titanium compd. and a network forming ion with a potassium compd. in a specified ratio, heating and melting the obtained mixture, and quenching and vitrifying the melt to obtain an amorphous solid which is then heat-treated. CONSTITUTION:Potassium tetratitanate fiber or the mixed fiber of potassium tetratitanate and potassium hexatitanate is obtained by the following method. Namely, a mixture obtained by mixing a titanium compd. forming titanium dioxide (TiO2) on heating and a network forming ion (N, W, F) in 0.05-0.3 molar ratio of (N, W, F)/(N, W, F + TiO2) is mixed with a potassium compd. forming potassium oxide (K2O) on heating in 2.5-5 molar ratio of (TiO2 + N, W, F)/K2O. The obtained mixture is heated and melted, and the melt is then quenched and vitrified. The obtained amorphous solid is subsequently heat-treated.

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 (K2O・nTi
o2) is a synthetic inorganic fiber with excellent heat resistance, abrasion resistance, reinforcing properties, etc.

The melting method, which is known as a typical manufacturing method, combines a titanium compound that becomes titanium dioxide (TiO2) by heating and a potassium compound that becomes potassium oxide (KzO) by heating at a molar ratio of T i Oz / K z O. A process of heating and melting the raw material mixture using a mixture mixed so that the Potassium dititanate (K2O・2
TiO2) A cooling solidification step to obtain a fiber mass which is an aggregate of fibers, followed by a water washing (dealkalization) step in which the fiber mass is washed with water and ions are eluted until the molar ratio of Ti0z/KzO becomes approximately 5, and water washing. It consists of a step of drying and heat-treating the hydrated potassium titanate fibers recovered through the process, and a step of further performing pickling and heat treatment if desired.

[Problem that the invention seeks to solve]

Potassium titanate fibers obtained by conventional melting methods generally have a thick fiber diameter of about 10 to 30 μm (and the fiber morphology (thickness, length) is uneven and lacks homogeneity. During unidirectional solidification in a cooling mold, the cooling rate differs between the parts that are in contact with the mold and the parts that are not, resulting in irregular shapes of the primary phase fibers, and variations in the shapes can be caused by subsequent water washing, heat treatment, etc. By leaving a strong influence on the morphology of the product fibers (potassium tetratitanate fiber, potassium hexatitanate fiber, etc.) obtained through compositional and structural transformations.

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.

Depending on the use of potassium titanate fibers, there may be no problem even if the fibers have a large diameter as described above, but excellent performance as a filling reinforcing material for plastics, for example, cannot be expected.

The present invention aims to provide an improved method for producing potassium titanate fibers having a small fiber diameter and excellent homogeneity, in order to expand and diversify the uses of potassium titanate fibers.

[Means and effects for solving the problems] The method for producing potassium titanate fibers of the present invention involves adding network-forming ions (N, W, F,) to a titanium compound that becomes titanium dioxide (TiO2) by heating. .

A mixture in which the molar ratio of W, F, / (N, W, F, +'l' i 0x) is 0.05 to 0.3 and potassium oxide (K t O) is formed by heating. Potassium compound, (TiOl +N, W, F,)/Kz
After mixing with O: 2.5 to 5 (molar ratio) and heating and melting, the melt is rapidly cooled and vitrified, and then the amorphous solidified product is heat-treated to produce potassium tetratitanate fibers or tetratitanate fibers. It is characterized by growing mixed fibers of potassium and potassium hexatitanate.

The method of the present invention differs from the conventional method in which fibers are immediately produced from a heated melt, and is first rapidly cooled to form an amorphous solidified product that does not have a fiber form. There is no problem of irregular shapes, and by subjecting the amorphous solidified material to a predetermined heat treatment, it is possible to obtain homogeneous fibers with a small fiber diameter.

Furthermore, in the method of the present invention, (T i O
□+N, W, F, )/Kzo (molar ratio) is 2.5
Since it was decided to adjust the temperature to 5 to 5, there was no need for water washing (dealing process) as in the conventional method, and by heat-treating the amorphous solidified material, potassium tetratitanate fibers or potassium tetratitanate fibers were immediately formed. A mixed fiber of large potassium titanate is obtained, and by subjecting it to a predetermined depotassium treatment and heat treatment as required, a potassium hexatitanate single-phase fiber can be obtained.

The fibers are approximately 0.5 to 2 μm in diameter and 10 to 2 μm in length.
It is 30 μm.

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

In raw material preparation, network-forming ions (N, W).

The reason for blending F,) is to achieve sufficient vitrification in the quenching step after heating and melting the raw material mixture. The titanium compound and the potassium compound are
A heated melt obtained by mixing O2/ with a molar ratio of O around 2 can be vitrified relatively easily, but when the molar ratio is as high as 2.5 to 5, industrial quenching becomes difficult. However, it is difficult to achieve complete vitrification, and the rapidly solidified product often contains a mixture of amorphous and potassium hexatitanate phases. Therefore, in the present invention, a part of the titanium compound is replaced with network-forming ions (N, W, F,), thereby making it possible to completely amorphize the titanium compound.

Titanium compounds that become titanium dioxide (T i O□) when heated include highly purified titanium oxide, synthetic rutile,
Alternatively, natural rutile sand, natural anatase sand, etc. can be used. Potassium oxide (K2O
) is typically potassium carbonate (
KzCoff), but its hydroxide, nitrate, etc. can also be used. In addition, network-forming ions (N, W
, F,) are preferable examples of 3 i 4 + ,
Examples include p 5 *, B 3 +, and the like. These ions are provided as silicon dioxide (SiO□), mini phosphorous oxide (PzOs), boron sesquioxide (BzO2), and the like.

The molar ratio (N) of the network-forming ions (N, W, F,) in the mixture with the titanium compound.

W, F/ (T i O □ 1N, W, F)), 0.0
The reason why it is set at 5 or more is because if it is less than that, the vitrification effect will be insufficient, and on the other hand, the reason why the upper limit is set at 0.3 is because if it exceeds it, ties and octahedral chains will not be formed and fiber growth will be inhibited. This is because it is inhibited. Network-forming ions (N, W, F,)
One type can be used alone or two or more types can be used in combination. In the case of combined use, they may be blended so that the total amount satisfies the above regulations.

The blending ratio of the potassium compound to the mixture of the titanium compound and network-forming ions is (TiOz+N.

The reason why we decided to adjust the molar ratio of W, F, This is because potassium tetratitanate fibers or mixed fibers of potassium tetratitanate and potassium hexatitanate can be grown immediately by heat-treating the crystalline solidified product. In this case, if the molar ratio is adjusted to a range of 2.5 to 3.3, potassium tetratitanate single-phase fiber can be obtained, and if the molar ratio is adjusted to a higher molar ratio, potassium tetratitanate and hexatitanate fibers can be obtained. Mixed fibers of acid potassium can be obtained.

The heating and melting treatment of the above raw materials is carried out at a temperature of 1300 to 150.
It can be carried out at 0°C.

For example, as shown in FIG.
While rotating the metal twin rolls (3, 3) at high speed, the molten material (M) is fed from the nozzle (2) of the melting furnace or the retractor (1).
This can be done by flowing down and passing through the nip between the rolls. In addition, as shown in Figure 2, a metal rotary disk (
4), the melt (M) flows down onto its upper surface under high speed rotation, and relatively fine amorphous solidified material is recovered by contact with the rotary disk (4) and scattering to the surroundings due to centrifugal force. You can also do this. In this case, spraying a refrigerant (for example, liquid nitrogen) from the nozzle (5) is effective as an auxiliary means for increasing the cooling rate of the melt.

The amorphous solidified product obtained by the rapid cooling treatment is then subjected to a heat treatment to produce fibers. If the amorphous solidified material has a coarse shape, it is recommended that it be made into fine particles (for example, 10/Jm or less) by a grinding means such as a disk mill prior to heat treatment. It is effective in producing a large number of thin fibers and promoting growth.

The above heat treatment is preferably performed at a temperature of 900 to 1100°C.
This is achieved by holding it for an appropriate amount of time. Through this heat treatment, potassium tetratitanate fibers grown in the b-axis direction,
Alternatively, a thin and long mixed fiber of potassium tetratitanate and potassium hexatitanate can be obtained.

The fibers obtained through the above heat treatment are in a state where the fibers are slightly agglomerated together, but if this is suspended in water and stirred with a mixer, sufficiently defibrated mixed fibers can be recovered. be able to.

Further, if desired, the fibers may be subjected to depotassium treatment and heat treatment to obtain potassium hexatitanate single-phase fibers. The depotassium treatment is preferably carried out using an acid aqueous solution, for example, a sulfuric acid aqueous solution having a concentration of 0.5% to 1%. By the depotassium treatment, potassium tetratitanate is converted into a composition equivalent to potassium hexatitanate, and then heat treatment is applied to convert the crystal structure from the layered structure of potassium tetratitanate to the tunnel structure of potassium hexatitanate. A potassium hexatitanate single-phase fiber is obtained. The heat treatment is preferably carried out at a temperature of 2800 to 1000°C.
This is achieved by holding it for an appropriate amount of time.

〔Example〕

Disaster Recipient CI) Raw Material Preparation (1) Titanium Compound: Natural Rutile Sand (Purity 96
．． 5%, produced in Australia) (2) Potassium compound: Potassium carbonate (purity 99.5%)
) (3) Network-forming ions (N, W, F,): S i”(
4) Mixing ratio of network forming ions (N, W, F,) (N,
Number of moles of W and F/(TiO□+N.

Number of moles of W, F, ): 0.1 (5) (TiO□+N, W, F,)/to! O (molar ratio): 3.0 ([3 Heat-melted raw material powder mixture was heated and melted in a platinum crucible at 1300°C for 30 minutes.

(III) Quenched glass treatment As shown in Fig. 1, the heated molten material was
, 3) and collect the flaky amorphous solidified material. Roll body diameter: 80φ, roll body length: 150I! , roll spacing:
0.3 m, rotation speed: 90 rpm.

(1'/) Grinding of amorphous solidified material The above-mentioned amorphous π solidified material was ground in a disk mill for 6 minutes, and the particle size after grinding was 0.5 to 10 μm.

(V) Place the heat-treated pulverized amorphous solidified material in an aluminum crucible,
Place in a furnace set at 0°C and hold for 24 hours.

(VI) After the defibration heat treatment, it is suspended in 10 times (by weight) water, stirred with a mixer, defibrated for 15 minutes, and then dehydrated and dried.

The obtained fibers have a diameter of 0.5-2 μm and a length of 10-30 μm.
μm (scanning electron microscope) and has a mixed composition of potassium tetratitanate and potassium hexatitanate (X-ray diffraction).

Large blood sample 1 was prepared using the same process as in Example 1, except that the raw materials were prepared so that the molar ratio of 20 to (T i O □ 1 N, W, F,)/ was 4.5. A mixed fiber of potassium titanate and potassium hexatitanate was obtained. The fiber diameter is 0.5 to 2 μm and the length is 10 to 30 μm.

Example 3 The mixed fiber obtained in Example 1 is subjected to depotassium treatment and heat treatment to obtain potassium hexatitanate fiber (single phase).

(I) Depotassium treatment The mixed fibers are immersed in a sulfuric acid aqueous solution (0.6%) as a washing solution (1 g of fiber/10 cc of washing solution), and the ions are eluted over about 60 minutes.

(n) Heat Treatment After washing and drying the depotassium-treated fibers, they are placed in an aluminum crucible and placed in a furnace set at 900°C, and the heat treatment is completed in about 2 hours.

XyA diffraction shows that the obtained fiber is a potassium hexatitanate single phase. The fiber morphology is almost the same as the mixed fiber obtained in the previous example.

The mixed fiber obtained in Example 2 was subjected to the same depotassium treatment and heat treatment as in Example 3 to obtain potassium hexatitanate fiber (single phase). The fiber morphology is almost the same as the mixed fiber of Example 3.

Potassium hexatitanate fiber (single phase) is produced by the traditional melting method.

CI) Raw material preparation (1) Titanium compound: Same as Example 1 (2) Potassium compound: Same as Example 1 (31T i 02
/ KzO (molar ratio): 2 (n) Heat molten raw material mixed powder into a platinum crucible and heat at 1100°C x 40
Heat and melt for minutes.

(III) Cooling treatment (unidirectional pseudo-solidification) The melt is poured into a metal cooling dish and cooled from the bottom to obtain a lump of potassium nititanate fibers as 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] Heat treatment After washing with water, the fibers were dehydrated, dried, and kept in a furnace at 1050° C. for 3 hours to undergo structural transformation, thereby obtaining potassium hexatitanate fibers. Fiber diameter is 10-30μm, length is 50-20μm
It is coarse and irregular at 0 μm.

〔Effect of the invention〕

The potassium titanate fiber obtained by the improved melting method of the present invention has a small diameter, long size, and excellent homogeneity, so it can be used as a heat-resistant material, a heat insulating material, a friction material, a filtration material, a reinforcing material, etc. It is particularly suitable as a filling reinforcing material for plastics.

In addition, since the method of the present invention increases the molar ratio of T i Oz to 20 in the raw material preparation, the water washing step after cooling and solidification, which is an essential step in the conventional method, is not necessary, and the process is therefore simpler. In addition, loss of potassium content due to water washing is reduced, raw material costs are reduced, and the yield of the fiber is high.

[Brief explanation of the drawing]

FIGS. 1 and 2 are cross-sectional explanatory views showing an example of a method of rapidly cooling and vitrifying a heated melt. 1: Melting furnace (ladle), 3.3: Twin rolls, 4: Rotating plate,
5: Refrigerant nozzle.

Claims (2)

[Claims] (1) Network-forming ions (N.W.F.) are added to a titanium compound that becomes titanium dioxide (TiO_2) by heating.
W. F. /(N.W.F.+TiO_2) molar ratio is 0
．． (TiO_2+N.WF.)/K_2O: 2.5
~5 (molar ratio), heated and melted, then rapidly cooled and vitrified, and the amorphous solidified product is heat-treated to produce potassium tetratitanate fibers or mixed fibers of potassium tetratitanate and potassium hexatitanate. A method for producing potassium titanate fiber, which comprises growing potassium titanate fiber. (2) Potassium tetratitanate fibers or mixed fibers of potassium tetratitanate and potassium hexatitanate are depotassium treated to convert the potassium tetratitanate phase into a potassium hexatitanate composition, and then heat treated to produce hexatitanium. The method for producing potassium titanate fibers according to item 1 above, which comprises obtaining potassium titanate single-phase fibers.