JPH05105447A - Production of potassium hexatitanate fiber - Google Patents

Abstract

PURPOSE:To produce fine homogeneous potassium hexatitanate fibers. CONSTITUTION:A mixture of a titanium compd. with a potassium compd. in 1.5-2.5 molar ratio of TiO2 to K2O is melted by heating and rapidly cooled. The resulting amorphous solidified body is heat-treated at 750-950 deg.C to form fibers of potassium dititanate crystals. Ions of K<+> are then leached from the fibers so as to attain conversion into a chemical compsn. corresponding to that of potasium hexatitanate and the fibers are fired so as to attain conversion into a crystal structure corresponding to that of potassium hexatitanate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing potassium hexatitanate fiber which is useful as a material for sliding parts, an additive for paints, a luster pigment and the like.

[0002]

_2. Description of the Prior Art Potassium hexatitanate fiber [K ₂ Ti ₆ O
₁₃ ] is a synthetic inorganic fiber having abrasion resistance, fire resistance / heat resistance, heat insulation, reinforcement, etc., and its industrial application has been tried as an asbestos substitute in various fields. The melting method, which is known as a typical manufacturing method thereof, comprises a titanium compound which becomes titanium dioxide (TiO ₂ ) when heated and a potassium compound which becomes potassium oxide (K ₂ O) when heated, in TiO ₂ / K ₂ The starting materials were mixed by mixing so that the molar ratio of O was about 2, and the starting materials mixture was heated and melted. Then, the heated and melted material was poured into a cooling mold, and potassium dititanate crystals [K ₂ Ti ₄ O ₅ ], the cooling and solidifying step is carried out, and the cooled and solidified product (fiber lump) is treated with a washing liquid such as water or an aqueous acid solution to elute K ⁺ ions, thereby forming a fiber composition. A potassium hexatitanate fiber is obtained through a potassium removal treatment for conversion and a firing treatment for conversion of the crystal structure of the fiber.
The size of the potassium hexatitanate fiber obtained through the above steps is relatively large (fiber diameter: about 20 to 50 μm, length: about 100 to 300 μm), and the fiber morphology greatly varies and lacks homogeneity. ..

For the purpose of improving the fiber morphology, Japanese Patent Laid-Open No. 63-64997 discloses that a heating melt of a starting raw material is subjected to rapid cooling by a twin roll method or the like instead of directional cooling to be amorphous. Since it does not become a solidified substance (glass) and K ⁺ ions cannot be eluted in the whole glass, it is subjected to a short heat treatment to convert it into potassium dititanate crystals, and further the conversion of the chemical composition, and A method for producing potassium hexatitanate fiber through a treatment step such as crystal structure conversion is disclosed. The fibers obtained by the production method are relatively fine (fiber diameter: about 0.2) as described therein.
˜2 μm, length: about 10 to 30 μm).

[0004]

However, in the above-mentioned fiber manufacturing method, in the heat treatment for precipitating potassium dititanate crystals from the amorphous coagulated product, the potassium dititanate crystals are not formed into fibers but in a uniform particle size. The resulting heat-treated product is subjected to K ⁺ ion elution treatment and firing treatment to obtain potassium tetratitanate crystals [K ₂ Ti ₄ O ₉ ] and potassium hexatitanate crystals [K ₂ T].
After passing through the intermediate step of forming the mixed phase fiber of i ₆ O ₁₃ ], elution of K ⁺ ions and baking treatment are carried out again to obtain potassium hexatitanate fiber, which is inevitable. Further, the homogeneity of the size and morphology of the potassium hexatitanate fiber thus obtained, the mixed phase ratio of potassium tetratitanate crystals and potassium hexatitanate crystals in the intermediate step,
The firing process will be different depending on the conditions of the firing process that is repeatedly performed, and the process that is cumbersome to control the fiber size and morphology is inevitable. In view of the above, the present invention provides a method for producing potassium hexatitanate fiber, which has a simpler process, is easy to control the fiber size and morphology, and is excellent in homogeneity.

[0005]

Means and Actions for Solving the Problems The method for producing potassium hexatitanate according to the present invention comprises a titanium compound which becomes titanium dioxide (TiO ₂ ) by heating and a potassium compound which becomes potassium oxide (K ₂ O) by heating. To TiO ₂ /
The heated melt of the mixture compounded so that the molar ratio of K ₂ O is 1.5 to 2.5 is rapidly cooled to form an amorphous coagulated product, and the amorphous coagulated product is heated at a temperature of 750 to 950 ° C. After the potassium dititanate crystal fibers are produced by heat treatment, the heat-treated product is treated in a washing liquid to give K
^{+ The} ions are eluted to convert the composition of the potassium dititanate crystal fiber to the hydrated potassium titanate fiber having the composition equivalent to potassium hexatitanate, and the fiber mass is defibrated, dehydrated, dried, and fired. It is characterized in that the hydrated potassium titanate fibers are structurally converted into potassium hexatitanate crystals. Hereinafter, the present invention will be described in the order of steps.

Various titanium compounds such as purified titanium oxide, synthetic rutile, titanium slag, natural rutile sand and natural anatase sand are used as the titanium compound which is one of the constituents of the starting material and becomes titanium dioxide by heating. The potassium compound to be added to the titanium compound is typically potassium carbonate (K ₂ CO ₃ ), and hydroxides, nitrates and the like can also be used. The mixing ratio of titanium compound and potassium compound is Ti
The molar ratio of O ₂ / K ₂ O is set to 1.5 to 2.5 in order to efficiently precipitate potassium dititanate in the heat treatment of the amorphous solid obtained by rapidly cooling the heated melt.
The melting temperature of the above starting materials is about 950 to 1100.
It can be performed at ° C.

After the starting material mixture is heated and melted, the melt is subjected to a quenching treatment to obtain an amorphous solidified product. The quenching process is performed by, for example, the twin roll method. By rotating the metal twin rolls at a high speed and allowing the melt to flow into the gap between the twin rolls, an amorphous solidified product in the form of foil can be efficiently obtained.

The amorphous solidified product obtained by the above quenching treatment is heat-treated to produce potassium dititanate crystal fibers as primary phase fibers. In this heat treatment, the amorphous solidified product is heated to a temperature of 750 to 950 ° C. for an appropriate time (about 30 to 60 ° C.).
Min) It is achieved by heating and holding. The lower limit of the treatment temperature is set to 750 ° C. Even if crystals of potassium dititanate are formed at a lower temperature, the particles remain in the form of fine particles having a particle size of about 0.1 μm, and fibers can be formed. This is because it cannot be done, and the reason why the upper limit is 950 ° C. is that the melting starts when the temperature exceeds it. The fiber length of the resulting potassium dititanate crystal is about 2 to 50 μm,
The diameter is about 0.5 to 10 μm, and as the heat treatment temperature is increased, the fiber length and the aspect ratio of the produced crystal increase.

The fiber morphology of potassium hexatitanate fiber obtained through the above-mentioned heat treatment followed by conversion of crystal composition by potassium removal treatment and conversion of crystal structure by calcination treatment is the same as the primary phase fiber produced in the heat treatment. It is almost the same as that of potassium titanate crystal. That is, according to the method of the present invention, the fiber morphology of the final target potassium hexatitanate fiber is controlled by the treatment temperature in the heat treatment for producing the primary phase potassium dititanate crystal fiber from the amorphous coagulated product. Other manufacturing conditions, which can be
For example, strict control of the clearance between twin rolls in the rapid solidification of a heated melt is not required, and if it is amorphized at a sufficient cooling rate, it is possible to obtain a relatively fine and homogenous material only by controlling the heat treatment temperature. An excellent potassium hexatitanate fiber can be stably obtained.

Elution and defibration of K ⁺ ions from the fiber mass composed of potassium dititanate crystals subjected to the above heat treatment can be carried out with water (normal temperature), heated water (about 50 to 80 ° C.), or various kinds of water. Aqueous acid solution, eg, about 0.05-0.3% sulfuric acid solution, about 0.05-0.3% hydrochloric acid, about 0.1-1%
The acetic acid aqueous solution or the like can be used as a washing liquid. By this potassium removal treatment, the molar ratio of TiO ₂ / K ₂ O is about 6
The K ⁺ ion is eluted until it becomes to convert the primary phase potassium dititanate crystal into hydrated potassium titanate having a chemical composition equivalent to potassium hexatitanate. The elution amount of K ⁺ ions can be adjusted by the amount of treatment liquid used, the treatment time, and the like. In addition, the fiber mass is cleaved by hydration and swelling.
It is defibrated with peeling. In order to improve the treatment efficiency of this potassium removal and defibration, a stirring flow is added to the treatment liquid by a propeller or the like, if necessary.

The chemical composition of the fiber obtained through the above potassium removal treatment is equivalent to that of potassium hexatitanate, but the crystal structure has the crystal structure (layered structure) of the precursor potassium dititanate. Therefore, it is converted into a crystal structure (tunnel structure) of potassium hexatitanate. This structural transformation is achieved by a calcination process at a temperature of about 700 to 1000 ° C (preferably about 900 ° C). As a result, a potassium hexatitanate fiber having a perfect composition and structure is obtained.

The potassium hexatitanate fiber thus obtained is a polycrystalline fiber having substantially the same fiber morphology as the primary phase fiber produced in the heat treatment step of the amorphous solidified material, and its fiber length is about 2 to 50 μm. It has a diameter of about 0.5 to 10 μm (aspect ratio of about 2 to 6), has little variation in fiber form, and has excellent homogeneity.

[0013]

【Example】

[I] Starting material Natural rutile sand as a titanium compound (purity: 95.6
%, Made in Australia), industrial potassium carbonate (purity: 99.5%) as a potassium compound, TiO ₂ / K ₂
Mix in such a ratio that the molar ratio of O becomes 2.0. [II] Heating and Melting Put the starting raw material mixed powder in a platinum crucible, 1100 ° C. × 4
Heat and melt for 0 minutes. [III] Quenching Treatment The heated melt is allowed to flow down into the roll gap of a metallic twin roll rotating at high speed to obtain a flake-like solidified product. The coagulum is completely amorphous (X-ray diffraction). [IV] Heat treatment The flaky amorphous solidified product is placed in an alumina crucible and heat treated. Treatment temperature: 750 ° C., 800 ° C., 900 ° C. Treatment time: 40 minutes [V] Potassium removal and defibration treatment with a washing solution Using water as a washing solution, the heat-treated product is immersed in 200 times the amount of water (normal temperature). , Propeller agitated, treated for 3 hours. The fibers recovered from the washing liquid are hydrated potassium titanate fibers having a composition corresponding to potassium hexatitanate (X-ray diffraction). [VI] Firing treatment The above fibers were dehydrated and dried, and then put in an alumina crucible for 900
Hold in a furnace held at ℃ for 3 hours. The obtained fiber is a potassium hexatitanate polycrystalline fiber.

Table 1 shows the fiber length measurement results of potassium hexatitanate fibers obtained through the above steps. In the table, L (5
0) is an integrated amount of 50 in the weight-based integrated distribution of fiber length.
% Means the fiber length, and L (25) and L (75) mean the fiber length corresponding to the integrated amounts of 25% and 75%, respectively. FIG. 1 is a graph showing the measurement results of Table 1. The processing temperature is 750 ° C
The aspect ratio of the potassium hexatitanate fiber obtained after the heat treatment of about 2 is about 2, and the aspect ratio of the potassium hexatitanate fiber obtained after the heat treatment of about 800 ° C. and 900 ° C. is about 3 and about respectively. It is 4.

[0015]

[Table 1]

From the above, the potassium hexatitanate fiber of the present invention has its fiber morphology controlled by the treatment temperature in the heat treatment for producing fibers of primary phase potassium dititanate crystals from the amorphous coagulated product, It can be seen that relatively fine and homogeneous fibers are obtained.

[0017]

According to the method of the present invention, potassium hexatitanate fibers can be obtained as relatively fine fibers and excellent in homogeneity, and the fiber morphology is different depending on the heat treatment temperature of the amorphous solidified product. It can be controlled freely and easily. The potassium hexatitanate fiber obtained by the method of the present invention is useful as a base fiber for producing a sliding material such as a wet paper clutch from the fiber form, or as an additive for paints and a luster pigment.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the fiber length of potassium hexatitanate fiber obtained by the method of the present invention and the heat treatment temperature of an amorphous solidified product.

Claims (1)

[Claims] 1. A titanium compound which becomes titanium dioxide (TiO ₂ ) when heated and potassium oxide (K ₂ O) when heated.
And a potassium compound to be mixed so that the molar ratio of TiO ₂ / K ₂ O is 1.5 to 2.5, the heated melt is rapidly cooled to form an amorphous solidified product. The coagulated product is heat-treated at a temperature of 750 to 950 ° C. to generate potassium dititanate crystal fibers, and then the heat-treated product is treated in a washing liquid to elute K ⁺ ions and dititanium. The composition of the potassium acid titanate crystal fiber is converted into hydrated potassium titanate fiber having a composition equivalent to that of potassium hexatitanate, and the lumps of the fiber are defibrated, dehydrated, dried, and fired to form hexahydrated potassium titanate fiber. A method for producing a potassium hexatitanate fiber, which comprises converting the structure into a potassium titanate crystal.