JP2816908B2 - Method for producing potassium hexatitanate fiber - Google Patents

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 useful as a material for a sliding portion, an additive for a paint, a gloss pigment, and the like.

[0002]

_2. Description of the Related Art Potassium hexatitanate fiber [K ₂ Ti ₆ O
₁₃ ] is a synthetic inorganic fiber having abrasion resistance, fire / heat resistance, heat insulating property, reinforcing property, etc., and its industrial application has been attempted as an asbestos substitute in various fields. A melting method known as a typical production method is a method in which a titanium compound which becomes titanium dioxide (TiO ₂ ) by heating and a potassium compound which becomes potassium oxide (K ₂ O) by heating are mixed with TiO ₂ / K ₂ The starting material is mixed by mixing so that the molar ratio of O becomes about 2, and the starting material mixture is heated and melted. The heated melt is poured into a cooling mold, and the potassium dititanate crystal [K ₂ Ti ₄ O ₅ ], a fiber coagulation process in which the coagulation (fiber lump) is treated with a washing liquid such as water or an acid aqueous solution to elute K ⁺ ions. A potassium hexatitanate fiber is obtained through a depotassium treatment for conversion and a baking treatment for converting the crystal structure of the fiber.
The size of the potassium hexatitanate fiber obtained through the above steps is relatively coarse (fiber diameter: about 20 to 50 μm, length: about 100 to 300 μm), and the fiber form is largely uneven and poor in homogeneity. .

For the purpose of improving the fiber morphology, Japanese Patent Application Laid-Open No. 63-64997 discloses that a heated molten material of a starting material is subjected to rapid cooling by a twin roll method or the like instead of directional cooling to obtain an amorphous material. Since the solidified coagulate (glass) is not formed and the K ⁺ ion cannot be eluted before the glass, it is subjected to a short-time heat treatment to convert it into potassium dititanate crystals, and further to change the chemical composition, and A method for producing a potassium hexatitanate fiber through a processing step such as a crystal structure conversion is disclosed. The fibers obtained by the process are relatively fine (fiber diameter: about 0.2
２2 μm, length: about 10-30 μm).

[0004]

However, in the above fiber production method, in the heat treatment for depositing potassium dititanate crystals from the amorphous coagulated material, the potassium dititanate crystals are not formed as fibers, but in a uniform particle size. The heat-treated product is subjected to K ⁺ ion elution treatment and calcination treatment to obtain potassium tetratitanate crystal [K ₂ Ti ₄ O ₉ ] and potassium hexatitanate crystal [K ₂ T
After passing through an intermediate step of forming a mixed-phase fiber of [i ₆ O ₁₃ ], K ⁺ ions are eluted and calcined again to obtain a potassium hexatitanate fiber, so that the steps are inevitably complicated. In addition, the homogeneity of the size and morphology of the potassium hexatitanate fiber thus obtained is determined by the mixed phase ratio between the potassium tetratitanate crystal and the potassium hexatitanate crystal in the intermediate step,
It becomes different depending on the conditions of the repeated baking treatment and the like, and it is inevitable that the treatment is troublesome for controlling the fiber size and shape. The present invention has been made in view of the above, and provides a method for producing potassium hexatitanate fiber having simpler processes, easy control of fiber size and shape, and excellent homogeneity.

[0005]

The method for producing potassium hexatitanate fiber of 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. And TiO
₂ / K ₂ O molar ratio of the molten product of the mixture was blended so that 1.5 to 2.5, and rapidly cooled by a metal double roll method amorphous coagulum and without amorphous coagulum At a temperature of 750
After heating at 950 ° C. to form potassium dititanate crystal fibers, the heat-treated product is treated in a washing solution to elute K ⁺ ions to form potassium dititanate crystal fibers. The composition is converted to hydrated potassium titanate fiber equivalent to potassium titanate, and the fiber mass is defibrated, dehydrated, dried, and calcined to form the hydrated potassium titanate fiber into potassium hexatitanate crystals. It is characterized by conversion. 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 one of the starting materials, a titanium compound which becomes titanium dioxide by heating. The potassium compound to be compounded in the titanium compound is typically potassium carbonate (K ₂ CO ₃ ), and in addition, a hydroxide, a nitrate, or the like can be used. The mixing ratio of the titanium compound and the potassium compound is
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 rapidly solidified amorphous solidified product.
The heating and melting of the starting material is performed at a temperature of about 950 to 1100.
C. can be performed.

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 a twin roll method. The melt contacts the metal roll by allowing the melt to flow down the twin roll gap while rotating the pair of metal rolls facing each other at high speed.
While passing through the roll gap while being quenched,
And is discharged downward. Due to the quenching effect, an amorphous solidified product can be obtained efficiently.

[0008] The amorphous coagulated material obtained by the quenching treatment is subjected to a heat treatment 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., because even if crystals of potassium dititanate are formed at a lower temperature, they remain in the form of fine particles having a particle size of about 0.1 μm, and fibers are formed. The reason for this is that the upper limit is set to 950 ° C., because if it exceeds that, melting starts. The fiber length of the generated 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 generated crystals increase.

[0009] The fiber form of the potassium hexatitanate fiber obtained through the step of converting the crystal composition by the potassium removal treatment following the heat treatment and the step of changing the crystal structure by the calcination treatment is the same as the fiber formed as the primary phase fiber by 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 generating the primary phase potassium dititanate crystal fiber from the amorphous coagulated product. Can be other manufacturing conditions,
For example, it is not necessary to strictly control the clearance between twin rolls in rapid solidification of a heated melt, and if it is made amorphous at a sufficient cooling rate, it will be relatively fine and homogeneous only by controlling the heat treatment temperature. An excellent potassium hexatitanate fiber can be stably obtained.

[0010] The elution and fibrillation of K ⁺ ions from the fiber mass made of the potassium dititanate crystal subjected to the heat treatment can be performed by using water (normal temperature), heated water (about 50 to 80 ° C), or various kinds of water. Aqueous acid solution, for example, about 0.05-0.3% aqueous sulfuric acid, about 0.05-0.3% hydrochloric acid, about 0.1-1%
Acetic acid aqueous solution or the like can be used as a washing liquid. By the potassium removal treatment, the molar ratio of TiO ₂ / K ₂ O becomes about 6
The potassium dititanate crystals in the primary phase are converted into hydrated potassium titanate having a chemical composition equivalent to potassium hexatitanate by eluting K ⁺ ions until the temperature becomes. The amount of K ⁺ ion eluted can be adjusted by the amount of the processing solution used, the processing time, and the like. In addition, the fiber mass is cleaved and swelled by hydration swelling.
It is defibrated with peeling. In order to increase the processing efficiency of the potassium removal and the defibration, a stirring flow is added to the processing liquid by a propeller or the like as necessary.

The chemical composition of the fiber obtained through the above depotassium treatment corresponds to that of potassium hexatitanate, but the crystal structure has a crystal structure (layer structure) of the precursor potassium dititanate. This is converted into a crystal structure (tunnel structure) of potassium hexatitanate. This structural transformation is achieved by a calcination treatment at a temperature of about 700-1000C (preferably about 900C). This results in a potassium hexatitanate fiber that is complete both structurally and structurally.

[0012] The potassium hexatitanate fiber thus obtained is a polycrystalline fiber having almost the same fiber morphology as the primary phase fiber produced in the heat treatment step of the amorphous coagulated product, and has a fiber length of 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 is excellent in homogeneity.

[0013]

【Example】

[I] Starting material Natural rutile sand (purity: 95.6) as a titanium compound
%, Produced in Australia), industrial potassium carbonate (purity: 99.5%) as a potassium compound, TiO ₂ / K ₂
Mixed at a ratio where the molar ratio of O becomes 2.0. [II] Heat melting Put the starting material mixed powder in a platinum crucible, 1100 ° C × 4
Heated and melted for 0 minutes. [III] Quenching treatment The heated melt is allowed to flow down into the gap between the metal twin rolls rotating at high speed to obtain a flake-like solidified product. The coagulate is completely amorphous (X-ray diffraction). [IV] Heat treatment The flake-like amorphous solidified product is put into an alumina crucible and heat-treated. Treatment temperature: 750 ° C., 800 ° C., 900 ° C. Treatment time: 40 minutes [V] Depotassium removal and defibration treatment by washing liquid The water is used as a washing liquid, and the heat-treated product is immersed in 200-fold amount of water (normal temperature) Treatment for 3 hours while stirring with a propeller. The fibers recovered from the washing solution are hydrated potassium titanate fibers having a composition equivalent to potassium hexatitanate (X-ray diffraction). [VI] Baking treatment After dehydrating and drying the above fiber, put it in an alumina crucible 900
Hold for 3 hours in a furnace maintained at ° C. The resulting fiber is a potassium hexatitanate polycrystalline fiber.

Table 1 shows the fiber length measurement results of the potassium hexatitanate fiber obtained through the above steps. In the table, L (5
0) is the integrated amount 50 in the weight-based integrated distribution of the fiber length.
%, And L (25) and L (75) mean fiber lengths 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 through the heat treatment is about 2, and the aspect ratio of the potassium hexatitanate fiber obtained through the heat treatment at 800 ° C. and 900 ° C. is about 3, and about 4.

[0015]

[Table 1]

Thus, the potassium hexatitanate fiber of the present invention has its fiber morphology controlled by the treatment temperature in the heat treatment for forming the fiber of the initial phase potassium dititanate crystal from the amorphous coagulated material. It can be seen that relatively fine and homogeneous fibers can be obtained.

[0017]

According to the method of the present invention, potassium hexatitanate fiber can be obtained as a relatively fine fiber having excellent homogeneity, and its fiber morphology can be compared by the heat treatment temperature of the amorphous coagulated material. 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 paint, a gloss pigment and the like.

[Brief description of the 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 coagulated product.

Continuation of the front page (56) References JP-A-60-104522 (JP, A) JP-A-52-37832 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C30B 1 / 00-35/00 C01G 1/00-57/00

Claims (1)

(57) [Claims] 1. A titanium compound which becomes titanium dioxide (TiO ₂ ) by heating and potassium oxide (K ₂ O) by heating
A hot melt of a mixture obtained by mixing a potassium compound to become a TiO ₂ / K ₂ O molar ratio of 1.5 to 2.5 is rapidly cooled by a metal twin roll method to form an amorphous solidified product. After heat-treating the amorphous coagulated product at a temperature of 750 to 950 ° C. to generate potassium dititanate crystal fibers, the heat-treated product is treated in a washing solution to obtain K ⁺ ions. To convert the potassium dititanate crystal fiber into a hydrated potassium titanate fiber equivalent to potassium hexatitanate, disintegrate the fiber mass, dehydrate, dry, bake and hydrate A method for producing potassium hexatitanate fiber, comprising converting the structure of potassium titanate fiber into potassium hexatitanate crystal.