JPH0274527A - Method for producing titanate fibers or membranes having hollandite structure - Google Patents

Abstract

PURPOSE:To readily obtain a fibrous or filmy substance of a high-purity titanate having a hollandite structure W dissolving respective raw materials of a prescribed composition ratio in an aqueous solution of a specific organic acid, concentrating the resultant solution, spinning and forming the resultant concentrated spinning solution and calcining the formed fiber or filmy substance. CONSTITUTION:A fibrous or filmy substance of a titanate having a hollandite structure expressed by the general formula AxMyTi8-yO16 (A is K, Rb, Cs or Ba; M is Mg, Zn, Ni, Al, Fe or Cr; x is 0.5-2.0; y is x/2 when M is bivalent metal and the value of x when M is trivalent metal) is formed by the following method. That is a titanium alkoxide and metal alkoxide or carbonate of the component (M) and carbonate of the component (A) are respectively used as raw materials of the composition ratio expressed by the above-mentioned general formula and dissolved in an aqueous solution of citric acid, tartaric acid alone or a mixed organic acid in a molar amount of >=0.8 based on the total amount of the titanium alkoxide and the metal alkoxide of the component (M). The resultant solution is concentrated to provide a spinning solution, which is then spun, formed into a fibrous or filmy substance and subsequently calcined at 1200-1400 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a process for producing titanate fibers or membranes having a hollandite structure. These have excellent heat resistance and insulation properties, and are useful as heat-resistant and insulation materials, as well as plastics. It is also used as a reinforcing material for metals, cement, etc.

Conventional technology Conventional methods for producing inorganic fibers such as alumina fibers and zirconia fibers include precursor polymer method, slurry method, inorganic salt method,
The sol method is known. Representative examples of these methods are as follows.

In the precursor polymer method, a silicate ester is mixed into a viscous solution containing polyaluminoxane, an inorganic polymer having a main chain consisting of -AI-〇, and the mixture is dry spun and fired.

The slurry method uses ^1!03 fine powder and a small amount of M[CI□・6
Al2(011)3C1 as a binder component in H10
is added to make a viscous slurry, which is then dry spun and fired.

In the inorganic salt method, a water-soluble organic polymer such as polyethylene oxide or PVA is added to an aqueous solution of an aluminum salt, and water-soluble polysiloxane is further mixed to form a viscous liquid, which is blown out from a nozzle and fired.

In the sol method, silica sol and phosphoric acid are added to alumina sol containing ions such as HCOO and C1bCOO to form a viscous liquid.
This is spun and fired.

These methods cannot produce the titanate fibers or membranes having the hollandite structure of the present invention.

As a method for producing titanate fibers having a hollandite structure, the flux property (
Japanese Patent Application No. 58-116459) is known. The method is to add molybdate metal salt to the raw material, melt it, and grow crystals from the melt.

This method requires a long time to produce, resulting in poor production efficiency and problems in that only short fibers of less than 10 strands can be obtained, limiting the field of application.

Purpose of the Invention The present invention was made to eliminate the problems of the above-mentioned method, and its purpose is to prepare a viscous spinning solution containing the composition raw materials, extrude it through a nozzle, shape it, and then sinter it. The general formula % formula % (where A is K, Rb, Cs or Ba, and M is M
g.

Zn, Ni, At, Fe or Cr, x is 0.
5 to 2.0, y represents the value of x when M is divalent / 2.0 when M is trivalent) be.

Structure of the Invention As a result of intensive research to achieve the above object, the present inventors have found that (+1) As the composition raw materials indicated by the above-mentioned - binding margin, titanium is titanium alkoxide, M component is metal alkoxide or carbonate of M component, A The carbonate is used as an ingredient, and it is mixed with (2) citric acid in a specific ratio to the alkoxide,
When tartaric acid alone or a mixture is dissolved and concentrated in a mechanical acid aqueous solution, a viscous liquid suitable for spinning can be obtained.(3) When this is extruded from a nozzle and then fired, it does not generate harmful gases and contains no impurities. It has been found that long fibers or films of titanate having an excellent hollandite structure can be easily produced and obtained. The present invention was completed based on this knowledge.

The gist of the present invention is the general formula A, MyTis-yo+th (where A is Rh, Cs or Ba, and M is Mg.

7, n, Ni, AI, Fe or Cr, X is 0.5 to 2.0, y is x when M is a divalent metal/2. represents the value of X when it is a trivalent metal) Titanium alkoxide and metal alkoxide or carbonate as component M and carbonate as component A are used as raw materials for producing titanate having a hollandite structure.
Citric acid in an amount of 0.8 times or more moles or more relative to the total mole amount of the metal alkoxide components.

Dissolve tartaric acid alone or in addition to an aqueous solution of mixed organic acids;
A method for producing a titanate fiber or film having a hollandite structure, which comprises concentrating the spinning solution to form a spinning solution, spinning it into a fiber or film, and firing it. .

Component A in the composition represented by the general formula in the present invention is a metal that coordinates in the tunnel structure in a hollandite structure, and the raw material for this is a carbonate. Also, the M component is a tie that creates the framework of the tunnel.

is a metal that can replace and occupy the T1 seat in the octahedron of , and its raw material is an alkoxide or carbonate. The raw material for the Ti component is also an alkoxide.

Examples of the titanium alkoxide include titanium tetraisopropoxide, titanium tetra-normal butoxide, and the like. Examples of the metal alkoxide of the M component include isopropoxide, normal butoxide, and ethoxide of the M component metal. However, the invention is not limited to the examples.

Titanium alkoxide and the alkoxide of the M component react very easily with citric acid and tartaric acid to obtain a transparent and uniform solution, which can be converted into an oxide by firing. When the carbonates of component A and component M are mixed with the organic acid, COt is released and a transparent homogeneous solution is formed.

It is necessary that the value of X in the binding margin is 0.5 to 2.0, preferably 1.0 to 1.7. Further, the value of y needs to be the value of x when M is a divalent metal and the value of X when it is a trivalent metal. Outside this range, titanate having a hollandite structure cannot be obtained.

When these raw material compounds are added to an aqueous solution of citric acid or tartaric acid alone or a mixture of organic acids, and dissolved and concentrated, a viscous liquid with stringiness is obtained. In this case, the amount of citric acid and tartaric acid is 0.8 times or more, preferably 1 mole or more, based on the total mole of titanium and M component alkoxide.
．． It is necessary that the amount is 0 to 1.2 times by mole. If the amount is not 0.8 times the mole or more, the resulting spinning dope will not exhibit spinnability and cannot be formed into fibers or membranes.

The aqueous solution of the organic acid has a ratio of 1 mole of the metal alkoxide,
It is preferable to use 20 to 50 times the molar amount of water.

This gives a clear homogeneous solution. When this is heated and concentrated to a viscosity of about 1-100 voids, it becomes 90-10 viscosity.
A viscous liquid with stringiness is obtained at 0°C.

This liquid solidifies as the temperature decreases. Therefore, it is preferable to perform the spinning at 90-100''C.

When spinning is performed using a nozzle, long fibers are obtained, and when extruded through a slit, a membrane-like material is obtained. Moreover, it can be made into ultra-fine short fibers by extruding it through a thick diameter nozzle and burning and blowing it away with flame.

The resulting fibers and membranes were dehydrated and heated to 700 to 100
After heating in air at 0'C to decompose and remove organic matter, 1
When fired at 200 to 1400° C., titanate fibers or membranes having a hollandite structure are obtained.

Sintering is not completed below 1200°C, and begins to melt when it exceeds 1400°C.

Example 1 2.84 g of titanium tetraisopropoxide was added dropwise to a solution of 2.37 g of citric acid dissolved in 20 ml of distilled water, and the mixture was stirred for 3 hours. The solution in this state was suspension-like, and 0.51 g of aluminum isopropoxide was added to this suspension and stirred. This resulted in a transparent and uniform solution. 0.16 g of potassium carbonate was gradually added to this solution and stirred until the solution became transparent and homogeneous. All the above operations were performed at room temperature. The resulting solution was heated to 100"C and concentrated until the viscosity reached 100 voids. When the solution was allowed to cool, the viscosity gradually increased and it had good stringability.

The material in an appropriate viscous state was extruded through a nozzle at room temperature under a dry atmosphere to obtain long fibers with a diameter of 5 to 100 μm. This fiber was colorless and transparent.

The obtained fibers were dried at 100°C overnight, then heat treated at 900°C for 2 hours, and then fired at 1300°C for 3 hours. The obtained fibers are ni+, sAl+, 5Tii, S
It was a titanate fiber possessing a hollandite type structure with a composition of OI&.

Example 2 2.84 g of titanium tetrapropoxide was added dropwise to a solution of 1.50 g of tartaric acid dissolved in 201 g of distilled water, and the mixture was stirred for 3 hours. Add 0.154 g of potassium carbonate to this solution,
The mixture was stirred until the carbon dioxide bubbles disappeared and the liquid became transparent. Then, 0.094 g of magnesium carbonate was gradually added, and the mixture was stirred until the carbon dioxide bubbles disappeared and the liquid became transparent. All operations above were performed at room temperature. went. The resulting solution was heated to 100'
The mixture was heated to a temperature of 0.4°C and reduced until the viscosity reached 100 voids. When this was allowed to cool, the viscosity gradually increased and it had good spinnability.

The material in an appropriate viscous state was extruded through a nozzle at room temperature under a dry atmosphere to obtain long fibers with a diameter of 5 to 100 μm. This fiber was colorless and transparent.

The obtained fibers were dried at 100°C overnight, then heat treated at 900°C for 2 hours, and then fired at 1350°C for 3 hours. The obtained fibers are ni+, Jgo, aTi7. to
It was a titanate fiber possessing a hollandite type structure with a composition of lb.

Example 3 2.84 g of titanium tetraisopropoxide was added dropwise to a solution of 2.72 g of citric acid dissolved in 2011 distilled water.
Stirred for 3 hours. 0.92 g of aluminum isopropoxide was added to this solution and stirred to obtain a transparent homogeneous solution. All operations above were performed at room temperature.

The obtained 7'@ liquid was heated to too 'C, barium carbonate O9 old ε was gradually added thereto, and the mixture was stirred until the carbon dioxide bubbles disappeared and a transparent homogeneous liquid was obtained.9 Then at 100°C. The a-condensation was carried out until the viscosity reached +00 poise.

The material in an appropriate viscous state was extruded through a nozzle at room temperature in a dry atmosphere to obtain long fibers with a diameter of 5 to 100 μm. This fiber was colorless and transparent.

The obtained fibers were dried at 100°C overnight, then heat treated at 900°C for 2 hours, and then fired at 1350°C for 3 hours.

The fibers obtained were 1la1. +eAIz, ziTis
It was a titanate fiber having a hollandite-type structure with a bao1h composition.

Although representative examples of the A component and the M component have been shown above, components not shown here can also be produced in the same manner.

A film-like product is obtained, and when extruded through a wide diameter nozzle and burned and blown away with flame, ultrafine short fibers are obtained.

Effects of the Invention The present invention enables the production of titanate fibers having a hollandite structure, which cannot be obtained by the conventional method of producing inorganic fibers by spinning, by the spinning method. Since long fibers or membrane-like products can be produced and the composition raw materials are alkoxides or carbonates, and the spinning solution is also an organic acid, no harmful gases are generated during production, and the resulting fibers or membrane-like products have no harmful effects. It has an excellent effect of achieving high purity without contamination with impurities.

Patent applicant Takashi Nagase, Institute of Inorganic Materials, Science and Technology Agency
belief

Claims (1)

[Claims] General formula A_xM_yTi_8_-_yO_1_6 (where A is K, Rb, Cs or Ba, M is Mg, Zn,
Ni, Al, Fe or Cr, x is 0.5 to 2.0, y
represents the value of x/2 when M is a divalent metal, and represents the value of x when M is a trivalent metal. ) Titanium alkoxide, a metal alkoxide as an M component, or a carbonate and a carbonate as an A component are used as raw materials for producing a titanate having a hollandite structure represented by Alkoxide and M
It is added to an aqueous solution of a single or mixed organic acid such as citric acid or tartaric acid in an amount of 0.8 times the mole or more based on the total amount of metal alkoxide as a component, dissolved and concentrated to obtain a spinning solution, which is then spun to form a fiber or film. 1. A method for producing a titanate fiber or film having a hollandite-type structure, which comprises forming the titanate into a shape and firing at 1200 to 1400°C.