JPH04202099A - Production of alkali titanate whisker - Google Patents

Abstract

PURPOSE:To obtain linear high-quality whiskers having a high aspect ratio by adding prescribed amts. of carbonaceous starting material and alkali halide to a mixture contg. a Ti source and an alkali source in a prescribed ratio and firing them. CONSTITUTION:A Ti source is mixed with an alkali source so as to obtain 2-8 molar ratio of titanium oxide (TiO2) to alkali oxide (M2O) when the sources are expressed in terms of the oxides. Carbonaceous starting material and alkali halide are added to the mixture and they are fixed. At this time, a solid-liq. interfacial reaction is accelerated by the reducing atmosphere of gaseous CO generated from the carbonaceous starting material. The alkali halide acts as a flux in the crystal growth of alkali titanate, accelerates the growth in the longitudinal direction while inhibiting the growth in the diametral direction and attains a high aspect ratio.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to alkali titanate whiskers, specifically reinforcing materials such as plastics, ion adsorbents, ion exchange materials, molecular adsorbents, friction materials, etc. The present invention relates to a method for producing fibrous alkali titanate whiskers, particularly fibrous alkali titanate whiskers with a high aspect ratio, which are used as filtration media, catalyst carriers, heat insulating materials, and various other uses.

[Prior Art] Conventional methods for producing alkali titanates include, for example, a firing method in which a raw material mixture is fired and synthesized by a solid phase reaction (Japanese Patent Application Laid-open No. 53-26298), and a method in which a raw material mixture is fired and synthesized by solid phase reaction, and a method in which a raw material mixture is fired and synthesized by solid phase reaction (Japanese Patent Application Laid-open No. 53-26298), and a method in which a raw material mixture is fired and synthesized by solid phase reaction, and Flux method (flux method) to obtain alkali titanate by growing crystals of alkali titanate and eluting and removing the flux after cooling.
(Japanese Patent Application Laid-Open No. 51-122700), a melting method in which a stoichiometrically prepared mixture is melted and then cooled and solidified to crystallize it (Japanese Patent Application Laid-Open No. 51-89900), which uses a solvent to reach the critical point of water. Examples include the hydrothermal method (JP-A-50-64526), which synthesizes under high temperature and high pressure.

[Problems to be solved by the invention] In the conventional firing method as described above, the fibers obtained are short fibers with low crystallinity of several micrometers, and in the flux method, a water washing step is required to remove the flux, and Flux recovery equipment is required, resulting in high costs. Furthermore, in the melting method, the crystals grow in close contact with each other, making dissociation treatment difficult, and the resulting fibers have large diameters, low aspect ratios, and poor strength, making them undesirable as reinforcing materials.

Furthermore, in the hydrothermal method, synthesis operations are carried out in a highly alkaline solution under high pressure, which requires safety equipment, increases the cost of the entire facility, requires special materials such as Ag, and requires continuous operation. difficult.

Each of the conventional methods has the above-mentioned problems, and none of them makes it possible to obtain whiskers with a high aspect ratio.

As a result of intensive research into a method for obtaining high-quality alkali titanate whiskers with a high aspect ratio, the present inventors have developed a mixed powder of a titanium source and an alkali source in which an alkali halide and carbon coexist in powder form. The present invention was completed by discovering that alkali titanate whiskers with a high aspect ratio can be easily obtained by firing.

To provide a method for efficiently producing high-quality alkali titanate whiskers by a shortened process without requiring specific pre-processing steps such as molding, washing with water, and other conventional methods. .

[Means for Solving the Problems 1] In order to achieve the above object, the method of the present invention involves adding a carbon raw material to the mixture when firing a mixture of a titanium source and an alkali source to produce a fibrous alkali titanate. and an alkali halide, and are then fired.

Examples of the titanium source include TiO□ and TiOH<, and examples of the alkali source include M2CO3 (where M is an alkali metal). The carbon raw material may be any raw material whose main component is carbon, such as carbon black (channel black, thermal black, furnace black, etc.), graphite activated carbon, etc.
Although not particularly limited, it is preferable to use a material with low ash content and other impurities in order to obtain a highly pure product.

As alkali halides, KCj2, KF, NaC
12, NaF, etc., and one or more of them can be used, and those that evaporate during calcination are preferred because they yield products with high purity. These raw materials are usually mixed in powder form and fired.

The mixing ratio of titanium source and alkali source is preferably oxidized titanium:
/ (T i 02 ), using TiO□/R20 = 2 to 8 as the main raw material in terms of molar ratio in terms of fulkaline oxide (R20),
Carbon raw material and alkali halide each from 0.1 to 2
0% by weight is added and mixed and fired at 900-1200°C.

[Function] The present invention was arrived at as a result of repeated research based on the knowledge that the solid-liquid interface reaction between TiO2 particles formed by firing and molten alkali is important, and the role of the carbon raw material in the present invention is It is presumed that the instantaneous combustion and the reducing atmosphere of the generated CO gas promote the solid-liquid interfacial reaction. In addition, it makes the fired product porous and promotes the growth of whiskers.Although the amount of alkali halide is extremely small, its action is to make the alkali halide act as a flux for crystal growth of alkali titanate, promoting reaction growth and increasing the growth of whiskers in the radial direction. This suppresses the growth of the metal and increases the aspect ratio.

The amount of carbon raw material and alkali halide added to the titanium source and alkali source raw materials to form a composition corresponding to an alkali metal titanate represented by M20 ・nT 102 (M is an alkali metal) is an addition that can be vaporized depending on the firing conditions. In terms of quantity, since the fired product consists only of alkali titanate, a water washing step is not necessary.

Incidentally, since a tunnel furnace or the like can be used for this firing, continuous firing can be performed.

[Example 1] Potassium carbonate], 15 kg, titanium oxide 4.00 kg
, carbon black, 0.36 kg, potassium chloride 0.
Mix 40 kg with a Henschel mixer at 20°C,
It was baked at 00°C for 2 hours. The fired product was identified by X-ray diffraction and was found to be potassium hexatitanate. Further, when magnified with a scanning electron microscope, it was found to be a single fiber with a high aspect ratio, with an average fiber diameter of 07 μm and an average fiber length of 30 μm.

[Example 2] Sodium carbonate 0.88 kg, titanium oxide 4.00 kg
, artificial graphite 6.70kg, sodium chloride 0.20kg
, 0.40 kg of potassium fluoride was mixed and heated at 1100°C.
It was baked for 5 hours. The generated phase obtained by X-ray diffraction is sodium hexatitanate, and has a high aspect ratio in the form of single fibers with an average fiber diameter of 0.8 μm and an average fiber length of 40 μm.

[Example 3] Potassium carbonate 1.72 kg, titanium oxide 3.97 kg,
Carbon black 0.03kg, potassium fluoride 0.02
The mixture of g was calcined at 1000°C for 30 minutes, and the resulting phase was potassium titanate with an average fiber diameter of 0.
51 tm, average fiber length 50 μm, single fiber state, high aspect ratio.

[Comparative Example 11 1.15 kg of potassium carbonate and 400 kg of titanium oxide were mixed and fired in the same manner as in Example 1, and evaluated.

The generated phase is potassium hexticunate, but the average fiber diameter is 1
．． It is a block of sintered rods with an average fiber length of 5 μm and an average fiber length of 2.0 μm.

[Comparative Example 21 Potassium carbonate 1.1'5 kg, titanium oxide 400 kg,
0.36 kg of carbon black was mixed and fired in the same manner and evaluated.

The generated phase is potassium hexatitanate, but the average fiber diameter is 1
It is a sintered block of rods with a diameter of 3 μm and an average fiber length of 2.5 μm.

[Comparative Example 3] Potassium carbonate 1.15 kg, titanium oxide 4.00 kg,
0.40 kg of potassium chloride was mixed and fired in the same manner and evaluated.

The generated phase is potassium hexticunate, but the average fiber diameter is 1
．． It is a block of sintered rods with an average fiber length of 0 μm and an average fiber length of 5 μm.

As explained above, the alkali titanate obtained by the present invention can be easily obtained in the form of a fiber with a high aspect ratio, which is easy to use for its applications.

Furthermore, the alkali titanate whisker according to the present invention is characterized in that it can be obtained in one step with high quality and few defects.

FIG. 1 is a transmission electron micrograph of the material obtained in Example 1. What was obtained by the conventional flux method is
Although dislocations and defects are observed as shown in FIG. 2, the crystals obtained by the present invention have almost no crystal defects.

[Effects of the Invention] According to the present invention, high-quality alkali titanate whiskers that are linear and have an extremely high aspect ratio, which could not be obtained by conventional methods, can be obtained by a washing process in water after calcination or a dissociation process in water, etc. Obtained in high yield without the need for special post-treatment,
The process is simple, shortened, and can be manufactured at low cost, making it extremely useful. It is also possible to produce long fibers of several millimeters or more, making it possible to expand the range of applications.

[Brief explanation of the drawing]

The drawings are transmission electron micrographs; FIG. 1 shows alkali titanate whiskers obtained by the method of the present invention, and FIG. 2 shows alkali titanate fibers obtained by the conventional flux method.

Claims (1)

[Claims] 1. In producing fibrous alkali titanate by firing a mixture of a titanium source and an alkali source, a carbon raw material and an alkali halide are allowed to coexist in the mixture before firing. A method for producing an alkali titanate whisker. 2. The mixing ratio of titanium source and alkali source is titanium oxide (T
iO_2), T in molar ratio converted to alkali oxide (R_2O)
The method for producing an alkali titanate whisker according to claim 1, wherein iO_2/R_2O=2 to 8. 3. M_2O・nTiO_2 (M is an alkali metal)
The titanic acid according to claim 1, wherein the amounts of the carbon raw material and the alkali halide added to the titanium source and alkali source raw materials forming the composition corresponding to the alkali metal titanate represented by are each 0.1 to 20% by weight. Method for producing alkali whiskers.