JPH0434809A - Fibrous dielectric and manufacture thereof - Google Patents

Abstract

PURPOSE:To manufacture a fibrous dielectric by a simple method wherein no special devices are necessary but the surface of a fibrous substance is covered with titanic acid alkaline earth metallic salt. CONSTITUTION:Titanate whisker or titanium whisker oxide is preferable as a fibrous substance. The surface of fibrous substance is covered with titanic acid alkaline earth metallic salt. A titanium compound is dissolved in a disperse solution of fibrous substance and a alkali earth metallic compound, therein, and a preciptant is concurrently or separately added to those mixed solutions while it is being agitated so that the titanium compound and an alkaline earth metallic compound both of which are unsoluble in a dispersion medium are made to be deposited on the surface of the fibrous substance and then heated at 500 - 1300 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a novel fibrous dielectric material useful as a fine ceramic material, a reinforcing material for plastics, and an electronic/electrical material, and a method for producing the same.

(Prior art) Alkaline earth metal titanates are widely used as raw materials for ceramics and dielectrics, but most of these are powders and are often used exclusively by sintering. . However, since it is a powder, it has the following drawbacks. In other words, ■Close-packing with fine particles is an effective means to obtain a high-performance sintered body, even if it is a powder, but advanced processing and synthesis technology is required to obtain fine particles of alkaline earth metal titanate. At the same time, the finer the raw material powder, the more grain boundaries (junction points between particles) will occur in the resulting sintered body, and defects will occur due to poor contact between the powders, so it is difficult to control the grain boundaries. Advanced technology is required.

■Alkaline earth metal titanate salts are generally hard, and it is difficult to post-process the sintered body (cutting, surface polishing, etc.), and it is necessary to form it into the desired shape before sintering. The compact has a characteristic Ilness caused by sintering the powder, which makes post-processing difficult.

In recent years, with the diversification of needs, the search for new performance and applications based on shape anisotropy has begun for these alkaline earth metal titanates. Development is desired, such as hydrothermal synthesis ^
Synthesis of fibrous alkaline earth metal titanate salts using hot special reactions has been studied, but these known methods require a high level of skill in selecting reaction conditions and special equipment, making them difficult to use industrially. The utility value was not recognized.

Alkaline earth metal titanate is an isomer with an elemental ratio of M/T i of 1 or more, represented by the general formula MO·nTio2 (wherein M is an alkaline earth metal and n is a real number from 1 to 12). It has been known.

Industrial equipment is also well known and used.
The fibrous alkaline earth metal salt having an elemental ratio of n=1 cannot be obtained by known production methods.

The present inventor has conducted research on titanic acid compounds for many years, and has announced various new titanic acid compounds, production methods, and their uses. A patent is pending for a manufacturing method effective for directly obtaining fibrous alkaline earth metal titanate from a mixture of However, these are all fibrous materials made of alkaline earth metal titanate, and the fiber shape is limited by the synthesis method and the mechanical strength of the fiber is limited by the type of alkaline earth metal titanate. However, the drawback was that it was difficult to respond to diversifying needs.

(Problems to be Solved by the Invention 1) An object of the present invention is to provide a fibrous dielectric material that can be obtained by a simple method without requiring any special equipment, and a method for manufacturing the same.

Another object of the present invention is to provide a fibrous dielectric material that can be composited with polymer materials and ceramic materials and can meet various needs, and a method for producing the same.

(Means for Solving the Problems) The present invention relates to a fibrous dielectric material whose surface is coated with an alkaline earth metal titanate salt, and a method for producing the same.

The fibrous material of the present invention is one that exhibits a fiber shape with an aspect ratio (ratio of fiber length/fiber diameter) of 10 or more, and each fiber length and fiber diameter are selected depending on the use. be. However, the fiber diameter is 0.
A diameter of 01 μm or more is preferable, and a diameter smaller than this tends to be insufficient in strength as a reinforcing composite material. The fiber length is also selected depending on the application, but in order to provide uniform strength when the fibrous dielectric of the present invention is used as a molding material, whisker-shaped fibers with a fiber length of 5 to 30 μm are preferable. When used as a fabric, it is preferably in the form of spun fibers.

In the present invention, the fibrous material of the present invention can be arbitrarily selected from substances exhibiting a fiber shape, and typical examples include a fibrous material selected from spun-type fiber materials such as glass fiber, alumina fiber, and silica fiber. substance, also silicon carbide whiskers,
Examples include fibrous substances selected from fine fibrous materials such as silicon nitride whiskers, titanate whiskers, zinc oxide whiskers, and magnesium oxide whiskers.These fibrous substances exhibit heat resistance of 500°C or higher, and
The fiber shape was selected from those that did not change or deform in the heated atmosphere at ℃, and in order to be used as a dielectric material,
A material with high electrical insulation is preferred. In addition, in the present invention, if the fibrous material is particularly selected, titanate whiskers and the like have excellent adhesion to the surface of the alkali titanate coating layer and the ability to form a homogeneous coating layer. Titanium oxide whiskers are preferred.

Typical titanate whiskers and titanium oxide whiskers have the general formula aM 20 ・T io 2 ・nH2
0 (M is an alkali metal, a is a real number of 0≦a≦1, n is 0
≦n≦10), examples include sodium titanate, potassium titanate, titanium oxide, etc., and are industrially produced in large quantities and have excellent thermal and electrical properties.・4 T i O2・nH2O, K2
O"6TiO2'nH2O, K20'8 T i O2
Potassium titanate salts such as (n is the same as above) are preferred. In addition, T obtained by acid extraction from these titanates
Although hydrated titania whiskers represented by iO2・nHxO (n is the same as above) can also be used as the fibrous material of the present invention, the aqueous solution of titanate and alkali, which is the representative production method of the present invention When the product obtained by the insolubilization reaction with an aqueous solution of an earth metal compound is heat-treated at 500 to 1300°C (using watery titania whiskers as a fibrous material), the insolubilized and precipitated alkaline earth metal compound is Although it shows good results in improving pickling properties, the production reaction of alkaline earth metal titanate for the coating layer requires skill in designing the molar ratio of titanium and alkaline earth metal and controlling the reaction. .

The fibrous dielectric of the present invention is the above-mentioned fibrous material whose surface is coated with an alkaline earth metal titanate,
What is alkaline earth metal titanate? General formula: bM'o-T
io Calcium titanate, magnesium titanate, barium titanate,
Beryllium titanate, strontium titanate, etc., Be
, Mg, Cat Sr.

Examples include titanates of alkaline earth metals such as Ba and Ra. Incidentally, from the viewpoint of dielectric properties, it is well known that b=1, and a coating layer made of barium titanate is particularly preferable, but it is not limited to this. Further, the alkaline earth metal titanate in the coating layer may be one type, a mixture of two or more types, or a composite alkaline earth metal titanate, such as Ba1-x.5rx-TiO2 (in the formula, 0<x<1). Furthermore, a small amount of different metals and/or metal oxides may be present together.

The fibrous dielectric of the present invention is a fibrous material whose surface is coated with an alkaline earth metal titanate salt, and the amount of coating is selected depending on the purpose of use, the combination of the coating layer and the fibrous material, etc. Although not particularly limited, the surface of the fibrous material as a core material is
It is coated with a thickness of ~50n-.If it is too thin, the physical properties of the coating layer will be insufficient and the surface will only be modified.If it is too thick, the surface will become convex and the surface will become uneven. When used as a material for composite materials due to decreased smoothness,
The filler density decreases, making it difficult to demonstrate the utilization effect, and furthermore, the aspect ratio (ratio of fiber length/fiber diameter) decreases, which also affects the development of physical strength of the composite material. In the case of a whisker-shaped fibrous material, the maximum thickness of the alkaline earth metal titanate layer is preferably about 1/2 of the fiber diameter of the whisker, preferably about 1/4 of the fiber diameter.

As a method for manufacturing the fibrous dielectric of the present invention, any method such as a physical or chemical method for coating the surface of a fibrous material serving as a core material with an alkaline earth metal titanate salt can be used. As a physical method, a PVD method in which alkaline earth metal salt vapor is deposited on a fibrous material that is a core material is advantageous for forming a thin coating layer. Additionally, a CVD (vapor phase chemical reaction) method can also be used.

In the present invention, based on various researches on titanic acid compounds, as a manufacturing method for making the fibrous dielectric of the present invention inexpensive and of high quality, the fibrous material of the present invention is used as a core material, and the surface of the fibrous material is subjected to a solution reaction. Particularly preferred is a method in which a titanium compound and an alkaline earth metal salt are deposited and then heat treated at 00 to 1300°C.

In the present invention, solution reaction refers to a solution in which a solution of a titanium compound and an alkaline earth metal compound are dissolved in a dispersion solution of a fibrous material, simultaneously or separately, or in the presence of a precipitant in a mixed solution of these. The titanium compound and the alkaline earth metal compound, which are insoluble in the dispersion medium, are added to the surface of the fibrous material while stirring.

The concentration of the fibrous substance in the dispersion medium is selected depending on the type of fibrous substance, but it is generally preferable that the dispersion medium can flow or be stirred smoothly, usually 1 to 30%, preferably 3%.
A range of ~20% is preferable; if the concentration is too low, productivity will decrease. Also, if the concentration is too high, problems will arise in the homogeneity of the deposition resulting from the solution reaction of the present invention, which is not preferable.

The solution in which the titanium compound is dissolved is an aqueous solution or an organic solvent solution of the titanium compound, and preferred specific examples include an acidic aqueous solution containing titanate ions, an acidic aqueous solution of a titanium compound, and an alcoholic solution of titanium alcoholade. It will be done.

The solution in which the alkaline earth metal compound is dissolved may be either an aqueous solution or an organic solvent solution, but an aqueous solution is preferable from the viewpoint of economy and environmental pollution. As the alkaline earth metal compound, among hydrohalides, nitrates, acetates, formates, hydroxides, etc., those soluble in water or organic solvents can be used. One or a mixture of two or more of these alkaline earth metal compounds can also be used. still,
Hydrohalides, particularly hydrochlorides and nitrates, are preferred from the viewpoint of availability, ease of reaction, etc., and MgCl2
, Ca Cl2, BaCf2, Mg(N O3h, C
a(NOl)2, S r(NOs)z, Ba(NOz
)z and their hydrates.

The precipitating agent of the present invention is one that precipitates a titanium compound insoluble in a dispersion medium from a solution containing a titanium compound, and also one that precipitates a compound insoluble in a dispersion medium from a solution in which an alkaline earth metal compound is dissolved. In general, examples include hydrolyzing agents, neutralizing agents, carbonate ions, etc. If the solution is alcohol etc., water can be used as a dispersion medium and used as a precipitating agent. However, in the present invention, alkaline aqueous solutions such as ammonia water etc. , alkaline earth metal solutions, and aqueous solutions (solutions containing carbonate ions) such as ammonium carbonate, carbon dioxide gas, ammonium hydrogen carbonate carbamate, and ammonium bicarbonate are preferable. Insoluble alkaline earth metal carbonate is deposited on the surface of the fibrous material, and although the reason is not clear, when the alkaline earth metal carbonate and the insolubilized titanium compound are later calcined, alkaline earth metal titanate is formed. Salt is efficiently generated, and when deposited with other alkaline earth metal salts, alkaline earth metal oxides and titanium oxides are formed in addition to alkaline earth metal titanates when fired, depending on the firing conditions. Therefore, the solution reaction of the present invention is most preferably an acidic solution of titanic acid, especially an acidic solution of hydrochloric acid, an aqueous solution of an alkaline earth metal hydroxide and/or chloride, and/or an aqueous solution of hydrochloric acid, and a carbonate ion such as ammonium carbonate. Using an aqueous solution containing as a neutralizing agent, a hydrochloric acid solution of an alkaline earth metal compound and a hydrochloric acid solution of titanic acid are added to an aqueous dispersion of a fibrous material or a fibrous material dispersed in a precipitant under stirring. After uniformly depositing the titanium compound and alkaline earth metal carbonate on the surface of the fibrous material, the material is washed with water and dried. Note that these reactions proceed either at room temperature or with heating.

In the present invention, the concentration of these solutions is not particularly limited, but is usually 0.1 to 50-1%, preferably 0.0% in terms of solubility of various compounds and uniform deposition on the surface of fibrous substances. The ratio of the alkaline earth metal and titanium compound deposited on the surface of the fibrous material is the alkaline earth metal titanate salt represented by the general formula bM'o.T + 02. In order to obtain b=i in good. In the present invention, titanium compounds and alkaline earth metal compounds are deposited on the surface of the fibrous material obtained by the above-mentioned method by solution reaction, and then heated in an electric furnace in a temperature range of 500 to 1300°C.
A fibrous dielectric material in which the surface of the fibrous material is coated with an alkaline earth metal titanate salt can be obtained by heat treatment in a conventional heating and firing furnace such as a high-frequency furnace or a high-frequency furnace. The reaction mechanism at this time is not clear, but according to X-ray diffraction and infrared absorption spectrum analysis, titanic acid or water titania is produced by heat treatment, and then these and alkaline earth metal compounds are decomposed by a thermal diffusion reaction. It is thought that the alkaline earth metal titanate salt is produced homogeneously on the surface of the fibrous material as it diffuses.

Here, the above-mentioned heat treatment temperature conditions in the present invention cannot be specified depending on the type of alkaline earth metal and the target substance, but in general, alkaline earth metal titanates are difficult to form at temperatures below 500°C, and fibrous substances form at temperatures above 1300°C. deformation due to thermal deterioration, and grain growth of the alkaline earth metal titanate salts produced, which may fall off from the surface of the fibrous material or form grain boundaries, making it difficult to obtain a continuous film and reducing dielectric properties. . Therefore, the temperature range is 500-1300°C, preferably 8
The temperature range is 00 to 1100°C. The reaction is completed in a heat treatment time of 30 minutes to 4 hours, preferably 1 to 2 hours.

The fibrous dielectric obtained by this process can be used as a heat-treated product, but depending on the purpose, it may be washed with water, pickled, classified, etc. Furthermore, it can also be used after being treated with various surface treatment agents. In particular, the fibrous dielectric of the present invention can be used in molded bodies, films, paints, adhesives, fiber materials, etc. by being composited with molecular materials, and can also be used in fiber-reinforced ceramics, by being composited with other ceramic materials, etc. Can be used as electronic ceramics.

(Example) EXAMPLES Next, the present invention will be explained in more detail by way of examples.

Example 1 Potassium titanate whiskers (manufactured by Daiichi Kagaku, Teismo D, average fiber diameter 0.3μ, average fiber length 15μ)4.
5g to 3.75N sodium hydroxide aqueous solution 350mZ
After uniformly dispersing titanic acid (TiQ, -
2Hto) 2.3g (0.02mol) and barium chloride (BaC12) 4.2g (0.02so1)
was dissolved in 5N hydrochloric acid aqueous solution 400-1 and added dropwise over about 1 hour.

After that, ammonium carbonate ((NH4)2CO3・H
70) 4.6g (0.04+mol) of deionized water 5
The barium titanate precursor is added to the surface of the potassium titanate whiskers by adding the solution dissolved in 0-1 dropwise over about 30 minutes, reacting for about 1 hour under stirring at room temperature, and then washing separately with water and drying. 10. White powder with homogeneous adhesion.
4g was obtained. Transfer this white powder to a platinum crucible,
By applying heat treatment at ℃ for about 2 hours, a white powder 9.
1. was gotten. XIIIA diffraction analysis of this white powder revealed that it contained potassium titanate and barium titanate (BaO-T).
According to electron microscopy, it was found to be a fibrous dielectric material in which barium titanate uniformly coated the surface of potassium titanate whiskers. FIG. 1 is an X-ray diffraction chart of the fibrous dielectric obtained in Example 1, and FIG. 2 is an electron microscopy 41I before heat treatment.
(SEM) photograph, and Figure 3 is the SE after heat treatment.
This is an M photo.

Example 2 In Example 1, barium chloride was replaced with magnesium chloride (M
gC1z ・6 H20) 4. Ig (0.02 mol
), 7.5 g of white powder in which the magnesium titanate precursor was homogeneously adhered to the surface of potassium titanate whiskers was obtained by the same method.

By heat-treating this product at 950°C for 2 hours, 6.9 g of white powder was obtained. As a result of X-ray diffraction and electron microscopy observation, the obtained white powder was composed of potassium titanate and magnesium titanate (MgO- It was a composite of Ti02), and was a whisker-like substance in which the surface of potassium titanate whiskers was uniformly coated with magnesium titanate.

Example 3 In Example 1, barium chloride was replaced with calcium chloride (Ca
Cj! , 2H,O) 2.6g (0.02mol
), 8.1 g of white powder in which the calcium titanate precursor was homogeneously adhered to the surface of potassium titanate whiskers was obtained in the same manner as above.

By heat-treating this material at 850°C for about 3 hours, 6.9 g of white powder was obtained. As a result of X-ray diffraction and electron microscopy observation, the obtained white powder was composed of potassium titanate and calcium titanate (CaO -Ti02), and was a whisker-like substance in which the surface of potassium titanate whiskers was uniformly coated with calcium titanate.

Example 4 ■Titanic acid (same as above) 11.6g (0,1@01)
and barium carbonate (B *CO*) 19.7g (0.1m
ol) was uniformly mixed in an alumina ball mill and filled into a mold forming machine, and then heated at a pressure of 20 kg/cm'' to approx.
By press molding for 0 minutes, the diameter was 4c-1 and the thickness was 2.
A 5 cm disc-shaped molded body was created. This material was transferred to a platinum crucible and heated and fired at 700°C for about 3 hours to form a white sintered body 23.1. was gotten. This sintered body shows amorphous behavior according to X-ray diffraction and cannot be identified, but elemental analysis shows that Ba: 58.7%, Ti: 2
G, 6%, 0; has a composition of 20,7%, BaO・Ti
The element ratio was in good agreement with the element ratio of 1t.

The sintered body obtained as described above was thoroughly ground and dissolved in 5N hydrochloric acid at room temperature to obtain Ba; 2.94%,
Ti: 1,03% (5% as BJIO-Ti02
, 0.215 sol/1) was prepared.

■ After uniformly dispersing 1 G of Titania Whis Force (Tofuika T, manufactured by Nippon Whisker) in 250 soffi of 4N sodium hydroxide aqueous solution, B1+ prepared in the above
In Example 1, 200 mN of a hydrochloric acid solution containing
Drop by the same method as above, and then add ammonium carbonate (described above)
An aqueous solution of Jig (0.1 mol) dissolved in deionized water 100-1 was added dropwise as in Example 1, reacted at room temperature for about 1 hour, and washed separately with water to form titania whiskers. 22.7 g of one-color powder on the surface of which the barium titanate precursor was homogeneously adhered was obtained.

This product was further heat-treated at 1050° C. for about 2 hours to obtain 19.8 g of the desired white powder.

X-ray diffraction and electron microscopy confirmed that this material is a composite of titania (rutile) and barium titanate (Ba0/Ti02), and that the surface of the titania whisker is coated with barium titanate to form a whisker-like substance. .

Example 5 The same method as in Example 4 was used except that the titanium whisker force was changed to 10 g of potassium titanate whiskers (Oita Kagaku, Teismo N), and the surface of the potassium titanate whiskers was uniformly coated with barium titanate. Coated fibrous dielectric (average fiber diameter 0.45 μ−1 average fiber 11
5μm) 19.7gfyX# confirmed from the results of diffraction and electron microscopy observation.

Example 6 In Example 4, the titanium whisker force was replaced with magnesium borate whiskers (manufactured by Ohita Kagaku, Swanai) MgaB
2OS) The same method was followed except that the amount was changed to 10 g, and a fibrous dielectric material (average fiber diameter 0.711 m) in which barium titanate (BaO.T + 02 ) was uniformly coated on the surface of magnesium borate whiskers was prepared.

Average fiber #I length 16μ-) 18.7g was confirmed from the results of X-ray diffraction and electron microscopy.

Comparative Example 1 Potassium titanate whisker (manufactured by Ohita Kagaku, Ti
2.3g of H2O) and 4.2g of barium chloride were placed in a polyethylene bag and shaken well to form a homogeneous mixture.The mixture was transferred to a platinum crucible and heated at 900°C for about 2 hours. White powder (with some sintered parts) S
,S, was obtained. When this white powder was subjected to X-ray diffraction, no peak other than the peak of potassium titanate whiskers, which was the raw material, could be confirmed. Further, when the obtained white powder was observed under an electron microscope, potassium titanate whiskers and powdery granular material were confirmed, and it was found to be a mixture of whisker-like material and powdery granular material.

Comparative Example 2 A reaction was carried out in the same manner as in Example 1 except that titanic acid was not used, to obtain 4 g of a white powder precursor. 7. This white powder was heat-treated at 900° C. for about 2 hours in the same manner as in Example 1 to obtain a white powder (average fiber diameter: 0.3 μm, average fiber length: 13 μm). Og was obtained, but when this material was subjected to X-ray diffraction and electron microscopic observation, the powder and granules were found to have a composition of potassium titanate whiskers, barium oxide, and a trace amount of Ba0.5 T io 2. However, the material targeted by the present invention could not be obtained.

(Effects of the Invention) The fibrous dielectric material of the present invention can be used for new applications of the well-known alkaline earth metal titanate salt dielectric material. That is, since the dielectric material has an anisotropic shape, it enables new applications in which it is used in combination with polymeric materials and ceramic materials. Furthermore, the manufacturing method of synthesizing the desired fibrous dielectric material by coating the surface of the fibrous material of the present invention with a precursor of an alkaline earth metal titanate salt and then subjecting it to heat treatment is completely new. It has little industrial applicability in its industrialization.

[Brief explanation of the drawing]

Figure 1 is an X-ray diffraction chart of the fibrous dielectric obtained in Example 1, and Figure 2 is an electron microscope *(
SEM) photograph, and Figure 3 is the SEM after heat treatment.
It's a photo. (Above) Applicant Otsuka Chemical Co., Ltd. Representative Patent Attorney 1) Iwao Mura Figure 2 Figure 8 Procedural Amendment 1 Applicable (September 21, 1990)

Claims (5)

[Claims] (1) A fibrous dielectric material whose surface is coated with an alkaline earth metal titanate. (2) The fibrous dielectric material according to claim 1, wherein the fibrous substance is a titanate. (3) The fibrous dielectric material according to claim 1, wherein the fibrous material is a titanium oxide fiber. (4) Depositing titanium compounds and alkaline earth metal salts on the surface of the fibrous material by solution reaction at 500 to 1300°C.
A method for producing a fibrous dielectric material characterized by subjecting it to heat treatment. (5) The method according to claim 4, wherein the solution reaction is an insolubilization reaction using an aqueous solution of a titanium compound and an aqueous solution of an alkaline earth metal compound.