JP3229350B2 - Alkali titanate crystal, production method thereof and composite material thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alkali titanate crystal having a novel composition as a new ceramic material, a method for producing the same, and a composite material using the same.

[0002]

Among the Related Art K ₂ O · nTiO potassium titanate compounds represented by _2, the crystal such as whiskers of n = 2, 4, 6, 8 are known, n is stable otherwise No report has ever been found on crystals. Mar
Chand et al. (Material. Res. Bul)
l. , In _{15,1129 (1980)), K 2} O
If the offset-the composition of 8TiO ₂ the composition of K ₂ O rich side, have reported that K ₂ O · 4TiO ₂ and K ₂ O · 8TiO ₂ intergrowth (intergrowth) is produced.

As shown in Table 1, with respect to alkali titanate crystals represented by M ₂ O · nTiO ₂ (M is an alkali metal), Table 1 shown by n = 2, 3, 4, 6, 8
There are reports for each of the items marked with a 〇.

[0004]

[Table 1]

For Na ₂ O.7TiO ₂ , A.I. D.
Wadsley et al., ActaCryst., B2
4,392 (1968)), but Na ₂ O.
Intergrowth of 6TiO ₂ and Na ₂ O · 8TiO ₂ (Inter
(growth). In any case, M ₂ O
nTiO ₂ (M is an alkali metal, 7.0 ≦ n ≦ 7.8)
There is no report of pure crystals as.

[0006]

The inventor of the present invention differs from these conventionally known alkali titanate crystals in that M
_From the composition of ₂ O · 8TiO ₂ (M is an alkali metal), M
₂ O rich side and M ₂ O · 6TiO ₂ from a range in which the composition TiO ₂ rich side shifted, i.e., M ₂ O · nTiO
₂ It was found that stable crystals exist in the range of (7.0 ≦ n ≦ 7.8). Such a crystal is a stable single crystal different from the conventional alkali titanate crystal represented by M ₂ O · nTiO ₂ (n = 2, 4, 6, 8). It was confirmed that it had characteristics different from those of acid-alkali crystals. As the shape, a shape such as a fibrous plate shape or an amorphous shape that is more useful depending on the purpose of use is presented. That is, the crystal having the novel composition is distinguished from the conventional alkali titanate crystal as a reinforcing filler such as plastic or metal, a dielectric material, and the like. An object of the present invention is to provide a crystal having such a novel composition.

[0007]

SUMMARY OF THE INVENTION The present invention relates to a method for producing M ₂ O · nT.
iO ₂ (where M is an alkali metal, 7.2 ≦ n ≦ 7.
It is a novel alkali titanate crystal represented by the composition of 8). In the present invention, as the alkali metal, Li,
One or more selected from Na, K, Rb, and Cs can be used. It was also found that the alkali site of the alkali titanate crystal was replaced with 20 mol% or less of an alkaline earth metal to maintain the same crystal structure. In the present invention, ((1-m) M ₂ O · m (LO)) · nTiO _{2 in} which a part of an alkali metal is substituted with an alkaline earth metal.
(However, L is an alkaline earth metal, M is an alkali metal, 0
The present invention also provides a novel alkali titanate crystal represented by the composition of <m ≦ 0.2, 7.0 ≦ n ≦ 7.8). These materials can be used in the form of fibrous or plate-like irregular shapes that are advantageous as reinforcing fillers such as plastics and metals, dielectric materials, catalysts, ionic conductive materials, and the like. Also, the molar ratio of TiO ₂ n
Shows a specific composition of 7.0 to 7.8 and has a specific crystal structure. The present invention further provides a composite material exhibiting excellent properties in which these alkali titanate crystals are contained in a thermoplastic resin, a thermosetting resin, a paint, an inorganic material, or the like.

The method for producing a novel crystal of the present invention is as follows.

FIG. 7 shows an example of the first manufacturing method. The starting material is an alkali titanate having a layered structure such as a fibrous plate or amorphous shape. For example, K ₂ O.2TiO ₂ , K ₂ O.
A considerable amount of an acid (nitric acid, hydrochloric acid, sulfuric acid, etc.) for obtaining a target crystal composition is added to a slurry of a layered structure alkali titanate such as 4TiO ₂ , Na ₂ O.3TiO ₂ to elute excess alkali, For example, K ₂ O.nTiO ₂ .xH ₂ O
(However, 7.2 ≦ n ≦ 7.8) is obtained, and the obtained target composition is heated and dehydrated at 300 to 900 ° C. to obtain the crystal of the present invention. When the alkaline earth metal is introduced, the same step can be achieved by adding a predetermined amount of an aqueous solution of a soluble alkaline earth salt, for example, an aqueous solution containing Ca ions to the slurry. Further, when a different kind of alkali metal not contained in the starting material is introduced, it can be introduced by the same operation.

FIG. 8 shows a second manufacturing method. The first
In the same manner as in the production method, a layered structure alkali titanate is synthesized, a considerable amount of acid is added to the slurry, and a layered structure hydrous titanium oxide in which most alkalis are eluted is obtained, and a predetermined amount of alkali is added thereto. For example, K ₂ O.nTiO ₂ (7.
2 ≦ n ≦ 7.8) is obtained, and the target composition obtained as described above is fired at 300 to 900 ° C. to obtain the crystal of the present invention. In the case of introducing an alkaline earth metal, in the step of ion exchange, if the ion exchange is performed using a mixed aqueous solution of an aqueous solution containing an alkaline earth metal and an aqueous alkali metal solution, a crystal having a composite composition of an alkaline earth metal and an alkali metal is obtained. Can be obtained.

[0011]

[Function] M ₂ O.nTiO ₂ (However, 7.2 ≦ n ≦ 7.
When the lattice constant of the crystal of the present invention represented by the composition 8) was measured, a, b, c, and β could be determined as a monoclinic system. Also, the powder X-ray diffraction data could be satisfactorily indexed, indicating that the crystal structure was formed as a single phase. The crystal of the present invention has a relative dielectric constant of K ₂ O.6TiO ₂ or K ₂ O.8TiO ₂ .
Significantly higher than ₂ . When used as a plastic reinforcing material, an excellent reinforcing effect was observed. The reasons for these are not clear, but are presumed to reflect a unique crystal structure.

The shape of the crystal is derived in the form of a layered alkali metal titanate synthesized into a fibrous plate or amorphous shape as a starting material. For example, fibrous K ₂ O · 4Ti
By using O ₂ as a starting material, fibrous K ₂ O · n
Crystals of TiO ₂ (where 7.2 ≦ n ≦ 7.8) can be obtained.

[0013] Next, such a novel crystal production method is based on a host-guest reaction such as ion exchange, intercalation (insertion), and deintercalation (extraction) of a layered structure alkali titanate used as a starting material. Focusing on the characteristics of the present invention, the present invention has been achieved. That is, the layered structure alkali titanate is synthesized in advance, derived therefrom, a considerable amount of a mineral acid or an organic acid is added to an aqueous solution to obtain a target composition, and the obtained target composition is heated. The technical feature is a process consisting of processing. Furthermore, a stable crystal having the same structure can be produced by introducing an alkali or alkaline earth metal by ion exchange in an aqueous solution and performing heat treatment. The role of the heat treatment is to dehydrate the crystal water occupying the interlayer and to convert the structure from the layered structure.

[0014]

EXAMPLES [Example A] The alkali titanate crystals of the present invention were produced by the following steps, and the characteristics thereof were measured.

(1) Synthesis of Starting Materials The starting materials shown in Tables 2 and 3 were synthesized by the following means.

(1-1) Fibrous K ₂ O.4TiO ₂ was synthesized by a flux method using potassium molybdate as a flux. That is, the molar ratio of titanium dioxide (TiO ₂ ) to potassium carbonate (K ₂ CO ₃ ) was 4: 1, and potassium molybdate (K ₂ MoO ₄ ) was 50 wt% of all components.
The resulting mixture was fired at 980 ° C. for 30 minutes to obtain fibrous potassium tetratitanate (K ₂ O.4TiO ₂ ) crystals having a length of 10 to 20 μm and a width of 0.2 to 0.6 μm.

(1-2) Plate-like K ₂ O.2TiO ₂ was synthesized by a melting method. Titanium dioxide (TiO ₂ ) and potassium carbonate (K ₂ CO ₃ ) are mixed at a molar ratio of 2: 1 and 1
After melting at 100 ° C for 30 minutes, quench and cool to a length of 100-70.
A plate-like potassium dititanate (K ₂ O.2TiO ₂ ) crystal having a thickness of 0 μm and a width of 10 to 50 μm was obtained.

(1-3) Fibrous hydrous titanium oxide (H ₂ T)
i ₄ O ₉ .nH ₂ O) was produced from the fibrous crystals of potassium tetratitanate obtained in (1-1) above. 2N (N) potassium tetratitanate so that the solid concentration becomes 10%
, And filtered and washed.
For washing, the pH of pure water used as washing water and the pH of filtrate
Was repeated until 一致 matches. The filtrate was dried to obtain fibrous hydrous titanium oxide (H ₂ Ti ₄ O ₉ .H ₂ O). The shape remains that of potassium tetratitanate.

(1-4) Columnar Na ₂ O.3TiO ₂ was synthesized by a firing method. Titanium dioxide (TiO ₂ ) and sodium carbonate (Na ₂ CO ₃ ) are mixed at a molar ratio of 3 to 1 and baked at 850 ° C. for 2 hours to have a length of 1 to 10 μm and a width of 0.2 to 0.8 μm. Sodium trititanate (Na ₂ O
・ 3TiO ₂ ) columnar crystals were obtained.

(1-5) The fibrous potassium tetratitanate obtained by the method of the above (1-1) is pulverized with a ball mill,
An irregular shape was obtained.

(2) Production of Crystals of Examples (2-1) Examples 1, 2, 3, 5, 6 The starting materials obtained by the above method were immersed in water so as to have a solid concentration of 5% by weight. And a predetermined amount of a 6N (normal) hydrochloric acid (HCl) aqueous solution was added according to the desired composition. Thereafter, the mixture was stirred at a temperature of 23 ° C. for 2 hours and filtered. The obtained filtrate was further heated at 550 ° C. for 2 hours to obtain crystals of Examples 1, 2, 3, 5, and 6. The shape was derived as the fibrous, amorphous, or plate-like shape of the starting material.

(2-2) Example 4 The fibrous hydrous titanium oxide obtained by the method of the above (1-4) was used as a starting material and immersed and dispersed in water to a solid concentration of 4% by weight. . A predetermined amount of 8N (normal) potassium hydroxide (KOH) was added, and the mixture was brought into contact at a temperature of 25 ° C for 3 hours. After the contact, the mixture was separated by filtration and heat-treated at 600 ° C. for 1 hour to obtain the crystal K ₂ O.7.3TiO ₂ of Example 4.

(2-3) Example 9 Instead of the 8N (normal) potassium hydroxide (KOH) aqueous solution used in the above (2-2) Example 4, 7N (normal) potassium hydroxide (KOH) and 1N (Normal) The same treatment as in Example 4 was performed except that a mixed solution of sodium hydroxide (NaOH) was used, and the crystals of Example 9 {0.9 K ₂ O) (0.1
Na ₂ O)｝ · 7.2 TiO ₂ was obtained.

(2-4) Example 7 Instead of the 6N hydrochloric acid used in Examples 1, 2, 3, 5, and 6, a 6N (normal) hydrochloric acid aqueous solution in which 10% of calcium chloride (CaCl ₂ ) was dissolved was used. Example 1, except for using
The same processing as in 2, 3, 5, 6 was performed, and the crystal of Example 7 {0.9K ₂ O) (0.1CaO)} · 7.4TiO ₂
I got

(2-5) Example 8 A 6N (normal) hydrochloric acid aqueous solution was added in the same manner as in Examples 1, 2, 3, 5, and 6, and then a 20% magnesium chloride hexahydrate (MgCl ₂ .6H) was added. ₂ O) The same treatment as in Examples 1, 2, 3, 5, 6 was performed except that a predetermined amount of the aqueous solution was added.
_{{(0.8Na 2 O) (0.2MgO} )} · 7.6Ti
To give the O _2.

(3) Determination of Chemical Composition The above product is dissolved by heating in a sulfuric acid-ammonium sulfate solution, and titanium is quantified by absorption spectrophotometry, alkali metal is determined by atomic absorption, and alkaline earth metal is determined by ICP emission spectrometry. Then, the chemical compositions were determined. These are shown in Table 2.

(4) Measurement of Lattice Constant Using potassium chloride (KCl) as an internal standard, the lattice constant was refined by a least square method from X-ray diffraction lines. The values are shown in Table 2. Note that K ₂ O · 6TiO ₂ and K ₂ O
Tables 3 and 4 show the lattice constants of O · 8TiO ₂ .

(5) Measurement of relative permittivity The crystals obtained in Examples 1 to 9, the K ₂ O.7TiO ₂ crystal (Reference Example), and the commercially available K ₂ O.6TiO ₂ and K ₂
The relative permittivity of O · 8TiO ₂ was measured as follows.

The sample which was compression-molded so that the filling rate of the powder became 0.15 was dried at 120 ° C. to completely remove water, and then sandwiched between two copper concentric electrodes to adjust the relative humidity. While maintaining the temperature at 70%, the temperature was changed and an electric field of 1 V, 1 KHz was applied to measure the relative dielectric constant. The relative permittivity is shown in Table 5 and FIGS.

As is apparent from Tables 2 to 4, the alkali titanate crystal of the present invention has a different crystal structure from the conventional K ₂ O.6 TiO ₂ and K ₂ O.8 TiO _2, and thus has a physical property. It was confirmed that the characteristics were also different. For example, it has a significantly higher dielectric constant than conventional K ₂ O.6TiO ₂ and K ₂ O.8TiO ₂ . Table 5 also shows, for reference, values of the relative permittivity similarly measured for barium titanate powder, which is a typical conventional dielectric material.

[0031]

[Table 2]

[0032]

[Table 3]

[0033]

[Table 4]

[0034]

[Table 5]

Example B The M _{2 of} the present invention was used in an amount of 80 parts by weight of a polyacetal resin (trade name: Duracon M90, manufactured by Polyplastics Co., Ltd.).
20 parts by weight of O.nTiO ₂ (where 7.0 ≦ n ≦ 7.8) was added, and the mixture was melt-kneaded at 190 ° C. and pelletized. The obtained pellets are processed by an injection molding machine (cylinder temperature 1
90 ° C, mold temperature 80 ° C) Injection molding and ASTM D
No. 638, No. 1 tensile strength test piece and ASTM D790 bending strength test piece were prepared. For comparison, test pieces were produced in the same manner as above using commercially available K ₂ O.6TiO ₂ and K ₂ O.8TiO ₂ . Table 6 shows the results of the strength test.
4 to 6.

In order to clarify the reinforcing effect of the present invention, a comparison was made with K ₂ O · 6TiO ₂ and K ₂ O · 8TiO ₂ in the same shape. That is, the length of 8TiO ₂ is 10 to 20 μm and the width is 0.2 to 0.5 μm. As the product of the present invention having an equivalent shape, the product obtained in Examples 2, 4, 5, 6, 7, and 9 shown in Example A above was used.

[0037]

[Table 6]

[Example C] 15 parts by weight of titanium oxide (TiO ₂ ), 45 parts by weight of epoxy resin varnish, 1.5 parts by weight of additives and stabilizers, 7 parts by weight of solvent, and 15 parts by weight of polyamide resin varnish Example A
The K ₂ O · 7.3 TiO ₂ of the present invention obtained in 3 was
6.5 parts by weight were added, and the mixture was formed into a paint by an SGI sand mill. The steel plate was spray-coated and subjected to a Taber-type abrasion resistance test (grinding stone CS12, load 750 g, 1000 rotations). Table 7 shows the results.

[0039]

[Table 7]

Example D K ₂ O.7.6 TiO of the present invention obtained in Example A-5 was added to 65 parts by weight of ordinary Portland cement and 30 parts by weight of water.
₂ parts by weight, and after kneading with a mixer, demolding for 24 hours,
Curing in water at 20 ° C. was performed for 28 days, and a strength test was performed. For comparison, commercially available K ₂ O.6TiO ₂ and K ₂ O
· 8TiO ₂ was performed using the same way strength test. The results are shown in Table 8.

[0041]

[Table 8]

As described above, if the crystal of the present invention is used as a fibrous filler, potassium titanate whisker (K), which is widely used at present for reinforcing and friction materials, is used.
₂ O.6TiO ₂ and K ₂ O.8TiO ₂ ) are more effective and a suitable composite material can be obtained.

In recent years, researches on a piezoelectric material obtained by combining a ceramic dielectric material such as lead titanate with plastic or rubber have been actively conducted. Such a composite material has such characteristics that it has flexibility that cannot be obtained by simple ceramics, is resistant to impact and bending, has good moldability and is excellent in productivity.

The functional composite material filled with the crystal of the present invention is no exception, and the composite material of the present invention is not limited to the properties such as high strength, high elasticity, and abrasion resistance of this embodiment. Absent.

[0045]

As described above, as described above, the M ₂ O of the present invention is used.
TiO ₂ (where 7.2 ≦ n ≦ 7.8) or (m
LO · (1-m) M ₂ O) · nTiO ₂ (where L is an alkaline earth metal, M is an alkali metal, 0 <m ≦ 0.2,
The crystal of 7.0 ≦ n ≦ 7.8) is a crystal having a novel composition which has not been reported so far, has a specific relative dielectric constant, and is used as a thermistor, an electrorheological fluid, an actuator, a functional element and the like. be able to. In addition, fibrous M ₂ O.
nTiO ₂ (where 7.2 ≦ n ≦ 7.8) or (m
LO · (1-m) M ₂ O) · nTiO ₂ (where L is an alkaline earth metal, M is an alkali metal, 0 <m ≦ 0.2,
When the crystal of 7.0 ≦ n ≦ 7.8) is mixed with a thermoplastic resin, a thermosetting resin, a paint, a cement, or the like, a composite having excellent mechanical strength and abrasion resistance as compared with the conventional potassium titanate fiber is obtained. Material was found.

[Brief description of the drawings]

FIG. 1 is a graph of the relative dielectric constant of an alkali titanate crystal.

FIG. 2 is a graph of the relative dielectric constant of the crystal of the present invention.

FIG. 3 is a graph of the relative dielectric constant of the crystal of the present invention.

FIG. 4 is a graph of tensile strength of the present invention.

FIG. 5 is a graph of bending strength of the present invention.

FIG. 6 is a graph of the flexural modulus of the present invention.

FIG. 7 is a process chart showing a method for producing a crystal of the present invention.

FIG. 8 is a process chart showing a method for producing a crystal of the present invention.

Continuation of front page (72) Inventor Yoshihito Tachi 2-4-1 Shiba Park, Minato-ku, Tokyo Kawatetsu Mining Co., Ltd. (56) References Yogoyo-kyokai-shi 88 [8] 1980 p60-66 Solid State Ionics 42 (1990) 93-99 Report of the Institute of Scientific Measurements, Tohoku University, Vol. 37, No. 1, 115-125 (1988) (58) Fields investigated (Int. Cl. ⁷ , DB name) C01G 23/00 CA (STN)

Claims (7)

(57) [Claims] 1. An alkali titanate crystal having a composition of M ₂ O.nTiO ₂ (where M is an alkali metal and 7.2 ≦ n ≦ 7.8). 2. (mLO · (1-m) M ₂ O) · nTi
An alkali titanate crystal represented by the composition of O ₂ (where L is an alkaline earth metal, M is an alkali metal, and 0 <m ≦ 0.2, 7.0 ≦ n ≦ 7.8). 3. A composite material comprising the alkali titanate crystal according to claim 1 or 2. 4. A layered structure alkali titanate is used as a starting material, and a considerable amount of an acid for obtaining a target crystal composition is added to a slurry of the layered structure alkali titanate to elute excess alkali to form M ₂ O.nTiO. _2. × H ₂ O (where M is an alkali metal, 7.0 ≦ n ≦ 7.8) to obtain a target composition,
A method for producing an alkali titanate crystal, comprising subjecting the obtained target composition to a heat treatment at 300 to 900 ° C. 5. The method for producing alkali titanate crystals according to claim 4, wherein a predetermined amount of at least one kind of soluble alkaline earth metal ions or alkali metal ions is added to the slurry of alkali titanate. 6. Starting from a layered structure alkali titanate, a considerable amount of acid is added to a slurry of the layered structure alkali titanate, and the alkali is eluted to obtain a layered structure hydrous titanium oxide. The target composition of M ₂ O.nTiO ₂ (where M is an alkali metal, 7.0 ≦ n ≦ 7.8) is obtained by adding an alkali of A method for producing an alkali titanate crystal, which comprises performing a heat treatment. 7. The method for producing an alkali titanate crystal according to claim 6, wherein the target ions are taken in using a mixed aqueous solution of an aqueous solution containing an alkaline earth metal and an aqueous alkaline solution.