JP2875486B2 - Tantalum oxide sol and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tantalum oxide sol and a method for producing the same. More specifically, the present invention relates to a novel tantalum oxide sol, which is stabilized by oxalic acid firmly binding tantalum oxide sol particles, such as a catalyst,
An object of the present invention is to provide a tantalum oxide sol suitable for providing a tantalum raw material to an optoelectronic material, a semiconductor material, and the like.

[0002]

2. Description of the Related Art In recent years, there has been a high demand for the use of tantalum oxide for ceramic raw materials, electronic materials, and the like. Have been. However, the tantalum oxide raw material is generally used by baking raw material powder such as tantalum hydroxide and tantalum oxide and pulverizing the raw material, so that the particles are not only non-uniform, but also have a relatively large particle diameter. Is currently used. Therefore, at present, there is an increasing demand for a tantalum oxide raw material having a uniform and fine particle diameter as described above.

Under such circumstances, techniques for obtaining various elements in the form of fine particles have recently been developed to meet the above requirements. For example, Japanese Patent Application Laid-Open No. Sho 62-96319 discloses a technique of using tantalum alkoxide as a raw material and obtaining hydrate particles of tantalum oxide by a method of hydrolyzing tantalum alkoxide. However, the particle diameter of such tantalum oxide particles is about 500 angstroms at the lowest, and is not necessarily suitable as a uniform fine tantalum raw material. Therefore, at present, there is a demand for the appearance of uniformly fine tantalum oxide raw materials as tantalum oxide raw materials.

[0004]

Under the circumstances described above, the present inventors have proposed a method of obtaining such a tantalum oxide raw material in a uniformly fine sol state in order to obtain a uniformly fine tantalum oxide raw material. We studied diligently. as a result,
As a means of obtaining a sol of tantalum oxide, using an active tantalum hydroxide compound as a raw material, the sol obtained by reacting this tantalum compound and oxalic acid at a specific ratio is uniform fine particles, In addition, the inventors have found that the sol is a novel sol that is obtained as a stable sol and solves the above-mentioned problems, and has completed the present invention based on such findings.

[0005]

[SUMMARY OF Namely, the present invention relates to tantalum oxide and oxalic acid _{(HCOO) 2 / Ta 2 O} 5 particle size 500 comprised in the range of molar ratio 0.5 to 5 angstroms following oxidation Tantaruzoru . Further, the present invention adds an oxalic acid to the active tantalum hydroxide compound so that the molar ratio of (HCOO) ₂ / Ta ₂ O _{5 is in} the range of 5.0 to 30, and performs a heating reaction at a temperature of 90 ° C. or more for 2 hours or more. Oxalic acid and tantalum oxide are characterized in that (H
(COO) ₂ / Ta ₂ O ₅ Particle ratio 500 composed of a molar ratio in the range of 0.5 to 5
The present invention relates to a method for producing a tantalum oxide sol having a thickness of less than angstroms .

[0006]

First, the oxalic acid and tantalum oxide of the present invention are (H
(COO) ₂ / Ta ₂ O ₅ Particle ratio 50 consisting of a molar ratio of 0.5 to 5 50
The tantalum oxide sol of 0 Å or less will be described in detail.
The tantalum oxide sol of the present invention is a novel sol stabilized by the particles of tantalum oxide being firmly bound by oxalic acid. In further detailing the sol of the present invention, a description will be given below using specific examples.

(Specific example 1) Tantalum oxide (manufactured by Starck)
400 g was dissolved in 4.2 L of hydrofluoric acid (HF 10%). This solution was added to 2.8 L of aqueous ammonia (NH ₃ 15%) over 60 minutes, and then filtered and washed with a filter press to obtain tantalum hydroxide. As a result of composition analysis of this active tantalum hydroxide, Ta ₂ O ₅ was 23%. 174g of this tantalum hydroxide
To this was added 230 g of oxalic acid dihydrate (Kanto Chemical Reagent) so that the molar ratio of (HCOO) ₂ / Ta ₂ O was _{5 to} 20, and then water was added to bring the total amount to 0.8 kg. The solution was reacted at 100 ° C. for 3 hours under reflux with stirring. As the reaction progressed, the liquid gradually became blue and exhibited a uniform sol state.

Next, the sol obtained after the reaction was subjected to removal of impurities using an ultrafiltration module (SLP-1053 manufactured by Asahi Kasei Kogyo) to obtain a sol of the present invention. The composition of the obtained sol was analyzed, and the results are shown in Table 1.

Comparative Example 1 The active tantalum hydroxide used in Example 1 was dried at 130 ° C. to obtain a dried product of tantalum hydroxide (Ta ₂ O ₅ 87%). 46 g of this tantalum hydroxide is 524 g of water
And 230 g of oxalic acid dihydrate was added thereto so that the molar ratio of (HCOO) ₂ / Ta ₂ O was _{5 to} 20. Next, this liquid was kept at 100 ° C. for 8 hours under reflux while stirring. This liquid was still in a slurry state even after 8 hours. After the impurities were removed from the slurry using an ultrafiltration module, the composition of the slurry was analyzed. The results are shown in Table 1.

[0010] In the composition analysis shown in Table 1, the particle size was measured using a particle size distribution analyzer (PACIFIC
The measurement was performed using a NICOMP Model-370 (manufactured by SCIENTIFIC) and a centrifugal sedimentation type particle size distribution analyzer (SA-CP2 manufactured by Shimadzu Corporation).
Furthermore, after the sol obtained in Example 1 was allowed to stand at a temperature of 30 ° C. for 30 days, the state of the sol was observed.
Even after a day, the solution was stable without forming a precipitate.

[0011]

[Table 1]

The characteristics of the tantalum oxide sol of the present invention are newly listed as follows. First, since the sol of the present invention is composed of uniformly stable particles of tantalum oxide,
It can be stored for a long period of time, and can be applied to the surface of various materials and dried to form an oxide film having a uniform composition. This is significantly different from the conventional tantalum raw material obtained by baking and pulverizing a raw material powder such as tantalum oxide, and its use as a tantalum oxide raw material is widespread.

Secondly, since the sol of the present invention is composed of tantalum oxide particles of 500 Å or less, it is excellent in the addition of a small amount to various materials and uniform mixing. This is suitable for applications such as a humidity sensor element and an acid-resistant coating film, and has excellent performance. Further, the sol of the present invention can easily control the microstructure of ceramics due to such characteristics, and is suitable for use as a raw material for a dielectric. Further, the sol of the present invention is excellent in control of solid acidic acidity and improvement in heat resistance, and is excellent in use as a catalyst and the like. The sol of the present invention having the above-mentioned excellent characteristics is suitable not only for the applications described above but also as a tantalum raw material for producing, for example, piezoelectrics, semiconductors, various optoelectronic materials, superconductors, and the like. .

Next, the method for producing the tantalum oxide sol of the present invention will be described in detail. The method for producing a sol according to the present invention comprises adding an active tantalum hydroxide compound to a (HCOO) ₂ / Ta ₂ O ₅ molar ratio of 5.0.
Oxalic acid is added so as to be within the range of 30 to 30, and a heating reaction is carried out at a temperature of 90 ° C. or more for 2 hours or more. The active tantalum hydroxide compound used in the present invention can be produced by a known method previously filed by the present applicant (Japanese Patent Publication No. 4-576).
No. 16, No. 5-2614). That is, using tantalum or ore containing tantalum or other tantalum raw materials, dissolving them with hydrofluoric acid, separating tantalum by solvent extraction, and further reacting the solution obtained by stripping tantalum into an aqueous phase with aqueous ammonia. To precipitate as hydroxide.

Alternatively, such an active tantalum hydroxide compound is not limited to the above-mentioned method. For example, a raw material such as tantalum hydroxide, tantalum oxide, or tantalum chloride may be used, and this may be used as a mineral acid and / or a mineral acid. A solution obtained by neutralizing a solution decomposed and dissolved with hydrofluoric acid with an alkali such as ammonia water and washing the generated tantalum hydroxide with water or the like to remove impurities may be used. It is particularly important in the present invention that the active tantalum hydroxide thus obtained is used without removing water by means such as drying. When using a tantalum hydroxide that has been dried to remove water, the yield of the sol of the present invention will be low even if it is subjected to means for obtaining the sol of the present invention described later, and the sol of the present invention will hardly be obtained. .

The present invention then provides the active tantalum hydroxide compound thus obtained with a (HCOO) ₂ / Ta ₂ O ₅ molar ratio of 5.0
Oxalic acid is added so as to be in the range of ~ 30, and subjected to a heating reaction at a temperature of 90 ° C or more for 2 hours or more with appropriate stirring. In this case, the use of oxalic acid in the present invention is particularly important, and the sol of the present invention can be used even if acetic acid, maleic acid, malonic acid, or the like is used as an organic acid other than oxalic acid. Can not get.

The tantalum oxide of the present invention is obtained as a sol having a particle diameter of 500 angstroms or less, and such adjustment of the particle diameter is achieved by converting the tantalum raw material at the time of producing the above-mentioned active tantalum hydroxide into a mineral. The concentration can be adjusted by adjusting the tantalum concentration of the solution decomposed with acid or hydrofluoric acid, or by adjusting the concentration of alkaline agent and the rate of addition during neutralization. For example, in this case, as the concentration of the tantalum and the concentration of the alkali agent are increased, or as the addition speed of the alkali agent is increased, the particle size of the tantalum oxide sol obtained by the treatment of the present invention described later becomes smaller. The particle size can be adjusted by adjusting the temperature, time, tantalum concentration, and oxalic acid usage during the reaction in the sol production process of the present invention.

With respect to the amount of oxalic acid used, the molar ratio of (HCOO) ₂ / Ta ₂ O _{5 to} the active tantalum hydroxide compound is 5.0 to 30.
Is important. That is,
The amount of oxalic acid deviates from this range, and (HCOO) ₂ / Ta ₂ O ₅
If the molar ratio is less than 5.0, no sol can be obtained even if the subsequent reaction is carried out for a long time, and conversely, the (HCOO) ₂ / Ta ₂ O ₅ molar ratio becomes 30.
If it exceeds, the yield of the sol obtained after the reaction is extremely reduced, which is not industrial. It should be noted that the reaction was carried out in such a molar ratio range.
By performing, oxalic acid and tantalum oxide of the present invention
(HCOO) ₂ / Ta ₂ O ₅ Particle ratio 5 composed of molar ratio 0.5 to 5
It is possible to obtain tantalum oxide sol of less than 00 angstroms
You.

Further, with respect to the reaction temperature and time, the higher the reaction temperature or the longer the time, the smaller the particle size of the obtained tantalum oxide sol. However, in the present invention, the reaction is carried out at a temperature of 90 ° C. or more and 2 ° C. It is necessary to carry out the heating reaction for more than an hour. If the temperature exceeds 100 ° C,
The reaction may be performed by hydrothermal treatment using an autoclave or the like. The sol obtained after the heating reaction removes excess oxalic acid by means such as ultrafiltration or impurities such as chlorine ions and fluorine ions depending on the type of raw materials used in the production. By carrying out such a reaction, a fine, tantalum oxide sol of the present invention having a desired particle size and stable and uniformly dispersed can be obtained.

[0020]

The present invention will be further described below with reference to examples of the present invention, but the present invention is not limited to these examples. Also,
All percentages are by weight unless otherwise specified.

Example 1 3 kg of active tantalum hydroxide was obtained based on Example 1 of Japanese Patent Publication No. 4-57616, which was an invention previously filed by the present applicant. As a result of a composition analysis of this tantalum hydroxide, Ta ₂ O ₅ was 25%. This tantalum hydroxide 1
230 g of oxalic acid dihydrate (Kanto Chemical Reagent) was added to 60 g to give a (HCOO) ₂ / Ta ₂ O ₅ molar ratio of 20, and then water was added to bring the total amount to 0.8 kg. The solution was reacted at 100 ° C. for 3 hours under reflux with stirring. With the progress of the reaction, the liquid gradually turned blue and exhibited a uniform sol state. Next, the sol obtained after the reaction was subjected to removal of impurities using an ultrafiltration module (SLP-1053, manufactured by Asahi Kasei Kogyo Co., Ltd.) to obtain a sol of the present invention. As a result of a composition analysis of the obtained sol, the pH was 1.2 at Ta ₂ O ₅ 10%. The particle size was measured and the state of the sol was observed. The results are shown in Table 2.

Comparative Examples 2 to 4 Using the active tantalum hydroxide used in Example 1, acetic acid (Comparative Example 2) and maleic acid were used instead of the oxalic acid of Example 1 so as to have the same molar ratio.
The same test was performed using (Comparative Example 3) and malonic acid (Comparative Example 4). After adding these acids to tantalum hydroxide,
While stirring, it was kept at 100 ° C for 8 hours under reflux conditions,
These liquids were almost in a slurry state even after 8 hours.
Further, the particle diameter of these slurries was measured and the state of the liquid was observed, and the results are shown in Table 2.

[0023]

[Table 2]

Examples 2 to 4 Tantalum oxide (manufactured by Starck)
400 g was dissolved in 4.2 L of hydrofluoric acid (HF 10%). This solution was added to 2.8 L of aqueous ammonia (NH ₃ 15%) over 60 minutes, followed by filtration and washing with a filter press to obtain active tantalum hydroxide. To 174 g of this tantalum hydroxide (Ta ₂ O ₅ 23%), (HCO
O) ₂ / Ta ₂ O ₅ Oxalic acid 5 in a molar ratio of 5.0 (Example 2)
8 g was added followed by water to a total volume of 0.8 kg. The solution was reacted at 100 ° C. for 30 hours under reflux with stirring. Separately, instead of the above molar ratio, each molar ratio is
The same test was performed for 10 (Example 3) and 30 (Example 4).

The sol thus obtained was subjected to removal of impurities using an ultrafiltration apparatus to obtain a sol of the present invention. The composition of the obtained sol was analyzed, and the sol yield was calculated from the analysis result. Separately, the obtained sol of the present invention was adjusted to 10% as Ta ₂ O ₅ and this was adjusted at 30 ° C. to 3%.
After standing for 0 days and 3 months, the condition was observed. Table 3 shows the results.

(Comparative Examples 5 to 6) In Example 2 described above,
The molar ratio of oxalic acid added to tantalum hydroxide is (HCOO) ₂
The test was carried out in the same manner with the use of 2.5 (comparative example 5) and 35 (comparative example 6) in terms of / Ta ₂ O ₅ molar ratio, respectively. A composition analysis and the like were similarly performed on the obtained product, and the results are shown in Table 3.

[0027]

[Table 3] Note) ◎: Low viscosity stable

(Examples 5 to 7) The tantalum hydroxide (Ta ₂ O ₅ 25%) used in Example 1 was used.
To 60 g, the total amount by adding (HCOO) ₂ / Ta ₂ O such that the ₅ mole ratio of 20 was added oxalic acid dihydrate 230 g, then water 0.8k
g. The solution was reacted at 90 ° C. for 5 hours under reflux with stirring. (Example 5) Separately, only the heating reaction conditions were changed from the above conditions to 100
The reaction was carried out under the conditions of 6 ° C. for 6 hours (Example 6) and 100 ° C. for 8 hours (Example 7). The sol solution thus obtained was subjected to removal of impurities by using an ultrafiltration apparatus to obtain a sol of the present invention. The obtained sol was adjusted to 10% as Ta ₂ O ₅ , and the sol was allowed to stand at 30 ° C. for 30 days and for 3 months, and the results were shown in Table 4.

(Comparative Examples 7 and 8) The same conditions as in Example 5 were used except that only the heating reaction conditions were changed, and the conditions were 80 ° C. for 5 hours (Comparative Example 7) and 100 ° C. for 1 hour (Comparative Example 8). In the same manner. The obtained product was subjected to a similar test, and the results are shown in Table 4.

[0030]

[Table 4] Note) ◎: Low viscosity stable, ○: High viscosity stable

[0031]

The tantalum oxide sol of the present invention is composed of uniform tantalum oxide particles, and takes a stable form of particles presumed to be caused by oxalic acid being strongly bonded to tantalum oxide. Is very stable and can be stored for a long time. Also, the sol of the present invention
Since it is composed of tantalum oxide particles of 500 angstroms or less, it is excellent in small amount addition to various materials, uniform mixing property, and the like. Therefore, the tantalum oxide sol of the present invention is suitable as a tantalum raw material for producing a catalyst, an optoelectronic material, a semiconductor, a piezoelectric body, and the like, and its application is wide.

Claims (2)

(57) [Claims] (1) Oxalic acid and tantalum oxide are (HCOO) ₂ / Ta
A tantalum oxide sol having a particle diameter of 500 angstroms or less and a ₂ O ₅ molar ratio in the range of 0.5 to 5. 2. An active tantalum hydroxide compound, comprising (HCOO)
Oxalic acid and tantalum oxide are characterized by adding oxalic acid so that the molar ratio of ₂ / Ta ₂ O _{5 is in} the range of 5.0 to 30 and performing a heating reaction at a temperature of 90 ° C. or more for 2 hours or more (HCOO) ₂ / Ta ₂ O ₅
Particle size comprised within the range of molar ratio 0.5 to 5 500 angstroms or less
The method for producing the tantalum oxide sol below .