JP6156876B2 - Method for producing niobate sol - Google Patents

Description

  The present invention relates to a method for producing a niobate sol.

  In recent years, there is an increasing demand for niobium oxide having a high refractive index and dielectric constant in the fields of ceramic raw materials, electronic materials, surface treatment agents, and the like. In particular, in the fields of optoelectronic materials, semiconductor materials, surface protective agents, antireflection materials, refractive index modifiers, catalysts, etc., niobium raw materials having a small particle diameter and a uniform particle size distribution are required as raw materials. Niobium-based sols have been developed.

  The applicant of the present application has developed a technique related to an ammonium niobate sol described in Patent Document 1 as a niobium-based sol exhibiting excellent self-binding properties.

JP 2011-190115 A

  The ammonium niobate sol has room for improvement in applications where compatibility (mixing stability) with a hydrophilic solvent is required.

  As a result of intensive investigations on improving the compatibility of the ammonium niobate sol with the hydrophilic solvent, the present inventors reduced the ammonia content in the ammonium niobate sol, and added an amine compound as a dispersant in place of ammonia. It has been found that the above-mentioned problems can be solved by the use, and the present invention has been completed.

That is, the present invention is as follows.
[1] A method for producing a niobic acid sol, comprising a step of removing ammonia by heating an ammonium niobate sol in the presence of an amine compound.
[2] A method for producing a niobate sol, comprising: washing an ammonium niobate sol mixed with an inorganic acid to remove ammonia, and then heating in the presence of an amine compound.
[3] A step of further adding an organic acid after the production step according to [1] or [2],
A method for producing a niobate sol.
[4] A niobic acid sol produced by the production method according to any one of [1] to [3] above.
[5] The niobic acid according to the above [4], which has a characteristic that the amount of ethanol compatibility is 50 parts by mass or more with respect to 100 parts by mass of the niobate sol adjusted to a Nb ₂ O ₅ concentration of 6% by mass. Sol.
[6] The content of the amine compound is in the range of amine compound / Nb ₂ O ₅ (molar ratio) = 0.1 to 1.5.
The niobate sol as described in [4] or [5] above.
[7] A coating solution for forming a thin film comprising the niobate sol according to any one of [4] to [6] above and a hydrophilic solvent.

  Since the niobic acid sol of the present invention is excellent in compatibility with a hydrophilic solvent, it can be suitably used especially for applications using a hydrophilic solvent.

  The niobate sol production method of the present invention (hereinafter also referred to as “the present production method”) will be described in detail below. A feature of this production method is that ammonia is removed from the ammonium niobate sol to the extent that high compatibility with a hydrophilic solvent is obtained. That is, it is desirable that ammonia can be completely removed, but a certain amount of ammonia may remain as long as high compatibility with a hydrophilic solvent can be obtained by using a predetermined amount of amine compound.

  The following 1st manufacturing method and 2nd manufacturing method differ only in the removal method of ammonia, and the niobic acid sol obtained by both manufacturing methods has the same structure, and shows high compatibility with a hydrophilic solvent. It is.

  Here, the hydrophilic solvent is approximately 10% or more soluble in water such as alcohols such as methanol, ethanol, isopropanol and n-propanol, glycols such as ethylene glycol, diethylene glycol and glycerin, ketones such as acetone and the like. An organic solvent that can be used.

As for the compatibility with the hydrophilic solvent, for example, when ethanol is selected as the hydrophilic solvent, the ethanol phase is compared with 100 parts by mass of the niobate sol in which the Nb ₂ O ₅ concentration is adjusted to 6% by mass. If the dissolved amount is 50 parts by mass or more, it can be evaluated that the compatibility with the hydrophilic solvent is high.

  The first production method includes a step of removing ammonia by heating an ammonium niobate sol in the presence of an amine compound.

  The second production method includes a step of washing the ammonium niobate sol mixed with an inorganic acid to remove ammonia, and then heating in the presence of an amine compound.

Here, the ammonium niobate sol used as a raw material will be described. As the ammonium niobate sol, the ammonium niobate sol described in Patent Document 1 may be used, or a commercially available ammonium niobate sol, for example, the trade name “Vilar Nb-G6000” manufactured by Taki Chemical Co., Ltd. may be used. It may be used. Characterized ammonium niobate sol, ammonia and niobate when dried at 100 ° C. 10 hours, a range of NH ₃ / Nb ₂ O ₅ (molar ratio) = 0.5 to 1.5, a substantially organic acid It is not included.

  As the form of ammonia in the ammonium niobate sol, in addition to the ammonium ions present in the sol, a certain amount of ammonia is detected even after drying at 100 ° C. for 10 hours as described above. It is considered that ammonia adsorbed firmly on the surface of niobic acid colloidal particles (hereinafter referred to as “niobic acid-adsorbed ammonia”) exists.

  The method for producing an ammonium niobate sol is the method described in Patent Document 1, that is, (1) an aqueous solution obtained by dissolving a niobium compound in hydrofluoric acid or a mixed acid of hydrofluoric acid and sulfuric acid, and an aqueous ammonia solution with a pH of 8 or more. It is preferable to use a step of obtaining a dispersion containing fine particles of ammonium niobate by mixing and reacting while maintaining the above, and a step of filtering and washing the dispersion of (2) (1).

First, the first production method will be described.
In the first production method, after mixing an ammonium niobate sol and an amine compound, the ammonium ion in the sol is volatilized as ammonia by heating. The ammonium ions in the sol are considered to include those in which a part of the niobic acid-adsorbed ammonia is substituted with an amine compound to become ammonium ions in addition to the ammonium ions previously present in the sol. When the amount of the amine compound used is increased, the compatibility of the resulting niobic acid sol with the hydrophilic solvent tends to increase.
The mixing conditions are not particularly limited, and an amine compound may be added to the ammonium niobate sol, or vice versa. In addition, what is necessary is just to mix by normal stirring.

The amount of the amine compound used is preferably set so that the content of the amine compound in the resulting niobic acid sol is in the range of amine compound / Nb ₂ O ₅ (molar ratio) = 0.1 to 1.5. When the content is less than 0.1, the residual amount of ammonia in the niobate sol increases, so that it becomes difficult to obtain high compatibility with the hydrophilic solvent. On the other hand, even if the content exceeds 1.5, it is difficult to obtain compatibility corresponding to the content, which is not economical.

  Examples of amine compounds include primary amines, secondary amines, tertiary amines, quaternary ammonium hydroxides, aromatic amines, and alicyclic amines. Examples of the primary amine include methylamine, ethylamine, butylamine, monoethanolamine, and isopropanolamine. Examples of the secondary amine include dimethylamine, diethylamine, diethanolamine, diisopropanolamine and the like. Examples of the tertiary amine include trimethylamine, triethanolamine, triisopropanolamine and the like. Examples of the quaternary ammonium hydroxide include tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, trimethylethylammonium hydroxide, trimethylpropylammonium hydroxide, dimethyldiethylamine hydroxide. , Choline and the like. Examples of aromatic amines include benzylamine and phenethylamine. Examples of alicyclic amines include piperidine.

  The heating conditions are not particularly limited as long as ammonium ions in the sol are volatilized as ammonia, and the heating temperature is preferably, for example, 50 to 150 ° C. Moreover, what is necessary is just to set a heating time suitably according to heating temperature, but it is 1 to 8 hours as a standard. If the amount of amine compound used and the heating conditions are optimized, the ammonia content in the resulting niobate sol can be made below the detection limit.

  The (a) ammonia content, (b) pH, and (c) compatibility with the hydrophilic solvent of the niobate sol obtained by the first production method will be described.

The amount contained (a) ammonia, as a _{guide, NH 3 / Nb 2 O 5} ( molar ratio) = 0 (detection limit) in the range of 1.2. Here, below the detection limit is below the detection limit of nitrogen analysis by the Kjeldahl method.

  (b) The pH is preferably in the range of 6-10.

(c) Compatibility with a hydrophilic solvent will be described in terms of compatibility with ethanol. In the following, when ethanol is added to 100 parts by mass of sol with the Nb ₂ O ₅ concentration adjusted to 6% by mass by an appropriate method such as heat concentration, reduced pressure concentration or dilution, the amount of liquid increases. The amount of ethanol at the time when the viscosity is confirmed is referred to as “ethanol compatible amount”.
An example of the ethanol compatibility of conventional sols is 30 parts by mass with respect to the above-mentioned “Viral Nb-G6000”. Accordingly, the ethanol compatibility amount of the niobate sol of the present invention is preferably at least 50 parts by mass, more preferably 100 parts by mass or more. In particular, if the amine compound content is in the range of amine compound / Nb ₂ O ₅ (molar ratio) = 0.2 to 1.5, the ethanol compatibility tends to be at least 100 parts by mass. Although there is no restriction | limiting in particular about the upper limit of the amount of ethanol compatibility, Addition of a large amount of ethanol is not preferable because the content ratio of niobic acid decreases. The upper limit is about 500 parts by mass.

Next, the second manufacturing method will be described.
In the second production method, (i) a sol obtained by mixing an ammonium niobate sol and an inorganic acid is prepared, (ii) the sol is washed to remove ammonia, and (iii) the ammonia is removed from the sol. Amine compound is mixed and then (iv) heated.

In (i) above, ammonium niobate sol and an inorganic acid are mixed in order to remove ammonia in the following washing (ii). The amount of the inorganic acid used may be set as appropriate according to the target ammonia removal amount. However, in general, the inorganic acid / Nb ₂ O ₅ (molar ratio) is in the range of 0.2 to 1.5. Examples of the inorganic acid include hydrochloric acid, nitric acid, sulfuric acid and the like, and among these, hydrochloric acid is preferable. The mixing conditions are not particularly limited, and an inorganic acid may be added to the ammonium niobate sol or vice versa. In addition, what is necessary is just to mix by normal stirring.

  The washing in the above (ii) is not particularly limited as long as ammonia can be removed, and examples include ultrafiltration while adding water, Nutsche filtration, filter press, etc. Among these, ultrafiltration is particularly preferable. If the washing method and washing conditions are optimized, the ammonia content in the resulting niobic acid sol can be made below the detection limit. The standard of the end point of washing is preferably the time when the filtrate EC becomes 200 μS / cm, more preferably 50 μS / cm.

The amount of the amine compound used in the above (iii) is not particularly limited as long as it is an amount capable of stabilizing the sol instead of the removed ammonia. For example, in view of the stabilization and economic efficiency of the sol, the amine compound / Nb ₂ O ₅ (molar ratio) is preferably in the range of 0.1 to 1.5, more preferably in the range of 0.5 to 1.5. The mixing conditions are not particularly limited, and an amine compound may be added to the sol or vice versa. In addition, what is necessary is just to mix by normal stirring.

  In the heating of (iv) above, the heating conditions may be appropriately set so that the amine compound and niobic acid are reacted to stabilize the sol. As an example, the heating temperature is 50 to 150 ° C., and the heating time may be appropriately set according to the heating temperature, but it is 1 to 8 hours as a guide.

  Since the niobic acid sol obtained by the second production method is the same as the niobic acid sol obtained by the first production method, its characteristics (ammonia content, pH range and compatibility with hydrophilic solvents) ) Is the same as (a) to (c) above.

  In this production method, a step of adding an organic acid may be further provided after the production step of the first production method or the second production method. Addition of an organic acid improves the stability of the resulting niobic acid sol and further tends to improve compatibility with a hydrophilic solvent.

The addition amount of the organic acid is not economical because it is difficult to obtain an effect commensurate with the addition amount even if it is added excessively, and the addition effect is not exhibited if it is too small. For example, organic acid / Nb ₂ O ₅ (molar ratio) is preferably in the range of 0.05 to 0.20. When the addition amount of the organic acid is within the above range, the standard of the pH range of the obtained niobic acid sol is 4 to 9.

  Examples of the organic acid include monocarboxylic acid, dicarboxylic acid, and oxycarboxylic acid, and one or more of these can be used. For example, monocarboxylic acids include formic acid, acetic acid, propionic acid, n-butyric acid, valeric acid, and the like, and dicarboxylic acids include oxalic acid, succinic acid, maleic acid, malonic acid, fumaric acid, glutaric acid, and the like. Examples of the oxycarboxylic acid include citric acid, glycolic acid, lactic acid, tartaric acid, malic acid and the like. Of these, oxycarboxylic acids are preferred.

  Any niobic acid sol obtained by the above production method can be mixed with a hydrophilic solvent to form a coating solution for forming a thin film. The coating solution for forming a thin film requires various additives, for example, polymer compounds such as resin emulsions, silica compounds such as silica sols and silane coupling agents, surfactants, oxide sols having photocatalytic activity, and the like. It may be added accordingly.

  The method of forming a coating film on a substrate by applying a coating solution for forming a thin film on the substrate includes various known coating methods such as brush coating, spray coating, spin coating, dip coating, roll coating, gravure coating, and bar coating. However, it can be selected in consideration of the shape of the substrate. Although drying of a coating liquid changes with kinds of base material, it is preferable to heat-process normally at 300 degrees C or less. However, when glass or ceramics is used as the base material, high temperature treatment is desirable from the viewpoint of improving adhesion, and heat treatment at 500 ° C. or higher, in which niobium oxide is generated by sintering niobic acid, is desirable. On the other hand, when the substrate is a plastic such as acrylic, PET, polycarbonate, or vinyl chloride, the heat treatment temperature is preferably 150 ° C. or less because of the heat resistance of the substrate. If the adhesion between the base material such as plastic or metal and the niobic acid thin film is insufficient, put another metal oxide thin film, a film made of a silane coupling agent, a resin film, etc. between the base material and the niobic acid thin film. It can also be provided as a primer layer.

  EXAMPLES The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto. In Examples, “%” means “% by mass” unless otherwise specified.

[ Reference Example 1]
To 100 g of `` Vilal Nb-G6000 '' (Nb ₂ O ₅ = 6.2%) manufactured by Taki Chemical Co., Ltd., 0.9 g of tetramethylammonium hydroxide (hereinafter abbreviated as TMAH, 25.0%) is added, and 3% at 80 ° C. The heat treatment was performed for a time to obtain a niobate sol (Nb ₂ O ₅ = 6.2%, pH 8.9).
When ethanol was added to 100 parts by mass of the niobate sol with the Nb ₂ O ₅ concentration adjusted to 6%, thickening of the liquid was confirmed in the vicinity of 70 parts by mass of ethanol.

[ Reference Example 2]
A niobate sol (Nb ₂ O ₅ = 6.2%, pH 9.0) was obtained in the same manner as in Example 1 except that TMAH was changed to 1.7 g.
When ethanol was added to 100 parts by mass of the niobic acid sol with the Nb ₂ O ₅ concentration adjusted to 6%, thickening of the liquid was confirmed in the vicinity of 110 parts by mass of ethanol.

[ Reference Example 3]
A niobate sol (Nb ₂ O ₅ = 6.2%, pH 8.8) was obtained in the same manner as in Example 1 except that TMAH was changed to 4.3 g.
When ethanol was added to 100 parts by mass of the niobic acid sol with the Nb ₂ O ₅ concentration adjusted to 6%, thickening of the liquid was confirmed in the vicinity of 300 parts by mass of ethanol.
In addition, when the compatibility with a hydrophilic solvent other than ethanol was investigated, n-propanol was around 130 parts by mass and acetone was around 150 parts by mass with respect to 100 parts by mass of the niobate sol adjusted to 6% Nb ₂ O ₅ concentration. When the mixture was added to the vicinity of part by mass, thickening of the liquid was confirmed. Further, even when ethylene glycol was added up to 400 parts by mass, no thickening of the liquid was confirmed.

Example 4
After adding 0.9 g of TMAH (25.0%) to 100 g of `` Vilal Nb-G6000 '' (Nb ₂ O ₅ = 6.2%) manufactured by Taki Chemical Co., Ltd. Niobic acid sol (Nb ₂ O ₅ = 6.2%, pH 6.5) was obtained by adding 0.5 g of acid monohydrate.
When ethanol was added to 100 parts by mass of the niobic acid sol with the Nb ₂ O ₅ concentration adjusted to 6%, thickening of the liquid was confirmed in the vicinity of 100 parts by mass of ethanol.

Example 5
A niobate sol (Nb ₂ O ₅ = 6.2%, pH 6.2) was obtained in the same manner as in Example 4 except that citric acid monohydrate was changed to 1.0 g.
When ethanol was added to 100 parts by mass of the niobic acid sol with the Nb ₂ O ₅ concentration adjusted to 6%, thickening of the liquid was confirmed in the vicinity of 150 parts by mass of ethanol.

Example 6
A niobate sol (Nb ₂ O ₅ = 6.2%, pH 6.5) was obtained in the same manner as in Example 4 except that 4.3 g of TMAH was used.
When ethanol was added to 100 parts by mass of the niobate sol with the Nb ₂ O ₅ concentration adjusted to 6%, thickening was confirmed once in the vicinity of 400 parts by mass of ethanol. However, when ethanol was further added, thickening of the liquid was confirmed at a total ethanol addition amount of 600 parts by mass.
In addition, when the compatibility with a hydrophilic solvent other than ethanol was investigated, n-propanol was around 140 parts by mass and acetone was around 150 parts by mass with respect to 100 parts by mass of the niobate sol adjusted to 6% Nb ₂ O ₅ concentration. When the mixture was added to the vicinity of part by mass, thickening of the liquid was confirmed. Further, even when ethylene glycol was added up to 400 parts by mass, no thickening of the liquid was confirmed.

[ Reference Example 7]
To 100 g of “Vilal Nb-G6000” (Nb ₂ O ₅ = 6.2%) manufactured by Taki Chemical Co., Ltd. was added 2.3 g of choline (2hydroxyethyltrimethylammonium hydroxide 48.9%, manufactured by Nippon Finechem Co., Ltd.) Then, heat treatment was performed at 80 ° C. for 3 hours to obtain a niobate sol (Nb ₂ O ₅ = 6.2%, pH 8.9).
When ethanol was added to 100 parts by mass of the niobic acid sol with the Nb ₂ O ₅ concentration adjusted to 6%, thickening of the liquid was confirmed in the vicinity of 250 parts by mass of ethanol.

Example 8
After diluting 1000 g of `` Vilar Nb-G6000 '' (Nb ₂ O ₅ = 6.2%) manufactured by Taki Chemical Co., Ltd. to Nb ₂ O ₅ = 2.0% with ion-exchanged water, add 102.0 g of hydrochloric acid (5%). After stirring for about 10 minutes, ultracleaning was performed until the filtrate EC reached 100 μS / cm. To the obtained sol, 51.0 g of TMAH (25.0%) was added, and heat treatment was performed at 120 ° C. for 5 hours to obtain a niobate sol (Nb ₂ O ₅ = 6.2%, pH 8.3).
When ethanol was added to 100 parts by mass of the niobate sol with the Nb ₂ O ₅ concentration adjusted to 6%, thickening was confirmed once in the vicinity of 400 parts by mass of ethanol. However, when ethanol was further added, thickening of the liquid was confirmed at a total ethanol addition amount of 600 parts by mass.

Example 9
A niobate sol (Nb ₂ O ₅ = 6.2%, pH 7.7) was obtained in the same manner as in Example 8 except that hydrochloric acid was changed to 221.1 g.
When ethanol was added to 100 parts by mass of the niobate sol with the Nb ₂ O ₅ concentration adjusted to 6%, even when ethanol was added by 600 parts by mass, no thickening of the liquid was confirmed, and the dispersion of the liquid The property was good.

Table 1 shows the physical properties and ethanol compatibility of the sols obtained in each Example and Reference Example .
Ammonia in the sol was measured by the Kjeldahl method. In addition, the amine compound was measured for total organic carbon using a total organic carbon (TOC) analyzer TOC-V / CSN (manufactured by Shimadzu Corporation), and converted to the amount of amine compound. The amount of organic acid used was used because there was no loss during production. When an amine compound and an organic acid were used in combination, the amount of the amine compound was determined by subtracting the amount of the organic acid from the total amount of organic carbon.

Claims (6)

Heating the ammonium niobate sol in the presence of an amine compound to remove ammonia;
Next, a step of adding an organic acid,
A process for producing a niobic acid sol, comprising: A step of washing the ammonium niobate sol mixed with an inorganic acid to remove ammonia and then heating in the presence of an amine compound;
A process for producing a niobic acid sol, comprising: A step of further adding an organic acid after the production step according to claim 2 ,
A method for producing a niobate sol. An amine compound is contained in the range of amine compound / Nb ₂ O ₅ (molar ratio) = 0.1 to 1.5,
Containing an organic acid in the range of organic acid / Nb ₂ O ₅ (molar ratio) = 0.05-0.20,
Ammonia was contained in a range of NH ₃ / Nb ₂ O ₅ (molar ratio) = 0 (below detection limit) to 1.2,
Niobic acid sol.
Here, “below the detection limit” in the NH ₃ / Nb ₂ O ₅ (molar ratio) range is below the detection limit of nitrogen analysis by the Kjeldahl method. 5. The niobate sol according to claim 4, having a characteristic that the amount of ethanol compatibility is 50 parts by mass or more with respect to 100 parts by mass of the niobate sol adjusted to a Nb ₂ O ₅ concentration of 6% by mass. A coating solution for forming a thin film comprising the niobic acid sol according to claim 4 or 5 and a hydrophilic solvent.