JP3478395B2 - Silica sol and silica powder - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silica sol and a silica powder, and more particularly to a silica sol low in Na and a silica powder obtained from the silica sol. The silica sol is useful for applications in the fields of ceramics and catalysts.

[0002]

2. Description of the Related Art Conventionally, an aqueous solution of sodium silicate is the cheapest silica source as a raw material for a silica sol, and almost all ordinary silica sols are produced from an aqueous solution of sodium silicate, and Na ⁺ is unavoidable in its nature. Exists in. However, in many cases, especially in the field of ceramics and catalysts, the Na component in the silica sol causes deterioration of the physical properties, which is not preferable.

When the silica sol is dried, it becomes porous silica, and this porous silica has a specific surface area which is almost the same as the specific surface area converted from the particle size of silica particles in the sol. In the presence of Na, this porous silica is crystallized and vitrified at a temperature of 500 ° C. or higher, and the specific surface area is drastically decreased near 1000 ° C. and approaches zero. As the content of Na in porous silica increases, the specific surface area decreases at low temperatures, and when used in the field of ceramics and catalysts, shrinkage and distortion of the ceramics, generation of cracks, deterioration of catalytic activity, and the like occur.

On the other hand, the alkali-stabilized silica sol contains 1 wt% of Na ₂ O with respect to the weight of SiO ₂ , and the acidic silica sol from which alkali has been removed or the silica sol substituted with ammonia has a Na ₂ O content of 0. Contains 1 wt%. For example, porous silica obtained by drying silica sol having an average particle diameter of 13 nm has a BET specific surface area of about 200 m ² / g, but when 1 wt% of Na ₂ O is present, 8
The BET specific surface area at 00 ° C. is 1 m ² / g, 0.1 w
In the presence of t% Na ₂ O, the BET specific surface area at 1000 ° C. becomes 1 m ² / g.

Therefore, in the fields of ceramics and catalysts, many attempts have been made to produce silica sols containing less Na. The basic method is as follows:
As described in JP-A-5-10535, there is a method of removing Na from a silica sol stabilized with Na by ion exchange.

Further, as disclosed in Japanese Patent Laid-Open No. 61-158810, a method of using alkali ions for grain growth is mentioned.

[0007]

However, as a method for producing a silica sol containing a small amount of Na as described above, as described in JP-B-55-10535,
Na from silica sol stabilized with Na by ion exchange
In the method of removing the silica sol produced in SiO ₂
It contains Na ₂ O in an amount of 0.1 wt% or more based on the weight, and such a silica sol is not practical because the specific surface area remarkably decreases when heated and calcined.

The silica particle size of the silica sol is generally from 10 to 10.
It has a thickness of 20 nm and requires alkali ions for grain growth, and NaOH is usually used, and NaOH remains as a colloid stabilizer in the final product.
Part of Na ions is taken into the silica particles during the particle growth process. The incorporated Na cannot be removed by a treatment such as ion exchange.

Further, as disclosed in JP-A-61-158810, the content of Na can be reduced by using ammonium ions as alkali ions for the growth of silica particles. Grows to less than 5 nm . Further, the silica sol having a particle diameter of 5 Nm can be concentrated only up to a SiO ₂ concentration of 10 wt%, and a silica sol of 20 wt% or more like a commercial product cannot be obtained.

Thus, using sodium silicate as a raw material, Na
Since it is very difficult to produce a silica sol having a low content, it is necessary to rely on raw materials other than sodium silicate as in JP-A-60-127216.

The present invention has been made in order to solve the above-mentioned drawbacks of the prior art, and an object thereof is to provide a silica sol and a silica powder having a low content of Na.

[0012]

[Means for Solving the Problems] That is, what is intended to be provided by the present invention is to produce by adding tetraethanolammonium hydroxide or monomethyltriethanolammonium hydroxide to a silicic acid solution obtained from an aqueous sodium silicate solution. The silica sol has a particle size of silica particles in the sol of 10 to 20 nm and a Na component content of Si.
O ₂ to 0.011Wt% below as Na ₂ O, Al
The content of the component is 0.05 as Al ₂ O ₃ with respect to SiO _2.
It relates to a silica sol characterized in that the content is ˜2 wt% .

Further, according to the present invention, silica particles produced by adding tetraethanolammonium hydroxide or monomethyltriethanolammonium hydroxide to a silicic acid solution obtained from an aqueous sodium silicate solution have a particle size of 10 to 20.
The nm silica sol and a silica powder obtained by drying, the content of Na component is less than or equal 0.011Wt% to SiO ₂ as Na ₂ O, content of Al component SiO ₂
That to a 0.05～2Wt% as Al ₂ O ₃
It relates to the characteristic silica powder.

[0014]

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.
The silica particle diameter of the silica sol is generally 10 to 20 nm , alkali ions are required for particle growth, and NaOH is usually used. Alkali metals such as Li and K may be used. The use of or K is not usually done. However, we have
In the particle growth step, some of the Na ions are taken into the silica particles, but when quaternary ammonium hydroxide is used instead of NaOH, a silica sol containing a very small amount of sodium component and containing substantially no silica component is obtained. It has been found that it can be obtained.

The silica sol of the present invention is a silica sol.
Thorium component is SiO₂ Against Na ₂0.01 as O
It is 1 wt% or less and contains substantially no alkali component.
It is a silica sol.

When the silica sol of the present invention is pulverized, the following formula (1)

[0018]

[Equation 3]

(In the formula, S ₁ is silica sol at 150 ° C., 3
The dried powder and S ₂ are dried powder at 1100 ° C. for 3 hours.
Time calcined respective BET specific surface area of the powder (m ² /
g). However, the powder has a particle size of 100 to 500 μm.
It is in the range of. It is desirable that the specific surface area change rate (R) represented by () is 50% or less, preferably 40% or less.

The concentration of the silica sol of the present invention is usually 20 to
It is 50 wt%, preferably 30-40 wt%. Further, in the silica sol of the present invention, which does not substantially contain the alkali component, the alumina component is Si in order to impart heat resistance.
It is preferable that the content of Al ₂ O ₃ is 2 wt% at most, preferably 0.05 to 1.0 wt% with respect to O ₂ .

Next, the method for producing the silica sol of the present invention will be described. The first step of producing the silica sol of the present invention is to ion-exchange the diluted aqueous sodium silicate solution to form Na.
The process is to obtain an active silicic acid solution except for the above. However, in an industrial manufacturing scale, Na cannot be completely removed in this process, and Na ₂ O remains at about 0.04 wt% with respect to SiO ₂ . Silica sol particles grown with quaternary ammonium hydroxide have an Na content of 1 after the ion exchange treatment.
It can be removed up to about / 3.

That is, the present invention is a method of using a quaternary ammonium hydroxide in the particle growth step in the silica sol manufacturing step to remove the quaternary ammonium ions from the silica sol after particle growth by ion exchange. , A method of producing a silica sol containing little Na or other alkali metals.

The method for producing a silica sol of the present invention comprises a first step for obtaining an active silicic acid solution from which most sodium is removed by removing Na ⁺ from an aqueous sodium silicate solution by ion exchange, and the active silicic acid solution obtained in the first step. In the second step of adding quaternary ammonium hydroxide to make the mixture alkaline and then aging it by heat to form colloidal silicic acid. Then, the colloidal solution is again subjected to decationization treatment by ion exchange and, if necessary, subjected to a definite treatment. The solid content is concentrated by external filtration, or the third step of adding the NH ₃ component is included.

The silica sol produced by this method is characterized in that it contains 0.012 wt% or less of Na ₂ O with respect to SiO ₂ , and does not substantially contain Na ₂ .

By adding an Al salt to the activated silicic acid obtained in the first step and performing the second step and the third step, the heat resistance of the silica obtained can be improved. The heat resistance of silica can also be improved by adding an Al salt to the colloidal activated silicic acid obtained in the second step and performing the third step. When sodium aluminate is used as the Al salt, Na resulting from this enters, so in the silica sol produced by the method of adding Al, Na ₂ O is added to SiO ₂ .
Is 0.05 wt% or less. That is, the silica sol produced by the method of adding an Al salt contains Na ₂ O in an amount of 0.05 wt% or less with respect to SiO ₂ , and has a composition of Al ₂ O ₃
Is 0.05 wt% or more and at most 2 wt%. The dry powder of silica sol produced by the above method is 1
The product dried at 50 ° C. for 3 hours is characterized by having a specific surface area of 100 m ² / g or more and a specific surface area change rate (R) at 1100 ° C. of 50% or less.

The raw material sodium silicate is not particularly limited, and any commercially available product may be used, but normally, No. 3 sodium silicate can be used. In the first step, most of Na is removed by removing Na ⁺ from the aqueous solution of sodium silicate by ion exchange, but ion exchange is usually performed by diluting sodium silicate in a column packed with H ⁺ type cation exchange resin. This is done by passing an aqueous solution.

In the second step, a quaternary ammonium hydroxide is added to the silicic acid solution obtained in the first step to make it alkaline, and then it is heat-aged to form colloidal silicic acid. As the quaternary ammonium hydroxide, very general industrial chemicals can be used, for example, tetraethanolammonium hydroxide, monomethyltriethanolammonium hydroxide and the like can be used.

As the Al salt added after the first step and the second step, sodium aluminate solution, aluminum chloride and the like can be used in industrial chemical grade, but as is well known, it is dilute to prevent the formation of silica gel. It is better to add it in the form of an aqueous solution. First time to add aluminum chloride
After the step, the sodium aluminate solution may be added after the first step or the second step. The amount of Al salt added is S
Al ₂ O ₃ is preferably 0.05 wt% or more with respect to iO _{2, and} if it is less than 0.05 wt%, no remarkable improvement in heat resistance is observed.

In the third step, cation exchange is performed to remove quaternary ammonium and Na. Although any method may be used for the cation exchange, a method in which silica sol is passed through a column packed with an H ⁺ -type cation exchange resin is general. As the cation exchange resin, a sulfonic acid group-type strongly acidic resin of polystyrene-DVB copolymer is generally used, but the cation exchange resin is not particularly limited thereto. In order to remove the anion as an impurity, the anion exchange resin may be an OH ^- type anion exchange resin, or the anion exchange may be performed again after the anion exchange.

The silica sol from which cations have been removed is concentrated to a desired concentration by a conventional method such as the ultrafiltration method. The silica sol obtained is acidic with a pH of 2 to 5, and may be left as it is depending on the purpose of use. If alkaline is preferable, a volatile alkaline agent such as ammonia, amine, or quaternary ammonium may be added.

[0031]

EXAMPLES The present invention will be specifically described below with reference to examples.

Example 1 and Comparative Example 1 Commercially available No. 3 sodium silicate (SiO ₂ = 29.0 wt%, N
a ₂ O = 9.5 wt%) and diluted with water to obtain SiO ₂ = 4.
0 wt% diluted sodium silicate was prepared. An active silicic acid solution with SiO ₂ = 3.3 wt% was recovered by passing diluted sodium silicate through a column packed with a cation exchange resin which was previously made into H ⁺ type with dilute sulfuric acid. Exchange resin is polystyrene-DV
A sulfonic acid group-type strongly acidic resin of B copolymer was used. To 1.12 kg of this activated silicic acid solution, a 20 wt% aqueous solution of monomethyltriethanolammonium hydroxide was added with stirring to 12
0 g was added to adjust the pH to 9.0, and the mixture was heated to 100 ° C. and kept for 15 minutes. While maintaining the liquid temperature at 100 ° C., 9.0 kg of active silicic acid liquid was added at 22 g / min. After cooling, this silica sol was concentrated to SiO ₂ = 30 wt% by ultrafiltration,
Analysis and measurement of specific surface area were performed. Composition of silica sol, B
The ET specific surface area is shown in Table 1 as Comparative Example 1.

A silica sol stabilized with monomethyltriethanolammonium hydroxide was prepared by the same procedure as above, and an H ⁺ type cation exchange resin (polystyrene-DVB) was prepared.
Cations are removed by passing silica sol through a column filled with a copolymer sulfonic acid group-type strongly acidic resin), concentrated by SiO ₂ = 31 wt% by ultrafiltration, and 28 wt% ammonia water is added to adjust pH to 9. It was set to 4. This is exactly S
After adjusting to iO ₂ = 30 wt%, analysis and measurement of specific surface area were performed. The composition of the silica sol and the BET specific surface area are shown in Table 1 as Example 1.

Reference Example 1 and Comparative Example 2 Commercially available No. 3 sodium silicate (SiO ₂ = 29.0 wt%, N
a ₂ O = 9.5 wt%) and diluted with water to obtain SiO ₂ = 4.
0 wt% diluted sodium silicate was prepared. An active silicic acid solution with SiO ₂ = 3.3 wt% was recovered by passing diluted sodium silicate through a column packed with a cation exchange resin which was previously made into H ⁺ type with dilute sulfuric acid. Exchange resin is polystyrene-DV
A sulfonic acid group-type strongly acidic resin of B copolymer was used. 120 wt% aqueous solution of monomethyltriethanolammonium hydroxide was added to 1.12 kg of this activated silicic acid solution with stirring.
After adding g to pH 9.0, the mixture was heated to 100 ° C. and kept for 15 minutes. While maintaining the liquid temperature at 100 ° C., 9.0 kg of active silicic acid liquid was added at 22 g / min. After adding the active silicic acid solution, a sodium aluminate aqueous solution (Al ₂ O ₃ = 20 wt
%, Na ₂ O = 19 wt%) was diluted with 160 g of water and added. After cooling, this silica sol was concentrated to SiO ₂ = 30 wt% by ultrafiltration, and analyzed and BET specific surface area was measured. The composition of the silica sol and the BET specific surface area are shown in Table 1 as Comparative Example 2.

By the same operation as above, a stabilized silica sol was prepared from Al-added monomethyltriethanolammonium hydroxide, and an H ⁺ type cation exchange resin (polystyrene-DVB copolymer sulfonic acid group-type strongly acidic resin) was prepared. Remove the cations by passing the silica sol through the packed column,
28w after concentrated to SiO ₂ = 31wt% by ultrafiltration
The pH was adjusted to 9.4 by adding t% aqueous ammonia. This was accurately adjusted to SiO ₂ = 30 wt%, and analyzed and measured for the specific surface area. The composition of the silica sol and the BET specific surface area are shown in Table 1 as Reference Example 1.

Comparative Example 3 Na-stabilized SiO ₂ = 30 wt in the same manner as in Example 1 except that 10 wt% NaOH aqueous solution was used instead of monomethyltriethanolammonium hydroxide.
% Silica sol was prepared. Composition of silica sol, BET
The specific surface area is shown in Table 1 as Comparative Example 3.

[0037] Comparative Example 4 to create a stabilized silica sol with Na in the same procedure as Comparative Example 3, the cations through silica sol was removed in a column filled with H ⁺ type cation exchange resin, SiO ₂ by excessive ultrafiltration After concentration to 30 wt%, analysis and BET specific surface area measurement were performed. The composition of the silica sol and the BET specific surface area are shown in Table 1 as Comparative Example 4.

Example 2 Commercially available No. 3 sodium silicate (SiO ₂ = 29.0 wt%, N
a ₂ O = 9.5 wt%) and diluted with water to obtain SiO ₂ = 4.
0 wt% diluted sodium silicate was prepared. An active silicic acid solution with SiO ₂ = 3.3 wt% was recovered by passing diluted sodium silicate through a column packed with a cation exchange resin which was previously made into H ⁺ type with dilute sulfuric acid. Exchange resin is polystyrene-DV
A sulfonic acid group-type strongly acidic resin of B copolymer was used. 1.
3 g of AlCl ₃ .6H ₂ O was dissolved in 100 g of water and added to 10.12 kg of active silicic acid solution with stirring. 120 g of a 20 wt% aqueous solution of monomethyltriethanolammonium hydroxide was added to 1.12 kg of the activated silicic acid solution containing Al to PH 9.0, and the mixture was heated to 100 ° C. and kept for 15 minutes. Al keeping the liquid temperature at 100 ° C
The activated silicic acid solution added with was added at 9.0 g at 22 g / min. After cooling, H ⁺ type cation exchange resin (polystyrene-
The cation was removed by passing silica sol through a column packed with a sulfonic group-type strongly acidic resin of DVB copolymer,
% Ammonia water was added to adjust the pH to 9.4, and the silica sol was concentrated to SiO ₂ = 30 wt% by ultrafiltration, and the silica sol was analyzed and the BET specific surface area was measured. The composition of the silica sol and the BET specific surface area are shown in Table 1 as Example 2.

Example 3 A silica sol stabilized with monomethyltriethanolammonium hydroxide was prepared by the same procedure as in Example 2, and after cooling, the cation was removed by passing the silica sol through a column filled with an H ⁺ type cation exchange resin. Then, without adding ammonia, it was concentrated to SiO ₂ = 30 wt% by ultrafiltration to obtain an acidic silica sol. The silica sol was analyzed and the BET specific surface area was measured. The composition of the silica sol and the BET specific surface area are shown in Table 1 as Example 3.

[0040]

[Table 1]

(Note) (1) BET specific surface area is measured by using silica sol at 150 ° C.
Flow Soap Model 2300 (Shimadzu Corporation) for those dried in a mortar and pulverized in a mortar, and those pulverized in an electric furnace at a predetermined temperature for 3 hours and pulverized (Manufactured by the company). The degassing condition before measurement is 150 ° C. for 3 hours. (2)% indicates wt%. (3) "Nm" of the particle size indicates nm (nanometer).

In Table 1, the content of Na ₂ O component of Comparative Example 1 of 0.027 wt% is Na ₂ O which could not be completely removed from the sodium silicate by the first ion exchange. In the case where the particle growth step was performed using the quaternary ammonium hydroxide as in Example 1, Na was removed during the second ion exchange, and the content of Na ₂ O component was 0.0079 wt%. become.

The comparative example 4 in which the particle growth process is performed using Na uses a large amount of Na,
Naturally, the content of Na ₂ O component becomes 0.092 wt% even after the second ion exchange.

Reference Example 1 and Comparative Example 2 show that the addition of sodium aluminate improves the heat resistance of the introduction of the Al component. However, in Comparative Example 2, since the second ion exchange was not performed, the heat resistance was low due to the presence of Na due to sodium aluminate. Examples 2 and 3 are examples in which aluminum chloride is used as the Al source, and extremely high heat resistance is obtained.

[0045]

As described above, since the silica sol of the present invention does not substantially contain 0.011 wt% or less of Na ₂ O as Na ₂ O with respect to SiO _2.
The specific surface area change rate (R) of the calcined powder treated at 50 ° C. and 1100 ° C. is 50% or less, which makes it possible to further improve the performance as a silica sol used in fields such as ceramics and catalysts.

Continuation of the front page (56) Reference JP-A-63-123807 (JP, A) JP-A-62-3011 (JP, A) JP-A-1-294515 (JP, A) JP-A-1-317115 (JP , A) JP-A-4-65314 (JP, A) Japanese Patent Publication No. 30-3527 (JP, B1) European Patent Application Publication 464289 (EP, A 1) US Patent 2680721 (US, A) (58) Research Fields (Int.Cl. ⁷ , DB name) C01B 33/00-39/54

Claims (2)

(57) [Claims] 1. A silica sol produced by adding tetraethanolammonium hydroxide or monomethyltriethanolammonium hydroxide to a silicic acid solution obtained from an aqueous solution of sodium silicate, wherein the silica particles in the sol have a particle size of 10 ~ 20 nm , and the content of Na component is SiO
₂ to 0.011Wt% below as Na ₂ O, Al formed
The content of the component is 0.05 to Al ₂ O _{3 with} respect to SiO _2.
Silica sol characterized by being 2 wt% . 2. A silica sol having a silica particle size of 10 to 20 nm produced by adding tetraethanolammonium hydroxide or monomethyltriethanolammonium hydroxide to a silicic acid solution obtained from an aqueous sodium silicate solution is dried. The silica powder obtained as described above, wherein the content of Na component is 0.011 wt% as Na ₂ O based on SiO _2.
In the following, the content of Al component and Al ₂ O ₃ to SiO ₂
The silica powder is characterized by being 0.05 to 2 wt% .