JP3362793B2 - Method for producing silica sol - Google Patents

Description

Detailed Description of the Invention

[0001]

The present invention relates also relates <br/> the manufacturing method of the silica sol, and particularly relates to a method for producing a small silica sol and silica sol of Na sodium silicate aqueous solution as a raw material. The silica sol is useful for applications in the fields of ceramics and catalysts.

[0002]

2. Description of the Related Art Conventionally, sodium silicate aqueous solution is the cheapest silica source as a raw material for silica sol, and almost all normal silica sol is produced from sodium silicate aqueous solution as a raw material, and Na ⁺ is unavoidable in nature. Existing. 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 based on 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
BET specific surface area at 00 ° C becomes 1 m ² / g, 0.1 w
In the presence of t% Na ₂ O, the BET specific surface area at 1000 ° C. is 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 the JP-A-61-158810 are mentioned a method of using ammonia or amine to the growth of the particles.

[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 is 20 Nm, needs alkali ions for the growth of particles, 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 5 Nm or less. 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 to solve the above-mentioned drawbacks of the prior art.
It is an object to provide a method for easily producing Le.

[0012]

That is, the present invention is to provide an aqueous solution of sodium silicate by ion exchange.
The first step of removing Na ⁺ to obtain an active silicic acid solution,
Tetraethanol ammonium hydroxide or mono in the liquid
Methyltriethanolammonium hydroxide was added
Then, heat aging is performed to add activated silicic acid to a silica particle having a particle size of 10
~ 20 Nm colloidal forming second step, then
The colloidal liquid is again deionized by ion exchange.
Then, the content of Na component is changed to Na ₂ O with respect to SiO _2.
A special feature is that it consists of the third step, which is 0.011 wt% or less.
The present invention relates to a method for producing a silica sol. The present invention
In, Nm represents nm (nanometer).

[0013]

[0014]

In the present invention, "tetraethanolammonium hydroxide or monomethyltriethanolammonium hydroxide" is hereinafter referred to as "quaternary ammonium hydroxide".

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 the growth of particles, and NaOH is usually used. Alkali metals such as Li and K may be used, but Li and K The use of K is not common practice. However, although the present inventors have found that a part of Na ions is taken into the inside of silica particles during the particle growth process, the use of quaternary ammonium hydroxide instead of NaOH results in an extremely low sodium content. It has been found that a silica sol that does not substantially contain can be obtained.

In the silica sol of the present invention, the sodium component in the silica sol is 0.012 as Na ₂ O with respect to SiO _2.
It is a silica sol having a content of not more than wt% and containing substantially no alkali component.

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

[0019]

[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 Al ₂ O ₃ as compared with SiO _{2 at most 2} in order to impart heat resistance.
It is preferable that the content thereof is wt%, preferably 0.05 to 1.0 wt%.

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 for removing quaternary ammonium ions from the silica sol after particle growth by ion exchange, using a quaternary ammonium hydroxide in the particle growth step in the silica sol manufacturing step. , 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 deNa ⁺ of an aqueous sodium silicate solution, and the active silicic acid solution obtained in the first step. In the second step, a quaternary ammonium hydroxide is added to the mixture to make it alkaline, and then the mixture is heat-aged to form colloidal silicic acid. The solid content is concentrated by external filtration, or the third step of adding the NH ₃ component is included.

Silica sol produced by this method
Is SiO₂Against Na₂O is0.011 wt% or less
And, it is characterized in that it is not substantially contained.

When an Al salt is added to the activated silicic acid obtained in the first step and the second step and the third step are performed, 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 usually, No. 3 sodium silicate can be used. In the first step, the sodium silicate aqueous solution is ion-exchanged to remove Na ⁺ to remove most of Na, but the ion-exchange is usually performed by diluting sodium silicate in a column packed with an 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.

[0033]

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 described above, and a H ⁺ type cation exchange resin (polystyrene-DVB) was prepared.
Cations were removed by passing silica sol through a column packed with a copolymer sulfonic acid group-type strongly acidic resin), concentrated to SiO ₂ = 31 wt% by ultrafiltration, and then 28 wt% ammonia water was 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
A 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-DVB
A copolymer sulfonic acid group-type strongly acidic resin was used. 120 g of a 20 wt% aqueous solution of monomethyltriethanolammonium hydroxide was added to 1.12 kg of this activated silicic acid solution with stirring.
Add to pH 9.0, heat to 100 ° C. and hold 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%,
9.5 g of 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.

A stabilized silica sol was prepared from Al-added monomethyltriethanolammonium hydroxide by the same procedure as described above, and an H ⁺ type cation exchange resin (polystyrene-DVB copolymer sulfonic acid group-type strongly acidic resin) was used. Remove the cations by passing the silica sol through the packed column,
After concentration to SiO ₂ = 31 wt% by ultrafiltration, 28
The pH was adjusted to 9.4 by adding wt% 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 SiO ₂ stabilized with Na = 30 wt by the same procedure 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.

Comparative Example 4 By the same procedure as in Comparative Example 3, a silica sol stabilized with Na was prepared, and the cation was removed by passing the silica sol through a column packed with an H ⁺ type cation exchange resin, and SiO ₂ was removed by 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
A 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-DVB
A copolymer sulfonic acid group-type strongly acidic resin was used. 1.3
AlCl ₃ .6H ₂ O (g) was dissolved in 100 g of water and added to 10.12 kg of active silicic acid solution with stirring. To 1.12 kg of this active silicic acid solution containing Al, 1% of a 20 wt% aqueous solution of monomethyltriethanolammonium hydroxide was stirred.
Add 20 g to pH 9.0 and heat to 100 ° C for 15
Hold for minutes. While maintaining the liquid temperature at 100 ° C., 9.0 kg of an activated silicic acid liquid containing Al was added at 22 g / min.
After cooling, H ⁺ type cation exchange resin (polystyrene-DV
The cation was removed by passing silica sol through a column filled with a sulfonic acid group-type strongly acidic resin of B copolymer), pH was adjusted to 9.4 by adding 28% ammonia water, and SiO ₂ = 30 wt% by ultrafiltration. After concentration, 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 in the same manner as in Example 2, and after allowing to cool, 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 .

[0042]

[Table 1]

(Note) (1) BET specific surface area is measured by using silica sol at 150 ° C.
Flow Soap Model 2300 (Shimadzu Seisakusho Co., Ltd.) was dried in a mortar and crushed in a mortar, and also crushed in an electric furnace at a predetermined temperature for 3 hours and then crushed in the same manner (both having a particle size in the range of 100 to 500 μm). (Manufactured by the company). The degassing condition before measurement is 150 ° C. for 3 hours. (2)% indicates wt%.

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, so
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.

[0048]

[0049]

As described above , according to the method for producing a silica sol of the present invention, it is extremely simple to use a quaternary ammonium hydroxide as an alkali agent in the particle growth step of silica sol. By the method, a silica sol in which the sodium component is 0.011 wt% or less as Na ₂ O based on SiO ₂ and which does not substantially contain can be easily produced from sodium silicate.

Continuation of front page (56) Reference JP-A-63-123807 (JP, A) JP-A-61-158810 (JP, A) JP-A-49-58098 (JP, A) JP-A-3-137012 (JP , A) JP 4-74707 (JP, A) JP 4-231319 (JP, A) JP 49-7800 (JP, B1) JP 55-10535 (JP, B2) US Patent 4054536 (US, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C01B 33/00-33/54 CA (STN) WPI (DIALOG)

Claims (2)

(57) [Claims] [Claim 1] After the aqueous sodium silicate solution was added first step, tetraethanol ammonium hydroxide or monomethyl triethanolammonium hydroxide該珪acid solution to obtain a de-Na ⁺ to the active silicic acid solution by ion exchange, When heat-aged, activated silicic acid has a silica particle size of 10
Second step of forming a colloidal form of ˜20 Nm, and then decationizing the colloidal solution again by ion exchange so that the content of Na component is 0.011 wt% or less as Na ₂ O with respect to SiO ₂ . A method for producing a silica sol, which comprises the steps of: 2. The method for producing a silica sol according to claim 1, wherein aluminum chloride is added to the active silicic acid solution or colloidal silicic acid obtained in the first step or the second step.