JP2002173317A - Method for manufacturing high purity colloidal silica and high purity synthetic quartz powder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide colloidal silica of high purity enough to be used suitably for various purposes such as an abrasive for a silicon wafer, a binding material for a ceramic fiber, an adhesive binder for a phosphor when a cathode-ray tube is manufactured and a gelatinizing agent for an electrolytic liquid in a battery and to provide high purity synthetic quartz powder. SOLUTION: This method for manufacturing high purity colloidal silica comprises the first step to obtain silica aqueous solution by adding hydrogen peroxide to water glass and subjecting the hydrogen peroxide-added water glass to cation exchange treatment, the second step to mix the obtained silica aqueous solution with ammono alkali, which is then formed into colloidal silica. The third step to concentrate the obtained colloidal silica can be comprised in this method. This method for manufacturing high purity synthetic quartz powder comprises dehydrating and drying the colloidal silica after or before concentration to obtain silica particles, washing the obtained silica particles and firing the washed silica particles.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing high-purity colloidal silica, and further relates to a method for producing high-purity synthetic quartz powder using the high-purity colloidal silica obtained by this production method.

[0002]

2. Description of the Related Art Colloidal silica has been used in various applications as an abrasive for silicon wafers, a binder for ceramic fibers, an adhesive binder for phosphors in the manufacture of cathode ray tubes, and a gelling agent for electrolytes in batteries. Was. However, since these colloidal silicas contain a large amount of alkali, alkaline earth metal, and transition metal in the raw materials and the production process, these metallic impurities are substantially reduced particularly in the field where metal impurities are not to be mixed. The appearance of a high-purity colloidal silica that does not contain it has been desired.

[0003] Colloidal silica having high purity enough to obtain high-purity synthetic quartz powder has not been obtained.

As a method for producing high-purity colloidal silica, an alkali metal silicate is diluted with pure water, then contacted with a strong acid-type cation exchange resin to remove alkali, and further added with an acid to make it strongly acidic. Ammonia or amine is added to a part of the oligosilicic acid solution obtained by removing impurities using an ultrafiltration membrane, and heating is performed to prepare a heel sol. A method of obtaining silica sol (Japanese Patent Application Laid-Open No. 61-158810),
An alkali metal silicate aqueous solution treated with an acid in the same manner as above,
H-type strongly acidic cation exchange resin and OH-type strongly basic anion exchange resin are brought into contact, an aqueous alkali metal hydroxide solution is added thereto, and the mixture is heated to 60 to 150 ° C. to form a stable aqueous sol. Remove water through the outer filtration membrane,
Then, a method of contacting with an H type strongly acidic cation exchange resin and an OH type strongly basic anion exchange resin, and finally adding ammonia to produce a stable aqueous silica sol (Japanese Patent Laid-Open No. 4-26)
No. 06) is known.

[0005]

However, these methods have not been able to obtain sufficiently high-purity colloidal silica. Therefore, high purity synthetic quartz powder could not be obtained.

Accordingly, an object of the present invention is to provide a method for producing colloidal silica having high purity enough to be preferably used for the above-mentioned applications, and a method for producing high-purity synthetic quartz powder.

[0007]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above problems, and as a result, have found that the above object can be achieved by a manufacturing method including the following steps, and have completed the present invention. Was.

That is, the method for producing high-purity colloidal silica according to the present invention comprises a first step of adding hydrogen peroxide to water glass and subjecting it to a cation exchange treatment to obtain a silica aqueous solution. Mix with ammoniacal alkali,
And a second step of converting this into colloidal silica.

In this production method, a third step of concentrating the colloidal silica obtained in the second step may be included. In this case, the colloidal silica is preferably concentrated by an ultrafiltration method. Can be.

[0010] In the method for producing a high-purity synthetic quartz powder of the present invention, concentrated or non-concentrated high-purity colloidal silica is obtained by the above-mentioned production method, and the obtained high-purity colloidal silica is dehydrated or dried. The method is characterized by including a fourth step of obtaining particles, a fifth step of washing the obtained silica particles, and a sixth step of baking the washed silica particles.

In this production method, a freeze dehydration method can be suitably used for dehydrating or drying the colloidal silica.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The water glass used in the first step of the present invention is not particularly limited, and any water glass can be used. Preferably, SiO ₂ / M ₂ O (M is N
a, K, and Li, preferably Na, which is industrially easily available).
A water glass that is between 5 and 8.0 can be used. If the molar ratio is less than 0.4, excessive equipment is required for the cation exchange treatment, while if it exceeds 10.0, water glass cannot be industrially stable, and it becomes difficult to obtain water glass. All of them tend to lack industrial aptitude.

The concentration of SiO _{2 in} the water glass is not particularly limited, but is preferably 2-3.
0% by weight, more preferably 3 to 15% by weight. When the concentration is less than 2% by weight, the colloidal silica becomes only dilute colloidal silica, which does not cause any problem. However, practically, the use is extremely limited, or the efficiency of the concentration step in the case of concentration is reduced. In any case, it is low in industrial suitability. On the other hand, if it exceeds 30% by weight, the aqueous silica solution obtained in the first step tends to be unstable.

There are several methods for obtaining water glass having a concentration within the above range, but the simplest method is to use water glass having a concentration within the above range as it is. in this case,
The concentration may be adjusted in the production of water glass.
Next, there is a method of diluting water glass having a higher concentration than the above concentration with water (preferably pure water). Further, a powdery water-soluble alkali silicate is also commercially available, and can be obtained by dissolving this in water (preferably pure water) to obtain the above-mentioned concentration.

The hydrogen peroxide to be added to the water glass is
Preferably from 5% by weight to 50 ppm, based on SiO ₂ ,
More preferably, it is 2% by weight to 100 ppm.

The addition of hydrogen peroxide improves the removability of metal impurities, particularly polyvalent metal impurities, in the cation exchange treatment. However, if the amount is less than 50 ppm, the effect of use is not remarkable. %, The effect does not improve any more, and it is more likely to cause problems such as disposal of wastewater.

In the first step of the present invention, as described above, hydrogen peroxide is added to water glass, and this is subjected to a cation exchange treatment to obtain an aqueous silica solution. Here, a preferable cation exchange treatment is carried out. Examples thereof include a hydrogen-type cation exchange resin method. The hydrogen-type cation exchange resin used here is not particularly limited, and a commercially available hydrogen-type cation exchange resin such as a strongly acidic bead, fiber, cloth or the like can be used.

The method of passing water glass through the hydrogen-type cation exchange resin is not limited at all. For example, a method in which a column is filled with a hydrogen-type cation exchange resin and liquid is passed through, or a method in which water glass and hydrogen-type cation exchange resin are passed Well-known methods, such as treating a cation exchange resin in a batch system, can be used. The used hydrogen-type cation exchange resin can be regenerated to a hydrogen-type using a conventional method, that is, using an acid such as hydrochloric acid, sulfuric acid, or nitric acid.

The water glass is subjected to a cation exchange treatment to remove alkali metal ions, alkaline earth metal ions, polyvalent metal ions such as aluminum, iron, titanium, nickel, and copper from the water glass. The cation exchange treatment is carried out so that the pH becomes preferably 0.2 to 4, more preferably 2 to 3. p
When H exceeds 4, the obtained silica aqueous solution tends to be unstable, and on the other hand, it is difficult to reduce the pH to less than 0.2 from the viewpoint of industrial suitability.

In the second step of the present invention, the aqueous silica solution obtained in the first step is mixed with an ammoniacal alkali to form colloidal silica.

The ammoniacal alkali used herein is an alkaline substance obtained from ammonia,
For example, ammonia water, ammonia gas, liquid ammonia and the like can be used, but it is preferable to use ammonia water or ammonia gas for industrial suitability.

Further, the mixing of the aqueous silica solution and the ammoniacal alkali is carried out when the pH of the system is in a neutral region (generally pH 6.8 to 6.8).
(7.3) is preferably performed in view of stabilization of the system. For example, when ammonia water is used, an aqueous silica solution is gradually added to the ammonia water. When using ammonia gas, it is preferable to first blow ammonia gas into a small amount of aqueous silica solution to raise the pH, and then add the aqueous silica solution little by little. From the viewpoint of workability and efficiency, it is preferable to use aqueous ammonia.

Specifically, for example, ammonia water is charged into a reactor (diluted with water if necessary), and at a temperature of 50 to 100 ° C., at a dropping rate capable of maintaining pH 8.0 to 12.0 ( For example, a stable colloidal silica can be obtained by dropping the aqueous silica solution over 30 minutes to 10 hours (to form a colloidal silica).

Here, with respect to the decrease in pH due to the addition of the aqueous silica solution, ammonia water, ammonia gas, or the like may be appropriately added as necessary.

The amount of the ammoniacal alkali in the second step is not particularly limited, and may be selected depending on the use of the colloidal silica to be obtained. From the viewpoint of the efficiency of growing particles, the amount is preferably such that the pH is 7.5 or more. From the viewpoint of stability, more preferably, the amount is such that the pH is 8 or more.

Further, the molar ratio of NH ₄ OH to SiO ₂ [NH ₄ OH] / [SiO ₂ ] in the system is 0.05 to 0.5, preferably 0.1 to 0.3. Performing colloidal silica is desirable for obtaining stable colloidal silica.

The colloidal silica thus obtained is a high-purity colloidal silica having a very low metal content, particularly an extremely low alkali metal content.

The high-purity colloidal silica obtained in the present invention can be used as it is, but can be concentrated by a known method to obtain a high-purity colloidal silica that can be used for a wide range of applications. .

That is, the third step of the present invention is to concentrate the high-purity colloidal silica obtained as described above. The concentration method that can be used in the third step of the present invention is not limited at all, and a conventionally known method for condensing colloidal silica can be appropriately selected and used as desired. Method, evaporative concentration method and the like can be used, but it is preferable to use an ultrafiltration method in terms of stability, efficiency, suitability for industrialization and the like.

The thus obtained dilute or concentrated high-purity colloidal silica is used as a polishing material for silicon wafers, a binder for ceramic fibers, an adhesive binder for a phosphor in the manufacture of a cathode ray tube, and an electrolyte for a battery. It can be used in various applications as a gelling agent.

Next, in the method for producing a high-purity synthetic quartz powder according to the present invention, silica particles obtained by dehydrating or drying the concentrated or non-concentrated high-purity colloidal silica obtained as described above are washed. By firing this, a high-purity synthetic quartz powder can be obtained.

That is, the fourth step of the present invention is to obtain silica particles by dehydrating or drying the concentrated or non-concentrated high-purity colloidal silica.

In the fourth step of the present invention, the dilute high-purity colloidal silica obtained in the second step or the concentrated high-purity colloidal silica obtained in the third step is used. Although it does not matter,
It is preferable to use the concentrated high-purity colloidal silica obtained in the third step in view of the efficiency of dehydration or drying in the fourth step and the suitability for industrialization.

The method of dehydration or drying in the fourth step is not particularly limited, and a conventionally known method can be used. For example, a heating evaporative drying method (eg, gelling once at the time of concentration, Drying) can be used, but it is preferable to use a freeze-drying method from the viewpoint of energy cost and high purification. That is, high-purity colloidal silica is concentrated (heat evaporation concentration, partial ultrafiltration concentration, then natural evaporation concentration, or natural evaporation concentration over time, etc.) and gelling material (for example, ammonium sulfate, ammonium nitrate, etc.) It is possible to gel with an alkali metal salt, but it is not preferable because the alkali metal easily becomes an impurity), then freeze, and then thaw to separate water to filter silica particles. Separately, the silica particles may be dried by heating (for example, 40 to 200 ° C.). Alternatively, the high-purity colloidal silica itself may be frozen, thawed and separated from water, the silica particles may be separated by filtration, and the silica particles may be dried by heating.

The fifth step of the present invention is to remove impurities adhering to the silica particles by washing the silica particles obtained in the previous step. Prior to washing, it is preferable to pulverize the silica particles into fine particles in order to improve the washing effect. The grinding method is not particularly limited, and a method usually used for grinding silica particles can be employed. The silica particles can be dried if necessary for pulverization. The drying method is not particularly limited,
For example, it can be dried at a temperature of 40 to 200C.

The washing may be carried out by a commonly used method such as washing with water. However, iron may be mixed in the silica particles during pulverization. Therefore, washing is preferably carried out with an aqueous acid solution. In this case, it is desirable to rinse with water, preferably ultrapure water, after washing with the aqueous acid solution.

The aqueous solution of the acid is not particularly limited. For example, hydrochloric acid, sulfuric acid, nitric acid, etc. may be used, and these may be used alone or in combination of two or more. The concentration of the acid is not particularly limited,
Preferably, it is 2 to 20% by weight. This concentration is 2% by weight
The above effect is effective, but if it exceeds 20% by weight, the effect is not further improved, and the washing time and the washing water for rinsing after acid washing are rather wasteful.

Further, it is preferable to add hydrogen peroxide to the aqueous solution of the acid for washing, since a small amount of remaining metal can be removed. However, even if hydrogen peroxide is added in an amount of 2% or more, the effect is not improved any more, and it is rather easy to cause a problem such as disposal of wastewater. Although the effect of adding hydrogen peroxide is produced even in a very small amount, the effect is remarkable when it is preferably at least 100 ppm.

The washing of the silica may be carried out at the same level as that of the usual washing, and is preferably carried out at a temperature of not less than 40 ° C. and not more than the boiling point for about 10 minutes to 4 hours.

In the sixth step of the present invention, the silica particles obtained in the preceding step are calcined to obtain high-purity quartz powder having an extremely low OH content.

The sintering temperature and time may be the same as those for sintering conventionally performed to obtain high-purity quartz. It is preferable that high-purity quartz has as little OH content as possible, and if calcination is carried out at a higher temperature for a longer period of time, quartz having less OH content can be obtained, so conditions are appropriately set so that the desired OH content is obtained. do it.

When the silica particles obtained in the previous step contain water, it is efficient and industrially preferable to dry the silica particles once by a usual method and then perform calcination.

[0043]

The present invention will be further described with reference to the following examples, but the present invention is not limited to these examples. Example 1 Production of high-purity colloidal silica (1) Raw water glass (S) having a molar ratio of SiO ₂ / Na ₂ O = 3.2
SiO ₂ concentration of 6 to iO ₂ concentration 29 wt%) was diluted with pure water
% By weight of water glass, and 2000 ppm of hydrogen peroxide was added to the weight of SiO ₂ in the water glass. 1000 g of the water glass was passed through a column filled with a hydrogen-type cation exchange resin (Amberlite IR-120B manufactured by Organo Co., Ltd.) to remove alkali, and the SiO ₂ concentration was 5.0.
1150 g of a silica aqueous solution having a weight% of pH 2.5 was obtained.

Into 300 g of 5% aqueous ammonia heated to 90 ° C. in a flask, the aqueous silica solution 1 obtained above was added.
000 g was added over 3 hours. After the addition,
Aging time: 3.8% by weight of SiO ₂ concentration;
1 ppm, K content 0.03 ppm, Ca content 0.1 pp
m, Al content 1.0 ppm, Fe content 1.0 ppm, T
i content 0.1 ppm, below the detection limit of Ni content, below the detection limit of Cu content, pH 9.8, silica particle diameter (BET method)
A high-purity colloidal silica (1) having a high purity of 12 nm was obtained.

Example 2 High Purity Colloidal Silica
The high-purity colloidal silica (1) obtained in Production Example 1 of (2) was
Concentrate using a commercially available ultrafiltration device, pH 10.0, S
iO ₂ concentration 30.0% by weight, Na content 0.5ppm, K
Content 0.2 ppm, Ca content 0.5 ppm, Al content 5
ppm, Fe content 5 ppm, Ti content 0.5 ppm, N
An enriched high-purity colloidal silica (2) having an i content lower than the detection limit and a Cu content lower than the detection limit was obtained.

The ultrafiltration conditions are as follows. Ultrafiltration device: manufactured by Advantech Co., Ltd., trade name: Model UHP-90K Ultrafiltration membrane: manufactured by Advantech Co., Ltd., trade name: Ultrafilter UK10 Filtration area: 63 cm ² Filtration pressure: 0.3 MPa

Example 3 Production of High Purity Synthetic Quartz Powder (1)
Purity colloidal silica obtained in Concrete Example 2 (2) 50
g was heated to evaporate the water and dried sufficiently (the gelation was once effected during concentration, but the heating and drying were continued as it was) to obtain silica particles. 17 g of the silica particles was placed in a 3 liter quartz glass beaker, 1 liter of ultrapure water was added thereto, and the mixture was boiled for 2 hours, and then filtered through a polytetrafluoroethylene filter to separate the silica particles.
This operation was repeated five times. Next, the SiO in the silica particles
10 wt% containing ₂ minutes of 200ppm hydrogen peroxide
The silica particles were added to a hydrochloric acid solution, and the mixture was boiled for 1 hour, filtered, and washed by boiling with ultrapure water six times in the same manner as above to obtain high-purity silica particles.

The obtained high-purity silica particles were dried at 150 ° C. and calcined at 1200 ° C. for 20 hours to obtain 14 g of high-purity silica powder (1).

The impurities in the high-purity quartz powder (1) were as follows: Na content 0.2 ppm, K content 0.1 ppm, Ca content 0.1 ppm.
ppm, Al content 2.0 ppm, Fe content 1.5 pp
m, Ti content 0.3 ppm, Ni content below detection limit, C
The u content was below the detection limit.

Example 4 Production of High Purity Synthetic Quartz Powder (2)
Purity colloidal silica obtained in Concrete Example 2 (2) 50
g was dried by heating and concentrated to gel the system to obtain hydrous silica gel. This hydrous silica gel was frozen at −5 ° C. for 10 hours. Then thawed at room temperature. The water separated by thawing was removed by filtration to obtain silica particles.

Next, the obtained silica particles were pulverized with a quartz mortar and pestle and sieved with a 50-200 mesh polypropylene net to obtain fine silica particles. Thereafter, 15 g of the fine silica particles was placed in a 3 liter quartz glass beaker, 1 liter of ultrapure water was added, and the mixture was boiled for 2 hours. Then, the silica particles were separated by filtration with a polytetrafluoroethylene filter. This operation was repeated five times.
Next, a 10% by weight hydrochloric acid solution containing 200 ppm of hydrogen peroxide of SiO ₂ in the silica particles was added, the mixture was boiled for 1 hour, filtered, and washed by boiling with ultrapure water in the same manner as described above.
The process was repeated to obtain high-purity silica particles.

The obtained high-purity silica particles were dried at 150 ° C., and calcined at 1200 ° C. for 20 hours to obtain 14 g of high-purity silica powder (2).

The impurities in the high-purity quartz powder (2) were 0.1 ppm of Na, 0.05 ppm of K, and 0.1 ppm of Ca.
1 ppm, Al content 1.5 ppm, Fe content 1.0 pp
m, Ti content 0.1 ppm, Ni content below detection limit, C
The u content was below the detection limit.

[0054]

Industrial Applicability According to the present invention, it is suitably used in various applications such as abrasives for silicon wafers, binders for ceramic fibers, adhesive binders for phosphors in the manufacture of cathode ray tubes, and gelling agents for electrolytes in batteries. It is possible to obtain colloidal silica and high-purity synthetic quartz powder of sufficiently high purity.

Continuing on the front page (72) Inventor Hiroyuki Watanabe 4-2-16 Nihonbashi Muromachi, Chuo-ku, Tokyo Co., Ltd. Inside Watanabe Trading Co., Ltd. (72) Inventor Keishi Uehara 4-2-16 Nihonbashi Muromachi, Chuo-ku, Tokyo Co., Ltd. Watanabe Trading Co., Ltd. (72) Inventor Keiko Sampei 4-2-16 Nihonbashi Muromachi, Chuo-ku, Tokyo Inside Watanabe Trading Co., Ltd. (72) Inventor Jinichi Omi 7-35 Higashi-Oku, Arakawa-ku, Tokyo Asahi Denka Kogyo Co., Ltd. (72) Inventor Shuichi Tada 7-35 Higashi Oku, Arakawa-ku, Tokyo Asahi Denka Kogyo Co., Ltd. (72) Inventor Maki Takahashi 7-35 Higashi Oku, Arakawa-ku, Tokyo Asahi Denka Kogyo Co., Ltd. (72) Inventor Hiroshi Morita F-term (reference) 4G072 AA28 AA30 BB05 CC13 EE01 GG03 HH21 JJ03 JJ11 JJ23 JJ50 MM06 MM14 MM34 MM35 PP01 PP03 PP11 in Asahi Denka Kogyo Co., Ltd. UU01 UU30

Claims (5)

[Claims] A first step of adding hydrogen peroxide to water glass and subjecting it to a cation exchange treatment to obtain an aqueous silica solution;
A second step of mixing the obtained aqueous silica solution with an ammoniacal alkali and converting it into a colloidal silica, comprising the steps of: 2. The method for producing high-purity colloidal silica according to claim 1, further comprising a third step of concentrating the colloidal silica obtained in the second step. 3. The method for producing high-purity colloidal silica according to claim 2, wherein the concentration of the colloidal silica is performed by an ultrafiltration method. 4. A fourth step of obtaining high-purity colloidal silica by the production method according to claim 1, and then dehydrating or drying the obtained high-purity colloidal silica to obtain silica particles. And a fifth step of washing the obtained silica particles, and a sixth step of firing the washed silica particles. 5. The method for producing a high-purity synthetic quartz powder according to claim 4, wherein the dehydration or drying of the colloidal silica uses a freeze-drying method.