JP3225549B2 - Production method of high purity aqueous silica sol - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a polyvalent metal oxide having a SiO ₂ concentration of 30 to 50% by weight, an average particle diameter of colloidal silica of 10 to 30 mm, and a non-silica polyvalent metal oxide. The present invention relates to an improvement in a method for producing a stable aqueous silica sol having a so-called high purity substantially containing no. In particular, the silica sol obtained by the method of the present invention has an extremely low content of oxides of polyvalent metals such as iron and aluminum. Therefore, applications where the absence of these polyvalent metals in the silica sol is desired, for example, semiconductors Used as an abrasive.

[0002]

2. Description of the Related Art Stable aqueous silica sols of industrial products used for various applications are produced from water-soluble alkali metal silicates, especially water glass, an industrial product which is available at low cost. However, the stable aqueous silica sol produced from the water glass may be used in several applications, such as abrasives for semiconductor surfaces, raw materials for quartz fibers, and other applications where high-purity sols are desired. With the sophistication of silica, problems often arise due to metal oxides usually present in trace amounts in the silica sol, especially polyvalent metal oxides.

[0003] Processes for producing aqueous silica sols substantially free of alkali metal oxides are already known. For example, U.S. Pat. No. 4054536, as a production method of an aqueous silica sol substantially free of alkali metal oxides, the molar ratio of SiO ₂ to amine 2 to 10% of the silicate solution to a hot aqueous solution of the alkanolamine PH 8 to 1 obtained by distilling off water while adding to a ratio of 1 to 100 as
0, an aqueous sol of 5 to 55% of SiO ₂ is passed through an ion exchange resin to obtain an alkali metal content of 200 ppm or less, pH
A method is disclosed in which an aqueous silica sol having an alkali metal content of 200 ppm or less is obtained by forming an aqueous silica sol having a pH of 2 to 5 and adding ammonia to the aqueous silica sol to a pH of 9 to 10.

Further, Japanese Patent Application Laid-Open No. 61-158810 discloses that
An acid is added to a silicate solution obtained by contacting an aqueous solution of 0.5 to 7% by weight of an alkali silicate with a strong acid type cation exchange resin to remove alkali, pH 2.5 or less, temperature 0 to 98 ° C
The silicate solution is treated with, then, impurities in the solution after the treatment are removed by passing through an ultrafiltration membrane, and then passed through a mixed bed of an anion and cation exchange resin, a chelate resin layer, and the like.
Ammonia, amine, etc. are added to a part of the obtained oligosilicic acid solution to form a heel sol having a pH of 7 to 10.Colloidal silica particles are obtained by gradually dropping the rest of the oligosilicic acid solution into the heel sol at 60 to 98 ° C. There has been proposed a method of obtaining a silica sol having a low content of a polyvalent metal oxide other than silica by growing a sol.

[0005]

The above-mentioned U.S. Pat. No. 4,045,536 describes the use of an aqueous solution of activated silicic acid obtained by passing a dilute aqueous solution through a cation exchange resin layer using water glass as a commercial industrial product as a raw material. When an aqueous silica sol is produced by the method described in this document, an aqueous silica sol having an alkali metal content of 200 ppm or less based on silica can be obtained.However, the content of other metals, for example, iron and polyvalent metals such as aluminum is higher than that of silica. Only an aqueous silica sol containing 300 ppm or more can be obtained. The polyvalent metal present at this high content is derived from the polyvalent metal oxide contained in the raw water glass at about 300 ppm or more.

In the method described in Japanese Patent Application Laid-Open No. 61-158810, both alkali metals and polyvalent metals other than silicon present in the alkali metal silicate as a raw material such as water glass are used in the process of producing silica sol. Removal is performed. However, the method of this removal is to remove the impurities contained therein from the aqueous solution of active silicic acid containing the added acid by passing the solution through an ultrafiltration membrane. It is necessary to supply a separately prepared acid solution in an amount corresponding to 20 to 10,000 times, which is not efficient as an industrial production process of silica sol. Further, in the method described in JP-A-61-158810, it takes a long time of 760 hours for the growth of colloidal silica particles, and after completion of the particle growth, the silica sol is concentrated. Is still inefficient as an industrial production process.

[0007] When silica sol is used as a binder, the smaller the colloidal silica particle size of the sol used, the higher the binding force of the sol, but on the other hand, the smaller the colloidal silica particle size of the sol used. About
The sol becomes less stable, so to compensate for this,
The SiO ₂ concentration must be reduced. However, in general, when used as a binder, a binder having a high SiO ₂ concentration and sufficient binding strength is desired. Further, a sol made of colloidal silica having a distribution of particle diameters has a higher binding force than a sol made of colloidal silica having a uniform particle diameter.

[0008] As described above, it is an object to provide an improved silica sol as an inexpensive industrial product suitable for improving the performance of a product obtained by using the silica sol. The present invention is intended to solve such a problem and the problem of the above-mentioned conventional method for producing a silica sol having a low content of polyvalent metal oxides other than silica. Less than 300 ppm, 30
It has a SiO ₂ concentration of 50 wt%, and a stable aqueous silica sol which is the average particle size of 10-30 millimicrons colloidal silica, efficiently from alkali metal silicate containing polyvalent metal oxides as impurities produced To provide a way to do so.

[0009]

Means for Solving the Problems 30 to 50% by weight of the present invention
Has a SiO ₂ concentration of substantially no polyvalent metal oxide other than silica, and the average particle size of the colloidal silica
A method for producing a stable aqueous silica sol having a diameter of 10 to 30 mm is characterized by comprising the following steps (a), (b), (c), (d), (e), (f) and (g). And

(A) A water-soluble alkali metal silicate containing a polyvalent metal oxide other than silica in a ratio of 300 to 10,000 ppm based on silica is converted into 1 to ₂ parts of SiO ₂ derived from the silicate.
An aqueous solution of an alkali metal silicate dissolved at a concentration of 6% by weight is brought into contact with a hydrogen-type strongly acidic cation exchange resin to form an aqueous solution of activated silicic acid having a SiO ₂ concentration of 1 to 6% by weight. (B) adjusting the aqueous solution to pH 0 to 2.0 by adding a strong acid to the aqueous solution of active silicic acid recovered in step (a);
(C) keeping the aqueous solution obtained in step (b) in contact with a strongly acidic cation exchange resin of hydrogen type, and subjecting the resulting solution to a strong base of hydroxyl type. By contacting with a reactive anion exchange resin, an aqueous solution of activated silicic acid containing substantially no dissolved substance other than activated silicic acid and having a SiO ₂ concentration of 1 to 6% by weight is generated, and the generated liquid is recovered. (D) An aqueous solution of sodium or potassium hydroxide is added to the aqueous solution of active silicic acid recovered in step (c) by adding M ₂ O derived from the hydroxide (where M is a sodium atom or potassium Represents an atom.) And Si contained in the aqueous solution of the active silicic acid.
SiO ₂ / M ₂ O molar ratio of O ₂ is by adding so that 50 to 250, the aqueous solution of the stabilized active silicic acid having a pH of SiO ₂ concentration of 1-6 wt% and 7-9 (E) charging the aqueous solution of stabilized activated silicic acid obtained in the step (d) into a 1 part by weight container as a heel solution, keeping the temperature of the container solution at 70 to 100 ° C. While continuously supplying 5 to 20 parts by weight of the aqueous solution of stabilized activated silicic acid obtained in the step (d) as a feed solution into the vessel for 50 to 200 hours, the vessel By keeping the inside at normal pressure or reduced pressure, and removing water from the container by evaporation so that the liquid volume in the container is kept constant, it has a SiO ₂ concentration of 30 to 50% by weight, and has a colloidal A step of producing a stable aqueous silica sol having an average particle diameter of silica of 10 to 30 millimicrons, obtained in steps (f) and (e) After contacting a stable aqueous silica sol with a hydrogen-type strongly acidic cation exchange resin, the aqueous silica sol generated by this contact is contacted with a hydroxyl-type strong basic anion exchange resin to convert polyvalent metal oxides other than silica. (G) forming an acidic aqueous silica sol substantially free of, and (g) adding the p of the sol to the acidic aqueous sol generated in the step (f).
By adding ammonia so that H becomes 8 to 10.5, it has an SiO ₂ concentration of 30 to 50% by weight, is substantially free of polyvalent metal oxides other than silica, and has an average particle size of colloidal silica. Forming a stable aqueous silica sol having a particle size of 10-30 millimicrons.

As the alkali metal silicate used in step (a) of the production method of the present invention, commercially available industrial products may be used, and the alkali metal and silicon contained therein are SiO ₂ / M ₂ O (However, M represents an alkali metal atom.) A water-soluble compound having a molar ratio of about 0.5 to 4.5 is suitable. In particular, in order to produce silica sol on a large scale as an inexpensive industrial product, the inexpensive industrial product SiO ₂ /
It is preferable to use sodium water glass having a Na ₂ O molar ratio of about 2 to 4. However, the water glass of this commercial industrial product usually contains polyvalent metal oxides other than silica as impurities of about 300 to 10,000 ppm based on the SiO ₂ content in the water glass. The main polyvalent metals whose content is relatively high are aluminum, iron, calcium, magnesium and the like.

In the step (a), the alkali metal silicate containing such a polyvalent metal oxide other than silica as an impurity is contained in an amount of 1 to 6% by weight, preferably 2 to 6% by weight as SiO ₂ derived from the silicate. An aqueous alkali metal silicate solution obtained by dissolving in water to a concentration of 66% by weight is used. This water may be industrial water obtained by removing cations.

The hydrogen-type strongly acidic cation exchange resin used in the step (a) of the present invention may be one conventionally used for removing alkali metal ions from an aqueous solution of water glass, and is easily used as a commercially available industrial product. Obtained. An example is Amberlite IR-120B. In the step (a) of the present invention, the aqueous alkali metal silicate solution is brought into contact with the hydrogen-type strongly acidic cation exchange resin. This contact can be preferably performed by passing the solution through a column filled with the ion exchange resin, and the solution passing through the column has an SiO ₂ concentration of 1 to 6% by weight, preferably 2 to 6% by weight.
It is recovered as an aqueous solution of 6% by weight active silicic acid. The amount of the hydrogen-type cation exchange resin used may be an amount sufficient for exchanging the total amount of alkali metal ions in the aqueous alkali metal silicate solution with hydrogen ions. The speed of passage through the column is preferably a space velocity of about 1 to 10 per hour.

Examples of the strong acid used in the step (b) include:
Inorganic acids such as hydrochloric acid, nitric acid, sulfuric acid and the like can be mentioned, but nitric acid is most preferable to increase the removal rate of aluminum and iron. This strong acid is added to the aqueous solution of active silicic acid before the aqueous solution of active silicic acid recovered in step (a) does not undergo any alteration, preferably immediately after the recovery. The amount of the strong acid to be added is such that the pH of the solution is in the range of 0 to 2, preferably 0.5 to 1.8. In step (b), after this addition, the solution is
It is kept at 0.1 DEG C. for 0.1 hour or more, preferably 0.5 to 120 hours.

The hydrogen-type strongly acidic cation exchange resin used in the step (c) may be the same as that used in the step (a). (c) The hydroxyl group type strongly basic anion exchange resin used in the step may be the one conventionally used for removing anions in silica sol, and is easily available as a commercial product. An example is the trade name Amberlite IRA-41
0 is cited.

In the step (c), the aqueous solution obtained in the step (b) is first brought into contact with the hydrogen-type strongly acidic cation exchange resin. This contact can be preferably carried out by passing the solution through a column packed with the hydrogen-type strongly acidic cation exchange resin at a space velocity of 2 to 20 per hour at 0 to 60 ° C, preferably 5 to 50 ° C. Next, the aqueous solution obtained by this passage is preferably, immediately after being obtained, the above-mentioned hydroxyl group type strongly basic anion exchange resin, at 0 to 60 ° C., preferably 5 to 60 ° C.
Contact at 50 ° C. This contact also takes place in a column packed with the above-mentioned hydroxyl-type strongly basic anion exchange resin at 1 to 10 per hour.
It can be carried out preferably by passing the solution at a space velocity of It is more preferable that the aqueous solution obtained by this passing is contacted with the hydrogen-type strongly acidic cation exchange resin at 0 to 60 ° C., preferably 5 to 50 ° C. immediately after being obtained. This contact can also be preferably performed by passing the solution through the column filled with the hydrogen-type strongly acidic cation exchange resin at a space velocity of 1 to 20 per hour.
After this passage, the aqueous solution is recovered and subjected to the next step (d).

The aqueous solution of sodium hydroxide or potassium hydroxide used in the step (d) is preferably a commercial industrial product having a purity of 95% or more, which is preferably prepared by removing cations from sodium hydroxide or potassium hydroxide in industrial water. Is obtained by dissolving to a concentration of 2 to 20% by weight. In the step (d), the aqueous solution of sodium or helium hydroxide is added to the aqueous solution of activated silicic acid obtained in the step (c), preferably immediately after the recovery, with SiO ₂ / M ₂ O (where M is as described above). The same is applied.) The molar ratio is 50 to 250, preferably 60 to 200. This addition can be performed at room temperature to 60 ° C., but is preferably performed at room temperature in as short a time as possible. SiO ₂ concentration of 1-6 wt% by the addition, preferably having from 2 to 6 wt%, and the aqueous solution of the stabilized active silicic acid is obtained having a pH 7 to 9. This product liquid is stable for a long time, but it is particularly preferable to subject it to the step (e) within 30 hours.

(E) The equipment used in the process includes a usual acid-resistant, alkali-resistant and pressure-resistant container in which a stirrer, a temperature controller, a liquid level sensing device, a pressure reducing device, a liquid supply device, the above-mentioned cooling device, and the like are used. It may be provided. (e) In the process,
(d) All or 1/5 to 1/20 of the aqueous solution of stabilized activated silicic acid obtained in the step is poured as a heel solution into a container. In large-scale industrial production, this whole amount is used for heel fluid,
Separately, it is preferable to use an aqueous solution of the stabilized activated silicic acid formed through the above steps (a) to (d) as a feed solution in an amount of 5 to 20 times the heel solution. When the above 1/5 to 1/20 amount is used as the heel liquid, the remainder is used as the feed liquid.

In the step (e), the temperature in the container is 70 to 100 ° C.
Preferably, the temperature is maintained at 80 to 100 ° C. and the pressure is such that water evaporates from the liquid. The feed rate of the feed solution and the removal rate of the evaporating water are adjusted so that the amount of the solution in the container is kept constant, and the supply of the feed solution is completed within 50 to 200 hours. . The supply of the feed liquid and the removal of the evaporated water may be performed continuously or intermittently from the start to the end of the step (e), but the liquid amount in the container is kept constant. It is preferable to keep the feed rate of the feed liquid constant.

The hydrogen-type strongly acidic cation exchange resin used in the step (f) may be the same as that used in the steps (a) and (c). Further, the hydroxyl group type strongly basic anion exchange resin may be a usual one used in the step (c). (f) The contact between the stable aqueous sol and the ion exchange resin in the process,
(c) The contact can be performed in the same manner as in the contact in the step.
It is more preferable that the liquid generated by the contact with the anion exchange resin is further contacted with the cation exchange resin.

The ammonia used in the step (g) may be a commercially available industrial product, but is preferably of high purity.
It is preferable to use about 28% by weight of aqueous ammonia. In place of this ammonia, quaternary ammonium hydroxide, guanidine hydroxide, water-soluble amine, etc. can also be used, but ammonia is generally used unless it is particularly undesirable to use ammonia. It is convenient.

In the step (g), the above-mentioned ammonia is added to the aqueous sol obtained in the step (f), preferably immediately after the step is obtained. This addition can be performed at room temperature to 100 ° C., but is preferably performed at room temperature. The amount of ammonia added is preferably such that the pH of the silica sol becomes 8 to 10.5. In some cases, an acid or ammonium salt containing no metal component may be added in an amount of 1000 ppm or less in the sol.

The size of the colloidal particles of silica sol is B
It is calculated as an average particle diameter by a conventional method from a specific surface area (m ² / g) measured by a nitrogen gas adsorption method called an ET method. The size of the colloid particles can be observed with an electron microscope. The silica sol obtained by the step (g) generally has a minimum particle diameter of about 4 millimicrons for an average particle diameter of 10 millimicrons. Has a distribution over a maximum of about 20 millimicrons, and has an average particle size of 30.
Millimicrons have a distribution ranging from a minimum of about 10 millimicrons to a maximum of about 60 millimicrons.

[0024]

[Action] When an aqueous solution of an alkali metal silicate is brought into contact with a hydrogen-type strongly acidic cation exchange resin, an aqueous solution of activated silicic acid from which alkali metal ions have been removed is generated. In the form of fine particles of 3 mm or less composed of the low polymer, this aqueous solution is
About 1 at room temperature even if polyvalent metals such as aluminum are present
It is unstable enough to turn into a gel within 00 hours. This instability is greater as the SiO ₂ concentration in the liquid is higher and as the liquid temperature is higher. Therefore, especially when the silica sol is industrially produced on a large scale, about 6% by weight is required in the step (a). Exceed
It is preferable that an aqueous solution of active silicic acid having a concentration lower than the SiO ₂ concentration be generated at room temperature, while avoiding the SiO ₂ concentration. In particular, when an alkali metal, a polyvalent metal, or the like present in the raw material is incorporated into the silicic acid polymer particles, since these metals are difficult to remove, a low-concentration aqueous solution in which polymerization of the silicic acid is difficult to proceed is preferable. In order to avoid particle formation due to the gradual polymerization of silicic acid which cannot be avoided even at room temperature, it is preferable to use the entire amount of the generated aqueous solution of active silicic acid as early as possible even after the formation. If the concentration of SiO _{2 in} the aqueous solution of activated silicic acid is lower than about 1% by weight, the amount of water to be removed in concentrating the silica sol formed later becomes extremely large, which is not efficient.
The SiO ₂ concentration is preferably 2% by weight or more. (a) In the step, the SiO ₂ concentration of the generated aqueous solution of activated silicic acid is 1 to 6
The aqueous solution of the alkali metal silicate before contact with the hydrogen-type strongly acidic cation exchange resin is converted to SiO _{2 so} as to obtain
Adjusted to a concentration of 1-6% by weight.

The liquid passed through the column packed with a hydrogen-type strongly acidic cation exchange resin, which is preferably used in the step (a), is added at a rate of 1 hour per hour to remove as much metal ions as possible.
Preferably, a space velocity of about 10 is provided. A liquid temperature of about 0 to 60 ° C. is employed so that polymerization of the silicic acid, thickening or gelling in the aqueous solution of the activated silicic acid thus formed hardly occurs. From step (a) to step (c), no special method for stabilizing the aqueous solution of activated silicic acid is added,
The above concentration and temperature are adopted as the SiO ₂ concentration and temperature of the liquid.

The strong acid added in the step (b) converts active metal silicic acid or an impurity metal component such as an alkali metal or a polyvalent metal which is not in the state of dissociated ions bound in the polymer into the state of dissociated ions in the liquid. Let it be converted. Since the elution of the metal component by the strong acid is easier as the particles of the activated silicic acid having a smaller particle diameter are added, the addition of the strong acid to the aqueous solution of the activated silicic acid obtained in the step (a) is completed in as short a time as possible. Is preferred.

However, when the amount of the strong acid added is increased so that the pH of the aqueous solution of active silicic acid becomes 0 or less,
Although the elution effect of the metal component can be enhanced, it is easy to remove the anion in the step (c), and the elution effect of the metal component is poor when the amount of addition of the solution becomes 2 or more. Among the strong acids, nitric acid has a particularly high effect on elution of metal components such as aluminum and iron. In addition, the elution effect of the polyvalent metal component by the strong acid also depends on the temperature and elution time of the solution, and is 10 to 120 hours at a temperature of 0 to 40 ° C, 2 to 10 hours at a temperature of 40 to 60 ° C, and 60 to 100 ° C. 0.1 to 2 hours, especially 0.5
It is preferable to avoid standing for a long time exceeding this elution time because the solution may be thickened or gelled in some cases.

In the step (c), the metal ion eluted in the liquid in the step (b) and the anion due to the added acid are:
Excluded by strongly acidic cation exchange resins of the hydrogen type and strongly basic anion exchange resins of the hydroxyl group type. In the product liquid after the first hydrogen-type strongly acidic cation exchange resin treatment, anion of the added acid is present, so that ions of the eluted metal tend to remain in the liquid. In some cases, the amount of residual metal ions after treatment with a hydroxyl-type strongly basic anion exchange resin is 5 to 5 ml for the liquid.
It may be as high as a pH of 7, and in such cases the solution may gel within about 1 hour. If the treatment with the hydrogen-type strongly acidic cation exchange resin is performed for the second time after the anions have been removed by the hydroxyl-type strong basic anion exchange resin, such undesired eluting metal ions are further removed. Is preferred.

The aqueous solution of activated silicic acid obtained in the step (c) is unstable to such an extent that gelation may occur within 6 hours. ) It is sent to the process. If the amount of the sodium or potassium hydroxide added to the unstable aqueous solution of activated silicic acid is so large as to be 60 or less, particularly 50 or less as a molar ratio of SiO ₂ / M ₂ O, polymerization of the activated silicic acid is difficult. Is easy to occur,
(E) The particle growth in the step is suppressed or the produced sol tends to be unstable. On the contrary, the molar ratio is 200 or more, especially 250
With such a small amount, even if the obtained liquid is treated in the same manner as in the step (e), the particle diameter of the colloidal silica cannot be increased. The liquid obtained in step (d) is stable for a long time at room temperature, but at high temperatures polymerization of activated silica occurs. ) It is preferable to be transferred to the process. The sodium or potassium hydroxide added in the step (d) is replaced with another hydroxide when the colloidal silica particles are grown to a size of 10 to 30 mm in the step (e). It provides a colloidal silica particle growth rate about twice or more as fast as when a base such as ammonia or amine is used in the same molar ratio as the above sodium hydroxide or potassium hydroxide.

By the high particle growth rate, the feed rate of the feed solution can be increased in the step (e), so that the production rate of the silica sol is remarkably increased. The supply of the feed solution at a high rate performed in the step (e) also advantageously acts to make the particle size of the colloidal silica particles in the formed silica sol irregular and broaden the particle size distribution. (e)
In the process, in order to increase the production rate of the high-concentration silica sol, water is evaporated from the produced sol simultaneously with the supply of the feed liquid, and the evaporated water is removed.

If the liquid temperature in the step (e) is 70 ° C. or lower, the growth of colloidal silica particles in the liquid does not sufficiently occur, so that colloidal silica having an average particle diameter of 10 mm or less is formed in the liquid. I do. When the silica sol having such a small particle diameter is concentrated, the liquid may thicken or gel, and a stable sol having a SiO ₂ concentration of 30% by weight or more cannot be obtained. The temperature of the liquid gives a higher particle growth rate as the temperature is higher than 70 ° C., but if it is higher than 100 ° C., too high a particle growth rate tends to make it difficult to adjust the average particle diameter.

When the feed solution is added to the heel solution at 70 to 100 ° C., particles of colloidal silica grow in the mixed solution. However, depending on the supply of the feed solution of 5 times or less the heel solution, the average particle size is increased. Particles cannot be grown to a size of more than 10 millimicrons in diameter, and in this case, too, a stable sol concentrated to more than 30% by weight cannot be obtained. The average particle size of the colloidal silica increases with the supply amount of the feed solution, but if the amount is more than 20 times that of the heel solution, the average particle size exceeds 30 millimicrons, and the sol having a high binding force Can not be obtained.

However, the relationship between the amount of the feed solution and the average particle size of the colloidal silica is further affected by the feed rate of the feed solution, and the feed solution having a volume of 5 to 20 times the amount of the heel solution can be obtained within 50 hours. Average particle size 10 when supplied to heel fluid
Colloidal silica of millimeters or more is not generated. In this regard, in the step (e), it is probable that in the step (e), a part of the active silicic acid in the supplied feed solution does not deposit on the surface of the colloidal silica particles, and new core particles are formed in the liquid from the part of the active silicic acid. In particular, when the feed rate is high, a part of the activated silicic acid in the supplied feed solution is consumed for the particle growth, but the remaining amount of the activated silicic acid which produces new core particles in the same manner as described above is increased with respect to the amount. It is considered that colloidal silica particles having an average particle diameter of 10 millimicrons or more are not efficiently generated because the ratio of the amount increases. Therefore,
Feeding the feed solution too fast should be avoided, but feeding a feed solution of 5 to 20 times the amount of the heel solution over a long period of 200 hours or more is not efficient for the industrial production of silica sol. Further, in order to industrially produce silica sol of a constant quality, it is preferable to continuously supply the feed solution for 50 to 200 hours.

In the step (e), when the liquid level in the container fluctuates on the vessel wall due to the supply and the concentration performed at the same time, the gelled silica sol deposits on the fluctuated vessel wall. Therefore, in step (e), the feed rate of the feed liquid and the removal rate of the evaporating water are preferably adjusted to keep the amount of liquid in the container constant at step (e). If the SiO ₂ concentration of the silica sol formed in the step (e) is concentrated to 50% by weight or more, the viscosity of the sol may be increased to an undesired viscosity. It is better not to let it.

Since the sol produced in the step (e) contains the sodium or potassium added in the step (d), the treatment with the hydrogen-type strongly acidic cation exchange resin in the step (f) and The cations and anions therein are removed from the sol by treatment with a hydroxyl group type strongly basic anion exchange resin. In particular, in order to further remove alkali metal ions, a second hydrogen-type strongly acidic cation exchange resin treatment is preferably performed. The sol from which the cations have been removed in the step (f) does not exhibit instability like an aqueous solution of activated silicic acid, but it does not have sufficient stability, so that treatment with an ion exchange resin is not performed at as high a temperature as possible. It is better to stabilize in the step (g) as soon as possible after the step (f), preferably immediately. Ammonia used to give the sol a pH of 8 to 10.5 for this stabilization is not only available as high-purity and inexpensive ammonia water, but also can be easily volatilized from the used silica sol. It is convenient to use silica sol for various applications.

[0036]

【Example】

(a) Process As a water-soluble alkali metal silicate as a raw material, JIS No. 3 sodium water glass was prepared. The main components of this water glass other than water are SiO ₂ 28.8% by weight, Na ₂ O 9.47% by weight, Al ₂ O
₃ 280 ppm, Fe ₂ O ₃ 45 ppm, CaO 46 ppm, MgO 25 ppm.

5.25 kg of the above water glass was dissolved in 3675 kg of pure water, and 420 kg of an aqueous solution of sodium silicate having a SiO ₂ concentration of 3.6% by weight was dissolved.
Was prepared. Subsequently, the aqueous solution of sodium silicate at 25 ° C. was added to a strongly acidic cation exchange resin Amberlite IR-
After passing through a column packed with 120B at a space velocity of 3 per hour, the obtained aqueous solution of activated silicic acid at 25 ° C. having an SiO ₂ concentration of 3.54% by weight, a pH of 2.78 and an electric conductivity of 667.5 μS / cm was obtained at 357 kg.
Was collected in a container.

(B) Step As a strong acid to be used, a commercially available special-grade reagent nitric acid (specific gravity)
1.38, HNO ₃ 61.3% by weight). 121.2 g of the above nitric acid was added to 35.7 kg of the aqueous solution of activated silicic acid obtained immediately after the step (a) to adjust the pH to 1.54, and the mixture was kept at 20 ° C. for 48 hours to complete the step (b).

Example 1 After completion of the above step (b), a stable aqueous silica sol according to the present invention was produced through the following steps (c) to (g) in order. The hydrogen-type strongly acidic resin used was a cation exchange resin obtained by treating Amberlite IR-12B with a sulfuric acid aqueous solution having a hydrogen ion content equivalent to three times its cation exchange capacity. Further, as the hydroxyl group type strongly basic anion exchange resin, a resin obtained by treating Amberlite IRA-410 with an aqueous sodium hydroxide solution having a hydroxyl group content equivalent to three times the anion exchange capacity was used.

Step (c) 35.7 g of an aqueous solution of activated silicic acid immediately after the step (b)
The above-mentioned hydrogen type strong acidic cation exchange resin Amberlite
After passing through an IR-120B packed column at about 25 ° C. at a space velocity of 5 per hour, the entire amount of the obtained liquid is continued as it is and packed with the above-mentioned hydroxyl-type strongly basic anion exchange resin Amberlite IRA-410. The solution was passed through the column at about 25 ° C. at a space velocity of 3 per hour. Subsequently, the whole amount of the obtained liquid was passed through a column at about 25 ° C. filled with another hydrogen-type strongly acidic cation exchange resin Amberlite IR-120B at a space velocity of 5 per hour, and then the obtained liquid was obtained. 30.28Kg
Was collected in a container. The liquid collected in this container contains SiO ₂
It has a concentration of 3.52% by weight, pH 4.38, electrical conductivity of 27.20 μS / cm, 0.25 ppm of Al ₂ O ₃ , 0.19 ppm of Fe ₂ O ₃ , and 0.08 ppm of C
It contained aO and 0.02 ppm of MgO.

Step (d) Immediately after obtaining 178 g of a 10% by weight aqueous sodium hydroxide solution obtained by dissolving a commercially available special-grade reagent sodium hydroxide (purity 95%) in pure water, in step (c) An aqueous solution of activated silicic acid was obtained by adding to 30.28 kg of an aqueous solution of activated silicic acid at 25 ° C. This aqueous solution has a SiO ₂ concentration
3.5 wt%, SiO ₂ / Na ₂ O molar ratio 80, pH 8.20, an electrical conductivity
732 μS / cm.

(E) Process A reaction apparatus equipped with a stirrer, a cooler, a decompression device, a liquid level sensing device, a solenoid valve, a heating device, and the like was used in a glass reactor having an internal volume of 5 liters. 2.67 kg of the stabilized aqueous solution of activated silicic acid obtained immediately after the step (d) is charged into the reactor as a heel solution, and the temperature of the heel solution is adjusted to 90 ° C. by heating. The stabilized active silicic acid aqueous solution immediately after obtained in step 27 was fed continuously as a feed solution into the above-mentioned vessel over a period of 95 hours as a feed liquid, and the liquid temperature in the vessel was kept at the boiling point of 90 ° C and the pressure was reduced. The liquid content in the container was kept constant by continuously removing the evaporated water. The feed rate of the feed solution was 292.4 g / H. In this way, the supply of the feed liquid having a total amount of 27.78 kg was completed. The silica sol generated in the vessel was cooled to room temperature, and a total amount of 3.23 kg was discharged outside the vessel.

The silica sol thus obtained has a specific gravity of 1.233,
It has a pH of 9.92, a viscosity of 26.0 cp at 20 ° C., an average particle size of 13.2 millimicrons by the BET method, an electrical conductivity of 3240 μS / cm, and shows stability of not changing for more than one month at 60 ° C., and SiO ₂ 33.0
Wt%, SiO ₂ / Na ₂ O molar ratio _{85.2, Al 2 O 3 2.34ppm,} Fe 2 O
_{3 It} contained 1.78 ppm. (f) Step The silica sol obtained in the step (e) is passed through a column at about 25 ° C. packed with a hydrogen-type strongly acidic cation exchange resin Amberlite IR-120B at a space velocity of 3 per hour. And then pass the silica sol obtained by this passage onto a column at about 25 ° C. packed with a hydroxyl-type strongly basic anion exchange resin Amberlite IRA-410 at a space velocity of 3 per hour. And finally, the silica sol obtained by this passage was successively filled with hydrogen-type strongly acidic cation exchange resin Amberlite IR-120B to about 25%.
3.15 kg of an acidic aqueous silica sol were obtained by passing through a column at a rate of 3 hourly space velocity.

This sol has a specific gravity of 1.205, a pH of 4.72, a viscosity of 20 ° C. of 3.6 cp, an electric conductivity of 70 μS / cm, a SiO ₂ concentration of 30.7% by weight, a Na ₂ O content of 190 ppm, and a SiO ₂ / Na ₂ O molar ratio of 1670. Was. (g) Step 2015 g of silica sol was obtained by adding 15.0 g of 28% aqueous ammonia, a commercially available special-grade reagent, to the silica sol at 25 ° C. immediately after the above step (f).

The obtained sol had a specific gravity of 1.205 and a pH of 9.2.
0, viscosity at 20 ° C 9.8cp, electrical conductivity 2820μS / cm, 1 at 60 ° C
It has stability that it does not deteriorate for more than a month, SiO ₂ 30.5% by weight, SiO ₂ / (NH ₄ ) ₂ O molar ratio 83, Al ₂ O ₃ 2.16 ppm, Fe ₂ O ₃ 1.6
It contained 5 ppm, 190 ppm Na ₂ O, 6.0 ppm Cl, 8.2 ppm SO ₄ , and the colloidal silica particle size by electron microscopy had a broad distribution ranging from a minimum of 4 millimicrons to a maximum of 20 millimicrons.

Example 2 In this example, a silica sol was produced from an aqueous solution of activated silicic acid prepared in the same manner as in step (c) of Example 1 through the following steps (d) to (g). The same aqueous solution of sodium hydroxide, aqueous ammonia, ion exchange resin, reactor and the like as those used in Example 1 were used.

Step (d) The aqueous silicic acid solution obtained immediately after the step (c) is added to 40.4 kg of an aqueous solution.
By adding 146 g of a 10% by weight aqueous solution of sodium hydroxide at a temperature of 40 ° C., 40.55 g of an aqueous solution of activated silicic acid stabilized was obtained. The aqueous solution, SiO ₂ concentration of 3.5 wt%, pH7.82, SiO ₂
/ Na ₂ O molar ratio was 130 and electric conductivity was 612 μS / cm.

(E) Step The aqueous solution of stabilized activated silicic acid obtained in the step (d) is charged into a 2.54 kg reactor as a heel solution, and while maintaining the liquid temperature in the container at a boiling point of 95 ° C., (d) ) 38 kg of the aqueous solution of stabilized activated silicic acid obtained in the step was continuously supplied as a feed solution over 180 hours. During this time, the inside of the container was kept under reduced pressure, and the amount of liquid in the container was kept constant by continuously removing the evaporated water. The feed rate of the feed solution was 211 g / H. After the completion of the reaction, the obtained silica sol was cooled, and a total amount of 3.33 kg was discharged outside the vessel.

The obtained aqueous silica sol had a specific gravity of 1.3
20, pH9.76, 20 ° C viscosity 29.6cp, electrical conductivity 2020μS / cm,
BET average particle size 21.0 millimicron, stable at 60 ° C for no more than one month, SiO ₂ 42.6 wt%, Si
O ₂ / Na ₂ O molar ratio _{147, Al 2 O 3 2.89ppm,} Fe 2 O 3 2.20ppm
Was contained. (f) Step: The silica sol obtained in the step (e) is passed through a column at about 25 ° C. packed with a hydrogen-type strongly acidic cation exchange resin at a space velocity of 3 per hour. Was passed through a column at about 25 ° C. packed with a hydroxyl group type strongly basic anion exchange resin at a space velocity of 3 per hour, and finally obtained by this passage. Subsequently, the silica sol was passed through a column at about 25 ° C. packed with a hydrogen-type strongly acidic cation exchange resin at a space velocity of 3 per hour to obtain 3.1 kg of an acidic aqueous silica sol.

The obtained sol had a specific gravity of 1.293 and a pH of 4.7.
0, 20 ° C viscosity 5.6cp, electrical conductivity 120μS / cm, SiO ₂ concentration 4
It had 0.7% by weight, 700 ppm of Na ₂ O, and a SiO ₂ / Na ₂ O molar ratio of 601. (g) Step 19 g of 28% by weight aqueous ammonia and 10% by weight aqueous nitric acid are added to 3000 g of the aqueous silica sol immediately after the step (f) under stirring.
By adding 9.6 g at a liquid temperature of 25 ° C., 3030 g of silica sol was obtained.

This sol has a specific gravity of 1.293, a pH of 9.5, a viscosity of 20 cp at 22 ° C., an electric conductivity of 3920 μS / cm, a stability of not changing for more than one month at 60 ° C., a SiO ₂ concentration of 40.3% by weight,
₂ / (NH ₄ ) ₂ O molar ratio 143, Al ₂ O ₃ 2.75 ppm, Fe ₂ O ₃ 2.09pp
m, Na ₂ O 693 ppm, Cl 9.7 ppm, SO ₄ 14.5 ppm, NO ₃ 32
It contained 0 ppm, and the particle size of colloidal silica measured by an electron microscope showed a wide distribution ranging from a minimum of about 7 mm to a maximum of about 40 mm, and the shape of the particles was distorted.

Comparative Example 1 In this example, the supply time of the feed liquid in the step (e) in Example 1 was changed to 32 hours, and the feed liquid was supplied at a higher speed than the supply rate in the step (e) in Example 1. Was done. When the SiO ₂ concentration in the liquid in the container reached about 25%, the viscosity of the liquid in the container began to increase. At this time, a small amount of the liquid was withdrawn from the container, and the average particle size of the colloidal silica was determined by the BET method. When the supply of the feed solution was further advanced, the viscosity of the solution was extremely high at the end of the supply, and the formation of a gel was clearly observed.
This high-viscosity liquid was difficult to discharge smoothly from the container, and when it was taken out and left at room temperature, it turned into a non-flowable gel.

[0053]

According to the method of the present invention, 30 to 50% by weight
A stable aqueous silica sol having an SiO ₂ concentration and having an average particle size of colloidal silica of 10 to 30 mm,
From the water glass raw materials of ordinary industrial products containing polyvalent metals as impurities, the alkali metal oxide content is less than 2000 ppm based on silica, and the polyvalent metal oxide content is lower than 300 ppm based on silica. It can be produced efficiently as an industrial product of purity.

The aqueous silica sol produced by the method of the present invention is widely used for silica sols which have been conventionally used. Particularly, a polishing agent for a semiconductor surface, a binder for a catalyst, and other binders of which high purity is desired. It is suitable for use as an agent.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-2606 (JP, A) JP-A-63-285112 (JP, A) JP-A-61-158810 (JP, A) (58) Investigation Field (Int. Cl. ⁷ , DB name) C01B 33/12-33/193 JICST file (JOIS) WPI / L (QUESTEL)

Claims (1)

(57) [Claims] (1) The following steps (a), (b), (c), (d), (e),
(f) and (g), having a SiO ₂ concentration of 30 to 50% by weight, and substantially free of a polyvalent metal oxide other than silica;
A method for producing a stable aqueous silica sol having an average particle size of colloidal silica of 10 to 30 millimicrons. (a) a polyvalent metal oxide other than silica
An aqueous solution of alkali metal silicate water-soluble alkali metal silicate contained in the ratio of 10000ppm is dissolved in a concentration of 1-6 wt% as SiO ₂ minutes from the silicate, hydrogen type strongly acidic cation SiO ₂ by contact with exchange resin
(B) producing an aqueous solution of active silicic acid having a concentration of 1 to 6% by weight, and collecting the resulting solution; (b) adding an strong acid to the aqueous solution of active silicic acid recovered in step (a) to bring the aqueous solution to pH 0 to After adjusting to 2.0, 0
(C) keeping the aqueous solution obtained in step (b) in contact with a strongly acidic cation exchange resin of hydrogen type, and subjecting the resulting solution to a strong base of hydroxyl type. By contacting with a reactive anion exchange resin, an aqueous solution of activated silicic acid containing substantially no dissolved substance other than activated silicic acid and having a SiO ₂ concentration of 1 to 6% by weight is generated, and the generated liquid is recovered. (D) An aqueous solution of sodium or potassium hydroxide is added to the aqueous solution of active silicic acid recovered in step (c) by adding M ₂ O derived from this hydroxide (where M is a sodium atom or potassium Represents an atom.) And Si contained in the aqueous solution of the active silicic acid.
SiO ₂ / M ₂ O molar ratio of O ₂ is by adding so that 50 to 250, the aqueous solution of the stabilized active silicic acid having a pH of SiO ₂ concentration of 1-6 wt% and 7-9 (E) charging the aqueous solution of stabilized activated silicic acid obtained in the step (d) into a 1 part by weight container as a heel solution, keeping the temperature of the container solution at 70 to 100 ° C. While continuously supplying 5 to 20 parts by weight of the aqueous solution of stabilized activated silicic acid obtained in the step (d) as a feed solution into the vessel for 50 to 200 hours, the vessel By keeping the inside at normal pressure or reduced pressure, and removing water from the container by evaporation so that the liquid volume in the container is kept constant, it has a SiO ₂ concentration of 30 to 50% by weight, and has a colloidal A step of producing a stable aqueous silica sol having an average particle diameter of silica of 10 to 30 millimicrons, obtained in steps (f) and (e) After contacting a stable aqueous silica sol with a hydrogen-type strongly acidic cation exchange resin, the aqueous silica sol generated by this contact is contacted with a hydroxyl-type strong basic anion exchange resin to convert polyvalent metal oxides other than silica. (G) forming an acidic aqueous silica sol substantially free of, and (g) adding the p of the sol to the acidic aqueous sol generated in the step (f).
By adding ammonia so that H becomes 8 to 10.5, it has an SiO ₂ concentration of 30 to 50% by weight, is substantially free of polyvalent metal oxides other than silica, and has an average particle size of colloidal silica. Generating a stable aqueous silica sol having a particle size of 10-30 millimicrons.