JPH0585718A - Production of high-purity water-base silica sol - Google Patents

Abstract

PURPOSE:To efficiently obtain a silica sol by passing a specified soln. through such a process to produce an aq. soln. of active silicic acid by bringing the soln. into contact with a hydrogen-type strongly acidic cation exchange resin (HIR). CONSTITUTION:The water-base silica sol is produced by the following processes (a)-(f). (a) An aq. soln. of active silicic acid is obtd. by bringing an aq. soln. of Na2SiO3 containing 300-10000ppm polyvalent metal oxide except for Si and 1-6wt.% of SiO2 into contact with HIR. (b) The soln. obtd. in the process (a) is maintained to pH 0-2.0. (c) This soln. is brought into contact with HIR and then into contact with hydroxyl group-type strongly alkaline anion exchange resin (OIR) to obtain an active Si aq. soln. containing no dissolving matter except for active Si. (d) Then NaOH of specified concn. is added to the soln. (c) to obtain an active Si aq. soln. of pH7-9. (e) The soln. (d) is maintained at its temp. as a heeling liquid to obtain a water-base Si sol containing 30-50wt.% SiO2. (f) The sol (e) is brought into contact with HIR and then with OIR, and pH of the sol is controlled. Thus, the water-base silica sol which is a colloidal silica having 10-30mmu average particle size containing no polyvalent metal oxide except for Si is obtd.

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 silica other than silica. The present invention relates to an improvement in a method for producing a stable aqueous silica sol having a so-called high purity that does not substantially contain 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, so applications where the absence of these polyvalent metal components in the silica sol is desired, for example, semiconductors Used as a polishing agent.

[0002]

2. Description of the Related Art Stable aqueous silica sols for industrial products used for various purposes are produced from water-soluble alkali metal silicates, especially water glass of industrial products which are available at low cost. However, the stable aqueous silica sol produced from this water glass has several applications, for example, abrasives for semiconductor surface, raw material for quartz fiber, and other applications in which high-purity sol is desired, and the technology of those fields is used. With sophistication, the problems often occur due to metal oxides, especially polyvalent metal oxides, which are usually present in trace amounts in the silica sol.

Methods for producing an aqueous silica sol substantially free of alkali metal oxides are already known. For example, U.S. Pat.No. 4,054,536 discloses a method for producing an aqueous silica sol substantially free of alkali metal oxides, wherein a hot aqueous solution of alkanolamine is added to a 2-10% silicic acid aqueous solution to obtain a molar ratio of SiO ₂ to amine. The pH obtained by distilling off the water while adding in a ratio of 1 to 100
0, SiO ₂ 5-55% aqueous sol is passed through the ion exchange resin to obtain an alkali metal content of 200 ppm or less, pH
A method for producing a silica sol having an alkali metal content of 200 ppm or less by producing an aqueous silica sol of 2 to 5 and adding ammonia to the aqueous silica sol so as to have a pH of 9 to 10 is disclosed.

Further, in Japanese Patent Laid-Open No. 61-158810, the density is
Acid is added to the silicic acid solution obtained by contacting a 0.5 to 7% by weight aqueous solution of alkali silicate with a strong acid type cation exchange resin to dealkalize it to pH 2.5 or less, at a temperature of 0 to 98 ° C.
The silicic acid solution is treated with, then the impurities in the solution after this treatment are removed by passing through an ultrafiltration membrane, and then passed through a mixed bed of anion and cation exchange resins, a chelate resin layer, etc.,
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, and the rest of the oligosilicic acid solution is gradually added dropwise to the heel sol at 60 to 98 ° C to form particles of colloidal silica. Has been proposed to obtain a silica sol having a low polyvalent metal oxide content other than silica.

[0005]

The above-mentioned US Pat. No. 4,054,536, using an aqueous solution of activated silicic acid obtained by passing a diluted aqueous solution of water glass of a commercial industrial product as a raw material through a cation exchange resin layer. When an aqueous silica sol is produced by the method described in the document, it is possible to obtain an aqueous silica sol having an alkali metal content of 200 ppm or less with respect to silica, but other metals, for example, the content of a polyvalent metal such as iron or aluminum with respect to silica. Only an aqueous silica sol containing 300 ppm or more can be obtained. The polyvalent metal present in this high content is derived from the polyvalent metal oxide contained in the water glass as a raw material in an amount of about 300 ppm or more.

In the method described in the above-mentioned JP-A-61-158810, both the alkali metal present in the raw material alkali metal silicate such as water glass and the polyvalent metal other than silicon are produced in the process of producing silica sol. Removal is done. However, the method of this removal is such that when the impurities contained therein are removed from the aqueous solution of active silicic acid containing the added acid by passing through the ultrafiltration membrane, the solution of this solution is added to the aqueous solution of active silicic acid. It is necessary to replenish a separately prepared acid solution in an amount corresponding to 20 times 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 particle growth of colloidal silica, and the silica sol is concentrated after the particle growth is completed. Is still not an efficient industrial production process.

When silica sol is used as a binder, the smaller the particle size of the colloidal silica in the sol used, the higher the binding strength of the sol. On the other hand, the smaller the particle size of the colloidal silica in the sol used. 、
The sol becomes less stable, so to compensate for this, the sol
The SiO ₂ concentration must be lowered. However, when used as a binder, it is generally desired that the SiO ₂ concentration be high and that the bond strength be sufficient. Further, a sol made of colloidal silica having a distribution in particle size has a higher binding force than a sol made of colloidal silica having a uniform particle size.

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

[0009]

30-50% by weight of the present invention
Has a SiO ₂ concentration of, substantially does not contain a polyvalent metal oxide other than silica, and the average particle size of colloidal silica is
The method for producing a stable aqueous silica sol having a particle size of 10 to 30 millimicrons 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 with respect to silica is 1 to ₂ as the SiO ₂ content derived from the silicate.
By contacting an aqueous solution of an alkali metal silicate dissolved in a concentration of 6% by weight with a hydrogen-type strongly acidic cation exchange resin, an aqueous solution of active silicic acid having a SiO ₂ concentration of 1 to 6% by weight is produced. The step of recovering the solution, (b) After adjusting the pH of the aqueous solution of active silicic acid recovered in step (a) to 0 to 2.0 by adding a strong acid, the solution is adjusted to 0.1 to 12 at 0 to 100 ° C.
Step of holding for 0 hours, (c) after contacting the aqueous solution obtained in (b) with a hydrogen-type strongly acidic cation exchange resin, the liquid produced by this contact with the hydroxyl type strongly basic anion exchange resin A step of producing an aqueous solution of active silicic acid having substantially no dissolved substance other than active silicic acid and having a SiO ₂ concentration of 1 to 6 wt% by contacting, and collecting the product solution; (d) An aqueous solution of sodium or potassium hydroxide was added to the aqueous solution of active silicic acid recovered in step (c), and M ₂ O derived from this hydroxide (where M represents a sodium atom or a potassium atom). Stable with a SiO ₂ concentration of 1 to 6 wt% and a pH of 7 to 9 by adding it so that the SiO ₂ / M ₂ O molar ratio with SiO ₂ contained in the aqueous solution of active silicic acid is 50 to 250. To generate an aqueous solution of activated silicic acid, stabilized in step (e) and (d) 1 part by weight of an aqueous solution of silicic acid as a heel solution is kept in the container, the temperature of the liquid in the container is maintained at 70 to 100 ° C., and the stabilized aqueous solution of activated silicic acid obtained in the step (d) 5 to 5 While continuously supplying 20 parts by weight as a feed liquid into the container for 50 to 200 hours, the inside of the container was kept at normal pressure or reduced pressure during this time, and the liquid amount in the container was kept constant. By removing the water from the container by evaporation so that
A step of producing a stable aqueous silica sol having a SiO ₂ concentration of wt% and an average particle diameter of colloidal silica of 10 to 30 millimicrons, (f) a stable aqueous silica sol obtained in the step (e) Is contacted with a hydrogen type strong acidic cation exchange resin, and then the aqueous silica sol produced by this contact is contacted with a hydroxyl group type strong basic anion exchange resin to substantially contain a polyvalent metal oxide other than silica. The pH of the sol is 8 to 10.5 in the acidic aqueous sol produced in the steps (g) and (f).
By adding ammonia so that it has a 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 of 10 to 30 mm. Generating a stable aqueous silica sol that is micron.

The alkali metal silicate used in step (a) of the production method of the present invention may be a commercially available industrial product, but the alkali metal and silicon contained therein are SiO ₂ / M ₂ O. (However, M represents an alkali metal atom.) A water-soluble one 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, 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 a polyvalent metal oxide other than silica as an impurity of about 300 to 10,000 ppm with respect to the SiO ₂ content in the water glass. The main polyvalent metals having a relatively high content are aluminum, iron, calcium, magnesium and the like.

In the step (a), an 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% by weight as SiO ₂ content derived from the silicate. An aqueous solution of an alkali metal silicate obtained by dissolving it in water to a concentration of ˜6% by weight is used. This water may be industrial water that has been subjected to cation removal treatment.

The hydrogen-type strongly acidic cation exchange resin used in the step (a) of the present invention may be one that has been conventionally used for removing alkali metal ions from an aqueous solution of water glass, and can be easily used as a commercially available industrial product. To be obtained. An example thereof is the product name Amberlite IR-120B. In the step (a) of the present invention, the alkali metal silicate aqueous solution is brought into contact with the hydrogen type strong acid cation exchange resin. This contact can be preferably carried out by passing a liquid through a column packed with this ion exchange resin, and the liquid passing through the column has a SiO ₂ concentration of 1 to 6% by weight, preferably 2 to
Recovered as an aqueous solution of 6 wt% activated silicic acid. The amount of hydrogen type cation exchange resin used may be an amount sufficient to exchange all the amount of alkali metal ions in the aqueous solution of alkali metal silicate with hydrogen ions. The space velocity of the column is preferably 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 and sulfuric acid, and nitric acid is the most preferable for increasing the removal rate of aluminum and iron.
The strong acid is added to the aqueous solution of active silicic acid recovered in step (a) before the aqueous solution of active silicic acid does not undergo alteration, preferably immediately after the recovery. The amount of strong acid added is
The pH of the liquid is in the range of 0 to 2, preferably 0.5 to 1.8. In step (b), after this addition, the liquid should be at 0-100 ° C.
It is maintained for 0.1 hour or longer, preferably 0.5 to 120 hours.

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

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

The aqueous solution of sodium hydroxide or potassium hydroxide used in (d) is preferably a commercially available industrial product having a purity of 95% or more, which is preferably sodium hydroxide or potassium hydroxide in industrial water from which cations have been removed. Can be obtained by dissolving to a concentration of 2 to 20% by weight. In the step (d), to the aqueous solution of the active silicic acid obtained in the step (c), preferably immediately after the recovery, the sodium or erium hydroxide aqueous solution is SiO ₂ / M ₂ O (where M is the above the same.)
It is added so as to have a molar ratio of 50 to 250, preferably 60 to 200. This addition can be carried out at room temperature to 60 ° C., but it is preferably carried out at room temperature in the shortest possible time. With this addition, the SiO ₂ concentration is 1 to 6% by weight, preferably 2 to 6%.
An aqueous solution of stabilized activated silicic acid having a weight% and a pH of 7-9 is obtained. This product solution is stable for a long time, but it is particularly preferable to subject it to the step (e) within 30 hours.

The equipment used in the step (e) includes an agitator, a temperature control device, a liquid level sensing device, a decompression device, a liquid supply device, the above cooling device, etc. in an ordinary container of acid resistance, alkali resistance and pressure resistance. It may be provided. (e) In the process,
All or 1/5 to 1/20 of the aqueous solution of the stabilized activated silicic acid obtained in the step (d) is put into the container as a heel liquid. In large-scale industrial production, this whole amount is used for heel fluid,
Separately, it is preferable to use an aqueous solution of stabilized activated silicic acid prepared through the above steps (a) to (d) as a feed solution in an amount of 5 to 20 times as much as this heel solution. When the above 1/5 to 1/20 amount is used as the heel liquid, the rest is used as the feed liquid.

In the step (e), the liquid temperature in the container is 70 to 100 ° C.
The temperature is preferably maintained at 80 to 100 ° C. and the pressure at which water evaporates from the liquid. Then, the feed rate of the feed solution and the removal rate of the evaporated water are adjusted so that the amount of the solution in the container is kept constant and the feed solution is finished within 50 to 200 hours. .. The feeding 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 that the feeding rate of the feed liquid is kept constant.

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

The ammonia used in step (g) may be a commercially available industrial product, but high purity is preferable, and
It is preferably used as ammonia water of about 28% by weight. Quaternary ammonium hydroxide, guanidine hydroxide, water-soluble amine, etc. can be used in place of this ammonia, but ammonia is generally preferred unless ammonia is particularly undesired. It is convenient.

In step (g), the above-mentioned ammonia is added to the aqueous sol obtained in step (f), preferably immediately after it is obtained. This addition can be carried out at room temperature to 100 ° C., but preferably at room temperature. The amount of ammonia added is preferably such that the pH of the silica sol is 8 to 10.5. In some cases, an acid containing no metal component, ammonium salt, etc. 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
From the specific surface area (m ² / g) measured by the nitrogen gas adsorption method called ET method, it is calculated as an average particle diameter by a conventional method. The size of the colloidal particles can be observed by an electron microscope, and the silica sol obtained by the step (g) usually has a minimum particle size of about 4 mm when the average particle size is 10 mm. , With a distribution over a maximum of 20 millimicrons, and an average particle size of 30
In the case of millimicrons, the distribution ranges from a minimum of about 10 millimicrons to a maximum of about 60 millimicrons.

[0024]

[Operation] 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 active silicic acid from which alkali metal ions have been removed is produced. The active silicic acid in this aqueous solution is silicic acid or In the form of fine particles of 3 millimicron or less composed of the low polymer, this aqueous solution
Approximately 1 at room temperature even in the presence of polyvalent metals such as aluminum
It is so unstable that it turns into a gel within 00 hours. Since this instability increases as the concentration of SiO _{2 in} the liquid increases and the temperature of the liquid increases, about 6% by weight in the (a) step, especially in the case of industrial production of silica sol on a large scale. Cross over
It is preferable to avoid the SiO ₂ concentration and generate an aqueous solution of active silicic acid having a concentration lower than that concentration at room temperature. In particular, when an alkali metal present in the raw material, a polyvalent metal or the like is taken inside the polymer particles of silicic acid, these metals are difficult to remove, and thus a low-concentration aqueous solution in which the polymerization of silicic acid is difficult to proceed is preferable. In order to avoid particle formation due to gradual polymerization of silicic acid which is unavoidable even at room temperature, it is preferable to use the entire amount of the aqueous solution of active silicic acid produced as soon as possible after the production. When the concentration of SiO _{2 in} the aqueous solution of this active silicic acid is lower than about 1% by weight, the amount of water to be removed in the concentration of the silica sol that is generated later becomes significantly large, which is not efficient.
The SiO ₂ concentration is preferably 2% by weight or more. In step (a), the SiO ₂ concentration of the generated aqueous solution of activated silicic acid was 1 to 6
The aqueous solution of alkali metal silicate before contact with the hydrogen-type strongly acidic cation exchange resin is changed to SiO ₂ so that it can be used for the step (b) immediately after its formation so that the content becomes SiO _2.
The concentration is adjusted to 1 to 6% by weight.

In order to remove as many metal ions as possible, the passage of the hydrogen-type strongly acidic cation exchange resin-packed column preferably used in the step (a) is 1 hour per hour.
It is preferable to provide a space velocity of about -10. A liquid temperature of about 0 to 60 ° C. is adopted so that polymerization of the silicic acid, thickening or gelation of the generated active silicic acid solution is unlikely to occur. From steps (a) to (c), no special method is added to stabilize the aqueous solution of activated silicic acid.
The above-mentioned concentration and temperature are adopted as the SiO ₂ concentration and temperature of the liquid.

The strong acid added in the step (b) is a state in which an impurity metal component such as an alkali metal or a polyvalent metal, which is not in the state of dissociated ions bonded to active silicic acid or its polymer, is converted into a state of dissociated ions in the liquid. Convert it. The smaller the particle size of the active silicic acid particles, the easier the elution of the metal component with this strong acid is.Therefore, it is also possible to add this strong acid to the aqueous solution of active silicic acid obtained in step (a) as soon as possible. Is preferred.

However, if the amount of the strong acid to be added is increased to such an extent that the pH of the aqueous solution of activated silicic acid becomes 0 or less,
Although it is possible to enhance the elution effect of the metal component, it is difficult to remove the anion in the step (c), and the elution effect of the metal component is poor at the addition amount such that the pH of the solution is 2 or more. Among the strong acids, nitric acid has a particularly high effect on the elution of metal components such as aluminum and iron. The elution effect of the polyvalent metal component by this strong acid also depends on the temperature and elution time of the liquid.It 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. For 0.1 to 2 hours, especially 0.5
Approximately 2 hours is preferable, and it is preferable to avoid leaving the solution for a long time exceeding this elution time because the solution may thicken or gel in some cases.

In the step (c), the metal ions eluted in the liquid in the step (b) and the anion due to the added acid are
It is removed by hydrogen type strong acid cation exchange resin and hydroxyl type strong basic anion exchange resin. Since the anion of the added acid is present in the product solution after the first hydrogen-type strongly acidic cation exchange resin treatment, the ions of the eluted metal are likely to remain in the solution. Depending on the case, the amount of residual metal ions after the treatment with the hydroxyl group-type strongly basic anion exchange resin is 5 to 5 times.
In some cases, the liquid may cause gelation within about 1 hour. When a second treatment with a hydrogen-type strongly acidic cation-exchange resin is performed after the anions have been removed by the hydroxyl-type strongly basic anion-exchange resin, such undesired eluted metal ions are further removed. It is preferable because it can

Since the aqueous solution of activated silicic acid obtained by the step (c) is so unstable that gelation may occur within 6 hours, it may be formed as soon as possible, preferably immediately after (d) ) Referred to the process. If the amount of sodium or potassium hydroxide added to the unstable aqueous solution of activated silicic acid is 60 or less, especially 50 or less as a SiO ₂ / M ₂ O molar ratio, the polymerization of activated silicic acid is performed. Is likely to occur,
In the step (e), particle growth is suppressed and the produced sol tends to become unstable. On the contrary, the molar ratio is 200 or more, especially 250.
With the above-mentioned small amount, the particle size of colloidal silica cannot be increased even if the obtained liquid is treated in the same manner as in the step (e). The liquid obtained by the step (d) is stable for a long time at room temperature, but the liquid obtained by the step (d) is heated within 30 hours due to the polymerization of activated silicic acid at a high temperature. ) It is preferable that the step is sent to the step. Sodium or potassium hydroxide added in the step (d) may be replaced with other hydroxides when the colloidal silica particles are grown to have an average particle size of 10 to 30 mm in the step (e). It gives a colloidal silica particle growth rate which is 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.

Due to this high particle growth rate, the feed rate of the feed solution can be increased in the step (e), so that the production rate of silica sol is significantly increased. Further, the feeding of the feed liquid at a high speed performed in the step (e) also serves to make the particle diameters of the colloidal silica particles in the produced silica sol uneven so as to broaden the particle diameter distribution. (e)
In the step, in order to increase the production rate of the high-concentration silica sol, water is evaporated from the produced sol at the same time as the feed liquid is supplied, and the evaporated water is removed.

When the liquid temperature in step (e) is 70 ° C. or less, the growth of colloidal silica particles in the liquid does not sufficiently occur, so that colloidal silica having an average particle size of 10 mm or less is generated in the liquid. To do. When the silica sol having such a small particle size is concentrated, the solution may thicken or gel, and a stable sol having a SiO ₂ concentration of 30% by weight or more cannot be obtained. When the temperature of the liquid is higher than 70 ° C, the particle growth rate is high. However, when the temperature is higher than 100 ° C, the too high particle growth rate makes it difficult to control the average particle diameter.

When the feed solution is added to the heel solution at 70 to 100 ° C., particle growth of colloidal silica occurs in the mixture solution. The particles cannot be grown to a size of 10 millimicrons or more, and in this case too, a stable sol concentrated to 30% by weight or more cannot be obtained. The average particle size of colloidal silica increases with the increase of the feed liquid supply, but if it is more than 20 times as much as that of the heel liquid, the average particle size exceeds 30 millimicrons, and the sol having a high binding force. Can't get

However, the relationship between the amount of the feed liquid and the average particle size of the colloidal silica is further influenced by the feed speed of the feed liquid, and 5 to 20 times as much as the heel liquid is fed within 50 hours. Average particle size of 10 when supplied to heel fluid
Colloidal silica of millimicron or more is not formed. With respect to this point, it is probable that in step (e), some 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 from this part of the active silicic acid enter the solution. Particularly, when the feed rate is high, a part of the active silicic acid in the feed liquid that is fed is consumed for particle growth. It is considered that colloidal silica particles having an average particle diameter of 10 mm or more are not efficiently generated due to the increase in the ratio of the amount of. Therefore,
Feeding the feed liquid too fast should be avoided, but feeding 5 to 20 times as much feed liquid as the heel liquid in a long time of 200 hours or more is not efficient for industrial production of silica sol. Further, in order to industrially produce silica sol having a constant quality, it is preferable that the feed solution is continuously supplied for 50 to 200 hours.

When the liquid level in the container fluctuates on the vessel wall due to the supply and the concentration performed at the same time in the step (e), the silica sol gelation product is deposited on the varied vessel wall. Since it is easy and it is difficult to produce a preferable product sol, in the step (e), it is preferable to control the feed rate of the feed solution and the removal rate of the evaporated water to keep the amount of the solution in the container constant. If the SiO ₂ concentration of the silica sol produced in the step (e) is concentrated to 50% by weight or more, the viscosity of the sol may increase to an undesired viscosity. Therefore, such a high concentration sol is produced in the step (e). It is better not to let it.

Since the sol produced in step (e) contains the sodium or potassium component added in step (d), the hydrogen-type strong acidic cation exchange resin treatment in step (f) and The cations and anions in the sol are removed from the sol by the treatment with the hydroxyl group type strongly basic anion exchange resin. In particular, in order to further remove the alkali metal ions, it is preferable to carry out the second hydrogen type strong acid cation exchange resin treatment. The sol from which cations have been removed in step (f) does not show instability like the aqueous solution of activated silicic acid, but does not have sufficient stability, so treatment with an ion exchange resin should not be carried out at as high a temperature as possible. It is better to stabilize in the step (g) as soon as possible after the completion of the step (f), preferably immediately. The ammonia used to give the sol a pH of 8 to 10.5 for this stabilization is not only highly pure and inexpensively available as aqueous ammonia, but can be easily volatilized from the used silica zosol. , Silica sol is convenient for various uses.

[0036]

【Example】

(a) Step 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, and Al ₂ O.
_{It was 3} 280 ppm, Fe ₂ O ₃ 45 ppm, CaO 46 ppm, and MgO 25 ppm.

5.25 kg of the above-mentioned water glass is 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 prepared. Then, the above-mentioned sodium silicate aqueous solution at 25 ° C. was treated with hydrogen type strong acid cation exchange resin Amberlite IR-
After passing through a column packed with 120B at a space velocity of 3 per hour, the obtained SiO ₂ concentration was 3.54% by weight, pH was 2.78, and the electrical conductivity was 667.5 μS / cm.
Was collected in a container.

(B) Step As the strong acid used, nitric acid (specific gravity
1.38, HNO ₃ 61.3% by weight) was prepared. 123.2 g of the above nitric acid was added to 35.7 kg of the aqueous solution of activated silicic acid immediately after obtained in the step (a) to adjust the pH to 1.54 and kept at 20 ° C. for 48 hours to complete the step (b).

Example 1 After the above step (b) was completed, the stable aqueous silica sol according to the present invention was manufactured through the following steps (c) to (g). As the hydrogen type strong acid resin cation exchange resin, Amberlite IR-12B treated with an aqueous sulfuric acid solution having a hydrogen ion content corresponding to three times the cation exchange capacity was used. As the hydroxyl group-type strongly basic anion exchange resin, used was Amberlite IRA-410 treated with an aqueous sodium hydroxide solution having a hydroxyl group content corresponding to 3 times its anion exchange capacity.

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

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

(E) Step A reaction apparatus was used which was equipped with a stirrer, a cooler, a decompression device, a liquid level sensing device, a solenoid valve, a heating device, etc. in a glass reactor having an internal volume of 5 liters. 2.67 kg of a stabilized aqueous solution of activated silicic acid immediately after being obtained in step (d) was charged into the above reactor as a heel liquid, and the temperature of the heel liquid was adjusted to 90 ° C. by heating, followed by the above step (d). The solution of 27.78 kg of the stabilized activated silicic acid solution immediately after being obtained in 1. was continuously fed into the above container as a feed liquid over 95 hours, and the liquid temperature in the container was kept at the boiling point of 90 ° C and the pressure was reduced. The amount of liquid in the container was kept constant by keeping it constant and evaporating water continuously. The feed rate of the feed solution was 292.4 g / H. In this way, the supply of the total feed liquid of 27.78 kg was completed. The silica sol produced in the container was cooled to room temperature, and 3.23 kg in total was discharged out of the container.

The obtained silica sol has a specific gravity of 1.233,
It has a pH of 9.92, a viscosity of 20 ° C of 26.0 cp, a BET average particle size of 13.2 millimicron and an electrical conductivity of 3240 μS / cm, and shows a stability of not deteriorating at 60 ° C for more than 1 month, and SiO ₂ 33.0.
% By weight, 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 filled with hydrogen-type strongly acidic cation exchange resin Amberlite IR-120B at a temperature of about 25 ° C at a space velocity of 3 per hour. Then, the silica sol obtained by this passage was continuously passed through a column of about 25 ° C. packed with a hydroxyl group type strongly basic anion exchange resin Amberlite IRA-410 at a space velocity of 3 per hour. Finally, the silica sol obtained by this passage was continuously charged with hydrogen type strongly acidic cation exchange resin Amberlite IR-120B at about 25.
3.15 kg of acidic aqueous silica sol was obtained by passing through the column at a rate of space velocity of 3 per hour.

This sol has a specific gravity of 1.205, pH 4.72, viscosity at 20 ° C. of 3.6 cp, electric conductivity of 70 μS / cm, SiO ₂ concentration of 30.7 wt%, Na ₂ O 190 ppm and SiO ₂ / Na ₂ O molar ratio of 1670. Was. Step (g) By adding 15.0 g of 28% ammonia water as a commercial grade reagent to the silica sol at 25 ° C. immediately after being obtained in the step (f) under stirring, 2015 g of silica sol was obtained.

The obtained sol has a specific gravity of 1.205 and a pH of 9.2.
0, 20 ℃ viscosity 9.8cp, electric conductivity 2820μS / cm, 1 at 60 ℃
A stability of not altered or months, SiO ₂ 30.5 _{wt%, SiO 2 / (NH 4} ) 2 O molar ratio _{83, Al 2 O 3 2.16ppm,} 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 had a broad distribution of particle size of colloidal silica by electron microscopy ranging from a minimum of 4 millimicrons to a maximum of 20 millimicrons.

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

(D) Step 25 Immediately after obtaining in step (c), 25
40.55 g of an aqueous solution of activated silicic acid stabilized by adding 146 g of a 10% by weight sodium hydroxide aqueous solution at 0 ° C was obtained. This aqueous solution has a SiO ₂ concentration of 3.5% by weight, pH 7.82, and SiO ₂
It had a molar ratio of / Na ₂ O of 130 and an electric conductivity of 612 μS / cm.

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

The obtained aqueous silica sol had a specific gravity of 1.3.
20, pH 9.76, 20 ℃ viscosity 29.6cp, electric conductivity 2020μS / cm,
BET average particle size 21.0 mm, stable at 60 ° C for more than 1 month without deterioration, SiO ₂ 42.6% by weight, Si
O ₂ / Na ₂ O molar ratio 147, Al ₂ O ₃ 2.89ppm, Fe ₂ O ₃ 2.20ppm
Was included. (f) Step The silica sol obtained in the step (e) is passed through a column of about 25 ° C packed with a hydrogen-type strongly acidic cation exchange resin at a space velocity of 3 per hour, and then this passage is performed. The silica sol obtained by (1) was subsequently passed through a column of 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. The silica sol was subsequently 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 acidic aqueous silica sol.

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

[0051] This sol had a specific gravity of 1.293, pH 9.5,20 ℃ viscosity 22Cp, has a stability of not electric conductivity 3920μS / cm, 60 ℃ at least 1 month alteration, SiO ₂ concentration of 40.3 wt%, SiO
₂ / (NH ₄ ) ₂ O molar ratio 143, Al ₂ O ₃ 2.75ppm, Fe ₂ O ₃ 2.09pp
m, Na ₂ O 693ppm, Cl 9.7ppm, SO ₄ 14.5ppm, NO ₃ 32
The particle size of colloidal silica containing 0 ppm showed a wide distribution ranging from a minimum of about 7 millimicrons to a maximum of about 40 millimicrons, and the shape of the particles was a distorted shape.

Comparative Example 1 In this example, the feed time of the feed liquid in the step (e) in Example 1 was changed to 32 hours, and the feed liquid was fed at a rate higher than that 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 liquid was withdrawn from the container, and the average particle diameter of the colloidal silica was determined by the BET method, and it was 6.8 millimicrons. When the feeding of the feed liquid was further advanced, the viscosity of the liquid was remarkably high at the end of the feeding, and the formation of gel was clearly recognized.
This highly viscous liquid was difficult to be smoothly discharged from the container, and when taken out and allowed to stand at room temperature, it became a non-flowing gel.

[0053]

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

The aqueous silica sol produced by the method of the present invention is widely used for the applications of conventionally used silica sol, and in particular, a polishing agent for a semiconductor surface, a binder for catalysts, and other bonds for which high purity is desired. It is suitable for use as an agent.

Claims (1)

[Claims] 1. The following steps (a), (b), (c), (d) and (e)
, (F) and (g), having a SiO ₂ concentration of 30 to 50% by weight, containing substantially no polyvalent metal oxide other than silica, and having an average particle size of colloidal silica of 10 to A method of making a stable aqueous silica sol that is 30 millimicrons. (a) Polyvalent metal oxide other than silica is added to silica in an amount of 300-
An aqueous solution of an alkali metal silicate in which a water-soluble alkali metal silicate contained in a ratio of 10000 ppm is dissolved in a concentration of 1 to 6% by weight as SiO ₂ content derived from this silicate is used as a hydrogen-type strong acidic cation. SiO ₂ by contact with exchange resin
A step of generating an aqueous solution of active silicic acid having a concentration of 1 to 6% by weight and recovering the resulting solution; (b) adding a strong acid to the aqueous solution of active silicic acid recovered in step (a) After adjusting to 2.0, 0 ~
Step of holding at 100 ℃ for 0.1 to 120 hours, (c) After contacting the aqueous solution obtained in (b) with a strongly acidic cation-exchange resin of hydrogen type, the liquid produced by this contact is made into a strongly basic hydroxyl group. By contacting with an anion exchange resin, an active silicic acid aqueous solution containing virtually no dissolved substances other than active silicic acid and having a SiO ₂ concentration of 1 to 6 wt% is produced, and this product solution is recovered. In the aqueous solution of activated silicic acid recovered in the step (d) and (c), an aqueous solution of sodium or potassium hydroxide is added to M ₂ O derived from this hydroxide (where M is a sodium atom or a potassium atom). And Si contained in the aqueous solution of activated 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 1 part by weight of the stabilized active silicic acid aqueous solution obtained in the steps (e) and (d) as a heel liquid is charged into the container, and the liquid temperature in the container is kept at 70 to 100 ° C. While continuously supplying 5 to 20 parts by weight of the aqueous solution of the stabilized activated silicic acid obtained in the step (d) as a feed liquid into the above container for 50 to 200 hours, the above container for this time. The inside of the container is kept at normal pressure or reduced pressure, and by removing water from the container by evaporation so that the liquid amount in the container is kept constant, it has a SiO ₂ concentration of 30 to 50% by weight, and is colloidal. Obtained in the steps (f) and (e) of forming a stable aqueous silica sol in which the average particle size of silica is 10 to 30 millimicrons After contacting a stable aqueous silica sol with a hydrogen-type strongly acidic cation exchange resin, the aqueous silica sol produced by this contact is contacted with a hydroxyl group-type strongly basic anion exchange resin to remove polyvalent metal oxides other than silica. The step of forming an acidic aqueous silica sol substantially not containing the acidic aqueous sol produced in the steps (g) and (f),
By adding ammonia so that H becomes 8 to 10.5, it has a SiO ₂ concentration of 30 to 50% by weight, contains substantially no polyvalent metal oxide other than silica, and has an average particle diameter of colloidal silica. To produce a stable aqueous silica sol having a particle size of 10 to 30 millimicrons.