JP2004203729A - Method for producing silica sol and silica sol - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a silica sol by adding an activated silicic acid particle with a predetermined size to a seed particle dispersion liquid and performing rapid particle growth of a seed particle. <P>SOLUTION: The method for manufacturing the silica sol comprises adding continuously or intermittently the activated silicic acid particle dispersion liquid (b) to the seed particle dispersion liquid (a) while heating them, and carrying out the particle growth by sticking the activated silicic acid particle to the seed particle. (a) is a water-based seed particle dispersion liquid with an average particle diameter (D<SB>LS</SB>) measured with a dynamic light scattering method using a laser beam in the range of 5-1,000 nm, and with a pH in the range of 7-12. (b) is the activated silicic acid particle dispersion liquid with an average particle diameter (D<SB>LF</SB>) measured with the dynamic light scattering method using the laser beam in a range of 2-50 nm (provided, however, that the average particle diameter (D<SB>LF</SB>) is smaller than the average particle diameter (D<SB>LS</SB>) ) and the average particle diameter (D<SB>NaF</SB>) measured with the NaOH titration method is in the range of 0.9-6 nm. Furthermore, the ratio (D<SB>LF</SB>)/(D<SB>NaF</SB>) of the average particle diameter (D<SB>LF</SB>) to the average particle diameter (D<SB>NaF</SB>) is in the range of 1.8-30 and the pH is in the range of 5-11. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  The present invention relates to a method for producing a silica sol using a seed particle dispersion and a silica sol obtained by the method.

  Conventionally, many proposals have been made for a method for producing silica sol. Among them, in the method of adding an acidic silicate solution obtained by dealkalizing an alkali metal silicate to a seed particle dispersion, the particle size of the obtained silica colloid particles is uniform, and it is possible to adjust the particle size to a desired particle size. For example, the inventors of the present invention prepared seed particles in Japanese Patent Application Laid-Open No. 63-45114 (Patent Document 1), and added them to an alkali metal silicate such as water glass. Disclosed is a method for producing a silica sol by adding an acidic silicic acid solution obtained by dealkalizing an aqueous solution with an ion exchange resin or the like, bonding, laminating, and depositing an acidic silicic acid on the seed particle surface to grow the seed particles. .

However, in the method of adding an acidic silicic acid solution to such a seed particle dispersion liquid, (1) the degree of polymerization of the acidic silicic acid is as low as about 1 to 4, so that a long time is required for particle growth, and in particular, uniform and large In order to obtain a silica sol containing silica particles having a particle diameter, it was necessary to repeatedly grow particles. In addition, (2) the particle surface area decreases with the growth of the particles. For example, it is necessary to reduce the rate of addition of the acidic silicic acid solution, so that the production capacity and productivity are reduced. When the addition rate of the silicic acid solution is increased, there is a problem that the particles are aggregated or new fine particles are generated, and the particle size distribution of the obtained silica sol becomes non-uniform. In addition, (3) the acidic silicate solution has low stability, so that there is a problem that the conditions for process control must be considerably strict.
JP-A-63-45114

The present invention provides a method for producing a silica sol capable of rapidly growing seed particles by adding a dispersion containing active silica particles of a predetermined size to the seed particle dispersion.
Still another object of the present invention is to provide a silica sol obtained by the production method.

The method for producing a silica sol according to the present invention comprises continuously or intermittently adding an active silicic acid particle dispersion of the following (b) to a seed particle dispersion of the following (a) while heating, and then adding active silicic acid particles to the seed particles. It is characterized in that particles are grown by attaching them.
(a) An aqueous dispersion of seed particles having an average particle diameter (D _LS ) measured by a dynamic light scattering method using laser light in the range of 5 to 1000 nm, and having a pH in the range of 7 to 12. Dispersion
(b) The average particle diameter (D _LF ) measured by the dynamic light scattering method using laser light is in the range of 2 to 50 nm (however, the average particle diameter (D _LF ) is smaller than the average particle diameter (D _LS )). And the average particle size (D _NaF ) measured by the NaOH titration method is in the range of 0.9 to 6 nm, and the ratio (D _NaF ) between the average particle size (D _LF ) and the average particle size (D _NaF ) An aqueous dispersion of activated silica particles having a ratio of ( _LF ) / (D _NaF ) in the range of 1.8 to 30, wherein the pH is in the range of 5 to 11.

In this manufacturing method, it is desirable to perform the heating in a temperature range of 60 to 160 ° C.
Further, the active silicate particles, (a) activated silica particles obtained by peptizing the silica hydrogel formed by neutralizing an alkali silicate with an acid, or (b) neutralizing the alkali silicate with an acid. It is desirable to use activated silica particles obtained by mechanically pulverizing the produced silica hydrogel while pulverizing it with an alkali.
The average particle diameter of the active silicic acid particles (D _LF), when the average particle diameter of the seed particles (D _LS) is 12nm below are 7/10 or less of the average particle diameter (D _LS), When the average particle diameter (D _LS ) of the seed particles exceeds 12 nm, the average particle diameter (D _LS ) is preferably 5/10 or less of the average particle diameter (D _LS ).
The silica sol according to the present invention has an average particle diameter (D _LZ ) measured by a dynamic light scattering method using laser light in a range of 12 to 200 nm, and an average particle diameter (D _NaZ ) measured by a NaOH titration method of 5 to 5 _nm. It is characterized in that it is in the range of 30 nm and that the ratio (D _LZ ) / (D _NaZ ) of the average particle diameter (D _LZ ) to the average particle diameter (D _NaZ ) is in the range of 2 to 30.

  According to the method for producing a silica sol according to the present invention, the reactive silicic acid particles having a particle diameter in a predetermined range and having high reactivity are attached to the surface of the seed particles to grow the particles. it can. This is very economical because the production time of the silica sol is shortened. Further, a silica sol containing silica particles having a uniform and large particle diameter can be obtained.

Hereinafter, the present invention will be described specifically.
(Seed particle dispersion)
The seed particle dispersion of the present invention is an aqueous dispersion of seed particles having an average particle diameter (D _LS ) measured by a dynamic light scattering method using laser light in the range of 5 nm to 1000 nm, and having a pH of 7 to Those in the range of 12 are used.
The seed particles of the seed particle dispersion for use in the present _{invention, SiO 2, Al 2 O 3} , although fine particles of TiO _2, inorganic oxides such as ZrO ₂ or the composite oxide thereof is used, SiO ₂ Among It is preferable to use These seed particles are usually used in the form of an aqueous sol dispersed in water.
In addition, other conventionally known seed particle dispersions can be used. For example, the seed liquid disclosed in the above-mentioned JP-A-63-45114 can be suitably used. Specifically, an alkali silicate aqueous solution and / or an alkali aqueous solution are mixed with an acidic silicate solution, and the mixture is adjusted to have a SiO ₂ / M ₂ O (M: alkali metal) molar ratio of 2.8 to 10 By aging at a temperature of 60 ° C. or higher, a seed liquid (seed particle dispersion) can be obtained.

The particle diameter of the seed particles can be appropriately selected and used in consideration of the silica particle diameter of the silica sol to be finally obtained, but in the method for producing a silica sol according to the present invention, since the particle growth rate is high, It is not always necessary to prepare seed particles that have been enlarged over time, and seed particles having a small particle size can be used as long as they function as seed particles.
The average particle diameter of such seed particles, when measured by a dynamic light scattering method using laser light, is generally in the range of 5 to 1000 nm, preferably 7 to 100 nm. When the average particle size is less than 5 nm, the seed particles are unstable, and may gel or aggregate when the active silica particle dispersion is added. On the other hand, when the average particle diameter exceeds 1000 nm, it usually takes time to prepare the seed particles, which is inconsistent with the gist of the present invention of rapidly growing the seed particles to improve the productivity.

The concentration of the seed particle dispersion is not particularly limited, but is usually in the range of 0.1 to 20% by weight, preferably 0.5 to 10% by weight in terms of oxide. If this value is less than 0.1% by weight in terms of oxide, the concentration is so low that the particles are easily dissolved and the particles are reduced or disappear, and the particles do not function as seed particles. is there. If the concentration of the seed particle dispersion exceeds 20% by weight in terms of oxide, the seed particles may be aggregated, so that a monodispersed sol having a uniform particle size may not be obtained. In addition, since the concentration of the seed particles is high, it is necessary to reduce the supply speed of the active silica particle dispersion to prevent aggregation and the like. Furthermore, since the number of seed particles is large, the growth rate of each particle is suppressed, and rapid particle growth may be prevented.
Usually, the pH of the seed particle dispersion is preferably in the range of 7 to 12, more preferably 8 to 11. When the pH is less than 7, the potential of the particle surface decreases and the particles may aggregate. When the pH exceeds 12, the seed particles may be dissolved or the added active silica particles may be dissolved. The growth may be slow or the particle size distribution may be non-uniform.

It is preferable to add an aqueous solution of an alkali metal such as NaOH or KOH or an aqueous solution of an amine to the seed particle dispersion, if necessary. The SiO ₂ / M ₂ O (M: alkali metal) mole in the seed particle dispersion is preferably added. It is preferred that the ratio be in the range of 2.8 to 200, especially 2.8 to 120. When the SiO ₂ / M ₂ O molar ratio is less than 2.8, the seed particles may be dissolved. On the other hand, when the SiO ₂ / M ₂ O molar ratio exceeds 200, the active silica particles are added to the seed particle dispersion. When the dispersion is supplied, the pH of the dispersion lowers, and the particles may aggregate.

(Active silica particle dispersion)
As the active silica particle dispersion of the present invention, the average particle diameter (D _LF ) measured by a dynamic light scattering method using laser light is in the range of 2 to 50 nm (provided that the average particle diameter (D _LF ) is the average particle diameter (D _LF ) D _LS ), the average particle diameter (D _NaF ) measured by NaOH titration is in the range of 0.9 to 6 nm, and the average particle diameter (D _LF ) and the average particle diameter (D _LF ) an aqueous dispersion of the active silicic acid particles the ratio _{(D LF) / (D NaF} ) is in the range of 1.8 to 30 and D _NaF), is used as the pH is in the range of 5 to 11 .
The activated silicate particles used in the present invention are required to have a predetermined particle diameter range in order to contribute to rapid growth of seed particles. Further, in order for the active silicic acid particles to adhere to the seed particles and grow, the average particle diameter of the active silicic acid particles is required to be smaller than that of the seed particles. As the active silicic acid particles used in the present invention, porous active silicic acid particles are used. The method for producing such activated silica particles is not particularly limited, and includes, for example, activated silica particles prepared using silica hydrogel as a raw material. Further, since the activated silicate particles used in the present invention are porous, not only a measurement value by a dynamic light scattering method using a laser beam but also a measurement value by a NaOH titration method is required as a method for defining the average particle diameter. It becomes.

Hereinafter, these will be described in detail.
When an active silicic acid particle dispersion having an average particle diameter (D _LF ) of less than 2 nm is added to the seed particle dispersion, the seed particle growth rate is slow, and such an active silicic acid particle dispersion Is unstable like the acidic silicate solution, and it is difficult to increase the concentration. When a low concentration of the active silicic acid particle dispersion is added to the seed particle dispersion, the concentration of the seed particles in the dispersion also decreases, and as a result, the production efficiency decreases.
On the other hand, when the average particle size (D _LF ) of the activated silica particles exceeds 50 nm, it hardly contributes to the growth of the seed particles. Therefore, the average particle diameter (D _LF ) is preferably in the range of 3 to 40 nm.

The particle size by the dynamic light scattering method using laser light can be measured by, for example, a particle size distribution measuring device (NICOMP-380 manufactured by Particle Sizing Systems), and a visually measured value can be obtained.
Further, in order to obtain a more rapid particle growth rate, the average particle diameter (D _LF ) of the activated silica particles is, when the average particle diameter (D _LS ) of the seed particles is 12 nm or less, the average particle diameter (D _LS ) D _LS) is at 7/10 or less of, when the average particle diameter of the seed particles (D _LS) exceeds 12 nm, it is preferable the average is 5/10 or less of a particle diameter (D _LS).

Further, the activated silica particles have an average particle diameter (D _NaF ) measured by a NaOH titration method in the range of 0.9 to 6 nm, and have an average particle diameter (D _LF ) and an average particle diameter (D _NaF ). (D _LF ) / (D _NaF ) is required to be in the range of 1.8 to 30.
When the average particle diameter (D _NaF ) is less than 0.9 nm, the growth rate of the seed particles is as slow as in the case of using the conventional acidic silicate solution, and the stability of the active silicate particle dispersion is insufficient. In this case, the concentration of the activated silica particle dispersion cannot be increased, and improvement in productivity cannot be expected. If the average particle diameter (D _NaF ) exceeds 6 nm, it does not precipitate selectively on the surface of the seed particles, depending on the particle diameter of the seed particles, and new particles are formed. The resulting silica particles tend to have a non-uniform particle size distribution.
The ratio (D _LF ) / (D _NaF ) of the average particle diameter of the activated silica particles measured by the dynamic light scattering method using laser light to the average particle diameter of the activated silica particles measured by the NaOH titration method is 1 If it is less than 0.8, the reactivity of the activated silicate particles is low, depending on the average particle diameter (D _LF ), and the effect of increasing the particle growth rate is insufficient. On the other hand, when the ratio (D _LF ) / (D _NaF ) of the average particle diameter exceeds 30, the particle strength of the obtained silica particles becomes weak. For example, the silica particles used as abrasive particles for polishing materials such as semiconductor substrates. In such a case, a sufficient polishing rate may not be obtained.

The particle size by the NaOH titration method can be determined by measuring the specific surface area (SA _Na ) of active silicic acid calculated by the Sears method and then calculating by the following equation (1).
D _Na = 6000 / (2.2 × SA _Na ) (1)
In equation (1), the constant 2.2 is the true specific gravity of silica. In the measurement by the NaOH titration method, when the particles are not porous, the measured values are almost the same as the values measured by the laser light. However, when the particles are porous, the particle diameter is calculated to be small apparently.
It is considered that the porous activated silicic acid particles have high reactivity with the seed particles and adhere to the seed particles to cause active particle growth.
As the active silicic acid particle dispersion, those having a pH in the range of 5 to 11 are mainly used for reasons of their synthesis. If the ratio is outside this range, it will be difficult to obtain a sufficient particle growth rate.

(Production of active silica particle dispersion)
The activated silicic acid particles described above can be produced by various methods, but (a) pulverize the silica hydrogel with an alkali, or (b) pulverize the silica hydrogel with an alkali and mechanically refine the silica hydrogel. The activated silicic acid particles thus obtained are preferred as the activated silicic acid particles of the present invention. Further, the activated silicic acid particles obtained by the methods (a) and (b) may be mixed and used.
As the silica hydrogel, a silica hydrogel formed by neutralizing an alkali silicate with an acid is preferable. At this time, the alkali silicate can be obtained by using an alkali metal silicate such as sodium silicate or potassium silicate, and adding an acid such as hydrochloric acid, nitric acid or sulfuric acid to the aqueous solution.

The concentration of the aqueous alkali metal silicate solution at the time of neutralization is 1 to 10% by weight, more preferably 2 to 8% by weight as SiO ₂ , the temperature is normal temperature (normally 15 to 35 ° C), and the pH after neutralization is 3 to It is preferably in the range of 7. If this concentration is less than 1% by weight as SiO ₂ , the polymerization (gelation) of silicic acid is insufficient, the particle size (D _LF ) of the obtained activated silicic acid particles becomes small, and the particle growth rate becomes insufficient. Sometimes. On the other hand, if this concentration exceeds 10% by weight as SiO ₂ , it cannot be uniformly neutralized, and the polymerization of silicic acid becomes uneven, and the particle size (D _LF ) distribution of the obtained activated silicic acid particles becomes uneven. Tend.
It is preferable to use the silica hydrogel obtained by neutralization in this way after washing as necessary.

As a first method for producing an active silicic acid particle dispersion, a method of pulverizing the silica hydrogel by adding an alkali to the dispersion of the silica hydrogel may be mentioned. At this time, the concentration of the dispersion liquid of the silica hydrogel is from 0.5 to 5 wt% as SiO _2, and more preferably in the range of 1-4 wt%. If this concentration is less than 0.5% by weight, the proportion of dissolved silica increases, the average particle diameter (D _LF ) of the obtained activated silica particles becomes small, and it is difficult to obtain the effect of increasing the particle growth rate. If this concentration exceeds 5% by weight as SiO ₂ , the average particle size (D _LF ) of the obtained activated silica particles may exceed 50 nm or may be non-uniform, and the size of the seed particles may be reduced. However, the particle size distribution of the obtained silica sol may be non-uniform.

As the alkali, an alkali metal hydroxide such as KOH or NaOH, ammonium hydroxide, or an aqueous amine solution can be used. The amount of alkali, silica hydrogel SiO ₂ moles in the dispersion of the gel (M _S) and the number of moles of alkali (expressed as M ₂ O) (M _A) and the ratio of _{(M S) / (M A} ) Is preferably in the range of 5 to 100, more preferably 10 to 50. When the molar ratio (M _S ) / (M _A ) is less than 5, the average particle diameter (D _NaF ) measured by NaOH titration tends to be less than 0.9 nm, and the proportion of dissolved silica increases. However, the production efficiency and yield of the silica sol decrease. On the other hand, when the molar ratio (M _S ) / (M _A ) exceeds 100, peptization becomes insufficient, the average particle diameter (D _NaF ) exceeds 6 nm, and the activity of the active silica particle dispersion Due to the decrease, the number of activated silica particles used for growing the seed particles decreases, and the particle size distribution of the obtained silica sol becomes non-uniform. The pH at the time of peptization is preferably in the range of 5 to 11. When the pH is less than 5, the viscosity of the dispersion becomes high, so that it is difficult to obtain stable activated silica particles. When the pH exceeds 11, silica is easily dissolved and becomes unstable.

The temperature at which the silica hydrogel is peptized with an alkali is preferably in the range of 50 to 150C, more preferably 60 to 95C. If the temperature is lower than 50 ° C., sufficiently uniform peptization may not be achieved. When the temperature exceeds 150 ° C., the average particle size (D _NaF ) also exceeds 10 nm, and the particle size distribution of the obtained silica sol tends to be non-uniform.
As a second method for producing the active silicic acid particle dispersion, a method of pulverizing silica hydrogel mechanically while pulverizing it with an alkali may be mentioned. The pulverization is performed by subjecting the dispersion of the silica hydrogel to a pulverizer such as a sand mill or a ball mill for about 10 minutes to several hours while pulverizing the dispersion by adding an alkali.

(Production of silica sol)
In the method for producing a silica sol according to the present invention, the active silica particle dispersion is added to the seed particle dispersion continuously or intermittently while heating. The temperature of the seed particle dispersion at this time is preferably in the range of 60 to 160C, more preferably 70 to 120C. If this temperature is lower than 60 ° C., the rate of precipitation of the active silica particles on the surface of the seed particles is low, so that it is necessary to reduce the rate of addition of the active silica particle dispersion, which hinders rapid particle growth of the seed particles. May result. On the other hand, if the temperature exceeds 160 ° C., the amount of silica dissolved in the seed particles increases, and aggregated particles tend to be generated and the yield of silica sol tends to decrease. In addition, when adding the active silica particle dispersion to the seed particle dispersion, it is usually preferable to stir gently. This operation may be performed using an autoclave as needed.

The active silicic acid particle dispersion to be added may be the same as the active silicic acid particle dispersion obtained by the above method and having a concentration as SiO ₂ of about 0.5 to 5% by weight. Alternatively, it can be used after being concentrated. In this case, the concentration of the active silicic acid particle dispersion liquid when adding 0.5 to 10 wt% as SiO _2, and more preferably in the range of 1-8 wt%. When the concentration is less than 0.5% by weight, the concentration of the seed particle dispersion decreases with the addition of the active silica particle dispersion, and the solubility of silica increases when the particles are grown under heating. The liquid may become unstable, causing particles to aggregate or the yield to decrease. On the other hand, if the concentration exceeds 10% by weight, depending on the addition rate of the active silicic acid particle dispersion, new fine particles may be formed, and a silica sol having a uniform particle size distribution may not be obtained.

The ratio of adding the active silica particle dispersion to the seed particle dispersion varies depending on the concentration of the seed particles in the seed particle dispersion, the particle diameter of the seed particles, the degree of polymerization of the active silica particles, the temperature of the seed particle dispersion, and the like. However, it is preferable to adjust the seed particles so that the growth rate of the particle diameter is in the range of 0.5 to 5 nm / hour, more preferably in the range of 1 to 4 nm / hour. The addition rate of the active silicic acid particle dispersion so that the growth rate of the particle diameter of the seed particles is less than 0.5 nm / hour is not much different from the conventional method for producing silica sol using an acidic silicic acid solution, and the effect of increasing the particle growth rate Is not fully exhibited. In addition, the addition of an active silicic acid particle dispersion in which the growth rate of the particle diameter of the seed particles exceeds 5 nm / hour is too fast to generate new fine particles between the active silicic acid particles, and a uniform particle size distribution. May not be obtained.
After the addition of the active silicic acid particle dispersion, aging can be performed if necessary. When aging is performed, a silica sol having a more uniform particle size is obtained.

As described above, the silica sol obtained by the method for producing a silica sol according to the present invention has an average particle size (D _LZ ) of 12 to 200 nm, preferably 15 to 180 nm, measured by a dynamic light scattering method using laser light, The average particle size (D _NaZ ) measured by the NaOH titration method is in the range of 5 to 30 nm, preferably 5 to 20 nm.
The ratio (D _LZ ) / (D _NaZ ) of the average particle diameter is in the range of 2 to 30, preferably 2 to 20. When the ratio (D _LZ ) / (D _NaZ ) is less than 2, aging for a long time or aging at a high temperature may be required, and the rapid particle growth effect of the present invention is offset. become. On the other hand, if the ratio (D _LZ ) / (D _NaZ ) exceeds 30, the particle strength of the silica particles becomes insufficient. For example, when the silica particles are used as polishing particles in an abrasive such as a semiconductor substrate, a desired polishing rate is obtained. May not be obtained.

The silica sol of the present invention can be used after being concentrated or diluted as necessary. Examples of the concentration method include a method of evaporating water by heating and a method of using an ultrafiltration membrane. At this time, the concentration of the silica sol as SiO ₂ is usually adjusted in the range of 10 to 50% by weight.
Further, the silica sol of the present invention can be replaced with an organic solvent as necessary to form an organosol. Examples of the organic solvent used for the solvent replacement include alcohols such as methanol, ethanol, propanol, butanol, diacetone alcohol, furfuryl alcohol, tetrahydrofurfuryl alcohol, ethylene glycol and hexylene glycol; acetic acid methyl ester and acetic acid ethyl ester Esters such as diethyl ether, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether; ketones such as acetone, methyl ethyl ketone, acetylacetone, acetoacetate; And amides such as N-methylpyrrolidone and dimethylformamide. These may be used alone or as a mixture of two or more.
Further, the silica sol of the present invention can be used after imparting hydrophobicity by surface treatment with a silane coupling agent, and, if necessary, alkali in the silica sol can be removed by using an ion exchange resin or the like.

Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited to these examples. In the following Examples and Comparative Examples, the average particle diameter of the seed particles, active silica particles and silica sol was measured using a dynamic light scattering method using laser light (particle diameter distribution measuring device [Particle Sizing Systems: NICOMP model 380]) and the results are shown in Table 1. In addition, for the activated silicic acid particles and the silica sol, the average particle size was calculated from the specific surface area calculated by the NaOH titration method (Sears method), and the results are also shown in Table 1.
Further, Table 1 shows the pH values of the seed particle dispersion and the active silica particle dispersion used in the following Examples and Comparative Examples, the average particle diameter (D _LF ) and the average particle diameter (D _NaF ) of the active silica particles. ) ratio of (D _LF) / (the ratio of the value of D _NaF), and the average particle size of an average particle diameter (D _LF) and the seed particles of the active silicic acid particles _{(D LS) (D LF)} / ( D _LS ) are also shown.

Preparation of Acid Silicic Acid Solution An aqueous solution of sodium silicate having a SiO ₂ concentration of 24% by weight (SiO ₂ / Na ₂ O molar ratio of 3.1) was diluted with ion-exchanged water to give a SiO ₂ concentration of 5.2. A weight% diluted sodium silicate aqueous solution was prepared. This solution was passed through a column filled with a hydrogen-type ion exchange resin (manufactured by Mitsubishi Chemical Corporation: Diaion SK-1B) to prepare an acidic silicate solution. The acidic silicic acid solution had a SiO ₂ concentration of 5.0% by weight and a pH of 2.7. The average particle diameter measured by a dynamic light scattering method using laser light was 1 nm.
Preparation of Seed Particle Dispersion (1) In a 30 L stainless steel vessel equipped with a reflux condenser, a stirrer, and a temperature detector, a sodium silicate aqueous solution (SiO ₂ / Na ₂ O molar ratio of 24% by weight as SiO ₂ ) was prepared. 3.1) 163 g was diluted with 2760 g of ion-exchanged water. 4420 g of the acidic silicic acid solution prepared separately was mixed with this solution, and heated at 60 ° C. for 30 minutes to prepare a seed particle dispersion liquid (1) having a concentration of 4.6% by weight as SiO ₂ . The average particle diameter (D _LS ) of the seed particles measured by the dynamic light scattering method using laser light was 5 nm, and the SiO ₂ / Na ₂ O molar ratio was 20.

Preparation of Active Silicate Particle Dispersion (1) An aqueous sodium silicate solution (SiO ₂ / Na ₂ O molar ratio: 3.1) having a concentration of 24% by weight as SiO ₂ was diluted with ion-exchanged water to obtain an SiO ₂ dispersion. A diluted sodium silicate aqueous solution having a concentration of 5.2% by weight was prepared. The aqueous sodium silicate solution was neutralized by adding sulfuric acid to prepare a silica hydrogel. After sufficiently washing the silica hydrogel with water, 43 kg of a silica hydrogel dispersion having a concentration of 5% by weight as SiO ₂ was added, and 955 g of a 20% by weight aqueous NaOH solution was added thereto, followed by peptization at 80 ° C. for 3 hours. Thus, an active silica particle dispersion liquid (1) was prepared. SiO ₂ concentration of 3 wt% of this time, SiO ₂ molar number (M _S) and the ratio between the alkali moles of (M ₂ O represents _{a) (M A) (M S} ) / (M A) is 15 Met. The average particle diameter (D _LF ) measured by a dynamic light scattering method using laser light was 3 nm, and the average particle diameter (D _NaF ) measured by a NaOH titration method was 1 nm.
Preparation of silica sol (1) 42716 g of an activated silicic acid particle dispersion (1) was added to 410 g of a seed particle dispersion (1) prepared at a temperature of 80 ° C over 11 hours to prepare a silica sol (1). Table 1 shows the SiO ₂ concentration of the silica sol, the average particle diameter (D _LZ ) measured by a dynamic light scattering method using a laser beam, the average particle diameter (D _Na ) measured by a NaOH titration method, and the particle growth rate. The average particle diameter (D _LZ ) measured by the dynamic light scattering method using laser light was used for the calculation of the particle growth rate.

Preparation reflux seed particle dispersion (2), a stirrer, in a stainless steel container 30L equipped with a temperature sensing device, the concentration of the SiO ₂ of 24 wt% aqueous sodium silicate solution (SiO ₂ / Na ₂ O molar ratio 3.1) 163 g was diluted with 2760 g of ion-exchanged water. After mixing this solution with 18200 g of an acidic silicic acid solution prepared in the same manner as in Example 1, the mixture was heated at 80 ° C. for 30 minutes to obtain a seed particle dispersion (2) having a concentration of 4.6% by weight as SiO _2. Prepared. The average particle size (D _LS ) measured by a dynamic light scattering method using laser light was 12 nm, and the SiO ₂ / Na ₂ O molar ratio was 70.
Preparation of Active Silicate Particle Dispersion (2) According to the method for preparing active silica particle dispersion (1), except that only 480 g of a 20% by weight aqueous NaOH solution was used, the active silica particle dispersion (2) was prepared. Was prepared. SiO ₂ concentration of 3 wt% of this time, SiO ₂ molar number (M _S) and the ratio between the alkali moles of (M ₂ O represents _{a) (M A) (M S} ) / (M A) is 30 Met. The average particle diameter (D _LF ) measured by a dynamic light scattering method using laser light was 6 nm, and the average particle diameter (D _NaF ) measured by a NaOH titration method was 2 nm.
Preparation of Silica Sol (2) Silica sol (2) was prepared by adding 24556 g of activated silica particle dispersion (2) to 410 g of seed particle dispersion (2) prepared at a temperature of 80 ° C. over 15 hours. Table 1 shows the SiO ₂ concentration, the average particle diameter, and the particle growth rate of the silica sol in the same manner as in Example 1.

Preparation of Activated Silicate Particle Dispersion (3) An aqueous sodium silicate solution (SiO ₂ / Na ₂ O molar ratio: 3.1) having a concentration of 24% by weight as SiO ₂ was diluted with ion-exchanged water to obtain an SiO ₂ dispersion. A diluted sodium silicate aqueous solution having a concentration of 5.2% by weight was prepared. The aqueous sodium silicate solution was neutralized by adding sulfuric acid to prepare a silica hydrogel. After sufficiently washing the silica hydrogel with water, a silica hydrogel dispersion having a concentration of 5% by weight as SiO ₂ was prepared. To 25 kg of the silica hydrogel dispersion, 555 g of a 20% by weight aqueous NaOH solution was added. The mixture was pulverized for a time to prepare an active silica particle dispersion liquid (3). SiO ₂ concentration of 3 wt% of this time, SiO ₂ molar number (M _S) and the number of moles of alkali (expressed as M ₂ O) (M _A) ratio of _{(M S) / (M A} ) is 25 Met. The average particle diameter (D _LF ) measured by a dynamic light scattering method using a laser beam was 4 nm, and the average particle diameter (D _NaF ) measured by a NaOH titration method was 2 nm.
Preparation of silica sol (3) Silica sol (3) was prepared by adding 24556 g of active silica particle dispersion (3) to 410 g of seed particle dispersion (2) prepared at a temperature of 80 ° C for 15 hours. Table 1 shows the SiO ₂ concentration, the average particle diameter, and the particle growth rate of the silica sol in the same manner as in Example 1.

The concentration of 24 wt% aqueous sodium silicate solution as prepared SiO ₂ of active silicic acid particle dispersion liquid _{(4) (SiO 2 / Na} 2 O molar ratio 3.1) was diluted with deionized water, as SiO ₂ A diluted sodium silicate aqueous solution having a concentration of 5.2% by weight was prepared. The aqueous sodium silicate solution was neutralized by adding sulfuric acid to prepare a silica hydrogel. After sufficiently washing the silica hydrogel with water, a silica hydrogel dispersion having a concentration of 5% by weight as SiO ₂ was prepared. To 35 kg of the silica hydrogel dispersion, 167 g of a 20% by weight aqueous NaOH solution was added. The mixture was pulverized for a time to prepare an active silica particle dispersion (4). SiO ₂ concentration of 3 wt% of this time, SiO ₂ molar number (M _S) and the ratio between the alkali moles of (M ₂ O represents _{a) (M A) (M S} ) / (M A) is 70 Met. The average particle diameter (D _LF ) measured by a dynamic light scattering method using laser light was 8 nm, and the average particle diameter (D _NaF ) measured by a NaOH titration method was 2 nm.
Preparation of silica sol (4) Silica sol (4) was prepared by adding 24556 g of the active silica particle dispersion (4) to 410 g of the seed particle dispersion (2) prepared at a temperature of 80 ° C over 15 hours. Table 1 shows the SiO ₂ concentration, the average particle diameter, and the particle growth rate of the silica sol in the same manner as in Example 1.

Preparation of Seed Particle Dispersion (3) In a 30 L stainless steel vessel equipped with a reflux condenser, a stirrer, and a temperature detector, a sodium silicate aqueous solution (SiO ₂ / Na ₂ O molar ratio of 24% by weight as SiO ₂₎ was used. 3.1) 163 g was diluted with 2760 g of ion-exchanged water. This solution was mixed with 25220 g of an acidic silicic acid solution prepared in the same manner as in Example 1, and then heated at 90 ° C. for 30 minutes to obtain a seed particle dispersion liquid (3) having a concentration as SiO ₂ of 4.6% by weight. Prepared. The average particle diameter (D _LS ) of the seed particles measured by the dynamic light scattering method using laser light was 25 nm, and the SiO ₂ / Na ₂ O molar ratio was 100.
Preparation of Active Silicic Acid Particle Dispersion (5) According to the method for preparing the active silicic acid particle dispersion (1), only 480 g of a 20% by weight aqueous solution of NaOH was used. A particle dispersion (5) was prepared. SiO ₂ concentration of 3 wt% of this time, SiO ₂ molar number (M _S) and the ratio between the alkali moles of (M ₂ O represents _{a) (M A) (M S} ) / (M A) is 30 Met. The average particle diameter (D _LF ) measured by a dynamic light scattering method using laser light was 12 nm, and the average particle diameter (D _NaF ) measured by a NaOH titration method was 2 nm.
Preparation of Silica Sol (5) 12382 g of activated silica particle dispersion (5) was added to 410 g of seed particle dispersion (3) adjusted to a temperature of 87 ° C. over 17 hours to prepare silica sol (5). Table 1 shows the SiO ₂ concentration, the average particle diameter, and the particle growth rate of the silica sol in the same manner as in Example 1.

Preparation of Seed Particle Dispersion (4) In a 30 L stainless steel vessel equipped with a reflux condenser, stirrer, and temperature detector, catalyzed S1-80P (manufactured by Catalyst Chemicals, Inc.) was mixed with 363 g of ion-exchanged water. A seed particle dispersion (4) having a concentration of 4.6% by weight as SiO ₂ was prepared. The average particle diameter (D _LS ) of the seed particles measured by a dynamic light scattering method using laser light was 100 nm, and the SiO ₂ / Na ₂ O molar ratio was 100.
Preparation of Active Silicate Particle Dispersion (6) According to the method for preparing active silica particle dispersion (1), except that only 20 g of a 20 wt% aqueous NaOH solution was used in an amount of 320 g, active silica particle dispersion (6) was prepared. Was adjusted. SiO ₂ concentration of 3 wt% of this time, SiO ₂ molar number (M _S) and the number of moles of alkali (expressed as M ₂ O) (M _A) ratio of _{(M S) / (M A} ) is 45 Met. The average particle diameter (D _LF ) measured by a dynamic light scattering method using a laser beam was 20 nm, and the average particle diameter (D _NaF ) measured by a NaOH titration method was 2 nm.
Preparation of silica sol (6) Silica sol (6) was prepared by adding 2728 g of activated silica particle dispersion (6) to 410 g of seed particle dispersion (4) prepared at a temperature of 95 ° C for 20 hours. Table 1 shows the SiO ₂ concentration, the average particle diameter, and the particle growth rate of the silica sol in the same manner as in Example 1.

The concentration of 24 wt% aqueous sodium silicate solution as prepared SiO ₂ of active silicic acid particle dispersion liquid _{(7) (SiO 2 / Na} 2 O molar ratio 3.1) was diluted with deionized water, as SiO ₂ A diluted sodium silicate aqueous solution having a concentration of 5.2% by weight was prepared. The aqueous sodium silicate solution was neutralized by adding sulfuric acid to prepare a silica hydrogel. After sufficiently washing the silica hydrogel with water, a silica hydrogel dispersion having a concentration as SiO ₂ of 3% by weight was treated with a pulverizer (manufactured by Yaskawa Electric Co., Ltd .: sand mill) for 0.5 hours. An activated silica particle dispersion (7) was prepared. At this time, the SiO ₂ concentration was 3% by weight, the average particle diameter (D _LF ) measured by a dynamic light scattering method using a laser beam was 3 nm, and the average particle diameter (D _NaF ) measured by a NaOH titration method was 1 nm. .
Preparation of silica sol (7) 42716 g of an active silicic acid particle dispersion (7) was added to 410 g of a seed particle dispersion (1) prepared at a temperature of 80 ° C over 11 hours to prepare a silica sol (7). Table 1 shows the SiO ₂ concentration, the average particle diameter, and the particle growth rate of the silica sol in the same manner as in Example 1.

Preparation of Seed Particle Dispersion (5) According to the method for preparing the seed particle dispersion (4), except that the cataloid S1-80P was changed to Spherica slurry 100P (manufactured by Catalyst Kasei Kogyo Co., Ltd.), the seed particles were prepared in the same manner. Dispersion (5) was prepared. At this time, the SiO ₂ concentration was 4.6% by weight, and the average particle size (D _LS ) measured by a dynamic light scattering method using laser light was 120 nm. The SiO ₂ / Na ₂ O molar ratio was 100.
Preparation of Active Silicate Particle Dispersion (8) According to the method of preparing the active silica particle dispersion (1), except that only 285 g of a 20 wt% aqueous NaOH solution was used, the active silica particle dispersion (8) was prepared in the same manner. Was adjusted. SiO ₂ concentration of 3 wt% of this time, SiO ₂ molar number (M _S) and the ratio between the alkali moles of (M ₂ O represents _{a) (M A) (M S} ) / (M A) is 15 Met. The average particle diameter (D _LF ) measured by a dynamic light scattering method using laser light was 40 nm, and the average particle diameter (D _NaF ) measured by a NaOH titration method was 2 nm.
Preparation of silica sol (8) 1600 g of activated silica particle dispersion (8) was added to 410 g of seed particle dispersion (5) adjusted to a temperature of 150 ° C over 20 hours to prepare silica sol (8). Table 1 shows the SiO ₂ concentration, the average particle diameter, and the particle growth rate of the silica sol in the same manner as in Example 1.

Comparative Example 1

Preparation of Active Silicate Particle Dispersion (9) According to the method for preparing active silica particle dispersion (1), except that only 950 g of a 20% by weight aqueous NaOH solution was used, the active silica particle dispersion (9) was prepared. Was prepared. SiO ₂ concentration of 3 wt% of this time, SiO ₂ molar number (M _S) and the ratio between the alkali moles of (M ₂ O represents _{a) (M A) (M S} ) / (M A) is 15 Met. The average particle diameter (D _LF ) measured by laser light was 3 nm, and the average particle diameter (D _NaF ) measured by NaOH titration was 2 nm.
Preparation of silica sol (9) Silica sol (9) was prepared by adding 1744 g of activated silica particle dispersion (9) to 400 g of seed particle dispersion (2) adjusted to a temperature of 80 ° C over 15 hours. . Table 1 shows the SiO ₂ concentration, the average particle diameter, and the particle growth rate of the silica sol in the same manner as in Example 1.

Comparative Example 2

Preparation of Active Silicate Particle Dispersion (10) According to the method for preparing the active silica particle dispersion (1), except that only 20 g of a 20% by weight aqueous NaOH solution was used in an amount of 240 g, the active silica particle dispersion (10) was prepared. Was prepared. SiO ₂ concentration of 3 wt% of this time, SiO ₂ molar number (M _S) and the ratio between the alkali moles of (M ₂ O represents _{a) (M A) (M S} ) / (M A) is 60 Met. The average particle diameter (D _LF ) measured by laser light was 80 nm, and the average particle diameter (D _NaF ) measured by NaOH titration was 2 nm.
Preparation of silica sol (10) Silica sol (10) was prepared by adding 1744 g of activated silica particle dispersion (10) to 400 g of seed particle dispersion (3) adjusted to a temperature of 87 ° C over 15 hours. Table 1 shows the SiO ₂ concentration, the average particle diameter, and the particle growth rate of the silica sol in the same manner as in Example 1.

The silica sol of the present invention can be suitably used particularly as a hard coating agent for a transparent substrate such as transparent plastic and glass, a plastic filler, and an abrasive for lenses and silicon wafers.

Claims (5)

The method is characterized in that an active silica particle dispersion of the following (b) is continuously or intermittently added to the seed particle dispersion of the following (a) while heating, and the active silica particles are attached to the seed particles to grow the particles. A method for producing a silica sol.
(a) An aqueous dispersion of seed particles having an average particle diameter (D _LS ) measured by a dynamic light scattering method using laser light in the range of 5 to 1000 nm, and having a pH in the range of 7 to 12. Dispersion
(b) The average particle diameter (D _LF ) measured by the dynamic light scattering method using laser light is in the range of 2 to 50 nm (however, the average particle diameter (D _LF ) is smaller than the average particle diameter (D _LS )). And the average particle diameter (D _NaF ) measured by the NaOH titration method is in the range of 0.9 to 6 nm, and the ratio (D _NaF ) between the average particle diameter (D _LF ) and the average particle diameter (D _NaF ) An aqueous dispersion of activated silica particles having a ratio of ( _LF ) / (D _NaF ) in the range of 1.8 to 30, wherein the pH is in the range of 5 to 11.   The method for producing a silica sol according to claim 1, wherein the heating is performed in a temperature range of 60 to 160C.   The active silicic acid particles, (a) activated silicic acid particles obtained by peptizing the silica hydrogel produced by neutralizing an alkali silicate with an acid, or (b) produced by neutralizing an alkali silicate with an acid 3. The method for producing a silica sol according to claim 1, wherein the silica hydrogel is activated silicic acid particles obtained by mechanically pulverizing silica hydrogel while pulverizing it with an alkali. The average particle size of the active silicic acid particles (D _LF), when the average particle diameter of the seed particles (D _LS) is 12nm below are 7/10 or less of the average particle diameter (D _LS), the seed If the average particle diameter of the particles (D _LS) is greater than 12 nm, according to claim 1, claim 2 or claim 3 silica sol, wherein said average is particle diameter 5/10 or less of the (D _LS) Manufacturing method. The average particle diameter (D _LZ ) measured by the dynamic light scattering method using laser light is in the range of 12 to ₂₀₀ nm, and the average particle diameter (D _NaZ ) measured by the NaOH titration method is in the range of 5 to 30 nm. A silica sol, wherein the ratio (D _LZ ) / (D _NaZ ) of the average particle diameter (D _LZ ) to the average particle diameter (D _NaZ ) is in the range of 2 to 30.