JP6927732B2 - Method for producing irregularly shaped silica particles - Google Patents

Description

The present invention relates to a method for producing deformed silica particles having a particle size and strength suitable for an abrasive.

As the abrasive grains for high-speed polishing for substrates such as Si wafers, glass HD, and aluminum HD, abrasive grains of hard crystals such as diamond abrasive grains and α-alumina are used. However, although these hard abrasive grains have a high polishing rate, they are irregularly shaped particles having a crushed surface, and since it is difficult to control the particle size distribution, they often contain coarse particles, which causes deep scratches on the polished surface. As a result, the subsequent finish polishing process is overloaded, which may eventually reduce productivity.

Therefore, if amorphous silica particles with a large particle size, which have low hardness but do not have a sharp crushed surface, are used, the contact area with the polished substrate increases due to the large primary diameter, and the dynamic contact area due to the deformation ( By increasing the Feret diameter), the effect of obtaining a high polishing speed can be expected.

As a method for preparing deformed silica particles having a particle size suitable for an abrasive, a method of adding a silicic acid solution to a deformed seed particle prepared from water glass or the like to grow a large particle size has been conventionally known (patented). Document 1).

Japanese Patent No. 5127452

In the manufacturing process of hard disks and semiconductors, polishing is applied to the manufacturing process in order to flatten the substrate. At the time of polishing, so-called polishing slurry in which abrasive grains such as silica and ceria are dispersed in water and a chemical component is added to control the polishing performance is used. In particular, it is known that abrasive grains have a great influence on polishing performance, and the performance required for abrasive grains is that the polishing speed is high and there is no defect such as scratches on the polished surface.

As a method of obtaining a high polishing rate, it is common to use abrasive grains having a large particle size, but if the particle size becomes too large, the number of particles decreases, so that the polishing rate decreases and scratches also increase. Tend to do. Therefore, in order to obtain a high polishing rate without causing scratches, a method of making the abrasive grains non-spherical has been studied, and it is known that a high polishing rate can be obtained by using irregularly shaped particles.

As a method for obtaining deformed silica particles, a method of aggregating silica particles during nucleation using water glass as a raw material is known, but it has been difficult to obtain deformed silica particles having a particle size of 100 nm or more by this method. Further, in a method in which irregularly shaped silica particles having a particle diameter of 100 nm or less as obtained by this method are used as seed particles and a silicic acid solution is added to grow the particle size to a large size, the silicic acid solution is prepared so that the particle size is 200 nm or more. When used, the seed particles grow spherically or substantially spherically, so that it is difficult to grow the deformed seed particles in a deformed state to obtain relatively large deformed silica particles.

Further, as another method for preparing the deformed silica particles, the inventors of the present application examined a method for obtaining the deformed silica particles by pulverizing wet silica or the like, and although the deformed silica particles were obtained, the wet type having a gel structure was obtained. The deformed silica particles made of silica have a weak particle strength in order to control the particle size and particle size distribution by pulverization, and the obtained deformed silica particles also have a weak particle strength. Therefore, when used as abrasive particles, The required polishing rate could not be obtained.

In the present invention, as the seed particles, instead of the deformed seed particles obtained from the conventional water glass, particles made of a deformed porous gel obtained by crushing porous silica gel under specific conditions are used to prepare a silicic acid solution. In addition, a method for producing irregularly shaped silica particles obtained by growing the seed particles was studied. The particles made of this irregularly shaped porous gel were obtained by wet-crushing soft porous silica gel with a bead mill, for example, under alkaline pH of 8.0 to 11.5 until the average particle size became 150 nm to 400 nm. It has almost no coarse particles, has a relatively uniform particle size, and generally retains the pore structure of the raw material porous silica gel.

When the particles made of such a deformed porous gel are used as seed particles and the seed particles are grown in the coexistence of a silicic acid solution, the silicic acid deposited on the silica surface preferentially fills the pores (recesses) of the seed particles. The seed particles can be grown in a deformed state, and the silicic acid fills the pores inside the seed particles to increase the particle strength of the obtained deformed silica particles. Further, since the deformed porous gel having few coarse particles is used as the seed particles, the obtained deformed silica particles contain almost no coarse particles. It has been found that when these irregularly shaped silica particles are used as polishing particles, the polishing speed is relatively high and the generation of scratches (streak marks) on the polished surface is significantly suppressed.

Based on the above findings, the present invention uses a method in which particles made of a deformed porous gel obtained by crushing porous silica gel are used as seed particles, and a silicic acid solution is added to grow the seed particles. Provided is a method for efficiently producing irregularly shaped silica particles having a particle size and strength suitable for the above. In the following description, the silicic acid solution is deposited on the silica surface of the seed particles, and due to the difference in solubility, it preferentially reacts with the pores that are not related to the particle size to fill the pores, and the silica is formed on the outer surface of the particles. The growth of particles by depositing silica is called build-up.

The production method of the present invention is a method for producing deformed silica particles, which comprises the following steps a to c, and is a production method that solves the above-mentioned conventional problems by the configuration of the following steps a to c.
(Step a) A step of wet-crushing porous silica gel under alkaline conditions to obtain a solution containing particles composed of a deformed porous gel.
(Step b) A siliceous solution is added to a solution containing particles made of the deformed porous gel under alkaline conditions to heat the solution, and the pores of the particles made of the deformed porous gel are filled by reaction with the silicic acid to form a deformed shape. The process of growing the particles as they are into irregularly shaped silica particles,
(Step c) A step of recovering the grown irregularly shaped silica particles.

Specifically, the production method of the present invention
In step a, the porous silica gel having a specific surface area of 300 to 800 m ² / g is made into particles made of a deformed porous gel having an average particle diameter of 150 to 400 nm.
In step b, the pores of the particles made of the deformed porous gel are filled by the reaction with the silica acid ^{to reduce the specific surface area of the particles made of the deformed porous gel to 100 m 2} / g or less, and the average particle diameter is 200 to 200 to This is a method for producing the deformed silica particles, which are grown into the deformed silica particles having a diameter of 500 nm.

Further, specifically, the production method of the present invention is described.
In step a, the porous silica gel is wet-crushed under alkalinity of pH 8.0 to 11.5 to prepare a solution containing particles composed of a deformed porous gel. By wet pulverization under alkaline conditions in the pH range, the silica in the neck portion between the particles constituting the porous silica gel is dissolved to promote the progress of pulverization, and at the same time, the coarse particles are preferentially pulverized. .. In addition, since the pH of the solution is high, the crushed particles are given a negative charge to stabilize them, and reaggregation does not occur, so that new coarse particles are unlikely to be generated. It can be a solution containing particles of gel.
_{In step b, the SiO 2} concentration of the solution containing the particles of the irregularly shaped porous gel is adjusted to 1 to 10% by mass, heated to 60 ° C. to 170 ° C., and a silicic acid solution under alkaline pH of 9 to 12.5. Is continuously or intermittently added to fill the pores of the particles made of the deformed porous gel by reaction with silicic acid to reduce the specific surface area of the particles and grow the particles in a deformed state.
In step c, the solution containing the grown deformed silica particles is concentrated to recover the deformed silica particles.

The manufacturing method of the present invention, in step b and more specifically, the addition amount of the silicic acid solution is, SiO ₂ moles of該珪acid liquid to SiO ₂ molar concentration of the solution containing the particles consisting of irregular porous gel This is a method for producing the deformed silica particles whose concentration is in the range of 2 to 5 mol times.

Further, the present invention includes a polishing abrasive grain dispersion liquid containing deformed silica particles obtained by any of the above-mentioned production methods.

In the production method of the present invention, the porous silica gel is wet-crushed under alkaline conditions to form a solution containing particles made of a deformed porous gel, and the particles made of the deformed porous gel are used as seed particles to prepare a silicic acid solution. When added, the silica gel solution preferentially reacts with the pores of the seed particles to grow the particles while filling the pores, and the silica gel solution is also consumed in the reaction with the pores, so that the seed particles remain deformed. It can grow big. Further, the pores of the particles are filled by the reaction with silicic acid, so that the specific surface area is reduced and the strength of the particles is increased. As a result, irregularly shaped silica particles having a particle size and strength suitable for an abrasive can be obtained.

Since the deformed silica particles obtained by the production method in the present invention have a particle size and strength suitable for an abrasive, the polishing speed is high when used as an abrasive, and the abrasive grains pierce the base material. Since there is no scratch and the scratch can be easily recovered in the secondary polishing process of the subsequent process, the efficiency of the polishing work can be significantly improved.

SEM photograph of particles made of irregularly shaped porous gel of Example 1 SEM photograph of the deformed silica particles produced in Example 1

Hereinafter, the production method of the present invention will be specifically described.
The production method of the present invention comprises the step a of wet crushing porous silica gel under alkaline conditions to obtain a solution containing particles made of deformed porous gel, and silicic acid under alkaline conditions in a solution containing particles made of the deformed porous gel. The build-up step b, in which the liquid was added and heated to grow the particles in the deformed shape while filling the pores of the particles made of the deformed porous gel by the reaction with the silicic acid to form the deformed silica particles, was grown. A method for producing deformed silica particles, which comprises a step c of recovering the deformed silica particles.

[Step a]
The production method of the present invention uses porous silica gel as a starting material. By using porous silica gel, the added silicic acid reacts with the pores of the particles made of the irregularly shaped porous gel, and the silica deposited on the outer surface of the particles while filling the pores promotes the growth of the particles. By this build-up, the convex part of the outer surface of the particle contributes to the increase of the outer diameter, and the concave part contributes less to the outer shape. It is possible to produce irregularly shaped silica particles having a large diameter.

The porous silica gel is preferably a gel that is easily crushed, and for example, a wet hydrogel obtained by washing a gel of the water glass method, a gel of the alkoxide method, or the like is preferable. Since the gel obtained by the alkoxide method has few hydroxyl groups that dehydrate and condense, the dry powder is soft and highly productive dry powder can be used. It is preferable that the particle size distribution of the particles composed of the irregularly shaped porous gel obtained by crushing the porous silica gel is controlled within a certain range, and if it is a large gel mass that is difficult to crush, it takes time to crush it. , It is not preferable because the particle size distribution becomes wide.

Porosity and specific surface area are examples of parameters indicating the porosity of porous silica gel. In the case of pores with open pores, if the pore diameters are the same, the specific surface area and the pore volume are generally in a proportional relationship. .. In the present invention, the specific surface area was used as a parameter indicating the porosity of the porous silica gel.

The porous silica gel preferably has a specific surface area in the range of ^{300 to 800 m 2 / g.} When the specific surface area is ^{smaller than 300 m 2} / g, the pores of the gel are small. Since the amount of silicic acid that permeates the pores of the particles is small, it is difficult for the pores to be filled by the reaction with silicic acid, and the added silicic acid solution is consumed so as to grow the particles round, making it difficult to maintain the irregular shape. Further, if the specific surface area is ^{larger than 800 m 2} / g, the strength is too weak, and the strength is sufficient even if the inside of the particles made of the deformed porous gel obtained by crushing is built up by the reaction with silicic acid and partially filled. It is difficult to obtain irregularly shaped silica particles.

The porous silica gel is crushed into particles made of a deformed porous gel. Particles made of a deformed porous gel are prepared by simultaneously deforming and crushing relatively soft silica gel having a specific surface area of ^{about 300 to 800 m 2 / g under a strong share such as a bead mill.} For crushing, for example, a sand mill crusher containing a glass medium or a bead mill may be used. Crushing is preferably performed multiple times.

The deformation of particles can be evaluated by the degree of deformation. The degree of deformation is obtained by dividing the weight average particle size [nm] of the particles measured by the disk-type centrifugal particle size distribution measuring device by the equivalent sphere-equivalent particle size [nm] calculated from ^{the specific surface area [m 2 / g] of the particles.} It is represented by. The deformed silica particles of the present invention preferably have a degree of deformity in the range of 1.5 to 10.0. The equivalent sphere-equivalent particle size (r) is calculated from the following equation using the specific surface area (SA) measured by the BET method and the particle density (ρ) [ρ = 2.2 in the case of silica]. .. r = 6000 / (SA × ρ)

In the present invention, the average particle size of the particles made of the deformed porous gel and the average particle size of the deformed silica particles after the particle growth mean the average particle size of the weight-equivalent particle size distribution. (In the present application, the average particle size of this weight-equivalent particle size distribution is also referred to as "weight average particle size"). The method of obtaining the average particle size of the weight-equivalent particle size distribution is described later.

Normally, when powder is crushed with a bead mill or the like, the particle size of the powder decreases in proportion to the crushing time, but for soft materials with a high specific surface area such as silica gel, the change in particle size with respect to the crushing time is slow. It is crushed into irregularly shaped particles with a particle size of about 200 nm measured by the light scattering method, and has a coarse structure containing a considerable number of pores while maintaining the specific surface area before crushing. .. Therefore, even if the deformed silica particles are used as an abrasive as they are, they tend to collapse due to insufficient strength, and only a very low polishing rate can be obtained. Therefore, in the production method of the present invention, a siliceous solution is added to a solution containing particles made of a deformed porous gel, and the pores inside the particles made of the deformed porous gel are built up and filled with the siliceous solution to fill the particles. The strength is increased.

The porous silica gel is preferably crushed by wet crushing under alkaline conditions, and the alkalinity is preferably in the range of pH 8.0 to 11.5. As the pH drops below the alkaline range, the negative potential gradually drops and becomes unstable in the neutral to acidic range, so that the particles generated by crushing cannot exist stably and immediately aggregate. Further, when the pH is 11.5 or more, the dissolution of silica is promoted, which is also not preferable because it aggregates. The pH at the time of wet crushing is preferably in the range of 8.5 to 11.0.

The average particle size of the particles made of the irregularly shaped porous gel is preferably in the range of 150 to 400 nm. If the average particle size of the particles is smaller than 150 nm, it is difficult to obtain a particle size suitable for the abrasive even if the silicate solution is added to grow the particles. Further, if the average particle size of the particles made of the irregularly shaped porous gel is larger than 400 nm, it exceeds the particle size suitable for the abrasive, which is not preferable. Further, coarse particles having an average particle size of more than 400 nm are not preferable because they cause scratches. Centrifugation may be performed for the purpose of removing coarse particles contained in the irregularly shaped porous gel. The average particle size of the particles made of the deformed porous gel is preferably in the range of 160 to 350 nm.

By performing the crushing in multiple stages with media of different sizes, it is possible to suppress the spread of the particle size distribution of the particles made of the irregularly shaped porous gel. Further, the adjustment of the particle size can also be controlled by changing the size of the media.

[Step b]
A silicic acid solution is added to a solution containing particles made of a deformed porous gel under alkaline conditions to heat the solution, and the pores inside the particles made of the deformed porous gel are filled by a reaction with silicic acid and the particles are grown in a deformed shape. .. _{The SiO 2} concentration of the solution containing the particles of the irregularly shaped porous gel is preferably in the range of 1 to 10% by mass. _{If the SiO 2} concentration of the solution containing the particles made of the deformed porous gel is less than 1% by mass, the efficiency of producing the obtained deformed silica particles is lowered. Further, if the SiO2 concentration is more than 10% by mass, the particle growth of the obtained deformed silica particles tends to be non-uniform, which is not preferable.
Further, as another method of filling the pores of the deformed porous gel, there is also a method of adding a silicic acid solution while hydrothermally treating the deformed porous gel. This is because at the same time as filling the pores with the added silicic acid solution, a part of the deformed porous gel dissolves and the pores are preferentially filled.

The heating temperature is preferably in the range of 60 ° C to 170 ° C. This is because if the temperature is lower than 60 ° C., the growth of the particles made of the deformed porous gel is slow, and if the temperature is higher than 170 ° C., the obtained deformed silica particles tend to be spherical. The heating temperature is more preferably in the range of 60 ° C to 100 ° C.

The pH when the silicic acid solution is added to the solution containing the particles of the irregularly shaped porous gel is preferably in the range of 9 to 12.5. When the pH is less than 9, the solubility of silica is low, so that the degree of supersaturation becomes extremely high, and the added silicic acid solution is not consumed for particle growth and is easily generated as fine particles. In addition, since the negative potential is also low, the particles tend to aggregate, which is not preferable. Further, if the pH is higher than 12.5, the dissolution of silica is promoted, which is not preferable.

The pH of the solution containing the particles of the irregularly shaped porous gel is adjusted as necessary. The adjusting means is not particularly limited, but it is usually adjusted by adding an alkaline substance. Examples of such alkaline substances include sodium hydroxide, water glass and the like. A suitable pH range of 9.5 to 12.0 is recommended when the silicic acid solution is added to the solution containing the particles of the irregularly shaped porous gel.

The addition amount of the silicic acid solution is in the range of SiO ₂ molar該珪acid liquid to SiO ₂ molar concentration of the solution containing the particles consisting of the profiled porous gel is 2 to 5 times by mole are preferable. If the amount of the silicic acid solution added is less than the above range, the growth of the obtained deformed silica particles becomes insufficient, and the production efficiency of the deformed silica particles is lowered. On the other hand, if the amount of the silicic acid solution added is larger than the above range, the remaining amount of unreacted silicic acid increases, which is not preferable. It is desirable to add the silicic acid solution continuously or intermittently.

The silicate liquid penetrates into the inside of the particles through the pores of the particles made of the irregularly shaped porous gel, and builds up to reduce the specific surface area of the particles and increase the strength of the particles. The specific surface area of the particles consisting of irregular porous gel 100 m ² / g or less, it is desirable that preferably in the range of a specific surface area of 15m ² / g~50m ² / g. If the specific surface area of the particles made of the deformed porous gel is ^{larger than 100 m 2} / g, the strength of the obtained deformed silica particles is insufficient, and when used as an abrasive, the particles tend to collapse and the polishing speed tends to be slow.

Further, since the silicic acid solution binds to the surface of the particles made of the deformed porous gel to grow the particles, it is possible to obtain the deformed silica particles having a large particle size while maintaining the deformed shape. The particle size of the deformed silica particles after the particle growth is preferably an average particle size of 200 to 500 nm.

[Step c]
Collect the grown variant silica particles. Specifically, for example, the solution containing the grown deformed silica particles is cooled to about room temperature to about 40 ° C., concentrated using an ultrafiltration membrane or the like, and further concentrated using an evaporator or the like, and the remaining deformed silica particles remain. Should be collected. Centrifugation may be performed to remove even coarser particles.

Hereinafter, examples of the present invention will be shown together with comparative examples. In the examples and comparative examples, the specific surface area and the average particle size were measured, and the polishing test was performed as follows.
[Measurement of specific surface area by nitrogen adsorption method]
Adjust the pH of 50 ml of silica sol _{to 3.5 with HNO 3} , add 40 ml of 1-propanol, and dry the sample at 110 ° C. for 16 hours. It was used as a sample for use. Then, the specific surface area was calculated from the amount of nitrogen adsorbed by the BET 1-point method using the nitrogen adsorption method (BET method) using a specific surface area measuring device (manufactured by Yuasa Ionics, model number Multisorb 12).
In the specific surface area measuring device, 0.5 g of the sample after firing is taken in a measuring cell, degassed in a mixed gas stream of 30 v% nitrogen / 70 v% helium at 300 ° C. for 20 minutes, and then the sample is subjected to the above mixed gas. The temperature was maintained at the liquid nitrogen temperature in the air stream, and nitrogen was equilibrium-adsorbed to the sample. Next, the sample temperature was gradually raised to room temperature while flowing the mixed gas, the amount of nitrogen desorbed during that period was detected, and the specific surface area of the silica fine particles in the sample was calculated from a calibration curve prepared in advance.

[Measurement of average particle size]
The silica particle dispersion was diluted with a 0.5% by mass aqueous sodium dodecyl sulfate solution to a solid content concentration of 2% by mass, and the solution was applied to a disk centrifugal particle size distribution measuring device (model number: DC24000UHR, manufactured by CPS instruments, USA). .1 ml was injected with a syringe and measurements were taken at 18000 rpm in a density gradient solution of 8% to 24% sucrose. For the crushed silica hydrogel (particles made of irregularly shaped porous gel), the average particle size of the weight-equivalent particle size distribution was used. In addition, the deformed silica particles obtained by adding a silicic acid solution to this crushed product and building up were also used as the average particle size of the weight-equivalent particle size distribution.

[Polishing test]
Substrate to be polished As the substrate to be polished, a nickel-plated aluminum substrate for hard disks (nickel-plated substrate manufactured by Toyo Kohan Co., Ltd.) was used. This substrate is a donut-shaped substrate (outer diameter 95 mmφ, inner diameter 25 mmφ, thickness 1.27 mm).
Polishing test 344 g of a 9% concentration dispersion was prepared by adding ion-exchanged water to 30% concentration large particle deformed silica particles, and 5.65 g of 31% H2O2 was added thereto, followed by pH with 10% nitric acid. Was adjusted to 1.5 to prepare a polishing slurry.
The above-mentioned substrate to be polished is set in a polishing device (Nanofactor Co., Ltd .: NF300), and a polishing pad (Nitta Haas Co., Ltd. "SUBA-800") is used, the substrate load is 0.35 MPa, the surface plate rotation speed is 90 rpm, and the head. Polishing was performed for 5 minutes at a rotation speed of 60 rpm while supplying a polishing slurry at a speed of 20 g / min.
Polishing speed The polishing speed was calculated from the weight difference of the polishing substrate before and after polishing and the polishing time.

[Example 1]
Preparation of silica hydrogel 462.5 g of sodium silicate is dissolved in water _{, a 24 wt% sodium silicate aqueous solution is prepared in terms of SiO 2} , and then 25 wt% sulfuric acid is added so that the pH becomes 4.5 to obtain silica. A solution containing hydrogel was obtained. After maintaining this silica hydrogel solution at a temperature of 21 ° C. in a constant temperature bath and allowing it to stand for 5.75 hours for aging, the content of sodium sulfate is higher than that of silicon _{as SiO 2 contained in the silica hydrogel.} Purified silica hydrogel was obtained by washing with pure water until it became 0.05% by weight. The concentration of the purified silica hydrogel was such that the SiO ₂ content (concentration) was 5% by weight. The specific surface area was 600 m ² / g.
Crushing of silica hydrogel Next, 500 g of silica hydrogel was placed in a 2 L glass beaker, and a 4.8 wt% NaOH aqueous solution was added to adjust the pH to 10. 1135 g of a 0.25 mmφ glass medium was added thereto and crushed by a sand mill crusher. Similarly, several batches of crushing were carried out to obtain 2000 g of a 4% by weight crushed gel (a solution containing particles composed of a deformed porous gel). The average particle size of the particles made of the irregularly shaped porous gel was 184 nm. The SEM image is shown in FIG. Next, 2716 g of a crushed gel (a solution containing particles composed of a deformed porous gel) whose silica concentration was adjusted to 2.76% by weight with ion-exchanged water was placed in a 10 L separable flask, and an aqueous sodium hydroxide solution (aqueous solution of sodium hydroxide) was stirred. A concentration of 48% by mass) was added in an amount of 6.54 g, and the pH was adjusted to 10.5. Subsequently, the temperature was raised to 98 ° C. and held for 30 minutes. Next, while maintaining the temperature at 98 ° C., 5380 g of a 4.6 wt% silicic acid solution was added over 20 hours, and then stirring was continued for another 1 hour to obtain a mixed solution of silica particles. The pH of this formulation was 10.2. After cooling this preparation to about 40 ° C., the SiO ₂ concentration was concentrated to 12% by weight with an ultrafiltration membrane (Asahi Kasei SIP1013).
Next, the SiO2 concentration was concentrated to 30% by weight with a rotary evaporator, and large-sized irregularly shaped silica particles were recovered. The average particle size of the deformed silica particles was 230 nm. The SEM image of the silica particles is shown in FIG. A polishing test was performed on these irregularly shaped silica particles. The results are shown in Table 1.

[Example 2]
500 g of silica gel obtained in Example 1 was placed in a 2 L glass-ker and a 4.8 wt% NaOH aqueous solution was added to adjust the pH to 10. 2390 g of 1.0 mmφ zirconia medium was added thereto and crushed by a sand mill crusher. Similarly, several batches of crushing were carried out to obtain 2000 g of a 4% by weight crushed gel (a solution containing particles composed of a deformed porous gel). Next, 1135 g of 0.25 mmφ glass medium was added to 500 g of this crushed gel to perform several batches of crushing in the second stage, and 3.5% by weight of the crushed gel (a solution containing particles composed of a deformed porous gel) was obtained. 1900 g was obtained. The average particle size of the particles made of the obtained irregularly shaped porous gel was 230 nm. In the subsequent steps, the average particle size was measured and the polishing test was performed on the obtained deformed silica particles in the same manner as in Example 1. The results are shown in Table 1.

[Example 3]
500 g of silica gel obtained in Example 1 was placed in a 2 L glass-ker and a 4.8 wt% NaOH aqueous solution was added to adjust the pH to 10. 2390 g of 1.0 mmφ zirconia medium was added thereto and crushed by a sand mill crusher. Similarly, several batches of crushing were carried out to obtain 2000 g of a 4% by weight crushed gel (a solution containing particles composed of a deformed porous gel). The average particle size of the particles made of the irregularly shaped porous gel was 298 nm. In the subsequent steps, the average particle size was measured and the polishing test was performed on the obtained deformed silica particles in the same manner as in Example 1. The results are shown in Table 1.

[Comparative Example 1]
The crushed gel (solution containing particles composed of irregularly shaped porous gel) obtained in Example 1 was concentrated to 9% by weight in _{SiO 2 concentration with an ultrafiltration membrane (SIP1013 manufactured by Asahi Kasei).} Then, the silica particles obtained without the build-up with the silicic acid solution were subjected to a polishing test in the same manner as in Example 1. The results are shown in Table 1.

[Comparative Example 2]
In Example 1, 2716 g of a crushed gel (a solution containing particles composed of atypical porous gel) whose silica concentration was adjusted to 2.76% by weight with ion-exchanged water was placed in a 10 L separable flask, and water was stirred while stirring. 6.54 g of an aqueous sodium oxide solution (concentration 48% by mass) was added to adjust the pH to 10.5. Subsequently, the temperature was raised to 98 ° C. and held for 30 minutes. Next, while maintaining the temperature at 98 ° C., 1304 g of a 4.6 wt% silicic acid solution was added over 4.8 hours to adjust the pH to 10.4, and the modified silica particles were produced in the same manner as in Example 1. The average particle size was measured and the polishing test was performed. The results are shown in Table 1.

[Comparative Example 3]
The silica hydrogel obtained in Example 1 was dried overnight in a dryer at 100 ° C., then ground in an agate mortar and baked at 550 ° C. for 2 hours to prepare a solution containing particles of silica gel ^{having a surface area of 200 m 2 / g.} Obtained. An attempt was made to crush this under the same conditions as in Example 3, but it could not be crushed.

Claims (2)

A method for producing deformed silica particles, which comprises the following steps a to c.
(Step a) A step of wet-crushing a porous silica gel having a specific surface area of 300 to 800 m ² / g under alkaline conditions to obtain a solution containing particles composed of a deformed porous gel having an average particle diameter of 150 to 400 nm.
(Step b) the profiled porous silicic acid solution with an alkaline under the solution containing the particles consisting of the gel was heated by adding, filled by reaction with the pores of the particles consisting of the profiled porous gel the silicic acid the A step of reducing the specific surface area of particles made of a deformed porous gel to 100 m ² / g or less and growing the particles in a deformed shape to obtain deformed silica particles having an average particle diameter of 200 to 500 nm.
(Step c) A step of recovering the grown irregularly shaped silica particles. In step a, the porous silica gel is wet-crushed under alkalinity of pH 8.0 to 11.5 to obtain a solution containing particles composed of a deformed porous gel.
_{In step b, the SiO 2} concentration of the solution containing the particles of the irregularly shaped porous gel is adjusted to 1 to 10% by mass, the temperature is increased to 60 ° C. to 170 ° C., and the silicic acid solution is prepared under alkaline pH of 9 to 12.5. It is added continuously or intermittently to fill the pores of the particles made of the deformed porous gel by reaction with silicic acid to reduce the specific surface area of the particles and to grow the particles in a deformed state.
The method for producing deformed silica particles according to claim 1, wherein in step c, the solution containing the grown deformed silica particles is concentrated to recover the deformed silica particles.

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