JP5405024B2 - Colloidal silica composed of silica particles with ethylenediamine immobilized - Google Patents

Description

The present invention includes an ink-absorbing filler for printing paper and a spreadability improving agent for paints, a hydrophilic coating material on various material surfaces, a high-strength binder, a high-purity silica gel, a raw material for high-purity ceramics, a binder for catalysts, In particular, the present invention relates to colloidal silica useful for abrasives for electronic materials, and a method for producing the same.

With respect to colloidal silica produced using alkali metal silicate (mainly sodium silicate) as a raw material, many methods for obtaining colloidal silica having a low alkali metal content have been proposed. For example, Patent Document 1 describes that colloidal silica with less sodium can be obtained by using an active silicic acid aqueous solution of a water glass method and tetraalkylammonium hydroxide.
Even if sodium is removed by cation exchange from ordinary colloidal silica produced using water-silica activated silicic acid aqueous solution and sodium hydroxide, sodium present in the silica particles gradually elutes into the liquid phase. That is well known. Therefore, in Patent Document 2, after sodium is removed from colloidal silica by cation exchange, ammonia is added to make it alkaline, and it is treated in an autoclave at 98 to 150 ° C. to forcibly dispose sodium present in the silica particles. It describes a method of elution in the liquid phase and removal by cation exchange.

Many colloidal silicas composed of non-spherical silica particles have also been proposed. In Patent Document 3, elongated amorphous colloidal silica particles having a uniform thickness within a range of 5 to 40 millimicrons as observed by an electron microscope and extending only in one plane are dispersed in a liquid medium. A stable silica sol is described. Patent Document 4 describes a silica sol composed of elongated silica particles obtained by a production method in which a metal compound such as an aluminum salt is added before, during or after the addition of a silicic acid solution. Patent Document 5 describes colloidal silica composed of saddle-shaped silica particles having a major axis / minor axis ratio of 1.4 to 2.2 by hydrolysis of alkoxysilane. Patent Document 6 describes a colloidal containing non-spherical silica particles using a hydrolyzed solution of alkoxysilane instead of an active silicic acid aqueous solution of the water glass method, and using tetraalkylammonium hydroxide as an alkali. It is described that silica is obtained.

JP 2003-89786 A Japanese Patent Application Laid-Open No. 2004-189534 Japanese Patent Application Laid-Open No. 1-317115 Japanese Patent Laid-Open No. 4-187512 Japanese Patent Application Laid-Open No. 11-60232 JP-A-2001-48520 Claims and Examples

The colloidal silica described in Patent Document 1 is preferable in terms of a small amount of sodium, but in industrial production, there is much volatilization of tetraalkylammonium hydroxide by heating, and there is a problem in measures against odor. Since the production method of colloidal silica described in Patent Document 2 contains ammonia as an essential component, it will contain ammonia inside the particles, and its use is not limited,
There is a disadvantage in that the manufacturing process is not long and energy use is excessive.
In the production of colloidal silica described in Patent Document 3, there is a step of adding a water-soluble calcium salt, magnesium salt or a mixture thereof, and these remain as impurities in the product. In the production of colloidal silica described in Patent Document 4, there is a step of adding a water-soluble aluminum salt, and these remain as impurities in the product. The colloidal silica described in Patent Document 5 and Patent Document 6 is preferable because of high purity because alkoxysilane is used as a silica source, but there are disadvantageous aspects such as removal of by-produced alcohol and cost.

Accordingly, an object of the present invention is to provide a colloidal silica having a low alkali metal content and capable of being produced without using a metal compound other than silicon, and containing a non-spherical irregularly shaped particle group, and a method for producing the same.

As a result of intensive studies, the present inventors have been able to solve the above problems.
That is, the first invention of the present invention is colloidal silica having a silica / ethylenediamine molar ratio of 20 to 120 from silica particles in which ethylenediamine is immobilized inside the particles.
The second invention is a colloidal silica comprising silica particles in which ethylenediamine is immobilized by disposing a coating mainly composed of silica containing ethylenediamine on the surface, and having a silica / ethylenediamine molar ratio of 20 to 120. It is. Ethylenediamine is contained inside the silica particles and / or on the surface of the silica particles .

Both silica particles with ethylenediamine fixed inside the particles and silica particles with ethylenediamine fixed by disposing a coating mainly composed of silica containing ethylenediamine on the surface are referred to as “ethylenediamine fixed” below. Silica particles ”.
The third invention contains ethylenediamine, the major axis / minor axis ratio of the silica particles by observation with a transmission electron microscope is 1.5 to 15, and the average value of the major axis / minor axis ratio is 2.5 to This is colloidal silica having a non-spherical irregular particle group of 6, and a silica / ethylenediamine molar ratio of 20-120 . The alkali metal content is preferably 50 ppm or less per silica.
Moreover, it is preferable that the average minor axis | shaft by the transmission electron microscope observation of the silica particle of this colloidal silica is 5-30 nm, and the density | concentration of a silica is 10-50 weight% .

According to a fourth aspect of the present invention, an aqueous silicic acid solution is contacted with a cation exchange resin to prepare an aqueous active silicic acid solution. Next, ethylenediamine is added to the active silicic acid aqueous solution to make it alkaline, and then heated to form colloidal particles. Then, while maintaining the alkalinity under heating, a method for producing colloidal silica in which activated silica aqueous solution and ethylenediamine are added to grow particles.
In the following, the formation of colloidal particles and the growth of particles may be collectively referred to as “particle growth” or “growth”.

The manufacturing method of the said colloidal silica is substantially the same as the manufacturing method using the alkali metal hydroxide and alkali silicate which are the usual methods for an alkali agent. That is, the process for producing an active sol from sodium silicate is exactly the same, the only difference is that ethylenediamine is used as the alkali agent in the particle growth process, and the process is the same in the process of concentrating into a product.

By using the colloidal silica of the present invention, an ink-absorbing filler for printing paper, a spreadability improving agent for paints, a hydrophilic coating material on various material surfaces, a high-strength binder, a high-purity silica gel, and a high-purity ceramic Colloidal silica containing a non-spherical irregularly shaped particle group can be provided at low cost with a low content of alkali metals useful for raw materials, binders for catalysts, abrasives for electronic materials, and the like.

The present invention will be further described below.
The colloidal silica of the present invention is colloidal silica obtained using ethylenediamine as an alkali agent when particles of active silicic acid are grown using the alkali agent. For this reason, ethylenediamine has three forms: (1) a form fixed inside the particle during the particle growth process, (2) a form fixed on the particle surface after particle growth, and (3) a form dissolved in the liquid phase. Exists in form.
In the colloidal silica of the present invention, the major axis / minor axis ratio of silica particles by observation with a transmission electron microscope is 1.5 to 15, and the average value of the major axis / minor axis ratio is 2.5 to 6. It is a group of spherical irregular particles.

Colloidal silica contains ethylenediamine, a suitable range of which is a silica / ethylenediamine molar ratio of 20-120. It preferably contains ethylenediamine used in the colloidal particle growth step. In addition to the role as an alkaline agent for stabilizing the colloid, ethylenediamine has an important function. That is, when used as a ceramic or a binder for a catalyst, colloidal silica becomes a solid silica binder by drying, but ethylenediamine has an action of preventing the occurrence of cracks due to drying. Therefore, it is desirable to exist in the above range. Ethylenediamine is dissolved in the aqueous phase and decreases with water in the concentration step by ultrafiltration. When the molar ratio is insufficient, it is also preferable to replenish after the concentration.

However, the presence of organic matter may cause secondary problems in wastewater treatment. Considering such a case, a product from which ethylenediamine has been removed is also required. A method of reducing ethylenediamine as much as possible by effectively utilizing ultrafiltration is also included in the category as one of the production methods of the present invention. Even in that case, it is preferred that the silica / ethylenediamine molar ratio does not exceed 120. If it exceeds 50, the stability of the colloid decreases. Ethylenediamine is a weak base whose logarithmic value (pKa) of the reciprocal of the acid dissociation constant at 25 ° C. is 7.5 and 10.7, and must be used in a relatively large amount in order to make the pH higher than 8. More preferably, the silica / ethylenediamine molar ratio is 20-100.

For the same reason, a method in which ethylenediamine and a quaternary ammonium hydroxide that is a strong base are used in combination is also preferable. As the quaternary ammonium hydroxide, tetramethylammonium hydroxide, tetraethylammonium hydroxide, and trimethyl-2-hydroxyethylammonium hydroxide (also known as choline hydroxide) are preferable.

The alkali metal content per silica is 50 ppm or less. In applications such as ceramics, binders for catalysts, and abrasives for electronic materials, it is necessary to have this alkali metal content. More preferably, it is 30 ppm or less.
Colloidal silica that is a group of non-spherical irregularly shaped particles is a bent rod-like shape, and represents colloidal silica of particles having different shapes, and specifically has a shape as shown in FIG. Colloidal silica containing silica particles. The major axis / minor axis ratio is in the range of 1.5-15. Most of the particles are particles that do not extend linearly, and some particles do not extend. This is an example, and the shape varies depending on the manufacturing conditions, but most of them are non-spherical particles.

The silica particles of the colloidal silica of the present invention have a shape very similar to that of fumed silica. The silica particles of fumed silica are generally a group of elongated irregular particles having a major axis / minor axis ratio of 5 to 15. What is referred to as the primary particle size of fumed silica (sometimes simply referred to as the particle size) is the short diameter (thickness) of the primary particles and is usually 7 to 40 nm. Further, the particles are aggregated to form secondary particles, and the appearance of the slurry is white. For this reason, there are defects such as a problem that the particles settle when the slurry is left for a long time and a transparent film or coating film is not formed.

However, the silica particles of the present invention have a shape similar to the primary particles of fumed silica, but secondary particles are not formed by aggregation, and the appearance of the slurry is transparent or translucent. There is no problem that the particles settle, and a transparent film or coating film can be obtained.

The colloidal silica production method of the present invention is obtained by using an active silicic acid aqueous solution of a water glass method as a silica source and using ethylenediamine as an alkali agent, and a conventional alkali metal hydroxide is used in the colloidal particle growth step. Without using ethylenediamine.

First, as the alkali silicate aqueous solution used as a raw material, a sodium silicate aqueous solution usually called water glass (water glass No. 1 to No. 4 etc.) is preferably used. This is relatively inexpensive and can be easily obtained. Also, in semiconductor applications that dislike Na ions, an aqueous potassium silicate solution is suitable as a raw material. There is also a method of preparing an alkali silicate aqueous solution by dissolving a solid alkali metal silicate in water. Alkali metasilicates are produced through a crystallization process, and therefore some of them have few impurities. The aqueous alkali silicate solution is diluted with water as necessary.

The cation exchange resin used in the present invention can be appropriately selected from known ones and is not particularly limited. The contact step between the aqueous alkali silicate solution and the cation exchange resin is, for example, diluted with an aqueous alkali silicate aqueous solution to a silica concentration of 3 to 10% by weight, then contacted with an H-type strongly acidic cation exchange resin for dealkalization, and if necessary It can carry out by making it contact with OH type strong basic anion exchange resin, and carrying out a deanion. By this step, an active silicic acid aqueous solution is prepared. There have been various proposals for details of the contact conditions, and any known conditions can be adopted in the present invention.

Next, a colloidal particle growth step is performed. In this growth process, ethylene diamine is used instead of a conventional alkali metal hydroxide.
In the growth step, in addition to ethylenediamine, tetramethylammonium hydroxide, tetraethylammonium hydroxide, and choline hydroxide can be used in combination. These quaternary ammonium hydroxides are more basic than ethylenediamine and can be grown in a short time, which is an advantageous production method.

In this growth step, a conventional operation is performed. For example, for the growth of colloidal particles, ethylenediamine is added so that the pH is 8 or more, and heated to 60 to 240 ° C. to obtain particles of 5 to 20 nm. it can. There is also a method of taking a build-up method and adding activated silicic acid and ethylenediamine to a pH of 8 to 11 to a seed sol having a pH of 8 or higher and 60 to 240 ° C. In this way, particles having a silica particle size of 10 to 150 nm can be obtained.

Next, silica is concentrated, but concentration is performed by ultrafiltration. Although evaporation and concentration of water may be performed, ultrafiltration is more advantageous in terms of energy.

The ultrafiltration membrane used when concentrating silica by ultrafiltration will be described. In the separation to which the ultrafiltration membrane is applied, the target particle is 1 nm to several microns, but since the dissolved polymer substance is also targeted, the filtration accuracy is expressed by the fractional molecular weight in the nanometer range. In the present invention, an ultrafiltration membrane having a fractional molecular weight of 15000 or less can be preferably used. When a film in this range is used, particles of 1 nm or more can be separated. More preferably, an ultrafiltration membrane having a molecular weight cutoff of 3000 to 15000 is used. If the membrane is less than 3000, the filtration resistance is too large and the treatment time becomes long and uneconomical. If it exceeds 15000, the degree of purification is low. The material of the membrane includes polysulfone, polyacrylonitrile, sintered metal, ceramic, carbon and the like. Any of them can be used, but polysulfone is easy to use because of its heat resistance and filtration speed. There are spiral, tubular, and hollow fiber types that can be used, but the hollow fiber type is compact and easy to use. In addition, if the ultrafiltration step also serves to wash out and remove excess ethylenediamine, if necessary, it is further washed out by adding pure water even after reaching the target concentration, thereby increasing the removal rate. You can also do work. In this step, it is preferable to concentrate so that the silica concentration is 10 to 50% by weight.

Further, a purification step using an ion exchange resin can be added as needed before or after the ultrafiltration step. For example, non-immobilized ethylenediamine can be removed by contact with an H-type strongly acidic cation exchange resin, and purified by deanion by contacting with an OH-type strongly basic anion exchange resin. Purity can be measured.

As described above, colloidal silica containing ethylenediamine inside the silica particles and / or on the surface of the silica particles is obtained. The alkali metal content per silica is 50 ppm or less, and the silica particles have a non-spherical irregular particle group having a major axis / minor axis ratio of 1.5 to 15, and the silica concentration is 10 to 50% by weight. The colloidal silica of the present invention is obtained.

Hereinafter, the present invention will be described in more detail with reference to examples. The following apparatus was used for the measurement in the examples.
(1) TEM observation: Hitachi, Ltd., transmission electron microscope H-7500 type was used.
(2) BET specific surface area: Shimadzu Corporation, Flowsorb 2300 type was used.
(3) Total ethylenediamine analysis: Shimadzu Corporation, total organic carbon meter TOC-5000A, SSM-5000A were used. Converted to ethylenediamine from the amount of carbon. Specifically, the total organic carbon amount (TOC) was obtained by measuring TOC = TC-IC after measuring the total carbon amount (TC) and the inorganic carbon amount (IC). A glucose aqueous solution having a carbon content of 1% by weight was used as a standard for TC measurement, and sodium carbonate having a carbon content of 1% by weight was used as a standard for IC measurement. Calibration curves were prepared using ultrapure water as the standard with 0% by weight of carbon, using the standards shown above, with TC of 150 μl and 300 μl, and IC of 250 μl. In the TC measurement of the sample, about 100 mg of the sample was collected and burned in a 900 ° C. combustion furnace. In IC measurement, about 20 mg of a sample was collected, about 10 ml of (1 + 1) phosphoric acid was added, and the reaction was promoted in a 200 ° C. combustion furnace.
(4) Liquid phase ethylenediamine analysis: The liquid phase was taken out from the sample by ultrafiltration and measured by the same method as in (3) above.
(5) Calculation of immobilized ethylenediamine: The liquid ethylenediamine amount was subtracted from the total ethylenediamine amount to calculate the immobilized ethylenediamine amount.
(6) Metal element analysis: HORIBA, Ltd., ICP emission analyzer, ULTIMA2 was used.

Example 1
Silica was obtained by adding 5.2 kg of JIS No. 3 sodium silicate (SiO ₂ : 28.8 wt%, Na ₂ O: 9.7 wt%, H ₂ O: 61.5 wt%) to 28 kg of deionized water and mixing uniformly. Diluted sodium silicate having a concentration of 4.5% by weight was prepared. This dilute sodium silicate was passed through a 20 liter column of H-type strongly acidic cation exchange resin (Amberlite IR120B manufactured by Organo Co., Ltd.) regenerated with hydrochloric acid in advance to remove alkali, and the silica concentration was 3.7 wt% and the pH was 2.9. 40 kg of active silicic acid was obtained.
Separately, anhydrous ethylenediamine (reagent) was added to pure water to prepare a 10% ethylenediamine aqueous solution.
Next, the build-up method was taken to grow colloidal particles. That is, 16 g of a 10% aqueous ethylenediamine solution was added to 500 g of a part of the obtained active silicic acid with stirring to adjust the pH to 8.5, kept at 100 ° C. for 1 hour, and allowed to cool. The obtained liquid had a pH of 10.8 at 25 ° C., and was observed to be non-spherical silica having a minor axis of about 6 nm and a major axis / minor axis ratio of 1.5 to 15 when observed with a transmission electron microscope (TEM). It was colloidal silica composed of irregularly shaped particles. The colloidal silica was calculated to have a silica / ethylenediamine molar ratio of 28 based on the amounts of active silicic acid and ethylenediamine used.
Next, the colloidal silica was heated again to 98 ° C., and 600 g of active silicic acid was added over 8 hours. During the addition of the active silicic acid, the temperature was maintained at 98 ° C., and 6 g of 10% ethylenediamine aqueous solution was added on the way to maintain the pH of 9-10. After standing to cool by evaporation of water during addition, 560 g of colloidal silica was obtained. This colloidal silica has a pH of 9.7 at 25 ° C., a non-spherical silica irregular particle having a minor axis of about 10 nm and a major axis / minor axis ratio of 1.5 to 10 as observed with a transmission electron microscope (TEM). It was colloidal silica consisting of a group. The silica concentration was 6.7%.
Next, 600 g of pure water was added to the 560 g of colloidal silica for dilution, and then 7 kg of active silicic acid was added over 8 hours. During the addition, a 10% aqueous ethylenediamine solution was added to maintain the pH at 9 to 10, and the temperature was maintained at 98 ° C. After completion of the addition, the mixture was aged at 98 ° C. for 1 hour and allowed to cool. The added 10% ethylenediamine aqueous solution was 90 g. 7.46 kg of colloidal silica was obtained, and the pH was 9.7.
Subsequently, pressure filtration is performed by pump circulation using a hollow fiber type ultrafiltration membrane having a molecular weight cut off of 6000 (Microsa UF module SIP-1013 manufactured by Asahi Kasei Co., Ltd.) and concentrated to a silica concentration of 23% by weight. About 1.35 kg of colloidal silica was recovered. This colloidal silica has a particle diameter of 18.6 nm by the BET method, a non-spherical irregular particle group having a minor axis of about 20 nm and a major axis / minor axis ratio of 1.5 to 7 as observed with a transmission electron microscope (TEM). The average value of the major axis / minor axis ratio was 5. The total ethylenediamine content was 0.258% by weight and the silica / ethylenediamine molar ratio was 89. Since the liquid phase ethylenediamine was 0.053% by weight, the immobilized ethylenediamine was calculated to be 0.217% by weight. It was confirmed that most of the ethylenediamine was fixed to silica. Further, the contents of Na and K per silica were 10 ppm and 0 ppm, respectively. Colloidal silica with few alkali metal ions was obtained by using ethylenediamine. A TEM photograph of the silica particles is shown in FIG.

( Reference Example 1 )
In the same manner as in Example 1, 40 kg of active silicic acid having a silica concentration of 3.7 wt% and a pH of 2.9 was obtained. Separately, 34 g of diethylenediamine hexahydrate (reagent) was added to pure water to make a total amount of 190 g to prepare an 8% diethylenediamine aqueous solution.
To 500 g of active silicic acid, 30 g of 8% diethylenediamine aqueous solution was added with stirring to adjust the pH to 8.5, and after heating and maintaining at 100 ° C. for 1 hour, 2000 g of active silicic acid was added over 4 hours. During the addition, 8% diethylenediamine aqueous solution was added to maintain pH 9 to 10, and the temperature was kept at 100 ° C. After completion of the addition, the mixture was aged at 95 ° C. for 1 hour and allowed to cool. The added 8% diethylenediamine aqueous solution was 92 g. 2.39 kg of colloidal silica was obtained, and the pH was 9.98.
Subsequently, pressure filtration was performed by pump circulation using a hollow fiber type ultrafiltration membrane having a molecular weight cut off of 6000 (Microsa UF module SIP-1013 manufactured by Asahi Kasei Co., Ltd.), and a silica concentration of 17.5% by weight Until about 504 g of colloidal silica was recovered. This colloidal silica has a BET method particle size of 11.3 nm, a non-spherical irregular particle group having a minor axis of about 12 nm and a major axis / minor axis ratio of 1.5 to 7 as observed with a transmission electron microscope (TEM). In addition, the average value of the major axis / minor axis ratio was 3.5. The total content of diethylenediamine was 1.04% by weight and the silica / diethylenediamine molar ratio was 24. Since the liquid phase diethylenediamine was 0.12% by weight, the fixed diethylenediamine was calculated to be 0.94% by weight. It was confirmed that most of the diethylenediamine was fixed on the silica. Further, the contents of Na and K per silica were 15 ppm and 0 ppm, respectively. Colloidal silica with few alkali metal ions was obtained by using diethylenediamine. A TEM photograph of the silica particles is shown in FIG.

( Reference Example 2 )
In the same manner as in Example 1, 40 kg of active silicic acid having a silica concentration of 3.7 wt% and a pH of 2.9 was obtained. Separately, 34 g of diethylenediamine hexahydrate (reagent) was added to pure water to make a total amount of 190 g to prepare an 8% diethylenediamine aqueous solution.
To 500 g of active silicic acid, 30 g of 8% diethylenediamine aqueous solution was added with stirring to adjust the pH to 8.5, and after heating and maintaining at 100 ° C. for 1 hour, 9500 g of active silicic acid was added over 9 hours. During the addition, 8% diethylenediamine aqueous solution was added to maintain pH 9 to 10, and the temperature was maintained at 99 ° C. After completion of the addition, the mixture was aged at 99 ° C. for 1 hour and allowed to cool. The added 8% diethylenediamine aqueous solution was 152 g. 8.38 kg of colloidal silica was obtained, and the pH was 9.35.
Subsequently, pressure filtration was performed by pump circulation using a hollow fiber type ultrafiltration membrane having a molecular weight cut off of 6000 (Microsa UF module SIP-1013 manufactured by Asahi Kasei Co., Ltd.), and a silica concentration of 29.0% by weight. To about 1218 g of colloidal silica. This colloidal silica has a particle diameter by BET method of 24.6 nm, a non-spherical irregular particle group having a minor axis of about 25 nm and a major axis / minor axis ratio of 1.5 to 7 as observed with a transmission electron microscope (TEM). The average value of the major axis / minor axis ratio was 3. The total diethylenediamine content was 0.86% by weight and the silica / diethylenediamine molar ratio was 48. Since the liquid phase diethylenediamine was 0.12% by weight, the fixed diethylenediamine was calculated to be 0.77% by weight. It was confirmed that most of the diethylenediamine was fixed on the silica. Further, the contents of Na and K per silica were 8 ppm and 0 ppm, respectively. Colloidal silica with few alkali metal ions was obtained by using diethylenediamine. A TEM photograph of the silica particles is shown in FIG.

( Reference Example 3 )
In advance, about 2 g of 25% tetramethylammonium hydroxide aqueous solution was added to 10 kg of pure water and mixed to prepare a tetramethylammonium hydroxide aqueous solution having a pH of 10.8. Of the approximately 1218g of colloidal silica in silica concentration 29.0% by weight obtained in Example 3, after the pH of 1000g was diluted with 1000g of aqueous tetramethylammonium hydroxide solution 10.8, in Reference Example 2 Concentration by the same ultrafiltration as performed was performed to obtain a silica concentration of 29.0% by weight. Thus, diethylenediamine was removed by repeating dilution and concentration 10 times. In the finally obtained colloidal silica, no diethylenediamine could be detected in the liquid phase. The total content of diethylenediamine was 0.65% by weight, and the silica / diethylenediamine molar ratio was 64. Therefore, the immobilized diethylenediamine decreased from 0.77 wt% to 0.65 wt%, and the diethylenediamine immobilized on the silica particle surface was washed away with an aqueous tetramethylammonium hydroxide solution. As a result.

(Comparative Example 1)
Colloidal silica was prepared by the production method described in Japanese Patent Application Laid-Open No. 2003-89786 using a 20% tetramethylammonium hydroxide aqueous solution as an alkaline agent. This colloidal silica is a particle having a minor axis of about 16 nm, many spherical particles, a major axis / minor axis ratio of 1 to 4, and an average value of major axis / minor axis ratio of 1.8 in transmission electron microscope (TEM) observation. It was a group. The contents of Na and K per silica were 13 ppm and 0 ppm, respectively. By using tetramethylammonium hydroxide, colloidal silica with few metal ions was obtained, but particles having a target shape were not obtained. A TEM photograph of the silica particles is shown in FIG.

2 is a TEM photograph of colloidal silica obtained in Example 1. FIG. 2 is a TEM photograph of colloidal silica obtained in Reference Example 1 . 4 is a TEM photograph of colloidal silica obtained in Reference Example 2 . 4 is a TEM photograph of colloidal silica obtained in Comparative Example 1.

Claims (7)

Colloidal silica comprising silica particles in which ethylenediamine is immobilized inside the particles and having a silica / ethylenediamine molar ratio of 20 to 120 . Colloidal silica comprising silica particles having ethylenediamine immobilized by disposing on the surface a film mainly composed of silica containing ethylenediamine, and having a silica / ethylenediamine molar ratio of 20 to 120 . Non-spherical deformed particles containing ethylenediamine and having a major axis / minor axis ratio of 1.5 to 15 and an average ratio of major axis / minor axis ratio of 2.5 to 6 by observation with a transmission electron microscope Colloidal silica, characterized in that the molar ratio of silica / ethylenediamine is 20 to 120 . The colloidal silica according to any one of claims 1 to 3 , wherein an alkali metal content per silica is 50 ppm or less. The colloidal silica according to any one of claims 1 to 4, wherein the average minor axis of the silica particles by observation with a transmission electron microscope is 5 to 30 nm, and the concentration of silica is 10 to 50% by weight. The following step (a) a step of bringing an aqueous alkali silicate solution into contact with a cation exchange resin to prepare an active silicate aqueous solution,
(B) Next, after adding ethylenediamine to the active silicic acid aqueous solution to make it alkaline, heating to form colloidal particles,
(C) a step of growing colloidal particles by adding the active silicic acid aqueous solution and ethylenediamine while maintaining alkalinity to the colloidal particles formed in the previous step under heating conditions;
The method for producing colloidal silica according to any one of claims 1 to 5, wherein: (C) After step,
(D) a step of concentrating colloidal silica;
The method for producing colloidal silica according to claim 6 , comprising: