JP2009184858A - Colloidal silica composed of silica particles with fixed hydrazine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a colloidal silica useful for an ink absorbing filler for printing paper and a spreading property improving agent for paint, a hydrophilic coating material on various material surfaces, a strong binder, and further a high purity silica gel, a raw material of high purity ceramics, a binder for a catalyst, a polishing material for electronic material and the like. <P>SOLUTION: The colloidal silica comprises groups of non-spherical heteromorphic particles having a major axis/minor axis ratio of a silica particle of 1.5-15, and an average value of the major axis/minor axis ratio of 2.5-6. This can be manufactured by contacting an aqueous alkali silicate solution with a cation exchange resin to prepare an aqueous active silicic acid solution, thereafter adding hydrazine to the aqueous active silicic acid solution, and heating to grow crystals by a buildup method. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

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 polishing materials for electronic materials, resist stripping / polishing materials, and the like, 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 JP-A-1-317115 Patent Claim Japanese Patent Laid-Open No. 4-187512 Japanese Patent Application Laid-Open No. 11-60232 Japanese Patent Application Laid-Open No. 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 a problem that the price of tetraalkylammonium hydroxide is high. 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 comprising silica particles in which hydrazine is immobilized inside the particles.
Moreover, 2nd invention is colloidal silica which consists of a silica particle by which the hydrazine was fix | immobilized by distribute | arranging the film which has a silica which contains hydrazine as a main component on the surface. Hydrazine is contained inside the silica particles and / or on the surface of the silica particles.

Note that both silica particles with hydrazine immobilized inside the particles and silica particles with hydrazine immobilized by arranging a coating containing hydrazine-containing silica as the main component on the surface are referred to as “hydrazine fixed Silica particles ”.
The third invention contains hydrazine, 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 6 is colloidal silica that is a non-spherical irregularly shaped particle group. 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%.
Furthermore, the colloidal silica contains hydrazine, a suitable range of which is a silica / hydrazine molar ratio of 5-30.

According to a fourth aspect of the present invention, an aqueous silicic acid solution is brought into contact with a cation exchange resin to prepare an active silicic acid aqueous solution, then hydrazine is added to the active silicic acid aqueous solution to make it alkaline, and then heated to form colloidal particles. This is a method for producing colloidal silica in which particle growth is performed by adding an aqueous active silicic acid solution and hydrazine while maintaining alkalinity under heating.
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 hydrazine is used as an alkaline 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 The content of alkali metals useful for raw materials, catalyst binders, abrasives for electronic materials, resist stripping / abrasives, etc. is small, and colloidal silica containing non-spherical irregularly shaped particles can be provided at low cost.

The present invention will be further described below.
The colloidal silica of the present invention is colloidal silica obtained by using hydrazine as an alkaline agent when particles of active silicic acid are grown using the alkaline agent. For this reason, hydrazine 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 hydrazine, a suitable range of which is a silica / hydrazine molar ratio of 5-30. It preferably contains hydrazine used in the colloidal particle growth step. Hydrazine present dissolved in the aqueous phase decreases with water in the concentration step by ultrafiltration. Therefore, as the silica concentration by ultrafiltration proceeds, the silica / hydrazine molar ratio increases. When the molar ratio is less than the expected value, it is also preferable to add and replenish after concentration.

However, since hydrazine is a harmful substance to the environment, secondary problems may occur in wastewater treatment. Considering such a case, a product from which hydrazine has been removed is also required. A method of effectively using ultrafiltration to reduce hydrazine as much as possible is also included in the category as one of the production methods of the present invention. Even in that case, it is preferable that the molar ratio of silica / hydrazine does not exceed 30. If it exceeds 30, the stability of the colloid decreases. After adding hydrazine to the activated silicic acid aqueous solution to make it alkaline, the colloidal particles are grown by heating, but the pH needs to be 8 or more. Although hydrazine is a strong reducing agent, it has a pKa of about 8 as a base and is a weak base. Therefore, in order to make the pH higher than 8, it must be used in a relatively large amount. More preferably, the silica / hydrazine molar ratio is 5-25.

In consideration of the harmfulness of hydrazine, it is also preferable to use a minimum amount of hydrazine necessary for modifying the particle shape of silica and to use a tetraalkylammonium hydroxide in combination with other alkali agents. As the tetraalkylammonium 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, which is a group of non-spherical irregularly shaped particles, is a worm-like or bent rod-like shape and represents colloidal silica of particles having different shapes. Specifically, FIG. 1 and FIG. Colloidal silica containing silica particles of the shape shown. 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 hydrazine as an alkaline agent, and a conventional alkali metal hydroxide is used in the growth process of colloidal particles. Without using hydrazine.

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 step, hydrazine is used instead of a conventional alkali metal hydroxide.
In the growth step, in addition to hydrazine, tetramethylammonium hydroxide, tetraethylammonium hydroxide, and choline hydroxide can be used in combination. These tetraalkylammonium hydroxides are less harmful to the environment than hydrazine and are advantageous because the hydrazine content can be reduced.

In this growth step, conventional operations are performed. For example, for the growth of colloidal particles, hydrazine 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. Further, there is a method of taking a build-up method and adding active silicic acid and hydrazine to a pH of 8 to 11 to a seed sol having a pH of 8 or more 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, when the ultrafiltration process also serves to wash out and remove excess hydrazine, if necessary, it is further washed out by adding pure water after reaching the target concentration to increase 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, hydrazine that has not been immobilized can be removed by contacting 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 hydrazine 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) Hydrazine analysis: Shimadzu Corporation, absorptiometer UV-VISIBLERECORDING SPECTROTOPHOTERTER UV-160 was used. Measurement was carried out by p-dimethylaminobenzaldehyde spectrophotometry described in JIS B8224. Specifically, the absorbance of a yellow compound produced by acidifying the sample with hydrochloric acid and adding p-dimethylbenzaldehyde was measured to quantify hydrazine ions. The hydrazine concentration was calculated from the obtained hydrazine ion value.
(4) Metal element analysis: HORIBA, Ltd., ICP emission spectrometer, ULTIMA2 was used.

(Example 1)
JIS No. 3 sodium silicate (SiO ₂ : 28.8 wt%, Na ₂ O: 9.7 wt%, H ₂ O: 61.5 wt%) is added to 2.1 kg of deionized water and mixed uniformly. A diluted sodium silicate having a silica 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% by weight and the pH was 2.9. 2.7 kg of active silicic acid was obtained.
Separately, hydrazine (hydrated hydrazine, N2H4 · H2O reagent) was added to pure water to prepare a 5.1% hydrazine aqueous solution.
Next, the build-up method was taken to grow colloidal particles. That is, 24 g of a 5.1% hydrazine aqueous solution was added to 800 g of a part of the obtained active silicic acid with stirring to adjust the pH to 8.2, kept at 100 ° C. for 1 hour, and allowed to cool. This solution had a pH of 8.7, and a 5.1% hydrazine solution was added to this solution to adjust the pH to 9.2. The silica concentration of the obtained solution was 3.5% by weight. Further, the BET particle diameter is 6.0 nm, and a transmission electron microscope (TEM) observation shows a group of irregular particles of non-spherical silica having a minor axis of about 6 nm and a major axis / minor axis ratio of 1.5 to 15. The average value of the major axis / minor axis ratio was 6. A TEM photograph of the silica particles is shown in FIG.
In this colloidal silica, the molar ratio of silica / hydrazine was calculated to be 5.3 from the amounts of active silicic acid and hydrazine used. The total content of hydrazine was 0.34% by weight, and the hydrazine concentration in the liquid phase was measured with a filtrate obtained by pressure filtration, and found to be 0.29% by weight. Therefore, the hydrazine fixed to the silica particles was calculated to be 0.06% by weight.

(Example 2)
In the same manner as in Example 1, about 5 kg of active silicic acid having a silica concentration of 3.7% by weight and a pH of 2.9 was obtained.
Separately, hydrazine (hydrated hydrazine, N2H4 · H2O reagent) was added to pure water to prepare a 2.6% hydrazine aqueous solution.
The colloidal silica obtained in Example 1 was heated again to 100 ° C., and 4.2 kg of active silicic acid was added over 3.8 hours. During the addition of active silicic acid, the temperature was maintained at 100 ° C., and a 2.6% hydrazine aqueous solution was simultaneously added to maintain pH 9-10. The 2.6% hydrazine aqueous solution used in the simultaneous addition was 0.57 kg. This colloidal silica has a pH of 9.2 at 25 ° C., a BET particle diameter of 12 nm, a short axis of about 12 nm as observed with a transmission electron microscope (TEM), and a long axis / short axis ratio of 1.5 to The colloidal silica was composed of 10 non-spherical silica irregularly shaped particles.
Subsequently, pressure filtration 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 concentration to a silica concentration of 18% by weight is performed. About 970 g of colloidal silica was recovered. This colloidal silica has a pH of 8.6 at 25 ° C., a non-spherical deformed particle group having a minor axis of about 12 nm and a major axis / minor axis ratio of 1.5 to 10 as observed with a transmission electron microscope (TEM). The average value of the major axis / minor axis ratio was 3.5.
The total content of hydrazine was 0.64% by weight, and the silica / hydrazine molar ratio was 15. It was 0.50 weight% when the hydrazine density | concentration in the filtrate by pressure filtration was measured. Therefore, the hydrazine immobilized on the silica particles was calculated to be 0.23% by weight. Further, the contents of Na and K per silica were 2 ppm and 0 ppm, respectively. Colloidal silica with few alkali metal ions was obtained by using hydrazine. A TEM photograph of the silica particles is shown in FIG.

(Example 3)
A part of the colloidal silica obtained in Example 2 was further subjected to ultrafiltration, and concentrated to a silica concentration of 30% by weight. The total content of hydrazine in the obtained colloidal silica was 0.73% by weight, and the silica / hydrazine molar ratio was 22. When the hydrazine concentration in the liquid phase was measured, it was 0.50% by weight. Therefore, the hydrazine fixed to the silica particles was calculated to be 0.38% by weight.

2 is a TEM photograph of colloidal silica obtained in Example 1. FIG. 3 is a TEM photograph of colloidal silica obtained in Example 2. FIG.

Claims (8)

Colloidal silica comprising silica particles in which hydrazine is immobilized inside the particles. Colloidal silica comprising silica particles in which hydrazine is immobilized by disposing a coating containing hydrazine-containing silica as a main component on the surface. Non-spherical deformed particles containing hydrazine and having a major axis / minor axis ratio of 1.5 to 15 and an average value of the major axis / minor axis ratio of 2.5 to 6 by observation with a transmission electron microscope Colloidal silica characterized by being a group. 4. The colloidal silica according to claim 1, wherein the molar ratio of silica / hydrazine is 5-30. The colloidal silica according to claim 1, wherein the alkali metal content per silica is 50 ppm or less. The colloidal silica according to any one of claims 1 to 5, wherein an average minor axis of silica particles by observation with a transmission electron microscope is 5 to 30 nm, and a 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 hydrazine to the activated silicic acid aqueous solution to make it alkaline, heating to form colloidal particles,
(C) a step of growing the colloidal particles by adding the active silicic acid aqueous solution and hydrazine while maintaining alkalinity to the colloidal particles formed in the previous step under heating conditions;
The method for producing colloidal silica according to claim 1, comprising: (C) After step,
(D) a step of concentrating colloidal silica;
The method for producing colloidal silica according to claim 7, comprising: