JP2013227177A - Colloidal silica and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a colloidal silica useful for an ink absorbing filler for printing papers, a spreading property improving agent for paint, a hydrophilic coating material for various material surfaces, a high strength binder, a high purity silica gel, a raw material for high purity ceramics, a binder for a catalyst, a polishing material for an electronic material and the like.SOLUTION: A colloidal silica is produced by using an active silicic acid as a raw material in the presence of polyvinyl pyrrolidone, and contains: polyvinyl pyrrolidone; and a group of non-spherical heteromorphic silica particles which has a major axis/minor axis ratio by a transmission electron microscope in the range of 1.2-15 and an average value of the major axis/minor axis ratio of 1.5-10. This can be produced by contacting an aqueous alkali silicate solution with a cation exchange resin to prepare an aqueous active silicic acid solution, thereafter adding polyvinyl pyrrolidone to the aqueous active silicic acid solution to be made alkaline, and then heating to form seed particles and subsequently growing up the particles by a buildup technique.

Description

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

  Many colloidal silicas composed of non-spherical silica particles have been proposed. In Patent Document 1, elongated amorphous colloidal silica particles having a uniform thickness within a range of 5 to 40 millimicrons by electron microscope observation and extending only in one plane are dispersed in a liquid medium. A stable silica sol is described. Patent Document 2 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 a silicic acid solution addition step. Patent Document 3 describes colloidal silica composed of bowl-shaped silica particles having a major axis / minor axis ratio of 1.4 to 2.2 by hydrolysis of alkoxysilane. In Patent Document 4, a hydrolyzed solution of alkoxysilane is used instead of an active silicic acid aqueous solution of the water glass method, a tetraalkylammonium hydroxide is used as an alkali, and a colloid containing non-spherical silica particles. It is described that silica is obtained.

On the other hand, polyvinylpyrrolidone: (C ₆ H ₉ NO) _n is a water-soluble polymer that is used in a large amount for adhesives and fiber processing. Products with a molecular weight of 10,000 to 700,000 are commercially available depending on the application.
Also in semiconductor polishing, polyvinylpyrrolidone has been introduced as an additive for improving the characteristics of the polished surface of a semiconductor substrate. There are a large number of patent documents describing polyvinyl pyrrolidone. To name a few, Patent Document 5 includes a description of blending polyvinyl pyrrolidone into an abrasive for a semiconductor having copper wiring. Patent Document 6 describes that a semiconductor aluminum film is polished with a slurry containing polyvinylpyrrolidone. Patent Document 7 describes that a silicon wafer is polished with colloidal silica containing polyvinylpyrrolidone. Below, polyvinylpyrrolidone may be described as PVP.

JP-A-1-317115 (Claims) JP-A-4-187512 (Claims and Examples 1 and 2) Japanese Patent Laid-Open No. 11-60232 (Claims and Examples 1 and 2) JP 2001-48520 A (Claims and Examples 1 to 3) JP 2006-310596 A (Claims and Embodiments 1 to 6) JP 2001-15461 A (Claims and Embodiments of the Invention) JP-A-63-272459 (Claims and Example 1)

The colloidal silica described in Patent Document 1 has a process of adding a water-soluble calcium salt, magnesium salt or a mixture thereof in the production thereof, and uses thereof are limited because they remain as impurities in the product. The colloidal silica described in Patent Document 2 has a step of adding a water-soluble aluminum salt in the production thereof, and uses thereof are limited because they remain as impurities in the product.
The colloidal silica described in Patent Document 3 and Patent Document 4 uses alkoxysilane as a silica source and is preferable because of its high purity, but has disadvantageous aspects such as removal of by-produced alcohol and cost.
In Patent Documents 5 to 7, no consideration is given to the shape of the silica particles.

  Accordingly, an object of the present invention is to provide a colloidal silica that can be produced without using a polyvalent metal compound other than silicon, and that includes a group of non-spherical irregularly shaped silica particles, and a method for producing the same.

  As a result of intensive studies, the present inventors have been able to obtain a novel colloidal silica and have also solved the above problems.

  That is, the present invention is colloidal silica produced using active silicic acid as a raw material in the presence of PVP, which contains PVP, and has a major axis / minor axis ratio in the range of 1.2 to 15 by observation with a transmission electron microscope. It is colloidal silica containing non-spherical irregularly shaped silica particles having an average value of the major axis / minor axis ratio of 1.5 to 10. 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%.

This colloidal silica production method comprises contacting an alkali silicate aqueous solution with a cation exchange resin to prepare an active silicic acid aqueous solution. Next, an alkali agent is added to make the mixture alkaline, and then heated to form seed particles. Subsequently, while maintaining the alkalinity under heating, an active silicic acid aqueous solution and an alkali agent are added to the seed particle colloid solution to form particles. A step of performing growth. An appropriate range is that the weight average molecular weight of PVP is 10,000 to 100,000.
In addition, both formation of seed particles and particle growth may be collectively referred to as “particle growth” or “growth” below. Further, the active silicic acid aqueous solution is hereinafter referred to as “active silicic acid”.

  The manufacturing method of the said colloidal silica is substantially the same as the manufacturing method which used the alkali metal hydroxide and alkali silicate which are the usual methods for the alkali agent. That is, the process for producing active silicic acid from sodium silicate is the same as that in the usual method, but the step of forming seed particles is different in that an alkaline agent is used in the presence of PVP. The step of concentrating the obtained colloidal silica is the same as the conventional method. The alkali agent may be an alkali metal hydroxide used in a conventional manner or an organic alkali.

  According to the present invention, an ink-absorbing filler for printing paper, a spreadability improving agent for paints, a hydrophilic coating material on the surface of various materials, a high-strength binder, a high-purity silica gel, a raw material for high-purity ceramics, a binder for catalysts, Colloidal silica useful as an abrasive for electronic materials can be provided at low cost.

2 is a TEM photograph of colloidal silica that has undergone the seed particle formation step of Example 1. FIG. 2 is a TEM photograph of colloidal silica obtained in Example 1. FIG. 4 is a TEM photograph of colloidal silica that has undergone the seed particle formation step of Example 2. FIG. 3 is a TEM photograph of colloidal silica obtained in Example 2. FIG. 4 is a TEM photograph of colloidal silica obtained in Comparative Example 1.

The present invention will be further described below.
The colloidal silica of the present invention is colloidal silica obtained by using an alkali agent in the presence of PVP when particles of active silicic acid are grown using an alkali agent, and the major axis / minor axis by observation with a transmission electron microscope. A non-spherical irregularly shaped silica particle group having a ratio in the range of 1.2 to 15 and an average value of the major axis / minor axis ratio of 1.5 to 10 is contained.
The major axis / minor axis ratio in the present invention is determined by assigning a scale to the obtained transmission electron micrograph of colloidal silica and, for 100 randomly selected silica particles, the longest side a and the shortest side b of the silica particles. , And using this value (a1, a2,..., A100 and b1, b2,..., B100), the major axis / minor axis ratio (a1 / b1, a2 / b2,... A100 / b100) is calculated, and the arithmetic average value of the five values on the minimum value side is set as the upper limit, and the arithmetic average value of the five values on the maximum value side is set as the lower limit. In addition, the average value of the major axis / minor axis ratio in the present invention refers to the longest side a of the silica particles for 100 randomly selected particles by assigning a scale to the obtained transmission electron micrograph of colloidal silica. The shortest side b of the silica particles is measured, and using this value (a1, a2, a3 to a100 and b1, b2, b3 to b100), the major axis / minor axis ratio (a1 / b1, a2 / a100 / b100) is calculated from b2, a3 / b3, and is an arithmetic average value of 90 points excluding 5 values on the maximum value side and the minimum value side.

  The colloidal silica of the present invention contains PVP. This PVP is used when forming seed particles. The aqueous solution of PVP has a slightly acidic or neutral pH and is not alkaline, so it does not contribute to particle growth. However, it affects the particle shape during particle growth. PVP seems to be bound or adsorbed on the surface of the growing silica particles to inhibit particle growth at the binding site and prevent spherical growth.

PVP is added to activated silica having a silica concentration of 3 to 5% by weight, and the concentration is preferably 20 to 200 ppm. Activated silicic acid is polymerized to form so-called “seed particles” when heated with an alkaline pH of 8 to 11, but if the concentration of PVP is 200 ppm or less, it becomes elongated irregular shaped silica particles. When the concentration of is higher than 200 ppm, the polymerization of the active silicic acid is inhibited more than necessary, and the seed particles are not enlarged and a large number of fine seed particles are generated. Most of the fine seed particles are spherical particles, and there are few elongated irregular shaped silica particles.
The concentration of PVP is preferably 20 ppm or more. If it is lower than 20 ppm, the effect is not clear and the presence of elongated irregularly shaped particles cannot be recognized. Therefore, it is desirable that PVP exists in the range of 20 to 200 ppm. More preferably, it exists in the range of 20-100 ppm. When the PVP used in the seed particle forming step is in the above range, the silica / PVP weight ratio in the obtained colloidal silica is 1000 to 100,000.
As PVP used by this invention, what has the weight average molecular weight of 10,000-100,000 is preferable from the point of the shape control and productivity of a silica particle. When the weight average molecular weight of PVP is less than 10,000, the effect of controlling the shape of the silica particles is small. If the weight average molecular weight of PVP is greater than 100,000, viscosity may increase and subsequent ultrafiltration may be difficult.

  Colloidal silica containing non-spherical irregularly shaped silica particles is a colloidal silica having a shape like a spider or a bent rod-like shape like a hookworm, and containing silica particles with different shapes. . Specifically, it is colloidal silica containing silica particles having a shape as shown in FIGS. The major axis / minor axis ratio is in the range of 1.2-15. Some of the silica particles are nearly spherical, but most of them are non-spherical particles. The silica particles shown in FIG. 1 to FIG. 4 are examples, and the shape varies depending on the production conditions, but particles that are not truly spherical occupy the majority.

  The method for producing colloidal silica of the present invention is characterized in that the above-mentioned alkaline agent is used in the presence of PVP, using activated silica in the water glass method as a silica source. In the seed particle formation process, the presence of PVP is indispensable. On the other hand, in the colloidal particle growth process, since the PVP added in the previous process remains in the liquid phase, the particle growth is performed by adding only the alkali metal hydroxide or the organic alkali compound used in the usual method. be able to.

  First, as the alkali silicate aqueous solution used as a raw material, usually a sodium silicate aqueous solution called water glass (water glass No. 1 to No. 4 etc.) is preferably used. This is relatively inexpensive and can be easily obtained. Moreover, it is preferable to use potassium silicate aqueous solution as a raw material for the semiconductor use which dislikes Na ion. 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, active silicic acid 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, seed particles are formed. In this seed particle forming step, ordinary operations are performed except that PVP is added to the active silicic acid. For example, PVP is added to activated silicic acid in such an amount that the concentration of PVP is 20 to 200 ppm, then an alkali agent is added, the pH is set to 8 or more, and heating is performed at 60 to 240 ° C. to form seed particles. Either of the PVP and the alkaline agent may be added first.

  In the particle growth step, silica particles are grown by adding active silicic acid and an alkaline agent to a seed particle colloid solution having a pH of 8 or higher and a temperature of 60 to 240 ° C. so that the pH is 8 to 11. In this way, the average minor axis of the silica particles is preferably 5 to 30 nm.

  As the alkali agent used in the seed particle formation step and the particle growth step, an alkali metal hydroxide such as sodium hydroxide is the easiest material. When alkali metals are not preferred, nitrogen-containing organic alkali compounds such as amines and quaternary ammonium hydroxide can be used. As the amines, tertiary amines such as triethanolamine having low volatility, secondary amines such as piperazine, and aliphatic amines such as ethylenediamine can be used. Examples of the quaternary ammonium hydroxide include tetramethylammonium hydroxide, tetraethylammonium hydroxide, and trimethyl-2-hydroxyethylammonium hydroxide (also known as choline hydroxide).

  By using the above nitrogen-containing organic alkali compound, the alkali metal content per silica can be 50 ppm or less. In the use of ceramics, a binder for catalysts, an abrasive for electronic materials, and the like, it is preferable that the alkali metal content is about this level. More preferably, it is 30 ppm or less.

  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, etc., any of which can be used. Polysulfone membranes are easy to use in terms of heat resistance and filtration speed. The shape of the membrane includes a spiral type, a tubular type, a hollow fiber type and the like, and any of them can be used, but the hollow fiber type is compact and easy to use. It is good to concentrate so that the density | concentration of a silica may be 5 to 50 weight% at this process.

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-2700 type was used.
(2) BET specific surface area: Yuasa Ionics Co., Ltd., NOVA-4200e type was used.
(3) PVP analysis: Shimadzu Corporation, Total Organic Carbon Meter TOC-V _CPH, and Solid Sample Combustor SSM-5000A were used. It converted into PVP from the total amount of organic carbon. Specifically, after measuring the total carbon content (TC) and the inorganic carbon content (IC), the total organic carbon content (TOC) was determined by TOC = TC-IC. The IC component is estimated to be carbon dioxide absorbed from the atmosphere.
For the measurement of PVP in colloidal silica, Shimadzu Corporation, Total Organic Carbon Meter TOC-V _CPH, and Solid Sample Combustor SSM-5000A were used. A glucose aqueous solution having a carbon content of 0.02 wt% was used as a standard for TC measurement, and a sodium carbonate aqueous solution having a carbon content of 0.02 wt% was used as a standard for IC measurement. A calibration curve was prepared using ultrapure water as a standard with a carbon content of 0% by weight, using the above-mentioned standards, TC of 125 μl and 250 μl, and IC of 100 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 100 mg of a sample was collected, about 0.5 ml of (1 + 1) phosphoric acid was added, and the reaction was accelerated in a 200 ° C. combustion furnace.
In addition, for the measurement of PVP in the liquid phase of colloidal silica, a small sample of colloidal silica was ultrafiltered to measure PVP in the filtrate. For the measurement, Shimadzu Corporation, Total Organic Carbon Meter TOC-V _CPH was used. As standard for TC measurement, a calibration curve was prepared using 32 μl each of an aqueous solution of potassium hydrogen phthalate having a carbon content of 1 × 10 ⁻³ wt%, a carbon content of 5 × 10 ⁻⁴ wt% and a carbon content of 0 wt%. did. As a standard for IC measurement, 40 μl each of a mixed aqueous solution of sodium hydrogen carbonate and sodium carbonate having a carbon content of 1 × 10 ⁻³ wt% and a carbon content of 5 × 10 ⁻⁴ wt% and ultrapure water having a carbon content of 0 wt% was used. A calibration curve was created. In the TC measurement of the sample, 32 μl of the sample was used and burned in a 680 ° C. combustion tube. In IC measurement, 40 μl of the sample was used and reacted with (1 + 1) phosphoric acid.

[Example 1]
(A) Preparation of active silicic acid aqueous solution deionized water 28kg No. 3 sodium silicate _(SiO 2: 28.8 _wt%, Na 2 O: 9.7 _wt%, H 2 O: 61.5 wt%) 5.2 kg Was added and mixed uniformly to prepare diluted sodium silicate having a silica concentration of 4.5% by weight. This diluted sodium silicate was passed through a 20 liter column of H-type strongly acidic cation exchange resin (Amberlite (registered trademark) IR120B manufactured by Organo Corp.) regenerated with hydrochloric acid in advance, and the silica concentration was 3.7% by weight. 40 kg of active silicic acid having a pH of 2.9 was obtained.

(B) Formation of seed particles PVP (reagent, powder, weight average molecular weight of about 40000) was previously dissolved in pure water to prepare a 10 wt% PVP aqueous solution. Next, to 1 kg of the obtained active silicic acid, an amount of PVP aqueous solution with a PVP concentration of 30 ppm was added with stirring, and then a 5 wt% aqueous sodium hydroxide solution was added to adjust the pH to 8.2. For 1 hour and allowed to cool. The obtained liquid was 950 g by evaporation of water, and the silica concentration was 3.9% by weight. In addition, the pH at 25 ° C. is 9.0, the average minor axis is about 7 nm and the major axis / minor axis ratio is in the range of 2 to 10 and the major axis / minor axis is observed in a transmission electron microscope (hereinafter referred to as TEM). It contained non-spherical irregularly shaped silica particles having an average minor axis ratio of 5. A TEM photograph is shown in FIG.
In this colloidal silica, the weight ratio of silica / PVP was calculated to be about 1200 from the amount of active silicic acid used and the amount of PVP used.

(C) Growth of silica particles A 5 wt% aqueous sodium hydroxide solution was added to the colloidal silica obtained above to adjust the pH to 9.5, heated again to 100 ° C, and a build-up method was taken. Activated silicic acid was added over 5 hours. During the addition of activated silicic acid, the temperature was maintained at 100 ° C., and a 5 wt% aqueous sodium hydroxide solution was added simultaneously to maintain pH 9-10. After cooling by evaporation of water during addition, 5.8 kg of colloidal silica was obtained. The silica concentration was 5.1% by weight. This colloidal silica has a pH of 9.6 at 25 ° C., an average minor axis of about 15 nm, a major axis / minor axis ratio in the range of 1.2 to 3 and a major axis / minor axis ratio of TEM observation. It contained non-spherical irregularly shaped silica particles having an average value of 1.5. A TEM photograph is shown in FIG. The particle diameter in terms of specific surface area by BET method was 17 nm.
In this colloidal silica, the weight ratio of silica / PVP was calculated to be about 9900 from the amount of active silicic acid used and the amount of PVP used.

(D) Concentration of silica The colloidal silica obtained above was concentrated. Using a hollow fiber type ultrafiltration membrane having a molecular weight cut off of 6,000 (Microsa (registered trademark) UF module SIP-1013 manufactured by Asahi Kasei Co., Ltd.), pressure filtration is performed by pump circulation and a silica concentration of 30. Concentrated to 1% by weight to recover about 980 g of colloidal silica. This colloidal silica has a pH of 9.5 at 25 ° C., an average minor axis of about 15 nm, a major axis / minor axis ratio in the range of 1.2 to 3 and a major axis / minor axis ratio of TEM observation. It contained non-spherical irregularly shaped silica particles having an average value of 1.5. Further, since the PVP concentration in the filtrate was 3 ppm, the colloidal silica was calculated to have a silica / PVP weight ratio of about 97000 from the silica concentration of 30.1% by weight and the analysis value of PVP.

[Example 2]
To 1 kg of a part of the same active silicic acid as used in Example 1, an amount of 10 wt% PVP aqueous solution with a PVP concentration of 100 ppm was added with stirring, and then 5 wt% aqueous sodium hydroxide solution was added to adjust the pH. 8.2, kept at 100 ° C. for 1 hour, and allowed to cool. The obtained liquid had a pH of 9.9 at 25 ° C., an average minor axis of about 5 nm in TEM observation, a major axis / minor axis ratio in the range of 2 to 7, and an average of the major axis / minor axis ratio. It contained a non-spherical irregularly shaped silica particle group having a value of 4. A TEM photograph is shown in FIG.
The resulting colloidal silica was then heated again to 100 ° C. and 7 kg of active silicic acid was added over 7 hours. During the addition of activated silicic acid, the temperature was maintained at 100 ° C., and a 5 wt% aqueous sodium hydroxide solution was added simultaneously to maintain pH 9-10. After cooling by evaporation of water during addition, 5.8 kg of colloidal silica was obtained. This colloidal silica has a pH of 9.5 at 25 ° C., an average minor axis of about 10 nm, a major axis / minor axis ratio in the range of 1.2 to 5 and a major axis / minor axis ratio of TEM observation. It contained a non-spherical irregularly shaped silica particle group having an average value of 2. A TEM photograph is shown in FIG.
Subsequently, the obtained colloidal silica was concentrated. Using the same hollow fiber type ultrafiltration membrane as that used in Example 1, pressure filtration by pump circulation was performed to concentrate the silica concentration to 20.1% by weight, and about 1.47 kg of colloidal silica was recovered. . This colloidal silica has a pH of 9.1 at 25 ° C., an average minor axis of about 10 nm in TEM observation, a major axis / minor axis ratio in the range of 1.2 to 5, and a major axis / minor axis ratio. It contained a non-spherical irregularly shaped silica particle group having an average value of 2. Further, since the PVP concentration in the filtrate was 12 ppm, this colloidal silica had a silica concentration of 20.1% by weight and an analysis value of PVP, the weight ratio of silica / PVP was 20900.

[Comparative Example 1]
Colloidal silica was produced under the same conditions as in Example 1 except that the amount of PVP added in Example 1 was changed to an amount that resulted in a PVP concentration of 1000 ppm. A TEM photograph is shown in FIG. A large number of fine seed particles are generated without increasing the seed particles. Most of the fine seed particles are spherical particles, and there are few elongated irregular particles.

Claims (5)

  Colloidal silica produced from activated silicic acid as a raw material in the presence of polyvinyl pyrrolidone, containing polyvinyl pyrrolidone, having a major axis / minor axis ratio in the range of 1.2 to 15 by observation with a transmission electron microscope and a major axis / A colloidal silica comprising a group of non-spherical irregularly shaped silica particles having an average minor axis ratio of 1.5 to 10.   The colloidal silica according to claim 1, 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 5 to 50% by weight. The following steps: (a) A step of bringing an alkali silicate aqueous solution into contact with a cation exchange resin to prepare an active silicate aqueous solution;
(B) Next, polyvinylpyrrolidone is added to the active silicic acid aqueous solution in an amount such that the concentration of polyvinylpyrrolidone is 20 to 200 ppm, and then alkalinized by adding an alkali agent, and then heated to form seed particles; and 2. The method according to claim 1, further comprising the step of growing seed particles by adding an active silicic acid aqueous solution and an alkaline agent to the colloid liquid of seed particles formed in the previous step under heating conditions. A method for producing colloidal silica.   The method for producing colloidal silica according to claim 3, further comprising (d) a step of concentrating silica after the step (c).   The method for producing colloidal silica according to claim 3 or 4, wherein the polyvinyl pyrrolidone has a weight average molecular weight of 10,000 to 100,000.

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