JP5341613B2 - Colloidal silica and method for producing the same - Google Patents

Description

  The present invention relates to colloidal silica useful for ink-absorbing fillers for printing paper, paint spreadability improvers, hydrophilic coating materials on various material surfaces, high-strength binders, binders for catalysts, abrasives for electronic materials, and the like. It relates to the manufacturing method.

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 obtained 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. Patent Document 5 describes a silicon wafer abrasive comprising catechol, ethylenediamine and colloidal silica.
Patent Documents 6 to 8 describe that catechol is blended as a component of a resist remover, a cleaning agent, an etching agent, and the like of a semiconductor wafer and functions as an anticorrosive agent on the metal surface by reaction with the metal surface. Yes.

JP-A-1-317115 (Claims) Japanese Patent Laid-Open No. 4-187512 Japanese Patent Laid-Open No. 11-60232 (Claims) JP 2001-48520 A (Claims and Examples) JP-A-8-339980 (Claims) Japanese Patent Laid-Open No. 7-325404 (Claims) JP 2002-296804 A (Claims and Examples) JP 2007-503115 A (Claims and Examples)

  Since the colloidal silica described in Patent Document 1 includes a step of adding a water-soluble calcium salt, magnesium salt or a mixture thereof in the production process, they remain as impurities in the product. The colloidal silica described in Patent Document 2 includes a step of adding a water-soluble aluminum salt in the production process, and these remain as impurities in the product. Since the colloidal silica described in Patent Documents 3 and 4 uses alkoxysilane as a silica source, the product has high purity, but a recovery process for the by-produced alcohol is required, and the price of the alkoxysilane itself is high. There is a problem. As described in Patent Documents 5 to 8, many catechol uses have been proposed for semiconductors, but there is no description regarding the production of colloidal silica.

  Therefore, the object of the present invention is obtained by a method for producing colloidal silica containing non-spherical irregularly shaped silica particles without using a metal compound other than silicon such as calcium salt, magnesium salt, and aluminum salt, and the production method thereof. It is providing the colloidal silica which can be obtained.

As a result of intensive studies, the present inventors have been able to solve the above problems.
That is, the present invention is a colloidal silica produced using activated silicic acid as a raw material in the presence of catechol, which contains catechol and has a major axis / minor axis ratio of 1.2 to 10 by observation with a transmission electron microscope. This is colloidal silica containing a group of irregular shaped silica particles. The colloidal silica, the molar ratio of silica / catechol Ru der 20 to 700.

  The colloidal silica preferably has an average minor axis of silica particles of 5 to 30 nm and a silica concentration of 10 to 50% by weight as observed with a transmission electron microscope.

The production method of this colloidal silica includes 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) a step of adding catechol and an alkaline agent to the activated silicic acid aqueous solution to make it alkaline, and then heating to form silica particles, and (c) subsequently, while maintaining alkalinity under the heating conditions, There is a step of growing silica particles by adding an aqueous silicic acid solution and an alkali agent, or adding an aqueous active silicic acid solution, an alkali agent and catechol.
Moreover, it is preferable that this manufacturing method of colloidal silica further has the process of concentrating a silica after (c) process.

  The production method of the colloidal silica is substantially the same as the production method of colloidal silica using an alkali metal hydroxide or alkali silicate as an alkali agent, which is a conventional method. That is, in the above-mentioned colloidal silica production method, the process of producing an active silicic acid aqueous solution from sodium silicate is the same as that of a conventional method, except that catechol and an alkali agent are used in the silica particle formation process. In the silica particle growth step, catechol may or may not be added. The step of concentrating the obtained colloidal silica is the same as the conventional method.

  INDUSTRIAL APPLICABILITY According to the present invention, colloidal useful as an ink-absorbing filler for printing paper, a paint spreadability improving agent, a hydrophilic coating material on various material surfaces, a high-strength binder, a binder for a catalyst, an abrasive for electronic materials, and the like. Silica can be provided at low cost.

2 is a TEM photograph of colloidal silica that has undergone the silica particle forming step of Example 1. FIG. 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. 4 is a TEM photograph of colloidal silica obtained in Comparative Example 1 without adding catechol.

The present invention will be further described below.
The colloidal silica of the present invention is produced using activated silicic acid as a raw material in the presence of catechol. Since the bond between catechol and silica is strong, catechol is present in two forms: a form fixed on and / or on the surface of silica particles and a form dissolved in a liquid phase through the process of silica particle formation and growth. doing.
Moreover, the colloidal silica of this invention contains the nonspherical irregular-shaped silica particle group whose major axis / minor axis ratio is 1.2-10 by transmission electron microscope observation. The major axis / minor axis ratio in the present invention refers to the longest side a and the shortest side b of the silica particles of 100 randomly selected silica particles obtained by assigning a scale to the obtained transmission electron micrograph of colloidal silica. And using these values (a1, a2,..., A100 and b1, b2,..., B100), the major axis / minor axis ratio (a1 / b1, a2 / b2,. ... A100 / b100) is an arithmetic average value of 90 points excluding 5 points on the maximum value side and the minimum value side.

Catechol (catechol, C ₆ H ₆ O ₂ ) is a kind of phenols, which is an organic compound having two hydroxy groups in the ortho position on the benzene ring, also known as pyrocatechol, pyrocatechin, o-dihydroxybenzene. is there.
Catechol is a unique organic compound that forms a strong bond with silica and has been used for analysis of silica. It is surmised that the specific properties of the catechol affect the formation and growth of silica particles. The reaction product of silica and catechol develops in a dark brown hue. The liquid phase part of the colloidal liquid develops color mainly because the reaction product of silica molecules and catechol is dissolved in the colloidal liquid. Furthermore, from the results of instrumental analysis, it is presumed that in the colloidal silica of the present invention, some catechol is immobilized inside and / or on the surface of the silica particles.

The colloidal silica of the present invention contains catechol, and the preferred molar ratio of silica / catechol is 20-60. A 1% aqueous solution of catechol has a pH of about 4.8 and is not alkaline, so it does not contribute to particle growth itself. However, it affects the particle shape during particle growth. Catechol binds to the surface of the growing silica particles and appears to inhibit particle growth at the binding site and prevent spherical growth. When the silica / catechol molar ratio is less than 20, the particle growth may be excessively inhibited to generate a silica gel. On the other hand, if the silica / catechol molar ratio is larger than 60, the effect of adding catechol may not be sufficiently obtained, resulting in spherical particles. However, the silica / catechol molar ratio here is based on the amount of catechol in the particle formation step and the growth step of silica particles. Since catechol is discharged together with water in the concentration step by ultrafiltration and reduced in weight, the amount of catechol in the finally obtained colloidal silica is 20 to 700 in terms of silica / catechol molar ratio .

The molar ratio of silica / catechol in the present invention is calculated from the number of moles of SiO ₂ obtained from the silica concentration of the active silicic acid aqueous solution and the number of moles of catechol added to the active silicic acid aqueous solution.

  However, the presence of organic matter may cause secondary problems in wastewater treatment. Considering such a case, a product from which catechol is removed is also necessary. A method of reducing the amount of catechol as much as possible by effectively utilizing ultrafiltration is also included in the category as one of the production methods of the present invention.

  Colloidal silica containing a group of non-spherical irregularly shaped silica particles in the present invention has various shapes such as egg shape, peanut shape, bowl shape, rod shape, bent rod shape, and silica particles having different shapes. It is a colloidal silica contained. Specifically, it is colloidal silica containing silica particles having a shape as shown in FIGS. The major axis / minor axis ratio of the silica particles is in the range of 1.2-10. Most of the silica particles are non-spherical silica particles, and some of the silica particles are also present. The silica particles shown in FIGS. 1 to 3 are merely examples, and the shapes thereof vary depending on the production conditions. However, in the colloidal silica of the present invention, silica particles that are not truly spherical occupy the majority.

  The method for producing colloidal silica according to the present invention is characterized in that a catechol and an alkaline agent are used in the particle formation step using an active silicic acid aqueous solution of a water glass method as a silica source. In the particle growth step, an active silicic acid aqueous solution and an alkali agent and catechol are added, or an active silicic acid aqueous solution and an alkali agent are added.

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

  By using the above nitrogen-containing organic alkali compound, the alkali metal content per silica can be 50 ppm or less. In applications such as ceramics, binders for catalysts, abrasives for electronic materials, etc., it is necessary to have such an alkali metal content. More preferably, it is 30 ppm or less.

  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. Such an aqueous solution of sodium silicate is relatively inexpensive and can be easily obtained. For semiconductor applications that dislike Na ions, an aqueous potassium silicate solution is preferably used as a raw material instead of an aqueous sodium silicate solution. 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 to dealkali, It can be carried out by contacting with an OH type strongly basic anion exchange resin to 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, silica particles are formed. In this particle forming step, conventional operations are performed except that catechol is added. For example, silica particles can be formed by adding catechol and an alkaline agent to an active silicic acid aqueous solution so that the pH is 8 or more and heating to 60 to 240 ° C.

  Next, particle growth is performed using a build-up method using the silica particles formed above as a seed sol. In this particle growth step, a seed sol having a pH of 8 or higher is heated to 60 to 240 ° C., and while maintaining the pH at 8 to 11, an active silicic acid aqueous solution, catechol and an alkaline agent are added, or an active silicic acid aqueous solution. And an alkali agent are added to grow silica particles. In this manner, silica particles can be grown to particles having an average minor axis of preferably 5 to 30 nm, more preferably 10 to 20 nm.

  Colloidal silica obtained through the particle formation step and the particle growth step can be concentrated as required. The silica may be concentrated by evaporating water, but in terms of energy, ultrafiltration is more advantageous.

  The ultrafiltration membrane used when concentrating silica by ultrafiltration will be described. Separation to which the ultrafiltration membrane is applied targets particles of 1 nm to several microns, but also targets dissolved polymer substances, and therefore, filtration accuracy is expressed by a molecular weight cut off in the nanometer range. In the present invention, an ultrafiltration membrane having a fractional molecular weight of 15,000 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 fractional molecular weight of 3,000 to 15,000 is used. If the membrane is less than 3,000, the filtration resistance is too large and the treatment time becomes long, which is uneconomical. 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, and a hollow fiber type, and any of them can be used. Hollow fiber membrane is compact and easy to use. In addition, if the ultrafiltration process also serves to wash out and remove excess catechol, if necessary, it is further washed out by adding pure water after reaching the target silica concentration to remove catechol. You can also work to increase the rate. In this step, it is preferable to concentrate so that the silica concentration is 10 to 50% by weight.

  Moreover, in this invention, you may refine | purify the obtained colloidal silica with an ion exchange resin after a particle growth process or an ultrafiltration process as needed. For example, the colloidal silica is contacted with an H-type strongly acidic cation exchange resin to remove the alkaline agent, or the colloidal silica is contacted with an OH-type strongly basic anion exchange resin to deanion to further increase the purity. Can be planned.

  As described above, by producing colloidal silica using active silicic acid as a raw material in the presence of catechol, it contains catechol and has a nonspherical shape having a major axis / minor axis ratio of 1.2 to 10 by observation with a transmission electron microscope. Colloidal silica containing a deformed silica particle group can be obtained. The colloidal silica thus obtained does not contain any metal compound other than silicon such as calcium salt, magnesium salt, aluminum salt, etc., so that the ink absorbing filler for printing paper, the spreadability improving agent for paints, It is useful for hydrophilic coating materials on the surface of materials, high-strength binders, binders for catalysts, abrasives for electronic materials, and the like.

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) Total catechol analysis: Shimadzu Corporation, total organic carbon meter TOC-5000A and solid sample combustion apparatus SSM-5000A were used, and converted into catechol from the total organic carbon amount obtained. Specifically, the total organic carbon amount (TOC) was determined by 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.
(3) Liquid phase catechol analysis: The liquid phase was taken out from the sample by ultrafiltration and measured by the same method as in (2) above.
(4) Calculation of immobilized catechol: The amount of liquid catechol was subtracted from the total amount of catechol to calculate the amount of immobilized catechol.

[Example 1]
(A) Preparation of active silicic acid aqueous solution No. 3 sodium silicate (SiO ₂ : 28.8 wt%, Na ₂ O: 9.7 wt%, H ₂ O: 61.5 wt%) to 13 kg of deionized water 2.1 kg Was added and mixed uniformly to prepare diluted sodium silicate having a silica concentration of 4.0% by weight. This dilute sodium silicate was passed through a column of 4000 ml of H-type strongly acidic cation exchange resin (Amberlite (registered trademark) IR120B manufactured by Organo Corp.) previously regenerated with hydrochloric acid to remove the alkali, and at a silica concentration of 3.5% by weight, pH 2 .9 active silicic acid aqueous solution 15 kg was obtained.

(B) Formation of Silica Particles Next, catechol was added to the obtained active silicic acid aqueous solution, and then an alkali agent was added to make it alkaline and heated to form silica particles. That is, to 500 g of a part of the obtained active silicic acid aqueous solution, with stirring, catechol was added so that the silica / catechol molar ratio was 20, and then a 5 wt% aqueous sodium hydroxide solution was added to adjust the pH to 8. The mixture was kept at 100 ° C. for 1 hour and then allowed to cool.

  The obtained colloidal silica was reduced in weight by evaporation of water, and the silica concentration was about 4% by weight. The major axis / minor axis ratio of the silica particles was measured by observation with a transmission electron microscope (TEM), and confirmed to be colloidal silica composed of non-spherical deformed silica particles of 1.2 to 10. A TEM photograph is shown in FIG. Moreover, the average minor axis of the silica particles was 5 to 6 nm. Since the total catechol concentration of colloidal silica was 0.343 wt% and the liquid phase catechol concentration was 0.291 wt%, the immobilized catechol concentration was calculated to be 0.064 wt%. It was confirmed that a part of the added catechol was fixed to silica.

(C) Growth of silica particles Subsequently, the obtained colloidal silica was heated again to 100 ° C., a build-up method was taken, and 1,800 g of an active silicic acid aqueous solution was added over 3 hours. During the addition of the active silicic acid aqueous solution, catechol and a 5 wt% aqueous sodium hydroxide solution were added simultaneously. Catechol was added so that the silica / catechol molar ratio was 20, and 5 wt% aqueous sodium hydroxide solution was added so that the pH was in the range of 9.5 to 10.5. After completion of the simultaneous addition, the mixture was kept at 100 ° C. for 1 hour, matured and then allowed to cool.

(D) Concentration of colloidal silica Finally, by pump circulation 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.) The solution was filtered under pressure until the silica concentration was 29% by weight. The pH of the obtained colloidal silica was 9.1.

The average minor axis and major axis / minor axis ratio of the silica particles are measured by transmission electron microscope (TEM) observation, the average minor axis is 14 nm, and the major axis / minor axis ratio is 2 to 4. It was confirmed to be colloidal silica made of a group. A TEM photograph is shown in FIG.
The total catechol concentration of colloidal silica was 0.334% by weight, and the liquid phase catechol concentration was 0.296% by weight. From this, it was confirmed that a part of the added catechol was fixed to silica, and the amount was calculated to be 0.124% by weight. Moreover, since a part of catechol was removed by ultrafiltration, the molar ratio of silica / catechol was 159.

[Example 2]
Colloidal silica was produced in the same manner as in Example 1 except that catechol was not added in the silica particle growth step. Finally, pressure filtration by pump circulation is performed using a hollow fiber type ultrafiltration membrane with a molecular weight cut off of 6,000 (Microsa (registered trademark) UF module SIP-1013 manufactured by Asahi Kasei Co., Ltd.), and silica It was concentrated until the concentration was 17.5% by weight. The obtained colloidal silica had a pH of 9.2.

The average minor axis and major axis / minor axis ratio of the silica particles are measured by observation with a transmission electron microscope (TEM), the average minor axis is 15 nm, and the major axis / minor axis ratio is 1.2 to 2.0. It was confirmed that the colloidal silica contains a group of irregular shaped silica particles. A TEM photograph is shown in FIG.
The total catechol concentration of colloidal silica was 0.0497% by weight, and the liquid phase catechol was 0.0345% by weight. From this, it was confirmed that a part of the added catechol was fixed to silica, and the amount was calculated to be 0.0235% by weight. Moreover, since a part of catechol was removed by ultrafiltration, the molar ratio of silica / catechol was 646.

[Comparative Example 1]
To 500 g of the same active silicic acid aqueous solution used in Example 1, 5 wt% aqueous sodium hydroxide solution was added with stirring to pH 8, heated to 100 ° C. for 1 hour, and then allowed to cool.
When the silica particles were observed with a transmission electron microscope (TEM), it was confirmed to be colloidal silica composed of spherical silica particles having an average particle diameter of 7 nm. Subsequently, the obtained colloidal silica was heated again to 100 ° C., and a build-up method was taken. 1,800 g of an active silicic acid aqueous solution was added over 3 hours. During the addition of the active silicic acid aqueous solution, a 5 wt% sodium hydroxide aqueous solution was simultaneously added so that the pH was in the range of 9.5 to 10.5. After completion of the simultaneous addition, the mixture was kept at 100 ° C. for 1 hour, aged, and then allowed to cool. Finally, pressure filtration by pump circulation is performed using a hollow fiber type ultrafiltration membrane with a molecular weight cut off of 6,000 (Microsa (registered trademark) UF module SIP-1013 manufactured by Asahi Kasei Co., Ltd.), and silica The solution was concentrated until the concentration reached 20% by weight. The pH of the obtained colloidal silica was 9.1.

  When the silica particles were observed with a transmission electron microscope (TEM), it was confirmed to be colloidal silica composed of spherical silica particles having an average particle diameter of 15 nm. A TEM photograph is shown in FIG.

Claims (4)

The active silicic acid in the presence of catechol a colloidal silica prepared as a raw material, containing catechol, major axis / minor axis ratio by transmission electron microscopic observation Ri der 1.2 to 10, moles of silica / catechol A colloidal silica comprising a group of non-spherical irregularly shaped silica particles having a ratio of 20 to 700 .   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 10 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) a step of adding catechol and an alkaline agent to the activated silicic acid aqueous solution to make it alkaline, followed by heating to form silica particles, and (c) subsequently maintaining the alkalinity under heating conditions, 2. The method for producing colloidal silica according to claim 1, comprising a step of growing silica particles by adding an active silicic acid aqueous solution and an alkali agent or adding an active silicic acid aqueous solution, an alkali agent and catechol. 3. . The method for producing colloidal silica according to claim 3 , further comprising (d) a step of concentrating silica after the step (c).

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