Method for producing chelating agent-containing water glass and silica sol

Abstract

[Problem] To provide a method for heating anhydrous sodium silicate (cullet), a chelating agent, and water to obtain a sodium silicate aqueous solution and a method for producing a high-purity silica sol using the sodium silicate aqueous solution (water glass). [Solution] A method for producing a sodium silicate aqueous solution that heats and mixes anhydrous sodium silicate, a chelating agent, and water at 100-270°C. A method for producing a sodium silicate aqueous solution that heats and mixes anhydrous sodium silicate and a chelating agent-containing aqueous solution at 100-270°C. A method for producing a sodium silicate aqueous solution in which the chelating agent is 0.1-3000 ppm relative to SiO2. A method for producing a silica sol that includes a step (a): a step for bringing a sodium silicate aqueous solution obtained by the above production method into contact with a cation-exchange resin and obtaining an active silicic acid aqueous solution, a step (b): a step for heating the active silicic acid aqueous solution obtained in step (a) to obtain a silica sol, and a step (c): a step for ultrafiltering the silica sol obtained in step (b).

Description

[Technical field]

[0001] The present invention relates to a method for producing a silica sol with a low content of polyvalent metal compounds. [Background technology]

[0002] Alkaline silicate aqueous solutions (water glass) are used in a wide range of fields, including as foundry sand binders, bonding agents, additives for pulp and paper, additives for soap, pharmaceutical raw materials, and additives for civil engineering and building materials. In addition, various silica products, such as colloidal silica dispersions (silica sols), silica gel, silica powder, lithium silicate aqueous solutions, and potassium silicate aqueous solutions, are produced using aqueous alkali silicate solutions as the starting material. The silica sols are produced by heating active silicic acid obtained by subjecting aqueous alkali silicate solutions to cation exchange. Some compositions using these materials have applications requiring compositions with very low levels of metal oxides other than silica, such as polishing agents for semiconductor wafers and semiconductor devices. Metal oxides other than silica as impurities in the aqueous alkali silicate solution are derived from the raw materials used to produce the aqueous alkali silicate solution and are contained in the aqueous alkali silicate solution during the production process. Anhydrous sodium silicate (cullet) is obtained by washing and drying silica sand or silica rock, mixing it with soda ash (sodium carbonate) or caustic soda, melting it, and then cooling it. Silica sand contains metal compounds other than silica that are naturally occurring, and soda ash and caustic soda also contain metal compounds other than silica, and these metal compounds remain in the cullet. The aqueous alkali silicate solution (water glass) is obtained by dissolving the cullet in a high-pressure dissolving vessel equipped with a boiler, etc. The aqueous alkali silicate solution produced by the conventional method is produced as an aqueous solution containing relatively large amounts of metal compounds other than silica.

[0003] As a method for producing active silicic acid that has been highly purified using an aqueous solution of an alkali silicate, a method for producing a high-purity aqueous solution of active silicic acid has been disclosed, which comprises, for example, mixing an iminodiacetic acid type chelating agent with an aqueous solution of an alkali silicate to obtain an aqueous solution of an alkali silicate containing the chelating agent, then contacting the aqueous solution of the alkali silicate containing the chelating agent with an H-type cation exchanger, and contacting the aqueous solution of the active silicic acid containing the chelating agent with an anion exchanger (see Patent Document 1). Also disclosed is a method for producing a silica sol using the aqueous active silicic acid solution produced by the above method (see Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 3691047 [Patent Document 2] Patent No. 3691048 Summary of the Invention [Problem to be solved by the invention]

[0005] In the complexation reaction between the polyvalent metal compound contained in anhydrous sodium silicate (cullet) and a chelating agent, the chelate forming ability may vary greatly depending on the form of the silicate ion. In the process of dissolving anhydrous sodium silicate (cullet) in water by heating, the sodium-containing silicate ion monomer forms a sodium-containing colloidal silicate ion micelle and polymerizes. The inventors have found that the ability of polyvalent metal ions to form a complex with a chelating agent varies greatly depending on whether they coexist in the state of the silicate ion monomer or whether colloidal silicate ion micelles are formed and incorporated into the polymer. In the present invention, it has been found that in the process of dissolving anhydrous sodium silicate (cullet) in water by heating, the polyvalent metal ion forms a complex with a chelating agent before the silicate ion is polymerized, and the chelate complex can be removed by cation exchange or ultrafiltration without being incorporated into the silica matrix. This invention aims to produce a high-purity active silicic acid aqueous solution and a high-purity silica sol.

[0006] That is, the present invention aims to provide a method for obtaining an aqueous sodium silicate solution by heating anhydrous sodium silicate (cullet), a chelating agent, and water, and a method for producing a high-purity silica sol using the aqueous sodium silicate solution (water glass). [Means for solving the problem]

[0007] A first aspect of the present invention is a method for producing an aqueous sodium silicate solution, the method comprising the step of heating and mixing anhydrous sodium silicate, a chelating agent, and water at 100 to 270°C; As a second aspect, the method for producing the aqueous sodium silicate solution according to the first aspect, wherein the step of heating and mixing includes a step of preparing an aqueous solution containing a chelating agent, and a step of heating and mixing the anhydrous sodium silicate and the aqueous solution containing a chelating agent at 100 to 270°C. As a third aspect, the method for producing a sodium silicate aqueous solution according to the first or second aspect, wherein the chelating agent is added in an amount of 0.1 to 3000 ppm relative to the total mass of the SiO2 component contained in the anhydrous sodium silicate. As a fourth aspect, the method for producing a sodium silicate aqueous solution according to any one of the first to third aspects, wherein the heating time is 0.1 to 50 hours. As a fifth aspect, the method for producing the sodium silicate aqueous solution according to any one of the first to fourth aspects, wherein the components are heated and mixed under a pressure of 1 to 60 atm. as a sixth aspect, the method for producing a sodium silicate aqueous solution according to any one of the first to fifth aspects, in which a molar ratio of SiO2 / Na2O in the sodium silicate aqueous solution is 1 to 10; As a seventh aspect, the method for producing a sodium silicate aqueous solution according to any one of the first to sixth aspects, wherein the chelating agent is a chelating agent having a carboxyl group, a hydroxyl group, a phosphonic acid group, or a combination of these groups. As an eighth aspect, the method for producing a sodium silicate aqueous solution according to any one of the first to seventh aspects, wherein the chelating agent is an aminocarboxylic acid chelating agent, a phosphonic acid chelating agent, a gluconic acid chelating agent, or a metal salt thereof. As a ninth aspect, the method for producing a sodium silicate aqueous solution according to any one of the first to eighth aspects, wherein the chelating agent is ethylenediaminetetraacetic acid, hydroxyethylethylenediaminetriacetic acid, diethylenetriaminepentaacetic acid, nitrilotriacetic acid, gluconic acid, hydroxyethyliminotriacetic acid, L-aspartic acid-N,N-diacetic acid, hydroxyiminodisuccinic acid, aminotrimethylenephosphonic acid, hydroxyethanephosphonic acid, or a salt thereof; As a tenth aspect, a method for producing an active silicic acid aqueous solution, the method comprising a step of contacting the aqueous sodium silicate solution obtained by the production method according to any one of the first to ninth aspects with an H-type cation exchange resin. As an eleventh aspect, the method comprises the following steps (a) to (c): Step (a): contacting an aqueous sodium silicate solution obtained by the method according to any one of the first to ninth aspects with a cation exchange resin to obtain an aqueous activated silicic acid solution; Step (b): A step of heating the active silicic acid aqueous solution obtained in step (a) to obtain a silica sol; (c) step: a step of ultrafiltering the silica sol obtained in (b); As a twelfth aspect, the method for producing a silica sol according to the eleventh aspect, wherein the step (a) further includes a step of performing anion exchange before and / or after contacting the aqueous sodium silicate solution with a cation exchange resin; As a thirteenth aspect, the method for producing a silica sol according to the eleventh aspect, wherein the step (c) includes a step of performing cation exchange and / or anion exchange before and / or after ultrafiltration of the silica sol; As a fourteenth aspect, the method for producing a silica sol according to any one of the eleventh to thirteenth aspects, in which the anhydrous sodium silicate is cullet, and the silica sol obtained in the step (c) has a Cu content of 180 ppb or less and a Ni content of 100 ppb or less, based on the total mass of the SiO2 component. As a fifteenth aspect, an aqueous sodium silicate solution containing a sodium-containing silicate ion monomer (A1) and a compound (B) in which a chelating agent having a carboxyl group, a hydroxyl group, a phosphonic acid group, or a combination of these groups is bonded to a polyvalent metal ion M; As a sixteenth aspect, an aqueous sodium silicate solution containing a sodium-containing silicate ion monomer (A1) and a compound (B) containing at least one partial structure selected from the partial structures represented by the following formulas (1) to (3): [ka] (In the formula, M represents a polyvalent metal ion, wavy line 1 represents a covalent bond between a carbon atom or a phosphorus atom and an adjacent atom, wavy line 2 represents an ionic bond between the polyvalent metal ion M and an oxygen atom or a coordinate bond between the polyvalent metal ion M and a nitrogen atom or an oxygen atom, provided that a plurality of wavy lines 2 may exist for the polyvalent metal ion M, and the dotted line represents a coordinate bond between the polyvalent metal ion M and an oxygen atom.) As a seventeenth aspect, the sodium silicate aqueous solution according to the fifteenth or sixteenth aspect, in which the polyvalent metal ion M is a copper ion or a nickel ion; and According to an eighteenth aspect, the aqueous sodium silicate solution according to any one of the fifteenth to seventeenth aspects further contains a sodium-containing colloidal silicate ion micelle (A2). Effect of the Invention

[0008] According to the present invention, there can be provided a method for obtaining an aqueous sodium silicate solution by heating or heating and mixing anhydrous sodium silicate (cullet), a chelating agent and water, and a method for producing a high-purity silica sol using the aqueous sodium silicate solution. In one embodiment of the present invention, at the step of dissolving anhydrous sodium silicate (cullet), i.e., before the formation of an aqueous sodium silicate solution, a chelating agent is made to coexist with anhydrous sodium silicate (cullet), and in this state, the anhydrous sodium silicate (cullet) is heated and dissolved in water, and the resulting aqueous sodium silicate solution is brought into contact with a cation exchanger to obtain an aqueous activated silicic acid solution, which is then subjected to a heating process to produce a silica sol, and a high-purity silica sol is formed by further carrying out ultrafiltration.

[0009] Anhydrous sodium silicate (cullet) is obtained by heating and melting silica sand or silica stone with soda ash (sodium carbonate) or caustic soda, then cooling it. To produce sodium silicate aqueous solution (water glass), anhydrous sodium silicate (cullet) is heated and dissolved in water. Metal compounds other than silica derived from the raw materials used in the production of anhydrous sodium silicate (cullet), such as silica sand and silica stone, as well as soda ash and caustic soda, remain in the cullet, so the sodium silicate aqueous solution produced from it contains metal compounds other than silica. In the present invention, the behavior of silicate ions and polyvalent metal ions during the process of dissolving anhydrous sodium silicate (cullet) in water by heating has been focused on, and it has been found that the presence of a chelating agent is necessary when dissolving cullet. In the process of dissolving cullet in water by heating, anhydrous sodium silicate contains sodium ions, polyvalent metal ions, and silicate ions, but the silicate ions are easily polymerized by heating, and the silicate ion monomers are polymerized into silicate ion dimers and colloidal silicate ion micelles. When polymerization proceeds to colloidal silicate ion micelles, the polyvalent metal ions are trapped in the silica matrix (i.e., polysiloxane), and it is not possible to form a chelate compound between the polyvalent metal ions and the chelating agent, and the polyvalent metal ions are present in active silicic acid and even silica particles, resulting in a silica sol containing a large amount of polyvalent metals. On the other hand, when anhydrous sodium silicate (cullet) is dissolved in water, the presence of a chelating agent in the initial state, i.e., when the polymerization of silicate ions has not yet progressed sufficiently, allows polyvalent metal ions to form chelate compounds by the chelating agent, so that when sodium is removed from silicate ion monomers containing sodium ions or polyvalent metal ions using an H-type cation exchange resin to produce active silicic acid, the polyvalent metal ions are not incorporated into the silica matrix. Also, when an aqueous alkali silicate solution is applied to an H-type cation exchange resin, the polyvalent metal ions in the chelate compound of the polyvalent metal ions that have come into contact with the sulfonic acid groups are cation-exchanged together with the sodium ions, so that some of the polyvalent metal ions are removed during the production of active silicic acid, and high-purity active silicic acid is obtained. Furthermore, when this high-purity activated silicic acid is used to produce a silica sol by thermal polymerization, the polyvalent metal ions remaining in the silica sol exist as chelate compounds of polyvalent metal ions and are not incorporated into the silica particles. Instead, the silica sol consists of silica particles and chelate compounds of polyvalent metal ions. By subjecting this silica sol to ultrafiltration, the chelate compounds of polyvalent metal ions are discharged from the silica sol to the outside of the system, thereby producing a high-purity silica sol.

[0010] Conventionally, even if a chelating agent is added after dissolving cullet in water to form a sodium silicate aqueous solution, the sodium-containing silicate ions are already polymerized into sodium-containing colloidal silicate ion micelles, and the polyvalent metal ions are taken into the silica matrix (polysiloxane), so even if a chelating agent is added, the polyvalent metal ions cannot form a chelate compound of the polyvalent metal ions. In other words, the polyvalent metal ions are present in the silica matrix, and remain in the activated silicic acid and in the silica particles produced from the activated silicic acid, and the polyvalent metal ions cannot be removed even by cation exchange, anion exchange, or ultrafiltration. In other words, when a chelating agent is added during heating and dissolving of the anhydrous sodium silicate (cullet) of the present invention in water, a sodium-containing silicate ion monomer and a polyvalent metal ion chelate compound containing at least one of the partial structures represented by the above formulas (1) to (3) are present.

[0011] However, in the prior art, when a chelating agent is not present when anhydrous sodium silicate (cullet) is dissolved in water by heating, and a chelating agent is added after an aqueous sodium silicate solution (water glass) is formed, sodium-containing silicate ion monomers are not present, but sodium-containing colloidal silicate ion micelles are present, and in this state, a chelate complex of a polyvalent metal ion is not formed, so that a chelate compound of a polyvalent metal ion containing at least one of the partial structures represented by the above formulas (1) to (3) cannot be formed. In other words, a high-purity silica sol cannot be obtained.

[0012] The present invention has discovered a production method in which, when anhydrous sodium silicate (cullet) is heated and dissolved in water, the presence of a chelating agent makes it possible to form a chelate compound of polyvalent metal ions, and high-purity active silicic acid is obtained by cation exchange treatment. When the high-purity active silicic acid is further heated to produce silica sol, the produced silica sol is ultrafiltered, and the remaining chelate-processed product of polyvalent metal ions is discharged outside the ultrafiltration membrane system, thereby producing an even higher purity silica sol. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] The present invention relates to a method for producing an aqueous sodium silicate solution by heating or heating and mixing anhydrous sodium silicate (cullet), a chelating agent and water at 100 to 270°C, 100 to 180°C, or 110 to 180°C. A preferred method for producing an aqueous sodium silicate solution comprises heating and mixing anhydrous sodium silicate with an aqueous solution containing a chelating agent obtained by mixing a chelating agent with water.

[0014] Anhydrous sodium silicate (cullet) is obtained by heating and melting silica sand or silica stone (SiO2) with soda ash (sodium carbonate) or caustic soda, and then cooling it. Depending on the mixing ratio of silica sand or silica stone to soda ash or caustic soda, various cullets with SiO2 / Na2O molar ratios of about 2 to 10 are produced. For example, the molar ratios are 2.1, 2.3, 3.1, 3.2, and 3.7, and these are dissolved in water (hot water) to obtain sodium silicate aqueous solutions (water glass) with the above molar ratios. These are used as JIS standard sodium silicate aqueous solutions (water glass) No. 1, No. 2, No. 3, No. 4, and No. 5. In the present invention, anhydrous sodium silicate (cullet) having the above molar ratio can be used as a raw material. These anhydrous sodium silicates (cullet) are available from Tokuyama Corporation, Oriental Silica Corporation, PQ Corporation, and the like.

[0015] The chelating agent can be used at an addition ratio of 0.00005 to 0.15% by mass, or 0.00005 to 0.015% by mass, or 0.00005 to 0.01% by mass, typically 0.00001 to 0.001% by mass, which is expressed in ppm units, and the chelating agent can be used at an addition ratio of 0.5 ppm to 1500 ppm, or 0.5 ppm to 150 ppm, or 0.5 ppm to 100 ppm, typically 0.1 ppm to 10 ppm, relative to the anhydrous sodium silicate. In addition, the chelating agent can be used at an addition ratio of 0.00001 to 0.3 mass%, or 0.00001 to 0.03 mass%, or 0.00001 to 0.02 mass%, or 0.0001 to 0.02 mass%, based on the total mass of the silica (SiO2) component of the anhydrous sodium silicate (cullet), typically at an addition ratio of 0.0001 to 0.002 mass%. In terms of ppm, the chelating agent can be used at an addition ratio of 0.1 ppm to 3000 ppm, or 0.1 ppm to 300 ppm, or 0.1 ppm to 200 ppm, or 1 ppm to 200 ppm, based on the total mass of the silica (SiO2) component of the anhydrous sodium silicate (cullet), typically at an addition ratio of 1 ppm to 20 ppm.

[0016] Chelating agents for use in the present invention can include chelating agents that contain a carboxyl group, a hydroxyl group, a phosphonic acid group, or a combination of these groups. These chelating agents are, for example, aminocarboxylic acid chelating agents, phosphonic acid chelating agents, gluconic acid chelating agents, or metal salts thereof (chelating metal salt chelating agents). The salts of chelating agents having a carboxyl group (chelating metal salts) can be alkali metal salts, such as sodium salts, potassium salts, and lithium salts, and preferably sodium salts. Among the chelating agents, it is preferable to use an aminocarboxylic acid-based chelating agent, which is a nitrogen-containing chelating agent. The aminocarboxylic acid-based chelating agent has an amino group and a carboxyl group in the structure, and may further have a hydroxyl group. The carboxyl group can form the above-mentioned salt, for example, may form a sodium salt. The amino group of the aminocarboxylic acid chelating agent can be a secondary amino group or a tertiary amino group. The secondary amino group and the tertiary amino group can be present alone or in combination in one molecule of the chelating agent. A chelating agent having a tertiary amino group is preferably used. The chelating agent can have one or more amino groups in one molecule, for example, 1 to 6, 1 to 4, or 2 to 4 amino groups.

[0017] The structure of the chelating agent that forms a chelate complex with a metal ion is a group that contains a carboxyl group, a hydroxyl group, a phosphonic acid group, or a combination of these groups as a functional group for forming a chelate. In addition, a nitrogen atom in the chelating agent molecule can also participate as a functional group for forming a chelate, and when a hydroxyl group or a phosphonic acid group is contained, these groups can also participate as functional groups for forming a chelate. When a chelating agent forms a complex with a metal ion, if the chelating agent has multiple carboxyl groups, one molecule of the chelating agent and one molecule of a polyvalent metal ion form a chelate complex. However, if the chelating agent has a single carboxyl group, the hydroxyl group or phosphonic acid group can perform chelation, and a chelate structure can be formed by multiple chelating agents with one molecule of a polyvalent metal ion.

[0018] Examples of the chelating agent include the following. [ka] [ka] R in the above formulas (4-1) to (4-10) 1 ~R 5 R represents a hydrogen atom, an alkali metal, or NH4, and examples of the alkali metal include sodium and lithium. 1 ~R 5 may be the same or different. In particular, R 1 ~R 5 are preferably a hydrogen atom or sodium.

[0019] Formula (4-1) represents ethylenediaminetetraacetic acid or a salt thereof, formula (4-2) represents hydroxyethylethylenediaminetriacetic acid or a salt thereof, formula (4-3) represents diethylenetriaminepentaacetic acid or a salt thereof, formula (4-4) represents nitrilotriacetic acid or a salt thereof, formula (4-5) represents gluconic acid or a salt thereof, formula (4-6) represents hydroxyethyliminotriacetic acid or a salt thereof, formula (4-7) represents L-aspartic acid-N,N-diacetic acid or a salt thereof, formula (4-8) represents hydroxyiminodisuccinic acid or a salt thereof, formula (4-9) represents aminotrimethylenephosphonic acid or a salt thereof, and formula (4-10) represents hydroxyethanephosphonic acid or a salt thereof.

[0020] In the present invention, one type of chelating agent can be used, or two or more types of chelating agents can be used in combination. In the present invention, the chelating agent is typically ethylenediaminetetraacetic acid or a salt thereof represented by the formula (4-1), and tetrasodium ethylenediaminetetraacetate can be preferably used.

[0021] The method for producing an aqueous sodium silicate solution of the present invention is a production method including a step of heating or heat-mixing anhydrous sodium silicate, a chelating agent, and water at 100 to 270° C., and typically includes a step of heating or heat-mixing anhydrous sodium silicate and an aqueous solution containing a chelating agent at 100 to 180° C. When an aqueous solution containing a chelating agent is used, the chelating agent can be dissolved in water to prepare an aqueous solution of the chelating agent having a concentration of, for example, 0.001 to 10% by mass or 0.01 to 5% by mass.

[0022] Since the heating temperature is 100 to 270°C, or 100 to 180°C, or 110 to 180°C, steam containing a chelating agent can be used. For example, in a method for producing an aqueous sodium silicate solution, heating or heating and mixing can be performed under a pressure of 1 atm to 60 atm, or 1 atm to 10 atm, or 1.5 atm to 10 atm, and the heating time can be 0.1 to 50 hours. The heating time can be 50 hours or more, but can be up to 50 hours for economic reasons.

[0023] The sodium silicate aqueous solution has a SiO2 / Na2O molar ratio in the range of about 1 to 10, or 1 to 4, or 2 to 4. This molar ratio depends on the molar ratio of the components contained in the anhydrous sodium silicate (cullet).

[0024] The concentration of the sodium silicate aqueous solution is determined by the mixing ratio of anhydrous sodium silicate (cullet) and water (aqueous solution containing a chelating agent), and it can be produced at a low concentration and then concentrated, or anhydrous sodium silicate (cullet) can be dissolved to produce a high concentration. Generally, sodium silicate aqueous solutions are commercially available at 30% to 50% by mass, but when manufacturing products using this sodium silicate as a raw material, the sodium silicate aqueous solution can be diluted with water to 1% to 10% by mass before use.

[0025] It is believed that when anhydrous sodium silicate (cullet) is dissolved by heating in water (hot water), the presence of a chelating agent efficiently causes polyvalent metal ions to form complexes with the chelating agent, and the sodium silicate aqueous solution contains a chelate complex having any one of the partial structures shown in formulas (1) to (3), or a partial structure combining two or more of these partial structures. In formulas (1) to (3), the polyvalent metal ion is represented by polyvalent metal ion M. However, since the chelating agent is exposed to a highly alkaline aqueous solution having a pH of 9 to 14 or 10 to 13, there is a possibility that the structure of the chelating agent may partially decompose. However, when an active silicic acid aqueous solution is subsequently produced, it is possible to remove the polyvalent metal ion M together with the sodium ion of the sodium silicate using an H-type cation resin. Therefore, it is considered that a chelate complex having at least one of the partial structures shown in formulas (1) to (3), or a partial structure which is a combination of two or more of these partial structures, is present in the sodium silicate aqueous solution.

[0026] In the present invention, by adding the above-mentioned chelating agent when dissolving anhydrous sodium silicate (cullet) in water (hot water), a chelate compound of a silicate ion monomer before polymerization of the silicate ion proceeds and a polyvalent metal ion M is present. That is, there is an aqueous solution of alkali silicate (water glass) containing a sodium-containing silicate ion monomer (A1) and a compound (B) in which a chelating agent having a carboxyl group, a hydroxyl group, a phosphonic acid group, or a combination of these groups is bonded to a polyvalent metal ion M. More specifically, the present invention relates to a sodium-containing silicate ion monomer (A1) and the following Mode and a compound (B) that includes at least one partial structure selected from the partial structures represented by formulas (1) to (3). When anhydrous sodium silicate (cullet) is dissolved in water (hot water), the sodium-containing silicate ion is a monomer, but over time due to heating, the sodium-containing silicate ion monomer changes into a sodium-containing colloidal silicate ion micelle. Therefore, the solution of anhydrous sodium silicate (cullet) in water (hot water) can be said to be an aqueous solution of alkali silicate containing sodium-containing silicate ion monomer (A1) and a compound (B) in which a chelating agent having a carboxyl group, a hydroxyl group, a phosphonic acid group, or a combination of these groups is bound to a polyvalent metal ion M, and further containing sodium-containing colloidal silicate ion micelle (A2). More specifically, it can be said to be an aqueous alkali silicate solution containing a sodium-containing silicate ion monomer (A1) and a compound (B) containing at least one partial structure selected from the partial structures represented by the following formulas (1) to (3), and further containing a sodium-containing colloidal silicate ion micelle (A2). During this process, the polyvalent metal ion M forms a chelate complex with the chelating agent and is not incorporated into the silica network that constitutes the polysilicate ion such as colloidal silicate ion micelles. Therefore, it can be removed by cation exchange and also by subsequent ultrafiltration.

[0027] The polyvalent metal ion M is a polyvalent metal ion M other than an alkali metal ion contained in the raw material anhydrous sodium silicate (cullet). Examples of the polyvalent metal ion M contained in the cullet include calcium ion, magnesium ion, aluminum ion, barium ion, copper ion, nickel ion, cobalt ion, iron ion, titanium ion, chromium ion, manganese ion, zinc ion, zirconium ion, and tin ion. The present invention is aimed at obtaining an aqueous sodium silicate solution and a silica sol with reduced polyvalent metal ion M, particularly reduced copper ion and nickel ion. In the present invention, the aqueous sodium silicate solution obtained by heating anhydrous sodium silicate (cullet) in water contains 300 ppb or more of copper ions and 120 ppb or more of nickel ions relative to the silica in the sodium silicate.

[0028] In the present invention, a silica sol can be produced through steps (a) to (c). Step (a): a step of contacting the aqueous sodium silicate solution obtained by the above-mentioned production method with a cation exchange resin to obtain an aqueous activated silicic acid solution; Step (b): A step of heating the active silicic acid aqueous solution obtained in step (a) to obtain a silica sol; A method for producing a silica sol, comprising: (c) ultrafiltering the silica sol obtained in (b).

[0029] The cation exchange resin used in step (a) is a cation exchange resin having a functional group capable of exchanging hydrogen ions with other cations. A sulfonic acid type H-type strongly acidic cation exchange resin or a carboxylic acid type H-type weakly acidic cation exchange resin can be used, and among them, it is preferable to use a sulfonic acid type strongly acidic cation exchange resin adjusted to the H type. As these sulfonic acid type strongly acidic cation exchange resins, for example, Amberlite IR-120B (trade name) manufactured by Organo Corporation can be used.

[0030] In the step (a), alkali metal ions (especially sodium) are removed from an aqueous alkali silicate solution by cation exchange to obtain an aqueous activated silicic acid solution. In the cation exchange, some of the polyvalent metal ions can also be removed from a chelating agent that contains polyvalent metal ions. In step (a), a sodium silicate aqueous solution having a SiO2 component concentration of 1 to 10% by mass or 1 to 6% by mass can be contacted with a cation exchange resin. The contact can be performed in a batch or column manner, and industrially, a method can be used in which an ion exchange tower is filled with a cation exchange resin and an aqueous sodium silicate solution is passed through the tower. The flow rate is 1 to 30 in space velocity (1 / hr), and the temperature can be 10 to 80°C.

[0031] In step (a), the Cu content in the obtained active silicic acid aqueous solution can be set to 230 ppb or less, for example 180 ppb or less, typically 50 ppb to 180 ppb, and the Ni content can be set to 140 ppb or less, for example 100 ppb or less, typically 50 ppb to 100 ppb, relative to the mass of the SiO2 component.

[0032] The concentration of the SiO2 component in the active silicic acid aqueous solution obtained in the step (a) is, for example, about 1 to 10 mass %, or about 1 to 6 mass %. In step (a), anion exchange can be optionally carried out before or after cation exchange. For example, the aqueous sodium silicate solution can be contacted with an anion exchange resin before or after contacting the aqueous sodium silicate solution with a cation exchange resin. As the anion exchange resin, a strong basic anion exchange resin or a weak basic anion exchange resin can be used.

[0033] Step (b) is a step of producing silica sol by heating and aging the active silicic acid aqueous solution obtained in step (a). The heating temperature is about 50 to 180°C. Pressurized granulation is possible even at temperatures exceeding 100°C, and a closed pressurizer or an open pressurizer can be used. The mixture is heated at the above temperature under stirring to size-regulate the silica, thereby producing a silica sol. A multi-stage build-up process can be used for size-regulation. That is, an alkaline substance is added to the above-mentioned active silicic acid aqueous solution to prepare a heel liquid having a pH of 9 to 11, and then the above-mentioned active silicic acid aqueous solution is charged into the heel liquid to size-regulate the silica particles. The size-regulation time for forming silica particles is about 1 to 100 hours, and the size-regulation time can be adjusted to obtain the desired silica particle diameter.

[0034] Step (c) is a step of ultrafiltering the silica sol obtained in step (b). An example of the ultrafiltration step is passing through an ultrafiltration device. By passing through an ultrafiltration device, the SiO2 concentration of the silica sol can be increased and concentrated. In the present invention, free metal ions in the silica sol, chelating agents, and metal compound-containing chelating agents (polyvalent metal ion chelating compounds) derived from the above-mentioned aqueous alkali silicate solution can be removed from the silica sol along with the concentration. When the silica particles are heated in the above-mentioned (b) step of sizing, the polyvalent metal ions remaining in the active silicic acid aqueous solution without being removed in (a) step are captured by a chelating agent to form a chelate complex, so that in the process in which the silicic acid monomers and oligomers in the active silicic acid form polysilicic acid (polysiloxane structure) and become silica particles, they are not incorporated into the polysiloxane skeleton and exist in a free state in the silica sol. Therefore, the chelate compound of the polyvalent metal ions is discharged out of the system by ultrafiltration in (c) step, and a silica sol with a further reduced amount of metal ions in the silica sol can be produced. In step (c), cation exchange and / or anion exchange can be carried out before or after ultrafiltration.

[0035] The silica sol obtained through step (c) of the present invention has a Cu content of 180 ppb or less, typically 50 ppb to 180 ppb, based on the total mass of the SiO2 component, and a Ni content of 100 ppb or less, typically 50 ppb to 100 ppb, based on the total mass of the SiO2 component. The ultrafiltration in the step (c) uses an organic membrane such as a cellulose acetate membrane, an aromatic polyamide membrane, a polyvinyl alcohol membrane, a polysulfone membrane, or a ceramic membrane, and continues to flow the silica sol in a certain direction along the surface of the membrane, continuously discharging water in which impurities (in this case, a compound in which a chelating agent and a polyvalent metal ion are combined) are concentrated, and the silica sol is highly purified and the silica concentration of the silica sol is increased and concentrated. The membrane can have a pore size of about 0.1 μm to 0.001 μm or about 0.01 μm to 0.001 μm and a molecular weight cutoff of about 30,000 to 3,000,000. The ultrafiltration can be performed under the conditions possible depending on the heat resistance, pressure resistance, etc. of the membrane. For example, in the case of an organic membrane, filtration can be performed at a temperature of 10 to 80°C and a pressure of 0.3 MPa or less, and in the case of a ceramic membrane, filtration can be performed at a temperature of 300°C or less and a pressure of 10 MPa or less.

[0036] The particle size of the silica particles in the silica sol obtained in the step (c) is expressed as an average primary particle size (nm) and is calculated from the specific surface area measured by the nitrogen gas adsorption method (BET method). In the step (c), a silica sol can be obtained in which silica particles having an average primary particle size of 1 to 500 nm, 1 to 200 nm, or 5 to 100 nm are dispersed in an aqueous medium. The silica concentration of the silica sol can be arbitrarily adjusted within the range of 1 to 40 mass%, 5 to 40 mass%, 10 to 30 mass%, or 20 to 30 mass% of SiO2.

[0037] In step (c) of the present invention, ion exchange can be optionally carried out before ultrafiltration, after ultrafiltration, or both before and after ultrafiltration. Ion exchange can be cation exchange, anion exchange, or a combination of cation exchange and anion exchange. In the present invention, the active silicic acid aqueous solution obtained in step (a) and the silica sol obtained in step (c) can be filtered through a filter to remove coarse particles. For example, a filter that has a removal rate of 50% or more of silica particles with a primary particle size of 1.0 μm or more can be used. As these filters, membrane type filters, pleated type filters, depth type filters, spool type filters, surface type filters, roll type filters, depth pleated type filters, diatomaceous earth-containing filters, etc. can be used, and among them, membrane type filters can be preferably used. The absolute pore size of the above filters can be set to 0.3 μm to 3.0 μm.

[0038] In the step (c), a pH adjuster can be added to the obtained silica sol to arbitrarily set the pH to 0.5 to 13, and an alkaline silica sol or an acidic silica sol can be obtained. Known acids and alkalis can be used as the pH adjuster. Examples of the acid include inorganic acids such as sulfuric acid, hydrochloric acid, and nitric acid, and organic acids such as formic acid, acetic acid, oxalic acid, citric acid, and paratoluenesulfonic acid. Examples of the alkali include inorganic alkalis such as NaOH, KOH, and ammonia, amines such as ethylamine, diethylamine, triethylamine, monoethanolamine, diethanolamine, and triethanolamine, and quaternary ammonium hydroxides such as tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetrabutylammonium hydroxide. These can be used alone or as a mixture.

[0039] The shape of the silica particles in the silica sol can be changed by the silica particle sizing step (b), and it is possible to obtain silica particles having a ratio of (average particle size in nm as measured by dynamic light scattering) / (average primary particle size in nm as measured by nitrogen gas adsorption) of, for example, 1.1 to 40, or 1.1 to 20, or 1.1 to 10, or 1.1 to 5, or 1.1 to 4.

[0040] The dispersion medium of the silica sol can be changed from an aqueous medium to an organic solvent by evaporation using an evaporator or ultrafiltration using an ultrafiltration membrane. Examples of organic solvents include methanol, ethanol, n-propanol, iso-propanol, butanol, methyl cellosolve acetate, ethyl cellosolve acetate, propylene glycol, propylene glycol monomethyl ether, propylene glycol monoethyl ether, methyl isobutyl carbinol, propylene glycol monobutyl ether, propylene glycol monomethyl ether acetate, propylene glycol monoether ether acetate, propylene glycol monopropyl ether acetate, propylene glycol monobutyl ether acetate, toluene, xylene, methyl ethyl ketone, cyclopentanone, cyclohexanone, ethyl 2-hydroxypropionate, ethyl 2-hydroxy-2-methylpropionate, ethyl ethoxyacetate, ethyl hydroxyacetate, methyl 2-hydroxy-3-methylbutanoate, methyl 3-methoxypropionate, ethyl 3-methoxypropionate, ethyl 3-ethoxypropionate, methyl 3-ethoxypropionate, methyl pyruvate, ethyl pyruvate, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol monopropyl ether acetate, ethylene glycol monobutyl ether acetate, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dipropyl ether, diethylene glycol dibutyl ether propylene glycol monomethyl ether, propylene glycol dimethyl ether, propylene glycol diethyl ether, propylene glycol dipropyl ether, propylene glycol dibutyl ether, ethyl lactate, propyl lactate, isopropyl lactate, butyl lactate, isobutyl lactate, methyl formate, ethyl formate, propyl formate, isopropyl formate, butyl formate, isobutyl formate, amyl formate, isoamyl formate, methyl acetate,Ethyl acetate, amyl acetate, isoamyl acetate, hexyl acetate, methyl propionate, ethyl propionate, propyl propionate, isopropyl propionate, butyl propionate, isobutyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, isopropyl butyrate, butyl butyrate, isobutyl butyrate, ethyl hydroxyacetate, ethyl 2-hydroxy-2-methylpropionate, methyl 3-methoxy-2-methylpropionate, methyl 2-hydroxy-3-methylbutyrate, ethyl methoxyacetate, ethyl ethoxyacetate, methyl 3-methoxypropionate, ethyl 3-ethoxypropionate, ethyl 3-methoxypropionate, 3-methoxybutyl acetate, 3-methoxypropyl acetate, 3-methyl-3-methoxybutyl acetate, 3-methyl-3-methoxybutyl propionate, 3-methyl-3-methoxybutyl butyrate, methyl acetoacetate, toluene, xylene, methyl ethyl ketone ketone, methyl propyl ketone, methyl butyl ketone, 2-heptanone, 3-heptanone, 4-heptanone, cyclohexanone, N,N-dimethylformamide, N-methylacetamide, N,N-dimethylacetamide, N-methylpyrrolidone, 4-methyl-2-pentanol, 1-pentanol, 1-hexanol, 1-octanol, 2-ethyl-1-hexanol, allyl alcohol, benzyl alcohol, cyclohexanol, 1,2-ethanediol, 1,2-propanediol, 2-methoxyethanol, 2-ethoxyethanol, 2-propoxyethanol, 2-(methoxyethoxy)ethanol, 1-methoxy-2-propanol, dipropylene glycol monomethyl ether, diacetone alcohol, ethyl carbitol, butyl carbitol, dimethylacetamide, N-methylpyrrolidone, N-ethylpyrrolidone, γ-butyl lactone, cyclohexanone, and the like. The organic solvent may be used alone or in combination of two or more kinds.

[0041] In the above silica sol, the surfaces of the silica particles can be coated with at least one silane compound (silane coupling agent) selected from the group consisting of silane compounds represented by the following formulas (5) and (6). [ka] In formula (5), R 11 represents an organic group having an acryloxy group, a methacryloxy group, an aryl group, an alkyl group, an epoxy group, a mercapto group, an amino group, or a cyano group, or a combination thereof, the functional group may contain a nitrogen atom, an oxygen atom, or a sulfur atom, and the functional group is bonded to a Si atom via a Si-C bond; R 12 represents a hydrolyzable group consisting of an alkoxy group, an acyloxy group, or a halogen group, and a represents an integer of 0 to 3, or 1 to 3. When the silane compound represented by formula (5) coats the surface of a silica particle, at least one R 12 The hydrolyzable group exhibiting the formula (I) forms a Si-O-Si bond on the surface of the silica particle. In formula (6), R 13 represents an alkyl group and is bonded to a silicon atom by a Si-C bond, and R 14 represents an alkoxy group, an acyloxy group, or a halogen group, Y represents an alkylene group, an arylene group, an NH group, or an oxygen atom, d represents an integer of 0 to 3, and e represents an integer of 0 or 1. When the silane compound represented by formula (6) coats the surface of a silica particle, at least one R 14 The group having the formula (I) forms a Si-O-Si bond on the surface of the silica particle.

[0042] The alkyl group may be an alkyl group having 1 to 10 carbon atoms, such as a methyl group, an ethyl group, an n-propyl group, an i-propyl group, a cyclopropyl group, an n-butyl group, an i-butyl group, an s-butyl group, a t-butyl group, a cyclobutyl group, a 1-methyl-cyclopropyl group, a 2-methyl-cyclopropyl group, an n-pentyl group, a 1-methyl-n-butyl group, a 2-methyl-n-butyl group, a 3-methyl-n-butyl group, a 1,1-dimethyl-n-propyl group, or a 1,2-dimethyl-n-propyl group. Examples of the alkylene group include those derived from the above-mentioned alkyl groups. Examples of the aryl group include a phenyl group, a naphthyl group, and an anthryl group. Examples of the arylene group include groups derived from the above aryl groups, such as a phenylene group, a naphthylene group, and an anthrylene group. The alkoxy group mentioned above includes alkoxy groups having 1 to 10 carbon atoms, such as a methoxy group, an ethoxy group, an n-propoxy group, an i-propoxy group, an n-butoxy group, an i-butoxy group, an s-butoxy group, a t-butoxy group, an n-pentyloxy group, a 1-methyl-n-butoxy group, and a 2-methyl-n-butoxy group. The acyloxy group mentioned above is an acyloxy group having 2 to 10 carbon atoms, such as a methylcarbonyloxy group, an ethylcarbonyloxy group, an n-propylcarbonyloxy group, an i-propylcarbonyloxy group, an n-butylcarbonyloxy group, or the like. The halogen group includes fluorine, chlorine, bromine, iodine, and the like.

[0043] Examples of the silane compound (silane coupling agent) represented by the above formula (5) include tetramethoxysilane, tetrachlorosilane, tetraacetoxysilane, tetraethoxysilane, tetra-n-propoxysilane, tetraisopropoxysilane, tetra-n-butoxysilane, tetraacetoxysilane, methyltrimethoxysilane, methyltrichlorosilane, methyltriacetoxysilane, methyltrippropoxysilane, methyltriacetylsilane, methyltributoxysilane, methyltrippropoxysilane, methyltriamyloxysilane, and methyl Triphenoxysilane, methyltribenzyloxysilane, methyltriphenethyloxysilane, glycidoxymethyltrimethoxysilane, glycidoxymethyltriethoxysilane, α-glycidoxyethyltrimethoxysilane, α-glycidoxyethyltriethoxysilane, β-glycidoxyethyltrimethoxysilane, β-glycidoxyethyltriethoxysilane, α-glycidoxypropyltrimethoxysilane, α-glycidoxypropyltriethoxysilane, β-glycidoxypropyltrimethoxysilane, β-glycidoxypropyltriethoxysilane, glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropyltripropoxysilane, γ-glycidoxypropyltributoxysilane, γ-glycidoxypropyltriphenoxysilane, α-glycidoxybutyltrimethoxysilane, α-glycidoxybutyltriethoxysilane, β-glycidoxybutyltriethoxysilane, γ-glycidoxybutyltrimethoxysilane, γ-glycidoxybutyltriethoxysilane, δ-glycidoxybutyltrimethoxysilane , δ-glycidoxybutyltriethoxysilane, (3,4-epoxycyclohexyl)methyltrimethoxysilane, (3,4-epoxycyclohexyl)methyltriethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, β-(3,4-epoxycyclohexyl)ethyltriethoxysilane, β-(3,4-epoxycyclohexyl)ethyltripropoxysilane, β-(3,4-epoxycyclohexyl)ethyltributoxysilane, β-(3,4-epoxycyclohexyl)ethyltriphenoxysilane,γ-(3,4-epoxycyclohexyl)propyltrimethoxysilane, γ-(3,4-epoxycyclohexyl)propyltriethoxysilane, δ-(3,4-epoxycyclohexyl)butyltrimethoxysilane, δ-(3,4-epoxycyclohexyl)butyltriethoxysilane, glycidoxymethylmethyldimethoxysilane, glycidoxymethylmethyldiethoxysilane, α-glycidoxyethylmethyldimethoxysilane, α-glycidoxyethylmethyldiethoxysilane, β-glycidoxyethylmethyldimethoxysilane, β-glycidoxy Ethyl ethyl dimethoxy silane, α-glycidoxypropyl methyl dimethoxy silane, α-glycidoxypropyl methyl diethoxy silane, β-glycidoxypropyl methyl dimethoxy silane, β-glycidoxypropyl ethyl dimethoxy silane, γ-glycidoxypropyl methyl dimethoxy silane, γ-glycidoxypropyl methyl diethoxy silane, γ-glycidoxypropyl methyl dipropoxy silane, γ-glycidoxypropyl methyl dibutoxy silane, γ-glycidoxypropyl methyl diphenoxy silane, γ-glycidoxypropyl ethyl dimethy , γ-glycidoxypropylethyldiethoxysilane, γ-glycidoxypropylvinyldimethoxysilane, γ-glycidoxypropylvinyldiethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, vinyltrimethoxysilane, vinyltrichlorosilane, vinyltriacetoxysilane, vinyltriethoxysilane, vinyltriacetoxysilane, methoxyphenyltrimethoxysilane, methoxyphenyltriethoxysilane, methoxyphenyltriacetoxysilane, methoxyphenyltrichlorosilane, methoxyphenyltrimethoxysilane, Dimethyltrimethoxysilane, methoxybenzyltriethoxysilane, methoxybenzyltriacetoxysilane, methoxybenzyltrichlorosilane, methoxyphenethyltrimethoxysilane, methoxyphenethyltriethoxysilane, methoxyphenethyltriacetoxysilane, methoxyphenethyltrichlorosilane, ethoxyphenyltrimethoxysilane, ethoxyphenyltriethoxysilane, ethoxyphenyltriacetoxysilane, ethoxyphenyltrichlorosilane, ethoxybenzyltrimethoxysilane, ethoxybenzyltriethoxysilane,Ethoxybenzyltriacetoxysilane, Ethoxybenzyltrichlorosilane, Isopropoxyphenyltrimethoxysilane, Isopropoxyphenyltriethoxysilane, Isopropoxyphenyltriacetoxysilane, Isopropoxyphenyltrichlorosilane, Isopropoxybenzyltrimethoxysilane, Isopropoxybenzyltriethoxysilane, Isopropoxybenzyltriacetoxysilane, Isopropoxybenzyltrichlorosilane, t-Butoxyphenyltrimethoxysilane, t-Butoxyphenyltriethoxysilane silane, t-butoxyphenyl triacetoxysilane, t-butoxyphenyl trichlorosilane, t-butoxybenzyl trimethoxysilane, t-butoxybenzyl triethoxysilane, t-butoxybenzyl triacetoxysilane, t-butoxybenzyl trichlorosilane, methoxynaphthyl trimethoxysilane, methoxynaphthyl triethoxysilane, methoxynaphthyl triacetoxysilane, methoxynaphthyl trichlorosilane, ethoxynaphthyl trimethoxysilane, ethoxynaphthyl triethoxysilane, ethoxy Sinaphthyltriacetoxysilane, ethoxynaphthyltrichlorosilane, γ-chloropropyltrimethoxysilane, γ-chloropropyltriethoxysilane, γ-chloropropyltriacetoxysilane, 3,3,3-trifluoropropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-mercaptopropyltriethoxysilane, β-cyanoethyltriethoxysilane, chloromethyltrimethoxysilane, chloromethyltriethoxysilane, dimethyldimethyl Examples of the silane include γ-methacryloxypropylmethyldimethoxysilane, γ-methacryloxypropylmethyldiethoxysilane, γ-mercaptopropylmethyldimethoxysilane, γ-mercaptomethyldiethoxysilane, methylvinyldimethoxysilane, and methylvinyldiethoxysilane.

[0044] Examples of the silane compound (silane coupling agent) represented by formula (6) include methylene bistrimethoxysilane, methylene bistrichlorosilane, methylene bistriacetoxysilane, ethylene bistriethoxysilane, ethylene bistrichlorosilane, ethylene bistriacetoxysilane, propylene bistriethoxysilane, butylene bistrimethoxysilane, phenylene bistrimethoxysilane, phenylene bistriethoxysilane, phenylene bismethyldiethoxysilane, phenylene bismethyldimethoxysilane, naphthylene bistrimethoxysilane, bistrimethoxydisilane, bistriethoxydisilane, bisethyldiethoxydisilane, and bismethyldimethoxydisilane.

[0045] Further, examples of the silane compound (silane coupling agent) represented by the formula (6) include the following compounds. [ka] Formula (6-1) is hexamethyldisilazane, formula (6-2) is hexamethyldisilane, and formula (6-3) is hexamethyldisiloxane. These silane compounds (silane coupling agents) are available from Tokyo Chemical Industry Co., Ltd.

[0046] The silica sol obtained by the present invention can be used for general purposes, such as foundry sand binders, bonding agents, additives for paper pulp, additives for soap, raw materials for medicines, additives for civil engineering and building materials. Taking advantage of its high purity, it is particularly useful as an abrasive for silicon wafers, an abrasive for semiconductor devices (CMP), catalysts, catalyst carriers, high-purity ceramic raw materials, columns for pharmaceutical refining, and coating components for plastic lenses and glass surfaces. EXAMPLES

[0047] (Material preparation) Anhydrous sodium silicate (cullet): cullet manufactured by Oriental Silica Corporation was prepared. The SiO2 / Na2O molar ratio was 3.2. Tetrasodium ethylenediaminetetraacetate: Chelest Corporation, trade name Chelest OD was prepared. Hydroxyethanephosphonic acid: Chelest PH-210 (trade name), manufactured by Chelest Corporation, was prepared. Sodium gluconate: Chelest GB (trade name), manufactured by Chelest Corporation, was prepared. H-type strongly acidic cation exchange resin: A commercially available cation exchange resin was converted to H-type with an aqueous sulfuric acid solution to prepare the resin.

[0048] (Measurement method) Measurement of average primary particle size: The average primary particle size (nm) was measured by the nitrogen gas adsorption method (BET method). Measurement of pH: Measured using a pH measuring device manufactured by DKK-TOA Corporation. Measurement of electrical conductivity: Measurement was performed using an electrical conductivity measuring device manufactured by DKK-TOA Corporation. Measurement of polyvalent metal components and their contents: Qualitative and quantitative analysis was performed using an ICP emission spectrometer manufactured by PerkinElmer, Inc.

[0049] Example 1 159g of anhydrous sodium silicate cullet, 1041g of pure water, and 0.02g of 1% by mass tetrasodium ethylenediaminetetraacetate aqueous solution were added to a 3-liter stainless steel autoclave vessel and heated at 150°C for 1 hour to prepare a sodium silicate aqueous solution with a silica concentration of 10% by mass. This sodium silicate aqueous solution had Cu and Ni contents of 364ppb and 152ppb per silica contained in the aqueous solution, respectively. This sodium silicate aqueous solution was diluted with pure water to a silica concentration of 4% by mass, and passed through a column packed with H-type strongly acidic cation exchange resin (trade name: Amberlite IR-120B) to obtain an active silicic acid aqueous solution with a silica concentration of 3.4% by mass. Next, 29 g of the above-mentioned sodium silicate aqueous solution having a silica concentration of 10% by mass and 265 g of pure water were placed in a 3-liter glass container and heated to 80° C. in an oil bath under stirring. 2261 g of the above-mentioned active silicic acid aqueous solution having a silica concentration of 3.4% by mass was continuously fed thereto over 6 hours, and the liquid temperature was maintained at 80° C. for 1 hour and 40 minutes, and then adjusted to 100° C. and maintained for 4 hours and 20 minutes. After the supply of active silicic acid was completed, the liquid temperature was adjusted to 98° C. and heating was continued for 4 hours to obtain a reaction liquid. This reaction liquid was a silica sol having a silica concentration of 3.2% by mass, pH 10.0, electrical conductivity of 427 μS / cm, and an average primary particle diameter of silica particles by nitrogen gas adsorption method (BET method specific surface area converted particle diameter) of 13 nm. Subsequently, 2427 g of this reaction liquid was heated to 70° C. and concentrated using a commercially available ultrafiltration membrane (molecular weight cutoff: 200,000) until the silica concentration became approximately 30% by mass, to obtain 236 g of silica sol. This silica sol had a silica concentration of 30.5 mass %, a pH of 9.2, an electrical conductivity of 2020 μS / cm, a Cu content relative to the silica of 108 ppb, and a Ni content relative to the silica of 92 ppb. Examples 2 to 9, Comparative Examples 1 to 3, and Reference Example 1 were carried out in the same manner as in Example 1. The procedures and results are shown in the following table.

[0050] [Table 1] Table 1 shows the procedure for dissolving anhydrous sodium silicate (cullet) in water by heating. In Table 1, item X1 indicates the mass (g) of anhydrous sodium silicate (cullet) charged into the stainless steel autoclave apparatus, item X2 indicates the mass (g) of pure water charged into the stainless steel autoclave apparatus, item X3 indicates the mass (g) of the chelating agent-containing aqueous solution charged into the stainless steel autoclave apparatus, Examples 1 to 7 and Comparative Example 3 indicate the mass (g) of an aqueous solution of tetrasodium ethylenediaminetetraacetate having a concentration of 1% by mass, Example 8 indicates the mass (g) of an aqueous solution of hydroxyethanephosphonic acid having a concentration of 1% by mass, Example 9 indicates the mass (g) of an aqueous solution of sodium gluconate having a concentration of 1% by mass, and Reference Example 1 indicates the mass (g) of an aqueous solution of tetrasodium ethylenediaminetetraacetate having a concentration of 0.02% by mass. Item X4 indicates the amount (ppm) of chelating agent added to anhydrous sodium silicate (cullet) when dissolving anhydrous sodium silicate (cullet), item X5 indicates the amount (ppm) of chelating agent added to anhydrous sodium silicate (cullet) when dissolving anhydrous sodium silicate (cullet), item X6 indicates the silica concentration (%) in anhydrous sodium silicate (cullet) in a stainless steel autoclave apparatus, item X7 indicates the temperature (℃) at which anhydrous sodium silicate (cullet) is dissolved by heating in water, and item X8 indicates the time (hours) at which anhydrous sodium silicate (cullet) is dissolved by heating in water.

[0051] [Table 2] In Table 2, items X9 to X13 show the procedures and physical properties after the sodium silicate aqueous solution (water glass) is prepared. In Table 2, item X9 indicates the mass (g) of a 1% by mass concentration tetrasodium ethylenediaminetetraacetate aqueous solution to be added to the sodium silicate aqueous solution (water glass) after dissolving anhydrous sodium silicate (cullet) in water by heating to prepare a sodium silicate aqueous solution (water glass). Item X10 indicates the amount (ppm) of a chelating agent added to the sodium silicate aqueous solution (water glass) after dissolving anhydrous sodium silicate (cullet) in water by heating to prepare a sodium silicate aqueous solution (water glass). Item X11 indicates the amount (ppm) of a chelating agent added to the sodium silicate aqueous solution (water glass) after dissolving anhydrous sodium silicate (cullet) in water to prepare a sodium silicate aqueous solution (water glass). Item X12 indicates the copper content (ppb) relative to silica in the obtained sodium silicate aqueous solution (water glass). Item X13 indicates the nickel content (ppb) relative to silica in the obtained sodium silicate aqueous solution (water glass).

[0052] In Example 7, the test was conducted until an aqueous sodium silicate solution (water glass) was prepared by dissolving anhydrous sodium silicate (cullet) in water by heating. In Comparative Example 3, the test was not conducted because anhydrous sodium silicate (cullet) could not be dissolved in water by heating.

[0053] [Table 3] Table 3 shows the procedure for producing the aqueous solution of active silicic acid and the physical properties of the aqueous solution of active silicic acid obtained. In Table 3, item Y1 indicates the mass (g) of the sodium silicate aqueous solution (water glass), item Y2 indicates the mass (g) of pure water added for dilution, item Y3 indicates the mass (g) of the obtained active silicic acid aqueous solution, item Y4 indicates the copper content (ppb) relative to silica (SiO2) in the obtained active silicic acid aqueous solution, and item Y5 indicates the nickel content (ppb) relative to silica (SiO2) in the obtained active silicic acid aqueous solution.

[0054] [Table 4] Table 4 shows the physical properties of the reaction liquid (silica sol before ultrafiltration). In Table 4, item Z1 indicates the silica concentration (mass%) of the silica sol, item Z2 indicates the pH of the silica sol, item Z3 indicates the electrical conductivity (μS / cm) of the silica sol, and item Z4 indicates the average primary particle size (nm) measured by the nitrogen gas adsorption method (BET method).

[0055] [Table 5] Table 5 shows the physical properties of the silica sol after ultrafiltration. In Table 5, item Z5 indicates the mass (g) of silica sol charged to the ultrafiltration device, item Z6 indicates the mass (g) of silica sol obtained by passing through the ultrafiltration device, item Z7 indicates the silica concentration (%) of the silica sol obtained by passing through the ultrafiltration device, item Z8 indicates the pH of the silica sol obtained by passing through the ultrafiltration device, item Z9 indicates the electrical conductivity (μS / cm) of the silica sol obtained by passing through the ultrafiltration device, item Z10 indicates the copper content (ppb) relative to the silica of the silica sol obtained by passing through the ultrafiltration device, and item Z11 indicates the nickel content (ppb) relative to the silica of the silica sol obtained by passing through the ultrafiltration device.

[0056] In the above Examples 1 to 6 and Examples 8 to 9, a chelating agent was present when anhydrous sodium silicate (cullet) was heated and dissolved in water, and it was found that polyvalent metals were reduced at the stage of the active silicic acid aqueous solution in process (a) and at the stage of producing silica sol in process (c) regardless of the type of chelating agent.

[0057] On the other hand, in Comparative Example 2, the chelating agent was added after the active silicic acid aqueous solution was formed, and the polyvalent metals in the obtained silica sol were not sufficiently reduced. In Comparative Example 3, the temperature at which anhydrous sodium silicate (cullet) was heated and dissolved in water was 60° C., and the anhydrous sodium silicate (cullet) could not be sufficiently dissolved.

[0058] Furthermore, it was found from Reference Example 1 that the effect of the present invention can be achieved even with a small amount of the chelating agent when anhydrous sodium silicate (cullet) is dissolved in water by heating. However, in applications where polyvalent metals are highly undesirable as impurities, it is necessary to further reduce them, and the amount can be set to 0.1 to 3000 ppm, or 0.1 to 300 ppm, relative to the silica in the anhydrous sodium silicate (cullet). [Industrial Applicability]

[0059] This method involves heating anhydrous sodium silicate (cullet), a chelating agent, and water to obtain a sodium silicate aqueous solution, and a method for producing a high-purity silica sol using the sodium silicate aqueous solution (water glass). The resulting high-purity silica sol can be used for general purposes, such as foundry sand binders, bonding agents, additives for paper and pulp, additives for soap, pharmaceutical raw materials, and additives for civil engineering and building materials. Taking advantage of its particularly high purity characteristics, it is useful as an abrasive for silicon wafers, an abrasive for semiconductor devices (CMP), catalysts, catalyst carriers, high-purity ceramic raw materials, columns for pharmaceutical refining, and coating components for plastic lenses and glass surfaces.

Claims

1. The method according to claim 1, comprising the steps (a) to (c) below: (a) step: a step of heating and mixing anhydrous sodium silicate, a chelating agent, and water at 100 to 270°C; the step of heating and mixing includes the steps of preparing an aqueous solution containing a chelating agent, and heating and mixing the anhydrous sodium silicate and the aqueous solution containing a chelating agent at 100 to 270°C. a step of contacting the aqueous sodium silicate solution obtained by the method for producing an aqueous sodium silicate solution with a cation exchange resin to obtain an aqueous activated silicic acid solution; Step (b): a step of heating the aqueous active silicic acid solution obtained in step (a) to obtain a silica sol; Step (c): a step of ultrafiltering the silica sol obtained in step (b). Including, The anhydrous sodium silicate is a cullet containing a polyvalent metal compound, and The silica sol obtained in the step (c) has a Cu content of 180 ppb or less based on the total mass of the SiO 2 component and a Ni content of 100 ppb or less based on the total mass of the SiO 2 component; A method for producing silica sol.

2. The addition ratio of the chelating agent is determined by the ratio of SiO contained in the anhydrous sodium silicate. ２ The method for producing a silica sol according to claim 1, wherein the content of the silica sol is 0.1 to 3000 ppm based on the total mass of the components.

3. The method for producing a silica sol according to claim 1 or 2, wherein the heating time is 0.1 to 50 hours.

4. The method for producing a silica sol according to any one of claims 1 to 3, wherein the components are heated and mixed under a pressure of 1 to 60 atm.

5. SiO in the sodium silicate aqueous solution ２ / Na ２ The method for producing a silica sol according to any one of claims 1 to 4, wherein the molar ratio of O is 1 to 10.

6. The method for producing a silica sol according to any one of claims 1 to 5, wherein the chelating agent is a chelating agent having a carboxyl group, a hydroxyl group, a phosphonic acid group, or a combination of these groups.

7. 7. The method for producing a silica sol according to claim 1, wherein the chelating agent is an aminocarboxylic acid chelating agent, a phosphonic acid chelating agent, a gluconic acid chelating agent, or a metal salt thereof.

8. The method for producing a silica sol according to any one of claims 1 to 7, wherein the chelating agent is ethylenediaminetetraacetic acid, hydroxyethylethylenediaminetriacetic acid, diethylenetriaminepentaacetic acid, nitrilotriacetic acid, gluconic acid, hydroxyethyliminotriacetic acid, L-aspartic acid-N,N-diacetic acid, hydroxyiminodisuccinic acid, aminotrimethylenephosphonic acid, hydroxyethanephosphonic acid, or a salt thereof.

9. A method for producing a silica sol, wherein the cation exchange resin is an H-type cation exchange resin.

10. 10. The method for producing a silica sol according to claim 1, wherein the step (a) further comprises a step of performing anion exchange before or after contacting the aqueous sodium silicate solution with a cation exchange resin.

11. The method for producing a silica sol according to any one of claims 1 to 9, wherein the step (c) comprises a step of performing cation exchange and / or anion exchange before or after ultrafiltration of the silica sol.

12. A method for producing a composition comprising the steps of heating and mixing anhydrous sodium silicate, a chelating agent, and water at 100 to 270°C, the step of heating and mixing includes the steps of preparing an aqueous solution containing a chelating agent, and heating and mixing the anhydrous sodium silicate and the aqueous solution containing a chelating agent at 100 to 270°C; and the anhydrous sodium silicate is a cullet containing a polyvalent metal compound, A method for producing an aqueous sodium silicate solution containing the polyvalent metal ion chelate compound.

13. The method for producing a sodium silicate aqueous solution according to claim 12, wherein the chelating agent is added in an amount of 0.1 to 3000 ppm based on the total mass of the SiO 2 component contained in the anhydrous sodium silicate.

14. A method for producing a sodium silicate aqueous solution according to claim 12 or claim 13, wherein the heating time is 0.1 to 50 hours.

15. A method for producing the aqueous sodium silicate solution according to claim 12, wherein the aqueous sodium silicate solution is heated and mixed under a pressure of 1 to 60 atmospheres.

16. The method for producing an aqueous sodium silicate solution according to claim 12, wherein the molar ratio of SiO 2 / Na 2 O in the aqueous sodium silicate solution is 1 to 10.

17. The method according to claim 12, wherein the chelating agent is a chelating agent having a carboxyl group, a hydroxyl group, a phosphonic acid group, or a combination of these groups. A method for producing a sodium phosphate aqueous solution.

18. A method for producing a sodium silicate aqueous solution described in any one of claims 12 to 17, wherein the chelating agent is an aminocarboxylic acid chelating agent, a phosphonic acid chelating agent, a gluconic acid chelating agent, or a metal salt thereof.

19. A method for producing a sodium silicate aqueous solution according to any one of claims 12 to 18, wherein the chelating agent is ethylenediaminetetraacetic acid, hydroxyethylethylenediaminetriacetic acid, diethylenetriaminepentaacetic acid, nitrilotriacetic acid, gluconic acid, hydroxyethyliminotriacetic acid, L-aspartic acid-N,N-diacetic acid, hydroxyiminodisuccinic acid, aminotrimethylenephosphonic acid, hydroxyethanephosphonic acid, or a salt thereof.

20. A method for producing an activated aqueous silicic acid solution, comprising a step of contacting an aqueous sodium silicate solution obtained by the method for producing an activated silicic acid solution according to any one of claims 12 to 19 with an H-type cation exchange resin.

21. A sodium silicate aqueous solution comprising a sodium-containing silicate ion monomer (A1) and a compound (B) in which a chelating agent having a carboxyl group, a hydroxyl group, a phosphonic acid group, or a combination of these groups is bonded to a polyvalent metal ion M.

22. A sodium silicate aqueous solution containing a sodium-containing silicate ion monomer (A1) and a compound (B) containing at least one partial structure selected from the partial structures represented by the following formulas (1) to (3): 【Chemistry 1】 (In the formula, M represents a polyvalent metal ion, the wavy line 1 represents a covalent bond between a carbon atom or a phosphorus atom and an adjacent atom, the wavy line 2 represents an ionic bond between the polyvalent metal ion M and an oxygen atom or a coordinate bond between the polyvalent metal ion M and a nitrogen atom or an oxygen atom, provided that a plurality of wavy lines 2 may exist for the polyvalent metal ion M, and the dotted line represents a coordinate bond between the polyvalent metal ion M and an oxygen atom.)

23. 23. The sodium silicate aqueous solution according to claim 21 or 22, wherein the polyvalent metal ion M is a copper ion or a nickel ion.

24. Claims 21 to 23 further comprising sodium-containing colloidal silicate ion micelles (A2).

24. The sodium silicate aqueous solution according to any one of claims 23.

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