TWI888388B - Method for producing water glass containing chelating agent and silica sol - Google Patents

Abstract

The present invention provides a method for obtaining an aqueous sodium silicate solution by heating anhydrous sodium silicate (glass scraps), a chelating agent and water, and a method for producing a high-purity silica sol using the aqueous sodium silicate solution (water glass). A method for producing an aqueous sodium silicate solution by heating and mixing anhydrous sodium silicate, a chelating agent and water at 100-270°C. A method for producing an aqueous sodium silicate solution by heating and mixing anhydrous sodium silicate and an aqueous solution containing a chelating agent at 100-270°C. A method for producing an aqueous sodium silicate solution in which the chelating agent is 0.1-3000 ppm relative to _SiO2 . A method for preparing silica sol comprises: (a) a step of contacting a sodium silicate aqueous solution obtained by the above-mentioned preparation method with a cation exchange resin to obtain an active silicic acid aqueous solution; (b) a step of heating the active silicic acid aqueous solution obtained in step (a) to obtain silica sol; and (c) a step of super-filtering the silica sol obtained in step (b).

Description

Method for producing water glass and silicon dioxide sol containing chelating agent

The present invention relates to a method for producing a silica sol having a low content of polyvalent metal compounds.

Alkali silicate aqueous solution (water glass) has been used in a wide range of fields such as foundry sand binders, binders, pulp additives, soap additives, pharmaceutical raw materials, and civil engineering and construction material additives.

Moreover, various silica products such as colloidal silica dispersion (silica sol), silica hydrogel, silica powder, lithium silicate aqueous solution, and potassium silicate aqueous solution are produced using alkaline silicate aqueous solution as the starting material. The above-mentioned silica sol is produced by subjecting the alkaline silicate aqueous solution to cation exchange and heating the resulting active silicic acid.

Compositions using these materials have applications where the content of metal oxides other than silicon dioxide must be extremely low, such as polishing agents for semiconductor wafers or semiconductor devices.

The metal oxides other than silicon dioxide as impurities in the aqueous solution of alkaline silicate are derived from the raw materials used to manufacture the aqueous solution of alkaline silicate and are contained in the manufacturing process.

Anhydrous sodium silicate (glass scraps) is obtained by washing and drying silica sand or silica rock, mixing it with soda ash (sodium carbonate) or caustic soda for a melting reaction, and then cooling it. Silica sand contains metal compounds other than silicon dioxide from natural sources, and soda ash or caustic soda also contains metal compounds other than silicon dioxide. These metal compounds remain in the glass scraps.

The aqueous solution of sodium silicate (water glass) is obtained by dissolving the above-mentioned glass scraps in a high-pressure dissolving vessel equipped with a boiler. The aqueous solution of sodium silicate produced by the conventional method is produced as an aqueous solution containing a relatively large amount of metal compounds other than silicon dioxide.

As a method for producing highly purified active silicic acid using an aqueous silicate solution, there is disclosed a method for producing a high-purity active silicic acid aqueous solution by mixing an iminodiacetic acid type chelating agent in an aqueous silicate solution to obtain an aqueous silicate solution containing the chelating agent, and then contacting the aqueous silicate solution containing the chelating agent with an H-type cation exchanger and contacting the aqueous silicate solution containing the chelating agent with an anion exchanger (see patent document 1).

The invention also discloses a method for producing a silica sol using an aqueous solution of active silicic acid produced by the above method (see patent document 2).

[Prior Art Literature] [Patent Literature]

[Patent document 1] Japanese Patent No. 3691047

[Patent Document 2] Japanese Patent No. 3691048

In the complexation reaction between the polyvalent metal compound contained in anhydrous sodium silicate (glass scraps) and the chelating agent, the chelation formation energy varies greatly depending on the form of the silicate ions. The inventors of the present invention have found that when anhydrous sodium silicate (glass scraps) is heated and dissolved in water, the sodium-containing silicate ion monomers form colloidal silicate ion micelles containing sodium and become polymerized. The inventors have found that the polyvalent metal ions coexist in the form of these silicate ion monomers, or form colloidal silicate ion micelles and are pulled into their polymers, so the complex formation energy with the chelating agent varies greatly. The present invention discovered that in the process of dissolving anhydrous sodium silicate (glass scraps) by heating with water, since the polyvalent metal ions and the chelating agent form a complex before the silicate ions polymerize, the chelated complex is not pulled into the silica matrix. It is found that it can be removed by cation exchange or superfiltration, and based on this, a high-purity active silicic acid aqueous solution and a high-purity silica sol are intended to be produced.

That is, the purpose of the present invention is to provide a method for obtaining an aqueous sodium silicate solution by heating anhydrous sodium silicate (glass chips), a chelating agent and water, and a method for producing a high-purity silica sol using the aqueous sodium silicate solution (water glass).

The first aspect of the present invention is a method for producing an aqueous sodium silicate solution, comprising the step of heating and mixing anhydrous sodium silicate, a chelating agent and water at 100-270°C. The second aspect is the method for producing an aqueous sodium silicate solution of the first aspect, wherein the heating and mixing step comprises the following steps: preparing an aqueous solution containing a chelating agent, and heating and mixing the anhydrous sodium silicate and the aqueous solution containing the chelating agent at 100-270°C. The third aspect is the method for producing an aqueous sodium silicate solution of the first aspect or the second aspect, wherein the addition ratio of the chelating agent is 1:1 relative to the SiO contained in the anhydrous sodium silicate. ₂ components, the total mass is 0.1 to 3000 ppm, as a fourth aspect, it is a method for producing an aqueous sodium silicate 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, it is a method for producing an aqueous sodium silicate solution according to any one of the first to fourth aspects, wherein the heating and mixing are carried out under a pressure of 1 to 60 atmospheres, as a sixth aspect, it is a method for producing an aqueous sodium silicate solution according to any one of the first to fifth aspects, wherein the SiO ₂ /Na ₂ The molar ratio of O is 1 to 10. As a seventh aspect, it is a method for producing an aqueous sodium silicate 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, it is a method for producing an aqueous sodium silicate 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 chelating agent, a gluconic acid-based chelating agent or a metal salt thereof, as a ninth aspect, is a method for producing an aqueous sodium silicate 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, hydroxyethylaminotriacetic acid, aminodisuccinic acid, aminotrimethylenephosphonic acid or hydroxyethanephosphonic acid or salts thereof; as a tenth aspect, a method for producing an aqueous solution of active silicic acid, comprising the step of contacting an aqueous sodium silicate solution obtained by the production method of any one of the first to ninth aspects with an H-type cation exchange resin; as an eleventh aspect, a method for producing a silica sol, comprising the following step (a) Step (a) is a step of contacting the sodium silicate aqueous solution obtained by the production method of any one of the first aspect to the ninth aspect with a cation exchange resin to obtain an active silicic acid aqueous solution; Step (b) is a step of heating the active silicic acid aqueous solution obtained in step (a) to obtain a silica sol; Step (c) is a step of super-filtering the silica sol obtained in step (b).

As a twelfth aspect, it is a method for producing a silica sol according to the eleventh aspect, wherein step (a) further comprises a step of anion exchange before and/or after the sodium silicate aqueous solution is brought into contact with the cation exchange resin. As a thirteenth aspect, it is a method for producing a silica sol according to the eleventh aspect, wherein step (c) further comprises a step of anion exchange before and/or after the sodium silicate aqueous solution is brought into contact with the cation exchange resin. The colloid comprises the steps of performing cation exchange and/or anion exchange before and/or after filtering. As a 14th aspect, it is a method for producing a silica sol according to any one of aspects 11 to 13, wherein the anhydrous sodium silicate is glass scraps, and the silica sol obtained in the step (c) has a Cu content of less than 180 ppb relative to the total mass of _SiO2 components, and a Ni content of less than 100 ppb relative to the total mass of _SiO2 components.

As a fifteenth aspect, an aqueous sodium silicate solution comprises a sodium-containing silicate ion monomer (A1) and a compound (B), wherein the compound (B) is a chelating agent having a carboxyl group, a hydroxyl group, a phosphonic acid group or a combination of these groups and a polyvalent metal ion M bonded together. As a sixteenth aspect, an aqueous sodium silicate solution comprises a sodium-containing silicate ion monomer (A1) and a compound (B), wherein the compound (B) has at least one partial structure among the partial structures represented by the following (1) to (3).

(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 represents a coordination bond between the polyvalent metal ion M and a nitrogen atom or an oxygen atom, but there may be multiple wavy lines 2 for the polyvalent metal ion M, and dotted lines represent multiple polyvalent metal ions. M and oxygen atom coordination bond), as the 17th aspect, it is the sodium silicate aqueous solution of the 15th aspect or the 16th aspect, wherein the polyvalent metal ion M is a copper ion or a nickel ion, and as the 18th aspect, it is the sodium silicate aqueous solution of any one of the 15th to 17th aspects, which further comprises colloidal silicate ion micelles (A2) containing sodium.

According to the present invention, a method for obtaining an aqueous sodium silicate solution by heating or heating and mixing anhydrous sodium silicate (glass chips), a chelating agent and water, and a method for producing a high-purity silicon dioxide sol using the aqueous sodium silicate solution can be provided.

In one embodiment of the present invention, in the stage of dissolving anhydrous sodium silicate (glass chips), that is, before forming a sodium silicate aqueous solution, anhydrous sodium silicate (glass chips) is allowed to coexist with a chelating agent, and in this state, the anhydrous sodium silicate (glass chips) is heated and dissolved with water, and the obtained sodium silicate aqueous solution is brought into contact with a cation exchanger to obtain an active silicic acid aqueous solution, and then the active silicic acid aqueous solution is heated to produce a silica sol, and then superfiltration is performed to form a high-purity silica sol.

Anhydrous sodium silicate (glass scraps) is obtained by heating and dissolving silica sand or silica with soda ash (sodium carbonate) or caustic soda and then cooling. In the case of manufacturing sodium silicate aqueous solution (water glass), anhydrous sodium silicate (glass scraps) and water are heated and dissolved.

Since metal compounds other than silicon dioxide from silica sand or silica stone and soda ash or caustic sodium, which are raw materials for the production of anhydrous sodium silicate (glass scraps), remain in the glass scraps, the sodium silicate aqueous solution produced based on them contains metal compounds other than silicon dioxide.

The present invention focuses on the behavior of silicate ions and polyvalent metal ions in the process of dissolving anhydrous sodium silicate (glass shavings) by heating with water, and finds that a chelating agent must be present when dissolving glass shavings. In the step of dissolving glass shavings by heating with water, anhydrous sodium silicate contains sodium ions or polyvalent metal ions and silicate ions, but silicate ions are easily polymerized by heating, and silicate ion monomers polymerize into silicate ion dimers or colloidal silicate ion micelles. If the polymerization proceeds to colloidal silica ion micelles, the polyvalent metal ions are locked into the silica matrix (i.e., polysiloxane), and a chelate compound of the polyvalent metal ions and the chelating agent cannot be formed. The polyvalent metal ions exist in the active silica and then in the silica particles, resulting in a silica sol containing a large amount of polyvalent metals. On the other hand, when anhydrous sodium silicate (glass chips) dissolves in water, a chelating agent is present in the initial state, i.e., when the polymerization of silicate ions has not yet fully proceeded, and the chelating agent can form chelate compounds with polyvalent metal ions. Therefore, when active silicate is produced by removing sodium from silicate ion monomers containing sodium ions or polyvalent metal ions through H-type cation exchange resin, polyvalent metal ions will not be pulled into the silicon dioxide matrix. Furthermore, when an aqueous solution of alkaline silicate is applied to an H-type cation exchange resin, the chelate compound of the polyvalent metal ions in contact with the phosphonic acid group causes the polyvalent metal ions to undergo cation exchange together with sodium ions. Therefore, during the production stage of active silicic acid, a portion of the polyvalent metal ions are removed to obtain high-purity active silicic acid. When the high-purity active silicic acid is used to produce silica sol by heating and polymerization, the polyvalent metal ions remaining in the silica sol exist as chelate compounds of polyvalent metal ions and will not be pulled into the silica particles. The silica sol contains chelate compounds of silica particles and polyvalent metal ions. The silica sol can be superfiltered to discharge the chelate compounds of polyvalent metal ions from the silica sol to the outside of the system, thereby obtaining a high-purity silica sol.

In the past, after glass chips were dissolved in water to form a sodium silicate aqueous solution, even if a chelating agent was added, since the sodium-containing silicate ions had been polymerized into colloidal silicate ion micelles containing sodium, the polyvalent metal ions were pulled into the silica matrix (polysiloxane). Therefore, even if a chelating agent was added, the polyvalent metal ions could not form a chelate compound of the polyvalent metal ions. In other words, the polyvalent metal ions exist in the silica matrix, and there are residual polyvalent metal ions in the active silica and in the silica particles produced from the active silica. Even if cation exchange, anion exchange or superfiltration is performed, the polyvalent metal ions cannot be removed.

That is, when the anhydrous sodium silicate (glass scraps) of the present invention is heated and dissolved in water and a chelating agent is added, there exists a chelate compound of sodium-containing silicate ion monomers and a polyvalent metal ion containing at least one of the partial structures shown in the above formulas (1) to (3).

However, in the prior art, when anhydrous sodium silicate (glass scraps) is heated and dissolved in water, no chelating agent is present. When a chelating agent is added after a sodium silicate aqueous solution (water glass) is formed, there are no sodium-containing silicate ion monomers, but sodium-containing colloidal silicate ion micelles. In this state, a chelate complex of a polyvalent metal ion is not formed, so a chelate compound of a polyvalent metal ion containing at least one of the partial structures shown in the above formulas (1) to (3) cannot be formed. That is, a high-purity silica sol cannot be obtained.

The present invention is based on the discovery that when anhydrous sodium silicate (glass scraps) is heated and dissolved in water, a chelating agent is present, which can form a chelated compound of polyvalent metal ions. High-purity active silicic acid is obtained by cation exchange treatment. When the high-purity active silicic acid is heated to produce silica sol, the produced silica sol is subjected to superfiltration, and the chelated processed products of the remaining polyvalent metal ions are discharged to the outside of the system beyond the filter membrane, thereby obtaining a method for producing a silica sol with higher purity.

The present invention is a method for producing an aqueous sodium silicate solution by heating or mixing anhydrous sodium silicate (glass chips), a chelating agent and water at 100-270°C, 100-180°C or 110-180°C.

A preferred method is to prepare a sodium silicate aqueous solution by heating and mixing anhydrous sodium silicate and an aqueous solution containing a chelating agent obtained by mixing a chelating agent with water.

Anhydrous sodium silicate (glass scraps) are obtained by heating and melting silica sand or silica (SiO ₂ ) and soda ash (sodium carbonate) or caustic soda and then cooling them. Various glass scraps with a SiO ₂ /Na ₂ O molar ratio of about 2 to 10 are produced by adjusting the mixing ratio of silica sand or silica and soda ash or caustic soda. For example, molar ratio 2.1, molar ratio 2.3, molar ratio 3.1, molar ratio 3.2, molar ratio 3.7 are dissolved in water (hot water) to obtain sodium silicate aqueous solution (water glass) of the above molar ratio. These are used as sodium silicate aqueous solution (water glass) of JIS specification No. 1, No. 2, No. 3, No. 4, and No. 5.

In the present invention, the above-mentioned molar ratio of anhydrous sodium silicate (glass chips) can be used as a raw material.

Such anhydrous sodium silicate (glass chips) can be obtained from TOKUYAMA, ORIENTAL SILICA CORPORATION, PQ COPORATION, etc.

The chelating agent can be used at a ratio of 0.00005~0.15 mass%, or 0.00005~0.015 mass%, or 0.00005~0.01 mass% relative to anhydrous sodium silicate, and typically can be used at a ratio of 0.00001~0.001 mass%. If it is expressed in ppm units, the chelating agent can be used at a ratio of 0.5ppm~1500ppm, or 0.5ppm~150ppm, or 0.5ppm~100ppm relative to anhydrous sodium silicate, and typically can be used at a ratio of 0.1ppm~10ppm.

Furthermore, the chelating agent can be used in an addition ratio of 0.00001-0.3 mass%, 0.00001-0.03 mass%, 0.00001-0.02 mass%, or 0.0001-0.02 mass%, relative to the total mass of the silicon dioxide (SiO ₂ ) component of the anhydrous sodium silicate (glass scraps), and typically can be used in an addition ratio of 0.0001-0.002 mass%. If it is expressed in ppm units, the chelating agent can be used in an addition ratio of 0.1ppm-3000ppm, 0.1ppm-300ppm, 0.1ppm-200ppm, or 1ppm-200ppm relative to the total mass of the silicon dioxide (SiO ₂ ) component of the anhydrous sodium silicate (glass scraps), and typically can be used in an addition ratio of 1ppm-20ppm.

The chelating agent used in the present invention may be, for example, a chelating agent having a carboxyl group, a hydroxyl group, a phosphonic acid group, or a combination of these groups.

Such chelating agents are, for example, aminocarboxylic acid chelating agents, phosphonic acid chelating agents, gluconic acid chelating agents or metal salts thereof (chelated metal salt chelating agents). The salt of the chelating agent having a carboxyl group (chelated metal salt) may be an alkaline metal salt, for example, sodium salt, potassium salt, lithium salt, preferably sodium salt.

Among the chelating agents, aminocarboxylic acid-based chelating agents, which are nitrogen-containing chelating agents, are also preferably used. Aminocarboxylic acid-based chelating agents have an amino group and a carboxyl group in their structure, and may also have a hydroxyl group. Moreover, the carboxyl group can form the above-mentioned salt, for example, a sodium salt.

As the amino group of the aminocarboxylic acid chelating agent, a secondary amine group or a tertiary amine group can be used. A chelating agent can have a secondary amine group and a tertiary amine group in one molecule, or a combination of the two. It is preferred to use a chelating agent having a tertiary amine group. The above-mentioned chelating agent can have one or more amine groups in one molecule, for example, 1 to 6, or 1 to 4, or 2 to 4 amine groups.

The structure of the chelating agent and the metal ion to form a chelate complex includes carboxyl, hydroxyl, phosphonic acid or a combination of these groups as the functional group to form the chelate. In addition, the nitrogen atom in the chelating agent molecule can also participate as the functional group to form the chelate, and in the case of including hydroxyl or phosphonic acid groups, these groups can also participate as the functional group to form the chelate.

When a chelating agent forms a complex with a metal ion, if the chelating agent has multiple carboxyl groups, one chelating agent molecule forms a chelate complex with one polyvalent metal ion molecule. However, in the case of a chelating agent with a single carboxyl group, a hydroxyl group or a phosphonic acid group can form a chelate, and a chelate structure can be formed in which one polyvalent metal ion molecule chelates multiple chelating agents.

Examples of the above-mentioned chelating agents are as follows.

In the above formula (4-1) to formula (4-10), R ¹ to R ⁵ represent hydrogen atom, alkali metal or NH ₄ , respectively. Examples of alkali metal are sodium and potassium. R ¹ to R ⁵ may be the same or different. It is particularly preferred that R ¹ to R ⁵ are hydrogen or sodium.

Formula (4-1) represents ethylenediaminetetraacetic acid or a salt thereof, formula (4-2) represents hydroxyethylenediaminetriacetic 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.

In the present invention, one chelating agent may be used, or two or more chelating agents may be used in combination.

In the present invention, the chelating agent is represented by ethylenediaminetetraacetic acid or its salt represented by formula (4-1), and tetrasodium ethylenediaminetetraacetate is preferably used.

The method for producing an aqueous sodium silicate solution of the present invention comprises the steps of heating or mixing anhydrous sodium silicate, a chelating agent and water at 100-270°C, but typically the method comprises the steps of heating or mixing anhydrous sodium silicate and an aqueous solution containing a chelating agent at 100-180°C. When using an aqueous solution containing a chelating agent, the chelating agent can be dissolved in water to prepare an aqueous solution of the chelating agent with a concentration of, for example, 0.001-10 mass % or 0.01-5 mass %.

The heating temperature is 100~270℃, or 100~180℃, or 110~180℃, and water vapor containing a chelating agent can be used. For example, in the method for manufacturing a sodium silicate aqueous solution, heating or heating mixing can be performed at a pressure of 1 atmosphere to 60 atmospheres, or 1 atmosphere to 10 atmospheres, or 1.5 atmospheres to 10 atmospheres, and the heating time can be set to 0.1~50 hours. The heating time can also be set to more than 50 hours, but it can be set to a maximum of 50 hours for economic reasons.

The sodium silicate aqueous solution may be one in which the molar ratio of SiO ₂ /Na ₃ O in the sodium silicate aqueous solution is in the range of about 1 to 10, or 1 to 4, or 2 to 4. The molar ratio depends on the molar ratio of the components contained in the anhydrous sodium silicate (glass scraps).

Moreover, the concentration of sodium silicate aqueous solution is determined by the mixing ratio of anhydrous sodium silicate (glass chips) and water (aqueous solution containing chelating agent). It can be manufactured and concentrated at a low concentration, or anhydrous sodium silicate (glass chips) can be dissolved to a high concentration. Generally, sodium silicate aqueous solution is sold at 30% to 50% by mass, but when using this sodium silicate as a raw material to manufacture products, the sodium silicate aqueous solution can also be diluted with water to 1% to 10% by mass.

It is believed that when anhydrous sodium silicate (glass scraps) is heated and dissolved in water (hot water), the presence of a chelating agent causes the polyvalent metal ions to efficiently form a complex with the chelating agent, and a chelate complex having any of the partial structures represented by formula (1) to formula (3) or a combination of two or more of these partial structures exists in the sodium silicate aqueous solution. In formula (1) to formula (3), the polyvalent metal ion is represented by the polyvalent metal ion M.

However, since the chelating agent is exposed to a high alkaline aqueous solution with a pH of 9-14 or 10-13, there is a possibility that part of the structure of the chelating agent is decomposed. However, when the active silicate aqueous solution is subsequently prepared, the sodium ions of sodium silicate can be removed together with the polyvalent metal ions by the H-type cationic resin. Therefore, it is believed that a chelate complex having at least any of the partial structures represented by formula (1) to formula (3) or a combination of two or more of these partial structures exists in the sodium silicate aqueous solution.

In the present invention, when anhydrous sodium silicate (glass chips) is dissolved in water (hot water), due to the presence of the above-mentioned chelating agent, a chelate compound of silicate ion monomers and polyvalent metal ions M before the silicate ions are polymerized exists. That is, there is a silicate aqueous solution (water glass) containing sodium-containing silicate ion monomers (A1) and compound (B), and the compound (B) is a chelating agent having a carboxyl group, a hydroxyl group, a phosphonic acid group or a combination of these groups and a polyvalent metal ion M bonded.

More specifically, there is an aqueous silicate solution (water glass) containing a sodium-containing silicate ion monomer (A1) and a compound (B), wherein the compound (B) contains at least one of the partial structures represented by the following formulas (1) to (3).

When anhydrous sodium silicate (glass scraps) is dissolved in water (hot water), the sodium-containing silicate ions are monomers, but as time passes by due to heating, the above-mentioned sodium-containing silicate ion monomers are transformed into sodium-containing colloidal silicate ion micelles. Therefore, the anhydrous sodium silicate (glass scraps) dissolved in water (hot water) contains sodium-containing silicate ion monomers (A1) and compound (B), wherein the compound (B) is a chelating agent having a carboxyl group, a hydroxyl group, a phosphonic acid group or a combination of these groups bonded to a polyvalent metal ion M, and further, it can be said to be a silicate aqueous solution containing sodium-containing colloidal silicate ion micelles (A2).

More specifically, it is a sodium-containing silicate ion monomer (A1) and a compound (B), wherein the compound (B) contains at least one partial structure among the partial structures represented by the following formula (1) to (3), and further, it can be said that it is a silicate aqueous solution containing sodium-containing colloidal silicate ion micelles (A2).

In this transformation process, since the polyvalent metal ions M form chelate complexes through chelating agents, they will not be incorporated into the silica network of polysilicate ions that constitute colloidal silica ion micelles, etc., and can therefore be removed by cation exchange or subsequent superfiltration.

The polyvalent metal ions M are polyvalent metal ions M other than alkali metal ions contained in anhydrous sodium silicate (glass scraps) as a raw material. Examples of the polyvalent metal ions M include calcium ions, magnesium ions, aluminum ions, barium ions, copper ions, nickel ions, cobalt ions, iron ions, titanium ions, chromium ions, manganese ions, zinc ions, zirconium ions, and tin ions contained in glass scraps. The purpose of the present invention is to obtain a sodium silicate aqueous solution and a silicon dioxide sol in which the polyvalent metal ions M are reduced, especially the copper ions and nickel ions are reduced.

In the present invention, the sodium silicate aqueous solution obtained by heating anhydrous sodium silicate (glass scraps) with water contains more than 300 ppb of copper ions and more than 120 ppb of nickel ions relative to silicon dioxide in the sodium silicate.

The present invention can produce silica sol through steps (a) to (c).

Step (a): contacting the sodium silicate aqueous solution obtained by the above-mentioned manufacturing method with a cation exchange resin to obtain an active silicic acid aqueous solution; Step (b): heating the active silicic acid aqueous solution obtained in step (a) to obtain a silica sol; Step (c): super-filtering the silica sol obtained in step (b).

The cation exchange resin used in step (a) is a cation exchange resin having a functional group that can exchange 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 it is preferred to adjust the sulfonic acid type strongly acidic cation exchange resin to the H-type for use.

Such sulfonic acid type strong acid cation exchange resins can be used, for example, the product name of which is AMBERLITE IR-120B manufactured by ORGANO Co., Ltd.

Step (a) is a step of removing alkaline metal ions (especially sodium) from an aqueous solution of alkaline silicate by cation exchange to obtain an aqueous solution of active silicic acid. A portion of polyvalent metal ions are also removed by cation exchange from a chelating agent containing polyvalent metal ions.

In step (a), a sodium silicate aqueous solution having a _SiO2 content of 1 to 10 mass %, or 1 to 6 mass %, can be brought into contact with the cation exchange resin. The contact can be carried out in a batch or column manner. Industrially, a method can be used in which a cation exchange resin is filled in an ion exchange tower and a sodium silicate aqueous solution is passed through the tower. The flow rate can be expressed as a space velocity (1/hr) of 1 to 30 and a temperature of 10 to 80°C.

In step (a), the Cu content contained in the obtained active silicic acid aqueous solution is 230 ppb or less, for example, 180 ppb or less, typically 50 ppb to 180 ppb, relative to the mass of the _SiO2 component, and the Ni content is 140 ppb or less, for example, 100 ppb or less, typically 50 ppb to 100 ppb, relative to the mass of the _SiO2 component.

The _SiO2 concentration of the active silicic acid aqueous solution obtained in step (a) is, for example, about 1 to 10 mass %, or about 1 to 6 mass %.

In step (a), anion exchange can be performed arbitrarily before or after cation exchange. For example, the sodium silicate aqueous solution can be brought into contact with the anion exchange resin before or after the sodium silicate aqueous solution is brought into contact with the cation exchange resin. As the anion exchange resin, a strongly alkaline anion exchange resin or a weakly alkaline anion exchange resin can be used.

Step (b) is a step of heating and aging the active silicic acid aqueous solution obtained in step (a) to produce silica sol. The heating temperature is about 50~180℃ . The whole granules can also be pressurized at a temperature exceeding 100℃, and a closed press or an open press can be used.

The silica sol can be manufactured by heating the silica at the above temperature under stirring. A multi-stage build-up step can be used for the granulation. That is, after adding alkaline substances to the above active silicic acid aqueous solution to make a heel liquid with a pH of 9 to 11, the above active silicic acid aqueous solution is charged in the heel liquid to granulate the silica particles. The granulation time for forming silica particles is about 1 to 100 hours, and the granulation time can be adjusted to achieve the desired silica particle size.

Step (c) is a step of superfiltering the silica sol obtained in step (b). An example of the superfiltering step is a step of passing the silica sol through a superfilter device. By passing through the superfilter device, the _SiO2 concentration of the silica sol can be increased and concentrated. In the present invention, free metal ions in the silica sol, or chelating agents, chelating agents containing metal compounds (chelated compounds of polyvalent metal ions) derived from the above-mentioned aqueous solution of alkali silicate can be removed from the silica sol together with the concentration.

During the heating process of the silica particles in step (b) above, the polyvalent metal ions remaining in the active silica aqueous solution that were not removed in step (a) can be captured by the chelating agent to form a chelating agent complex. Therefore, during the process of the silica monomers or oligomers in the active silica forming polysilicic acid (polysiloxane structure) to form silica particles, they will not be pulled into the polysiloxane skeleton, but will exist in a free state in the silica sol. Therefore, by performing the super-filtration step in step (c), the chelated compound of the polyvalent metal ions can be discharged out of the system, and the silica sol with the metal ions in the silica sol can be produced.

(c) Step cation exchange and/or anion exchange may also be performed before or after filtering.

The Cu content of the silica sol obtained through step (c) of the present invention is less than 180 ppb relative to the total mass of the _SiO2 component, typically 50 ppb~180 ppb, and the Ni content is less than 100 ppb relative to the total mass of the _SiO2 component, typically 50 ppb~100 ppb.

The superfiltration in step (c) uses an organic membrane such as cellulose acetate membrane, aromatic polyamide membrane, polyvinyl alcohol membrane, polysulfone membrane, or ceramic membrane. The silica sol flows continuously in a certain direction along the membrane surface, and the impurities (compounds formed by chelating agents and polyvalent metal ion bonds in this case) are continuously discharged through the concentrated water to make the silica sol highly purified, and at the same time, the silica concentration of the silica sol is increased and concentrated. The pore size of the membrane that can be used is about 0.1μm~0.001μm or about 0.01μm~0.001μm, and the molecular weight of the separation is about 30,000~3 million. As the super-filtration condition, it can be implemented within the possible range according to the heat resistance and pressure resistance of the membrane. For example, in the case of organic membrane, it can be filtered at a temperature of 10~80℃ and a pressure below 0.3MPa. In the case of ceramic membrane, it can be filtered at a temperature below 300℃ and a pressure below 10MPa.

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

In step (c) of the present invention, ion exchange may be performed before filtering, after filtering, or before and after filtering. As the ion exchange, cation exchange, anion exchange, and a combination of cation and anion exchange may be performed.

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 with a removal rate of more than 50% for silica particles with a primary particle size of more than 1.0 μm can be used for filtering. As such filters, membrane filters, pleated filters, deep filters, wire-wound filters, surface filters, roller filters, deep pleated filters, diatomaceous earth filters, etc. can be used, among which membrane filters can be preferably used. The absolute pore size of the above-mentioned filter can be set to 0.3 μm~3.0 μm.

The pH of the silica sol obtained in step (c) can be adjusted to 0.5 to 13 by adding a pH adjuster, and can be adjusted to an alkaline silica sol or an acidic silica sol. As the pH adjuster, known acids and bases can be used. Examples of acids 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 p-toluenesulfonic acid. Examples of bases include inorganic bases 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 individually or as a mixture.

The shape of the silica particles in the above-mentioned silica sol can be changed according to the granulation step of the silica particles in step (b), and the silica particles with (average particle size by dynamic light scattering method nm)/(average primary particle size measured by nitrogen adsorption method nm) of, for example, 1.1-40, or 1.1-20, or 1.1-10, or 1.1-5, or 1.1-4 can be obtained.

Furthermore, the dispersion medium of the silica sol can be changed from an aqueous medium to an organic solvent. The solvent change can be performed by an evaporation method using an evaporator or a superfiltration method using a superfiltration membrane. Examples of the organic solvent include methanol, ethanol, n-propanol, isopropanol, butanol, methyl cellulose acetate, ethyl cellulose acetate, propylene glycol, propylene glycol monomethyl ether, propylene glycol monoethyl ether, methyl isobutyl carbitol, propylene glycol monobutyl ether, propylene glycol monomethyl ether acetate, propylene glycol monoethyl 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 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 Ester, 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 acetylacetate, toluene, xylene, methyl ethyl ketone, 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-propylene glycol, 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-butyrolactone, cyclohexanone, etc. The organic solvent may be used alone or in combination of two or more.

The above-mentioned silica sol can be coated on the surface of the silica particles by at least one silane compound (silane coupling agent) selected from the group of silane compounds represented by the following formula (5) and formula (6).

In formula (5), R ¹¹ represents an acryloxy group, a methacryloxy group, an aryl group, an alkyl group, or an organic group having an epoxy group, an alkyl 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, the functional group is bonded to a Si atom via a Si-C bond, R ¹² represents a hydrolyzed group formed of an alkoxy group, an acyloxy group, or a halogen group, and a represents 0 to 3, or an integer of 1 to 3. When the silane compound represented by formula (5) covers the surface of the silica particle, it means that at least one hydrolyzed group of R ¹² 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 via a Si-C bond, 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) covers the surface of the silica particle, it means that at least one R ¹⁴ forms a Si-O-Si bond on the surface of the silica particle.

Examples of the above-mentioned alkyl group include alkyl groups having 1 to 10 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, cyclopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, cyclobutyl, 1-methyl-cyclopropyl, 2-methyl-cyclopropyl, n-pentyl, 1-methyl-n-butyl, 2-methyl-n-butyl, 3-methyl-n-butyl, 1,1-dimethyl-n-propyl, 1,2-dimethyl-n-propyl, etc.

Examples of the alkylene group include alkylene groups derived from the above-mentioned alkyl groups.

Examples of aryl groups include phenyl, naphthyl, anthracenyl, etc., and aryl groups are groups derived from the above aryl groups, examples of which include phenylene, naphthylene, anthracenyl, etc.

Examples of the above-mentioned alkoxy group include alkoxy groups having 1 to 10 carbon atoms, such as methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy, sec-butoxy, tert-butoxy, n-pentoxy, 1-methyl-n-butoxy, 2-methyl-n-butoxy, etc.

Examples of the above-mentioned acyloxy group include acyloxy groups having 2 to 10 carbon atoms, such as methylcarbonyloxy, ethylcarbonyloxy, n-propylcarbonyloxy, isopropylcarbonyloxy, n-butylcarbonyloxy, etc.

Examples of the above-mentioned halogen groups include fluorine, chlorine, bromine, iodine, etc.

Examples of the silane compound (silane coupling agent) represented by the formula (5) include tetramethoxysilane, tetrachlorosilane, tetraacetoxysilane, tetraethoxysilane, tetra-n-propoxysilane, tetraisopropoxysilane, tetra-n-butoxysilane, tetraacetoxysilane, methyltrimethoxysilane, methyltrichlorosilane, methyltriacetoxysilane, methyltripropoxysilane, methyltriacetoxysilane, silane, methyltributoxysilane, methyltriprotoxysilane, methyltripentoxysilane, methyltriphenoxysilane, methyltripenyloxysilane, methyltriphenethoxysilane, glycidyloxymethyltrimethoxysilane, glycidyloxymethyltriethoxysilane, α-glycidyloxyethyltrimethoxysilane, α-glycidyloxyethyltriethoxysilane, β-glycidyloxyethyl trimethoxysilane, β-glycidyloxyethyl triethoxysilane, α-glycidyloxypropyl trimethoxysilane, α-glycidyloxypropyl triethoxysilane, β-glycidyloxypropyl trimethoxysilane, β-glycidyloxypropyl triethoxysilane, γ-glycidyloxypropyl trimethoxysilane, γ-glycidyloxypropyl triethoxysilane, γ- Glycidyloxypropyl tripropoxysilane, γ-glycidyloxypropyl tributoxysilane, γ-glycidyloxypropyl triphenoxysilane, α-glycidyloxybutyl trimethoxysilane, α-glycidyloxybutyl triethoxysilane, β-glycidyloxybutyl triethoxysilane, γ-glycidyloxybutyl trimethoxysilane, γ-glycidyloxybutyl triethoxysilane, silane, δ-glycidyloxybutyltrimethoxysilane, δ-glycidyloxybutyltriethoxysilane, (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)butyltrimethoxy silane, δ-(3,4-epoxycyclohexyl)butyltriethoxysilane, glycidyloxymethylmethyldimethoxysilane, glycidyloxymethylmethyldiethoxysilane, α-glycidyloxyethylmethyldimethoxysilane, α-glycidyloxyethylmethyldiethoxysilane, β-glycidyloxyethylmethyldimethoxysilane, β-glycidyloxyethylethyl Dimethoxysilane, α-glycidyloxypropylmethyldimethoxysilane, α-glycidyloxypropylmethyldiethoxysilane, β-glycidyloxypropylmethyldimethoxysilane, β-glycidyloxypropylethyldimethoxysilane, γ-glycidyloxypropylmethyldimethoxysilane, γ-glycidyloxypropylmethyldiethoxysilane, γ-glycidyloxypropyl methyl dipropoxysilane, γ-glycidyloxypropyl methyl dibutoxysilane, γ-glycidyloxypropyl methyl diphenoxysilane, γ-glycidyloxypropyl ethyl dimethoxysilane, γ-glycidyloxypropyl ethyl diethoxysilane, γ-glycidyloxypropyl vinyl dimethoxysilane, γ-glycidyloxypropyl vinyl diethoxysilane, ethyl trimethyl Oxysilane, ethyltriethoxysilane, vinyltrimethoxysilane, vinyltrichlorosilane, vinyltriacetoxysilane, vinyltriethoxysilane, vinyltriacetylsilane, methoxyphenyltrimethoxysilane, methoxyphenyltriethoxysilane, methoxyphenyltriacetoxysilane, methoxyphenyltrichlorosilane, methoxybenzyltrimethoxysilane, methoxybenzyltriethoxysilane Silane, methoxybenzyl triacetoxysilane, methoxybenzyl trichlorosilane, methoxyphenethyl trimethoxysilane, methoxyphenethyl triethoxysilane, methoxyphenethyl triacetoxysilane, methoxyphenethyl trichlorosilane, ethoxyphenyl trimethoxysilane, ethoxyphenyl triethoxysilane, ethoxyphenyl triacetoxysilane, ethoxyphenyl trichlorosilane, ethoxybenzyl Trimethoxysilane, Ethoxybenzyltriethoxysilane, Ethoxybenzyltriacetoxysilane, Ethoxybenzyltrichlorosilane, Isopropoxyphenyltrimethoxysilane, Isopropoxyphenyltriethoxysilane, Isopropoxyphenyltriacetoxysilane, Isopropoxyphenyltrichlorosilane, Isopropoxybenzyltrimethoxysilane, Isopropoxybenzyltriethoxysilane, Isopropoxybenzyltriacetoxysilane Silane, isopropoxybenzyl trichlorosilane, tert-butoxyphenyl trimethoxysilane, tert-butoxyphenyl triethoxysilane, tert-butoxyphenyl triacetoxysilane, tert-butoxyphenyl trichlorosilane, tert-butoxybenzyl trimethoxysilane, tert-butoxybenzyl triethoxysilane, tert-butoxybenzyl triacetoxysilane, tert-butoxybenzyl trichlorosilane, methoxynaphthyl Trimethoxysilane, methoxynaphthyl triethoxysilane, methoxynaphthyl triacetoxysilane, methoxynaphthyl trichlorosilane, ethoxynaphthyl trimethoxysilane, ethoxynaphthyl triethoxysilane, ethoxynaphthyl triacetoxysilane, ethoxynaphthyl trichlorosilane, γ-chloropropyl trimethoxysilane, γ-chloropropyl triethoxysilane, γ-chloropropyl triacetoxysilane, 3,3, 3-Trichloropropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-butylpropyltrimethoxysilane, γ-butylpropyltriethoxysilane, β-cyanoethyltriethoxysilane, chloromethyltrimethoxysilane, chloromethyltriethoxysilane, dimethyldimethoxysilane, phenylmethyldimethoxysilane, dimethyldiethoxysilane, phenylmethyldiethoxysilane , γ-chloropropylmethyldimethoxysilane, γ-chloropropylmethyldiethoxysilane, dimethyldiethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, γ-methacryloxypropylmethyldiethoxysilane, γ-butylpropylmethyldimethoxysilane, γ-butylmethyldiethoxysilane, methylvinyldimethoxysilane, methylvinyldiethoxysilane, etc.

Examples of the silane compound (silane coupling agent) represented by the above formula (6) include methylenebistrimethoxysilane, methylenebistrichlorosilane, methylenebistriacetoxysilane, ethylbistriethoxysilane, ethylbistrichlorosilane, ethylbistriacetoxysilane, propylbistriethoxysilane, butylbistrichlorosilane, Bistrimethoxysilane, bistrimethoxyphenylsilane, bistriethoxyphenylsilane, bismethyldiethoxyphenylsilane, bismethyldimethoxyphenylsilane, bistrimethoxynaphthylsilane, bistrimethoxydisilane, bistriethoxydisilane, bisethyldiethoxydisilane, bismethyldimethoxydisilane, etc.

As the silane compound (silane coupling agent) represented by formula (6), the following compounds can be exemplified.

Formula (6-1) is hexamethyldisilazane, formula (6-2) is hexamethyldisilazane, and formula (6-3) is hexamethyldisiloxane. These silane compounds (silane coupling agents) can be obtained from Tokyo Chemical Industry Co., Ltd.

The silica sol obtained by the present invention can be used for general purposes such as sand binders for casting, binders, additives for paper pulp, additives for soap, raw materials for pharmaceuticals, and additives for civil engineering and construction materials. In particular, the high purity feature is utilized to make it useful in abrasives for silicon wafers, abrasives for semiconductor devices (CMP), catalysts, catalyst carriers, high-purity ceramic raw materials, purified columns for medicines, coating components for plastic lenses or glass surfaces, etc.

[Implementation example] (Material preparation)

Anhydrous sodium silicate (glass chips): glass chips manufactured by ORIENTAL SILICA CORPORATION were prepared. The _{SiO 2} /Na ₂ O molar ratio was 3.2.

Tetrasodium ethylenediaminetetraacetate: Prepared by CHELEST Co., Ltd., trade name CHELEST OD.

Hydroxyethanephosphonic acid: prepared by CHELEST Co., Ltd., trade name CHELEST PH-210.

Sodium gluconate: Prepared by CHELEST Co., Ltd., trade name CHELEST GB.

H-type strongly acidic cation exchange resin: Commercially available cation exchange resin is prepared in H-type using aqueous sulfuric acid solution.

(Measurement method)

Determination of average primary particle size: The average primary particle size (nm) was determined by nitrogen adsorption method (BET method).

pH measurement: pH measurement was performed using a pH measuring device manufactured by DKK East Asia Co., Ltd.

Conductivity measurement: Conductivity measurement equipment manufactured by DKK East Asia Co., Ltd. is used for measurement.

Determination of polyvalent metal components and their contents: qualitative and quantitative analysis using ICP luminescence analyzer manufactured by PERKIN ELMER INC.

(Implementation Example 1)

In a 3-liter stainless steel autoclave container, 159 g of anhydrous sodium silicate glass scraps, 1041 g of pure water, and 0.02 g of a 1% by mass tetrasodium ethylenediaminetetraacetic acid aqueous solution were added, and heated at 150°C for 1 hour to prepare a sodium silicate aqueous solution with a silicon dioxide concentration of 10% by mass. The content of Cu and Ni per silicon dioxide in the sodium silicate aqueous solution was 364 ppb and 152 ppb, respectively. Pure water was added to the sodium silicate aqueous solution to dilute it to a silica concentration of 4 mass %, and the solution was passed through a column filled 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 mass %.

Next, 29 g of the aforementioned sodium silicate aqueous solution with a silicon dioxide concentration of 10 mass % and 265 g of pure water were added to a glass container with a volume of 3 liters, and heated to 80°C in an oil bath while stirring. 2261 g of the aforementioned active silicic acid aqueous solution with a silicon dioxide concentration of 3.4 mass % was continuously supplied therein for 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 continued to be heated for 4 hours to obtain a reaction solution. The reaction solution is a silica sol with a silica concentration of 3.2 mass %, pH 10.0, conductivity 427μS/cm, and an average primary particle size of silica particles obtained by nitrogen adsorption method (BET method specific surface area converted particle size) of 13nm.

Next, the reaction solution (2427 g) was heated to 70°C and concentrated using a commercially available superfilter (molecular weight cutoff 200,000) to a silica concentration of about 30% by mass to obtain 236 g of silica sol.

The silica sol has a silica concentration of 30.5 mass%, a pH of 9.2, a conductivity of 2020μS/cm, a Cu content of 108ppb relative to silica, and a Ni content of 92ppb relative to silica.

Perform the same operation as Example 1 to perform Examples 2 to 9, Comparative Examples 1 to 3 and Reference Example 1. The operation and results are shown in the table below.

Table 1 shows the operation of heating and dissolving anhydrous sodium silicate (glass chips) in water.

In Table 1, item X1 represents the mass (g) of anhydrous sodium silicate (glass scraps) fed into the stainless steel autoclave, item X2 represents the mass (g) of pure water fed into the stainless steel autoclave, item X3 represents the mass (g) of aqueous solution containing chelating agent fed into the stainless steel autoclave, and Examples 1 to 7 and Comparative Example 3 represent the mass of 1 Example 8 represents the mass (g) of a 1% concentration of a tetrasodium ethylenediaminetetraacetic acid aqueous solution, Example 9 represents the mass (g) of a 1% concentration of a sodium gluconate aqueous solution, and Reference Example 1 represents the mass (g) of a 0.02% concentration of a tetrasodium ethylenediaminetetraacetic acid aqueous solution. Item X4 indicates the amount of chelating agent added relative to anhydrous sodium silicate (glass shavings) when anhydrous sodium silicate (glass shavings) is dissolved (ppm), Item X5 indicates the amount of chelating agent added relative to silicon dioxide in anhydrous sodium silicate (glass shavings) when anhydrous sodium silicate (glass shavings) is dissolved (ppm), Item X6 indicates the concentration of silicon dioxide in anhydrous sodium silicate (glass shavings) in a stainless steel autoclave device (%), Item X7 indicates the temperature (℃) at which anhydrous sodium silicate (glass shavings) is heated and dissolved in water, and Item X8 indicates the time (hours) for heating and dissolving anhydrous sodium silicate (glass shavings) in water.

Items X9 to X13 in Table 2 show the operations and physical properties after making sodium silicate aqueous solution (water glass).

In Table 2, item X9 represents the mass (g) of 1 mass % concentration of tetrasodium ethylenediaminetetraacetic acid aqueous solution added to the sodium silicate aqueous solution (water glass) after anhydrous sodium silicate (glass scraps) is heated and dissolved in water to prepare the sodium silicate aqueous solution (water glass). Item X10 represents the amount (ppm) of chelating agent added to the sodium silicate aqueous solution (water glass) after anhydrous sodium silicate (glass scraps) is heated and dissolved in water to prepare the sodium silicate aqueous solution (water glass). Item X11 indicates the amount of chelating agent added relative to the amount of silicon dioxide in the sodium silicate aqueous solution (water glass) obtained by heating anhydrous sodium silicate (glass scraps) and dissolving them in water (ppm). Item X12 indicates the amount of copper relative to silicon dioxide in the obtained sodium silicate aqueous solution (water glass) (ppb). Item X13 indicates the amount of nickel relative to silicon dioxide in the obtained sodium silicate aqueous solution (water glass) (ppb).

In addition, Example 7 is a test to dissolve anhydrous sodium silicate (glass chips) in water to make a sodium silicate aqueous solution (water glass). In addition, since anhydrous sodium silicate (glass chips) cannot be dissolved in water by heating in Comparative Example 3, the subsequent tests were not carried out.

Table 3 shows the operation of preparing the active silicic acid aqueous solution and the physical properties of the obtained active silicic acid aqueous solution.

In Table 3, item Y1 represents the mass (g) of the sodium silicate aqueous solution (water glass), item Y2 represents the mass (g) of the pure water added for dilution, item Y3 represents the mass (g) of the obtained active silicic acid aqueous solution, item Y4 represents the content (ppb) of copper relative to silicon dioxide (SiO ₂ ) in the obtained active silicic acid aqueous solution, and item Y5 represents the content (ppb) of nickel relative to silicon dioxide (SiO ₂ ) in the obtained active silicic acid aqueous solution.

Table 4 shows the physical properties of the reaction solution (silica sol before filtration).

In Table 4, item Z1 represents the silica concentration (mass %) of the silica sol, item Z2 represents the pH of the silica sol, item Z3 represents the conductivity (μS/cm) of the silica sol, and item Z4 represents the average primary particle size (nm) obtained by the nitrogen adsorption method (BET method).

Table 5 shows the physical properties of the silica sol after filtration.

In Table 5, item Z5 represents the mass (g) of the silica sol fed into the superfiltration device, item Z6 represents the mass (g) of the silica sol obtained by the superfiltration device, item Z7 represents the silica concentration (%) of the silica sol obtained by the superfiltration device, and item Z8 represents the p of the silica sol obtained by the superfiltration device. H, Item Z9 represents the conductivity (μS/cm) of the silica sol obtained by the superfiltration device, Item Z10 represents the content of copper relative to silica in the silica sol obtained by the superfiltration device (ppb), and Item Z11 represents the content of nickel relative to silica in the silica sol obtained by the superfiltration device (ppb).

In the above-mentioned Examples 1-6 and Examples 8-9, a chelating agent is present beforehand when anhydrous sodium silicate (glass chips) is heated and dissolved in water. It can be seen that regardless of the type of chelating agent, the polyvalent metal is reduced in the stage of the active silicic acid aqueous solution in step (a) and the stage of the formation of the silica sol in step (c).

On the other hand, in Comparative Example 2, a chelating agent is added after the active silicic acid aqueous solution is formed, and the resulting silica sol cannot be one in which the polyvalent metals are sufficiently reduced.

In addition, in Comparative Example 3, the temperature at which anhydrous sodium silicate (glass chips) is heated and dissolved in water is 60°C, which fails to fully dissolve the anhydrous sodium silicate (glass chips).

Furthermore, the chelating agent content when anhydrous sodium silicate (glass scraps) is heated and dissolved in water can be seen from Reference Example 1 that the effect of the present invention can be exerted even with a small amount. However, in applications where polyvalent metals are highly rejected as impurities, it is necessary to further reduce the content, which can be set to 0.1~3000ppm, or 0.1~300ppm relative to the silicon dioxide in anhydrous sodium silicate (glass scraps).

[Industrial availability]

A method of heating anhydrous sodium silicate (glass chips), a chelating agent and water to obtain a sodium silicate aqueous solution and a method of using the sodium silicate aqueous solution (water glass) to produce a high-purity silica sol. The obtained high-purity silica sol can be used for general purposes such as sand binders for casting, binders, additives for paper pulp, additives for soap, pharmaceutical raw materials, and additives for civil engineering and construction materials. In particular, the high-purity characteristics are utilized to make it useful in abrasives for silicon wafers, abrasives for semiconductor devices (CMP), catalysts, catalyst carriers, high-purity ceramic raw materials, purified columns for medicines, coating components for plastic lenses or glass surfaces, etc.

Claims (18)

A method for preparing a sodium silicate aqueous solution comprises the steps of heating and mixing anhydrous sodium silicate, a chelating agent and water at 100-270°C, wherein the anhydrous sodium silicate is glass scraps. The method for producing an aqueous sodium silicate solution of claim 1, wherein the heating and mixing step comprises the following steps: preparing an aqueous solution containing a chelating agent, and heating and mixing the anhydrous sodium silicate and the aqueous solution containing the chelating agent at 100-270°C. The method for producing an aqueous sodium silicate solution of claim 1 or 2, wherein the addition ratio of the aforementioned chelating agent is 0.1-3000 ppm relative to the total mass of _SiO2 contained in the anhydrous sodium silicate. The method for producing an aqueous sodium silicate solution of claim 1 or 2, wherein the heating time is 0.1 to 50 hours. A method for producing an aqueous sodium silicate solution as claimed in claim 1 or 2, wherein the mixture is heated and mixed under a pressure of 1 to 60 atmospheres. The method for producing a sodium silicate aqueous solution of claim 1 or 2, wherein the molar ratio of SiO ₂ /Na ₂ O in the sodium silicate aqueous solution is 1-10. The method for producing an aqueous sodium silicate solution of claim 1 or 2, 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. The method for producing a sodium silicate aqueous solution according to claim 1 or 2, 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. A method for producing an aqueous sodium silicate solution as claimed in claim 1 or 2, 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 or hydroxyethanephosphonic acid or salts thereof. A method for producing an aqueous solution of active silicic acid comprises the step of contacting an aqueous sodium silicate solution obtained by the production method of any one of claims 1 to 9 with an H-type cation exchange resin. A method for preparing a silica sol, comprising the following steps (a) to (c): Step (a): contacting a sodium silicate aqueous solution obtained by the preparation method of any one of claims 1 to 9 with a cation exchange resin to obtain an active silicic acid aqueous solution, Step (b): heating the active silicic acid aqueous solution obtained in step (a) to obtain a silica sol, Step (c): super-filtering the silica sol obtained in step (b). A method for producing a silica sol as claimed in claim 11, wherein step (a) further comprises an anion exchange step before or after the sodium silicate aqueous solution is contacted with the cation exchange resin. The method for producing a silica sol as claimed in claim 11, wherein step (c) comprises a step of performing cation exchange and/or anion exchange before or after super-filtering the silica sol. A method for producing a silica sol as claimed in any one of claims 11 to 13, wherein the silica sol obtained in step (c) contains a Cu content of less than 180 ppb relative to the total mass of _SiO2 components, and a Ni content of less than 100 ppb relative to the total mass of _SiO2 components. A sodium silicate aqueous solution comprises a sodium-containing silicate ion monomer (A1) and a compound (B), wherein the compound (B) is a chelating agent having a carboxyl group, a hydroxyl group, a phosphonic acid group or a combination of these groups and a polyvalent metal ion M bonded together. A sodium silicate aqueous solution comprises a sodium-containing silicate ion monomer (A1) and a compound (B), wherein the compound (B) has at least one partial structure among the partial structures represented by the following (1) to (3), (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 represents a coordination bond between the polyvalent metal ion M and a nitrogen atom or an oxygen atom, but there may be multiple wavy lines 2 for the polyvalent metal ion M, and the dotted line represents a coordination bond between the polyvalent metal ion M and an oxygen atom). The sodium silicate aqueous solution of claim 15 or 16, wherein the polyvalent metal ions M are copper ions or nickel ions. The sodium silicate aqueous solution of claim 15 or 16 further comprises colloidal silicate ion micelles (A2) containing sodium.