阅读说明：本技术 具有细长的粒子形状的硅溶胶的制造方法 (Method for producing silica sol having elongated particle shape ) 是由 村上智 福冈拓也 黑岩和也 于 2019-02-25 设计创作，主要内容包括：通过向活性硅酸水溶液中添加成为阴离子源的化合物和作为碱源的氨,并在规定的温度下进行加热,来提供金属杂质少的、细长粒子形状的胶体二氧化硅粒子分散于溶剂中而成的硅溶胶的制造方法。一种硅溶胶制造方法,所述硅溶胶通过动态光散射法测得的平均粒径(D<Sub>L</Sub> nm)与通过氮气吸附法测得的一次粒径(D<Sub>B</Sub> nm)之比D<Sub>L</Sub>/D<Sub>B</Sub>为2.5以上,所述制造方法包括(a)工序和(b)工序,所述(a)工序是制作原料液的工序,其包括向SiO<Sub>2</Sub>浓度为1～6质量％、且pH为2～5的活性硅酸的胶体水溶液中添加氨和相对于SiO<Sub>2</Sub>的质量比成为3.0～7.0的量的成为阴离子源的化合物的步骤,所述化合物是选自无机酸、有机酸、及它们的铵盐中的至少1种,所述(b)工序是将通过(a)工序得到的原料液在80～200℃加热0.5～20小时来制造硅溶胶的工序。(A method for producing a silica sol in which colloidal silica particles having a shape of elongated particles and containing few metal impurities are dispersed in a solvent is provided by adding a compound serving as an anion source and ammonia serving as an alkali source to an active silicic acid aqueous solution and heating the mixture at a predetermined temperature. A process for producing a silica sol having an average particle diameter (D) as measured by a dynamic light scattering method L nm) and primary particle diameter (D) measured by nitrogen adsorption B nm) ratio D L /D B The method comprises a step (a) of preparing a raw material solution, the raw material solution including SiO 2 A concentration of 1 to 6 mass%, andadding ammonia and SiO to a colloidal aqueous solution of active silicic acid having a pH of 2 to 5 2 The step (b) is a step of heating the raw material liquid obtained in the step (a) at 80 to 200 ℃ for 0.5 to 20 hours to produce a silica sol, wherein the mass ratio of the compound (a) to the compound (b) is 3.0 to 7.0.)

1. A process for producing a silica sol, which comprises a silica sol,

the silica sol is SiO in which elongated colloidal silica particles are dispersed in a liquid medium₂A silica sol having a concentration of 6 to 30 mass%,

the average particle diameter D of the colloidal silica particles having an elongated shape measured by a dynamic light scattering method_LAnd primary particle diameter D measured by nitrogen adsorption method_BRatio of D_L/D_BIs 2.5 or more, the D_L30 to 300nm and a particle length measured by electron microscope observation in the range of 50 to 1000nm, wherein D is_LAnd said D_BThe unit of (a) is nm,

the manufacturing method comprises the following steps (a) and (b),

(a) the step of preparing a raw material solution includes adding SiO₂Adding ammonia and SiO to a colloidal aqueous solution of active silicic acid having a concentration of 1 to 6 mass% and a pH of 2 to 5₂A compound which becomes an anion source in an amount of 3.0 to 7.0% by mass, wherein the compound is at least 1 selected from the group consisting of inorganic acids, organic acids, and ammonium salts thereof,

(b) the step (a) is a step of heating the raw material solution obtained in the step (a) at 80 to 200 ℃ for 0.5 to 20 hours to produce a silica sol.

2. The method for producing a silica sol according to claim 1,

(a) the colloidal aqueous solution of active silicic acid used in the step is prepared by reacting SiO₂/M₂An alkali metal silicate aqueous solution having an O molar ratio of 1 to 4.5, wherein M represents sodium or potassium, is contacted with a strong acid type cation exchange resin or with a strong base type cation exchange resin and a strong base type anion exchange resin.

3. The method for producing a silica sol according to claim 2,

(a) the colloidal aqueous solution of active silicic acid used in the step is obtained by adding a strong acid to the aqueous solution of alkali metal silicate, treating the aqueous solution at a temperature of 1 to 98 ℃, and then contacting the treated aqueous solution with a strong acid type cation exchange resin or with a strong acid type cation exchange resin and a strong base type anion exchange resin.

4. The method for producing a silica sol according to claim 2 or 3,

(a) the colloidal aqueous solution of active silicic acid used in the step is obtained by further contacting the aqueous alkali solution or the treated aqueous solution with a carboxylic acid type chelate resin, a hydroxyl type chelate resin, and/or an amine type chelate resin before or after the aqueous alkali solution or the treated aqueous solution is contacted with a strong acid type cation exchange resin, or a strong acid type cation exchange resin and a strong base type anion exchange resin.

5. The method for producing a silica sol according to claim 1 to 4,

(a) the compound to be an anion source used in the step is at least 1 selected from the group consisting of nitric acid, sulfuric acid, phosphoric acid, boric acid, hydrofluoric acid, hydrochloric acid, acetic acid, formic acid, oxalic acid, citric acid, lactic acid, malic acid, gluconic acid, tartaric acid, ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA), and ammonium salts thereof.

6. The method for producing a silica sol according to claim 1 to 5,

(a) the colloidal particles contained in the colloidal aqueous solution of active silicic acid used in the step have an average particle diameter of less than 5 nm.

7. The method for producing a silica sol according to claim 1 to 6,

the ammonia to be added in the step (a) is added in the form of ammonia gas or an aqueous ammonia solution.

8. The method for producing a silica sol according to claim 1 to 7,

(a) the process comprises the following steps: adding the compound that becomes a source of anions to the colloidal aqueous solution of activated silicic acid, followed by adding the ammonia.

9. The method for producing a silica sol according to claim 1 to 7,

(a) the process comprises the following steps: adding the ammonia to the colloidal aqueous solution of the activated silicic acid, then adding the compound that becomes the anion source, and then adding the ammonia.

10. The method for producing a silica sol according to claim 1 to 9,

the pH of the raw material liquid obtained in the step (a) is 8 to 12.

11. The method for producing a silica sol according to claim 1 to 10,

(b) the heating of the raw material liquid in the step is carried out by heating the raw material liquid at 100 to 180 ℃ in an autoclave apparatus.

12. The method for producing a silica sol according to claim 1 to 11,

further comprising: bringing the silica sol obtained in the step (b) into contact with a strongly acidic ion exchange resin and/or a strongly basic ion exchange resin.

13. The method for producing a silica sol according to claim 12,

further comprising: and (b) contacting the silica sol obtained in step (b) with a carboxylic acid type chelating resin, a hydroxyl type chelating resin, and/or an amine type chelating resin before or after contacting the silica sol with a strongly acidic ion exchange resin and/or a strongly basic ion exchange resin.

14. The method for producing a silica sol according to claim 1 to 13,

further comprises a solvent replacement step of replacing the aqueous medium of the obtained silica sol with an organic medium.

15. The method for producing a silica sol according to claim 1 to 14,

in the silica sol, Ca and Mg are relative to SiO₂The mass ratio of (A) to (B) is 2 to 100 ppm.

16. The method for producing a silica sol according to claim 1 to 15,

in the silica sol, Na is relative to SiO₂In a mass ratio of 2 to 1000ppm, and K is in relation to SiO₂The mass ratio of (A) to (B) is 2 to 100 ppm.

17. The method for producing a silica sol according to claim 1 to 16,

the average particle diameter D of the colloidal silica particles having an elongated shape measured by a dynamic light scattering method_LAnd primary particle diameter D measured by nitrogen adsorption method_BRatio of D_L/D_BIs3 to 30, wherein D is_LAnd said D_BIn nm.

18. The method for producing a silica sol according to claim 1 to 17,

the silica sol is acidic silica sol or ammonia type alkaline silica sol.

Technical Field

The present invention relates to a method for producing a silica sol in which elongated colloidal silica particles are dispersed in a liquid medium, and particularly to a method for efficiently producing a silica sol having a low content of alkali metals and alkaline earth metals.

Background

The shape of the colloidal silica particles is roughly classified into two types, i.e., a shape close to a spherical shape and a non-spherical shape. The non-spherical type is expected to have various effects (for example, binding force, adsorption force, and light transmittance) by controlling the shape thereof, and is used for a microfiller for various coating agents, a binder, a modifier, a catalyst carrier, an abrasive for electronic materials (for example, an abrasive for silicon wafers, and a CMP abrasive for device wafers for polishing silicon oxide films and metals such as copper and aluminum), and the like.

Silica particles having a long and thin shape in which silica particles having a shape close to a spherical shape are connected in a chain or a moniliform form are also non-spherical silica particles, and there is a silica sol in which the non-spherical silica particles are stably dispersed in an aqueous medium or an organic medium.

For example, the following methods have been disclosed for producing a silica sol in which colloidal silica particles having a long and narrow shape are dispersed in a liquid medium: to SiO₂In a colloidal aqueous solution of active silicic acid having a concentration of 1 to 6 mass%, CaO (calcium oxide), MgO (magnesium oxide) or both are addedSiO of activated silicic acid₂(silicon dioxide) is added in an amount of 1500 to 8500ppm by mass, wherein the amount is an amount obtained by adding an aqueous solution containing a water-soluble calcium salt, a water-soluble magnesium salt or a mixture thereof, and further adding an alkali metal hydroxide, an organic base or a silicate of an aqueous solution thereof, the amount being calculated as SiO₂/M₂Formula represented by O (wherein, SiO)₂The total content of the silica derived from the active silicic acid and the silica of the water-soluble silicate is shown, and M represents the alkali metal atom or the molecule of the organic base) is 20 to 300 mol ratio, and then the mixture is heated at 60 to 300 ℃ for 0.5 to 40 hours (see patent document 1). ).

Further, a silica sol in which silica particles are connected in a chain shape and the relationship between the reduced viscosity and the silica concentration is expressed by a specific function is disclosed, and a method for producing the silica sol is disclosed as follows: before adding silicic acid to an alkali metal silicate aqueous solution, polyvalent metal ions such as Ca, Mg, Al, In, Ti, Zr, Sn, Si, Sb, Fe, Cu, or rare earth metals are added, and the mixture is heated to a temperature of 60 ℃ or higher to add silicic acid again (see patent document 2).

Further, there is disclosed a colloidal silica produced by using active silicic acid as a raw material in the presence of potassium ions, which contains potassium ions and contains non-spherical irregularly shaped silica particles having a major axis/minor axis ratio in the range of 1.2 to 10 as measured by transmission electron microscope observation; also disclosed is a method for producing colloidal silica, which comprises: a compound serving as a potassium ion supply source and an alkali agent are added to an active silicic acid aqueous solution to make the solution alkaline, and then the mixture is heated to form silica particles, and an active silicic acid aqueous solution, an alkali agent, and a compound serving as a potassium ion supply source are added under heating (see patent document 3).

Prior art documents

Patent document

Patent document 1: japanese laid-open patent publication No. 1-317115

Patent document 2: japanese laid-open patent publication No. 4-187512

Patent document 3: japanese patent laid-open publication No. 2011-098859

Disclosure of Invention

The silica sol may be unusable depending on the application due to the metal impurities contained in the silica sol. The purpose of the present invention is to provide a method for producing a silica sol in which non-spherical silica having a low content of metal impurities is dispersed in a solvent.

The present invention can easily produce a silica sol in which a compound to be an anion source and ammonia as an alkali source are added to an active silicic acid aqueous solution and heated at a predetermined temperature, and which is formed by dispersing colloidal silica having a long and thin particle shape and containing few metal impurities in a solvent.

The present invention is as follows. In view of the above, the present invention provides a method for producing a silica sol containing SiO in which elongated colloidal silica particles are dispersed in a liquid medium₂A silica sol having a concentration of 6 to 30 mass%, wherein the colloidal silica particles having an elongated shape have an average particle diameter (D) measured by a dynamic light scattering method_Lnm) and primary particle diameter (D) measured by nitrogen adsorption_Bnm) ratio D_L/D_BIs 2.5 or more, the D_L30 to 300nm and a particle length measured by electron microscope observation in the range of 50 to 1000nm, comprising the following steps (a) and (b),

(a) the step of preparing a raw material solution includes adding SiO₂Adding ammonia and SiO to a colloidal aqueous solution of active silicic acid having a concentration of 1 to 6 mass% and a pH of 2 to 5₂A compound which becomes an anion source in an amount of 3.0 to 7.0% by mass, wherein the compound is at least 1 selected from the group consisting of inorganic acids, organic acids, and ammonium salts thereof,

(b) the step (a) is a step of heating the raw material solution obtained in the step (a) at 80 to 200 ℃ for 0.5 to 20 hours to produce a silica sol.

As a2 nd aspect of the present invention, there is provided the method for producing a silica sol according to the 1 st aspect, wherein the colloidal aqueous solution of active silicic acid used in the step (a) is SiO₂/M₂The molar ratio of O (wherein M represents sodium or potassium) is 1-4.5 in contact with a strong acid type cation exchange resin or with a strong acid type cation exchange resin and a strong base type anion exchange resin.

As aspect 3, the method for producing a silica sol according to aspect 2, wherein the colloidal aqueous solution of active silicic acid used in the step (a) is obtained by further adding a strong acid to the aqueous solution of alkali metal silicate, treating the solution at a temperature of 1 to 98 ℃, and then contacting the treated aqueous solution with a strong acid type cation exchange resin or with a strong acid type cation exchange resin and a strong base type anion exchange resin.

As aspect 4, the method for producing a silica sol according to aspect 2 or aspect 3, wherein the colloidal aqueous solution of active silicic acid used in the step (a) is obtained by further contacting a carboxylic acid type chelating resin, a hydroxyl type chelating resin, and/or an amine type chelating resin before or after the aqueous alkali solution or the treated aqueous solution is contacted with the strong acid type cation exchange resin, or the strong acid type cation exchange resin and the strong base type anion exchange resin.

In view 5, the method for producing a silica sol according to any one of views 1 to 4, wherein the compound to be an anion source used in the step (a) is at least 1 selected from the group consisting of nitric acid, sulfuric acid, phosphoric acid, boric acid, hydrofluoric acid, hydrochloric acid, acetic acid, formic acid, oxalic acid, citric acid, lactic acid, malic acid, gluconic acid, tartaric acid, ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA), and ammonium salts thereof.

As aspect 6, the method for producing a silica sol according to any one of aspects 1 to 5, wherein the average particle diameter of the colloidal particles contained in the colloidal aqueous solution of active silicic acid used in the step (a) is less than 5 nm;

in view of 7, the method for producing a silica sol according to any one of views 1 to 6, wherein the ammonia added in the step (a) is ammonia gas or an aqueous ammonia solution.

In view 8, the method for producing a silica sol according to any one of views 1 to 7, wherein the step (a) comprises the steps of: the compound to be an anion source is added to the colloidal aqueous solution of active silicic acid, and then the ammonia is added.

In view of 9, the method for producing a silica sol according to any one of views 1 to 7, wherein the step (a) comprises the steps of: the ammonia is added to the colloidal aqueous solution of the active silicic acid, and then the compound that becomes the anion source is added, and then the ammonia is added.

In view of 10, the method for producing a silica sol according to any one of views 1 to 9, the pH of the raw material liquid obtained in the step (a) is 8 to 12.

In view of 11, the method for producing a silica sol according to any one of view 1 to view 10, wherein the heating of the raw material liquid in the step (b) is performed by heating the raw material liquid at 100 to 180 ℃ in an autoclave apparatus.

As a12 th aspect, the method for producing a silica sol according to any one of the 1 st to 11 th aspects, further comprising: bringing the silica sol obtained in the step (b) into contact with a strongly acidic ion exchange resin and/or a strongly basic ion exchange resin.

In view 13, the method for producing a silica sol according to view 12 further comprises: and (b) contacting the silica sol obtained in step (b) with a carboxylic acid type chelating resin, a hydroxyl type chelating resin, and/or an amine type chelating resin before or after contacting the silica sol with a strongly acidic ion exchange resin and/or a strongly basic ion exchange resin.

The method for producing a silica sol according to any one of aspects 1 to 13, wherein the method further comprises a solvent replacement step of replacing the aqueous medium of the obtained silica sol with an organic medium.

The 15 th aspect of the present invention is the method for producing a silica sol according to any one of the 1 st to 14 th aspects, wherein Ca and Mg are in the silica sol relative to SiO₂The mass ratio of (A) to (B) is 2 to 100 ppm.

AsViewpoint 16 is the method for producing a silica sol according to any one of viewpoints 1 to 15, wherein in the silica sol, Na is present relative to SiO₂In a mass ratio of 2 to 1000ppm, and K is in relation to SiO₂The mass ratio of (A) to (B) is 2 to 100 ppm;

in view 17, the method for producing a silica sol according to any one of views 1 to 16, wherein the elongated colloidal silica particles have an average particle diameter (D) measured by a dynamic light scattering method_Lnm) and primary particle diameter (D) measured by nitrogen adsorption_Bnm) ratio D_L/D_BIs3 to 30.

In view 18, the method for producing a silica sol according to any one of views 1 to 17, wherein the silica sol is an acidic silica sol or an ammonia-based alkaline silica sol.

The present invention can obtain a silica sol in which highly purified, elongated colloidal silica particles having a small amount of metal impurities are dispersed by producing active silicic acid by bringing an aqueous alkali metal silicate solution into contact with a cation exchange resin or with a cation exchange resin and an anion exchange resin, adding at least 1 compound that is an anion source selected from an inorganic acid, an organic acid, and an ammonium salt thereof, and ammonia that is an alkali source to the active silicic acid to obtain the prepared active silicic acid (raw material liquid), and heating (preferably, autoclaving) the obtained active silicic acid.

Silica sols in which non-spherical silica particles are dispersed can be expected to have various effects (for example, binding force, adsorption force, and light transmittance) due to the particle shape, and are used in applications such as microfillers for various coating agents, binders, modifiers, catalyst carriers, and abrasives for electronic materials (for example, abrasives for silicon wafers, and CMP abrasives for device wafers for polishing metals such as silicon oxide films, copper, and aluminum).

In these applications, the content of metal impurities is strictly limited, and the silica sol obtained in the present invention is a high-purity silica sol with a low content of metal impurities, and can be applied to these applications.

The high purity is not high purity obtained by using an alkali metal based on Na or K as an alkali source, but high purity obtained by using ammonia as an alkali source.

Examples of the high purity include: the step (a) of preparing active silicic acid, the step (b) of forming a silica sol, or both the steps.

The purification of the metal impurities can be carried out by bringing the colloidal aqueous solution of active silicic acid obtained in the step (a) or the silica sol obtained in the step (b) into contact with a strong acid type cation exchange resin and/or a strong base type anion exchange resin, and further bringing the colloidal aqueous solution of active silicic acid and the silica sol into contact with a weak acid type (carboxylic acid type) chelate resin and/or a weak base type (amine type) chelate resin.

The colloidal aqueous solution of active silicic acid used in the step (a) can be treated at room temperature or under heating by adding a strong acid to elute (leach) the metal impurities incorporated into the colloid of active silicic acid into the aqueous solution, and the aqueous solution is brought into contact with a strong acid type cation exchange resin and/or a strong base type anion exchange resin, and also brought into contact with a weak acid type (carboxylic acid type) chelate resin and/or a weak base type (amine type) chelate resin to remove the eluted substances, thereby achieving high purity.

The metal impurities are Na, K, Ca, Mg, Ni, Cu, Fe, Co, Zn, Ti, etc., and in the present invention, ammonia is used as an alkali source, so that the content of Na and K is low, and a Ca and Mg source is not used for adjusting the metal impurities into a slender shape, so that a method for producing a silica sol having a low content of Ca and Mg can be provided. In addition, the polyvalent metal can be removed from the silica sol by using an ion exchange resin or a chelate resin in combination.

Drawings

Fig. 1 is a TEM (transmission electron microscope) photograph (magnification of 25 ten thousand times) of the colloidal silica particles having a long and thin shape obtained in example 1.

Fig. 2 is a TEM (transmission electron microscope) photograph (magnification of 25 ten thousand times) of the colloidal silica particles having a long and thin shape obtained in example 2.

Fig. 3 is a TEM (transmission electron microscope) photograph (magnification of 25 ten thousand times) of the colloidal silica particles having a long and thin shape obtained in example 3.

Fig. 4 is a TEM (transmission electron microscope) photograph (magnification of 25 ten thousand times) of the colloidal silica particles having a long and thin shape obtained in example 4.

Fig. 5 is a TEM (transmission electron microscope) photograph (magnification of 25 ten thousand times) of the colloidal silica particles having a long and thin shape obtained in example 5.

Fig. 6 is a TEM (transmission electron microscope) photograph (magnification of 25 ten thousand times) of the colloidal silica particles having a long and thin shape obtained in comparative example 1.

Fig. 7 is a view for explaining a method of obtaining the particle length (L) of the elongated colloidal silica particles from a TEM (transmission electron microscope) photograph.

Detailed Description

The present invention relates to a method for producing a silica sol which is an SiO dispersion of elongated colloidal silica particles in a liquid medium₂A silica sol having a concentration of 6 to 30 mass%, wherein the colloidal silica particles having an elongated shape have an average particle diameter (D) measured by a dynamic light scattering method_Lnm) and primary particle diameter (D) measured by nitrogen adsorption_Bnm) ratio D_L/D_BIs 2.5 or more, the D_L30 to 300nm and a particle length measured by electron microscope observation in the range of 50 to 1000nm, comprising the following steps (a) and (b),

(a) the step of preparing a raw material solution includes adding SiO₂Adding ammonia and SiO to a colloidal aqueous solution of active silicic acid having a concentration of 1 to 6 mass% and a pH of 2 to 5₂A compound which becomes an anion source in an amount of 3.0 to 7.0% by mass, wherein the compound is at least 1 selected from the group consisting of inorganic acids, organic acids, and ammonium salts thereof,

(b) the step (a) is a step of heating the raw material solution obtained in the step (a) at 80 to 200 ℃ for 0.5 to 20 hours to produce a silica sol.

The liquid medium is an aqueous medium (water) or an organic medium (organic solvent).

Average particle diameter (D) by dynamic light scattering_Lnm) is measured based on a dynamic light scattering method, and can be measured, for example, by a dynamic light scattering particle size measuring apparatus (product name ゼーターサイザーナノ manufactured by スペクトリス). Average particle diameter (D) measured by dynamic light scattering method_Lnm) is in the range of 30-300 nm.

Primary particle diameter (D)_Bnm) is a specific surface area S m measured by the nitrogen adsorption method (BET method)²G is according to (D)_B2720/S, means the diameter of a hypothetical spherical silica particle having the same specific surface area as that of the colloidal silica particle having a long and narrow shape. Thus, D can be considered to be_L/D_BMeaning the elongation of the elongated shape of the silica particles. The elongated colloidal silica particles are not particles in which the particles are three-dimensionally aggregated, and do not have a three-dimensional network structure. The structure in which the particles are connected to each other in a moniliform shape and/or a chain shape is shown, and it is considered that the silica particles having the same particle diameter and/or different particle diameters are connected to each other in a moniliform shape or a chain shape.

In the present specification, the elongation of the silica particles means the degree of connection (degree of length) of colloidal silica particles connected in a moniliform and/or chain shape.

In the present invention, D_L/D_BThe ratio is 2.5 or more, and can be, for example, 2.5 to 50.0, 3.0 to 30.0, or 3.0 to 15.0.

The elongated colloidal silica particles of the present invention may be either crystalline or amorphous, or may be a mixture of crystalline and amorphous particles. Amorphous colloidal silica particles having an elongated shape are preferable.

The particle length of the colloidal silica particles can be confirmed by observing the particle shape with an electron microscope (transmission electron microscope), and the particle length is 50 to 1000nm or 60 to 800 nm.

In the present specification, the particle length of the elongated colloidal silica particles is represented by: when the colloidal silica particles connected in a moniliform and/or chain shape are regarded as 1 silica particle, the length (L) of the long side of the circumscribed (circumscribed) rectangle having the smallest area, which is in contact with (tangent to) an image formed by projecting the particle on a plane, is the length (L).

(a) The colloidal aqueous solution of active silicic acid used in the step can be prepared by using SiO₂/M₂An aqueous alkali metal silicate solution having an O molar ratio (wherein M represents sodium or potassium.) of 1 to 4.5 is contacted with a strong acid type cation exchange resin or an ion exchange resin such as a strong acid type cation exchange resin and a strong base type anion exchange resin to obtain a colloidal aqueous solution of active silicic acid. The method of bringing the aqueous alkali metal silicate solution into contact with the ion exchange resin is not particularly limited, and examples thereof include a method of bringing the aqueous alkali metal silicate solution into contact with the ion exchange resin by passing the aqueous alkali metal silicate solution through a column packed with the ion exchange resin.

The aqueous solution of alkali metal silicate is prepared so that the solid content thereof is 1 to 10% by mass, and the aqueous solution is brought into contact with an ion exchange resin, whereby a colloidal aqueous solution of active silicic acid can be produced. In the present specification, the solid component refers to a component obtained by removing an aqueous medium or an organic medium component from the total components of an aqueous solution or a silica sol. As the alkali metal silicate aqueous solution, commercially available sodium silicate No. 1, sodium silicate No. 2, and sodium silicate No. 3 can be diluted with pure water or the like to obtain an aqueous solution.

The strong acid type cation exchange resin may be a hydrogen type cation exchange resin, and a cation exchange resin which is converted into a hydrogen type by packing a column with a cation exchange resin and introducing a strong acid aqueous solution into the column can be used. Examples of the strong acid type cation exchange resin include アンバーライト IR-120B and アンバージェット 1020B manufactured by ダウ & ケミカル, DOWEX MARATHON GH, ダイヤイオン SK104 and ダイヤイオン PK208 manufactured by Mitsubishi ケミカル ホ ー ル デ ィ ン グ ス, and デュオライト C20J manufactured by Suzuki ケムテック.

The strongly basic ion exchange resin may be a hydroxyl ion exchange resin, and an anion exchange resin converted to a hydroxyl ion by packing an anion exchange resin in a column and introducing a strongly basic aqueous solution into the column can be used. Examples of the strongly basic anion exchange resin include アンバーライト IRA400J, アンバーライト IRA410J, アンバージェット 4400 manufactured by ダウ & ケミカル, ダイヤイオン SA10A and ダイヤイオン SA20A manufactured by mitsubishi ケミカル ホ ー ル デ ィ ン グ ス, and デュオライト UBA120 manufactured by tanhua ケムテック.

The colloidal aqueous solution of the above active silicic acid can be SiO₂A colloidal aqueous solution of active silicic acid having a solid content concentration of 1 to 10 mass%, preferably 1 to 6 mass%.

As the colloidal aqueous solution of active silicic acid used in the step (a), a colloidal aqueous solution of active silicic acid obtained by further contacting a carboxylic acid type chelate resin, a hydroxyl type chelate resin, and/or an amine type chelate resin can be used.

As the chelate resin, those containing 2 or more electron donating atoms such as N, S, O, P can be used, and examples thereof include N-O, S-N, N-N and O-O chelate resins, and examples thereof include iminodiacetic acid type (-N (CH)₂COO－)₂) Polyamine type (-NH (CH)₂CH₂NH)_nH) The chelating resin of (1). Examples thereof include trade names ダイヤイオン CR11, ダイヤイオン CR20, ダイヤイオン CRB03 and ダイヤイオン CRB05 manufactured by Mitsubishi ケミカル. The adsorbed metal ions can be regenerated in an aqueous inorganic acid solution (aqueous hydrochloric acid solution, aqueous sulfuric acid solution) and used. The chelate resin having metal ions adsorbed thereon can be regenerated by removing the metal ions with an aqueous inorganic acid solution (aqueous hydrochloric acid solution or aqueous sulfuric acid solution).

(a) The colloidal aqueous solution of active silicic acid used in the step can be further purified by repeating the flow of the solution through a column packed (packed) with the ion exchange resin or chelate resin.

The ion exchange resin and the chelating resin can be filled (packed) into a column, and the aqueous solution can be used for 1 to 30 hours^-1Or 1 to 15 hours^-1The liquid is introduced at the space velocity of (2).

(a) The colloidal aqueous solution of active silicic acid used in the step can be purified by treating the solution at a temperature of 1 to 98 ℃ by further adding a strong acid, and then contacting the treated solution with a strong acid type cation exchange resin or with a strong acid type cation exchange resin and a strong base type anion exchange resin. The colloidal aqueous solution of active silicic acid is considered to form a fine colloidal aqueous solution (for example, a particle diameter of 5nm or less, or less than 5nm, or 3nm or less, or 1nm or less), and metal impurities may be contained in these colloidal particles. When the metal impurities in the colloidal particles cannot be removed by using an ion exchange resin or a chelate resin, the metal impurities can be eluted from the inside of the colloidal particles into an aqueous solution by adding an aqueous acid solution to an aqueous colloidal solution of active silicic acid and treating the solution at 1 to 98 ℃ preferably at room temperature. These metal impurities are adsorbed and separated from the aqueous solution by contacting them with the ion exchange resin or the chelate resin, and therefore the colloidal aqueous solution of active silicic acid can be highly purified. This also enables the finally obtained silica sol to be highly purified.

As the compound to be an anion source used in the step (a), at least 1 selected from nitric acid, sulfuric acid, phosphoric acid, boric acid, hydrofluoric acid, hydrochloric acid, acetic acid, formic acid, oxalic acid, citric acid, lactic acid, malic acid, gluconic acid, tartaric acid, ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA), and ammonium salts thereof can be used. For example, an aqueous solution of nitric acid, sulfuric acid, oxalic acid, or the like can be used. These anion sources may be added in the form of ammonium salts, or may be used by converting ammonia for pH adjustment into ammonium salts. The concentration of the aqueous solution can be used, for example, in the range of 0.1 to 50 mass%, or 0.1 to 10 mass%, or 0.1 to 5 mass%, or 0.1 to 1 mass%, or 0.1 to 0.2 mass%.

The ammonia used for pH adjustment in the step (a) may be ammonia gas or an aqueous ammonia solution. Examples thereof include: a method of adjusting the pH by directly introducing ammonia gas into the colloidal aqueous solution of active silicic acid, or a method of adjusting the pH by adding an aqueous ammonia solution to the colloidal aqueous solution of active silicic acid. The ammonia water solution can be used at a concentration of 28 mass%, or can be diluted with pure water to a concentration of 1 mass% or more and less than 28 mass%.

Examples of the step (a) include: a method comprising the step of adding the compound to be an anion source to the colloidal aqueous solution of active silicic acid, and then adding the ammonia.

Examples of the step (a) include: the method comprises the steps of adding the ammonia to the colloidal aqueous solution of the active silicic acid, then adding the compound that becomes the anion source, and then adding the ammonia.

The pH of the raw material liquid (colloidal aqueous solution of active silicic acid) obtained in the step (a) can be adjusted to 8 to 12, 9 to 11, or 9 to 10 by pH adjustment.

(b) The step (a) is a step of heating the raw material solution (colloidal aqueous solution of active silicic acid) obtained in the step (a) at a temperature of 80 to 200 ℃, or 100 to 180 ℃, or 120 to 150 ℃ for 0.5 to 20 hours while stirring to obtain a silica sol. By heating to a temperature of 100 to 200 ℃ or 100 to 180 ℃ using an autoclave apparatus, a silica sol in which colloidal silica particles having a high profile degree and a long and thin shape are dispersed can be produced. In the step (b), an ammonia-type alkaline silica sol having a pH of 8 to 11 or 9 to 11 can be obtained.

The silica sol obtained in the step (b) can be concentrated by using an ultrafiltration membrane or concentrated by evaporation under reduced pressure or normal pressure to obtain SiO as required₂The concentration is adjusted to 6 to 30 mass%.

The silica sol obtained in the step (b) can be brought into contact with a strongly acidic ion exchange resin and/or a strongly basic ion exchange resin to obtain a high-purity silica sol. For example, the silica sol obtained in the step (b) may be brought into contact with a strongly acidic ion exchange resin, or a strongly acidic ion exchange resin and a strongly basic ion exchange resin to obtain a high-purity silica sol.

The silica sol obtained in the step (b) may be contacted with a carboxylic acid type chelating resin, a hydroxyl type chelating resin, and/or an amine type chelating resin before or after the silica sol is contacted with a strongly acidic ion exchange resin and/or a strongly basic ion exchange resin, thereby obtaining a high-purity silica sol. For example, the silica sol obtained in the step (b) may be contacted with a strongly acidic ion exchange resin, or with a strongly acidic ion exchange resin and a strongly basic ion exchange resin, and then contacted with a carboxylic acid type chelating resin, a hydroxyl type chelating resin, and/or an amine type chelating resin to obtain a high purity silica sol.

The acidic silica sol can be produced by bringing the silica sol obtained in the step (b) into contact with a strongly acidic ion exchange resin.

The acidic silica sol can be produced by replacing the aqueous medium with an organic medium (organic solvent). The solvent substitution can be performed by an evaporation method using an apparatus such as a rotary evaporator. D of colloidal silica particles in elongated form even by solvent substitution_L/D_BThe ratio is also unchanged.

As the organic solvent, alcohol, glycol, ester, ketone, nitrogen-containing solvent, and aromatic solvent can be used. Examples of the solvent include organic solvents such as methanol, ethanol, propanol, ethylene glycol, propylene glycol, glycerol, ethylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, acetone, methyl ethyl ketone, dimethylformamide, N-methyl-2-pyrrolidone, toluene, xylene, and dimethylethane. In addition, polyethylene glycol, silicone oil, a reactive diluent solvent containing a radical polymerizable vinyl group and/or an epoxy group, and the like can also be used.

The surfaces of the elongated colloidal silica particles can be treated with a silane coupling agent such as tetraethoxysilane, trimethylmonoethoxysilane, or hexamethyldisilane.

In the obtained silica sol, the metal impurity can be in the form of SiO₂Contains Ca in an amount of 2 to 100ppm or 2 to 50ppm based on SiO₂The amount of Mg is 2 to 100ppm or 2 to 50ppm by mass.

Furthermore, the silica sol can be prepared in a manner comparable to SiO₂In a mass ratio of 2 to 1000ppm or 2 to 500ppm, Na is contained in an amount of 2 to 1000ppm or 2 to 500ppm based on SiO₂The mass ratio of (A) is 2 to 100ppm, or 2 to 50ppm, and K is contained.

The silica sol obtained in the step (b) can be brought into contact with a strongly acidic ion exchange resin to prepare an acidic silica sol, and then high-purity ammonia gas or an aqueous ammonia solution can be added thereto to prepare an ammonia-type alkaline silica sol.