A method for preparing a silica sol using an ion exchange method

Abstract

The present application belongs to the technical field of silica sol preparation, and particularly relates to a silica sol preparation method using ion exchange method. In the prior art, the silica sol growth time is shortened by optimizing the preparation and impurity removal process, and the silica sol seed mother liquor is prepared under ultrasonic assistance. The organic alkali catalyst maintains the silica sol growth pH and the metal ions in the complex solution, so that the impurities are reduced during the silica sol growth. After the introduction of dodecyltrimethoxysilane, hexadecyltrimethoxysilane and methyltrimethoxysilane as the hydrophobic group surface modification, the impurity metal ions are filtered through the complexing agent and the ammonium type resin. The three ethylene tetramine ethanol solution modifies the ammonium type resin, enhances the selective adsorption of the resin to the metal ions, and the maleic anhydride crosslinking agent and nano silicon dioxide modify the ammonium type resin, increase the service life of the ammonium type resin. The prepared silica sol has high purity, good mechanical properties and dispersibility, and excellent hydrophobic performance.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of silica sol preparation, and particularly relates to a silica sol preparation method using an ion exchange method. BACKGROUND

[0002] Silica sol is a colloidal solution of amorphous nanoscale silicon dioxide particles in water or solvent, and has the properties of non-toxicity, non-odor, high adsorption performance, large specific surface area and insulation, and is widely used in polishing, papermaking, coating, fabric and catalyst fields. The ion exchange method is the most mature silica sol preparation method, and generally includes the following steps: using water glass as raw material, and preparing silica sol through ion exchange reaction, seed preparation, particle growth reaction, concentration step and purification step.

[0003] A silica sol preparation method for acrylonitrile catalyst is disclosed in Chinese patent CN105329906B: an industrial sodium silicate aqueous solution with a silicon dioxide content of 3-5wt% is added with sulfuric acid aqueous solution to a pH of 9.0-9.5, and then heated to 90-95℃ and kept for 1-2 hours to form a silica sol bottom liquid; industrial sodium silicate with a modulus of 3.0-3.3 is added with water to prepare a 3-5wt% silicon dioxide aqueous solution, and cation exchange resin is suspended with deionized water, then water glass is added and the outlet pH after ion exchange is controlled to 2-3 to prepare silicic acid, the silicic acid is added to the prepared silica sol bottom liquid at a speed of 100-200ml / min, and the pH is kept at 9-9.5, and then kept at a temperature of 90-95℃ for 1-2 hours and cooled to room temperature; the product is ion exchanged with strong acid cation exchange resin regenerated with hydrochloric acid, while the pH is kept at 1-2, and then ammonia water is added to adjust the pH to 9-9.5; finally, the prepared silica sol is added with a dispersant and concentrated by ultrafiltration to prepare silica sol, the prepared silica sol has an average particle size of 20-25nm, a sodium ion content of less than 0.05%, a concentration of 40-50%, and a viscosity of less than 20cps. However, the silica sol prepared by the ion exchange method has the technical problems of more impurities and insufficient dispersion stability. SUMMARY

[0004] The purpose of the present application is to provide a silica sol preparation method using an ion exchange method, which solves the technical problems of more impurities and insufficient dispersion stability of the silica sol prepared by the ion exchange method in the prior art.

[0005] In order to achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0006] A silica sol preparation method using an ion exchange method, comprising the following steps:

[0007] S1, pretreatment: deionized water and solid sodium silicate are added to a dissolving kettle, steam is introduced to heat to 65-75℃ and stirring is promoted to facilitate dissolution, and the waste residue is filtered by a plate and frame filter to obtain a sodium silicate solution;

[0008] S2, dilute silicic acid preparation: the sodium silicate solution is added to deionized water to prepare a 5-10wt% dilute sodium silicate solution, which is then slowly added to an exchange kettle, filtered by cation exchange resin exchange, and the pH is controlled to 2-3 to obtain dilute silicic acid;

[0009] S3, silica sol preparation: dilute silicic acid is slowly added to a reaction kettle, silica sol seed mother liquor and organic base catalyst are added to adjust the pH in the reaction kettle to 9.5-10.5, steam is introduced into the reaction kettle to maintain 90-95℃ during the feeding process, and stirring is carried out for 1-2h to obtain a crude silica sol;

[0010] S4, surface modification: the crude silica sol is added to an organic acid to adjust the pH to 2-4, a modifier is added at 50-60℃, and ultrasonic treatment is carried out for 0.5-1h to obtain a modified crude silica sol;

[0011] S5, complexing and impurity removal: the modified crude silica sol is added to a complexing agent, and then modified ammonium resin is introduced for ammonium stabilization treatment to obtain an ammonium type crude silica sol;

[0012] S6, filtration and concentration: the ammonium type crude silica sol is filtered and concentrated by ultrafiltration to remove waste water, and a high-concentration silica sol product is obtained.

[0013] Preferably, the mass ratio of deionized water to solid sodium silicate in S1 is 100:10-20, the steam flow rate is 4-6m / s, and the plate and frame filter aperture is 1-10μm.

[0014] Preferably, the container containing the dilute sodium silicate solution in S2 is washed with deionized water and then added to the dissolving kettle in S1 for recycling.

[0015] Preferably, the regeneration of the cation exchange resin in S2 includes the following steps:

[0016] S11, deionized water is used to rinse the cation exchange resin to remove sodium silicate solution, 3-5wt% hydrochloric acid is prepared, and the mass of the hydrochloric acid used is 2-2.5 times that of the cation exchange resin, which is slowly added to the cation exchange resin, and the addition is completed within 40-60min;

[0017] S12, the cation exchange resin is rinsed with deionized water until the filtrate pH is 7, and the regeneration of the cation exchange resin is completed.

[0018] Preferably, the preparation method of the silica sol seed mother liquor in S3 includes the following steps:

[0019] S21, 5-10wt% of the total mass of the dilute silicic acid prepared in step S2 is added to the dilute sodium silicate solution prepared in step S2 to adjust the pH to 9.5-10.5 to obtain a mixed solution;

[0020] S22, the temperature of the mixed solution is kept at 65-75℃, and seed crystals are generated by ultrasonic assistance for 3-6min to obtain a silica sol mother liquor.

[0021] As a preferred, the organic base catalyst in S3 is one or more combinations of trimethyl phosphine, guanidyl methyl phosphoric acid and N-methyl imidazole.

[0022] As a preferred, the silica sol content in the silica sol crude product in S3 is 4-9wt%.

[0023] As a preferred, the organic acid in S4 is one or more combinations of glacial acetic acid, tartaric acid and citric acid.

[0024] As a preferred, the modifier in S4 is one or more combinations of dodecyl trimethoxysilane, hexadecyl trimethoxysilane and methyl trimethoxysilane, and the ratio of the amount of modifier added to the silica sol content in the silica sol crude product is 0.7-1:1.

[0025] As a preferred, the complexing agent in S5 is one or more combinations of ethylenediaminetetraacetic acid, triethanolamine and 8-hydroxyquinoline, and the ratio of the amount of complexing agent added to the silica sol content in the silica sol crude product is 0.1-0.3:1.

[0026] As a preferred, the preparation method of the modified ammonium type resin in S5 comprises the following steps:

[0027] S31, the 732 type cationic resin is soaked in saturated sodium chloride solution for 24-48h to remove residual impurities, anhydrous ethanol is introduced until the leaching solution is neutral, an ethanol ammonia water solution is prepared, and the 732 type cationic resin is soaked in the ethanol ammonia water solution for 1-2h;

[0028] S32, the 732 type cationic resin is added to a maleic anhydride crosslinking agent, a triethylene tetramine ethanol solution and nano silicon dioxide, stirred at 40-60℃ for 24-36h, filtered and dried to obtain a modified ammonium type resin.

[0029] As a preferred, the ethanol content in the ethanol ammonia water solution in S31 is 30-40wt%, and the pH is 12-13.

[0030] As a preferred, the triethylene tetramine content in the triethylene tetramine ethanol solution in S32 is 60-70wt%.

[0031] As a preferred, the nano silicon dioxide particle size in S32 is 15-25nm.

[0032] Preferably, the amount of each substance in S32 is 5-10g of type 732 cationic resin, 0.5-1g of maleic anhydride crosslinking agent, 30-60ml of triethylenetetramine ethanol solution and 10-30mg of nano-silica.

[0033] In summary, due to the adoption of the above technical solutions, the present application has the following advantages:

[0034] 1. In the prior art, the preparation and impurity removal process are optimized, the ultrasonic-assisted preparation of the silica sol seed mother liquor shortens the growth time of the silica sol, the organic alkali catalyst maintains the pH of the silica sol growth and the metal ions in the complexing solution, the impurities are reduced during the growth of the silica sol, the hydrophobic groups are introduced for surface modification, and the impurity metal ions are filtered through the complexing agent and the ammonium resin, so that the prepared silica sol has high purity, good mechanical properties and dispersibility, and excellent hydrophobic performance.

[0035] 2. The present application introduces ultrasonic-assisted preparation of the silica sol mother liquor, which greatly shortens the preparation time of the silica sol, and the nano-silica seeds formed in the preparation of the silica sol mother liquor have high activity, so that the subsequent process of the silica sol has improved dispersibility and high specific surface area.

[0036] 3. In the surface modification process, the hydrophobic groups are introduced, the grafting of the hydrophobic groups forms a protective siloxane film on the surface of the silica sol, which can effectively improve the stability of the silica sol in water, avoid irreversible gelation of the silica sol, make the silica sol easy to form large particle size spherical particles, and the hydrophobic groups introduced by surface modification greatly improve the hydrophobic performance and hardness of the silica sol.

[0037] 4. In the modification process, the organic acid is added to inhibit the adsorption of metal ions on the surface of the silica sol, and in the subsequent impurity removal step, the complexing agent is added to complex the metal ions and the residual impurities in the surface modification, and the triethylenetetramine ethanol solution modifies the ammonium resin to enhance the selective adsorption of the resin to the metal ions, and the maleic anhydride crosslinking agent and nano-silica modify the ammonium resin to increase the service life of the ammonium resin, so that the prepared silica sol has high purity. BRIEF DESCRIPTION OF DRAWINGS

[0038] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the following embodiment or prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0039] Figure 1 A process flow chart of a silica sol preparation method using ion exchange method is shown. DETAILED DESCRIPTION

[0040] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0041] Embodiment 1, a silicon sol preparation method using ion exchange method, comprising the following steps:

[0042] S1, pretreatment: 100 parts of deionized water and 20 parts of solid sodium silicate are added to a dissolving kettle, steam is introduced at 4 m / s to warm to 70℃ and stirring is promoted to facilitate dissolution, and waste residue is filtered through a plate frame with a pore size of 5 μm to obtain a sodium silicate solution;

[0043] S2, dilute silicic acid preparation: after the sodium silicate solution is added to deionized water to configure a 10wt% dilute sodium silicate solution, the dilute sodium silicate solution is slowly added to an exchange kettle, filtered by 732 type cation exchange resin and controlled to have a pH of 2.5, and dilute silicic acid is obtained;

[0044] S3, silicon sol preparation: the dilute silicic acid is slowly added to a reaction kettle, a silicon sol seed mother liquor and trimethyl phosphine are added at the same time to adjust the pH in the reaction kettle to 10, steam is introduced into the reaction kettle to keep 95℃ during the feeding process, and stirring reaction is carried out for 1 h to obtain a silicon sol content of 9wt% silicon sol crude product;

[0045] S4, surface modification: 100 g of the silicon sol crude product is added to glacial acetic acid to adjust the pH to 4, 8 g of methyltrimethoxysilane is added at 60℃ for modification, and ultrasonic treatment is carried out for 1 h to obtain a modified silicon sol crude product;

[0046] S5, complexing and impurity removal: after the modified silicon sol crude product is added to 1.8 g of a complexing agent with a mass ratio of ethylenediaminetetraacetic acid to triethanolamine of 1:1, modified ammonium type resin is introduced for ammonium stabilization treatment to obtain an ammonium type silicon sol crude product;

[0047] S6, filtration and concentration: the ammonium type silicon sol crude product is filtered and concentrated by ultrafiltration to filter waste water, and a high-concentration silicon sol product is obtained.

[0048] The preparation method of the silicon sol seed mother liquor in S3 comprises the following steps:

[0049] S21, 10wt% of the total mass of the dilute silicic acid prepared in S2 is added to the dilute sodium silicate solution prepared in S2 to adjust the pH to 10 to obtain a mixed solution;

[0050] S22, the temperature of the mixed solution is kept at 70℃, and crystal seeds are generated by ultrasonic assistance for 6 min to obtain a silicon sol mother liquor.

[0051] The preparation method of the modified ammonium type resin in S5 comprises the following steps:

[0052] S31, soak the 732 type cationic resin in saturated sodium chloride solution for 48 h to remove residual impurities, pass dry ethanol into the leaching solution until it is neutral, prepare ethanol ammonia solution with an ethanol content of 30wt% and a pH of 13, and soak the 732 type cationic resin in the ethanol ammonia solution for 1-2 h;

[0053] S32, add 10 g of 732 type cationic resin to 1 g of maleic anhydride crosslinking agent, 60 ml of triethylenetetramine ethanol solution with a triethylenetetramine content of 65wt%, and 30 mg of nano silicon dioxide with a particle size of 20 nm, stir at 40℃ for 24 h, filter and dry to obtain the modified ammonium type resin.

[0054] Example 2, a silica sol preparation method using ion exchange method, comprising the following steps:

[0055] S1, pretreatment: add 100 parts of deionized water and 30 parts of solid sodium silicate to a dissolving kettle, pass in 6 m / s steam to warm up to 75℃ and stir to promote dissolution, filter the waste residue through a plate and frame filter with a pore size of 10 μm to obtain a sodium silicate solution;

[0056] S2, preparation of dilute silicic acid: after adding the sodium silicate solution to deionized water to prepare a 10wt% dilute sodium silicate solution, slowly add it to an exchange kettle, exchange filter through a 732 type cation exchange resin and control the pH to 2 to obtain dilute silicic acid;

[0057] S3, preparation of silica sol: slowly add the dilute silicic acid to a reaction kettle, at the same time add silica sol seed mother liquor and N-methyl imidazole to adjust the pH in the reaction kettle to 9.5, pass steam into the reaction kettle to keep the temperature at 90℃ during the feeding process, and stir for 2 h to obtain a silica sol crude product with a silica sol content of 8wt%;

[0058] S4, surface modification: add 100 g of silica sol crude product to ice acetic acid and citric acid to adjust the pH to 3, the mass ratio of ice acetic acid and citric acid is 1:1, add 8 g of dodecyl trimethoxysilane at 50℃, and ultrasonic for 1 h to obtain a modified silica sol crude product;

[0059] S5, complexing and impurity removal: add 2 g of ethylenediaminetetraacetic acid and 8-hydroxyquinoline complexing agent with a mass ratio of 1:1 to the modified silica sol crude product, then pass through the modified ammonium type resin for ammonium stabilization treatment to obtain an ammonium type silica sol crude product;

[0060] S6, filtration and concentration: pass the ammonium type silica sol crude product through an ultrafiltration concentration to filter waste water to obtain a high concentration silica sol product.

[0061] The preparation method of the silica sol seed mother liquor in S3 comprises the following steps:

[0062] S21, 5wt% of the total mass of the dilute silicic acid prepared in the step S2 is added to the dilute sodium silicate solution prepared in the step S2 to adjust the pH to 9.5, and a mixed solution is obtained;

[0063] S22, the temperature of the mixed solution is kept at 70℃, and the seed is generated by ultrasonic assistance for 4min to obtain a silica sol mother liquor.

[0064] The preparation method of the modified ammonium type resin in S5 comprises the following steps:

[0065] S31, the 732 type cationic resin is soaked in a saturated sodium chloride solution for 24h to remove residual impurities, anhydrous ethanol is introduced until the leaching solution is neutral, an ethanol ammonia water solution with an ethanol content of 40wt% and a pH of 12 is prepared, and the 732 type cationic resin is soaked in the ethanol ammonia water solution for 2h;

[0066] S32, 5g of the 732 type cationic resin is added to 0.5g of a maleic anhydride crosslinking agent, 30ml of a triethylenetetramine ethanol solution with a triethylenetetramine content of 70wt%, and 10mg of nano silicon dioxide with a particle size of 15nm, and stirred at 60℃ for 24h, and then filtered and dried to obtain a modified ammonium type resin.

[0067] Example 3, a silica sol preparation method using ion exchange method, comprising the following steps:

[0068] S1, pretreatment: 100 parts of deionized water and 25 parts of solid sodium silicate are added to a dissolving kettle, steam is introduced to heat to 70℃ and stirring is promoted to promote dissolution, and the waste residue is filtered through a plate frame with a pore size of 1μm to obtain a sodium silicate solution;

[0069] S2, dilute silicic acid preparation: the sodium silicate solution is added to deionized water to prepare an 8wt% dilute sodium silicate solution, which is then slowly added to an exchange kettle, filtered by a 732 type cation exchange resin, and the pH is controlled to 3 to obtain dilute silicic acid;

[0070] S3, silica sol preparation: the dilute silicic acid is slowly added to a reaction kettle, and a silica sol seed mother liquor and a guanidyl methyl phosphoric acid are added to adjust the pH in the reaction kettle to 9.5, steam is introduced into the reaction kettle to keep the temperature at 90℃ during the feeding process, and stirring is reacted for 1h to obtain a silica sol crude product with a silica sol content of 7wt%;

[0071] S4, surface modification: 100g of the silica sol crude product is added to glacial acetic acid to adjust the pH to 3.5, 6g of dodecyltrimethoxysilane is added at 60℃, and ultrasonic modification is performed for 1h to obtain a modified silica sol crude product;

[0072] S5, complex impurity removal: the modified silica sol crude product is added to 2g of ethylenediaminetetraacetic acid, triethanolamine and 8-hydroxyquinoline complexing agent with a mass ratio of 1:2:1, and then ammonium type resin is introduced for ammonium stabilization treatment to obtain an ammonium type silica sol crude product;

[0073] S6, filtration and concentration: the ammonium type silica sol crude product is filtered and concentrated by ultrafiltration to remove waste water, and a high-concentration silica sol product is obtained.

[0074] The preparation method of the silica sol seed mother liquor in S3 comprises the following steps:

[0075] S21, 9wt% of the total mass of dilute silicic acid prepared in S2 is added to the dilute sodium silicate solution prepared in S2 to adjust the pH to 10.5, and a mixed solution is obtained;

[0076] S22, the temperature of the mixed solution is kept at 70℃, and the seed is generated by ultrasonic assistance for 5min to obtain a silica sol mother liquor.

[0077] The preparation method of the modified ammonium type resin in S5 comprises the following steps:

[0078] S31, the 732 type cationic resin is soaked in saturated sodium chloride solution for 24h to remove residual impurities, anhydrous ethanol is introduced until the leaching solution is neutral, an ethanol ammonia water solution with an ethanol content of 30wt% and a pH of 12 is prepared, and the 732 type cationic resin is soaked in the ethanol ammonia water solution for 1h;

[0079] S32, 10g of 732 type cationic resin is added to 0.5g of maleic anhydride crosslinking agent, 30ml of triethylene tetramine ethanol solution with a triethylene tetramine content of 70wt%, and 25mg of nano silicon dioxide with a particle size of 20nm, and stirred at 50℃ for 36h, then filtered and dried to obtain a modified ammonium type resin.

[0080] Example 4, a silica sol preparation method using ion exchange method, comprising the following steps:

[0081] S1, pretreatment: 100 parts of deionized water and 20 parts of solid sodium silicate are added to a dissolving kettle, steam is introduced to heat to 70℃ and stirring is promoted to promote dissolution, and the waste residue is filtered through a plate frame with a pore size of 1μm to obtain a sodium silicate solution;

[0082] S2, dilute silicic acid preparation: the sodium silicate solution is added to deionized water to prepare a 10wt% dilute sodium silicate solution, which is then slowly added to an exchange kettle, filtered and exchanged by a 732 type cationic exchange resin, and the pH is controlled at 2.5 to obtain dilute silicic acid;

[0083] S3, Preparation of silica sol: dilute silicic acid is slowly added to the reaction kettle, while adding silica sol seed mother liquor and guanidyl methyl phosphoric acid to adjust the pH in the reaction kettle to 10.5, the reaction kettle is connected with steam to keep 95℃ during the feeding process, and the stirring reaction is carried out for 1h to obtain a silica sol content of 9wt% silica sol crude product;

[0084] S4, Surface modification: 100g of silica sol crude product is added to tartaric acid to adjust the pH to 3.3, 8g of methyltrimethoxysilane is added at 60℃, and ultrasonic treatment is carried out for 1h to obtain modified silica sol crude product;

[0085] S5, Complex impurity removal: the modified silica sol crude product is added with 1.8g of ethylenediaminetetraacetic acid, and then connected with modified ammonium type resin for ammonium stabilization treatment to obtain ammonium type silica sol crude product;

[0086] S6, Filtration and concentration: the ammonium type silica sol crude product is concentrated and filtered by ultrafiltration to remove waste water, and high concentration silica sol product is obtained.

[0087] The preparation method of the silica sol seed mother liquor in S3 comprises the following steps:

[0088] S21, 8wt% of the total mass of the dilute silicic acid prepared in S2 is added to the dilute sodium silicate solution prepared in S2 to adjust the pH to 10.5 to obtain a mixed solution;

[0089] S22, the temperature of the mixed solution is kept at 70℃, and the seed is generated by ultrasonic treatment for 5min to obtain the silica sol mother liquor.

[0090] The preparation method of the modified ammonium type resin in S5 comprises the following steps:

[0091] S31, the 732 type cationic resin is soaked in saturated sodium chloride solution for 24h to remove residual impurities, anhydrous ethanol is introduced until the leaching solution is neutral, an ethanol ammonia water solution with an ethanol content of 30wt% and a pH of 13 is prepared, and the 732 type cationic resin is soaked in the ethanol ammonia water solution for 1h;

[0092] S32, 10g of 732 type cationic resin is added with 1g of maleic anhydride crosslinking agent, 60ml of triethylene tetramine ethanol solution with a triethylene tetramine content of 60wt%, and 25mg of nano silicon dioxide with a particle size of 25nm, stirred at 40℃ for 36h, filtered and dried to obtain the modified ammonium type resin.

[0093] Example 5, a silica sol preparation method using ion exchange method, comprising the following steps:

[0094] S1, pretreatment: 100 parts of deionized water and 20 parts of solid sodium silicate are added to a dissolving kettle, steam is introduced to heat to 65℃ and stirring is promoted to facilitate dissolution, and the waste residue is filtered through a plate and frame filter with a pore size of 5μm to obtain a sodium silicate solution;

[0095] S2, dilute silicic acid preparation: after the sodium silicate solution is configured into a 5wt% dilute sodium silicate solution, the solution is slowly added into an exchange kettle, filtered by 732 type cation exchange resin exchange, and the pH is controlled to be 2.5, to obtain dilute silicic acid;

[0096] S3, silica sol preparation: the dilute silicic acid is slowly added into a reaction kettle, while silica sol seed mother liquor and trimethyl phosphine are added to adjust the pH in the reaction kettle to be 9.5, the reaction kettle is ventilated with steam to keep 95℃ during the feeding process, and stirring reaction is performed for 1h, to obtain 4wt% silica sol crude product;

[0097] S4, surface modification: 100g of the silica sol crude product is added into citric acid to adjust the pH to be 2.4, 4g of hexadecyl trimethoxysilane is added at 60℃ for modification, and ultrasonic treatment is performed for 1h to obtain modified silica sol crude product;

[0098] S5, complexing and impurity removal: after the modified silica sol crude product is added into 1.2g of 8-hydroxyquinoline, modified ammonium type resin is ventilated to perform ammonium stabilization treatment, to obtain ammonium type silica sol crude product;

[0099] S6, filtration and concentration: the ammonium type silica sol crude product is filtered and concentrated by ultrafiltration to filter waste water, to obtain high-concentration silica sol product.

[0100] The preparation method of the silica sol seed mother liquor in S3 comprises the following steps:

[0101] S21, 5wt% of the total mass of the dilute silicic acid prepared in the S2 step is added into the dilute sodium silicate solution configured in the S2 step to adjust the pH to be 9.5, to obtain a mixed solution;

[0102] S22, the temperature of the mixed solution is kept at 65℃, and seed crystals are generated by ultrasonic assistance for 5min, to obtain a silica sol mother liquor.

[0103] The preparation method of the modified ammonium type resin in S5 comprises the following steps:

[0104] S31, the 732 type cation resin is soaked in saturated sodium chloride solution for 24h to remove residual impurities, anhydrous ethanol is ventilated until the soaking solution is neutral, an ethanol ammonia water solution with an ethanol content of 40wt% and a pH of 13 is configured, and the 732 type cation resin is soaked in the ethanol ammonia water solution for 2h;

[0105] S32, 10g of the 732 type cation resin is added into 1g of maleic anhydride crosslinking agent, 50ml of triethylene tetramine ethanol solution with a triethylene tetramine content of 60wt%, and 30mg of nano silicon dioxide with a particle size of 15nm, stirring is performed at 40℃ for 24h, and the modified ammonium type resin is obtained by filtration and drying.

[0106] Comparative Example 1, the difference between this comparative example and Example 1 is that no silica sol seed mother liquor is prepared, and the dilute silicic acid is directly used for silica sol growth in the reaction kettle.

[0107] Comparative Example 2, the difference between this comparative example and Example 1 is that the organic alkali catalyst is replaced by a 10wt% sodium hydroxide solution.

[0108] Comparative Example 3, the difference between this comparative example and Example 1 is that the organic acid in the surface modification step is replaced by 12.5wt% dilute hydrochloric acid.

[0109] Comparative Example 4, the difference between this comparative example and Example 1 is that no complexing agent is added.

[0110] Performance test

[0111] Test Example 1

[0112] The silica sol prepared in each example and comparative example is detected for silica content, viscosity, average particle size and metal ion content by a commercially available detection device, and the test results are shown in Table 1:

[0113] Table 1

[0114]

[0115]

[0116] As shown by the data in Table 1, the silica sol prepared in Examples 1-5 has a silica concentration of 39-42.7wt% and a metal ion content of less than 20ppm, indicating that the silica sol prepared by the present application has a high effective component content and high purity; the viscosity is 21.2-27.0mPa / S and the average particle size is 54-65nm, indicating that the silica sol prepared by the present application has good stability and high dispersibility. Comparative Example 1 does not prepare a silica sol seed mother liquor, and the dilute silicic acid is directly used for silica sol growth in the reaction kettle, resulting in a too long silica sol growth time, reduced silica sol dispersibility, and partial silica sol adhesion to form a glue, resulting in a reduced silica effective component content; Comparative Example 4 does not add a complexing agent to complex impurities, and the impurities are directly removed by modified ammonium resin, resulting in incomplete filtration of metal ions, and a metal ion content of 65ppm, which is much higher than the metal ion content of each example.

[0117] Test Example 2

[0118] Silica sol coating preparation: a glass slide is immersed in the silica sol prepared in each example and comparative example for 3min, slowly taken out and placed in an oven for drying at 60°C, to obtain a glass slide with silica sol coating attached.

[0119] The glass slides with the silica sol coating prepared by each example and the comparative example were detected by the commercially available detection equipment to detect the light transmittance, hardness, adhesion and water drop rolling angle, and the test results are shown in Table 2:

[0120] Table 2

[0121]

[0122] From the data in Table 2, it can be seen that the light transmittance of the silica sol coating prepared by using the silica sol prepared by Examples 1-5 as raw material is between 81.9-85.1%, which indicates that the silica sol prepared by the present application has good dispersibility and uniform particle size, and the prepared silica sol coating is smooth and has high light transmittance; the hardness of the silica sol coating is 7H and the adhesion is grade 1, which indicates that the silica sol prepared by the present application has high hardness and good adhesion; the water drop rolling angle is between 26.5-28.3°, which indicates that the silica sol prepared by the present application has excellent hydrophobicity. In the surface modification process of Comparative Example 3, the organic acid is replaced by 12.5wt% dilute hydrochloric acid, which causes part of the metal impurities to be adsorbed on the surface of the silica sol, and a protective siloxane film is formed on the surface of the silica sol, which causes the hardness and adhesion of the silica sol to decrease and the water drop rolling angle to increase, i.e. the hydrophobicity to decrease; the residual amount of metal ions in Comparative Example 4 is relatively high, which reduces the smoothness of the silica sol coating and causes the light transmittance to decrease.

[0123] The above description is only for the preferred embodiments of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art can make equivalent substitutions or changes to the technical solution and the inventive concept of the present application within the technical scope disclosed by the present application, which should be covered within the protection scope of the present application.

[0124] The preferred embodiments of the present application disclosed above are only used to help explain the present application. The preferred embodiments do not describe all the details and do not limit the present application to the specific embodiments. Obviously, many modifications and changes can be made according to the content of the present specification. The present specification selects and describes these embodiments in order to better explain the principles and practical applications of the present application, so that the person skilled in the art can well understand and utilize the present application. The present application is limited by the claims and the entire scope and equivalents thereof.

Claims

1. A method for preparing silica sol using ion exchange, characterized in that, Includes the following steps: S1. Pretreatment: Deionized water and solid sodium silicate are added to a dissolving vessel, steam is introduced to raise the temperature to 65~75℃ and stirred to promote dissolution, and the sodium silicate solution is obtained by filtering the waste residue through a plate and frame filter. S2. Preparation of dilute silicic acid: Add sodium silicate solution to deionized water to prepare a 5-10 wt% dilute sodium silicate solution, then slowly add it to the ion exchange vessel, filter it through cation exchange resin and control the pH to 2-3 to obtain dilute silicic acid; S3. Preparation of silica sol: Dilute silica acid is slowly added to the reactor, and silica sol seed mother liquor and organic base catalyst are added at the same time to adjust the pH of the reactor to 9.5~10.

5. During the feeding process, steam is introduced into the reactor to maintain 90~95℃. The reaction is stirred for 1~2 hours to obtain crude silica sol. S4. Surface modification: Add organic acid to the crude silica sol to adjust the pH to 2-4, add modifier at 50-60℃, and sonicate for 0.5-1h to obtain modified crude silica sol. S5. Complexation and impurity removal: After adding a complexing agent to the crude modified silica sol, it is passed through a modified ammonium-type resin for ammonium stabilization treatment to obtain the crude ammonium-type silica sol. S6. Filtration and Concentration: The crude ammonium silica sol is concentrated by ultrafiltration to filter the wastewater and obtain a high-concentration silica sol product. The regeneration of the cation exchange resin in S2 includes the following steps: S11. Rinse the cation exchange resin with deionized water to remove sodium silicate solution. Prepare 3-5 wt% hydrochloric acid. Take 2-2.5 times the mass of the cation exchange resin and slowly add the hydrochloric acid to the cation exchange resin. The addition should be completed within 40-60 minutes. S12. Rinse the cation exchange resin with deionized water until the pH of the filtrate is 7. The regeneration of the cation exchange resin is complete. The preparation method of the silica sol seed mother liquor in S3 includes the following steps: S21. Take 5-10 wt% of the total mass of dilute silicate obtained in step S2, add the dilute sodium silicate solution prepared in step S2 to adjust the pH to 9.5-10.5, and obtain a mixed solution. S22. Maintain the temperature of the mixture at 65~75℃ and generate seed crystals with ultrasonic assistance for 3~6 minutes to obtain silica sol seed mother liquor. The preparation method of the modified ammonium resin in S5 includes the following steps: S31. Soak the 732 type cation resin in a saturated sodium chloride solution for 24-48 hours to remove residual impurities, then pass anhydrous ethanol through until the leachate is neutral, prepare an ethanol-ammonia solution, and soak the 732 type cation resin in the ethanol-ammonia solution for 1-2 hours. S32. Add maleic anhydride crosslinking agent, triethylenetetramine ethanol solution and nano silica to 732 type cationic resin, stir at 40~60℃ for 24~36h, filter and dry to obtain modified ammonium type resin. The ethanol-ammonia solution in S31 contains 30-40 wt% ethanol and has a pH of 12-13; the triethylenetetramine ethanol solution in S32 contains 60-70 wt% triethylenetetramine and has nano-silica particles with a diameter of 15-25 nm. The amounts of each substance are 5-10 g of 732 type cation exchange resin, 0.5-1 g of maleic anhydride crosslinking agent, 30-60 ml of triethylenetetramine ethanol solution, and 10-30 mg of nano-silica.

2. The method for preparing silica sol using ion exchange according to claim 1, characterized in that, In S1, the mass ratio of deionized water to solid sodium silicate is 100:10~20, the steam flow rate is 4~6m / s, and the pore size of the plate and frame filter is 1~10μm; in S2, the container holding the dilute sodium silicate solution is cleaned with deionized water, and the cleaned liquid is added to the dissolving vessel in S1 for recycling.

3. The method for preparing silica sol using ion exchange according to claim 1, characterized in that, The organic base catalyst in S3 is one or more combinations of trimethylphosphine, guanidinomethylphosphonic acid and N-methylimidazole, and the silica sol content in the crude silica sol is 4~9wt%.

4. The method for preparing silica sol using ion exchange according to claim 1, characterized in that, The organic acid in S4 is one or more combinations of glacial acetic acid, tartaric acid and citric acid, and the modifier is one or more combinations of dodecyltrimethoxysilane, hexadecyltrimethoxysilane and methyltrimethoxysilane. The ratio of the amount of modifier added to the content of silica sol in the crude silica sol is 0.7~1:

1.

5. The method for preparing silica sol using ion exchange according to claim 1, characterized in that, The complexing agent in S5 is one or more combinations of ethylenediaminetetraacetic acid, triethanolamine and 8-hydroxyquinoline, and the ratio of the amount of complexing agent added to the silica sol content in the crude silica sol is 0.1~0.3:1.

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