Method for preparing silica sol by using ion exchange method

Abstract

The invention belongs to the technical field of silica sol preparation, and particularly relates to a method for preparing silica sol by using an ion exchange method. In the prior art, preparation and impurity removal processes are optimized, the growth time of the silica sol is shortened by ultrasonic-assisted preparation of the silica sol seed crystal mother liquor, and the organic base catalyst maintains the growth pH of the silica sol and metal ions in the complexing solution, so that impurity mixing is reduced when the silica sol grows; after dodecyltrimethoxysilane, hexadecyltrimethoxysilane and methyltrimethoxysilane are introduced as hydrophobic groups for surface modification, impurity metal ions are filtered through a complexing agent and ammonium type resin, and the ammonium type resin is modified by a triethylene tetramine ethanol solution, so that selective adsorption of the resin to the metal ions is enhanced; the maleic anhydride cross-linking agent and the nano silicon dioxide modified ammonium type resin prolong the service life of the ammonium type resin, and the prepared silica sol is high in purity, good in mechanical property and dispersity and excellent in hydrophobic property.

Description

Technical Field

[0001] The invention belongs to the technical field of silica sol preparation, and in particular relates to a method for preparing silica sol by using an ion exchange method. Background Art

[0002] Silica sol is a colloidal solution formed by amorphous nano-sized silicon dioxide particles in water or solvent. It is non-toxic and odorless, has high adsorption performance, large specific surface area and insulation properties, and is widely used in polishing, papermaking, coatings, fabrics and catalysts. The ion exchange method is the most mature preparation method for silica sol. The general steps include using water glass as raw material, preparing silica sol through ion exchange reaction, seed preparation, particle growth reaction, concentration step, purification step and other processes.

[0003] The Chinese invention patent with publication number CN105329906B discloses a method for preparing silica sol for acrylonitrile catalyst: adding sulfuric acid aqueous solution to an industrial sodium silicate aqueous solution with a silicon dioxide content of 3-5 wt% to a pH of 9.0-9.5, heating to 90-95°C and keeping warm for 1-2 hours to form a silica sol base solution; adding water to industrial sodium silicate with a modulus of 3.0-3.3 to prepare a 3-5 wt% silicon dioxide aqueous solution, suspending a cation exchange resin with deionized water, then adding water glass and controlling the outlet pH after ion exchange to 2-3 to obtain silicic acid, and separating the silicic acid into a silica sol base solution; 100-200ml / min is added to the prepared silica sol base liquid, and the pH is maintained at 9-9.5. After keeping the temperature at 90-95℃ for 1-2 hours, it is cooled to room temperature; the product is ion exchanged with a strong acidic cation exchange resin regenerated with hydrochloric acid, while maintaining the pH at 1-2. After the exchange, 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 obtain silica sol. The average particle size of the prepared silica sol is 20-25nm, the sodium ion content is less than 0.05%, the concentration is 40-50%, and the viscosity is less than 20cps. However, the prior art has the technical problems that the silica sol prepared by the ion exchange method has more impurities and the dispersion stability is not enough. Summary of the invention

[0004] The object of the present invention is to provide a method for preparing silica sol by ion exchange method, so as to solve the technical problems that the silica sol prepared by ion exchange method in the prior art has more impurities and insufficient dispersion stability.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] A method for preparing silica sol using an ion exchange method comprises the following steps:

[0007] S1. Pretreatment: deionized water and solid sodium silicate are added into a dissolving kettle, steam is introduced to raise the temperature to 65-75° C. and stirred to promote dissolution, and the waste residue is filtered through a plate and frame to obtain a sodium silicate solution;

[0008] S2, preparation of dilute silicic acid: adding deionized water to a sodium silicate solution to prepare a 5-10 wt% dilute sodium silicate solution, and then slowly adding the solution to an exchange kettle, and filtering the solution through a cation exchange resin and controlling the pH to 2-3 to obtain dilute silicic acid;

[0009] S3, preparation of silica sol: slowly add dilute silicic acid into the reactor, and add silica sol seed mother liquor and organic base catalyst to adjust the pH in the reactor to 9.5-10.5. During the addition process, steam is introduced into the reactor to maintain 90-95°C, and the reaction is stirred for 1-2h to obtain a crude silica sol;

[0010] S4, surface modification: adding organic acid to the crude silica sol to adjust the pH to 2-4, adding a modifier at 50-60°C for modification, and ultrasonicating for 0.5-1h to obtain a modified crude silica sol;

[0011] S5, complexation and impurity removal: adding a complexing agent to the crude modified silica sol, and then introducing a modified ammonium type resin for ammonium stabilization treatment to obtain a crude ammonium type silica sol;

[0012] S6. Filtration and concentration: The crude ammonium silica sol is concentrated by ultrafiltration to filter the wastewater to obtain a high-concentration silica sol product.

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

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

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

[0016] S11, eluting the cation exchange resin with deionized water to remove the sodium silicate solution, preparing 3-5wt% hydrochloric acid, taking 2-2.5 times the mass of the cation exchange resin and slowly adding the hydrochloric acid to the cation exchange resin, and adding the hydrochloric acid within 40-60 minutes;

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

[0018] Preferably, the method for preparing the silica sol seed crystal mother solution in S3 comprises the following steps:

[0019] S21, taking 5-10wt% of the total mass of the dilute silicic acid prepared in step S2, adding 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, maintaining the temperature of the mixed solution at 65-75°C, generating seed crystals with the aid of ultrasound for 3-6 minutes, and obtaining a silica sol mother solution.

[0021] Preferably, the organic base catalyst in S3 is one or more combinations of trimethylphosphine, guanidinomethylphosphonic acid and N-methylimidazole.

[0022] Preferably, the silica sol content in the crude silica sol in S3 is 4-9wt%.

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

[0024] Preferably, the modifier in S4 is one or more combinations of dodecyltrimethoxysilane, hexadecyltrimethoxysilane and methyltrimethoxysilane, and the ratio of the amount of the modifier added to the content of silica sol in the crude silica sol is 0.7 to 1:1.

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

[0026] Preferably, the method for preparing the modified ammonium type resin in S5 comprises the following steps:

[0027] S31, soaking the 732 type cationic resin in a saturated sodium chloride solution for 24 to 48 hours to remove residual impurities, passing anhydrous ethanol until the leaching solution is neutral, preparing an ethanol ammonia solution, and soaking the 732 type cationic resin in the ethanol ammonia solution for 1 to 2 hours;

[0028] S32, add maleic anhydride crosslinking agent, triethylenetetramine ethanol solution and nano-silica to 732 type cationic resin, stir at 40-60°C for 24-36 hours, filter and dry to obtain modified ammonium type resin.

[0029] Preferably, the ethanol content in the ethanolammonia aqueous solution in S31 is 30-40 wt % and the pH is 12-13.

[0030] Preferably, the triethylenetetramine content in the triethylenetetramine ethanol solution in S32 is 60-70 wt%.

[0031] Preferably, the particle size of the nano-silicon dioxide in S32 is 15 to 25 nm.

[0032] Preferably, the amounts of the substances in S32 are 5-10 g of 732 type cationic resin, 0.5-1 g of maleic anhydride crosslinking agent, 30-60 ml of triethylenetetramine ethanol solution and 10-30 mg of nano-silicon dioxide.

[0033] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0034] 1. The present invention optimizes the preparation and impurity removal processes in the prior art, uses ultrasound to assist in the preparation of silica sol seed mother liquor to shorten the growth time of silica sol, uses an organic base catalyst to maintain the pH of silica sol growth and the metal ions in the complexing solution to reduce the mixing of impurities during the growth of silica sol, introduces hydrophobic groups to modify the surface, and filters the impure metal ions through a complexing agent and an ammonium type resin. The prepared silica sol has high purity, good mechanical properties and dispersibility, and excellent hydrophobic properties.

[0035] 2. The present invention introduces ultrasound-assisted preparation of silica sol mother liquor, which greatly shortens the preparation time of silica sol, and the nano-silicon dioxide seeds formed in the preparation of silica sol mother liquor have high activity, which improves the dispersibility of silica sol in subsequent processes and has a higher specific surface area.

[0036] 3. The present invention introduces hydrophobic groups in the surface modification process, and the grafted hydrophobic groups form a protective siloxane film on the surface of the silica sol, which can effectively improve the stability of the silica sol in water, avoid the irreversible gelation of the silica sol, make the silica sol easy to form a spherical particle with a larger particle size, and the hydrophobic groups introduced by the surface modification greatly improve the hydrophobic properties and hardness of the silica sol.

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

[0038] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0039] Figure 1 The process flow chart of the present invention shows a method for preparing silica sol using an ion exchange method. DETAILED DESCRIPTION

[0040] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0041] Embodiment 1: A method for preparing silica sol by ion exchange method in this embodiment comprises the following steps:

[0042] S1, pretreatment: 100 parts of deionized water and 20 parts of solid sodium silicate are added to a dissolution kettle, 4m / s steam is introduced to raise the temperature to 70°C and stirred to promote dissolution, and the waste residue is filtered through a plate and frame with a pore size of 5μm to obtain a sodium silicate solution;

[0043] S2, preparation of dilute silicic acid: sodium silicate solution is added to deionized water to prepare a 10 wt% dilute sodium silicate solution, which is then slowly added to an exchange kettle, and the solution is exchanged and filtered through a 732 type cation exchange resin and the pH is controlled to be 2.5 to obtain dilute silicic acid;

[0044] S3, silica sol preparation: dilute silicic acid was slowly added into the reactor, and silica sol seed mother solution and trimethylphosphine were added to adjust the pH in the reactor to 10. During the addition process, steam was introduced into the reactor to maintain 95°C, and the reaction was stirred for 1 hour to obtain a silica sol crude product with a silica sol content of 9wt%;

[0045] S4, surface modification: 100 g of crude silica sol was added with glacial acetic acid to adjust the pH to 4, 8 g of methyltrimethoxysilane was added at 60°C for modification, and ultrasonic treatment was performed for 1 h to obtain a modified crude silica sol;

[0046] S5, complexation and impurity removal: add 1.8g of ethylenediaminetetraacetic acid and triethanolamine in a mass ratio of 1:1 to the modified silica sol crude product, and then pass the modified ammonium type resin into the modified silica sol crude product for ammonium stabilization treatment to obtain an ammonium type silica sol crude product;

[0047] S6. Filtration and concentration: The crude ammonium silica sol is concentrated by ultrafiltration to filter the wastewater to obtain a high-concentration silica sol product.

[0048] The method for preparing the silica sol seed mother solution in S3 comprises the following steps:

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

[0050] S22, maintaining the temperature of the mixed solution at 70°C, generating seed crystals with ultrasound assistance for 6 minutes, and obtaining a silica sol mother solution.

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

[0052] S31, soaking the 732 type cationic resin in a saturated sodium chloride solution for 48 hours to remove residual impurities, passing anhydrous ethanol until the leaching solution is neutral, preparing an ethanol ammonia aqueous solution with an ethanol content of 30wt% and a pH of 13, and soaking the 732 type cationic resin in the ethanol ammonia aqueous solution for 1 to 2 hours;

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

[0054] Embodiment 2, a method for preparing silica sol by ion exchange method of this embodiment comprises the following steps:

[0055] S1, pretreatment: 100 parts of deionized water and 30 parts of solid sodium silicate are added to a dissolution kettle, 6m / s steam is introduced to raise the temperature to 75°C and stirred to promote dissolution, and the waste residue is filtered through a plate and frame with a pore size of 10 μm to obtain a sodium silicate solution;

[0056] S2, preparation of dilute silicic acid: sodium silicate solution is added to deionized water to prepare a 10 wt% dilute sodium silicate solution, which is then slowly added to an exchange kettle, and the solution is exchanged and filtered through a 732 type cation exchange resin and the pH is controlled to be 2 to obtain dilute silicic acid;

[0057] S3, silica sol preparation: dilute silicic acid was slowly added into the reactor, and silica sol seed mother solution and N-methylimidazole were added to adjust the pH in the reactor to 9.5. During the addition process, steam was introduced into the reactor to maintain 90°C, and the reaction was stirred for 2h to obtain a silica sol crude product with a silica sol content of 8wt%;

[0058] S4, surface modification: 100 g of crude silica sol was added with glacial acetic acid and citric acid to adjust the pH to 3, the mass ratio of glacial acetic acid to citric acid was 1:1, 8 g of dodecyltrimethoxysilane was added at 50°C for modification, and ultrasonic treatment was performed for 1 h to obtain a modified crude silica sol;

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

[0060] S6. Filtration and concentration: The crude ammonium silica sol is concentrated by ultrafiltration to filter the wastewater to obtain a high-concentration silica sol product.

[0061] The method for preparing the silica sol seed mother solution in S3 comprises the following steps:

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

[0063] S22, maintaining the temperature of the mixed solution at 70°C, generating seed crystals with ultrasound assistance for 4 minutes, and obtaining a silica sol mother solution.

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

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

[0066] S32, add 0.5 g of maleic anhydride crosslinking agent, 30 ml of triethylenetetramine ethanol solution with a triethylenetetramine content of 70 wt% and 10 mg of nano-silica with a particle size of 15 nm to 5 g of 732 type cationic resin, stir at 60°C for 24 hours, filter and dry to obtain modified ammonium type resin.

[0067] Embodiment 3, a method for preparing silica sol by ion exchange method of this embodiment comprises the following steps:

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

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

[0070] S3, preparation of silica sol: dilute silicic acid was slowly added into the reactor, and silica sol seed mother solution and guanidinomethylphosphonic acid were added to adjust the pH value in the reactor to 9.5. During the addition process, steam was introduced into the reactor to maintain 90° C., and the reaction was stirred for 1 hour to obtain a crude silica sol with a silica sol content of 7 wt%;

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

[0072] S5, complexation and impurity removal: add 2g of ethylenediaminetetraacetic acid, triethanolamine and 8-hydroxyquinoline in a mass ratio of 1:2:1 to the crude modified silica sol, and then pass modified ammonium type resin into it for ammonium stabilization treatment to obtain the crude ammonium type silica sol;

[0073] S6. Filtration and concentration: The crude ammonium silica sol is concentrated by ultrafiltration to filter the wastewater to obtain a high-concentration silica sol product.

[0074] The method for preparing the silica sol seed mother solution in S3 comprises the following steps:

[0075] S21, taking 9wt% of the total mass of the dilute silicic acid prepared in step S2, adding the dilute sodium silicate solution prepared in step S2 to adjust the pH to 10.5, to obtain a mixed solution;

[0076] S22, maintaining the temperature of the mixed solution at 70°C, generating seed crystals with ultrasound assistance for 5 minutes, and obtaining a silica sol mother solution.

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

[0078] S31, soaking the 732 type cationic resin in a saturated sodium chloride solution for 24 hours to remove residual impurities, passing anhydrous ethanol until the leaching solution is neutral, preparing an ethanol ammonia aqueous solution with an ethanol content of 30wt% and a pH of 12, and soaking the 732 type cationic resin in the ethanol ammonia aqueous solution for 1 hour;

[0079] S32, add 0.5 g of maleic anhydride crosslinking agent, 30 ml of triethylenetetramine ethanol solution with a triethylenetetramine content of 70 wt% and 25 mg of nano-silica with a particle size of 20 nm to 10 g of 732 type cationic resin, stir at 50°C for 36 hours, filter and dry to obtain modified ammonium type resin.

[0080] Embodiment 4, a method for preparing silica sol by ion exchange method of this embodiment comprises the following steps:

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

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

[0083] S3, silica sol preparation: dilute silicic acid was slowly added into the reactor, and silica sol seed mother solution and guanidinomethylphosphonic acid were added to adjust the pH value in the reactor to 10.5. During the addition process, steam was introduced into the reactor to maintain 95°C, and the reaction was stirred for 1 hour to obtain a silica sol crude product with a silica sol content of 9wt%;

[0084] S4, surface modification: 100 g of crude silica sol was added with tartaric acid to adjust the pH to 3.3, 8 g of methyltrimethoxysilane was added at 60°C for modification, and ultrasonic treatment was performed for 1 h to obtain a modified crude silica sol;

[0085] S5, complexation and impurity removal: add 1.8 g of ethylenediaminetetraacetic acid to the modified silica sol crude product, and then introduce modified ammonium type resin to perform ammonium stabilization treatment to obtain ammonium type silica sol crude product;

[0086] S6. Filtration and concentration: The crude ammonium silica sol is concentrated by ultrafiltration to filter the wastewater to obtain a high-concentration silica sol product.

[0087] The method for preparing the silica sol seed mother solution in S3 comprises the following steps:

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

[0089] S22, maintaining the temperature of the mixed solution at 70°C, generating seed crystals with ultrasound assistance for 5 minutes, and obtaining a silica sol mother solution.

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

[0091] S31, soaking the 732 type cationic resin in a saturated sodium chloride solution for 24 hours to remove residual impurities, passing anhydrous ethanol until the leaching solution is neutral, preparing an ethanol ammonia aqueous solution with an ethanol content of 30wt% and a pH of 13, and soaking the 732 type cationic resin in the ethanol ammonia aqueous solution for 1 hour;

[0092] S32, add 1 g of maleic anhydride crosslinking agent, 60 ml of triethylenetetramine ethanol solution with a triethylenetetramine content of 60 wt% and 25 mg of nano-silica with a particle size of 25 nm to 10 g of 732 type cationic resin, stir at 40°C for 36 hours, filter and dry to obtain modified ammonium type resin.

[0093] Embodiment 5, a method for preparing silica sol by ion exchange method of this embodiment comprises the following steps:

[0094] S1, pretreatment: 100 parts of deionized water and 20 parts of solid sodium silicate are added to a dissolution kettle, steam is introduced to raise the temperature to 65°C and stirred to promote dissolution, and the waste residue is filtered through a plate and frame with a pore size of 5 μm to obtain a sodium silicate solution;

[0095] S2, preparation of dilute silicic acid: sodium silicate solution is added to deionized water to prepare a 5wt% dilute sodium silicate solution, and then slowly added to an exchange kettle, and filtered through a 732 type cation exchange resin and the pH is controlled to be 2.5 to obtain dilute silicic acid;

[0096] S3, silica sol preparation: dilute silicic acid was slowly added into the reactor, and silica sol seed mother solution and trimethylphosphine were added to adjust the pH in the reactor to 9.5. During the addition process, steam was introduced into the reactor to maintain 95°C, and the reaction was stirred for 1 hour to obtain a silica sol crude product with a silica sol content of 4wt%;

[0097] S4, surface modification: 100 g of crude silica sol was added with citric acid to adjust the pH to 2.4, 4 g of hexadecyltrimethoxysilane was added at 60°C for modification, and ultrasonic treatment was performed for 1 h to obtain a modified crude silica sol;

[0098] S5, complexation and impurity removal: add 1.2 g of 8-hydroxyquinoline to the modified silica sol crude product, and then pass it into a modified ammonium type resin for ammonium stabilization treatment to obtain an ammonium type silica sol crude product;

[0099] S6. Filtration and concentration: The crude ammonium silica sol is concentrated by ultrafiltration to filter the wastewater to obtain a high-concentration silica sol product.

[0100] The method for preparing the silica sol seed mother solution in S3 comprises the following steps:

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

[0102] S22, maintaining the temperature of the mixed solution at 65°C, generating seed crystals with ultrasound assistance for 5 minutes, and obtaining a silica sol mother solution.

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

[0104] S31, soaking the 732 type cationic resin in a saturated sodium chloride solution for 24 hours to remove residual impurities, passing anhydrous ethanol until the leaching solution is neutral, preparing an ethanol ammonia aqueous solution with an ethanol content of 40wt% and a pH of 13, and soaking the 732 type cationic resin in the ethanol ammonia aqueous solution for 2 hours;

[0105] S32, add 1 g of maleic anhydride crosslinking agent, 50 ml of 60 wt% triethylenetetramine ethanol solution and 30 mg of nano-silica with a particle size of 15 nm to 10 g of 732 type cationic resin, stir at 40°C for 24 h, filter and dry to obtain modified ammonium type resin.

[0106] Comparative Example 1: This comparative example differs from Example 1 in that no silica sol seed solution is prepared, and dilute silicic acid is used directly in the reaction vessel to grow silica sol.

[0107] Comparative Example 2: This comparative example differs from Example 1 in that the organic base catalyst is replaced with a 10 wt % sodium hydroxide solution.

[0108] Comparative Example 3: This comparative example differs from Example 1 in that the organic acid in the surface modification step is changed to 12.5 wt % dilute hydrochloric acid.

[0109] Comparative Example 4: This comparative example differs from Example 1 in that no complexing agent is added.

[0110] Performance Testing

[0111] Test Example 1

[0112] The silica sols prepared in the examples and comparative examples were tested for silica content, viscosity, average particle size and metal ion content using commercially available testing equipment. The test results are shown in Table 1:

[0113] Table 1

[0114]

[0115]

[0116] As shown in the data of Table 1, the silica sol silica concentration prepared in Examples 1 to 5 is between 39 and 42.7 wt% and the metal ion content is less than 20 ppm, indicating that the silica sol silica prepared in the present invention has a high content of effective ingredients and a high purity; the viscosity is between 21.2 and 27.0 mPa / S and the average particle size is between 54 and 65 nm, indicating that the silica sol prepared in the present invention has good stability and high dispersibility. Comparative Example 1 does not prepare silica sol seed mother liquor, and dilute silicic acid is directly used in the reactor to grow silica sol, resulting in a long growth time of silica sol, a decrease in the dispersibility of silica sol, and some silica sols adhere to form sticky glue, resulting in a decrease in the content of effective ingredients of silica; Comparative Example 4 does not add a complexing agent to complex impurities and directly removes impurities through a modified ammonium type resin, resulting in incomplete filtration of metal ions, and the metal ion content is 65 ppm, which is much larger than the metal ion content of each embodiment.

[0117] Test Example 2

[0118] Preparation of silica sol coating: soak a glass slide in the silica sol prepared in each example and comparative example for 3 minutes, slowly take it out and put it in an oven to dry at 60° C. to obtain a glass slide with a silica sol coating attached.

[0119] The glass slides attached with the silica sol coatings prepared in the embodiments and comparative examples were tested for transmittance, hardness, adhesion and water droplet rolling angle by commercially available testing equipment. The test results are shown in Table 2:

[0120] Table 2

[0121]

[0122] It can be seen from the data in Table 2 that the light transmittance of the silica sol coating prepared with the silica sol prepared in Examples 1 to 5 as raw materials is between 81.9 and 85.1%, indicating that the silica sol prepared in the present invention has good dispersibility and uniform particle size, and the prepared silica sol coating is smooth and light-transmitting; the hardness of the silica sol coating is 7H and the adhesion is level 1, indicating that the silica sol prepared in the present invention has high hardness and good adhesion performance, and the water droplet rolling angle is between 26.5 and 28.3°, indicating that the hydrophobic performance of the silica sol prepared in the present invention is excellent. In the surface modification process of Comparative Example 3, the organic acid is changed to 12.5wt% dilute hydrochloric acid, resulting in the adsorption of some metal impurities on the surface of the silica sol, and the surface of the silica sol forms a protective siloxane film for you, resulting in the hardness and adhesion of the silica sol. The water droplet rolling angle increases, that is, the hydrophobic performance decreases; the metal ion residue in Comparative Example 4 is relatively high, which reduces the smoothness of its silica sol coating and causes its light transmittance to decrease.

[0123] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

[0124] The preferred embodiments of the present invention disclosed above are only used to help explain the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to only specific implementation methods. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for preparing silica sol using an ion exchange method, characterized in that: The steps include: S1. Pretreatment: deionized water and solid sodium silicate are added into a dissolving kettle, steam is introduced to raise the temperature to 65-75° C. and stirred to promote dissolution, and the waste residue is filtered through a plate and frame to obtain a sodium silicate solution; S2, preparation of dilute silicic acid: adding deionized water to a sodium silicate solution to prepare a 5-10 wt% dilute sodium silicate solution, and then slowly adding the solution to an exchange kettle, and filtering the solution through a cation exchange resin and controlling the pH to 2-3 to obtain dilute silicic acid; S3, preparation of silica sol: slowly add dilute silicic acid into the reactor, and add silica sol seed mother liquor and organic base catalyst to adjust the pH in the reactor to 9.5-10.

5. During the addition process, steam is introduced into the reactor to maintain 90-95°C, and the reaction is stirred for 1-2h to obtain a crude silica sol; S4, surface modification: adding organic acid to the crude silica sol to adjust the pH to 2-4, adding a modifier at 50-60°C for modification, and ultrasonicating for 0.5-1h to obtain a modified crude silica sol; S5, complexation and impurity removal: adding a complexing agent to the crude modified silica sol, and then introducing a modified ammonium type resin for ammonium stabilization treatment to obtain a crude ammonium type silica sol; S6. Filtration and concentration: The crude ammonium silica sol is concentrated by ultrafiltration to filter the wastewater to obtain a high-concentration silica sol product.

2. The method for preparing silica sol by ion exchange method according to claim 1, characterized in that: The mass ratio of deionized water to solid sodium silicate in S1 is 100:10-20, the steam flow rate is 4-6 m / s, and the plate and frame filter aperture is 1-10 μm; the container containing the dilute sodium silicate solution in S2 is washed with deionized water and then added to the S1 dissolution kettle for recycling.

3. The method for preparing silica sol by ion exchange method according to claim 1, characterized in that: The regeneration of the cation exchange resin in S2 comprises the following steps: S11, eluting the cation exchange resin with deionized water to remove the sodium silicate solution, preparing 3-5wt% hydrochloric acid, taking 2-2.5 times the mass of the cation exchange resin and slowly adding the hydrochloric acid to the cation exchange resin, and adding the hydrochloric acid within 40-60 minutes; S12, eluting the cation exchange resin with deionized water until the pH of the filtrate is 7, and the regeneration of the cation exchange resin is completed.

4. The method for preparing silica sol by ion exchange method according to claim 1, characterized in that: The method for preparing the silica sol seed crystal mother solution in S3 comprises the following steps: S21, taking 5-10wt% of the total mass of the dilute silicic acid prepared in step S2, adding the dilute sodium silicate solution prepared in step S2 to adjust the pH to 9.5-10.5, to obtain a mixed solution; S22, maintaining the temperature of the mixed solution at 65-75°C, generating seed crystals with the aid of ultrasound for 3-6 minutes, and obtaining a silica sol mother solution.

5. The method for preparing silica sol by ion exchange method 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 content of silica sol in the crude silica sol is 4-9wt%.

6. The method for preparing silica sol by ion exchange method 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, the modifier is one or more combinations of dodecyltrimethoxysilane, hexadecyltrimethoxysilane and methyltrimethoxysilane, and the ratio of the amount of the modifier added to the silica sol content in the crude silica sol is 0.7 to 1:

1.

7. The method for preparing silica sol by ion exchange method 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 added amount of the complexing agent to the content of silica sol in the crude silica sol is 0.1-0.3:

1.

8. The method for preparing silica sol by ion exchange method according to claim 1, characterized in that: The method for preparing the modified ammonium type resin in S5 comprises the following steps: S31, soaking the 732 type cationic resin in a saturated sodium chloride solution for 24 to 48 hours to remove residual impurities, passing anhydrous ethanol until the leaching solution is neutral, preparing an ethanol ammonia solution, and soaking the 732 type cationic resin in the ethanol ammonia solution for 1 to 2 hours; S32, add maleic anhydride crosslinking agent, triethylenetetramine ethanol solution and nano-silica to 732 type cationic resin, stir at 40-60°C for 24-36 hours, filter and dry to obtain modified ammonium type resin.

9. The method for preparing silica sol by ion exchange method according to claim 8, characterized in that: The ethanol content in the ethanolammonia aqueous solution in the S31 is 30-40wt%, and the pH is 12-13; the triethylenetetramine content in the triethylenetetramine ethanol solution in the S32 is 60-70wt%, and the nano-silicon dioxide particle size is 15-25nm. The amounts of each substance used are 5-10g of 732 type cationic resin, 0.5-1g of maleic anhydride crosslinking agent, 30-60ml of triethylenetetramine ethanol solution and 10-30mg of nano-silicon dioxide.

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