Preparation process of special coating small particle size high purity and high stability silica sol
By employing a three-stage tandem ion exchange process of "cation-anion-cation" and precisely controlling reaction conditions, a silica sol with small particle size, high purity, and high stability was prepared, solving the problems of inhomogeneity and poor stability of silica sol in existing technologies. This method is suitable for the field of high-performance special coatings.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- 浙江洁华新材料股份有限公司
- Filing Date
- 2026-01-23
- Publication Date
- 2026-05-29
Smart Images
Figure SMS_1
Abstract
Description
Technical Field
[0001] This invention belongs to the field of nanomaterial preparation technology, specifically relating to a preparation process for small-particle-size, high-purity, and highly stable silica sol for special coatings. Background Technology
[0002] Silica sol is an odorless, non-toxic nanomaterial with high specific surface area and high dispersibility. It is a dispersion of nano-sized silica particles in water or other solvents and is widely used in coatings, catalysts, electronic materials, precision casting, and other fields. Silica sol is an irreversible colloid with a large surface energy, exhibiting a tendency to spontaneously decrease its surface energy. It easily aggregates spontaneously into large particles or gels. Many factors affect the stability of silica sol, such as temperature, pH, and concentration. Therefore, optimizing the preparation process of small-particle-size, high-purity, and highly stable silica sol is crucial. Currently, the main industrial methods for preparing silica sol include ion exchange, elemental silica dissolution, and silane hydrolysis. Among these, ion exchange is the most widely used due to its relatively simple process and low cost. Traditional ion exchange uses industrial water glass (Na₂O·nSiO₂) as a raw material. Water glass contains a large amount of Na₂O. + K + Ca 2+ Fe 3+ Cl - Plasma impurities. While conventional ion exchange can partially remove these impurities, it is difficult to completely eliminate them, especially trace amounts of multivalent metal ions. Traditional ion exchange methods for preparing silica sol often suffer from inaccurate process control and poor purification results, leading to silica sols with uneven particle size distribution, low purity, and poor stability. These defects significantly limit the application of silica sols in demanding special coating fields, such as anti-reflective coatings for displays, display panels, high-precision optical lens coatings, and precision casting.
[0003] While some existing technologies report on the preparation of silica sol via ion exchange, these techniques often fail to precisely optimize key process parameters or establish a complete multi-stage purification system. This results in products that cannot meet the high-precision requirements of special coatings in terms of particle size uniformity, purity, and dispersion stability. Therefore, developing a silica sol preparation process that is simple and controllable, has low production costs, produces high-purity and stable products suitable for high-performance special coatings, has significant practical application value and market prospects. Summary of the Invention
[0004] To address the problems existing in the prior art, the present invention aims to provide a preparation process for small-particle-size, high-purity, and highly stable silica sol for special coatings. By optimizing the purification and reaction process, a synergistic improvement in particle size, purity, and stability of the silica sol is achieved. This process enables the preparation of silica sols with small particle size, high specific surface area, high purity, and high stability, meeting the requirements of high-performance special coating fields. For example, when used as a surface polishing agent, a nanoscale surface treatment process with stringent surface quality requirements can effectively improve the surface finish and precision of optical lenses and display panels.
[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A process for preparing small-particle-size, high-purity, and highly stable silica sol for special coatings specifically includes the following steps: A water glass of a certain modulus and mass concentration is sequentially passed through a cation exchange column, an anion exchange column, and another cation exchange column at a certain flow rate to obtain an initial silicic acid solution. An alkaline catalyst is added to the initial silicic acid solution, and the reaction is carried out for a certain time at a specific temperature and stirring rate to form an initial silica sol. The initial silica sol is then concentrated to an aqueous silica sol with a silica mass fraction of 20-40%. The concentrated silica sol is filtered to remove any large particles that may be present, thus obtaining the target silica sol. The cation exchange column is filled with cation exchange resin, and the anion exchange column is filled with anion exchange resin.
[0006] As a further preferred embodiment of the present invention, the water glass has a modulus of 2.2-3.5 (preferably 3.2) and a mass concentration of 1-10% (e.g., including but not limited to 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, preferably 5%).
[0007] As a further preferred embodiment of the present invention, the cation exchange resin is a 732 type cation exchange resin or a D001 type cation exchange resin, and the anion exchange resin is a 717 type anion exchange resin or a D201 type anion exchange resin (preferably a 732 type cation exchange resin and a 717 type anion exchange resin).
[0008] As a further preferred embodiment of the present invention, the flux through the cation exchange resin and anion exchange resin is 0.5-2.5 mL / (cm²). 2 (·min), preferably 1.0 mL / (cm) 2 ·min).
[0009] As a further preferred embodiment of the present invention, the alkaline catalyst is one or more of potassium hydroxide, sodium hydroxide, ammonia, or an organic base (preferably ammonia).
[0010] As a further preferred embodiment of the present invention, the heating and stirring reaction temperature is 60-95℃ (e.g., including but not limited to 60℃, 65℃, 70℃, 75℃, 80℃, 85℃, 90℃, 95℃, preferably 80℃), the stirring rate is 100-400r / min (e.g., including but not limited to 100r / min, 200r / min, 300r / min, 400r / min, preferably 100r / min), and the reaction time is 2-10h (e.g., including but not limited to 2h, 4h, 6h, 8h, 10h, preferably 4h).
[0011] As a further preferred embodiment of the present invention, the concentration is vacuum distillation concentration or ultrafiltration concentration (preferably vacuum distillation concentration).
[0012] As a further preferred embodiment of the present invention, the filtration adopts a microporous membrane or ultrafiltration, and the pore size of the membrane is 0.1-2μm (preferably 1μm).
[0013] The present invention particularly recommends the following preparation process for the small-particle-size, high-purity, and highly stable silica sol used for special coatings: Water glass with a modulus of 3.2 and a mass concentration of 5% is added at a concentration of 1.0 mL / (cm³). 2 An initial silica solution was obtained by passing the 732-type cation exchange resin, the 717-type anion exchange resin, and the 732-type cation exchange resin. An ammonia solution was added to the initial silica solution, and the mixture was heated and stirred at 80°C and 100 r / min for 4 hours to form an initial silica sol. The solution was then concentrated to 20-40% aqueous silica sol by ultrafiltration. The concentrated silica sol was then filtered through a 1 μm pore size filter membrane to remove any large particles that may be present.
[0014] This invention creatively employs a three-stage tandem ion exchange process of "cation-anion-cation" for deep impurity removal. The first-stage cation exchange column removes most of the cations (such as Na+) from the water glass. + The second-stage anion exchange column, while removing anions, introduces OH-. - , with H in the solution + Neutralization produces water, bringing the effluent close to neutral. However, this may cause the breakage of functional groups on some anion exchange resin backbones, introducing trace amounts of organic amine cation impurities. The crucial third-stage cation exchange column not only removes any trace cations that may have been introduced or remain in the first two steps, but more importantly, it restores the solution pH to weakly acidic, effectively inhibiting premature polymerization of silicic acid molecules. This results in an initial silicic acid solution with extremely low metal ion content (<50 ppm) and highly homogeneous chemical state. This is fundamental to achieving high purity and high stability. Therefore, a specific three-stage tandem ion exchange process with a specific "cation-anion-cation" sequence is a crucial condition for achieving the target product characteristics.
[0015] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention prepares silica sol by ion exchange method. The three-stage series ion exchange process of "cation-anion-cation" can deeply remove various anion and cation impurities in water glass raw materials. The silica sol obtained has extremely low metal ion content and high purity, and is suitable for special coating fields with extremely high purity requirements.
[0016] (2) By precisely controlling the reaction temperature, time, and stirring rate, and combining it with a specific alkaline catalyst, uniform nucleation and controllable growth of silica particles were achieved. The resulting silica sol has a narrow particle size distribution, good stability, and does not affect purity. The alkaline environment promotes the deprotonation of silica surface particles, which carries a negative charge and forms electrostatic repulsion, thus promoting the stability of silicic acid. The precise process window (e.g., 80℃, 100r / min, 4h) ensures the balance between the nucleation rate and the growth rate, thereby obtaining silica sol with small particle size (as low as 3-10 nm) and narrow distribution.
[0017] (3) The product is concentrated to a suitable application concentration (20-40%) and then filtered with microporous filter to effectively remove any large particles or gel particles that may be generated during the concentration or storage process, thus ensuring the physical stability and reliability of the final product.
[0018] (4) The process parameter ranges for each key step are clearly defined, ensuring the repeatability of the production process and the consistency of product batches, making it suitable for large-scale industrial production.
[0019] (5) The small-particle-size high-purity and high-stability silica sol prepared is particularly suitable for special coatings, such as anti-reflective coatings for displays and optical lenses. Detailed Implementation
[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.
[0021] Example 1
[0022] A water glass solution with a modulus of 2.2 and a mass concentration of 5% was dispensed at a rate of 1.0 mL / (cm³). 2The silica solution (min) was sequentially passed through a 732-type cation exchange resin, a 717-type anion exchange resin, and a 732-type cation exchange resin to obtain 1000 mL of initial silica solution with a silica content of 3.15%. Ammonia solution was added to the initial silica solution to adjust the pH to 9-10. The mixture was heated and stirred at 80℃ and 100 r / min for 4 h to form an initial silica sol. Then, it was concentrated by vacuum distillation at 1 kPa and 60℃ to approximately 15% of the raw material volume. The concentrated silica sol was filtered through a 1 μm pore size filter to remove any large particles. The mass concentration, average particle size, and total metal ion content of the silica sol at this point are shown in Table 1.
[0023] Example 2
[0024] A water glass solution with a modulus of 3.2 and a mass concentration of 1% was dispensed at a rate of 1.0 mL / (cm³). 2 The silica solution (min) was sequentially passed through a 732-type cation exchange resin, a 717-type anion exchange resin, and a 732-type cation exchange resin to obtain 1000 mL of initial silica solution with a silica content of 0.75%. Ammonia solution was added to the initial silica solution to adjust the pH to 9-10. The mixture was heated and stirred at 80℃ and 100 r / min for 4 h to form an initial silica sol. Then, it was concentrated by vacuum distillation at 1 kPa and 60℃ to approximately 15% of the raw material volume. The concentrated silica sol was filtered through a 1 μm pore size filter to remove any large particles. The mass concentration, average particle size, and total metal ion content of the silica sol at this point are shown in Table 1.
[0025] Example 3
[0026] A water glass solution with a modulus of 3.2 and a mass concentration of 5% was dispensed at a rate of 1.0 mL / (cm³). 2 The silica solution (1000 mL) was obtained by sequentially passing it through a 732-type cation exchange resin, a 717-type anion exchange resin, and a 732-type cation exchange resin to obtain an initial silica solution with a silica content of 4.35%. Ammonia solution was added to the initial silica solution to adjust the pH to 9-10. The mixture was heated and stirred at 80℃ and 100 r / min for 4 h to form an initial silica sol. Then, it was concentrated by vacuum distillation at 1 kPa and 60℃ to approximately 15% of the raw material volume. The concentrated silica sol was filtered through a 1 μm pore size filter to remove any large particles. The mass concentration, average particle size, and total metal ion content of the silica sol at this point are shown in Table 1.
[0027] Example 4
[0028] A water glass solution with a modulus of 3.2 and a mass concentration of 5% was dispensed at a rate of 2.5 mL / (cm³). 2The silica solution (min) was sequentially passed through a 732-type cation exchange resin, a 717-type anion exchange resin, and a 732-type cation exchange resin to obtain 1000 mL of initial silica solution with a silica content of 3.15%. Ammonia solution was added to the initial silica solution to adjust the pH to 9-10. The mixture was heated and stirred at 80℃ and 100 r / min for 4 h to form an initial silica sol. Then, it was concentrated by vacuum distillation at 1 kPa and 60℃ to approximately 15% of the raw material volume. The concentrated silica sol was filtered through a 1 μm pore size filter to remove any large particles. The mass concentration, average particle size, and total metal ion content of the silica sol at this point are shown in Table 1.
[0029] Example 5
[0030] A water glass solution with a modulus of 3.2 and a mass concentration of 5% was dispensed at a rate of 1 mL / (cm³). 2 The silica solution (min) was sequentially passed through a 732-type cation exchange resin, a 717-type anion exchange resin, and a 732-type cation exchange resin to obtain 1000 mL of initial silica solution with a silica content of 4.35%. Ammonia solution was added to the initial silica solution to adjust the pH to 9-10. The mixture was heated and stirred at 95℃ and 100 r / min for 4 h to form an initial silica sol. Then, it was concentrated by vacuum distillation at 1 kPa and 60℃ to approximately 15% of the raw material volume. The concentrated silica sol was filtered through a 1 μm pore size filter to remove any large particles. The mass concentration, average particle size, and total metal ion content of the silica sol at this point are shown in Table 1.
[0031] Example 6
[0032] A water glass solution with a modulus of 3.2 and a mass concentration of 5% was dispensed at a rate of 1 mL / (cm³). 2 The silica solution (min) was sequentially passed through a 732-type cation exchange resin, a 717-type anion exchange resin, and a 732-type cation exchange resin to obtain 1000 mL of initial silica solution with a silica content of 4.35%. Ammonia solution was added to the initial silica solution to adjust the pH to 9-10. The mixture was heated and stirred at 80℃ and 300 r / min for 4 h to form an initial silica sol. Then, it was concentrated by vacuum distillation at 1 kPa and 60℃ to approximately 15% of the raw material volume. The concentrated silica sol was filtered through a 1 μm pore size filter to remove any large particles. The mass concentration, average particle size, and total metal ion content of the silica sol at this point are shown in Table 1.
[0033] Example 7
[0034] A water glass solution with a modulus of 3.2 and a mass concentration of 5% was dispensed at a rate of 1 mL / (cm³). 2The silica solution (1000 mL) was obtained by sequentially passing it through a 732-type cation exchange resin, a 717-type anion exchange resin, and a 732-type cation exchange resin to obtain an initial silica solution with a silica content of 4.35%. Ammonia solution was added to the initial silica solution to adjust the pH to 9-10. The mixture was heated and stirred at 80℃ and 100 r / min for 10 h to form an initial silica sol. Then, it was concentrated by vacuum distillation at 1 kPa and 60℃ to approximately 15% of the raw material volume. The concentrated silica sol was filtered through a 1 μm pore size filter to remove any large particles. The mass concentration, average particle size, and total metal ion content of the silica sol at this point are shown in Table 1.
[0035] Comparative Example 1: Referring to the silica sol preparation process parameters in Example 3, this comparative example is basically the same as Example 3, except that the third-stage cation exchange resin is omitted. The mass concentration, average particle size, and total metal ion content of the silica sol at this time are shown in Table 1.
[0036] Comparative Example 2: Referring to the silica sol preparation process parameters in Example 3, this comparative example is basically the same as Example 3, except that no alkaline catalyst was added. Under these conditions, the concentrated silica sol transforms into a gel.
[0037] Comparative Example 3: Referring to the silica sol preparation process parameters in Example 3, this comparative example is basically the same as Example 3, except that the concentrated silica sol was not filtered. The mass concentration, average particle size, and total metal ion content of the silica sol at this time are shown in Table 1.
[0038] Comparative Example 4: Referring to the silica sol preparation process parameters in Example 3, this comparative example is basically the same as Example 3, except that the water glass solution is passed sequentially through a 732-type cation exchange resin, a 732-type cation exchange resin, and a 717-type anion exchange resin. The mass concentration, average particle size, and total metal ion content of the silica sol at this time are shown in Table 1.
[0039] Table 1. Mass concentration, average particle size, total metal ion concentration, and stability results of each silica sol.
[0040] In Example 1, water glass with a low modulus was used, resulting in a low silica content in the initial silicic acid after ion exchange. This increased power consumption during concentration, and the small silica particle size and high surface energy led to low stability. In Example 2, the water glass was diluted to 1%, and the silica content in the initial silicic acid after ion exchange was only 0.75%, resulting in a low yield. Concentrating it to over 20% would significantly increase power consumption. The process parameters in Example 3 can produce small-particle-size, high-purity, and highly stable silica sol. In Example 4, the water glass was passed through the ion exchange resin at a relatively high flow rate, resulting in incomplete exchange of some water glass, leading to larger particle size and lower purity. In Example 5, the excessively high temperature during aging intensified the condensation of silica particles, resulting in larger particle size. In Example 6, the excessively high stirring rate during aging reduced the probability of silica particles meeting and condensing, resulting in smaller particle size and lower stability. In Example 7, the excessively long aging time increased the condensation time of silica particles, leading to larger particle size. As shown in the table above, the nano-silica sol prepared in this invention has small particle size and high purity. Furthermore, the silica sol with a particle size of 5 nm or more can be stored for more than six months under suitable storage conditions, exhibiting high stability. As a special coating material, it has broad application prospects.
[0041] The results of Comparative Example 1 (omitting the third-stage cation column) showed that the total metal ion concentration was significantly increased (>50 ppm), demonstrating the necessity and ingenuity of the three-stage design.
[0042] Comparative Example 2 (without catalyst) directly gelled, highlighting the crucial role of the catalyst in this controllable gelation process.
[0043] The average particle size of the product in Comparative Example 3 (unfiltered) was significantly increased and the particle size distribution was wide, indicating that the filtration step is crucial for maintaining small particle size and uniformity.
[0044] Comparative Example 4, which uses a sequential cation-cation-anion exchange resin, introduces trace amounts of organic amine cations, leading to a decrease in purity, thus verifying the importance of the ion exchange sequence.
[0045] In summary, the present invention features a simple process, low cost, and good repeatability. The resulting silica sol has small particle size, high purity (total metal ions <50ppm), and excellent stability (storage period >180 days), perfectly meeting the stringent requirements for raw materials in the field of special coatings. It has significant industrial application value and outstanding substantive features and remarkable progress.
[0046] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.
Claims
1. A process for preparing high-purity, high-stability silica sol with small particle size for special coatings, characterized in that, The process is as follows: Water glass of a certain modulus and mass concentration is passed sequentially through a cation exchange column, an anion exchange column, and another cation exchange column at a certain flow rate to obtain an initial silicic acid solution. An alkaline catalyst is added to the initial silicic acid solution, and the reaction is carried out for a certain time at a specific temperature and stirring rate to form an initial silica sol. The initial silica sol is then concentrated to an aqueous silica sol with a silica mass fraction of 20-40%. The concentrated silica sol is filtered to remove large particles, thus obtaining the target silica sol. The cation exchange column is filled with cation exchange resin, and the anion exchange column is filled with anion exchange resin.
2. The preparation process of a small-particle-size, high-purity, and highly stable silica sol for special coatings according to claim 1, characterized in that, The water glass has a modulus of 2.2-3.5 and a mass concentration of 1-10%.
3. The preparation process of a small-particle-size, high-purity, and highly stable silica sol for special coatings according to claim 1, characterized in that, The cation exchange resin is either type 732 cation exchange resin or type D001 cation exchange resin, and the anion exchange resin is either type 717 anion exchange resin or type D201 anion exchange resin.
4. The preparation process of a small-particle-size, high-purity, and highly stable silica sol for special coatings according to claim 1, characterized in that, The flux through cation exchange resins and anion exchange resins is 0.5-2.5 mL / (cm²). 2 ·min).
5. The preparation process of a small-particle-size, high-purity, and highly stable silica sol for special coatings according to claim 1, characterized in that, The alkaline catalyst is one or more of potassium hydroxide, sodium hydroxide, ammonia, or organic bases.
6. The preparation process of a small-particle-size, high-purity, and highly stable silica sol for special coatings according to claim 1, characterized in that, The specific temperature is 60-95℃, the stirring rate is 100-400 r / min, and the reaction time is 2-10 h.
7. The preparation process of a small-particle-size, high-purity, and highly stable silica sol for special coatings according to claim 1, characterized in that, The concentration is achieved through vacuum distillation or ultrafiltration.
8. The preparation process of a small-particle-size, high-purity, and highly stable silica sol for special coatings according to claim 1, characterized in that, The filtration process employs microporous membranes or ultrafiltration, with membrane pore sizes ranging from 0.1 to 2 μm.