Ultrahigh-purity low-turbidity silica sol, preparation method thereof and glass canning liquid using silica sol

Abstract

The invention discloses ultra-high-purity low-turbidity silica sol which is prepared by taking common silica sol as a raw material through adsorption of an amino phosphonic acid modified molecular sieve and separation of a nano-film, the PDI of the silica sol is less than or equal to 0.03, and the content of Fe is 1t; 0.01 ppm, and a closed pore structure of 22 + / -2nm is included. The invention has the following beneficial effects: the technical scheme enables the Fe content to be 1t through a bifunctional molecular sieve adsorption technology; the problem of yellowing caused by metal impurities in the traditional silica sol is solved; according to the technical scheme, a 22nm closed pore structure is realized through a membrane separation-seed crystal coupling process, the light transmittance is improved to 97.2%, and the haze is lt; 0.1 part; the low viscosity of 36 mPa.s is matched with low-temperature stepped curing, and the bubble rate is lt; therefore, the strict requirements of building fireproof glass on optical performance and safety are met.

Description

Technical Field

[0001] This invention relates to the field of technology, and more particularly to an ultra-high purity, low-turbidity silica sol, its preparation method, and a glass jar for using the silica sol. Background Technology

[0002] Silica sol, as an important inorganic nanomaterial, is widely used in the liquid matrix of inorganic composite fireproof glass due to its excellent film-forming properties, high-temperature resistance, and optical transparency. Fireproof glass forms a heat-insulating and fire-resistant layer at high temperatures through the liquid matrix, and its performance directly depends on the purity, particle size distribution, and microstructure of the silica sol. High purity avoids yellowing caused by metal ions, narrow particle size distribution (low PDI) reduces light scattering, and a controllable closed-cell structure inhibits bubble formation and improves light transmittance.

[0003] However, the preparation of silica sol in existing technologies still faces three major challenges: Insufficient purity: Traditional molecular sieve adsorbents have limited selective adsorption capacity for transition metal ions such as Fe³⁺ and Cu²⁺ (adsorption capacity is usually <8mg / g), resulting in a general content of metal impurities in the silica sol >0.5ppm, which can easily cause yellowing of fireproof glass (Δb*>2.0) under long-term use or ultraviolet irradiation; Wide particle size distribution: Conventional membrane separation technologies (such as ceramic membranes above 100nm) are difficult to precisely control the particle size of silica sol, with PDI often >0.1, resulting in severe light scattering and a light transmittance of fireproof glass <85%; Uncontrollable closed-cell structure: There is a lack of effective pore formation control methods, and after the silica sol solidifies, it is easy to form interconnected channels. During the stepped solidification process of the fireproof glass jar liquid (50-70℃), water evaporation generates a large number of bubbles (bubble rate >15%), further reducing optical performance and structural stability.

[0004] In existing fire-resistant glass jar liquid formulations, the compatibility between silica sol and additives such as ethylene glycol and glycerol is insufficient, and the curing process is not optimized for the microstructure of silica sol. As a result, the finished glass is prone to cracking after thermal cycling (-40~120℃), and the fire resistance limit is generally <120min.

[0005] Therefore, developing an ultra-high purity, low PDI, narrow-distribution closed-pore structure silica sol, along with a suitable canning liquid formulation and curing process, is key to solving the problems of yellowing, turbidity, and bubbling in inorganic composite fireproof glass. Summary of the Invention

[0006] The main technical problem solved by this invention is to provide an ultra-high purity, low turbidity silica sol, its preparation method, and a glass jar for using the silica sol, thereby solving one or more of the above-mentioned prior art problems.

[0007] To solve the above-mentioned technical problems, the present invention adopts a technical solution as follows: an ultra-high purity, low turbidity silica sol, which uses ordinary silica sol as raw material. Its innovation lies in the fact that it is prepared by adsorption of aminophosphonic acid modified molecular sieve and separation by nanomembrane. The silica sol has a PDI≤0.03, Fe³⁺ content<0.01ppm, and contains a closed-pore structure of 22±2nm.

[0008] In some embodiments, the aminophosphonic acid modified molecular sieve is an aminophosphonic acid-grafted MCM-41 molecular sieve with an Fe³⁺ adsorption capacity ≥25mg / g.

[0009] In some implementations, the closed-cell structure has a closed-cell rate of ≥98% and a specific surface area of ​​420 m² / g.

[0010] A method for preparing ultra-high purity, low-turbidity silica sol, characterized by comprising the following steps:

[0011] a) A three-stage gradient molecular sieve adsorption column was used for deep impurity removal at an adsorption flow rate of 0.8 BV / h;

[0012] b) Tangential flow filtration was performed using a 20nm zirconium-aluminum composite ceramic membrane under the following operating conditions: transmembrane pressure 0.35MPa and tangential flow velocity 8m / s.

[0013] c) Add SiO2@ZrO2 core-shell seeds under vacuum conditions and concentrate them.

[0014] In some embodiments, the diameter ratio of the three-stage gradient adsorption column in step a) is 1:1.5:2, and the molecular sieve removal rate is >99.99%.

[0015] In some implementations, the membrane separation cycle ratio in step b) is 8:1 (concentrate:permeate), and the operating temperature is 40°C.

[0016] In some embodiments, the vacuum concentration in step c) is carried out at a temperature of 60°C and a pressure of -0.09 MPa, and after concentration to a solid content of 50%, it is kept warm and matured for 30 minutes.

[0017] A glass-bottled liquid, comprising 40-50% ultra-high purity, low turbidity silica sol, 10-15% ethylene glycol, 10-15% glycerol, 0.1-0.5% clearing agent, 0.1-0.5% antioxidant, 0.1-0.2% bactericide, and 28.3-49.7% pure water.

[0018] In some implementations, the anti-reflective agent is an additive that improves the transparency of the system, and the antioxidant is a reagent that enhances the antioxidant properties of the membrane.

[0019] In some implementations, the canned liquid is treated with a three-stage curing process: 50°C for 60 min, 60°C for 90 min, and 70°C for 90 min.

[0020] The beneficial effects of this invention are:

[0021] Breakthrough in material purity: Dual-function molecular sieve adsorption technology reduces Fe³⁺ content to <0.01ppm, solving the yellowing problem caused by metallic impurities in traditional silica sol.

[0022] Precise and controllable structure: The membrane separation-seed coupling process achieves a 22nm closed-pore structure, increasing the light transmittance to 97.2% and the haze to <0.1.

[0023] High process adaptability: Low viscosity of 36 mPa·s is matched with low temperature step curing, with a bubble rate of <0.03%, which meets the stringent requirements of building fireproof glass for optical performance and safety. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort, wherein:

[0025] Figure 1 This is a flowchart of a method for preparing ultra-high purity, low turbidity silica sol according to the present invention. Detailed Implementation

[0026] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] like Figure 1 As shown, embodiments of the present invention include:

[0028] The preparation of ultra-high purity, low-turbidity silica sol is as follows:

[0029] Molecular sieve deep impurity removal: MCM-41 molecular sieve grafted with aminophosphonic acid was used as the adsorbent and packed in a three-stage gradient tower (diameter ratio 1:1.5:2). The silica sol precursor solution was introduced at a flow rate of 0.8 BV / h. After elution and regeneration with 0.1 M citric acid and 200 cycles, the Fe³⁺ adsorption capacity remained at 25 mg / g, the removal rate was >99.99%, and the Fe³⁺ content in the effluent was <0.01 ppm.

[0030] Precise particle control through membrane separation: Using a 20nm zirconium-aluminum composite ceramic membrane, tangential flow filtration (recirculation ratio 8:1) was performed under the conditions of transmembrane pressure 0.35MPa, tangential flow velocity 8m / s, and temperature 40℃ to obtain an intermediate product with PDI=0.03 and a particle size distribution half-peak width <2nm.

[0031] Vacuum seeding: The above product was concentrated under reduced pressure at 60℃ and -0.09MPa to a solid content of 50%, and 0.1% SiO2@ZrO2 core-shell seed crystals (particle size 5nm) were added. The mixture was then kept at the temperature for 30 minutes to form a silica sol with a closed pore rate of 98% and an average pore size of 22nm.

[0032] This silica sol was tested and found to have a PDI of 0.002 (ISO 22412 standard), Fe³⁺ content of 0.008 ppm (ICP-MS test), turbidity of 0.10 NTU (ASTM D1003 standard), closed-cell rate of 98%, and average pore size of 22 nm (BET verification). After 90 days of accelerated storage at 40°C, the PDI change was <0.001, with no gelation, demonstrating excellent stability.

[0033] Example 1: Fire-resistant glass jar liquid

[0034] By weight percentage, the prepared silica sol (40%), ethylene glycol (10%), glycerol (10%), clearing agent (0.1%), antioxidant (0.1%), bactericide (0.1%) and pure water (49.7%) are mixed and stirred evenly to obtain the canned liquid.

[0035] Example Results: After three-stage curing (50℃ / 60min→60℃ / 90min→70℃ / 90min), the fire-resistant glass jar liquid of this example has a light transmittance of 97.2% (ISO 9050 standard), a yellowing index of 0.15 (CIE Lab* standard), a bubble rate of 0.03% (GB / T 9962 standard), no cracking after 100 cycles of thermal cycling from -40 to 120℃, and a fire resistance limit of 195min (1100℃ burn test).

[0036] Example 2: Fire-resistant glass jar liquid

[0037] By weight percentage, the prepared silica sol (50%), ethylene glycol (15%), glycerol (15%), clearing agent (0.5%), antioxidant (0.5%), bactericide (0.2%) and pure water (28.3%) are mixed and stirred evenly to obtain the canned liquid.

[0038] Example Results: After curing, the fireproof glass jar liquid in this example has a light transmittance of 96.8%, a yellowing index of 0.18, a yellowing index change of 0.18 after 5000h of ultraviolet aging (ISO 11431 standard), and a bubble rate of 0.05%. Its comprehensive performance meets the requirements of optical stability and high temperature resistance for fireproof building glass.

[0039] Comparative example: Bottled liquid prepared from commercially available silica sol

[0040] Commercially available silica sol (PDI=0.15, Fe³⁺ content>0.5ppm) was used to replace the silica sol prepared above, and the canned liquid was prepared according to the formulation of Example 1.

[0041] The canned liquid prepared using commercially available silica sol has a light transmittance of only 84.2% after curing, a yellowing index >2.0, a bubble rate >15%, and shows obvious cracking after thermal cycling. Its fire resistance limit is <120 min, which cannot meet the application requirements of high transparency and low yellowing.

[0042] Performance Comparison Table

[0043] Testing items Example 1 (Canned Liquid) Example 2 (Canned Liquid) Comparative example (bottled liquid) PDI 0.03 0.03 0.15 Fe³⁺ content (ppm) 0.009 0.010 >0.5 Turbidity (NTU) 0.12 0.13 2.5 Light transmittance (%) 97.2 96.8 84.2 Yellowing index (Δb*) 0.15 0.18 >2.0 Bubble rate (%) 0.03 0.05 >15

[0044] Ultra-high purity, low turbidity silica sol: Metal impurities are removed by three-level gradient adsorption of aminophosphonic acid modified molecular sieve, particle size distribution is precisely controlled by 20nm membrane separation, and 22nm closed-pore structure is formed by vacuum seeding, which synergistically achieves PDI≤0.03 and turbidity<0.1NTU performance.

[0045] Fire-resistant glass jar liquid: Silica sol is used as the matrix to form a high-temperature resistant system with ethylene glycol and glycerol. Anti-reflective agents reduce light scattering, and antioxidants inhibit aging. The three-stage curing process (50℃ / 60min→60℃ / 90min→70℃ / 90min) gradually evaporates moisture to avoid bubble formation, ultimately obtaining highly transparent and low-yellowing fire-resistant glass.

[0046] The advantages of this technical solution are:

[0047] Breakthrough in material purity: Dual-function molecular sieve adsorption technology reduces Fe³⁺ content to <0.01ppm, solving the yellowing problem caused by metallic impurities in traditional silica sol.

[0048] Precise and controllable structure: The membrane separation-seed coupling process achieves a 22nm closed-pore structure, increasing the light transmittance to 97.2% and the haze to <0.1.

[0049] High process adaptability: Low viscosity of 36 mPa·s is matched with low temperature step curing, with a bubble rate of <0.03%, which meets the stringent requirements of building fireproof glass for optical performance and safety.

[0050] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. An ultra-high purity low-turbidity silica sol, using a common silica sol as a raw material, characterized in that: The silica sol is prepared by adsorption of amino phosphonic acid modified molecular sieve and nanometer membrane separation, wherein the PDI of the silica sol is ≤0.03, the Fe³⁺ content is <0.01 ppm, and the closed pore structure is 22±2 nm. ​ 2. The ultra-high purity low-turbidity silica sol according to claim 1, characterized in that: The amino phosphonic acid modified molecular sieve is amino phosphonic acid grafted MCM-41 molecular sieve, and the Fe³⁺ adsorption capacity is ≥25 mg / g.

3. The ultra-high purity low-turbidity silica sol according to claim 1, characterized in that: The closed pore rate of the closed pore structure is ≥98%, and the specific surface area is 420 m² / g.

4. A method of making the silica sol of claim 1, characterized by: The method comprises the following steps: a) deep impurity removal by using a three-stage gradient molecular sieve adsorption column, and the adsorption flow rate is 0.8 BV / h; b) tangential flow filtration by using a 20 nm zirconium-aluminum composite ceramic membrane, and the operation conditions are a transmembrane pressure of 0.35 MPa and a tangential flow rate of 8 m / s; c) addition of SiO2@ZrO2 core-shell crystal seeds under vacuum and concentration.

5. The method according to claim 4, wherein the method is characterized by: In step a), the diameter ratio of the three-stage gradient adsorption column is 1:1.5:2, and the molecular sieve removal rate is >99.99%.

6. The method of claim 4, wherein the method further comprises the step of: In step b), the circulation ratio of membrane separation is 8:1 (concentrated liquid: permeate), and the operation temperature is 40℃. ​ 7. The method according to claim 4, wherein the method is characterized by: In step c), the vacuum concentration temperature is 60℃, the pressure is -0.09 MPa, and after concentration to a solid content of 50%, the system is kept for aging for 30 min.

8. A glass jarred liquid characterized by: The tank liquid is treated by a three-stage curing process: 50℃ for 60 min, 60℃ for 90 min, and 70℃ for 90 min.

9. A glass jarred liquid as claimed in claim 8, wherein: The antifouling agent is an additive for improving the transparency of the system, and the antioxidant is an agent for enhancing the oxidation resistance of the membrane.

10. A glass jarred liquid as defined in claim 8, wherein: The tank liquid is treated by a three-stage curing process: 50℃ for 60 min, 60℃ for 90 min, and 70℃ for 90 min.

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