Aqueous Active Silica Solution Stabilization for Particle Control
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Solution Overview
Problem
Existing methods for producing silica sols face challenges in controlling the particle diameter distribution and shape of silica particles due to the instability of aqueous active silica solutions, leading to difficulties in reproducibility and handling.
Innovation Solution
A stabilized aqueous active silica solution is prepared by incorporating specific amounts of stabilizers such as acids, potassium hydroxide, ammonia, or organic bases, followed by controlled polycondensation processes to achieve silica particles with defined properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If cation-exchange resin is used to remove cations from liquid glass to prepare aqueous active silica solution, then silica particles can be formed through polycondensation, but the aqueous active silica solution becomes unstable and active silica undergoes uncontrolled polycondensation
Solution Approach 1:
The patent applies preliminary action by adding a stabilizer to the aqueous active silica solution before polycondensation occurs. This stabilizer prevents premature polycondensation and maintains solution stability during storage and handling, allowing controlled particle formation only when desired. The stabilizer is incorporated in advance to suppress unwanted reactions before the actual silica particle production process begins.
Solution Approach 2:
The patent employs parameter changes by adjusting the pH of the aqueous active silica solution through stabilizer addition. By controlling pH within specific ranges, the patent achieves both solution stability and controlled polycondensation. The pH parameter is carefully regulated to prevent uncontrolled particle formation while maintaining solution stability, thus resolving the contradiction between stability and manufacturing precision.
2Manufacturing precision
If strong acid is added to aqueous active silica solution and brought into contact with cation-exchange resin and anion-exchange resin, then purity is improved, but the solution becomes more unstable and difficult to handle
Solution Approach 1:
The stabilizer is added in advance to the aqueous active silica solution to prevent polycondensation during the purification process. This preliminary stabilization allows the solution to undergo acid treatment and ion-exchange resin contact without suffering from uncontrolled particle formation, thereby maintaining both purity and handling ease.
Solution Approach 2:
The stabilizer acts as an intermediary substance that mediates between the purifying agents (strong acid and ion-exchange resins) and the active silica. It allows the purifying agents to perform their function while preventing harmful interactions between these agents and the active silica, thus maintaining solution stability and ease of operation during purification.
3Manufacturing precision
If aqueous ammonia solution is added and aging is performed, then silica sol is produced, but particle diameter distribution and shape cannot be controlled due to solution instability
Solution Approach 1:
The stabilizer is added before the aging process to ensure solution stability throughout the entire production sequence. This preliminary stabilization prevents uncontrolled polycondensation during aging, allowing reproducible particle formation with controlled diameter distribution and shape. The stabilizer ensures that each production batch follows the same controlled pathway.
Solution Approach 2:
The patent employs parameter changes by controlling pH through stabilizer addition to achieve both solution stability and controlled polycondensation during aging. By maintaining pH within specific ranges, the patent ensures reproducible particle formation with controlled diameter distribution and shape, thereby improving reliability while maintaining manufacturing precision.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution results in a silica sol with controlled particle diameter distribution and shape, ensuring stability and reproducibility of the production process.
Implementation Method 1
an aqueous alkali silicate solution is treated with a cation-exchange resin to thereby prepare a cation-removed aqueous active silica solution
Implementation Method 2
active silica undergoes polycondensation in the aqueous solution. Thus, the methods described in Patent Documents 1 to 3 pose a problem that difficulty is encountered in controlling the particle diameter distribution and particle shape of silica particles
Data Source
AI summary
A stabilized aqueous active silica solution including at least one stabilizing agent selected from an acid, potassium hydroxide, ammonia and an organic base, whose content is 0.167 to 10% by mass/SiO2 relative to solution. The acid is an inorganic or organic acid. The inorganic acid is sulfuric or nitric acid. The organic acid is citric acid. The base is an amine or quaternary ammonium hydroxide. The viscosity of the solution that has a SiO2 concentration of 2.8 to 3.3% by mass, measured by the Ostwald method at 23° C. within 3 hours after production, is 0.5 to 20 mPa·s. The viscosity of the solution measured after storage at 23° C. for 3 days is higher by 5.0 times or less than that of the solution measured within 3 hours. Also, a silica sol including silica particles having an average primary particle diameter of 5 to 300 nm.