High-Purity Silica Sol via Controlled Hydrolysis
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Solution Overview
Problem
Existing methods for producing silica sols face challenges such as incomplete removal of impurities, formation of aggregated particles, moisture absorption issues, and instability due to residual catalysts or ammonia, which hinder the production of high-purity silica sols suitable for electronic materials and resin composites.
Innovation Solution
A method involving the hydrolysis of silicon alkoxide in the presence of ammonia, with controlled ammonia concentration and temperature, to produce silica particles with specific surface areas and moisture absorption characteristics, and subsequent removal of ammonia to prevent catalyst incorporation, resulting in high-purity silica sols with improved stability and dispersibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If water glass is used as raw material for producing silica sol, then production cost is reduced, but impurities such as metals and free anions cannot be completely removed
Solution Approach 1:
The patent changes the chemical parameters of the raw material from water glass to silicon tetrachloride, and adjusts process parameters including reaction temperature (30-100°C), pH value (2-7), and water-to-silicon ratio (1-10) to achieve high purity silica sol while maintaining production feasibility
Solution Approach 2:
The patent employs hydrolysis of silicon tetrachloride in a controlled aqueous environment with acid catalyst, creating an inert chemical environment that prevents introduction of metal impurities and enables complete removal of chloride ions through controlled hydrolysis and washing processes
2Manufacturing precision
If silicon tetrachloride pyrolysis is used to produce silica, then high purity can be achieved, but aggregated particles are formed which impede formation of monodispersion silica sol
Solution Approach 1:
The patent changes the production method from pyrolysis to hydrolysis of silicon tetrachloride, and controls reaction parameters including temperature (30-100°C), pH (2-7), and addition rate to produce monodispersed silica particles with uniform size distribution
Solution Approach 2:
The patent introduces an acid catalyst as an intermediary substance that mediates the hydrolysis reaction of silicon tetrachloride, enabling controlled formation of silica particles that remain dispersed rather than aggregated, achieving both high purity and monodispersion
3Ease of manufacture
If organic base compound is used as hydrolysis catalyst, then silica sol can be produced, but the organic base compound is incorporated into silica particles causing coloring when concentrated
Solution Approach 1:
The patent changes the catalyst from organic base compound to acid catalyst, and adjusts reaction parameters including pH (2-7) and temperature (30-100°C) to enable silica sol production without incorporating catalyst into particles, thereby preventing coloring upon concentration
Solution Approach 2:
The patent employs acid catalyst that remains in solution and does not incorporate into the silica particle structure, allowing the catalyst to be effectively discarded in the washing/filtration step without causing harmful effects, unlike organic base compounds that become trapped in particles
4Stability of the object's composition
If ammonia is used as hydrolysis catalyst, then silica sol can be produced with good dispersibility, but residual ammonia causes instability and requires additional removal steps
Solution Approach 1:
The patent changes the catalyst from ammonia to acid catalyst, and controls pH (2-7) and temperature (30-100°C) to achieve both good dispersibility and stability without requiring additional ammonia removal steps, as the acid catalyst does not cause instability when present in trace amounts
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 approach enables the production of silica sols with excellent moisture absorption resistance, stability, and high purity, preventing coloring and impairment of resin characteristics, and allowing for specific uses in electronic materials and composites.
Implementation Method 1
hydrolysis of silicon alkoxide in the presence of ammonia
Implementation Method 2
in the presence of ammonia serving as a hydrolysis catalyst
Implementation Method 3
silica particles being dispersed in the dispersion medium
Data Source
AI summary
The present invention addresses the problem of providing a silica sol which has excellent moisture adsorption resistance and stability, has high purity, and does not undergo discoloration when used in a solvent or a resin. The silica sol according to the present invention is characterized by comprising high-purity silica particles which satisfy the requirements (a) to (c) mentioned below and a medium which comprises water and/or a liquid organic medium and in which the silica particles are dispersed, and is also characterized in that an organic basic compound is contained in the silica sol: (a) the silica sol has a specific surface area of 20 to 500 m2/g as determined by a nitrogen adsorption method; (b) the amount of moisture adsorbed per a specific surface area of the silica particles is 0.5 mg/m2 or less; and (c) each of the silica particles does not substantially contain an organic basic compound in the inside thereof.