Silica Sol Production via Conductivity-Controlled Hydrolysis
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Solution Overview
Problem
Conventional methods for producing silica sols face challenges in achieving high purity and homogeneity due to the formation of fine particles when increasing the amount of raw materials, leading to reduced quality and productivity.
Innovation Solution
A method involving a reaction liquid with alkoxysilane, water, and an alkali catalyst, where the alkali catalyst is not supplemented after the reaction start, and the electrical conductivity is maintained at 90% or more of its initial maximum value for 90% of the reaction time, preventing the formation of fine particles by maintaining hydroxide ion concentration and promoting silica particle growth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the amount of raw materials is increased to improve productivity, then the amount of silica produced per batch increases, but fine particles are formed and homogeneity decreases
Solution Approach 1:
The invention changes the chemical parameters of the reaction system by specifying precise molar ratios between alkoxysilane, water, and alkali catalyst, and by controlling the electrical conductivity of the reaction liquid. These parameter changes enable the system to maintain homogeneity even when scaling up the amount of raw materials, thus resolving the contradiction between productivity and manufacturing precision.
2Productivity
If the amount of raw materials is increased to improve productivity, then the amount of silica produced per batch increases, but the quality of silica sol decreases due to fine particle formation
Solution Approach 1:
The invention introduces electrical conductivity as a feedback parameter to monitor and control the reaction process. By maintaining the electrical conductivity at 90% or more of its maximum value during the reaction, the system can prevent fine particle formation and ensure high quality silica sol even when producing large amounts per batch, thus resolving the contradiction between productivity and reliability.
3Speed
If alkali catalyst is continuously supplemented to maintain reaction rate, then the synthesis speed increases, but fine particles are formed and homogeneity decreases
Solution Approach 1:
The invention applies preliminary action by pre-calculating and pre-adding the exact amount of alkali catalyst needed based on the molar ratio with alkoxysilane. This eliminates the need for continuous supplementation during the reaction, maintaining both high synthesis speed and homogeneity by avoiding the fine particle formation that occurs with excessive catalyst addition.
4Manufacturing precision
If conventional ion exchange method is used to increase purity of starting material, then the purity improves to some extent, but the purification is limited and high-purity silica sol cannot be obtained
Solution Approach 1:
The invention extracts the problematic ion exchange purification step from the production process and replaces it with a direct hydrolysis method using high-purity alkoxysilane. This eliminates the limitation of conventional purification methods and enables the production of high-purity silica sol with better productivity, as the purity is determined by the starting material selection rather than extensive purification processes.
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
This approach effectively suppresses the formation of fine particles, enhancing the homogeneity and productivity of silica sols by allowing silica particles to grow sufficiently, even with increased raw material amounts, resulting in higher quality and quantity of silica produced per batch.
Implementation Method 1
allowing the alkoxysilane or condensate thereof to react with the water in the presence of the alkali catalyst
Implementation Method 2
the proportion of the value of the electrical conductivity of the reaction liquid is more than 90% relative to the value of the electrical conductivity at the time when 5 minutes have elapsed from the time point when the local maximum is reached
Data Source
AI summary
The present invention provides a means capable of suppressing the formation of fine particles in a method for producing a silica sol. The present invention relates to a method for producing a silica sol, including synthesizing a silica sol by, in a reaction liquid containing an alkoxysilane or a condensate thereof, water, and an alkali catalyst, allowing the alkoxysilane or condensate thereof to react with the water in the presence of the alkali catalyst, wherein the alkali catalyst is not additionally supplied after the start of the synthesis until the finish time of the synthesis, and during 90% or more of the time between when 5 minutes have elapsed from the time point when the electrical conductivity of the reaction liquid reaches a local maximum for the first time and the finish time of the synthesis, the proportion of the value of the electrical conductivity of the reaction liquid is more than 90% relative to the value of the electrical conductivity at the time when 5 minutes have elapsed from the time point when the local maximum is reached.