Alkali Silicate Filtration for Plate-like Particle Removal
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Solution Overview
Problem
Current methods fail to effectively remove plate-like fine particles from alkali silicate aqueous solutions, which are used as abrasives in magnetic disk and semiconductor substrate polishing, leading to surface defects and low filtration rates unsuitable for mass production.
Innovation Solution
A method involving adjusting the silica concentration of alkali silicate solutions and filtering them through filters with high removal rates for particles of specific sizes, followed by cation-exchange and polymerization to produce a silica sol with reduced plate-like fine particles, using filters with pore sizes of 0.3 to 3.0 μm and filters like membrane, pleats, or depth type filters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If ultrafiltration membrane with molecular weight cut-off of 15,000 or less is used to remove particles, then particle removal efficiency is improved, but filtration rate becomes significantly low making it unsuitable for mass production
Solution Approach 1:
The filtration process is divided into multiple stages with different filter types. A pre-filter removes larger particles first, followed by a main filter that removes plate-like fine particles. This segmentation allows each filter to be optimized for its specific function, maintaining high removal efficiency while preserving filtration rate for mass production.
Solution Approach 2:
The invention changes the filtration parameters by using filters with specific pore sizes (0.03 to 0.1 μm) and specific removal rates (80% or more for plate-like fine particles). This parameter optimization allows effective particle removal while maintaining acceptable filtration rates for industrial production.
2Quantity of substance
If related-art washing method is used to remove colloidal silica, then spherical abrasive grains are removed, but plate-like fine particles cannot be easily removed
Solution Approach 1:
The invention introduces a specifically designed filter as an intermediary between the washing process and the final product. This filter acts as a mediator that selectively removes plate-like fine particles that are not removed by conventional washing methods, while preserving the spherical abrasive grains and colloidal silica.
Solution Approach 2:
The invention uses porous filter materials with specific pore sizes (0.03 to 0.1 μm) that are optimized to capture plate-like fine particles. The porous structure allows the filter to selectively trap particles based on their shape and size, removing plate-like particles while allowing spherical grains to pass through.
3Manufacturing precision
If filter with high removal rate for 1.0 μm particles is used, then particle removal is improved, but filtration rate decreases
Solution Approach 1:
The filtration system is segmented into a pre-filter stage and a main filtration stage. The pre-filter handles larger particles with higher flow rates, while the main filter focuses on removing plate-like fine particles. This segmentation distributes the filtration load, maintaining overall high removal efficiency without sacrificing filtration rate.
Solution Approach 2:
The invention optimizes filtration parameters by selecting filters with pore sizes of 0.03 to 0.1 μm and removal rates of 80% or more for plate-like fine particles. This parameter optimization achieves high particle removal while maintaining filtration rates suitable for mass production, resolving the contradiction between removal efficiency and productivity.
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 method efficiently reduces the amount of plate-like fine particles, enhancing filtration rates and enabling mass production of purified alkali silicate solutions and silica sols, preventing particle remnants on substrates during polishing and ensuring surface smoothness.
Implementation Method 1
filtering the alkali silicate aqueous solution with a filter having a removal rate of particles with a primary particle size of 1.0 μm of 50% or more
Implementation Method 2
preparing an active silicic acid solution by subjecting the purified alkali silicate aqueous solution to cation-exchange
Implementation Method 3
adding the active silicic acid solution into an alkaline aqueous solution to obtain a mixture, and heating the mixture to polymerize active silicic acid
Data Source
AI summary
To provide a method for producing an alkali silicate aqueous solution containing a reduced amount of foreign substance of plate-like fine particles and a method for producing a silica sol containing a reduced amount of foreign substance of plate-like fine particles. A method for producing an alkali silicate aqueous solution fulfilling the following condition: the existing amount of plate-like fine particles having a length of one side of 0.2 to 4.0 μm and a thickness of 1 to 100 nm is determined to be 0 to 30%. The method for producing an alkali silicate aqueous solution includes the steps of adjusting a silica concentration of an alkali silicate aqueous solution to 0.5 to 10.0% by mass and filtering the alkali silicate aqueous solution through a filter having a removal rate of particles with a primary particle size of 1.0 μm of 50% or more.