Semi-Batch Colloidal Silica Production for Low Viscosity
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Solution Overview
Problem
Conventional colloidal silica sols with high solids content and low viscosity that maintain high surface area and stability are not achievable using conventional production methods, and existing solutions require surface modification with aluminum for stability.
Innovation Solution
A semi-batch process involving the addition of alkali metal silicate to a cationic ion exchange resin under controlled temperature and pH conditions to produce aqueous colloidal silica products with 16-18% SiO2 solids, achieving low viscosity (4-20 mPas) and high surface area (750-850 m2/g) without aluminum modification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional production methods are used to increase colloidal silica solids content, then viscosity increases beyond acceptable limits, but low viscosity is required for practical application
Solution Approach 1:
The patent changes the pH parameter during production (maintaining pH 9-11) and uses controlled addition rates to achieve unusual viscosity characteristics. The semi-batch process with specific addition rates (first quantity at rate sufficient to allow addition to last 1-45 minutes, second quantity at rate sufficient to allow addition to last 5-120 minutes) creates a product with 16-18% solids content and viscosity of 4-20 mPas, which would not be achievable with conventional batch methods
2Quantity of substance
If conventional production methods are used to produce high solids content colloidal silica, then stability deteriorates requiring aluminum modification, but aluminum-free stability is desired
Solution Approach 1:
The patent maintains pH within 9-11 during the entire semi-batch production process, which is higher than conventional methods. This pH control, combined with the semi-batch addition process, produces colloidal silica with 16-18% solids content that remains stable for extended periods without aluminum modification, achieving both high solids content and reliability
3Quantity of substance
If high solids content colloidal silica is produced, then surface area decreases, but high surface area is required for effective papermaking performance
Solution Approach 1:
The patent uses controlled pH (9-11) and semi-batch addition with specific rates to produce colloidal silica particles with optimized morphology. The process produces particles with 16-18% solids content while maintaining specific surface area of 750-850 m2/g, which would not be achievable with conventional batch methods that produce larger aggregates at high solids content
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 process results in stable colloidal silica sols with enhanced performance as retention and dewatering aids in papermaking, achieving improved first pass ash retention and reduced microparticle dosage, while maintaining stability for extended periods without aluminum treatment.
Implementation Method 1
adding a first quantity of alkali metal silicate to water and a partially regenerated cationic ion exchange resin under agitation, thereby forming a first intermediate composition comprising a first portion of aqueous colloidal silica product
Data Source
Figure 1
AI summary
An aqueous colloidal silica product, a method of using the aqueous colloidal silica product, and a method of producing an aqueous colloidal silica product, are disclosed. The method of producing the aqueous colloidal silica product incorporates semi-batch addition of alkali metal silicate, which is capable of achieving an aqueous colloidal silica product having desirable physical and chemical characteristics. The aqueous colloidal silica product has been found to be particularly useful as an additive in a papermaking process.