Alkoxy-Group Colloidal Silica Production for Storage-Stable Small Particles
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Solution Overview
Problem
Existing methods for producing colloidal silica with small particle size and high abrasiveness are complex, costly, and result in increased particle size and aggregation after storage, leading to defects on polished surfaces.
Innovation Solution
A production method involving a mother liquor with an alkaline catalyst and water, followed by addition of alkoxysilane and an alkaline catalyst, results in colloidal silica with primary particle sizes of 20 nm or less, high alkoxy group content, and suppressed secondary particle size increase, achieving high density and storage stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a hydrolyzed solution obtained by hydrolyzing an alkoxysilane is added to a mother liquor containing an alkaline catalyst, then particles with excellent compactness and high particle density are formed, but the production process becomes multiple steps and complicated and costly
Solution Approach 1:
The patent combines the hydrolysis step and the particle formation step into a single integrated process. By adding alkoxysilane directly to the mother liquor containing alkaline catalyst, the hydrolysis and condensation occur simultaneously in one reactor, eliminating the need for separate hydrolysis and mixing steps. This merging of operations reduces process complexity while maintaining high particle density.
Solution Approach 2:
The patent prepares the mother liquor with alkaline catalyst in advance, and then directly adds the alkoxysilane to initiate hydrolysis and particle formation. This preliminary preparation of the catalytic environment allows the process to proceed efficiently in one step without requiring separate hydrolysis step.
2Reliability
If an alkoxysilane is once hydrolyzed to prepare a hydrolyzed solution, then high abrasiveness is achieved, but the resulting silica particles contain a reduced amount of alkoxy groups and defects such as scratches increase on the surface of polished objects
Solution Approach 1:
The patent maintains continuous presence of alkoxy groups on silica particle surfaces by controlling the hydrolysis process to proceed gradually in the alkaline catalyst environment. The continuous addition of alkoxysilane and controlled hydrolysis ensure that alkoxy groups remain on the particle surfaces throughout the process, providing both abrasiveness and preventing surface defects.
Solution Approach 2:
The patent controls the hydrolysis degree and pH conditions to optimize the balance between abrasiveness and surface quality. By adjusting the alkaline catalyst concentration and hydrolysis time, the process achieves sufficient particle strength for abrasiveness while maintaining intact alkoxy groups that prevent surface scratching.
3Manufacturing precision
If tetramethoxysilane and methanol are added dropwise to a liquid containing methanol, a small amount of water, and a small amount of aqueous ammonia, then silica with a small particle size and excellent storage stability is produced, but the addition of a dispersion stabilizer such as ammonia is undesirable for high purity requirements
Solution Approach 1:
The patent replaces the use of ammonia as a dispersion stabilizer with an alternative approach using organic solvents and controlled hydrolysis conditions. This substitution eliminates the need for ammonia additive, achieving high purity requirements while maintaining small particle size through careful control of the hydrolysis process parameters.
Solution Approach 2:
The patent adjusts the solvent composition, pH, and temperature parameters to achieve small particle size without requiring ammonia as a stabilizer. By optimizing these parameters, the process maintains particle dispersion and small size through controlled hydrolysis kinetics rather than through ammonia stabilization.
4Reliability
If silica particles with a small average primary particle size are produced, then high abrasiveness is achieved, but the silica particles are likely to aggregate after storage, resulting in an increase in the average secondary particle size
Solution Approach 1:
The patent introduces organic solvents and controlled hydrolysis conditions as intermediaries to prevent aggregation of small silica particles during storage. These intermediaries create a stable colloidal environment that maintains particle dispersion without requiring additional stabilizing agents, thus preserving both small particle size and storage stability.
Solution Approach 2:
The patent creates a composite colloidal system where silica particles are dispersed in a controlled solvent matrix with specific pH and ionic conditions. This composite structure provides steric and electrostatic stabilization, preventing aggregation of small particles while maintaining their high abrasiveness characteristics.
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 method produces colloidal silica with reduced defects and enhanced abrasiveness, maintaining small particle size and stability over time, suitable for polishing applications.
Implementation Method 1
a production method in which a hydrolyzed solution obtained by hydrolyzing an alkoxysilane is added to a mother liquor
Implementation Method 2
the silica particles are likely to aggregate after storage, resulting in an increase in the average secondary particle size
Data Source
AI summary
Colloidal silica containing silica particles that have a small particle size (e.g., an average primary particle size of 20 nm or less) and that contain alkoxy groups, and a method for producing the colloidal silica, are disclosed. The colloidal silica containing silica particles can have a small particle size and exhibit a suppressed increase in the average secondary particle size after storage. The colloidal silica containing silica particles wherein the silica particles have an average primary particle size of 20 nm or less, the silica particles have a ratio (m/n) of the content of alkoxy groups m (ppm) to the average primary particle size n (nm) of 300 or more, the silica particles have a particle density of 1.95 or more, and the silica particles have an increase rate of average secondary particle size of 12% or less in a storage stability test.