Stable Ethylpolysilicate via Two-Step Hydrolysis
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Solution Overview
Problem
Existing ethylpolysilicate polymers used in applications like chemical mechanical polishing, pressure-sensitive adhesives, and zinc-rich coatings face limitations due to high levels of low boiling alcohol by-products, leading to increased volatile organic components (VOCs) and the presence of low molecular weight materials that are detrimental to their performance.
Innovation Solution
A two-step process using a mineral acid catalyst followed by phosphonitrilic chloride (PNC) catalyst for hydrolyzing tetraethyl orthosilicate (TEOS) to achieve a stable ethylsilicate polymer with 50-60% SiO2 content, resulting in lower viscosity and improved viscosity stability, while minimizing low molecular weight components and VOCs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If higher hydrolysis percentage is used to increase silica content, then available SiO2 increases, but VOC emissions increase due to more alcohol by-products
Solution Approach 1:
The patent changes the chemical parameters of the hydrolysis process by using a two-stage catalytic approach with different catalysts (mineral acid followed by PNC) and controlling water addition rates, enabling achievement of 50-60% SiO2 content while managing alcohol by-product formation through optimized reaction conditions
Solution Approach 2:
The hydrolysis process is segmented into two distinct stages: first stage using mineral acid catalyst to initiate hydrolysis, second stage using PNC catalyst to complete the reaction. This segmentation allows better control over the hydrolysis rate and alcohol by-product management, enabling higher SiO2 content with reduced VOC emissions
2Quantity of substance
If more water is added to increase hydrolysis, then silica content increases, but viscosity stability decreases
Solution Approach 1:
The patent applies preliminary action by first adding mineral acid catalyst to initiate controlled hydrolysis, then subsequently adding PNC catalyst to complete the reaction. Water is added in controlled amounts during the first stage to prepare the system for the second stage, ensuring viscosity stability is maintained throughout the process while achieving high silica content
3Object-generated harmful factors
If hydrolysis is increased to reduce alcohol by-products, then VOC emissions decrease, but low molecular weight materials increase
Solution Approach 1:
The patent uses PNC catalyst as an intermediary in the second stage of hydrolysis to promote complete reaction and polymerization. This intermediary catalyst helps convert intermediate products into higher molecular weight species, reducing low molecular weight materials while maintaining controlled alcohol by-product formation through the two-stage process
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 produces a stable, flowable ethylsilicate polymer with enhanced viscosity stability and reduced VOC emissions, suitable for applications requiring higher silica content and reduced low molecular weight materials, such as MQ Resins and zinc-rich coatings, improving their performance and environmental sustainability.
Implementation Method 1
TEOS is hydrolyzed and condensed with mineral acid catalysts such as hydrochloric acid or sulfuric acid
Implementation Method 2
TEOS is mixed with sufficient alcohol to allow its reactant water to be partially miscible in the presence of an acid catalyst. This allows the initial reaction to take place where one of the ethoxy groups is replaced by a water molecule
Implementation Method 3
A two-step process using a mineral acid catalyst followed by phosphonitrilic chloride (PNC) catalyst for hydrolyzing tetraethyl orthosilicate (TEOS)
Implementation Method 4
The condensation of silanol groups derived from the hydrolysis reaction is a competing reaction in the presence of acid catalyst. This is illustrated by the following diagram: (C2H5O)3SiOH+HOSi(OC2H5)3→(C2H5O)3SiOSi(OC2H5)3+H2O
Implementation Method 5
The mixture is heated to about 72° C. and acidified water added over a period of time
Implementation Method 6
After completion of the water addition, a second catalyst step includes the addition of a condensation catalyst... and all the alcohol removed by distillation
Data Source
AI summary
A stable MQ resin solution with over 50% SiO2 and having viscosity of 50 cps at 25° C. to about 750 cps at 25° C. and which is essential free of monomer is disclosed. The stable resin solution is made by a two step addition of catalysts wherein a hydrolysis catalysts, as for example, hydrochloric acid is added initially and a second catalysts such as Phosphonitrilic chloride trimer is added subsequently.