Silane-Terminated Polymer Production Using Bismuth Catalyst
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Solution Overview
Problem
The use of traditional catalysts in producing silane-terminated polymers results in storage stability issues and handling complications due to their residual presence in the end product, which can catalyze reactions with moisture, leading to impaired stability and increased effort in drying polyols to avoid secondary reactions.
Innovation Solution
A method involving the reaction of hydroxy-functional polymers with isocyanate-containing compounds in the presence of a bismuth-containing catalyst, where the reaction mixture maintains a water content of 50 to 250 ppm, allowing for reduced catalyst concentrations and potentially eliminating the need for extensive drying, thereby enhancing reaction efficiency and product stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional catalysts are used to produce silane-terminated polymers, then high reaction rates are achieved, but storage stability deteriorates due to residual catalyst promoting moisture-induced condensation
Solution Approach 1:
The harmful residual catalyst is removed from the system by using a water-soluble catalyst that can be extracted with water after the reaction, leaving the organic silane-terminated polymer free of catalyst residues that would otherwise promote unwanted moisture-induced condensation during storage
Solution Approach 2:
A phase transfer catalyst is introduced as an intermediary substance that enables the water-soluble inorganic base catalyst to effectively catalyze the reaction between hydroxy-functional polymers and isocyanate-functional silanes while allowing the catalyst to remain in the aqueous phase and be easily removed, thus maintaining high reaction rates without compromising storage stability
2Manufacturing precision
If polyols are extensively dried to avoid secondary reactions with water, then product purity is improved, but process complexity and time increase
Solution Approach 1:
The previously harmful effect of water (causing secondary reactions and requiring extensive drying) is converted into a beneficial feature by using a water-soluble catalyst system where water is part of the reaction medium and catalyst delivery system, eliminating the need for extensive drying while maintaining product purity
Solution Approach 2:
The water content parameter in the reaction mixture is changed from being minimized (trace amounts only) to being present at significant levels (as the reaction medium), fundamentally altering the process requirements and eliminating complex drying steps while maintaining product quality
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 simplifies the production process, maintains high reaction rates with low catalyst concentrations, and results in silane-terminated polymers with improved storage stability and reduced moisture reactivity, facilitating easier handling and processing.
Implementation Method 1
reacting at least one hydroxy-functional polymer (a) with at least one compound having at least one isocyanate group, in the presence of at least one bismuth-containing catalyst (K)
Implementation Method 2
these have high catalytic activity for accelerating the reaction of hydroxy-functional polymers with isocyanates, but at the same time only comparatively weakly catalyze the hydrolysis and condensation of silane groups
Data Source
AI summary
Silane-terminated polymers of the formula (I)Y—[Z—C(═O)—NR3—(CR12)b—SiRa(OR2)3-a]x (I),are produced by reacting at least one hydroxy-functional polymer (a), comprising at least one polyether, polyester and/or polyacrylate unit, with at least one compound having at least one isocyanate group, in the presence of at least one bismuth-containing catalyst (K), with the proviso that the reaction mixture comprises 50 to 250 ppm water at the start of the reaction.