Silane Polymer Curing Without Toxic Catalysts
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Solution Overview
Problem
Curable compositions based on silane-functional polymers often require catalysts like organometallic and acidic compounds, which can be toxic, cause unwanted coloration, corrosion, and migration issues, and are not ideal for achieving high storage stability and mechanical properties without VOC emissions.
Innovation Solution
Incorporating between 0.1 and 5 wt.% of a specific organosilane OS in a moisture-curable composition without catalytically active organometallic or acidic compounds, enabling suitable curing rates and improved mechanical properties such as tensile strength, elongation at break, and Shore A hardness, while minimizing VOC levels and avoiding methanol release.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If catalysts like organometallic and acidic compounds are used to achieve suitable curing rates, then the curing speed is improved, but toxicity, unwanted coloration, corrosion, and migration issues occur
Solution Approach 1:
The patent removes harmful catalysts (organometallic and acidic compounds) from the composition entirely, replacing them with a basic compound catalyst that eliminates toxicity, coloration, and migration issues while maintaining curing performance
Solution Approach 2:
The patent changes the chemical nature of the catalyst from acidic/organometallic to basic (using compounds like imidazoles, pyridines, or phosphazenes), fundamentally altering the catalytic mechanism to avoid harmful side effects while preserving curing rate
2Productivity
If highly reactive polymers like alpha STP polymers are used to increase reactivity, then the curing rate is improved, but considerable amounts of drying agents are required which impact VOC and mechanical properties
Solution Approach 1:
The patent modifies the polymer structure by introducing electron-donating groups in α-position to the reactive silicon atom, increasing reactivity without requiring excessive drying agents, thus avoiding VOC emissions and mechanical property degradation
Solution Approach 2:
The patent uses standard silane-functional polymers with moderate reactivity rather than highly reactive alpha polymers, eliminating the need for considerable drying agents and their associated VOC and mechanical property issues
3Reliability
If catalysts are contained in significant amounts to ensure useful curing behavior, then the curing reliability is improved, but storage stability and homogeneous curing are negatively affected due to migration
Solution Approach 1:
The patent uses a basic compound as an intermediary catalyst that can be contained in small amounts (0.01-5 wt.%) without causing migration issues, ensuring both curing reliability and storage stability through controlled catalytic activity
Solution Approach 2:
The patent changes the catalyst type to basic compounds with appropriate solubility and mobility characteristics, allowing effective curing at low concentrations without the migration problems associated with traditional catalysts
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 composition achieves excellent mechanical properties and low VOC levels, providing a stable and efficient curing process without the need for toxic catalysts, making it suitable for use as adhesives, sealants, or coatings with improved storage stability and reduced environmental impact.
Implementation Method 1
reactive silane groups, which hydrolyze under the influence of moisture, condense with one another as silanol groups and thus form siloxane bonds
Implementation Method 2
reactive silane groups, which hydrolyze under the influence of moisture, condense with one another as silanol groups and thus form siloxane bonds
Implementation Method 3
These catalysts catalyze the hydrolysis and/or the condensation of the reactive silane groups of the polymers
Data Source
AI summary
A moisture-curable composition, including at least one polymer P containing reactive silane groups; between 0.1 and 5 wt.-%, based on the total composition, of at least one organosilane OS of the formula (I), wherein R20 independently stands for a monovalent, optionally cyclic or branched, hydrocarbyl or heterocarbyl radical, optionally comprising aromatic moieties, which contains 1 to 12 carbon atoms and wherein the carbon atom next to the silicon atom either bonds via a C═C double bond to another carbon atom or bonds to a heteroatom selected from O, N, and S; R21 independently stands for a linear, cyclic, or branched divalent hydrocarbyl radical having 2 to 12 carbon atoms and optionally containing aromatic moieties; R22 stands for a hydrogen atom or a group of the formula (Ia); characterized in that the curable composition does not contain catalytically active organometallic or acidic compounds.