Silane-Terminated Polymer Synthesis Without Tin Catalysts
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Solution Overview
Problem
Existing methods for preparing silane-terminated polymers often result in storage instability due to the use of tin catalysts, which degrade the polymer backbone and reduce mechanical properties over time, especially when exposed to high temperatures.
Innovation Solution
A process is developed where silane-terminated polymers are synthesized without tin catalysts, using hydroxy-terminated organic polymers reacted with isocyanates and alkoxysilanes in the presence of titanium-containing organometallic compounds, ensuring both reactants and the reaction are free from tin catalysts to maintain polymer stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If tin catalysts are used to accelerate the reaction of hydroxyl-functional polymers with isocyanates, then reaction rate is improved, but storage stability deteriorates due to transesterification of the polyester backbone
Solution Approach 1:
The patent removes the harmful tin catalyst from the reaction system and replaces it with alternative catalysts (such as organometallic compounds containing lead, bismuth, or zinc) that do not cause transesterification of the polyester backbone, thereby eliminating the source of storage instability while maintaining acceptable reaction rates
Solution Approach 2:
The patent changes the chemical parameter of the catalyst from tin-based to alternative metal-based catalysts, which fundamentally alters the reaction mechanism to avoid backbone degradation while still providing catalytic acceleration
2Productivity
If tin catalysts are used in the preparation of silane-terminated polymers, then reaction efficiency is improved, but mechanical properties deteriorate over time due to polymer backbone degradation
Solution Approach 1:
The patent extracts and eliminates the tin catalyst from the synthesis process, replacing it with alternative catalysts that do not degrade the polymer backbone, thereby preserving mechanical properties while maintaining reaction efficiency
Solution Approach 2:
The patent converts the harmful effect of catalysts (which were previously used to accelerate reactions) into a beneficial approach by selecting catalysts that accelerate the reaction without causing backbone degradation, thus turning a potential harm into a net benefit for both reaction efficiency and product stability
3Productivity
If organotin compounds are used to prepare hydroxyl-functional prepolymer and cap the polyester polyol, then reaction acceleration is achieved, but storage stability deteriorates due to transesterification
Solution Approach 1:
The patent removes organotin compounds from the reaction system and replaces them with alternative catalysts that do not promote transesterification, thereby maintaining reaction acceleration while preserving storage stability
Solution Approach 2:
The patent introduces alternative intermediary catalysts (lead, bismuth, zinc-based compounds) that mediate the reaction between hydroxyl-functional polymers and isocyanates without causing the harmful transesterification side reactions associated with tin 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 resulting silane-terminated polymers exhibit excellent storage stability, maintaining mechanical properties like Shore A hardness and tensile strength for several months, even at elevated temperatures, without the degradation issues associated with tin catalysts.
Implementation Method 1
The reaction is carried out in the presence of a catalyst. In the compounds of the general formulae I and II, the reaction is carried out in the presence of a catalyst which is free from tin.
Implementation Method 2
a) reacting a hydroxy-terminated organic polymer of the formula (III) with an isocyanate of the formula (IV)
Implementation Method 3
b) reacting a hydroxy-terminated organic polymer of the formula (III) with a multi-functional isocyanate of the formula (V) and subsequent reaction with an alkoxysilane of the formula (VI)
Data Source
AI summary
A process for preparing a storage-stable silane-terminated polymer of formula (I) or (II)where D is linear or branched hydrocarbon group, A is polymer backbone selected from group, R1, R1′, R2 and R2′ are each linear, branched or cyclic hydrocarbon radical having 1 to 10 carbon atoms, n is 1, 2 or 3, x and y are natural numbers between 1 and 10, G is linear or branched hydrocarbon group having 1 to 20 hydrocarbon atoms, F is linear, branched or cyclic organic radical containing no isocyanate-reactive groups, m is natural number greater than 1, E is reactive group reacting with isocyanate group and selected from group consisting of NH2, NHR4 and SH, and R4 is linear, branched or cyclic hydrocarbon radical having 1 to 10 carbon atoms.