Inhibited Tin Catalysts for Silicone Command Cure
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Solution Overview
Problem
Existing curable silicone compositions have a short open pot life due to rapid curing, which restricts manufacturing processes and are not stable under heat, fire, or weather conditions, and are costly when using addition cure chemistry.
Innovation Solution
Inhibited tin or titanate catalysts are used in condensation cure systems to achieve a command cure with a long open pot life, which are deactivated at room temperature but activate upon heating, providing a cost-effective solution with improved stability and adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional tin or titanate catalysts are used in condensation cure systems, then rapid curing is achieved, but the open pot life becomes very short
Solution Approach 1:
The catalyst is pre-inhibited by complexing with compounds containing active hydrogen (alcohols, carboxylic acids, water, amines, mercaptans) before use. This preliminary inhibition action prevents the catalyst from being active during storage and handling, extending open pot life while maintaining the ability to cure rapidly when needed.
Solution Approach 2:
Compounds containing active hydrogen serve as intermediary substances that temporarily bind to the catalyst, deactivating it during storage. These intermediaries can be removed or deactivated to release the catalyst's activity when curing is required, thus mediating between the need for long storage stability and rapid curing.
2Productivity
If conventional tin catalysts are used, then rapid crosslinking is achieved, but the catalyst remains active and catalyzes reversal reactions under heat, fire, or weather conditions
Solution Approach 1:
The catalyst system parameters are changed by introducing inhibition through complexing agents. This modifies the catalyst's activity state from permanently active to conditionally active, making it stable under various environmental conditions while maintaining crosslinking capability when needed.
Solution Approach 2:
The inhibited catalyst system uses up the inhibition capacity of compounds containing active hydrogen during storage, and once these are consumed or deactivated, the catalyst becomes active for curing. After curing, the catalyst is effectively depleted or deactivated, preventing reversal reactions under extreme conditions.
3Loss of time
If addition cure chemistry with inhibited platinum catalysts is used to achieve command cure, then long open pot life is achieved, but the product cost increases significantly
Solution Approach 1:
The patent replaces expensive inhibited platinum catalysts with cheaper tin or titanate catalysts that are inhibited by compounds containing active hydrogen. This substitution maintains the command cure functionality and long open pot life while significantly reducing material costs.
Solution Approach 2:
The catalyst type parameter is changed from precious metal (platinum) to base metal (tin or titanate), and the inhibition mechanism is changed from proprietary inhibited catalysts to compounds containing active hydrogen. This parameter change achieves similar functional results at lower cost.
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 inhibited catalysts extend the pot life to several days or months when protected from moisture and ensure a fast cure upon activation, resulting in a stable and cost-effective silicone composition suitable for various applications, including coatings and sealants, with enhanced heat, fire, and weather resistance.
Implementation Method 1
They cure through condensation of the silanol end groups on the silicone polymer with water as the by-product
Implementation Method 2
These reactions are often catalyzed by metal complexes, most commonly tin and titanate complexes such as dibutyltindilaurate and tetrabutyltitanate
Implementation Method 3
Some existing condensation catalysts, like tin and titanate compounds, cure so well at room temperature that they have very short use times... It is desirable to have a system where the materials can be open to the air, applied to the surface of a substrate and then the cure mechanism is triggered
Implementation Method 4
Inhibited tin or titanate catalysts are used in condensation cure systems to achieve a command cure with a long open pot life, which are deactivated at room temperature but activate upon heating
Data Source
AI summary
Inhibited tin or titanate catalysts are used in condensation cures of silicone materials. Such catalysts are command cure systems with long open pot life, yet have relatively fast cure when the cure mechanism is triggered. This combines the advantages of the inhibited addition cure systems (command cure) with the advantages of the condensation cure systems (lower cost).