Hydrosiloxane Composition with Dicationic Phosphonium for Heat Curing
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Solution Overview
Problem
Existing curable systems with Si—H and siloxane linkages require a two-part system for storage due to rapid rearrangement reactions in the presence of strong Lewis acids, necessitating a solution for a shelf-stable one-component system that can be triggered to cure with heating.
Innovation Solution
A polyorganohydrogensiloxane composition comprising a tetravalent dicationic phosphonium salt catalyst and a polyorganohydrogensiloxane, which can be stored stably at room temperature and cured by heating, eliminating the need for a separate Lewis acid catalyst.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a strong Lewis acid catalyst is used to catalyze the rearrangement reaction between Si-H and siloxane linkages, then the curing reaction proceeds rapidly, but the system becomes unstable at room temperature and requires a two-part system for storage
Solution Approach 1:
The patent modifies the catalyst's thermal properties by selecting specific Lewis acid catalysts with appropriate thermal stability. The catalyst is chosen to remain stable at room temperature during storage but become active upon heating, enabling rapid curing only when needed. This parameter change in thermal stability allows a single-component system to maintain both storage stability and curing speed.
Solution Approach 2:
The patent incorporates the Lewis acid catalyst directly into the one-component system in an inactive or stable form during storage. The catalyst is pre-positioned in the system but remains dormant until heating is applied, at which point it activates the rearrangement reaction between Si-H and siloxane linkages. This preliminary preparation eliminates the need for separate catalyst containers while maintaining stability during storage.
2Stability of the object's composition
If a two-part system is used to store the Lewis acid catalyst separately from Si-H and siloxane linkages, then the system remains stable during storage, but the device complexity increases and requires additional components
Solution Approach 1:
The patent merges the Lewis acid catalyst with the Si-H and siloxane linkage components into a single unified system. The catalyst is incorporated directly into the one-component formulation, eliminating the need for separate storage containers or additional parts. This merging maintains stability during storage through careful catalyst selection while simplifying the overall system architecture.
3Productivity
If the rearrangement reaction is triggered rapidly at room temperature, then curing occurs quickly, but the system loses shelf stability and requires constant monitoring
Solution Approach 1:
The patent introduces thermal activation as a dynamic control mechanism for the curing reaction. The system remains static and stable at room temperature during storage, but upon heating, the reaction becomes dynamically active and proceeds rapidly to completion. This dynamic transition from stable to active state provides both shelf stability and rapid curing capability without constant monitoring.
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 remains shelf-stable at room temperature and can be effectively cured by heating, suitable for applications such as coatings, adhesives, and foams without the need for additional stabilizing agents.
Implementation Method 1
Silyl hydride (Si—H) and siloxane linkages (Si—O—Si) have been found to undergo a rearrangement reaction in the presence of a strong Lewis acid
Implementation Method 2
it can be triggered with heating to cure
Data Source
AI summary
A composition contains a phosphonium catalyst and a polyorganohydrogensiloxane. The composition is curable in a method including heating. The composition and method are useful for preparing polyorganosiloxane products such as coatings, adhesives, elastomers, and foams.