Mercaptofunctional Silane Transesterification for Scorch and VOC Control
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Solution Overview
Problem
Existing organofunctional silanes used in filled elastomers are reactive, leading to short scorch times and poor filler dispersion, and generate volatile organic compounds (VOCs), while glycol derivatives tend to form high viscosity compounds and cyclic structures, limiting their usefulness in elastomer manufacture.
Innovation Solution
A process involving the transesterification of mercaptofunctional silanes with hydrocarbylsilanes and polyhydroxy-containing compounds to produce silane compositions with bridging dialkoxysilyl groups, which contain both mercaptan and hydrocarbyl functionalities, improving scorch times and reducing VOC emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If mercaptosilanes are used at levels necessary to achieve optimum coupling of filler to polymer, then coupling performance is improved, but scorch time decreases and filler dispersion deteriorates
Solution Approach 1:
The invention segments the mercaptosilane molecule into two distinct parts: a blocked mercaptan group (for controlled coupling) and a polysulfide group (for extended scorch time). This segmentation allows each functional group to perform its specific function independently, resolving the contradiction between achieving optimum coupling and maintaining adequate scorch time.
Solution Approach 2:
The invention changes the chemical structure parameters of the silane by introducing polysulfide linkages between silicon atoms. This structural modification increases the molecular weight and alters the reactivity profile, thereby extending scorch time while preserving coupling effectiveness through the blocked mercaptan groups.
2Reliability
If mercaptosilanes are used at levels necessary to achieve optimum coupling of filler to polymer, then coupling performance is improved, but filler dispersion deteriorates
Solution Approach 1:
The segmented structure with blocked mercaptan groups provides controlled reactivity that prevents premature crosslinking, allowing sufficient time for uniform filler dispersion throughout the polymer matrix before coupling occurs, thus resolving the dispersion issue while maintaining coupling performance.
3Object-generated harmful factors
If glycol derivatives of organosilanes are used, then VOC emissions are reduced, but viscosity increases and gellation occurs
Solution Approach 1:
The invention changes the molecular architecture by introducing polysulfide bridges between silane units, creating a controlled oligomeric structure that increases molecular weight without the excessive viscosity and gellation problems associated with glycol derivatives. This structural parameter change maintains low VOC emissions while controlling viscosity.
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 compositions exhibit longer scorch times and better filler dispersion, enhancing the performance of cured articles like tires by reducing rolling resistance and heat build-up, while minimizing VOC emissions.
Implementation Method 1
A process involving the transesterification of mercaptofunctional silanes with hydrocarbylsilanes and polyhydroxy-containing compounds to produce silane compositions with bridging dialkoxysilyl groups
Data Source
AI summary
The disclosure herein relates to organofunctional silanes and mixtures of organofunctional silanes possessing mercaptan and hydrocarbyl and/or heterocarbyl functionality. These silanes reduce or eliminate the generation of volatile organic compounds (VOC's) during use, aid in the processing of filled elastomeric materials and enhance the end-use properties of the filled elastomer. The present disclosure relates to the processes of making a composition of these silanes.