Organofunctional Silane Composition with Blocked Mercaptan
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Solution Overview
Problem
Existing organosilane derivatives, such as glycol derivatives and polyether-based sulfur silanes, face issues like high viscosities, gellation, flammability risks, and volatile organic compound (VOC) emissions, which limit their effectiveness in elastomer manufacturing and tire production, particularly in improving coupling efficiency between inorganic fillers and organic polymers.
Innovation Solution
A process for creating organofunctional silane compositions with both mercaptan and blocked mercaptan functionalities through transesterification of silane reactants with polyhydroxy-containing compounds, resulting in silane dimers and oligomers with bridging dialkoxysilane groups, which reduces VOC emissions and enhances coupling efficiency while maintaining processability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If glycol derivatives of organosilanes are used, then coupling efficiency is improved, but viscosity increases and gellation occurs
Solution Approach 1:
The patent changes the chemical structure parameters of the silane derivative by using specific glycol spacers with controlled chain lengths and introducing blocked mercaptan groups that prevent premature crosslinking. This modifies the molecular architecture to reduce intermolecular interactions that cause gellation while preserving coupling functionality.
Solution Approach 2:
The mercaptan groups are blocked with protective groups during synthesis and storage, preventing premature crosslinking reactions. The blocking is removed only when needed for the coupling reaction, allowing the material to maintain low viscosity during handling and processing while providing high coupling efficiency when activated.
2Reliability
If polyether-based sulfur silanes are used, then coupling efficiency is improved, but flammability risk increases due to peroxide formation
Solution Approach 1:
The patent extracts and eliminates the polyether backbone structure that is prone to peroxide formation and flammability hazards. Instead, it uses alternative hydrocarbon-based spacers that do not contain ether linkages, thereby removing the source of peroxide formation while retaining the coupling agent functionality.
3Ease of manufacture
If blocked mercaptosilanes with monofunctional alcohol-derived groups are used, then manufacturing steps are reduced, but VOC emissions increase
Solution Approach 1:
The patent changes the parameters of the blocking groups by using specific monofunctional alcohols with higher molecular weights and lower volatility. This reduces VOC emissions during processing while maintaining the ease of manufacture advantage by keeping the blocking mechanism simple and effective.
4Reliability
If mercaptosilane level is increased to improve coupling efficiency, then scorch time decreases
Solution Approach 1:
The mercaptan groups are blocked during storage and handling, preventing premature crosslinking and scorching. The blocking is removed only when the silane is ready for use in the coupling reaction, allowing higher mercaptosilane content to be maintained without loss of scorch time control.
Solution Approach 2:
The blocking group acts as an intermediary that temporarily deactivates the mercaptan functionality. This allows the mercaptosilane to be stored and handled at higher concentrations without premature reaction, and the blocking is removed only when needed for the coupling reaction, thus decoupling concentration from reactivity timing.
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 improved coupling efficiency, reduced VOC emissions, and extended scorch times, leading to better performance in elastomeric articles like tires with reduced rolling resistance, heat buildup, and wear, while minimizing premature curing and viscosity issues.
Implementation Method 1
reacting at least one silane reactant possessing mercaptan functionality or blocked mercaptan functionality and further possessing at least one transesterifiable group with at least one polyhydroxy-containing compound under transesterification conditions
Data Source
AI summary
A process is provided for preparing organofunctional silanes, inclusive of dimers and oligomers, in which individual silanes possess both free and blocked mercaptan functionality or particular mixtures of the organofunctional silanes possess both free and blocked mercaptan functionality. The organofunctional silanes and silane mixtures are useful, inter alia, as coupling agents for elastomeric compositions, e.g., rubber formulations employed in the manufacture of tires, where they exhibit a desirable balance of low scorch and good performance properties.