Blocked Mercaptosilane Coupling Agents for Rubber
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Solution Overview
Problem
Existing sulfur silane coupling agents used in mineral filled elastomers suffer from high reactivity leading to premature curing, high viscosities, and odor issues, while less reactive alternatives do not achieve sufficient bonding under high stress conditions, resulting in wear and degradation of elastomeric properties.
Innovation Solution
Development of blocked mercaptosilanes with multiple mercapto groups directly linked to the silicon atom through carbon-carbon bonds, which are initially non-reactive and can be deblocked during manufacturing to form multiple linkages with organic polymers, enhancing bonding efficiency without premature curing or viscosity issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If mercaptosilane coupling agents are used to achieve high bonding reactivity with organic polymers, then bonding strength is improved, but premature curing and high viscosity occur during processing
Solution Approach 1:
The mercapto groups are blocked in advance by reacting with a blocking agent (such as epoxides or isocyanates) to form stable blocked mercaptosilanes. This preliminary blocking action prevents premature reaction during processing while allowing the silane to be pre-mixed and handled easily. The blocking groups are subsequently removed or reacted during the curing cycle to enable the desired bonding.
Solution Approach 2:
The chemical reactivity parameter of the mercaptosilane is dynamically controlled by changing its state from blocked (low reactivity) to unblocked (high reactivity). During processing, the blocked form maintains low viscosity and prevents premature curing. During curing, thermal or chemical activation transforms it to the reactive form that provides strong bonding.
2Reliability
If mercaptosilane coupling agents are used to achieve strong bonding, then coupling efficiency is improved, but odor and premature curing issues worsen
Solution Approach 1:
A blocking agent serves as an intermediary substance that temporarily masks the reactive mercapto groups. Common blocking agents include epoxides (forming beta-hydroxyethyl mercaptosilanes) or isocyanates (forming mercapto urethanes). These intermediaries prevent odor and premature curing during handling while allowing the silane to be incorporated into the rubber compound. The blocking groups are then removed or transformed during the curing process to restore bonding capability.
3Ease of manufacture
If less reactive sulfur silane coupling agents are used to avoid premature curing, then processing ease is improved, but bonding strength under high stress deteriorates
Solution Approach 1:
The silane is prepared in a blocked form during processing to ensure ease of manufacture and handling. The blocking action is a preliminary measure that is intentionally reversed or removed during the curing cycle, allowing the full bonding potential to be realized under service conditions.
Solution Approach 2:
The reactivity of the coupling agent is made dynamic rather than static. The blocked mercaptosilane transitions from a low-reactivity state during processing to a high-reactivity state during curing and service. This dynamic adjustment allows the system to optimize both processing ease and bonding strength at different stages.
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 use of blocked mercaptosilanes provides improved bonding between rubber and fillers, reducing wear and degradation under high stress conditions while avoiding processing issues like premature curing and high viscosities, resulting in better cured rubber properties such as modulus and abrasion resistance.
Implementation Method 1
blocked mercaptosilanes with multiple mercapto groups directly linked to the silicon atom through carbon-carbon bonds
Implementation Method 2
improved bonding between rubber and fillers, reducing wear and degradation under high stress conditions
Data Source
AI summary
The invention relates to sulfur silane coupling agents containing multiple blocked mercapto groups which are in a state of reduced activity until activated. The coupling agents are advantageously used in rubber formulations, for example, for fabricating tires with low rolling resistance.