Silica-Coupled Rubber Composition Mixing to Prevent Premature Vulcanization
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Solution Overview
Problem
Existing rubber compositions with highly saturated diene elastomers face premature vulcanization issues during thermomechanical mixing, leading to increased viscosity and difficulty in industrial processing, which compromises the deformability and rolling resistance required for tire treads.
Innovation Solution
A two-step process involving high-temperature mixing of highly saturated diene elastomers with a reinforcing filler and a silane coupling agent, followed by low-temperature incorporation of sulfur and a sulfenamide, using a dithiocarbamate as a secondary accelerator, to prevent premature vulcanization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If sulfur and accelerators are introduced at high temperature during thermomechanical mixing, then the vulcanization reaction is accelerated, but premature vulcanization occurs leading to increased viscosity and processing difficulties
Solution Approach 1:
The silane coupling agent is introduced during the first high-temperature mixing phase along with the elastomer and filler, but the actual vulcanization crosslinking is delayed until the second phase when sulfur and accelerators are added at lower temperatures. This preliminary placement of the coupling agent prepares the system for subsequent vulcanization without triggering it prematurely.
Solution Approach 2:
The mixing process is divided into two distinct phases: a first phase for thermomechanical mixing of elastomer, filler, and silane coupling agent at high temperature, and a second phase for incorporating sulfur and accelerators at lower temperature. This segmentation allows each phase to perform its specific function without causing premature vulcanization or processing difficulties.
2Ease of manufacture
If sulfur and accelerators are introduced at low temperature, then premature vulcanization is prevented, but the vulcanization reaction rate is reduced
Solution Approach 1:
The silane coupling agent is pre-introduced during high-temperature mixing to prepare the system, then sulfur and accelerators are added at lower temperatures to initiate controlled vulcanization. This preliminary preparation allows the subsequent low-temperature vulcanization to proceed effectively without premature reaction.
Solution Approach 2:
The process utilizes changes in temperature parameters between two phases: high temperature (130-180°C) in the first phase for mixing, and lower temperature (below 110°C) in the second phase for vulcanization. This parameter change enables prevention of premature vulcanization while maintaining acceptable reaction rates.
3Productivity
If high temperature mixing is used for thermomechanical processing, then mixing efficiency is improved, but premature vulcanization is triggered
Solution Approach 1:
The mixing process is segmented into two phases: first phase at high temperature (130-180°C) for efficient thermomechanical mixing of elastomer, filler, and silane coupling agent without sulfur or accelerators; second phase at lower temperature (below 110°C) for incorporating vulcanization system. This segmentation maintains mixing efficiency while ensuring vulcanization control.
Solution Approach 2:
The sulfur and accelerator components are extracted from the first mixing phase and introduced only in the second phase at lower temperatures. This extraction prevents these components from triggering premature vulcanization during high-temperature thermomechanical mixing, while still allowing them to function effectively in the second phase.
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 process maintains the deformability and reduces hysteresis of rubber compositions, enhancing their suitability for tire treads without compromising industrial processing.
Implementation Method 1
a silane coupling agent
Implementation Method 2
using a dithiocarbamate as a secondary accelerator
Implementation Method 3
incorporation of sulfur and a sulfenamide
Data Source
AI summary
The invention relates to a method for preparing a rubber composition which comprises more than 50 phr of a highly saturated diene elastomer, a reinforcing filler comprising silica and a silane coupling agent, the diene elastomer being a copolymer containing at least 50 mol.% of ethylene units and units of a 1,3-diene of formula CH2=CR-CH=CH2, symbol R representing a hydrocarbon chain having 3 to 20 carbon atoms. The method comprises mixing the diene elastomer, the reinforcing filler and the coupling agent with a secondary dithiocarbamate accelerator by kneading at a temperature of greater than 110°C, then incorporating sulfur and a sulfenamide into the rubber composition by kneading at a temperature of less than 110°C. A tyre containing a rubber composition thus obtained in its tread has an improved compromise between rolling resistance and grip properties.