Twin-Screw Rubber Devulcanization for Polymer Chain Preservation
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Solution Overview
Problem
Existing devulcanization processes lead to shortening of rubber polymer chains, resulting in poorer quality of rubber mixtures, particularly in tire production.
Innovation Solution
A process involving comminuting vulcanized rubber to granular particles, extruding them in a twin-screw extruder at low shear rates and controlled temperatures, followed by cooling in a further kneading unit to maintain longer polymer chains.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high shear rates are applied during devulcanization to split sulfur-sulfur bonds, then the crosslinking is broken, but the polymer chains are shortened leading to poorer quality rubber
Solution Approach 1:
The patent applies parameter changes by controlling the shear rate within a specific range (10-100 s⁻¹) and maintaining temperature between 100-200°C during extrusion. These parameter optimizations allow effective devulcanization while preventing excessive polymer chain shortening, thus resolving the contradiction between devulcanization effectiveness and polymer chain length preservation
Solution Approach 2:
The patent replaces purely mechanical high-shear mixing with a controlled extrusion process that combines mechanical processing with thermal treatment. This substitution allows bond breaking through controlled shear forces while thermal energy prevents excessive chain scission, maintaining polymer chain length
2Reliability
If high temperatures are used during devulcanization to break crosslinks, then sulfur-sulfur bonds are split, but polymer chains are shortened and quality deteriorates
Solution Approach 1:
The patent optimizes temperature parameters to a specific range (100-200°C) during extrusion, which is sufficient to break sulfur-sulfur crosslinks but not high enough to cause excessive polymer chain scission. This parameter optimization resolves the contradiction between crosslink breaking efficiency and polymer chain integrity
Solution Approach 2:
The patent maintains continuous thermal and mechanical action during the extrusion process, ensuring that crosslinks are continuously broken while the controlled temperature prevents chain shortening. This continuous processed resolves the contradiction by sustaining effective devulcanization without compromising polymer chain integrity
3Productivity
If conventional devulcanization processes are used to reuse rubber, then material reuse is achieved, but the rubber mixture quality is poorer due to chain shortening
Solution Approach 1:
The patent changes the processing parameters (shear rate: 10-100 s⁻¹, temperature: 100-200°C) to optimize the devulcanization process. These parameter modifications enable effective rubber reuse while maintaining high mixture quality by preventing polymer chain shortening, thus resolving the contradiction between reuse capability and manufacturing precision
Solution Approach 2:
The patent replaces conventional high-shear mechanical processing with a controlled extrusion process that combines moderate shear forces with thermal treatment. This substitution enables successful rubber reuse while preserving polymer chain length and mixture quality
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 produces devulcanized rubber mixtures with improved properties, including longer polymer chains, as measured by Mooney viscosity, Shore hardness, resilience, and 300 modulus, while minimizing chain shortening.
Implementation Method 1
extruding the vulcanized rubber particles produced in step B) in a twin-screw extruder at a shear rate of less than 100 s−1
Implementation Method 2
where the temperature of the vulcanized rubber particles during extrusion is less than 200° C., to give a devulcanized rubber mixture having a temperature above 100° C.
Implementation Method 3
cooling the devulcanized rubber mixture in a further kneading unit, so as to give a devulcanized rubber mixture having a temperature in the range from 50° C. to 100° C.
Data Source
AI summary
The invention relates to a process for devulcanizing a vulcanized rubber mixture, comprising the following steps: A) providing or producing a vulcanized rubber mixture, B) comminuting the vulcanized rubber mixture to a granular material composed of vulcanized rubber particles, where the vulcanized rubber particles have a maximum particle diameter of 100 mm, C) extruding the vulcanized rubber particles produced in step B) in a twin-screw extruder at a shear rate of less than 100 s−1, where the temperature of the vulcanized rubber particles during extrusion is less than 200° C., to give a devulcanized rubber mixture having a temperature above 100° C., D) cooling the devulcanized rubber mixture in a further kneading unit, so as to give a devulcanized rubber mixture having a temperature in the range from 50° C. to 100° C. The invention further relates to an apparatus for performing the process and to the use of the apparatus for devulcanization of a vulcanized rubber mixture.