Rubber Devulcanization with Low-Shear Extrusion to Preserve Polymer Chains
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Solution Overview
Problem
Existing devulcanization methods lead to shortening of rubber polymer chains, resulting in lower quality rubber compounds and tires.
Innovation Solution
A method involving a twin-screw extruder with a shear rate less than 100 s⁻¹ and temperatures below 200 °C, combined with a single-screw extruder and/or gear pump, to devulcanize vulcanized rubber compounds, maintaining low shear rates and controlled temperatures to prevent polymer chain shortening.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high shear rate and high temperature are applied during devulcanization, then the cross-linking between rubber polymers is effectively broken, but the polymer chains are shortened leading to lower quality rubber compounds
Solution Approach 1:
The patent applies parameter changes by carefully controlling shear rate (keeping it below 100 s⁻¹) and temperature (keeping it below 200 °C) during the devulcanization process. These parameter adjustments allow effective breaking of cross-links while preventing polymer chain shortening, thus resolving the contradiction between devulcanization effectiveness and polymer chain length preservation.
Solution Approach 2:
The patent replaces traditional high-shear mechanical devulcanization methods with a controlled extrusion process that uses lower shear rates combined with thermal energy. This substitution allows achieving devulcanization without the excessive mechanical stress that causes polymer chain breakage.
2Loss of substance
If conventional devulcanization methods are used, then sulfur-sulfur compounds are separated, but polymer chains are also broken leading to shortened average chain length
Solution Approach 1:
The patent uses parameter changes by maintaining specific shear rate (<100 s⁻¹) and temperature (<200 °C) conditions during extrusion. These controlled parameters enable selective separation of sulfur-sulfur cross-links while preserving polymer chain integrity, thus achieving sulfur removal without the chain shortening that occurs in conventional high-shear methods.
3Manufacturing precision
If low shear rate and controlled temperature are maintained during extrusion, then polymer chain shortening is prevented, but the devulcanization process requires precise process control
Solution Approach 1:
The patent implements feedback control by continuously monitoring and adjusting shear rate and temperature parameters during the extrusion process. This feedback mechanism ensures that the shear rate remains below 100 s⁻¹ and temperature below 200 °C, maintaining polymer chain length while achieving effective devulcanization, thus managing the complexity through systematic control.
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 method produces devulcanized rubber compounds with longer polymer chains, exhibiting improved properties such as higher Mooney viscosity, Shore hardness, rebound elasticity, and modulus 300, 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
the temperature of the vulcanized rubber particles during extrusion is less than 200 °C
Implementation Method 3
Cooling the devulcanized rubber compound in a further kneading unit, so that a devulcanized rubber compound with a temperature in the range of 50 °C to 100 °C is produced
Data Source
Figure 1~2
Figure 3
AI summary
The invention relates to a method for the devulcanization of a vulcanized rubber mixture, comprising the following steps: A) providing or producing a vulcanized rubber mixture, B) comminuting the vulcanized rubber mixture into a granulate of vulcanized rubber particles, the vulcanized rubber particles having a maximum particle diameter of 100 mm, C) extruding the vulcanized rubber particles, which were produced in step B), in a twin-screw extruder with a shear rate of less than 100 s-1, wherein the temperature of the vulcanized rubber particles during the extrusion is smaller than 200 °C and a devulcanized rubber mixture having a temperature of more than 100 °C is obtained, D) cooling the devulcanized rubber mixture in a further kneading unit, so that a devulcanized rubber mixture having a temperature in the range from 50 °C to 100 °C is obtained. The invention also relates to a device for carrying out the method and to the use of the device for the devulcanization of a vulcanized rubber mixture.