Multi-Stage Screw Extruder for Continuous Reclaimed Rubber Devulcanization
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Solution Overview
Problem
Existing methods for preparing reclaimed rubber face challenges such as uneven devulcanization, high energy consumption, and poor mechanical properties due to the formation of 'core-shell' structures, which are difficult to overcome using traditional bond energy or elastic coefficient mechanisms.
Innovation Solution
A continuous method using multi-stage screw extruders, where waste rubber powder is mixed with a softener and devulcanizing agent, undergoing preliminary devulcanization in a counter-rotating twin screw extruder, followed by devulcanization and refinement in subsequent extruders under controlled temperature and shear conditions, ensuring uniform penetration and minimizing oxygen exposure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If traditional high temperature and pressure dynamic desulfurization tank is used, then desulfurization can be achieved, but uniform devulcanization cannot be achieved due to outside-in permeation causing core-shell structure
Solution Approach 1:
The patent divides the devulcanization process into multiple stages using a multi-stage screw extruder system. The extruder is segmented into different zones (heating zone, reaction zone, cooling zone) with distinct temperature and shear conditions, allowing progressive and uniform devulcanization from multiple directions simultaneously, preventing core-shell structure formation.
Solution Approach 2:
Instead of outside-in permeation as in traditional tanks, the patent uses intensive shear stress from counter-rotating screws to break crosslinks throughout the material volume simultaneously. The devulcanization proceeds through mechanical action rather than diffusion, effectively inverting the permeation direction and mechanism.
2Ease of operation
If multiple high-speed double roller mills are used for refinement, then processing property can be improved, but safety risk increases due to high-speed operation
Solution Approach 1:
The patent replaces the high-speed mechanical refinement system (double roller mills) with a controlled shear system using counter-rotating and co-rotating screw extruders. The shear stress is generated through screw rotation and material drag, providing refinement at lower speeds with inherent safety while maintaining processing property improvement.
3Device complexity
If intermittent batch operation is used, then equipment simplicity is maintained, but productivity decreases due to inefficiency and scaling issues
Solution Approach 1:
The patent implements continuous operation of the multi-stage screw extruder system, where waste rubber powder continuously feeds through heating, devulcanization, and cooling zones without interruption. This eliminates idle time between batches and prevents scaling accumulation, maintaining equipment simplicity while dramatically improving productivity through continuous processing.
4Strength
If low devulcanization degree is used to avoid mechanical property deterioration, then mechanical properties are preserved, but energy consumption increases
Solution Approach 1:
The patent changes multiple parameters simultaneously: uses counter-rotating screws for intensive shear, implements multi-stage temperature control, and adjusts residence time. These parameter changes enable complete devulcanization (breaking S-S and C-S bonds) while maintaining mechanical properties through controlled shear that selectively breaks crosslinks without degrading the polymer backbone, reducing energy consumption by avoiding excessive processing.
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
This approach results in reclaimed rubber with improved mechanical properties, reduced energy consumption, and stable production, avoiding 'core-shell' structures and ensuring safety and environmental protection.
Implementation Method 1
uniform penetration of softener into the waste rubber powder
Implementation Method 2
forms S—S and C—S bond to connect linear macromolecule chains and generates crosslinked network
Implementation Method 3
breaks crosslinking network and makes it quasi-linearized
Implementation Method 4
The elastic coefficient between chemical bonds is different; thus, the C—C bonds, C—S bonds and S—S bonds can be selectively broken by shear stress
Implementation Method 5
control the temperature of barrel and mandrel of the multi-stage screw extruder
Implementation Method 6
cool the devulcanized rubber powder to 25° C. to 60° C. under airtight conditions in continuous cooling apparatus
Data Source
AI summary
The invention relates to a method of preparing reclaimed rubber, especially using multi-stage screw extruders, which belongs to the field of recycling and reusing of waste rubber. The rubber powder and softener which were preliminarily mixed are compacted and added into first counter rotating twin screw extruder through thermal insulation and metering apparatus, the softener permeates the waste rubber powder uniformly under the action of temperature in the extruder to finish primary desulfurization of rubber waste powder; add preliminary devulcanized material continuously into second multi screw extruder after cooling by transformation device, rapid desulfurization and regeneration can be achieved by means of activator and shear action; The desulfurized rubber powder is cooled and transported into the third multi-screw extruder in series, the performance of deprocessing can be improved by shear action under low temperature; After extrusion, the recycled rubber is obtained by molding device and cooling device. The whole process is completed under closed oxygen isolation condition, realizing safe, simple and continuous desulfurization regeneration. It is energy saving and environmental protection with excellent properties.