Scavenger-Assisted EPDM Devulcanization in Extruders
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Solution Overview
Problem
Existing devulcanization processes for sulfur-cured EPDM rubber face challenges due to the degradation of equipment caused by sulfur and sulfur-bearing species, which limits the effectiveness and longevity of recycled rubber products, particularly in roofing membranes, as they cannot be reincorporated into new rubber matrices without losing physical properties.
Innovation Solution
A thermo-mechanical devulcanization process involving the use of a scavenging agent within an extruder to remove sulfur and sulfur-bearing species, combined with the use of degradation-resistant metals in extruder components, allowing for partial devulcanization and recycling of sulfur-cured EPDM rubber while maintaining its physical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If sulfur-cured EPDM rubber is mechanically ground and recycled, then the rubber can be physically processed into small pieces, but the recycled rubber remains vulcanized and cannot successfully interact with the rubber matrix of new roofing membranes
Solution Approach 1:
The patent applies chemical devulcanization agents (such as amines, thiols, or metal complexes) to change the chemical state of the vulcanized rubber, breaking the crosslinks and converting the material from a thermosetting state to a thermoplastic state, enabling it to be reprocessed and reincorporated into new rubber matrices
Solution Approach 2:
The patent introduces chemical devulcanization agents as intermediaries that facilitate the breakdown of sulfur crosslinks in the rubber. These agents act as mediators between the vulcanized rubber and the devulcanization process, enabling the transformation without directly modifying the rubber structure
2Productivity
If chemical devulcanization is used to devulcanize EPDM rubber, then the rubber can be processed for recycling, but sulfur and sulfur-bearing species degrade the equipment and limit the effectiveness of recycled rubber products
Solution Approach 1:
The patent converts the harmful sulfur by-products into beneficial removal targets by using scavenging agents that specifically bind to and remove sulfur and sulfur-bearing species. The harmful sulfur that causes equipment degradation is transformed into a removable contaminant that can be selectively eliminated
Solution Approach 2:
The patent extracts harmful sulfur and sulfur-bearing species from the devulcanization process by introducing scavenging agents that selectively bind and remove these contaminants, separating them from the recycled rubber material to prevent equipment degradation
3Productivity
If ground rubber particles are mixed with virgin polymers, then the ground rubber can be incorporated into new products, but the ground rubber remains phase separated and cannot become incorporated into the rubber matrix upon curing
Solution Approach 1:
The patent changes the physical and chemical parameters of the ground rubber through devulcanization, transforming it from a vulcanized thermosetting material to a thermoplastic material that can mix homogeneously with virgin polymers and become incorporated into the rubber matrix during curing
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 effectively devulcanizes sulfur-cured EPDM rubber, enabling the reuse of recycled materials in new roofing membranes that meet performance standards, with retained physical properties even after heat aging, such as high tensile strength and tear resistance retention.
Implementation Method 1
introducing from about 0.5 to about 20 wt % scavenging agent, based upon the total weight of the EPDM and scavenging agent
Implementation Method 2
mixing and masticating the EPDM at a temperature sufficient to at least partially devulcanize the sulfur-cured EPDM
Implementation Method 3
mixing and masticating the EPDM
Data Source
AI summary
A process for devulcanizing EPDM rubber comprising the step of introducing sulfur-cured EPDM to an extruder, introducing from about 0.5 to about 20 wt % scavenging agent, based upon the total weight of the EPDM and scavenging agent, and mixing and masticating the EPDM at a temperature sufficient to at least partially devulcanize the sulfur-cured EPDM.