Devulcanized Rubber Mixture via Twin-Screw Extrusion

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Solution Overview

Problem

Existing devulcanization processes for vulcanized rubber result in the breaking of both sulfur-sulfur bonds and C—C bonds, leading to shorter polymer chains and poorer quality rubber products with reduced breaking elongation and accelerated aging, necessitating a method to preserve chain length and improve resilience.

Innovation Solution

A process involving the use of a twin-screw extruder with a regeneration reagent comprising silane, plasticizer, and aging stabilizer to devulcanize vulcanized rubber, which prevents chain shortening and enhances the properties of the resulting rubber mixture, including improved breaking elongation and extended product lifespan.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If conventional devulcanization processes are used to break sulfur-sulfur bonds in vulcanized rubber, then the crosslinking is split and rubber polymers can be recrosslinked, but the C—C bonds of the polymer chains are also broken leading to shorter average chain length and lower breaking elongation

Engineering Contradiction:
Improvecrosslinking structureVSAvoidbreaking elongation
Core Design Contradiction:
Stability of the object's compositionVSStrength

Solution Approach 1:

The patent applies parameter changes by controlling the devulcanization process conditions (temperature, time, mechanical energy input) to selectively break sulfur-sulfur bonds while preserving C—C bonds. The process parameters are optimized to achieve devulcanization without excessive chain scission, thereby maintaining polymer chain length and breaking elongation properties.

Inventive Principle:
Principle #35Parameter changes

2Ease of manufacture

If high shear rate mechanical treatment is applied to achieve non-degrading treatment of kneaded rubber, then mechanical processing is improved, but polymer chain shortening occurs leading to poorer quality rubber mixtures

Engineering Contradiction:
Improvemechanical processingVSAvoidrubber mixture quality
Core Design Contradiction:
Ease of manufactureVSReliability

Solution Approach 1:

The patent applies partial action by using controlled shear rates that are sufficient to achieve the desired mechanical processing and devulcanization effects without exceeding the threshold that causes excessive polymer chain scission. The mechanical energy input is carefully dosed to achieve the necessary processing without degradation.

Inventive Principle:
Principle #16Partial or excessive action

3Productivity

If devulcanized rubber is produced using prior art methods, then post-consumer rubber can be reused, but the resulting rubber articles exhibit faster aging compared to references

Engineering Contradiction:
Improverubber reuse efficiencyVSAvoidservice life
Core Design Contradiction:
ProductivityVSDuration of action of stationary object

Solution Approach 1:

The patent introduces an intermediary substance during the devulcanization process that protects polymer chains from excessive scission and maintains their integrity. This intermediary enables the devulcanization of post-consumer rubber while preserving the molecular structure, thereby extending the service life of the resulting rubber articles.

Inventive Principle:
Principle #24Intermediary (Mediator)

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 a devulcanized rubber mixture with improved processability and longer lifespan, characterized by reduced Mooney viscosity and enhanced breaking elongation, effectively addressing the limitations of prior art by maintaining polymer chain length and stability.

Implementation Method 1

the one devulcanization process consists of applying shear stress to the vulcanized rubber particles

Methodology Applied
Scientific EffectShear stress: Shear Stress

Implementation Method 2

wherein during the extruding in step C) at least one regeneration reagent is added to the extruded rubber particles, wherein the one regeneration reagent comprises at least one silane, at least one plasticizer, at least one aging stabilizer or mixtures thereof

Methodology Applied
Scientific EffectChemical protection:

Data Source

PatentUS20230212369A1Method for the devulcanisation of a vulcanisaed rubber mixture, device for carrying out the method, as well as a rubber mixture and vehicle pneumatic tyre, comprising a component made of the rubber mixture
Publication Date: 2023.07.06 CONTINENTAL REIFEN DEUTSCHLAND GMBH

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 into a granulate of vulcanized rubber particles, C) extruding the vulcanized rubber particles produced in step B) in a twin-screw extruder to form a devulcanized rubber mixture, wherein, during the extruding in step C) at least one regeneration reagent is added to the extruded rubber particles, wherein the regeneration reagent comprises at least one silane, at least one plasticizer, at least one aging stabilizer or mixtures thereof. The invention also comprises an apparatus for performing the method and the uses of the apparatus, and a rubber mixture and also a pneumatic vehicle tyre or a technical rubber article comprising a component composed of the rubber mixture.