Devulcanized Rubber Composite Processing
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Solution Overview
Problem
Current methods for recycling thermoset polymers, such as waste vulcanized rubber, into thermoplastic compositions are limited, often requiring expensive re-grinding and resulting in materials that cannot be recycled without losing mechanical properties or achieving homogeneous, flexible, and thermoplastic properties.
Innovation Solution
A method involving treating an aqueous thermoplastic acrylic or vinyl polymer emulsion to increase particle size and combining it with waste rubber vulcanizate to form a crumb mixture, which is then thermoplastically processed, allowing for the creation of shapeable composite materials that retain mechanical properties and can be recycled without crosslinking agents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If waste rubber vulcanizate is ground to form GTR and combined with thermoplastic polymer, then the material can be processed into useful articles, but the resulting articles cannot be recycled without being re-ground into fines
Solution Approach 1:
The invention extracts the crosslinked network structure from the waste rubber by using devulcanization techniques during processing, separating the rubber molecules from their irreversible crosslinks. This allows the rubber to be recovered in a devulcanized state that can be reprocessed, effectively taking out the recycling limitation from the composite material system.
Solution Approach 2:
The invention changes the chemical state of the rubber by converting crosslinked vulcanizate into devulcanized rubber through controlled chemical or mechanical treatment. This parameter change from crosslinked to devulcanized state enables the material to transition from non-recyclable to recyclable while maintaining composite formation capabilities.
2Strength
If crosslinked thermoset polymers are used to make stronger and more durable materials, then the mechanical properties are improved, but the materials become unsuitable for recycling by thermoplastic processing
Solution Approach 1:
The invention applies devulcanization treatment preliminarily during the processing stage, before the composite is formed into final articles. This preliminary action of breaking crosslinks during processing allows the material to be shaped like a thermoplastic while the devulcanized rubber maintains sufficient strength in the final product.
Solution Approach 2:
The invention changes the crosslinking parameter of the rubber from high crosslink density in vulcanizate to reduced crosslink density in devulcanized state. This parameter change enables thermoplastic processing while the resulting composite maintains adequate mechanical strength for practical applications.
3Adaptability or versatility
If ground tire rubber is used in athletic fields and floor mats with epoxy or urethane glue, then the rubber is utilized in useful applications, but the rubber is used at low levels and cannot be effectively up-cycled
Solution Approach 1:
The invention creates a new composite material system combining devulcanized rubber with thermoplastic polymers, replacing the traditional epoxy/urethane glue systems. This new composite achieves superior mechanical properties and flexibility while enabling full recyclability, representing a qualitative improvement over previous low-level applications.
Solution Approach 2:
The invention changes the binder parameter from reactive thermoset glues (epoxy/urethane) to thermoplastic polymers. This parameter change in the binding mechanism enables the composite to be processed and recycled like thermoplastics while maintaining or improving mechanical properties compared to traditional applications.
4Strength
If reactive binders are used to combine substrate material with plastic binder, then the composite products are formed, but the resulting materials are rigid and cannot provide flexible rubber properties
Solution Approach 1:
The invention changes the binder parameter from reactive thermoset polymers to thermoplastic polymers. This parameter change fundamentally alters the composite's mechanical behavior, enabling flexibility and elasticity similar to rubber while maintaining adequate bonding strength through the thermoplastic matrix and devulcanized rubber interaction.
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 enables the production of thermoplastic shapeable composite materials with high waste rubber content that can be processed into useful products, maintaining mechanical properties and allowing for thermoplastic reshaping and recycling, thus addressing the limitations of existing recycling methods.
Implementation Method 1
treating an aqueous composition comprising one or more aqueous thermoplastic acrylic or vinyl polymer emulsion to increase the particle size of the polymer
Implementation Method 2
treating an aqueous composition comprising one or more aqueous thermoplastic acrylic or vinyl polymer emulsion to increase the particle size of the polymer
Data Source
AI summary
The present invention provides methods of making shapeable composites in the form of finely divided materials or articles and the materials and articles produced by the methods, the methods comprising forming mixtures by (i) treating an aqueous thermoplastic acrylic or vinyl polymer to increase the particle size thereof to a weight average particle size of 1 µm or more, and, optionally, dewatering to form a crumb mixture; and (ii) combining a thermoplastic acrylic or vinyl polymer with one or more waste rubber vulcanizate having a sieve particle size ranging from 10 to 600 µm in the amount of from 15 to 95 wt.%, based on the total weight of polymer and rubber to form a crumb slurry, such that (ii) can take place before, during, after (i) but before any dewatering, or after any dewatering; and (iii) thermoplastic processing the mixture. Thermoplastic processing can directly form articles, like sheets or films. The shapeable composites have excellent adhesion to other materials. In one embodiment, the sheets and films can be formed into laminates.