Rubber Devulcanization Using P-Phenylene Diamine Agents
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Solution Overview
Problem
Existing devulcanization methods for rubber vulcanizates result in poor properties due to structural changes from severe shear and high temperatures, and are not commercially viable due to odor issues from sulfur-containing devulcanizing agents.
Innovation Solution
A method using p-phenylene diamine compounds as devulcanizing agents, with minimal organosulfur content, at temperatures between 170°C and 280°C, and optionally with swelling agents, to break sulfur-containing cross-links without significant polymer chain scission or odor production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If intensive physical forces and high temperature are applied in devulcanization methods, then crosslink scission is achieved, but polymer chain breakage occurs causing poor properties
Solution Approach 1:
The invention changes the chemical parameter of the devulcanizing agent from traditional organosulfur compounds to p-phenylene diamine compounds, which fundamentally alters the devulcanization mechanism. This parameter change enables effective crosslink scission through a different chemical pathway that does not rely on intensive physical forces and high temperature, thereby preserving polymer chain integrity and avoiding the trade-off between scission efficiency and chain breakage.
2Reliability
If organosulfur compounds are used as devulcanizing agents, then devulcanization is achieved, but odor problems occur during the process
Solution Approach 1:
The invention extracts and removes the harmful sulfur-containing component from the devulcanizing agent system. By using p-phenylene diamine compounds that are substantially free of organosulfur compounds, the invention eliminates the source of odor emission while maintaining devulcanization effectiveness through an alternative chemical mechanism that does not generate harmful sulfur odors.
3Reliability
If traditional devulcanization methods are used, then crosslinks are broken, but recombination of radical moieties occurs leading to poor properties
Solution Approach 1:
The p-phenylene diamine compound acts as an intermediary agent that facilitates crosslink cleavage through a controlled chemical mechanism. Instead of generating free radicals that lead to recombination and structural instability, the intermediary agent enables crosslink breaking through a more controlled pathway, preserving the stability of the polymer composition while achieving effective devulcanization.
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 effectively devulcanizes rubber without degrading properties and minimizes odor, producing re-vulcanized products with improved properties and reduced odor issues compared to traditional methods.
Implementation Method 1
the mixture is brought to a temperature sufficient to cause cleavage of the sulfur-containing cross-links
Data Source
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AI summary
A method of devulcanizing a rubber vulcanizate of polymer chains and sulfur-containing cross-links between the polymer chains is disclosed. The method comprises mixing the rubber vulcanizate with a devulcanizing agent and bringing the mixture to a temperature sufficient to cause cleavage of the sulfur-containing cross-links, wherein the devulcanizing agent comprises a p-phenylene diamine compound having the following formula: wherein R and R' can be the same or different groups, and may be hydrogen, alkyl or aryl, and the devulcanizing agent is substantially free of an organosulfur compound. The method is efficient and releases fewer odors than with known methods.