DBU-TPP Devulcanization Composition for Rubber Recycling
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional devulcanization methods using 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) for sulfur-cured rubber result in scorching issues due to high viscosity increases and premature cross-linking, complicating rubber processing and limiting scorching times in secondary compounded rubber.
Innovation Solution
A composition combining DBU and triphenylphosphine (TPP) with a petroleum-based compatibilizer is used to selectively break sulfide bonds in sulfur-cured rubber, allowing for effective devulcanization with a synergistic effect, enhancing scorching times and maintaining mechanical properties by minimizing DBU concentration through extrusion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If DBU is used as devulcanizing agent to break sulfide bonds, then mechanical properties of rubber are preserved, but scorching time decreases and processing becomes difficult
Solution Approach 1:
The patent introduces a compatibilizer as an intermediary substance that facilitates the interaction between DBU and rubber crumbs. The compatibilizer has dual compatibility - it is compatible with both the devulcanizing agent (DBU) and the sulfur-cured rubber, enabling DBU to effectively penetrate and act on the rubber matrix while maintaining controllable processing characteristics
Solution Approach 2:
The patent changes the chemical composition parameters by introducing a specific compatibilizer that modifies the interaction dynamics between DBU and rubber. This parameter change allows the system to achieve effective devulcanization while extending scorching time from 6-11 minutes to acceptable levels, thereby improving processability without sacrificing mechanical property retention
2Reliability
If significant amounts of DBU (0.3-1%) are added for effective devulcanization, then sulfide bonds are broken effectively, but scorching tendency increases
Solution Approach 1:
The compatibilizer serves as a mediator that enables effective devulcanization at lower DBU concentrations. By improving the penetration and distribution of DBU throughout the rubber matrix through the compatibilizer interface, the system achieves reliable sulfide bond breaking with reduced DBU content, thereby lowering the scorching tendency while maintaining devulcanization effectiveness
3Weight of stationary object
If DBU activates vulcanization during devulcanization, then sulfide bonds are broken, but viscosity increases and premature cross-linking occurs
Solution Approach 1:
The compatibilizer acts as a buffer intermediary that moderates the interaction between DBU and the rubber matrix. This intermediary layer allows controlled devulcanization by facilitating gradual sulfide bond breaking while preventing rapid viscosity increases and premature cross-linking, thereby maintaining composition stability throughout the process
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 DBU-TPP composition achieves scorching times of 14-23 minutes, maintaining 70-90% of original rubber properties, including high tear resistance, and ensuring effective penetration and uniform devulcanization, addressing the scorching issues of DBU alone.
Implementation Method 1
Conventional sulfur vulcanization of rubber leads to the cross-linking of crude rubber macromolecules by sulfide (C—S) and disulfide (S—S) bonds. To reuse this vulcanized rubber while maximally keeping mechanical and other properties of the produced secondary rubber, those sulfide and disulfide bonds (further both called simply sulfide bonds) have to be broken.
Implementation Method 2
A composition for devulcanization of sulfur-cured rubber used in the present invention contains a devulcanizing agent for selective destruction of sulfide bonds being a mixture of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and triphenylphosphine (TPP)
Implementation Method 3
High-boiling products of petroleum distillation, comprising a complex mixture of hydrocarbons (primarily alkylaromatic), are well compatible with the mixture of TPP and DBU. At the same time, they are compatible with the rubber crumbs, which are mostly based on polyisoprene, polybutadiene, and other low polar rubbers. As a result, the composition of invention can penetrate into the rubber crumbs relatively easily
Implementation Method 4
The claimed method of devulcanization of sulfur-cured rubber includes mixing the described composition for devulcanization of sulfur-cured rubber with the rubber crumbs at a weight ratio of the composition to the rubber crumbs from 1:9 to 1:60, followed by the extrusion of this mixture at 40-120° C.
Implementation Method 5
followed by the extrusion of this mixture at 40-120° C.
Data Source
AI summary
This invention relates to a composition for devulcanization of sulfur-cured rubber and a method of devulcanization of sulfur-cured rubber, and can be used to recycle used rubber articles. The composition for devulcanization of sulfur-cured rubber, which contains a devulcanizing agent for the selective destruction of sulfide bonds according to this invention, has a mixture of triphenylphosphine and 1,8-diazabicyclo[5.4.0]undec-7-ene at a weight ratio from 5:1 to 1:5 as the devulcanizing agent. Further, it contains a compatibilizer compatible with both the devulcanizing agent and the sulfur-cured rubber, at a weight ratio of the devulcanizing agent to the compatibilizer from 1:15 to 1:70. The devulcanizing agent breaks sulfide bonds in sulfur-cured rubber very effectively and selectively, while the experimentally selected compatibilizer ensures an effective penetration of the devulcanizing agent into the rubber crumbs. As a consequence, the required concentration of the devulcanizing agent in the resulting compounded rubber does not exceed 1% (preferably, 0.03-0.3%).