The ultimate model which addresses all possible aspects of environmental sustainability in rubber recycling is still Devulcanization but should start right from the collection of tires. This means the starting point should be at the tire collection centers or in the US possibly at the landfills. Here we are not talking about solid waste management anymore but effectively managing a vital raw material in process.
Addressed properly the tires would not be dumped in the open but would be separated out between passenger car and commercial vehicle (truck) tires, making it possible to split up the feedstock into types ie. Mostly Natural Rubber (80/20) from Commercial vehicle tires and Mostly Synthetic (60/40) for passenger car tires. This important step also makes it possible to shoe horn in a step which could see the eventual removal of the Butyl inner liners by grinding or peeling off. The resultant by-products would be butyl scrap feedstock and butyl free scrap tire feedstock, an interesting and very significant change to the current situation.
The fact is Butyl rubber is an expensive material used in the inner liner compound to enhance the tires air impermeability properties allowing it to be tubeless. However the butyl compound which is petroleum based is entirely incompatible with natural and synthetic rubber used in the tires. The butyl layer is bonded/gummed to the inner liner of the tires but when crumbed together becomes an inseparable part of the tire dust whose incompatibility will reduce the recoverable performance parameters of the resultant compound post devulcanization. By the same token removing the butyl liner though an added step will enhance the recoverable properties in a very meaningful way.
The removal of the butyl liner should not be looked at as just another cost center as it is also feedstock for devulcanization and the resultant Butyl Compound can be introduced into butyl tube applications and butyl automotive applications in substantial proportions without loss of properties. It is actually another valuable profit center from a feedstock that was never before available as it was lost through homogenization or becoming an unidentified part of a greater blend.
The next step is to incorporate the latest of energy saving technologies to one of the most energy intensive areas of size reduction of the tires starting with shredding through to the grinding stages. While it has to be accepted that to ensure that we avoid degradation of the polymer that heat is to be avoided, a certain level of energy consumption cannot be avoided in order to reach the requisite 40 mesh powder specification, however there are cutting edge technologies which can reduce energy consumption as much as 30% with enhanced levels of separation efficiency (metal and fiber separation).
The following are the 5 changes to the status quo that I intend to make.
- Devulcanization – Producing Rubber Compounds
- Production of NR based and SR based Compounds
- Production of Butyl Compound
- Energy savings in Tire Shredding process
- Improved Performance in Butyl Free NR & SR Compounds
The rationale for burning, burying and other retrograde processes to address the scrap tire (End of Life Tires) will no longer be justifiable. These changes will not only demolish the status quo but will bring real solutions and positive change that will impact the environment in a meaningful way while being profitable.