[GreenYes] Re: [ZWIA] Devulcanising Rubber

Petra Group, out of Malaysia, has the DeLink process, which is a commercialized devulcanization process. Some of my clients met with them a few weeks ago in China. Their website: http://www.petragroup.net/html/environmental.html The advantage to DeLink is that it doesn't need big reactors -- it just requires shearing the ground rubber for 10 minutes with their mixture added.

My associates in Beijing have a devulcanizing factory in the Beijing Rubber compound. It uses a more complex process and equipment (reactors and electronic controllers) bought from Germany, but the product is truly devulcanized, and it gets used at various usage levels, up to the 100% level, in a neighboring molded rubber mat factory (also in the Beijing Rubber complex).

The limitation to devulcanized tire rubber is that the end uses have to be tailored to what comes out of the devulcanizing process: material that is mixed natural rubber/butadiene rubber/EPDM/halobutyl, containing everything else that went into the tire rubber compound, including amorphous silica, carbon black, processing oils, special-purpose resins, etc., and including staining antioxidants and antiozonants. Therefore, it's good for rubber mats and footwear outsoles -- black items. It's usually used in blends, because you can't rely on a uniform feedstock, due to variations in tire compounds. You couldn't risk using it back into passenger tires, because tire compounds are so precisely tuned to their application; and if somebody died while driving on your tires, and the compound contained even a small amount of recycled, you'd be in a massive liability situation. However, retread truck tires are OK, since they can blow up on the road and the semi-trailer is still riding on numerous other tires.

Advac Elastomers in Wisconsin (http://www.advacwi.com/applications.htm) and another guy that I know of in Australia are using the Tirecycle process. I visited the Tirecycle people up in Minneapolis about 2 years ago, and they use a digested virgin polymer to interpenetrate with (and bond with) the ground recycle. That's not actually devulcanized -- it's "activated particle". However, it works, and you can use up to about 50% back into virgin compound. Their process is a little complicated by the need to strip off all the different rubber components (inner walls, side walls, tread, carcass) so that you can separate the tire into the component polymer rubber types into separate streams and treat each one with an appropriate activator. This is being used in the U.S. and Australia for tire tread for retreads, and also for butyl bladders for various applications.

The limits to using all of these methods are partly market limits -- the cost of transporting tires, grinding them up, matching up the material produced with the appropriate end users, and lining up investment money to make the system work. There is another limit, which is: finding enough applications that can use this material that is itself a variable mixture of many other materials. As I mentioned above, you just can't use it in light-colored items or mission-critical products that would have a potential for high liability risk.

I was in central China a year ago and visited a number of rubber molding plants in the Nanjing area. They all have their own pile of tires outside the factory, waiting to be ground up and mixed into virgin compound at the 10% level for mats, molded mechanical parts, etc. In many products, if you don't exceed 10%, you can get away without any devulcanization or other chemical treatment. Of course, China still has a great preponderance of bias-ply tires over radial tires, so they don't have to deal with steel belting -- just cut out the steel bead around the rim and grind up on open mills.