AKRON—Goodyear has patented a solvent-based devulcanization process it said can recover up to 80 percent of the rubber in a used tire. Furthermore, the recovered rubber retains the rubber's chemical composition and molecular weight, making the Goodyear process different from previous devulcanization attempts, the company said.
``We're working at getting the recovery rate even higher,'' a Goodyear spokeswoman said. But the process is still in the laboratory stage, and it will be some time before the company knows whether it will prove economically feasible on a large scale, she warned.
Goodyear, which received the patent April 6, didn't announce its discovery until Sept. 8. In the tradition of Charles Goodyear's accidental discovery of vulcanization by dropping sulfurized rubber on a hot stove, Goodyear researchers Larry Hunt and Ron Kovalak discovered their devulcanization process by accident while attempting to dissolve rubber polymers out of a cured rubber compound.
The scientists found that, under laboratory conditions, 2-butanol, a commonly used, alcohol-based rubber solvent, recovered polymers with all their virgin properties restored, including composition and molecular weight. They had a 40-percent recovery rate of the polymers at first and were able to double that rate through process improvements.
The unique conditions of the experiment made the discovery possible, said Ron Dill, Goodyear director of analytical and materials testing.
``Under standard atmospheric conditions, 2-butanol is no different from any other alcohol solvent,'' Mr. Dill said. ``But under the conditions of very high pressure and very high temperature, it devulcanized the rubber.''
Experts in scrap tire management were encouraged by Goodyear's announcement, but stopped short of proclaiming it the magic bullet for the world's scrap tire problems.
``If you see the patent, it talks about gram-sized units of rubber tested with several different reagents and alcohols,'' said John Serumgard, chairman of the Scrap Tire Management Council and executive vice president of the Rubber Manufacturers Association.
``Obviously, we're interested and intrigued, and we hope this will be a positive addition to the technology,'' Mr. Serumgard said. ``But whether it will scale up—that's the big question. And the question ultimately is, even if the process scales up, is it cost-effective?''
At this point, Goodyear has ``absolutely no idea'' of the answers to those questions, the company spokeswoman said. ``We're still in discovery,'' she said.
The company is ``still in the invention stage of this project,'' with plans to build a large-scale devulcanization production unit still in their infancy, Mr. Dill said.
``Our biggest roadblock is time,'' he said. ``Just give us the time to work on this project, and we'll find the answers. We think this is a feasible project; we just need to put the gut work into it and get it going.''
The company spokeswoman declined to say when the scale-up might be complete. ``We have internal projections of when this might happen,'' she said, ``and I'm sure our competitors would love to know them.''
Goodyear is not the first company to come forward with a patented devulcanization process, but it is the first major tire manufacturer to do so.
Back in the mid-1980s, Minneapolis-based Rubber Research Elastomerics Inc. patented a liquid polymer which was applied to the surface of ground scrap tire rubber to create a product called ``Tirecycle.''
RRE claimed its process ``revitalized'' the rubber particles, enabling them to form chemical bonds similar to those formed by virgin rubber.
With significant state and local backing, RRE built a full-scale plant in northern Minnesota to produce Tirecycle, but eventually went bankrupt when the material failed to attract high-end-use customers.
In 1995, B.C. Sekhar, former chairman of the Malaysian Rubber Research and Development Board, formed a new company, STI Corp. Sdn. Bhd., to market his patented ``De-Link'' chemical devulcanizing agent and ``DeVulc'' devulcanized rubber. Mr. Sekhar claimed De-Link could recover up to 75 percent of the virgin properties of vulcanized rubber.
Tests performed at a British laboratory showed that tire compounds could include up to 40 percent DeVulc without losing virgin properties.
However, STI was forced to close its U.S. subsidiary, STI-K Polymers America Inc., in 1998. A lack of deep-pocket clients and the Southeast Asian financial crisis were blamed for STI-K's demise.
In August 1999, another firm, Landstar Inc., announced completion of a demonstration plant in Dayton, Ohio, for its ``Activated Modified Rubber'' process for devulcanizing crumb rubber.
According to the STMC, the U.S. generated about 280 million scrap tires last year and has more than 800 million stockpiled. The 1998 recycling rate for scrap tires was 67 percent, down from 75 percent a year or two earlier because of a dip in the demand for tire-derived fuel.