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Goodyear Patents Process to Recover Rubber from Tires

9 September 1999

Goodyear Patents Process to Recover Rubber from Tires

    AKRON, Ohio, Sept. 8 -- Most people don't know it, but tires
are a lot like cakes -- you can't "unbake" a cake into flour, eggs and other
ingredients.
    It's been the same way with tires ever since the inventor of
vulcanization, Charles Goodyear, mixed and baked sulfur and rubber together,
creating a tough, cured compound that could withstand the heat, stress and
strain demanded of tires.
    Until now.
    The Goodyear Tire & Rubber Company, the world's largest tiremaker has
patented a process for devulcanizing cured rubber products.
    For years, conventional wisdom has held that reversing the vulcanization
process was as implausible as retrieving the raw eggs from baked goods.
    "The recycling of cured rubber has proven to be very challenging because
once vulcanized, rubber cannot be easily melted and reformed into other
products," said Goodyear's Larry Hunt, section head, who discovered the
process with co-inventor Ron Kovalak, master chemical technician, analytical
sciences at corporate headquarters.
    Vulcanization, discovered by Charles Goodyear in 1839, is the process of
heating and hardening rubber compounds to make them serviceable and is similar
to baking a cake.
    "A number of devulcanization techniques have been developed over the
years, but none have been commercially viable," Hunt said.  "This process,
however, appears to offer considerably higher recovery rates than any earlier
attempts and could ultimately reduce the amounts of petroleum and natural
rubber needed to manufacture rubber goods."
    Earlier methods devulcanized by using everything from microwaves,
cryogenic processes, pyrolysis, ultrasonic waves, alkali metals to organic
solvents, which typically yielded 1 to 2 percent recovery, Kovalak said. "We
believed we could substantially increase the amount of recovered material."
    Goodyear's process preserves the rubber's chemical composition and
molecular weight, leaving the rubber suitable for recompounding and recuring
into new products.  It uses an environmentally friendly, recyclable solvent.
    "Initial tests resulted in a 40 percent recovery rate of the raw polymer
with its structure essentially preserved, and through process improvements,
we've been able to achieve an 80 percent recovery level.  This demonstrates
that the chemistry to recover polymer close to its original state is
possible."
    Currently the process only has been used to recover laboratory quantities,
however if it can be fully developed, it could offer a viable solution to the
recycling of more than 800 million scrap tires in North America alone.   In
addition, the process could provide a means of increasing recycled content in
automotive components, a priority for automakers.
    Goodyear's experimentation with using recovered raw polymer in other items
is the latest step in the company's decades of innovative recycling
technologies for worn out rubber products.
    During the 1990s, Goodyear championed the controlled combustion of scrap
tires for energy with electric utilities and nurtured a network for scrap tire
collection through its retail network.
    In 1989, Goodyear spearheaded the formation of the Scrap Tire Management
Council, a division of the Rubber Manufacturers' Association, to focus intense
efforts on scrap tire management.  At the time, only 10 percent of scrap tires
in the United States were utilized in some fashion compared with 81 percent
recovered in 1998, a level exceeding the 63 percent recycle rate of aluminum
cans.
    Earlier in the '80s, Goodyear invested in an enterprise to use scrap tires
in the concrete and paper manufacturing industries paved the way for scrap
tires to be used as supplemental fuel and added fuel sources to reduce the
nation's energy dependency and conserve national resources.  Tires have more
energy value per pound than coal and burning a passenger car tire generates
the heat value of almost two gallons of fuel oil.
    Goodyear pioneered scrap tire initiatives in the 1970s that included
protective shore barriers, fish habitats, highway impact barriers and
playground equipment.  The company also explored using ground scrap tires in
asphalt road surfaces and supported the construction of a pyrolysis plant to
recover oil, carbon black and steel.