industry/Business
Overcapacity greets new EPDM producer B. F. Goodrich becomes fifth producer of ethylenepropylene rubber, U.S. capacity of which is double current demand This week marks an important milestone for ethylene-propylene rubber production in the U.S.: B. F. Goodrich starts up its 25,000 long-ton-peryear plant at Orange, Tex., using a new computer-controlled polymerization process. Making Goodrich the fifth U.S. producer—along with Du Pont, Uniroyal, Copolymer Rubber & Chemical, and Enjay Chemical—the new plant adds to an already existing overcapacity problem. Producers have high hopes for the elastomer, however, and expect growth in demand to absorb available capacity and spur expansion within three or four years. Ethylene-propylene polymers resist weathering, ozone, and temperature extremes by virtue of complete saturation of carbon bonds along the polymer chain. To make these polymers sulfur-curable, and at the same time compatible for blending with other rubber, producers usually incorporate in the polymer structure a third component—an unsaturated diene monomer (4 to 8% by weight). Most of these terpolymers, called EPDM, contain as the third monomer ethylidene norbornene, as do most of Goodrich's elastomers. Some producers also use as third monomer dicyclopentadiene and 1,4hexadiene. Enjay and Goodrich both make a copolymer of ethylene and propylene with no third monomer, but the copolymer requires a relatwely costly peroxide cure system. Commercially available for only about 10 years, ethylene-propylene elastomers have become one of the fastest growing elastomers in the rubber industry. These elastomers have been highly successful in penetrating a long list of markets, ranging from wire insulation to auto radiator hose, where weatherability and resistance 18
C&EN JULY 19, 1971
to temperature extremes have given them the edge over other elastomers. Consumption of ethylene-propylene elastomers in the U.S. last year was about 52,000 long tons, up almost 16% from about 45,000 long tons in 1969. This year, Goodrich economists say, consumption will reach 60,000 long tons. Outlet. Largest outlet for ethylenepropylene rubbers is the auto-truckbus industry, which accounts for about two thirds of annual consumption in the U.S. This huge market— about 34,000 long tons last year—is divided equally between tire and related uses (white sidewall strips and truck tire tubes, for example) and a variety of nontire uses (radiator and heater hose, gaskets, and door seals, for example). For all their general uses, however, ethylene-propylene elastomers have failed to fulfill early predictions that they would penetrate the biggest of all rubber markets—tire tread and carcass stocks. Without breaking into this market, ethylene-propylene elastomers cannot, by definition, become a "general-purpose" rubber. "We don't see ethylene-propylene elastomers as a tire rubber today," says B. F. Goodrich Chemical Co. president Tom Nantz. "We do see them as an intermediate," he adds, "falling somewhere between generalpurpose rubbers and specialty rubbers." Although ethylene-propylene elastomers have many properties that are desirable for tire treads and carcasses, tire engineers are so occupied with different tire constructions and
tire cord materials that they're not anxious to tackle the additional problem of adapting other polymers for tread and carcass stocks—especially when rubber blends already in use perform extremely well. As in the past several years, EPDM producers do not agree on projections of growth for the elastomers. Conservative spokesmen say demand will grow 15 to 20% a year for several years, reaching about 104,000 long tons by 1975. More liberal projections put U.S. consumption of the elastomers in 1975 at about 200,000 long tons. Annual capacity, meantime, looks as if it wll stay well ahead of demand, increasing from about 150,000 long tons this year to about 250,000 long tons in 1975, according to Goodrich projections. Several factors, along with ethylene-propylene elastomers' wide-ranging properties, will likely contribute to increasing demand for the elastomer. Goodrich Chemical's new products manager for elastomers, N. Grover Duke, notes that consumerism, for instance, could accelerate growth of the elastomers as people insist on better quality or longer lasting rubber products. New markets will likely open up in innovative products, he says—for example, rubber film for modular housing roofing or pond liners. And ethylene-propylene rubbers have a potential market in specialty tires that need more resistance to long-term weathering, because of longer service, than do regular auto or truck tires—for instance, snow tires, trac-
Total EPDM capacity in U.S. exceeds 150,000 long tons a year Location
Capacity (Long tons per year)
Copolymer Rubber & Chemical
Addis, La.
25,000
Du Pont
Beaumont, Tex.
35,000
Enjay Chemical
Baton Rouge, La.
22,500
Goodrich
Orange, Tex.
25,000
Uniroyal
Geismar, La.
45,000
TOTAL
152,500
Gaskets cut from EPDM await packing
tor tires, bicycle tires, and snowmobile treads. By 1980, Mr. Duke says, ethylene-propylene elastomers may account for 12% of synthetic rubber use in the U.S., compared to less than 4% last year. Cost. Two economic factors could also boost wider use of ethylenepropylene elastomers—the price of raw polymer in relation to that of competitive polymers, and the pound-volume cost of compounded stocks. The pricing structure of styrene-butadiene rubber (SBR), with which ethylene-propylene elastomers must compete, may well change within the next few years, Mr. Duke says. By about 1973 or 1974, U.S. rubber producers will be running out of SBR capacity, he says, and no plans for new plants have been disclosed. At that time rubber producers will have to build new SBR plants or switch to other polymers. Capital investment by SBR producers would likely drive up the price of SBR or at least tighten up current pricing practices, Mr. Duke says. (Price of SBR is now about 23 cents per pound, but it trades lower; price of normal-cure ethylene-propylene elastomers is about 29.5 cents per pound.) Because some types of EPDM can be highly loaded with oil, carbon black, and other fillers, the elastomers can be compounded for many applications at a lower pound-volume cost than for SBR. For instance, in compounding recipes with SBR and EPDM for appliance drain hose designed to achieve comparable tensile strength, hardness, angle tear resistance, and compression set, the poundvolume cost of the EPDM hose is 12.6 cents and that of SBR hose is 13.4
cents, according to Goodrich. Other commercial examples of which EPDM pound-volume cost is lower than or equal to that of SBR include molded appliance feet, auto bumper pads, tire flaps, bicycle tires, and traffic cones, Goodrich says. For some of these applications, EPDM is the material of choice, regardless of cost, because of its ozone and weather resistance. Entry. Goodrich's entry in the EPDM market is the result of a long cooperative project with Italy's Montedison. Using Montedison's early concepts of EPDM polymerization, Goodrich has spent several years developing the process in its laboratories and then in a pilot plant at Avon Lake, Ohio (C&EN, July 28, 1969, page 8). Goodrich says it has also worked closely with developmental and commercial-scale operations in Italy at a Montedison pilot plant and small production unit, which for the past three years has been supplying Goodrich with ethylene-propylene elastomers for marketing in the U.S. Goodrich's process is based on a Ziegler catalyst system (alkyl aluminum compounds plus a cocatalyst). Unlike competitive processes, which use solution polymerization, Goodrich's process uses suspension polymerization which yields a slurry consisting of small granules (about rice size) of rubber in liquid propylene. Continuous polymerization occurs in a single reactor, the company says, rather than in the usual series of three to six reactors for solution systems. The new plant has two such reactors in parallel. According to E. W. Harrington, general manufacturing manager for elastomers at Goodrich Chemical, the rubber-laden slurry is very fluid and doesn't become viscous regardless of the molecular weight of the polymer. With the slurry, Mr. Harrington says, there is no solvent to remove and
recover, as there is in solution systems. In addition, the slurry contains from two to four times the 6 to 8% dissolved ethylene-propylene elastomer usually obtained with solution systems. Computer. The polymerization section of Goodrich's Orange plant is controlled by a computer, which is designed to accurately control all factors in polymerization and which is ultimately aimed at providing lot-tolot uniformity of ethylene-propylene elastomers. According to Mr. Harrington, the computer allows precise control of concentrations of ethylene, propylene, and third monomer at the reaction site. Among conditions in the reactor monitored by the computer are vapor content above the reaction mixture and temperature of the mixture. Altering the process to produce any one of a variety of ethylene-propylene elastomers is easily done, Mr. Harrington points out. By varying the relative amounts of the three components of EPDM, Goodrich's process yields elastomers with a range of Mooney viscosity and cure rate. The process also provides control of molecular weight distribution of the elastomer, Mr. Harrington says. The company initially plans to market nine varieties of its Epcar elastomers, but other types may follow later. Goodrich says the suspension process simplifies systems for recovering unreacted monomers and removing catalyst. The extruder, dryer, baling, and packaging systems in the plant are conventional. The new plant, engineered and built by Bechtcl Corp., Houston, will be comparatively simple to expand, Goodrich says.
Goodrich's new EPDM plant uses a computer-controlled polymerization process
