Science & Technology: CHEMISTRY
RESHAPING THE FUTURE OF PLASTIC
The rush is on to cash in on a big breakthrough in catalysts
Since the 1930s, modern plastics have been a triumph of experience over theory. At the core of the huge industry are critically important chemicals called catalysts--witches' brews that guide the intricate linking of molecular building blocks into thousands of different plastics. Until now, these catalysts have been so poorly understood that new plastics have come about through trial and error--mostly error.
But in the past few years, scientists around the world have cracked the code of one important class of these workhorse molecules. They're called single-site catalysts. Now that chemists are learning how to fine-tune them, plastics manufacturers can make use of inexpensive precursors to produce plastics with tailor-made properties such as toughness, stretchiness, and the ability to withstand temperature extremes. Soon, they hope to supplant commonplace plastics with new plastics that are light-absorbing, electrically conductive, or even magnetic.
PATENT PUNCH-UP. Plastics aren't the only frontier. Single-site catalysts are grabbing the attention of chemists for everything from fabrics and pesticides to drug design. The breakthrough has sparked a patent battle involving some of the world's biggest corporations. Exxon, for instance, has challenged patents filed by Dow Chemical, Fina, and one of its own former scientists.
Meanwhile, the fear of falling behind has been driving rival companies into technology alliances. Exxon and Union Carbide agreed in August to join their research efforts, just days after a similar deal linked Dow Chemical and British Petroleum. Other major league players include Germany's Hoechst and Japan's Mitsui Petrochemical Industries and Mitsubishi Chemical Corp.
The giants initially are targeting polyethylene and polypropylene--plastics that ring up sales of $43 billion a year in everything from trash bags to milk bottles. Eventually, single-site catalysts could make all kinds of plastics better and cheaper. They could also speed the development of more environmentally friendly plastics to replace chlorine-containing plastics that harm the ozone layer. Progress with the new catalysts represents "the most significant polymer catalyst advancement in 50 years," says John J. Murphy of Catalyst Group, a consulting outfit located in Spring House, Pa.
At the center of it all: colorful powders of magenta, pink, lavender, and orange that stitch simple molecules into chains. They are called single-site catalysts because the part of them that helps form molecules into chains is a single metal atom at their core. They encourage the molecules to attach to one another in a highly predictable manner (illustration). Older polymer catalysts are a jumble of active sites, each behaving in a slightly different way. As a result, they have less predictable effects.
Because of their uniformity, single-site catalysts can be used to construct plastics with ultraprecise features. For manufacturers, that means a plastic can be many times stronger or clearer than the less uniform plastics produced in the old way. Exxon is using the catalysts to develop plastic for bags that won't tear when softened by the sun--ideal replacements for fertilizer bags that now can rip open and spill when moved.
FABRICS, TOO. Then there's clothing. At Stanford University, chemist Robert M. Waymouth has devised a catalyst that could lead to curious new fabrics that would be ideal for sports enthusiasts. Some fabrics might go into outdoor clothing with two features that haven't been combined before: The clothing could wick moisture away from the body as efficiently as polypropylene and yet stretch as easily as Lycra.
The new single-site catalysts have the potential to save money someday by producing high-tech plastics out of cheaper ingredients. In the short term, however, their cost remains an obstacle. Plastics made from single-site catalysts cost 2 cents to 7 cents a pound more than conventional catalysts. Use of single-site catalysts adds roughly 15% to the cost of certain polyethylene products. That's a problem in a commodity business, especially since customers aren't expressing any dissatisfaction with existing products.
But that hurdle isn't diminishing the enthusiasm of plastics makers, who think they can solve the cost problem. Judging from the worldwide wave of investment in research and manufacturing capacity, single-site catalysts have a bright future. They are likely to be working at many, many sites before the decade is over.By Gary McWilliams in Houston