Winning Technologies: Polylactide Polymers

Dec. 21, 2004
Cargill Dow's new plastics and fibers made from corn help the environment.

For more than a century companies had been trying to develop plastics from lactic acid -- with no success. Enter Pat Gruber. Fresh out of graduate school, Gruber joined commodity grain processor Cargill Inc. in 1988. His assignment: find new uses for corn sugars. Twelve years later Gruber finds himself at the forefront of a new era in industrial chemistry as the founder of the first family of polymers made entirely from annually renewable resources -- in this case, corn. The new NatureWorks PLA (polylactide) polymer from Cargill Dow LLC, a joint venture of Cargill and Dow Chemical Co., has important process advantages. The company says 30% to 50% less fossil fuel is required and less carbon dioxide is emitted. In addition, PLA products are fully compostable in commercial composting facilities. Products made from NatureWorks PLA today are limited to small quantities because of the 16-million-lb production limit at Cargill Dow's semicommercial test plant. But already they are being used to make sports apparel and active wear, upholstery fabrics, and in packaging such as candy twist wraps, plastic film wraps for foods, blister packs, and plastic windows in boxes. By contrast, when Cargill Dow's $300 million PLA polymer plant now under construction in Blair, Nebr., is up and running in early 2002, its annual production of 300 million lb of NatureWorks PLA -- made from 40,000 bushels of corn daily -- likely will be sold out. And Cargill Dow expects production to more than triple to one billion pounds within seven years. To be sure, that's barely a dent in an industry that produces over 265 billion pounds of plastics a year. "But what we have done refutes the people who said you won't see any of these things soon," says Gruber, now vice president and chief technology officer at Cargill Dow, Minnetonka, Minn. "We broke a paradigm in the chemical industry. We have combined very inexpensive large-scale fermentation with chemical processing to bring a value-added polymer product to the marketplace that improves the environment as well. This will make renewable resource-based chemicals happen." Achieving this technological breakthrough didn't come without some bumps and detours for Gruber and Cargill, which originally targeted 1996 for full-scale PLA polymer production. In his initial talks with chemical companies Gruber was told that he'd never find a low-cost supply of lactic acid and that you couldn't develop a polymer with the potential to be used in a variety of applications. However, Gruber, with no preconceived notions and a conviction that the chemistry of lactic acids made his dream possible, kept asking people in the chemical industry what the perfect polymer product would look like and what its performance parameters would be. Taking what he learned, he focused on the development of the best fermentation and distillation process to create polymers derived from corn. When he couldn't find a partner, he and Cargill built a test plant in 1994 to learn how to adjust the process to change the perform-ance of the polymer for different applications. That was enough to persuade potential partners. After joining forces with Dow in 1995, Gruber says the two began to "match up unmet needs in the marketplace with product performance." Two years and one month after Cargill Dow was officially established in December 1997 ground was broken on the Blair plant. Although as Gruber says, "We got the fundamental technology vision right," he believes that the partners "did not have the mix of applications right in our original projections. We felt it would be weighted toward packaging" rather than being split as it is today between packaging and fiber applications. In addition, he says, the market opportunity is "much bigger than we imagined because of the ability to alter the process to change the performance attributes" of the polymer. He's also convinced that part of the reason that NatureWorks PLA has found such quick acceptance since it linked with Dow is that Cargill Dow has focused on working with plastics converters and fiber and fabric makers to develop products with unique performance characteristics, rather than creating me-too products that simply benefited the environment. For example, NatureWorks PLA has an inherent ability "to take moisture away from the skin," says Jim Lunt, global director of fibers product development for Cargill Dow. That in turn attracted interest from sportswear makers and manufacturers of hygiene products. What's more, the soft feel and wrinkle resistance appeals to the fashion industry. When blended with cotton and wool, PLA polymers result in lighter garments that absorb moisture better. "It bridges the gap between synthetic materials and natural materials," Lunt notes. "PLA will allow . . . cottons and wools to penetrate markets that they couldn't in the past" by creating washable and ironable blends. In packaging, Jim Hobbs, global packaging business leader at Cargill Dow, expects that in three to four years PLA films will dominate in applications such as candy twist wraps, floral wraps, and meat and baked-goods overwraps where cellophane now dominates. "There is an advantage in our cost,"he says, because corn is a less expensive feedstock than wood pulp and the manufacturing process is less complex. In addition, companies that make cooking oils and health and beauty products are looking to use PLA polymers for bottles and tubes because they are more oil- and grease-resistant and provide a better flavor and odor barrier than existing chemical polymers. What's more, their ability to be composted has fast-food chains and food packagers researching PLA for use as rigid containers for fresh fruit, paper cups, and plastic ware. Polymers made from PLA also have two properties particularly useful in fabrics for drapes, window furnishings, and outdoor furniture. They exhibit strong resistance to ultraviolet light, so fabrics show little fading, and their refractive index is low, which means fabrics made from PLA polymers can be made with deep colors without using as much dye. What's next? Cargill Dow is working on modifying the fermentation process so that its NatureWorks technology can use other annually renewable resources such as wheat, sugar beets, and agricultural waste as feedstocks. "People have known for years that plants hold the potential to meet a number of our society's needs," says Gruber. "[We] have learned how to tap into [a basic plant function] to make two of the world's most-used items, plastics and fibers . . . in an environmentally and socially responsible manner. Our job is to build the capacity and knowledge so that we can grow this into a relatively key business sector."

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