Making plastics “greener” usually involves replacing some of their petrochemical constituents with alternatives derived from sources other than petroleum. Sometimes the alternative can come from recycled plastics, other times from bio-based chemicals. Polyurethanes are increasingly taking the latter route. Some of the urethane formulations used in reaction-injection molding have for years made use of soy-oil-based polyols. And now suppliers of urethane foams have likewise developed polyols based on soy beans or other oil seeds. Currently, these bio-polyols can typically displace only a portion of petroleum-based polyols because the foam's physical properties and consistency suffer. And because the isocyanate component of these urethanes remains a petrochemical, bio-based polyols don't exactly make a urethane completely sustainable. “But they're a good start,” says Bobby Bush, vice president of environmental affairs at Hickory Foam, which uses bio-based urethanes. Here's a look at three recent developments in urethane foams as well as related efforts in related urethanes such as adhesives and elastomers.
Hickory Springs Goes Green
Hickory Springs Mfg. Co. has, for the past year, been using Cargill's soy-based polyols in its Preserve urethane foam, and the company's experience highlights both the progress and challenges in switching to a sustainable chemistry. According to Bobby Bush, vice president of environmental affairs at Hickory Foam, the company has so far been able to replace about 25 percent of its petroleum polyols with the soy-based alternative. Any more than that and the foam properties suffer. “Our goal is to get to 100 percent,” he says. “But we're not there yet.” Aside from their environmental benefits, foams with bio-based polyols offer some promising property improvements. Bush reports the foams offer slightly better mechanical properties, including support factor and dynamic flex fatigue. The bio-based foams are also showing better resistance to yellowing, he adds.
Cargill Tackles Urethanes
Cargill's expertise in processing agricultural feedstocks has spilled over into urethanes with the introduction of its “BiOH” polyols. The company previously had not been in the urethane business at all. “We saw an opportunity in polyols and started with a clean sheet of paper four years ago,” says Yusuf Wazirzada, the company's business manager for BiOH polyols. Since that time, the company has started to deliver its polyols to some of the largest polyurethane foam makers. The Woodbridge Group, one of the largest suppliers of urethane foam for automotive seating, is evaluating BiOH. According to Wazirzada, Cargill's big breakthrough has been making polyols that don't smell like they came off the farm. “Odor was one of the biggest technical challenges, and it's one we've solved,” he says. Though Cargill has started with flexible foams for business reasons, Wazirzada predicts the company will apply its bio-based approach into “all mainstream urethane chemistries,” including coatings, adhesives, sealants and elastomers.
Dow Commits to Bio-Polyols
Dow Polyurethanes has already dipped its toe into sustainable urethanes and soon plans to jump right in. The company currently has sampling quantities of bio-based polyols available. And in the fall of 2007, the company plans to open a plant capable of producing the polyols in commercial quantities, reports business development manager Erin O'Driscoll. Initially, Dow's bio-polyols will be based on soy oil. “We're looking at other oil seeds as well,” O'Driscoll adds. In slab and molded foam applications, depending on the application requirements, Dow's bio-based polyols will be able to replace about 30 to 70 percent of their petroleum-based counterparts, according to O'Driscoll. And while Dow's initial focus will be foams, O'Driscoll says the same bio-based approach can also be extended into coatings, sealants, adhesives and elastomers.