The Greening of an Industry: Soybeans make for green PUR

PLA and PHA have a new green acronym in their ranks—NOP (natural-oil polyols)—with seed oil joining corn sugars to chip away at fossil-fuel-based chemicals, in this instance the polyurethane (PUR) precursor.

The biggest push on this front was announced at the Utech event (Sept. 24-26; Orlando, FL), where Dow Chemical (Midland, MI) realized the culmination of work dating back to the early ’90s, with an assist from a Union Carbide technology acquired in 2000, to commercialize its soy-based polyol, dubbed Renuva. Dow claims to be the largest producer of polyether polyol in the world, with more than 20 PUR manufacturing and system-house sites, as well as $5 billion in annual sales, putting the weight of a market leader behind a green alternative.

Dow says this first-generation of soybean-oil-based polyols will target flexible applications in foam and CASE (coatings, adhesives, sealants, elastomers), creating an open-cell foam that is viscoelastic over a wide temperature range, which generates immediate opportunities in bedding and furniture. First-generation foams have had 20% biobased resources in them, and on the basis of its own lifecycle analysis, Dow says Renuva is greenhouse-gas neutral, and uses up to 60% fewer fossil fuels.

Work is underway on rigid applications, with Dow representatives bringing a Renuva-based bumper fascia to Orlando as an example. Dow representatives stressed that beyond sustainability, Renuva in some applications has performance benefits over petroleum-derived foams, citing an improved compression set and enhanced hardness for greater durability.

Right now Renuva is targeting transportation, bedding, furniture, carpet, and CASE markets, with applications including seating, arm, headrest, and headliner foams in vehicles; viscoelastic “memory” foam for bedding; carpet backing; and coatings, spray elastomers, and one- and two-component adhesives and sealants.

Tear it down, reassemble, repeat

Dow’s process has four steps: methanolysis, hydroformulation, hydrogenation, and polymerization, with the second step being the former Union Carbide technology that Dow says differentiates Renuva. Depending on where they were grown and other variables, like the hotness or dryness of the season, soybeans’ fatty acid combinations can vary, and hydroformulation is used to overcome that irregularity, creating what Dow says are predictable results. In the hydroformulation reaction, which is also known as the oxo process, esters cleaved from the seed oil’s triglycerides are reacted with carbon monoxide and hydrogen, attaching an aldehyde group at the alkyl chain’s unsaturation site. This reduces any residual carbon-carbon bonds making it resistant to auto-oxidation, or in plain English, smelling, since as a food oil, the soy can go rancid.

According to Dow, polyols used for molded foam typically have a higher molecular weight, higher functionality, and are more reactive, with the polyols capped with ethylene oxide blocks to create polymer chains terminating in the reactive primary hydroxyl group, which was one challenge for using natural-oil polyols in molded foams.

Another potential challenge is increasing use of seed oils for biodiesel, which President Bush has emphasized, creating a potential competitor for the feedstock.

In a 2005 speech at Virginia BioDiesel, Bush said biodiesel sales grew from 500,000 gallons in 1999 to 30 million gallons in 2004, with government incentives, including tax breaks and subsidies, in place to stoke growth.

“The soybean-oil market has changed dramatically in the last two to three years,” Erin O’Driscoll, Dow PUR business development manager, told MPW. “All vegetable oil pricing has gone up.” To combat this, Dow is looking at alternative seed oils, including ones derived from sunflowers, safflowers, and rapeseed, but it will have to weigh the chemical impact on the final product. “We’d like to have feedstock diversity, but we want to know what that diversity will bring,” O’Driscoll said. Dow has largely ruled out one potential alternative, palm oil, on the basis of its impact on properties.

According to a University of Illinois study, the cash price of soybeans in central Illinois during August 2007 was an average of 42% higher than in September 2006, when a record U.S. crop was harvested. Soybean-oil prices increased by 48% over that same period, in spite of the fact that the U.S. Dept. of Agriculture reports U.S. soybean-oil production has nearly doubled since 1981, rising from 11 billion lb to 20.2 billion lb in 2006.

A growing field

Biobased polyol competitor Cargill (Minneapolis, MN) had its own news at the Utech event, announcing that it would expand manufacturing of its BiOH polyols to South America, with technology added to an existing vegetable-oil processing site in São Paolo. Yusuf Wazirzada, business manager Cargill BiOH, told MPW that its product has been commercially available for two years, and although he wouldn’t offer a specific capacity figure, said the company could supply tens of millions of pounds.

“Cargill is in a unique position to make biobased polyol a success,” Wazirzada said, reasoning that Cargill isn’t also selling competitive petroleum-based polyols. The company’s BiOH is used in flexible and rigid foams, with biobased sourcing up to 30-35% in the polyol and 15-20% in the finished product. Wazirzada says the attraction to biobased polyols goes beyond ’being green’ to bottom-line benefits. “Customers are plagued with the petrochemical supply chain’s volatility, and [sourcing outside that] is huge for them.”

Jack Dai, senior application development engineer at Cargill, says BiOH, which was recognized by the U.S. Environmental Protection Agency with a 2007 Presidential Green Chemistry award, offers a 25% reduction in total energy demand and 36% less greenhouse emissions.

Cargill, as well as Dow, described this polyol as first generation, with second-generation monomers in the pipeline that could lead to rigid PUR systems. To speed that development, Cargill opened a 19,000-ft2 R&D facility for polyols in Plymouth, MN, which features a KraussMaffei (Munich) reaction injection molding system.

“From an equipment perspective, very few things change when running soy polyol,” explains John-Paul Mead, VP of reaction process machinery at KM, with the addition of a feed pump being one notable difference.

PUR leader Bayer MaterialScience (Leverkusen, Germany) is undertaking its own work on renewable polyols, looking at soybean and other oils, according to Kirk Bourgeois, head of BaySystems North America. The company has two commercial applications in the field, using Baydur 730S with soy polyol.

The company had a soy-polyol headrest at its Utech booth, adding that it has worked with all the major automakers to approve the materials through their tier suppliers. The first commercial application will be seat-cushion and seat-back foam for Ford’s 2008 Mustang.

The soy polyol for that particular application comes from Urethane Soy Systems (Volga, SD), which, unlike many of its new competitors in the field, is “backward integrated” to the farm, growing its own soybeans, according to Eric Geiger, director of research and development. Geiger says the market has been impacted by new players and biodiesel initiatives, but on the whole, vegetable oil is still less volatile than petroleum. Out of the company’s 1 billion-gallon capacity, 100 million gallons of soybean oil are committed to biodiesel. While the company’s capacity for soy-based polyol is 50 to 75 million lb, it sells 350 million lb of soybean oil on an annual basis.

Doug Warner, polyols business director at Dow, took time at the onset of the conference to recognize that Utech was marking its 50th anniversary, with the inaugural event held in 1957, when the first flexible foamswere still on the horizon. Today, annual PUR sales in the U.S. are $19 billion and the industry employs 200,000 in the states, displaying marked growth. The awakening green consciousness of consumers, however, leads Warner to believe changes will have to be made to ensure the industry''s future. “To be successful and make it to the next 50 years, we have to understand sustainability,” Warner said. “We need to be sustainable and safe.”