2002 Greener Reaction Conditions Award
Cargill Dow LLC (now NatureWorks LLC)
NatureWorks™ PLA Process
Innovation and Benefits: The NatureWorks™ process makes biobased, compostable, and recyclable polylactic acid (PLA) polymers using 20–50 percent less fossil fuel resources than comparable petroleum-based polymers. The synthesis of PLA polymers eliminates organic solvents and other hazardous materials, completely recycles product and byproduct streams, and efficiently uses catalysts to reduce energy consumption and improve yield.
NatureWorks™ polylactic acid (PLA) is the first family of polymers derived entirely from annually renewable resources that can compete head-to-head with traditional fibers and plastic packaging materials on a cost and performance basis. For fiber consumers, this will mean a new option for apparel and carpeting applications: a material that bridges the gap in performance between conventional synthetic fibers and natural fibers such as silk, wool, and cotton. Clothing made with NatureWorks™ fibers features a unique combination of desirable attributes such as superior hand, touch, and drape, wrinkle resistance, excellent moisture management, and resilience. In packaging applications, consumers will have the opportunity to use a material that is natural, compostable, and recyclable without experiencing any tradeoffs in product performance.
The NatureWorks™ PLA process offers significant environmental benefits in addition to the outstanding performance attributes of the polymer. NatureWorks™ PLA products are made in a revolutionary new process developed by Cargill Dow LLC that incorporates all 12 green chemistry principles. The process consists of three separate and distinct steps that lead to the production of lactic acid, lactide, and PLA high polymer. Each of the process steps is free of organic solvent: water is used in the fermentation while molten lactide and polymer serve as the reaction media in monomer and polymer production. Each step not only has exceptionally high yields (over 95 percent) but also utilizes internal recycle streams to eliminate waste. Small (ppm) amounts of catalyst are used in both the lactide synthesis and polymerization to further enhance efficiency and reduce energy consumption. Additionally, the lactic acid is derived from annually renewable resources, PLA requires 20–50 percent less fossil resources than comparable petroleum- based plastics, and PLA is fully biodegradable or readily hydrolyzed into lactic acid for recycling back into the process.
While the technology to create PLA in the laboratory has been known for many years, previous attempts at large-scale production were targeted solely at niche biodegradable applications and were not commercially viable. Only now has Cargill Dow been able to perfect the NatureWorks™ process and enhance the physical properties of PLA resins to compete successfully with commodity petroleum-based plastics. Cargill Dow is currently producing approximately 8.8 million pounds of PLA per year to meet immediate market development needs. Production in the first world-scale 310-million-pound-per-year plant began November 1, 2001.
The NatureWorks™ process embodies the well-known principles of green chemistry by preventing pollution at the source through the use of a natural fermentation process to produce lactic acid, substituting annually renewable materials for petroleum-based feedstock, eliminating the use of solvents and other hazardous materials, completely recycling product and byproduct streams, and efficiently using catalysts to reduce energy consumption and improve yield. In addition, NatureWorks™ PLA products can be either recycled or composted after use.
Read on about the 2002 Designing Greener Chemicals Award.
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