Factsheet 4: Biochemical Substitutions in the Polymer Industry

Biochemical Substitutions in the Polymer Industry

Plastics represent one of the most diverse categories of products from organic chemicals. The main component of plastics are polymers, large molecules composed of chains of basic building blocks (called monomers) linked together. Polymers are combined with additives which give the final plastic better functional properties like strength, flexibility and stability. The great diversity of plastics is achieved by using different blends of polymers and additives.

The manufacture of polymers, the raw materials for plastics, generated over l54 million pounds of toxic chemical releases and transfers in the Great Lakes basin during 1992 [1]. Analysis of the EPA's Toxic Chemical Release Inventory (TRI) data shows two dominant sources of hazardous waste. These are: raw materials for polymers, such as ethylene and styrene; and solvents, such as methyl isobutyl ketone, acetone and methylene chloride [2].

Monomer building blocks are linked together in a process called polymerization. The polymerization process is induced by the application of heat and pressure or by the use of chemical catalysts [3]. In industrial polymerization, this reaction is frequently carried out with the monomer in solution with water or a petroleum derived solvent. Sources of pollution from the manufacture of polymers includes losses of raw materials during processing, contaminated solvents used in polymerization, and solvents used to clean built up polymers from the walls of reactor vessels. This cleaning is necessary to insure proper operation [4].

The majority of chemicals used in the polymer industry are derived from petroleum. The use of biochemicals, chemicals derived from plant matter, is one solution to the pollution problems associated with the manufacture of polymers. Biochemicals are less toxic and biodegrade more rapidly than petrochemicals, and consequently have less negative impact on the environment. Alternative solvents for the cleaning and processing of polymers, as well as alternative raw materials and additives for plastics, are available.

Inland Technologies (Tacoma, WA) specializes in formulating alternative cleaning solvents tailored to meet the cleaning needs of their clients. Many of their solvents are based on the terpene d-limonene, a powerful natural solvent derived from the peels of citrus fruits. D-limonene is not listed on the EPA 313 Toxic Release Inventory or as a Hazardous Air Pollutant (HAP). Inland produces solvent blends designed to replace methylene chloride and acetone in the cleaning of resins including polyesters, urethanes, vinyls and epoxies [5].

Purac America manufactures the Purasolv® line of lactate ester solvents which have been used for cleaning applications for urethanes, and could be used as a solvent for polyvinyl acetate, acrylics, phenolic resins, epoxies, polyvinyl butyral, hexamethoxy melamine, polyethyl methacrylate, urea formaldehyde resins, polymethyl methacrylate, cellulose acetate, and blocked isocyanate phenol. Purac states that in cleaning applications, these solvents have excellent solvency, are non-toxic and biodegradable, and are easily recovered through distillation [6]. Lactate esters are not listed on the EPA section 313 Toxic Release Inventory or as HAPs.

Gaylord Chemical (Slidell, LA) is the world's leading producer of dimethyl sulfoxide (DMSO), which Gaylord manufactures from lignin, a byproduct of the manufacture of paper. DMSO is a powerful organic solvent with applications in cleaning a variety of resins and as a polymerization solvent for high value polymers [7]. DMSO costs $0.96/lb and compares favorably to alternative solvents of similar solvent strength such as DMAC, Butyrolactone and NMP, which range in cost from $0.92-$1.62/lb. DMSO is not listed on the EPA section 313 Toxic Release Inventory or as a HAP.

Some biochemicals are well established in the manufacture of plastics. Itaconic acid, a component of acrylic latex polymers, is manufactured through fermentation by the Pfizer Chemical Company (New York, NY), the only producer of itaconic acid in the United States. Itaconic Acid is not listed on the EPA section 313 Toxic Release Inventory or as a HAP. While itaconic acid can be made from petroleum, the biochemical is now the sole means of commercial production [8].

Another well established biochemical polymer is nylon 11, which is derived from sebacic acid from castor oil. Nylon 11 resins are not listed on the EPA section 313 Toxic Release Inventory or as HAPs. Elf Atochem manufactures Rilsan®, a nylon 11 resin that is used in metal coating applications. Rilsan® produces coatings with exceptional chemical and mechanical resistance. Nylon 11 resins are relatively expensive, $4.94-$7.94/lb compared to $2.95 - 3.95/lb for Nylon-12, a similar though less versatile resin made from fossil fuels. Despite this the markets for nylon-11 are growing because of its relatively low melting point of 186 degrees Celsius (as compared to greater than 200 degrees Celsius for many resins) and superior abrasion, impact and chemical resistance. The fact that nylon 11 resins do not require the additional curing step required by most powder coating resins further improves the economics of production by reducing processing time [9].

Plasticizers are used as additives to make plastics function better by giving them properties like greater flexibility and strength. There are many biochemical plasticizers, such as epoxidized vegetable oils and acrylic esters derived from diverse sources such as palm oil, castor oil, and the wood extractive tall oil [10]. One area with particular promise is epoxidized soybean oil (ESO). ESO is currently used as a plasticizer for polyvinyl chloride (PVC), but is limited in applications because at high concentrations it causes PVC to become brittle. Future research is being considered by the American Soybean Association that could overcome the current technological problems of ESO. These technological advances could open a large market for ESO in the replacement of dioctyl phthalate (DOP), a petroleum derived chemical which currently dominates the plasticizer market for PVC. ESO costs $0.78/lb., compared to $0.52/lb. for DOP. However, ESO does not leach or evaporate from PVC, as dioctyl phthalate does, and is not listed on the EPA section 313 Toxic Release Inventory or as a HAP. These superior properties, combined with technical advances, could increase the market for ESO from the current 100 million pounds per year to as much as 1,300 million pounds per year [11].

1. U.S. EPA, 1992 Toxic Chemical Release Inventory : SIC 2821.
2. Ibid.
3. Carley, J. F., "A Plastics Primer," Modern Plastics v. 67, October 1990.
4. U.S. EPA, Dupont Chambers Works Waste Minimization Project, EPA/600/R-93/203, November 1993.
5. Product information supplied by Eric Lethe, Inland Technology Inc., Tacoma, WA.
6. Product information supplied by John Ketelaar, Purac America, Lincolnshire, IL.
7. Product information supplied by Rodney Willer, Gaylord Chemical Corp, Slidell, LA.
8. Product Information provided by Pfizer Chemical, New York, NY.
9. Product information supplied by Craig Schmehl, Elf Atochem North America Inc.
10. Beach, E.D. et al, "Biopolymers: An Engineering and Economic Assessment of an Emerging Industry," Advances in Solar Energy: An Annual Review of Research and Development, American Solar Energy Society, Golden, CO, 1994.
11. Information supplied by the American Soybean Association.

POLLUTION SOLUTIONS is a series of fact sheets about pollution prevention strategies with biochemical substitutes prepared by the Institute for Local Self-Reliance (ILSR). If you would like more information, contact:

Tel: (612) 379-3815 FAX: (612) 379-3920