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Rensselaer The Howard P. lsermann Department of Chemical Engineering RENSSELAER'S SELECTIVE DISSOLUTION PROCESS FOR PLASTICS RECYCLING - A ECONOMIC AND TECHNICAL UPDATE December 1992 E. Bruce Nauman, Project Director Phone: (518) 276-6726 and Jerry C. Lynch, Project Manager Phone: (518) 276-6931 The lsermann Department of Chemical Engineering Rensselaer Polytechnic Institute Troy, NY 12180-3590 Fax: (518) 276-4030 Rensselaer Polvtedimr Insntu'f- \>-v. : -k IjIsi.- , m i 51'^) 276-6377 R&S 144205 Background The various plastics used for packaging and for structural or durable applications are physically incompatible. In manufacturing operations, reworking of parts is difficult or impossible once plastics have been combined. Direct recycling of commingled post-consumer plastics gives mixtures with poor physical properties and little commercial value. Mechanical sorting is sometimes possible but expensive. Manual sorting tends to be expensive and inadequate, even with third-world labor costs. The thermodynamic differences that cause plastics to be incompatible cause them to be separable by Rensselaer's selective dissolution process. Individual, functionally-pure polymers can be obtained by dissolving one polymer at a time from a complex mixture. The process uses a single solvent or a small number of solvents at different temperatures. Recovering the plastics in solution ensures homogeniety on a molecular scale. Filtration removes contaminates. Impact modifiers can be added to enhance properties for the plastic's second life in structural and durable applications. The dissolution solvent is separated from the plastics and returned to the process for reuse. The major emphasis of Rensselaer's research program has been on post consumer packaging wastes, those materials typically found in household trash. However, the general technology is also applicable to a variety of pre-consumer materials such as manufactured assemblies and multilayer film. Post-Consumer Waste Household packaging waste consists of six major polymers: high density polyethylene (HDPE), low density polyethylene (LDPE), polypropylene (PP), polyethylene terephthalate (PET), polystyrene (PS), and polyvinyl chloride (PVC). The six plastics can be separated into individual, funtionally pure polymers of near virgin quality. Molecular weights and physical properties are essentially unchanged from those of the virgin resins. Our current technology, now suitable for commercialization, retains pigmentation so that applications are limited to dark color and colorinsensitive applications. Technology under development includes depigmentation and .. fine-tuning of the average molecular weigt. The ultimate goal is to produce recycled materials which are functionally indistinguishable from virgin polymers and which cost less than virgin polymers. This goal appears achievable with Rensselaer's technology. 2- - R&S 144206 Pre-Consumer Sources Rensselaer's selective dissolution technology is directly applicable to many preconsumer waste streams. To date, we have developed high efficiency separation schemes involving the following plastics: ABS EVA EVOH HOPE LDPE LLDPE Noryl Nylon 6 Nylon 66 PC PET PMMA PP PS PVC SAN SMA Surlyn Separation schemes involving two to eight of the these polymers have shown essentially quantitative yields. The heat history of Rensselaer's recovery process is moderate, giving little or no change in polymer properties. In general, the recovered polymers are directly suitable for reworking into the original manufacturing operation. Economics The M.W. Kellogg Company has prepared a preliminary design package for a 100 pound per hour pilot plant and a 70 million pound per year commercial plant for separating post-consumer packaging waste into its component polymers. (Note that Rensselaer is the owner of this study and that Kellogg has no rights to the technology.) Based on this study, capital costs have been estimated to be $4,640,000 for the pilot plant and $33,100,000 for the commercial plant. Table I shows utilities requirements for the commercial plant and Table II shows projectaed economics. Markets in excess of one billion pounds per year are believed to exist for the products of this plant given selling prices in the range of 25 to 30 cents per pound. A simpler version of the technology - suitable for countries with low labor costs - is available. Commercialization Rensselaer and its partners in this technology are exploring several routes to its commercialization. Interested parties should contact Bruce Nauman, 518-276-6726, for preliminary discussions. Special Evaluations We are able to provide custom evaluations of specialized waste streams. Kilogram size samples of the individual, recovered polymers can be produced. Recovery conditions suitable for scaleup can be defined. When necessary, confidentiality can be maintained. A list of available process and analytical equipment is provided in Table III. R&S 144207 3- - Additional Information A description of Rensselaer's selective dissolution technology as applied to post consumer waste is given in: Battle, K.E., Moore, A.P., Lynch, J.C., and Nauman, E.B., "Plastics Recycling by Selective Dissolution", Paper presented at the 1992 Petrochemical Review, sponsored by DeWitt & Co., Houston, March 26, 1992. Earlier versions of Rensselaer's selective dissolution technology have been described in the following publications: Lynch, J.C., and Nauman, E.B., "Separation of Commingled Plastics by Selective Dissolution", Proc. SPE-RETEC, Charlotte, NC, October 30, 1989. Lynch, J.C., and Nauman, E.B., "Recycling of Commingled Plastics via Selective Dissolution", Proc. 10th Inti. Coextrusion Conf., 99-110, 1989. See also Discovery magazine, December 1992, p. 23. Publications describing Rensselaer's technology for impact modification and solution processing include: Nauman, E.B., Ariyapadi, M.V., Balsara, N.P., Grocela, T.A., Fumo, J.S., Lui, S.H., and Mallikarjun, R., "Compositional Quenching: A Process for Forming Polymerin-Polymer Microdispersions and Interpenetrating Networks", Chem. Eng. Commun., 66, 29-55 (1988). Grocela, T.A. and Nauman, E.B., "Impact Polystyrenes of Novel and Controlled Morphology", Proc. ACS Div. Poly. Matls.,63, 488-492 (1990). Furno, J.S. and Nauman, E.B., "A Novel Heat Resistant Blend Produced by Compositional Quenching: A Thermoplastic Polyimide Impact Modified with a Fluoroelastomer", Polymer, 32, 87-94 (1991). Nauman, E.B., "Flash Devolatilization", Encyclopedia of Polymer Science and Engineering, Supplement Volume, 317-323, Wiley, New York, 1989. Nauman, E.B., "Fine Particle Dispersions of Incompatible Polymer in Polymer Matrices, U.S. Patent No. 4,594,371, June 10, 1986. Nauman, E.B., "Cocontinuous Phase Dispersions of Incompatible Polymer Matrices", U.S. Patent No. 4,666,961, May 19, 1987. Fumo, J.S. and Nauman, E.B., "Impact Modification of a Heat Resistant Thermoplastic Polyimide", U.S. Patent No. 4,987,188, Jan. 22, 1991. 4- - R&S 144208 TABLE I Maa<Etrafl amqfl IEmtrgy lallaaKCfBS i?t Mb Cmim(Eirc5iifl IPflam II Utilities fresh water inert gas compressed air natural gas electricity Annual Rate 60,254,032 gallons 7.536.000 pounds 1.600.000 pounds 306,225,618 SCF* 22.226.400 KW hours Input Streams commingled plastic waste polymer masterbatches replacement solvents Annual Rate 71.890.400 pounds 2,093,012 pounds 620,095 pounds Output Streams product wash system solids hazardous waste solids water purge to sewer solvent/heavies to oil burner water from boiler blowdown Annual Rate 70,693,393 pounds 2.800.000 pounds 1.540.000 pounds 6,548,461 gallons 620,095 pounds 18,097,572 gallons* *69,035,256 SCF/yr of natural gas can be replaced by a 65,952,000 pounds/yr of 200 psig steam. The onsite boiler blowdown would also be eliminated 5* - 31 W 4444 NJ O CO TABLE II COST ESTIMATE FOR NOMINAL 70,000,000 PQUND/YEAR COMMERCIAL PLANT Item Utilities Fresh Water Inert Gas Compressed Air Natural Gas Electricity Unit Cost 700/1000 gal 120/1000 scf 60/1000 scf $2.00/10^ btu 6.60/KWH Total Utilities Cost Per Pound of Products. Cents 0.06 0.02 0.00 0.67 2.07 2.82 Other Plant Costs Makeup Solvent Waste Disposal Direct Labor Maintenance Plant Overheads Waste Plastic Feedstock; at 40/lb 120/lb $200/ton $35,000/operator 2% of fixed investment 100% of direct labor Total Other Plant Costs Conversion Cost 0.11 0.22 0.60 0.93 Plant Cost 2M 5.28 4.07 9.35 Sales Expenses and Corporate Overheads Depreciation at 10% of Fixed Investment * TOTAL COST 2.00 LSI 16.02 Profit at 20% of Fixed Investment -9-34 PROFIT INCLUDED SELLING PRICE 25.36 R&S 144210 6- - 1 ABLE III RENSSELAER'S IPLYMEE 0>CE EAIBOIRATOIRIIES Major Equipment Items Item Primary Dissolution Vessel Flash Devolatilization Apparatus Twin Screw Extruder Single Screw Extruder Single Screw Extruder Injection Molding Machine Compression Molding Press Tensile Tester Tensile Tester Izod Impact Tester Melt Indexer High Temperature GPC Rooirt Temperature GPC Gas Chromatograph Differential Scanning Calorimeter Thermogravimetric Analyzer Gradient Density Column Optical Microscope Supplier, Model American Reactor Company, 30 gallon From components, 2 Ibs/hr, to 1 Torr Werner & Pfleiderer, 30 mm Killion, 1 inch, powder feed Killion, 1 inch, pellet feed Sandretto, 60 ton, with feedback control Carver Instron, Model 1402 with environmental chamber Tinius Olsen TMI, with notch cutter Tinius Olsen Walters Associates, Model 150CV with viscometer Perkin-Elmer Perkin-Elmer Perkin-Elmer Perkin-Elmer Fisher Olympic R&S 144211 7- -