Recycling mixed plastic

Current methods of feedstock recovery are reviewed. Brief details are given of pyrolysis, hydrogenation, gasification, and chemolysis. Activities of some European companies are briefly discussed in the areas of recycling mixed plastics waste and closed-loop recycling. 

Mechanical Recycling (%) Mixed Plastic Recycling (%) Feedstock Recycling (%) Energy Recovery in MWI (%) Landfill (%)... 

J.-R. Pauquet, F. Sitek, R. Todesco, Process for stabilizing recycled mixed plastics, U.S. Patents 5,298,540, 29 Mar 1994, Appl. 25 Mar 1992, priority 27 Mar 1991, to Ciba-Geigy Corp. 

Hammer s Plastic Recycling Corp. buys off specilkation or off-grade resins and obsolete or surplus virgin resins. Formed m 1984, Hammer s Plastic Recycling manufactures products made Irom 100% recycled mixed plastic wastes. 

Processes designed to use thermal treatment to decompose the plastics into liquid and/or gaseous materials have often had mixed technical and economic success. For example, BASF planned to build a 661-million-lb/year facility for recycling mixed plastic wastes into hydrocarbon feedstocks, but eventually canceled the plans. 

Some industrial or laboratoiy attempts are based on reprocessing at low temperatirres. In these attempts high melting polymers are used as sohd filt ers." Another useful method comprises the use of compatibilizers and stabihzers in the pol3rmer blends. Mechanical properties of these recycled mixed plastics are generally inferior, the sruface properties are poor, and in some cases the cost of compatibihzers and stabihzers is too high for recycled materials. 

TABLE 2. Mechanical properties of recycled mixed plastics waste... 

Hence, there is a considerable deterioration of mechanical properties when commingled recycled mixed plastics waste is directly compounded. Because of this deterioration, the possibilities of direct use of recycled plastics is limited. However, they may be used for less demanding applications - this is the origin of the expression... 

This procedure is in the direct competition to the incineration plant for the PVC recovery. The process can recycle mixed plastics with a high PVC content, like that produced from building waste. LINDE-KCA DRESDEN GmbH (a subsidiary of LINDE AG) offers a plant of this type with throughput rates of up to 8 t/h. The plant may also be operated efficiently as a stand-alone plant for small quantities of waste. It recovers the chlorine in the form of aqueous HCl directly during depolymerisation. 

Camacho, W. and S. Karlsson, NIR, DSC, and FTIR as Quantitative Methods for Compositional Analysis of Blends of Polymers Obtained from Recycled Mixed Plastic Waste. Polym. Eng. ScL, 2001. 41 1626-1635. 

Michigan Molecular Institute. Recycling mixed plastics. NIST-ATP 91-01-0088. status-reports. atp. nist. go v/reports/91-01-0088PDF. pdf 1991. 

A possible route to recycle mixed plastics wastes to obtain secondary materials with acceptable mechanical properties could be to blend them with virgin polymers or, at least, with recycled homopol3rmers. In a previous paperprocessing and properties of blends of virgin low density polyethylene (LDPE) and mixed plastics waste (MPW), have been presented. The experimental results have shown that all the mechanical properties, with an exception of elongation at break, are very similar to those of the virgin material if the MPW content does not exceed 50%. 

Deutschland System (DSD) [13] that to compete with conventional materials such as wood and concrete, plastics recycled from domestic waste would have to last 3.3 times as long as the materials they replace. From the known properties of recycled mixed plastics it is most unlikely that this could be achieved [10]. 

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