Plastics Recycling by Selective Dissolution
Publication Date: 2012-Jun-06
The IP.com Prior Art Database
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PLASTICS RECYCLING &\\7b
K.E. Battle, Dr. AP.Moore
J.C. Lynch, Dr. E.B. Nauman
Presenter Ken Battle
The DeWitt Conference March 25-27,D92
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Thank you for the opportunity to talk to you about an exciting new plastics recycling process being developed by Rensselaer Polytechnic Institute and The M.W. Kellogg Company.
Plastics are an increasingly large component of municipal solid wastes. There are volumes being printed about the magnitude of the "problem". There are social and environmental concerns about which we will not spend time here summarizing what has already been spoken and published. Both Rensselaer and Kellogg are of the opinion that the only solution
to this situation will be one driven by economics.
We view the situation this way there are valuable raw materials going to the dump; and the public is paying to put them there! The plastics going to the dump have a new value of 30to 90 cents per pound for the most part. Why should this value not be recovered?
The Rensselaer process is called selective dissolution. In this talk we will first give an overview of the process and its advantages for recycling municipal solid waste plastics. Then we will describe what Rensselaer sees as the total recycling process from source to end use. We have a simplified process flow diagram to present and we willbriefly explain each process step.
At the end of this talk we will also give a glimpse of some sources of waste containing far more valuable plastics which the Rensselaer process can also recover.
11. Overview of the process
There are six major plastics in the domestic solid waste stream: Polystyrene (PS), Low Density Polyethylene (LDPE), High Density Polyethylene (HDPE), Polypropylene (PP), Polyvinyl Chloride (PVC) and Polyethylene Terephthalate (PET).
amounts of packaging material produced each year for each polymer (see Figure 1). Although these materials are all polymers, they are not compatible with one another. Each type plastic must first be separated before they canbe reused with properties similar to their original ones.
Current technologies to separate these plastics include manual sorting and specific gravity separations. These separations are difficult and by no means 100 percent effective. Using conventional extrusion or molding technology to produce a recycled product requires very high purity of a single type polymer. If this purity is not achieved the thermodynamic differences between the mixed polymers will cause the recycled product to have infenor properties. In contrast, the selective dissolution process uses these very same thermodynamic differences to achieve the separation.
The thermodynamic differences between the six major polymers causes each polymer to dissolve at a different temperature in a solvent. Alternatively different solvents can be used to obtain a separation. By testing a wide variety...