Improved in-line solid-state polymerization of polyethylene terephthalate flakes to produce plastic straps by removing amorphous material from recovered polyethylene terephthalate

摘要

A process for preparing a PET flake mixture for use in connection with the fabrication of high performance plastic strapping comprises the steps of initially collecting post consumer and non post consumer PET materials having an initially wide range of relatively low intrinsic viscosity (IV) values with a relatively low average intrinsic viscosity (IV) value, and processing the same through solid state polymerization (SSP) so as to obtain a wide range of relatively high intrinsic viscosity (IV) values with a relatively high average intrinsic viscosity (IV) value. The initially collected materials are chopped into flakes and chunks, and the chunks are removed by a suitable destoner so as to render the remaining mixture comprised substantially entirely of flake materials or segments. This is advantageous because the flake segments, as opposed to the chunk segments, are able to be substantially increased in intrinsic viscosity (IV) values and within a relatively short period of time, and in addition, the flake segments are essentially crystalline while the chunk segments are essentially non-crystalline which would otherwise undergo rapid crystallization and generate a substantial amount of heat of crystallization. Such heat of crystallization undesirably raises the temperature of the polymerization process whereby the materials tend to become sticky and agglomerate thereby impeding the flow of the materials being processed as well as tending to clog components of the processing apparatus.