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bioplasticsMAGAZINE_0904

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bioplasticsMAGAZINE_0904

Bottle Applications

Bottle Applications Using Near-Infrared to Recycle Article contributed by Tim Vanyo, Principal Applications Engineer, NatureWorks LLC Minnetonka, Minnesota, USA In the last several years, new plastic bottles made from renewably resourced Ingeo (polylactic acid) PLA have entered the market. Brand-owner and retailer demand for such bottles continues to be strong, signifying society’s demand for more sustainable products and market development. Since Ingeo bottles look and feel similar to PET bottles, recyclers often assume that material identification between the two is difficult and have been concerned that appreciable contamination of PET with PLA may result. In order to continue to introduce Ingeo biopolymer into the plastic bottle market in a responsible way, NatureWorks LLC and Primo Water Corp. conducted a commercial-scale bottle recycling evaluation to determine whether automated systems being used today in the recycling industry are capable of separating PLA bottles from PET bottles with good accuracy and efficiency. In this evaluation, near-infrared (NIR) equipment was used since it is a common sortation technology in large recycling operations and can accurately identify many different types of polymers. Objectives The objective of the work was to determine whether plant made PLA materials can be effectively separated from the PET plastic bottle recycling stream and does not appreciably contaminate downstream recycled PET (rPET) extrusion processes. The test involved spiking in a known level of Primo’s PLA bottles into a PET deposit stream during the sortation process. That level was chosen so as to simulate market share significantly above today’s level. The field tests, held earlier this year at major recycling and rPET sheet extrusion facilities, were conducted under actual operating conditions. A TITECH near-infrared optical sorter already being run at the facility was used for the test. Step 1. Set-up and calibrate NIR equipment for PLA bottle sortation. Step 2. Spike known amt. of PLA bottles into clear PET deposit bale during largescale run. Step 3. Determine sorting process efficiencies. Step 4. Make lab plaques and compare test flake to control flake after the washing process. Step 5. Complete largescale PET sheet run. Determine how spiked PLA level affects PET sheet quality. Is PET sheet spiked with PLA sellable and accepted by market? Figure 1 - Process Flow for NIR Sortation Study using PLA Bottles 24 bioplastics MAGAZINE [04/09] Vol. 4

Bottle Applications Sorting PLA Bottles The objectives of this work: • Determine whether NIR equipment now in the field is able to recognize PLA’s NIR signature and capable of sortation at commercial-scale production rates • Process and evaluate using existing equipment under normal processing conditions Fig 2: Flake Samples (Left – rPET Control Flake; Right – rPET Test Flake) • Determine sorting process efficiencies • Compare the clear rPET test flake (spiked with PLA bottles) with the clear rPET control flake in terms of haze and color in lab plaque samples • Validate the impact clear rPET test flake (spiked with PLA) has on commercial sheet quality (haze and color) and endproduct value (sellable or not). Field test The process flow in figure 1 illustrates the steps carried out for this sortation study. Tests were conducted on a commercial recycling line where a feedstock of PET bottles was being run at over 2,000 kg/hr. For the test, Primo bottles, made with Ingeo biopolymer, were inserted into the PET stream at a volume assuming Primo were the fourth largest water brand in North America (a level significantly higher than Primo’s current market share). The spiking level was achieved by adding in a calculated number of Primo bottles matched to the measured throughput of the PET feedstock on the sorting line. Current industry guideline suggests levels of more than 1,000 parts per million (ppm) of PLA in the PET post-sort stream would cause contamination. The amount of Primo bottles that entered the recycled PET stream after NIR sorting was measured at 453 ppm. The low amount of PLA in the recycled PET was due to high efficiency in sorting the PLA from PET using the NIR Titech sorter already in use at the facility. The sorter was calibrated and fine-tuned by a technician for PLA recognition before the test run without any significant problems. The Titech NIR sorting efficiency test results are summarized in [Table 1]. Using the control and test rPET flake from the sorting tests, commercial sheet was made to determine how the spiked PLA material would affect PET sheet extrusion and product quality. 1.3 mm (0.021-0.022 inch) sheet was made on an existing Parameter TITECH sorter effective width Type of sorting (for PET) Table 1: TITECH NIR Sorting Efficiency Results for PLA Bottles Result 40 inches Positive Bale spiking level 0.68 % PLA spiking level in clear PET flake 0.75 % Total line throughput Removal efficiency 3 % 2118 kg/hr bioplastics MAGAZINE [04/09] Vol. 4 25

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