Below you will find documents from the TAPPI International Flexible Packaging and Extrusion Division's Conferences (Formerly referred to as the PLACE Division Conference). To find documents prior to 2010, please visit the conference document archives in TAPPI's eLibrary.
Rethinking the Paper Cup – Beginning with Extrusion Process Optimization for Compostability and Recyclability
By Nicole Whiteman, Industry Manager, NatureWorks LLC Andrea Auchter, Applications Development, NatureWorks LLC Andrew Christie, Managing Director, SAM North America Michael Prue, Lab Manager, SAM North America
More than 50 billion disposable paper cups used for cold and hot beverages are sold within the United States each year. Most of the cups are coated with a thin layer of plastic – low density polyethylene (LDPE) – to prevent leaking and staining. While the paper in these cups is both recyclable and compostable, the LDPE coating is neither. In recycling a paper cup, the paper is separated from the plastic lining. The paper is sent to be recycled and the plastic lining, if LDPE, is sent to landfill. In an industrial composting environment, the paper and lining can be composted together if the lining is made from compostable materials. Coating paper cups with a compostable performance material uniquely allows for used cups to be processed by either recycling or composting, thus creating multiple pathways for these products to flow through a circular economy.
A segment of the paper-converting industry uses an extrusion grade of polylactic acid (PLA), frequently for zero-waste venues and for municipalities with local composting and food service items ordinances. The results among these early adopters reveal process inefficiencies that elevate manufacturing costs while increasing scrap and generally lowering output.
NatureWorks and Sung An Machinery (SAM) North America researched the extrusion coating process utilizing the incumbent polymer (LDPE) and PLA. Ingeo™ 1102 is a new, compostable, and bio-based PLA grade designed specifically for the extrusion coating process. The research team identified the optimum process parameters for new, dedicated PLA extrusion coating lines. The team also identified changes to existing LDPE extrusion lines that processors can make today to improve output. The key finding is that LDPE and PLA are significantly different polymers and that processing them on the same equipment without modification of systems and/or setpoints can be the root cause of inefficiencies. These polymers each have unique processing requirements with inverse responses. Fine-tuning existing systems may improve overall output for the biopolymer without capital investment and this study showed an increase in line speed of 130% by making these adjustments. However, the researchers found that highest productivity can be achieved by specifying new systems for PLA. An increase in line speed of more than 180% and a reduction in coat weight to 8.6 µm (10.6 g/m2 or 6.5 lb / 3000 ft2 ) was achieved in this study. These results show that Ingeo 1102 could be used as a paper coating beyond cups.