Bags made from coextruded PP/PE film (typically 30-38 microns) are long time market favorites because they provide the required stiffness, tear and optical performance for this application. However, as multi-material packaging solutions, they can be difficult to recycle. The challenge was to produce a thinner mono-material film solution with excellent sealability, optical properties and tear resistance that can be produced on existing bread bag making lines, ensuring compatibility and efficiency.
Alpine’s Machine Direction Orientation (MDO) technology was employed to produce non-laminated mono-material films. The MDO PE films were produced in 25-microns on an Alpine 5-layer coextrusion line, with potential for further downgauging. Unique TRIO and vacuum technology allow further material saving by significantly reducing the trim wastage. “The MDO technology contributed to the high stiffness of the thinner bags,” said Frank Bernotat, Technical Sales Manager – Blown Film, Hosokawa Alpine. “It also helped to provide a level of optical performance normally found when using polypropylene-based formulations.” ExxonMobil Signature Polymers’ resins ensured high performance film properties were achieved in a mono-material design. Films of different stiffnesses have been produced, demonstrating the ability to tailor the formulation according to market needs. Resins in the MDO PE films included:
• Exceed™ HD 6107: An HDPE grade designed for flawless processing of MDO applications.
• Exceed™ Stiff+ m 0238: Contributed to the stiffness and mechanical properties.
• Exceed Stiff+ m 0820: Enhanced the overall processability and performance of the film.
BW Converting successfully converted the MDO PE film into gusseted bread bags. “We performed trials to convert the MDO PE films into bread bags on our Hudson-Sharp Apollo wicketer machine,” said Peter Sztehno, Sales Director EMEA Bag Converting and Printing, BW Converting. “This is the thinnest film for bag making we’ve run on our lines,” said Heidi Hilbert, Marketing, BW Converting. HOBA, a producer of manual and automated bag filling and bag closing machines, evaluated the closing systems’ performance with the new bags, confirming their suitability for automated bread packaging. “This was a great collaboration, resulting in an innovative solution.” said Kevin Plomp, Sales, HOBA.
Results
• Successfully produced 25-micron thin bread bags, the thinnest ever run on BW Converting’s Hudson-Sharp lines.
• Demonstrated trouble-free bag making on dual-use lines for PE and PP structures, allowing easy and cost-effective switchovers.
• Achieved excellent critical TD tear resistance, crucial for packing crusty bread types.
• Anticipate high performance under freezer conditions, compared to PP-based bags.
• Achieved PP-level optical properties with the MDO PE solution (low film haze values of 6 – 7.5)
The development of the thin MDO PE bread bags designed for recyclability* not only met the technical and performance challenges but also provided a mono-material alternative to traditional PP/PE structures. The collaboration across the value chain ensured the successful validation of this innovative packaging solution.