Q&A: Improving the Performance of Food-grade Films and Draw-Tape Ribbon
Nirav Desai is the director of operations at Haremar Plastic Manufacturing Ltd. He has been working with the company for 10 years.
Q: How can film gauge contribute to a more efficient and effective sealing process for liquid pouches?
A: Good roll geometry, winding tension and minimum gauge variation across the web are key factors in ensuring performance of thin films used to package liquid on a form/fill/seal machine. Roll geometry and winding tension ensure smooth flow of film over the forming cone, eliminating any built in stresses during the heat seal process. Tight control of extrusion parameters, along with auto gauge control and distribution systems and stringent tension control during roll winding help ensure a flat roll.
A lower-gauge film meeting these parameters can also be sealed using ultrasonic technology instead of traditional heat contact sealing, which provides further advantages such as short seal times, excellent reliability when sealing through contaminants and better seal integrity. As well, reduction in sealing temperatures and fewer moving parts result in higher output and lower costs.
Q: Biodegradable film for food pouches presents significant challenges in manufacture. Please explain the importance of film consistency in the metallization process.
A: The metalizing process occurs by evaporating a metal, such as aluminium or silver, in a vacuum chamber to create a very thin layer of metal vapour that condenses on the film surface and imparts a barrier to protect against moisture, light and gases. Barrier properties in a film are essential to food preservation and extending the shelf-life of packaged foods.
Since the metalization processes take place in a vacuum chamber at high speeds, it is very important to have a suitable film to ensure uniform adhesion of the metal particles. The film must have excellent gauge control, must be free from surface imperfection and void of any migratory additives that interfere with the adhesion of the metal particles. Another important factor to consider is an absolutely flat and wrinkle-free roll. Any wrinkle or gauge band may cause inconsistent deposit of metal particles leading to inconsistent barrier properties in film. These factors become even more critical when developing PLA-based biodegradable film for use in food packaging, a project Haremar recently undertook in partnership with BASF. The film’s high modulus posed a challenge in making a flat wrinkle-free roll, highlighting the importance of tight process parameters and control on the extrusion line.
Q: How do consistency and sealability contribute to improved yields in the manufacturing of draw-tape bags?
A: A typical draw-tape bag consists of a high-modulus draw-tape or ribbon attached to a lower-modulus LLDPE bag. The draw tape is inserted into the bag by creating an opening/gusset that is heat-sealed at the ends making the tape integral part of the bag. In order to achieve higher yields, a low CoF; high modulus and tensile strength; and a low seal initiation temperature are essential to have.
Some of the other factors that play an important role but not normally discussed are the quality of slit ribbon roll and its diameter. A ribbon roll without any notches with the highest possible diameter ensures long uninterrupted runs reducing down time and changeovers, resulting in significant improvement in yields.
Haremar Plastic Manufacturing Limited
(905) 761-7552; www.haremar.com