The biodegradable and compostable plastics sector is growing steadily and this is partly due to the fact that several measures have been taken, especially in the EU, to cut down on single-use plastics. For instance, it is estimated that the market for PVA (polyvinyl alcohol), a water-soluble thermoplastic polymer predominantly used in food packaging, will record a compound annual growth rate (CAGR) of more than 6% over the 2021–2026 period. Bausano meets these new requirements thanks to its special PVOH extrusion lines, from the MD Nextmover product family, for the production of water-soluble bioplastic granules, which are ideal for the subsequent blown film extrusion process.
What is PVA?
“Polyvinyl alcohol (PvOH), also known as PVA, is a material that has a low environmental impact as it is fully biocompatible and non-toxic. It also has low oxygen permeability in the absence of moisture,” comments Mr. Alessandro Ruotolo, our Materials Engineer, who adds, “As a result, PVA films are increasingly used for the packaging of food, pharmaceuticals and personal care products, as well as in disposable packaging, such as detergent tablets. In addition, water-soluble bioplastics made from plant-based raw materials are available as an alternative to polyvinyl alcohol. In both cases, given the complexity of the material, the granulation process requires a different approach to traditional plastics, which is why all of Bausano’s special lines are a powerhouse of technology that can be fully tailored to the customer’s specific requirements.”
PVOH extrusion: extruder configuration
In order to determine how to correctly configure counter-rotating twin-screw extruders, which perform better than co-rotating extruders in the case of water-soluble bioplastics, our team of experts takes several aspects into consideration.
The first aspect is the length of the barrel, which must allow the material to pass through for the time strictly necessary for the screws to process it. In fact, if it remains there for too long, it will be subject to excessive stress.
The second aspect is temperature. Processing takes place at much higher temperatures than with PVC, for example. Moreover, in order to obtain a granule without impurities, the gel point must be determined with absolute accuracy.
The final aspect is the type of head and cutting technology used. These help to determine the correct way to cool the extrudate, which is water-soluble and therefore cannot be cooled with water, unlike polymers such as polyolefins. Bausano pays special attention to this step to ensure that the quality of the granules is as high as possible.
PVOH extrusion: developing new technologies to process eco-friendly plastics
“Our special lines for bioplastics processing, and particularly water-soluble plastics, are a clear example of the fact that our company is committed to respecting the environment. Biodegradable films are now considered an integral part of sustainable global economic development and, in order to meet the demands of an increasingly discerning and conscious market, we allocate substantial resources to researching and developing new technologies to process eco-friendly plastics. Efforts are, therefore, being made to support all manufacturers who, in these times of ecological transition, are entering this business,” concludes Mr. Alessandro Ruotolo.