Recycling | process feature
Vicent Martínez of Aimplas explains how supercritical carbon dioxide can help to recover valuable materials from packaging fi lm
Recovery position
Plastics account for more than one-third of all materi- als used in packaging applications, and it’s easy to see why: they offer important advantages including mechanical strength, low weight, high barrier, design fl exibility and recyclability. The packaging sector is under pressure from
stringent legislation regarding plastic materials for food contact applications. Furthermore plastics processors are largely responsible for reducing the generation of packaging waste. Many of them use in-plant recovery systems to reuse out-of-specifi cation fi lm, off-cuts, process scrap, over makes, or old redundant stock. The amount of scrap generated can reach more than 10% depending on the converting process. The scrap is usually mixed with virgin resin to obtain
new products. There are currently several state-of-the- art recycling technologies for shredding and agglomer- ating this type of scrap, making it possible to continu- ously and homogeneously feed extrusion fi lm lines.
Ink removal But when it comes to recovering printed and laminated fi lm waste, the inks used in conventional fl exographic or rotogravure printing lead to colouring of the reprocessed thermoplastic material, limiting its reuse in applications where clarity and transparency are important. There- fore, the waste is used to manufacture low value
www.fi lmandsheet.com
products such as rubbish bags, plant pots or irrigation pipes – or diverted to landfi ll as a mixed plastic fraction. This is because the recycled compound has a dark brown coloration as a result of the inks. Furthermore printing inks are based on organic components that decompose during reprocessing generating gases, volatiles and an unpleasant smell. This recyclate can also be diffi cult to process as blown fi lm. The presence of a multitude of gels affects the
mechanical properties of fi lms. The amount of printed fi lms for fl exible packaging
applications is increasing considerably. A number of recycling technologies have been proposed in order to remove the inks, adhesives and other contaminants, from the fi lms, so they can be reused for added value applications.
Many of these approaches are based on removing
the layer of ink on the fi lm surface, by physical or chemical means. Plastic fi lms used in fl exible packaging applications
can be as thin as 15 microns and are diffi cult to handle due to very low apparent density. So, the fi rst step in these de-inking methods consists of shredding the fi lms into homogeneous, small-sized particles. Physical methods rely on rotating chambers where ceramic beads remove the ink layer by eroding the fi lm surface. Chemical processes use organic solvents or solutions
January/February 2014 | FILM & SHEET EXTRUSION 11
Reels of waste printed fi lm
often end up in landfi ll
because they
are diffi cult to recycle
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46