Coating & Laminating Extrusion or adhesive lamination?
the use of new materials, high-performance designs for packaging structures, and the continual development of creative applications. With these considerations in mind, converters
F
need to evaluate the need for laminating machines before making a significant capital investment. Understanding the near-term direction for
market performance is a key part of the evaluation of choosing a laminating machine. Factors such as performance, scrap and quality must be considered. The drive for high-variety, short-run printing, due to consumer impulse buying, leads to ever-shorter product runs for converters operating laminators. Benchmarks for current lamination machinery
range from 550-700 metres per minute for commodity packaging structures such as snack food and simple wraps. The influential criteria at these speeds are web uniformity and flatness, adhesion levels and roll geometry. Technical developments in lamination are driving out cost by reducing product thickness, thus creating thinner products at faster rates. Due to these factors, and the globalisation of
the converting industry, there is greater interest in comparing the benefits of extrusion lamination and adhesive lamination. Most flexible packaging structures can be
processed using either extrusion lamination or adhesive lamination. While it is not as simple as replacing the adhesive with an extruded LDPE, both processes are viable to achieve quality products. The method used often depends more on process familiarity, currently installed
26 July/August 2017
lexible packaging manufacturers are seeing demand for improved quality as well as innovative and cost-effective manufacturing techniques. This includes
equipment, and perception of reduced cost rather than any true product differences between the two processes. Extrusion lamination typically wins in terms of
its thickness characteristics. When making a structure through adhesive lamination, the adhesive adds little to the overall thickness of the structure, yet creates the rigidity or ‘stand-up’ ability. With extrusion lamination, processors can affect the thickness by increasing or decreasing the amount of resin used. Various substrates have their own converting cost based on thickness. By replacing the substrate thickness with an LDPE extrudate, the structure is based on pellet cost as opposed to a converted substrate cost. When considering optics and transparency, an
adhesive laminate has no haze when properly applied, whereas an LDPE extrudate will have some amount of crystallinity and therefore a haze. When an adhesive laminator needs to create a
coloured background on a product, a ‘flood coat’ is added or a pigmented film is purchased, while an extrusion laminating converter can apply the pigment directly into the extrudate. Once the product is made, it has to effectively
run through a form, fill, and seal machine (FFS). Most FFS machinery manufacturers have very little info on comparing products from each process. When running a vertical FFS machine, the coeffecient of friction (COF) of the inside layer (sealing) must be lower than the outside layer. Leakage is minimised through extrusion lamination compared to adhesive lamination. Heat seals are created when heat permeates through the structure to the sealing point. Polymers are a great insulator and will resist this heat transfer. It is possible that changing from a thin adhesive to a thicker plastic extrudate, the heat transfer
resistance, caused by the extrudate, can adversely affect the clamping process by preventing the clamp heat from getting to the sealing surface. It is possible to run both processes on a single piece of equipment through modifications. However it is also important to understand that changing a structure from adhesive lamination to extrusion lamination requires more than replacing the adhesive with an extrudate. There is no need to pick one or the other when
you can have both in a single machine. One of the most exciting developments in flexible packaging is the growth of sequential manufacturing, which addresses the need to produce more complex structures. Structure complexity is driven by the necessity for improved properties, which include improved physical, barrier, optical, seal and performance properties; use of thin alluminium foils for high barrier products, reducing the need for expensive resins; and elimination of solvent odours, flammability and pollution, just to name a few. New manufacturing technologies that sequentially combine separate processes into one line are being used for producing complex, multi-layer products. Some of these machines merge solution coating, cast film, and sheet production with an extrusion coating process. With only one line, processors can create unique, high-value composite webs consisting of several layers and/or diverse materials. Volume and quality will continue to drive new innovation and improved technologies. A machinery supplier committed to all of these processes qualifies to lead innovation in manufacturing techniques for packaging materials both rigid and flexible.
www.davis-standard.com
www.convertermag.co.uk
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