The 11 layer blown film coex line in the Hosokawa Alpine test centre

New 11 layer layout gives extra flexibility

From Dr. Holger Niemeier, Member of the Management Board and Technical Manager  Dipl.-Ing. (FH) Michael Heinecker, Manager Research and Development Hosokawa Alpine AG, Film Extrusion Division, Augsburg 

In 2014 the worldwide usage of high barrier films reached a market volume of 1.76 million tons with a market value of 15.9 Billion US$ as announced by Smithers Pira their market report “The Future of High Barrier Packaging Films to 2019”. Until 2019 consumption is expected to increase by 5% annually. In this context high barrier films are defined as films that are flexible, have a thickness of under 250µm and, at a thickness of 25µm, have an oxygen transmission rate of less than 5cm3/m2/24h. The reason for the increasing usage of high barrier films is an increase in demand for packaging materials with improved product protection. This is particularly the case for food and drink but also for pharmaceutical products.

Special Packaging Solutions are in strong demand

High barrier films offer excellent protection against oxygen, nitrogen and carbon dioxide and not only ensure that sensitive food products such as fresh meat can be packaged but also enhance substantially their shelf life. Particularly in industrialised countries, where changing lifestyles, an increasing number of single households and aging communities are becoming more common, smaller packaging units and case ready packs for fresh food, both of which require high barrier film, are growing in importance. Also stand-up pouches from high barrier film are becoming much more common as their suitability for retort and microwave applications are of great benefit to the consumer. According to the Smithers Pira report stand-up pouches will show the greatest growth rates over the next five years. However not only the rising demand for increasingly specialized packaging solutions in the industrialised countries but also the increasing use of packaging in developing countries will contribute to the market growth.

Current state of the art with high barrier blown films is 9 layer

In comparison to commodity packaging high barrier films represent a relatively small market segment nevertheless this market offers not only the described outlook and growth perspectives but also very interesting profit margins and thus presents a good opportunity for investors. According to current estimates around 20 new barrier lines for blown film alone are installed yearly, For the manufacture of high barrier films 7 and 9 layer lines have become firmly established whereby in the recent past 9 layer lines have come to represent the state of the art technology. Typically, for the production of high barrier films for food applications, polyolefin are combined with layers of EVOH and / or polyamide by means of tie layers in order to achieve the required properties. Apart from the complex production machinery required particularly the barrier materials represent a significant cost factor and are therefore used in as thin as possible layers optimized for a given application. With the most common barrier material EVOH layers as thin as 1µm can be reliably achieved in continuous production.

Two additional layers enable significantly more flexibility

An investment in 11 layer technology is not only suited for companies that are well-established regarding high-barrier films, but also for newcomers who wish to be ideally equipped for future new developments and market requirements. Flexibility, not only in respect of 5 to 11 layer barrier films but also in respect of the enormous versatility of raw materials. Primarily responsible for the high degree of flexibility is the new 11 layer die head of the patented X Series from Hosokawa Alpine. One of the market leaders in the field of blown film lines the company developed a co-extrusion die head with 11 spiral distributors based upon the highly successful X-die heads. The focus of the die head design was the enormous flexibility of the extrusion line which is facilitated by 11 equal layers. An unprecendented variety of layer structures is possible as the whole spectrum of suitable materials despite their very differing viscosities can be employed in any of the extruders and thus any layer without changing the screw. Both symmetrical for example for lamination film and asymmetrical structures for thermoforming applications are possible as well as layer structures with equal or very differing layer thicknesses. Thicker layers, for example from low cost materials, can be achieved by extruding the same material through neighbouring extruders and hence neighbouring layers.

Last but not least the increased number of layers of an 11 layer line offers the possibility of completely new material combinations which could lead to a reduction in layer thickness and result in cost savings or enable new products to be developed which e.g. eliminate the need for downstream lamination.

Amortisation in less than one year

To ensure that the enormous flexibility can be fully exploited under production conditions short material change-over and purging times were given a great deal of attention in the design phase of the die head. For example the change over from a PE film, which of course can also be produced on an 11 layer line, to a high barrier film can be achieved in less than one hour. To enable customers to verify this themselves Hosokawa Alpine operates an 11 layer line in their customer test center which is available for customer tests. On this line, together with customers, new structures are implemented and, with raw material manufacturers, new materials and material combinations are developed and their process properties investigated.

That the flexibility achieved with an 11 layer line is affordable is shown by the following example:

Based upon the assumption that the personnel requirement and energy consumption per produced kilogram of film remain constant a production comparison between a 2000mm wide, 40µm thick film with a symmetrical 9 layer structure and an 11 layer film with the same dimensions is made. The layer structure is as follows: 5 % mLLDPE, 33 % LLDPE, 5 % TIE, 5 % PA, 4 % EVOH, 5 % PA, 5 % TIE, 33 % LLDPE und 5 % mLLDPE.

With the 9 layer film a maximum output of 420 kg/h can be achieved whereas with the 11 layer film the output is 30% higher at 550kg/h. The higher output is achievable with the 11 layer structure as the two individual LLDPE layers in the 9 layer structure are each replaced by two neighboring layers with each layer totaling 16.5% layer ratio. Thus higher outputs are possible as the limiting factor is the throughput in the melt channel. As a result of the higher output by equipment availability of 87.5% a return on investment in under one year can be obtained. Were a 9 layer line to be configured for the same output capability then substantial limitations in the flexibility of the individual layers would be incurred.

A sensible and prudent investment

In summary, it can be stated that the additional investment costs for an 11 layer blown film line, which amount approximately to an additional 10% to 15% over those for a 9 layer line, definitely pay off. The producer profits from a the highest degree of flexibility, can gain a competitive advantage with new structures, can run an almost infinite variety of films from simple PE structures through to 11 layer high barrier films all on a single line and on certain products benefits from significantly higher outputs. Multilayer structures often offer commercial benefits in that certain functional layers can be added by co-extrusion eliminating the requirement for downstream lamination steps. Where very stringent demands are imposed upon the final product the combination of an 11 layer high barrier film with e.g. a metalized outer layer can offer a solution. The integration of an in-line MDO (mono-axial machine direction orientation line) offers an additional possibility to increase the barrier functions and the film stiffness. At the same time use of the MDO ensures that films display excellent flatness (planity) and thickness tolerances, which have a very positive effect on downstream processes such as printing and lamination.