Technical Papers Plastics
Latest innovations in specialty films being developed to provide appropriate barrier and protective properties

Latest innovations in specialty films being developed to provide appropriate barrier and protective properties

The flexible packaging market in Europe is valued at around Euros 20 bln as per Andrew Reynolds, the Research Director at Applied Market Information. There is room for growth to replace rigid packaging and reduce weight, as per the new YES pack from Kraft, which is replacing a bottle. There is increasing globalisation in this market as both food and packaging companies expand their geographical footprint. The focus for packaging is both on consumer appeal and product differentiation, and on improving sustainability in the supply chain. Specialty films are being developed to provide appropriate barrier and protective properties and the latest innovations were highlighted at the annual AMI international conference on Multilayer Packaging Films 2011, held in Cologne

Leading brand owner, Procter & Gamble, is constantly looking for superior innovation combining the needs of the consumer with leading technology from the supply chain. The company had US$80 bln of sales in 2010 and spends more than US$700 mln on packaging films. There are more than 500 packaging researchers, aiming to improve sustainability and fast track new products. P&G is famous for its FMOT - First Moment of Truth- thinking, which is the point when a consumer sees a product and makes a decision to purchase. The development process can be reverse engineered from that starting place and needs to consider factors such as decorative effects, pack differentiation, affordable functionality and a good consumer experience in use. The 5 sustainability mantras are: reduce, reuse, recycle, remove and replace. Procter & Gamble is looking to build relationships with packaging suppliers who have a global reach and can speed up cost-effective packaging development.

Dow is producing sealing layer materials to improve film seal integrity, thus reducing food waste. In a 2009 study conducted by WRAP and the University of Lincoln it was found that around 8% of packages failed in the supply chain. Three factors should be considered in VFFS performance: heat seal, hot tack and caulkability. The hot tack performance is the ability of the material to resist the spring back force, and the caulking property is the ability to flow into gussets and wrinkles. Thus a polyolefin plastomer (POP) that fills the gaps enables hermetic sealing and Dow has an octene-based range of these materials. Also in the adhesives and sealants category, Henkel is looking at food safe adhesive interlayers for multilayer packaging films. The focus has been on low migration, low toxicity materials for applications from Alu/PETP/CPP retortable pouches to coextruded OPP/LDPE packaging films. A new laminating product range has been developed for bio-based films from renewable raw materials, based on low viscosity, solvent-free PUR. Polybutene products from LyondellBasell are used in peal-seal films and to modify the seal initiation temperature in BOPP and COPP from 115°C down to 75°C. In multilayers the PB-1 is blended with PE depending on the final requirements. There is a new family of C4 Koattro resins developed for PP modification and in pilot production in Italy. In terms of manufacturing technology,

Film producer RKW processes around 350,000 tons of PE and PP per year at 21 sites and co-extrudes up to 7-layer films. The company is conscious of the carbon footprint of its products and materials and is looking at improving sustainability. For example, a highly mineral-filled polyolefin wrapper can replace an aluminium laminate and reduce the carbon footprint by 35-60%. The company has many new products including laminate PP films for retortable pouches that are heat stable to 125°C for 45 minutes. Reifenhauser Extrusion is a leader in extrusion equipment. The company sees demand for high flexibility, short product changeover time, ultra-tight tolerances, and energy saving. The trend is for wider lines over 5 m in Asia rather than Europe or the USA, and for 5- and 7-layer lines over 3m wide for high barrier film. Cast coextrusion is used to reduce the thickness of expensive layers like EVOH, and allows a wide range of film thickness on the same die. The end use markets for barrier films include liquid packaging and MAP packs for meat, fish and cheese. The level of barrier required varies with the product, for example fresh fruit and vegetables tolerate a water vapour transmission rate (WVTR) of 10-3000 whereas baby food and dried coffee need a much higher seal of 0.7-3 and similarly for the oxygen transmission rate (OTR). A typical 5-layer barrier might include outer layers of LDPE around EVOH in an adhesive /tie layer sandwich. As one example, an extrusion coated bread pack comprised OPET at 12 microns, LLDPE at 21 microns, tie layer 3 microns, EVOH 3 microns, tie layer 3 microns and an outer LLDPE layer at 20 microns. Biaxially oriented films are found in barrier applications from MAP to vacuum skin packaging. Multiple bubble systems are used to produce many of these films from shrink bag and film to lidding films and GAP Srl provides systems for this. In a three-bubble line the plastic is extruded through a circular die and immediately water quenched; the resulting tube is then re-heated and blown and at this point the non-contact orientation occurs; the second bubble is air cooled and flattened, then a third bubble is annealed in ovens. Orientation improves mechanical properties, enhances impermeability, dimensional stability and gives a gloss effect. The layer thickness in barrier films ranges from 25 microns down to 1440 Angstroms. Extrusion Dies Industries is involved in microlayer production and studied the gauge required to achieve the right properties. For example, the oxygen permeability of EVOH is around 10 cc/ at 4 microns thick and down to 1.4 at 25 microns thickness. Oxygen barrier properties also improve with a higher level of crystallinity, which in turn is affected by cooling rate, orientation and annealing.

Polyamide is often used for its barrier properties, for example in gas flushed barrier laminates for Dairy Crest resealable cheese packs. Ube has capacity to produce over 155 kT per year of PA at sites in Asia and Europe and copolymers of PA6 and 6,6 are produced for film use. They are found in applications such as shrink bags, for example in 7-layers with EVOH, PE and tie layers at a total thickness of 50 microns, or with a PET in a 9-layer structure. The 7-layer film tested by Ube has good puncture resistance, which is important for wrapping products with sharp edges like bones in meat. Another grade of PA, Terpalex, which has a much higher CO2 transmission rate, is used for packaging items that need to �breathe� like respiring cheese. These types of films are replacing PVDC-based bags and are around 40% lower gauges. There are new metallocene polyolefins available from Total Petrochemicals. The company is focusing research on sustainability, which includes PLA (bioplastics) and renewable feedstocks. The metallocene technology uses less energy in production. The ultimate goal is a film material that is highly transparent and stiff with good tear resistance for applications like bread bags, magazine packaging and lamination film. A Lumicene coextruded structure can provide the necessary properties. This metallocene polymer can also be used in each layer in a PE/PP combination for interlayer adhesion without a tie layer, optimising the optical performance. A new Supertough material is in development, which would allow more downgauging. MAH-modified polyolefin is extrudable adhesive, and is supplied by companies such as Yparex. The MAH reacts with the hydroxyl group of minerals, glass and EVOH, and with the amine group of polyamide. During the K show in 2010 an Yparex resin was run in a 16-layer demonstration film by Windmoeller and Hoelscher. PP based Yparex grades have higher heat resistance, so are suitable for applications such as hot fill. In three-bubble film lines the adhesion time is very limited as the film is quenched after exiting the die and there is a high level of stretching, so appropriate adhesive has been developed. A new player has come into the tie-layer resin marketplace: Industrie Polieco MPB Srl of Italy. The company grafts MAH onto LLDPE and has compounds and resins for blown and cast film extrusion, EVOH and PA.

Quality control of multilayer film is under investigation. There are a variety of possible defects including insects, gels, black specs, contamination, die lines, oil stains, holes and fish eyes. 40% of defects originate during pellet transport, 25% in the resin (either the recipe or contamination) and 15% of problems arise during processing. OCS Optical Control Systems is developing technology for monitoring defects and feeding the results back into the production process including the raw material supply system, according to the specification for each film type, from optical sheets to food films. One area where quality control is critical is in the pharmaceutical industry. Amcor Flexibles works in this sector and produces active pharma packaging with a desiccant. The outer film layer is OPA at 25 microns, the next layer is aluminium at 45 microns and the inner layer is PE. Dessicant particles can be incorporated into the inner layer to inhibit cross diffusion and keep moisture to a minimum in cold form blisters. Calcium oxide is the active component and it is blended into a mineral-filled, blue PE masterbatch, which is then coated onto aluminium foil. Formpack Dessiflex has been shown to keep the blister cavity dry for more than 5 years at 40°C/75% r.h.

The environment and sustainability are the hottest topics in the packaging industry. Innovia has been at the forefront of developing barrier films from renewable sources. The NatureFlex range comprises a transparent cellulose film with barrier coatings, and the wood pulp feedstock is from managed forests and not from food crops, which means that the product content is 94% renewable carbon. This film has excellent twist properties, provides an aroma barrier and is heat resistant to 200°C. It is used in Quality Street (Nestle chocolate) wrappers in rainbow colours and is being tested for barrier properties in paper laminates. It has recently been tested and found to be a good barrier to mineral oil, which has been the subject of recent food safety research. One supplier of bioplastics in Europe, FKuR Kunststoff has also looked at combining bioplastics with other materials, including the use of coextrusion. There are two types of bioplastics: biodegradable (fossil or renewable carbon source) and biobased (renewable carbon source). The biodegradable materials can be difficult to process on conventional equipment, so they are compounded to improve properties. The company�s Bio-Flex range comprises PLA and co-polyester and can be incorporated in a 3-layer film that can be processed on conventional LLDPE blown-film extruders and contains 60-80% renewable carbon. Another innovation in the retail industry is the development of smart packaging. The Fraunhofer Research Institution for Modular Solid-State Technologies is studying sensor technology and has developed a colour-changing film, which can be integrated into packaging and detects amines from decaying food such as fish and meat, changing colour from yellow to blue. When the blue colour is very evident, the food is not safe to eat.
The specialty packaging films industry continues to grow and expand in complexity, with new materials, new barrier testing and quality control. AMI has scheduled the next conference on Multilayer Packaging Films 2012 to highlight the latest trends.
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