Meeting sustainability goals with flexible packaging

A conference on the latest developments in materials and production technology for Multilayer Packaging Films, was organised by AMI in June 2010. Multilayer packaging films facilitate low weight product protection with longer shelf-life, thus reducing waste. Andrew Reynolds, Consulting Director at AMI described the growth in convenience packaging to cater more to single families, and the move to both partners in employment. Currently global film markets consume 68 bln lbs of polyethylene, 13.3 bln lbs of polypropylene and other materials including polyester account for 7.7 bln lbs. The latter group is expected to grow at 7.7% pa.
The food packaging industry has been changing with mergers of companies such as Amcor/Alcan and Berry Plastics/Pliant according to Kraft Foods. There are many challenges for such brand owners including the variety of global food products, the wide range of form-fill-seal equipment in use including vintage; increasing consumer demands such as snap and seal bags; sustainability and packaging reduction targets; shelf-life and quality concerns. There are moves from foil to metallized plastic, which need to be evaluated for barrier properties. One example of a Kraft initiative is the move from glass jars to Kenco Coffee multilayer film refill bags.
Reifenhauser described the move towards bag packaging for milk. As an example, 60 lbs of beverage is typically packaged in 50 lbs of glass, and could potentially be packaged in 1.3 lbs of flexible plastics. The new milk bags are made from LDPE/LLDPE blends and fit in a reusable pitcher. When EVOH is used in bags for UHT milk, there is a shelf-life of about 3 months at ambient temperature. In Dubai, Taghleef Industries has been developing new films following on from its production of BOPP films with good moisture barrier properties. Alternatives include metallised PET for food items like coffee. Similarly, PE can be combined with EVOH as a gas barrier for sliced meat.
In the 1960s, Chisholm and Schrenck took patents on coextrusion. Many advances have followed since then. Extrusion Dies Industries has introduced layer multiplication technology to improve physical properties, formability and to improve barrier performance. In one trial on rigid barrier packaging, a 7-layer sheet (PP/PP/tie laye/EVOH/tie/PP/PP was multiplied up to a 16-layer and a 76-layer sheet. The company is testing material combinations and interactions, and looking at performance such as oxygen barrier properties.
The Bollore packaging group was founded in 1822 and is now one of the top 500 global companies with turnover of US$10 bln. The Bolphane division has innovative multilayer shrink film formulations of 5 layers including skin, core, and sealant and tie layers: there is high compatibility between the PE and PP copolymers. Long-term shelf packaging can be formed from laminates with interlayer adhesives. LPS Industries works in this field to produce films with high moisture vapor transmission rate and low oxygen transmission, as well as acting as a light barrier. Film production is limited by factors such as pumping capacity, melt temperature, bubble stability, and cooling capacity. Davis-Standard is looking at ways to raise output in blown film extrusion systems, such as intensive cooling with a new Triple Lip Air Ring. The company is working with Dow Chemical to look at the properties of the resulting films. Output of LLDPE was raised by around 120% using this new system. Metallocene PE from ExxonMobil Chemical has good stiffness and toughness, which leads to significant downgauging opportunities and the possibility of simplifying formulation. By combining different grades in coextruded films, properties like clarity can be improved. The target markets for these materials are packaging films including shrink and overwrap. Windmoeller & Hoelscher has studied multilayer stretch film. In 2000 the first 9-layer film was produced, and in 2005 the first microlayer stretch product was prepared (21-layer). Currently 11 layers is quite common and over 30 microlayers are possible. The company has a nanolayer stretch film comprising LLDPE (release layer)/metallocene PE/ULDPE/metallocene PE/ULDPE/ULDPE/metallocene PE/ULDPE (cling layer).
A biodegradable material must completely break down and return to nature within a relatively short time according to the Federal Trade Commission�s advertising guidelines. Flexible packaging already has a lower carbon footprint because it is lower weight. Innovia Films has developed multilayer film comprising bio-laminates of cellulose films with compostable coatings. It can be used as print carrier web and barrier web, which can include metallized versions. The cellulose is from renewable wood pulp so the product has over 90% renewable content. Another bioplastic, polylactic acid (PLA) from Natureworks, has been used in Sun Chips packaging at 100% in 2009. It can be coextruded, for example with a tie layer and HDPE or with a core PVOH layer to improve properties. It has also been laminated with OPP and OPET using an interlayer adhesive. Cardia Bioplastics is an Australian company with manufacturing in Nanjing, China. It has both compostable resins and biohybrids which combine bioplastics and conventional polymers like PE. The company has produced multilayer film structures including combinations such as PE sandwiching a biohybrid, and PE/biohybrid/PE/PET. Filmquest is a leader in the polyester film market. It has been developing a high barrier coating using vermiculite nano platelets. The traditional barrier film comprised an outer PET or BOPP film, a barrier coating, adhesive and an inner PE sealant film. The nano layer is used at the barrier coating point. The negatively charged vermiculite is expected to bind to the positively charged aroma and flavor molecules. In tests on cloves, cinnamon and peppermint, the volatile oil was retained at very high levels at 11 weeks compared to a usual loss of 25-50% at this time point.
Polyolefin films can be combined using adhesive resins, such as those manufactured by Mitsui Chemicals America. Polyolefins are difficult to bond and adhesive layers allow them to be combined with other materials, such as high gas barrier polyamide or EVOH. A typical structure for a bag of chips might be: PET/PE/tie/EVOH/tie/PE. The adhesive bonds to the polyolefin by diffusion and it bonds to the polar barrier material by chemical reaction. Heat energy is required for good adhesion to take place, so processing conditions are important. The latest grades have better performance with OPP films. PVDC is a well-known barrier plastic supplied in North America by Solvay Advanced Polymers. It prevents moisture, oxygen, odour and fat transfer, and supplies seal integrity and transparency. Currently there are investigations into using renewable feedstocks to advance sustainability. As an example of its effectiveness in cutting food waste, only 0.3 gm combined with 2.2g of BOPP film can double the shelf-life of crackers and cookies. PVDC extrusion requires streamlined flow and corrosion-resistant machine parts. As well as coextrusion, it can be used as a coating to create a multilayer structure.
Chevron Phillips Chemical produces styrene block copolymers, which can be used to improve the properties of LDPE and LLDPE films. As a smooth extruded outer layer, this copolymer can eliminate surface haze giving a clear, glossy film, which is attractive in the retail environment. A rise in material stiffness permits downgauging, cutting the amount of packaging required, and adds a �crisp� feel to the film. As with all new products entering the food markets, the FDA is keen to ensure safe use: currently there is a case by case evaluation of nanotechnology. This situation has been reviewed by Keller and Heckman. European Union Food Contact Regulations Articles 12 and 13, which permit manufacturing �with substances other than those included in the Community list� for layers that are �not in direct contact with food�, specifically exclude �substances in nanoform�. Despite this, the value of the nano business in the food and beverage packaging industry is expected to reach US$7.3 bln by 2014.
Specialty films offer the opportunity for weight reduction in packaging and a longer shelf-life for food, moving towards sustainable packaging goals. The next networking opportunities from AMI will take place in 2011.