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The greening of packaging films and stretch-blown bottles

Recent advances in sustainable packaging

Posted on Thursday, 05 October 2017. Posted in Sustainability & Health . Written by S Chidambar

Recent advances in sustainable packaging Coca-Cola Plant Bottle

One major area of sustainability where a lot of progress has been made recently is the substitution of resins based on non-renewable inputs like fossil fuels by those based on inputs sourced from renewable resources like agricultural produce (plants). The other is light-weighting and source reduction in flexible packaging laminates. Major success areas in packaging have been ‘green’ PET resins (used for the production of oriented films and stretch-blown bottles) and the development of suitable lower thickness biaxially oriented film substrates for use in multi-layered flexible packaging structures.

Lower thickness substrates
Development of film substrates of lower thicknesses has been an area that film manufacturers have been working on continuously for a long time and, over the years, the lowest thicknesses used for making flexible laminates had come down from 20 microns to 10 – 12 microns for biaxially oriented polyester (BOPET) films and 20 – 25 microns to 15 – 20 microns for biaxially oriented polypropylene (BOPP) films. Incidentally, it was the Indian film industry and the Indian flexible packaging industry that pioneered and established these developments.

The establishment of even lower thicknesses was hampered by the consequent substantial reduction in rigidity or stiffness. Mechanical strength and dimensional stability of the films led to production problems on web handling, stretching, creasing, lower running speeds and throughput and higher wastage during conversion operations like lamination and coating (including extrusion coating) and printing and high-barrier metallisation.

About 3 years ago, Indian film manufacturers were able to develop new resin formulations and tweak process parameters to overcome these problems and this resulted in suitable lower thickness oriented film substrates that were acceptable to the conversion industry. As a result, the lowest thicknesses have now come down to 6.7 – 7 microns for BOPET films and 8 microns for BOPP films. These films run just as well as the thicker films used earlier without any sacrifices on running speeds (tests were carried out at 300 meters per minute or more) or wastage and have now been widely accepted by the flexible packaging conversion industry and end-users and brand owners. Indeed, film manufacturers have won several prestigious international awards for sustainability and innovation for these developments.

An additional benefit was that these lower thickness substrates were able to deliver longer film lengths per roll resulting in less change-overs during conversion operations. Laminates made from the lower thickness films resulted in substantial light-weighting of packages and packaged goods with savings on freight, transportation and storage of both film rolls and packaged products. The source reduction achieved on the bare substrates was as much as 30% - 40% on BOPET films and over 40% on BOPP films. All these films are also now available in heat-sealable grades.

Development of ‘Green’ PET resins
Considerable progress has also been made in the development of ‘green’ PET resins used in the manufacture of BOPET packaging films and stretch-blown bottles. This has been due to the replacement of some non-renewable petro-based inputs by inputs based on renewable resources like plants in the resin manufacturing process.

The two major inputs used in PET resin manufacture are monoethylene glycol (MEG) and purified terephthalate acid (PTA). MEG, which constitutes 30% by weight, was conventionally made from ethanol that was obtained by the fractional distillation of non-renewable naphtha or natural gas feedstock. With the development of bioethanol sourced from plants, it became possible to use this for the manufacture of ‘green’ MEG. This green MEG delivered PET resins that were just as good as the petro-based resins used hitherto in the production of BOPET films and stretch-blown bottles. The first green PET product perfected was green BOPET film in 2010-2011; this was followed by green PET bottle grade resins, based on which Coca-Cola launched their now well-known PlantBottle in 2011. Initially, only a limited amount of green MEG was available but this has now been scaled up substantially. Green BOPET films and the PlantBottle had the same properties and recyclability as conventional products made from petro-based resources which meant they were drop-in replacements for existing products and no adjustments had to be made for their successful use. These developments were also spearheaded by Indian BOPET film manufacturers and their innovations won them several prestigious international awards.

Focus was then shifted to the development of ‘green’ PTA, which made up the balance 70% by weight of the inputs in PET resin manufacture. PTA is made from paraxylene (PX) that is obtained from the processing of non-renewable petro-based feedstocks. Although PX could also be made from agricultural resources, the technology was expensive and not commercially viable.

A couple of years ago, Virent developed its BioForming technology for the production of PX based on sugars sourced from plants. Subsequent pilot-scale production established the commercial feasibility of this technology. Virent then signed a collaboration agreement with Renmatix (producers of industrial sugars using its patented Plantrose technology platform) to jointly exploit the development of bio-based chemicals including PX. Renmatix have also signed up on a joint development agreement with BASF to extend the development of plant-based chemicals like PX from the Plantrose technology.

Replacement of PET with plant-based PEF
In the meantime, a lot of work has also gone into the development of polyethylene furanoate (PEF) polymers based on agricultural furanes. This new resin can replace PET in both film and bottle applications and is claimed to have superior properties. Tests have shown that PEF delivers gas barrier properties that are 10X PET for oxygen and 5X PET for carbon dioxide. It also has much higher tensile strength and mechanical properties compared to PET and this should enable down-gauging (usage of lower thicknesses) while providing the same critical properties as PET.

Avantium, a company founded in 2000 as a spin-off from Shell, has developed their YXY technology, a cost-competitive process for the production of a chemical compound called furandicarboxylic acid (FDCA), which is the main building block for a range of polymers including PEF. YXY technology produces FDCA from agricultural inputs like wood, starches and lignin.

Avantium has formed a JV with BASF called Synvina to exploit the YXY technology and the combine is setting up a 50,000 MT/annum commercial scale plant at BASF's Verdun facility in Antwerp, Belgium. Various other commercial agreements have been signed, details of which are given below.

Commercial agreements for establishing green polyesters
Leading users of PET bottles for beverages and drinking water like Coca-Cola, Pepsi, Nestle and Danone have been particularly active in formulating strategies for the establishing of 100% green bottle-grade polyester resins based entirely on bio-based inputs.

Coca-Cola has been in the forefront of this thrust. It first signed three agreements in 2011 – with Virent, Gevo and Avantium – to fund investments in green polyester development and unveiled the world's first PlantBottle made entirely from plants at the World Expo in Milan in June 2015.

Avantium has signed strategic partnership deals with Mitsui and Toyobo for the development of film, sheet and fibre products in Asia. The deals include preferential allotment of resins from Synvina's Antwerp plant when it is commissioned.

Pepsi has initiated a detailed development programme for the establishing of 100% plant-based bottles. Nestle and Danone, the world’s two largest manufacturers of drinking water joined forces in May 2017 to jointly develop a totally green polyester bottle that is based on waste materials like sawdust and crop residues.

In September 2016, Andeavor Corporation (formerly Tesoro Incorporated), a Fortune 100 and fortune Global 500 company specializing in petroleum exploration and refining, announced an agreement to take over Virent; Virent will now become a fully owned subsidiary of Andeavor and focus on developing high-quality renewable fuels and chemicals. The take-over is likely to see a substantial increase in investments to commercialize BioForming technology.

All in all, we can expect to see a lot of action in the near future towards the development of 100% green polyesters for packaging applicationa.

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