Special • thirdly, the
Special • thirdly, the very good quality features of PLA products, which are certainly comparable in many cases to those of PET: namely excellent clarity and gloss, very good mechanical properties (high material rigidity and stiffness, good crack resistance), resistance to oil and fat, good flavour and oxygen barrier, good printability. And in addition there are properties which are even superior to those of traditional plastics. For instance the water vapour permeability (breathability) which leads to a longer shelf life for fruit and vegetables, and even for fresh pasta. • last but not least, the positive effects of bioplastics on the environment: complete renewability, biodegradability, reduction of fossil energy and of carbon dioxide emissions. And concerning the cost, Michele adds that for many clients it is important to differentiate themselves from the ‘others’. These kinds of clients that are investing in communicating their ‘green’ credentials are willing to pay a little bit more, because this ‘investment’ enables them to stand out. Nevertheless ILPA is determined to optimize its processes in order to influence the dynamics of costs as much as they can. Michele Bertoli: “Our target, in fact, is to do our best to reduce the price gap between PLA and traditional plastic products“. Processing on standard equipment “PLA can be produced on standard thermoforming equipment,” as Hans Lochner, R&D Manager at Kiefel GmbH Freilassing, Germany points out. “As PLA is a hydrophilic resin like other polyesters, it must be dried to less than 200- 250 ppm residual moisture. Typical drying conditions for crystallized granules are 4 hours at 70ºC. After drying the material should not be exposed to atmospheric conditions”, he adds. The relatively high modulus of elasticity of PLA compared to other thermoformable materials allows automatic stacking of PLA containers. “However, to allow easier de-stacking, it is necessary to add an antiblocking agent during the production of PLA sheet,” says Martin Barth, plastic engineer in R&D at Illig Maschinenbau, Heilbronn, Germany. Martin Barth explains further that PLA sheet can be thermoformed with vacuum, compressed air/vacuum or only compressed air assistance. The radiant heaters must be set to very low temperatures when thermoforming PLA. Preheating is not necessary, however preheating has the general advantage that the sheet is heated quite homogeneously. PLA does not suffer significant sheet sagging during heating in the thermoforming process as it can be seen with PP. The low processing temperature must be noted. Thermoformed articled produced from PLA sheet can have outstanding forming definition. PLA requires a relatively short cooling phase in the mould, nearly the cooling time from PET. Rim rolling of thermoformed drinking cups is possible. (Photo: Nedupack) (Photo: natura packaging) bioplastics MAGAZINE [03/08] Vol. 3 25
Special Thermoformed PLA articles can be punched out either in a separate step or inline (punch and drop). “However, the PLA skeleton was rather brittle in past, so we had to use a special winder for winding the skeleton,” Martin Barth says, “with the actual PLA-Qualities we can use standard winders. If processed properly PLA can easily be reground and fed back into the process.” (Photo: Nedupack) (Photo: ILIP) But even if standard equipment can be used, most converters have invested in modifying their production lines and in optimizing their processes. The ‘what’ and ‘how’, remain, however, confidential. Market development The market for rigid PLA packaging is developing quite well. However, when comparing PLA packaging with packaging products made from traditional plastics, most companies still see bioplastics as a niche market. Others, like Nedupack, report that PLA products already generate about 10% of their total sales, and are receiving an increasing number of enquiries. “This includes all kind of clamshells, tray and lid combinations and trays with inserts“, as Jhon Bollen pointed out. In addition Nedupack manufactures blisters for a broad range of non-food applications. Patrick Gerritsen, Business Unit Manager of natura packaging is enthusiastic about the development. natura packaging is a German trading company for biodegradable packaging and sells products of companies like ILIP, Nedupack and others to all major retailers and discounters. Patrick: “In the last two years we saw a really dramatic growth in the field of rigid PLA packaging”. Did they sell about 20 million units of rigid PLA packagings in 2007, Patrick expects more than 50 million for this year, based on orders booked and serious requests, as he added. In the beginning, PLA trays, punnets and clamshells replaced rather the standard products such as PET-packs for tomatoes etc. Today Patrick Gerritsen is more and more faced with cumstom made packagings for a much wider variety of filling goods. “Our clients ask for packaging for grapes, wild tomatoes, mushrooms or even fresh herbs,” he says. The packagings range from open trays with loose lids to hinged containers. And even in the field of meat and meat products Patrick is expecting a very positive development. “At least for Germany and Holland, the areas we supply most of our products to,” he adds. These PLA trays are closed with a so called sealed lid made from PLA film. This film is barrier-coated with an SiOx-layer. www.ilip.it www.nedupack.nl www.naturapackaging.com 26 bioplastics MAGAZINE [03/08] Vol. 3
