Thermoforming | machinery
Drawing strength: innovations in thermoforming technology
Thermoforming is creeping further into many estab- lished packaging applications – including some new and demanding ones. For instance, Greiner Packaging, Motan and Luger have pooled their expertise in order to develop a production process to make thermoformed coffee capsules. The process, used at Greiner’s production plant in
Kremsmünster in Austria, combines Motan’s dosing and conveying technology with extrusion technology from Luger.
The capsules are made from a seven-layer film,
which incorporates EVOH as a barrier layer. This helps the capsule to resist the ingress of water and oxygen, as well as the escape of aromas and moisture. The film has internal and external layers of polypro-
pylene (PP), and a middle layer of EVOH, which is sandwiched between two adhesion promoter layers. The structure also includes two regrind layers – made from punching waste left over from the production of the capsules. Around 60% of the final structure of the capsule is made from this regrind. The punched frame and waste parts are ejected
directly from the deep-drawing machine and fed into a mill. The regrind is then stored, and later fed to the extrusion plant – where it is made into a mixed polymer and used in the capsule production. Four other extruders are then used to make the
outer layer, barrier layer, adhesion layers, and inner layer. There is no need for a coupling station or intermediate material drying. The regrind is supplied via gravimetric dosing units and a downstream mixing system, which overcome
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fluctuations in the bulk density. Also, the regrind does not cool completely when it is added to the process, so can be melted more quickly in the extruder – leading to energy savings.
Helmut Reckziegel, head of the capsules business
unit at Greiner Packaging, said: “The regrind fed back into the multi-layer foil comprises materials of five different viscosities. It was our objective to achieve stable mixing and flow properties for this mixture. An unstable material composition – whether due to fluctuating bulk density or a change in material proportions – leads to reductions in quality of the extrudate, especially when seven layers have to harmonise with each other.” All machine components are activated and
operated via remote-controlled electronic modules developed by Motan for this purpose. These are Gravinet for gravimetric dosing units and Volunet for volumetric dosing units. They are connected to a ControlNet of the central machine control via Ethernet or TCP/IP. This
June 2017 | FILM & SHEET EXTRUSION 15
Main image: Greiner is making
thermoformed
coffee capsules using seven- layer barrier film
Advances in thermoforming technology – from thickness control
to incorporating a barrier layer – are helping to make it a more widely used process. Lou Reade reports
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