While cast film extrusion is the established manufacturing process for deep-draw thermoforming films, a new development from Kuhne Anlagebau GmbH is set to challenge this.
Together with its customers, the Germany-based blown-film specialist has developed new, 5-layer mono-material ’Triple Bubble’ films for packaging food products such as bread, meat and cheese. Produced on Triple Bubble blown film lines, the films are roughly 50% thinner than conventional cast films, with excellent barrier properties despite their mono-material structure.
Thermoforming films for food packaging must meet a number of steep requirements, among which good barrier properties to ensure a long shelf life of the packaged goods; sealability; printability; appealing surface properties; and transparency. They must be as thin as possible and easily thermoformable. Cast film extrusion has long been the accepted manufacturing process for deep-draw thermoforming films, but at Kuhne’s R&D centre: “We have succeeded in producing films that, compared to 150 to 180 μm (6 to 7 mil) thick cast films, are only 80 μm (3.15 mil) thick. This represents a dramatic thickness reduction of roughly 50%,” said managing director Jürgen Schiffmann, calling it the ‘first big step on the path to more environmentally friendly thermoforming films’.
Moreover, according to the initial feedback from customers, the Triple Bubble films thermoform better than comparable cast films. This is due both to the relaxation and fixation that the film undergoes in the third film bubble, which, said Schiffmann, is decisive for deep-drawability, and to the more uniform wall thicknesses achieved.
The Triple Bubble films for deep-drawing applications on the market today are typically 9-layer structures with EVOH and PA barrier layers. These new films, developed together with a German film manufacturer, feature a 5-layer PP-based mono-material structure. Because they contain no more than 5% of non-PP material, they are fully recyclable.
According to Schiffman, the films produced on the Triple Bubble lines therefore truly represent a ‘quantum leap’ in terms of thickness reduction and recyclability.