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Polypropylene film used to create self-venting microwavable packaging

By Rory Harrington , 08-Nov-2010

Temperature resistance and balanced seal-peel properties combine to provide a unique venting feature for multilayer blown film for microwaveable food packaging, said Borouge of its new multimodal polypropylene (PP) film.

The company, a joint venture between Borealis and the Abu Dhabi National Oil Company (ADNOC), said it has supplied its multimodal Borclear and Steripeel PP materials to provide the “performance layers” for an innovative microwaveable pouch made by TPN FlexPak of Thailand. Multimodal polymers include more than one molecular weight fraction.

The packaging, known as the M-Vent Pouch, has a novel sealing feature that allows it to “breathe out” while its contents cook in a microwave oven, said the Austria-based company. The feature allows for “the safe and reliable release of steam from inside the pouch without requiring partial opening or puncturing before placing in the microwave," it added.

Properties

In developing the product, the Thai company said that it was looking for a film with special property combinations beyond those of the capabilities of a single film material. Preservation of food flavour and odours, as well as suitable peel and seal characteristics to enable the self venting process and allow easy opening were vital, said the company. Also important was both high and low temperature performance, as the pouch had to be capable of accepting both hot-fill up to 100°C and frozen storage down to -20°C, as well as transition from freezer to microwave oven temperatures.

Combining multimodal polyethylene (PE) and PP in a multilayer structure provided the solution made up of a PE outer layer laminated to a PET substrate and a Borclear PP carrier layer to deliver good heat resistance and a robust seal, said Borouge.

The firm said the strong seal and venting characteristics were facilitated by its Steripeel material, while the organoleptic performance requirements were delivered by its Borstar film. The two materials are also easily processed on existing PE blown film lines, eliminating the need to invest in new production equipment.

“This contributes to widening the possibilities for the M-Vent Pouch to be used economically for small series runs to serve markets for niche food products,” said the company.

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