Cross-laminated film offers high strength, more stiffness

An idea, which is expected to compete against heavy-duty paper, woven sacks, and bioriented polypropylene bags, is counting on its light weight and high strength to corner a market share. Developed by Ole-Bendt Rasmussen, director of O-B R. Enterprise (Walchwil, Switzerland), the cross-laminated film has mini-flutes on one side of the structure and takes advantage of high-tear propagation resistance. This is provided in the cross-laminated films in a manner similar to the crisscross grain of plywood.

One side of the material is a film oriented in the transverse direction, which can be printed, while the other machine-direction-oriented web consists of a fluted film structure. Each flute is about 1 mm running parallel to the main direction of the orientation. The flutes provide stiffness and resilience while reducing weight. Channels formed by the flutes can be used to "bury" protective substances such as oxygen scavengers or fire retardants. Such a solution can solve problems of highly sensitive additives, which might decompose at high extrusion temperatures.

The fluted configuration is produced by intermeshing rollers, one with sharp crests and heated to 70C and the other with rounded slots operating at room temperature. The film, which meets the crests, is preheated. The flutes are shaped and heated on a transfer roll at 110C and then heat laminated, or spot welded, to the cross-stretched substrate film. The rolls can be designed to spot-burn micro holes for substance release in the mini-flutes.

Rasmussen previously developed Valeron, a cross-plastics, high-strength film for packaging processor Van Leer (Essen, Belgium), which is still being produced. But the lack of stiffness and heat-sealing problems of cross-plastics laminated films led him to the mini-flute development, he says. Rasmussen is licensing the technology (www.xf-plasticfilms.com) and will not produce the film himself. Markets include industrial bags, tarpaulins, stand-up pouches, and diaper film.

Robert Colvin
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