Environmentally friendly barrier coating moves to packaging

November 30, 2003
Two recent developments in plastics barrier coatings for paperboard packaging of beverage and household products could steal market share from blowmolded containers as packagers try to skirt recycling charges.

One example is detergent and home products manufacturer Henkel Group (Dusseldorf, Germany), which has just switched to a new packaging design to save costs and improve moisture barrier.

Henkel has changed from a cardboard box covered with a bioriented polypropylene (BOPP) film for its Sil-brand stain remover, to cardboard with an integrated moisture barrier that''s extrusion coated of Topas-brand cyclic olefin copolymer (COC) from polymer producer Ticona (Frankfurt, Germany). Since the plastics content remains below an established 5% limit, it fulfills Germany''s Green Dot/DSD recycling agency criteria for ecologically friendly paper packaging—qualifying it as a single material, with consequently lower recycling charges.

Supplied by processor Van Genechten Nicolaus (Kempten, Germany), the extrusion-coated packaging has a paper cover laminated on the other side of the cardboard during the same process. A 20 g/sq m thick COC layer gives the required moisture protection. After being opened and fully reclosed, the new solution reportedly provides better moisture barrier. The previous BOPP solution provided protection against moisture only until the outer film was broken.

The COC adheres directly to the carton after very high flame, ozone, or corona treatment. It can also be coextruded between two layers of LDPE with one layer acting as the tie layer to the cardboard structure, says Wolfram Goerlitz, market development engineer, Topas/COC.

Another fully recyclable polymer barrier coating for paper packaging, developed after 20 months of R&D, has been commercialized by BASF (Ludwigshafen, Germany). Epotal-brand polymer dispersions now on the market are based on styrene butadiene or acrylates and protect packaged goods against moisture, odor, grease, and oil. They can be integrated into existing production processes without major production changes, says Hermann Seyffer of BASF''s functional polymers division. Blocking properties can be adjusted with fillers, thickening agents, or pigments. The barrier can be applied by roller, gravure, blade coating, or air knife. He says the aqueous coating is also feasible for multilayer curtain coating systems.

The first Epotal application is being produced by Stora Enso, based in Wisconsin Rapids, WI. "We can coat the polymer dispersions directly on to the paper or board," says Keith Damarell, Stora Enso''s business development manager. It helps cut costs by being carried out at higher production speeds than the manufacture of composite packaging, he says.

Martin Brudemuller, head of BASF''s functional polymers division, says the proprietary process is an alternative to costly and complex composites packaging and eliminates problems associated with recycling wax coatings, aluminum, and plastics films.

Unlike extrusion-coated paper, multilayer composites, or wax-impregnated paper, the dispersion-coated paperboard is easily recyclable. Epotal dispersion coatings are reduced to very small particles during recycling, and separation is not required.

The barrier-coated paper is being used for fatty fast-food wrappings, pet-food packaging, and ream wraps in non-food sectors.

Robert Colvin bcolvin@modplas.com

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