Polymer coated heat sealable packaging material

Process for the production of a heat-sealable packaging material in which a layered polymer coating layer is extruded onto a fibrous base layer (3) comprising an external polymer heat-seal layer (1, 8) and at least one water vapour Infiltrating the inner polymer barrier layers (2, 7, 10) below the heat-seal layer, the method being characterized in that a cyclo-olefin copolymer (COC) is incorporated in the barrier layers (2, 7, 10) The extrusion produces an amorphous layer that does not undergo post-crystallization in the polymer.

The invention relates to a heat-sealable packaging material coated with a polymer, a preparation method thereof and a sealed package prepared therefrom. The material comprises a fibrous base layer (3) of a wrapper or a packaging board, an outer polymer heat-seal layer (1, 8), for example LDPE, and an interior made partly or wholly of cycloolefin copolymer (COC) according to the invention Polymer water vapor barrier (2, 7). The COC vapor barrier and the heat seal layer are extruded onto the fiber base layer and they can be placed on one side of the fiber base layer or placed on both sides of the fiber base layer in order to achieve moisture barrier on both sides of the package. Also polymeric oxygen barriers such as EVOH or polyamide layers can be incorporated in the packaging material. The COC is amorphous and its use as an extruded water vapor barrier prevents curling of the packaging material. The package of the present invention includes cartons, boxes, and bags for dry and liquid foods.