| 摘要 |
A flexible packaging material for making dimensionally-stable containers, intended especially for food and exhibiting barrier qualities, comprises a stiffening, polymeric core layer (1) which on both sides has a protective layer (2, 3) of polymeric material connected thereto. The core layer (1) consists of a foamed thermoplastic and has a thickness that makes up about 70-95 % of the total thickness of the material, while the protective layer or layers (2, 3) consist of non-foamed thermoplastic and make up the remainder of the thickness of the material. A container made of this material has a trough element with a circumferential flange, as well as a lid element with a corresponding circumferential flange. These flanges are applicable against each other, and at least the one flange is provided with an adhesive for original sealing of the container. In a method for producing the packaging material, the core layer (1) is brought to a viscosity (iv) of 0.68-0.82 before the lamination, and the protective layers (2, 3) are brought to a viscosity (iv) of 0.68-0.72. The lamination is so controlled that the difference in viscosity (iv) between the core layer (1) and the protective layers (2, 3) at all times exceeds 0.04. The packaging material is primarily used for making dimensionally-stable liquid-tight containers, which are produced by thermoforming or other mechanical processing and which exhibit barrier qualities. |
