Method of closing a container with a lid
A lid for closing containers includes an at least two-layered composite assembly. A layer facing the container seals against a container edge and forms an opening by layer separation, for removing contents. The layers have a continuous construction without weakening lines. The layer facing the container is made mainly of a plastic having an intrinsic tearing resistance being lower in the region of the opening than its adhesion to the layer facing away from the container in a remaining region and an adhesion to the container edge being greater at least in the region of an opening aid than to the other layer. The plastic adheres so strongly to the outer layer in the region of the opening that a region corresponding to the opening is torn out upon opening and a remaining layer of the lid facing the container continues to adhere to the container edge by sealing action.
1. A method of closing a container with a lid, the method which comprises the following steps:
forming the lid entirely without weakening lines from a composite assembly having only two continuous assembly layers without weakening lines and an opening aid in an opening aid region, the two assembly layers including an assembly layer facing the container and an assembly layer facing away from the container;
bonding the composite assembly to the container as the lid provided entirely without weakening lines;
the assembly layer facing the container sealing against a container edge and forming a removal opening produced by separating the assembly layers for removal of package contents located in the container;
the assembly layer facing the container having an assembly adhesion to the assembly layer facing away from the container provided without a bonding agent between the assembly layers;
producing the assembly layer facing the container mainly of a plastic having an intrinsic tearing resistance that is lower in a removal opening lid region than the assembly adhesion to the assembly layer facing away from the container in the remaining lid region; and
producing the assembly layer facing the container with an assembly adhesion to the container edge greater at least in the opening aid region than the assembly adhesion to the assembly layer facing away from the container; and
subjecting the composite assembly formed of the assembly layers of the lid without weakening lines to increased pressure and increased temperature with sealing tools in the form of rollers, one of said rollers having raised surface portions corresponding to a predetermined region for the removal opening having increased assembly adhesion adjusted to lie in a range from 5 N to 160 N/15 mm and portions which are not raised corresponding to regions outside the removal opening having assembly adhesion adjusted to lie in a range from 0.1 to 5 N/15 mm.
2. The method according to claim 1 , which comprises adjusting the assembly adhesion outside the removal opening to lie in a range from 0.2 to 0.4 N/15 mm.
3. The method according to claim 1 , which comprises selecting the plastic of the assembly layer facing the container from the group consisting of polyethylene, polypropylene, polyester, polystyrenes, copolymers thereof and mixtures thereof.
4. The method according to claim 3 , which comprises adding fillers to the plastic of the assembly layer facing the container.
5. The method according to claim 4 , wherein the fillers are at least one of talc, silica, and/or chalk.
6. The method according to claim 1 , which comprises utilizing a plastic for the assembly layer facing the container to seal against the container edge.
7. The method according to claim 1 , which comprises providing the plastic assembly layer facing the container with a heat-sealable layer.
8. The method according to claim 1 , which comprises forming the assembly layer facing away from the container with aluminum or plastic.