CONTAINER CONSISTING OF A RIGID OUTER CONTAINER AND A DEFORMABLE INNER BAG, AND METHOD FOR MANUFACTURING SUCH A CONTAINER

Description

[0001] The invention relates to a method for manufacturing a container consisting of a rigid outer container and a deformable inner bag, which consists of at least two layers, wherein the material layer facing the outer container does not form a welded connection with the material of the outer container, wherein in the method a first screw conveyor feeds a first thermoplastic material for the outer container and at least a second and a third screw conveyor feed at least a second and a third material for the inner bag to an extruder, which co-extrudes a preform consisting of at least the first, second and third layers, which is arranged between the open halves of a blow mold, wherein the blow mold is closed when the preform has reached the length required to manufacture the container.wherein excess material in the bottom area of ​​the container to be produced is squeezed off and a bridge made of material from the outer container is formed in which the welded bottom seam of the inner bag is clamped, and wherein the preform is inflated by a pressure medium to conform to the wall of the blow mold, the excess material under the weld seam is knocked off and the container is removed from the blow mold.

[0002] Such a method is known, for example, from DE 196 26 967 C2. This document also discloses that at least one wall opening in the outer container is formed by drilling or piercing the wall of the outer container with a drill, auger, or piercing needle, wherein, after complete penetration of the outer container wall, a pressure medium is blown or sprayed against the wall of the inner bag to push it back so that it is not damaged by the drill or piercing needle. When contents are dispensed from the inner bag, ambient air flows through this wall opening into the space between the outer container and the inner bag to equalize the pressure.

[0003] Although the different thermoplastic materials of the outer container and the inner bag do not form a welded bond, they do adhere to each other when the container is manufactured using the co-extrusion process described above. Before such a container can be used—that is, filled with a liquid or, for example, a paste-like substance, which is then gradually dispensed, for example, using an airless pump or by squeezing the container—the inner bag must be detached from the outer container wall and then reattached. This can be achieved by creating a vacuum through the container opening on the inner bag, causing it to contract sharply. Compressed air is then introduced into the inner bag through the container opening to reseal it to the outer container.If the inner bag is not detached from the wall of the outer container in a largely uniform manner, a relatively large negative pressure occurs in the inner bag when filling material is dispensed, despite pressure equalization openings in the wall of the outer container, which can impair the functionality of a pump that is usually provided.

[0004] In DE10 2006 012487 A1, an improved detachment method is disclosed in which a pressure medium is introduced into the space between the outer container and the inner bag after the outer container has been pierced and the container opening has been sealed, wherein the introduction of the pressure medium into the space is stopped when a predetermined second pressure threshold is reached in the inner bag, wherein after pressure relief a pressure medium is introduced into the inner bag to reattach the inner bag to the container wall.

[0005] US Patent 10,364,087 discloses a process in which microbodies made of a material that does not melt during the manufacture of the container are integrated into the layer of the inner bag facing the outer container and / or into the layer of the outer container facing the inner bag, creating irregularities on the surface of the layer. These microbodies are preferably glass beads.

[0006] EP 2 851 308 B1 discloses a co-extruded, blow-molded multi-layer container which contains as its innermost layer a mixture of an ethylene-phenyl alcohol copolymer and a soft resin. This innermost layer is firmly bonded to the outer container layer and gives the multi-layer container particularly high impact resistance.

[0007] The previously known process steps for detaching the inner bag from the container wall and subsequently attaching it to the wall of the outer container are complex and increase the manufacturing time of usable containers of the type under consideration.

[0008] The present invention is based on the objective of providing a better solution to this problem.

[0009] The invention also relates to a container comprising a rigid outer container and a deformable inner bag that rests against the outer container, with a crimp seam at the bottom of the container in which the welded bottom seam of the inner container is held, wherein the inner bag consists of at least two layers and is not welded to the outer container during its manufacture by co-extrusion. In this container, the inner bag is intended to rest loosely, i.e., essentially without adhesion, against the outer container, without pressure equalization holes being formed in the wall of the outer container.

[0010] These problems are solved according to the invention by the features of claims 1 and 11.

[0011] Advantageous embodiments of the invention are characterized in the dependent claims.

[0012] The inventive method provides that the second thermoplastic polymer, which forms the outer layer of the inner bag that rests against the outer container, has a rough surface with microscopically small elevations and depressions in the hardened state, so that the adhesive forces between the outer container and the inner bag are minimized.

[0013] For this purpose, a material compound consisting of a mixture of EVOH and an elastic plastic is fed into the second screw conveyor. The EVOH component has the property of forming a rough surface upon solidification or cooling. This material also possesses a relatively high stiffness, making it unsuitable on its own for a readily deformable inner bag. Therefore, the EVOH component is mixed with a uniformly distributed elastic plastic.

[0014] Surlyn, which is present in the dispersed phase in the EVOH, is used with particular advantage for this elastic material.

[0015] According to another suggestion of the invention, the Surlyn (ionomer) can be mixed with very small glass spheres, which create a non-smooth surface of the Surlyn with low adhesion forces.

[0016] Several concentration variants have proven suitable for the second material layer. Particularly noteworthy are 85 EVOH 15 SY, 52 EVOH, 75 EVOH25SY, and 75 PCTG25SY, although other similar material mixtures can also be used for this purpose.

[0017] Furthermore, the inventive method provides that the third material layer, which forms the inner layer of the inner bag and is therefore the product-contacting layer, consists of Surlyn, Purell, or Dowlex, although this list is not exhaustive. The third layer can be welded to the second layer during co-extrusion, and a fourth layer can also be added to the inner bag during the extrusion process via an associated fourth screw conveyor.

[0018] After the preform is inflated to form the (almost) finished container, the blow mold is opened, at least partially pulling open or tearing the crimp seam of the outer container, thus creating an air gap for pressure equalization that enlarges with continued use of the container. This allows the inner bag, which adheres to the outer container with very weak adhesion, to be detached. For this purpose, the container removed from the blow mold can be pressed laterally, preferably with two opposing plungers, causing the inner bag to detach abruptly from the outer container due to its rigidity. This detachment process according to the invention is also audible, producing a loud "pop". Alternatively, the container can be guided by a clamping conveyor belt.

[0019] This peeling process is quick and easy to carry out compared to the conventional method, thus significantly reducing the production time of usable containers.

[0020] In the container according to the invention, the outer layer of the inner bag facing the outer container has a rough surface with microscopically small bumps and depressions that are not perceptible to the naked eye. The crimp seam of the outer container is at least partially open, allowing air to enter the space between the outer container and the inner bag from both sides.

[0021] The inner bag can also detach from the outer container simply due to the negative pressure created when the container contents are dispensed.

[0022] Particularly suitable materials for the outer container of the container according to the invention are PP, PCTG, PET-G, HDPE, PCR, or HDPE, without this list being exhaustive. The container according to the invention preferably has a bottle shape.

[0023] Figure 1 The figure shows, in a purely schematic way and on a greatly enlarged scale, layer 1 of the outer container and surface 4 of the easily removable outer layer 2 of the inner bag. The schematic Figure 2 shows the extruded layers of the preform, namely layer 1 made of polypropylene, layer 2 made of an EVOH / Surlyn mixture and inner layer 3 of the inner bag made of Surlyn or Purell or Dowlex, without this listing being complete.

[0024] The material distribution of a preferred embodiment of the container is: approximately 80% outer container, 5% outer layer of the inner bag, 15% product-contacting inner layer of the inner bag.

Claims

1. A method of manufacturing a container consisting of a stiff outer container and a deformable inner bag wherein a first screw conveyor supplies a first thermoplastic plastic material for the outer container and at least one second and one third screw conveyor supply at least one second and third thermoplastic plastic materials for the inner bag to an extruder, which coextrudes a preform consisting of at least the first, second and third layers, which is arranged between the open halves of a blow mould, wherein the blow mould is closed when the preform has the length necessary for the manufacture of the container, wherein excess material is squeezed out in the base region of the container to be manufactured and a web is formed from material of the outer container, in which the welded base seam of the inner bag is clamped, and wherein the preform is inflated by a pressure medium into engagement with the wall of the blow mould, the excess material below the weld seam is severed and the container is removed from the blow mould, characterised in that the second thermoplastic plastic material, which forms the outer layer (2) of the inner bag, which engages the outer container (1), consists of a mixture of EVOH and a plastic material with elastic properties, which has the property that, in the hardened state, it has a rough surface (4) with microscopically small protuberances and recesses so that the adhesive forces between the outer container and the inner bag are minimised.

2. A method as claimed in Claim 1, characterised in that the material with the elastic properties is Surlyn®.

3. A method as claimed in Claim 2, characterised in that the Surlyn® is mixed with small glass balls.

4. A method as claimed in one of Claims 1 to 3, characterised in that the material mixture of the second layer consists of 85 EVOH15SY.

5. A method as claimed in one of Claims 1 to 3, characterised in that the material mixture of the second layer consists of 52 EVOH.

6. A method as claimed in one of Claims 1 to 3, characterised in that the material mixture of the second layer consists of 75 EVOH25SY.

7. A method as claimed in one of Claims 1 to 3, characterised in that the material mixture of the second layer consists of 75 PCTG25SY.

8. A method as claimed in one of Claims 1 to 7, characterised in that the third layer, which forms the inner layer of the inner bag, consists of Surlyn®, Purell® or Dowlex®.

9. A method as claimed in one of Claims 1 to 8, characterised in that after removal from the blow mould the container is pressed in laterally by punches or a clamping conveyor belt, whereby the inner bag peels away from the outer container.

10. A method as claimed in Claim 9, characterised in that the peeling process is acoustically perceptible.

11. A container consisting of a stiff outer container and a deformable inner bag, which engages the outer container without being welded to it, with a pinch seam at the base of the outer container, in which the welded base seam of the inner bag is held, wherein the inner bag consists of at least two layers, characterised in that the layer of the inner bag directed towards the outer container consists of a mixture of EVOH and a plastic material with elastic properties, which has a rough surface with microscopically small protuberances and recesses and that the pinch seam of the outer container is at least partially open so that air can enter into the gap between the outer container and the inner bag.