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

Abstract

The method for producing a container consisting of a rigid outer container and a deformable inner bag. A first screw conveyor supplies a first thermoplastic plastics material for the outer container and at least a second and a third screw conveyor supplies at least a second and a third thermoplastic plastics material for the inner bag to an extruder which coextrudes a parison consisting of at least the first, second and third layers. The parison is inflated by a pressure medium to bring it into contact with the wall of the blow mould, where excess material below the welded seam is cut off and the container is removed from the blow mould. The second thermoplastic plastics material forming the outer layer of the inner bag consists of a material which, in the hardened state, has a rough surface having microscopically small elevations and depressions.

Claims

1. A method for producing a container consisting of a rigid outer container and a deformable inner bag, the method comprising: supplying a first thermoplastic plastics material for the outer container using a first screw conveyor and at least a second and a third screw conveyor supplying at least a second and a third thermoplastic plastics material for the inner bag to an extruder; coextruding a parison consisting of at least the first, second and third layers, which parison is arranged between the opened halves of a blow mould, wherein the blow mould is closed once the parison has the length required for producing the container, wherein excess material in the base region of the container to be produced is pinched off and a web composed of material of the outer container is formed in which the welded base seam of the inner bag is clamped; inflating the parison by a pressure medium in order to bring it into contact with the wall of the blow mould, the excess material below the welded seam is cut off and the container is removed from the blow mould; and, forming the outer layer of the inner bag, which outer layer is in contact with the outer container, consists of a material which, in the hardened state, has a rough surface having microscopically small elevations and depressions, so that the adhesive forces between the outer container and the inner bag are minimal.

2. The method according to claim 1, wherein the second screw conveyor is supplied with a material compound which consists of a mixture of EVOH and a plastics material having resilient properties.

3. The method according to claim 1, wherein the material having the resilient properties is Surlyn®.

4. The method according to claim 3, wherein the Surlyn® has been mixed with small glass beads.

5. The method according to claim 1, wherein the material mixture of the second layer consists of 85 EVOH15SY.

6. The method according to claim 1, wherein the material mixture of the second layer consists of 52 EVOH.

7. The method according to claim 1, wherein the material mixture of the second layer consists of 75 EVOH25SY.

8. The method according to claim 1, wherein the material mixture of the second layer consists of 75 PCTG25SY.

9. The method according to claim 8, wherein the third layer, which forms the inner layer of the inner bag, consists of Surlyn®, Purell® or Dowlex®.

10. The method according to claim 1, wherein the container, once it has been removed from the blow mould, is pressed in at the sides by punches or a clamping conveyor belt, so that the inner bag becomes detached from the outer container.

11. The method according to claim 10, wherein the detachment operation is audibly perceptible.

12. A container comprising: a rigid outer container and a deformable inner bag which is in contact with the outer container without being welded thereto, having, at the base of the outer container, a pinch-off seam in which the welded base seam of the inner bag is held, wherein the inner bag consists of at least two layers, the layer of the inner bag that faces towards the outer container has a rough surface having microscopically small elevations and depressions; and the pinch-off seam of the outer container has been at least partly opened, so that air is able to enter the intermediate space between the outer container and the inner bag.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] FIG. 1 is a schematic drawing of the present container.

[0011] FIG. 2 is a cross-sectional view of extruded layers of the container of FIG. 1.

DETAILED DESCRIPTION

[0012] The method according to the invention provides that the second thermoplastic plastics material forming the outer layer of the inner bag, which outer layer is in contact with the outer container, has, in the hardened state, a rough surface having microscopically small elevations and depressions, so that the adhesive forces between the outer container and the inner bag are minimal.

[0013] For that purpose, the second screw conveyor is supplied with a material compound which consists of a mixture of EVOH and a plastics material having resilient properties.

[0014] The material content composed of EVOH has the property of forming the rough surface on solidification or cooling, but this material has the further property of relatively great rigidity, so that it is not, on its own, suitable for a readily deformable inner bag. For that reason, the material content EVOH is mixed with a uniformly distributed plastics material having resilient properties.

[0015] As that resilient material it is especially advantageous to use Surlyn which is present in the disperse phase in the EVOH.

[0016] In accordance with a further proposal of the invention, the Surlyn (ionomer) can be mixed with very small glass beads which impart to the Surlyn a non-smooth surface having very low adhesion forces.

[0017] In respect of the second material layer, various concentration variants have proved suitable, special emphasis being given to 85 EVOH 15 SY or 52 EVOH or 75 EVOH25SY or 75 PCTG25SY, but further similar material mixtures can also be used for the said purpose.

[0018] In addition, the method according to the invention provides that the third material layer, which forms the inner layer of the inner bag and accordingly is the product-contacting layer, consists of Surlyn, Purell or Dowlex, without this list being exhaustive. The third layer can have been welded to the second layer during the coextrusion, it also being possible for a fourth layer to be added to the inner bag during the extrusion operation by means of an associated fourth screw conveyor.

[0019] After the inflation of the parison to form an (almost) finished container, the blow mould is opened, the pinch-off seam of the outer container being at least partly pulled or torn open, with the result that an air slot for pressure equalisation is formed which becomes larger during ongoing use of the container. This allows the detachment of the inner bag, which adheres to the outer container only very slightly. For that purpose, the container, once removed from the blow mould, can be pressed in at the sides, preferably with two mutually opposite punches, so that the inner bag, on account of its rigidity, abruptly becomes detached from the outer container. This detachment operation in accordance with the invention is also audibly perceptible in that a loud “plop” is generated. Alternatively, the container can be guided by a clamping conveyor belt.

[0020] In comparison with the conventional procedure, such a detachment operation is quick and easy to perform, so that the production time for ready-to-use containers is significantly reduced.

[0021] In the container according to the invention, the outer layer of the inner bag that faces towards the outer container has a rough surface having microscopically small elevations and depressions which are imperceptible to the naked eye. The pinch-off seam of the outer container has been at least partly opened, so that air is able to enter the intermediate space between the outer container and the inner bag at both ends.

[0022] The inner bag can also be detached from the outer container solely by the partial vacuum during the discharge of container contents.

[0023] Especially suitable materials for the outer container of the container according to the invention are PP or PCTG or PET-G or HDPE or PCR or HDPE, without this list being exhaustive. The container according to the invention preferably has a bottle shape.

[0024] FIG. 1 shows purely diagrammatically and on a greatly enlarged scale the layer 1 of the outer container and a surface 4 of the readily detachable outer layer 2 of the inner bag. The diagrammatic FIG. 2 shows the extruded layers of the parison, that is to say layer 1 composed of polypropylene, layer 2 composed of an EVOH/Surlyn mixture, and inner layer 3 of the inner bag composed of Surlyn or Purell or Dowlex, without this being a complete list.

[0025] The material distribution of a preferred embodiment of the container is: about 80% outer container, 5% outer layer of the inner bag, 15% product-contacting inner layer of the inner bag.