Integrally blow-moulded bag-in-container having an inner layer and the outer layer made of the same material and preform for making it

Abstract

An integrally blow-moulded bag-in-container has as integrally blow-moulded bag-in-container wherein the same polymer is in contact on either side of the interface between the inner and outer layers. A preform for blow-moulding a bag-in-container has an inner layer and an outer layer, wherein the preform forms a two-layer container upon blow-moulding, and wherein the thus obtained inner layer of the container releases from the thus obtained outer layer upon introduction of a gas at a point of interface between the two layers. The inner and outer layers are of the same material.

Claims

1. A preform for blow-moulding a bag-in-container, comprising: an inner layer and an outer layer, wherein the preform forms a two layer container upon blow-moulding, and wherein the thus obtained inner layer of said container releases from the thus obtained outer layer upon introduction of a gas at at least one point of interface between the two layers, wherein the inner and outer layers are the same material; wherein the preform comprises a mouth defined in a neck region, the mouth comprising a circumferentially-extending lip which defines an axially outer surface of the preform; and wherein the at least one point of the interface is a vent disposed at, and oriented coaxially with, the mouth, the vent extending axially from an opening in the axially outer surface of the preform at least partway through the neck region.

2. The preform according to claim 1 wherein the inner and outer layers are of a semicrystalline material.

3. The preform according to claim 2, wherein the inner and outer layer consist of a material selected from PET, PEN, PTT, PA, PP, PE, HDPE, EVOH, PGAc, PLA, and copolymers or blends thereof.

4. The preform according to claim 1, wherein the vent is in the shape of a wedge with the broad side at the level of the opening thereof and getting thinner as it penetrates deeper into the vessel, until the inner and outer layers meet to form the interface.

5. The preform according to claim 1, wherein more than one vent is distributed around the lip of the preform's mouth.

6. The preform according to claim 5, wherein the more than one vent is oriented coaxially with the preform's mouth.

7. The preform according to claim 1, wherein the inner and outer layers of the preform are connected by an interface throughout substantially the whole inner surface of the outer layer.

8. The preform according to claim 1, wherein the inner and outer layers of the preform are separated over a substantial area of the preform's body by a gap containing air and which is in fluid communication with at least one interface vent.

9. The preform according to claim 1, having an assembly of two separate inner and outer preforms fitted into one another.

10. The preform according to claim 1, having an integral preform obtained by injection moulding one layer on top of the other.

11. The preform according to claim 1, wherein the introduction of the gas collapses the inner layer of the container to dispense a liquid contained therein.

12. The preform according to claim 1, wherein the vent is connectable to a source of compressed gas.

13. The preform according to claim 1, wherein a release agent is applied to one or more of the inner and outer layers at the interface.

14. The preform according to claim 1, wherein the vent is elongate.

15. The preform according to claim 1, wherein the inner and outer layers both define an axially outer surface of the preform.

16. The preform according to claim 1, wherein the outer layer entirely surrounds the inner layer save for at the lip at the axially outermost surface of the preform.

17. The preform according to claim 1, wherein the vent extends axially through an entirety of the neck region.

18. A preform for blow-moulding a dispensing bag-in-container, comprising: an inner layer and an outer layer joined at least at a neck region by an interface that extends at least partway between the inner layer and the outer layer, the interface being in fluid communication with atmosphere by one or more interface vents disposed at, and oriented coaxially with, a mouth of the preform defined by the neck region, wherein the preform forms a two layer container upon blow-moulding, and wherein the thus obtained inner layer of said container releases from the thus obtained outer layer upon introduction of a pressurised gas through the one or more interface vents to dispense a liquid contained therein, wherein the inner and outer layers are the same material, wherein the inner and outer layers both define an axially outer surface of the preform.

19. A preform for blow-moulding a dispensing bag-in-container, comprising: an inner layer and an outer layer joined at least at a neck region by an interface that extends at least partly between the inner layer and the outer layer, the interface being in fluid communication with atmosphere by a plurality of interface vents disposed at, distributed around, and oriented coaxially with, a mouth of the preform defined by the neck region, wherein the preform forms a two layer container upon blow-moulding, and wherein the thus obtained inner layer of said container releases from the thus obtained outer layer upon introduction of a pressurised gas through the plurality of interface vents, wherein the inner and outer layers are the same material.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1A is a schematic cross-sectional representation of a first embodiment of a preform according to the present invention and the bag-in-container obtained after blow-moulding thereof.

(2) FIG. 11B: is a schematic cross-sectional representation of a second embodiment of a preform according to the present invention and the bag-in-container obtained after blow-moulding thereof.

DETAILED DESCRIPTION OF THE INVENTION

(3) Referring now to appended FIGS. 1A and 1B, there is illustrated an integrally blow-moulded bag-in-container (2) and a preform (1)&(1) for its manufacturing. The preform (1) comprises an inner layer (11) and an outer layer (12) joined at least at the level of the neck region (6) by an interface (shown on the right hand side). The region between inner and outer layers (11) and (12) may either consist of an interface (14) wherein the two layers are substantially contacting each other, or comprise a gap (14) in fluid communication with at least one vent (3) opening to the atmosphere in (4).

(4) Many vent geometries have been disclosed and it is not critical which geometry is selected. It is preferred, however, that the vent be located adjacent to, and oriented coaxially with said preform's mouth (5) as illustrated in FIG. 1. More preferably, the vents have the shape of a wedge with the broad side at the level of the opening (4) thereof and getting thinner as it penetrates deeper into the vessel, until the two layers meet to form an interface (14) at least at the level of the neck region. This geometry allows for a more efficient and reproducible delamination of the inner bag upon use of the bag-in-container. The container may comprise one or several vents evenly distributed around the lip of the bag-in-container's mouth. Several vents are advantageous as they permit the interface of the inner and outer layers (21) and (22) of the bag-in-container (2) to release more evenly upon blowing pressurized gas through said vents. Preferably, the preform comprises two vents opening at the vessel's mouth lip at diametrically opposed positions. More preferably, three, and most preferably, at least four vents open at regular intervals of the mouth lip.

(5) The preform may consist of an assembly of two separate preforms (11) and (12) produced independently from one another and thereafter assembled such that the inner preform (11) fits into the outer preform (12). This solution allows for greater freedom in the design of the neck and vents. Alternatively, it can be an integral preform obtained by injection moulding one layer on top of the other. The latter embodiment is advantageous over the assembled preform in that it comprises no assembly step and one production station only is required for the preform fabrication. On the other hand, the design of the vents in particular is restricted by this process.

(6) When intuition suggests, and all the prior art teaches to use [different and]mutually nonadhesive synthetic resins for the inner and outer layers of a preform for making a bag-in-container (cf. JPA2005047172), it has surprisingly been discovered that excellent delamination results between the inner and outer layers can be obtained also with preforms wherein both inner and outer layers consist of the same material. Similar results were obtained both with preform assemblies as well as with integral preforms. In the case of integral, over-moulded preforms, it is generally believed that better results are obtained with semi-crystalline polymers.

(7) Preferred materials for the layers of the preform and bag-in-container of the present invention are polyesters like PET, PEN, PTT, PTN; polyamides like PA6, PA66, PA11, PA12; polyolefins like PE, PP; EVOH; biodegradable polymers like polyglycol acetate (PGAc), Polylactic acid (PLA); and copolymers and blends thereof.

(8) The same polymer is considered in contact on either side of the interface between the inner and outer layers in the following cases: inner and outer layers consist of the same material (e.g., PET.sub.inner-PET.sub.outer, regardless of the specific grade of each PET); or the inner and outer layers consist of a blend or copolymer having at least one polymer in common, provided said polymer in common is at the interface, whilst the differing polymer is substantially absent of said interface (e.g., (0.85 PET+0.15 PA6).sub.inner(0.8 PET+0.2 PE).sub.outer.

(9) The presence of low amounts of additives is not regarded as departing from the scope of the present invention so far they do not alter the interface substantially.

(10) The two layers (11) and (12) of the preform may be connected by an interface (14) throughout substantially the whole inner surface of the outer layer (cf. (1) in FIG. 1A). Inversely, they may be separated over a substantial area of the preform's body by a gap (14) containing air and which is in fluid communication with at least one interface vent (3) (cf. (1) in FIG. 1B). The latter embodiment is easier to realize when using a preform assembly designed such that the inner preform is firmly fixed to the outer preform at the neck region (6) and a substantial gap (14) may thus be formed between inner and outer layers (11) and (12).

(11) The bag-in-container (2) of the present invention can be obtained by providing a preform as described above; bringing said preform to blow-moulding temperature; fixing the thus heated preform at the level of the neck region with fixing means in the blow-moulding tool; and blow-moulding the thus heated preform to form a bag-in-container. The inner and outer layers (21) and (22) of the thus obtained bag-in-container are connected to one another by an interface (24) over substantially the whole of the inner surface of the outer layer. Said interface (24) is in fluid communication with the atmosphere through the vents (3), which maintained their original geometry through the blow-moulding process since the neck region of the preform where the vents are located is held firm by the fixing means and is not stretched during blowing.

(12) It is essential that the interface (24) between inner and outer layers (21) and (22) releases upon blowing pressurized gas through the vents in a consistent and reproducible manner. The success of said operation depends on a number of parameters, in particular, on the interfacial adhesive strength, the number, geometry, and distribution of the vents, and on the pressure of the gas injected. The interfacial strength is of course a key issue and can be modulated by the choice of the material for the inner and outer layers, and by the process parameters during blow-moulding; the pressuretimetemperature window used is of course of prime importance and greatly depends on the material selected for the inner and outer layers.

(13) Excellent results can be obtained if the blow-moulding process is carried out on a preform as described above, of the type wherein a gap containing air separates the inner and outer layers over a substantial area of the preform's body and wherein said gap is in fluid communication with at least one interface vent and wherein, in a first stage, a gas is blown into the space defined by the inner layer to stretch the preform, whilst the air in the gap separating the preform inner and outer layers is prevented from being evacuated by closing said at least one preform interface vent with a valve located in the fixing means; and in a second stage, when the air pressure building up in said gap reaches a preset value, the valve opens thus allowing evacuation of the air enclosed in the gap.

(14) By this method, the inner layer is prevented from entering into contact with the outer layer by the air cushion enclosed within the gap separating the two layers when their respective temperatures are the highest. As stretching proceeds, the gap becomes thinner and air pressure within the gap increases. When the pressure reaches a preset value, the valve closing the vent opening releases, the air is ejected, and the inner layer is permitted to contact the outer layer and form an interface therewith at a stage where their respective temperatures have dropped to a level where adhesion between the layers cannot build up to any substantial level.

(15) A release agent may be applied at the interface on either or both surfaces of the inner and outer preforms, which are to form the interface of the bag-in-container. Any release agents available on the market and best adapted to the material used for the preform and resisting the blowing temperatures, like silicon- or PTFE-based release agents (e.g., Freekote) may be used. The release agent may be applied just prior to loading the preforms into the blowmoulding unit, or the preforms may be supplied pretreated.

(16) The application of a release agent is particularly beneficial with respect to the design of the inner layer. Indeed, lowering the interferential adhesive strength facilitates delamination of the inner layer from the outer layer and hence reduces stress exerted on the inner layer upon delamination, as such the inner layer can be designed very thin and flexible without risking that the inner layer is damaged upon delamination. Clearly, the flexibility of the inner bag is a key parameter for the liquid dispensing and moreover costs savings can be achieved in terms on material savings when the inner layer can be designed very thin.

(17) Additionally, application of the release agent allows a reduction of the width of the gap separating the inner and outer layers. By reducing the width of said gap, the inner layer of the preform can be designed with a same thickness but a larger radial cross section, resulting in a reduction of the stretch ratio of the inner layer during blow-moulding and hence a reducing potential formation of micro-cracks in the inner layer.

Example

(18) A preform according to the present invention was produced by injecting a melt into a first mould cavity to form the preform's inner layer (11). A melt was injected into a second mould cavity cooled to form the preform's outer layer (12). The two preform components were assembled to form a preform according to the present invention.

(19) The preform produced as explained above was heated in an oven comprising an array of IR-lamps and then fixed into a blow-moulding mould which walls were maintained at a desired temperature. Air was blown into the preform under pressure. The thus produced bag-in-container was then filled with a liquid and connected to an appliance for dispensing beverage comprising a source of compressed air in order to determine the delamination pressure.

(20) The delamination pressure was determined as follows. The interface vents of said bag-in-container were connected to the source of compressed air. Air was injected through the vents at a constant pressure and the interface between inner and outer layers was observed; the pressure was increased stepwise until delamination pressure was reached. Delamination pressure is defined as the pressure at which the inner bag separates from the outer layer over the whole of their interface and collapses. The surfaces of the thus separated layers were examined for traces of bonding.

(21) The delamination pressure of the bag-in-container described above was of about 050.1 bar overpressure and showed little trace of cohesive fracture between the inner and outer layers. This example demonstrates that bag-in-containers of excellent quality can be produced with integral preforms according to the present invention.