Integral Two Layer Preform, Process and Apparatus for the Production Thereof, Process for Producing a Blow-Moulded Bag-in-Container, and Bag-in-Container Thus Produced

Abstract

The invention is an integral two-layer preform (1) for the production of integrally blow-moulded bag-in-containers (2). The preform has an inner layer (11) and an outer layer (12), 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 of the two layers. The melting temperature of the inner layer is greater than or equal to the melting temperature of the outer layer.

Claims

1. An integral two-layer preform for the production of integrally blow-moulded bag-in-containers, said preform comprising: an inner layer and an outer layer, wherein said 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 a point of interface of said two layers; and the melting temperature of the inner layer is greater or equal to the melting temperature of the outer layer.

2. The preform according to claim 1 wherein at least one of the inner and outer layers comprises a semi-crystalline material.

3. The preform according to claim 1, wherein the inner and outer layer consist of different materials.

4. The preform according to claim 1, wherein the inner and outer layer consist of the same material.

5. The preform according to claim 1, wherein the inner and outer layers consist of a material selected from PET, PEN, PTT, PA, PP, PE, HDPE, EVOH, PGAc, PLA, and copolymers or blends thereof.

6. The preform according to claim 1, wherein the at least one point of interface is a vent 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 an interface.

7. The preform according to claim 6, wherein more than one vent are distributed around the lip of the preform's mouth.

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

9. The preform according to claim 1 wherein the inner and outer layers and are fixed to one another through mechanical interlocking means located in the preform's neck region.

10. A process for the production of a preform having an inner layer and an outer layer, wherein said 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 a point of interface of said two layers; and the melting temperature of the inner layer is greater or equal to the melting temperature of the outer layer, comprising the following sequential steps: injection moulding the inner layer onto a core; injection moulding the outer layer onto the inner layer, and extracting the thus formed preform from the core.

11. The process according to claim 10, wherein said core is adapted for forming vents fluidly connecting the interface between the inner and outer layers to the atmosphere.

12. A tool of the core shell type suitable for the production of a preform having an inner layer and an outer layer, wherein said 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 a point of interface of said two layers, and the melting temperature of the inner layer is greater or equal to the melting temperature of the outer layer, comprising a core mould provided at the base thereof with at least one pin suitable for forming a vent at the interface between the first and second layers of said preform.

13. The tool according to claim 12 comprising more than one pin disposed around the perimeter of the core base.

14. The tool according to claim 12, wherein the pins have the shape of a wedge.

15. An apparatus for producing a preform having an inner layer and an outer layer, wherein said 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 a point of interface of said two layers, and the melting temperature of the inner layer is greater or equal to the melting temperature of the outer layer, comprising: support means provided with at least two similar male cores; at least first and second shell female moulds each connected to an extruder, such that the first shell mould is dimensioned for producing the inner layer and the second shell mould for producing the outer layer on top of the inner one; at least one optional extraction station, and means for moving the support means so that each core can be positioned sequentially opposite the first shell mould, the second shell mould and, optionally, the extraction station.

16. The apparatus according to claim 15, wherein said means for moving the support impart a linear movement to the support means.

17. The apparatus according to claim 15, wherein said means for moving the support impart a rotational movement to the support means.

18. Integrally blow-moulded bag-in-container produced by blow-moulding a preform comprising: an inner layer and an outer layer, wherein said 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 a point of interface of said two layers, and the melting temperature of the inner layer is greater or equal to the melting temperature of the outer layer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] FIG. 1 is a schematic cross-sectional representation of a preform and the bag-in-container obtained after blow-moulding thereof.

[0026] FIG. 2 is a cutaway perspective view of the mouth and neck region of a preform or bag-in-container according to a preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0027] 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).

[0028] 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 as illustrated in FIG. 2. 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.

[0029] The preform of the present invention consists of an integral preform obtained by injection moulding one layer on top of the other. This solution offers a number of advantages over preform assemblies, like for instance, that it requires no assembly step and one production station only is sufficient for the integral preform fabrication when at least two are required for a preform assembly.

[0030] 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. The requirement according to the present invention for the materials of the inner and outer layers is that the melting temperature of the outer layer is lower than, or equal to the one of the inner layer, T.sub.m,outerT.sub.m,inner. This condition is exactly the opposite to the one taught in EPA1356915 and U.S. Pat. No. 6,649,121. This departure from the teaching of said prior art is rendered possible by the discovery by the present inventors that the integral preform can advantageously be produced with the following sequential steps: [0031] injection moulding the inner layer first onto a core; [0032] followed by injection moulding the outer layer onto the inner layer; and [0033] extracting the thus formed preform from the core;

[0034] This approach is more advantageous than the one proposed in EPA1356915 and U.S. Pat. No. 6,649,121 for the following reasons. As discussed in the review of the background art, a bag-in-container must comprise at least one interface vent fluidly connecting the interface between inner and outer layers to the atmosphere. In the field of beverage dispensing containers, the assembled (i.e., not integrally blow-moulded) bag-in-containers used to date, traditionally and for practical reasons, are provided with vents located adjacent to, and oriented coaxially with the bag-in-container's mouth. So as to progressively replace the traditional, assembled bag-in-containers by integrally blow-moulded ones, and so as to allow the consumer to keep the same appliance the bag-in-container is to be mounted into, the same vents location is preferably maintained. The present process allows to provide integral preforms with vents fluidly connecting the interface between inner and outer layers to the atmosphere, provided an appropriate tool is used.

[0035] The tool is of the core-shell type and comprises a core mould provided at the base thereof with at least one pin suitable for forming a vent at the interface between the first and second layers of the preform. The core may comprise a single pin, but it preferably comprises more than one pin in order to have several vents opening around the lip of the container's mouth. The pins preferably have the shape of a wedge as, on the one hand, a wedge shaped vent has the advantages discussed above and, on the other hand, it allows for easier extraction of the thus produced integral preform from the mould core. The dimensions of the pins depend on the size of the bag-in-container and, in particular, of the mouth and lip thereof. For a typical home beverage dispenser of a capacity of about 56 liters, the pins have a height of about 5 to 75 mm, preferably 5 to 50 mm, most preferably 10 to 20 mm and their base, forming the vents openings, preferably are in the shape of an arc section of length comprised between 3 and 15 mm, preferably 5 and 10 mm and of width comprised between 0.5 and 5 mm, preferably 0.5 and 2 mm.

[0036] Preferably, the integral preform of the present invention comprises mechanical interlocking means (8) for fixing the inner layer to the outer layer. This allows an easier and safer handling of the preform and facilitates the extraction of the preform from the injection moulding core.

[0037] The preform of the present invention can be produced semicontinuously with an apparatus comprising: [0038] support means provided with at least two similar cores (male), preferably of the type described above; [0039] at least first and second shell moulds (female) each connected to an extruder, such that the first shell mould is dimensioned for producing in combination with a core the inner layer and the second shell mould for producing the outer layer on top of the inner one; [0040] optionally at least one extraction station, [0041] means for moving the support means so that each core can be positioned sequentially opposite the first shell mould, the second shell mould, and optionally the extraction station.

[0042] The apparatus of the present invention may include a separate extraction station, for example to allow further cooling of the part prior to extraction or, if the preform is extracted upon opening the mould after the injection of the second layer, it may well do without one. The means for moving the support means from one shell mould to the other and, optionally, to the extraction station may be linear, using a shuttle, or rotational, using a carrousel.

[0043] The two layers (11) and (12) of the preform according to the present invention are connected by an interface (14) throughout substantially the whole inner surface of the outer layer. Although the inner and outer layers of the preform may adhere at said interface (14), the inner and outer layers (21) and (22) of the bag-in-container (2) produced by blow-moulding the preform (1) do delaminate upon injection of a pressurized gas at a point of the interface. It is generally believed that better results are obtained when at least one of the inner and outer layers comprises a semi-crystalline polymer.

[0044] It has surprisingly been observed that excellent delamination results between the inner and outer layers of bag-in-containers can be obtained also with integral preforms wherein both inner and outer layers consist of the same material. This discovery is in contradiction with the teaching of the prior art with respect to the choice of materials of the inner and outer layer which, as quoted from JPA2005047172, must consist of mutually non-adhesive synthetic resins. It has now been shown that excellent integrally blow-moulded bag-in-containers may be produced with the inner and outer layers made of the same material. Hence, according to the present invention, the melting temperature of the inner layer can be equal to the melting temperature of the outer layer.

[0045] The same polymer is considered in contact on either side of the interface between the inner and outer layers in the following cases: [0046] inner and outer layers consist of the same material (e.g., PET.sub.innerPET.sub.outer, regardless of the specific grade of each PET); or [0047] 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.

[0048] The presence in a layer of low amounts of additives is not regarded as rendering the material different, so far as they do not alter the interface substantially.

[0049] 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.

[0050] 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 pressure-time-temperature window used is of course of prime importance and greatly depends on the material selected for the inner and outer layers.

[0051] A release agent may be applied on the outer surface of the inner layer prior to injection moulding the outer layer onto the inner layer. Hence the release agent is positioned at the interface and facilitates delamination of the inner layer and outer layer. 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.

[0052] 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.

EXAMPLE

[0053] A preform according to the present invention was produced by injecting a melt into a first mould cavity cooled to form the preform's inner layer. The core comprising the inner layer was moved to a second cavity cooled at the same temperature as the first one, and a melt was injected over the inner layer present in the cavity and the preform was extracted. It comprised vents (3) and interlocking means (8) as illustrated in FIG. 2.

[0054] 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.

[0055] The delamination pressure was determined as follows. The interface vents of the 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.

[0056] 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.