Integrally Blow-Moulded Bag-in-Container Having a Bag Anchoring Point, Process for the Production Thereof, and Tool Thereof

Abstract

The invention is an integrally blow-moulded bag-in-container obtainable by blow-moulding an injection moulded multi-layer preform. The bag-in-container includes an inner layer forming the bag and an outer layer forming the container, and a single opening, the mouth, fluidly connecting the volume defined by the bag to the atmosphere. The container further includes at least one interface vent fluidly connecting the interface between inner and outer layers to the atmosphere, wherein the bag is anchored to the outer layer at at least one point remote from the single opening and interface vent. The invention also relates to a process and a mould for the production of the blow-moulded bag-in-container.

Claims

1. An integrally blow-moulded bag-in-container obtainable by blow-moulding an injection moulded multi-layer preform, said bag-in-container comprising: an inner layer forming the bag and an outer layer forming the container; a single opening, the mouth, fluidly connecting the volume defined by the bag to the atmosphere; and at least one interface vent fluidly connecting the interface between inner and outer layers to the atmosphere, wherein the bag is anchored to the outer layer at at least one point remote from said single opening and interface vent.

2. The bag-in-container according to claim 1, wherein the anchoring point is obtained by locally enhanced chemical or physical adhesion between the inner and outer layers.

3. The bag-in-container according to claim 1, wherein the anchoring point is obtained by locally enhanced mechanical adhesion between the inner and outer layers.

4. The bag-in-container according to claim 3, wherein mechanical adhesion is locally enhanced by a protrusion formed by both inner and outer layers.

5. The bag-in-container according to claim 1, wherein the inner and outer layers are different materials.

6. The bag-in-container according to claim 1, wherein the inner and outer layers are the same material.

7. The bag-in-container according to claim 1, wherein the inner and outer layer are a material selected from PET, PEN, PTT, PA, PP, PE, HDPE, EVOH, PGAc, PLA, and copolymers or blends thereof.

8. The bag-in-container according to claim 1, wherein the at least one 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 an interface.

9. The bag-in-container according to claim 1, wherein more than one vent is distributed around the lip of the bag-in-container's mouth.

10. A process for producing a bag-in-container according to any one of the preceding claims, comprising the following steps: providing an injection moulded polymer preform comprising two layers; bringing said preform to blow-moulding temperature; and blow-moulding the heated preform to form a bag-in-container; wherein, during the process, the bag is anchored to the outer layer at at least one point remote from said single opening.

11. The process according to claim 10, wherein the anchoring point is obtained by local thermal control of the layers in order to enhance chemical or physical adhesion between the inner and outer layers.

12. The process according to claim 10, wherein the anchoring point is obtained by locally enhanced mechanical adhesion between the inner and outer layers.

13. The process according to claim 12, wherein mechanical adhesion is locally enhanced by a protrusion formed by both inner and outer layers engaging in a sump formed in the tool.

14. A mould for the production of a blow-moulded bag-in-container having an inner layer forming the bag and an outer layer forming the container; a single opening, the mouth, fluidly connecting the volume defined by the bag to the atmosphere; and at least one interface vent fluidly connecting the interface between inner and outer layers to the atmosphere, wherein the bag is anchored to the outer layer at at least one point remote from said single opening and interface vent. said mould comprises: at at least one point means suitable for creating an anchoring point between the inner and outer layers upon blow-moulding of said container, said point being remotely located from the container's opening mouth.

15. The mould according to claim 14 wherein said means is suitable for creating mechanical adhesion between the inner and outer layers and includes a sump.

16. The mould according to claim 14 wherein said means is suitable for enhancing physical or chemical adhesion between the inner and outer layers and includes specific heating means located at the desired anchoring area.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] 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.

[0022] FIG. 1B: 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.

[0023] FIG. 2: is a schematic representation of a blow-moulding tool with a bag-in-container therein.

DETAILED DESCRIPTION OF THE INVENTION

[0024] 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 (I) 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). Said vent (3) comprises an opening to the atmosphere in (4).

[0025] 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.

[0026] The preform may consists of an assembly of two independent injection moulded 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, as well as in the choice of materials constituting each preform component. 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 and the respective melting temperatures of the inner and outer layers must be carefully matched depending on which layer is injected first; the rule of thumb being that the layer being injected first generally requires a higher melting temperature.

[0027] The inner and outer layers of the preform (1) may consist of different materials or the same material. In case different materials are used, some requirements must be fulfilled depending on the process parameters in the injection moulding of the preform as well as in the blow-moulding of the bag-in-container. It is important of course that both materials may be processed in a rather similar process window and that they will not form too strong an interface which would not satisfactorily release upon injecting pressurized gas at the interface.

[0028] Alternatively and surprisingly, good results can be obtained also with preforms wherein both inner and outer layers consist of the same material. Particularly in case of integral, over-moulded preforms, it is generally believed that better results are obtained with semi-crystalline polymers.

[0029] The same polymer is considered in contact on either side of the interface between the inner and outer layers in the following cases: [0030] 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 [0031] 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.
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.

[0032] Preferred materials for 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. In case different materials are used for the inner and outer layers, their optimal blow-moulding temperature should not differ from one another by more than 70° C., preferably 40° C., most preferably 10° C., and ideally should have the same blow-moulding temperature.

[0033] 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. 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). 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).

[0034] The bag-in-container (2) of the present invention is obtained by providing a preform as described above; bringing the inner and outer layers of 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, such that the inner layer is locally anchored to the outer layer at a location (7) remote from the bag-in-container's neck region.

[0035] 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.

[0036] 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, the pressure of the gas injected, and the inner bag stability. The latter can be substantially improved by fixing the inner layer to the outer layer at a location remote from the neck region and mouth of the bag-in-container, such that the interface between inner and outer layers will not release at said anchoring point upon injecting pressurized gas at a point of the interface. The bag is thus fixed at two points remote from one another: the neck region and the anchoring point. This allows to better control the collapse of the bag, which is essential for a reliable and reproducible operation of the bag-in-container.

[0037] The anchoring of the inner to the outer layers may be provided by a locally enhanced mechanical, physical, or physical adhesion. Mechanical adhesion includes any interaction between inner and outer layers at all scales spanning from macroscopic mechanical interlocking to cross-crystallinity as well as molecular inter-diffusion across the interface, all phenomena well known to the person skilled in the art. Physical and chemical adhesion is also well studied and involves dispersive forces (e.g., London and Keaton forces), acid base interactions (sometimes also referred to as polar forces), hydrogen bonds, and covalent bonds.

[0038] All, but macroscopic interlocking, of the above adhesion mechanisms are temperature dependent and may be locally promoted, e.g., by controlling the local temperature of the interface at the point where anchoring is desired. In case of preform assemblies, an adhesive may be applied at the desired anchoring point prior to fitting the inner preform into the outer one. The adhesive must resist the blow-moulding temperature and be compliant enough to stretch with the preform upon blowing.

[0039] Macroscopic interlocking may be achieved by using a blow-moulding tool comprising a sump or depression at the desired anchoring point, preferably at the bottom of the container as illustrated in FIG. 1. Upon blow-moulding the heated preform expands and the inner and outer layers engage into the sump. The angle, α, formed by the sump wall with the surrounding container's body wall maybe greater to or equal to 90 degrees, in which case an anchoring point is formed by enhanced friction between the inner and outer layer at the level of the thus produced protrusion or, alternatively, the angle can be smaller than 90 degrees, in which case a mechanical interlocking of the two layers is formed like a rivet.

[0040] Preferably a stretching rod drives the preform downwards during the blow-moulding process to promote longitudinal stretching and to ensure that good contact of the preform with the tool's wall is effected at the desired point of anchoring.

[0041] In the case the angle, α, formed by the sump wall with the surrounding container's body wall is smaller than 90 degrees and the mechanical interlocking of the two layers is formed like a rivet, the anchoring point comprises an undercut. The creation of this undercut can be achieved in several methods, some of which are described below.

[0042] According to a first method, the undercut is created by using a blow-moulding tool comprising two half-moulds that are only partially closed at the location of the sump, the side walls of the half-moulds at the sump location defining a negative of the anchoring point to be created. The preform is driven down in the sump by means of a stretching rod, where after both half-moulds are moved towards each other to entirely close the mould, creating the undercut.

[0043] According to another method, a blow-moulding tool is used comprising axially moving pins that can be introduced in the mould cavity during blow-moulding, allowing creation of the undercut.

[0044] According to yet another method, the blow-moulding tool with half-moulds defining a sump negative to the anchoring point to be created. The preform being driven into the sump by means of the fluid pressure applied during blow-moulding thereof. In this method, a stretching rod may be used that either stops at a position distant from the sump or that extends into the sump. In the last case, it is preferred to use a stretching rod provided with a central fluid channel and lateral openings at its distal end (the end extending in the blow-moulding tool) that extends into the sump during stretching, such that part of the fluid used to stretch the preform is guided through the fluid channel and the lateral openings to facilitate stretching of the preform into the sump and against the inner wall the mould cavity defining the sump.

[0045] FIG. 2 schematically represents a blow-moulding tool with provided therein a chime comprising said sump or depression at the desired anchoring point. This chime is inserted in the blow-moulding tool prior to blow-moulding the preform, such that upon blow moulding the heated preform expands and the inner and outer layers engage into the sump. In this manner, the desired macroscopic interlocking is achieved and additionally a chime is provided on the container. In the case the sump defined by the chime is designed for the creation of an anchoring point in the form of a rivet, the anchoring point can successfully be created by means of fluid pressure forcing the material of the preform into the sump. Both methods applying a stretching rod and not applying a stretching rod can be used.

[0046] A release agent may be applied at the interface on either or both surfaces of the inner and outer layer, which are to form the interface of the bag-in-container. In the case the outer layer is injection moulded onto the inner layer, the release agent can be applied at the outer surface of the inner layer prior to moulding the 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. The release agent may be applied just prior to loading the preforms into the blowmoulding unit, or the preforms may be supplied pretreated.

[0047] 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.