CA2878104A1

CA2878104A1 - Multi-layer laminate for tubes with an embedded barrier layer and tube produced therefrom and use of such a laminate

Info

Publication number: CA2878104A1
Application number: CA2878104A
Authority: CA
Inventors: Arno Holzmuller; Manfred Marz; Matthias Schragle; Manfred Wieser; Eddy Daelmans
Original assignee: Huhtamaki Flexible Packaging Germany GmbH and Co KG
Current assignee: Huhtamaki Flexible Packaging Germany GmbH and Co KG
Priority date: 2012-07-23
Filing date: 2013-07-19
Publication date: 2014-01-30
Anticipated expiration: 2033-07-19
Also published as: BR112015000965A2; DE102013102138A1; CA2878104C; WO2014016221A1; LT2874811T; ES2710116T3; IN2015DN01298A; SI2874811T1; PL2874811T3; EP2874811B1; EP2874811A1

Abstract

The invention relates to a multi-layer laminate for tubes with an embedded barrier layer (50), the laminate having an outer cover layer (30a) delimiting the laminate on one side, and an inner cover layer (30i) delimiting the laminate on the other side, between which cover layers the barrier layer (50) is disposed, the laminate having an asymmetrical structure in relation to the barrier layer (50), particularly in respect of the cover layers (30a, 30i), wherein, in particular a molecular orientation of the inner cover layer (30i) differs from a molecular orientation of the outer cover layer (30a), each in relation to expansion or stretching in the machine direction (MD) and transverse to the machine direction (CD). The invention further relates to a tube produced from such a laminate and the use of such a laminate.

Description

MULTI-LAYER LAMINATE FOR TUBES WITH AN EMBEDDED BARRIER
LAYER AND TUBE PRODUCED THEREFROM AND USE OF SUCH A
LAMINATE
Description The present application relates to a multilayer laminate for tubes with an embedded barrier layer according to the preamble of patent claim 1, a tube according to the preamble of patent claim 13 produced therefrom and use of such a laminate according to the preamble of patent claim 14.
Multilayer laminates are needed in the packaging industry sector, in particular also for the production of tubes.
Depending on the thickness of the laminate, they have flexible to relatively dimensionally stable properties and are used inter alia for the production of tubes, bags and other packaging. In particular, multilayer laminates which have an embedded barrier layer, for example in the form of an aluminum foil, are suitable for packaging aroma-containing substances. This is based on the fact that a barrier layer present in the laminate, such as an aluminum foil, acts as a barrier layer for many, mainly volatile, substances. However, it has been found to be a problem here that the barrier layer itself, and here in particular an aluminum layer, is attacked by aggressive substances such as for example acids and aggressive organic substances, so that shielding of the barrier layer or aluminum layer against the contents of the tube is necessary. This was hitherto achieved by the layers encasing the barrier layer being of great material strengths and thus great thickness, so that the particular aggressive substances attacking the aluminum layer had to surmount a longer diffusion path. In addition, an aluminum layer was if necessary shielded against the packaging

- 2 -content by an additional barrier layer, e.g. of ethylene vinyl alcohol copolymer (EVOH).
However, the need for the use of such thick laminate layers has the result that the multilayer laminate as a whole becomes very thick, stiff and difficult to handle and not least becomes expensive because of the large quantity of material to be used.
Thus the thicknesses of the laminates used, for example in the toothpaste tube sector, vary in the order of magnitude of a quarter of a millimeter, which in lap or fin seal regions leads to material thicknesses of half a millimeter and more. This great material thickness has adverse effects both esthetically and as regards process technology in all regions of a tube in which overlapping of the laminate is necessary. Such overlapping is for example necessary in the production of a tubular lap seal article from a flat laminate blank.
A further disadvantage of such thick laminates also consists inter alia in that with use of such laminates it is difficult to impossible to produce a uniformly shaped tube body. This difficulty arises firstly from the greatly decreased flexibility and stiffness of seal regions which are necessary for the production of a tube body by lap sealing. In addition, with laminates known from the state of the art, stretched or orientated film material is often used. However, particularly during sealing, such oriented film material has the disadvantage that during heating during the sealing process the film material at least partly loses its orientation and as a result at least partly shrinks. This effect is a particular problem in the production of tubes, since here because of the great layer thickness in the sealing region a sealing temperature is

- 3 -not constant over the cross-section of the laminate thickness to be sealed, which has the result that any shrinkage of an oriented film is not constant over a cross-section of the laminate, but instead takes place unevenly. Thus, with such a laminate, particularly if as aforesaid this necessitates a large laminate thickness, practically no actually round, but instead in all cases an oval tube shape is produced, which is not only visually ugly, since the tube has a very thick lap seal weld, which is unsatisfactory visually and also to the touch, since this weld can be seen and felt as a linear thickening.
A further disadvantage which results from the use of such thick laminates known from the state of the art further consists in that during the tube production it is in practice impossible to produce a round tube body into which a tube head is then sealed, since the stiffness of previous laminates, particularly in the region of the lap seal weld of a tube, has the result that the radius of curvature in the region of the lap seal weld is greater than in the remaining extent of the tube. Since the tube head is usually designed essentially completely round, difficulties thus arise in inserting this round tube head into a non-round tube body, so that according to the current state of the art additional measures and auxiliary devices are necessary for this, which entail additional work processes and slowing of tube production.
A further disadvantage of previous laminates also consists in the risk of delamination, which is naturally all the greater the thicker the laminate-forming layers since during rolling of the laminate the individual laminate layers are exposed to a greater shear stress the thicker the individual layers. Here, the risk of delamination

- 4 -further intensifies with the sensitivity of the materials used to the particular contents of the tube.
Further, the haptic properties are also unsatisfactory with previously known laminates, which is essentially also attributable to the necessary high layer thicknesses of previously known laminates since owing to the material thickness in the region of the lap seal weld these always entail a certain stiffness and ovality and a ridge along the lap seal weld as a result of this.
The purpose of the invention is to provide a multilayer laminate with an embedded barrier layer and packaging produced therefrom which enables improved barrier properties simultaneously with thinner layer thicknesses of the individual laminate layers and simple, rapid and inexpensive process technology for production of round laminate pipes, in particular tubes, wherein the laminate can be inexpensively produced and individually better printed and furthermore articles produced therefrom provide improved haptic properties and improved environmental compatibility.
This problem is solved by a multilayer laminate as claimed in patent claim 1, and by a tube as claimed in patent claim 13 produced from such a laminate and also by the use of such a laminate for production of a tube as claimed in patent claim 14.
In particular, the problem is solved by a multilayer laminate for tubes with an embedded barrier layer, wherein the laminate has an outer covering layer bounding the laminate on one side and an inner covering layer bounding the laminate on the other side, between which the barrier layer is positioned, wherein the laminate has an

- 5 -asymmetric structure relative to the barrier layer, particularly with regard to the covering layers, namely the outer and the inner covering layer, wherein in particular a molecular orientation of the inner covering layer differs from a molecular orientation of the outer covering layer, each in relation to elongation or stretching in the machine direction (MD) and transverse to the machine direction (CD). This means that the outer covering layer has an orientation, while the inner covering layer has no orientation, or that an orientation of the outer covering layer is other, in particular greater, than an orientation of the inner covering layer.
An essential concept of the invention here consists in that according to the invention it was discovered that the effect of shrinkage of an oriented covering layer in the course of production of a lap seal for production of a tubular pipe can be influenced astonishingly simply in that the two covering layers bounding a multilayer laminate for tubes towards the exterior are implemented differently, wherein a stretching or elongation of an outer covering layer is other, in particular greater, than the stretching or elongation of an inner covering layer.
Here according to the invention it was further found advantageous if the outer covering layer is biaxially oriented or biaxially stretched, while the inner covering layer is elongated or stretched monoaxially or not at all.
Hence according to the invention the outer covering layer has a biaxial orientation with stretching in the machine direction (MD) of 200% to 800%, preferably of 400% to 600%
and particularly preferably of essentially 500% and transverse to the machine direction (CD) of 500% to 1300%, preferably of 700% to 900% and particularly preferably of I
,

- 6 -essentially 800%, while the inner covering layer has a monoaxial orientation or none.
In this manner, it is possible to prevent the inner covering layer from shrinking or alternatively to establish a specific shrinkage of the inner covering layer in the course of a sealing process, so that as a result an optimized round laminate tube closed by lap seal for production of tubes can be created.
As regards the material of the embedded barrier layer, according to the invention the barrier material aluminum can be used. It is however also possible to use polyamide, in particular amorphous and/or aromatic and/or partly aromatic polyamide, ethylene vinyl alcohol copolymer (EVOH), polyacrylonitrile (PAN), polyethylene terephthalate (PET) or SiOx or aluminum oxide as barrier layer material. The choice of the particular barrier material here depends on the particular contents of the tube produced or on the aggressive materials which have to be retained.
The invention is now explained below on the basis of a multilayer laminate for tubes with an embedded aluminum layer, however it should be noted that a barrier layer of ethylene vinyl alcohol copolymer, optionally in combination with polyamide, can also excellently be used in the multilayer laminate according to the invention.
Further, it should be noted that the barrier layer used in the laminate according to the invention can itself also be multilayer, for which recourse can preferably be had to prefabricated, for example coextruded, foil configurations.

- 7 -Here for example an ethylene vinyl alcohol copolymer layer which is embedded between two polyolefin layers, such as for example polyethylene layers, by means of a bonding agent has proved effective. A composite of polyamide-ethylene vinyl alcohol copolymer-polyamide, i.e. an ethylene vinyl alcohol copolymer layer embedded between two polyamide layers, has also proved effective, where in this case both the externally lying polyamide layers each can be bonded to a respective polyolefin layer, such as a polyethylene layer, by means of a bonding agent. These aforesaid structures can be prefabricated and be integrated into the multilayer laminate according to the invention. Alternatively, simultaneous extrusion of the individual layers of the multilayer laminate according to the invention is also possible, if the particular individual layers are extrudable.
As aforesaid, the problem of the invention is thus solved by a multilayer laminate for tubes with an embedded aluminum layer, wherein the laminate has an outer, in particular biaxially, oriented coextruded covering layer bounding the laminate on the outside and an inner covering layer, not oriented or less so than the outer covering layer, bounding the laminate on the inside, wherein the outer covering layer is bonded to the barrier layer or aluminum layer, via an outer intermediate layer material and the inner covering layer according to one embodiment is bonded to the optionally multilayer barrier layer, in this case with the aluminum layer, via an inner intermediate layer material.
According to a further embodiment of the invention, the inner covering layer can also be bonded directly with the barrier or aluminum layer, where in this case the inner covering layer has a shell layer which can be designed as

- 8 -a skin layer, which preferably consists of a polyolef in, preferably of a polyethylene, and which bounds the barrier or aluminum layer, if necessary via a bonding agent.
A further important concept of the invention consists in that the barrier layer, namely here the aluminum layer, is surrounded on one or both sides and preferably directly by an intermediate layer material, namely an outer intermediate layer material facing an oriented coextruded outer covering layer on one side and an inner intermediate layer material facing a non- or monoaxially oriented inner covering layer on the other side, or alternatively the barrier layer is surrounded directly on the inside by the non- or monoaxially oriented covering layer, wherein the inner covering layer is in every case less oriented than the outer covering layer or not oriented.
A further important aspect of the invention also consists in that the laminate according to the invention is on the one side bounded on the outside by an oriented coextruded covering layer and on the other side, i.e. on the side of the laminate not lying opposite the oriented coextruded covering layer, is bounded by a covering layer not or less than the outer covering layer or by a monoaxially oriented covering layer.
It should at this point be noted that the feature that "the inner covering layer is less oriented than the outer covering layer" in the context of this invention means that the inner covering layer is not oriented, while the outer covering layer is oriented, or that the inner covering layer is oriented in one direction, while the outer covering layer is oriented in more than one direction or that a degree to which the inner covering layer is oriented is less than a degree to which the outer

- 9 -covering layer is oriented, or that the inner covering layer is oriented in more than one direction, while the outer covering layer is also oriented in more than one direction and furthermore with a higher stretch or blow-up ratio than the inner covering layer.
In the production of a tube from the laminate according to the invention, the outer side of the tube is by definition formed from the oriented coextruded covering layer, while the inner side of the tube is formed by the non-oriented layer. Based on this arrangement, the oriented coextruded covering layer is therefore described in the context of this invention as the outer covering layer, while the non-or slightly oriented covering layer facing the interior of the tube is described as the inner covering layer.
Both the outer covering layer and also the inner covering layer are respective layers bounding the laminate on the outside and the inside, which however, if necessary, can have print and optionally a protective layer covering the print.
A further important aspect of the invention also consists in that the laminate according to the invention is asymmetrically structured at least as regards its inner and outer covering layer, wherein the outer covering layer in every case is an oriented coextruded covering layer, which is stretched either monoaxially, or, preferably, biaxially, i.e. in the machine direction and also transverse to the machine direction, while the inner covering layer has no or a lesser orientation and/or stretching than the outer covering layer, or alternatively has a monoaxial stretching or a lesser orientation ratio than the outer covering layer.

- 10 -Concerning this, it should be noted that a monoaxial outer covering layer is not preferred, but under some circumstances can be combined with a non-oriented inner covering layer.
In contrast, a preferred embodiment of the invention consists in the use of a biaxially oriented outer covering layer in combination with a non- or monoaxially oriented inner covering layer. Here the inner covering layer is either formed as stretched film or, preferred according to the invention, as blown film, wherein the blow-up ratio in machine direction (MD) to transverse direction (CD) is in the range from 1:1 to 1:2.5, preferably in the range from 1:1.05 to 1:1.75 and particularly preferably in the range from 1:1.2 to 1:1.9. Here the ratio information should in each case be understood to mean that a stretching or elongation of the inner covering layer is always effected only in one direction, i.e. either in machine direction or transverse thereto, so that in every case an unstretched or an only monoaxially stretched or elongated film is present within the stated limits.
It has been found according to the invention that with a laminate which has such an asymmetrical structure it is possible to manufacture tubular articles which have exceptionally good roundness, which has been found particularly advantageous in particular in the tube manufacturing process, wherein the laminate has high stability, improved haptic properties compared to the state of the art and moreover very good barrier properties, also in particular as regards protection of an aluminum layer or film.
Thus the embedded barrier layer is protected both by the outer intermediate layer material and also by the oriented

- 11 -coextruded outer covering layer on the one hand and also optionally by the inner intermediate layer material and in every case by the inner covering layer on the other hand both in the mechanical sense and also with regard to diffusible substances, since these must firstly diffuse from a side of the laminate facing the inside of a tube through the inner non-oriented covering layer and then through the intermediate layer material or alternatively only through the inner covering layer, if this itself has a barrier layer protecting the embedded barrier layer, in particular aluminum layer, in order to reach the embedded barrier layer, for example aluminum layer.
The oriented coextruded outer covering layer is, exactly like the outer intermediate layer material, present outside the embedded barrier layer, so that protection of the barrier layer against aggressive substances is also optimized from a tube exterior.
According to the invention, the coextruded oriented outer covering layer is designed at least two-layer and comprises at least one oriented polymer layer and at least one, optionally two or more, shell layers. The shell layers, which are also described as skin layers, surround the polymer layer and are themselves printable on their side facing the polymer layer.
According to the invention and preferably, these skin layers are designed very thin and have a layer thickness in the range from 0.2 pm to 10 pm, preferably in the range from 0.8 pm to 6 pm and particularly preferably in the range from 1 pm to 2.5 pm and thus form a kind of skin surrounding the polymer layer.

- 12 -Further, these skin layers are designed sealable, so that a lap seal or a fin seal sealing of such laminates is easily possible. Here a preferred embodiment of the outer covering layer consists in that a polymer layer, for example of polypropylene, is surrounded on both sides by a skin layer, where the skin layers positioned on both sides are similar or identical as regards thickness and material. The thickness of the polymer layer here according to the invention is 6 to 100 times, preferably 14 to 81 times and particularly preferably 50 to 70 times or for example 10 to 30 times the thickness of the skin layer. This means that the skin layers are designed very thin relative to the polymer layer, so that as a result a thin outer covering layer is produced, which according to a preferred embodiment of the invention has a thickness in the range from ca. 40 to ca. 70 pm.
According to the invention, the outer covering layer is coextruded, wherein the polymer layer and the skin layer or layers are extruded and bonded in one operation. After application of the skin layer or layers, the coextruded covering layer is stretched, in particular biaxially, so that after the stretching process the whole covering layer is oriented. This also relates in particular to the skin layer.
As aforesaid, the inner covering layer of the laminate according to the invention in every case consists of a material which according to the above definition according to the invention is less oriented than the outer covering layer.
The inner covering layer of the laminate according to the invention can be designed as monofilm or as two- or three-layer multilayer film.

- 13 -In the case where the inner covering layer is designed as monofilm, this essentially consists of sealable materials, such as for example polyolefins, such as polyethylene (PE), in particular polyethylene with weakly branched polymer chains and hence high density (HDPE), polyethylene with strongly branched polymer chains and hence low density (LDPE) or linear polyethylene of low density (LLDPE) and/or polypropylene (PP), since these materials are particularly suitable for the production of a fin or preferably lap seal, with which a tubular article can be shaped into a pipe and then further processed.
In the case where the inner covering layer is designed as two- or three-layer multilayer film, the inner covering layer is essentially composed of one or two skin layer(s) and/or a polymer layer and/or an inner barrier layer.
Here according to the invention the skin layer or layers are based on sealable materials such as for example polyolefins, such as in particular and preferably polyethylene, since this/these material(s) is/are particularly suitable for the production of a fin or preferably lap seal, with which a tubular article can be shaped into a pipe and then further processed. Further, the polyolefins usable for a skin layer can be the sealable materials HDPE, LDPE or LLDPE and/or polypropylene (PP).
The individual layers of an inner covering layer designed as a two- or three-layer multilayer film can be the same or different polyolefins, such as for example polyethylene or polypropylene, which are bonded together. Such bonding of different layers to form the inner covering layer can according to the invention for example be effected by

- 14 -coextrusion, wherein the individual layers can for example consist of high density polyethylene (HDPE) or of low density polyethylene (LDPE) or of linear low density polyethylene (LLDPE). In this regard, for example a core layer of polypropylene with respective skin layers of polyethylene, which can for example be structured analogously to the outer covering layer is also conceivable.
In this, it is particularly advantageous if, for forming a lap seal bond for forming the tube body, identical materials are used for the outer oriented coextruded covering layer and for the inner non-oriented covering layer which are sealed together. This means that for the outer oriented covering layer and the inner non-, or slightly oriented covering layer either similar skin layers made of polyethylene or polypropylene are used or else a respective monofilm designed as the inner covering layer consists of the same material as the layer of the outer covering layer with which the monofilm is sealed in a lap sealing operation.
Thus in a multilayer embodiment the inner covering layer comprises a polymer layer which at least on one side, preferably on both sides, comprises one or more, in particular essentially identical, shell layer(s) in the form of respective skin layers, which are preferably positioned symmetrically relative to the polymer layer.
The skin layers are designed thick, preferably each equally thick, relative to the polymer layer, and bonded to the polymer layer by coextrusion.
Alternatively, in a multilayer embodiment, the inner covering layer can have a, preferably central, inner barrier layer which is surrounded on each side, and

- 15 -preferably symmetrically relative to the inner barrier layer by an, in particular essentially identical, shell layer, for example in the form of a skin layer, wherein between the inner barrier layer and the respective skin layer a bonding agent or adhesive, particularly a laminating adhesive, is optionally, in particular preferably, provided.
As materials of the inner barrier layer according to the invention, polyamide, in particular amorphous and/or aromatic and/or partly aromatic polyamide, ethylene-vinyl alcohol copolymer (EVOH), polyacrylonitrile (PAN), polyethylene terephthalate (PET), aluminum, SiO., AlOx and mixtures and/or combinations of the aforesaid materials are possible, wherein it should be noted that an inner barrier layer layer sequence of polyamide-EVOH-polyamide is a particularly effective protective barrier against gaseous and/or diffusible substances, as has been found according to the invention. If a multilayer inner barrier layer is used, the respective layers of the inner barrier layer can as required be bonded to a laminating adhesive.
The same applies for bonding of the inner barrier layer to respective adjacent layers.
According to the invention, the outer intermediate layer material facing the tube exterior is designed at least single-layer, but preferably multilayer, in particular one- to three-layer and particularly preferably two-layer and comprises a first and/or a second and/or a third bonding layer.
The inner intermediate layer material facing the tube interior is at least single-layer, preferably multilayer, in particular one- to five-layer, wherein one to three layers thereof have the material of the first and/or the

- 16 -second and/or the third bonding layer. A particularly preferred embodiment of the inner intermediate layer is made two-layer of different polymers.
Further, according to one embodiment, the inner intermediate layer material facing the tube interior comprises at least one additional barrier layer which optionally has a bonding layer, in particular an adhesive layer, a bonding agent or a laminating adhesive on at least one side. This bonding layer ensures that the additional barrier layer is optimally integrated into the inner intermediate layer material and has optimal bonding with the layers surrounding the additional barrier layer.
This additional barrier layer can also itself be made multilayer and form a composite of the aforesaid organic barrier layer materials, where again already prefabricated barrier layer composites, which optionally comprise skin layers, can also be used.
Further, it should be noted that an inner intermediate layer material which has an additional barrier layer can be replaced by an inner covering layer with an inner barrier layer.
The materials used according to the invention are listed in the following table and can each be present in the respective layer alone or in combination:

- 17 -Layer Material(s) outer shell polyolefin(s), such as covering layer polyethylene (PE), in particular layer (10o) or HDPE, LDPE or LLDPE and/or (30a) skin layer polypropylene (PP), polyethylene terephthalate (PETP), polyethylene terephthalate glycol (PETG), mixtures of aforesaid materials oriented polyolefin(s), such as polymer polyethylene (PE), in particular layer HDPE, LDPE
or LLDPE and/or (20o) polypropylene (PP), polyethylene terephthalate (PET), polyamide (PA).
inner shell polyolefin(s), such as covering layer polyethylene (PE), in particular layer (10n) or HDPE, LDPE or LLDPE and/or (30i) skin layer polypropylene (PP), polyethylene terephthalate (PETP), polyethylene terephthalate glycol (PETG), mixtures of aforesaid materials polymer polyolefin(s), such as layer polyethylene (PE), in particular (20n) HDPE, LDPE
or LLDPE and/or polypropylene (PP), polyethylene terephthalate (PET), polyamide (PA).
inner polyamide, in particular barrier amorphous and/or aromatic and/or layer (55) partly aromatic polyamide, ethylene vinyl alcohol copolymer (EVOH), polyacrylonitrile (PAN), polyethylene terephthalate (PET),

- 18 -mixtures and combinations of aforesaid materials first bonding layer maleic anhydride (MA), ethylene (43) methacrylate (EMA), ethylene-acrylic acid copolymers (EAA), ionomers, terpolymers (ethylene-acrylic acid-maleic anhydride), ethylene-vinyl acetates (EVA), modified olefins, mixtures of aforesaid materials second bonding layer maleic anhydride (MA), ethylene (45) methacrylate (EMA), ethylene-acrylic acid copolymers (EAA), ionomers, terpolymers (ethylene-acrylic acid-maleic anhydride), ethylene-vinyl acetates (EVA), polyolef ins, in particular polyethylene (PE), polypropylene (PP), modified olefins, mixtures of aforesaid materials third bonding layer maleic anhydride (MA), ethylene (47) methacrylate (EMA), ethylene-acrylic acid copolymers (EAA), ionomers, terpolymers (ethylene-acrylic acid-maleic anhydride), ethylene-vinyl acetates (EVA), polyolef ins, in particular polyethylene (PE), polypropylene (PP), modified olefins, mixtures of aforesaid materials bonding layer (60) maleic anhydride (MA), ethylene methacrylate (EMA), ethylene-acrylic acid copolymers (EAA), ionomers, terpolymers (ethylene-acrylic acid-maleic anhydride),

- 19 -ethylene-vinyl acetates (EVA), modified olefins, mixtures of aforesaid materials barrier layer (50) polyamide, in particular amorphous and/or aromatic and/or partly aromatic polyamide, ethylene vinyl alcohol copolymer (EVOH), polyacrylonitrile (PAN), polyethylene terephthalate (PET), in particular oriented polyethylene terephthalate (OPET), aluminum, Si0,, Al0x, mixtures and combinations of aforesaid materials additional barrier polyamide, in particular layer (70) amorphous and/or aromatic and/or partly aromatic polyamide, ethylene vinyl alcohol copolymer (EVOH), polyacrylonitrile (PAN), polyethylene terephthalate (PET), in particular oriented polyethylene terephthalate (OPET), mixtures and combinations of aforesaid materials The respective layer thicknesses of the individual layers can be seen from the following table:
Layer Layer Preferred layer Particularly thickness thickness preferred layer thickness shell layer (10) or skin 0.2 pm - 10 0.8 pm - 6 pm 1 pm - 2.5 pm layer pm oriented polymer layer 10 pm - 100 15 pm - 80 pm 30 pm - 50 pm

(20) pm first bonding layer (43) 5 pm - 140 8 pm - 95 pm 10 pm - 50 pm Pm second bonding layer (45) 5 pm - 140 8 pm - 95 pm 10 pm - 50 pm Pm third bonding layer (47) 5 pm - 140 8 pm - 95 pm 10 pm - 50 pm Pm bonding layer (60) 1.5 pm - 25 3 pm - 18 pm 4.5 pm - 12 pm Pm barrier layer (50) or 3 pm - 60 pm 3.8 pm - 40 pm 4 pm - 28 pm additional barrier layer (70) or inner barrier layer (55) (not in case of an aluminum foil, SiOx or Al0x) barrier layer (50) in case 3 pm - 70 pm 5 pm - 40 pm 8 pm - 15 pm of an aluminum foil =

- 21 -Further, the thickness of the barrier layer materials SiOx and AlOx usually lies in the region of 1 Angstrom. These barrier layer materials are usually vapor deposited and thus advantageously have only a very small layer thickness.
Furthermore, at this point it should once again be noted that the shell layer must be differentiated, namely in that an outer shell layer is present oriented and an inner shell layer not or only slightly oriented.
Through the multilayer design of the intermediate layer material, both for the side facing the tube interior and the side facing the tube exterior, materials can be combined whose properties in an unforeseeable manner interact advantageously at small layer thicknesses and in this way afford an intermediate layer material which has high mechanical and also high chemical stability. In particular, in this regard a high ductility with at the same time high tear and pierce resistance and high resistance to diffusion may be mentioned.
As regards the material thickness of the first, second and third bonding layer, it has according to the invention been found particularly advantageous if the layer material provided in these layers is available with sufficiently high layer thickness and thermoplastic consistency, so that the layer material which forms the outer intermediate layer and in particular also the inner intermediate layer are pressed out from the respective intermediate layer under the action of pressure and heat in the course of a sealing operation and in this manner can overflow and cover an adjacent, in particular exposed, cut edge of an aluminum layer so that the aluminum cut edge is

- 22 -effectively protected against attack by any aggressive substances, in particular from the tube interior.
This effect is particularly advantageous against aggressive contents of the tube produced according to the invention. It is however also possible in this manner to protect the aluminum layer against substances which lie outside the tube. Through such overmelting of a cut edge of the laminate according to the invention it is moreover possible to protect all layers bounding the cut edge, except for the melt layer itself, against outside influences and influences of the tube contents.
In this connection, it should further be mentioned that according to the invention the inner intermediate layer material is made at least as thick and/or at least as multi-layered as the respective outer intermediate layer material used or can comprise more and/or thicker layers.
Here, a two-layer outer intermediate layer material and a two- to three-layer inner intermediate layer material has proved especially effective. In this manner, in the course of a sealing operation to create a lap seal for forming a round tubular article, melting of the inner intermediate layer material and the outer intermediate layer material and overmelting of a cut edge with this melted intermediate layer material both from inside and also from outside the aluminum layer of the laminate according to the invention is possible.
Furthermore, through the provision of the oriented coextruded outer covering layer according to the invention and the non-, or less than the outer covering layer or monoaxially, oriented inner covering layer each of sealable material or with at least one sealable skin layer, good external stability of the laminate according

- 23 -to the invention with at the same time good sealability and, resulting therefrom, high stability of the seals and hence of the tube produced therefrom is obtained.
According to the invention, printing can be effected both on an outer skin layer facing the tube exterior. In addition, it is possible to print the inner shell layer or the corresponding skin layer facing the tube exterior or the tube interior on its side facing the outer intermediate layer material by means of a so-called "reverse print". This is possible since according to the invention the polymer layer positioned between the skin layers can be designed transparent.
For the case that the use of a "reverse print" is desired, a further bonding layer is preferably provided between the color layer positioned on the inner shell layer or the corresponding skin layer and the outer intermediate layer material, in order to ensure good adhesion of the color layer to the intermediate layer material.
Through the use of the materials according to the invention and in particular the layer sequence described, it is possible to create layer thicknesses in the stated thickness ranges and in this manner to achieve a considerably thinner laminate thickness compared to the state of the art, while the multilayer laminate at the same time has improved barrier properties and optimized mechanical and chemical properties and is particularly suitable for the production of round tubular articles with no significant tendency to ovality.
The production of the intermediate layer material according to the invention is effected by joint extrusion of the layers forming the intermediate layer material,

- 24 -whereby the laminate can be produced in the course of a tandem extrusion, wherein in a first extrusion step one side of the barrier layer is coated and in a second extrusion step the other side of the barrier layer. These extrusion steps can be performed as coextrusion steps, wherein a multilayer composite of layers is extruded simultaneously. Provided that the barrier layer is extrudable, such as for example EVOH, this can also be extruded jointly with the intermediate layer material.
Further, the invention also comprises a method for production of a multilayer laminate for tubes with an embedded aluminum layer, wherein the aluminum layer is coated on both sides with intermediate layer material and with an outer oriented coextruded covering layer on one side and on the other side with a non-, less than the outer covering layer or monoaxially, oriented inner covering layer. The oriented coextruded outer covering layer is itself produced by at least one-sided coating, in particular coextrusion, of the polymer layer with a skin layer. Preferably the polymer layer is coated on both sides with a, preferably identical, skin layer. After a coating of the polymer layer with the particular assigned skin layer, the outer covering layer resulting from this is stretched, in particular biaxially. The non-oriented inner covering layer can also be produced by coextrusion, if this is to be made multilayered. Further, production of the inner covering layer as blown film is possible, where an essentially monoaxial elongation of the film occurs in the course of the blowing.
Further, the layers forming the intermediate layer material are coextruded and extruded essentially simultaneously or directly consecutively with formation of the laminate.

- 25 -In summary, it can thus be stated that the essential inventive concept is based on the fact that the inventors surprisingly discovered that a laminate can be molded particularly well into a round film article if an outer covering layer bounding the laminate on one side is oriented, in particular biaxially oriented, and consists of a central layer which can be a polymer layer and preferably two skin layers which surround the central polymer layer, wherein the polymer layer together with the skin layers applied onto this on both sides is oriented, i.e. stretched.
This oriented polymer layer together with the oriented skin layers here is the outer covering layer, which in combined action with a further non-, less than the outer covering layer or monoaxially oriented inner covering layer bounding the laminate on the other side results in the manifestation of the advantageous properties essential here, which make it possible to produce a tubular article which is designed round, and not oval as previously in the state of the art, since through the use of the inner non-oriented covering layer according to the invention extremely advantageously a shrinkage process can be avoided or, decided by the degree and/or direction of stretching or orientation "adjusted", which occurred uncontrolled or to an undesirably high extent in films according to the state of the art in the course of lap sealing of previous laminates, when these previous laminates were shaped into a tubular article.
Moreover, the problem according to the invention is also solved by a tube which is produced from a laminate according to the present explanations, and further through

- 26 -the use of an above-described laminate for production of packaging with tubular articles, namely a tube.
Further embodiments of the invention follow from the subclaims.
The invention is described below on the basis of practical examples which are explained in more detail on the basis of the diagrams. These show:
Fig.1 a schematic diagram of a first embodiment of a laminate according to the invention;
Fig.2 a schematic diagram of a second embodiment of a laminate according to the invention;
Fig.3 a schematic diagram of a third embodiment of a laminate according to the invention;
Fig.4 a schematic diagram of a further embodiment of a laminate according to the invention;
Figs.5-7 schematic diagrams of further embodiments of laminates according to the invention on the basis of the embodiments according to Fig.1, Fig.2 and Fig.4, but with additional barrier layer;
Figs.8 & 9 schematic diagrams of further embodiments of laminates according to the invention;
and Figs.10-12 schematic diagrams of different barrier layer composites which can be used according to the invention as an embedded barrier layer and/or additional barrier layer and/or inner barrier layer.
In the description below, the same reference numerals are used for identical and identically acting parts.

bonding layer 45 and a third bonding layer 47. In this case also, the inner covering layer 30i can alternatively to the above-described embodiment according to Fig.4 also be structured according to Figures 10 or 12 described below, wherein the inner covering layer in these cases is also not or not significantly oriented.
Figs.5, 6 and 7 as regards their outer structure in relation to the aluminum layer 50 correspond to the embodiments according to Figs.1, 2 and 4. The inner structure of the laminate is modified in that an additional barrier layer 70 which is surrounded on both sides by a bonding layer 60 is integrated into a first or second bonding layer 43, 45 forming the inner intermediate layer material 40i.
With a laminate structure according to Figures 5 to 7, according to the invention it is possible that the inner intermediate layer material 40i forms the inner covering layer 30i, so that in this case the inner covering layer 30i bounds the embedded barrier layer 50 directly or optionally via a bonding agent or laminating adhesive.
Further, also in the case of a laminate structure according to Figures 5 to 7 it is possible that the inner covering layer 30i can alternatively to the above-described embodiment according to Figures 5 to 7 also be structured according to Figures 10 or 12 described below, wherein the inner covering layer in these cases is also not or not significantly oriented.
Moreover, it should be noted that although the embedded barrier layer 50 according to Figures 1 to 7 was by way of example described as an aluminum layer, the embedded barrier layer 50 can however as required, for example for creating a transparent laminate, also consist of one or more plastic material(s) according to the above explanations. In this case, the embedded barrier layer 50 has a layer thickness in the range from 3.8 pm to 40 pm, preferably in the range from 4 pm to 28 pm. In the case of the use of aluminum as the barrier layer material for the embedded barrier layer 50, a nontransparent laminate according to the invention is obtained.
In addition it should be mentioned that the embedded barrier layer 50, and also the additional barrier layer 70, and also the inner barrier layer 55 can be formed by barrier layer composites according to Figures 10 to 12.
Fig.8 shows a further schematic diagram of a multilayer laminate according to the invention for tubes with an embedded aluminum layer 50. According to Fig.8, the aluminum layer 50 is surrounded on both sides by a second bonding layer 45 of a copolymer. The copolymer of the second bonding layer 45 in the direction of the coextruded oriented outer covering layer 30a together with a first bonding layer 43 forms an outer intermediate layer material 40a, via which the aluminum layer 50 is bonded to the coextruded oriented outer covering layer 30a. The coextruded oriented outer covering layer 30a is in turn composed of a central oriented polymer layer 20o and oriented skin layers 10o bonded to this oriented polymer layer 20o on both sides. The coextruded oriented outer covering layer here is produced by coextrusion of the oriented polymer layer 20o and the two oriented skin layers 10o, wherein the oriented polymer layer 20o consists of a transparent biaxially oriented polypropylene with a layer thickness of 50 pm.

On the side of the aluminum layer 50 facing the coextruded oriented outer covering layer 30a, an inner intermediate layer material 40i is attached to this, which, as aforesaid, consists of a second bonding layer 45 of a copolymer and a third bonding layer 47 of a polymer. The aluminum layer 50 itself is bonded to a non-oriented inner covering layer 30i via the inner intermediate layer material 40i. This non-oriented inner covering layer 30i is formed by a transparent monofilm in the form of a polyethylene film with a layer thickness of 50 pm. This polyethylene film is designated with the reference symbol 20n. The two bonding layers which form the outer intermediate layer material 40a are a white polyethylene with a layer thickness of 20 pm. This white polyethylene film is the first bonding layer 43. The copolymer forming the second bonding layer 45 adjoining this first bonding layer is also made white, i.e. nontransparent and has a layer thickness of 15 pm. The aluminum layer 50 has a layer thickness of 12 pm, while the copolymer forming the second bonding layer 45 of the inner intermediate layer material 40i has a layer thickness of 17 pm. This copolymer is designed transparent. The third bonding layer 47 adjacent to the copolymer of the second bonding layer 45 is a polyethylene copolymer which is transparent and has a layer thickness of 20 pm.
Fig.9 also shows a schematic diagram of a further embodiment of a multilayer laminate according to the invention for tubes with an embedded aluminum layer 50.
The layer structure of the laminate shown in Fig.9 essentially corresponds to that in Fig.8, with the difference that the oriented polymer layer 20o of the coextruded oriented outer covering layer 30a according to Fig.9 only has a layer thickness of 30 pm. Also the bounding layer of white polyethylene which forms the first bonding layer 43 of the outer intermediate layer material 40a has a layer thickness of 18 pm. The layer thickness of the adjacent copolymer which forms the second bonding layer 45 is about 15 pm. The layer thickness of the aluminum sheet 50 lies in the region of 9 pm. The polymer layer which forms the third bonding layer 47 of the inner intermediate layer material 40i is again a polyethylene copolymer which like the bounding copolymer is designed transparent. The polyethylene copolymer layer has a layer thickness of 23 pm.
The further Figures 10 to 12 show further different structures for an embedded barrier layer 50, an additional barrier layer 70 or an inner barrier layer 55. It should be explicitly noted here that the aforesaid examples each mentioned an aluminum layer as barrier layer material for the embedded barrier layer 50. However, this barrier layer can be replaced by a layer of ethylene-vinyl alcohol copolymer (EVOH) or another organic barrier layer and a combination of the plastic barrier layer materials discussed in each case. Further, these plastic barrier layer materials can also be used for the additional barrier layer 70 and/or the inner barrier layer 55.
Furthermore, for example alternatively to a monolayer of EVOH, the barrier layer composites shown in Figs.10 to 12 can also be used. These are advantageously already obtainable as finished composite and can in this manner extremely simply be integrated into the multilayer laminate according to the invention. In this context, it should further be noted that the composites shown can also be combined with the barrier layer materials, such as for example polyethylene terephthalate, polyacrylonitrile or silicon oxide or aluminum oxide, if this is desired or necessary.

As regards the choice of the particular barrier layer material, it should be mentioned that a barrier layer of aluminum is preferably used when a nontransparent multilayer laminate is to be created or is desired. In contrast to this, as shown in Figs.10 to 12,the barrier layers based on polymers are preferably used for multilayer laminates which are to be transparent, for example when it is desired that the filling of a tube be visible from outside.
Thus the multilayer laminate according to the invention and a tube produced therefrom is usable in very many ways and displays substantial advantages and improvements compared to previous laminates for tubes, particularly as regards manufacturing technology possibilities and also as regards barrier properties.
As materials for the stated layers, the aforesaid materials are possible, but it should be emphasized that adjacent layers are preferably different in nature.
At this point, it should be noted that all parts described above seen in themselves alone and in any combination, in particular the details shown in the diagrams, are claimed as essential to the invention. Modifications thereof are familiar to those skilled in the art.

List of Reference Symbols 10o oriented skin layer 10n non-oriented skin layer 20o oriented polymer layer 20n non-oriented polymer layer 30a coextruded oriented outer covering layer 301 non-oriented inner covering layer 40a outer intermediate layer material 40i inner intermediate layer material 43 1st bonding layer 45 2nd bonding layer 47 3rd bonding layer 50 embedded barrier layer 55 inner barrier layer 60 bonding layer 70 additional barrier layer

Claims

CLAIMS:

1. A multilayer laminate for tubes with an embedded barrier layer (50), characterized in that the laminate has an outer covering layer (30a) bounding the laminate on one side and an inner covering layer (30i) bounding the laminate on the other side, between which the barrier layer (50) is positioned, wherein the laminate has an asymmetric structure relative to the barrier layer (50), particularly with regard to the covering layers (30a and 30i), wherein in particular a molecular orientation of the inner covering layer (30i) differs from a molecular orientation of the outer covering layer (30a), each in relation to elongation or stretching in the machine direction (MD) and transverse to the machine direction (CD).

2. The multilayer laminate as claimed in claim 1, characterized in that the outer covering layer (30a) has a biaxial orientation with stretching in the machine direction (MD) of 200% to 800%, preferably of 400% to 600% and particularly preferably of essentially 500% and transverse to the machine direction (CD) of 500% to 1300%, preferably of 700%
to 900% and particularly preferably of essentially 800% and the inner covering layer (30i) has a monoaxial orientation or none.

3. The multilayer laminate as claimed in one of the previous claims, characterized in that the outer covering layer (30a) is bonded to the barrier layer (50), preferably directly, via an outer intermediate layer material (40a) and the inner covering layer (30i) is bonded to the barrier layer (50), preferably directly, via an inner intermediate layer material (40i).

4. The multilayer laminate as claimed in one of the previous claims, characterized in that the outer covering layer (30a) is at least two-layer and comprises at least one polymer layer (20) and at least one shell layer (10) in the form of a skin layer, preferably a shell layer (10) on each side of the polymer layer (20), in particular essentially of the same nature as regards thickness and material, each in the form of a skin layer, and is preferably coextruded and then stretched.

5. The multilayer laminate as claimed in one of the previous claims, characterized in that the inner covering layer (30i) is formed as monofilm or as, in particular coextruded, preferably two- or three-layer, multilayer film, wherein the monofilm in particular is a polymer layer (20) or wherein the multilayer film has a polymer layer (20), which at least on one side, preferably on both sides, comprises one or more, in particular essentially identical, shell layers (10) in the form of respective skin layers which are preferably symmetrically positioned relative to the polymer layer (20) or wherein the multilayer film has a, preferably central, inner barrier layer (55) which is surrounded on each side, and preferably symmetrically relative to the inner barrier layer (55) by an essentially identical shell layer (10), for example in the form of a skin layer, wherein between the inner barrier layer (55) and the respective skin layer (10) a bonding agent or adhesive, particularly a laminating adhesive, is provided.

6. The multilayer laminate as claimed in one of the previous claims 3 to 5, characterized in that one thickness of the polymer layer (20) is 6 to 100 times, preferably 14 to 81 times and particularly preferably 50 to 70 times the thickness of the shell layer (10), in particular of the skin layer.

7. The multilayer laminate as claimed in one of the previous claims, characterized in that the inner covering layer (30i) is a blown film with a blow-up ratio in the machine direction (MD) : transverse to the machine direction (CD) in the range from 1:1 to 1:2.5, preferably in the range from 1:1.05 to 1:1.75 and particularly preferably in the range from 1:1.2 to 1:1.9.

8. The multilayer laminate as claimed in one of the previous claims 3 to 7, characterized in that the outer intermediate layer material (40a) is at least single-layer, preferably multilayer, in particular one- to three-layer, particularly preferably two-layer, and has a first (43) and/or a second (45) and/or a third bonding layer (47).

9. The multilayer laminate as claimed in one of the previous claims 3 to 8, characterized in that the inner intermediate layer material (40i) is at least single-layer, preferably multilayer, in particular one- to five-layer, wherein one to three layers thereof alternatively or in combination are the first (43) and/or the second (45) and/or the third bonding layer (47).

10. The multilayer laminate as claimed in one of the previous claims 3 to 9, characterized in that the inner intermediate layer material (40i) comprises at least one additional barrier layer (70) which optionally has a bonding or bonding agent or adhesive layer (60).

11. The multilayer laminate as claimed in one of the previous claims, characterized in that the respective layers contain materials according to the following table, each alone or in combination:

12. The multilayer laminate as claimed in one of the previous claims, characterized in that the respective layers have a thickness according to the following table:

13. A tube produced from a laminate as claimed in one of the previous claims.

14. Use of a laminate as claimed in one of the previous claims 1 to 12 for production of a pack, in particular a tubular bag pack or a tube.