Sterilizable barrier layer laminate, as well as methods for manufacturing the laminate and its use

Abstract

The invention relates to a sterilizable barrier layer laminate (10) with a polypropylene outer layer (20) having barrier properties and a reverse print (30), a primer layer (40) applied to the print (30), and a polypropylene inner layer (60), wherein a polypropylene compound layer (50) is extruded between the primer layer (40) and the polypropylene inner layer (60), and wherein the polypropylene inner layer (60) exhibits stretching in the machine direction and, at a temperature of 130°C over a period of 30 minutes, a maximum shrinkage of -2.5%, preferably -2%, and particularly preferably -1.8% in the machine direction and a maximum shrinkage of -1%, preferably -0.8%, and particularly preferably -0.5% in the transverse direction, as well as a method for producing such a sterilizable barrier layer laminate (10) and its use for manufacturing packaging, in particular food packaging.Animal feed or medicine packaging, wherein the polypropylene inner layer (60) of the barrier layer laminate (10) is used as a sealing layer, in particular as a low-temperature sealing layer.

Description

[0001] The invention relates to a sterilizable barrier layer laminate according to the preamble of claim 1, a method for producing such a laminate according to the preamble of claim 13 and its use according to the preamble of claim 14.

[0002] Sterilizable barrier layer laminates have been known for some time and are used, for example, for packaging food, animal feed or medicines, especially when perishable goods need to be packaged in a watertight and airtight manner.

[0003] However, a significant disadvantage of previously known sterilizable barrier layer laminates is that previously known laminates always had adhesive(s) to ensure adhesion between the different laminate layers, although this adhesive, usually based on polyurethane, tended to migrate within the laminate and led to contamination of the contents packaged in packaging made from or with such laminates.

[0004] Another significant disadvantage of such previously known sterilizable barrier layer laminates is that, due to the high proportion of adhesive material, they cannot be recycled in an acceptable manner.

[0005] Furthermore, such previously known sterilizable barrier laminates were also complex in their construction and expensive due to high material requirements, as they required a three-layer polypropylene structure: an inner polypropylene layer, an outer polypropylene layer, and an intermediate central polypropylene layer coated with aluminum oxide and / or silicon oxide, which was held between the two outer polypropylene layers by an adhesive. The outer polypropylene layer was also necessary, among other things, to provide a printing layer, typically for reverse printing. Fig. Figure 1 schematically shows such a structure of a sterilizable barrier layer laminate known from the prior art.

[0006] A further disadvantage of previously known sterilizable barrier layer laminates was that they could not be torn in a straight line and had extremely low stiffness, since for these previous barrier layer laminates only standard cast or blown polypropylene could be used in production.

[0007] This disadvantage, particularly the low stiffness and non-linear tearability, was addressed in the past by conducting trials with stretched polypropylenes. However, this proved impractical because such stretched polypropylenes experienced shrinkage and undesirable elongation, especially during sealing processes, but also during heat sterilization, such as autoclaving, of the barrier layer laminate itself or of packaging made from it. As a result, such barrier layer laminates, particularly due to their large variance in elongation and shrinkage of up to almost 20% of the length in the machine direction and over 1% of the width in the transverse direction, for example for 60 µm films at an oven temperature of 130°C for a period of 30 minutes, i.e.,Autoclave conditions were not suitable for the production of packaging.

[0008] The object of the invention is to avoid the aforementioned disadvantages and to provide a sterilizable barrier laminate that is cost-effective to produce with reduced material requirements, is easily recyclable, and is suitable for the production of packaging for, among other things, food, animal feed, and pharmaceuticals. It is also aesthetically sealable and, in particular, heat-sterilizable. Furthermore, the object of the invention includes a method for producing such a barrier laminate and its use in the production of packaging for, among other things, food, animal feed, and pharmaceuticals.

[0009] This problem is solved by a sterilizable barrier layer laminate according to claim 1, as well as by a method for producing such a laminate according to claim 13 and a use of such a laminate for producing a packaging according to claim 14.

[0010] In particular, this problem is solved by a sterilizable barrier layer laminate with a polypropylene outer layer exhibiting barrier properties and featuring reverse printing, as well as a primer layer applied to the printing and a polypropylene inner layer, wherein a polypropylene compound layer is extruded between the primer layer and the polypropylene inner layer, and wherein the polypropylene inner layer exhibits stretching in the machine direction and, at a temperature of 130°C over a period of 30 minutes, exhibits a maximum shrinkage of -2.5%, preferably -2% and particularly preferably -1.8% in the machine direction and a maximum shrinkage of -1%, preferably -0.8% and particularly preferably -0.5% in the transverse direction.

[0011] A significant advantage of such a sterilizable barrier layer laminate according to the invention is that this new barrier layer laminate structure requires only two polypropylene layers instead of the previous three: an outer polypropylene outer layer with barrier properties, which also advantageously serves as a printable layer, and an inner polypropylene layer, which, in the case of using the new barrier layer laminate according to the invention for the production of packaging, faces the product to be packaged and serves as a sealing layer.According to the invention, these two polypropylene layers are joined by a very thin polypropylene compound layer extruded between them, which is chemically identical to the two outer polypropylene layers in its polymer composition. Excellent adhesion between this thin, extruded polypropylene compound layer and the inner polypropylene layer is ensured due to the chemically identical material. Optimal adhesion is also ensured with respect to the reverse-printed (i.e., from the back) polypropylene outer layer due to the use of an extrudable or printable primer on the printed surface, i.e., facing the polypropylene compound layer.

[0012] Another extremely important aspect of the invention is that the polypropylene inner layer has a stretch in the machine direction and is simultaneously temperature-stable, sealable, and sterilizable, where the term "temperature-stable" in this case means that the polypropylene inner layer can be heated to a temperature of 130°C for a period of 30 minutes, for example by autoclaving, without being subject to shrinkage exceeding a degree of shrinkage of -2.5%, preferably -2%, and particularly preferably -1.8% in the machine direction and a maximum shrinkage of -1%, preferably -0.8%, and particularly preferably -0.5% in the transverse direction.

[0013] This highly advantageous property of the polypropylene inner layer of the sterilizable barrier layer laminate according to the invention is achieved by using a polypropylene film that, during its production, has been stretched and tempered and subsequently relaxed, wherein the stretching and tempering are carried out at a temperature in the range of 130°C to 145°C and the subsequent relaxation is achieved by reducing the speed of the last of the rollers used for stretching to a factor in the range of 0.9–0.99, preferably in the range of 0.95–0.975. In this way, a stretched polypropylene film could be produced according to the invention which, during a sealing process and / or sterilization, even in humid environments, and at a temperature of 130°C for a period of up to half an hour, exhibits practically no significant shrinkage or elongation.

[0014] A further significant advantage of such a polypropylene inner layer according to the invention is that the sterilizable barrier layer laminate according to the invention achieves a significantly improved stiffness compared to previous sterilizable barrier layer laminates, which on the one hand significantly improves the machine processability of the sterilizable barrier layer laminate according to the invention, and on the other hand significantly improves the feel and stability of packaging made from this barrier layer laminate.

[0015] In summary, the sterilizable barrier layer laminate according to the invention thus exhibits significantly higher stiffness, very good, especially straight, tearability, and very reduced, almost non-existent, shrinkage compared to previously known sterilizable barrier layer laminates.

[0016] Thus, the sterilizable barrier layer laminate according to the invention can be easily sealed and sterilized even at high temperatures, such as those found in an autoclave, i.e., in a hot steam atmosphere at 120 °C to 130 °C under pressure, without the risk of shrinkage and / or stretching and / or becoming brittle and / or the associated risk of loss of the barrier layer.

[0017] According to the invention, one or even several adhesive layers, as were necessary in previous barrier layer laminates, can therefore be dispensed with.

[0018] Likewise, according to the invention, an additional central polypropylene layer arranged within the laminate structure, which provides the barrier property there according to the prior art, can be dispensed with.

[0019] Several significant advantages of the sterilizable barrier layer laminate according to the invention are that the laminate requires considerably less material, namely only two polypropylene layers: an inner polypropylene layer and an outer polypropylene layer exhibiting barrier properties. Furthermore, the structure of the barrier layer laminate according to the invention requires no adhesive, and in particular no polyurethane-based adhesive, thus eliminating the migration risk associated with such an adhesive. As a further advantage, the barrier layer laminate according to the invention, particularly due to the absence of adhesive, is practically material-free, with the exception of an extremely thin printing and primer layer. This significantly improves the recyclability of the sterilizable barrier layer laminate according to the invention compared to previously known sterilizable barrier layer laminates.

[0020] According to a preferred embodiment of the invention, the polypropylene outer layer exhibiting barrier properties has a SiO₂ facing the reverse printing. x - and / or AlO x -layer on.

[0021] According to this embodiment, the barrier properties of the polypropylene outer layer are improved by applying a layer of silicon dioxide and / or aluminum oxide directly onto the polypropylene outer layer. The reverse printing of the polypropylene outer layer is therefore not applied directly to the polypropylene outer layer, but rather to the layer of silicon dioxide and / or aluminum oxide. The primer is then applied to this printed layer, for example by extrusion.

[0022] According to a further advantageous embodiment of the invention, the polypropylene outer layer having barrier properties has an orientation, preferably in the machine direction and in the transverse direction, by which the barrier layer effect of the polypropylene outer layer is further improved or increased.

[0023] According to the invention, the polypropylene outer layer having barrier properties has a layer thickness in the range of 10 µm to 40 µm, preferably in the range of 15 µm to 30 µm and particularly preferably in the range of 18 µm to 25 µm.

[0024] Furthermore, according to the invention, the primer layer has a layer thickness in the range of 0.1 µm to 3 µm, preferably in the range of 0.5 µm to 2 µm and particularly preferably in the range of 1 µm to 1.5 µm.

[0025] According to a further advantageous embodiment of the invention, the primer layer is applied to the printed surface by means of a printing process or by extrusion. Such an application is particularly advantageous because the primer layer can be applied in this way with an extremely thin layer thickness, namely down to a minimum of 0.1 µm, to the polypropylene outer layer exhibiting barrier properties, or to the reverse print. Such a thin primer layer thickness, namely in the aforementioned range of 0.1 µm to 3 µm, preferably in the range of 0.5 µm to 2 µm, and particularly preferably in the range of 1 µm to 1.5 µm, contributes significantly to the excellent recyclability of the sterilizable barrier layer laminate according to the invention, since this allows the proportion of foreign matter in the otherwise chemically almost pure polypropylene material to be extremely minimized.

[0026] According to the invention, the polypropylene inner layer has a layer thickness in the range of 35 µm to 100 µm, preferably in the range of 50 µm to 90 µm and particularly preferably in the range of 60 µm to 80 µm.

[0027] The polypropylene inner layer thus constitutes the key stabilizing layer of the barrier layer laminate according to the invention and also forms a contact layer with a filling material that is filled into or packaged in a container made from the sterilizable barrier layer laminate according to the invention. As mentioned above, this polypropylene inner layer is stretched in the machine direction, which, in addition to the aforementioned extremely positive properties with regard to stiffness, processability, dimensional stability, and tear resistance, also contributes to increasing the barrier effect of the barrier layer laminate according to the invention. Furthermore, the contact transparency with respect to any filling material can be adjusted, for example, by adding titanium dioxide to the polypropylene inner layer to whiten it.

[0028] According to a particularly preferred embodiment of the invention, the polypropylene inner layer has at least a two-layer structure, wherein a layer of the two-layer structure facing a sealing side comprises a, in particular soft, randomly heterophasic copolymer, for example of the polymer components polypropylene and polyethylene, with a copolymer matrix and two components of these randomly arranged copolymers, each having two different melt flow indices. Furthermore, a layer facing a laminating side, i.e.,The layer of the two-layer structure facing the polypropylene compound layer (50) comprises a, in particular, a soft, randomly heterophasic copolymer, for example again consisting of the monomer units of polypropylene and polypropylene, with a copolymer matrix, which further comprises a heterophasic copolymer with a homo-polypropylene matrix or a copolymer matrix, and, if the laminate according to the invention is to be opaque, a white masterbatch, or alternatively, if the laminate according to the invention is to be transparent, no white masterbatch, wherein the layer facing the sealing side preferably corresponds to substantially one quarter to one third of the layer thickness of the layer of the two-layer structure facing the laminating side, and both layers are preferably joined together by coextrusion.According to the invention, the layer facing the sealing side is a low-temperature sealing layer made of polypropylene, which melts at a temperature in the range of 110°C to 135°C, preferably at a temperature in the range of 120°C to 130°C, wherein the polypropylene, in particular in random arrangement, comprises a polyolefin with a lower melting point than polypropylene, preferably polyethylene, wherein the polyolefin content with the lower melting point, preferably a polyethylene content, is less than 50%, particularly preferably less than 35% and particularly preferably about 30%.

[0029] According to the invention, the at least two-layer structure can also be three-layered or, preferably, five-layered, or have more than five layers, wherein the outermost layer facing the sealing side essentially corresponds to the specifications given above and represents a low-temperature sealing layer. The respective layers of this respective structure are preferably co-extruded.

[0030] A significant advantage of the invention resulting from this two- or multi-layer structure is that such a stretched and relaxed polypropylene inner layer has an extremely low sealing start-up temperature, at which a very good sealing strength in the range of up to 200 N / 15 mm, but in any case greater than or equal to 100 N / 15 mm, can already be achieved.Such a very low sealing start temperature, which is extremely useful according to the invention, is achieved in particular by the fact that the two- or multi-layer structure used for the polypropylene inner layer is functionally composed of at least two or more parts, namely in the form of one or more relatively thick layer(s) facing a lamination side and a comparatively relatively thin layer facing a sealing side, which in turn is ultimately responsible for the low sealing start temperature and the high sealing strength even at a low sealing temperature, while the side or layer facing the lamination side of the two- or multi-layer structure serves primarily to ensure the structural integrity and stability of the polypropylene inner layer.

[0031] Furthermore, it should be noted that, according to the invention, the heterophasic copolymer with homo matrix can also be replaced by a heterophasic copolymer with copolymer matrix if desired, since the shrinkage of the laminate according to the invention can be improved and its stiffness increased, among other things, in at least the two aforementioned cases, thanks to the special technology of the invention.

[0032] Furthermore, it should be noted that, according to the invention, the polypropylene compound layer is designed as an extruded layer and is therefore very thin, thus saving material. According to the invention, the polypropylene compound layer has a thickness of only 10 µm to 18 µm, preferably 12 µm to 17 µm, and particularly preferably 15 µm to 16 µm.

[0033] As mentioned above, a significant advantage of the barrier layer laminate according to the invention is that this new barrier layer laminate is free of adhesives, and in particular free of polyurethane-based adhesives, thus preventing adhesives from migrating into any contents of packaging made from this new barrier layer laminate and contaminating them. Avoiding such contamination is particularly important with regard to the packaging of food, animal feed, and pharmaceuticals, and represents a significant advantage of the barrier layer laminate according to the invention.

[0034] A further significant advantage of the sterilizable barrier layer laminate according to the invention is its very good recyclability, which is based on the fact that the laminate according to the invention is almost pure and has a polypropylene content of greater than 91 wt.%, preferably greater than 95 wt.% and particularly preferably greater than 98 wt.%, in particular greater than 99 wt.%.

[0035] As a further particularly advantageous feature of the invention, it should also be noted that the laminate according to the invention can be sealed without damage and essentially without shrinkage and / or stretching, and / or can also be sterilized with hot steam, in particular at a temperature in the range of 120°C to 130°C. This is based on the fact that the individual layers of the sterilizable barrier layer laminate according to the invention adhere extremely well and inseparably to one another. This is achieved according to the invention by extruding the polypropylene compound layer in a hot state between the polypropylene inner layer and the polypropylene outer layer, which has barrier properties, so that an intimate bond is created between the polypropylene compound layer and the polypropylene inner layer due to the material properties.Compared to the polypropylene outer layer, the primer layer applied to the printing also creates an excellent bond between the polypropylene compound layer and the polypropylene outer layer, so that the barrier layer laminate according to the invention is also resistant to hot steam and high temperatures in the range of 120 °C to 130 °C.

[0036] Particularly with regard to preventing shrinkage of the sterilizable barrier layer laminate during a sealing process or heat sterilization, for example autoclaving, at elevated temperatures up to approximately 130 °C for a period of up to approximately half an hour, the use of the aforementioned oriented and relaxed two-layer polypropylene structure is an important point, since this oriented and relaxed, i.e.After the actual stretching of the two-layer polypropylene structure, the relaxed two-layer polypropylene structure as a component of the sterilizable barrier layer laminate according to the invention is particularly dimensionally stable even under elevated temperatures and, unlike previously known stretched polypropylene films, exhibits practically no significant shrinkage at temperatures up to 130°C ± 10% even under humid conditions and is nevertheless ideally suited as a low-temperature sealing layer with very good strength values ​​after sealing.

[0037] Furthermore, the problem according to the invention, as mentioned above, is also solved by a method for producing a sterilizable barrier layer laminate according to the foregoing descriptions, wherein a polypropylene outer layer is printed using a reverse printing process and the printed layer is subsequently coated, optionally by means of a printing process, with a primer layer to produce a barrier layer structure, wherein the barrier layer structure is connected to a polypropylene inner layer by means of a polypropylene bonding layer, wherein the polypropylene bonding layer is extruded between the barrier layer structure and the polypropylene inner layer, and wherein a polypropylene film with a stretch in the machine direction is used as the polypropylene inner layer, which has a maximum shrinkage of -2.5%, preferably -2% and particularly preferably -1%, at a temperature of 130°C over a period of 30 minutes.8% in the machine direction and a maximum shrinkage of -1%, preferably -0.8% and particularly preferably -0.5% in the transverse direction.

[0038] It should be noted here that the polypropylene outer layer, preferably stretched in the machine direction, may have an inner coating of aluminum oxide and / or silicon oxide, pointing towards the polypropylene inner layer, to further improve the barrier effect, particularly against gases, which does not noticeably affect the transparency of the polypropylene outer layer. This layer of aluminum oxide and / or silicon oxide may be present on the polypropylene outer layer as standard or, if desired, applied separately as part of the process according to the invention.

[0039] Furthermore, the object of the invention, as mentioned above, is also achieved by using a sterilizable barrier layer laminate according to the above descriptions for the production of packaging, in particular food, animal feed or pharmaceutical packaging, it being particularly emphasized that, especially due to the absence of adhesive in the sterilizable barrier layer laminate according to the invention, excellent cat acceptance can be ensured for packaging made from this barrier layer laminate, which is a clear indicator that the barrier layer laminate according to the invention is adhesive-free.

[0040] An important advantage of the invention is that the production of packaging using the sterilizable barrier layer laminate according to the invention is particularly preferred, since the sealing layer is in the form of a low-temperature sealing layer which, in the case of sealing and also in the case of any subsequent heat sterilization, essentially does not deform, i.e., in particular, does practically not warp, shrink and stretch.

[0041] The main points of the invention can therefore be summarized as follows.

[0042] A well-known sterilizable barrier laminate on the market is a triplex OPP (oriented polypropylene) / OPP barrier / PP (polypropylene) structure laminated with adhesive. Adhesives reduce the polypropylene content and thus the recyclability.

[0043] According to the invention, by using extrusion lamination, both the polypropylene (PP) content and the recyclability can be increased.

[0044] According to the invention, an OPP barrier film, i.e., the polypropylene outer layer, is printed with an extrusion primer. The printed OPP barrier film is then extrusion laminated with a polypropylene sealing layer, i.e., the polypropylene inner layer.

[0045] Previously known machine-oriented polypropylene films (MOPP) cannot currently be used in mono-polypropylene laminates because their shrinkage during sealing and sterilization is too high.

[0046] The invention is a machine-oriented polypropylene film with reduced shrinkage during sterilization and sealing.

[0047] The stiffness of previously known mono-polypropylene duplex structures (OPP / PP) is very low, leading to problems with marking and machine performance. According to the invention, the stiffness of a sterilizable barrier layer laminate can be improved with an OPP / MOPP structure. Until now, this type of sterilizable barrier layer laminate structure was not possible due to the shrinkage of known machine-oriented polypropylene films. Instead of MOPP, standard cast polypropylene or blown polypropylene was preferably used in accordance with the prior art.

[0048] According to the invention, this existing problem is solved by using specific parameters regarding temperature and speed of the stretching and tempering rollers, respectively, after the film has been drawn for tempering. For the polypropylene inner layer according to the invention, particularly for its sealing side, polypropylene granules with a polyethylene content are used to generate the aforementioned LOW SIT (Sealing Initiation Temperature) property, i.e., the low-sealing polypropylene layer with polyethylene content for the low-temperature sealing layer. This treatment allows the film to harden and relax, thus avoiding the previous shrinkage problem, especially during sealing and sterilization processes, according to the invention.

[0049] A further major advantage of the invention lies in the possibility of printing on an OPP barrier film, i.e., the polypropylene outer layer, and carrying out extrusion lamination of the printed polypropylene outer layer, particularly for sterilization applications. Furthermore, the previously known structure of a sterilizable barrier layer laminate according to the prior art is reduced from three polypropylene layers to two, thus saving material. With the extrusion primer used, sufficient to very good bond strength can be achieved for the sterilizable barrier layer laminate according to the invention.

[0050] The advantages of the invention can therefore be summarized as follows. - Increased polypropylene content of up to 99 wt.% compared to adhesive lamination according to the state of the art with max. 91 wt.%; - resulting in increased recyclability; - reduced number of polypropylene layers from three to two layers; - free of adhesives (avoiding the migration risk of adhesives and improving cat acceptance of pouches or packaging for pet food or pharmaceutical applications); - reduced to practically non-existent shrinkage during sealing and sterilization processes.

[0051] Further embodiments of the invention are set out in the dependent claims.

[0052] The invention is described below using an exemplary embodiment, which is explained in more detail with reference to the figure. The figure shows: Fig. 1 A schematic representation of the sterilizable barrier layer laminate according to the invention in a preferred embodiment of the invention.

[0053] In the following description, the same reference numbers are used for identical and equivalent parts.

[0054] Fig.Figure 1 shows a schematic representation of the sterilizable barrier layer laminate 10 according to a preferred embodiment of the invention, wherein this barrier layer laminate 10 according to the invention comprises only two polypropylene layers: a barrier-property polypropylene outer layer 20 with a thickness of 20 µm, which in turn has a silicon dioxide and / or aluminum oxide layer on its inner side, i.e., facing a print 30, as desired. The sterilizable barrier layer laminate 10 according to the invention has a second polypropylene inner layer 60 with a thickness of either 60 µm or 80 µm. This polypropylene inner layer 60 can be colored white, for example with titanium dioxide, as desired, to improve its contact transparency.The polypropylene inner layer 60 consists of a two-layer structure with a layer facing a sealing side, which has a soft random heterophasic copolymer based on polypropylene, forming a copolymer matrix of two random polypropylene-based polymers, wherein the two random polymers, for example polypropylene and polyethylene, have different melt flow indices, and a layer facing a lamination side, i.e. the polypropylene compound layer 50, which has a soft random heterophasic copolymer with a copolymer matrix and further has a heterophasic copolymer together with a homo-polypropylene matrix, i.e. a polymer matrix consisting essentially exclusively of polypropylene, and with a white masterbatch.

[0055] According to a preferred embodiment of the invention, the layer of the two-layer structure facing the sealing side consists of a low-melting polypropylene, i.e., at a temperature in the range of 110°C to 135°C, preferably at a temperature in the range of 120°C to 130°C, which, particularly in random arrangement, comprises a polyolefin with a lower melting point than polypropylene, preferably polyethylene, wherein the polyolefin content with the lower melting point, preferably a polyethylene content, is less than 50%, particularly preferably less than 35% and particularly preferably about 30%.

[0056] The polypropylene inner layer 60 is designed as a low-temperature sealing layer with its sealing-side layer facing the machine. At a temperature of 130°C over a period of 30 minutes, the polypropylene inner layer 60 exhibits very low shrinkage of -1.8% in the machine direction and very low shrinkage of -0.5% in the transverse direction. The seal strength, or tensile strength, of a seal with the 60 µm thick polypropylene inner layer 60 is 100 N / 15 mm, which is essentially twice the strength of standard polypropylene cast films with a strength of approximately 50 N / 15 mm.These two polypropylene layers are connected to each other by means of a polypropylene bonding layer 50, wherein this polypropylene bonding layer 50 is extruded in a warm or hot state between the polypropylene outer layer 20 and the polypropylene inner layer 60, wherein adhesion to the printing 30 applied to the polypropylene outer layer 20 is optimized by applying a primer layer 40 to the printing 30.

[0057] It should be noted here that all the parts described above, considered individually and in any combination, especially the details shown in the drawings, are claimed to be essential to the invention. Modifications to this are familiar to those skilled in the art. Reference symbol list 10 laminate Polypropylene outer layer exhibiting 20 barrier properties 25 SiO x - / AlO x -Layer 30 printing 40 primer layer 50 Polypropylene compound layer 60 Polypropylene inner layer 80 adhesive layer

Claims

[1] Sterilizable barrier layer laminate (10) with a polypropylene outer layer (20) having barrier properties and a reverse print (30), with a primer layer (40) applied to the print (30) and with a polypropylene inner layer (60), wherein a polypropylene compound layer (50) is extruded between the primer layer (40) and the polypropylene inner layer (60), and wherein the polypropylene inner layer (60) exhibits a stretch in the machine direction and, at a temperature of 130°C over a period of 30 minutes, a maximum shrinkage of -2.5%, preferably -2% and particularly preferably -1.8% in the machine direction and a maximum shrinkage of -1%, preferably -0.8% and particularly preferably -0.5% in the transverse direction. [2] Laminate (10) according to claim 1, characterized by , that the polypropylene outer layer (20) exhibiting barrier properties faces the reverse printing (30) a SiO x - and / or AlOx -layer (25) has. [3] Laminate according to any one of the preceding claims, characterized by , that the polypropylene outer layer (20) having barrier properties has an orientation, preferably in the machine direction and in the transverse direction. [4] Laminate according to any one of the preceding claims, characterized by , that the polypropylene outer layer (20) having barrier properties has a layer thickness in the range of 10 µm to 40 µm, preferably in the range of 15 µm to 30 µm and particularly preferably in the range of 18 µm to 25 µm. [5] Laminate according to any one of the preceding claims, characterized by , that the primer layer (40) has a layer thickness in the range of 0.1 µm to 3 µm, preferably in the range of 0.5 µm to 2 µm and particularly preferably in the range of 1 µm to 1.5 µm. [6] Laminate according to any one of the preceding claims, characterized by, that the primer layer (40) is applied to the printing by means of a printing process or by means of extrusion. [7] Laminate according to any one of the preceding claims, characterized by , that the polypropylene inner layer (60) has a layer thickness in the range of 35 µm to 100 µm, preferably in the range of 50 µm to 90 µm and particularly preferably in the range of 60 µm to 80 µm. [8] Laminate according to any one of the preceding claims, characterized by, that the polypropylene inner layer (60) has at least a two-layer structure, wherein a layer of the two-layer structure facing a sealing side comprises a soft random heterophasic copolymer with a copolymer matrix having two components of random copolymers having two different melt flow indices, and a layer of the two-layer structure facing a lamination side, i.e., the polypropylene compound layer (50), comprises a soft random heterophasic copolymer with a copolymer matrix, which further comprises a heterophasic copolymer and a homo-polypropylene matrix or a copolymer matrix, and optionally a white masterbatch, wherein the layer facing the sealing side optionally corresponds substantially to one quarter to one third of the thickness of the layer of the two-layer structure facing the lamination side, and both layers are preferably joined together by coextrusion. [9] Laminate according to any one of the preceding claims, characterized by , that the polypropylene compound layer (50) has a layer thickness in the range of 10 µm to 18 µm, preferably in the range of 12 µm to 17 µm and particularly preferably in the range of 15 µm to 16 µm. [10] Laminate according to any one of the preceding claims, characterized by , that the laminate (10) is free of adhesive, in particular free of polyurethane-based adhesive. [11] Laminate according to any one of the preceding claims, characterized by , that the laminate (10) has a polypropylene content of greater than 91 wt.%, preferably greater than 95 wt.% and particularly preferably greater than 98 wt.%, especially greater than 99 wt.%. [12] Laminate according to any one of the preceding claims, characterized by , that the laminate (10) can be sealed without damage and essentially without shrinkage and / or sterilized with hot steam, especially at a temperature in the range of 120°C to 130°C.[13] A method for producing a sterilizable barrier layer laminate (10) according to one of the preceding claims, wherein a polypropylene outer layer (20) is printed with a design (30) using a reverse printing process, and the design (30) is subsequently coated with a primer layer (40), optionally by means of a printing process, to produce a barrier layer structure, wherein the barrier layer structure is connected to a polypropylene inner layer (60) by means of a polypropylene compound layer (50), wherein the polypropylene compound layer (50) is extruded between the barrier layer structure and the polypropylene inner layer (60), and wherein the polypropylene inner layer (60) is a polypropylene film with a stretch in the machine direction which, at a temperature of 130°C over a period of 30 minutes, exhibits a maximum shrinkage of -2.5%, preferably -2%, and particularly preferably -1%.8% in the machine direction and a maximum shrinkage of -1%, preferably -0.8% and particularly preferably -0.5% in the transverse direction. [14] Use of a sterilizable barrier layer laminate (10) according to any one of the preceding claims 1 to 12 for the manufacture of packaging, in particular food, animal feed or drug packaging, wherein the polypropylene inner layer (60) of the barrier layer laminate (10) is used as a sealing layer, in particular as a low temperature sealing layer.

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