Sterilizable polypropylene for producing cast films and / or laminates, use thereof for producing a film or a laminate, film produced therefrom and / or laminate produced therewith, method therefor, and packaging made of a film of this type and / or a laminate of this type

Abstract

The invention relates to a sterilizable polypropylene for producing cast films and / or laminates, wherein the polypropylene has a melt flow index (MFI) of less than 6, measured according to ISO 1133 in g / 10 min at a temperature of 230°C and a test load of 2.16 kg, to the use thereof for producing a sterilizable film and / or a sterilizable laminate, to a method for producing a sterilizable film and / or a sterilizable laminate, and to a sterilizable film produced from a sterilizable polypropylene of this type and / or to a sterilizable laminate produced therewith, and to a packaging made of a film of this type and / or a laminate of this type.

Description

[0001] Huhtamaki Flexible Packaging Germany January 28, 2026 GmbH & Co. KG M / VRG-203-PC PF / lz

[0002] Sterilizable polypropylene for the production of cast films and / or laminates, its use for the production of a film or laminate, film and / or laminate produced therefrom, together with the process for doing so, and packaging made from such a film and / or laminate

[0003] Description

[0004] The invention relates to a sterilizable polypropylene for the production of cast films and / or laminates, according to the preamble of claim 1, as well as a use of a sterilizable polypropylene according to the preamble of claim 8, as well as a film produced from such polypropylene according to the preamble of claim 9, a laminate produced with such polypropylene according to the preamble of claim 10, as well as a method for producing such a film or such a laminate according to the preamble of claim 11, and packaging produced with or from such a film or such a laminate using the aforementioned polypropylene, in particular for food and / or animal feed according to the preamble of claim 12.

[0005] Polypropylene has been known for some time and is used to manufacture films and laminates. The polypropylene is typically supplied as granules and melted in an extruder. The molten polypropylene is then forced through a slot die, producing a continuous sheet of polypropylene film with a predefined width. Similarly, polypropylene can also be extruded as a laminate layer within or onto a composite film, or applied as an outer layer to such a composite. A film produced in this way is called a cast film.

[0006] Packaging can subsequently be manufactured from such films or from laminates containing one or more such polypropylene films or polypropylene layers, which can be used, for example, for packaging food or animal feed. Meissner Bolte 2 M / VRG-203-PC

[0007] Since food or animal feed packaged in this way usually needs to be preserved, these packages are subjected to a so-called retort process in which they are sterilized under pressure and humidity and a temperature of up to approximately 129°C, for example in an autoclave.

[0008] However, a disadvantage of such packaging made from films or laminates of or with polypropylene has proven to be the fact that these packages, or rather the packaging material, acquire an unpleasant odor and / or taste during the sterilization process, which persists even after sterilization and has a very negative impact on the packaged goods, since these odor and / or taste substances produced during the sterilization process transfer into the packaged goods and adversely alter their sensory properties.

[0009] This sensory impairment of the packaged goods has proven particularly detrimental with regard to the packaging of food and pet food in such polypropylene packaging or packaging with polypropylene layers, since the presence of odor and / or taste substances produced during the sterilization process also alters the smell and / or taste of the packaged goods, so that subsequent users of the packaged goods no longer accept this sensorily impaired packaging. The latter manifests itself, for example, in the fact that cats no longer accept the product after such sterilization.

[0010] The invention is based on the objective of solving the aforementioned problem and providing a means for films and laminates made with or from polypropylene, which are used in particular for the production of packaging, to undergo a sterilization process under the influence of pressure, moisture and temperature without such a previously described sensory impairment, so that, for example, cat acceptance of the contents packaged in such packaging is maintained.

[0011] This objective is achieved by a sterilizable polypropylene according to claim 1, and furthermore by using such a sterilizable polypropylene to produce a sterilizable film and / or a sterilizable laminate and / or a packaging according to claim 8, and furthermore by a film made from such a polypropylene according to Meissner Bolte 3 M / VRG-203-PC

[0012] Claim 9 and furthermore by a laminate made from or with such polypropylene according to claim 10 and furthermore by a method for producing such a sterilizable polypropylene film or such a sterilizable polypropylene-containing laminate according to claim 11 and packaging according to claim 12, which is produced using such a film or such a laminate.

[0013] In particular, the problem is solved by a sterilizable polypropylene, especially for the production of cast films and / or laminates, wherein the polypropylene has a melt flow index (MFI) of less than 6, measured according to ISO 1133 in g / 10 min at a temperature of 230°C and a test load of 2.16 kg.

[0014] According to a preferred embodiment of the invention, the polypropylene has a melt flow index (MFI) of less than 4.5 and according to a particularly preferred embodiment of the invention, the polypropylene has a melt flow index (MFI) of less than 3.

[0015] It has unexpectedly been found that, during a sterilization process under pressure and with the use of moisture at a temperature in the range of 129°C ± 2K, polypropylene is sensorially more stable the lower its melt flow index (MFI) is, where the melt flow index (MFI) is also referred to as the "melt mass flow rate" (MFR) according to ISO 1133.

[0016] In this respect, it has proven particularly advantageous according to the invention that a polypropylene with an MFI value of less than 6, preferably less than 4.5 and particularly preferably less than 3 is particularly sensorially stable in the course of a retort process, especially when the polypropylene is processed by means of flat film extrusion into a so-called cast film or as a layer in a laminate produced by means of flat film extrusion or slot die extrusion.

[0017] Accordingly, in a particularly preferred embodiment of the invention, exclusively polypropylenes with a melt flow index of at least less than 6, preferably less than 5, and particularly preferably less than 3 are used for the production of sensorially particularly stable films and laminates, as well as packaging made therefrom. Meissner Bolte 4 M / VRG-203-PC

[0018] It has been found to be particularly advantageous according to the invention that such polypropylenes can be produced during a retort process, i.e.

[0019] During sterilization processes under the influence of increased pressure, humidity, and temperature, these polypropylenes exhibit high molecular stability and thus odor and taste stability, and are significantly less prone to developing an unpleasant taste and / or odor than those of previously known polypropylenes. Consequently, such polypropylenes with a melt flow index as described in the invention are considerably better suited for the production of films and laminates, as well as packaging made from such films and laminates, compared to previously known polypropylenes. This is because, when using a polypropylene according to the invention, there is no risk of the contents packaged in such a polypropylene becoming contaminated and thus rendered unusable by any unpleasant odors or tastes that may arise during a retort process.

[0020] According to a further embodiment of the invention, the polypropylene according to the invention has a molecular weight distribution with a polydispersity index (PD) in the range of 1.5 to 8, preferably in the range of 1.8 to 5.5 and particularly preferably in the range of 2 to 3.5.

[0021] In this regard, it has been found according to the invention that, in order to avoid the formation of any bad odors or tastes during a retort process, it is advantageous to use a polypropylene with a melt flow index in the range of less than 3 to a maximum of 6 and a molecular weight distribution that is preferably in the range of 1.8 to 5.5 or closer, since the use of such a polypropylene according to the invention contributes to optimized homogeneity and thus molecular stability of the polypropylene used and improves the sensory stability of this polypropylene during a retort process according to the invention.

[0022] According to a further advantageous embodiment of the invention, the polypropylene has a maximum proportion of migration-promoting stearates in the range of 0.1 to 0.7 g stearate per kg polypropylene, preferably 0.2 to 0.5 g stearate per kg polypropylene and particularly preferably 0.3 to 0.4 g stearate per kg polypropylene.

[0023] Furthermore, the polypropylene advantageously has a maximum proportion of migration-promoting secondary antioxidants in the range of 0.2 to 2.5 g antioxidant per kg polypropylene, preferably 0.3 to 2 g antioxidant per kg Meissner Bolte 5 M / VRG-203-PC

[0024] Polypropylene and especially preferably 0.5 to 1.5 g of antioxidant per kg of polypropylene.

[0025] In this respect, it has proven extremely advantageous according to the invention if the polypropylene according to the invention contains only a small proportion of such migration-promoting substances as described above, since this makes it particularly easy to avoid the migration-promoting substances themselves causing any unpleasant odors or tastes, as is the case with the prior art, which would consequently impair the overall sensory properties of the polypropylene used. According to the invention, this can be avoided in a highly advantageous, simple, and cost-effective manner.

[0026] Furthermore, the polypropylene according to the invention has a maximum proportion of erucamide in the range of 1.5 to 4 g erucamide per kg polypropylene, preferably 1.8 to 3 g erucamide per kg polypropylene and particularly preferably 2 to 2.2 g erucamide per kg polypropylene.

[0027] With regard to a use of erucamide known from the prior art, it could be recognized according to the invention that a proportion of erucamide in the polypropylene according to the invention below 0.4 wt.%, preferably below 0.3 wt.% and particularly preferably below 0.2 to 0.22 wt.% also contributes significantly to the avoidance of bad odors or tastes in the course of a retort process.

[0028] Furthermore, the object of the invention is also achieved by using a previously described sterilizable polypropylene for the production of a sterilizable film and / or a sterilizable laminate and / or packaging.

[0029] A film produced in this way, or a laminate made from the sterilizable polypropylene according to the invention, as well as any packaging made from such a film or laminate, have the essential advantage according to the invention that both such a film and such a laminate, and consequently also packaging made from such a sheet, can be sterilized in a warm, humid environment under pressure, for example in an autoclave, and at the same time, unlike what must be feared with the prior art, no unpleasant odors or tastes form from the polypropylene according to the invention during autoclaving, which, for example, might be associated with a Meissner Bolte 6 M / VRG-203-PC.

[0030] The contents could be dispensed in packaging made from these materials.

[0031] Furthermore, the problem according to the invention is also solved by a film made of polypropylene according to the preceding descriptions. The problem according to the invention is also solved by a laminate comprising a layer or film made of polypropylene according to the preceding descriptions. The film can be arranged within a film composite or as a film or layer laminated to the outside of the film composite.

[0032] According to a further advantageous aspect of the invention, the object of the invention is also solved by a method for producing a sterilizable polypropylene film or a sterilizable polypropylene-containing laminate, wherein a polypropylene according to the above descriptions is processed, in particular extruded, to the sterilizable polypropylene film or the sterilizable polypropylene-containing laminate by means of flat film extrusion.

[0033] In this regard, it has surprisingly emerged during the development of the invention that such a polypropylene according to the invention, which until now could not be used for the production of blown film and, with regard to its melt flow index, could at best be used for the production of a film or a laminate by means of flat film extrusion, can also be used for the production of a film or a laminate by means of flat film extrusion, and that it is possible to produce sterilizable films and laminates and, advantageously as a consequence, optimized odorless and tasteless packaging by means of the process according to the invention.

[0034] Furthermore, the object of the invention is also achieved by packaging, in particular food or animal feed packaging, which is made from one of the aforementioned films or laminates and, particularly with regard to polyolefins used for the packaging, is manufactured exclusively using one of the aforementioned polypropylene materials. It should be noted that the term "exclusively" in this context refers only to the polypropylene used. It should be explicitly noted in this regard that any barrier layer materials, such as silicon dioxide, aluminum oxide, ethylene vinyl alcohol copolymer, polyvinyl alcohol copolymer, or polyamide, are not used in a Meissner Bolte 7 M / VRG-203-PC

[0035] The laminate according to the invention and packaging made from such a laminate may be included.

[0036] Furthermore, an important advantage of the invention arises from the fact that such packaging according to the invention can be manufactured from a film or laminate produced by flat film extrusion rather than blown film, since films and laminates produced by flat film extrusion offer significant advantages, for example, with regard to their sealability. For this reason, a key aspect of the invention is also that the polypropylene according to the invention is made accessible for flat film extrusion to produce a so-called cast film or a laminate produced by flat film extrusion.

[0037] The core of the invention can therefore be summarized as follows.

[0038] There are currently no requirements specifying which polypropylenes are suitable for good, i.e., "taste- and odor-neutral," use in a retort process. Based on the standard food conformity regulations for packaging, the selected polypropylene must meet all requirements to be approved for use in a retort process, i.e., a sterilization process. However, sensory properties are not yet considered in the selection of polypropylene. As it turns out, different polypropylenes can impart, or transfer, different tastes to a product, especially food or animal feed.

[0039] With existing polypropylene packaging, or rather the polypropylenes used for it, a bad taste and / or odor develops on and in the packaging, which is made from or with monopropylene laminates, during a retort process. This is particularly detrimental for sensitive animals like cats, which are very sensitive, especially if the taste of the food is affected by the packaging film.

[0040] Up to now, according to the state of the art, cast films with a melt flow index (MFI) of at least 6 and higher, for example > 8 and above, have been used for the production of films and laminates as well as for packaging made therefrom. Meissner Bolte 8 M / VRG-203-PC

[0041] The inventors observed that polypropylenes with an MFI of 6, and especially those with an MFI of 8 or higher, result in poor sensory taste and odor in food or animal feed after a retort process. The invention consists of using only polypropylenes with an MFI of at least less than 6, preferably less than 4.5, and ideally below 3. Such polypropylenes are not currently used for cast films according to the prior art.

[0042] Polypropylene with such a low MFI has so far been used exclusively for blown films, but blown films have several disadvantages, as they are cooled less during the manufacturing process and therefore already have a stronger odor / taste, and furthermore have a higher crystallinity in the finished state and thus exhibit poorer sealability.

[0043] During the development of the invention, it became apparent that it is necessary to use polypropylene with a narrow molecular weight distribution and very few volatile oligomers. Investigations revealed that polypropylenes with a higher MFI are mostly degraded during polymerization, leading to higher levels of volatile substances that are responsible for an unpleasant taste, particularly after a retort process.

[0044] Furthermore, all polypropylenes generally contain additives.

[0045] According to the invention, it is therefore important to ensure that as few migrating or migratory additives as possible are used, such as, in particular, erucamide.

[0046] According to a key aspect of the invention, it was surprisingly found that the amount of any sensorially adverse substances originating from the polypropylene, which may transfer from the film or laminate used to manufacture the packaging to the food, can be greatly minimized by using the polypropylene according to the invention with the lowest possible melt flow index (MFI), namely less than 6, preferably less than 4.5 and particularly preferably less than 3.

[0047] According to the invention, cast films, i.e., in particular polypropylenes, with such a low melt flow index (MFI), Meissner Bolte 9 M / VRG-203-PC are therefore used for the production of sensorially optimized films and laminates as well as for packaging produced therefrom.

[0048] namely less than 6, preferably less than 4.5 and especially preferably less than 3, is used.

[0049] The melt flow index (MFI) for polypropylene is measured in g / 10 min at 230 °C, 2.16 kg (ISO 1133). The lower the MFI value of the polypropylene, the higher its viscosity, among other properties.

[0050] Currently, no factors are known to determine whether polypropylene has a good or bad taste / odor after a retort process. The invention describes factors that must be considered to determine whether films, laminates, and packaging made from polypropylene have a good or bad taste / odor, particularly after a retort process. The solution according to the invention consists of, and in particular exclusively, the use of polypropylene for cast films and laminates with a very low minimum film intensity (MFI).

[0051] It is essential to consider the taste and smell that are transferred from the packaging to the food or animal feed. This is particularly important for critical products such as baby food, pharmaceuticals, etc.

[0052] Further embodiments of the invention are set out in the dependent claims.

[0053] The invention will now be explained in more detail using exemplary embodiments.

[0054] A polypropylene film is produced from a polypropylene with a melt flow index (MFI) of 3.5, measured according to ISO 1133 in g / 10 min at a temperature of 230°C and a test load of 2.16 kg. This film is then used as blank material for the production of a sterilizable package. After sterilizing the package at a temperature of 129°C for 20 minutes, no sensory changes, particularly no changes in odor or taste, can be detected in the package or the film used to produce it. According to another embodiment, a package is produced from a barrier laminate in which an ethylene vinyl alcohol copolymer layer is embedded between an inner and an outer polypropylene layer.The two polypropylene layers consist of a polypropylene with a melt flow index (MFI) of 3.0 each, using a Meissner Bolte 10 M / VRG-203-PC.

[0055] The molecular weight distribution exhibits a polydispersity index (PD) of 3, a stearate content of 0.4 g / kg polypropylene, and an erucamide content of 1.8 g / kg polypropylene. Packaging manufactured from this laminate can be autoclaved at 129°C for 20 minutes without any detectable sensory changes, particularly with regard to odor and taste, during this sterilization process. The melt flow index (MFI) was determined analogously to embodiment 1.

[0056] It should be noted that all the parts described above are considered individually and are claimed as essential to the invention in every combination. Modifications to this are familiar to those skilled in the art.

Claims

Huhtamaki Flexible Packaging Germany January 28, 2026 GmbH & Co. KG M / VRG-203-PC PF / lz Sterilizable polypropylene for the production of cast films and / or laminates, its use for the production of a film or laminate, film and / or laminate produced therefrom, together with the process for doing so, and packaging made from such a film and / or laminate Claims 1. Sterilizable polypropylene for the production of cast films and / or laminates, characterized by the fact that The polypropylene has a melt flow index (MFI) of less than 6, measured according to ISO 1133 in g / 10 min at a temperature of 230°C and a test load of 2.16 kg.

2. Polypropylene according to claim 1, characterized by the fact that The polypropylene has a melt flow index (MFI) of less than 4.

5.

3. Polypropylene according to any one of the preceding claims, characterized by the fact that The polypropylene has a melt flow index (MFI) of less than 3.

4. Polypropylene according to any one of the preceding claims, characterized by the fact that The polypropylene has a molecular weight distribution with a polydispersity index (PD) in the range of 1.5 to 8, preferably in the range of 1.8 to 5.5 and particularly preferably in the range of 2 to 3.

5.

5. Polypropylene according to any one of the preceding claims, characterized by the fact that The polypropylene has a maximum content of migration-promoting stearates in the range of 0.1 to 0.7 g stearate per kg polypropylene, Meissner Bolte 2 M / VRG-203-PC preferably contains 0.2 to 0.5 g stearate per kg polypropylene and particularly preferably 0.3 to 0.4 g stearate per kg polypropylene.

6. Polypropylene according to any of the preceding claims, characterized by the fact that The polypropylene has a maximum proportion of migration-promoting secondary antioxidants in the range of 0.2 to 2.5 g antioxidant per kg polypropylene, preferably 0.3 to 2 g antioxidant per kg polypropylene and particularly preferably 0.5 to 1.5 g antioxidant per kg polypropylene.

7. Polypropylene according to any of the preceding claims, characterized by the fact that the polypropylene has a maximum proportion of erucamide in the range of 1.5 to 4 g erucamide per kg polypropylene, preferably 1.8 to 3 g erucamide per kg polypropylene and particularly preferably 2 to 2.2 g erucamide per kg polypropylene.

8. Use of a sterilizable polypropylene according to any of the preceding claims for the production of a sterilizable film and / or a sterilizable laminate and / or packaging.

9. Film made of or with a polypropylene according to any one of the preceding claims 1 to 7.

10. Laminate comprising a film according to claim 9, in particular produced using a polypropylene according to any one of the preceding claims 1 to 7.

11. Method for producing a sterilizable polypropylene film or a sterilizable polypropylene-containing laminate, characterized in that a polypropylene according to one of the preceding claims 1 to 7 is processed, in particular extruded, by means of flat film extrusion to the sterilizable polypropylene film or the laminate containing sterilizable polypropylene.

12. Packaging, in particular food or animal feed packaging, made with or from a film according to claim 9 and / or a laminate according to claim 10, wherein the film and / or the laminate is in particular made by a method according to claim 11.