BR112018067510B1 - FILM FOR FOOD PACKAGING AND MANUFACTURING METHOD FOR THE PRODUCTION OF THE SAME - Google Patents

Abstract

The present invention relates to a multilayer film, especially a multilayer thermoplastic film, which can be used for food packaging, wherein the multilayer film according to the present invention can be provided, on its inner side, with a food additive , particularly with a flavoring and/or coloring and/or flavor producing food additive (e.g. liquid smoke), which food additive is then released and transferred to the surface of a food product packaged in the multilayer film during cooking and/or food processing.

Description

FIELD OF THE INVENTION

[0001] The present invention relates to the technical field of films for food packaging and, particularly, to the treatment of packaged or encapsulated (embedded) food products in them, especially with the aim of releasing or transferring food additives (particularly those that provide flavors and/or colors and/or an aroma, such as liquid smoke or other food additives) on the surface of the packaged or encapsulated food product, the food additives of which were previously supplied to the food packaging films.

[0002] In particular, the present invention relates to a multilayer film, especially a multilayer thermoplastic film, particularly for use in food packaging, and a method of manufacturing such a multilayer film, as well as the use of such a film multilayer, especially its use for releasing and/or transferring at least one food additive onto the surface of a food product.

[0003] Furthermore, the present invention relates to a film for food packaging capable of releasing and/or transferring at least one food additive to a surface of a food product packaged therein and to a method of manufacturing such a film for food packaging, as well as the use of such film for food packaging, especially its use for releasing and/or transferring at least one food additive onto the surface of a food product.

[0004] Furthermore, the present invention also relates to a packaged food product, especially a thermally processed food product containing a fat and/or protein, preferably a food product containing a meat, which food product is packaged in a film to food packaging of the present invention.

[0005] Additionally, the present invention also relates to a method for releasing and/or transferring at least one food additive to the surface of a food product and/or for providing at least one food additive to the surface of a food product.

BACKGROUND OF THE INVENTION

[0006] Films, especially plastic films, particularly tubular films, are often used as sausage casings for processing and packaging sausages, including steamed or soaked sausages. Wrappers are also used to process and package larger products such as various types of specialty meat cuts made from chicken, beef and ham.

[0007] A particularly typical casing is made from regenerated cellulose, in which the viscose can be extruded through an annular die in a coagulation and regeneration bath to produce a tube of regenerated cellulose; this is well known in the prior art. Generally, such tubes made from regenerated cellulose are subsequently washed, plasticized and may be impregnated with a water-soluble flavoring or food coloring permeable to the casing, then dried and inflated under considerable air pressure. After drying, this non-fibrous cellulosic wrapper is wound onto bobbins and subsequently pleated or shirred, especially on high-speed crimping machines.

[0008] Non-fibrous casings are typically used to process small-diameter sausages, including Polish, Viennese (Wieners) or hot dog (Frankfurters) and are generally removed from sausages after processing.

[0009] Non-fibrous cellulosic wrappers can be reinforced by applying viscose to a substrate such as paper or fabric, increasing the strength of the wrapper, which is a desired feature when producing large-sized special (deli) products.

[0010] Food additives (especially food coloring and/or flavoring and/or those that impart a flavor to food), as well as a variety of processing and peeling aids, may be introduced into the interior of the casing during the manufacturing process. In tubular casings, these additives are usually introduced by slugging fluidization (also known as "slugging") or spraying, whereas flat films can have these additives applied to the last internal surface in contact with the food by methods such as foil coating or printing. , for example, using a rotogravure method.

[0011] Food additives, especially food colorings and/or flavorings and/or those that provide an aroma, are used to provide color and/or flavor and/or odor to food processed therewith. These additives can be found as formulations of aqueous solutions, dispersions and oil-based emulsions, among others. References to "food additives" in this application include all such formulations. In particular, the production of sausages (sausages) or smoked or browned meats has been carried out through the use of casings containing liquid smoke or caramel, which transfer to the surface of the sausage meat product during processing.

[0012] Historically, food colors and flavorings have been applied to various food products, such as sausage and cheese surfaces, by various means. For example, sausages have been colored and/or flavored by smoking them with gaseous or liquid wood smoke, or by immersing the peeled sausages in a container containing a dye, or by spraying or dipping the encapsulated sausages with a dye and/or flavoring. permeable liquid to the casing, or by filling (stuffing), with sausage meat, casings which have their inner surfaces coated with transferable food colorings and/or flavourings.

[0013] Other types of enclosures are made from thermoplastic films or tubes and can be single-layer or multi-layer. Thermoplastic films and wrappers are advantageous over cellulosic coatings primarily due to ease of production and lower production costs. Production usually involves melting and extruding a resin, usually through a suitable die, to create a particular shape, then heating, cooling and optionally stretching or guiding it while forming it into a film or tube. No equipment is needed for handling the wood pulp and for dissolving and regenerating it, as in the manufacture of cellulose casings.

[0014] A particularly commonly used thermoplastic shell is a single-layer tubular polyamide. Others are laminated films produced by layering various materials such as polyamides (nylons, PA), polyolefins such as polyethylenes (PE) or polypropylenes (PP), ethylene vinyl acetates (EVA), ethylene vinyl alcohols (EVOH), polyvinylidene chloride (PVDC) copolymers and blends or copolymers or for polymers thereof, to name just a few, directly or indirectly adjacent to each other, with or without the use of adhesives, so as to produce films with various desired properties.

[0015] In a typical manufacturing method, flat films are made and strips of desired widths are cut and formed into tubes and sealed closed by various methods, such as by overlapping the ends of the tube and sealing these ends together using adhesives, either by applying tape to the edges and sealing it with adhesives, or by welding the tape over adjacent edges with heat. Thermoplastic films are also produced by extruding a molten resin through an annular die and, optionally, stretching the tube, for example by expanding it with air. Multiple layers can be made by coextruding multiple layers together. Multilayer thermoplastic films can also be made by extrusion lamination, in which the thermoplastic layer is extruded through a slit die directly onto an adhesive layer already placed over a non-adhesive layer or over other plastic layers.

[0016] An important requirement of laminated films is that there is no separation of the layers during handling, cooking and, particularly, when peeling from packaged cooked products. It is extremely disadvantageous to have a film layer partially or completely left on the skin of a cooked sausage, as such a product would be considered unfit for consumption. Furthermore, these films must maintain high strength and low elongation properties. They must be sealable and the seal must withstand processing conditions.

[0017] Additional characteristics necessary for films that provide flavors and/or colors to packaged foods include the ability of these films to absorb, in their inner layer in contact with food, adequate amounts of flavoring and/or coloring materials, for example, smoke liquid or caramel, and after transferring such flavoring and/or coloring materials to a packaged food product.

[0018] Other properties, including water (vapour) barrier and oxygen barrier properties, are also desired in order to maintain water levels in the cooked product to minimize weight loss and to keep the product from spoiling if it is stored with the wrapper or film.

[0019] The prior art wrappers described above are generally supplied to the food processor in a shirred form. Shirring (or shirring) is a method of pleating a long piece of flat wrapper, especially tubular, into a much shorter tube called a rod. For example, a crimped stick of small-diameter thermoplastic casing measuring about 15 inches long can hold about 185 feet of casing. These rods are used in automatic filling machines, where the rods are held in place and the food product, in particular sausage emulsions, is introduced at high speed and pressure into the rod, simultaneously deshirring the rod and forming the sausages. Larger diameter wrappers are used in machines for stuffing processed and formed meats, hams or other whole muscle meats, as well as various types of specialty meats (deli meats). These wrappers are removed after cooking and the processed meats can be automatically sliced and packaged for sale to the final consumer.

[0020] Generally, wrappers containing a food additive, especially a flavoring and/or food coloring and/or a flavoring additive, should have an absorbent inner surface. Cellulosic wrappers or wrappers comprising an inner layer of paper or fabric have the ability to absorb liquids. It has been found that these inner layers must absorb sufficient liquid to provide the desired effect on packaged food products.

[0021] However, thermoplastic films do not have the ability to absorb aqueous solutions to any appreciable extent, but usually only from about 1 to 3% by weight, and even when absorbing a small amount of colorants and/or flavorings food, the amount of this solution transferred to the embedded food is low and normally dispersed unevenly on the surface of the food.

[0022] European patent publication EP 0 992 194 B1 discloses a barrier casing for food products which are poached, boiled or otherwise heated in the casing, particularly for sausages, ham, pickles or processed cheese, wherein the casing consists of in a film which is impermeable to at least water-vapour and/or gas and has, joined thereto, an absorbent inner coating consisting of individual fibers or a fabric or mesh, preferably a non-woven fabric, and wherein this internal coating is impregnated with colorants and/or flavorings. However, since the inner layer consists of individual fibers or a fabric or mesh, the barrier casing cannot be produced in a coextrusion process, i.e., manufacturing the barrier casing is not very economical. Furthermore, the absorbent inner liner, consisting of individual fibers or a woven or knitted fabric, has a limited load-bearing or absorption capacity with respect to food coloring and/or flavoring. In addition, during cooking and/or processing of food products packaged in a barrier wrap, fibers from the inner liner may partially adhere to food product surfaces in an undesirable manner.

[0023] The European patent publication EP 1 559 323 B1 refers to a smokeable polymeric envelope, made of a continuous (seamless) smokeable tubular film, biaxially elongated, heat shrinkable, comprising a mixture of polyamide, a specific polyvinyl alcohol and, optionally, an anti-sticking agent. This polymeric shell is itself smokeable, but cannot absorb food colors and/or flavorings to any significant extent.

[0024] The U.S. patent No. 4,377,187 refers to cellulosic, reinforced, fibrous food wrappers impregnated with liquid wood-derived smoke, having smoke color, odor and aroma constituents embedded in the wall of the wrapper. However, the load capacity of these food wrappers is quite limited. Furthermore, the barrier properties, especially against oxygen and/or water vapour, are very poor. Furthermore, such casings cannot be produced by a simple co-extrusion method.

OBJECTS OF THE PRESENT INVENTION

[0025] What is needed in the food packaging industry is therefore preferably a multilayer thermoplastic film (e.g. in a flat or preferably tubular form), which multilayer film can be provided (e.g. absorbed in or impregnated) with food additives and retains such food additives (solutions or emulsions of food additives) in or on its inner layer(s) in contact with food, which additives Foodstuffs can then be transferred to the surface of any packaged and processed food product.

[0026] Particularly, in view of the prior art described above, the problem underlying the present invention is especially to preferably provide a thermoplastic multilayer film (especially to be used as a film for food packaging), particularly in the form of a film flat or tubular multilayer thermoplastic, whose multilayer film must be able to at least substantially avoid or at least improve the above-described disadvantages of the prior art.

[0027] Especially, a particular problem addressed by the present invention is to preferably provide a thermoplastic multilayer film (preferably a flat or tubular thermoplastic multilayer food packaging film), especially for use as a food packaging film. food, which has an improved efficiency with respect to its capacity for absorbing or carrying capacity of reversible food additives (e.g. coloring and/or flavoring and/or flavoring additives).

[0028] In particular, such food packaging film must have an inner food contact surface with a food additive (for example, an aqueous solution of coloring and/or flavoring and/or flavoring additives), the additives of which Foodstuffs are then transferred to the surface of any packaged food during cooking and/or processing.

SUMMARY OF THE INVENTION

[0029] The present invention, according to a first aspect of the present invention, relates to a multilayer film, especially a thermoplastic multilayer film, particularly to be used for food packaging, as defined in claim 1; Additional particularly advantageous embodiments of this aspect of the present invention are the subject of the respective dependent claims (i.e. claims 2 to 32).

[0030] Furthermore, according to a second aspect of the present invention, the present invention also relates to a thermoplastic film for food packaging capable of releasing and/or transferring at least one food additive onto a surface of a packaged food product in it, as defined in the respective independent claim (ie, claim 33); Additional particularly advantageous embodiments of this aspect of the present invention are the subject of the respective dependent claims (i.e. claims 34 to 37).

[0031] Furthermore, according to a third aspect of the present invention, the present invention also relates to a packaged food product of claim 38, especially a heat-processed food product containing fat and/or protein, preferably a food product containing a meat, wherein the food product is packaged in a food packaging film of the present invention; a further particularly advantageous embodiment of this aspect of the present invention is the subject of the respective dependent claim (i.e. claim 39).

[0032] Furthermore, according to a fourth aspect of the present invention, the present invention also relates to the inventive use of an inventive multilayer film for releasing and/or transferring at least one food additive onto a surface of a food product packaged therein as defined in the respective independent claim (ie claim 40); a further particularly advantageous embodiment of this aspect of the present invention is the subject of the respective dependent claim (i.e. claim 41).

[0033] Additionally, according to a fifth aspect of the present invention, the present invention also relates to the inventive use of food packaging film for the release and/or transfer of at least one food additive onto a surface of a food product , as defined in the respective independent claim (i.e. claim 42); a particularly advantageous further embodiment of this aspect of the present invention is the subject of the respective dependent claim (i.e. claim 43).

[0034] Furthermore, according to a sixth aspect of the present invention, the present invention also relates to an inventive method for releasing and/or transferring at least one food additive onto a surface of a food product and/or for providing a surface of a food product with at least one food additive as defined in the respective independent claim (i.e. claim 44).

[0035] Furthermore, according to a seventh aspect of the present invention, the present invention also relates to an inventive method for manufacturing an inventive multilayer film as defined in the respective independent method claim (i.e. claim 45); Additional particularly advantageous embodiments of this aspect of the present invention are the subject of the respective dependent claims (i.e. claims 46 to 48).

[0036] Finally, in accordance with an eighth aspect of the present invention, the present invention also relates to an inventive method for manufacturing an inventive food packaging film, as defined in the respective independent method claim (i.e. claim 49); additional, particularly advantageous embodiments of this aspect of the present invention are the subject of the respective dependent claims (i.e. claims 50 to 54).

[0037] Before the present invention is described in more detail below, the following general remarks are made:

[0038] It will be appreciated and it is not necessary to mention that, below, any embodiments, particulars, advantages, explanations, indications, configurations and the like that are described or cited below for only one aspect of the present invention, for the purpose of avoiding the repetition, of course, also apply correspondingly and mutatis mutandis, with respect to all other aspects of the present invention.

[0039] Furthermore, it will be appreciated that in the case of any values, numbers, quantities, ranges, etc. below, any intervals, etc. stated should not be construed restrictively. It will be evident to a person skilled in the art that, depending on the individual case and/or based on the respective application, it is possible to deviate from the ranges, numbers, values, etc., without departing from the scope of the present invention.

[0040] In addition, any values, numbers, quantities, intervals, parameters and the like indicated below can be determined or verified, in principle, by standardized or expressly specified determination methods, or else by determination methods well known to those skilled in the art. subject.

[0041] Having said this and with these provisions in mind, the present invention will be described in more detail below.

DETAILED DESCRIPTION OF THE INVENTION

[0042] According to a first . aspect of the present invention, the present invention relates to a multilayer film, especially a multilayer thermoplastic film, particularly to be used for food packaging, wherein the multilayer film comprises at least three layers and/or layer composites, especially at least three layers and/or polymeric layer composites: (A) a composite inner layer, especially a food contact composite inner layer, wherein the composite inner layer comprises a plurality of individual inner layers bonded and/or adhered to one another , especially co-extruded with one another, wherein the individual inner layers are each composed of at least one polymer foam comprising at least one polyolefin and wherein the individual inner layers each comprise a plurality of voids, especially open cells or pores, capable of reversibly retaining and/or absorbing at least one food additive; (B) a composite outer layer, wherein the composite outer layer comprises a plurality of individual outer layers bonded and/or adhered to one another, especially co-extruded with one another, wherein the individual outer layers each comprise at least a polyamide; (C) an adhesive layer (binding layer) disposed between the inner composite layer and the outer composite layer, specially adhered and/or co-extruded with the inner composite layer and the outer composite layer.

[0043] The multilayer film of the present invention is linked to a multitude of advantages and particularities, some of which are described below in a non-limiting manner:

[0044] Due to its porous structure, especially due to the presence of a multitude of voids in the composite inner layer, the multilayer film of the present invention is capable of absorbing or being loaded with a large amount of a food additive, the amount of which can even exceed the weight of the inventive multilayer film itself.

[0045] Since the voids, especially in the form of cells and open pores, are able to absorb and release (reversibly retain) a food additive, the multilayer film of the present invention, when provided or impregnated with a food additive in the its inner side, is capable of transferring or releasing the food additive onto the surface of a food product packaged (or embedded) in the multilayer film, especially during cooking and/or processing of the food product.

[0046] Especially, the applicant surprisingly found that, since the composite inner layer comprises a plurality of individual porous inner layers bonded and/or adhered to each other, it leads to an increase in the load-bearing capacity or the absorption capacity relative to the food additive compared to a single porous layer of the same thickness. Without being bound by any theory, this phenomenon can be explained by the existence of capillary effects or capillary forces due to the presence of a plurality of individual porous inner layers.

[0047] The plurality of individual inner layers form a complex three-dimensional porous system of voids, especially open cells or pores, which effectively absorb or retain food additive in a reversible manner (i.e., in contact with the surface of a food product, food additives are released or transferred to the surface of the food product packaged in the inventive multilayer film).

[0048] In contrast to fibrous cellulosic casings or casings containing, on the inner side, textile materials for the absorption of food additives, the multilayer films of the present invention do not use any fibrous or textile material, but provide porosity based on a polymeric material, especially a thermoplastic material. This significantly facilitates manufacturing processes, as the multilayer films of the present invention can be easily produced by coextrusion. Furthermore, any potential contamination of the surface of the food product due to fibers is completely avoided.

[0049] In this regard, it is completely surprising that a thermoplastic material allows a great absorption capacity or load capacity with respect to food additives.

[0050] Since the inventive multilayer films can be easily produced by coextrusion techniques, seamless tubular shapes of the inventive multilayer films can be easily produced, which can then be further processed as pouches or bags, especially pouches or bags for food packaging .

[0051] Furthermore, in contrast to the prior art of food packaging comprising textile inner materials, the multilayer films of the present invention can be easily further processed, for example, by stretching, tensioning, or orienting the coextruded films (e.g. , by monoaxial or biaxial orientation or stretching).

[0052] Furthermore, the applicant has also found, surprisingly, that due to the fact that the composite outer layer also comprises a plurality of individual outer layers bonded and/or adhered to each other, the mechanical and physicochemical properties are improved in compared to an individual outer layer of the same thickness, i.e. the structure of the multi-layer outer composite (which is composed of general individual outer layers) surprisingly leads to a significant improvement in physical-chemical and mechanical properties such as tensile strength, elongation burst strength, puncture resistance, oxygen barrier, water vapor transmission, etc.

[0053] The porosity of the inventive multilayer film, especially of the inner composite layer, can be easily modified by stretching or orientation of the multilayer film after coextrusion: the stretching or orientation of the multilayer film after extrusion (for example, monoaxial or biaxial orientation) leads to a significant enlargement of empty spaces, especially cells and pores. In addition, closed voids are broken or forced open, resulting almost completely in an open pore cellular structure, such that nearly all voids are capable of reversibly retaining and/or absorbing at least one food additive. .

[0054] Due to their large porosity, especially due to the capillary system formed by the multiplicity of voids of the individual inner layers of the composite inner layer, the multilayer films of the present invention can be easily provided, especially impregnated with food additives (for example, by spraying, slugging or similar).

[0055] Due to their excellent mechanical properties, the multilayer films of the present invention, especially in tubular form, can be easily crimped into rods, which is a decisive advantage when used in food packaging industries, especially with regard to machines for automatic crimping. Due to the high porosity and loading capacity towards food additives, there is essentially no loss of absorbed food additives during crimping of the inventive multilayer films. Thus, as can be seen above, the multilayer films of the present invention are linked to a large number of features and advantages.

[0056] According to a particular embodiment of the present invention, the inventive multilayer film is a multilayer thermoplastic film for food packaging, especially a biaxially oriented thermoplastic multilayer film for food packaging, preferably a coextruded biaxially oriented thermoplastic multilayer film for packaging of food.

[0057] According to another particular embodiment, the multilayer film of the present invention is oriented (stretched) mono- or biaxially, preferably oriented (stretched) biaxially.

[0058] Furthermore, according to another particular embodiment of the present invention, the multilayer film of the present invention is flat (i.e. planar) or tubular, preferably tubular.

[0059] Especially, the multilayer film of the present invention forms and/or is a tube, especially a seamless tube.

[0060] Particularly, the multilayer film of the present invention can be a tubular film, preferably a seamless tubular film.

[0061] According to a specific embodiment of the present invention, the multilayer film of the present invention forms and/or is a wrapper, especially a tubular wrapper, preferably a seamless tubular wrapper.

[0062] According to a further embodiment of the present invention, the multilayer film can be crimped. This modality applies specifically when the multilayer film is a tube, that is, a tubular film.

[0063] According to this specific embodiment, it is preferred that the multilayer film of the present invention forms and/or is a shirred wrapper, especially a shirred tubular wrapper, preferably a shirred seamless tubular wrapper.

[0064] As used herein, the term "envelope(s)" may mean flat or tubular films or in the form of pouches or bags. Tubular films can also be seamless or seamless. Any other variation of enclosures as practiced by those skilled in the art are included in this definition. The terms "enclosure(s)", on the one hand, and "film(s)", on the other hand, may especially be used herein as synonyms and/or interchangeably.

[0065] Generally, the multilayer film of the present invention has been coextruded and/or produced by coextrusion, respectively.

[0066] Particularly, the layers and/or composites of the layers of the inventive multilayer film are co-extruded. In particular, the layers and/or composite layers of the multilayer film are adhered or bonded together by coextrusion.

[0067] In order to be usable in the food packaging industry, the inventive multilayer film must provide certain physicochemical and mechanical properties.

[0068] For example, the inventive multilayer film must provide a certain shrinkage capacity (retraction). According to a specific embodiment of the present invention, a multilayer film of the present invention has a shrinkage value (shrinkage) in the range from 10% to 70%, in particular from 20% to 60% and preferably from 30% to 50%. % at a temperature of 90 °C in the longitudinal and/or transverse direction, preferably in both the longitudinal and transverse directions, especially as determined in accordance with ASTM D2732. In particular, the shrinkage (shrinkage) value can be determined as unrestricted shrinkage at a temperature of 90 °C (water bath) for 10 seconds.

[0069] Furthermore, it is desirable for the inventive multilayer film to provide certain oxygen barrier properties.

[0070] Particularly, the multilayer film of the present invention has an oxygen transmission rate (O2 transmission rate) of less than 90 cm3/m2/24 hours, especially less than 80 cm3/m2/24 hours, preferably less than 75 cm3/m2/24 hours and more preferably less than 65 cm3/m2/24 hours at a pressure of 1 atmosphere (101.325 kPa) and a temperature of 23°C. Such oxygen transmission rate can be determined according to ASTM D-3985-81.

[0071] Preferably, the multilayer film of the present invention has an oxygen transmission rate (O2 transmission rate) in the range of 1 to 90 cm3/m2/24 hours, especially in the range of 5 to 80 cm3/m2/ 24 hours, preferably in the range of 10 to 75 cm3/m2/24 hours and more preferably in the range of 20 to 65 cm3/m2/24 hours, at a pressure of 1 atmosphere (101.325 kPa) and a temperature of 23 °C, especially as determined in accordance with ASTM D-3985-81.

[0072] Furthermore, for use in the packaging industry, it is desirable that the multilayer film of the present invention provide a WVTR (Water Vapor Transmission Rate) defined in the range of 5 to 500 g/m2 24 hours , especially in the range 10 to 400 g/m2/24 hours, preferably in the range 25 to 300 g/m2/24 hours and more preferably in the range 50 to 250 g/m2/24 hours. The WVTR can be determined especially in accordance with ASTM F1249-06.

[0073] Furthermore, for use in the packaging industry, it is also desirable for the multilayer film of the present invention to provide certain mechanical properties.

[0074] According to a particular embodiment, the multilayer film of the present invention has a tensile strength in the longitudinal and/or transverse direction, preferably in both the longitudinal and transverse directions, in the range of 15 to 100 MPa, especially in the range from 20 to 80 MPa, preferably in the range from 25 to 75 MPa and more preferably in the range from 30 to 60 MPa. Tensile strength can be determined especially in accordance with ASTM D-882, method A.

[0075] Furthermore, according to another particular embodiment of the present invention, the multilayer film of the present invention has an elongation at break in the longitudinal and/or transverse direction, preferably in both the longitudinal and transverse directions, in the range of 20 to 300%, especially in the range of 40 to 200%, preferably in the range of 60 to 175% and more preferably in the range of 75 to 160%. Elongation at break can be determined especially in accordance with ASTM D-882, method A.

[0076] Furthermore, according to another particular embodiment of the present invention, the multilayer film of the present invention has a modulus (elasticity) in the longitudinal and/or transverse direction, preferably in both the longitudinal and transverse directions, in the range of 100 to 400 MPa, especially in the range of 150 to 400 MPa, preferably in the range of 175 to 375 MPa and more preferably in the range of 200 to 350 MPa. The respective modulus (of elasticity) can be determined especially from the respective tensile curve.

[0077] In order to be usable in the food packaging industries, the multilayer film of the present invention must provide a certain total thickness. Generally, the multilayer film of the present invention has a total thickness in the range of 50 to 500 micrometers, especially in the range of 10 to 400 micrometers, preferably in the range of 20 to 300 micrometers, more preferably in the range of 30 to 200 micrometers and even more preferably in the range of 40 to 150 micrometers.

[0078] In order to meet certain mechanical requirements and/or physicochemical requirements, it is preferred that the multilayer film of the present invention has a total thickness of at least 5 micrometers, especially at least 10 micrometers, preferably at least 20 micrometers, more preferably at least 30 micrometers and even more preferably at least 40 micrometers.

[0079] On the other hand, it is preferred that the multilayer film of the present invention has a total thickness of up to 500 micrometers, especially up to 400 micrometers, preferably up to 200 micrometers, more preferably up to 150 micrometers, and even more preferably up to 100 micrometers.

[0080] In addition to the total thickness of the multilayer film of the present invention, also the thickness of the various individual layers and composite layers of the multilayer film of the present invention, as well as their proportions are important, that is, also the individual thicknesses of the various individual layers and composites of the layers determine certain general properties of the inventive multilayer film.

[0081] In particular, to provide certain defined mechanical properties and oxygen barrier and water vapor transmission properties, it is important that the composite outer layer has a certain minimum thickness. The same applies to inner layer composites and individual inner layers: in order to have a certain absorption capacity or load capacity, it is also important that the composite inner layer and/or the individual inner layers respectively have a certain minimum thickness. Finally, regarding the adhesive layer, it is important that the adhesive layer ensures reliable adhesion between the inner composite layer and the outer composite layer (which also requires a certain minimum thickness of the adhesive layer).

[0082] According to a preferred embodiment of the present invention, the inner composite layer of the inventive multilayer film comprises from 20% to 50%, especially from 25% to 45% and preferably from 30% to 40% of the total thickness of the film multilayer.

[0083] Furthermore, it is preferred that the composite inner layer of the inventive multilayer film has a thickness in the range of 5 to 200 micrometers, especially in the range of 7.5 to 100 micrometers, preferably in the range of 10 to 75 micrometers, more preferably in the range of 12.5 to 50 micrometers and even more preferably in the range of 20 to 40 micrometers.

[0084] Furthermore, according to a preferred embodiment, each individual inner layer of the composite inner layer, independently of one another, has a thickness in the range of 1 to 100 micrometers, especially in the range of 2 to 50 micrometers, preferably in the in the 2.5 to 25 micrometer range, more preferably in the 3 to 20 micrometer range, and even more preferably in the 5 to 15 micrometer range.

[0085] With regard to the composite outer layer of the inventive multilayer film, it is preferred that the composite outer layer of the inventive multilayer film comprises from 45% to 90%, especially from 50% to 80% and preferably from 55% to 70% of the full thickness of the multilayer film.

[0086] Furthermore, it is preferred that the composite outer layer of the inventive multilayer film has a thickness in the range of 5 to 300 micrometers, especially in the range of 10 to 150 micrometers, preferably in the range of 12.5 to 100 micrometers, more preferably in the range of 15 to 75 micrometers and even more preferably in the range of 20 to 50 micrometers.

[0087] Furthermore, it is preferred that each individual outer layer of the composite outer layer, independently of one another, has a thickness in the range of 2 to 100 micrometers, especially in the range of 5 to 50 micrometers, preferably in the range of 7, 5 to 40 micrometers, more preferably in the 10 to 30 micrometer range, and even more preferably in the 12.5 to 25 micrometer range.

[0088] With regard to the adhesive layer (binding layer) of the inventive multilayer film, it is sufficient that the adhesive layer comprises from 1% to 25%, especially from 2% to 20% and preferably from 5% to 15% of the thickness total of the multilayer film.

[0089] Generally, the adhesive layer of the inventive multilayer film has a thickness in the range of 1 to 75 micrometers, especially in the range of 2 to 50 micrometers, preferably in the range of 3 to 40 micrometers, more preferably in the range of 4 to 35 micrometers and even more preferably in the range of 5 to 30 micrometers.

[0090] As explained above, the thickness ratios of the various layers and composite layers of the inventive multilayer film are important and determine the physicochemical and mechanical properties of the inventive multilayer film. Typically, it is preferred that the thickness ratio [composite outer layer: composite inner layer: adhesive layer] is [45-80:20-50:120], especially [50-75:40-25:2-15] and preferably [5575:25-45:1-10].

[0091] Normally, all the layers and composites of the layers of the inventive multilayer film are adhered to each other. Especially, all layers and layer composites of the inventive multilayer film are co-extruded.

[0092] As explained above, the multilayer film, especially the thermoplastic multilayer film of the present invention can be used for food packaging, especially for providing a food additive to the packaged food. For this purpose, the multilayer film of the present invention, on its inner side, must be provided or loaded with at least one food additive. To meet this requirement, the multilayer film of the present invention must have a certain absorption capacity or load capacity with respect to the at least one food additive to be transferred and/or released on the surface of the food product to be treated.

[0093] Particularly, the multilayer film of the present invention has a weight bearing capacity (absorption capacity), with respect to the at least one food additive, based on the total dry weight of the multilayer film, of at least 10% in weight, especially at least 20% by weight, preferably at least 25% by weight, more preferably at least 30% by weight and even more preferably at least 40% by weight.

[0094] According to a particular embodiment, the multilayer film of the present invention has a weight bearing capacity (absorption capacity), with respect to the at least one food additive, based on the total dry weight of the multilayer film, of up to 50% by weight, especially up to 75% by weight, preferably up to 90% by weight, more preferably up to 100% by weight and even more preferably up to 100% by weight.

[0095] Typically, the multilayer film of the present invention has a weight bearing capacity (absorption capacity), with respect to at least one food additive, based on the total dry weight of the multilayer film, in the range of 10% to 150% by weight, especially in the range from 20% to 130% by weight, preferably in the range from 25% to 120% by weight, more preferably in the range from 30% to 115% by weight and even more preferably in the range from 40% to 110% by weight.

[0096] This means that the inventive multilayer film can absorb more additive even than its own weight. This is due to the foam structure of the composite inner layer of the inventive multilayer film and also because of the capillary effect resulting from having multiple porous inner layers, as will be explained in more detail below.

[0097] With respect to the at least one food additive, this food additive may comprise a flavoring and/or coloring and/or flavoring food additive, preferably especially in the form of an aqueous solution or dispersion, particularly a liquid smoke or caramel. An emulsion made from a food grade oil and particulate herbs or spices, such as ground peppers, may also be a preferred food additive. These additives are well known to a person skilled in the art.

[0098] Typically, the multilayer film of the present invention, especially the composite inner layer with the plurality of individual inner layers, is capable of reversibly retaining and/or absorbing the at least one food additive and again releasing and/or transferring the food additive retained and/or absorbed into a food product packaged in the multilayer film or with the multilayer film, especially when the packaged food product is subjected to cooking and/or processing.

[0099] In order to provide a high load capacity or absorption capacity with respect to food additives, the multilayer film of the present invention should have a certain porosity. Particularly, the multilayer film of the present invention has a relative porosity based on volume, based on the total volume of the inventive multilayer film, in the range of 5 to 80% by volume, especially in the range of 10 to 75% by volume, preferably in the range of range from 15 to 70% by volume. Particularly, the porosity of the multilayer film is provided by the multiplicity of voids comprised by the individual inner layers of the composite inner layer.

[0100] With regard to the composite inner layer of the inventive multilayer film, the following properties are useful for use in the food packaging industry:

[0101] Generally, the composite inner layer comprises at least two and preferably at least three individual inner layers. Surprisingly, the Applicant found that, likely due to capillary effects (without being bound by any theory), the fact that a composite inner layer consisting of two or three or more individual inner layers absorbs or retains more food additive than a single individual inner layer of the same total thickness.

[0102] Generally, the plurality of individual inner layers of the composite inner layer are bonded and/or adhered to each other through coextrusion.

[0103] The various individual inner layers of the composite inner layer may have the same chemical compositions or different chemical compositions, and preferably the same chemical composition.

[0104] Particularly, the various individual inner layers of the composite inner layer, whether they are the same or different and independently of each other, each comprises at least one polyolefinic polymer, copolymer or terpolymer, especially at least one polyethylene polymer, copolymer or terpolymer , especially one selected from the group consisting of LDPE, LLDPE, VLDPE, as well as blends and copolymers and terpolymers thereof, particularly copolymers and terpolymers with C3-C10-alpha-olefins or alkyl (meth)acrylates.

[0105] Especially, the various individual inner layers of the composite inner layer, whether these are the same or different and independently of each other, each comprises at least one polyolefin, especially at least one polyolefin polymer, copolymer or terpolymer having a density in the range of 0.910 to 0.940 g/cm3, especially as determined in accordance with ASTM D792.

[0106] According to a particular embodiment of the present invention, it is preferred that the various individual inner layers of the composite inner layer, whether they are the same or different and independently of each other, each comprise at least 60% by weight, especially at least 75% by weight, preferably at least 80% by weight, more preferably at least 85% by weight, even more preferably at least 90% by weight and even more preferably at least 95% by weight of at least a polyolefin, especially of the at least one polyolefin polymer, copolymer or terpolymer, based on the total dry weight of the respective individual inner layer.

[0107] As described above, the individual inner layers of the composite inner layer of the inventive multilayer film each comprise a plurality of voids, especially open cells or pores, which voids are capable of reversibly retaining and/or absorbing at least a food additive.

[0108] Particularly, the multiplicity of voids of the individual inner layers of the composite inner layer is particularly generated by (co)extrusion of the individual inner layers in the presence of at least one foaming agent. Particularly, the at least one foaming agent can be selected from the group consisting of physical and chemical foaming agents, preferably chemical foaming agents, especially chemical foaming agents that release gaseous compounds, preferably selected from organic or inorganic carbonates, organic carboxylic acids and their esters, azo compounds, hydrazine derivatives, semicarbazides, tetrazoles and combinations thereof. Particularly useful results are obtained if a combination of alkali or alkaline earth metal carbonates and bicarbonates together with an organic carboxylic acid, particularly citric acid, is used as a foaming agent. During the (co)extrusion process, the chemical foaming agent is decomposed, releasing gaseous compounds, especially carbon dioxide or other gases. This leads to a porous structure of the individual inner layers of the composite inner layer, presenting a multitude of voids as described above. By stretching or subsequent orientation of the coextruded multilayer film, the voids can be extended or widened and, if necessary, opened, so as to result in a plurality of open voids.

[0109] As described above, the voids of the individual inner layers of the composite inner layer are voids especially in the form of open cells or pores. This allows absorption of a food additive.

[0110] Particularly, the individual inner layers are each in the form of a rigid, solidified or hardened foam with open voids, especially having an irregular and/or random structure of the type of net, of the type of screen, mesh, reticulated, or alveolar, with respect to a two-dimensional projection plane of the foam. Particularly, the empty spaces are entirely surrounded and/or delimited by walls composed of the polymer comprising at least one polyolefin.

[0111] Generally, the voids of the individual inner layers of the composite inner layer each have absolute sizes of cross sections, with reference to the two-dimensional projection plane, in the range of 0.001 to 10 mm2, especially in the range of 0.005 to 8 mm2, preferably in the range of 0.01 to 7 mm2, as determined by digital image processing of two-dimensional micrographs of the individual inner layers of the composite inner layer. In particular, 30% to 80% of the voids have absolute cross-sectional sizes of less than 1.0 mm2, especially less than 0.8 mm2. In particular, 70% to 95% of the voids have absolute cross-sectional sizes of less than 3 mm2, especially less than 1.5 mm2.

[0112] According to a particular embodiment, the voids of the individual inner layers of the composite inner layer each have average (i.e., median) transverse dimensions, in reference to a two-dimensional projection plane, in the range of 0, 01 to 5 mm2, especially in the range 0.05 to 2 mm2, preferably in the range 0.1 to 1 mm2, especially determined by digital image processing of two-dimensional micrographs of the individual inner layers.

[0113] Especially, it is preferred that the voids of the individual inner layers of the composite inner layer comprise in their entirety from 10% to 80%, especially from 20% to 70% and preferably from 30% to 60% of the area of surface of the individual inner layers, with reference to a two-dimensional projection plane, specially determined by digital image processing of two-dimensional micrographs of the individual inner layers of the composite inner layer.

[0114] With respect to the composite outer layer of the multilayer film of the present invention, the composite outer layer generally comprises a plurality of individual outer layers bonded and/or adhered to each other, especially co-extruded with each other, wherein the individual outer layers each comprise at least one polyamide.

[0115] The composite outer layer of the inventive multilayer film is mainly responsible for the mechanical properties and part of the physicochemical properties, especially the O2 and WVTR barrier properties.

[0116] Generally, the composite outer layer comprises at least two and preferably at least three individual outer layers. Surprisingly, also with reference to this aspect of the present invention, the Applicant has found that a plurality of individual outer layers provide improved physical-chemical and mechanical properties compared to a single outer layer of the same thickness.

[0117] According to a specific embodiment of the present invention, the plurality of individual outer layers of the composite outer layer are bonded and/or adhered to each other by coextrusion.

[0118] The various individual outer layers of the composite outer layer may have the same chemical compositions or different chemical compositions, and preferably the same chemical composition.

[0119] Especially, the various individual outer layers of the composite outer layer, whether they are the same or different and independently of each other, each comprises at least one polyamide, particularly at least one polyamide ("PA") polymer, copolymer or terpolymer , specially selected from the group consisting of aliphatic, semi-acrobatic and aromatic polyamides, as well as mixtures thereof, particularly selected from the group consisting of PA 6, PA 66, PA 6.66, PA 6.11, PA 6.12, PA 11 and PA 12, as well as mixtures thereof, optionally combined with at least one amorphous polyamide or copolyamide such as PA 6I/6T.

[0120] According to a typical embodiment, the various individual outer layers of the composite outer layer, whether they are the same or different and independently of one another, each comprises at least 70% by weight, in particular at least 75% by weight, of preferably at least 80% by weight, more preferably at least 85% by weight, even more preferably at least 90% by weight and even more preferably at least 95% by weight of the at least one polyamide, based on weight total dryness of the respective individual outer layer.

[0121] Regarding the adhesive layer (binding layer) of the multilayer film of the present invention, the adhesive layer is arranged between the composite inner layer and the composite outer layer, specially adhered and/or co-extruded with the composite inner layer and the composite layer composite exterior.

[0122] Generally, the adhesive layer, through its opposite sides, is directly adhered and/or directly co-extruded with the composite inner layer, on the one hand, and the composite outer layer, on the other.

[0123] The adhesive layer preferably comprises a single, continuous layer of adhesive. Since the function of the adhesive layer is to securely adhere the composite inner layer on the one hand to the composite outer layer on the other hand, it is sufficient to provide this function by a single layer adhesive layer. However, it is also possible to use a multi-layer adhesive structure, although this is not preferred according to the present invention.

[0124] In order to ensure secure adhesion, the adhesive layer generally comprises an adhesive composition compatible with and/or adherent to both the inner composite layer and the outer composite layer.

[0125] According to a preferred embodiment of the present invention, the adhesive layer preferably comprises an elastomeric adhesive based on polyolefin, especially preferably an elastomeric adhesive based on polyethylene, especially selected from the group consisting of polyethylenes modified with rubberized and/or grafted, particularly selected from the group consisting of polyethylenes modified with rubber and/or grafted with maleic anhydride.

[0126] According to a particular embodiment of the present invention, an inventive multilayer film is provided, as described above, wherein the composite outer layer comprises at least two individual outer layers, particularly exactly two individual outer layers, wherein the outer layers individual layers are bonded and/or adhered to each other by coextrusion and/or wherein the individual outer layers, independently of one another, each comprise at least one polyamide, particularly at least one polyamide polymer, copolymer or terpolymer specially selected from the group consisting of aliphatic, aromatic and semi-aromatic polyamides, as well as mixtures thereof, particularly selected from the group consisting of PA 6, PA 66, PA 6.66, PA 6.11, PA 6.12, PA 11 and PA 12, as well as mixtures thereof, optionally combined with at least one amorphous polyamide or copolyamide such as PA 6I/6T; and wherein the composite inner layer comprises at least four individual inner layers, in particular exactly four individual inner layers, which individual inner layers are bonded and/or adhered to each other by co-extrusion and/or wherein the individual inner layers independently of one another others, each comprises at least one polyolefinic polymer, copolymer or terpolymer, especially at least one polyethylene polymer, copolymer or terpolymer, especially selected from the group consisting of LDPE, LLDPE, VLDPE, as well as mixtures and copolymers and terpolymers thereof, particularly copolymers and terpolymers with C3-C10-alpha-olefins or alkyl (meth)acrylates, and/or in the individual inner layers, independently of one another, each comprising at least one polyolefin, in particular at least one polymer, copolymer or terpolymer polyolefin having a density in the range of 0.910 to 0.940 g/cm3, especially as determined in accordance with ASTM D792.

[0127] According to yet another particular embodiment of the present invention, there is provided an inventive multilayer film as described above, wherein the multilayer film further comprises at least one additional layer disposed between the inner composite layer and the specially adhered adhesive layer and/or co-extruded with the inner composite layer and the adhesive layer. Especially, according to this particular embodiment, the additional layer is preferably a continuous layer, especially a uniform and/or homogeneous and/or continuous and/or non-foam layer, particularly without voids. This particular embodiment provides several additional advantages: on the one hand, by the presence of the additional and preferably continuous layer disposed between the inner composite layer and the adhesive layer, adhesion is improved, as a continuous layer provides better adhesion than a layer foam and non-continuous; on the other hand, the presence of the additional and preferably continuous layer also improves the barrier properties of the invention, especially the water vapor barrier properties. According to this particular embodiment, it is preferred that the additional layer comprises from 1% to 30%, especially from 2% to 25% and preferably from 5% to 20% of the total thickness of the multilayer film. Furthermore, according to this particular embodiment, it is also preferred that the additional layer has a thickness in the range of 1 to 80 micrometers, especially in the range of 2 to 60 micrometers, preferably in the range of 3 to 45 micrometers, more preferably in the 4 to 40 micrometer range, even more preferably in the 5 to 35 micrometer range. In particular, the additional layer can have a chemical composition that is compatible with and/or similar and/or equal to that of the composite inner layer, especially the individual inner layers.

[0128] According to the particular embodiment of the present invention described above, according to which the multilayer film additionally comprises at least one additional layer arranged between the inner composite layer and the adhesive layer, it is further preferred that the additional layer comprises at least at least one polyolefinic polymer, copolymer or terpolymer, especially at least one polyethylene polymer, copolymer or terpolymer, especially one selected from the group consisting of LDPE, LLDPE, VLDPE, as well as mixtures and copolymers and terpolymers thereof, particularly C3 copolymers and terpolymers -C10-alpha-olefins or alkyl (meth)acrylates. Especially, the additional layer may comprise at least one polyolefin, especially at least one polyolefin polymer, copolymer or terpolymer having a density in the range of 0.910 to 0.940 g/cm3, especially as determined in accordance with ASTM D792. Especially, the additional layer may comprise at least 60% by weight, especially at least 75% by weight, preferably at least 80% by weight, more preferably at least 85% by weight, even more preferably at least 90% by weight. weight, even more preferably at least 95% by weight of the at least one polyolefin, especially the at least one polyolefin polymer, copolymer or terpolymer, based on the total dry weight of the respective individual inner layer.

[0129] According to the particular embodiment of the present invention described above, according to which the multilayer film additionally comprises at least one additional layer arranged between the composite inner layer and the adhesive layer, it is also preferred that the composite outer layer can be comprising at least two individual outer layers, in particular exactly two individual outer layers, whose individual outer layers are bonded and/or adhered to each other by co-extrusion and/or whose individual outer layers, independently of one another, each comprise at least one polyamide , in particular at least one polyamide polymer, copolymer or terpolymer, especially selected from the group consisting of aliphatic, aromatic and semi-aromatic polyamides, as well as mixtures thereof, particularly selected from the group consisting of PA 6, PA 66, PA 6.66, PA 6.11 , PA 6.12, PA 11 and PA 12, as well as mixtures thereof, optionally combined with at least one amorphous polyamide or copolyamide such as PA 6I/6T; and that the composite inner layer comprises at least three individual inner layers, in particular exactly three individual inner layers, which individual inner layers are bonded and/or adhered to each other by coextrusion and/or wherein the individual inner layers independently of each other , each comprising at least one polyolefinic polymer, copolymer or terpolymer, especially at least one polyethylene polymer, copolymer or terpolymer, especially selected from the group consisting of LDPE, LLDPE, VLDPE, as well as mixtures and copolymers and terpolymers thereof, particularly copolymers and terpolymers with C3-C10-alpha-olefins or alkyl (meth)acrylates, and/or whose individual inner layers, independently of one another, each comprise at least one polyolefin, in particular at least one polyolefin polymer, copolymer or terpolymer having a density in the range of 0.910 to 0.940 g/cm3, especially as determined in accordance with ASTM D792.

[0130] Altogether, the present invention therefore constitutes a significant milestone with regard to the supply of high-performance coextrudable thermoplastic multilayer films, with a great absorption capacity or load capacity in relation to food additives, especially based on flavorings and/or colorants and/or flavoring agents, particularly preferably based on aqueous solutions or dispersions thereof.

[0131] Below, typical embodiments of the present invention will be described in more detail, without being limiting of the present invention.

[0132] The present invention therefore solves the old problem described above by providing a thermoplastic multilayer film impregnated with, for example, a solution or dispersion of at least one food additive in its inner layer in contact with food. The food additive may be selected from the group consisting of food colors, food flavorings, flavor producing additives, food processing and peeling aids, as well as mixtures thereof. Such a casing, when stuffed with food products, particularly sausage or whole meat emulsions, releases its additive onto the surface of the packaged food product during processing, thereby producing a flavored and/or colored final food product.

[0133] The inventive film is preferably a thermoplastic multilayer wrapper of at least three layers of composite materials with the following structure: a first composite inner layer composed of several layers, each comprising a polyolefin foam, a second outer barrier or wear-resistant composite outer layer composed of several layers, each comprising a polyamide, and finally a third intermediate adhesive or bonding layer disposed therebetween (ie between the first and second layer composites). The first composite inner layer is the food contact layer. A typical structure of an inventive multilayer film can also be presented as follows, starting from the first composite inner layer to the second composite outer layer: polyolefin foam composite inner layer (composed of 2 or more individual inner layers) / layer barrier adhesive/composite outer layer or wear resistant polyamide (composed of 2 or more individual outer layers).

[0134] The composite inner layer of the inventive film contains open or ruptured pore foam cells due to the addition of a foaming agent to the polyolefin resin before extrusion. These cells are reservoirs for any food additive that is introduced into this layer.

[0135] Foaming agents are well known in the art and include chemical foaming agents and physical foaming agents. Chemical foaming agents are especially the additives used in the manufacture of foam products. Most are organic chemicals, although some inorganic chemicals are also used. They are introduced into the polymeric resin prior to extrusion and foam upon decomposition at processing temperatures, releasing gases into the polymeric melt, thereby forming bubbles or cells in the extruded polymer. Nucleating agents can be a part of chemical foaming agents and will remain in the polyolefin foam layer. Alternatively, physical blowing agents do not undergo chemical transformation, rather their blowing gas is released by physical processes, such as, for example, the vaporization of a low-boiling liquid, or by the release of pressure in a compressed gas.

[0136] Currently, in the state of the art, the main reason for manufacturing foam plastics of any type is to reduce its density, which reduces the weight of the finished product and reduces the cost of raw materials. An excellent example of an expanded polymer is the production of Styrofoam® (Styrofoam). Other products made from polymer foam or an expanded polymer are garbage bags (to reduce their cost and increase their strength) and bottle cap liners (to have a deformable liner inside the screw neck of a bottle). ). However, according to the state of the art, foaming agents have not yet been used to provide greater absorption capacity in thermoplastic multilayer films.

[0137] A preferred embodiment of the present invention is preferably a thermoplastic multilayer shell with at least one three-layer composite comprising a first inner composite layer of polyethylene foam composed of several individual inner layers and a second outer composite layer of polyamide composed of several individual outer layers as well as an intermediate adhesive monolayer.

[0138] For the composite inner layer material, according to a particularly preferred embodiment of the present invention, polyethylene selected from the group consisting of low density polyethylenes and linear low density polyethylenes, as well as mixtures thereof, may be used.

[0139] According to a particular embodiment, additional layers can be added to the inventive film to provide additional characteristics to the film, such as improved oxygen and/or moisture barrier properties, or to add strength to the film. For example, multiple layers directly adjacent to individual foam inner layers produce deeper voids or cells, which in turn provide for the retention of greater amounts of, for example, food additive solutions or dispersions, than would be provided by an individual foam layer of the same total thickness.

[0140] In addition, color can be added to each of the individual layers by introducing color concentrates into the resin before extrusion. One or more of the layers can be colored a single color to produce a solid color film, or the individual layers can be colored different colors than the other layers, and some of the layers may not have dyes added to them, so that form specific patterns on the finished film.

[0141] After film production, the composite inner layer may receive or be impregnated with a food additive selected from processing aids, peeling aids, liquid smoke and/or caramel or other flavoring and/or coloring additives and/or producers aroma, or mixtures thereof. Additional components of these solutions comprising food additives may also include polyethylene glycol, anti-foaming agents, stain prevention agents and alkaline hydroxides, each ingredient providing different properties, as is well known in the art. Additional stripping modifiers and processing aids can also be added.

[0142] The coating or impregnation with the food additive can be applied to the inventive film in a variety of well-known ways, such as spraying, fluidizing, knife coating or roll coating.

[0143] If the inventive film is produced as a flat sheet, it can be formed into a tube and sealed with a strip of compatible thermoplastic material. Any other sealing method well known to those skilled in the art can also be used. At this point, the casing may be impregnated with the desired food additive materials, filled with the food product and further processed.

[0144] If the inventive casing is tubular, it can be crimped and then stuffed in automatic filling machines and thermally processed to produce sausages, delicatessen products and special meats (deli) or other food products.

[0145] During the cooking cycle, the flavoring and/or coloring retained in the inner layer in contact with food is transferred from this layer of the casing to the outer surface of the packaged baked product, thus providing the desired flavoring and/or coloring.

[0146] Although the inventive film is described as having three composite layers, more layers can be added if desired. For example, if different oxygen or moisture barrier properties are desired, additional inner and outer layers can be added to the laminate by methods well known to those skilled in the art. In one example of this, it is known that the barrier layer can comprise any suitable material, for example the preferred nylon of this invention, nylon 6, or ethylene vinyl alcohol, or polyvinylidene chloride, and this is preferably positioned between the adhesive layer and the thermoplastic outer layer, possibly adjacent to the preferred polyamide outer layer, with or without an additional adhesive layer. Another example is a second moisture barrier layer adjacent to the thermoplastic outer layer. Alternatively, the thermoplastic layers can be placed next to each other while still hot, allowing the layers to fuse or bond to each other, as well as the two outer layers bonding directly to each other. In these cases, the adhesive layer is not necessary for the inventive film. A preferred thermoplastic multilayer film comprising a polyolefin foam composite inner layer, an intermediate adhesive layer and a polyamide thermoplastic composite outer layer and an additional outer thermoplastic layer, wherein the thermoplastic composite outer layer may comprise an oxygen barrier and wherein the additional outer thermoplastic layer may comprise a moisture barrier and wear resistant layer, is another example of an inventive film.

[0147] A preferred embodiment of the present inventive film consists of the following layers (from the inside out): (A) a food contact composite inner layer (composed of 3 or more individual inner layers containing porous polyethylene foam) / (C ) adhesive layer (usually composed of 1 layer) / (B) composite outer layer (composed of two or more individual inner layers containing polyamide). Variations in the order of the layers can be made, as known to those skilled in the art, but once the tubular shell is formed, the polyolefin foam layer must be the inner layer that is adjacent to the food product and the polyamide layer must be be the outer layer due to its barrier, wear resistance and melting properties.

[0148] The inner layers containing polyolefin foam can be made of one or more polyolefins, such as low density polyethylenes (LDPE), linear low density polyethylenes (LLDPE), very low density polyethylenes (VLDPE), polypropylenes, copolymers of ethylene with at least one C3-C10-alpha-olefin and polymers of ethylene having at least one functional moiety selected from the group of esters, anhydrides and carboxylic acids, including copolymers of ethylene with a vinyl ester, copolymers of ethylene with an acrylate of alkyl and mixtures of these polyolefins. The inner layers of polyolefin foam must be capable of absorbing sufficient amounts of flavoring and/or food coloring solution so that, after processing the packaged food product, the absorbed flavoring and/or coloring is transferred to the surface of the sausage or packaged food product in the desired quantity.

[0149] The term polyolefin as used herein particularly refers to a hydrocarbon polymer derived from a single olefin, for example polyethylene or polypropylene, and copolymers and terpolymers of such olefins. The polyolefins used in the present invention, unless otherwise indicated, are substantially free (except for incidental amounts such as trace amounts of catalyst residue or process-related contaminants) of halogens, oxygen or elements other than carbon and hydrogen. However, these polyolefins can optionally have other polymers or substances, such as processing aids, ultraviolet light stabilizers or antioxidants, in the blend.

[0150] The term polyethylene, as used herein, is especially the name of a polymer whose basic structure is characterized by the (CH2-CH2)n chain. Polyethylene homopolymers are generally described as being solid at room temperature, having a partially amorphous phase and a partially crystalline phase with a density of 0.915 to 0.970 g/cm3. The relative crystallinity of polyethylene is known to affect its physical properties. The amorphous phase imparts flexibility and high impact strength while the crystalline phase imparts a high softening temperature and stiffness.

[0151] Foaming agents are also well known in the art and include chemical blowing agents and physical blowing agents. Chemical blowing agents are additives used in the manufacture of foam products. Most are organic chemicals, although some inorganic chemicals are also used. They are introduced into the polymer prior to extrusion and foam upon decomposition at processing temperatures, releasing gases into the polymeric melt, thereby forming bubbles or cells in the polymer. Physical blowing agents do not undergo chemical transformation, rather their blowing gas is released by physical processes, such as, for example, the vaporization of a low-boiling liquid, or the release of pressure in a compressed gas. The main reason for manufacturing foam plastics is their greatly reduced density, reducing the weight of the finished product and reducing raw material costs.

[0152] A composite layer of polyolefin or polyethylene foam, as used herein for the composite inner layer, and which when formed into a tube is the inner food contact layer of the inventive wrapper comprising the polyolefin or polyethylene that has been mixed with a chemical foaming agent and processed at the temperature required to undergo the chemical reaction, resulting in the release of the blowing gas, while other reaction products, such as sodium remaining from the use of sodium bicarbonate, remain in the polyolefin or polyethylene composite layer. The composite inner layer can also be expanded with physical blowing agents which generally do not leave any reaction products in the polyolefin layer.

[0153] As for the adhesive layer or bonding layer, various adhesives are well known in the art and can be used for adhesion of the absorbent composite inner layer to the polyamide-containing composite outer layer. In particular, it has been found that a maleic anhydride-modified elastomeric polyolefin adhesive is a preferred adhesive since the foam composite inner layer does not easily delaminate from the nylon composite layer after the food has been processed. Other adhesives can be used in this adhesive layer, as are well known in the prior art.

[0154] The composite outer layer containing polyamide is usually both a wear resistant layer and a moisture and oxygen barrier layer. Wear resistant layers are required to withstand contact with sharp objects and provide abrasion resistance. As for the outer surface or PA composite outer layer of the multilayer film of the invention, this is therefore subjected to handling and use, for example, as protection against equipment during packaging and against rubbing against other surfaces during the production of food products. cooked. This contact causes abrasive forces, stresses and pressures that can tear the film, causing perforations or violations in the integrity of the package and causing loss of food product due to contamination. Therefore, the outer surface of the PA composite outer layer can typically be made of materials chosen to be resistant to abrasive forces and puncture forces and other stresses that the package may encounter during use. Generally, the outer surface of the layer should be easy to machine (ie, easy to feed and manipulate by machines when forming into tube casings and filling with food emulsions). Stiffness, flexibility, bending-breaking strength, modulus of elasticity, tensile strength, coefficient of friction, printability, optical properties, etc. they are also often given to the outer layers by the proper choice of materials.

[0155] Therefore, it is preferred that the composite outer layer is composed of individual outer layers of bioriented polyamide, particularly of bioriented nylon 6. Polyamides are well known in the prior art as film layers. Polyamides and copolyamides, such as nylon 6.66, are useful in providing a measure of mechanical strength, ease of stretch orientation, and oxygen barrier properties to the film. Polyamides are polymers having recurring amide linkage units (-CONH-) in the molecular chain and include nylon resins, which are well-known polymers having a multitude of uses, including utility as packaging films, bags and overwraps. Nylon is a generic term for synthetic and generally high molecular weight (Mw^10,000) linear polyamides. Suitable nylons are commercially available and can be prepared by well known methods, including addition or self-condemnation reactions, for example, of amino acids or lactams, and condensation reactions of diamines with diacids. Nylon polymers can be aliphatic, aromatic or amorphous. Suitable nylon polymers can be homopolymers or copolymers, such as bipolymers, terpolymers, and mixtures and modifications thereof. Nylons suitable for use in the present inventive film include nylon 6, nylon 12, nylon 66, nylon copolymer 6/12, nylon copolymer 6/66, nylon copolymer MXD6 and amorphous nylons such as PA 6I, PA 6T and PA 6I /6T. Especially preferred polyamides are aliphatic nylons such as nylon 6 and its copolymers. The nylon films used can be biaxially stretched, producing biaxially oriented films (that is, stretched or oriented in both the machine direction and the transverse film direction).

[0156] In particular, the flexible oriented thermoplastic multilayer films of the present invention are useful for food packaging. It is further contemplated that blends of nylons can be used and that blends of aliphatic nylons with aromatic nylons can be used. Preferred blends include blends of semicrystalline aliphatic nylons or a blend of one or more semicrystalline aliphatic nylons with an amorphous nylon. A preferred amorphous nylon is nylon 6I/6T copolymer (which is commercially available under the trademark Selar® PA 3426 from the DuPont Company of Wilmington, Del., USA).

[0157] After all layers have been laminated together, a flavoring and/or coloring solution can be applied to the inner layer of absorbent foam in contact with food. This solution may comprise the coloring and/or flavoring agent, such as liquid smoke or caramel, water and, optionally, a peeling agent.

[0158] A coloring solution that imparts a brown color level to the final processed product and that can be applied to the absorbent inner layer is an aqueous caramel solution composed of water, caramel and a peeling aid. The final formula will depend on the type of caramel used and the desired color of the final product.

[0159] A flavoring agent used in the meat industry is liquid smoke, which can also be considered a coloring agent, depending on the type of liquid smoke used. Liquid smoke is also used to impart a smoky flavor to packaged meat. Both tar-containing and tar-free liquid smokes can be used in the inventive film. The liquid smoke solution useful in the present invention comprises an aqueous solution of a peeling aid and liquid smoke. Additional solution components may include propylene glycol, sodium hydroxide to adjust the pH of the solution, and an antifoaming agent.

[0160] This solutions can be applied to the absorbent inner foam layer of the film in several ways. The solution can be sprayed onto the foam layer. It can be applied by the blade coating method, a method where a coating solution is applied to a film that is usually supported and transported by a resilient backing roller using a flexible blade located some distance from the edge of a film. applicator leak, which serves to level the applied coating. In general, an excess of coating material is applied and the drag blade doses or removes the excess while spreading the coating evenly over the surface of films (see US Patent 4,250,211).

[0161] Thus, as can be seen from the above description and explanations, inventive multilayer films can be formed according to various modalities.

[0162] According to a second aspect of the present invention, there is provided a food packaging film capable of releasing and/or transferring at least one food additive to a surface of a food product packaged therein, wherein the food packaging film food comprises a multilayer film of the present invention as defined above, wherein the multilayer film of the present invention, preferably on its inner side, especially on the composite inner layer side, is provided with at least one food additive.

[0163] With regard to the food packaging film of the present invention, the multilayer film, preferably its inner side, especially the composite inner layer side, is impregnated with at least one food additive. As described above, the multilayer film, preferably its inner side, especially its composite inner layer, reversibly retains and/or absorbs at least one food additive.

[0164] Also as described hereinabove, the at least one food additive comprises a flavoring and/or coloring and/or flavoring food additive, preferably especially in the form of an aqueous solution or dispersion, particularly a liquid smoke or caramel .

[0165] The amounts of the at least one food additive comprised by the inventive food packaging film can vary over wide ranges.

[0166] Generally, the food packaging film of the present invention is provided with at least one food additive in relative amounts by weight, based on the total dry weight of the multilayer film, of at least 10% by weight, especially of at least 20% by weight, preferably at least 25% by weight, more preferably at least 30% by weight and even more preferably at least 40% by weight.

[0167] Furthermore, also according to the usual embodiment of the present invention, the food packaging film of the present invention is provided with at least one food additive in relative amounts by weight based on the total dry weight of the multilayer film, up to 50% by weight, especially up to 75% by weight, preferably up to 90% by weight, more preferably up to 100% by weight and even more preferably up to 100% by weight.

[0168] Additionally, according to a typical embodiment, the food packaging film of the present invention is provided with at least one food additive in relative amounts by weight, based on the total dry weight of the multilayer film, in the range of 10% to 150% by weight, especially in the range from 20% to 130% by weight, preferably in the range from 25% to 120% by weight, more preferably in the range from 30% to 115% by weight and even more preferably in the range range from 40% to 110% by weight.

[0169] According to a preferred embodiment of this aspect of the present invention, the present invention preferably relates to a thermoplastic multilayer food film, especially a wrapper, having a composite inner food contact layer composed of several layers individual inner layers of open-cell polyolefin foam impregnated with a preferred food additive, which may include flavoring and/or coloring agents, wherein the food additive reversibly retained in the inner composite foam layer can be transferred to the surface of a product packaged food during cooking and/or processing, thus resulting in a colored and/or flavored food product.

[0170] With regard to further details of the second aspect of the present invention, reference may be made to the above description of the first aspect of the present invention, which likewise also applies to the second aspect of the present invention.

[0171] Furthermore, according to a third aspect of the present invention, there is provided a packaged food product, especially a thermally processed food product containing fat and/or protein, preferably a food product containing a meat, which food product is packaged in a food packaging film of the present invention.

[0172] Regarding this aspect of the present invention, the food product is usually in direct contact with the inner layer, especially with the composite inner layer of the food packaging film and/or adheres to it.

[0173] With regard to further details of the third aspect of the present invention, reference may be made to the above explanations related to the other inventive aspects, which, in this way, also apply to the third aspect of the present invention.

[0174] Furthermore, according to a fourth aspect of the present invention, the present invention also relates to the use of a multilayer film of the present invention, as defined above, for the release and/or transfer of at least one food additive to a surface of a food product, wherein the multilayer film, preferably on its inner side, especially on the composite inner layer side, receives and/or is impregnated with at least one food additive, followed by packaging of a food product to be treated in the multilayer film thus provided and/or impregnated.

[0175] For this purpose, the food product is placed in direct contact with the inner layer, especially with the composite inner layer of the multilayer film and/or is adhered to it.

[0176] With regard to further details of the fourth aspect of the present invention, reference may be made to the above explanations related to the other inventive aspects, which, in this way, also apply to the fourth aspect of the present invention.

[0177] Furthermore, according to a fifth aspect of the present invention, the present invention also relates to the use of a food packaging film of the present invention, as defined above, for the release and/or transfer of at least one food additive to a surface of a food product.

[0178] To this end, the food product is packaged in the film for food packaging, in which the food product is especially placed in direct contact with the inner layer, especially with the composite inner layer of the film for food packaging and/ or is adhered to it.

[0179] With regard to further details of the fifth aspect of the present invention, reference may be made to the above explanations related to the other inventive aspects, which, in this way, also apply to the fifth aspect of the present invention.

[0180] Furthermore, according to a sixth aspect of the present invention, the present invention relates to a method for releasing at least one food additive onto a surface of a food product and/or for providing a surface of a product food additive with at least one food additive, the method comprising the following steps: (a) supplying and/or impregnating a multilayer film of the present invention as defined above, preferably on its inner side, especially the composite inner layer side, with at least one food additive; then (b) packaging (encapsulating) a food product to be treated in the multilayer film thus provided and/or impregnated, in particular by placing the food product to be treated in direct contact with the inner layer, especially the composite inner layer of the multilayer film ; then (c) releasing and/or transferring the at least one food additive to a surface of the food product packaged in the multilayer film, especially during cooking and/or processing of the food product.

[0181] Applying the inventive method, it is possible to easily provide food product surfaces with at least one food additive.

[0182] With regard to further details of the sixth aspect of the present invention, reference may be made to the above explanations related to the other inventive aspects, which, in this way, also apply to the sixth aspect of the present invention.

[0183] Further, in accordance with the seventh aspect of the present invention, there is provided a method for manufacturing a multilayer film of the present invention, as defined above, wherein the method comprises coextruding a plurality of individual inner layers for forming a composite inner layer, a plurality of individual outer layers for forming a composite outer layer, and an adhesive layer (binding layer) disposed between the composite inner layer and the composite outer layer, wherein coextrusion of the individual inner layers is carried out in the presence of at least one foaming agent, generating a plurality of voids in the individual inner layers and/or in the composite inner layer.

[0184] Generally, the at least one foaming agent can be selected from the group consisting of physical and chemical foaming agents, preferably chemical foaming agents, especially chemical foaming agents that release gaseous compounds, preferably selected from organic or inorganic carbonates, organic carboxylic acids and their esters, azo compounds, hydrazine derivatives, semicarbazides, tetrazoles and combinations thereof.

[0185] According to a preferred embodiment, the at least one foaming agent is a chemical foaming agent that releases gaseous compounds selected from a combination of carbonate and bicarbonate of alkaline or alkaline earth metals with an organic carboxylic acid or its esters, of preferably citric acid.

[0186] Particularly good results are obtained if the at least one foaming agent is used in amounts of 0.1 to 20% by weight, especially 0.5 to 10% by weight, particularly 1 to 6% by weight, with based on the weight of the co-extruded starting material of the individual inner layers.

[0187] In order to obtain an efficient porosity of the composite inner layer and individual inner layers, respectively, the coextrusion is carried out above the decomposition temperature of at least one foaming agent, thus leading to the release of gaseous compounds generating a multitude of voids in the individual inner layers and/or in the composite inner layer.

[0188] According to a common embodiment, the coextrusion is carried out using an annular die, especially a multilayer annular die. Especially, the annular matrix preferably comprises a plurality of ring-like channels, with each channel being assigned and/or corresponding to an individual layer of the multilayer film resulting from the present invention.

[0189] Optionally, according to a preferred embodiment of the inventive manufacturing method, coextrusion is followed by stretching, especially monoaxial or biaxial stretching, preferably biaxial stretching of the coextruded multilayer film of the present invention.

[0190] With regard to further details of the seventh aspect of the present invention, reference may be made to the above explanations related to the other inventive aspects, which, in this way, also apply to the seventh aspect of the present invention.

[0191] Finally, according to an eighth aspect of the present invention, the present invention also relates to a method for manufacturing an inventive food packaging film, as defined above herein, wherein the method comprises the following steps : (a) co-extruding a plurality of individual inner layers to form a composite inner layer, a plurality of individual outer layers to form a composite outer layer, and an adhesive layer (binding layer) disposed between the composite inner layer and the outer layer composite, in which the coextrusion of the composite inner layers is carried out in the presence of at least one foaming agent, generating a plurality of voids in the individual inner layers and/or in the composite inner layer, especially in such a way as to result in an inventive multilayer film as defined hereinabove; then (b) optionally stretching, especially monoaxial or biaxial stretching, preferably biaxial stretching of the coextruded multilayer film obtained in step (a); then (c) providing the resulting and optionally stretched multilayer film, preferably on its inner side, especially on the composite inner layer side, with at least one food additive.

[0192] According to a customary embodiment, the at least one foaming agent used in step (a) can be selected from the group consisting of physical and chemical foaming agents, preferably chemical foaming agents, especially chemical foaming agents that release gaseous compounds , preferably selected from organic or inorganic carbonates, organic carboxylic acids and their esters, azo compounds, hydrazine derivatives, semicarbazides, tetrazoles and combinations thereof.

[0193] Preferably, the at least one foaming agent used in step (a) may be a chemical foaming agent that releases gaseous compounds, selected from a combination of carbonate and bicarbonate of alkali or alkaline earth metals with an organic carboxylic acid or its esters, preferably citric acid.

[0194] According to a customary embodiment, the at least one foaming agent used in step (a) can be used in amounts of 0.1 to 20% by weight, in particular 0.5 to 10% by weight, in particular of 1 to 6% by weight, based on the weight of the starting material from the coextrusion of the individual inner layers.

[0195] Particularly, the coextrusion in step (a) is carried out above the decomposition temperature of at least one foaming agent, thus leading to the release of gaseous compounds generating a multitude of voids in the individual inner layers and/or in the composite inner layer .

[0196] According to a preferred embodiment, the coextrusion in step (a) is carried out using an annular die, especially a multilayer annular die, especially wherein the annular die may preferably comprise a plurality of ring-like channels, with each channel being assigned and/or corresponding to an individual layer of the resulting multilayer film.

[0197] With regard to step (c) of the inventive manufacturing method for inventive food packaging, in step (c) the multilayer film, preferably on its inner side, especially on the side of the composite inner layer, can be impregnated with o at least one food additive (generally by internal contact with the at least one food additive, for example by fluidization aggregation).

[0198] By the inventive manufacturing method for the inventive food packaging, the multilayer film, preferably on its inner side, especially on its composite inner layer, reversibly retains and/or absorbs the at least one food additive.

[0199] As described above with respect to other aspects of the present invention, the at least one food additive used in the inventive manufacturing method for the inventive food packaging may typically comprise a flavoring and/or coloring and/or flavoring food additive preferably especially in the form of an aqueous solution or dispersion, particularly a liquid smoke or caramel.

[0200] As described above also with respect to other aspects of the present invention, the amounts of the at least one food additive used in the manufacture of the inventive food packaging film may vary within wide ranges:

[0201] According to a common embodiment, the food packaging film can be provided with at least one food additive in amounts relative to weight, based on the total dry weight of the multilayer film, of at least 10% by weight, especially of at least 20% by weight, preferably at least 25% by weight, more preferably at least 30% by weight, even more preferably at least 40% by weight.

[0202] On the other hand, also according to another common embodiment of the present invention, the film for food packaging is provided with at least one food additive in relative amounts by weight, based on the total dry weight of the inventive multilayer film, of up to 50% by weight, especially up to 75% by weight, preferably up to 90% by weight, more preferably up to 100% by weight, even more preferably up to 150% by weight.

[0203] Generally, the food packaging film can be provided with at least one food additive in relative amounts by weight, based on the total dry weight of the inventive multilayer film, in the range of 10% to 150% by weight, especially in the in the range from 20% to 130% by weight, preferably in the range from 25% to 120% by weight, more preferably in the range from 30% to 115% by weight, even more preferably in the range from 40% to 110% by weight Weight.

[0204] With regard to further details of the eighth aspect of the present invention, reference may be made to the above explanations related to the other inventive aspects, which, accordingly, also apply to the eighth aspect of the present invention.

[0205] Hereinafter, the present invention will be described in more detail using preferred embodiments and figures. In relation to the explanation of these preferred embodiments, which, however, are in no way restrictive regarding the present invention, additional advantages, particularities, properties, aspects and characteristics of the present invention will also be shown.

[0206] In the figures:

[0207] Figs. 1, 1A and 1B show schematic cross-sectional views of various inventive multilayer films of the present invention, in accordance with particular embodiments;

[0208] Figs. 2A, 3A, 4A show transmitted light micrographs of inner layer composites, especially food contact inner layer composites, of three different multilayer films of the present invention, according to three particular embodiments;

[0209] Figs. 2B, 3B, 4B show the corresponding binary images (inverted color or negative, respectively) of transmitted light micrographs shown in Figs. 2A, 3A, 4A;

[0210] Figs. 2C, 3C, 4C show the corresponding results of the void size analysis of the inner layer composites, especially the inner food contact layer composites, of the three different inventive multilayer films whose transmitted light micrographs are shown in Figs. . 2A, 3A, 4A;

[0211] Fig. 5A shows the frequency distribution of void space sizes (in mm 2 ) of different inventive multilayer films according to a particular embodiment;

[0212] Fig. 5B shows the percent cumulative distribution of the void area size distribution (in mm 2 ) of different inventive multilayer films according to a particular embodiment;

[0213] Fig. 6 shows a typical course of a process of an inventive manufacturing method for producing an inventive multilayer film or an inventive food packaging film, respectively, according to a particular embodiment.

[0214] Figs. 1, 1A and 1B show schematic cross-sectional views of various inventive multilayer films of the present invention, in accordance with particular embodiments. Especially, Figs. 1, 1A, 1B show schematic cross-sectional views of inventive multilayer films 1, especially thermoplastic multilayer films, particularly to be used for food packaging.

[0215] Fig. 1 shows a schematic cross-sectional view of an inventive multilayer film 1, especially a thermoplastic multilayer film, particularly to be used for food packaging, where the multilayer film 1 comprises at least three layers and/or composite layers 2, 3, 4 ; 2a, 2b, 2c; 3a, 3b, 3c, especially at least three polymeric and/or composite layer layers, namely: (A) a composite inner layer 2, especially a food contact composite inner layer, wherein the composite inner layer 2 comprises a plurality of individual inner layers 2a, 2b, 2c bonded and/or adhered to each other, especially co-extruded with each other, wherein the individual inner layers 2a, 2b, 2c are each composed of at least one polymer foam comprising at least one polyolefin and wherein the individual inner layers 2a, 2b, 2c each comprise a plurality of voids, especially open cells or pores, capable of reversibly retaining and/or absorbing at least one food additive; (B) a composite outer layer 3, wherein the composite outer layer 3 comprises a plurality of individual outer layers 3a, 3b, 3c bonded and/or adhered to each other, especially co-extruded with each other, wherein the individual outer layers 3a, 3b, 3c each comprise at least one polyamide; (C) an adhesive layer (binding layer) 4 arranged between the inner composite layer 2 and the outer composite layer 3, specially adhered and/or co-extruded with the inner composite layer 2 and the outer composite layer 3. The specific embodiment shown in Fig. 1 relates to an inventive multilayer film 1 comprising: a composite outer layer 3 comprising three individual outer layers 3a, 3b, 3c; an adhesive layer (binding layer) 4 disposed between the outer composite layer 3 and the inner composite layer 2; and a composite inner layer 2 comprising three individual inner layers 2a, 2b, 2c.

[0216] Fig. 1A shows a schematic view of a cross-section of an inventive multilayer film 1, especially a thermoplastic multilayer film, particularly to be used for food packaging, according to another particular embodiment. The specific embodiment shown in Fig. 1A relates to an inventive multilayer film 1 comprising: a composite outer layer 3 comprising two individual outer layers 3a, 3b bonded and/or adhered to each other, especially co-extruded with each other, wherein the individual outer layers 3a, 3b, each comprises at least one polyamide; an adhesive layer (binding layer) 4 (which is disposed between the outer composite layer 3 and the inner composite layer 2); and, finally, a composite inner layer 2, especially a food contact composite inner layer, comprising four individual inner layers 2a, 2b, 2c, 2d bonded and/or adhered to each other, especially co-extruded with each other, with each one of the individual inner layers 2a, 2b, 2c, 2d being composed of at least one polymer foam comprising at least one polyolefin and with each of the individual inner layers 2a, 2b, 2c, 2d comprising a plurality of voids, especially cells open or porous, capable of reversibly retaining and/or absorbing at least one food additive; wherein all layers 2a, 2b, 2c, 2d, 3a, 3b, 4 and/or all composite layers 2, 3, respectively, are co-extruded and/or adhered to each other.

[0217] Fig. 1B shows a schematic view of a cross-section of an inventive multilayer film 1, especially a thermoplastic multilayer film, particularly to be used for food packaging, according to yet another particular embodiment. According to this particular embodiment, the inventive multilayer film 1 additionally comprises at least one additional layer 4a arranged between the composite inner layer 2 and the adhesive layer 4, specially adhered and/or co-extruded with the composite inner layer 2 and the composite layer 4. adhesive 4 on its opposite sides. Preferably, the additional layer 4a can be a continuous layer, especially a uniform and/or homogeneous and/or continuous and/or non-foam layer, particularly without voids. As previously explained, this particular modality provides additional advantages, on the one hand, by the presence of the additional and preferably continuous layer disposed between the inner composite layer and the adhesive layer, the adhesion is improved, since a continuous layer provides a better adhesion of the than a layer of foam and not continuous; on the other hand, the presence of the additional and preferably continuous layer also improves the barrier properties of the invention, especially the water vapor barrier properties. The specific embodiment shown in Fig. 1B relates to an inventive multilayer film 1 comprising: a composite outer layer 3 comprising two individual outer layers 3a, 3b bonded and/or adhered to each other, especially co-extruded with each other, wherein the individual outer layers 3a, 3b, each comprises at least one polyamide; an adhesive layer (binding layer) 4 (which is disposed between the outer composite layer 3 and the additional layer 4a); an additional and preferably continuous layer 4a (which is arranged between the adhesive layer 4 and the inner composite layer 2); and, finally, a composite inner layer 2, especially a food contact composite inner layer, comprising three individual inner layers 2a, 2b, 2c bonded and/or adhered to each other, especially co-extruded with each other, with each of individual inner layers 2a, 2b, 2c being composed of at least one polymer foam comprising at least one polyolefin and with each of the individual inner layers 2a, 2b, 2c comprising a plurality of voids, especially open cells or pores, capable of retain and/or reversibly absorb at least one food additive; wherein all layers 2a, 2b, 2c, 3a, 3b, 4, 4a and/or all composite layers 2, 3, respectively, are co-extruded and/or adhered to each other.

[0218] Figs. 2A, 3A, 4A show transmitted light micrographs micrographs of composite inner layers, especially food contact composite inner layers of three different multilayer films of the present invention, according to three particular embodiments, while Figs. 2B, 3B, 4B show the corresponding binary images (inverted color or negatives, respectively) of the transmitted light micrographs shown in Figs. 2A, 3A, 4A. As can be seen in these figures, the voids of the inner composite layers or the individual inner layers are, respectively, voids, especially in the form of open cells or pores. The composite inner layers or the individual inner layers, respectively, are each in the form of a rigid, solidified or stiffened foam with open voids, especially having an irregular and/or random structure of the net, screen, mesh, lattice type , or alveolar, with respect to a two-dimensional projection plane of the foam. Particularly, the empty spaces are entirely surrounded and/or delimited by walls composed of the polymer comprising at least one polyolefin.

[0219] Figs. 2C, 3C, 4C show the results of the analysis of the size of the voids corresponding to the inner composite layers, especially the inner composite food contact layers of the three different inventive multilayer films, whose transmitted light micrographs are shown in Figs. 2A, 3A, 4A, wherein Fig. 5A shows the frequency distribution of the sizes of void areas (in mm 2 ) of different inventive multilayer films according to a particular embodiment, and Fig. 5B shows the cumulative percent distribution of void area sizes (in mm 2 ) of different inventive multilayer films according to a particular embodiment.

[0220] As can be seen in these figures, the voids of the individual inner layers each have absolute cross-section sizes with reference to a two-dimensional projection plane in the range of 0.001 to 10 mm2, especially in the range of 0.005 to 8 mm2, preferably in the range of 0.01 to 7 mm2, as determined by digital image processing of two-dimensional micrographs of the individual inner layers of the composite inner layer. In particular, 30% to 80% of the voids have absolute cross-sectional sizes of less than 1.0 mm2, especially less than 0.8 mm2. In particular, 70% to 95% of the voids have absolute cross-sectional sizes of less than 3 mm2, especially less than 1.5 mm2. As can be seen from these figures, the voids of the individual inner layers each have absolute cross-sectional sizes, with reference to a two-dimensional plane of projection, in the range of 0.001 to 5 mm2, especially in the range of 0.005 to 2 mm2 , preferably in the range of 0.01 to 1 mm 2 , as determined by digital image processing of two-dimensional micrographs of the individual inner layers. Especially, the voids of the individual inner layers comprise, as a whole, from 10% to 80%, especially from 20% to 70%, preferably from 30% to 60% of the surface area of the individual inner layers, with reference to a two-dimensional plane of projection, determined by digital image processing of two-dimensional micrographs of the individual inner layers.

[0221] Finally, Fig. 6 shows a typical process diagram of one of an inventive manufacturing method for producing an inventive multilayer film or an inventive food packaging film, respectively, according to a particular embodiment.

[0222] According to a particular embodiment shown in Fig. 6, an inventive multilayer film can be produced using a triple bubble method, known in particular for the production of oriented shrink wrappers for sausages. By this method, a multilayer primary tube can be formed by melt extrusion through a multilayer annular die. It can be a multi-layer array (eg six, seven, eight, etc. layers) providing the required numbers and ratios of layers. Resins or resin blends can be fed from feed hoppers into single screw extruders, where the resins are plasticized and thermally extruded through the annular die. Extrusion temperatures are configured appropriately for the resins or resin blends used in each particular layer. A mixture of polyethylene and foaming aid is fed to two, three or more inner layers, based on an available die design. The extruded tube can be quenched by quenching in water as it passes through a caliper of a given size. The temperature of the coolant (eg water) is significantly lower than the temperature of the molten primary tube, i.e. this is crucial for creating sufficient amorphous areas in the polymers for further stretching. Refrigeration temperature is preferably in the range of 4 to 15 °C. The cooled primary tube is collapsed and drawn through the heating zone to obtain its stretching temperature, which is equal to or several degrees centigrade above the glass transition temperature of the polymers used in the film composition. The reheated primary tube can be radially expanded in the transverse direction (DT), e.g. e.g., using air bubbles trapped between two pinch rollers, and drawn in the machine direction (DM), e.g., using a faster drag pinch roller speed. The simultaneous expansion and stretching of the tube can be accompanied by an extreme, i.e. rapid, thickness reduction. This allows obtaining good mechanical properties, shrinkage and glossy appearance of the final casing. Additionally, stretching the inner foam layers increases voids or cell size from microns in the primary tube to millimeters. A typical range of orientation ratios may be, for example, 2.0 to 2.6 in the transverse direction (DT) and 3.0 to 3.5 in the machine direction (DM). The extended tube is brought into contact with a stream of cooling air, the temperature of which is at least several degrees lower than the temperature of the tube. The high-velocity air stream is blown in the same direction as the tube moves. The collapsed and cooled tube is filled again with air between the two following pressure rollers, to obtain an air bubble that is placed in the annealing furnace where the temperature is defined by means of infrared heaters or with hot air. The temperature is a function of the velocity and the diameter of the tube. The film is relaxed, for example, from 10% to 20% in flat width and from 2% to 20% in longitudinal direction. Relaxation stops free shrinkage and relieves internal tensions in the film. Tube diameter is controlled by adjusting the length of the annealing bubble to provide stable flat width within the required tolerance. The extended tube is brought into contact with a stream of cooling air, the temperature of which is at least several degrees lower than the temperature of the tube. The high-velocity air stream is blown in the same direction as the tube moves. The collapsed film is wound onto the core with a controlled tension. The film reel of the invention with an inner layer of foam is placed on the unwinder of the apparatus for coating an inner surface of several tubular films with aqueous color and smoke solutions. The flat film is pulled through two pressure rollers, between which the tube is filled with a bubble of aqueous solution. The amount of food additive solution that is absorbed by the film is adjusted by the pressure of the upper pressure roller and depends on the roller design. The flat film is impregnated with a certain solution of the food additive and wound onto the core under controlled tension.

[0223] As shown in Fig. 6, inventive multilayer films according to this specific embodiment are produced on a triple bubble line, i.e. by a known method, in particular oriented towards the production of oriented shrink wrappers for sausages. This includes the following main steps: (a) melting, mixing and homogenizing the polymers in an extruder followed by extruding the molten plastic through an annular die and then rapid cooling of the primary tube in the water calibrator. (It is important here to cool the plastic as quickly as possible to create enough amorphous areas in the polymer for further stretching. Cooling temperature is typically 4 to 10 °C); (b) preheating the main tube in a water bath to obtain the glass transition temperature for the orientation (the water temperature is 75 to 85 °C); (c) biaxial orientation or stretching of the polymeric film necessary to obtain good mechanical properties, thickness, shrinkage, gloss, etc. (The stretch factor in DM is 2.0 to 2.6 and in DT it is 3.0 to 3.5); (d) annealing (controlled relaxation to relieve internal tensions of the film.); (e) winding on cores. Typically, the inventive multilayer films produced are in most cases 7-layer films (i.e. two outer layers of PA, an adhesive layer and three inner layers containing voids of PE). Particularly, it is preferred to produce such an internal foam structure as a structure of at least 3 layers.

[0224] The outer layers may comprise polyamides (for example, polyamide 6, polyamide and/or polyamide 6.66 and/or other aromatic polyamides or copolyamides or mixtures thereof). They may optionally contain 5% to 10% amorphous copolyamide (e.g. PA 6I/6T) as a processing aid. It is preferred that the minimum total thickness of all outer layers be about 50% of the total film thickness, as this is advantageous for the stability of the extrusion process (i.e. bubble breaks, size stability, etc.) and for sufficient mechanical properties and barrier properties of the wrapper.

[0225] The adhesive interlayer may comprise polyethylene grafted with maleic anhydride. It is preferred that the layer thickness is 5% to 10% of the film thickness to provide sufficient interlayer adhesion.

[0226] The inner composite layer of foam is based on polyolefins (for example, low density polyethylenes, in particular in a mixture with 1% to 10% of a chemical foaming agent). It is preferred to obtain relatively high thicknesses of this composite inner layer to provide sufficient depth to the void spaces, especially cells and pores, and consequently their volumes. The composite inner layer is composed of at least two, preferably at least three, thinner individual layers, which provide an overlapping pattern of the foam layers, thus creating a more sophisticated cellular structure capable of retaining greater amounts of aqueous additive solutions. preferred foods, probably due to the capillary effect (without getting hung up on that theory).

[0227] In Fig. 6, reference numerals 5a, 5b and 5c designate the first bubble, second bubble and third bubble, respectively, while reference numeral 6 designates the plurality of extruders, reference numeral 7 designates rapid cooling and water calibration and the reference number 8 designates the film blowing head. In Fig. 6, the heating bath 9 is followed by an orientation unit (stretching unit) 10, a width measuring device 11 and a thermosetting unit 13, followed by cooling through a cooling ring 14 supplied with cold air by a cold air blower 12. The inventive multilayer film produced is then wound onto rolls through a winder 15.

[0228] Configurations, adaptations, variations, modifications, peculiarities, particularities and additional advantages of the present invention are immediately apparent and implementable by a person skilled in the art, by reading or studying the present application, without departing from the scope of the present invention.

[0229] The present invention will be illustrated in the following by the various examples that will be described below, but which are not intended to limit the present invention in any way.

EXAMPLES: General description of the manufacturing method for the inventive examples

[0230] All inventive and comparative films are produced in a production unit shown in Fig. 6 and according to a manufacturing method as described above.

[0231] All inventive thermoplastic multilayer films produced comprise (A) a composite inner layer, i.e. a food contact composite inner layer comprising a plurality of individual inner layers (usually 2 - 4 individual inner layers) bonded to each other and each being composed of at least one polymer foam comprising at least one polyolefin, (B) a composite outer layer comprising a plurality of individual outer layers (generally 2 individual outer layers) bonded together and each comprising at least one polyamide and finally (C) an adhesive layer (binding layer) disposed between the inner composite layer on the one hand and the outer composite layer on the other.

[0232] All of the inventive and comparative multilayer films are produced by a coextrusion method as described hereinabove, using an annular ring die comprising a plurality of ring-like channels, each channel being assigned to a single layer of the resulting multilayer film.

[0233] All multilayer films produced have total thicknesses in the range of 75 to 300 μm, with individual inner layers ranging from 7.5 to 25 μm each and individual outer layers ranging from 5 to 50 μm each, however, with the condition that the composite outer layer composed of the various individual outer layers constitute at least 50% of the total film thickness and the composite inner layer composed of the various individual inner layers constitute at least 25% of the total film, while the adhesive layer varies from 3 to 20 micrometers thick and typically comprises 5% to 15% of the total film thickness.

[0234] All inventive multilayer films produced have the following structure (from the inside out): (A) a food contact composite inner layer (composed of 2 or more individual inner layers containing porous PE foam) / (C) adhesive layer (composed of 1 layer) / (B) composite outer layer (composed of two or more individual outer layers containing PA).

[0235] The polyolefin used for the individual foam inner layers is especially LLDPE (eg DOWLEXTM 2740G from Dow Chemical Company), especially with a density of about 0.940 g/cm 3 (ASTM D792). Before coextrusion, this polyolefin is mixed with 3% by weight to 10% by weight of a chemical foaming agent (CFA), preferably based on a carbonate or bicarbonate with citric acid (for example, Hydrocerol® 591 from Clariant International, Ltd.).

[0236] The polyamide used for the individual outer layers is especially a polyamide 6.66 copolymer (for example, UBE 5033 FDX57 from UBE Engineering Plastics SA) and/or a polyamide 6 (for example, Akulon® F136-C1 from DSM Engineering Plastics or UBE 1030B from UBE Engineering Plastics S.A.), optionally blended with a partially aromatic polyamide such as polyamide 6I/6T (e.g. Grivory® G-21 from EMS Grivory).

[0237] The adhesive used for the individual intermediate adhesive layer is especially an elastomeric or thermoplastic polyethylene, especially a polyethylene modified with rubber and/or grafted with maleic anhydride (for example Admer® AT1955A from Mitsui Chemicals America, Ltd.).

[0238] The impregnation and/or coating of the inner sides of all inventive and comparative multilayer films with a food additive such as caramel or liquid smoke, is carried out by slugging, as is well known in the prior art .

[0239] All properties, parameters, etc., indicated for the films obtained are determined by usual and well-known methods, especially by standardized methods as indicated above for the various parameters.

[0240] A schematic cross-sectional view of the inventive thermoplastic multilayers produced in the examples is given in Fig. 1, while Figs. 2A, 3A and 4A show microscopic views of the inner food contact layers of various inventive multilayer films.

[0241] The results obtained are discussed below; in particular, the relevant results obtained with respect to the various films produced are indicated in the respective tables below.

Examples from Serie A

[0242] Three inventive multilayer films (Films No. A1, A2 and A3) with the following film structure are produced: (A) a composite inner layer of porous food contact foam (composed of 4 individual inner layers containing foam of porous PE) / (C) adhesive layer (composed of 1 layer) / (B) composite outer layer (composed of 2 individual outer layers containing PA). The properties are indicated in Table 1.

[0243] Loading with food additive (aqueous caramel solution or liquid smoke) through the impregnation method by aggregative fluidization ("slugging") leads to the absorption of 61% to 77% by weight of the food additive, based on dry weight of the multilayer film. Comparative films comprising an individual inner layer of porous foam of the same overall thickness have reduced load capacity; additional comparative films based on cellulose also provide only 50% to 70% by weight feed additive filler. Table 1 Med.= mean nd = not determined

Examples from Series B

[0244] Five inventive multilayer films (Films No. B1 to B5) with the following film structure are produced: (A) a composite inner layer of porous food contact foam (composed of 4 individual inner layers containing PE foam porous) / (C) adhesive layer (composed of 1 layer) / (B) composite outer layer (composed of 2 individual outer layers containing PA). Loading with food additive (aqueous caramel solution) via the slugging method leads to an absorption of 52% to 104% by weight of the food additive, based on the dry weight of the multilayer film. The properties are indicated in Table 2.

Examples from Series C

[0245] Various other inventive and comparative multilayer films are produced, which can also be loaded with a food additive (for example, aqueous caramel solution or liquid smoke) by the method of aggregative fluidization. The results obtained are indicated in the respective Tables 3A to 3L (in which layer thicknesses are indicated in micrometers, densities are indicated in g/cm3 and all percentages are based on weight, unless otherwise indicated and where the Med. indicates average). Table 3A Multilayer film with 7 layers Table 3B Multilayer film with 7 layers Table 3C Multilayer film with 7 layers Table 3D Multilayer film with 5 layers (comparative) Table 3E Multilayer film with 5 layers (comparative) Table 3F Multilayer film with 7 layers Table 3G Multilayer Film with 5 layers (comparative) Table 3H Multilayer film with 5 layers (comparative) Table 3I Multilayer film with 5 layers (comparative) Table 3J Multilayer film with 5 layers (comparative) Table 3K Multilayer film with 5 layers (comparative) Table 3L Multilayer film with 5 layers (comparative)

Examples from Series D

[0246] Other inventive and comparative multilayer films with the following film structure are produced (see Tables 4A and 4B). Table 4A Structure of 7 layers (inventive) Table 4B 5-layer structure (comparative) Table 4C 7-layer structure (inventive)

Examples from the E Series

[0247] Two inventive multilayer films (Films No. E1 and E2) with the following film structure are produced: (A) a composite inner layer of porous food contact foam (composed of 3 individual inner layers containing porous PE foam ) / (C) adhesive layer (composed of 1 layer) / (B) composite outer layer (composed of 2 individual outer layers containing PA). Charging with water leads to good absorption. The properties are indicated in Table 5. Table 5

Examples from the F Series

[0248] Five additional inventive multilayer films (Films No. F1 to F5) with the following film structure are produced: (A) a composite inner layer of porous food contact foam (composed of 3 individual inner layers containing foam of porous PE) / (C) adhesive layer (composed of 1 layer) / (B) composite outer layer (composed of 2 individual outer layers containing PA). Filling with food additive (aqueous caramel solution) by the fluidization aggregative impregnation method leads to good absorption of the food additive. The properties are indicated in Table 6. Table 6 List of reference numbers: 1 multilayer film, especially thermoplastic multilayer film 2 composite inner layer 2a, 2b, 2c, 2d individual (inner) composite inner layer layers 3 composite outer layer 3a, 3b, 3c individual (outer) layer layers composite outer 4 adhesive layer (= bonding layer) 5 the additional, preferably continuous layer 5a, 5b, 5c first bubble, second bubble, third bubble 6 plurality of extruders 7 rapid cooling and water calibration 8 film blowing head 9 heating bath 10 orientation (stretch) unit 11 width measuring device 12 cold air blower 13 thermosetting unit 14 cooling ring 15 winder

Claims (17)

1. Multilayer film (1), especially a thermoplastic multilayer film, particularly for use in food packaging, characterized in that the multilayer film (1) comprises at least three layers and/or composite layers (2, 3, 4; 2a, 2b, 2c; 3a, 3b, 3c), especially at least three polymeric layers and/or composite layers: (A) a composite inner layer (2), especially a food contact composite inner layer, wherein the The inner composite (2) comprises a plurality of individual inner layers (2a, 2b, 2c) co-extruded with each other, wherein the individual inner layers (2a, 2b, 2c) are each composed of at least one foam of polymer comprising at least one polyolefin and wherein the individual inner layers (2a, 2b, 2c) each comprise a plurality of voids, especially open cells or pores, capable of reversibly retaining and/or absorbing at least one food additive, wherein the multiplicity of voids is generated by coextruding the individual inner layers (2a, 2b, 2c) in the presence of at least one chemical foaming agent which releases gaseous compounds; (B) a composite outer layer (3), wherein the composite outer layer (3) comprises a plurality of individual outer layers (3a, 3b, 3c) co-extruded with each other, wherein the individual outer layers (3a, 3b , 3c) each comprise at least one polyamide; (C) an adhesive layer (binding layer) (4) arranged between the inner composite layer (2) and the outer composite layer (3) wherein the adhesive layer (4) is co-extruded with the inner composite layer (2) and the composite outer layer (3). 2. Multilayer film, according to claim 1, characterized in that the multilayer film (1) of the present invention has a shrinkage value (retraction) in the range of 10% to 70%, especially from 20% to 60% , preferably from 30% to 50%, at a temperature of 90 °C in the longitudinal and/or transverse direction, preferably in both the longitudinal and transverse directions, particularly determined as unrestricted shrinkage at a temperature of 90 °C (water bath ) for 10 sec. 3. Multilayer film, according to any one of the preceding claims, characterized in that the multilayer film (1) has an oxygen transmission rate (O2 transmission rate) in the range of 1 to 90 cm3/m2/24 hours, especially in the range 5 to 80 cm3/m2/24 hours, preferably in the range 10 to 75 cm3/m2/24 hours, more preferably in the range 20 to 65 cm3/m2/24 hours, at a pressure of 1 atmosphere (101.325 kPa) and a temperature of 23 °C, especially as determined in accordance with ASTM D-3985-81; wherein the multilayer film (1) has a water vapor transmission rate (WVTR) in the range of 5 to 500 g/m2/24 hours, especially in the range of 10 to 400 g/m2/24 hours, preferably in the range of 25 to 300 g/m2/24 hours, more preferably in the range of 50 to 250 g/m2/24 hours especially as determined in accordance with ASTM F1249-06. 4. Multilayer film, according to any one of the preceding claims, characterized in that the multilayer film (1) has a tensile strength in the longitudinal and/or transverse direction, preferably in both the longitudinal and transverse directions, in the range 15 to 100 MPa, especially in the range 20 to 80 MPa, preferably in the range 25 to 75 MPa, more preferably in the range 30 to 60 MPa, especially as determined in accordance with ASTM D-882, Method A; wherein the multilayer film (1) has an elongation at break in the longitudinal and/or transverse direction, preferably in both the longitudinal and transverse directions, in the range of 20 to 300%, especially in the range of 40 to 200%, preferably in the range of 60 to 175%, more preferably in the range of 75 to 160%, especially as determined in accordance with ASTM D-882, Method A. 5. Multilayer film, according to any one of the preceding claims, characterized in that the multilayer film (1) has a modulus (of elasticity) in the longitudinal and/or transverse direction, preferably in both the longitudinal and transverse directions, in the range 100 to 400 MPa, especially in the range 150 to 400 MPa, preferably in the range 175 to 375 MPa, more preferably in the range 200 to 350 MPa, especially as determined from the respective tensile stroke. 6. Multilayer film, according to any one of the preceding claims, characterized in that the composite inner layer (2) comprises from 20% to 50%, especially from 25% to 45% and preferably from 30% to 40% the total thickness of the multilayer film (1); and/or wherein the composite inner layer (2) has a total thickness in the range of 5 to 200 micrometers, especially in the range of 7.5 to 100 micrometers, preferably in the range of 10 to 75 micrometers, more preferably in the range from 12.5 to 50 micrometers, even more preferably in the 20 to 40 micrometer range. 7. Multilayer film, according to any one of the preceding claims, characterized in that the composite outer layer (3) comprises from 45% to 90%, especially from 50% to 80%, preferably from 55% to 70% the total thickness of the multilayer film (1); and/or wherein the composite outer layer (3) has a total thickness in the range of 5 to 300 micrometers, especially in the range of 10 to 150 micrometers, preferably in the range of 12.5 to 100 micrometers, more preferably in the range from 15 to 75 micrometers, even more preferably in the 20 to 50 micrometer range. 8. Multilayer film, according to any one of the preceding claims, characterized in that the multilayer film (1) has a load capacity relative to weight (absorption capacity), with respect to at least one food additive, based on on the total dry weight of the multilayer film (1), in the range from 10% to 150% by weight, especially in the range from 20% to 130% by weight, preferably in the range from 25% to 120% by weight, more preferably in the range of 30% to 115% by weight, even more preferably in the range of 40% to 110% by weight. 9. Multilayer film according to any one of the preceding claims, characterized in that the at least one food additive comprises a flavoring and/or coloring and/or odor producing food additive, preferably especially in the form of an aqueous solution or dispersion, particularly a liquid smoke or caramel. 10. Multilayer film, according to any one of the preceding claims, characterized in that the various individual inner layers (2a, 2b, 2c) the same or different and independently of each other, each comprises at least one polymer, copolymer or polyolefin terpolymer, especially at least one polyethylene polymer, copolymer or terpolymer, especially selected from the group consisting of LDPE, LLDPE, VLDPE, as well as mixtures and copolymers and terpolymers thereof, particularly copolymers and terpolymers with C3-C10-alpha-olefins or alkyl (meth)acrylates; and/or wherein the various individual inner layers (2a, 2b, 2c) the same or different and independently of one another, each comprises at least one polyolefin, in particular at least one polyolefin polymer, copolymer or terpolymer having a density in the range of 0.910 to 0.940 g/cm3, especially as determined in accordance with ASTM D792; and/or in which the various individual inner layers (2a, 2b, 2c), the same or different and independently of one another, each comprise at least 60% by weight, especially at least 75% by weight, preferably at least 80% by weight, more preferably at least 85% by weight, even more preferably at least 90% by weight, even more preferably at least 95% by weight of the at least one polyolefin, especially of the at least one polymer, copolymer or terpolymer polyolefin, based on the total dry weight of the respective individual inner layer (2a, 2b, 2c). 11. Multilayer film according to any one of the preceding claims, characterized in that the voids of the individual inner layers (2a, 2b, 2c) are open voids, especially in the form of open cells or pores. 12. Multilayer film, according to any one of the preceding claims, characterized in that the various individual outer layers (3a, 3b, 3c), whether they are the same or different and independently of each other, each comprises at least one polyamide , particularly at least one polyamide polymer, copolymer or terpolymer, especially one selected from the group consisting of aliphatic, semi-aromatic and aromatic polyamides, as well as mixtures thereof, particularly selected from the group consisting of PA 6, PA 66, PA 6.66, PA 6.11, PA 6.12, PA 11 and PA 12, as well as mixtures thereof, optionally combined with at least one amorphous polyamide or copolyamide such as PA 6I/6T; and/or in which the various individual outer layers (3a, 3b, 3c), the same or different and independently of one another, each comprises at least 70% by weight, especially at least 75% by weight, preferably at least 80% by weight, more preferably at least 85% by weight, even more preferably at least 90% by weight, even more preferably at least 95% by weight of the at least one polyamide, based on the total dry weight of the respective outer layer individual (3a, 3b, 3c). 13. Multilayer film according to any one of the preceding claims, characterized in that the composite outer layer (3) comprises at least two individual outer layers (3a, 3b), particularly exactly two individual outer layers (3a, 3b) , whose individual outer layers (3a, 3b) are bonded and/or adhered to each other by co-extrusion and/or whose individual outer layers (3a, 3b), independently of one another, each comprise at least one polyamide, particularly at least a polyamide polymer, copolymer or terpolymer, especially one selected from the group consisting of aliphatic, semi-aromatic and aromatic polyamides, as well as mixtures thereof, particularly selected from the group consisting of PA 6, PA 66, PA 6.66, PA 6.11, PA 6.12, PA 11 and PA 12, as well as mixtures thereof, optionally combined with at least one amorphous polyamide or copolyamide such as PA 6I/6T; and wherein the composite inner layer (2) comprises at least four individual inner layers (2a, 2b, 2c, 2d), in particular exactly four individual inner layers (2a, 2b, 2c, 2d), whose individual inner layers (2a, 2b, 2c, 2d) are bonded and/or adhered to each other by coextrusion and/or whose individual inner layers (2a, 2b, 2c, 2d), independently of one another, each comprise at least one polymer, copolymer or terpolymer polyolefinic, especially at least one polyethylene polymer, copolymer or terpolymer, specially selected from the group consisting of LDPE, VLDPE, LLDPE, as well as mixtures and copolymers and terpolymers thereof, particularly copolymers and terpolymers with C3-C10-alpha-olefins or ( alkyl meth)acrylates, and/or whose individual inner layers (2a, 2b, 2c, 2d), independently of one another, each comprise at least one polyolefin, especially at least one polyolefin polymer, copolymer or terpolymer having a density in the range of 0.910 to 0.940 g/cm3, especially as determined in accordance with ASTM D792. 14. Food packaging film characterized by being able to release and/or transfer at least one food additive to a surface of a food product packaged therein, wherein the food packaging film comprises a multilayer film (1) as defined in according to any one of claims 1 to 13, wherein the multilayer film (1), preferably on its inner side, especially on the composite inner layer (2) side, is provided with at least one food additive. 15. Film for food packaging, according to claim 14, characterized in that the multilayer film (1), preferably on its inner side, especially on the side of the composite inner layer (2), is impregnated with at least a food additive; and/or wherein the multilayer film (1), preferably its inner side, especially its composite inner layer (2), reversibly retains and/or absorbs at least one food additive. 16. Use of a multilayer film (1) according to any one of claims 1 to 13, characterized in that it is for the release and/or transfer of at least one food additive on a surface of a food product, in which the multilayer film (1), preferably on its inner side, especially on the composite inner layer side (2), is provided with and/or is impregnated with at least one food additive, followed by packaging a food product to be treated in the multilayer film (1) so provided and/or impregnated. 17. Method for releasing and/or transferring at least one food additive to the surface of a food product and/or for providing at least one food additive to the surface of a food product, characterized in that the method comprises the following steps: (a ) supplying and/or impregnating a multilayer film (1) as defined according to any one of claims 1 to 13, preferably on its inner side, especially the side of the composite inner layer (2), with at least one food additive; then (b) packaging a food product to be treated in the multilayer film (1) thus provided and/or impregnated, especially placing the food product to be treated in direct contact with the inner layer, especially with the composite inner layer (2 ) of the multilayer film (1); then (c) releasing and/or transferring the at least one food additive onto a surface of the food product packed in the multilayer film (1), especially during cooking and/or processing of the food product.