MXPA01001367A - Gas-tight laminating film and packaging material produced therefrom - Google Patents

Abstract

The invention relates to a sealable, multilayer laminating film constructed of at least 6 layers essentially made of thermoplastic synthetic materials having an inner layer made of ethylene/vinyl alcohol copolymer (EVOH). The invention also relates to a packaging material which contains this laminating film as a sealing layer, and to the use thereof.

Description

Film: gas tight and gasket materials produced from the same Description of the Invention The present invention relates to a multi-laminated film-heat seal layer composed of at least substantially six layers of thermoplastic polymers with an inner layer of ethylene / vinyl alcohol copolymer (EVOH), and for a packaging material containing the laminated film as a thermal sealing coating. The invention also covers packaging materials containing such a laminated film as a thermal seal coating. The invention also provides the use of laminated film and packaging materials that contain it for the production of packaging, and the use of packaging for packaging food and other articles. Many articles require protection of the surrounding air c from the surrounding atmosphere to be transported and / or stored. Therefore, they must be packaged in a way that is adequate to exclude as completely as possible all or certain constituents of the surrounding atmosphere. A particularly critical constituent of the atmosphere Ref: 126400 surrounding is oxygen. The presence of oxygen could, for example, in many packaged products, such as, for example, food, lead to spoilage by oxidation or the growth of bacteria, which likewise spoil the packaged product. In many cases, such packages are produced by heat sealing one or more conventional packaging materials for packaging, for example, a bag or a container lid. In doing so, the packaged material is firmly sealed by melting the heat seal coating, in the example of the bag, against itself or, in the case of a packaging lid, against the heat sealing coating. of other packaging material. It produces a thermal seal union that seals the packaging. In many cases, the thermal seal union must meet many stringent requirements. The heat sealing joint must be capable of absorbing high mechanical stresses caused by the contents of the container, transport or other influences. In many cases this applies immediately after sealing when the heat seal union is still hot. For example, in sealing machines also called vertical filling, the contents are introduced into the tube formed when the transverse sealing instrument is still closed, for reasons of time. When the sealing jaws are opened, the total weight of the content presses into the heat sealing union that has not yet cooled and thus exposes the latter to a tension stress. In other cases, even without external stress, a similar type of charge in the still hot heat seal union could occur only due to the elasticity of the packaging material, for example, when a fold is sealed or in the wrapping region of the packaging material. If the cohesion of the heat seal union is very low, the joint will rise in such cases and consequently the packaging will fail. The strength of the joint in the hot state, immediately after sealing, is usually called hot tack. Hot elevated adhesiveness is an important prerequisite for high packaging speeds in cases of the type described above. A method of measuring the property of hot adhesiveness is to give the connection with the examples according to the invention. In qualitative terms, the measurement is made by placing two sections of packaging material in contact with a defined pressure at a certain temperature and for a given time and then, while the thermal seal union is still hot, remove them. It is particularly important here whether and to what degree a time delay is allowed between the release of the sealing instrument and the application of force. It is possible to measure the maximum force that can be absorbed by the packaging material when it is removed, or the resultant deformation of the thermal seal union for a given force. In principle, a distinction should be made between the hot adhesive strength as the maximum force that can be absorbed, without failures, by the thermal seal bond, the hot adhesive temperature range as the temperature range in which a minimum level of hot adhesive strength can be achieved under other given sealing conditions. In addition, the heat sealing joint in the cold state must form a strong seal, i.e., it must be capable of absorbing, in this state, high stresses at which the packaging could be exposed during transport or storage, without mechanical failure. It should be possible for one to join. of strong thermal sealing of this type obtained with the shortest sealing time possible, as an additional condition for an efficient packaging process, i.e. fast and without defects. If the voids, known as channels, are present between the inside and the outside of the packaging, the surrounding atmosphere will penetrate and, under certain circumstances, the contents will be damaged. The sealing of folds is particularly critical there. The package could thus contain folds extending within the heat sealing joint, intentionally in the form of a longitudinal ply on the side of a bag or at the intersection of the longitudinal and transverse joint, or unintentionally in the event of Machine-poor control For airtight sealing of such a crease, the thermal seal coating must be formed quickly and durably during the sealing process to completely fill in the region in and around the crease, so that continuous contact between the internal surfaces of the crease (The) heat seal coating (s) is present along the heat sealing joint, even in the crease region.If the sealing times required to obtain a hermetic seal are too long, the processing speed of The film in the packaging machine will be reduced at the same time The partial steps that are carried out during a sealing process are described iben by way of example in Meka and Steh l ing, Hea t Sealing of Semi cri s talline Polymer Films. II. Effect of Mel ting Di stributi on on Hea t -Sealing Behavi or of Polyol efins, Journal of Appli ed Polymer Sci e nce, Vol. 51, pgs. 1 05-119 (1994).

Initially, the wetting in the thermal sealing joint is carried out due to melting and pressure. In the further course of the operation, the polymer chain segments diffuse on both sides of the heat seal junction, on the opposite side in each case and thus create molecular entanglements in and beyond the junction. After 5 that the sealing instrument has been removed, the seal is cooled and, with partially crystalline materials, crystals also develop in and beyond the joint. If the heat seal union is mechanically forced, immediately: after the sealing instrument is removed, the polymers of the heat seal union should therefore exhibit a sufficiently high melt elasticity to be able to absorb this stress.

The short sealing times mentioned above could be obtained in particular by the fact that the required properties, such as high sealing strength, high. Hot adhesiveness and hermetic sealing are achieved at low temperatures. Thus, for a given temperature of the sealing instrument - in many cases this is limited by the heat resistance of the substrate or substrate of the packaging material - a temperature high enough to meet the aforementioned requirements can be obtained at the thermal seal junction in a relatively short time.

The following terms, measurement methods and definitions apply to all additional explanations: - Abbreviations for plastics are used according to DIN 7728 and ISO 1043-1987 (E) for the description of the polymers contained in the individual layers, unless the opposite is identified. - In multi-layer structures, the sequence of the layer is reproduced by placing together the abbreviations of the polymers of the corresponding layers or symbols explained in another way, separated one from the other by means of vertical lines. The side of the heat seal coating: .co is always on the right. In addition, only a part of the entire sequence of layers that make up the structure could be indicated. In these cases, the side of the heat seal coating is always equally to the right, and layers or combinations of layers not indicated are identified by three points, ... Polymers of the same type could be distinguished from each other by numbering , for example, in the form of PE-LD-1 | PE-LD-2 | PE-LD-3. Mixtures of different polymers are identified by the + sign and the summary of the components in parentheses (). Optionally, additional details on the percentage of the composition could be provided here. In such cases, unless otherwise stated, these are always weight ratios that are based on the total weight of the mixture. For example, the expression ... I PA | EVOH | ... | (PE-LD-1 + PE-LLD) | d describes a structure with an unspecified outer layer or outer sequence of layers, followed by a layer composed substantially of polyamide, followed by a layer substantially of ethylene / vinyl alcohol copolymer (EVOH), followed by an unspecified layer or sequence of layers, followed by a layer comprising a mixture of a low density polyethylene provided with the number 1 (PE-LD-1) and an ethylene / α-olefin copolymer (PE-LLD), and a layer qus follows in the sealing side to be specified in more detail with d. The layers that serve mainly to mechanically link the layers adjacent to these on both sides are hereinafter referred to by ... | HV | ... where HV is an abbreviation for the coupling agent. The polymers-; typically used as coupling agents are described below. - The melting point specification refers hereinafter to the value determined according to ASTM 3418 by DSC analysis (Differential Scanning Calorimetry Analysis). - The specification of the softening point is referred to in the following to the value determined according to ISO 306. - The specification of the melt flow rate refers in the following to the value determined according to DIN ISO 1133. If they are not given more details, the condition of measurement in the form of temperature and the weight of application is assumed to be condition D in DIN ISO 1133 with a temperature of 190 ° C and an application weight of 2.16 kg. - The density of the raw material refers to the method of measurement according to ISO 1183 (A). As will be explained later, it is not possible to achieve both high hot tack and good joint integrity simultaneously with heat seal coatings which form a barrier to oxygen, in packaging materials according to the prior art. A high hot tack strength is achieved by the selection of the polymer in the case of heat seal coatings. Copolymers of ethylene and acrylic acids (E / AA, E / MAA) allow high hot adhesive strengths and wide ranges of hot adhesive temperature, from the point of view of hydrogen bonding between molecules that They are effective even at high temperatures.This is true even to a greater degree than ionomers, neutralized acid copolymers containing metal ions, due to the ionic bond strengths, however, the use of acid copolymers and Lonomers is disadvantageous, that, with relatively high acid contents and / or degrees of neutralization that first allow the aforementioned properties, they are not compatible with polyethylene-based polymers.This makes it impossible to use the thermal seal coating to seal with a coating. additional thermal sealing based on polyethylene, for example, in a lid packaging, in view of the low strength of the sealing joint or thermal that can be achieved in this way. Experimentation has shown that, with non-polar sealing means such as low density and high density polyethylene (PE-LD, PE-HD), ethylene-α-olefin copolymers (PE-LLD), ethylene copolymers and propylene (E / P) or polypropylene (PP), a relatively high hot tack can be obtained with reduced MFR, ie with relatively long chain polymers and as a result of the relatively short branching of the long chain. In the case of PE-LLD, the strength of hot tackiness can be markedly improved with types that were produced using metallocene catalysts, hereinafter referred to as mPE-LLD, and which, compared to conventional types produced with Ziegler-Natta catalysts , have a narrower molecular weight distribution and a more uniform distribution of the comonomer content in molecules of different lengths. In all cases, an increase in density leads to only a small change in the strength of hot tack, but the temperature range deviates to higher values. Copolymers of ethylene and vinyl acetate (EVA) or ethylene and unsaturated esters such as butyl acrylate or ethyl acrylate (E / BA, E / EA) achieve lower sealing temperatures with the increase of the comonomer content, but the Hot adhesive strength also decreases. In order to achieve good joint integrity, polymers with low melting point and high MFR, i.e., are usually used. low viscosity. In this way, even at low sealing temperatures, the polymer of the heat seal coating is able to flow in irregularly shaped sections of the heat seal joint, such as in the region of folds, and seal them like this. However, these materials exhibit generally low hot stickiness. The requirement for high seal strength with short seal times could also be met by means of a specific selection of the polymer (s) that form the thermal seal coating. Thus, a good resistance of the heat seal union can also be obtained with polymers which have a high tear strength per se. In particular, such polymers are copolymers of ethylene and α-olefins (PE-LLD) in the highest density range, i.e. with densities above about 0.910 g / cm3. However, it is not possible, with the polymers, to obtain short sealing times comparable to those obtained using ethylene copolymers such as, for example, EVA, E / AA, E / MAA, or the like. For ease of processing with approximately the same bond strength, the aforementioned ethylene-α-olefin copolymers could be mixed with branched polymers such as PE-LD. In this way, if necessary, the sealing initiation temperature could also be diverted to lower values. The following structures are described in the patent literature in this connection: EP 560 495 describes a five-layer film with the structure of the ethylene-polymer polymer | HV | EVOH | HV | ethylene, wherein the layers of the coupling agent contain copolymers of an unsaturated carboxylic acid or a derivative thereof with propylene or copolymers of an unsaturated carboxylic acid or a derivative thereof with olefin / propylene copolymers. This film can shrink under the influence of heat after the previous stretch and is characterized by high resistance to be folded, high seal strength and high hardening. EP 561 428 describes a five or seven layer film with the polymer structure | HV | EVOH | HV | polymer or polymer | HV | PA | EVOH | PA | HV | polymer, which in turn can contract under the influence of heat after the previous stretch. US 4 726 984 describes a five-layer structure (E / P + PP) | HV | EVOH | HV | (E / P + PP) that is claimed that allows high packaging speeds. US 4 547 433 describes a five-layer structure PE-1 | HV | EVOH | HV | PE-2, wherein PE-1 and PE-2 each contain a PE-LLD and optionally additional proportions of an EVA copolymer. The PE-1 layer is crisscrossed, while PE-2 is not cross-linked, for better sealability. Therefore, the film has good contraction properties after stretching. A common thermal side of the mentioned structures is that, in the composite body with a substrate, they do not achieve a hermetic seal with good integrity of the joint with a hot adhesiveness suitable for high packing speeds and a heat seal bond strength. high enough Therefore, the objective was to provide a laminated film with high oxygen barrier, hot sealing, for packaging materials that allow both high hot tack as well as a hermetic seal with good sealing integrity, with short sealing times, and therefore allows, in the composite body of a packaging material containing this sealing means, relatively high packaging speeds. In addition, the heat seal coating should have a sufficiently high thermal seal strength. According to the invention, this was achieved by means of a laminated film containing an inner layer (d) of an ethylene / vinyl alcohol copolymer (EVOH) which is enclosed on both sides by the coupling layers (c) and ( e). On the side of the laminate of this composite body, the laminated film according to the invention contains at least one additional layer (f) and on the sealing side an outer layer (a), and at least one additional layer (b) which in each case it contains a thermoplastic polymer or mixtures of thermoplastic polymers. The laminated film according to the invention is also characterized in that, with the exception of layer (d) containing EVOH and optionally of the coupling layers (c) and (e) enclosing the EVOH layer, each of 7a other layers which contain a thermoplastic polymer or mixtures of thermoplastic polymers and do not lie outside the sealing side have a lower softening point than the layer (a) located outside the sealing side. The multi-layer heat-sealed laminated film according to the invention is characterized by a barrier effect of; high oxygen and improved sealing properties, particularly by a combination of the strength of the high heat seal bond immediately after sealing, and of fast sealing without the formation of channels in the heat seal joint. As a result, very high processing speeds or packaging machines of conventional design could be obtained in the composite body with a substrate. The laminated film according to the invention is preferably composed of an outer layer (a) on the side of the seal, followed to the side laminated by a thermoplastic layer (b), followed in turn by a coupling layer (c), a layer (d) containing an ethylene / vinyl alcohol copolymer, an additional coupling layer (e), an additional thermoplastic layer (f), the softening points of the layers (b) and (f) are smaller than the softening points: nt of layer (a). The softening point of layers (b) and (f) is preferably 5 ° C, particularly preferably 10 ° C lower than the softening point of layer (a).

In the preferred form, the softening points of the material compositions forming the layers (c) and (e) are also lower than the softening point of the material forming the layer (a). A particularly advantageous embodiment of the laminated film according to the invention is one in which the softening points of the coupling layers (c) and (e) are at least 5 ° C, in a particularly preferred form at least 10 ° C less than the softening point of the material forming the layer (a). The layer (a) of the laminated film according to the invention preferably has a thickness of at least 3 μm and at most 30 μm, in a still suitable form at more than 15 μm, and in a particularly preferred embodiment more than 10 μm auf. The sum of the weights per unit area of layers (b) and (f) and those of additional layers that have a softening point less than layer (a) is, based on the weight per unit area of the total laminated film, preferably at least 30%, more preferably at least 40%, particularly preferably at least 50%. The thickness of layer (d) is preferably 3 μm to 15 μm, more preferably 4 μm to 10 μm and particularly preferably 4 μm to 8 μm. Layers (a), (b) and (f) and optionally additional layers containing a thermoplastic polymer or thermoplastic polymer blends preferably contain polymers or polymer blends of the group comprising polypropylene (PP), ethylene and propylene copolymers ( E / P), ethylene vinyl acetate (EVA) copolymers, particularly preferably with a vinyl acetate content, based on the total weight of the polymer, of at most 20%, ethylene copolymers and unsaturated esters such such as butyl acrylate or ethyl acrylate (E / BA or E / EA), copolymers of ethylene and unsaturated carboxylic acids (E / AA, E / MAA), particularly preferably with a comonomer content of carboxylic acid, based on weight total of the polymer, of at most 15%, in an even more preferred form of at most 8%, salts of the copolymers of ethylene and unsaturated carboxylic acids, particularly E / MAA, (ionomers), particularly preferably with a carboxylic acid comonomer content, based on the total weight of the ionomer, of at most 15%, in an even more preferred form of at most 10%, low density polyethylene (LDPE), particularly preferably in a density of at least 0.91 g / cm3 and at most 0.935 g / cm3, high density polyethylene (PE-HD), copolymers (PE-LLD) of ethylene and olefins having at least 3 carbon atoms, such as, in particular , butene, hexene, octene, 4-methyl-1-pentene. The copolymers (PE-LLD) of ethylene and olefins could be prepared with conventional catalysts or with metallocene catalysts. Particularly preferred are copolymers (PE-LLD) of ethylene and olefins with a density of at least 0.90 g / cm 3 and at most 0.94 g / cm 3. The layer (a) contains, of the polymers mentioned, preferably PE-LLD, PE-LD, EVA, E / AA, E / MAA or ionomers or mixtures of the mentioned substances. Particularly preferred are the modalities with mixtures of PE-LLD and a branched polymer such as EVA or preferably PE-LD, the weight content of the PE-LLD in this is from 50% to 100%. The PE-LLD could be prepared either with Ziegler-Natta catalysts or with metallocene catalysts. An embodiment of the layer (a) with a composition with a melt flow rate, measured at 190 ° C and an application weight of 2.16 kg, of at least 0.1 g / 10 min and at more than 3 g / 10 min, particularly preferably at least 0.5 g / 10 min and at most 2 g / 10 min. An embodiment in which the layer (a) contains an ionomer of the type described above is also advantageous. In this case, a structure of the sequence of the layer according to the invention which contains, in layer (b), a copolymer of ethylene and unsaturated carboxylic acids (E / AA) is also advantageous., E / MAA). Layers (b) and (f) contain, from the polymers mentioned above, particularly preferably polymers or polymer blends of the group comprising EVA, particularly preferably with a vinyl acetate content, based on the total weight of the polymer, of at least 4% and at most 20%, PE-LD, particularly preferably in a density of at least 0.91 g / cm3 and at most 0.925 g / cm3, E / AA or E / MAA, particularly preferably with a content of carboxylic acid comonomer, based on the total weight of the polymer, of at least 4% and at most 15%, in an even more preferred form at least 4% and at most 8%. Layers (b) and (f) preferably contain a composition with a melt flow rate, measured at 190 ° C and with an application weight of 2.16 kg, of at least 0.1 g / 10 min and at most 3 g / 10 min, paricularly preferably at least 0.5 g / 10 min and at most 2 g / lO.min. The layer (cl) preferably contains at least 50% by weight, based on its total weight, of an EVOH with at least 40 mol% and at most 85 mol% vinyl acetate, of which at least 90% is saponified . The caps (c) and (e) contain a coupling agent that is extruded. The coupling agents used are preferably modified polyolefins such as, in particular, polyethylene, polypropylene, ethylene / propylene copolymers, ethylene / olefin copolymers or ethylene / vinyl acetate copolymers which are inserted with at least one monomer of the a group comprising the monounsaturated α, β-dicarboxylic acids, such as, in particular, maleic acid, fumaric acid, itaconic acid or the acid anhydrides, acid esters, acid amides and acid imides thereof. In addition, the coupling agents that are extruded that could be used include copolymers of ethylene with α, β-dicarboxylic monounsaturated acids such as acrylic acid, methacrylic acid and / or metal salts thereof with zinc or sodium and / or esters (Cj ^ - C4) of the same, which could also be inserted cor. at least one monomer from the group comprising the a, mono-unsaturated dicarboxylic acids such as, in particular, maleic acid, fumaric acid, itaconic acid or the acid anhydrides, acid esters, acid amides and acid imides thereof. In addition, polyolefins such as, in particular, polyethylene, polypropylene, ethylene / propylene copolymers or ethylene / α-olefin copolymers which are inserted with copolymers of ethylene with a, mono-unsaturated dicarboxylic acids, such as acrylic acid, can also be used. methacrylic and / or metal salts thereof with zinc or sodium and / or the alkyl esters (C! -C4) thereof. Particularly suitable coupling agents are oleyolefins, particularly ethylene / α-olefin copolymers with inserted α, β-dicarboxylic monounsaturated anhydride, particularly maleic anhydride. The layers (c) and (e) could also contain an ethylene / vinyl acetate copolymer, preferably: with a vinyl acetate content of at least 20% by weight. In a special embodiment of the laminated film, layer (a), layer (b) or both layers contain, in addition to the aforementioned polymers, a thermoplastic raw material that is not miscible with the polymers contained in layer (a) , to obtain a seal that flakes off. The thermoplastic raw material is preferably: polybutylene. The favorable concentrations of the thermoplastic raw material are in the range of 5% to 25% by weight, based on the total weight of the layer in which the thermoplastic raw material is contained, All or individual layers of the laminated film could additionally be provided with conventional additives: that improve the functional properties of the film. Examples include solid inorganic particles well known as antiblocking agents that project outside the outer surface of the heat seal coating and thereby improve the surface sliding behavior of the film. Silica, calcium carbonate, magnesium silicate, aluminum silicate, calcium phosphate, talc and the like are suitable for this purpose. Preferably, silica is used. The effective amounts fall in the range of 0.05% to 2% by weight, preferably 0.1% to 0.8% by weight. The average particle size is from 1 μm to 10 μm, preferably from 2 μm to 5 μm, the particles with a spherical shape are par- ticularly suitable here. These particles are preferably used only in layer (a). Other additives that improve the surface sliding of the film, also in its combined action with the aforementioned solid particles, include the higher aliphatic acid amides, higher aliphatic acid esters, waxes, metal soaps and polydimethyl siloxanes usually known as lubricants. The effective amount of lubricants is in the range of 0.01% to 3% by weight, preferably 0.02% to 1% by weight. The addition of higher aliphatic acid amides in the range of 0.01 to 0.25% by weight is particularly suitable. A particularly suitable aliphatic acid amide of the aforementioned polymers used in the laminated film is erucic acid lei-amide. The laminated film according to the invention could also be colored by the addition of conventional dyes. The laminated film according to the invention could also contain other conventional additives such as antibrume agents or antistatic agents. The esters or fatty acids are preferably used here. Particularly suitable are the optionally ethoxylated esters of carboxylic acids and polyhydric alcohols, in particular of sorbic acid, stearic acid or oleic acid and glycerol. In a preferred form, the laminated film is pretreated on the laminated side with conventional processes to obtain increased surface tension. It is possible, with the multi-layer laminated film according to the invention, to provide a sealing means which is a high oxygen barrier, which can be integrated into a packaging material, this medium is characterized not only by good hot tack but also that also surprisingly for the high integrity of the joint. A packaging material containing the laminated film according to the invention unexpectedly allows high packaging speeds in packaging machines of conventional design, with a low proportion of leaks or inadequately sealed packages. Therefore, the invention also provides a packaging material containing the multi-layer heat-sealing laminated film according to the invention and the use of the packaging material, particularly for packaged foods, tea, coffee and tobacco products, products doctors and products of any kind that are packaged with a modified atmosphere whose composition does not correspond to the surrounding atmosphere, or which are perishable in the presence of moisture and / or oxygen. The laminated film according to the invention and the packaging material containing it can be prepared in the conventional plant for the production of multi-layer composite bodies. The packaging material according to the invention containing the laminated film could be, in particular, a composite body with a flexible substrate, preferably made of paper, cardboard, metal, textiles or plastics, selected in particular from the group comprising paper, aluminum, cellulose film, polypropylene, polyalkylene terephthalate, polyamide, polycarbonate, polyvinyl alcohol, EVOH, polystyrene or combinations thereof, and the thermoplastic substrates could be oriented or unoriented. The substrate and the laminated film according to the invention are pre-prepared separately and attached to the packaging material according to the invention by the use of a laminated adhesive. The laminated film according to the invention could be prepared by coextrusion as a blown film or flat spread film in the conventional plant. Alternatively, the multi-layer thermal seal coating according to the invention could also be prepared by means of the extrusion of the coating, that is, the application of one or more layers of the laminated film in the molten state to the other layers present in the solid state, or by extrusion lamination, that is, the application of one or more fused layers of the laminated film between two layers of the laminated film present in the solid state. The laminated pelid according to the invention could also undergo an orientation process. The orientation could be carried out only in the longitudinal direction, only in the transverse direction, initially in the longitudinal direction and then in the transverse direction, simultaneously in the longitudinal and transverse direction, or in combinations of these steps. The orientation could be carried out with the laminated film alone according to the invention 0 with the packaging material that contains it.

E li cs E i p e 1 A laminated film with the structure EVA | HV- 1 | EV0H | HV-1 | EVA | (80% PE-LLD + 20% PE-LD-1) with layer thicknesses of 10 | 5 | 5 | 5 | 20 | 5 μm was prepared by co-extrusion as a film by blowing and laminated in a packaging material with a laminated adhesive according to the biaxially oriented commercial polyamide, having a thickness of 15 μm. PE-LD-1 has a density of 0.923 g / cm3, a melting point of L08 ° C, a softening point of 96 ° C and an MFR of 2 g / 10 min, and was provided with 500 ppm of Erucic acid amide and 1000 ppm silica with an average particle size of 15 μm. PE-LLD is an ethylene-octene copolymer with a density of 0.920 g / cm3, a melting point of 124 ° C, a softening point of 100 ° C and an MFR of 1.1 g / 10 min. EVA has a vinyl acetate content of 4.5%, a density of 0.928 g / cm3, a melting point of 105 ° C, a softening point of 87 ° C and an MFR of 2 g / 10 min. HV-1 is an EVA inserted with maleic anhydride with a density of 0.935 g / cm3, a melting point of 100 ° C, a softening point of 77 ° C and an MFR of 2 g / 10 min. EVOH is an ethylene / vinyl alcohol copolymer with an ethylene content of 32%, a melting point of 183 ° C and one. MFR of 1.7 g / 10 min.

Comparison Example 2 The packaging material of Example 1, wherein the heat seal coating has the structure of (80% PE-LLE '+ 20% PE-LD-1) | HV-2 | EVOH | HV-2 | (80% PE-LLD + 20% PE-LD-l) with layer thicknesses of 15 J 5 | 5 | 5 j 20 μm and materials as in example 1, and was prepared as in example 1. HV-2 is a PE-LLD inserted with maleic anhydride with a density of 0.920 g / cm 3, a melting point of 124 ° C , a softening point of 98 ° C and an MFR of 2 g / 10 min.

Comparison Example 3 The packaging material of Example 1, wherein the thermal seal coating has the structure of EVA | HV-1 | EVOH | HV-I I EVA with the layer thicknesses of 15 | 5 | 5 | 5 | 20 μir. and materials as in example 1 and as compared to example 2, and was prepared as in example 1. The following properties were measured in the film example according to the invention and to the comparison examples: - Seal strength Two Clean sample strips, without failures, are taken from the sheet of film to be tested. In order to seal, they are placed one on top of the other with the surfaces to be sealed and are maintained in this way between the sealing jaws, so that the sample protrudes at least 1 cm on each side . The heat seal is carried out perpendicular to the direction of the film path. The sealing jaws are smooth and are heated on both sides to the nominal sealing temperature. The sealing is carried out in the standard manner for 0.5 seconds at a pressure of 50 N / cm2. Comparison measurements for shorter seal times were also carried out by way of example. In the tables that follow, the data is given without establishing that the sealing time always refers to a sealing time of 0.5 s. The deviation from the conditions of: the test is established from this. After cooling, a 15 mm wide test strip is cut from the heat seal joint thus prepared and tested on a tension testing machine with a speed of 100 mm / min and a splice distance of 20 mm. The maximum value of the force required to separate the sealed films is known as the sealing resistance.

- Strength of hot adhesiveness Our strips of approximately 90 mm long and 45 mm wide are taken from the material to be tested in the direction of the sheet path and, with the sealing sides against each other, Stresses in the sample carrier. The sealing is carried out under the same conditions that are considered of the sealing instrument, pressure and time in the sealing resistance, i.e. in a distance of 20 mm. Immediately after the sealing test is finished, the heat seal bond strength test is carried out at a drawing speed of 25 m / min. The force curve is measured electronically and stored by the PC. The maximum heat of the force is read from a graphical representation of the force curve.

- Integrity of the joint The material to be tested is cut in the 20 x 20 cm format and folded into an edge with the sides to be sealed. This edge is then sealed in the manner described according to the "sealing strength", and the resultant thermal sealing union is known as the "longitudinal joint". The tube thus formed is then sealed in the same manner on one of the transverse sides that are still open, with the longitudinal extended connection flat. The flat extended longitudinal joint forms by doing so a fold. A volume of approximately: 5 mm depth of methanol dyed with methylene blue is poured into the middle of the bag, thus formed in the junction plate of the longitudinal and transverse junction. Any channel in the joint is shown by the penetration of the methylene blue solution through it. It is observed if leaks occur or if the transverse union is hermetically sealed in its full width. The results are summarized in the following table: Properties of films according to the invention and comparison samples The required hermetic sealing is thus obtained by the thermal seal coating according to the invention in the manner shown by way of example, at sealing temperatures much lower than with comparable types. of the previous art. The hot tack and the seal strength are not adversely affected. However, the absence of channels obtained at lower temperatures also indicates, however, that this is possible at the same sealing temperature and with a shorter sealing time. This fact is verified by halving the sealing time by way of example.

It is noted that in relation to this date, the best method known by the applicant to carry out the aforementioned invention, is the conventional one for the manufacture of the objects to which it relates.

Claims (15)

CLAIMS Having described the invention as above, the content of the following claims is claimed as property:

1. Thermally sealed multi-layer laminated film containing an inner layer (d) of an ethylene / vinyl alcohol copolymer (EVOH) which is enclosed on both sides by the coupling layers (c) and (e), and contains in the laminate side of this body composed of at least one additional layer (f) and on the sealing side an outer layer (a) and at least one additional layer (b), in each case contains a thermoplastic polymer or mixtures of thermoplastic polymers, characterized in that, with the exception of the layer (d) containing EVOH and optionally of the coupling layers (c) and (e) enclosing the EVOH layer, each of the other layers containing a thermoplastic polymer or Mixtures of polymers: ermoplasics, and without being located outside the sealing side, have a softening point lower than the layer (a) located outside the sealing side.

2. A laminated film according to claim 1, characterized in that the softening points of the layers (b) and (f) and of all the other layers containing a thermoplastic polymer or mixtures of thermoplastic polymers are at least 5 ° C, particularly 10 ° C lower than the softening point of layer (a).

3. A laminated film according to one of claims 1 to 2, characterized in that the softening points of the coupling layers (c) and (e) are lower than the softening point of the layer (a).

4. A laminated film according to claim 3, characterized in that the softening points of the layers (c) and (e) are at least 5 ° C, particularly at least 10 ° C lower than the softening point of the layer (a).

5. A laminated film according to any of claims 1 to 4, characterized in that the thickness of the layer (a) is at least 3 μm and at most 30 μm.

6. A laminated film according to any of claims 1 to 5, characterized in that the weight per unit area of all the layers having a softening point lower than that of the layer (a), based on the weight per unit area of the total laminated film, is at least 30% in total.

7. A laminated film according to any of claims 1 to 6, characterized in that the thickness of the layer (d) is 3 μm to 15 μm. A laminated film according to any of claims 1 to 7, characterized in that the layers (a), (b) and (f) and optionally the additional layers containing a thermoplastic polymer or mixtures of thermoplastic polymers contain polymers or mixtures of polymers of the group comprising polypropylene, copolymers of ethylene and propylene, copolymers of ethylene and vinyl acetate (EVA), copolymers of ethylene and unsaturated esters such as butyl acrylate or ethyl acrylate (E / BA and E / EA), copolymers of ethylene and unsaturated carboxylic acids (E / AA, E / MAA), salts of copolymers of ethylene and unsaturated carboxylic acids (ionomers), polybutylene, low density polyethylene (PE-LD), high density polyethylene (PE-HD) and copolymers (PE-LLD) of ethylene and olefins having at least 3 atoms of carbon, which could be prepared with conventional catalysts or with metallocene catalysts. 9. A laminated film according to any of claims 1 to 8, characterized in that the layer (a) contains a composition with a speed of: luxury of melting, measured at 190 ° C and with an application weight of 2.16 kg. , of at least 0.1 g / 10 min and at most 3 g / 10 min. A laminated film according to any of claims 1 to 9, characterized in that the layers (c) and / or (e) contain a coupling agent that is extruded from the group of polyolefins modified with carboxyl groups such as polyethylene, polypropylene, ethylene / propylene copolymers, ethylene / olefin copolymers or ethylene / vinyl acetate copolymers, which are inserted with at least one monomer from the group of mono-, di-unsaturated dicarboxylic acids, such as maleic acid, fumaric acid, itaconic acid or the acid anhydrides, acid esters, acid amides and acid imides thereof, or coupling agents which are extruded selected from or compounds of the group comprising ethylene copolymers with monounsaturated fatty acids, dicarboxylic acids such as acrylic acid, methacrylic acid, metal salts thereof with zinc or sodium, alkyl esters (Cx-C4) or the corresponding inserted polymers in polyolefins such as, in particular, polyethylene, polypropylene, ethylene / propylene copolymers or copolymers of ethylene / olefin, which are inserted polymerized with a monomer of the aforementioned unsaturated acids, or contain an ethylene copolymer or vinyl acetate with a vinyl acetate content of at least 20% p as coupling agent which is extruded. A laminated film according to any of claims 1 to 10, characterized in that one or more layers contain additional organic or inorganic additives such as pigments, dyes, lubricants, antiblocking agents, antistatic agents or antibrume agents. 12. A laminated film according to any of claims 1 to 11, characterized in that the laminate ladc is pretreated to obtain an increased surface tension. 13. A packaging material, characterized in that it contains a laminated film according to any of claims 1 to 12 in a composite body with a flexible substrate. 14. A packaging material according to claim 13, characterized in that the flexible substrate is composed of plastic, metal, cardboard, paper, cardboard or textiles. 15. The use of the packaging material according to claim 13 or 14 for packaging food, tea, coffee and tobacco products, or medical products, or other products that are perishable in the presence of moisture and / or oxygen, or products that They are packaged in a modified atmosphere. Gas-tight laminated film and packaging materials produced from it SUMMARY OF THE INVENTION The invention relates to a laminated, multi-layer film that is sealed, constructed of at least 6 layers essentially made of thermoplastic synthetic materials having an inner layer made of ethylene / polyvinyl alcohol copolymer (EVOH). The invention also relates to a packaged material containing this laminated film as a sealing layer, and to the use thereof.