MXPA00005477A - Flexible, thermoformable multi-layer film with improved movement in a machine - Google Patents

Abstract

The invention relates to a multi-layered sealable film with an internal polyamide layer and an outer layer comprised of a linear, alternating constructed copolymer made of carbon monoxide and at least one ethylenically unsaturated olefin. The invention also comprises a sealing layer produced at least as a single-layer and situated on the other film outer side, and optional additional bonding connection layers. The invention also relates to the application of said film on machines used for producing thermoformed packaging and to the utilization of the film for packaging food stuffs.

Description

Multilayer sheet thermosonformf l e and fle ible with pc step > r improved machines The present invention relates to a multilayer sealable sheet with an inner polyamide layer as well as an outer layer of an alternating structured linear copolymer of carbon monoxide and at least one ethylenically unsaturated olefin, a sealing layer executed at least as monolayer on the other outer face of the sheet as well as possibly other adhesive bonding layers. The invention also comprises the use of the indicated sheet in machines for the manufacture of thermoformed containers as well as the use of the sheet for food packaging. Foods are often packed in so-called sausage containers. These containers are manufactured in deep drawing machines from a drawing sheet that in these machines will give rise to a thermoformed concavity as well as a thermoformed sheet. Both sheets after the stuffing and the application of the filling article in the concavity thus manufactured are joined together by thermosealing giving a closed container. The mode of operation of such machines as well as the structure of the sheets processed preferably in such machines is described for example in The Wiley Encyclopedia of Packaging Technology (Ed M. Bakker, REF, 120735 D. Eckroth, John Wiley &Sons, 1986) as well as in Nentwig (Joachim Nentwig: Kunststof f-Folien, Cari Hanser Verlag 1994, Munich). For economic reasons, speeds of passage through the elevated machines are advantageous for carrying out this process.

This places special demands on the flexible packaging film used. Thus, the thermoformed containers are often transported immediately after leaving the deep drawing machine on ramps and conveyor belts to be assembled in a subsequent station in a transport container. A similar transport container is for example a cardboard box. Typically, individual sausage packages are placed by hand in a compact package side by side and superimposed. In this process it is important that the embedded packages, especially under the action of pressure, move extraordinarily easily against each other. If, on the other hand, the packages have a high friction and therefore a marked resistance against a similar displacement, then the packaging process is delayed in the transport container and consequently the overall packaging speed is reduced. The indicated ramps, on which the stuffed containers are transferred, for example, from a conveyor belt arranged above the deep-drawing machine to a conveyor belt arranged below the deep-drawing machine that moves away from it, are usually made of stainless steel superficially machined. Depending on the inclination and surface roughness of a similar ramp, there may be a blockage of the stuffed containers. In such cases the following packages stagnate at that point and force an interruption of the packaging process. An essential premise for high packaging speeds is therefore a high sliding capacity of the outer face of the sheet used against itself as well as against a metal. In the following description of the polymers contained in the different layers, the agreement stipulates that if not indicated otherwise, abbreviations are used for plastics according to DIN 7728 or ISO 1043-1987 (E). In multilayer structures the sequence of layers is represented by a successive enumeration of the abbreviations of the polymers of the corresponding layers or of other illustration symbols separated from each other by slashes. The side of the sealing layer is always to the right here. In this respect, only a part of the complete layer sequence constituting the sheet can also be indicated. In these cases the side of the sealing layer is also always on the right and layers or combinations of layers not indicated are represented by three points (...). A) Yes, the expression ... / PA / EVOH / ... / d describes for example a structure with an outer layer or an unspecified outer layer sequence, followed by a layer consisting substantially of polyamide, followed by a layer substantially constituted by an ethylene / vinyl alcohol copolymer followed by an unspecified layer or sequence of layers as well as a layer d to be specified in detail on the sealing side. The melting point data are referred to below the value determined according to ASTM 3418 by DSC analysis (analysis of "Differential Scanning Calorimetry"). They are usually thermoformable and heat sealable sheets structured in multiple layers and contain one or more layers of polyamide (PA) or mixtures with polyamide. As polyamide, PA6, ie, polycaprolactam, but also other types of PA are used as indicated in the Table below. These layers give the sheet a high mechanical stability at room temperature and at the usual temperatures of use. In addition, they soften upon heating and thus allow a substantially permanent thermal conformation of the sheet which results in a concavity. The sheets for such purposes of use contain, in addition to layers containing polyamide, also a layer sequence referred to hereafter as a sealing layer.

By "polyamide" is meant in the broadest sense polymeric compounds which are linked together by the amide group of acid -NH-CO- (see also Kunststoff -Handbuch tome VI, Polyamide, Carl Hanser Verlag Munich 1966). Two groups of polyamides are distinguished: synthesis from a monomer by polycondensation of α-aminocarboxylic acids or polymerization of its lactams giving polyamide type 6 and • those formed from two monomers (diamines and dicarboxylic acids) by polycondensation giving polyamide of kind 66 (Gnauck, Fründt: Einstieg in die Kunststoff chemie, Carl Hanser Verlag Munich 1991). The characterization of the polyamides is carried out by numbers indicating the number of C atoms in the starting substance or - in the case of two components - in the diamine (first number) and in the carboxylic acid (second number) or by an abbreviation of the name of diamine or dicarboxylic acid (eg PA) MXD6 of the diamine m-xylylenediamine and the dicarboxylic acid adipic acid).

Table for illustration of the polyamide nomenclature The sealing layer is constituted in the simplest case by a single layer. This layer is preferably composed of polyolefins, such as polyethylene (LDPE, HDPE) or ethylene / α-olefin copolymers (LLDPE), prepared with conventional Ziegler-Natta catalysts or with metallocene catalysts, or by polymers derived from olefins such as ethylene / vinyl acetate copolymers (EVA), copolymers of ethylene with unsaturated esters (eg EBA), copolymers of ethylene with unsaturated carboxylic acids (eg EAA, EMAA) and ionomers.

Mixtures of the classes of substances indicated for achieving the desired combinations of properties are also common. In particular, ethylene / α-olefin copolymers with low densities (less than 0.92 g / cm3) prepared with the metallocene catalyst technique are distinguished as sealing materials by their low temperatures at the beginning of the seal and their high hot fixation. ("hot-tack"). A multi-layered embodiment of the sealing layer is also state of the art. Thus, the aforementioned substances can be arranged in a similar case, for example for the optimization of costs, in such a way that the layer on the inner side of the sheet, directed towards the product, is characterized by a beginning of the sealing especially early and the layer next to this for the center of the sheet melts only at higher temperatures, which is nonetheless economical for it, or possessing a higher resistance to fusion, allows the production of a similar sealing layer as a blown film. Adhesive polymers prepared from the groups of substances indicated or based on them are also used, for example polymers modified by grafting with anhydride. Examples of such structures are the LDPE / EVA or LDPE / EAA / ionon layer sequences. The sealing layer enables a solid connection with the sealing layer of the cover sheet to be converted into the molten state. In this way it is possible to close the container hermetically to the air and mechanically solid. The most important characteristic of the sealing layer is therefore a melting at temperatures significantly lower than those of the layers containing polyamide. If appropriate, these films also contain other layers, such as, for example, layers that reduce the permeation of certain gases through the film. An example in this regard is an oxygen barrier layer of an ethylene / vinyl alcohol copolymer (EVOH). Here EVOH is preferably used in coextrusion between two layers of PA, ie with the sequence of layers PA / EVOH / PA and preferably contains from 40 to 85% by mole of vinyl acetate, which are saponified by at least 90%. . The sealing layer and the polyamide-containing layer or the polyamide-containing layer sequence are usually bonded to each other and possibly also one below the other by adhesive layers. Thus there is the possibility of coextruding all or a part of the layers together, that is, to make the polymers of these layers converge as melt flows and to pass them in the molten state through a common nozzle. For this procedure an adhesive is required for the extrudable joint. Such adhesives are polymers of the group comprising LDPE, LLDPE and EVA modified with maleic anhydride according to the state of the art, but an EAA or EMAA adhesive can also be used. The coextrusion process is, due to the smaller numbers of necessary process steps, basically more economically advantageous than the lamination of separate prefabricated layers. The sheets with the indicated structure can however also be manufactured by extrusion coating, that is to say by applying the sealing layer in the molten state on a support sheet containing prefabricated polyamide, which is already provided on the side to be coated of the coextruded adhesive or a primer applied after extrusion. If the supporting film and the sealing layer are prefabricated separately, then these can be joined according to the state of the art also using a laminated glue. Such adhesives are usually isocyanates and mixed polyols immediately before application, which upon application harden into polyurethanes. Of special significance for the sliding behavior of the embossing sheet is the fact that the deep-drawing process can temporarily reduce the sliding capacity in the deformed areas. This happens in accordance with experience, especially in the case of sheet structures containing polyamide on the outer face on the non-sealing side of the sheet. If on the contrary the indicated outer layer of the sheet is constituted by a polyolefin thermoplastic, for example by polyethylene (LDPE, HDPE), polypropylene, ethylene / propylene copolymers, ethylene / α-olefin copolymers or mixtures of these, then no it diminishes or does not noticeably the sliding capacity of this face in front of itself as well as in front of metals by the stuffing. Such structures corresponding to the state of the art have, in contrast to structures containing polyamide on the outside face on the non-sealing side of the sheet, the drawback that the sealing tools must be maintained at lower temperatures. The temperatures necessary for the sealing are usually achieved by contacting the outer face of the sheet opposite the sealing face with a heated plate or a profile heated to the shape of the area to be sealed by thermal conduction in the sheet and inside the sheet. same In this regard, the temperature of the side which is in contact with the heating of the sheet is always higher than that which is reached in the sealing layer. On the other hand, to melt the sealing layer, a given temperature in the sealing layer is required, and the shorter the heating time necessary to achieve that higher temperature, the temperature of the outer face opposite to the sealing face must be. and consequently the heating temperature of the sheet. In certain circumstances the heating time in the sealing station of a deep drawing machine is determinant of the total rate and therefore of the speed of packaging of this machine. For this reason it is generally advantageous to provide the outer face opposite the sealing face with a temperature resistance as high as possible in the direction described above by means of a sheet. The various types of polymer that are suitable and are used in addition to the polyamide as the material of the outer layer have specific advantages and disadvantages in this respect. Generally, a high melting point is suitable for the above reasons. The LDPE is suitable for working but presents a melting point with a density of approximately 0.935 g / m3 of DSC of only 115 ° C. With this material, higher melting points can not be achieved. The ethylene / -olefin copolymers (LLDPE) reach melting points up to about 128 ° C. In the case of processing as a flat sheet, they have the drawback that after leaving the nozzle, they contract in the melt strip to a greater extent than, for example, the polyamide and thus reduce the useful width of the multilayer film. The same is true even more for polypropylene homopolymer as well as for ethylene / propylene copolymers, which have melting points of around 160 ° C and 130 to 150 ° C, respectively. In comparison with this, polyamide 6 melts at clearly higher temperatures (220 ° C). PA 66, for example, a polymer of adipic acid and hexamethylenediamine, has a melting point of approx. 255 ° C. Furthermore, the above-mentioned polyolefin materials have the disadvantage that they are not resistant to scratches against metals and partly also to less hard materials such as wood or hard plastics. In transport, therefore, the visual appearance of the films made on the outer face with such polymers can clearly deteriorate and the attractiveness of the package can suffer. In addition to the indicated polyolefin thermoplastics, poly (ethylene terephthalate) (PET) is also frequently used as a component of the outer face of the sheet opposite the sealing face. Usually biaxially stretched poly (ethylene terephthalate) (OPET) is used in this respect. However, for embossing sheets this is basically inadequate, since it no longer allows the thermoformability of the sheet. Unstretched poly (ethylene terephthalate) can be processed basically by extrusion or co-extrusion with other layers to obtain a monolayer or multilayer sheet that can be deep-drawn. In this respect the PET must be dried before extrusion to exclude a break in the chains of the macromolecule due to the presence of water. The equipment required for this requires additional investment and operational costs. A pure PET film has the drawback of a high rigidity and for this reason it is equally unsuitable for flexible sheet applications. The sheets containing polyamide co-extruded with PET in the outer layer are difficult to manufacture, since for this combination of materials there are only insufficiently effective coextrudable adhesives. Certainly PET is resistant to temperature to a large extent, but to achieve a sufficiently high sliding capacity it is necessary in each case to add slip or non-stick agents. Thus, PET does not represent any advantage over an outer layer of polyamide. Accordingly, such coextruded structures are not useful for use in the field of application herein presented. The sliding capacity of both the indicated polyolefin materials and also of the polyamide is improved according to the state of the art with additives. For this purpose, anti-adhesion agents are used in the form of solid particles which protrude partially from the outer face of the sheet and thus reduce the effective contact surface with the adjacent medium. Examples are silicon oxide, calcium carbonate, magnesium silicate, aluminum silicate, calcium phosphate and the like. For this, silicon dioxide is preferably used. The effective amounts are in the range of 0.1 to 2% by weight. The average particle size is between 1 and 10 μm, spherical particles being particularly suitable here. In multilayer structures these particles are used pr-eferrable only in the outer layer. Other additives that improve the sliding ability of the sheet, also in conjunction with the indicated solid particles, are the higher aliphatic acid amides, higher aliphatic acid esters, waxes, metal soaps as well as polydimethylsiloxanes, usually referred to as slip agents. The effective amount of slip agent is in the range of 0.01 to 3% by weight, preferably 0.02 to 1% by weight. An acid amide commonly used for polyolefins is the erucic acid amide. The polyamides are usually structured with highly substituted amine acid amides. Usually, ethylene-bis-stearylamide is used here. The indicated materials are always limited only to the polymer with absorption capacity and consequently after processing to obtain a sheet they are deposited in the course of time on the outer faces. In this way a sliding film is formed there. Also, by means of a coordinated dosing of both slip agents and anti-adhesion agents, the above-described effect of temporarily reducing the sliding capacity of a sheet with an outer face of polyamide can be eliminated according to experience. The cause is possibly the fact that the above-mentioned polyamide slip agents are more compatible and therefore migrate more slowly outwards and the thinner film thinned by the stuffing can regenerate more slowly. However, an important requirement of the thermoformable sheets is also the mechanical strength. The criteria here are in addition to the resistance to breakage, determined according to DIN EN ISO 527, also resistance to perforation. The latter represents a measure of the resistance that a sheet opposes to slow penetration with a sharp object, for example to splinters of bones contained in the packaging article. A suitable measuring method for this magnitude is described in relation to the Examples.

The polyamide in the field of flexible thermoformable sheets has a clear advantage over the achievement of high breaking and puncture resistance to all known materials and in particular to polyolefins. Therefore, a layer of polyamide which reinforces the sheet in such a way can not be dispensed with. The known structures for flexible sheets and which can be deep-drawn therefore always contain polyamide for these reasons. In addition to the polymers mentioned above, the class of substances of the aliphatic polyketones has also been known for a long time. These are rigorously linear and alternating polymers of carbon monoxide and at least one ethylenically unsaturated olefin. For these materials, however, only a few applications for the manufacture of sheets are known. The disclosed applications take advantage of only the good barrier capacity against oxygen or can be heated with high frequencies of these materials. J.G. Bonner and A.K. Powell, Vortrag Maack Speciali and Film 96, describe a five-layer structure of PP / aliphatic adhesive / polyketone / adhesive / PP as a double-sided foil for food packaging. This structure is essentially characterized by being a good barrier against oxygen. For use in deep drawing machines for the manufacture of embedded packaging, it is basically inadequate due to the symmetrical structure with outer PP layer. WO 8607012 describes a multilayer laminate with at least two different extrudable polymers, at least one layer containing a polyketone, preferably an ethylene / carbon monoxide copolymer, and being joined to another layer preferably constituted by a halopolymer. This sheet is especially suitable for sealing by high frequency electromagnetic waves. The halopolymers used in the structure indicated as PVC or PVDC are certainly characterized by being able to be heated with radiofrequency waves, but they are not advantageous for reasons of food and ecological legislation for food packaging. US Pat. No. 5,232,786 discloses a multilayer coextruded structure with at least one corresponding aliphatic polyketone and a polyamide, polyvinyl chloride or copolyetherester. These structures are characterized by a small adhesion of the composite material and therefore an improved separation and recycling capacity. This property, as well as the insufficient sealing capacity of a similar composite material, renders them unsuitable for use as a packaging sheet that undergoes high stresses in deep drawing machines. In US 5077385 a two-layer laminate is described in which one of the layers is constituted by an aliphatic polyketone, preferably by a terpolymer of carbon monoxide, ethylene and propylene, and the other layer is formed with a polypropylene or polycarbonate . The essential characteristic of the described laminate is the preparation of the polyketone starting from the melt by means of cooling with a speed of 1 ° C to 20 ° C per minute. In this way it is understood that the material is a good barrier against water vapor, oxygen and carbon dioxide. The realization of a similar cooling process led to machines for the manufacture of a thermoformable sheet at extremely long machine dwell times and consequently to very expensive sheets. The indicated multilayer structure is also unsuitable for an early sealing sheet. Polymer mixtures based on aliphatic polyketones based on patent literature have also been disclosed. Thus, WO 09111470 describes a homogeneous mixture of an ethylene / vinyl alcohol copolymer and a copolymer of ethylene and carbon monoxide. The mixture is characterized as a good barrier against oxygen, can be heated by high frequency radiation as well as an improved melt strength with respect to the pure copolymer of ethylene and carbon monoxide and is therefore suitable inter alia for processing as a blown film. A similar polymer mixture and its use in monolayer or multilayer films is also described in document US 04965314. In addition to the abovementioned advantages of being able to heat with high frequencies and be a good barrier against oxygen, a sheet based on a mixture of Such polymers are characterized by an improved penetration resistance, that is to say increased resistance to a penetrating type solicitation with a blunt object. WO 09606889 and EP 00669374 also disclose mixtures of an aliphatic polyketone with a linear low density polyethylene (LLDPE) or a high density polyethylene (HDPE), which are characterized as improved barriers both against oxygen and against to steam water and hydrocarbons. For these reasons, certain containers and sheets of these materials suitable for housing food are also claimed. For the application herein, such mixtures are not convenient due to the early softening under the influence of heat of the aliphatic polyketones mixed with LLDPE or HDPE with respect to the pure copolymer of ethylene and carbon monoxide. It has been proposed to provide a flexible multilayer sheet with good passage through machines in deep drawing machines. For the good passage through the machines the outer face of the thermoformable sheet must also have a sufficiently high sliding capacity in the projections minutes after the deep drawing. The sheet must also be sealable on one side under the thermal influence in the shortest time possible against a corresponding cover sheet with a compatible sealing layer. In addition, the sheet, with respect to the application as a packaging medium, must have high breaking and puncture strengths as well as an outer surface resistant to scratching. In addition to this, it should be able to manufacture rationally in a few operational steps. According to the invention this is achieved by providing a multilayer, sealable and unstretched sheet, constituted by an outer layer (I), at least one layer (II) containing polyamide, a sealing layer (III) of at least one layer on the outer face opposite the layer (I) (the sealing face) of the sheet, as well as optionally other layers, the multilayer sheet being characterized in that the outer layer (I) contains an alternating linear copolymer (1) of carbon and at least one ethylenically unsaturated olefin and layer (II) containing polyamide contains at least 50% by weight of a polyamide. The alternating linear copolymer (1) of carbon monoxide and at least one ethylenically unsaturated olefin is preferably a copolymer of carbon monoxide and one or more olefins of the group comprising ethylene and C3 to C10 alkenes, such as, for example, propylene, 1-butene , 2-butene, 1-pentene, 1-hexene, 1-octene, 1-nonene, 1-decene, in a particularly preferred form is a terpolymer of carbon monoxide, ethylene and propylene and in a form of these again especially preferred such a terpolymer of carbon monoxide, ethylene and propylene with monomer units of ethylene (A) and propylene (B) statistically distributed in the polymer chain, the stoichiometric ratio B / A of these monomer units not exceeding the value of 0.5. The outer layer (I) of the sheet according to the invention can contain, in addition to the alternating linear copolymer of carbon monoxide and at least one ethylenically unsaturated olefin, also other polymers ter moplastics as mixing components. In this connection, ethylene / vinyl alcohol and / or polyamide copolymers are especially suitable. further, the alternating linear copolymer of carbon monoxide and at least one ethylenically unsaturated olefin may also contain conventional additives. Examples in this regard are antistatic, slip agents, anti-stick agents, pigments or other solid fillers of all kinds. The layer (II) containing polyamide preferably contains polyamide 6, polyamide 10, polyamide 12, polyamide 66, polyamide 610, polyamide 61, polyamide 6/12, polyamide 6/66, polyamide 6I / 6T, polyamide MXD6, polyamide 6/61 , polyamide 6 / 6T or mixtures thereof. Mixtures of the indicated polyamides with at least 80% by weight of polyamide 6, based on the total weight of the mixture, are especially preferred. The polyamide-containing layer (II) of the film according to the invention can also contain customary additives as slip agents, pigments or other solid charges of all kinds. Particularly suitable are inorganic or organic solid particles with sizes in the range below 1 μm for controlling the stiffness and the oxygen permeability of the polyamide layer (II). The sealing layer (III) is constituted by the polymers commonly used as sealing means. These are for example polyethylene (LDPE and HDPE) or polypropylene (PP). They can also. copolymerized ethylene / α-olefin (LLDPE). These can be prepared with conventional Ziegler-Natta catalysts or with metallocene catalysts. In addition, other copolymers of ethylene such as ethylene / propylene copolymers, ethylene / vinyl acetate copolymers (EVA), copolymers of ethylene with unsaturated esters (EBA), copolymers of ethylene with unsaturated carboxylic acids (EAA, EMAA) and ionomers can be used. . For the attainment of special properties, the aforementioned polymers which are admitted to the sealing layer can also be used in the form of mixtures with each other. The film according to the invention can also contain a sealing layer made in several layers. Thus, the aforementioned substances can, for example for cost optimization, be arranged in such a way that the layer on the inner face of the sheet, directed to the product, is characterized by a beginning of the sealing especially early and that it melts with respect to the layer consecutive to it of the center of the sheet only at higher temperatures, being nevertheless more economical for it or having a greater resistance to the fusion, it makes possible to produce a similar sealing layer as a blown sheet. Adhesive polymers of the groups of indicated substances or polymers based thereon, modified by grafting, for example with anhydride, can also be used. Examples of such structures are the LDPE / EVA or LDPE / EAA / ionomer layer sequences. All or some layers of the sealing layer may additionally be provided with additives that improve the functionality of the sheet. Examples of known solid inorganic particles are anti-adhesion agents that protrude from the outer surface of the sealing layer and thus improve the sliding behavior of the sheet. Suitable for this purpose are silicon oxide, calcium carbonate, magnesium silicate, aluminum silicate, calcium phosphate and the like. Preferably the silicon dioxide is used. The effective amounts are in the range of 0.1 to 2% by weight, preferably 0.1 to 0.8% by weight. The average particle size is between 1 and 10 μm, preferably between 2 and 5 μm, spherical particles being particularly suitable here. In sealing layers of several layers these particles are preferably used only in the outer layer. Other additives that improve the capacity of the sheet, also in cooperation with the indicated solid particles, are the amides of higher aliphatic acids, the higher aliphatic acid esters, waxes, metal soaps as well as polydimethylsiloxanes usually designated as slip agents. The effective amount of slip agent 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. An aliphatic acid amide especially suitable for the aforementioned polymers used in the sealing layer is the erucic acid amide. The film according to the invention can contain the outer layer (I), one or more layers (II) containing polyamide and / or optionally a barrier layer (V) joined together by one or several layers (IV) of adhesion , given the case of different compositions. In a preferred form, the film according to the invention contains a direct determined layer sequence of the outer layer (I) and a layer (II) containing polyamide which has been manufactured by co-extrusion, optionally with one or more layers Furthermore, a direct layer sequence, manufactured by co-extrusion as described above, of the outer layer (I) and a layer is especially suitable. (V) containing an ethylene / vinyl alcohol copolymer (EVOH) or / and a direct layer sequence of a layer (II) containing polyamide and a layer (V) containing an ethylene / vinyl alcohol copolymer (EVOH) as well as combinations of the indicated layer sequences, Preferred embodiments are the sequences of certain layers indicated a / b / ..., a / b / a / ..., ... / b / c / b / ... , a / c / b / ..., a / c / a / b / ..., a / b / c / b / ... or / b / c / b / a / ..., meaning a layer of a li copolymer alternating carbon monoxide and at least one ethylenically unsaturated olefin, b a layer containing polyamide and c a layer containing EVOH. The layers designated above by a, b and c usually require an adhesion layer (IV) to be bonded to the sealing layer (III). In this respect, it is possible to extrude all the layers together, that is to say, to make the polymers of all the layers come together as melt flows and to pass them in the molten state through a common nozzle. For this procedure, an extrudable adhesive is chosen. As such, modified polyolefins are preferably used. Preferably, these are polyolefins with carboxyl groups, such as, for example, polyethylene, polypropylene, ethylene / o-olefin copolymers or ethylene / vinyl acetate copolymers, grafted with at least one monomer from the group of dicarboxylic acids OI, β -monosunsaturated, such as for example maleic acid, fumaric acid, itaconic acid or its acid anhydrides, acid esters, acid amides and acid imides. As extrudable adhesives, it is also possible to use copolymers of ethylene with α, β-monounsaturated dicarboxylic acids, such as acrylic acid, methacrylic acid and / or their metal salts with zinc or sodium and / or their C] -C 4 alkyl esters. or corresponding graft copolymers of polyolefins such as, for example, polyethylene, polypropylene or ethylene / α-olefin copolymers which have been graft polymerized with a monomer of the indicated unsaturated acids. Polyolefins, such as ethylene / α-olefin copolymers, grafted with α, β-monounsaturated dicarboxylic acid anhydrides, in particular with maleic anhydride, are especially preferred for this purpose. The extrudable adhesive of the sheet according to the invention can also be, as a joining element between an inner layer (VI) designated above as a, ie one corresponding to the composition of the outer face (I), and the sealing layer (III), a polymer of the group of linear alternating copolymers of carbon monoxide and at least one ethylenically unsaturated olefin, in a preferred form a copolymer of carbon monoxide and one or more olefins of the group consisting of ethylene and C3-C alkenes ? 0 such as propylene, 1-butene, 2-butene, 1-pentene, 1-hexene, 1-octene, 1-nonene, 1-decene, in a particularly preferred form a terpolymer of carbon monoxide, ethylene and propylene and in a form thereof again especially preferred such a terpolymer of carbon monoxide, ethylene and propylene with monomer units of ethylene (A) and propylene (B) statistically distributed in the polymer chain, the stoichiometric ratio B / A of these monomer units being in this form especially preferred greater than the B / A ratio of the monomeric units of the polymer of the layer (VI). The sheet according to the invention can also be manufactured by extrusion coating, that is, by applying the sealing layer in the molten state on a prefabricated layer sequence containing at least layers (I) and (II), which is already provided on the face to be coated of the coextruded adhesive described above or of a primer applied after extrusion. In addition, the film according to the invention can be manufactured by separately prefabricating a support film containing at least the layers (I) and (II) and the sealing layer. As an adhesion layer, in such cases a glue of laminates to be applied on the support film or on the sealing layer is used, for example, with a roller applicator. Such glues are usually systems based on polyurethanes or polyesterurethanes. By using the sequence of layers according to the invention, it is possible to provide a processable foil to obtain a flexible thermoformed embossed article, which can be applied for fast sealing against a cover foil with high temperatures of the sealing tool. It was not to be expected that the sheet would also have an outstanding ability to slide against itself and against metals immediately after deep drawing. Also the resistance to perforation (drilling work) and the resistance to scratches is clearly greater with respect to the sheets with polyolefin outer layers. It is therefore also an object of the invention to use the sheet as an embossing sheet for the manufacture of deep drawn packings in thermoforming-filling-sealing machines. For the applicant, the finishing of the sheet according to the invention without additional adhesion layers between the outer layer according to the invention and a core layer containing polyamide by coextrusion in conventional machines for the manufacture of multilayer sheets is equally surprising. Another advantage of the sheet according to the invention is the unexpected uniform shrinkage of the strip of melt between the layers and consequently the good use of the width of a composite material coextruded as a flat film.

EXAMPLES Example i An alternating linear terpolymer of carbon monoxide as well as ethylene and 5% by weight of propylene, based on the total weight of polymer, with a melting point of 220 ° C, was melted in a conventional three zone extruder and it was brought to a temperature of 250 ° C. The terpolymer had a melt flow index (MFR), measured according to ISO 1133 at 240 ° C and with 2.16 kg of applied weight, of 5 g / 10 min. In another extruder, a polyamide 6 with a crystallite melting point of 220 ° C and a relative viscosity in sulfuric acid of 98% of 3.6 was also melted and heated to a temperature of 260 ° C. the polyamide contained 600 ppm of ethylene-bis-stearamide. The two melt flows were then brought together in an adapter and extruded together through a linear slot nozzle. The melt strip was then stretched as flat sheet by continuously applying it through a linear groove nozzle heated to 260 ° C with the PA face on a rotating casting roller with a surface temperature of 100 ° C. The sheet thus obtained had a layer with a thickness of 10 μm of the linear alternating terpolymer of carbon monoxide as well as of ethylene and 5% by weight of propylene and a layer of 40 μm in thickness of the polyamide 6 and was then cooled to temperature environment, it was again heated to 60 ° C and in this state it was coated with a solvent-free adhesive consisting of a polyol and a diisocyanate in a stoichiometric ratio suitable for crosslinking to form a polyurethane by roller application with a surface weight of 2 g / m2. To the side coated with the glue of this film was then attached another sheet made in a previous process step, the sealing layer, so that both sheets could be joined under pressure and also at 60 ° C in a roller pitch. The sealing layer was constituted by a mixture of 85% by weight of an ethylene / butene copolymer (LLDPE) with a density of 919 g / cm3, a melting point of 117 ° C as well as an MFR of 0.7 g / 10 min at 190 ° C and 2.16 kg and 15% by weight of a LDPE with a density of 923 g / cm3, a melting point of 111 ° C as well as an MFR of 2 g / 10 min at 190 ° C and 2.16 kg. The LLDPE contained 500 ppm of erucic acid amide.

Example 2 The terpolymer of carbon monoxide, ethylene and propylene (polyketone) indicated in Example 1 was melted in an extruder and heated to a temperature of 250 ° C. In another extruder, respectively, the polyamide of Example 1, a copolymerized ethylene / butene (LLDPE) modified by grafting with maleic anhydride as an adhesive with a density of 910 g / cm3 and an MFR of 4.4 g / 10 min were separately melted respectively. at 190 ° C and 2.16 kg and a melting point of 124 ° C, an LDPE with a density of 920 g / cm3, a melting point of 108 ° C and an MFR of 2 g / 10 min at 190 ° C C and 2.16 kg, and heated to a temperature of 250 ° C. The melt flows were brought together in a common annular nozzle and extruded to form a tubular sheet. The sheet tube was processed by standard methods of the blown sheet technique to obtain a flat sheet. The sheet had the polyketone / adhesive / PA 6 / adhesive / LDPE layer sequence, the thicknesses being increased in the indicated sequence to 30, 10, 30, 10 and 80 μm. COMPARATIVE EXAMPLE 3 The polyamide 6 of Example 1, with in addition 1000 ppm of a silicon oxide with a particle size of 15 μm, was processed as a monolayer flat film analogously to that described in Example 1 with a thickness of 50 μm and in the manner also described in Example 1 was laminated against the 100 μm thick sealing layer described in Example 1.

Comparative Example 4 The structure described in Example 2 was manufactured in the same way but with an ethylene / butene copolymer (LLDPE) with a density of 919 g / cm3, a melting point of 124 ° C and an MFR of 4.4 g / 10 min at 190 ° C and 2.16 kg provided with 500 ppm of erucic acid amide and 1000 ppm of silicon oxide of mean particle size of 15 μm instead of with the terpolymer of carbon monoxide, ethylene and propylene (polyketone) in the outer layer. The sheet had the sequence of layers LLDPE / adhesive / PA 6 / adhesive / LDPE, the thicknesses in the sequence indicated being 30, 10, 30, 10 and 80 μm. The following physical properties were measured in the finished samples as follows: • The friction behavior in accordance with DIN 53 375. Here coefficients of friction were determined for the adhesion bearing and sliding friction for the pair of sheet materials / sheet as follows: 2 strips without dust or defects of 200 x 75 were taken from the sheet in the longitudinal direction. One strip was spread with the side to be tested facing up on a polished steel test table, the other with the face to test down placed on top and fixed to a drag stop. A friction shoe of 200 g mass with a test surface of 64 x 63 mm, flatly polished and rubber coated, was installed without impact and without applying additional pressure to the specimen, so that during the test run total of 60 mm was found with the entire test surface on both test pieces. Immediately after placing it, the test was started with a starting speed of 100 mm / min which was reduced by a time relay so that after 15 seconds an increase in force began. The friction coefficient of adhesion is in this respect the ratio of the maximum force FR measured in the manner described above, which is still in an area in which there is a linear relationship between the advance of the friction shoe and the force transmitted over she by friction, by the force of the friction shoe weight. The friction coefficient of sliding is the ratio of the force FR extrapolated at the beginning of the movement to the force of the friction shoe weight. For the pair of sheet / metal materials, the coefficients of sliding friction and adhesion were determined analogously. Only the lower test strip was omitted so that the upper test strip rubbed against the polished steel plate. These tests were carried out both for the sheets in the unsolicited state, always determining the sliding capacity of the outer face, as well as after a previous longitudinal elongation of the sheet. For this, a strip measuring equally 200 x 75 mm was taken and extended on the long transverse sides in through fasteners 50 mm apart from each other. The fixings were then separated from each other with a speed of 100 mm / min a distance of 150 mm, the elongated specimen was removed and again correctly cut to the size of 200 x 75 mm. The test tubes thus obtained were tested in the above manner, as described. The start of the measurement was carried out here always 2 min after the pre-delay. The totality of the test steps was carried out at 23 ° C and 50% relative humidity of the air with sheets previously exposed for three days to this climate. For comparison, the friction coefficient of adhesion between sheet and sheet was used as a measure of the resistance to packaging in a transport container as well as to the sheet / metal sliding friction coefficient as a measure of the resistance to slip on a metal surface. The tests were performed on three respective samples and the results were averaged. The resistance to the perforation as the necessary force, the necessary displacement and the necessary work to perforate a sheet, stretched like a membrane with a sharp test punch. In this respect, the drilling work is the most suitable in practice according to the experience for the evaluation of the resistance against acute objects. The measurement is carried out with an electronic tensile testing machine of class 1 according to DIN 51 221 with a test speed of 100 mm / min. For this, circular samples with a diameter of 80 mm were taken from the sheet and tensioned in the form of a membrane in the fixation of samples of the test apparatus having a diameter of 50 mm. The test punch was made of metal and had a diameter of 2 mm. At its tip it narrowed along 5 mm to a diameter of 1 mm, the front being rounded with a radius of 0.5 mm. The drilling force and the drilling displacement is the deviation or force of the test punch achieved to the failure of the sheet. The drilling work is obtained by integrating the force acting on the test punch along the displacement traveled by it. The totality of the test steps was carried out at 23 ° C and 50% relative humidity of the air with sheets previously exposed for three days to this climate. The tests were performed on three respective samples and the results were averaged. Scratch resistance was determined qualitatively. For this purpose, a normal edge blade with the blade arranged vertically transversely to the direction of the blade was conducted and the trace it left behind in this way was assigned to the categories of "clear", "light" or "unobservable". This test was repeated with a fingernail as well as with a tensile specimen of a propylene homopolymer with sharp corners. The results as well as the temperature resistance of the outer face of the sheet in the form of its melting point according to ASTM 3418 are summarized in the following Table: It is noted that in relation to this date, the The best method known to the applicant to carry out the said invention is the conventional one for the manufacture of the objects or products to which it refers.

Claims (27)

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

1. Multilayer film constituted by an outer layer (I), at least one layer (II) containing polyamide, a sealing layer (III) of at least one stratum- on the outer face opposite to the layer (I) (the face of sealing) of the sheet, as well as optionally other layers, the multi-layer sheet being characterized in that the outer layer (I) contains an alternating linear copolymer (1) of carbon monoxide and at least one ethylenically unsaturated olefin and the layer (II). ) containing polyamide contains at least 50% by weight of a polyamide.

2. The invention relates to rejection 1, characterized in that it has a copolymer (1) of carbon monoxide and one or more olefins of the group comprising ethylene and C3 to C10 alkenes, such as, for example, propylene, 1-butene, 2-butene, 1-pentens, 1-hexene, 1-octene, 1-nonene, 1-decene.

3. Lamna ccpfcrrre to reJv-Lrr? RTrpa 2, characterized p rqué the copolymer (1) is a terpolymer (2) of carbon monoxide, ethylene and propylene.

4. Lamna cenß-rrre to claim 3, characterized perqué has a terpolimer (2) of carbon monoxide, ethylene and propylene with monomer units of ethylene (A) and propylene (B) statistically distributed in the polymer chain, not exceeding the ratio stoichiometric B / A of these monomer units the value of 0.5.

5. Sheet according to one of claims 1 to 4, characterized in that the layer (H) which contains polyamide contains at least 50% by weight, based on the weight of the layer (II), of at least one polyamide of the polyamide group 6, polyamide 10, polyamide 12, polyamide 66, polyamide 610, polyamide 61, polyamide 6/12, polyamide 6/66, polyamide 6I / 6T, polyamide MXD6, polyamide 6/61, polyamide 6 / 6T or mixtures thereof.

6. The invention relates to claim 5, wherein the layer (II) containing polyamide contains at least 80% by weight, based on the weight of the layer (II), of at least one polyamide of the group of polyamide 6, polyamide 10, polyamide 12, polyamide 66, polyamide 610, polyamide 61, polyamide 6/12, polyamide 6/66, polyamide 6I / 6T, polyamide MXD6, polyamide 6/61, polyamide 6 / 6T or mixtures thereof.

7. Sheet according to one of claims 1 to 6, characterized in that the PDliamide contained in the layer (n) containing polyamide contains at least 80% by weight of polyamide 6, based on the total weight of this polyamide.

8. Sheet according to one of the claims 1 to 7, characterized in that the layer (H) which protects polycarbonate is at least 80% by weight, based on the weight of layer (II), of polyamide 6.

9. Sheet according to one of claims 1 to 8, characterized in that the layer (H) which has a perforated surface does not contain, apart from polyamide, any other polymer.

10 Sheet according to one of claims 1 to 9, characterized in that the latrine is additionally added with at least one layer (V)? Μe contains an ethylene / vinyl alcohol copolymer (EVOH).

11. I-ar? Na s-rr brrre to the claim-jacd? I ID, characterized in that at least one layer (V) contains at least 50% by weight, based on the total weight of this layer, of an ethylene / alcohol copolymer vinyl (EVOH).

12 Sheet according to one of claims 1 to 11, characterized in that the outer layer (I) is directly adjacent to a layer (I I) containing polyamide without another joining layer.

13. 1-appin cr_r-Ecrrre a re ± V-LrrMcac-Lc 12, characterized perqué a layer (II) containing polyamide is directly between the outer layer (I) and another layer (VII) containing an alternating linear copolymer of carbon monoxide and at least one ethylenically unsaturated olefin without other tie layers.

14. The polymeric material is characterized in that the layers (I) and (VII) contain the same alternating linear copolymer of carbon monoxide and at least one ethylenically unsaturated olefin.

15. Sheet according to one of claims 1 to 11, characterized in that the outer layer (I) is directly adjacent to a layer (V) containing ethylene / vinyl alcohol copolymer (EVOH) without another binding layer.

16. Sheet according to one of claims 1 to 11, characterized in that the outer face opposite the sealing face has the sequences of layers determined a / b / a, a / c / b, a / c / a / b, a / b / c / boa / b / c / b / in the inside of the sheet the sequence of layers b / c / b, meaning a layer of an alternating linear copolymer of carbon monoxide and at least one ethylenically unsaturated olefin , b a layer containing polyamide and c a layer containing EVOH.

17. Sheet according to one of the claims 1 to 16, characterized in that the sealing layer (m) is ccptperturized by at least one layer, which contains respectively a polymer or a mixture of polymers from the group of polyethylenes (LDPE and HDPE), ethylene / α-olefin copolymers (LLDPE), prepared with conventional Ziegler-Natta catalysts or with metallocene catalysts, other copolymers of ethylene such as ethylene / propylene copolymers, ethylene / vinyl acetate copolymers (EVA), copolymerized ethylene with unsaturated esters (EBA), copolymers of ethylene with α, β-monounsaturated dicarboxylic acids, such as for example acrylic acid or methacrylic acid, their metal salts with zinc or sodium and their C 1 -C 4 alkyl esters as well as optionally additives such as silicon, calcium carbonate, magnesium silicate, aluminum silicate, calcium phosphate, higher aliphatic acid amides, higher aliphatic acid esters, waxes, metal soaps and / or polydimethylsiloxanes and / or containing polyolefins, such as polyethylene, polypropylene, ethylene / α-olefin copolymers or copolymers of ethylene with vinyl acetate or dicarboxylic, β-monounsaturated acids, such as acrylic acid or methacrylic acid, grafted with at least one monomer from the group of the dicarboxylic acids OÍ, β-monounsaturated, such as, for example, maleic acid, fumaric acid, itaconic acid or its acid anhydrides, acid esters, acid amides and acid imides.

18 Sheet according to one of claims 1 to 17, characterized in that it has one or more layers (3V) of action containing a polyolefin, such as, for example, polyethylene, polypropylene or ethylene / α-olefin copolymer, or a copolymerized ethylene / vinyl acetate, grafted with at least one monomer from the group of α, β-monounsaturated dicarboxylic acids, such as for example maleic acid, fumaric acid, itaconic acid or its acid anhydrides, acid esters, amides of acid and acid imides, and / or copolymers of ethylene with α, β-monounsaturated dicarboxylic acids, such as acrylic acid, methacrylic acid and / or their metal salts with zinc or sodium and / or their C este-CJ alkyl esters or corresponding graft polymers on polyolefins, such as, for example, polyethylene, polypropylene or ethylene / α-olefin copolymers, which are polymerized with a graft of a monomer from the group of dicarboxylic acids α, β-monounsaturated s, such as, for example, maleic acid, fumaric acid, itaconic acid or its acid anhydrides, acid esters, acid amides and acid imides.

19. Lárrina or iDcriiK to claim 18, characterized in that at least one adhesion layer (IV) contains an ethylene / α-olefin copolymer with grafted α, β-monounsaturated dicarboxylic acid anhydride.

20. Lárdna cn ficrpe a la rrivirri-j-aajch 15, characterized perqué at least one layer (IV) of adhesion contains an ethylene / α-olefin copolymer with grafted maleic anhydride. twenty-one .

Sheet according to one of claims 1 to 20, characterized in that at least one layer of adhesive adheres to a polymer of the group of polyurethanes, polyesterurethanes or polyacrylates.

22 Sheet according to one of claims 18 to ZL, characterized in that a layer of aóhererrpp joins together the outer layer (I) and a layer (II) containing polyamide.

2. 3 . Sheet according to one of claims 18 to ZL, characterized in that the adhesion layer binds together the sealing layer (I II) and a layer (I I) containing polyamide.

24 Sheet according to one of claims 1 to 23, characterized in that the outer layer (I) and at least one layer (H) containing polyamide have been manufactured by co-extrusion.

25. Use of the sheet according to one of claims 1 to 24 for the manufacture of closed containers everywhere.

26. Use of the sheet according to one of claims 1 to 24 as embossing sheet in forming-filling-sealing machines for the production of thermoformed containers closed by sealing together with a cover sheet.

27. Use of the sheet according to one of claims 1 to 27 for food packaging.