SK54594A3 - Flexible by heat-connectable multilayer foil from thermoplastic elastomers with clothing internal layer - Google Patents

Abstract

The present invention relates to heat-sealable, flexible, at least three-layered multilayer films having outer layers of thermoplastic polyurethane and/or copolyetherester elastomers and an inner barrier layer to fluid media of ethyl-vinyl alcohol copolymers, where the thermoplastic elastomers employed have a Shore D hardness of at least 35 and a Shore D hardness of at most 72, in each case measured in accordance with DIN 53 505, and the ethylene-vinyl alcohol copolymers used have an ethylene content of 10-40% by weight, based on the total weight of the ethylene-vinyl alcohol copolymer.

Description

Heat-sealable, flexible, at least three-layer multilayer film with outer layers of thermoplastic polyurethane and / or copolyetherester elastomer and inner closure layer against liquid media of ethylene-vinyl alcohol copolymers, the thermoplastic elastomers used having a Shore D hardness of at least 35 and a Shore D hardness of at least 35 measured according to DIN 53 505 and the ethylene-vinyl alcohol copolymer used contains a proportion of ethylene of 10 to 40% by weight, based on the total weight of the ethylene-vinyl alcohol copolymer.

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- 1 FLEXIBLE HEAT-CONNECTED MULTILAYER FOILED THERMOPLASTIC ELASTOMER FOIL WITH CLOSED INTERNAL LAYER

Technical field

The present invention relates to heat-sealable flexible multilayer films, the core layer and / or core layers of which are closed-layer polymers and whose outer layers are of thermoplastic elastomers. Due to the high sealing effect against organic liquids, especially hydrocarbons and alcohols, the film is suitable for the production of low-loss packages for the storage and / or transport of especially fuels.

BACKGROUND OF THE INVENTION

There are legal provisions for environmental protection for liquid storage containers that may be harmful to the environment. A well-known method is to install the container in a double-walled sump or in a double-walled design, with the priority being to protect the soil and water from the stored media.

In addition, DE-GM 9 109 544 provides a comprehensive overview of the methods of carrying out the liquid storage systems disclosed in the relevant patent literature.

Most of the known construction measures to achieve the desired protective effect are, due to their cost, only suitable for newly established liquid stores. Older liquid storage facilities often have no safety measures in place to comply with the new regulations. Since construction measures are often not feasible, they are used. protective systems with embedded foil bellows.

Yet! what protection of soil and water, as referred to in the Bau- und Prufgrundsätze für den Gewässerschutz, Vol. I and II, Institute

Bautechnik, Reichpietschufer 74-76, 10785 Berlin 30, is now well managed, efforts are being made to prevent or minimize the environmental damage caused by the evaporation of liquids, especially of an organic nature.

Bags formed from flexible sheets or bellows shaped according to larger containers or internal lining offer the possibility to close the stored liquids tightly and thus prevent evaporation of the liquid, which is otherwise made possible by the exchange of the vapor phase above the liquid. If, in addition, the moss-forming film is sufficiently flexible, the moss filled with stored goods can then be adapted to the volume of the stored liquid, as exemplified in German patent DE 40 00 427 A1, so that dispensing of steam in equilibrium with the stored the goods in the phase in this case, when the volume of the bladder is changed, only the ambient air, free of steam, is displaced.

The use of plastic films for the storage of high-boiling organic liquids such as fuel oils and / or the unloading of containers for their storage has been known for a long time and is disclosed in the corresponding production instructions, such as in Technische Regel für brennbare Flussigkeiten no. 501 (TRbF 501 Richtlinie / Bau- und Prufgrundsätze fúr Leckanzeigegeräte für Behälter), Verband der Technischen Úberwachungsvereine e. V. (Technische Regeln fur brennbare Flussigkeiten, 1991, published by Carl Heymann Verlag, 449, 50939 Köln 41). For such areas of application, TRbF 501 explicitly foresees the use of plasticized polyvinyl chloride (PVC) in construction. However, the resistance of plasticized PVC to many organic solvents and mineral products is unsatisfactory.

Rubber-based elastomers exhibit insufficient impermeability, and because of their cross-linked molecular molecular structure, they cannot always provide the shape flexibility necessary to adapt to current liquid storage systems.

Thermoplastic elastomers, on the other hand, are characterized by a combination of good mechanical properties, i.e., high tensile strength and resistance to further tearing, high elongation and flexibility in cold and chemical stability. Thermoplastic elastomers have long been known and consist of block copolymers. The different blocks or segments in their structure determine the different properties of thermoplastic elastomers, generally distinguishing hard and soft segments. The hard segment determines strength, while the soft segment determines elasticity and flexibility. The different blocks of hard and soft segments are mixed in the solid phase so that a dominant structure can be observed.

Integration of different material properties of strength and flexibility in one molecule is achieved by shifting the blocks. This so-called. internal softening causes the elasticity or softness of the plastic to be incorporated inside and cannot be influenced by a change in the composition of the additives, as happens in the case of migration.

The formation of physical cross-linking by sequentially shifting the hard segments into crystallites, glass-hydrogen bridge bonds make it reversible, thermoplastically bonding.

that is to say, to process, shape the stiffened domains and / or these networks are thermally possible and also thermoplastic

An overview of the construction, manufacture, properties and use of thermoplastic elastomers is given by Hofmann in Kunstoff 80 (1990) 10, Legge in Rubber Chemistry and Technology 62 (1989) 529 and Goyert in Swiss Plastics 4 (1982) 7.

In addition, when storing explosive media, there is a requirement for antistatic properties of the films used to eliminate the risk of fire. In the Technische Regel fur brennbare Flussigkeiten no. 401 (TRbF 401 Richtlinie fur Innebeschichtungen von Behälter zur Lagerung brennbarer

Flussigkeiten der Gruppe A, Gefahrenklasse I, II und der Gruppe B), Verband der Technischen Úberwachungsvereine e. V., which can be obtained from Carl Heymann Verlag KG, Luxembourg Street 449, 50939 Coll. 41, states, inter alia, that these coatings do not present a fire risk by electric charging if

The grounding resistance does not exceed 10 ° Ohm.

The hazards arising from the discharge of static electricity and the possible protective measures to prevent it are set out in Richtlinie Nr. 4 of the Berufsgenossenschaft der Chemischen Industrie (ZH 1/200). It is explained that hazardous solids need not be expected to charge dangerous if their surface resistance is less than or equal to 10 ⁹ Ohm, measured according to DIN 53482 / VDE 0303 Part 3 in a normal climate at 23 ° C and 50% relative humidity.

As with mass-produced plastics, the material properties of thermoplastic elastomers can be influenced by additives and fillers. Due to the antistatic properties of plastics, the incorporation of carbon black has proved to be useful, as reported by Hauf in Materialwissenschaft und Werkstofftechnik 23 (1992) 157 or Wessling in Polymer Engineering and Science 31 (1991) 1200.

Materials with a surface resistivity greater than 10 ¹³ ohm measured according to DIN 53 482 is generally referred to as insulating materials with resistances of less than 10 ⁵ ohms than conductive. Materials whose electrical resistance lies between the two limits are classified as static dissipating materials or often simply as antistatic materials.

The use of antistatic coatings or coatings is described differently in the respective patent literature, the example of DE-GM 1 822 483 relates to fully synthetic fabrics which are sealed with polyester urethane, the conductive coating being produced only on one side. In practice, coated fabrics exhibit an undesirable high proportion of micro-holes, so that micro-cracks cannot be excluded in such systems. Only a one-sided conductive coating is insufficient.

DE 3 103 772 A1 describes multilayer film compositions comprising a conductive outer layer of thermoplastic polyurethane. The use of plasticized PVC as the core layer material creates only an insufficient barrier to diffusing fuel particles. Also, using harder PVC types, there is only a slight improvement in the impermeability, but in addition there is a far-reaching loss of film flexibility.

Coated or laminated fabrics have a significantly more heterogeneous character than foils, which is an adverse phenomenon. These coatings carry the risk of accelerated lateral diffusion, so that possible damage to the material can be accelerated.

The two-layer film compositions described in JA 52-69486 have the disadvantage that it is not possible to join the two outer sides together.

Of particular importance is the unloading of containers for high vapor pressure stored goods, as is often the case with explosive substances such as fuels. These often result in enhanced diffusion of the plastic materials used to unload the container. EP 0 461 836 A1 describes the necessity of an additional sealing layer in polyolefinic materials for fuel storage and proposes the use of polyamides as the sealing layer material.

Polyamide is known as a material for its high strength and good resistance. A detailed overview of the properties, production and processing of this group of materials is given in the Kunststoff-Handbuch Handbook, Band VI, Polyamide, Vieweg, Müller (Hrsg.), Carl Hanser Verlag, Munich 1966. Use of polyamides at sufficient wall thickness to achieve adequate impermeability leads to an undesirable reduction in flexibility.

In addition, polyamide exhibits such permeability properties that are only partially sufficient for fuels, as reported by Leaversuch in Modern Plastics International, 12 (1991) 14.

It is known from relevant literature such as Rellmann and Schenck in Kunststoff 82 (1992) 729 that polymers such as ethylene / vinyl alcohol copolymers as well as saponified and / or partially saponified copolymers are used for the sealing layer to reduce the loss of stored goods in solid containers. ethylene / vinyl acetate copolymer. However, the systems described, for example, by Daubenbuchel, Kunststoffe 82 (1992) 201, are not suitable for flexible storage containers due to their material composition.

For these reasons, there is a need to provide a film which can be flexibly adapted to the outer shape and which is itself heat-sealable, i.e., weldable, so that it is possible to shape flexible containers such as bags, bellows or inner linings of canisters or tanks. For reasons of safety, these resilient containers should have the highest possible resistance to abrasion and puncture to prevent mechanical damage to the film during repeated filling and emptying processes. This means that the film should have a high tensile strength and elongation, while in the case of a negligible overload it may also have only a negligible strain.

Furthermore, the materials used should be resistant to the action of fuels and the foil produced therefrom should furthermore have good sealing properties against the action of as many organic solvents as possible.

Furthermore, it is a requirement to make the film such that it is heat-sealable, possibly weldable, and yet abrasion-resistant and, in addition to a certain minimum heat resistance, also have high chemical stability.

The desired permeability as the Super unleaded petrol should not exceed 1 g (m ^2/24 h.) As measured by

DIN 53 532.

Moreover, for the storage of high pressure organic solvents capable of oxidizing, i.e., explosive media, there is a requirement to achieve a sufficiently low surface resistance to eliminate the risk of inflammation by discharge of static electricity. This resistance should be less than 10 ⁸ Ohm, measured according to DIN 53 482 / VDE 0303, Teil 3, Elektrodenanordnung A.

It is also an advantage to provide sealing properties that are largely independent of environmental influences.

Despite the varying intensive efforts of experts in the plastics industry, such a film has so far not been able to prepare such a film despite the interest of the professional world in such a flexible film with a closure layer.

SUMMARY OF THE INVENTION

According to the invention, this has been achieved by preparing a heat-sealable, flexible, at least three-layer multilayer film composed of layers of different functional polymers, characterized in that it contains thermoplastic elastomers in the outer layers and an ethylene-vinyl alcohol cap layer in the core. associated by coextrusion and / or lamination.

The at least three-layer thermoplastic elastomer film with an inner closure layer of ethylene-vinyl alcohol copolymer for the manufacture of storage bags, sacks or interior linings is preferably 0.05 to 2 mm thick.

In addition to the at least three layers, the film may comprise further layers of other functional polymers which make it possible to further improve the properties of the film according to the invention or to adapt them to special requirements.

The sum of the fractions of the outer layers of thermoplastic elastomers is at least 20% and at most 98%, based on the total weight of the film. Preference is given to films in which the sum of the fractions of the outer layers is at least 30% and at most 80%, based on the total weight of the film.

In a preferred method, it is symmetrical so that it can be welded to the layer assembly.

In the embodiment, the film is assembled without loss of properties and without regard

Thermoplastic elastomers which are synthesized from hydrophilic raw materials are of particular interest for the storage of organic solvents and mineral oil products. Such are thermoplastic polyurethanes and copolyetheresters, as they have a negligible affinity for hydrophobic mineral oil-based fuels.

The insertion of a reinforcing fabric in the film is generally not necessary, since by using tear-resistant materials, in particular thermoplastic elastomers, the mechanical resistance and stability of the film according to the invention is generally sufficiently high. By avoiding the use of a reinforcing fabric, the film according to the invention gains chemical resistance because it prevents penetration of any harmful particles that may be contained in the stored product.

At least one of the heat-sealable outer layers may, if desired, be provided with an antistatic treatment. Suitable materials for antistatic treatments are conductive additives such as carbon black or the actual conductive polymers or metal particles. The incorporation of the conductive additives into the thermoplastic elastomer, previously brought into plastic form, is carried out by machines commonly used in the plastics industry, such as agitators or extruders, in particular twin screw extruders.

In the incorporation of the electrically conductive additives, processing aids which have a plasticizing effect can be used successfully and, after incorporating the additives, they completely protrude from the polymer matrix, so that there are no disturbing properties. Such volatile processing aids are preferably compressed gases having a high softening effect, for example carbon dioxide being particularly suitable.

Preferably, carbon black is used for antistatic treatment with a BET surface area greater than or equal to 600 m ² / g (ASTM D-3037) and an average particle size of less than 500 nm. Carbon blacks that meet these requirements are, for example, available on a commercial network such as Printex XE 2 from Degussa or Ketjenblack EC from Akzo Chemie. The proportion of carbon black for antistatic treatment is preferably 5 to 20%.

Since the sealing properties of ethylene-vinyl alcohol copolymers are very strongly dependent on the moisture content or moisture content of the environment, it is preferable not to use them as outer layers of the films but to incorporate them as the core barrier layer into the film construction.

As is known in food packaging films, by selecting suitable interlayers, the barrier properties of the closure layer have been stabilized within wide limits independently of the humidity of the environment. Polyolefinic materials are particularly suitable for forming such interlayers. In one preferred embodiment, a polyethylene polymer is used.

The sealing properties of the film of the invention to associated lead-free petrol is the Super strong and the permeability for the liquid has a value of less than 1 g (m ^2/24 hr.).

The properties of the polymeric raw materials used for the individual film layers according to the invention can be further improved by adding suitable conventional additives in just effective amounts with respect to the use according to the invention. For this purpose, it is possible to use, inter alia, glidants and lubricants, but also colored pigments, biocides and inorganic fillers or antiblocking agents, such as silicic acid.

The glidants used are preferably carboxylic acid amides, such as erucic amides, palmitic acid amides or else fluorinated stearic elastomers and polydiorganyl siloxanes, and inorganic glidants such as molybdenum disulfide, and also stearic acid salts.

Suitable antiblocking agents are, for example, organic polymers or inorganic substances such as silicates, silica and calcium carbonate, which are incompatible with the film matrix. Inorganic substances such as silica with a mean particle size of from 1 to 10 µm have proven to be particularly suitable antiblocking agents. The effective amount of these antiblocking agents is 0.5 to 6% by weight, preferably 2 to 4% by weight, based on the mean weight of the film.

Surprisingly, it has been found that in the electrically conductive treatment of the outer layers of the film according to the invention, preferably using the carbon black described above, the particles of which have a spacer effect so that the addition of other anti-blocking agents to the mass can be limited. or may not be used at all.

A detailed description of conventional additives and their mode of action is given by Gächter and Muller, Taschenbuch der Kunststoffaditive, Carl Hanser Verlag, Munchen 1989.

In order to make permanent use of the overall properties of the films according to the invention, they may contain suitable additions of stabilizers in just effective amounts, preferably hydrolysis stabilizers and / or photostabilizers and / or antioxidants.

Light absorbers are suitable as photostabilizers, in particular rich benzoates and / or phenyl salicylates, but also acylates and benzotriazoles which absorb ultraviolet light are used.

In addition, flame retardants, preferably nickel-organyl chelates and / or nickel dithiocarbamates, may be used for stabilization.

Carbodiimides are preferably used as hydrolysis stabilizers, in particular non-migrating variants such as polycarbodiimides or also hydroxyethyl ureas are used.

As antioxidants, they are suitable for use in the films according to the invention as so-called antioxidants. primary antioxidants, secondary phosphites or phosphonites sterically shielded by nitrogen substitution and / or sterically shielded phenols, as well as mixtures of primary and secondary antioxidants.

Suitable stabilization systems for the plastics used in the films of the invention are described, for example, by Rek and Bravar in J. Elast. Plastic. 12 (1980) 245.

The addition of the added substances can be carried out either by direct mixing in the production of the polymer or also by adding the entire dose corresponding to the desired dosage, or by adding a liquid or polymeric concentrate containing the additive.

All of the polymeric materials used to produce the film of the present invention can be processed on conventional plastics processing machines, such as extruders. For the preparation of the film, widely used tools are offered, such as flat film nozzles with a subsequent casting roll or subsequent application tool, as well as a film blowing head in combination with a suitable surface path.

In order to join the layers, it is possible to use tools for this purpose, for example coextrusion nozzles. If it is impossible to directly process two different materials which need to be joined into the film according to the invention if necessary due to their highly differentiated processing behavior in a single coextrusion tool, then the layers can also be joined together by additional thermal lamination using suitable bonding systems than any of the other 2 common laminating methods.

In one preferred embodiment, a polyurethane adhesive is used to laminate the different sheets of film using bonding systems characterized by strong molecular crosslinking, so that they are only slightly swollen by the migrating molecules of the stored media but will not dissolve.

The adhesion of the layers to one another can, if necessary, be substantially increased by the use of adhesion enhancing components.

Among such adhesion enhancers there is a wide variety of types available in the commercial network. They are mostly copolymers of at least two different comonomers, but also multipolymers with more than five different comonomers are used.

In particular, the preferred comonomer of the adhesion enhancing components is olefinic ethylene, which causes an improvement in the adhesion to the non-polar polymers. In addition, it is also preferred to use maleic anhydride in the adhesion promoter components. Due to its anhydride function, it causes a strong bond to polar, especially protic groups. In addition, vinyl acetates, acrylates, methacrylates and butyl acrylates are often used as the comonomers containing an acid group which, by virtue of its polar organic molecular structure, cause an increase in adhesion, with butyl acrylates being the preferred comonomers.

When using adhesion enhancers containing maleic anhydride, a strong bond is often found which further improves with the film storage time. This is due to the molecular reactions occurring during the processing process, but due to their slow progress, the desired level of adhesion-enhancing effect is only achieved later.

The film according to the invention can be modified on one or both sides to influence the surface properties. Corona, plasma or fluorine treatments are particularly suitable for this purpose. The latter means can also optimally adapt the sealing properties of the film according to the invention to the expected contact media which come into contact with the film or, if necessary, further improve them.

Such processes for the surface treatment of plastic films are detailed in, for example, Dorn and Wahono in Machinenmarkt 96 (1990) 34-39 or Milker and Moller in Kunststoff 82 (1992) 978-981.

Hereinafter, the invention will be explained in more detail by way of examples and comparative examples.

DETAILED DESCRIPTION OF THE INVENTION

Example 1

From a thermoplastic polyurethane with a soft segment consisting of a poly (oxytetramethylene) diol obtained from tetrahydrofuran and a hard segment formed from 4,4-diisocyanatodiphenylmethane and a butanediol of Shore-A 86 hardness, a symmetrically assembled ethylene copolymer film was produced by co-extrusion using a three-layer machine. vinyl alcohol. Ethylene copolymer used

- vinyl alcohol contains an ethylene content of 38% by weight, based on the total weight of the ethylene copolymer used

- vinyl alcohol. With this proportion of ethylene, the ethylene-vinyl alcohol copolymer exhibits only a minor sealing effect, but can be treated directly with thermoplastic polyurethane at similar processing temperatures.

The outer layers of the blown film have an average thickness of 90 μιη and the core layer has an average thickness of 20 μιη.

Example 2

The thermoplastic polyurethane was conductively treated with 10% high surface area carbon black, Ketjenblack EC 600. A thermoplastic polyurethane whose soft segment consists of adipic acid and hexamethylenediol and a hard segment

4,4-diisocyanatodiphenylmethane and butanediol, has a Shore-D hardness and hardness of 47. Amide waxes were used to incorporate the carbon black. The conductive thermoplastic polyurethane is treated with an ethylene-vinyl alcohol copolymer on a three-layer machine with an asymmetric composition by means of an adhesion promoter.

makes Shore-A 93 necessary

The ethylene-vinyl alcohol copolymer contains an ethylene proportion of 32% by weight, based on the total weight of the ethylene-vinyl alcohol copolymer. A copolymer of ethylene, butyl acrylate and maleic anhydride is used as an additive component. The ethylene fraction is generated by LLDPE.

The thickness of the thermoplastic polyurethane is 90 μιη, the adhesion promoter layer and the ethylene-vinyl alcohol copolymer layer have a thickness of 10 μιη.

In a further processing step, the upper surfaces of the ethylene-vinyl alcohol copolymer layers are melted by an infrared heat radiator, and by lifting both strips together, a symmetric film is formed comprising a core layer of ethylene-vinyl alcohol copolymer surrounded by layers of tackifier and outer layers of thermoplastic polyurethane.

Example 3

A plasticized PEE raw material with a Shore-D 60 hardness consisting of hard segments consisting of terephthalic acid and ethylene glycol and soft segments of poly (oxytetramethylene) diol incorporates an 8% by weight Ketjenblack EC 600 conductive carbon black in the mixer based on the total weight obtained. mixture. The blending does not use plasticizing aids that can migrate to the surface of the film. From this compound, as well as from the ethylene-vinyl alcohol copolymer with an ethylene content of 29% by weight, based on the total weight of the ethylene-vinyl alcohol copolymer used, a single-layer blown film is produced by extrusion. The PEE components and the ethylene-vinyl alcohol copolymer have processing temperatures that differ by more than 30 ° C, so that direct processing in a single machine cannot be performed. The sealing layer was joined by laminating a PEE film with a binder on both sides of the ethylene-vinyl alcohol copolymer film. For this purpose, a crosslinking polyurethane adhesive, dissolved in an organic polar non-protic solvent, is continuously applied to the laminating machine and the film is joined under pressure and temperature.

The layer thickness of the PEE film used is on average 100 μπι, the layer thickness of the ethylene-vinyl alcohol copolymer film used is on average 15 μπι.

Example 4

The conductive polyurethane prepared as in Example 2 is processed in a coextrusion blow molding machine with a thermoplastic polyurethane, the soft segment of which comprises adipic acid and hexamethylenediol and whose hard segment consists of 4,4-diisocyanate diphenylmethane and butanediol, with a Shore hardness. -A 96, optionally with a Shore-D 54 hardness, on a two-layer thermoplastic polyurethane film having a layer thickness of 50 μιη.

A coextruded triple layer film made of polyamide-6 and an ethylene vinyl alcohol copolymer having an outer layer of polyamide and a core layer of ethylene-vinyl alcohol copolymer is also used as the film for the closure layer. This symmetrical closure film has a thickness of 15 gm, the layer thickness of the ethylene vinyl alcohol copolymer being 2 gm and the thickness of the polyamide layers that close it is 6.5 gm.

The films according to the invention with a thickness of 220 gm can be obtained using a crosslinking polyurethane adhesive, wherein the above-described two-layer thermoplastic polyurethane films are laminated on both sides to the closure film. This is done so that the soot-conductive layers form the outer surfaces of the finished bonded film.

Example 5

In a three-layer coextrusion blow molding machine, a foil is produced, the core of which is formed by components for enhancing adhesion with a layer thickness of 10 gm. One of the outer sides, 50 gm thick, consists of a conductive thermoplastic polyurethane whose soft segment consists of adipic acid and hexamethylenediol and whose hard segment consists of 4,4-diisocyanatodiphenylmethane and butanediol. The Shore-A hardness of the thermoplastic polyurethane is 93, or the Shore-D 47 hardness. The other outer side also has a thickness of 50 gm and consists of a linear low density polyethylene of 0.935 g / cm ³ and an MFI of 0.5 measured at 190 ° C. , 16 kg.

A coextruded triple layer film made of polyamide-6 and an ethylene vinyl alcohol copolymer having a polyamide outer layer and a core layer of ethylene vinyl alcohol copolymer as a symmetric film is used as the seal layer (cf. Example 4). The film closure layer has a thickness of 80 gm, the layer thickness of the ethylene vinyl alcohol copolymer being 6 gm and the thickness of the polyamide layers that close it is 37 gm.

The films according to the invention can be obtained using a crosslinking polyurethane adhesive, the above-mentioned three-layer films being laminated on both sides to the sealing film. The lamination with the aid of the above-mentioned three-layer closure film films is carried out on low-density polyethylene layers which have no conductive treatment such that the outer sides of the finished bonded film form soot-treated thermoplastic polyurethane layers.

Example 1a (comparative)

After commercial melting of thermoplastic polyurethane with an elastic ether segment, a film is produced by extrusion and subsequent casting onto a cooling roll. The thermoplastic polyurethane has a built-in soft poly (oxytetramethylene) diol segment prepared from tetrahydrofuran and a hard segment formed from 4,4-diisocyanatodiphenylmethane and butanediol. The polyurethane used has a Shore-A 85 hardness. 2% silicon dioxide and 0.4% amide wax, each based on the total weight of the film, are added as processing aids. The film described here has a thickness of 400 μπι.

Example 2a (comparative)

Electrically conductive carbon black with a large Ketjenblack EC surface is incorporated into the thermoplastic polyurethane with a Shore-A 93 hardness or Shore-D 47 hardness using a mixer. Thermoplastic polyurethane is characterized by a soft segment of adipic acid and hexamethylenediol and a hard segment formed of 4,4-diisocyanatodiphenylmethane and butanediol. Amide wax should be added to the cautious plasticization during processing. A film with a thickness of 200 μιη is produced by extrusion blown film.

Example 3a (comparative)

As a further comparative film, a soft PVC film produced on a calender is used. Flexibility is achieved by adding 20% by weight of dioctyl phthalate, based on the total weight of the film. This comparative film has a thickness of 300 μιη.

Example 4a (comparative)

A PEE raw material with a Shore-A 60 hardness consisting of hard segments consisting of terephthalic acid and tetramethylene glycol and soft segments of poly (oxytetramethylene) diol is melted using an extruder. The foil hose is pulled out of the melt by means of a film blowing head. After comparing in the area, cutting off the edges and separations, the obtained film has a thickness of 200 μπι.

The results are summarized in the following table.

table

Table 1 Gas permeability g / ^(m2 / 24 hrs.) electrical surface ohm Tensile strength N / mm ² Elongation % temperature softening ° C Example 1 0.2 3.10 ¹² 55.2 360 143 Example 2 <0.1 6.10 ⁵ 51.1 550 135 Example 3 <0.1 10.07 ^ 27.6 480 157 Example 4 0.2 6.10 ⁵ 29.2 590 135 Example 5 0.1 5.10 ⁵ 23.1 690 · 148 Compared. Example 1 10.4 3.10 ¹² 72.0 4 80 140 Compared. Example 2 16.3 6.10 ⁵ 39.1 440 174 Compared. Example 3 33.8 6.10 ¹⁴ 12.5 170 74 Compared. Example 4 7.6 5.10 ¹² 36.1 64 5 157

It is clearly apparent from the comparison of the examples and the comparative examples that the films according to the invention exceed the comparative films in terms of the desired set of properties.

Measurement procedures

Determination of gasoline permeability:

The permeability of petrol foils is determined according to DIN 53 532 Determination of permeability of elastomeric foils for liquids. It is carried out according to DIN 50 014 at a temperature of 23 C of ambient air with a relative air humidity of 50% (normal climate 23/50). Conventional unleaded Super fuel, in accordance with DIN 51 607 / EN 228, shall be used as petrol.

Measurement of electrical surface resistance:

The measurement of the electrical surface resistance is carried out according to DIN 53 482 / VDE 0303 part 3 in a normal climate 23/50. A type A electrode arrangement is used consisting of two flexible parallel parallel electrodes having a length of 100 mm at a distance of 10 mm.

Determination of tensile strength and elongation:

The tensile strength and elongation are determined according to DIN 53 455. The environmental conditions correspond to the normal climate 23/50. Test strips with a tension length of 50 mm shall be used.

Determination of the softening interval:

The softening interval is determined on a Kofler block. For this purpose, a 30 x 200 mm foil strip is placed on a pre-calibrated Kofler block. After a period of 30 seconds, the strip starts to withdraw from the lower temperature region. The area in which the film remains adhering to the surface of the Kofler block indicates the softening interval.

Claims (10)

1. A heat-sealable, flexible, at least three-layer multilayer film with outer layers of thermoplastic polyurethane and / or copolymers of elastomers having a capped inner layer against liquid media, consisting of ethylene-vinyl alcohol copolymers, characterized in that the thermoplastic elastomers used have D hardness at least 35 and the highest Shore-D 72 hardness, measured in accordance with DIN 53 505 and the ethylene-vinyl alcohol copolymers used, comprise an ethylene-vinyl alcohol fraction of 10% by weight, based on the total weight of the ethylene-vinyl alcohol copolymer. Multilayer film according to claim 1, characterized in that the film comprises at least one further layer of at least one further thermoplastically processable polymer, preferably polyamide and / or polyolefin, between the outer layers of thermoplastic elastomers and the closure layer of ethylene-vinyl alcohol copolymers. Multilayer film according to claim 1 and / or 2, characterized in that reactive bonding systems, preferably polyurethane adhesives or adhesion-enhancing copolymers, are used to improve or produce interconnection. Multilayer film according to one of Claims 1 to 3, characterized in that the film has a symmetrical structure in terms of the position of the individual layers relative to the geometric center of the film. Multilayer film according to one of Claims 1 to 4, characterized in that at least one of the outer layers of thermoplastic elastomers contains conductive additives, so that its electrical surface resistance, measured according to DIN 53 482, has an arrangement of: 21 electrodes A is at most 10 µm. Film according to one of Claims 1 to 5, characterized in that its total thickness is 50 to 2000 μιη, preferably 200 to 800 μπι. Film according to one of Claims 1 to 6, characterized in that the sum of the thicknesses of the outer layers is 20% to 98%, preferably 30% to 80%, of the total thickness of the film layers. Use of a multilayer film according to one of Claims 1 to 7, for forming flexible containers and / or flexible bellows for the inner lining of dimensionally stable containers. Use of the film according to claim 8 as additional packaging and vapor closures in the storage of flammable liquids. Use of a film according to claims 8 and 9 for forming containers for storage of motor gasoline.