EP1068072A1

EP1068072A1 - Thermoplastic polyester amide films made of at least two layers and with improved sealing properties, method for producing same and their use

Info

Publication number: EP1068072A1
Application number: EP99913255A
Authority: EP
Inventors: Michael Kleemiss; Gregor Kaschel; Gunter Weber
Original assignee: Wolff Walsrode AG
Current assignee: Dow Produktions und Vertriebs GmbH and Co OHG
Priority date: 1998-03-18
Filing date: 1999-03-15
Publication date: 2001-01-17
Also published as: KR20010041920A; WO1999047349A1; AU3145099A; DE19811226A1; JP2002506755A

Abstract

The invention relates to a multi-layer film made of different polyester amides which differ in their molecular structure. The polyester amides can be biodegradable so that the entire multi-layer film is also biodegradable. The multi-layer film can be both non-oriented and monoaxially or biaxially oriented. To make it easier to process it can contain additives and has improved sealing properties.

Description

At least two-layer thermoplastic films made of polyester amide with improved sealing behavior, process for their production and their use

The invention relates to at least two-layer, thermoplastic films made of polyester amide.

Thermoplastic films made of polyester amide are known, for example, from DE-A-44 44 948 or (as part of composite multilayer films) from DE-A-196 32 799. Such single-layer films, however, have inadequate sealing behavior for many applications, in particular inadequate sealing strength.

The object of the present invention was therefore to produce a polyester amide film with improved sealing properties. This goal was achieved in that an at least two-layer film is made from different polyester amides, which differ in their molecular structure and thus thermal properties. The at least two layers are arranged in such a way that the polyesteramide layer on the outside has a lower melting point than the immediately adjacent inner layer. Each layer can consist of a single or a mixture of several polyester amides. In addition, the film can be equipped with conventional additives and auxiliaries for better production or better processing. The at least two-layer film is preferably produced by an extrusion process. In addition, the at least two-layer film can then be monoaxial or biaxial

Orientation.

It was surprising that the polyester amides can be processed thermoplastically and that, in the case of undrawn, monoaxially or biaxially stretched films, the at least two-layer structure of different polyester amides results in improved sealing behavior. The improved sealing properties of the - 2 -

Stretched and undrawn films, in contrast to a single-layer film, are noticeable by less deformation of the seal seam and a higher seal seam strength.

It is advantageous if the inner layer immediately adjacent to the outer layer

Layer has a higher proportion of polyamide structures than the outer layer.

A three-layer structure of the film according to the invention is very particularly preferred, in which a further inner (i.e. third) layer in turn has a lower melting point than the inner layer immediately adjacent to the outer layer and in particular has a composition identical to the outer layer.

The invention relates to an at least two-layer film which can be both unstretched and monoaxially or biaxially stretched and whose layers consist of different polyester amides or mixtures of several polyester amides and additionally with a maximum of 5% by weight of nucleating agents and a maximum of 5% by weight. % of the usual stabilizers and neutralizing agents and a maximum of 5% by weight of the usual lubricants and release agents in one, more or all layers and a maximum of 5% by weight of the conventional antiblocking agents, preferably in the outer

Contains top layers.

In a special form, the at least two-layer film can additionally be treated with a corona and / or flame and / or plasma pretreatment and / or an oxidizing substance and / or a depositable / depositable substance and / or a

Mixture of substances having an oxidative effect and / or attachable substances, for example gases with free radical components such as ozone or a plasma-excited gas mixture of, for example, hexamethyldisiloxane with nitrogen (N ₂ ) and / or oxygen (O ₂ ), are treated on the surface. In the case of the stretched films, the surface pretreatments mentioned are preferably carried out according to the orientation. - 3 -

The monoaxial or biaxial orientation takes place in the case of amorphous thermoplastics in temperature ranges above the glass transition temperature and in the case of partially crystalline thermoplastics above the glass transition temperature and below the crystallite melting temperature.

It is known that certain polyesteramides as well as other polymeric materials can be subject to biodegradation. Mainly materials that are obtained directly or after modification from naturally occurring polymers are to be mentioned, for example polyhydroxyalkanoates such as polyhydroxybutyrate, plastic celluloses, cellulose esters, plastic starches, chitosan and pullulan. A targeted variation of the polymer composition or the structures, as is desirable on the part of the polymer application, is difficult and often only possible to a very limited extent due to the natural synthesis process. For the purposes of this invention, the terms "biodegradable and compostable polymers or films" are understood to mean goods which correspond to the test according to DIN

V 54 900 from 1998 got the "biodegradability" tested.

However, many of the synthetic polymers are not attacked by microorganisms, or only very slowly. Mainly synthetic polymers that contain heteroatoms in the main chain are considered to be potentially biodegradable. An important class within these materials are the polyesters. Synthetic raw materials that only contain aliphatic monomers have a relatively good biodegradability, but can only be used to a very limited extent due to their material properties; see Witt et al. in Macrom. Chem. Phys., 195 (1994) pp. 793-802. Aromatic polyesters, on the other hand, show significantly deteriorated, biodegradability with good material properties.

Various biodegradable polymers have been known recently (see DE-44 32 161). These have the property that they can be processed easily thermoplastically and, on the other hand, are biodegradable, ie their entire polymer chain is split by microorganisms (bacteria and fungi) by means of enzymes and - 4 -

be completely broken down into carbon dioxide, water and biomass. A corresponding test in a natural environment under the influence of microorganisms, such as prevails in a compost, is among other things given in DIN V 54 900. Due to the thermoplastic behavior, these biodegradable materials can be processed into semi-finished products such as cast or blown films. However, the use of these semi-finished products is very limited. On the one hand, these films are characterized by poor mechanical properties and, on the other hand, the barrier properties with regard to water vapor and gases are very poor in comparison to films made from typical, but not biodegradable plastics such as polyethylene, polypropylene or polyamide.

The invention also relates to the use of certain biodegradable and compostable polyester amides or a mixture of these polymers for the production of the multilayer film.

Suitable according to the invention are aliphatic or partially aromatic polyester amides which are composed of the following monomers:

I) aliphatic bifiinktionellen alcohols, preferably linear C ₂ to _{C] 0} - dialcohols such as for example ethanediol, butanediol, hexanediol, more preferably butanediol, and / or optionally cycloaliphatic bifunctional alcohols, preferably having 5 to 8 carbon atoms, such as cyclohexanedimethanol , and / or partially or completely instead of the diols monomeric or oligomeric polyols based on ethylene glycol, propylene glycol, tetrahydrofuran or copolymers thereof with molecular weights up to 4000, preferably up to 1000, and / or optionally small amounts of branched bifunctional alcohols, preferably C ₃ -C ₁₂ - Alkyldiols, such as neopentylglygol and additionally optionally small amounts of higher-functional alcohols, preferably C ₃ -C ₁₂ -alkyl polyols, such as, for example, 1,2,3-propanetriol, trimethylolpropane, and from aliphatic bifunctional acids, preferably with 2 to 12 C- Atoms in the alkyl chain, such as, for example, and preferably succinic acid, adipic acid and / or optionally aromatic bifunctional acids such as, for example, terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid and, if appropriate, small amounts of higher-functional acids such as, for example, trimellitic acid or

II) from acid- and alcohol-functionalized building blocks, preferably with 2 to 12 carbon atoms in the carbon chain, for example hydroxybutyric acid, hydroxyvaleric acid, lactic acid, or their derivatives, for example ε-caprolactone or dilactide,

or a mixture and / or a copolymer of I) and II), the aromatic acids making up no more than 50% by weight, based on all acids, and

III) an amide content of aliphatic and / or cycloaliphatic bifunctional and / or optionally small amounts of branched bifunctional amines, preference is given to linear aliphatic C ₂ to C _{] 0} -diamines, and additionally optionally small amounts of higher-functional amines, among the amines preferably hexamethylenediamine, isophoronediamine and particularly preferably hexamethylenediamine, and from linear and / or cycloaliphatic bifunctional acids, preferably having 2 to 12 carbon atoms in the alkyl chain or C ₅ or C ₆ ring in the case of cycloaliphatic acids, preferably adipic acid, and / or optionally small amounts branched bi-functional and / or optionally aromatic bi-functional

Acids such as, for example, terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid and additionally, if appropriate, small amounts of higher-functional acids, preferably having 2 to 10 carbon atoms, or or a mixture of III) and IV) as the amide fraction, the ester fraction I) and / or II) being at least 3% by weight, based on the sum of I), II), III) and IV), preferably the weight fraction of the ester structures is 5 to 70% by weight, the proportion of the amide structures is 95 to 30% by weight and in a preferred form of the biodegradable polyester amides the ester proportion I) and / or II) is at least 30% by weight, based on the The sum of I), II), III) and IV) is preferably 30 to 70% by weight of the ester structures and 70 to 30% by weight of the amide structures.

The polyester amides suitable according to the invention can be both pure polyester amides and mixtures of different polyester amides.

The polyester amides suitable according to the invention can contain a maximum of 5% by weight for

Nucleating agents typically used in polyester (for example 1,5-naphthalenedisodium sulfonate or layered silicates, for example talc, or nucleating agents of nanoparticle size, ie average particle diameter <1 μm, of for example titanium nitride, aluminum hydroxyl hydrate, barium sulfate or zirconium compounds) and with a maximum of 5% by weight of usual stabilizers and

Neutralizing agents and with a maximum of 5% by weight of the usual lubricants and release agents and a maximum of 5% by weight of the usual antiblocking agents, and possibly with a corona or flame or plasma pretreatment or an oxidizing substance or mixture of substances, for example gases with radicals Components such as ozone or a plasma-excited gas mixture of, for example, hexamethyldisiloxane with nitrogen (N ₂ ) and / or oxygen (O ₂ ), have been treated on the surface.

The usual stabilizing compounds for polyester compounds can be used as stabilizers and neutralizing agents. The amount added is a maximum of 5% by weight. Phenolic stabilizers, alkali / alkaline earth stearates and / or alkali / alkaline earth carbonates are particularly suitable as stabilizers. Phenolic stabilizers are preferred in an amount of 0 to 3% by weight, in particular 0.15 to 0.3% by weight and with a molar mass of more than 500 g / mol. Pentaerythrityl tetrakis

3 (3,5-di-tertiary-butyl-4-hydroxyphenyl) propionate or 1,3,5-trimethyl-2,4,6-tris (3,5-di-tertiary-butyl-4-hydroxybenzyl) -benzene are special advantageous.

Neutralizing agents are preferably dihydrotalcite, calcium stearate, calcium carbonate and / or calcium montanate with an average particle size of at most 0.7 μm, an absolute particle size of less than 10 μm and a specific surface area of at least 40 m ² / g.

In a particularly preferred embodiment, the film has a nucleating agent content of 0.0001 to 2% by weight and a stabilizer and neutralizing agent content of 0.0001 to 2% by weight.

Lubricants and release agents are higher aliphatic amides, tertiary amines, aliphatic acid amides, higher aliphatic acid esters, low molecular polar modified waxes, montan waxes, cyclic waxes, phthalates, metal soaps and silicone oils.

The addition of higher aliphatic acid amides and silicone oils is particularly suitable.

Among the aliphatic amides, the supply forms from ethylene amide to stearyl amide are particularly suitable. Aliphatic acid amides are amides of a water-insoluble monocarboxylic acid (so-called fatty acids) with 8 to 24 carbon atoms, preferably 10 to 18 carbon atoms. Erucic acid amide, stearic acid amide and oleic acid amide are preferred among them. - 8th -

Also suitable as release agents or lubricants are compounds which contain both esterais and amide groups, such as stearamide ethyl stearate or 2 stear amido ethyl stearate.

A number of different compounds fall under the name montan waxes. See Neumüller et al. in Römpps Chemie-Lexikon, Franckh'sche Verlagshandlung, Stuttgart, 1974.

Examples of suitable cyclic waxes are components such as cyclic adipic acid tetramethylene esters or 1,6-dioxa-2,7-dioxocyclododecane, or the homologous hexamethylene derivative. Such substances are known as commercial products with the name Glycolube VL.

Suitable silicone oils are polydialkylsiloxanes, preferably polydimethylsiloxane, polymethylphenylsiloxane, olefin-modified silicone, and modified with polyethers

Silicone such as polyethylene glycol and polypropylene glycol as well as epoxyamino and alcohol modified silicone. The viscosity of the suitable silicone oils is in the range from 5,000 to 1,000,000 mm ^{2 /} s. Polydimenthylsiloxane with a viscosity of 10,000 to 100,000 mm ^{2 /} s is preferred.

The amount of lubricant added is at most 5% by weight. In a particularly preferred embodiment of the film, it has a lubricant content of 0.005 to 4% by weight. In a very particularly preferred embodiment of the film, it has a lubricant content of 0.05 to 1% by weight.

Suitable antiblocking agents are both inorganic and organic additives, which protrude from the film surface as an elevation and thus cause a spacer effect.

In a preferred form, the following are used as inorganic antiblocking agents

Fabrics used: - 9 -

Aluminum hydroxide

Aluminum silicates, for example kaolin or kaolin clay,

Aluminum oxides, for example Θ-aluminum oxide

Aluminum sulfate ceramics made of silica aluminum oxides

Barium sulfate natural and synthetic silicas

Layered silicates, for example asbestos,

Silicon dioxide Calcium carbonate of the calcite type

Calcium phosphate

Magnesium silicates

Magnesium carbonate

Magnesium oxide Titanium dioxide

zinc oxide

Micro glass balls and the following substances are used as organic antiblocking agents: organic polymers such as starch which are incompatible with the biodegradable polymer

Polystyrene

Polyamides

Polycarbonate cross-linked and uncross-linked polymethyl methacrylate cross-linked polysiloxane (e.g. Tospearl) polar-modified polyethylene (e.g. maleic anhydride-grafted polyethylene) polar-modified polypropylene (e.g. maleic anhydride-grafted polypropylene) statistical copolymer on ethylene or propylene acid or acrylic or acrylic acid or acrylic or methacrylic acid or acrylic methacrylic or methacrylate with acrylic alcohol - - 10 -

acid esters or metal salts of methacrylic acid or metal salts of methacrylic acid esters

Benzoguanamine formaldehyde polymers aliphatic and partially aromatic polyesters with different melting points than that

Film raw material aliphatic polyester amides with different melting points than the film raw material aliphatic polyester urethanes with different melting points than the film raw material aliphatic-aromatic polyester carbonates with different melting points than that

Foil raw material

The effective amount of antiblocking agent is up to a maximum of 5% by weight. In a particularly preferred embodiment, the film contains 0.005 to 4% by weight of antiblocking agent. In a very particularly preferred embodiment, the film contains 0.05 to 1% by weight of antiblocking agent. The average particle size is between 1 and 6 μm, in particular 2 and 5 μm, particles with a spherical shape, as described in EP-A-0 236 945 and DE-A-38 01 535, being particularly suitable. Combinations of different spacer systems are also particularly suitable. In a particularly preferred embodiment, the spacer systems are added to the outer cover layers.

According to the processes previously used, the polymers for the film provided with additives are provided with the desired amounts by weight of organic or inorganic fillers in the production of raw materials. This happens when the raw material is granulated, for example in twin-screw extruders, where the additives are added to the raw material. In addition to this type of additive, there is also the possibility that some or all of the necessary additives are added to a raw material that is not or only partially finished in the form of a masterbatch. The term masterbatch in the context of the present invention is to be understood as a masterbatch, in particular a granular, dust-free concentrate of a plastic raw material with high amounts of additives, which is used as an intermediate product in mass preparation (as a material addition to one) - 11 -

or only partially or incompletely with granules equipped with additives) in order to produce therefrom films which contain a certain amount of additives. The masterbatch is mixed in such amounts before the polymer granules are introduced into the extruder to the raw materials which are not or only partially or incompletely equipped with additives, so that the desired percentages by weight of fillers are achieved in the films.

The preferred materials from which the masterbatches are produced in addition to the additives are substances which are compatible with the polyesteramides mentioned in this invention.

For the subgroup of biodegradable polyester amides, the materials from which the masterbatches are produced in addition to the additives are also biodegradable in a particularly preferred form.

In corona treatment, the procedure is expediently such that the film is passed between two conductor elements serving as electrodes, such a high voltage, usually alternating voltage (approximately 5 to 20 kV and 5 to 30 kHz), being applied between the electrodes that spray or corona discharges can take place. The air above the film surface is ionized by the spray or corona discharge and reacts with the molecules of the film surface, so that additional polar deposits are formed in the polymer matrix.

For flame treatment with polarized flame (cf. US-A-4 622 237), an electrical direct voltage is applied between a burner (negative pole) and one

Cooling roller created. The level of the applied voltage is between 400 and 3000 V, preferably in the range from 500 to 2000 V. The applied voltage gives the ionized atoms increased acceleration and impacts the polymer surface with greater kinetic energy. The chemical bonds within the polymer molecule are broken up more easily and the

Radical formation is faster. The thermal load on the polymer - 12 -

is much lower than that of the standard flame treatment, and films can be obtained in which the sealing properties of the treated side are even better than those of the untreated side.

In a plasma pretreatment, gases, e.g.

Oxygen or nitrogen or carbon dioxide or methane or halogenated hydrocarbons or silane compounds or higher molecular compounds or also mixtures thereof, a high-energy field, e.g. Microwave radiation, exposed. High-energy electrons are created, which hit the molecules and transfer their energies. This creates local radical structures, the excitation states of which correspond to temperatures of a few tens of thousands of degrees Celsius, even though the plasma itself is almost at room temperature. This makes it possible to break chemical bonds and initiate reactions that can normally only take place at high temperatures. Monomer radicals and ions are formed. Short-chain oligomers are formed from the resulting monomer radicals, some of them already in plasma, which then condense and polymerize on the surface to be coated. A homogeneous film is deposited on the coating material.

However, before the monomer radicals or ions deposit on the substrate, there is also the option of adding a further material flow to the excited molecules in the so-called after-glow zone. This makes it possible to produce a substance or a mixture of substances which, when it strikes the polymer film surface, produces an oxidative attack on the substrate polymers. A glass-like and mostly highly cross-linked layer is formed, which with the

Foil surface is firmly connected. With a suitable material composition, this results in an increase in the surface tension on the film.

The at least two-layer film according to the invention is expediently produced using an extrusion process. The polyester amides in granular form are melted in extruders, homogenized, compressed and - 13 -

discharged through a multi-layer nozzle. The nozzle can be an annular nozzle for producing a seamless tubular film. The carried out or e.g. Film pulled out by roller pressers is then cooled until solidification. The cooling can take place both over air and over water or also by means of cooling rollers. The cooling can take place on one or both sides, in the case of a tubular film on the inside and outside or only on the inside or only on the outside. The tubular film can also be cut on one or both sides, so that a multilayer undrawn flat film is obtained.

The tubular film produced as described above can furthermore be tempered as a primary tube after cooling in the case of partially crystalline polyester amides at crystallite melting temperature and in the case of amorphous polyester amides above the glass transition temperature and then biaxially, ideally simultaneously. A particularly suitable method is simultaneous biaxial stretching using double-bubble technology, in which a primary bladder is stretched by applying internal pressure. The film can then be subjected to a heat treatment in order to adjust the shrink properties. In this fixing process, the film can be heated up again to just below the crystallite melting temperature.

The tubular film can then be subjected to an inside or outside surface treatment.

The invention also relates to an extrusion process for producing the multilayer film according to the invention, in which the multilayer nozzle is designed as a flat nozzle for producing a multilayer flat film. The discharged film is then cooled until solidification. The cooling can take place over water by means of cooling rollers. - 14 -

After cooling, the flat film can be tempered to temperatures below the crystallite melt temperature in the case of partially crystalline polyamides and above the glass transition temperature in the case of amorphous polyamides and then stretched one or more times monoaxially or biaxially. After the stretching stage or stages, the film can optionally be fixed in each case. After the stretching processes and the possibly prevailing fixing stages, the film thus produced can possibly be surface-pretreated in-line.

The invention also relates to a method for monoaxial or biaxial stretching of the film according to the invention. The biaxial stretching can be carried out in the simultaneous stretching process or in the two-stage sequential process, where both first longitudinal and then transverse stretching as well as first transverse and then longitudinal stretching, or in the three-stage sequential process, whereby both first longitudinal, then transverse and finally longitudinal stretching as can also first be stretched transversely, then lengthwise and finally crosswise, or in the four-stage sequential process, whereby both first stretched longitudinally, then crosswise, then lengthwise and finally crosswise as well as first crosswise, then lengthwise, then crosswise and finally can be stretched longitudinally. The film may be attached to each individual stretching. The individual stretching in the longitudinal and transverse directions can take place in one or more stages.

In a preferred form, the biaxial stretching of the film according to the invention is characterized in that it is a sequential process which begins with the longitudinal stretching.

In an even more preferred form, the monoaxial stretching of the film according to the invention is characterized in that the stretching ratio in the longitudinal direction is 1: 1.5 to 1:10. - 15 -

In an even more preferred form, the monoaxial stretching of the film according to the invention is characterized in that the stretching ratio in the longitudinal direction is 1: 2.8 to 1: 8.

In an even more preferred form, the biaxial stretching of the film according to the invention is characterized in that the total stretch ratio in the longitudinal direction is 1: 1.5 to 1:10 and the total stretch ratio in the transverse direction is 1: 2 to 1:20.

In an even more preferred form, the biaxial stretching of the film according to the invention is characterized in that the total stretch ratio in the longitudinal direction is 1: 2.8 to 1: 8 and the total stretch ratio in the transverse direction is 1: 3.8 to 1:15.

In a preferred form of the film according to the invention, it has a thickness which is less than 500 μm.

In an even more preferred form of the film according to the invention, it has a thickness which is less than 80 μm. It is therefore advantageous if the outer layer has a smaller thickness than the inner layer immediately adjacent to it. The outer layer particularly preferably has a thickness of 5 to 20 μm and the inner layer adjacent to it has a thickness of 20 to 40 μm. Any next inner layer that is present preferably has a thickness of 5 to 20 μm.

The invention also relates to the use of the invention

Foil. This film is used as a multilayer film in pretreated or untreated as well as in printed, unprinted or varnished form for packaging in the food and non-food sectors or as a multilayer film in pretreated or untreated form for protective and separating functions in connection with Cosmetics and

Hygiene articles, for example for baby diapers or sanitary napkins or as multi - 16 -

Layered film in pretreated or untreated form for surface protection or surface finishing in the area of cardboard, paper and letter window lamination or as a refined film that is used in pretreated or untreated as well as printed or unprinted form as well as provided with adhesive as a label or adhesive strip can be considered.

Furthermore, the multilayer film made of biodegradable polyester amides in pretreated or untreated form for greenhouse covers or mulch films in the fields of horticulture or agriculture or refined into sacks for storing and transporting goods, for example organic waste, can be used, the multilayer structure making them possible Orientation of the molecules / crystals and the painting / printing a control of the degradation rate can be achieved. Furthermore, the good permeability of the multilayer films made of various polyester amides to oxygen, carbon dioxide and water vapor is particularly important for the packaging of fresh food

Importance. The biodegradability of certain polyesteramides can be of great advantage for certain applications.

To improve pressure adhesion or adhesiveness, the film surface can be coated with a corona, a flame, a plasma or another oxidative substance or mixture of substances, e.g. gases with radical components such as ozone or a plasma-excited gas mixture of, for example, hexamethyldisiloxane during manufacture and / or subsequently during further processing with nitrogen (N ₂ ) and / or oxygen (O ₂ ), pretreated so that there is an increase in surface tension.

The invention also relates to the use of the multilayer film according to the invention as a coated film or in a film composite. The other films in the composite can be non-degradable films or also biodegradable and compostable films. In addition, the coating or adhesive used can be both normal - 17 -

non-degradable systems as well as biodegradable and compostable raw materials.

In a particularly preferred form of use of this multilayer film according to the invention, only those substances are used to produce the coated film or a film composite that the overall composite is also biodegradable and compostable in accordance with DIN V 54 900.

The invention furthermore relates to the use of the multilayer film according to the invention as a starting material for the production of a bag which releases its contents after the disintegration by the biodegradation process. The bag can be produced by gluing and sealing the film and can both be closed and have an opening with a corresponding closure or connection.

The invention also relates to the use of the multilayer film or composites according to the invention as a starting material for the production of a packaging or separating or surface protection film with very high water vapor permeability by piercing this film with a cold or tempered needle roller. The purpose of this film is the packaging of moisture-releasing goods, for example bread or various types of fruit or vegetables, or as a separating and protective film in the hygiene area.

- 18 -

example 1

A two-layer film with an AB structure was produced from two different polyester amides, whose structure belongs to the subgroup of biodegradable polyester amides. Material A (polyester amide from 54

% By weight ε-caprolactam, 23% by weight adipic acid, 23% by weight 1,4-butanediol with 60% by weight amide structures and 40% by weight ester structures, LP BAK 403-004, Bayer AG) an MFI of 7 (in g / lO min at 190 ° C, 2.16 kg, measured according to DIN 53 735), a melting point of 125 ° C, measured according to ISO 3146 / C2, a proportion of lubricant of 1% by weight % and an antiblock content of 0.1% by weight. The

Material B (polyester amide from 62% by weight ε-caprolactam, 29% by weight adipic acid, 17% by weight 1,4-butanediol with 65% by weight amide structures and 35% by weight ester structures, LP BAK 404- 002, Bayer AG) has an MFI of 10 (in g / 10 min at 190 ° C, 2.16 kg, measured according to DIN 53 735), a melting point of 140 ° C, measured according to ISO 3146 / C2 Lubricant of 0.4 wt .-% and a

Antiblock content of 0.1% by weight. The two-layer film was coextruded and then sequentially biaxially stretched. The maximum extrusion temperature for material A was 180 ° C, for material B 190 ° C. The melt was cooled as a flat film on a cooling roll mill at roll temperatures of 43 ° C. on the casting roll and 22 ° C. on the cooling roll. A solid thick film was formed, which in the next process step was heated to stretching temperature by tempering rolls at temperatures of 82 ° C. The actual stretching rollers were operated at a temperature of 85 ° C. The flat film was stretched in one step by the ratio 1: 4.2 in the longitudinal direction. The post-heating rollers over which the film then ran were at a temperature of 50 ° C. The preheating zones of the

The transverse stretching oven was heated to 130 ° C. The temperature in the actual transverse stretch was 120 ° C. Here the film was stretched transversely by a ratio of 1: 4.6. This resulted in a calculated area stretch ratio of 1: 19.3. After transverse stretching, the film was fixed at a temperature of 105 ° C. The production speed at the outlet of the transverse stretch was 18.0 m / min. A film with a thickness of 55 μm could be produced. - 19 -

Example 2

The same biodegradable polyesteramides from Example 1 were processed under the process conditions described in Example 1 to give a three-layer biaxially oriented ABA film. In this case, a film with a total thickness of 80 μm was produced, the polyester amide with the lower melting point forming the outer layers in order to achieve the improved sealing properties of the film.

Example 3

A three-layer ABA film was produced from the same biodegradable polyester amides from Examples 1 and 2 on a blown film line. The maximum extrusion temperature was 160 ° C. The melt was discharged through a multi-layer ring nozzle and cooled by air. The maximum nozzle temperature was also 160 ° C. In this case, a film with a total thickness of 75 μm and a width of 500 mm was produced, the polyester amide with the low melting point forming the outer layers.

Comparative example

A single-layer film was produced from the biodegradable polyester amide (material A) from Examples 1, 2 and 3 on a blown film line. The maximum extrusion temperature was 160 ° C. The melt was discharged through an annular die and cooled by air. The maximum nozzle temperature was also 160 ° C. In this case, a film with a thickness of 95 μm and a width of 300 mm was produced.

The following physical properties were measured as follows on the samples produced: - 20 -

Mechanical properties:

The mechanical parameters tear strength and elongation at break were determined on the samples both in the longitudinal and in the transverse direction in accordance with DIN 53 455. The E module in the longitudinal and transverse directions was determined in accordance with DIN 53 457. The

The thickness of the individual samples was determined in accordance with DIN 53 370.

Permeation properties:

The permeability of oxygen to the samples was measured at a temperature of 23 ° C. and a relative humidity of 75% in accordance with DIN 53 380. Furthermore, the permeability of water vapor at a temperature of 23 ° C and a relative humidity of 85% was determined in accordance with DIN 53 122.

Sealing seam strengths: The strength of the sealing seams, which were produced on a sealing device with a sealing tool heated on both sides, was determined on the samples. The seal strength is understood as the maximum force that is required to separate a seal seam produced under defined conditions (pressure, time, temperature). The sealing seam is given in N, the strip width is added as an index (N / 15mm). The sealing area is the temperature range in which a measurable

Seal strength is present.

Two clean, clean sample strips were removed from the film web to be tested. For sealing, they were placed on top of one another with the surfaces to be sealed and held between the sealing jaws in such a way that the sample protruded at least 1 cm on each side. Sealing must be perpendicular to the direction of film travel.

The seal strength test was carried out according to the following standard condition: - 21 -

Pressure: 50N / cm ²

Time: 0.5sec

Temperature: in 1 OK steps from 150 ° C.

A 15 mm wide test strip was cut from the center of the seal seam produced, exactly in the film running direction, using a test strip cutter. It was tested for seal strength using a tensile strength machine by separating it perpendicular to the seal seam. The maximum value of the force occurring during tearing was given in each case.

The results of the tests on the samples from Examples 1, 2 and 3 and the comparative example are shown in Table 1.

22

Table 1

m ≠ ύl φM'Z & b $ 3.

Mechanical properties

Thickness [µm] 56 77 74 95

Young's modulus along [MPa] 359 238 228 223

E-module transverse [Mpa] 216 384 215 244

Longitudinal tensile strength [MPa] 92 91 36 49

Tear strength across [MPa] 82 86 34 51

Elongation at break along [%] 156 228 620 765

Elongation at break across [%] 165 171 716 854

Permeation

Oxygen 23 ° C / 75% r. F. 466 391 408 360 [cm ³ / m ² / d / bar]

Water vapor 23 ° C / 85% r. F. 145 107 122 100 [g / 2 / d]

Seal strength

Tear force required [N / 15mm] not not measured 18 1 1 measured (at 150 ° C) (at 150 ° C)

Claims

- 23 patent claims

1. At least two-layer thermoplastic film, the layers of which essentially consist of at least one polyester amide and, if appropriate, additionally a maximum of 5 based on the total mass of the film

% By weight of nucleating agents and a maximum of 5% by weight of the customary stabilizers and neutralizing agents and a maximum of 5% by weight of the usual lubricants and release agents in one, more or all layers and a maximum of 5% by weight of the customary antiblocking agents in at least one contains outer layer, characterized in that the outer polyester amide layer has a lower melting point than the immediately adjacent inner layer.

2. A film according to claim 1, characterized in that the inner layer immediately adjacent to the outer layer has a higher proportion

Has polyamide structures as the outer layer.

3. Film according to one of claims 1 to 2, characterized in that the polyester amides are polyester amides made from aliphatic or partially aromatic polyesters

I) aliphatic bifunctional alcohols, preferably linear C ₂ to

C ₁₀ -dial alcohols such as, for example, ethanediol, butanediol, hexanediol, particularly preferably butanediol, and / or optionally cycloaliphatic bifunctional alcohols, preferably with 5 to 8 C-

Atoms, such as, for example, cyclohexanedimethanol, and / or partially or completely, instead of the diols, monomeric or oligomeric polyols based on ethylene glycol, propylene glycol, tetrahydrofuran or copolymers thereof with molecular weights up to 4000, preferably up to 1000, and / or optionally small amounts of branched bifunctional alcohols, preferably C. ₃ -C ₁₂ alkyl diols, such as - 24 -

for example, neopentylglygol and additionally, if appropriate, small amounts of higher-functional alcohols, preferably C ₃ -C ₂ -alkyl polyols, such as, for example, 1,2,3-propanetriol, trimethylolpropane, and from aliphatic bifunctional acids, preferably with 2 to 12 C atoms in the alkyl chain such as and preferred

Succinic acid, adipic acid and / or optionally aromatic bifunctional acids such as terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid and additionally optionally small amounts of higher functional acids such as trimellitic acid or

III) an amide portion of aliphatic and / or cycloaliphatic bifunctional and / or optionally small amounts of branched bifunctional amines, linear aliphatic C ₂ to C ₁₀ diamines are preferred, and additionally optionally small amounts of higher functional amines, among the amines preferably hexamethylenediamine,

Isophoronediamine and particularly preferably hexamethylenediamine, and from linear and / or cycloaliphatic bifunctional acids, preferably having 2 to 12 carbon atoms in the alkyl chain or C ₅ or C ₆ ring in the case of cycloaliphatic acids, preferably adipic acid, and / or if appropriate small amounts of branched bifunctional and / or optionally aromatic bifunctional - 25 -

Acids such as, for example, terephthalic acid, isophthalic acid, naphthalene dicarboxylic acid and additionally, if appropriate, small amounts of higher-functional acids, preferably having 2 to 10 carbon atoms, or

IV) an amide component from acid- and amine-functionalized building blocks, preferably with 4 to 20 carbon atoms in the cycloaliphatic chain, preferably ω-laurolactam, ε-caprolactam, particularly preferably ε-caprolactam,

or a mixture of III) and IV) as the amide fraction, the ester fraction I) and / or II) being at least 3% by weight, based on the sum of I), II), III) and IV), preferably the weight fraction of the ester structures is 5 to 70% by weight, the proportion of the amide structures is 95 to 30% by weight and, in a preferred form of the biodegradable polyesteramides, the ester content I) and / or II) based on at least 30% by weight to the sum of I),

II), III) and IV), preferably the proportion by weight of the ester structures is 30 to 70% by weight, the proportion of the amide structures is 70 to 30% by weight.

4. Film according to one of claims 1 to 3, characterized in that the polyester amides are both pure polyester amides and

Mixtures of different polyester amides can act.

5. Film according to one of claims 1 to 4, characterized in that the proportion of lubricants in the range of 0.005 to 4 wt .-% in one, more or all layers and the proportion of antiblock particles in the range of

0.005 to 4 wt .-% is preferably in the outer cover layers.

6. Film according to one of claims 1 to 5, characterized in that the proportion of lubricants in the range of 0.05 to 1 wt .-% in one, more or all layers and the proportion of antiblock particles in the range of

0.05 to 1 wt .-% is preferably in the outer layers. - 26 -

7. Film according to one of claims 1 to 6, characterized in that it is a three-layer film in which the further inner (third) layer in turn has a lower melting point than that of the outer layer immediately adjacent inner layer.

8. Film according to one of claims 1 to 7, characterized in that the film is stretched monoaxially in the longitudinal direction and the stretching ratio of the monoaxially stretched film in the longitudinal direction is 1: 1.5 to 1:10.

9. Film according to claim 8, characterized in that the stretching ratio of the monoaxially stretched film in the longitudinal direction is 1: 2.8 to 1: 8.

10. Film according to one of claims 1 to 7, characterized in that the film is biaxially stretched and the total stretch ratio of the biaxially stretched

Film in the longitudinal direction 1: 1.5 to 1:10 and the total stretch ratio in the transverse direction is 1: 2 to 1:20.

11. A film according to claim 10, characterized in that the total stretch ratio of the biaxially stretched film in the longitudinal direction 1: 2.8 to 1: 8 and that

Total stretch ratio in the transverse direction is 1: 3.8 to 1:15.

12. Film according to claims 10 or 11, characterized in that the biaxial stretching has been carried out in a sequential process starting with the longitudinal stretching.

13. Film according to one of claims 1 to 12, characterized in that the film thickness is less than 500 microns.

14. Film according to one of claims 1 to 13, characterized in that the

Film thickness is less than 80 μm. - 27 -

15. Film according to one of claims 1 to 14, characterized in that the outer layer has a thickness of 5 to 20 microns and its immediately adjacent inner layer has a thickness of 20 to 40 microns.

16. Film according to one of claims 1 to 15, characterized in that the polyester amides are all biodegradable and compostable.

17. Film according to one of claims 1 to 16, characterized in that the film in at least one layer for organic or inorganic pigments

Contains coloring,

18. Multi-layer film according to claim 17, characterized in that the pigments are biologically harmless and / or are contained in an amount of less than 1 wt .-%.

19. Use of the film according to one of claims 1 to 18 as a multilayer film in pretreated or untreated as well as in printed, unprinted or lacquered form for packaging in the areas of food or non-food or for greenhouse covers or mulch films in the fields of horticulture or Agriculture or sacks for the storage and transport of goods or for protective and separating functions in connection with cosmetics and hygiene articles or for surface protection or surface finishing in the area of cardboard, paper and letter window lamination or as a finished film in pretreated or untreated as well as in printed or unprinted form and provided with adhesive as a label or adhesive strip. - 28 -

20. Use of the film according to one of claims 1 to 18 for the production of coated films or composites or laminates made of the same or different polyester amides or with other non-biodegradable film types.

21. Use of the film according to claim 20, characterized in that all of the films and coating and adhesives used in the composite or laminate or in the coated film are biodegradable and compostable.

22. A process for producing an at least two-layer film according to any one of claims 1 to 18, characterized in that the polyester amides are first broken down by the action of heat and shear and the resulting melt is discharged in a tool as tubular film or flat film and cooled until solidification.

23. The method according to claim 22, characterized in that the tubular film is tempered after cooling with partially crystalline polyester amides to temperatures above the glass transition temperatures and below the crystallite melting temperatures and with amorphous polyester amides above the glass transition temperatures and then one or more biaxially stretched and after or individual stretches may be fixed and after these stretching and fixing processes may be surface-treated.

24. The method according to claim 22, characterized in that the flat film is tempered after cooling in the case of partially crystalline polyester amides to temperatures above the glass transition temperatures and below the crystallite melting temperatures and in the case of amorphous polyester amides above the glass transition temperatures and then stretched one or more monoaxially or biaxially and after the individual stretching or - 29 -

fixed and possibly surface treated after these stretching and fixing processes.