AU732420B2 - Biaxially stretched, biodegradable and compostible film - Google Patents

Description

WO 98/04627 PCT/EP97/03748 1 Biaxially stretched, biodegradable and compostible film The invention relates to a biaxially stretched, biodegradable and compostible film.

It is known that certain polymeric materials may be subject to biological degradation. Materials to be mentioned here are mainly those obtained from naturally occurring polymers, directly or after modification, for example polyhydroxy alkanoates such as polyhydroxy butyrate, plastic celluloses, cellulose esters, plastic starches, chitosan and pullulan. Purposeful variation of the polymer composition or of the stucts, such as is desirable from the point of view of polymer application, is only possible with difficulty and often in very limited manner by reason of the natural synthesis process.

Many of the synthetic polymers, on the other hand, are not attacked by microorganisms or are only attacked extremely slowly. Mainly synthetic polymers that contain heteroatoms in the principal chain are regarded as potentially biodegradable.

An important class within these materials is represented by the polyesters. Although synthetic raw materials that contain only aliphatic monomers exhibit relatively good biodegradability, by reason of their material properties they can be used only to an extremely limited extent; cf. Witt et al in Macrom. Chem. Phys. 195 (1994) pp 793 802. In comparison, aromatic polyesters, whilst having good material properties, show clearly impaired biodegradability.

In recent years various biodegradable polymers have become known (see DE 44 32 161). These have the property that they can be readily worked thermoplastically and, on the other hand, are biodegradable ie, their entire polymer chain is dissociated by micro-organisms (bacteria and moulds) by means of enzymes and is totally degraded into carbon dioxide, water and biomass. An appropriate test in the WO 98/04627 PCT/EP97/03748 2 natural environment subject to the action of micro-organisms such as prevails, inter alia, in a compost is given, inter alia, in DIN 54 900. By reason of their thermoplastic behaviour these biodegradable materials can be processed into semifinished products such as cast or blown films. Nevertheless, the use of these semifinished products is greatly restricted. On the one hand, these films are distinguished by poor mechanical properties and, on the other hand, the physical sealing properties with respect to water vapour and gases are very poor in comparison with films consisting of typical but non-biodegradable plastics such as polyethylene, polypropylene or polyamide.

The present invention provides a process for producing a biodegradable and compostible film having improved mechanical and optical properties as well as improved sliding properties. This objective is achieved by a biodegradable and compostible polymer or a mixture of several polymers which are each biodegradable and compostible being furnished with appropriate additives and subjected to biaxial orientation. The terms "biodegradable and compostible polymers or films" in the sense of the invention are to be understood to mean materials that, corresponding to the test according to DIN 54 900 from the draft dated 1996, are tested as having "biodegradability".

For the inventor it was surprising that these biodegradable polymers, in addition to their thermoplastic processing, can also be biaxially oriented and that as a result of the addition of certain additives an improvement arises with respect to the sliding properties of the film.

The invention provides a film that exhibits a biaxial orientation and consists of one or more polymers, all of which are biodegradable and compostible, and also contains, in addition, a maximum of 5 wt.% nucleation agents and a maximum of wt.% of the conventional stabilisers and neutralising agents and a maximum of WO 98/04627 PCT/EP97/03748 3 wt.% of the conventional lubricants and release agents and a maximum of 5 wt.% of the conventional anti-blocking agents.

In a special form the film may additionally be treated on the surface with a corona and/or flame and/or plasma pretreatment and/or with a substance acting oxidatively and/or a substance that is capable of being attached or deposited and/or with a substance mixture consisting of substances that act oxidatively or that are capable of being attached, for example gases with radical components such as ozone or a plasma-excited gas mixture consisting, for example, of hexamethyldisiloxane with nitrogen (N 2 and/or oxygen In this connection the stated surface pretreatments are preferably effected after the biaxial orientation.

The 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, below the crystallite melting-temperature.

The invention provides furthermore the use of certain biodegradable and compostible polymers or a mixture of these polymers for producing the film.

Suitable as polymers are: Aliphatic and partially aromatic polyesters formed from A) linear bifunctional alcohols, for example ethylene glycol, hexanediol or, preferably, butanediol, and/or, optionally, cycloaliphatic bifunctional alcohols, for example cyclohexanedimethanol, and, optionally in addition, small quantities of alcohols of higher functionality, for example 1,2,3-propanetriol or neopentyl glycol, and also from linear bifunctional acids, for example succinic acid or adipic acid, and/or, optionally, cycloaliphatic bifunctional acids, for example cyclohexanedicarboxylic acid, and/or, optionally, aromatic WO 98/04627 PCT/EP97/03748 4 bifunctional acids, for example terephthalic acid or isophthalic acid or naphthalenedicarboxylic acid, and, optionally in addition, small quantities of acids of higher functionality, for example trimellitic acid, or B) from acid-functionalised and alcohol-functionalised structural units, for example hydroxybutyric acid or hydroxyvaleric acid or derivatives thereof, for example e-caprolactone, or from a mixture or a copolymer of A and B whereby the aromatic acids make up a proportion of no more than 50 relative to all acids.

The acids may also be employed in the form of derivatives, for example acid chlorides or esters.

Aliphatic polyester urethanes formed from C) an ester portion formed from linear bifunctional alcohols, for example ethylene glycol, butanediol, hexanediol, preferably butanediol, and/or, optionally, cycloaliphatic bifunctional alcohols, for example cyclohexanedimethanol, and, optionally in addition, small quantities of alcohols of higher functionality, for example 1,2,3-propanetriol or neopentyl glycol, and also from linear bifunctional acids, for example succinic acid or adipic acid, and/or, optionally, cycloaliphatic and/or aromatic bifunctional acids, for example cyclohexanedicarboxylic acid and terephthalic acid, and, optionally in addition, small quantities of acids of higher functionality, for example trimellitic acid, or WO 98/04627 PCT/EP97/03748 D) from an ester portion formed from acid-functionalised and alcoholfunctionalised structural units, for example hydroxybutyric acid and hydroxyvaleric acid or derivatives thereof, for example e-caprolactone, or from a mixture or a copolymer of C) and D) and E) from the reaction product of C) and/or D) with aliphatic and/or cycloaliphatic bifunctional isocyanates and, optionally in addition, isocyanates of higher functionality, for example tetramethylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, and, optionally in addition, with linear and/or cycloaliphatic bifunctional alcohols and/or alcohols of higher functionality, for example ethylene glycol, butanediol, hexanediol, neopentyl glycol, cyclohexanedimethanol, whereby the ester portion C) and/or D) amounts to at least 75 relative to the sum of D) and E).

Aliphatic-aromatic polyester carbonates formed from F) an ester portion formed from linear bifunctional alcohols, for example ethylene glycol, butanediol, hexanediol, preferably butanediol, and/or cycloaliphatic bifunctional alcohols, for example cyclohexanedimethanol, and, optionally in addition, small quantities of alcohols of higher functionality, for example 1,2,3-propanetriol or neopentyl glycol, and also from linear bifunctional acids, for example succinic acid or adipic acid, and/or, optionally, cycloaliphatic bifunctional acids, for example cyclohexanedicarboxylic acid, and, optionally in addition, small quantities of acids of higher functionality, for example trimellitic acid, or WO 98/04627 PCT/EP97/03748 6 G) from an ester portion formed from acid-functionalised and alcoholfunctionalised structural units, for example hydroxybutyric acid or hydroxyvaleric acid or derivatives thereof, for example e-caprolactone, or from a mixture or a copolymer of F) and G) and H) from a carbonate portion which is produced from aromatic bifunctional phenols, preferably bisphenol A, and carbonate donors, for example phosgene, whereby the ester portion F) and/or G) amounts to at least 70 relative to the sum of G) and H).

Aliphatic polyester amides formed from I) an ester portion formed from linear and/or cycloaliphatic bifunctional alcohols, for example ethylene glycol, hexanediol or butanediol, preferably butanediol or cyclohexanedimethanol, and, optionally in addition, small quantities of alcohols of higher functionality, for example 1,2,3-propanetriol or neopentyl glycol, and also from linear and/or cycloaliphatic bifunctional acids, for example succinic acid, adipic acid, cyclohexanedicarboxylic acid, preferably adipic acid and, optionally in addition, small quantities of acids of higher functionality, for example trimellitic acid, or K) from an ester portion formed from acid-functionalised and alcoholfunctionalised structural units, for example hydroxybutyric acid or hydroxyvaleric acid or derivatives thereof, for example e-caprolactone, or from a mixture or a copolymer of I) and K) and -7- L) from an amide portion formed from linear and/or cycloaliphatic bifunctional amines and, optionally in addition, small quantities of amines of higher functionality, for example tetramethylene diamine, hexamethylene diamine, isophorone diamine, and also from linear and/or cycloaliphatic bifunctional acids and, optionally in addition, small quantities of acids of higher functionality, for example succinic acid or adipic acid, or M) from an amide portion formed from acid-functionalised and aminefunctionalised structural units, preferably o-laurolactam and, particularly 10 preferred, e-caprolactam, or from a mixture of L) and M) as amide portion, ao whereby the ester portion I) and/or K) amounts to at least 30 relative to the 15 sum of L) and

M).

In a particularly preferred aspect of the invention as claimed there is provided a film characterised in that it exhibits a biaxial orientation and in that it consists substantially of 20 one or more polymers, all of which are biodegradable and compostible, said polymers being formed from aliphatic polyester amides formed from an ester portion I) or an ester portion K) or from a mixture or a copolymer of I) and K) and an amide portion L) or an amide portion M) or from a mixture of L) and M as amide portion, whereby the ester portion I) and/or K) amounts to at least 30 relative to the sum of L) and M), and also additionally contains one or more additives selected from the group consisting of nucleation agents up to maximum of 5 conventional stabilisers and neutralising agents up to a maximum of 5 conventional lubricants and release agents up to a maximum of 5 and conventional anti-blocking agents up to a maximum of 5 wt.%, wherein L) and M) are as defined above.

7A The biodegradable and compostible raw materials according to the invention may be furnished with a maximum of 5 wt.% nucleation agents that are typically employed for polyesters (for example, 1,5-naphthalenedisodium sulfonate or sheet silicates, for example talc, or nucleating agents having a particle size in the nano range ie, mean particle diameter 1 pm consisting, for example, of titanium nitride, aluminium hydroxide, barium sulfate or zirconium compounds) and with a maximum of 5 wt.% of the conventional stabilisers and neutralising agents and with a maximum of wt.% of the conventional lubricants and release agents and a maximum of 5 wt.% of the conventional anti-blocking agents and may possibly be treated on the surface with a corona or flame or plasma pretreatment or with a substance or mixture of substances acting oxidatively, for example gases with radical components such as ozone or a plasma-excited gas mixture consisting, for example, of hexamethyldisiloxane with nitrogen (N 2 and/or oxygen (02).

9 WO 98/04627 PCT/EP97/03748 8 The conventional compounds having a stabilising effect for polyester compounds may be employed by way of stabilisers and neutralising agents. The added quantity thereof is a maximum of 5 wt.%.

Particularly suitable as stabilisers are phenolic stabilisers, alkali/alkaline-earth stearates and/or alkali/alkaline-earth carbonates. Phenolic stabilisers are preferred in a quantity from 0 to 3 in particular 0.15 to 0.3 and with a molar mass of more than 500 g/mole. Pentaerythrityl-tetrakis-3(3,5-di-tertiarybutyl-4hydroxyphenyl)propionate or 1,3,5-trimethyl-2,4,6-tris(3,5-di-tertiarybutyl-4hydroxybenzyl)benzene are particularly advantageous.

Neutralising agents are preferably dihydrotalcite, calcium stearate, calcium carbonate and/or calcium montanate having a mean particle size of at most 0.7 ptm, an absolute particle size of less than 10 ptm and a specific surface of at least 40 m 2g.

In a particularly preferred embodiment of the film the latter possesses a proportion of nucleation agent from 0.0001 to 2 wt.% and a proportion of stabilisers and neutralising agents from 0.0001 to 2 wt.%.

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, metallic soaps and also silicone oils. The addition of higher aliphatic acid amides and silicone oils is particularly suitable.

Amongst the aliphatic amides, the commercially available forms of ethylene amide to stearyl amide are particularly suitable. Aliphatic acid amides are amides of a water-insoluble monocarboxylic acid (so-called fatty acids) having 8 to 24 carbon atoms, preferably 10 to 18 carbon atoms. Amongst these, erucic amide, stearic amide and oleic amide are preferred.

WO 98/04627 PCT/EP97/03748 9 Suitable as release agent or lubricant are, in addition, compounds that contain both ester groups and amide groups, such as stearamide ethyl stearate or 2-stearamido ethyl stearate, for example.

The designation 'montan waxes' includes a number of different compounds. In this connection see Neumiller et al in R6mpps Chemie-Lexikon, Franckh'sche Verlagshandlung, Stuttgart, 1974.

Suitable as cyclic waxes are, for example, 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 under the name Glycolube VL.

Suitable silicone oils are polydialkyl siloxanes, preferably polydimethyl siloxane, polymethyl phenyl siloxane, olefin-modified silicone, silicone that has been modified with polyethers, such as, for example, polyethylene glycol and polypropylene glycol and also epoxyamino-modified and alcohol-modified silicone.

The viscosity of the suitable silicone oils lies in the range from 5,000 to 1,000,000 mm2/s. Polydimethyl siloxane having a viscosity from 10,000 to 100,000 mm2/s is preferred.

The quantity of the added lubricant amounts to a maximum of 5 In a particularly preferred embodiment of the film the latter has a lubricant proportion from 0.005 to 4 In a quite particularly preferred embodiment of the film the latter has a lubricant proportion from 0.05 to 1 wt.%.

Suitable anti-blocking agents are both inorganic and organic added substances that after the biaxial stretching protrude from the surface of the film in the form of an elevation and consequently give rise to a spacer effect.

WO 98/04627 PCT/EP97/03748 In a preferred form the following substances are employed as inorganic antiblocking agents: aluminium hydroxide aluminium silicates, for example kaolin or kaolin clay aluminium oxides, for example ®-aluminium oxide aluminium sulfate ceramics consisting of silica aluminium oxides barium sulfate natural and synthetic silicic acids sheet silicates, for example asbestos silicon dioxide calcium carbonate of the calcite type calcium phosphate magnesium silicates magnesium carbonate magnesium oxide titanium dioxide zinc oxide microscopic glass beads and the following substances are employed as organic anti-blocking agents: organic polymerisates that are incompatible with the biodegradable polymer, such as starch polystyrenes polyamides polycarbonates crosslinked and non-crosslinked polymethyl methacrylate crosslinked polysiloxane (for example, Tospearl) polar-modified polyethylene (for example, polyethylene grafted with maleic anhydride) WO 98/04627 PCT/EP97/03748 11 polar-modified polypropylene (for example, polypropylene grafted with maleic anhydride) random copolymers based on ethylene and propylene with vinyl alcohol or vinyl acetate or acrylic acid or acrylic ester or methacrylic acid or methacrylic ester or metallic salts of methacrylic acid or metallic salts of methacrylic ester benzoguanamine formaldehyde polymers aliphatic and partially aromatic polyesters having melting-points differing from that of the raw material of the film aliphatic polyester amides having melting-points differing from that of the raw material of the film aliphatic polyester urethanes having melting-points differing from that of the raw material of the film aliphatic-aromatic polyester carbonates having melting-points differing from that of the raw material of the film.

The active quantity of anti-blocking agent lies in the range up to a maximum of In a particularly preferred embodiment the film contains 0.005 to 4 wt.% antiblocking agent. In a quite particularly preferred embodiment the film contains 0.05 to 1 wt.% anti-blocking agent. The mean particle size lies between 1 and 6 tm, in particular between 2 and 5 im, particles having a spherical shape such as are described in EP-A-0 236 945 and DE-A-38 01 535 being particularly suitable. Also particularly suitable are combinations of various spacer systems.

According to the processes applied hitherto, the polymers for the film which is provided with additives are endowed with the desired quantities by weight of organic or inorganic fillers in the course of preparation of the raw material. This occurs in the course of granulation of the raw material, for example in twin-screw extruders where the additives are admixed to the raw material. Besides this manner of addition there is also the possibility of a fraction of the necessary additives or all the necessary additives being added to a non-endowed or partially endowed raw WO 98/04627 PCT/EP97/03748 12 material in the form of a master batch. The term 'master batch' within the scope of the present invention is to be understood to mean a parent mixture, in particular a granulated, dust-free concentrate of a plastic raw material having high quantities of additives which is used in bulk processing as an intermediate product (as a material addition to a granulate that is not endowed with additives or only partially or incompletely endowed with additives), in order to produce films therefrom that contain a certain quantity of additives. Prior to the charging of the polymer granulate into the extruder, the master batch is admixed in such quantities to the raw materials that are not endowed with additives or only partially or incompletely endowed with additives that the desired percentages by weight of fillers in the films are achieved.

The preferred materials from which, in addition to the additives, the master batches are produced are substances that are compatible with the biodegradable raw materials named in this invention. In a particularly preferred form the materials from which, in addition to the additives, the master batches are produced are likewise biodegradable materials.

In the course of the corona treatment the procedure is expediently such that the film is passed between two conductor elements serving as electrodes, in which connection such a high voltage, usually an AC voltage (approximately 5 to 20 kV and 5 to 30 kHz), is applied between the electrodes that spray discharges or corona discharges are able to take place. As a result of the spray discharge or corona discharge, the air above the surface of the film is ionised and reacts with the molecules of the surface of the film, so that, in addition, polar intercalations arise in the polymer matrix.

For a flame treatment with a polarised flame (cf. US-A-4,622,237) an electrical DC voltage is applied between a burner (negative pole) and a cooling roller. The level of the applied voltage amounts to between 400 and 3,000 V and preferably lies in the WO 98/04627 PCT/EP97/03748 13 range from 500 to 2,000 V. As a result of the applied voltage, the ionised atoms are given increased acceleration and strike the surface of the polymer with greater kinetic energy. The chemical bonds within the polymer molecule are broken down more easily and the formation of radicals proceeds more quickly. In this connection the thermal loading of the polymer is far less than in the case of the standard flame treatment, and films can be obtained having sealing properties on the treated side that are even better than those on the untreated side.

In the case of a plasma pretreatment, gases, for example oxygen or nitrogen or carbon dioxide or methane or halogenated hydrocarbons or silane compounds or higher-molecular compounds or also mixtures of such compounds, are subjected in a low-pressure chamber to a high-energy field, for example microwave radiation.

High-energy electrons arise which strike the molecules and transmit their energies.

As a result of this, locally radical structures arise, the excited states of which correspond to temperatures of some ten thousand degrees Celsius, although the plasma itself is almost at room temperature. As a result, there is the possibility of breaking down chemical bonds and of setting reactions in motion that are normally only able to proceed at high temperatures. Monomer radicals and ions are formed.

From the monomer radicals that have arisen short-chain oligomers are formed partly already in the plasma which then condense and polymerise on the surface to be coated. As a result, a homogeneous film is deposited on the material to be coated.

However, before the monomer radicals or ions are deposited on the substrate there is, in addition, the possibility of adding a further mass flux to the excited molecules in the so-called after-glow zone. By this means it is possible to generate a substance or a mixture of substances which, when it strikes the surface of the polymer film, gives rise to an oxidative attack in the case of the substrate polymers. A vitreous and usually highly crosslinked layer is formed which is firmly connected to the WO 98/04627 PCT/EP97/03748 14 surface of the film. Given a suitable substance composition, an increase in the surface tension on the film results by this means.

The invention provides furthermore the use of a certain material class of the biodegradable and compostible polymers for producing the film, it being a question, with this material class, of polyester amide. In this connection the film according to the invention may be produced from a polyester amide or from a mixture of various polyester amides.

The invention provides furthermore a process for producing the film according to the invention. This process is characterised in that the biodegradable and compostible material or materials is/are firstly broken down by the action of heat and shear, this melt is discharged in a tool, is cooled down until it solidifies, is subsequently regulated in the case of partially crystalline materials to temperatures below the crystallite melting-temperature and in the case of amorphous materials to temperatures above the glass transition temperature and is subsequently biaxially stretched once or several times. After the stretching stage or stages, in each instance a fixation of the film may optionally be effected. After the stretching processes and the possibly prevailing fixing stages, the film that has consequently been produced may possibly be subjected to in-line surface pretreatment. The pretreatment may be carried out with a corona, a flame, a plasma or with an oxidative substance or mixture of substances, for example gases with radical components such as ozone or with a plasma-excited gas mixture consisting, for example, of hexamethyldisiloxane with nitrogen (N 2 and/or oxygen (02) in such a way as to result in an increase in the surface tension on the film.

The invention provides furthermore a process for stretching the film. The biaxial stretching may be effected in a simultaneous stretching process or in a two-stage sequential process, whereby stretching may be effected both firstly longitudinally and then transversely and firstly transversely and then longitudinally, or in a three- WO 98/04627 PCT/EP97/03748 stage sequential process, whereby stretching may be effected both firstly longitudinally, then transversely and finally longitudinally, and firstly transversely then longitudinally and finally transversely, or in a four-stage sequential process, whereby stretching may be effected both firstly longitudinally, then transversely, then longitudinally and finally transversely and firstly transversely, then longitudinally, then transversely and finally longitudinally. Each individual stretching may possibly be immediately followed by a fixation of the film. The individual stretching, both in the longitudinal direction and in the transverse direction, may be effected in one stage or in several stages.

In a preferred form of the film according to the invention the biaxial stretching is characterised in that it is a question of a sequential process beginning with the longitudinal stretching.

In a still more preferred form of the film according to the invention the biaxial stretching is characterised in that the overall stretching ratio in the longitudinal direction amounts to 1: 1.5 to 1 10 and the overall stretching ratio in the transverse direction amounts to 1 2 to 1 In a still more preferred form of the film according to the invention the biaxial stretching is characterised in that the overall stretching ratio in the longitudinal direction amounts to 1 2.8 to 1 8 and the overall stretching ratio in the transverse direction amounts to 1: 3.8 to 1: In a still more preferred form of the film according to the invention the latter has a thickness that is less than 500 ptm.

In a still more preferred form of the film according to the invention the latter has a thickness that is less than 80 jim.

WO 98/04627 PCT/EP97/03748 16 The invention provides furthermore the application of the film according to the invention. The use of this film as a solo film in pretreated or non-pretreated form and also in printed or non-printed form for packaging in the food and non-food fields or as a solo film in pretreated or non-pretreated form for greenhouse coverings or mulch films in the fields of horticulture or agriculture or, finished so as to form sacks, for the storage and transport of materials, for example biowaste, or as a solo film in pretreated or non-pretreated form for protective and separating functions in connection with cosmetics and sanitary articles, for example for nappies or sanitary towels, or as a solo film in pretreated or non-pretreated form for surface protection or surface finishing in the field of cardboard lamination, paper lamination and window-envelope lamination or as a finished film which can be employed in pretreated or non-pretreated form and also in printed or non-printed form and also, provided with adhesive, as a label or an adhesive tape comes into consideration by way of application. With a view to improving the pressure adhesion or bonding properties, the surface of the film can be pretreated during production and/or subsequently during further processing with a corona, a flame, a plasma or with another oxidative substance or mixture of substances, for example gases with radical components such as ozone or with a plasma-excited gas mixture consisting, for example, of hexamethyldisiloxane with nitrogen (N 2 and/or oxygen (02) in such a way as to result in an increase in the surface tension.

The invention provides furthermore the application of the film according to the invention as a coated film or in a composite film. In this connection it may be a question, in the case of the other films of the composite, of non-degradable film or also likewise of biodegradable and compostible films. In addition, the coating substances or adhesives employed may pertain both to the normal non-degradable systems and to the biodegradable and compostible raw materials.

In a particularly preferred form of the application of this film according to the invention only substances that are biodegradable and compostible are employed for WO 98/04627 PCT/EP97/03748 17 the purpose of producing the coated film or a composite film, so that the overall composite is likewise biodegradable and compostible.

The invention provides furthermore the application of the film according to the invention as primary material for the production of a bag that releases its contents after decomposition as a result of the biological degradation process. The bag may be produced by adhesion bonding and also by sealing of the film and may either be closed or may possess an opening with an appropriate seal or connection.

The invention provides furthermore the application of the film or composites according to the invention as primary material for the production of a packaging or separating or surface-protecting film having very high water-vapour permeability, in that said film is pierced by a cold or temperature-regulated needle roller. The end use of this film is the packaging of goods that emit moisture, for example bread or various kinds of vegetable, or as a separating and protecting film in the sanitary field.

WO 98/04627 PCT/EP97/03748 18 Example 1 A biodegradable polyester amide having a melt viscosity of 250 Pas at 190 0

C

(measured in accordance with DIN 54 811 B) and also a melting-point of 125 0

C,

measured according to ISO 3146 C2, which possesses a lubricant proportion of 1 wt.% and an anti-blocking proportion of 0.1 wt.% was biaxially stretched subject to the following process parameters. The maximum extrusion-temperature amounted to 205 0 C. Correspondingly, the constant-temperature zones of the extruder were regulated to a maximum of 182 0 C and also the tool was regulated to a maximum of 205 0 C. The melt was cooled as a flat film on a cooling roller mill at roller temperatures of 20 0 C. A solid, thick film was formed which was heated up to stretching-temperature in the next process step by constant-temperature rollers having temperatures of 65 0 C. The actual stretching rollers were operated at a temperature of 70 0 C. In this process, firstly the flat film was stretched in the longitudinal direction in two stages, once by a ratio of 1 1.5 and then by a ratio of 1 2.5. Consequently, an overall stretching ratio in the longitudinal direction resulted of I 3.75. The reheating rollers, over which the film then ran, had a temperature of 0 C. The preheating zones of the transverse-stretching furnace were regulated to 100 0 C. The temperature in the actual transverse-stretching part amounted to 95 0

C.

Here the film was stretched in the transverse direction by a ratio of 1 Consequently, an arithmetical area-stretching ratio resulted of 1 18.75. After the transverse stretching, the film was fixed at a temperature of 105 0 C. The speed of production at the outlet of the transverse stretching amounted to 32.0 m/min. A film having a thickness of 46 pm was able to be produced.

Example 2 The same biodegradable polyester amide from Example 1 was worked under the process conditions of Example 1 that have been described so as to form a biaxially WO 98/04627 PCT/EP97/03748 19 oriented film. As a result of lowering the extrusion speed, a film was produced in this case having a thickness of 24 [tm.

Comparative Example 1 The same biodegradable polyester amide from Example 1, which, however, contained no lubricant portion, was worked under the process conditions of Example 1 that have been described so as to form a biaxially oriented film. It was possible for a film to be produced having a thickness of 50 [tm.

The following physical properties and compostibility in respect of the specimens produced were measured as follows: Mechanical properties: The mechanical variables constituted by tear resistance and elongation at tear were determined in respect of the specimens, both in the longitudinal direction and in the transverse direction, in accordance with DIN 53 455. The modulus of elasticity in the longitudinal and transverse directions was determined in accordance with DIN 53 457. The thickness of the individual specimens was determined in accordance with DIN 53 370. With a view to ascertaining the piercing force and the piercing distance, the specimens were analysed by the biaxial piercing test in accordance with DIN 53 373.

Sliding ability: The sliding ability of the films was measured in accordance with DIN 53 370 at room temperature and also film-against-film.

Optics: By way of optical properties, the surface lustre in accordance with DIN 67 530 at a test-angle of 200 and the haze in accordance with ASTM D 1003 were determined in WO 98/04627 PCT/EP97/03748 respect of the films. The lustre on both sides of the film was measured. An averaging of the values ascertained in this process was then carried out, and this average was presented as the result.

Compostibility: The compostibility was carried out in accordance with the test specification of DIN draft standard DIN 54 900 Part 3 dated 1996. On the basis of the results of the investigation, the film specimens are graded in the corresponding class, corresponding to the DIN standards.

The results of the investigations in respect of the specimens from Examples 1 and 2 and also from Comparative Example 1 are listed in Table 1.

WO 98/04627 PCT/EP97/03748 Example 1 Example 2 Comparative Example 1 Mechanical properties Thickness [jtm] 46 24 Modulus of elasticity, 226 252 230 longitudinal [MPa] Modulus of elasticity, transverse 292 306 295 [MPa] Tear resistance, longitudinal [MPa] 90 91 89 Tear resistance, transverse [MPa] 109 111 108 Elongation at tear, longitudinal 224 186 231 Elongation at tear, transverse 111 75 109 Piercing force 227 151 238 Piercing distance [mm] 18 16 19 Sliding property Sliding friction 0.38 0.38 0.78 Optics Lustre [GE] 110 120 125 Haze 14 3.3 12 Compostibility Biodegradability yes yes yes 22 The reference to any prior art in this specification is not, and should not be taken as, an acknowledgment or any form of suggestion that that prior art forms part of the common general knowledge in Australia.

Claims (14)

1. Film, characterised in that it exhibits a biaxial orientation and in that it consists substantially of one or more polymers, all of which are biodegradable and compostible, said polymers being formed from aliphatic polyester amides formed from I) an ester portion formed from linear and/or cycloaliphatic bifunctional alcohols and, optionally in addition, small quantities of alcohols of higher functionality and also from linear and/or cycloaliphatic bifunctional acids .1 and, optionally in addition, small quantities of acids of higher functionality or S. K) from an ester portion formed from acid-functionalised and alcohol- functionalised structural units or derivatives thereof L) from an amide portion formed from linear and/or cycloaliphatic bifunctional S 20 amines and, optionally in addition, small quantities of amines of higher *functionality and also from linear and/or cycloaliphatic bifunctional acids and, optionally in addition, small quantities of acids of higher functionality or M) from an amide portion formed from acid-functionalised and amine- functionalised structural units or from a mixture of L) and M) as amide portion, whereby the ester portion I) and/or K) amounts to at least 30 relative to the sum of L) and and also additionally contains one or more additives 24 selected from the group consisting of nucleation agents up to maximum of 5 wt.%, conventional stabilisers and neutralising agents up to a maximum of 5 wt.%, conventional lubricants and release agents up to a maximum of 5 and conventional anti-blocking agents up to a maximum of 5 wt.%.

2. Film according to Claim 1, characterised in that it is treated on the surface with a corona and/or flame and/or plasma pretreatment and/or with a substance acting oxidatively and/or with a substance that is capable of being attached or deposited and/or with a substance mixture consisting of substances that act oxidatively or that 10 are capable of being attached. *°oo 0 fe: 3. Film according to claim 1 or claim 2, characterised in that the proportion of lubricants lies in the range from 0.005 to 4 wt.% and the proportion of antiblocking particles lies in the range from 0.005 to 4 wt.%.

4. Film according to any of claims 1 to 3, characterised in that the proportion of lubricants lies in the range from 0.05 to I wt.% and the proportion of antiblocking particles lies in the range from 0.05 to 1 wt.%. S 20 5. Film according to any of claims 1 to 4, characterised in that the biodegradable and compostible material or materials is/are firstly broken down by the action of heat and shear, this melt is discharged in a tool, is cooled down until it solidifies, is subsequently regulated in the case of partially crystalline materials to temperatures below the crystallite melting-temperature and in the case of amorphous materials to temperatures above the glass transition temperatures and is subsequently biaxially stretched once or several times and after the stretching or individual stretching operations is possibly fixed and after these stretching and fixing processes is possibly subjected to surface pretreatment.

6. Film according to any of claims 1 to 5, characterised in that the biaxial stretching is effected in a simultaneous stretching process or in a two-stage sequential process, whereby stretching may be effected both firstly longitudinally and then transversely and firstly transversely and then longitudinally, or in a three-stage sequential process, whereby stretching may be effected both firstly longitudinally, then transversely and finally longitudinally, and firstly transversely, then longitudinally and finally transversely, or in a four-stage sequential process, whereby stretching may be effected both firstly longitudinally, then transversely, then longitudinally and finally transversely and firstly transversely, then longitudinally, then transversely and finally longitudinally, and each individual stretching may possibly be immediately followed by a fixation of the film.

7. Film according to any of claims 1 to 6, characterised in that the biaxial stretching is carried out in a sequential process beginning with the longitudinal stretching. a.

8. Film according to any of claims 1 to 7, characterised in that the overall stretching ratio in the longitudinal direction amounts to 1 1. 5 to 1 10 and the overall stretching ratio in the transverse direction amounts to 1 2 to 1 o. a

9. Film according to any of claims 1 to 8, characterised in that the overall stretching *a ratio in the longitudinal direction amounts to 1 2.8 to 1 8 and the overall stretching S 20 ratio in the transverse direction amounts to 1 3.8 to 1 Film according to any of claims 1 to 9, characterised in that the thickness of the film amounts to less than 500 jm.

11. Film according to any of claims 1 to 10, characterised in that the thickness of the film amounts to less than 80 pm.

12. Use of a. film according to any of claims 1 to 11 as a solo film in pretreated or non- pretreated form and also in printed or non-printed form for packaging in the food and non-food fields or as a solo film in pretreated or non-pretreated form for greenhouse coverings or mulch films in the fields of horticulture or agriculture or, finished so as 26 to form sacks, for the storage and transport of goods or as a solo film in pretreated or non-pretreated form and also in printed or non-printed form for protective and separating functions in connection with cosmetics and sanitary articles or as a solo film in pretreated or non-pretreated form for surface protection or surface finishing in the field of cardboard lamination, paper lamination and window-envelope lamination or as a finished film in pretreated or non-pretreated form and also in printed or non-printed form and, provided with adhesive, as a label or an adhesive tape.

13. Use of a film according to any of claims 1 to 11 for producing coated films or 10 composites or laminates consisting of the same or different biodegradable and compostible films or said film is employed with other, non-biodegradable types of o: film, in which the coating substances or adhesives used to connect the films do not a. a necessarily have to be biodegradable and compostible.

14. Use of a film according to any of claims 1 to 11 for producing composites and/or S•laminates consisting of the same or different biodegradable and compostible films or said film is employed with other types of film in which adhesives are used to connect the films, characterised in that all the films and coating substances and adhesives employed in the composite or laminate or in the coated film are biodegradable and compostible and consequently the composite or the laminate itself is also *biodegradable and compostible. A coated film, composite or laminate produced according to claim 13 or claim 14.

16. Use of a film according to any of claims 1 to 11 or a coated film, composite or laminate of claim 15, characterised in that a bag is formed from this film or the composite or the laminate, said bag being adapted to release its contents after decomposition, as a result of the biological degradation process.

17. Use of a film according to any of claims 1 to 11, or a coated film, composite or laminate or claim 15, characterised in that the film or composites according to the 27 invention serves as primary material for producing a packaging or separating or protecting film having very high water-vapour permeability, in that said film is pierced by a cold or temperature-regulated needle roller.

18. Biodegradable polyester amide films substantially as herein described with reference to the Examples (excluding the Comparative Example). DATED this 19th day of February 2001 Wolff Walsrode AG o 10 By its Patent Attorneys DAVIES COLLISON CAVE *o