PVC-free multilayered film

The invention relates to a non-PVC multilayer film having an outer layer, at least one middle layer, a support layer and optionally a sealing layer, all layers being essentially free of PVC and preferably containing polyolefin homopolymers and / or polyolefin copolymers as essential constituents. The invention further relates to a method for producing the multilayer film and the use thereof.

Multi-layer films have been widely used for many years. For example, multilayer films are used in the food industry for packaging food. But multilayer films have also been used in the medical field for a long time, for example for the production of medical bags.

The multilayer films for these bags have so far been made from polyvinyl chloride (PVC) in most cases. However, there are some disadvantages to using polyvinyl chloride. There is, on the one hand, the risk that plasticizers contained in the PVC film are released and - if the films are used in medical bags - can diffuse, for example, into the medical solution contained therein. In addition, there is a problem that hydrochloric acid is formed when heat-sealed. PVC also tends to absorb medication in infusion solutions.

Because of these disadvantages, other materials are increasingly used for multilayer films.

In this regard, the state of the art EP-A-0 179 639 = D1, EP-A-0 474 376 = D2 and the US-A-4,643,926 = D3.

For example, EP-A-0 179 639 describes a multilayer film which has, for example, two outer layers and an inner layer, the outer layers in each case being a blend of at least one propylene-based polymer and at least one linear low density polyethylene (LDPE) , and the inner layer contains at least one polymer which has a high gas barrier. For example, an ethylene-vinyl alcohol copolymer (EVOH) is used as the polymer with a high gas barrier.

A disadvantage of the multilayer films known from D1 is that the content of LDPE in the blend of the outer layer can lead to poor temperature resistance under the conditions of a sterilization treatment. In addition, the film known from D1 with a gas barrier middle layer (ie E> 2000) is not expected to have sufficient impact strength.

A multilayer film with a total of 5 or 7 layers is disclosed in D2. This multilayer film has an inner layer and two outer layers. One to two layers can each be arranged between the outer layers and the inner layer. The inner layer has a blend of a) a propylene homopolymer or copolymer and b) an ethylene copolymer or polybutene. The two outer layers are sealable and contain a plasticizer. Among other things, styrene-butadiene copolymers are used as the material for the outer layers. On the one hand, the multilayer film according to D2 has a symmetrical structure with two sealing layers. On the other hand, a plasticizer is required for the two styrene-butadiene copolymers and, moreover, the outer layers of the film have no defined softening point in accordance with D2. In addition, according to D2, there is no layer acting as a support layer. Overall, the film of the D2 thus has a rather unfavorable structure, which primarily 1) results in poor transparency, 2) gluing the outer layers, for example with a medical bag under conditions of sterilization, 3) due to the symmetrical structure clearly complex designing sealing process, 4) an insufficient force absorption of the film at 121 ° C and finally 5) can lead to disposal problems due to the combination of materials.

A multilayer film is also disclosed in US-A-4,643,926. The layer films of D3 have a sealing layer made of ethylene-propylene copolymer, modified ethylene-propylene copolymer or flexible copolyester, one or more inner layers which include elastic polymeric materials and an outer layer made of ethylene-propylene copolymer or a flexible copolyester .

The inner film layers (middle layer or inner layers) lack a support layer so that the inner or middle layer (s) of the multilayer film flow during sealing. In addition, according to current knowledge, the presence of at least one adhesion promoter layer is necessary for the disclosed material combinations for the layers. For this comes, for example an ethylene-methacrylate copolymer (EMA) or an ethylene-vinyl acetate copolymer (EVA) in question, which in turn leads to the disadvantage that the film cannot be heat sterilized without radiation crosslinking. Ultimately, the choice of materials disclosed in accordance with D3 also suggests that there may be disposal problems with used films.

In view of the prior art shown here and the disadvantages associated with this prior art, it was therefore an object of the invention to provide an impact-resistant, heat-sterilizable, flexible and as transparent as possible film which should be free of PVC and plasticizers easy to dispose of materials and which also allows the production of medical bags or multi-chamber bags and the like, which therefore still has a high impact strength, especially after a sterilization treatment.

The object of the invention is also to provide a method for producing such a multilayer film and the use of the film.

The above-mentioned tasks and other tasks not specified are solved by a non-PVC multilayer film of the type mentioned at the outset with the features of the characterizing part of claim 1. Advantageous embodiments are the subject of the subclaims which refer back to claim 1, while claim 14 is a solution to specifies the problem underlying the invention in procedural terms. The use of the non-PVC multilayer films according to the invention is protected in claims 16 and 17.

Characterized in that in the case of a non-PVC multilayer film which has an outer layer, a support layer and at least one middle layer, the outer and support layers have polymers whose Vicat softening temperatures are above approximately 121 ° C. and that at least one middle layer has polymers, whose softening temperatures are below about 70 ° C, it succeeds, an excellent for applications in the medical field, to provide suitable multilayer film, especially for contact with medical solutions or body fluids, which is also autoclavable, flexible and optically clear. In addition, the films according to the invention are not or only slightly permeable to water vapor and finally the non-PVC multilayer film according to the invention has excellent welding and sealing properties, which emphasizes its suitability for the production of medical bags. In addition, it has an extremely high impact strength for absorbing energy when subjected to impact without being destroyed.

According to the invention, therefore, a non-PVC multilayer film essentially has at least three layers which all fulfill certain functions. The core of the multilayer structure according to the invention is an inner layer, which was also referred to above as a middle layer in the text, which gives the finished film a high degree of flexibility. Depending on its function, the middle class can therefore also be called a flexibility layer. The at least one middle layer according to the invention is necessarily delimited by two neighboring layers within the scope of the invention, ie at least one on each side, and is thus arranged between two outer layers.

The softening temperature is determined for the polymer and plastic materials of the invention according to Vicat VST / A / 50, ie it is defined as the temperature at which an increasingly heated plastic sample defines a, according to method A, 10 N steel pin of 1 mm² Cross section penetrated 1 mm deep (old: DIN 53460, new: DIN-Iso-Norm 306, ASTM D1525). The softening temperature is usually substantially lower than the temperature at which the polymeric substance would completely reach a quasi-liquid state. Thus, when the partially crystalline polymers used according to the invention are heated, the amorphous regions begin to flow, while the crystalline regions maintain the structure.

It can be assumed that the melting behavior of the polymers with softening temperatures of less than about 70 ° C. generally gives the middle layer the property that it melts at temperatures <121 ° C. Melting is not to be understood here as meaning that the middle layer completely changes into the liquid state of aggregation, rather it is essentially a gelation of the middle layer at temperatures around 121 ° C., with sufficient areas of the middle layer remaining in the solid state of aggregation and residual shape stability excellent flexibility of the entire film.

The layers delimiting the middle layer, namely the outer layer and the support layer, can be different or the same. It is essential in the context of the invention, however, that they have polymers whose softening temperatures are above approximately 121 ° C., as a result of which the particular layer is generally given behavior with regard to the melting property which is considered to be highly melting, that is to say melting in the sense of the invention Temperatures of> 121 ° C can be called. With regard to their function, both layers according to the invention serve to support and stabilize the inner middle layer.

Although the combination of 3 layers (support layer, middle layer and outer layer) results in a non-PVC multilayer film with a high utility value, in a further development according to the invention the middle layer can have at least 2 layers with a low softening temperature, the layers with low softening temperatures containing polymers, whose softening temperatures are below about 70 ° C. These are separated by a layer with a high softening temperature which contains polymers whose softening temperatures are above approximately 121 ° C., the layers of low and high softening temperatures being arranged alternately. This means that the inner middle layer can be divided into several support and middle layers, so that the non-PVC multilayer film of the invention has at least three layers, but can also be 5-, 7- etc. layers. This multilayer of the middle layer does not deviate from the basic idea of ​​the invention, rather the flexibility of the entire film is significantly improved by structuring the middle layer in the entire structural structure. In the 5 or 7-layer structure, the three or five inner layers can, for example, two or have three layers with polymers which give the layers containing them a total softening temperature of <121 ° C, while in the first case between the two middle layers a layer with one or more polymers with softening temperatures of> 121 ° C and in the second case two such layers are arranged for support between the three middle layers.

In each of the cases, it is thus ensured that a middle layer is always adjacent to layers whose softening temperature is> 121 ° C or the polymers contain with a Vicat softening temperature of> 121 ° C (VST / A / 50 (10N).

The thickness of the individual layers of the non-PVC multilayer film according to the invention is not particularly critical per se. According to the invention, however, it is preferred that the middle layer is at least 90 μm and the outer and the support layer are each 10-20 μm thick. Despite their relatively small thickness, the outer and support layers, because of their support properties, enable particularly advantageously that deformation of the relatively flexible and thick middle layer is largely avoided due to the increased fluidity of the middle layer when exposed to heat.

If the multi-layer film changes from a 3-layer basic structure to a 5 or 7-layer structure, the values ​​for the 3-layer structure can be adhered to for the individual layers. However, it is equally possible and mostly preferred to make the thickness of the individual layers involved in the construction of the middle layer correspondingly thinner in order to keep the total thickness of the three or five "middle layers" approximately in the range of approximately 100 μm.

In a further expedient embodiment, the non-PVC multilayer film according to the invention additionally has a sealing layer. As the outermost layer, this is preferably arranged on the outer support layer. This advantageously allows the multilayer film of the invention to be welded on this side. Polymers which are compatible with the solution are generally used for the sealing layer, since the sealing layer in the case of a bag produced from the non-PVC multilayer film according to the invention lies inside after the bag has been produced. Furthermore, the polymers should be very easy to seal, so that a good and firm weld seam can be produced. A 4, 6, 8, etc. layered structure is thus realized, resulting in an asymmetrical film.

In a preferred embodiment, the sealing layer has polymers whose softening temperature is below the softening temperature of the outer layer, the support layer and the at least one layer with a high softening temperature which is arranged between "two middle layers". The sealing layer is expediently 15-30 μm thick. At the same time, it is advantageous for the invention if the plastic material of the sealing layer has a softening temperature of> 121 ° C. It should be noted above all that the sealing layer may contain rubber in order to achieve the desired properties. The sealing layer is preferably impact modified by at least 15% synthetic rubber. In any case, however, it is advantageous if the plastic material for the sealing layer is selected so that the material of the layer remains dimensionally stable under the conditions of steam sterilization, that is, at approximately 121 ° C.

As already mentioned at the beginning, the selection of the materials for all layers of a non-PVC multilayer film according to the invention is essentially based on the softening temperatures of the polymers contained in the individual layers formed from plastic materials.

At this point it should be pointed out that for the invention, "plastic material" is understood to mean those materials whose essential constituents consist of macromolecular organic compounds, the plastic materials also being referred to as polymers, for which purpose in particular homopolymers and copolymers (statistical, block and / or graft polymers) and mixtures (= blends) of the aforementioned substances.

In addition to the softening temperatures of the polymers and thus the plastic materials of the individual layers, the environmental compatibility of the materials used for the individual layers also plays an important role for the invention.

Previously used materials, such as PVC in particular, had several disadvantages due to the environmental problems (HCl, dioxin, furan), the release of added plasticizers and a lack of recyclability.

A very particularly preferred embodiment of the non-PVC multilayer film according to the invention is now characterized in that all layers which are involved in the construction of the film contain, as essential components, polyolefin homopolymers and / or polyolefin copolymers which are linked α-olefinically. By using such materials, the invention creates a multi-layer film that is completely suitable for medical purposes and yet is absolutely environmentally compatible because it is recyclable.

While known polyolefin films could not meet the applicable requirements with regard to their flexibility or clarity, all of these criteria are met according to the invention.

Among the materials which are suitable for the outer layer are the polymers or polymer mixtures which are known to the person skilled in the art and whose softening temperature is higher than that of the polymers or polymer mixtures of the other layers or equal to the softening temperature of the polymer or the polymer mixtures of the support layer (s ).

These preferably include polypropylene homopolymers, polypropylene block copolymers, polypropylene random copolymers with low to medium ethylene content and / or high-density polyethylene (HDPE). Polypropylene random copolymers are particularly preferred. The polymers mentioned can be used alone or in the form of mixtures, so-called blends.

For the middle layer or the at least one layer with a low softening temperature of the middle layers, there are mainly polyethylene copolymers, polypropylene homopolymers or copolymers with ρ <0.9 g / cm³, Low-density polyethylene (LDPE), styrene-ethylene / butylene-styrene block copolymers, styrene-ethylene / propylene-styrene block copolymers, SIS (styrene-isoprene-styrene), polyisobutylenes (PIBs) and / or blends of the polymers mentioned with polypropylene with ρ ≧ 0.9 g / cm³ and / or polyethylene in question.

The support layer and / or the at least one layer with a high softening temperature advantageously consist of a polypropylene homopolymer, a polypropylene copolymer, a high-density polyethylene (HDPE) or a linear low-density polyethylene (LLDPE) and / or blends mentioned polymers.

For the sealing layer, materials such as polypropylene copolymers, high-density polyethylenes (HDPEs), linear low-density polyethylenes (LLDPE) and / or blends of the stated polymers with a styrene-ethylene / butylene-styrene Block copolymer, a styrene-ethylene / propylene-styrene block copolymer, SIS (styrene-isoprene-styrene block copolymer) and / or an α-olefin copolymer, preferably from a blend of a polypropylene random copolymer and a synthetic rubber.

As already mentioned, the polymer materials for the individual layers are preferably polyolefins. The multilayer film according to the invention is particularly preferably characterized in that it can be essentially free of lubricants, plasticizers, antiblocking agents, antistatic agents and other fillers. It should be emphasized here in particular that sufficient adhesion can be assumed between the individual layers made of the different materials. However, the adhesion between the layers can advantageously be increased in that the individual layers each additionally have up to 70% by weight, based on 100% by weight of their composition, of those plastic materials which form one or both of the adjacent layers serve the non-PVC multilayer film.

This "material mediation" or the substitution of material significantly increases the compatibility of the layers formed into a film without questioning the other properties. In particular, this "fading in" enables a good connection of the layers to one another without the need for an adhesion promoter.

The non-PVC multilayer film of the invention can in principle be designed using molding processes familiar to those skilled in the art. According to the invention, the design as a flat or tubular (blown) film is preferred.

The invention also relates to a method for producing the non-PVC multilayer film, which is characterized in that the individual layers are coextruded with one another to obtain the non-PVC multilayer film. It is important for the invention that the coextrusion of several layers allows one to combine several desired properties in one film in order to increase the quality of the product obtained.

For this, especially in the coextrusion process, there is the possibility, with a suitable selection of the extrusion partner, to provide a customized multilayer film that allows in a unique way to dispense with any addition of adhesion promoters and still the required properties and, in addition, other important properties such as gas - and water vapor permeability, strength of the material, weldability, Transparency and temperature resistance.

The coextrusion of materials of the layers according to the invention is known in principle, but based on existing experience, the successful implementation of a complex multilayer film such as that according to the invention was not readily predictable. In this respect, the success according to the invention was surprising, since practice has repeatedly shown that even with the help of possibly tabulated properties of polymers, such as data on bond adhesion, the use of such materials does not necessarily lead to success. In other words, the solution to a given task by pure selection from known materials is fundamentally not readily possible with a multilayer coextrusion film.

Furthermore, in the method according to the invention it is possible for the film to be processed further in the usual ways after the actual shaping. For example, it can be stretched. However, it is preferably shock-cooled with water after molding. This achieves an optimal bond with high flexibility and sufficient toughness, but above all, the shock-like cooling of the film improves the transparency of the film, because the crystallization of the polymers involved in the build-up of the film is prevented during slow cooling. This leads to a low degree of crystallinity and thus to high transparency and toughness.

The non-PVC multilayer film according to the invention is outstandingly suitable for use in the medical field. The materials of the individual layers of the multilayer film are all selected so that the film is transparent and flexible, but in particular can also be melted and sealed so that it can be sterilized hot. The use of PVC, which always contains plasticizers, is avoided, and no adhesion promoters are required. could diffuse through the plastic material layers, which is particularly undesirable when used in the medical field.

Due to its excellent material and usage properties, the non-PVC multilayer film according to the invention is used with great advantage for the production of medical bags or medical multi-chamber bags.

The invention is explained in more detail below with reference to the attached figures.

The figures show:<dl id="dl0001"><dt>Fig. 1</dt><dd>a schematic cross section through a first embodiment of the non-PVC multilayer film according to the invention with a sealing layer.</dd><dt>Fig. 2</dt><dd>2 shows a schematic cross section through a second embodiment of the non-PVC multilayer film according to the invention, only the structure of layer 3 from FIG. 1 being shown with an otherwise unchanged structure for simplification.</dd><dt>Fig. 3</dt><dd>2 shows a schematic cross section through a third embodiment of the non-PVC multilayer film according to the invention, the outer, supporting and sealing layers from FIG. 1 also being omitted here for simplification; and</dd><dt>Fig. 4</dt><dd>a schematic cross section through a fourth embodiment of the non-PVC multilayer film according to the invention, again only the middle layer 3 is shown enlarged according to FIG. 1 and the outer layer and the support and sealing layer are omitted for simplicity.</dd></dl>

1 shows a first embodiment of a non-PVC multilayer film 1 according to the invention in cross section. The film was produced by coextrusion and a total of four layers 2, 3, 4 and 5 can be seen. Layer 2 is the outer layer, layer 3 is the middle layer, layer 4 is a support layer and layer 5 is a sealing layer.

According to the invention, the middle layer 3 can be divided into several layers 6 and 7. This can best be seen in FIGS. 2-4, which, when enlarged from FIG. 1, represent the middle layer with the omission of layers 2, 4 and 5. Layers 4 and 7 can have the same polymer structure.

The outer layer 2 usually consists of a polymer or a polymer mixture whose melting point is higher than the melting point of the polymers or polymer mixtures of the other layers or equal to the melting point of the polymer or polymer mixture of the support layer 4. The polymer or the polymer mixture of the outer layer 2 generally depends on the welding temperature of the sealing layer 5, so that when the outer layer and the welding tool come into contact, the outer layer 2 melts or sticks.

The middle layer 3 is preferably a soft or flexible layer which has a softening point or of the components of a softening point below the sterilization temperature of 121 ° C. and which can be divided by one or more layers 7 into identical or different layers 6. The layers 7 consist of polymers or contain polymers whose melting points are well above 121 ° C. During sterilization, the layers 7 form a matrix with the outer layer 2 and the support layer 4, which prevent the layers 6 from flowing. Layers 6, 7 and 4 can also have properties that favor a connection to the neighboring layer.

The support layer 4 fulfills the task of a flow barrier during the welding process. It usually consists of polymers or polymer mixtures with a softening point above the corresponding welding temperature.

The sealing layer 5 usually consists of a seal-friendly polymer or polymer mixtures which are suitable for contact with food, enteral or parenteral solutions.

Results of test trials

A) An exemplary film according to the invention can be realized, inter alia, by selecting and coextruding the following materials with the following properties:<ul id="ul0001" list-style="none"><li>a) outer layer 2 Novolen 1302 L (atactic polypropylene homopolymer with a Vicat A of 138 ° C), Novolen 1102 H (isotactic polypropylene homopolymer with a Vicat A of 154 ° C), PP 23 M 10 cs 259 (polypropylene random copolymer with a Vicat A at 135 ° C);</li><li>b) middle class 3 Teamex 1000 F (VLDPE with Vicat A = 66 ° C), Exxact 4024 (polyethylene copolymer with Vicat A = 70 ° C), Adflex 7029 XCP (polypropylene copolymer with Vicat A = 55 ° C)</li><li>c) support layer 4 as a)</li><li>d) sealing layer 5 Novolen 3200 HX (polypropylene random copolymer with Vicat A = 130 ° C).</li></ul>B) In a further test, the impact strength of a non-PVC multilayer film according to the invention was examined using a drop test. Using an example, it is shown how an impact-resistant multilayer film according to the invention behaves before and after hot steam sterilization, in a drop test from a height of 1 or 2 m. The test sample is a coextruded multilayer film, which is structured as follows: Seven-layer composite according to Fig. 1 and 3 with PP-H as outer layer 2; PE-C / PP blend as layer 6; PE-C according to layer 7; PP-H as a support layer 4 PP-R / SEBS blend as sealing layer 5 The percentage proportions (% by weight) of the entire film are as follows: 28% PP-H 60% PE / PP blend 12% impact modified PP-R. The material abbreviations mean in particular: PP-H, R: polypropylene homopolymer, random copolymer SEBS: styrene-ethylene-butylene-styrene block copolymer PE-C: polyethylene copolymer The film was co-extruded and is available wrapped as tubular film with a bed width of 180 mm and a film thickness of 140-150 µm. The film is slightly biaxially oriented in the manufacturing process with a stretch ratio of: longitudinal stretching / transverse stretching = 2.3 / 1.4. Films according to the invention and materials for films according to the invention are thus clearly different from the materials known from the prior art. The LLDPE described in D3, for example, is suitable for heat shrink films. LLPDE is a linear polymer. There are at most C on a linear chain₈Residues copolymerized. LLPDE therefore leads to oriented foils. As a rule, these are stretched more than forty times and therefore have the property of shrinking against their stretching direction during heat treatment. A film which can be used according to the invention does not exhibit this property. This can also be slightly oriented (4: 1), but not stretched (&gt; 40: 1). It is therefore not linearly oriented and shows no shrinkage property. The tubular film sample is cut to appropriate lengths and welded to a bag with two flexible hose connections using indirect thermal contact welding or laser welding (type of welding is not critical) and then filled with water as an incompressible filling material, so that the same filling quantities result. The two hose connections are sealed with pluggable connectors. In previous tests, the optimal parameters such as temperature, time, surface pressure, for welding were determined for the individual test samples. They are listed in the table below:<tables id="tabl0001" num="0001"><table frame="all"><tgroup cols="6" colsep="1" rowsep="1"><colspec colnum="1" colname="col1" colwidth="26.25mm" /><colspec colnum="2" colname="col2" colwidth="26.25mm" /><colspec colnum="3" colname="col3" colwidth="26.25mm" /><colspec colnum="4" colname="col4" colwidth="26.25mm" /><colspec colnum="5" colname="col5" colwidth="26.25mm" /><colspec colnum="6" colname="col6" colwidth="26.25mm" /><thead valign="top"><row><entry namest="col1" nameend="col1" rowsep="0" align="center">temperature</entry><entry namest="col2" nameend="col3" align="center">Time [s]</entry><entry namest="col4" nameend="col5" align="center">Surface pressure [N / m²]</entry><entry namest="col6" nameend="col6" rowsep="0" align="center">Filling amount of water [l]</entry></row><row><entry namest="col1" nameend="col1" /><entry namest="col2" nameend="col2" align="center">a</entry><entry namest="col3" nameend="col3" align="center">b</entry><entry namest="col4" nameend="col4" align="center">a</entry><entry namest="col5" nameend="col5" align="center">b</entry><entry namest="col6" nameend="col6" /></row></thead><tbody valign="top"><row rowsep="1"><entry namest="col1" nameend="col1" align="right">130</entry><entry namest="col2" nameend="col2" align="right">6</entry><entry namest="col3" nameend="col3" align="right">8</entry><entry namest="col4" nameend="col4" align="right">8</entry><entry namest="col5" nameend="col5" align="right">9</entry><entry namest="col6" nameend="col6" align="right">2</entry></row></tbody></tgroup></table></tables> The film is welded in a welding device by 2 welding bars, which are heated with resistance heating cartridges.<ul id="ul0002" list-style="none" compact="compact"><li>a) welding bar straight bottom seam</li><li>b) Welding bar for welding the connecting hoses</li></ul> Half of the finished bags are sterilized or not sterilized. Sterilization takes place in an autoclave, at 121 ° C and 35 min, under wet steam. The drop device allows variable adjustment of any height up to 2 m. It has a pneumatically operated flap unit, which serves to support the bags and is opened when pressure is applied. The bags lie on the stomach side, so that the impact occurs in the most unfavorable position on the stomach side. It turns out that the influence of sterilization, for example through a decrease in impact strength, is not noticeable. There has also been no decrease in the frequency of cases. Only the break of the sample happens at different places. While the film preferably shows damage before sterilization, the weak point in the weld seam lies after sterilization. A possible reason for this behavior is due to the increasing degree of crystallization and the spherulitic superstructures that form, with the consequences of a loss of toughness. The sealing layer is at the bottom. The film has been impact modified with PP-R / SEBS blend. The impact strength is improved by the rubber content as a discontinuous phase in a PP-R matrix. Provided that the two blend components are well tolerated, the rubber phases are able to absorb tensions in the brittle PP-R matrix and ensure greater elasticity. The far larger aspect with regard to drop resistance, however, is the middle layer 3. Provided there is sufficient seam strength, the energy introduced into the material upon impact must be absorbed. The film tested has a high proportion of PE / PP blend as the middle layer. The energy absorbed can be determined using the energy conservation law, from which it follows:<dl id="dl0002" compact="compact"><dt>W</dt><dd>= m * g * (h₁ - H₂)</dd><dt>H₁</dt><dd>= Drop height</dd><dt>H₂</dt><dd>= Rebound height</dd><dt>m</dt><dd>= Bag weight</dd><dt>G</dt><dd>= Acceleration due to gravity</dd></dl> The rate at which the samples are loaded must also be taken into account; it follows with<maths id="math0001" num=""><math display="block"><mrow><mtext mathvariant="italic">v</mtext><mtext> = </mtext><msqrt><mtext>2 * </mtext><mtext mathvariant="italic">G</mtext><mtext> * </mtext><msub><mrow><mtext mathvariant="italic">H</mtext></mrow><mrow><mtext>1</mtext></mrow></msub></msqrt></mrow></math><img file="EP0739713A2_D0001.tif" /></maths> (neglecting air resistance) the speed of the bag before impact. In the drop test, the test samples are partially elastic with a rebound height h₂ of 10-20 cm, so that a partially elastic impact can be assumed. The stress does not break the samples. Due to the high loading speeds and the low elongation of the samples, it can be said with good certainty that the load takes place in the energy-elastic range (Hooke's range). C) Furthermore, the impact strength was also measured on the film described under B) here: The impact strength was measured with a universal pendulum hammer of type 6545/023 from Ceast (Torino / Italy). The principle of the measurement is based on the conversion of potential into kinetic energy. A film sample (dimensions see below) is clamped in such a way that the pendulum hammer suddenly stresses the film as it passes through the zero position. The energy resulting from the destruction of the film is calculated from the energy balance between the potential energies before and after the destruction of the sample by determining the initial deflection h1 from the zero position of the pendulum and the final deflection h2 after the sample has broken. The following applies:<maths id="math0002" num=""><math display="block"><mrow><mtable><mtr><mtd><mrow><mtable><mtr><mtd><mrow><mtext>Epot1 = m * g * h1</mtext></mrow></mtd></mtr><mtr><mtd><mrow><mtext>Epot2 = m * g * h2</mtext></mrow></mtd></mtr></mtable></mrow></mtd></mtr></mtable></mrow></math><img file="EP0739713A2_D0002.tif" /></maths> and from this the damage energy:<maths id="math0003" num=""><math display="block"><mrow><mtext>Es = Epot1 - Epot2</mtext></mrow></math><img file="EP0739713A2_D0003.tif" /></maths> The measurements were carried out with a deflection of 90 ° from the zero position. The potential energy Epot1 was always 15 J. The device is equipped so that the values ​​for the impact strength are calculated after the test. The device used was operated with the following settings or had the following characteristics: DRWG Number (cod.): 6545/023 potential energy: 15 J acc. Weight at 90 ° C: 2181.7-2203.6 g Distance between rotation and impact axes: 373.8 ± 0.1 mm. Time for 50 oscillations. less than 5 ° = 60.98-61.59 s The impact strength of a film according to the invention (not sterilized, four samples each 0.15 mm clamped together with a thickness of 4 x 0.15 mm, a width of the test specimen of 4 mm and a vertical cross section of 0.6 mm²), was 12,935.8 mJ / mm². The value for the impact strength was sterilized at 5,560.3 mJ / mm². (Thickness: 4 x 0.14 mm, width unchanged, cross section: 0.56 mm²). A previously used PVC film usually has an impact strength in the range of 7150 mJ / mm² (not sterilized) or 6973 mJ / mm² (sterilized). It follows from this that with the film according to the invention all requirements for a particularly high impact strength are met even after sterilization. D) Determination of the evaporation residue according to DIN 58363 part 15 (July 1982) Another not insignificant advantage is the low migration of the additives. The additive loss during sterilization is 0.55 mg / dm for a PVC film², however, only 0.1 mg / dm in the film according to the invention² (at 121 ° C) measured in the evaporation residue according to DIN 58363. Further advantages and embodiments of the invention emerge from the following patent claims.