DE102010018866A1 - Peelable, biodegradable film arrangement useful in packaging industry for food packaging and other packaging products, comprises first film layer, peel layer, additional film layer, and cover layer as further outer layer - Google Patents

Abstract

The peelable, biodegradable film arrangement (1) comprises a first film layer (5A) (5-20 wt.%), a peel layer (10) (40-80 wt.%) that is a mixture of a polyhydroxy carboxylic acid and 25 wt.% relative to the peel layer comprising a biodegradable polyester that is different from the polyhydroxy carboxylic acid and the peel layer forms the film arrangement of an outer layer, an additional film layer (5B), and a cover layer (20) as a further outer layer. The first film layer includes a polyhydroxy carboxylic acid and a plasticizer. The peelable, biodegradable film arrangement (1) comprises a first film layer (5A) (5-20 wt.%), a peel layer (10) (40-80 wt.%) that is a mixture of polyhydroxy carboxylic acid and 25 wt.% a biodegradable polyester that is different from the polyhydroxy carboxylic acid and the peel layer forms an outer layer of the film arrangement, an additional film layer (5B), and a cover layer (20) as a further outer layer. The first film layer includes polyhydroxy carboxylic acid and a plasticizer. The additional film layer includes polyhydroxy carboxylic acid with the plasticizer, and is arranged on the first film layer. The film arrangement includes seal strength of less than 15 N/15 mm against a polyhydroxy carboxylic layer. The peel layer is free of bonding agents or adhesive. The inner side of the film arrangement on the first film layer has a higher proportion of the plasticizer than the outer side of the additional film layer. The film layers and/or the peel layer contain additives such as dyes. The cover layer contains polyhydroxy carboxylic acid. The cover layer contains the plasticizer, whose portion of the cover layer is lesser than the proportion of the plasticizer in the first film layer.

Description

Films of biodegradable thermoplastics, such as polyhydroxycarboxylic acids, such as polylactic acid (also referred to as polylactide or PLA), are used in the packaging industry for, among other things, food packaging and other packaged goods. Such films are very popular because they are both compostable and produced on the basis of renewable raw materials, but on the other hand also have many advantages of conventional thermoplastic polymers based on polyolefins.

In many different packaging, especially in food packaging, there is a need to open the packaging in a simple manner by opening a so-called top film opposite a bottom film. The required effort should not be so high and below 15 N / mm, so that the packaging can be opened easily by the consumer. Some polyhydroxycarboxylic acid based packaging, such as polylactides, when sealed against themselves, have very high seal strengths, sometimes greater than 20 N / 15 mm. Such high sealing seam strengths can also lead to the sealing seams generally having a higher strength than the upper or lower film itself, so that when the films are pulled off, the film, the so-called cohesive fracture, may break.

Further, a problem of film assemblies and also packaging materials based on polyhydroxycarboxylic acids, such as PLA, is that they have considerable rigidity and low tear strength. This rigidity disadvantageously limits the fields of use of the films. Even a slight tearing of the film is not desired by the consumer, since the film in one piece - and not in several fragments - should be deducted.

From the publication WO 2007/113077 A1 For example, a multilayer film is known which contains a peelable topcoat of a blend of a polylactic acid with a biodegradable starch, cellulose or a degradable polyester. Furthermore, a base layer is present which has polylactic acids. Such a film has a seal seam strength of 1 to 7 N / 15 mm with respect to itself. However, this multilayer film is relatively expensive, easily tearing and also very stiff.

It is therefore the object of some embodiments of the present invention to reduce the above-mentioned disadvantages known from the prior art. This technical problem is solved by a peelable, biodegradable film arrangement according to claim 1 and a peelable package according to claim 15. Methods for producing the film arrangement are the subject of further claims.

• – einer ersten Folienschicht, die eine Polyhydroxycarbonsäure und einen Weichmacher aufweist und
• – einer Peelschicht, die eine Mischung einer Polyhydroxycarbonsäure und zumindest 25 Gew.-% bezogen auf die Peelschicht eines biologisch abbaubaren Polyesters umfasst, wobei die Peelschicht eine Außenschicht der Folienanordnung bildet.

One embodiment of the present invention relates to a peelable, biodegradable film assembly having a seal seam strength of <15 N / 15 mm against a polyhydroxycarboxylic acid layer, comprising at least:

• A first film layer comprising a polyhydroxycarboxylic acid and a plasticizer, and
• A peel layer comprising a mixture of a polyhydroxycarboxylic acid and at least 25% by weight of the peel layer of a biodegradable polyester, the peel layer forming an outer layer of the film assembly.

The biodegradable ester is different from the polyhydroxycarboxylic acid, which is already biodegradable per se. With such a film arrangement, the polyhydroxycarboxylic acid dispersed in a continuous phase of the biodegradable polyester is generally present, resulting in a good peelability of the film arrangement. Furthermore, such a foil arrangement for polyhydroxycarboxylic acids has atypical high flexibility, tear strength, impact resistance and also low toughness, since the first foil layer, in addition to the polyhydroxycarboxylic acid, also has a plasticizer which reduces the naturally high rigidity of the polyhydroxycarboxylic acid.

The seal seam strength or also the composite adhesion of the film arrangement in N / 15 mm indicates the release force which is required for separating two layers of a multilayer film or of films sealed against one another. For this purpose, two adjacent layers in a multilayer film, whose seal seam strength is to be determined, separated on one side at least 50 mm wide mechanically far from each other and then brought the sample on a Abziehrolle, which was previously provided over the entire surface with double-sided adhesive tape. The peel roller is installed in a tensile strain tester and that side of the sample having the layers already segregated is placed in the upper clamp of the Tension-strain tester clamped. The layers are then pulled apart at a feed rate of the pulling clamp of 100 mm / min until complete separation. To determine the seal seam strength while a force-strain diagram is recorded and from the obtained peak values of the median and the span of the force corresponding to those in the German industrial standard DIN 53539-79 determined method determined.

If a film arrangement has several layers, then the seal seam strength is to be determined for each layer according to the above-mentioned method. The layers between which the lowest seal seam strength occurs, are first to be separated, otherwise it can come at the same time in the separation of other layers for the undesirable separation of multiple layers simultaneously.

For the purposes of the invention, "biodegradable films" is understood to mean films which are in accordance with the German Industrial Standard DIN EN 13432 described method can be completely biodegraded. In this case, a method for testing the aerobic compostability is used, which with the method ISO 14855: 1999 is identical. The test duration may not exceed a maximum duration of six months. The film arrangement to be tested must achieve a degree of degradation of at least 90% or 90% of the maximum value of a correspondingly suitable reference substrate in the plateau phase. Furthermore, a disintegration test is carried out as part of the aerobic composting. In this case a maximum of 10% of the original dry weight of the test material may be found after composting for a maximum of 12 weeks in a> 2 mm sieve fraction.

The peelable, biodegradable film arrangement according to the abovementioned embodiment of the invention advantageously has a sealed seam strength of <15 N / 15 mm, preferably less than 10 N / 15 mm, most preferably less than 5 N / 15 mm. It is further preferred if a packaging material which contains the peelable, biodegradable film arrangement can be opened with a force of approximately 1 N / 15 mm up to approximately 15 N / 15 mm, in which the cover film is pulled off the bottom film. With a seal seam strength of> 15 N / 15 mm, in particular at values of> 20 N / 15 mm, the top film can often no longer be removed from the bottom film due to the high adhesion, so that the cohesive break already mentioned above occurs.

The peelable, biodegradable film layer arrangement can be sealed with other films based on polyhydroxycarboxylic acids, in which case the preferably low seal seam strengths of less than 15 N / 15 mm result and at the same time the film arrangement has increased elongation at break, toughness, strength and stability.

The inventors have further found that at levels of less than 25% by weight of the biodegradable polyester on the scrub layer, the seal seam strength becomes unacceptably high and can easily reach values of> 20 N / 15 mm. With a proportion of at least 25% by weight of the biodegradable polyester on the peel layer, the entire peelable, biodegradable film arrangement can be prepared by standard conditions, for example temperatures of 80 to 120 ° C., a pressure of 0.5 bar to 10 bar and a Time span of 0.5 s to 10 s seal well with other polyhydroxycarboxylic acid films.

The plasticizer in the first film layer can be selected from glycerol, citric acid esters and polyalkylene glycols or any desired mixture of these plasticizers. These plasticizers are particularly suitable for use in film layer arrangements based on polyhydroxycarboxylic acids.

More preferably, the plasticizer is a polyalkylene glycol having a molecular weight of at least 1000. In the case of polyalkylene glycols having this molecular weight, it can be ensured on the one hand that the first film layer has sufficient softness, but on the other hand, because of the high molecular weight of the plasticizer, outward diffusion of the plasticizer out of the first film layer greatly reduced or prevented. Such plasticizers also do not lead to a disadvantageous discoloration of the plastic or odor nuisance. More preferably, polyethylene or polypropylene glycol having a molecular weight greater than 8,000, more preferably between 25,000 and 4 million, most preferably around 35,000 may be used. Polyethylene or polypropylene glycols having such high molecular weights are solids, so that outdiffusion of these plasticizers from the first film layer can be effectively prevented. Furthermore, it is possible that the polyalkylene glycol plasticizers are modified with a functional group, in particular a carboxylic acid function.

The mechanical properties of the biodegradable peelable film arrangement can be influenced particularly advantageously if the plasticizer is present in the first film layer in a proportion of about 1 to 20% by weight, preferably from 3 to 15% by weight.

As polyhydroxycarboxylic acids, it is possible to use polymers based on various hydroxycarboxylic acids, for example α-hydroxycarboxylic acids, such as glycolic acid or lactic acid, β-hydroxycarboxylic acids, such as mevalonic acid or 3-hydroxybutyric acid. A preferred variant of a polyhydroxycarboxylic acid is a polylactide, polylactic acid. Monomers of the polylactide may be D or L-hydroxycarboxylic acids. Polylactic acid is produced via catalytic ring-opening polymerizations of lactide, an annular condensation product of two lactic acid molecules, 1,4-dioxane-3,6-dimethyl-2,5-dione. The production of polylactic acid or polylactide is also for example in the U.S. Patents US 5,208,297 or US 5,357,035 to which reference is hereby incorporated by reference. It is also possible to use co-polymers of lactic acid or other polyhydroxycarboxylic acids which have different monomer units. Polylactides are easy to prepare, biodegradable polyhydroxycarboxylic acids that are also food grade.

Can be used, for example polylactides the NatureWorks ^®, for example, to the PLA polymer 2002D.

x = 0 – unendlich
y > 10
wie zum Beispiel Poly-4-hydroxybutyrat, Poly-3-hydroxybutyrat und Poly-3-hydroxyvalerat oder deren Co-Polymere.It is also possible to use polyhydroxyalkanoates of the general formula:

x = 0 - infinite
y> 10
such as poly-4-hydroxybutyrate, poly-3-hydroxybutyrate and poly-3-hydroxyvalerate or their co-polymers.

• – Adipinsäure, deren esterbildende Derivate, oder Mischungen davon,
• – Terephthalsäure, deren esterbildende Derivate, oder Mischungen davon und
• – C₂ bis C₆ Alkandiole, C₅ bis C₁₀ Cycloalkandiolen, oder Mischungen davon,

herstellbar sein.The biodegradable polyester, which is different from the polyhydroxycarboxylic acid, can be prepared, for example, by polymerization of a mixture consisting of:

• Adipic acid, its ester-forming derivatives, or mixtures thereof,
• Terephthalic acid, its ester-forming derivatives, or mixtures thereof and
• C ₂ to C ₆ alkanediols, C ₅ to C ₁₀ cycloalkanediols, or mixtures thereof,

be produced.

As C ₂ to C ₆ alkanediol, 1,4-butanediol is preferably used. The synthesis of such biodegradable polyesters is disclosed in, for example, the issued EP patents EP 0 792 309 B1 such as EP 1 838 784 B1 to which reference is hereby incorporated by reference.

These polyesters are particularly readily biodegradable, but with other polyhydroxycarboxylic acids, such as polylactide, form a polymer blend having a domain structure. Depending on the concentrations of the polyhydroxycarboxylic acids and the biodegradable polyester, either the polyester can form a continuous phase in which domains of the polyhydroxycarboxylic acid are incorporated, or vice versa. This results in the formation of a homogeneous domain-like "sponge" structure, especially when prefabricated blends of the biodegradable polyester are used with the polyhydroxycarboxylic As polymer blends of PLA and the biodegradable polyester polymer blends such as Ecovio ^® , especially Ecovio ^® L BX 8145 the company BASF. Through the use of prefabricated, compounded blends of the biodegradable polyester and a polyhydroxycarboxylic acid peel layers can be produced, which have over the entire peel homogeneous peel properties and no turbidity. The percentage by weight of the biodegradable polyester in the peel layer can be adjusted via the addition of additional polyhydroxycarboxylic acids.

Further, the biodegradable polyester product Ecoflex F BX ^® can also be used in pure form, for example, 7011 of the company BASF.

According to another embodiment of the present invention, it is advantageous if the biodegradable polyester in a proportion of at least 35 to 80 wt .-%, preferably 35-70 wt .-%, particularly preferably 45-65 wt .-% in the peel layer is present, since then particularly good sealing seam strengths of less than 15 N / 15 mm, in particular very good seal seam strengths of less than 6 N / 15 mm, preferably less than 4 N / 15 mm, more preferably less than 3.5 N / 15 mm can be achieved.

Furthermore, according to one embodiment of the invention, the peel layer of the film arrangement according to the invention can be free from adhesion promoters or other adhesives. Under the standard conditions mentioned above, the peelable film arrangement can be sealed securely with other polyhydroxycarboxylic acid films without any further use of adhesion promoters or adhesives and adhesives. The sealability of the present biodegradable film arrangement can therefore be ensured solely by the mixture of the polyhydroxycarboxylic acid and the at least 25% by weight of the biodegradable polyester.

In further embodiments of the invention, the film assembly may comprise further film layers comprising a polyhydroxycarboxylic acid with a plasticizer and disposed on the first film layer. By including further film layers, on the one hand, the thickness of the film arrangement can be varied particularly well and, on the other hand, the mechanical strength of the film can also advantageously be varied by different plasticizer concentrations in the different film layers. It is also possible to use other biodegradable film layers that have no plasticizers.

According to a further embodiment of a film arrangement according to the invention, the first film layer located in the interior of the film arrangement has a higher proportion of plasticizer than the at least one further film layer located further out. In particular, the film layers located further out in the film arrangement can have a plasticizer content of between 0.1 and 10% by weight, in particular between 0.1 and 5% by weight, and the inner layer can have a higher proportion of plasticizer. In the case of such a film arrangement, owing to the inner layer with the higher proportion of plasticizer, the mechanical load-bearing capacity of the film can advantageously be increased without the blocking tendency of the film arrangement becoming too high. The blocking tendency, ie the wedging of the different films relative to one another, can be reduced or prevented particularly well by the film layers located farther out in the film arrangement with a lower proportion of plasticizer.

The film layers present in the film arrangement and / or the peel layer may contain further additives, such as, for example, dyes, in order, for example, to give the film arrangement a specific color impression and also to enable printed shapes on the film arrangement.

Furthermore, it is possible that as a further outer layer on the film arrangement, a cover layer is present, which also contains a polyhydroxycarboxylic acid. Such a further cover layer may, for example, also contain further additives, such as antiblocking and slip additives, which have a significant influence on the coefficient of friction of the film arrangement against itself or against other substrates such as steel or glass.

In particular, the cover layer may also contain a plasticizer, but its proportion is preferably reduced in comparison to the inner film layers, in order to reduce or prevent the blocking tendency between several film arrangements.

• – eine erste Folienanordnung mit einer ersten Folienschicht, die eine Polyhydroxycarbonsäure enthält, und
• – einer Peelschicht, die eine Mischung einer Polyhydroxycarbonsäure und zumindest 25 Gew.-% bezogen auf die Peelschicht eines biologisch abbaubaren Polyesters umfasst und
• – eine zweite Folie, die eine Polyhydroxycarbonsäure umfasst, die frei von dem biologisch abbaubaren Polyester ist,
• – wobei die Peelschicht der ersten Folienanordnung gegen die zweite Folie mit einer Siegelnahtfestigkeit von < 15 N/15 mm gesiegelt ist.

The subject of a further embodiment of the invention is a peelable, biodegradable packaging, comprising:

• A first film arrangement comprising a first film layer containing a polyhydroxycarboxylic acid, and
• A peel layer comprising a mixture of a polyhydroxycarboxylic acid and at least 25% by weight, based on the peel layer of a biodegradable polyester, and
• A second film comprising a polyhydroxycarboxylic acid which is free of the biodegradable polyester,
• - wherein the peel layer of the first film assembly is sealed against the second film with a sealed seam strength of <15 N / 15 mm.

As already mentioned above, the biodegradable polyester is different from the polyhydroxycarboxylic acid. In contrast to the prior art, the inventors have surprisingly discovered that a film layer assembly containing a peel layer of the blend of a polyhydroxycarboxylic acid and a biodegradable polyester can be sealed to films containing a polyhydroxycarboxylic acid but not the biodegradable polyester. Such peelable packaging is thus much cheaper to produce than packaging from the prior art, since in particular the mixture of polyhydroxycarboxylic acid with the biodegradable polyester is very expensive and in the prior art only seals the mixture of polyhydroxycarboxylic acid with the biodegradable polyester against itself are known. In particular, the inventors have surprisingly found that at standard seal conditions of 80 to 120 ° C, a pressure of 0.5 to 10 bar and a sealing period of 0.5 to 10 s good seal strengths of less 15 N / 15 mm against polyhydroxycarboxylic acid films alone can be achieved.

Between the first film arrangement and the second film, a cavity is formed in the peelable packaging, which serves for receiving packaged goods, for example foods, and which is accessible by opening the first film arrangement against the second film.

The first film arrangement can be used both as a bottom film or as a top film, the second film then correspondingly forms the counter-film. According to this embodiment of the invention, the mixture of a polyhydroxycarboxylic acid and at least 25% by weight of a biodegradable polyester which causes the good peelability of the packaging must be present only in the bottom or top film, but not in both films.

Furthermore, it is advantageous that the first film arrangement has the suitability for deep drawing or thermoforming. In particular, when the first film assembly is part of the bottom film and this has the shape of a cup or a shell, which is formed by the thermoforming. PLA as the preferred polyhydroxycarboxylic acid fulfills all the prerequisites for deep drawing or thermoforming from the ground up and can be thermoformed excellently on the usual systems, the temperature range during thermoforming being selected between 75 ° C. and 120 ° C., preferably 90 ° C.-100 ° C. becomes.

In particular, a good sealability of the packaging can be achieved if the polyhydroxycarboxylic acid of the first film arrangement and the polyhydroxycarboxylic acid of the second film are the same, for example a polylactide. As already mentioned above, it is also possible for a plasticizer with the technical advantages already mentioned above to be present in each case in the first film layer of the first film arrangement.

The second film can also be part of a second, multilayer film arrangement which comprises further films, for example a cover film. The other films are preferably also biodegradable and include polyhydroxycarboxylic acids, such as PLA.

Both the first film arrangement, as well as the second film, or in the case of several layers, the second film arrangement of the packaging according to the invention can all have the features of the first film arrangement already mentioned above.

According to a further embodiment of the invention, packages for packaged goods are provided in which one of the two film arrangements, the bottom or the cover film is thicker than the respective other film arrangement. The thinner Folienanordung may have a thickness of 10-80 microns (preferably blown films) and the thicker film assembly has a thickness of 150-1000 microns (preferably cast films).

Particularly preferably, the thicker film is the bottom film, which is shaped, for example, in the form of a shell and receives the packaged goods, wherein the thinner lidding film then seals the bottom film. The peel layer is preferably integrated into the thicker bottom foil, since the lid foil is formed in a transparent manner in order to enable the consumer to view the packaged goods through the lid foil.

The thicker base films can be present, for example, as deep-drawn packages and are filled with food or other packaged goods and then sealed with the thinner lidding film in the context of the so-called FFS process (FORM-FILL-SEAL).

• – eine erste Mischung zur Herstellung der oben bereits beschriebenen Peelschicht umfassend eine Polyhydroxycarbonsäure und zumindest 25 Gew.-% eines biologisch abbaubaren Polyesters zusammen mit
• – einer zweiten Mischung der Polyhydroxycarbonsäure und des Weichmachers
• – koextrudiert werden.

The subject of a further embodiment of the invention is also a method for producing a peelable, biodegradable first film arrangement, wherein

• A first mixture for the preparation of the above-described peel layer comprising a polyhydroxycarboxylic acid and at least 25% by weight of a biodegradable polyester together with
• A second mixture of the polyhydroxycarboxylic acid and the plasticizer
• - be co-extruded.

During coextrusion, the first and the second mixture are solidified on top of each other, in which case the first film arrangement already described above forms. If the layers or mixtures can not be readily joined, it may be possible to additionally work with preferably biodegradable adhesion promoters.

To form the two layers can also be used from the prior art known blowing or casting process.

Prefabricated mixtures of the biodegradable polyester and the polyhydroxycarboxylic acid can be used particularly advantageously, which lead to peel layers with particularly homogeneous peel behavior, as already explained above.

In the following, various embodiments of the invention will be described in more detail for explaining the invention. All layers described in the following figures contain, for example polylactide of NatureWorks ^®, which is marketed under the brand name PLA 2002D. Show it:

1 a seven-layer embodiment of a first film arrangement according to the invention in cross-section, which was produced by means of a casting process,

2 a cross-section through a five-layer embodiment of a first film assembly according to the invention, which was produced by means of a blowing process,

3 an embodiment of a package according to the invention in cross section, in which a film assembly according to the invention is sealed as a lid sheet with a Polylactidbodenfolie.

1 shows an example of an embodiment of a first film arrangement according to the invention 1 , which was produced by means of a casting process. Here is a first layer of foil 5A and an identical further film layer 5B containing 10% by weight of the plasticizer PEG 35000, 5% of a dye and 85% by weight of polylactide. The thickness of these layers is 70.5 μm. This first and the further film layer 5A and 5B Flank a three-layer arrangement in the center of the film assembly 1 that consists of two identical layers 6 is constructed, which in turn has a central film layer 7 flank. The two PLA film layers 6 consist of 92.5 wt .-% PLA and 7.5 wt .-% as the plasticizer PEG 35000.

The thickness of the two polylactide layers 6 is 8 μm each. The central PLA layer 7 has the same composition as the PLA layers framing it 6 but the thickness thereof is 10 μm. The peel layer 10 , which forms an outer layer, consists of 53.35 wt .-% of a biodegradable ester, the ester Ecoflex ^® F BX 7011 from BASF and 3 wt .-% of a slip antiblock combination, Sukano ^® PLA DCS 511 and in Remaining from PLA. The thickness of the peel layer 10 is 90 μm. The peel layer 10 lies the cover layer 20 as a further outer layer opposite, which has a thickness of 43 microns and 8.25 wt .-% of the plasticizer PEG 35000 and the remainder of PLA. Such a film, when sealed with a PLA film, has excellent seal seam strengths in the range of <15 N / 15 mm.

2 shows in cross-section a further embodiment of a first film arrangement according to the invention, which was produced by the blowing process. This film arrangement has a first film layer 5A which consists of 15% of the plasticizer PEG 35000 and the remainder of PLA with a thickness of 8.34 microns and is flanked by other film layers 5B that have an identical composition to the layer 5A have, however, are somewhat thinner. The peel layer 10 consists of 53.9 wt .-% of the biodegradable polyester, to 2 wt .-% of the slip antiblock Sukano ^® PLA DCS 511 and consists of the rest of PLA (thickness 12.5 microns). In contrast, the top layer lies 20 , which consists of 98 wt .-% PLA and 2% of the aforementioned slip-antiblock combination and also has a thickness of 12.5 microns.

These two film assemblies are sealed at 100 ° C and a pressure of 6 bar for 0.5 s with the peel layer against composite films whose outer layers have only PLA and the aforementioned slip-antiblock combination, wherein in the film assembly according to 1 a peel value of 5.8 N / 15 mm and in the film arrangement according to 2 a peel value of 3.5 N / 15 mm was measured.

3 shows a peelable, biodegradable packaging 30 in which a film arrangement according to the invention 1 that a peel layer 10 consisting of polylactide and the biodegradable polyester and which further contains another PLA layer 5 has as the first film layer was sealed as a top film against a lower film 2 that is a pure PLA film layer 5 and further a topcoat 20 having. Inside the packaging is in the cavity 4 packaged goods 40 for example, a food. Such a package 30 On the one hand tight and allows a reliable storage of the packaged goods 40 , but on the other hand allows easy opening of the top film 1 opposite the bottom foil 2 , Furthermore, it is possible that the peel layer 10 in contrast to 3 not in the top film 1 but in the lower film 2 is integrated. Such a packaging, in contrast to packaging materials from the prior art has the advantage that only one instead of two peel layers are required for sealing.

In the following, experimentally determined seal seam strengths in N / 15 mm from first foil arrangements against composite foils are summarized in tabular form. In this case, the peel layer of the first film arrangement is sealed in each case against a pure PLA layer of the composite films under the standard conditions already mentioned above. Indicated in each case is the composition and thickness of the peel layer (in the line) and the thickness and nature of the pure PLA layer (in the associated column).

For comparison, the seal seam strengths of pure PLA layers are indicated against other PLA layers which do not comprise the peel layer according to the invention. PE = biodegradable polyester Ecoflex F BX 7011 ^®, registered in the form of Ecovio ^® L BX 8145; PLA = polylactide; SAK = Slip antiblock combination.

Clearly, it can be seen that in a seal of a peel layer according to the invention with at least 25 wt .-% of the biodegradable polyester against a PLA film good to very good seal seam strength and excellent opening characteristics when used for packaging can be achieved. For example, packaging systems with seal seam strengths of 3.5, 4.4 and 5.8 N / 15 mm - as stated in the examples - are absolutely leakproof and protect the packaged goods, but the packaging is very light and non-destructive and without the use of tools to open. In the example according to the invention with a sealed seam strength of 12.8 N / 15 mm - which was adjusted by slight reduction of the biodegradable polyester Ecoflex F BX 7011 - the opening of the packaging is slightly more difficult, but still possible without problems. If less than 25% by weight of the biodegradable polyester is present in the peel layer, the seal seam strengths increase sharply. A Packaging is in this case only very difficult to open, which does not meet the consumer. When sealing a pure PLA film against another PLA film, the seal seam strengths increase even further. In the latter case, sealing seam strengths significantly greater than 20 N / 15 mm are also referred to as "fixed closure". To open a considerable effort is possible, so that a nondestructive removal of the lid film is then no longer possible. In most cases, opening is only done with the aid of tools such as knives or scissors.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• WO 2007/113077 A1 [0004]
• US 5208297 [0017]
• US 5357035 [0017]
• EP 0792309 B1 [0021]
• EP 1838784 B1 [0021]

Cited non-patent literature

• DIN 53539-79 [0008]
• DIN EN 13432 [0010]
• ISO 14855: 1999 [0010]

Claims (22)

Peelable, biodegradable film arrangement ( 1 ) having a sealed seam strength of less than 15 N / 15 mm against a polyhydroxycarboxylic acid layer, comprising at least: - a first film layer ( 5A ) comprising a polyhydroxycarboxylic acid and a plasticizer, and - a peel layer ( 10 ) which comprises a mixture of a polyhydroxycarboxylic acid and at least 25% by weight, based on the peel layer of a biodegradable polyester different from the polyhydroxycarboxylic acid, and the peel layer comprises an outer layer of the film arrangement ( 1 ). Foil arrangement ( 1 ) according to claim 1, wherein the plasticizer is selected from glycerol, citric acid esters and polyalkylene glycols or any mixture of these plasticizers. Foil arrangement ( 1 ) according to any one of the preceding claims, wherein the plasticizer is a polyalkylene glycol having a molecular weight of at least 1000. Foil arrangement ( 1 ) according to one of the preceding claims, wherein the plasticizer is polyethylene glycol, in particular polyethylene glycol 35000. Foil arrangement ( 1 ) according to one of the preceding claims, wherein the plasticizer is present in a proportion of 5 to 20 wt .-% in the first film layer. Foil arrangement according to one of the preceding claims, - in which the polyhydroxycarboxylic acid is a polylactide. Foil arrangement ( 1 ) according to one of the preceding claims, wherein the biodegradable polyester is prepared by polymerization of a mixture consisting of: - adipic acid, its ester-forming derivatives, or mixtures thereof, - terephthalic acid, their ester-forming derivatives, or mixtures thereof, and - C ₂ to C ₆ alkanediols, C ₅ to C ₁₀ cycloalkanediols, or mixtures thereof, can be produced. Foil arrangement ( 1 ) according to the preceding claim, - wherein the biodegradable polyester is present in a proportion of 40 to 80 wt .-% in the peel layer. Foil arrangement ( 1 ) according to one of the preceding claims, - wherein the peel layer ( 10 ) is free of adhesion promoters or adhesives. Foil arrangement ( 1 ) according to one of the preceding claims, additionally comprising: - at least one further film layer ( 5B ) comprising a polyhydroxycarboxylic acid with a plasticizer and on the first film layer ( 5A ) is arranged. Foil arrangement ( 1 ) according to the preceding claim, - wherein the inside of the film assembly located first film layer ( 5 ) has a higher proportion of plasticizer than the further outward located at least one further film layer ( 15 ). Foil arrangement ( 1 ) according to the preceding claim, wherein - the film layers ( 5 . 15 ) and / or the peel layer ( 10 ) Contain additives such as dyes. Foil arrangement ( 1 ) according to one of the preceding claims, additionally comprising: - a cover layer ( 20 ) as a further outer layer, the cover layer containing a polyhydroxycarboxylic acid. Foil arrangement ( 1 ) according to the preceding claim, wherein - the cover layer ( 20 ) contains a plasticizer whose proportion of the top layer ( 20 ) is less than the proportion of the plasticizer on the first film layer ( 5 ). Peelable, biodegradable packaging ( 30 ), comprising: - a first foil arrangement ( 1 ) with a first film layer ( 5A ) containing a polyhydroxycarboxylic acid and a peel layer ( 10 ) containing a mixture of a polyhydroxycarboxylic acid and at least 25% by weight based on the peel layer of a biodegradable polyester different from the polyhydroxycarboxylic acid, and - a second film ( 5B ) comprising a polyhydroxycarboxylic acid which is free of the biodegradable polyester, - the peel layer ( 10 ) of the first film arrangement ( 1 ) against the second film ( 5B ) is sealed with a sealed seam strength of less than 15 N / 15 mm. Packaging according to the preceding claim, wherein - The polyhydroxycarboxylic acid of the first film assembly and the polyhydroxycarboxylic acid of the second film are the same. Packaging according to one of claims 15 or 16, wherein - The polyhydroxycarboxylic acid is a polylactide. A package according to any one of claims 15 to 17, wherein - In the first film layer of the first film assembly, a plasticizer is present. A package according to any one of claims 15 to 18, wherein - The seal was carried out at a temperature of 80 ° C to 120 ° C at a pressure of 0.5 bar to 10 bar for a period of 0.5 s to 10 s. A process for producing a peelable, biodegradable film assembly according to any one of claims 1 to 14, wherein a first mixture comprising the polyhydroxycarboxylic acid and at least 25% by weight of a biodegradable polyhydroxycarboxylic acid-containing polyester together with a second mixture comprising a polyhydroxycarboxylic acid and a plasticizer co-extruded. Method according to the preceding claim, in which - The first and second blends are co-extruded by blow molding or casting. Method according to one of the preceding claims 20 or 21, wherein - As a first mixture, a prefabricated mixture of the polyhydroxycarboxylic acid and the biodegradable of the polyhydroxycarboxylic acid of different polyester is used.

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