Multi-layer, coextruded polyester film with reduced puncture resistance, for use as blister cover film

Abstract

The present invention relates to a multi-layer, coextruded polyester film with reduced puncture resistance, the use of the film as a cover film for blister packs, in particular pharmaceutical blisters (drug blisters) and the resulting closed blisters. The invention likewise relates to a process for producing the polyester film according to the invention.

Description

[0001] Multilayer, coextruded polyester film with reduced puncture resistance for use as blister cover film

[0002] The present invention relates to a multilayer, co-extruded polyester film with reduced puncture resistance, the use of this film as a cover film for blister packs (hereinafter also referred to simply as "blisters"), in particular pharmaceutical blisters (medication blisters), and the resulting sealed blisters. Furthermore, the invention encompasses a process for producing the polyester film according to the invention. The special feature is that, when using the described films, the resulting blisters according to the invention can be opened by hand without any aids by pushing the packaged material through the cover film.

[0003] Description

[0004] Blister packs are used in many areas today. Such packaging consists of a molded plastic film ("molded part") comprising one or more chambers and a sealing material. The sealing material can be a welded film web, a paper web, or a sealed film web. The latter are the subject of the present invention, hereinafter also referred to as "cover film."

[0005] Particularly in the pharmaceutical packaging sector, blisters made of plastic films (usually PVC, polyester or polypropylene, either as a monomaterial or as a composite material with layers of other materials such as oPA, aluminum or paper) with multiple chambers are used. Typically, each chamber contains a tablet / capsule, and the blister is sealed on the back with a film strip (see, for example, https: / / de.wikipedia.org / wiki / Sichtverpackung). The sealing material is usually aluminum foil (usually 20-30 μm thick) with an applied sealing layer (sealing layer usually 3-5 μm thick). The aluminum foil is used due to its low puncture resistance so that the material in the chamber can be pushed through by hand.

[0006] The disadvantage of the existing solution, however, is the high basis weight of the aluminum foil, which leads to high transport costs and the high energy consumption during its production (high CO2 footprint), and in particular, disadvantages when recycling blister packs containing aluminum foil, which end up in residual waste. Pharmaceutical blister packs account for a relatively small proportion of residual waste, so sorting and recycling the aluminum is generally not worthwhile (theoretically, large-scale users such as hospitals are an exception). In the case of blister packs whose molded part is made of amorphous, unoriented polyester (APET), these could theoretically be separated with other polyester waste and chemically recycled via glycolysis. However, the aluminum still adhering to the used blister pack is a contaminant. The same applies to alternative disposal using pyrolysis of polypropylene (PP) or PVC-based blister packs.

[0007] In principle, such blisters can also be sealed with plastic film instead of aluminum foil. Biaxially oriented polyethylene terephthalate (PET) films are particularly suitable for this purpose, as they are sufficiently rigid, even at low thicknesses, to be applied to the blister without wrinkles. Furthermore, they can be sealed effectively at the sealing tool temperatures of 120 to 240 °C typical for blister filling systems, without melting on the contact side with the sealing tool and sticking to it. Temperatures at the upper end of this range are used, particularly in faster blister systems where sealing is performed using sealing rollers.

[0008] Sealable polyester films are described, for example, in DE102008046780, DE102008046781, EP2263868, or EP1138480. The films described in DE102008046781 generally seal against commercially available PVC medication blisters, and those described in EP1138480 seal against commercially available APET blisters. The disadvantages of all these prior art films, however, are that the tablet inside the blister cannot be pushed through the sealed film at all or only with extreme force. The resulting blister can then only be opened with the use of tools (e.g., scissors).

[0009] While the puncture resistance can be reduced to such an extent that puncture is possible by deliberately damaging the film surface (e.g., by cutting the surface with knife rollers or punching devices), this is a complex additional process step and also carries the risk that if the user accidentally bends the blister, a tear in the film could occur. In the worst case, this tear would go unnoticed and render the contents unusable.The object of the present invention was to provide a biaxially stretched polyester film with low puncture resistance for use as a cover film for a blister pack, which seals against commercially available blister moldings made of APET or PVC and can be processed on existing systems for pharmaceutical (medical) blisters and which allows the packaged contents (in particular tablets / capsules) to be pressed out and avoids the disadvantages described above, as well as the provision of the blisters produced therefrom.

[0010] The object is achieved by a multi-layer, co-extruded polyester film comprising a cover layer (A) and a base layer (B), wherein

[0011] (I) the cover layer (A) consists of at least 70% by weight of a polymer component which consists of at least 70% by weight of a copolyester which consists of 50 mol% of a dicarboxylic acid component and 50 mol% of a diol component, wherein the copolyester is derived from pure polyethylene terephthalate which consists of 50 mol% of ethylene glycol as the diol component and 50 mol% of terephthalic acid as the dicarboxylic acid component, in which a total of 15 to 50 mol% of the ethylene glycol and / or terephthalic acid are replaced by dicarboxylic acid components and / or diol components which are different from ethylene glycol and / or terephthalic acid;

[0012] (II) the base layer (B)

[0013] (a) consists of at least 78% by weight of a polymer component which

[0014] (i) consists of at least 70% by weight of a copolyester consisting of 50 mol% of a dicarboxylic acid component and 50 mol% of a diol component, wherein the copolyester is derived from pure polyethylene terephthalate, which consists of 50 mol% of ethylene glycol as the diol component and 50 mol% of terephthalic acid as the dicarboxylic acid component, in which a total of 2 to 35 mol% of the ethylene glycol and / or terephthalic acid are replaced by dicarboxylic acid components and / or diol components which are different from ethylene glycol and / or terephthalic acid,

[0015] (ii) consists of 0 to 30 wt.% of a polymer incompatible with polyethylene terephthalate (b) the base layer (B) contains 0 to 7 wt.% of a particle having an average particle diameter of d50 ≥ 1 μm, based on the total weight of the base layer (B), wherein the base layer (B) contains the incompatible polymer according to (ii) and / or the particles according to (b).

[0016] Terms and definitions

[0017] The terms blister cover film, blister film, and cover film are used synonymously below. A cover film is used to close a molded part, which is usually done by sealing.

[0018] The molded part of a blister pack serves to hold the contents of the blister pack. The molded part is formed using a suitable thermoforming process so that the contents can be accommodated by the cavities.

[0019] The terms "sealable," "sealed seam strength," "heat sealing," and "sealing" refer to the sealing process for closing the molded part with the blister cover film. This typically involves a heat-sealing process using pressure and heat. However, alternative methods, such as ultrasound, are also possible. For the purposes of the invention, the exact process is irrelevant. The suitability of the cover film for sealing a molded part can only be specified qualitatively due to the specific design of the corresponding blister filling machine.

[0020] The term "film stability" refers purely to the processability of a film during its manufacture or processing on a blister filling machine. Fast processing speeds require a certain degree of "stability" from films, essentially to withstand high tensile stress. Biaxially oriented films generally meet these requirements well.

[0021] For the purposes of this invention, however, film stability should not be confused with the property that it tears easily when the blister is opened, even under minimal mechanical stress. The term puncture resistance is used to consider tearing when the blister is opened, which also represents a separate measurement.

[0022] When manually opening the blister to remove the contents, pressure is usually applied with the thumb to one of the cavities of the molded part, causing the contents to pierce the blister cover film. Colloquially, the contents are "pushed through" the blister film. This expression will also be used below.

[0023] Certain types of polyester are used to produce polyester film, including copolyesters. The polyester structure is described in terms of repeating units. Accordingly, a polyester is generally composed of repeating units resulting from the esterification of diols with dicarboxylic acids. The repeating units are linked to one another in a linear fashion in the molecule, and thus belong to the group of thermoplastics. A repeating unit resulting from the esterification of a diol with a dicarboxylic acid accordingly contains a diol component derived from the diol used, and a dicarboxylic acid component derived from the dicarboxylic acid used. The term comonomer encompasses both the diol components and the dicarboxylic acid components. Therefore, the terms comonomer and diol or dicarboxylic acid component are used synonymously below.This means that the comonomers mentioned in the context (both diols and dicarboxylic acids) are present in polymerized form in the polyester / copolyester. In this context, the molar fractions of comonomers (comonomer proportions) are given in mol% relative to the total molar fraction of the diol components and dicarboxylic acid components in the polyester / copolyester in question. Thus, the sum of all diol and dicarboxylic acid components present in the polyester / copolyester is 100 mol%, while the sum of all diol components and dicarboxylic acid components present in the polyester / copolyester is 50 mol% each.

[0024] Furthermore, unless stated otherwise, a copolyester is based on a basic structure of ethylene and terephthalate units, i.e. polyethylene terephthalate (PET). This is referred to as pure polyethylene terephthalate because it consists of 50 mol% terephthalic acid as the dicarboxylic acid component and 50 mol% ethylene glycol as the diol component. This formulation is to be understood in such a way that terephthalic acid is used to produce the polymer and the polymerized form of terephthalic acid is present as the dicarboxylic acid component in the copolymer. The copolyesters according to the invention are based on pure polyethylene terephthalate, with a certain amount of the ethylene glycol as the diol component and / or the terephthalic acid as the dicarboxylic acid component being replaced by comonomers which are different from ethylene glycol and / or terephthalic acid. In the event that a diol orSince the dicarboxylic acid component can be derived from different monomers, it doesn't matter which specific monomer is used in polyester production. For example, the use of terephthalic acid (TPA) or dimethyl terephthalate (DMT) results in the same terephthalate unit in the polyester.

[0025] A copolyester within the meaning of the invention can be a copolyester, a mixture of two or more copolyesters, or a mixture of one or more homopolymers and one or more copolymers. The only restriction in this regard is that the copolyester / copolyester mixtures contained in the individual layers, as a whole, meet the requirements according to claim 1 with regard to the composition of the dicarboxylic acids and diols. For example, a mixture of the following copolyesters represents a copolyester according to the invention, as long as the resulting mixture, as a whole, meets the requirements according to claim 1 with regard to the composition of the dicarboxylic acids and diols:

[0026] 1. Polyethylene terephthalate raw material made from ethylene glycol and terephthalic acid with an SV value of 800 and 2 wt.% Irganox 1010 (BASF). The DEG content is 1.1 mol%, the IPA content is < 0.07 mol%;

[0027] 2. Polyethylene terephthalate raw material made from ethylene glycol and terephthalic acid with an SV value of 800 and 1.5 wt.% SiO2 particles with a d50 of 2.9 μm. The DEG content is 1.1 mol%, the IPA content is < 0.07 mol%.

[0028] 3. Polyethylene terephthalate raw material made from ethylene glycol, terephthalic acid and isophthalic acid with an SV value of 800. The DEG content is 1 mol%, the IPA content is 22 mol%.

[0029] With a puncture resistance of < 4 N (see measurement methods), an adult can open the blister by pushing through the contents. However, the puncture resistance is preferably < 3.5 N, particularly < 3 N, and ideally less than 2.7 N, as this achieves the puncture resistance of the commonly used 25 μm aluminum-based lidding foils.

[0030] The films used are at least two-layered, having a cover layer A that is sealable to the selected blister material, and a base layer B. The films according to the invention are monoaxially or biaxially oriented films, preferably biaxially oriented films. The sealable cover layer A (sealing layer) is at least 1 μm thick, preferably at least 1.5 μm, very particularly preferably at least 2 μm thick. The thicker the cover layer A, the more firmly it seals to the blister. Since the cover layer A contributes little to the stability of the film, a thicker cover layer A with a constant overall film thickness is also advantageous for achieving the low puncture resistance according to the invention. Above 8 μm, however, no further improvement in adhesive strength occurs.However, since the cover layer A also contributes little to the stability of the film during the film manufacturing process, thicknesses of the cover layer A above 3 μm and especially above 5 μm have proven less advantageous, as they provide no advantage in sealing the blisters but impair manufacturability (increased film tears). The cover layer A thus has a thickness of 1 μm to 8 μm, preferably 1.5 μm to 5 μm, particularly preferably 2 μm to 3 μm.

[0031] The polyester film according to the invention can have a three-layer structure. In this case, the polyester film comprises, in addition to the cover layer A and the base layer B, an additional cover layer C. The base layer B comprises a first and a second surface. The cover layer A is applied to one surface of the base layer B, and the cover layer C is applied to the other surface of the base layer B, facing away from the cover layer A. The base layer B is arranged between the cover layers A and C, thus creating a film structure ABC.

[0032] The top layer C is not sealable, consists predominantly (preferably at least 80 wt.%, particularly preferably at least 90 wt.% and ideally at least 99 wt.%) of a polyester which preferably consists of at least 92 mol% polyethylene terephthalate or, less preferably, polyethylene naphthalate (more expensive and more difficult to produce) and preferably has the lowest possible comonomer proportions of < 8 mol.%, particularly preferably < 2.5 mol.% and ideally < 1.8 mol.%. Thus, the top layer C is also based on pure polyethylene terephthalate (50 mol% ethylene glycol as the diol component and 50 mol% terephthalic acid as the dicarboxylic acid component) or pure polyethylene naphthalate (50 mol% ethylene glycol as the diol component and 50 mol% naphthalic acid as the dicarboxylic acid component), with less than 8 mol% of the ethylene glycol and / or the terephthalic acid orthe ethylene glycol and / or naphthalic acid are replaced by comonomers (diol and / or carboxylic acid components) that are different from ethylene glycol and / or terephthalic acid or ethylene glycol and / or naphthalic acid. The comonomer content thus refers to the sum of the diol and / or dicarboxylic acid components that are different from ethylene glycol and / or terephthalic acid (if polyethylene terephthalate is used as the starting material), or the comonomer content refers to the sum of the diol and / or dicarboxylic acid components that are different from ethylene glycol and / or naphthalic acid (if polyethylene naphthalate is used as the starting material). A low comonomer content leads to a low tendency to stick to the sealing tools of the blister filling system and thus to fewer deposits on them, thus allowing longer, trouble-free operation of the blister filling system.The top layer C can additionally contain inorganic or organic pigments (particles such as SiO2, CaCO3, BaSO4, PMMA = cross-linked polymethyl methacrylate particles, etc.) with an average particle size (d50) of more than 1 μm, of less than 1 wt.%, preferably of < 0.8 wt.% and particularly preferably of < 0.5 wt.%. If the top layer C has the aforementioned low comonomer contents and the low proportion of the aforementioned particles, it contributes particularly significantly to the stability of the film and thus facilitates its production, i.e. there are significantly fewer tears during the manufacturing process. This is particularly effective if this top layer C is at least 0.4 μm, preferably at least 0.6 μm and ideally at least 0.7 μm thick. If the top layer C has a low particle content and low comonomer content, then it significantly increases the impact resistance from a thickness of 1.5 μm.The cover layer C therefore preferably has a thickness of less than 3 μm, particularly preferably less than 2.0 μm and ideally less than 1.7 μm.

[0033] In principle, structures with more than three layers are also possible. However, this does not provide any additional advantages in the resulting blister and merely increases the complexity of manufacturing, making it less preferred.

[0034] Top layer A contains a polymer component (a mixture of one or more polymers) as well as other non-polymer additives. The polymer component of top layer A constitutes at least 70 wt.%, preferably at least 98 wt.%, particularly preferably 99.5 wt.%, and ideally 99.7 wt.% of the total weight of top layer A.

[0035] The polymer portion of cover layer A consists of at least 70 wt.%, preferably at least 85 wt.%, and particularly preferably at least 90 wt.% of a thermoplastic copolyester. Most preferably, the polymer portion of cover layer A consists of 100 wt.% of a copolyester. The copolyester consists of 50 mol% of a dicarboxylic acid component and 50 mol% of a diol component, with the copolyester being derived from pure polyethylene terephthalate, which consists of 50 mol% of ethylene glycol as the diol component and 50 mol% of terephthalic acid as the dicarboxylic acid component. The copolyester is based on repeating units derived from ethylene glycol and terephthalic acid (= polyethylene terephthalate, PET).In the copolyester of outer layer A, compared to pure PET, a total of 15 to 50 mol% of the ethylene glycol and / or terephthalic acid is replaced by dicarboxylic acid components and / or diol components that are different from ethylene glycol and / or terephthalic acid. Preferably, in the copolyester of outer layer A, a total of 18 to 40 mol%, preferably 20 to 36 mol%, particularly preferably 22 to 34 mol% of the ethylene glycol and / or terephthalic acid is replaced by dicarboxylic acid components and / or diol components that are different from ethylene glycol and / or terephthalic acid.The dicarboxylic acid components and / or diol components which are different from ethylene glycol and / or terephthalic acid are preferably selected from the group consisting of succinic acid, glutaric acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, isophthalic acid, naphthalenedicarboxylic acid, adipic acid, furandicarboxylic acid, 1,4-cyclohexanedimethanol, diethylene glycol, neopentyl glycol, propanediol and butanediol, particularly preferably from the group consisting of isophthalic acid, naphthalenedicarboxylic acid, adipic acid, furandicarboxylic acid, 1,4-cyclohexanedimethanol, diethylene glycol, neopentyl glycol.

[0036] The composition of the copolyester in the outer layer A depends on the blister molding to which the polyester film according to the invention is to be sealed. For the sealing of polyester-based blister moldings (e.g. kpNext™ R1 from Klöckner Pentaplast), it is preferred that the copolyester of the outer layer A contains 15 to 50 mol%, preferably 18 to 32 mol%, particularly preferably 20 to 29 mol% and ideally 22 to 28 mol% of polyethylene isophthalate. In addition to isophthalic acid (IPA), this polyester contains only 0 to 5 mol%, preferably 0.1 to 4 mol%, particularly preferably 0.1 to 3.5 mol% and very particularly preferably 0.1 to 3 mol% of diethylene glycol (DEG) as a further comonomer and 0 to 5 mol%, preferably 0 to 4 mol%, particularly preferably 0 to 3.5 mol% and very particularly preferably 0 to 3 mol% of further comonomers.This means that 15 to 50 mol%, preferably 18 to 32 mol%, particularly preferably 20 to 29 mol% and ideally 22 to 28 mol% of the terephthalic acid in pure polyethylene terephthalate is replaced by isophthalic acid as the dicarboxylic acid component, 0 to 5 mol%, preferably 0.1 to 4 mol%, particularly preferably 0.1 to 3.5 mol% and very particularly preferably 0.1 to 3 mol% of the ethylene glycol is replaced by diethylene glycol as the diol component and a further 0 to 5 mol%, preferably 0 to 4 mol%, particularly preferably 0 to 3.5 mol% and very particularly preferably 0 to 3 mol% of the ethylene glycol and / or terephthalic acid is replaced by dicarboxylic acid components and / or diol components which are different from ethylene glycol and / or terephthalic acid and are not isophthalic acid and diethylene glycol This is preferred because such blisters with a polyester-based molded part and polyester-based cover film are particularly easy to recycle.Since IPA and DEG are already present as comonomers in most polyester recycling streams (e.g., in polyester bottle recyclate), these monomers do not interfere with recycling. Other monomers such as naphthalenedicarboxylic acid (NDC) or cyclohexanedimethanol, on the other hand, are rather undesirable, as they are difficult or impossible to remove during recycling and can lead to undesirable effects in the recyclate (NDC, for example, leads to visible autofluorescence, and cyclohexanedimethanol to undesirable turbidity).

[0037] For sealing blister moldings based on polyvinyl chloride (PVC) or PVC copolymers (e.g., Blis | Form from Liveo Research), it is preferred that the copolyester contains 15 to 50 mol%, preferably 18 to 32 mol%, particularly preferably 20 to 29 mol%, and ideally 22 to 28 mol% of 1,4-cyclohexanedimethanol (CHDM) or, less preferably, neopentyl glycol (NPG), or, likewise less preferably, a combination of CHDM and NPG (in total to the ranges specified above). In addition, 0 to 10 mol%, preferably 0 to 8 mol%, particularly preferably 0 to 7 mol%, and most preferably 0 to 6 mol% of further comonomers such as IPA or DEG and further comonomers as defined in this application may be present in the copolyester. This means that starting from pure polyethylene terephthalate, the specified mol% of ethylene glycol and / or terephthalic acid are replaced by the respective comonomers.

[0038] The comonomer content in the polyester portion of outer layer A does not exceed 50 mol%, preferably ≤ 40 mol%, and particularly preferably ≤ 36 mol%. As the comonomer content increases, the risk increases that the wound film will seal at the back during storage and transport after production and then become unwindable. Furthermore, high PET content is generally desirable for recycling during the production of polyester film (edge ​​trimmings and pre-runs, as well as sorted rolls, are recycled directly during film production and fed back into the process) and for recycling the blisters used by the end customer.

[0039] The remaining 100 wt.% polymer content in outer layer A, a maximum of 30 wt.% based on the polymer content in outer layer A, consists of other polymers. These are preferably "incompatible" with the polyester, i.e., immiscible polymers, such as polyolefins or polymers and / or copolymers based on ethylene (e.g., LLDPE, HDPE, and copolymers), propylene (PP), copolymers containing the repeating unit -[CH2-CHCH3]-, cycloolefins (CO), amides (PA), or styrene (PS), preferably based on propylene (PP) and cycloolefins (CO). A copolymer is preferably used as the incompatible polymer. Examples include C2 / C3, C2 / C4, C3 / C4, C2 / C3 / C4 copolymers, or copolymers based on cycloolefins, such as norbornene / ethylene and tetracyclododecene / ethylene copolymers.The incompatible polymer is particularly preferably a copolymer based on cycloolefins (cycloolefin copolymer (COC)), such as norbornene / ethylene and tetracyclododecene / ethylene copolymers. Such cycloolefin copolymers are described, for example, in EP-A 1 068 949 or in JP 05-009319, which are incorporated herein by reference.

[0040] Among the cycloolefin copolymers, those containing polymerized units of polycyclic olefins with a norbornene core structure, particularly preferably norbornene or tetracyclododecene, are particularly preferred. Cycloolefin copolymers (COCs) containing polymerized units of acyclic olefins, particularly ethylene, are particularly preferred. Norbornene / ethylene and tetracyclododecene / ethylene copolymers containing 5 to 80 wt.% ethylene units, preferably 10 to 60 wt.% ethylene units (based on the mass of the copolymer), are very particularly preferred.

[0041] The COCs generally have glass transition temperatures between -20 and 400 °C. For the top layer A, COCs are preferred that have a glass transition temperature of less than 240 °C, preferably less than 190 °C, and particularly preferably less than 180 °C. The glass transition temperature should preferably be above 50 °C, preferably above 55 °C, in particular above 60 °C. Films containing a COC with a glass transition temperature of less than 80 °C are distinguished from those containing a COC with a glass transition temperature greater than 80 °C by a smaller reduction in puncture resistance based on the COC content in the layer (undesirable). EP-A-0 283 164, EP-A-0 407 870, EP-A-0 485 893 and EP-A-0 503 422 describe the production of

[0042] Cycloolefin copolymers (COCs) with catalysts based on soluble metallocene complexes are particularly preferred. Such COCs are commercially available; e.g., Topas® (Ticona, Frankfurt). The addition of such incompatible polymers reduces the seal strength (undesirable) but also reduces the puncture resistance (desirable).

[0043] In addition to the polymer content, the top layer A can consist of a maximum of 30 wt.%, preferably a maximum of 2 wt.%, particularly preferably a maximum of 0.5 wt.%, and ideally a maximum of 0.3 wt.% of other additives, such as inorganic particles. These can be white-coloring particles such as titanium dioxide and barium sulfate, or particles consisting of, for example, calcium carbonate, silicon dioxide, or aluminum trioxide. All of these additives reduce the seal seam strength (undesirable), but particles with an average particle size (d50) of more than 1 μm also reduce the puncture resistance (desirable).

[0044] Base layer B contains a polymer component and, optionally, other additives in particle form. Base layer B consists of at least 78% by weight of a polymer component comprising one or more thermoplastic polymers. The polymer component of base layer B contains at least 70% by weight, preferably at least 75% by weight, and particularly preferably at least 80% by weight, of a thermoplastic copolyester.

[0045] The copolyester of base layer B The copolyester consists of 50 mol% of a dicarboxylic acid component and 50 mol% of a diol component, whereby the copolyester is derived from pure polyethylene terephthalate, which consists of 50 mol% ethylene glycol as the diol component and 50 mol% terephthalic acid as the dicarboxylic acid component. The copolyester is based on repeating units derived from ethylene glycol and terephthalic acid (= polyethylene terephthalate, PET). In the copolyester of base layer B, compared to pure PET, a total of 2 to 35 mol%, preferably 3 to 18 mol%, particularly preferably 4 to 10 mol%, ideally 5 to 7 mol% of the ethylene glycol and / or terephthalic acid are replaced by dicarboxylic acid components and / or diol components that are different from ethylene glycol and / or terephthalic acid.The dicarboxylic acid components and / or diol components which are different from ethylene glycol and / or terephthalic acid are preferably selected from the group consisting of succinic acid, glutaric acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, isophthalic acid, naphthalenedicarboxylic acid, adipic acid, furandicarboxylic acid, 1,4-cyclohexanedimethanol, diethylene glycol, neopentyl glycol, propanediol and butanediol, particularly preferably from the group consisting of isophthalic acid, naphthalenedicarboxylic acid, adipic acid, furandicarboxylic acid, 1,4-cyclohexanedimethanol, diethylene glycol, neopentyl glycol.

[0046] The preferred comonomers are isophthalic acid and diethylene glycol as they do not interfere with the recycling of the finished blisters.

[0047] Surprisingly, it has been shown that a film with a base layer B containing a comonomer content as described above, in combination with the incompatible polymers and / or particles with d50 >: 1 μm described below, requires a lower puncture force than a film with a base layer B containing a lower content of such comonomers, although these comonomers should usually lead to better deformability of the film and thus to poorer puncture behavior.

[0048] However, if the comonomer content is too high, the film can be deformed too much, making it difficult to open the blister by pushing through it with the hand. In addition, the shrinkage of the film increases with increasing comonomer content, which can particularly disrupt the operation of the blister filling machine. Therefore, the comonomer content in base layer B is ≤ 35 mol%, preferably ≤ 25 mol%, particularly preferably ≤ 18 mol% and ideally ≤ 12 mol%. In a two-layer structure, the comonomer content is always ≤ 12 mol%, preferably ≤ 10 mol%, particularly preferably ≤ 8 mol% and ideally ≤ 7 mol%. In a two-layer structure, the risk of the non-sealable film surface sticking to the sealing tools of the blister filling machine and the tendency for deposits to form on these increases with increasing comonomer content.

[0049] In addition to the copolyester, base layer B contains either a polymer incompatible with the copolyester or 0.2 to 7 wt.% of a particle with a particle diameter of d50 > 1 μm or a combination of a polymer incompatible with the copolyester and a particle with a particle diameter of d50 > 1 μm. The incompatible polymer leads to a lower density of the film, which reduces the basis weight and thus the amount of film per blister. This leads to a better CO2 balance. The incompatible polymer also reduces the puncture force as the proportion increases. With increasing content, particularly above 25 wt.% and particularly above 30 wt.%, the manufacturability of the film (running safety) becomes significantly more difficult (tears in film production). The content of incompatible polymer is therefore ≤ 30 wt.%, preferably ≤ 25 wt.%. Below 2 wt.% and especially below 0.5 wt.-% the incompatible polymer hardly contributes to reducing the puncture resistance.

[0050] The incompatible polymer is "incompatible" with the polyester, i.e. not miscible. It is a polymer and / or copolymer based on ethylene (e.g. LLDPE, HDPE), propylene (PP), cycloolefins (CO), amides (PA) or styrene (PS) ), preferably based on propylene (PP) and cycloolefins (CO). A copolymer is preferably used as the incompatible polymer. Examples of these are C2 / C3, C2 / C4, C3 / C4, C2 / C3 / C4 copolymers, or copolymers based on cycloolefins, such as norbornene / ethylene and tetracyclododecene / ethylene copolymers. The incompatible polymer is particularly preferably a copolymer based on cycloolefins (cycloolefin copolymer (COC)), such as norbornene / ethylene and tetracyclododecene / ethylene copolymers. Such cycloolefin copolymers are described, for example, in EP-A 1 068 949 or in JP 05-009319, to which reference is made here.Compared to polyethylene-based polymers (ethylene-based polymers (LLDPE, HDPE), C2 / C4 copolymers, C2 / C3 / C4 copolymers), COCs have the advantage that they do not degrade as rapidly at the extrusion temperatures required for PET and are therefore less prone to gel formation. This advantage also exists (albeit to a lesser extent) over polypropylene-based (PP) polymers. PP and PP-based copolymers tend to exhibit a stronger yellowing in the film, which is undesirable, and to develop a stronger odor during film production, which is also undesirable.

[0051] Among the cycloolefin copolymers, those containing polymerized units of polycyclic olefins with a norbornene core structure, particularly preferably norbornene or tetracyclododecene, are particularly preferred. Cycloolefin copolymers (COCs) containing polymerized units of acyclic olefins, particularly ethylene, are particularly preferred. Norbornene / ethylene and tetracyclododecene / ethylene copolymers containing 5 to 80 wt.% ethylene units, preferably 10 to 60 wt.% ethylene units (based on the mass of the copolymer), are very particularly preferred.

[0052] The COCs generally have glass transition temperatures between -20 and 400 °C. For the invention, cycloolefin copolymers (COCs) are preferred which have a glass transition temperature of greater than 70 °C, particularly preferably greater than 90 °C and in particular greater than 130 °C. The lower the glass transition temperature from 130 °C downwards, the smaller the reduction in puncture resistance based on the amount of COC added. This means that more COC is required to achieve the low puncture resistances according to the invention. If the glass transition temperature is above 200 °C, the pressure in the extrusion during film production increases and leads to reduced service life of the melt filters used; therefore, COCs with a glass transition temperature greater than 200 °C are less preferred.

[0053] Instead of the incompatible polymer, base layer B can contain particles with a d50 ≥ 1 μm. The particles have a d50 ≥ 1 μm, preferably ≥ 1.5 μm and particularly preferably ≥ 2 μm. Smaller particles hardly reduce the puncture resistance, therefore only introduce undesirable material other than polyester and thus reduce regenerability. The particles have a d50 of ≤ 8 μm, preferably ≤ 6 μm and particularly preferably ≤ 5 μm. The larger the particles, the greater the reduction in impact resistance at the same concentration (desirable), but the worse the runnability and thus the producibility of the films (undesirable).

[0054] The particles used are preferably silicate-based particles (SiO2, aluminum silicates, etc.). Also suitable are aluminum oxides and particles made of cross-linked PMMA (less preferred because they are expensive and require higher dosage quantities). Particles based on barium sulfate, titanium dioxide, or calcium carbonate are less preferred, as they require more particles than the preferred silicate particles, which negatively impacts the running safety during film production. Concentrations below 0.3 wt.% and especially below 0.2 wt.% of the aforementioned particles contribute little to reducing puncture resistance.

[0055] In addition to the copolyester, base layer B can contain both a polymer incompatible with PET and particles with a d50 ≥ 1 μm (as defined above). This combination allows the low puncture force according to the invention to be achieved particularly effectively, while simultaneously optimizing the negative effect on runnability during film production due to the lower concentrations of the individual components.

[0056] If base layer B contains both a polymer incompatible with PET and particles with a d50≥1 μm, the proportion of incompatible polymer in the base layer is 4 to 17 wt.%, preferably 12 to 16 wt.% (based on the polymer content in base layer B). The proportion of particles with a d50 > 1 μm in this case is 1.0 to 3.0 wt.% and preferably 1.7 to 2.2 wt.% (based on the total weight of base layer B).

[0057] According to the invention, the polymer portion of the base layer B consists of 0.5 to 30 wt.%, preferably 2 to 25 wt.%, of a polymer incompatible with polyethylene terephthalate and the base layer B contains 0 wt.% of a particle with an average particle diameter of d50 ≥ 1 μm, or the polymer portion of the base layer B consists of 0 wt.% of a polymer incompatible with polyethylene terephthalate and the base layer B contains 0.2 to 7 wt.%, preferably 1.0 to 3.0 wt.% of a particle with an average particle diameter of d50 > 1 μm, or the polymer portion of the base layer B consists of 4 to 17 wt.%, preferably 12 to 16 wt.% of a polymer incompatible with polyethylene terephthalate and the base layer B contains 1.0 to 3.0 wt.%, preferably 1.7 to 2.2 wt.% of a particle with an average particle diameter of d50 ≥ 1 μm.

[0058] In addition to the ingredients mentioned, base layer B can consist of a maximum of 15 wt.%, preferably a maximum of 2 wt.%, particularly preferably a maximum of 0.5 wt.%, and ideally a maximum of 0.3 wt.% of other additives, such as inorganic particles or other polymers. These can be whitening particles such as titanium dioxide (in a special embodiment, higher whiteness than light and LJV protection may be desired) and barium sulfate, or smaller particles (d50 < 1 μm) consisting, for example, of calcium carbonate, silicon dioxide, or aluminum trioxide. All of these additives reduce runnability during film production and interfere with recycling, and are therefore less desirable.

[0059] In layers with a comonomer content of at least 2 mol%, it has proven advantageous to include 100 to 5000 ppm of an antioxidant (radical scavenger) as an additional additive in this layer. The antioxidant prevents excessive degradation of the polymers during extrusion and thus has a beneficial effect on running reliability. However, the antioxidant tends to increase the puncture force, which is undesirable. For this reason, the antioxidant content is preferably below 3000 ppm, particularly preferably below 2000 ppm, and ideally below 1500 ppm. If the comonomer content is below 2 mol%, the addition of antioxidants does not have any advantages for running reliability, but continues to have disadvantages due to an increased puncture force, and is therefore less preferred.

[0060] The total film thickness is at least 5 μm and a maximum of 50 μm. The thicker the film, the more difficult it becomes to achieve the maximum puncture resistance according to the invention with the films described below. Film thicknesses above 30 μm are therefore only useful if a puncture resistance in the upper range of the invention is intentionally sought. This is the case, for example, if the blister is to be more difficult for children to open. The low puncture resistance can be achieved particularly well with the film structures according to the invention at thicknesses below 25 μm, even better at below 20 μm and ideally at film thicknesses below 18 μm. This also reduces the basis weight (i.e. the amount of film per blister) and thus also the CO2 footprint.Particularly below 20 μm film thickness, at the usual processing speeds of the systems for filling and sealing blister packs and the usual sealing temperatures as well as short sealing times, the heat transfer through the film into the sealing layer is large enough to melt it and ensure a good seal.

[0061] Below 5 μm, the films according to the invention can no longer be produced economically, as they become so brittle under the production conditions that an intolerably high number of film tears occurs during the manufacturing process. The same applies to the subsequent cutting process to the film widths used on blister filling machines. Applying and sealing the films on these blister filling machines also becomes increasingly difficult with smaller thicknesses (creases and tears). Therefore, films with a total thickness of at least 8, particularly preferably at least 11 μm and ideally at least 13 μm are preferred. With higher film thicknesses, the sealing layer can also be produced economically with a greater thickness, since in conventional three-layer polyester film machines, the area output reaches an optimum when the outer layers each account for approximately 10% of the total thickness.According to the invention, the total film thickness of the polyester film is 8 μm to 25 μm, preferably 11 μm to 20 μm, particularly preferably 13 μm to 18 μm.

[0062] The film preferably has a density of ≤ 1.15 g / cm 3 , particularly preferably ≤ 1 .08 g / cm 3 and ideally ≤ 0.98 g / cm 3In addition to the already mentioned advantage of the lower basis weight, the cover film can then be detached from the blister during recycling in a heated alkaline water bath and then floats on top (if the bath is set to a suitable density), while both A-PET and PVC-based blisters sink. Thus, the two fractions can be separated and recycled separately, with the cover film ideally being recycled via chemical recycling. The A-PET blister can then be recycled both chemically and mechanically. These low densities are achieved by adding incompatible polymer to the base layer B, by adhering to the maximum thicknesses for layers A and, if applicable, C, and by the biaxial stretching used in the film manufacturing process.

[0063] The film preferably has an E-modulus in both film directions (TD and MD) of ≥ 2200 N / mm 2 and particularly preferably ≥ 2500 N / mm2 in the longitudinal and transverse directions. The elongation at break (DIN EN ISO 527-1 and -3) in both film directions is preferably ≥ 30%, particularly preferably ≥ 50%, and ideally ≥ 60%. The higher the elongation at break, the lower the tendency to tear during production or processing (e.g., narrow cutting). If the elastic moduli are above the specified limits, the film can be processed particularly well on blister filling machines, as it does not stretch excessively under tension and remains easy to guide. In addition, the film does not stretch too much upon puncture, thus facilitating manual pushing through. If the elastic moduli in both film directions (TD and MD) are above 3800 or even above 4000 N / mm 2 , the film stretches less during manual piercing and the required penetration force increases. Therefore, the elastic moduli in both film directions are preferably above 2200 and below 4000 N / mm 2and particularly preferably between 2500 and 3800 N / mm 2These mechanical properties can be adjusted and maintained by the formulations according to the invention and by varying the parameters of the biaxial stretching of the film within the framework of the process conditions specified below. The film preferably has a shrinkage in the longitudinal direction at 150 °C of ≤ 3%, particularly preferably ≤ 2.5% and ideally ≤ 1.8%. At 180 °C the film preferably has a shrinkage in the longitudinal direction of 4%, particularly preferably ≤ 3.7% and ideally ≤ 3.5%. In the transverse direction the film preferably has a shrinkage at 150 °C of ≤ 1.8%, particularly preferably ≤ 1.5% and ideally ≤ 1.2%. At 180 °C, the film preferably has a transverse shrinkage of ≤ 3.3%, particularly preferably ≤ 2.8%, and ideally ≤ 2.5%. Low shrinkage is preferred because the film is sealed to the blister at temperatures above 120 °C and frequently above 150 °C.If the shrinkage is too high, the resulting blisters will no longer be flat at higher sealing temperatures, but will be bent, making them more difficult to package. This is especially true if the shrinkage in the transverse direction is too high, as the film will still be stretched lengthwise by the heat.

[0064] The preferred shrinkage values ​​are determined by the setting temperatures and the convergence in the

[0065] Film manufacturing process, as well as by adhering to the maximum comonomer contents.

[0066] The film can be coated using conventional methods both during the manufacturing process (see below) and afterward (referred to as an offline process). A print pretreatment is applied, particularly to the non-sealable side. Suitable print pretreatments include acrylate-based coatings as described in EP 1916096, or preferably water-soluble copolyester-based coatings, as described, for example, in US2021331455 (primarily for water-based printing inks). This print pretreatment facilitates printing, for example, with product information.

[0067] Process for producing the cover film

[0068] The polyester polymers of the individual layers are produced by polycondensation using known processes.

[0069] The particles can be added during polyester production. For this purpose, the particles are dispersed in the diol, optionally ground, decanted, and / or filtered, and added to the reactor either during the (trans)esterification or polycondensation step. However, this method is associated with significantly higher production costs for the masterbatch compared to the following method. Preferably, a concentrated particle-containing polyester masterbatch can be produced using a gentle twin-screw extruder and diluted with particle-free polyester during film extrusion. This is the preferred method because it is more cost-effective.

[0070] The present invention comprises a process for producing a polyester film according to the invention, characterized in that the polymers for the individual layers of the film are melted in several extruders, the resulting melts are formed into flat melt films in a multi-layer die, pressed through a slot die, drawn off on a cooling roll and one or more take-off rolls, wherein the polyester film cools and solidifies, then is biaxially stretched, subsequently heat-set and then wound up, characterized in that

[0071] (I) the cover layer (A) consists of at least 70% by weight of a polymer component which consists of at least 70% by weight of a copolyester which consists of 50 mol% of a dicarboxylic acid component and 50 mol% of a diol component, wherein the copolyester is derived from pure polyethylene terephthalate which consists of 50 mol% of ethylene glycol as the diol component and 50 mol% of terephthalic acid as the dicarboxylic acid component, in which a total of 15 to 50 mol% of the ethylene glycol and / or terephthalic acid are replaced by dicarboxylic acid components and / or diol components which are different from ethylene glycol and / or terephthalic acid;

[0072] (II) the base layer (B)

[0073] (a) consists of at least 78% by weight of a polymer component which

[0074] (i) consists of at least 70% by weight of a copolyester consisting of 50 mol% of a dicarboxylic acid component and 50 mol% of a diol component, wherein the copolyester is derived from pure polyethylene terephthalate, which consists of 50 mol% of ethylene glycol as the diol component and 50 mol% of terephthalic acid as the dicarboxylic acid component, in which a total of 2 to 35 mol% of the ethylene glycol and / or terephthalic acid are replaced by dicarboxylic acid components and / or diol components which are different from ethylene glycol and / or terephthalic acid,

[0075] (ii) consists of 0 to 30 wt.% of a polymer incompatible with polyethylene terephthalate

[0076] (b) the base layer (B) contains 0 to 7 wt.% of a particle having an average particle diameter of d50 ≥ 1 μm, based on the total weight of the base layer (B), wherein the base layer (B) contains the incompatible polymer according to (ii) and / or the particles according to (b).

[0077] If the base layer B contains particles with an average particle diameter of d50 ≥ 1 μm, it is preferred that, before melting the polymers in the extruders, a particle-containing polymer is produced which contains the particles with an average particle diameter of d50 ≥ 1 μm of the base layer B and is mixed with particle-free polyester of the base layer B during melting in the extruder.

[0078] The incompatible polymer, if present, is preferably added directly to the extruder during film production. Addition via a masterbatch of the incompatible polymer in a polyester is less preferred, as this results in smaller domains of the incompatible polymer in the film, resulting in a higher puncture force than with direct addition, which is undesirable.

[0079] First, the polymer mixtures, along with other additives from the individual layers, are compressed and liquefied in extruders. In a preferred embodiment, the melting temperatures (temperature measured in the melt at the extruder outlet) are between 290°C and 300°C. At temperatures above 300°C, the yellowness index increases; at temperatures below 290°C, the risk of unmelted polymer components increases, which can lead to undesirable surface elevations in the resulting film. This temperature is adjusted via the throughput-to-revolutions ratio of the extruder or via the temperature of the extruder heater. These ratios and temperatures must be adjusted by a specialist depending on the type of extruder used.The melts are then formed into flat melt films in a multi-layer die, pressed through a slot die and drawn off onto a chill roll and one or more take-off rolls, where they cool and solidify. The film according to the invention is biaxially oriented, i.e. biaxially stretched. The biaxial stretching of the film is most frequently carried out sequentially. In this case, it is preferably stretched first in the longitudinal direction (i.e. in the machine direction, = MD direction) and then in the transverse direction (i.e. perpendicular to the machine direction, = TD direction). Stretching in the longitudinal direction can be carried out using two rolls running at different speeds depending on the desired stretch ratio. A suitable clip frame is generally used for transverse stretching. The longitudinal stretch ratio is in the range from 2.5:1 to 6:1, preferably from 2.8:1 to 4.5:1.A stretch ratio above 4.5:1 leads to significantly reduced manufacturability (tears). The transverse stretch ratio is generally in the range from 2.5:1 to 5.0:1, preferably from 3.2:1 to 4.0:1. By selecting suitable stretch parameters, the person skilled in the art can adjust the mechanical properties of the film, such as Young's modulus and extensibility. In a preferred embodiment, the stretch ratio here is above 2:1 in both film directions, more preferably above 2.5:1 and ideally above 3:1. The higher the areal stretch ratio (stretch ratio lengthwise to transverse), the lower the resulting puncture force and, when using incompatible polymer, the lower the resulting density.In a preferred embodiment, the stretch ratios do not exceed 5.5:1 in any film direction, more preferably 5:1 in any film direction, and ideally 4.7:1 in any film direction, since higher stretch ratios, while further reducing the puncture force, unnecessarily complicate the manufacturability of the film due to numerous tears during production. The areal stretch ratio (lengthwise to transverse stretch ratio) is therefore preferably at least 10:1, particularly preferably at least 10.5:1, ideally at least 10.8:1, preferably <21:1, particularly preferably <18:1, and ideally <15:1.

[0080] The temperature at which stretching is carried out can vary within a relatively wide range and depends on the desired properties of the film. In general, stretching is carried out in the longitudinal direction in a temperature range of 80 °C to 130 °C (heating temperatures 80 °C to 130 °C) and in the transverse direction in a temperature range of 90 °C (start of stretching) to 140 °C (end of stretching). To achieve the desired film properties, it has proven advantageous if the stretching temperature (in MD and TD) is below 125 °C and preferably below 118 °C. Before transverse stretching, one or both surfaces of the film can be coated in-line using methods known per se. In a preferred embodiment, the film is uncoated on the sealable side (top layer A).

[0081] During the subsequent heat-setting, the film is held under tension at a temperature of 150°C to 250°C for a period of approximately 0.1 s to 10 s. To achieve the desired shrinkage values, setting temperatures of at least 215°C are preferred, particularly preferably at least 220°C and ideally at least 225°C. At the end of the setting, the film is relaxed at temperatures of 200 to 130°C (ideally at temperatures of 190 to 150°C) by setting a convergence (reduction in frame width) of preferably at least 2%, particularly preferably at least 3% and ideally at least 3.5%. This further reduces the shrinkage values. The film is then wound up in the usual way.

[0082] The reclaimed material generated during film production can be added to all layers. However, the reclaimed material is preferably added only to the base layer.

[0083] The proportion of the base layer to the total film thickness is therefore preferably at least 50%, particularly preferably at least 65%, and most preferably at least 75%. This facilitates the economical recycling of the resulting reclaim.

[0084] Production of the blisters according to the invention

[0085] Furthermore, the present invention encompasses the use of the polyester film according to the invention as a cover film for a blister pack.

[0086] The blisters are sealed on commercially available blister filling systems such as the BEC 200 or BEC 300 from Uhlmann Pac-Systeme GmbH & Co. KG (Uhlmannstraße 14 - 18, 88471 Laupheim, Germany). The blister film is generally formed into the molded part in the same system that fills and seals the blisters. Alternatively, pre-formed blisters can also be fed. The cover film is fed to the previously formed blister film (including the material to be packaged in the cavities, such as tablets (solid product)) and sealed to the blister film by plate sealing or, preferably, by roller sealing at temperatures of 120 - 240 °C. The present invention also encompasses a blister pack consisting of a pre-formed film for receiving solid products and a cover film consisting of the polyester film according to the invention.

[0087] Application

[0088] The items enclosed in the blisters sealed with the inventive films (e.g., tablets or coated tablets) can be removed by pushing through them with the hand. The resulting blisters are therefore well suited for medical / pharmaceutical packaging applications, but are also suitable for other materials, such as chewing gum, batteries, etc.

[0089] Analytics

[0090] The following measurements were used to characterize the raw materials and the films:

[0091] Measurement of the mean particle diameter d 50

[0092] A Malvern Master Sizer 2000 is used to determine the particle diameter.

[0093] The samples are placed in a cuvette containing isopropanol, which is then placed in the measuring device. The dispersion is analyzed using a laser, and the particle size distribution is determined from the signal by comparing it with a calibration curve.

[0094] SEM or TEM measurements of the film produced using these particles show an average particle diameter that is 15–25% lower than the original particles. The particle diameter of the particles in the film can therefore be calculated from the particle diameters of the particles used to produce the film.

[0095] Mechanical properties

[0096] The mechanical properties were determined by tensile testing based on DIN EN ISO 527-1 and -3 (test specimen type 2) on 100 mm x 15 mm film strips.

[0097] Puncture resistance: The force required for puncture and the elongation upon puncture are determined using the puncture resistance test according to DIN EN 14477:2004. For this purpose, sample strips approximately 30 cm long and 2.5 cm wide are cut. In deviation from the standard, five individual measurements are taken on these strips, with the distance between the measuring points being at least 1.5 cm. The test speed is 100 mm / min. The samples are pierced from the sealed side.

[0098] Assessment of running safety

[0099] The film is produced on a line for the production of biaxially oriented polyester films with a final film width of at least 1 m. Each setting is produced for 12 hours, with a final film speed of at least 50 m / min. The number of breaks is counted (breaks due to external events such as power outages not directly related to film production are deducted).

[0100] A running safety of < 2 breaks is considered very good (++), 2 - 3 is considered good (+), 4 - 5 is considered sufficient (0), and > 5 is considered bad (-).

[0101] Examples

[0102] Film production

[0103] The polymer blends are melted at 292 °C and electrostatically applied through a slot die onto a chill roll heated to 50 °C. They are then stretched longitudinally and then transversely under the following conditions:

[0104] The following raw materials are used in the examples:

[0105] PET1 = Polyethylene terephthalate raw material made from ethylene glycol and terephthalic acid with an SV value of 820. The DEG content is 1 mol%, the IPA content is < 0.05 mol%

[0106] PET2 = Polyethylene terephthalate raw material made from ethylene glycol, terephthalic acid and isophthalic acid with an SV value of 800.

[0107] The DEG content is 1 mol%, the IPA content is 11 mol%

[0108] PET3 = Polyethylene terephthalate raw material made from ethylene glycol, terephthalic acid, and isophthalic acid with an SV value of 450 and 15 wt.% SiO2 with a d50 of 3.5 μm. The silicon dioxide particles were incorporated into the polymer in a twin-screw extruder.

[0109] The DEG content is 1.2 mol%, the IPA content is 11 mol%

[0110] PET4 = Polyethylene terephthalate raw material made from ethylene glycol and terephthalic acid with a SV value of 800 and 2 wt.% Irganox 1010 (BASF). The Irganox was incorporated into the polymer in a twin-screw extruder. The DEG content is 1.1 mol%, and the IPA content is < 0.07 mol%.

[0111] PET5 = Polyethylene terephthalate raw material made from ethylene glycol and terephthalic acid with an SV value of 800 and 1.5 wt.% SiO2 particles with a d50 of 2.9 μm. The silicon dioxide particles were added during polycondensation.

[0112] The DEG content is 1.1 mol%, the IPA content is < 0.07 mol%

[0113] PET6 = Polyethylene terephthalate raw material made from ethylene glycol and terephthalic acid with an SV value of 800 and 1.9 wt.% SiO2 particles with a d50 of 0.4 μm. The silicon dioxide particles were added during polycondensation.

[0114] The DEG content is 1.1 mol%, the IPA content is < 0.07 mol%

[0115] PET7 = Polyethylene terephthalate raw material made from ethylene glycol, terephthalic acid and isophthalic acid with an SV value of 800.

[0116] The DEG content is 1 mol%, the IPA content is 22 mol%

[0117] PET8 = Polyethylene terephthalate raw material made from ethylene glycol, terephthalic acid and 1,4-cyclohexanedimethanol (CHDM) with an SV value of 790.

[0118] The DEG content is 0.5 mol%, the CHDM content is 33 mol%

[0119] Incompatible polymer 1

[0120] COC Topas 6015 (manufacturer Topas Advanced Polymers GmbH Germany), glass transition temperature = 158 °C

[0121] Incompatible Polymer 2

[0122] COC 9903D-10 (manufacturer Topas Advanced Polymers GmbH Germany),

[0123] Glass transition temperature = 33 °C Recipes Properties according to the invention

[0124] Legend to table Properties according to the invention

[0125] Sealability classification:

[0126] • s1: Good against A-PET, sufficient against PVC

[0127] • s2: Sufficient against A-PET, good against PVC

[0128] Classification of manufacturability of blisters:

[0129] • q1: Producible, but due to folds individual sorting

[0130] • q2 Manufacturable

[0131] • q3 Machine had to be slowed down because more time was needed for sealing

Claims

Patent claims 1. Multilayer, co-extruded polyester film comprising a cover layer (A) and a base layer (B), wherein (I) the cover layer (A) consists of at least 70% by weight of a polymer component which consists of at least 70% by weight of a copolyester which consists of 50 mol% of a dicarboxylic acid component and 50 mol% of a diol component, wherein the copolyester is derived from pure polyethylene terephthalate which consists of 50 mol% of ethylene glycol as the diol component and 50 mol% of terephthalic acid as the dicarboxylic acid component, in which a total of 15 to 50 mol% of the ethylene glycol and / or terephthalic acid are replaced by dicarboxylic acid components and / or diol components which are different from ethylene glycol and / or terephthalic acid; (II) the base layer (B) (a) consists of at least 78% by weight of a polymer component which (i) consists of at least 70% by weight of a copolyester consisting of 50 mol% of a dicarboxylic acid component and 50 mol% of a diol component, wherein the copolyester is derived from pure polyethylene terephthalate, which consists of 50 mol% of ethylene glycol as the diol component and 50 mol% of terephthalic acid as the dicarboxylic acid component, in which a total of 2 to 35 mol% of the ethylene glycol and / or terephthalic acid are replaced by dicarboxylic acid components and / or diol components which are different from ethylene glycol and / or terephthalic acid, (ii) consists of 0 to 30 wt.% of a polymer incompatible with polyethylene terephthalate (b) the base layer (B) contains 0 to 7 wt.% of a particle having an average particle diameter of d50 ≥ 1 μm, based on the total weight of the base layer (B), wherein the base layer (B) contains the incompatible polymer according to (ii) and / or the particles according to (b).

2. Polyester film according to claim 1, characterized in that the polymer content of the cover layer A consists of at least 85 wt.%, preferably at least 90 wt.%, particularly preferably 100 wt.% of the copolyester.

3. Polyester film according to claim 1 or 2, characterized in that in the copolyester of the cover layer (A) a total of 18 to 40 mol%, preferably 20 to 36 mol%, particularly preferably 22 to 34 mol% of the ethylene glycol and / or terephthalic acid are replaced by dicarboxylic acid components and / or diol components which are selected from the group consisting of succinic acid, glutaric acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, isophthalic acid, naphthalenedicarboxylic acid, adipic acid, furandicarboxylic acid, 1,4-cyclohexanedimethanol, diethylene glycol, neopentyl glycol, propanediol and butanediol.

4. Polyester film according to one or more of claims 1 to 3, characterized in that in the copolyester of the base layer (B) a total of 2 to 35 mol%, preferably 3 to 18 mol%, particularly preferably 4 to 10 mol%, ideally 5 to 7 mol% of the ethylene glycol and / or terephthalic acid are replaced by dicarboxylic acid components and / or diol components which are selected from the group consisting of succinic acid, glutaric acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, isophthalic acid, naphthalenedicarboxylic acid, adipic acid, furandicarboxylic acid, 1,4-cyclohexanedimethanol, diethylene glycol, neopentyl glycol, propanediol and butanediol.

5. Polyester film according to one or more of claims 1 to 4, characterized in that the polymer content of the base layer B consists of 0.5 to 30 wt.%, preferably 2 to 25 wt.%, of a polymer incompatible with polyethylene terephthalate and the base layer B contains 0 wt.% of a particle with an average particle diameter of d50 > 1 μm; or the polymer portion of the base layer B consists of 0 wt.% of a polymer incompatible with polyethylene terephthalate and the base layer B contains 0.2 to 7 wt.%, preferably 1.0 to 3.0 wt.% of a particle having an average particle diameter of d50 > 1 μm; or the polymer portion of the base layer B consists of 4 to 17 wt.%, preferably 12 to 16 wt.% of a polymer incompatible with polyethylene terephthalate and the base layer B contains 1.0 to 3.0 wt.%, preferably 1.7 to 2.2 wt.% of a particle having an average particle diameter of d50 > 1 μm.

6. Polyester film according to one or more of claims 1 to 5, characterized in that the incompatible polymer is a polymer and / or copolymer based on ethylene, propylene, cycloolefins, amides or styrene polymer, preferably a C2 / C3, C2 / C4, C3 / C4, C2 / C3 / C4 copolymer, or copolymer based on cycloolefins, particularly preferably a norbornene / ethylene and / or tetracyclododecene / ethylene copolymer.

7. Polyester film according to one or more of claims 1 to 6, characterized in that the particles in the base layer B have an average particle diameter d50 of ≥ 1.5 μm, preferably of ≥ 2 μm and of ≤ 8 μm, preferably of ≤ 6 μm, particularly preferably of ≤ 5 μm.

8. Polyester film according to one or more of claims 1 to 7, characterized in that the particles in the base layer B are selected from the group consisting of silicon dioxide, aluminum silicates, aluminum oxide, crosslinked PMMA, barium sulfate, titanium oxide and calcium carbonate, and combinations thereof.

9. Polyester film according to one or more of claims 1 to 8, characterized in that the polyester film comprises a cover layer C, the base layer B being arranged between the cover layers A and C.

10. Polyester film according to one or more of claims 1 to 9, characterized in that the total film thickness is 8 μm to 25 μm, preferably 11 μm to 20 μm, particularly preferably 13 μm to 18 μm.

11. A process for producing a polyester film according to one or more of claims 1 to 10, characterized in that the polymers for the individual layers of the film are melted in several extruders, the resulting melts are formed into flat melt films in a multi-layer die, pressed through a slot die, drawn off on a cooling roll and one or more take-off rolls, the polyester film cooling and solidifying, then biaxially stretched, subsequently heat-set and then wound up, characterized in that (I) the cover layer (A) consists of at least 70% by weight of a polymer component which consists of at least 70% by weight of a copolyester which consists of 50 mol% of a dicarboxylic acid component and 50 mol% of a diol component, wherein the copolyester is derived from pure polyethylene terephthalate which consists of 50 mol% of ethylene glycol as the diol component and 50 mol% of terephthalic acid as the dicarboxylic acid component, in which a total of 15 to 50 mol% of the ethylene glycol and / or terephthalic acid are replaced by dicarboxylic acid components and / or diol components which are different from ethylene glycol and / or terephthalic acid; (II) the base layer (B) (a) consists of at least 78% by weight of a polymer component which (i) consists of at least 70% by weight of a copolyester consisting of 50 mol% of a dicarboxylic acid component and 50 mol% of a diol component, wherein the copolyester is derived from pure polyethylene terephthalate, which consists of 50 mol% of ethylene glycol as the diol component and 50 mol% of terephthalic acid as the dicarboxylic acid component, in which a total of 2 to 35 mol% of the ethylene glycol and / or terephthalic acid are replaced by dicarboxylic acid components and / or diol components which are different from ethylene glycol and / or terephthalic acid, (ii) consists of 0 to 30 wt.% of a polymer incompatible with polyethylene terephthalate (b) the base layer (B) contains 0 to 7 wt.% of a particle having an average particle diameter of d50 ≥ 1 µm, based on the total weight of the base layer (B), wherein the base layer (B) contains the incompatible polymer according to (ii) and / or the particles according to (b).

12. The method according to claim 11, wherein, before melting the polymers in the extruders, a particle-containing polymer is produced which contains the particles with an average particle diameter of d50 > 1 μm of the base layer B and is mixed with particle-free polyester of the base layer B during melting in the extruder.

13. The method according to claim 11 or 12, characterized in that the incompatible polymer of the base layer B is added to the extruder for melting.

14. Use of the polyester film according to one or more of claims 1 to 10 as a cover film for a blister pack.

15. Blister pack consisting of a preformed film for receiving solid products and a cover film according to one of claims 1 to 10. * * * * *

Images