Printable plastics film for production of security documents

Abstract

The invention relates to a security document S having a first outer side AS1 and a second outer side AS2 opposite the first outer side AS1 comprising at least: A5. a first polymer film A1, A6. optionally a second polymer film A2, A7. optionally at least one further polymer film A3, A8. a printing layer A4, 10, wherein at least the first polymer film A1 comprises a thermoplastic polyurethane TPU having a hardness in a range from 80 Shore A to 95 Shore D, preferably from 85 Shore A to 90 Shore D, particularly preferably from 90 Shore A to 85 Shore D, very particularly preferably from 95 Shore A to 80 Shore D, in an amount in a range from 50% to 100% by weight based on the total weight of the first polymer film A1 and forms at least the outer side AS1 of the security document S and wherein the printing layer A4 covers the surface of the security document S in a range from 1% to 100% based on the total surface area of the surface AS1, and to a process for producing such a security document S and to the use thereof and to the use of a TPU having a Shore hardness in a range from 80 Shore A to 95 Shore D for producing a polymer film A1 which is printable with dyes of the class of offset printing inks, flexographic printing inks, screen printing inks, digital printing inks with a resolution of 20 µm to 500 µm.

Description

[0001] Printable plastic film for the production of security documents

[0002] The invention relates to a security document S with at least one polymer film A1 and optionally A2, as well as optionally further polymer films A3, a print layer A4, wherein at least the first polymer film A1 contains a thermoplastic polyurethane TPU with a hardness in a range from 80 Shore A to 95 Shore D in an amount in a range from 50 to 100 wt.% and forms at least one of the outer sides AS1 or AS2 of the security document S, and wherein the print layer A4 covers the surface of the security document S in a range from 1 to 100%, preferably from 10 to 90%, based on the total surface of the surface AS1.

[0003] Printing substrates for valuable documents such as banknotes are subject to constant development in order to meet the ever-growing demands for durability, efficiency, counterfeit protection, and sustainability. To increase the lifespan of banknotes and security documents such as passports, security documents, especially banknotes, made of paper are increasingly being replaced with banknotes made of polymer films. Banknotes based on plastic films contribute to the sustainability of the means of payment because the lifespan of banknotes or other security documents can be increased by two to three times and the reusability of the material is increased. This significantly reduces the energy, materials, and natural resources required for the production of banknotes and other security documents.In addition, the longer lifespan of banknotes and other security documents can result in significant cost savings. For example, in Australia, banknotes using a polymer film as the printing substrate were introduced in 1988.

[0004] For the production of bank accounts made of polymer films, films based on polyolefins are almost exclusively used today. These films are biaxially stretched after extrusion (BOPP), as described in US5879028 A. Due to the process, these films can only be produced as transparent films. The films are then coated to obtain a white, opaque color and to improve the printability of the film. In a few exceptions, composites of film with paper or other materials, e.g., cotton fibers, are used for the production of banknotes, as described in WO006066431 A1. The outer paper layers form an alternative to the white coating of BOPP films.

[0005] A disadvantage of BOPP films is the fact that BOPP is a polymer that is used in countless everyday products such as packaging films, transparent films, sealing films, etc. in similar quality, making it easily available to potential counterfeiters for imitations. The fact that the substrate used is a stretched film proves to be particularly disadvantageous when the substrate is exposed to elevated temperatures, such as those that occur in everyday use, but also during printing on the film. Biaxially stretched polypropylene exhibits very significant shrinkage at higher temperatures. For example, a polymer banknote made of biaxially stretched polypropylene and exposed to a temperature above approximately 100°C was found to shrink in length and width by up to 20% of its original length and width.Furthermore, these polymer banknotes shrink to varying degrees in length and width, which leads to distortion of the banknote and thus, typically, the printed image. A further disadvantage of the polymer banknotes known to date, particularly those based on biaxially oriented polyolefins, is that the shrinkage described above is irreversible. It is entirely possible that such a polymer banknote will shrink irreversibly when exposed to a hot stovetop, under a halogen lamp, or during printing processes that generate or use heat.

[0006] Complex and cost-intensive manufacturing processes are necessary, especially to achieve the desired opacity of the film and the necessary surface energy to enable the absorption of printing inks. In addition, the tear resistance of BOPP films in particular is low. Even the slightest tear in the banknote leads to immediate failure of the banknote.

[0007] Both polyolefin-based films and composite films exhibit the disadvantages listed above and therefore there is a need to minimize or even eliminate these disadvantages.

[0008] One object of the invention was to further develop a generic method and a generic security document, for example in the form of a polymer printing substrate such as a banknote or a passport, in such a way that the disadvantages of the prior art are at least partially eliminated, in particular to increase the forgery security of the security document, in particular by means of a stable and high-resolution printing layer.

[0009] Furthermore, it was an object of the invention to provide a security document which meets the currently prevailing requirements for longevity, efficiency, in particular resource efficiency, forgery security and / or sustainability, in particular, if possible, none of these requirements is met with lower quality than can be derived from the current state of the art.

[0010] Furthermore, it was an object of the invention to provide a security document which has sufficient surface energy, if possible without further pretreatment, to enable the absorption of printing inks.

[0011] A further object of the invention was to provide an optimized, particularly more cost-effective method for a printed security document with the aforementioned advantages. A first aspect of the invention is a security document S having a first outer side AS1 and a second outer side AS2 opposite the first outer side AS1, comprising at least:

[0012] A 1. a first polymer film A 1 ,

[0013] A2. optionally a second polymer film A2,

[0014] A3. optionally at least one additional polymer film A3,

[0015] A4. a print layer A4, wherein at least the first polymer film A1 comprises a thermoplastic polyurethane TPU having a hardness in a range from 80 Shore A to 95 Shore D, preferably from 85 Shore A to 90 Shore D, particularly preferably from 90 Shore A to 85 Shore D, very particularly preferably from 95 Shore A to 80 Shore D, very particularly preferably from 60 Shore D to 90 Shore D, in an amount in a range from 50 to 100 wt.% and forms at least one of the outer sides AS1 or AS2 of the security document S, and wherein the print layer A4 covers the surface of the security document S in a range from 1 to 100%, preferably from 10 to 90%, based on the total surface area of ​​the surface AS1.

[0016] Preferably, the entire polymer film A1 has a hardness in a range from 80 Shore A to 95 Shore D, preferably from 90 Shore A to 90 Shore D, particularly preferably from 60 Shore D to 90 Shore D. Furthermore preferably, the entire security document S has a hardness in a range from 80 Shore A to 95 Shore D, preferably from 90 Shore A to 90 Shore D, particularly preferably from 60 Shore D to 90 Shore D.

[0017] The security document S can have any shape that a person skilled in the art would select for a security document S. Preferably, the security document S has a planar extension in the form of a square, a rectangle, a circle, an oval, or a polyhedron, particularly preferably in the form of a square or a rectangle.

[0018] The security document S preferably has a thickness in a range from 40 to 250 pm, more preferably in a range from 50 to 200 pm, particularly preferably in a range from 60 to 150 pm, most preferably in a range from 70 to 100 pm.

[0019] The aspect ratio between the thickness of the security document S and its area is preferably in a range from 1:100000 to 1:1000, more preferably in a range from 1:50000 to 1:500, particularly preferably in a range from 1:10000 to 1:100.

[0020] The first polymer film A1 preferably has a thickness in a range from 10 to 100 pm, more preferably in a range from 12 to 90 pm, more preferably in a range from 15 to 50 pm, more preferably in a range from 20 to 40 pm. The optional second polymer film A2 preferably has a thickness in a range from 20 to 150 pm, more preferably in a range from 30 to 100 pm, more preferably in a range from 40 to 90 pm, more preferably in a range from 50 to 80 pm.

[0021] The optional at least one further polymer film A3 preferably has a thickness in a range from 10 to 100 pm, more preferably in a range from 12 to 90 pm, more preferably in a range from 15 to 50 pm, more preferably in a range from 20 to 40 pm.

[0022] At least one polymer film selected from the group consisting of the first polymer film A1, A2, and A3 preferably has a length in a range from 1 to 100 cm, more preferably in a range from 2 to 80 cm, particularly preferably in a range from 5 to 50 cm. Preferably, all polymer films selected from the group consisting of the first polymer film A1, A2, and optionally A3 have a length that deviates by no more than 10% from the longest polymer film. Particularly preferably, all polymer films A1, A2, and A3 have the same length.

[0023] At least one polymer film selected from the group consisting of the first polymer film A1, A2, and A3 preferably has a width in a range from 1 to 100 cm, more preferably in a range from 2 to 80 cm, particularly preferably in a range from 5 to 50 cm. Preferably, all polymer films selected from the group consisting of the first polymer film A1, A2, and optionally A3 have a length that deviates by no more than 10%, based on the longest polymer film. Particularly preferably, all polymer films A1, A2, and A3 have the same width.

[0024] Preferably, the polymer films A1 and A2 and preferably also A3 are congruent in their planar extension direction.

[0025] The security document S is preferably selected from the group consisting of a banknote, a birth certificate, a postage stamp, a tax stamp, a visa page of a passport, a hinge for the data page of a passport, a carrier layer of an electromagnetic shield in the passport or a combination of at least two thereof.

[0026] The outer side AS1 is formed by the polymer film A1. The outer side AS2 can be formed from different polymer films, selected from polymer film A1, polymer film A2, or polymer film A3, or a combination of at least two of them. If it is a monofilm, the first polymer film A1 forms both the outer sides AS1 and AS2.

[0027] The security document S preferably further comprises security features A5 selected from the group consisting of a hologram, a security thread, a fluorescent fiber, a dye, a security pigment, carbon black, metallic or non-metallic micro- or nanoparticles, magnetic particles, an embossing or a combination of at least two thereof. In a preferred embodiment, the security document S comprises the second polymer film A2. The second polymer film A2 is preferably in direct contact with the first polymer film A1. The first polymer film preferably comprises a thermoplastic polyurethane TPU with a hardness in a range from 80 Shore A to 95 Shore D, preferably from 85 Shore A to 90 Shore D, particularly preferably from 90 Shore A to 85 Shore D, very particularly preferably from 95 Shore A to 80 Shore D, most preferably from 60 Shore D to 80 Shore D to at least 50 wt.-%, and the second polymer film A2 comprises a thermoplastic polyurethane TPU having a hardness in a range from 60 Shore D to 95 Shore D, preferably from 65 Shore D to 90 Shore D, particularly preferably from 70 Shore D to 85 Shore D to at least 50 wt.%.

[0028] In a preferred embodiment of the security document S, the printing layer A4 consists of printing inks selected from the group consisting of offset printing inks, flexographic printing inks, screen printing inks, digital printing inks, inks for intaglio printing or a combination thereof. The printing inks are preferably UV-curing inks or oxidatively curing inks. The printing layer A4 is preferably applied to the first polymer film A1 by the printing process with a nominal line width in a range from 10 to 500 pm, from 20 pm to 400 pm, preferably from 50 to 350 pm, particularly preferably from 100 to 300 pm. The printed line width preferably deviates from the nominal line width by no more than 2 to 20 pm. The line width preferably has a width variance of 1 to 20 pm, preferably from 2 to 15 pm, particularly preferably from 3 to 10 pm.Even crossing lines have a common width variance of 2 to 30 pm, preferably 4 to 20 pm, particularly preferably 5 to 15 pm.

[0029] In a preferred embodiment of the security document S, the print layer A4 has at least one, preferably at least two, particularly preferably at least three of the following properties:

[0030] (Dl) that it consists of at least one line, wherein the at least one line has a shape selected from the group consisting of a circle, a polygon, an oval, a polygon or a combination of at least two thereof;

[0031] (D2) that it has a line width of 20 pm to 500 pm, preferably of 50 to 400 pm, particularly preferably of 100 to 300 pm;

[0032] (D3) that at least one line of the printing layer A4 is formed with a deviation from the nominal line width in a range of 2 to 20 pm, preferably 3 to 15 pm, particularly preferably 4 to 10 pm;

[0033] (D4) has a height in a range of 0.5 pm to 15 pm;

[0034] (D5) increased abrasion resistance;

[0035] (D6) that it is formed from a dye selected from the group consisting of a powder, a printing paste; (D7) that it is at least partly black;

[0036] (D8) that it is at least partly coloured.

[0037] In a preferred embodiment of the security document S, at least one of the polymer films A1, A2 or optionally A3, preferably the entire security document S, has at least one of the following properties: a. a tear resistance in a range from 50 N / mm to 400 N / mm, more preferably from 60 N / mm to 350 N / mm, particularly preferably from 70 N / mm to 300 N / mm, determined according to DIN 53363:2003-10; b. a tensile strength in a range from 20 MPa to 200 MPa, more preferably from 25 MPa to 170 MPa, particularly preferably from 30 MPa to 150 MPa, determined according to ISO 527-3:1995; c. a light transmission in a range from 0% to 85%, preferably from 1 to 50%, particularly preferably from 5 to 30%, determined according to ISO 13468-2:2019; d. a crease recovery angle in a range from 120 to 170°, more preferably from 130 to 160°, particularly preferably from 140 to 150° according to DIN 53 890 / 91; e.a Vicat softening temperature of 60°C to 105°C, particularly preferably 65°C to 85°C according to DIN EN ISO 306; f. a surface tension of 32 to 55 mN / m according to DIN ISO 8296:2003.

[0038] Preferably, the security document S shows the properties or property combinations selected from the group consisting of a., b., c., d., e., f, a. + b., a. + c., a + d., a. + e., a. + f., b. + c., b. + d., b. + e., b. + f., c. + d., c. + e., c. + f., d. + e., d. + f., a. + b. + c., a. + b. + d., a. + b. + e., a. + b. + f., a. + c. + d., a. + c. + e., a. + c. + f., a. + d. + e., a. + d. + f., a. + e. + f., b. + c. + d., b. + c. + e., b. + c. + f., b. + d. + e., b. + d. + f., b. + e. + f., c. + d. + e., c. + d. + f., c. + e. + f., d. + e. + f., a. + b. + c. + d., a. + b. + c. + e., a. + b. + c. + f., a. + b. + d. + e., a. + b. + d. + f., a. + b. + e. + f., a. + c. + d. + e., a. + c. + d. + f., a. + c. + e. + f., a. + d. + e. + f., b. + c. + d. + e., b. + c. + d. + f., b. + d. + e. + f., c. + d. + e. + f., a. + b. + c. + d. + e., a. + b. + c. + d. + f., a. + b. + c. + e. + f., a. + b. + d. + e. + f., a. + c. + d. + e. + f., b. + c. + d. + e. + f., a. + b. + c. + d. + e. + f. up.Particularly preferably, the security document S has the properties a. and f.

[0039] The polymer films A1, A2, and / or optionally A3 preferably further comprise a UV stabilizer as additives. The polymer films A1, A2, and / or A3 preferably comprise the UV stabilizer in an amount ranging from 0.1 to 15 wt. %, more preferably from 1 to 10 wt. %, particularly preferably from 2 to 7 wt. %, based on the total weight of the respective polymer film A1, A2, or A3. The UV stabilizers are preferably commercially available products such as Tinuvin®P from BASF AG (Germany).If it is a multilayer film, the outer side AS2, which is not formed by the polymer film A1 but by the polymer film A2 or optionally a polymer film A3, preferably contains a thermoplastic elastomer (TPE) selected from the group consisting of a copolyester elastomer (TPC), a thermoplastic polyamide elastomer (TPA), in particular a polyether block amide (PEBA), an olefin-based thermoplastic elastomer (TPO), in particular PP / EPDM, a thermoplastic polyurethane (TPU), a thermoplastic polycarbonate (PC), a polyethylene terephthalate (PET), in particular a polyethylene terephthalate glycol (PETG), a thermoplastic styrene block copolymer (TPS), in particular styrene-butadiene block copolymer (SBC), or a mixture of at least two thereof. TPEs are elastomers that behave like classic representatives of elastomers at room temperature, but become deformable when heated.These are usually copolymers consisting of a soft elastomer and a hard thermoplastic component.

[0040] Suitable copolyester elastomers TPC (segmented polyester elastomers), hereinafter also simply called copolyesters, are composed, for example, of a large number of recurring, short-chain ester units and long-chain ester units which are united by ester bonds, wherein the short-chain ester units make up about 15-80 wt.% of the copolyester and have the formula (I). in which

[0041] R represents a divalent radical of a dicarboxylic acid having a molecular weight of less than about 350 g / mol,

[0042] D represents a divalent radical of an organic diol having a molecular weight of less than about 250 g / mol; the long-chain ester units make up about 20 to 85 wt.%, preferably 30 to 70 wt.%, particularly preferably 35 to 60 wt.%, of the copolyester and preferably have the formula IE in which

[0043] R represents a divalent radical of a dicarboxylic acid having a molecular weight of less than about 350 g / mol,

[0044] G represents a divalent residue of a long-chain glycol having an average molecular weight of approximately 350 to 6000 g / mol. The copolyesters used can be prepared by polymerizing a) one or more dicarboxylic acids, b) one or more linear, long-chain glycols, and c) one or more low-molecular-weight diols.

[0045] The dicarboxylic acids used to produce the copolyester are aromatic acids with 8-16 C atoms, especially phenylenedicarboxylic acids such as phthalic, terephthalic and isophthalic acid.

[0046] The low-molecular-weight diols used in the reaction to form the short-chain ester units of the copolyesters belong to the classes of acyclic, alicyclic, and aromatic dihydroxy compounds. The preferred diols have 2-15 carbon atoms, such as ethylene, propylene, tetramethylene, isobutylene, pentamethylene, 2,2-dimethyltrimethylene, hexamethylene, and decamethylene glycols, dihydroxycyclohexane, cyclohexanedimethanol, resorcinol, hydroquinone, and the like. Bisphenols suitable for this purpose include bis(p-hydroxy)diphenyl, bis(p-hydroxyphenyl)methane, bis(p-hydroxyphenyl)ethane, and bis(p-hydroxyphenyl)propane.

[0047] The long-chain glycols used to produce the soft segments of the copolyesters preferably have molecular weights of approximately 600 to 3000 g / mol. These include poly(alkylene ether) glycols, in which the alkylene groups have 2-9 carbon atoms.

[0048] Glycol esters of poly(alkylene oxide) dicarboxylic acids or polyester glycols can also be used as long-chain glycols.

[0049] Long-chain glycols also include polyformals, which are obtained by reacting formaldehyde with glycols. Polythioether glycols are also suitable. Polybutadiene and polyisoprene glycols, copolymers thereof, and saturated hydrogenation products of these materials represent satisfactory long-chain polymeric glycols.

[0050] Processes for synthesizing such copolyesters are known from DE-OS 2 239 271, DE-OS 2 213 128, DEOS 2 449 343 and US-A 3 023 192. Examples of suitable TPCs are polyether elastomers Hytrel® from DuPont™ (Germany) and polyether elastomer Keyflex® from LG Chemicals (Europe), preferably those representatives thereof with a hardness in the range of 80 Shore A to 95 Shore D.

[0051] The thermoplastic polyamide elastomer (TPA) can be any TPA that a person skilled in the art would select for this purpose. The TPA is preferably a polyether blockamide (PEBA). Suitable PEBAs include, for example, those consisting of polymer chains composed of repeating units according to formula (III). in which A is the polyamide chain derived from a polyamide having 2 carboxyl end groups by loss of the latter and

[0052] B is the polyoxyalkylene glycol chain derived from a polyoxyalkylene glycol with terminal OH groups by loss of the latter, and n is the number of units forming the polymer chain. The terminal groups are preferably OH groups or residues of compounds that terminate the polymerization.

[0053] The dicarboxylic acid polyamides with terminal carboxyl groups are obtained in known ways, for example, by polycondensation of one or more lactams and / or one or more amino acids, or by polycondensation of a dicarboxylic acid with a diamine, in each case in the presence of an excess of an organic dicarboxylic acid, preferably with terminal carboxyl groups. These carboxylic acids become part of the polyamide chain during the polycondensation and, in particular, attach to its end, thereby obtaining a p-dicarboxylic acid polyamide. Furthermore, the dicarboxylic acid acts as a chain terminator, which is why it is also used in excess.

[0054] The polyamide can be obtained starting from lactams and / or amino acids with a hydrocarbon chain consisting of 4-14 C atoms, such as caprolactam, oenantholactam, dodecalactam, undecanolactam, decanolactam, 11-amino-undecano or 12-aminododecanoic acid.

[0055] Examples of polyamides produced by polycondensation of a dicarboxylic acid with a diamine include the condensation products of hexamethylenediamine with adipic, azelaic, sebacic, and 1,12-dodecanedioic acid, as well as the condensation products of nonamethylenediamine and adipic acid, preferably those representatives thereof with a hardness in the range of 80 Shore A to 95 Shore D.

[0056] The dicarboxylic acids used for the synthesis of polyamide, on the one hand for fixing a carboxyl group at each end of the polyamide chain and on the other hand as chain terminating agents, are those with 4-20 C atoms, in particular alkanedioic acids, such as succinic, adipic, suberic, azelaic, sebacic, undecanedioic or dodecanedioic acid, and also cycloaliphatic or aromatic dicarboxylic acid, such as terephthalic or isphthalic or cyclohexane-1,4-dicarboxylic acid.

[0057] The polyoxyalkylene glycols containing terminal OH groups are unbranched or branched and contain an alkylene radical with at least 2 carbon atoms. These are preferably polyoxyethylene, polyoxypropylene, and polyoxytetramethylene glycol, as well as copolymers thereof.

[0058] The average molecular weight of these OH-terminated polyoxyalkylene glycols can vary widely; it is advantageously between 100 and 6000 g / mol, particularly between 200 and 3000 g / mol. The weight fraction of the polyoxyalkylene glycol, based on the total weight of the polyoxyalkylene glycol and dicarboxylic acid polyamide used to produce the PEBA polymer, is 5-85 wt.%, preferably 10-50 wt.%.

[0059] Processes for the synthesis of such PEBA polymers are known from FR-PS 7 418 913, DE-OS 28 02 989, DEOS 28 37 687, DE-OS 25 23 991, EP-A 095 893, DE-OS 27 12 987 and DEOS 27 16 004.

[0060] PEBA polymers that are particularly suitable are those that, unlike those described above, have a random structure. These polymers are produced using a mixture of:

[0061] 1. one or more polyamide-forming compounds from the group of aminocarboxylic acids or lactams with at least 10 carbon atoms,

[0062] 2. an a,a>-dihydroxy-polyoxyalkylene glycol,

[0063] 3. at least one organic dicarboxylic acid in a weight ratio of 1:(2+3) between 30:70 and 98:2, where in (2+3) hydroxyl and carbonyl groups are present in equivalent amounts, in the presence of 2 to 30% by weight of water, based on the polyamide-forming compounds of group 1, heated under the resulting autogenous pressure to temperatures between 23°C and 30°C and then, after removal of the water, further treated under exclusion of oxygen at normal pressure or under reduced pressure at 250 to 280°C.

[0064] The TPO can be any TPO that a person skilled in the art would select for a security document S according to the invention. Examples of TPOs are thermoplastic olefins of the KEYFLEX® type from LG Chemicals (Europe), such as KEYFFLEX® TP-1045D. The TPO is preferably a PP / EPDM. Examples of these TPO types are Santoprene™ from Advanced Elastomer Systems Ltd., a subsidiary of ExxonMobile Chemical Europe (Belgium), Saxomer® TPE-0 from PCW GmbH (Germany), and Elastron TPO from Elastron (Turkey / Germany), preferably those with a hardness in the range of 80 Shore A to 95 Shore D.

[0065] The thermoplastic polyurethane (TPU) may be any TPU that a person skilled in the art would select for the security document S according to the invention.

[0066] A preferred process for the preparation of thermoplastically processable polyurethane polymers is one which is carried out by reacting the components

[0067] (A) one or more substantially linear polyols, wherein the total amount of component (A) has an average molecular weight in the range from 500 g / mol to 5000 g / mol,

[0068] (B) one or more organic polyisocyanates, preferably organic diisocyanates,

[0069] (C) one or more linear diols having a molecular weight of 62 g / mol to 500 g / mol, (D) optionally in the presence of one or more catalysts,

[0070] (E) optionally in the presence of one or more additives, auxiliaries and / or additives, and

[0071] (F) optionally in the presence of one or more monofunctional chain terminators, wherein the process preferably comprises or consists of the following steps:

[0072] 1) Providing and reacting a mixture of the total amount of component (A), a partial amount of component (B) and optionally a partial amount or the total amount of component (D), component (E) and / or component (F) to form an NCO-functional prepolymer, wherein in process step 1) a molar ratio of component (B) to component (A) is in the range from 1.1:1.0 to 5.0:1.0,

[0073] 2) reacting the NCO-functional prepolymer from process step 1) with the total amount of component (C) to obtain an OH-functional prepolymer, optionally in the presence of a further portion of component (D), component (E) and / or component (F),

[0074] 3) reacting the OH-functional prepolymer with the remaining amount of component (B) and optionally the remaining amount of component (D), component (E) and / or component (F) to obtain the thermoplastically processable polyurethane, wherein over all process steps a molar ratio of component (B) to the sum of component (A) and component (C) in the range from 0.9:1.0 to 1.2:1.0 is present.

[0075] The preferred process enables the production of thermoplastic polyurethanes with good processing properties and good mechanical properties over a hardness range of approximately 80 Shore A to approximately 95 Shore D, while achieving good coupling of the hard and soft phases of the TPU, which leads to an optimally high molecular weight and thus to very good mechanical properties of the manufactured workpieces.

[0076] Within the context of the present invention, the word "one" in connection with countable quantities is to be understood as a numeral only if this is explicitly stated (e.g., by the expression "exactly one"). For example, when "one polyol" is mentioned below, the word "one" is to be understood merely as an indefinite article and not as a numeral; thus, it also encompasses an embodiment containing a mixture of at least two polyols.

[0077] “Essentially” in this context means that at least 95 mol%, preferably at least 98 mol%, particularly preferably at least 99 mol% and even more preferably at least 99.5 mol%, even more preferably at least 99.8 mol% and most preferably 100 mol% of the total amount of the polyols of component A) consist of linear polyols.

[0078] The hardness of the thermoplastically processable polyurethanes can be adjusted by selecting the molar ratio of component (A) to component (C) from 80 Shore A to 95 Shore D. The amounts of the reaction components for the NCO-functional prepolymer formation in step 1) are selected such that the NCO / OH ratio of polyisocyanate to polyol in step 1) is 1.1:1 to 5.0:1.

[0079] The components are thoroughly mixed and the NCO prepolymer reaction in step 1) is preferably brought to complete conversion (based on the polyol component).

[0080] Subsequently, at least component (C) is mixed in as a chain extender (step 2) to form an essentially OH-functional prepolymer.

[0081] Then, in step 3), the remaining amount of component (B) is added, maintaining an NCO / OH ratio of 0.9:1 to 1.2:1. Preferably, the same component (B) is used in step 3) as in step 1).

[0082] In process step 2), the molar ratio of NCO-functional prepolymer to component (C) is preferably less than 1.0. Component (C) is thus present in molar excess.

[0083] Suitable as component (A) are all linear polyols known to the skilled person and having an average molecular weight of greater than 500 g / mol. The following linear polyols are particularly suitable as component (A): a) polyester polyols, b) polyether polyols, c) polyether esters, d) polycarbonate polyols, e) polyether carbonates, or mixtures of at least two of the polyols a) to e).

[0084] Suitable polyester diols a) can be prepared, for example, from dicarboxylic acids having 2 to 12 carbon atoms, preferably 2 to 6 carbon atoms, and polyhydric alcohols. Suitable dicarboxylic acids include, for example, aliphatic dicarboxylic acids, such as succinic acid, glutaric acid, adipic acid, suberic acid, azelaic acid, and sebacic acid, dodecanedioic acid, and aromatic dicarboxylic acids, such as phthalic acid, isophthalic acid, and terephthalic acid. The dicarboxylic acids can be used individually or as mixtures, e.g., in the form of a succinic, glutaric, and adipic acid mixture. For the preparation of the polyester polyols, it may be advantageous to use the corresponding dicarboxylic acid derivatives, such as carboxylic acid diesters having 1 to 4 carbon atoms in the alcohol radical, carboxylic acid hydrides, or carboxylic acid chlorides, instead of the dicarboxylic acids.Examples of polyhydric alcohols are glycols having 2 to 12, preferably 2 to 6, carbon atoms, such as ethylene glycol, diethylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,10-decanediol, 1,12-dodecanediol, 2,2-dimethyl-1,3-propanediol, 1,3-propanediol, 1,2-propanediol, and dipropylene glycol. Depending on the desired properties, the polyhydric alcohols can be used alone or, if appropriate, in admixture with one another. Condensation products of hydroxycarboxylic acids, for example, hydroxycaproic acid, and polymerization products of lactones, for example, optionally substituted caprolactones, are also suitable. Preferably used polyester polyols are ethanediol polyadipates, 1,4-butanediol polyadipates, 1,6-hexanediol polyadipates, ethanediol-1,4-butanediol polyadipates, 1,6-hexanediol neopentyl glycol polyadipates, 1,6-hexanediol-1,4-butanediol polyadipates and polycaprolactones.The polyester diols have molecular weights in the range of 500 to 5000 g / mol, preferably in the range of 600 to 3500 g / mol, and particularly preferably in the range of 800 to 3000 g / mol. They can be used individually or in the form of mixtures.

[0085] Suitable polyether diols b) can be prepared by reacting one or more alkylene oxides having 2 to 4 carbon atoms in the alkylene radical with a starter molecule containing two active hydrogen atoms. Examples of suitable alkylene oxides include: ethylene oxide, 1,2-propylene oxide, epichlorohydrin, 1,2-butylene oxide, and 2,3-butylene oxide. Ethylene oxide, propylene oxide, and mixtures of 1,2-propylene oxide and ethylene oxide are preferably used. The alkylene oxides can be used individually, alternately one after the other, or as mixtures. Examples of suitable starter molecules include: water, amino alcohols such as N-alkyldiethanolamines, for example N-methyldiethanolamine, and diols such as ethylene glycol, 1,3-propylene glycol, 1,4-butanediol, and 1,6-hexanediol. If necessary, mixtures of starter molecules can also be used. Suitable polyether diols also include the hydroxyl-containing polymerization products of tetrahydrofuran.Trifunctional polyethers can also be used in proportions of 0 to 30 wt. %, based on the bifunctional polyethers, but no more than in an amount sufficient to produce a thermoplastically processable product. Suitable polyether diols have a number-average molecular weight of M. n from 500 to 5000 g / mol, preferably 750 to 5000 g / mol, and most preferably 900 to 4200 g / mol. They can be used individually or in mixtures.

[0086] Suitable polyetheresters c) can be prepared, for example, by reacting short-chain polyetherdiols, such as polytetrahydrofurans with molecular weights of 250 to 1000 g / mol, with organic dicarboxylic acids, such as succinic acid or adipic acid. The polyetheresterdiols have molecular weights of 600 to 5000 g / mol, preferably 700 to 4000 g / mol, and particularly preferably 800 to 3000 g / mol. They can be used individually or in the form of mixtures.

[0087] Suitable polycarbonate diols d) can be prepared, for example, by reacting short-chain diols, such as 1,4-butanediol or 1,6-hexanediol, with diphenyl carbonate or dimethyl carbonate with the aid of catalysts and eliminating phenol or methanol. The polycarbonate diols have a number-average molecular weight of 500 to 5000 g / mol, preferably 750 to 5000 g / mol, and particularly preferably 1000 to 4500 g / mol.

[0088] Suitable polyethercarbonate diols e) can be prepared, for example, by reacting short-chain polyetherdiols, such as polytetrahydrofurans having molecular weights of 250 to 1000 g / mol, with diphenyl or dimethyl carbonate with the aid of catalysts and eliminating phenol or methanol. Furthermore, polyethercarbonate diols can be prepared by copolymerizing alkylene oxides, such as ethylene oxide or propylene oxide, or mixtures thereof, with carbon dioxide with the aid of suitable catalysts, such as double metal cyanide catalysts. The polyethercarbonate diols have a number-average molecular weight of 500 to 8000 g / mol, preferably 750 to 6000 g / mol, and particularly preferably 1000 to 4500 g / mol.

[0089] Preferred organic polyisocyanates of component (B) used in steps 1) and 3) are aliphatic, cycloaliphatic, araliphatic, heterocyclic and aromatic polyisocyanates as described in Justus Liebigs Annalen der Chemie, 562, pp. 75-136.

[0090] The following may be mentioned as examples: aliphatic diisocyanates such as 1,6-hexamethylene diisocyanate, cycloaliphatic diisocyanates such as isophorone diisocyanate, 1,4-cyclohexane diisocyanate, 1-methyl-2,4-cyclohexane diisocyanate and 1-methyl-2,6-cyclohexane diisocyanate and the corresponding isomer mixtures, 4,4'-dicyclohexylmethane diisocyanate, 2,4'-dicyclohexylmethane diisocyanate and 2,2'-dicyclohexylmethane diisocyanate and the corresponding isomer mixtures, aromatic diisocyanates such as 2,4-tolylene diisocyanate, mixtures of 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate and 2,2'-diphenylmethane diisocyanate, mixtures of 2,4'-Diphenylmethane diisocyanate and 4,4'-Diphenylmethane diisocyanate, urethane-modified liquid 4,4'-Diphenylmethane diisocyanates and 2,4'-Diphenylmethane diisocyanates, 4,4'-Diisocyanatodiphenylethane-(1,2) and 1,5-Naphthylene diisocyanate.Preferred diisocyanates are 1,6-hexamethylene diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, diphenylmethane diisocyanate isomer mixtures with a 4,4'-diphenylmethane diisocyanate content of >96 wt.%, and in particular 4,4'-diphenylmethane diisocyanate and 1,5-naphthylene diisocyanate. These diisocyanates can be used individually or in mixtures. They can also be used together with up to 15 wt.% (calculated based on the total amount of diisocyanate) of a polyisocyanate, for example triphenylmethane-4,4',4"-triisocyanate or polyphenyl polymethylene polyisocyanates.

[0091] Preferably, a diphenylmethane diisocyanate isomer mixture having a 4,4-diphenylmethane diisocyanate content of greater than 96 wt.% based on the total weight of component (B) is used as component (B); preferably, component (B) is 4,4-diphenylmethane diisocyanate.

[0092] 1,6-Hexamethylene diisocyanate is preferably used as component (B).

[0093] Suitable as component (C) (chain extender) are all linear diols known to the person skilled in the art with a molecular weight of 62 g / mol to 500 g / mol. The diols and / or their precursor compounds can be obtained from fossil or biological sources. Suitable diols are preferably aliphatic diols having 2 to 14 carbon atoms, such as ethanediol, 1,4-butanediol, 1,6-hexanediol, 1,8-octanediol, 1,10-decanediol, 1,12-dodecanediol, diethylene glycol, and dipropylene glycol. However, diesters of terephthalic acid with glycols containing 2 to 4 carbon atoms, such as terephthalic acid bis-ethylene glycol or terephthalic acid bis-1,4-butanediol, hydroxyalkylene ethers of hydroquinone, such as 1,4-di-(hydroxyethyl)-hydroquinone, and ethoxylated bisphenols, are also suitable. Particularly preferred short-chain diols are ethanediol, 1,4-butanediol, 1,6-hexanediol, and 1,4-di-(hydroxyethyl)-hydroquinone. Mixtures of the aforementioned chain extenders can also be used.Small amounts of diamines and / or triamines may also be added.

[0094] Preferably, one or more diols selected from the group consisting of 1,2-ethanediol, 1,4-butanediol, 1,6-hexanediol, 1,4-di-(beta-hydroxyethyl)hydroquinone or a mixture of at least two of these are used as component (C), preferably 1,2-ethanediol, 1,4-butanediol or mixtures thereof are used as component (C) and particularly preferably 1,2-ethanediol is used as component (C).

[0095] The catalysts (D) that can be used are the conventional catalysts known from polyurethane chemistry. Suitable catalysts are known and conventional tertiary amines, such as triethylamine, dimethylcyclohexylamine, N-methylmorpholine, N,N'-dimethylpiperazine, 2-(dimethylaminoethoxy)ethanol, diazabicyclo[2,2,2]octane, and the like, and in particular organic metal compounds such as titanic acid esters, iron compounds, bismuth compounds, tin compounds, e.g. tin diacetate, tin dioctoate, tin dilaurate, or the tin dialkyl salts of aliphatic carboxylic acids such as dibutyltin diacetate, dibutyltin dilaurate, or the like. Preferred catalysts are organic metal compounds, in particular titanic acid esters, iron or tin compounds. Dibutyltin dilaurate, tin dioctoate, and titanic acid esters are very particularly preferred.

[0096] Further details and preferred embodiments of the manufacturing process for suitable TPUs can be found in EP 3 838 961 A.

[0097] The TPE preferably comprises a thermoplastic polyurethane (TPU), preferably produced by the method described above, in a range of 10 to 100 wt.%, further preferably in a range of 20 to 95 wt.%, more preferably in a range of 30 to 90 wt.%, particularly preferably in a range of 40 to 85 wt.%, based on the total weight of the TPE.

[0098] The polymer film A2 preferably comprises a TPU with a hardness in a range from 40 to 95 Shore D, preferably in a range from 55 to 90 Shore D, most preferably from 60 to 85 Shore D. The polymer film A2 preferably comprises the TPU, preferably produced by the method described above, in a range from 10 to 100 wt.%, more preferably in a range from 20 to 95 wt.%, based on the total weight of the polymer film A2.

[0099] Examples of TPU types that are suitable for both polymer film A1 and polymer film A2 are: Estane® from Uubrizol, Elastollan® from BASF AG (Germany), Desmopan® from Covestro Deutschland AG (Germany), preferably those with a hardness of 80 Shore A to 95 Shore D.

[0100] The thermoplastic polycarbonate (PC) can be any elastomeric PC that a person skilled in the art would select for this purpose. The PC is preferably manufactured according to the polycarbonate described in WO 2018 / 11436 A1, in particular the polycarbonate blends as described on page 3, last paragraph, to page 16, third paragraph. The polyethylene terephthalate (PET) can be any PET that a person skilled in the art would use for the security document S according to the invention. The PET is preferably a polyethylene terephthalate glycol (PETG), for example, Eastar® from EASTMAN Chemical GmbH (Germany).

[0101] The thermoplastic styrene block copolymer (TPS) can be any styrene block copolymer that a person skilled in the art would use for the security document S according to the invention. Preferred TPSs are styrene-ethylene-butylene-styrene block copolymer (SEBS), styrene-ethylene / propylene-styrene block copolymer (SEPS), styrene-isoprene-styrene block copolymer (SIS), styrene-ethylene-ethylene-butadiene-styrene (SEEPS), and methyl methacrylate-butadiene-styrene (MBS). Examples of SBS types are Styroflex® from BASF AG (Germany) and Thermolast® from Kraiburg Holding (Germany). Examples of SBES types are Saxomer® TPE-S from PCW GmbH (Germany), preferably those with a hardness of 40 to 95 Shore D.

[0102] The TPE preferably contains additives commonly found in plastics. Common additives include lubricants such as fatty acid esters, their metal soaps, fatty acid amides, and silicone compounds; antiblocking agents; inhibitors; stabilizers against hydrolysis, light, heat, and discoloration; flame retardants; dyes, pigments; inorganic or organic fillers; and reinforcing agents. Further information on these auxiliaries and additives can be found in specialist literature, for example, J.H. Saunders, K.C. Frisch: "High Polymers," Volume XVI, Polyurethanes, Parts 1 and 2, Interscience Publishers 1962 and 1964, respectively; R. Gächter, H. Müller (Ed.): Taschenbuch der Kunststoff-Additive, 3rd Edition, Hanser Verlag, Munich 1989; or DE-A 29 01 774.

[0103] Preferably, both outer sides AS1 and AS2 of the security document S comprise a TPU. Preferably, both outer sides AS1 and AS2 consist of a TPU. Preferably, one outer side AS1 of the security document S is formed by the first polymer film AS1 and the other outer side AS2 by a further polymer film A3, wherein the two polymer films A1 and A3 preferably have the same composition. Furthermore, the polymer film A2 preferably forms the core of the security document S, in the form of a layer structure with at least three layers in which the outer sides AS1 and AS2 each consist of the same material. Furthermore, in the layer structure with at least three layers in which the polymer layer A2 forms the core layer, the polymer layer A2 comprises a harder TPU than the outer sides AS1 and AS2, which are formed from the polymer layers A1 and A3.

[0104] Alternatively, the security document S can have a layer structure of at least three layers, which has as core layer a softer TPU layer in the form of the polymer layer A2 than the polymer layers A1 and A3, which form the outer sides AS1 and AS2.

[0105] Preferably, at least one of the polymer films A1, A2 and optionally A3, in particular the first polymer film A1, comprises a material that is suitable for building up an adhesive strength to the respectively adjacent one, i.e. the second polymer film A2 or the further polymer film A3, that is greater than the elongation at break of at least one of the polymer films A1, A2 or A3. The adhesive strength is higher than the breaking stress of the respective polymer film if one of the polymer films A1, A2 or A3 cannot be separated from the respectively adjacent polymer film without leaving residue. This means that when the first polymer film A1 is separated from the second polymer film A2 or optionally the second polymer film A2 from the further polymer film A3, at least one of the polymer films A1, A2 or A3 suffers a cohesive failure and not an adhesive failure in which the adhesive strength would be lower than the breaking stress of the polymer films.In contrast to an adhesive failure, which would represent a separation of the security document S at the adhesive surface between the respective films and would enable a residue-free separation of the films from each other, the cohesive failure occurs inside the layer and leaves residues of the polymer material on the respective other film that is to be separated.

[0106] This sufficiently high adhesion force therefore contributes to the security against counterfeiting of the security document S.

[0107] The polymer films A1, A2, and optionally A3 preferably have an adhesive force to their respective adjacent polymer film of at least 2 N / cm, more preferably of at least 3 N / cm, particularly preferably of at least 5 N / cm. The polymer films A1, A2, and optionally A3 preferably have an adhesive force to their respective adjacent polymer film in a range from 2 to 20 N / cm, more preferably from at least 3 N / cm to 15 N / cm, particularly preferably from at least 5 N / cm to 10 N / cm, measured according to ASTM D903-1998 at a tensile angle of 180°.

[0108] In a preferred embodiment of the security document S, the outer sides AS1 and AS2 of the security document S consist of a polymer film A1, A2 or A3 which contains or consists of a TPU.

[0109] In a preferred embodiment of the security document S, all polymer films A1, A2, and optionally A3 consist exclusively of polymers. Preferably, all polymer films A1, A2, and optionally A3 consist of a TPE, with at least the polymer film A1 containing at least 50 wt.% TPU. Most preferably, all polymer films A1, A2, and optionally A3 consist of an independently selected TPU. Preferably, the entire security document S consists of polymers, with the exception of the print layer A4 and the optional security feature A5.

[0110] In a preferred embodiment of the security document S, at least one of the polymer films selected from the group consisting of the second polymer film A2, the further polymer film A3, or both, contains the TPE in an amount ranging from 50 to 100 wt.%, preferably from 60 to 90 wt.%, particularly preferably from 70 to 80 wt.%, based on the total weight of the respective polymer film A2 or A3. Particularly preferably, the polymer films A2 and A3 consist of a TPE. Particularly preferably, the polymer films A2 and A3 consist of a TPU. In a preferred embodiment of the security document S, the security document S has at least one second polymer film A2, wherein the at least one second polymer film A2 contains a thermoplastic elastomer TPE in an amount ranging from 50 to 100 wt.%, preferably from 60 to 90 wt.%, particularly preferably from 70 to 80 wt.%, based on the total weight of the respective polymer film A2.

[0111] Preferably, at least one of the polymer films selected from the group consisting of the second polymer film A2, the further polymer film A3 or both polymer films A2 and A3 contains a polymer selected from the group consisting of a thermoplastic polyurethane (TPU), a copolyester or a mixture of at least two thereof or mixtures of TPU and further TPEs in an amount in a range from 50 to 100 wt.%, preferably from 60 to 90 wt.%, particularly preferably from 70 to 80 wt.%, based on the total weight of the respective polymer film A2 or A3.

[0112] The security document S preferably comprises at least one further polymer film A3, wherein the at least one further polymer film A3 contains the TPE in an amount ranging from 50 to 100 wt.%, preferably from 60 to 90 wt.%, particularly preferably from 70 to 80 wt.%, based on the total weight of the respective polymer film A3. Particularly preferably, the at least one further polymer film A3 consists of a TPE. Most preferably, the at least one polymer film A3 consists of a TPU.

[0113] Preferably, the at least one further polymer film A3 has the same composition as the polymer film A1 or A2. Most preferably, all three polymer films A1, A2, and A3 comprise at least 50 wt.%, preferably at least 80 wt.%, and particularly preferably 100 wt.% of a TPE, wherein the TPE is preferably one of the aforementioned TPEs, particularly preferably at least one TPU. The further polymer film A3 particularly preferably has the same composition as the first polymer film A1.

[0114] In a preferred embodiment of the security document S, the thermoplastic elastomer TPE is selected from the group consisting of a thermoplastic polyamide elastomer, an olefin-based thermoplastic elastomer, preferably PP / EPDM, a thermoplastic styrene block copolymer SBS, SEBS, SEPS, SEEPS and MBS, a thermoplastic polyurethane TPU, a copolyester elastomer, a polyether block amide, a copolyester, a polycarbonate, a polyethylene terephthalate PET, a polyethylene terephthalate glycol PETG or a mixture of at least two thereof.

[0115] In a preferred embodiment of the security document S, all polymer films A1, A2 and optionally A3 contain a polymer in an amount in a range from 50 to 100 wt. %, preferably from 60 to 90 wt. %, particularly preferably from 70 to 80 wt. %, based on the total weight of the respective polymer film A1, A2 or A3. In a preferred embodiment of the security document S, one of the polymer films selected from the group consisting of the second polymer film A2 or the at least one further polymer film A3 contains a polymer selected from the group consisting of a thermoplastic polyurethane TPU, a copolyester or a mixture of at least two thereof or mixtures of TPU and at least one further TPE in an amount in a range from 50 to 100 wt. %, preferably from 60 to 90 wt. %, particularly preferably from 70 to 80 wt. %, based on the total weight of the respective polymer film A2 or A3.

[0116] In a preferred embodiment of the security document S, the security document S has at least one of the following properties: a. a tear resistance in a range from 50 N / mm to 400 N / mm determined according to DIN 53363:2003-10; b. a tensile strength in a range from 20 MPa to 200 MPa determined according to ISO 527-3:1995; c. a light transmission in a range from 0% to 85%, determined according to ISO 13468-2:2019; d. a security pigment content in a range from 0.1 to 10 wt.%, based on the total weight of the security document S; e. a crease recovery angle in a range from 120 to 170°, more preferably from 130 to 160°, particularly preferably from 140 to 150° according to DIN 53 890 / 91; f. a surface tension of 32 to 55 mN / m according to DIN ISO 8296:2003.

[0117] A further aspect of the invention relates to a method for producing a security document S with a first outer side AS1 and a second outer side AS2 opposite the first outer side AS1, comprising the steps i) providing a first polymer A1', wherein the first polymer A1' comprises at least one TPU with a hardness in a range from 80 Shore A to 95 Shore D, preferably from 60 Shore D to 90 Shore D in an amount of 50 to 100 wt.%, based on the total weight of the polymer A1; ii) optionally providing a second polymer A2'; iii) optionally providing a further polymer A3'; iv) melting the polymers from step i), optionally ii) and optionally iii);v) Either forming a first polymer film as an extrudate from the melt of the polymer AU from step iv), or combining the polymer melts from step iv) to form a first polymer film A1 from the first polymer AU, a second polymer film A2 from the second polymer A2' and optionally a further polymer film A3 from the further polymer A3' as a coextrudate, or forming a laminate from a separate polymer film A1, A2 and optionally A3, which were formed from the melts in step iv), to obtain a layer structure with a first outer side AS1 formed by the first polymer film A1 and a second outer side AS2, which is opposite the first outer side AS1;vi) Optionally, incorporating a security feature A5, selected from the group consisting of a hologram, a security thread, a fluorescent fiber, a dye, a pigment, carbon black, metallic or non-metallic micro- or nanoparticles, magnetic particles or a combination of at least two thereof in or onto one of the polymer films A1, A2 or A3; vii) Printing at least the outer side AS1 of the layer structure from step v), which is formed from the first polymer film A1, with an ink that is dissolved in organic solvents and is optionally cured by means of UV light to obtain the security document S; viii) Optionally, joining, preferably by ultrasonic welding, vibration welding or laser welding, a polymer layer A6 to one of the outer layers AS1 or AS2 over an area of ​​at least 1 mm; 2, wherein the second outer side AS2 is formed by one of the polymer films A2 or A3, each of which contains or consists of a TPE, preferably a TPU.

[0118] The provision of the first polymer A1' in step i), the second polymer A2' in step ii), and / or optionally the further polymer A3' in step iii) can be carried out in any way known to the person skilled in the art. Preferably, the provision in steps i), ii), and / or iii) is carried out by introducing granules of the respective polymer into an extruder or other device in which the polymer can subsequently be melted.

[0119] In step iv), the polymers from steps i), ii), and optionally iii) are melted, preferably by heating the extruder with the extruder screw running. In step v), the polymer melts from step iv) are combined. This preferably takes place using a suitable nozzle. Alternatively, the melts from step iv) can also be applied sequentially to a substrate.

[0120] The melts in step v) are preferably co-extruded via a die in the form of extruded melts or formed by casting as individual polymer films. The melts in step v) are preferably extruded.

[0121] If the melts are each formed separately to form the polymer films A1, A2 or A3, they are preferably joined together by lamination to form the security document S as a laminate. If the melts are extruded together in step v) using a nozzle, the security document S is produced as an extrusion film or co-extrusion film after the melts have cooled. The viscosity of the melts is preferably in a range suitable for polymer processing, in particular for flat film production, between 20 and 2000 Pa s, preferably in the range from 50 to 1000 Pa s, particularly preferably in the range from 75 to 500 Pa s. It is immaterial whether the polymer melt is a polymer with a defined melting point Tm or a defined melting range Tm ± ΔT or whether it is a polymer without a defined melting point.During extrusion, particularly at the point of exit from the nozzle, it is preferred that the polymer is heated above the melting point Tm or the glass transition point Tg to such an extent that the viscosity of the polymer is reduced to such an extent that processing into a polymer film is possible.

[0122] During the extrusion of the melts in step v), at least one further film is preferably introduced between the individual melts as security feature A5 in step vi). The at least one supplied film preferably has a thickness in a range from 5 to 35 μm, more preferably from 7 to 25 μm, particularly preferably from 10 to 20 μm. This at least one further film can be introduced over the entire width of the melts in step v) or only over a section of the melts. Preferably, the at least one further film has a width which corresponds to 30 to 100%, further preferably 40 to 90%, particularly preferably 50 to 80% of the width of the melt. The at least one further film preferably serves to introduce the security feature A5.

[0123] After the polymer melts of the polymers A1', A2' and optionally A3' have been extruded through the die to form a film, the extruded film is preferably fed onto two rollers. One or both rollers preferably have a ductile surface. This allows a more homogeneous pressure distribution across the entire width of the extrudate. This can be particularly advantageous if the thin film fed into the roller gap, which serves as security feature A5, has cutouts or printed symbols with an ink layer thickness of up to 20 pm, in which area the pressure across the rollers can vary due to the missing or excess material. Ductile rollers can compensate for this pressure difference, resulting in improved adhesion in these areas as well. Such rollers are, for example, PTFE-coated or PTFE-sheathed rubber rollers or silicone-coated rollers.

[0124] In step vi), a further security feature A5 in the form of an embossing P is preferably incorporated into the resulting security document S by embossing. The embossing is preferably carried out using a metal embossing die, for example in the form of a cylinder or a flat sheet. The embossing die is pressed onto one side of the multilayer film at a temperature in the range of 15°C to 80°C with a pressure of 40 N / cm 2 up to 800N / cm 2pressed on so that the embossing P can be seen and felt on the outside AS1 or AS2 of the security document S, in one of the polymer films A1 or A3. The introduction of embossed structures is already known from EP 2 599 637 A2. In contrast, here the embossing takes place in security documents S which no longer contain a layer of paper but only have films made of polymers. This increases the resolution of the embossing, but above all reduces the standard deviation of the embossing. Structures with a resolution of 40 to 500 pm, particularly preferably of 45 to 400 pm, very particularly preferably of 50 to 300 pm, most preferably of 55 to 200 pm can preferably be achieved.Preferably, a ratio of relief height of the embossing tool to engraving depth in a range of 50 to 90%, more preferably 55 to 85%, particularly preferably 60 to 80%, most preferably 65 to 75% is achieved, even with an engraving depth of < 100 pm or 50 to 100 pm.

[0125] As already mentioned above, any combination of A5 security features can be incorporated into the resulting security document S. Preferred examples include: mottled fibers, planchettes, metallic fibers, marking substances, IR or UV dyes, security pigments, fluorescent dyes, effect pigments, or security threads. These A5 security features are added to the polymer mixture in granular form in step i) or to the melt in step iv), or are sprinkled near the roll gap in step v) or blown onto the melt flag, or, in the case of the security thread or a security film, are guided into the roll gap. It is equally possible to provide an A5 security feature in the thin, supplied film.Thus, the security features already known from the field of paper banknotes can be used without further modification, as described in DE 6 98 33 653 T2, in particular in claim 1, or in CH 704 788 A1 on page 7. Examples of security features known from paper documents include: security thread, OVD, mottled fibers, security pigments, iridescent color applications, chips, in particular RFID chips, and magnetic strips.

[0126] Alternatively, it is preferable to use an engraving roller as one of the rollers.

[0127] Extrusion is preferably carried out on the basis of a simple melt of a fully reacted polymer. Alternatively, it may be preferable to use a prepolymer, as described in CH 704 788 A1, as the starting material for forming one of the polymer films A1, A2 or optionally A3. The prepolymer is preferably fed before or after the roll nip to a further melt of a polymer that forms one of the other polymer films A1, A2 or optionally A3. The prepolymer is then chemically or physically cured and / or fully reacted and / or gelled. Furthermore, the present invention relates to a multilayer substrate as can be produced by a process described above or as is actually produced by a process as described above.

[0128] Preferably, a line pressure in a range of 0 to 500 N / cm, more preferably 250 to 450 N / cm, is applied between the pair of rollers immediately after the introduction of the melt. The pair of rollers is preferably kept at a temperature above room temperature, preferably in a range of 50 to 180 °C, more preferably 60 to 120 °C, particularly preferably 70 to 100 °C. Ideally, the roller temperature should not be above the melting temperature or above the glass transition point of the materials used for the resulting polymer films A1, A2 or optionally A3. Preferably, a roller temperature just below the glass transition point Tg and / or the melting point Tm of the lowest melting polymer is used. If the melt in step v) involves fully reacted polymers, the roller temperatures can also be just above the melting temperature or above the glass transition point.

[0129] The introduction of the security feature A5 in step vi) can be carried out in any way known to the person skilled in the art. Preferably, the introduction of the security feature A5 in step vi) is carried out by a measure selected from the group consisting of mixing a security thread, a fluorescent fiber, a dye, a pigment, carbon black, metallic or non-metallic micro- or nanoparticles, magnetic particles, an embossing, or a combination of at least two thereof with the respective polymer A1', A2', or A3', preferably in its melt in step iv), and introducing a hologram into the co-extrusion film or into the laminate from step v).

[0130] In step vii), the polymer film A1 is printed, preferably in the form of a co-extrusion film or a laminate from step v), using a process selected from the group consisting of offset printing, flexographic printing, screen printing, digital printing, intaglio printing, or a combination of at least two thereof. Preferably, the printing process applies at least one line to the first outer side AS1 of the security document S, which line, in terms of its resolution, line sharpness, and thickness, is suitable for printing banknotes. Preferably, the printing layer A4 produced by the printing process has the properties mentioned in connection with the security document S according to the invention.

[0131] Alternatively or additionally, the security feature A5 can be incorporated in the form of an embossing on one of the polymer layers A1, A2 or A3.

[0132] Optionally, fibers A6 can be introduced into, between, or onto the melts. These can also be applied as a separate layer to the resulting multilayer film or bonded to it. Preferably, fibers A6 are introduced into the melt of polymers A1' or A3'.

[0133] The optional joining of the further polymer layer A7 to one of the outer layers AS 1 or AS2 in step vii) over an area of ​​at least 1 mm 2 , can be achieved using any joining method known to a person skilled in the art for joining polymer films. Preferably, the joining process involves ultrasonic welding, vibration welding, laser welding, or a combination of at least two of these. Polymer layer A7, for example, is the data page of a passport.

[0134] The design of the polymer films A1, A2, and optionally A3 corresponds to the polymer films as specified in connection with the security document S according to the invention. In particular, the composition, thickness, length, and width, as well as the shape and properties, are the same as previously described for the polymer films A1, A2, and optionally A3. Preferably, all polymer films A1, A2, and A3 consist exclusively of polymers. Preferably, the entire security document S, with the exception of the security feature A5 and optionally the fibers A6, consists of polymers.

[0135] An advantage of the inventive method for producing a security document S lies in the high flexibility with regard to the variation of the polymers to be processed. Material changes are possible within a very short time, which also makes the production of smaller batch sizes attractive. Furthermore, marking substances in the form of a security feature A5, such as dyes, security pigments, fluorescent dyes, effect pigments, interference pigments, metallic pigments, reactive dyes, but also other additives such as UV absorbers, stabilizers and other additives, in particular those as already described in connection with the inventive security document S, preferably in the form of a masterbatch, can be easily added to the polymer granulate before extrusion. This enables simple customization, protection against environmental influences and further safeguarding of the security document S.The selection and quantity of the various security features A5 can be found in the explanations for the security document S according to the invention and also apply to the method according to the invention.

[0136] As previously mentioned for the security document S according to the invention, preferred materials for this purpose are, in particular, plastics from the group of thermoplastic elastomers, e.g., thermoplastic polyurethanes, copolyesters, polyether block amides, thermoplastic polyolefins, styrene block copolymers, and mixtures of at least two of the aforementioned polymers. Due to their chemical structure, these polymers exhibit particularly good compatibility during extrusion, coextrusion, and the production of blends. Therefore, after their combination during extrusion, lamination, or coating, they are characterized by a particularly close bond, resulting from a good material bond on the one hand and good compatibility of the individual components on the other. Further advantageous properties of a polymeric material for a security document S according to the invention include high chemical resistance to acids, bases, solvents, bleaching agents, etc.high thermal resistance, UV resistance, high opacity, high flexural strength and high softening temperatures.

[0137] Film composites produced by extrusion lamination are typically constructed in such a way that the thin film to be laminated, e.g., film Al made of the polymer AU, is fed onto a roughened, tempered, or cooled metal roller. The melt of the second polymer, e.g., A2', is pressed from the slot die against the first metal roller via a rubber-coated, roughened roller, pressing the polymer melt onto the fed film. The structure of the roughened surfaces of the rollers is transferred into the molten polymer as well as onto the fed film to be laminated. Cooling the tempered roller pair below the solidification temperature of the polymer prevents the film from adhering to the rubber roller.Since the polymer Al', A2' or optionally A3' directly impacts the fed thin film Al, A2 or optionally A3 in molten form, the heat influence on the fed film is brief and therefore hardly damaging. Preferably, the fed polymer film, for example polymer film Al, comprises a TPU, to which the melt of a PC is applied. It is possible to work with comparatively high melt temperatures in the range of 200°C to 250°C. This has the advantage that the high melt temperature allows a lower melt viscosity to be achieved, which leads to a better and faster bonding of the plastic layers and enables the more intimate bond required for a security document S. At the same time, faster process speeds are permitted.

[0138] The roller pair is preferably a temperature-controlled roller with a matte surface that transfers to a certain level to the extruded layer composite during extrusion. As an alternative to a roller pair consisting of a rubber roller and a metal roller, two metal rollers can also be used. Matte surfaces are primarily those with a roughness in the range of 10 to 30 μm.

[0139] If two metal rollers are used, one of the two metal rollers is preferably designed with a thin wall and pressurized from the inside. This metal roller thus functions like a rubber roller, allowing it to give way locally if thickening occurs, see printing with thick ink layers, etc.

[0140] Metal rollers with a highly polished surface produce foils with correspondingly smooth surfaces. These foils are not suitable for security printing because they stick together and can only be printed at high speeds with considerable effort. Typically, these foils are separated with ionized compressed air before being fed into the printing press. An alternative to polished rollers are rollers with only locally limited polished surfaces, which can later be found in specific places on security documents such as banknotes.

[0141] When producing the security document S by coextrusion of at least three polymer films A1, A2 and A3 in a symmetrical structure, for example with an inner polymer film A2 of a polymer A2' and an outer polymer film A1 or A3 of a polymer A1' or A3', where polymers A1' and A3' are particularly preferably identical, the softening temperature of the outer polymer A1' or A3' is preferably lower than that of the inner polymer A2'. Or, under the given processing conditions, the outer polymer A1' or A3' has a lower melt viscosity than the inner polymer A2'. In this way, the printability of the resulting security document S can be optimized by suitable selection of the outer polymer. Preferably, a polymer A2' is selected for the inner polymer film A2 for optimized mechanical properties of the film.Such a multilayer polymer layer preferably comprises largely compatible, i.e. easily co-extruded, polymers such as thermoplastic polyurethanes (TPU), copolyesters, polyether block amides, thermoplastic polyolefins, styrene block copolymers, and mixtures of at least two thereof. During the production process of the security document S, additional material is preferably incorporated between the polymer films A1 or A3 and A2. It is preferable to allow a security thread as security feature A5 to run into the roller gap, which is thus firmly incorporated between the individual layers. Ideally, the thread is provided with an adhesive, as is not uncommon for security threads, and is thus bonded to one of the outer polymer films A1 or A3 via the temperature-controlled roller.

[0142] Other, preferably symmetrically constructed security documents S are also preferred, comprising 1 to 15 foils. Security documents S with an odd number of foils are particularly preferred, in particular three or five foils with an exemplary structure with a sequence of polymer foils A1, A2, A3, A2, A1.

[0143] In a preferred embodiment of the process, at least one of the polymers is selected from the group consisting of polymer A1', polymer A2', optionally polymer A3', a polymer selected from the group consisting of a thermoplastic polyamide elastomer, an olefin-based thermoplastic elastomer, preferably PP / EPDM, a thermoplastic styrene block copolymer (SBS, SEBS, SEPS, SEEPS, and MBS), a thermoplastic polyurethane (TPU), a copolyester elastomer, a polyether block amide, a copolyester, a polycarbonate, a polyethylene terephthalate (PET), a polyethylene terephthalate glycol (PETG), or a mixture of at least two thereof, preferably TPU. Examples of these materials have already been described in the description of the security document S according to the invention and also apply to the materials used in the process according to the invention.

[0144] The second polymer film A2 preferably contains a polymer selected from the group consisting of a TPE, a copolyester, a polyether block amide or a mixture of at least two thereof in an amount in a range from 50 to 100 wt.%, preferably from 60 to 90 wt.%, particularly preferably from 70 to 80 wt.%, based on the total weight of the polymer film A2.

[0145] Preferably, the first polymer film Al contains the TPE in an amount in a range from 50 to 100 wt.%, preferably from 60 to 90 wt.%, particularly preferably from 70 to 80 wt.%, based on the total weight of the polymer film Al.

[0146] Furthermore, at least one of the polymers A1', A2' or A3' contains further additives for various purposes, such as UV protection, easier processing, coloring, etc. Examples of common additives are in particular those as already described in connection with the security document S according to the invention, or those as listed in the patent application with the application number PCT / EP2022 / 083290 on pages 28 to 31.

[0147] The polymers A1', A2' and / or A3' are obtained by mixing the appropriately selected, aforementioned additives with the starting materials for the polymers A1', A2' and / or A3'. The polymers A1', A2' and / or A3' preferably comprise one or more of the aforementioned additives, each in an amount ranging from 0.01 to 10 wt. %, more preferably from 0.05 to 5 wt. %, particularly preferably from 0.1 to 3 wt. %, based on the total weight of the respective polymer A1', A2' and / or A3'. Mixing can be carried out in any manner using known techniques, e.g. using kneaders or screw machines. Further processing is carried out using known techniques of thermoplastic processing, e.g. by extrusion or injection molding.

[0148] In a preferred embodiment of the method, a further layer is applied to at least one side AS1 or AS2 of the security document S, wherein the further layer is preferably a paper, a fiber composite, a textile, or a combination of at least two thereof. In this way, a security document S can be provided that serves, for example, to be used as an "end page" in passports. The end page is the outermost page sewn together with additional films and glued to the passport book cover.

[0149] A further aspect of the invention relates to the use of a thermoplastic polyurethane with a hardness in a range from 80 Shore A to 95 Shore D, preferably from 85 Shore A to 90 Shore D, particularly preferably from 90 Shore A to 85 Shore D, very particularly preferably from 60 Shore D to 90 Shore D, for producing a polymer film A1 that can be printed with dyes from the class of offset printing inks, flexographic printing inks, screen printing inks, digital printing inks or inks for intaglio printing with a resolution of 20 μm to 500 μm. The polymer film A1 is preferably the first polymer film A1 described above in connection with the security document S according to the invention. The polymer film A1 is preferably a component of the security document S described above.

[0150] A further aspect of the invention relates to the use of the security document S according to the invention or produced according to the method according to the invention as a banknote, birth certificate, postage stamp, tax stamp, visa page of a passport, hinge for the data page of a passport, or carrier layer of an electromagnetic shield in a passport. The security document S is preferably used for production as a banknote or the visa page of a passport.

[0151] Examples

[0152] Production of two masterbatches with 30% TiCh.

[0153] Masterbatch: Compounding of a highly concentrated TiCE masterbatch

[0154] The masterbatches for the production of polymer films A1 or A3 were produced using a conventional twin-screw compounding extruder (ZSK 32) at processing temperatures of 190°C to 250°C, which are typical for TPU. a) A masterbatch a) with the following composition was compounded and granulated: 70 wt. % Desmopan™ 9365D from Covestro Deutschland AG, Germany

[0155] 30 wt.% TiCE Kronos 2260 from Kronos Titan GmbH, Germany. b) A master batch b) with the following composition was compounded and granulated: 70 wt.% Desmopan™ 9385D from Covestro Deutschland AG (Germany)

[0156] 30 wt.% TiCh Kronos® 2260 from Kronos Titan GmbH, Germany

[0157] Production of the extruded or coextruded film for examples 1) to 4) involved a plant with the following parameters:

[0158] An extruder a) for single-layer films made of Al' or two extruders a) and b) for co-extrusion of the polymers Al' and A2', the extruders containing at least one screw of 60 mm diameter (D) and a length of 33 D and the screws having a devolatilization zone; a melt pump; a deflection head; a multilayer block; a slot die with a width of 450 mm; a three-roll smoothing calender with a horizontal roll arrangement, the third roll being pivotable by + / - 45° relative to the horizontal; a roller conveyor; a thickness measuring system; a device for applying protective film to both sides; a take-off device; a winding station.

[0159] Example 1) Production of a single-layer TPU film of Shore hardness 65D, thickness 90 pm as polymer film according to the invention Al

[0160] Granules of the plastic Desmopan™ 9365D from Covestro Deutschland AG (Germany) were conveyed from the dryer into the hopper of extruder a).

[0161] The Desmopan™ 9365D was melted in the plasticizing system, consisting of the barrel and screw of the extruder, at processing temperatures typical for TPUs of 190°C to 250°C, in particular 210 to 240°C, and pressures of 10 to 1500 bar, preferably 500 bar. The melt thus produced, conveyed from the screw to the slot die, then reached the smoothing calender. The final shaping and cooling of the film took place on the smoothing calender (consisting of three rolls). A matte steel roll and a matte silicone rubber roll were used to emboss the surfaces. The rubber roll used to structure the film surface is disclosed in US Pat. No. 4,368,240 to Nauta Roll Corporation. The film was then transported through a take-off device and then wound onto a roll.

[0162] The first polymer film Al formed from Desmopan™ 9365D was then printed according to the printing process described below. Example 2) Production of a single-layer TPU film with a Shore hardness of 85D and a thickness of 90 μm as the inventive polymer film Al

[0163] This film was manufactured in the same way as the film in Example 1), but using the plastic granulate Desmopan™ 9385D from Covestro Deutschland AG (Germany).

[0164] The first polymer film Al formed from the DesmopanTM 9385D was then printed according to the printing process described below.

[0165] Example 3) Production of a three-layer white TPU film, thickness 90 pm as a layer structure according to the invention with polymer film Al and polymer film A2.

[0166] Production of the co-extrusion film:

[0167] The granules of master batch a) were conveyed from the dryer into the hopper a) of extruder a). Additionally, granules of the plastic Desmopan™ 9365D from Covestro Deutschland AG were conveyed into the hopper a) of extruder a).

[0168] The granules of the master batch b) were conveyed from the dryer into the hopper b) of the extruder b).

[0169] The weight ratio of masterbatch a) to Desmopan™ 9365D in hopper a) was set as follows:

[0170] 50 wt.% masterbatch a) white

[0171] 50 wt% Desmopan™ 9365D.

[0172] In addition, granules of the plastic Desmopan™ 9385D from Covestro Deutschland AG were fed into the filling hopper b) of the extruder b).

[0173] The weight ratio of masterbatch b) to Desmopan™ 9385D in hopper b) was set as follows:

[0174] 50 wt% masterbatch b) white;

[0175] 50 Gew. -% Desmopan™ 9385D

[0176] In the extruder's barrel / screw plasticizing system, the materials were melted and conveyed at processing temperatures of 190°C to 250°C, in particular 210 to 240°C, which are typical for most TPEs, especially TPUs, and pressures of 10 to 1500 bar, preferably 500 bar. The materials from extruder a) and extruder b) were combined in the slot die in the form of a multilayer block to produce a three-layer extruded film. The material from extruder a) formed the two outer layers, namely the first polymer film A1 and another polymer film A3, each 15 μm thick, and the melt from extruder b) formed the middle layer in the form of the second polymer film A2, 50 μm thick. For this purpose, the melts from extruders a) and b) were fed to the smoothing calender via the slot die. The final shaping and cooling of the film took place on the smoothing calender (consisting of three rollers).A matte steel roller and a matte silicone rubber roller were used to emboss the surfaces. The rubber roller used to structure the film surface is disclosed in US Pat. No. 4,368,240, owned by Nauta Roll Corporation. The film was then transported through a haul-off unit and wound onto a roll. The first polymer film, Al formed from Desmopan™ 9365D, was then printed using the printing process described below.

[0177] Example 3a) Production of a three-layer white TPU film, thickness 90 μm as a layer structure according to the invention with polymer film A1 and polymer film A2.

[0178] For this example, the same materials and conditions were used as for Example 3, using Desmopan™ 9365D for the inner layer and Desmopan™ 9385D for the two outer layers.

[0179] Example 4) Production of a single-layer TPU film with a Shore hardness of 85A and a thickness of 90 μm as the polymer film Al according to the invention

[0180] This film was manufactured in the same way as the film in Example 1), but using the plastic granulate Elastollan® 1185A from BASF (Germany).

[0181] The first polymer film Al formed from the Elastollan® 1185A was then printed according to the printing process described below (Process Printing).

[0182] Example 5) Film made of stretched polypropylene (BOPP) uncoated, transparent, thickness 75 μm

[0183] Example 6) Film made of oriented polypropylene (BOPP) coated, thickness 90 jm

[0184] Printing process

[0185] Printing the foils and assessing the sharpness of the printed image

[0186] Printing ink: Sicpa offset printing ink 3SB dark blue.

[0187] Printing machine: Challenger 173 from Schläfli AG.

[0188] Nominal line width 150 pm for horizontal lines, nominal line width 170 pm for vertical lines, nominal line width 200 pm for diagonal lines.

[0189] Printing substrate: 90 pm TPU film with a hardness of Shore 85A to Shore 85D from the inventive examples 1) to 4) and the non-inventive examples from Table 1.

[0190] Conditions: Room temperature 23 °C, normal pressure between 1010 and 1020 mbar

[0191] All samples were printed using the same machine settings. Information such as contact pressure or print speed was not displayed by the machine and could only be adjusted within a narrow range. Therefore, only relative statements can be made regarding the print image on the various substrates. As the photos in Figures 1a to 1b, 2a to 2c, 3a to 3c, and 4a to 4c for examples 1 to 4 show, the sharpness of the lines increases with increasing hardness of the TPU printing substrate.

[0192] However, as the hardness of the printing substrate increases, the foldability, crease and smoothing properties decrease.

[0193] Particularly good results with regard to printability, in particular sharpness of the printed image, in combination with good folding, creasing and smoothing properties, as shown in Table 1, were provided by the printing substrate according to the invention from Example 3 with a combination of at least one soft first polymer layer 1 and a harder polymer layer 2.

[0194] Relaxing ability after wrinkles and creases

[0195] The printing substrates from Examples 1 to 6 were folded to a size of DIN A6 and crumpled into a closed fist in the hand. The substrates were then unfolded and smoothed with the palm of the hand. The samples from Examples 1 to 6 were then left on a flat surface for 72 hours, and the crease height was measured. The results are listed in Table 1.

[0196] Table 1: Results of relaxation ability after folding and creasing of examples 1) to 6)

[0197] As can be clearly seen, the inventive examples 1, 2, 3 and 4 have the same (Example 2) or significantly better relaxability (Examples 1, 3 and 4) than the non-inventive examples 5 and 6, since the height of the crease points is lower at 1 than that of BOPP at 5.

[0198] Abrasion test: Adhesion of the printing ink to the printing substrate

[0199] The printing substrates from inventive examples 1) to 4) as well as non-inventive examples 5 and 6 were tested for their abrasion behavior on an Abrex abrasion tester for ink adhesion. A metal dome was pressed onto the printed substrate with a force of 10 Newtons. Under this pressure, the machine performed 10 strokes over a friction distance of 10 mm. The repetition rate of the strokes was 1.2 Hz.

[0200] The printing substrates from Examples 1) to 4) exhibit significantly better ink adhesion than Examples 5 and 6 of the non-inventive substrates, as can be seen in the photographs in Figures 1c, 2c, 3c, and 4c compared to Figures 5c and 6c. The inventive films from Examples 1 and 3 provided the best combination of ink adhesion and good foldability and crease resistance.

[0201] Embossability of the printing substrate

[0202] The following printing substrates were tested for their embossability. Embossing was carried out without ink. This process is also known as "blind embossing."

[0203] The inventive TPU coex film 90 pm according to Example 3 served as substrate a), wherein a TPU with Shore hardness D65 was present on the outside and a TPU with Shore hardness D85 was present in the core.

[0204] Substrate b) was a 90 μm TPU coextruded film according to Example 3a, with a TPU with a Shore hardness of D85 on the outside and Shore D65 in the core. Substrate c) was a 90 μm Shore 85A TPU film according to Example 4.

[0205] The substrate d) was a film with a thickness of 90 pm made of coated BOPP according to Example 6.

[0206] The substrate e) was a foil with a thickness of 90 pm made of normal banknote paper (euro banknote).

[0207] The brass printing plate had linear engravings with a width of 250 μm. The depth of the engravings ranged from 50 μm to 200 μm in 50 μm increments. The stamping was carried out on a Bürkle flat press with a pressure of 300 N / cm. 2 and at a temperature of 80°C. The contact time is 2 seconds.

[0208] Table 2 shows the results of the embossing of the substrates a) to e). Table 2: Results of relief transfer when embossing reliefs of different depths into substrates a) to e)

[0209] As can be seen from Table 2, the embossed structure produced with the inventive substrates a) and b) is the highest, with values ​​for the ratio of relief depth to engraving depth of 61 to 82% for substrate a) and 57 to 77% for substrate b). Compared to the non-inventive substrate c), the ratio of relief height to engraving depth was three times higher and compared to substrate d) it was approximately twice as high. Even substrate e) had a ratio of relief height to engraving depth that was at least 10% lower than substrates a) and b).

[0210] Crease recovery angle

[0211] The following substrates were tested with regard to the crease recovery angle: a) Coex film 90 pm, Shore D65 outside and Shore D85 in the core, according to example 3), a) Single-layer TPU film with a Schore hardness of 65D, according to example 1) a) Single-layer TPU film with a Schore hardness of 85D, according to example 2) c) Single-layer TPU film with a Schore hardness of 85A, according to example 4) d) Plastic banknote made of BOPP, according to example 5, e) 5€ banknote

[0212] Testing was carried out according to the DIN 53890: 1972-01 standard on printed substrates after they had been printed as described under the "Printing" section. The test was carried out without drying and only in a dry state. The desired crease recovery angle is as low as possible to keep the banknote crease-free for as long as possible, for example, to ensure long-term insertion into vending machines.

[0213] Table 3: Crease recovery angle measurement on substrates a), a'), a”), c), d) and e)

[0214] The conventional banknote as substrate e) was listed at the top of Table 3 to ensure better comparability with the inventive substrates a), a') and a") listed directly below. A new banknote produced from the inventive film from Example 3, here substrate a), or the inventive film from Example 4, here substrate a"), both exhibited even better crease recovery in this property than the conventional paper banknote, substrate e) in this Table 3. Paper banknotes set the standard among the population. The inventive film thus even exceeds the requirements for conventional banknotes and is therefore the most convincing argument for switching from paper banknotes to polymer banknotes, which are significantly more environmentally friendly due to their significantly longer service life and better recycling properties.The banknotes made of coated BOPP, here substrate d), showed significantly higher crease recovery angles as well as very soft TPU substrates c).

[0215] Tear resistance

[0216] The printing substrate according to the invention from Example 3 was compared with the standard printing substrate not according to the invention, which is represented by the coated BOPP from Example 6.

[0217] The results are presented in Table 4.

[0218] Tested according to DIN 53363:2003

[0219] Table 4: Results of the tear resistance test on different substrates

[0220] The printing substrate according to the invention from Example 3 has a significantly higher tear resistance compared to the standard printing substrate made of BOPP from Example 6. This makes it possible to punch recesses into the new printing substrate, which can then be covered with a hologram foil to create transparent windows in the banknote, analogous to the process for euro banknotes.

[0221] Tensile strength, breaking stress, elongation at break, elastic modulus. The mechanical properties, measured according to ISO 527-3: 1995, of the inventive printing substrate of Examples 1 to 3 were compared with the properties of the non-inventive standard printing substrate of Example 6 and with a conventional 5 Euro banknote:

[0222]

[0223] Table 5 : Results of investigations of mechanical properties on different substrates.

[0224] The printing substrate according to the invention from Example 3 and Example 2 is in each case very close to the properties of a paper banknote, with Examples 1 and 4 also coming very close at least to the BOPP substrate from Example 6. All inventive

[0225] Examples 1 to 4 also exhibit significantly better elongation at break values ​​compared to the paper banknote and the BOPP substrate from Example 6, which, together with the good tear resistance, has a significant impact on the durability of the substrates, for example, as banknotes. Thus, all substrates according to the invention, but especially the substrate according to the invention from Example 3, are the most convincing candidates for a transition from paper banknotes to polymer banknotes, which are significantly more environmentally friendly due to their significantly longer service life and better recycling properties.

[0226] Light transmission

[0227] The light transmission was measured according to ISO 13468-2:2021. The inventive printing substrate from Example 3 was compared with the standard printing substrate "coated BOPP" from Example 6 and a 5-euro paper banknote. The inventive printing substrate from Example 3 had the highest opacity compared to the standards from Example 6.

[0228] Table 6: Results of light transmission studies on various substrates

[0229] Surface tension

[0230] Various printing substrates according to the invention from Examples 1 to 3 were compared with the standard printing substrate, coated BOPP from Example 6, paper banknote, and single-layer TPU film with a Shore hardness of 85A from Example 4. Testing was carried out according to the DIN 55660 standard using two media.

[0231] Table 7 : Results of surface tension investigations on various substrates

[0232] The printing substrate according to the invention from Examples 2 and 3 had the highest surface tension compared to the standards, ie the best printability and is therefore well suited as a banknote.

[0233] Figures

[0234] Figures 1-2 describe preferred embodiments of the security document S and the method for its production, which are not to be read as limiting. The figures show in

[0235] Figures 1a, 1b, 1c: Representation of a security document S according to the invention from example 1 with a mono-polymer film Al made of TPU with a Shore D hardness of 65D with a print layer A4 in the form of print lines;

[0236] Figures 2a, 2b, 2c: Representation of a security document S according to the invention from example 2 with a mono-polymer film Al made of TPU with a Shore D hardness of 85D with a print layer A4 in the form of print lines;

[0237] Figure 3a-3d: Representation of a security document S according to the invention (Example 3) with a

[0238] Polymer film Al made of TPU with a Shore D hardness of 65D and a polymer film A2 made of TPU with a Shore A hardness of 85D co-extruded with polymer film Al, wherein the polymer film Al has a printing layer A4 in the form of printing lines;

[0239] Figures 4a, 4b, 4c: Representation of a security document S according to the invention from example 4 with a polymer film Al made of TPU with a Shore A hardness of 85A with a print layer A4 in the form of print lines;

[0240] Figures 5a, 5b, 5c: Representation of an uncoated BOPP film not according to the invention with print lines;

[0241] Figures 6a, 6b, 6c: Representation of a BOPP film coated according to the invention with printed lines; Figure 7: a schematic representation of the process for producing a security document S according to the invention.

[0242] Figures 1a and 1b each show a photograph of an inventive polymer film Al 110, consisting of a TPU with a Shore hardness of 65D, produced according to Example 1, onto which vertical lines 101 and 104, horizontal lines 102 and 105, and an oblique line 103 were printed using an offset printer, as described above under the printing process, in order to obtain an inventive security document S 100. Figure 1c shows a printed polymer film Al according to Example 1 after the abrasion test method described above in the "Abrasion Test." Lines 101 and 102 appear virtually unchanged. Only slight ink abrasion 106 on the unprinted part of the substrate 110 can be seen.

[0243] Figures 2a and 2b each show a photograph of an inventive polymer film Al 210, consisting of a TPU with a Shore hardness of 85D, produced according to Example 2, onto which vertical lines 201 and 204, horizontal lines 202 and 205, and an oblique line 203 were printed, as described above under the printing process, in order to obtain an inventive security document S 200. Figure 2c shows a printed polymer film Al according to Example 2 after the abrasion test method described above in the "Abrasion Test." Lines 201 and 202 appear virtually unchanged. Only slight ink abrasion 206 can be seen on a line 201, without a significant portion of ink having been transferred to the substrate 110.

[0244] Figures 3a and 3b each show a photo of an inventive polymer film A1 310, consisting of a TPU with a Shore hardness of 65D, produced according to Example 3, which was coextruded together with a polymer film A2 consisting of a TPU with a Shore hardness of 85D, wherein lines 301 to 305, namely vertical lines 301 and 304, horizontal lines 302 and 305 and an oblique line 303, were printed on the polymer film A1, as described above under the printing process, in order to obtain a security document S 300 according to the invention. Figure 3c shows a printed polymer film A1 according to Example 3 after the abrasion test method described above in the “Abrasion Test”. Lines 301 and 302 appear slightly different. Clear color abrasion 306 onto the substrate 310 can be seen.

[0245] Figures 4a and 4b each show a photograph of a polymer film 410 according to the invention, consisting of a TPU with a hardness of 85 Shore A, produced according to Example 4, onto which vertical lines 401 and 404, horizontal lines 402 and 405, and an oblique line 403 were printed, as described above under the printing process, to thus obtain a security document S 400 according to the invention. Figure 4c shows a printed polymer film A1 according to Example 4 after the abrasion test procedure described above in the "Abrasion Test." Lines 401 and 402 appear slightly faded, but no color abrasion onto the substrate 410 is discernible.

[0246] Figures 5a and 5b each show a photograph of a non-inventive polymer film 510 consisting of a bidirectionally stretched polypropylene (BOPP) from Example 5, onto which vertical lines 501 and 504, horizontal lines 502 and 505, and an oblique line 503 were printed as described above under the printing process. Even if the general deviations at the indicated locations are no greater than for the inventive examples in Figures 1a, 1b, 2a, 2b, and 3a and 3b, it is clearly evident that the fluctuations in line width within the course of the line are considerably greater than in the inventive examples. Figure 5c shows a printed film according to non-inventive Example 5 according to the abrasion test method described above in the "Abrasion Test." Lines 501 and 502 appear heavily abraded at abrasion point 506. A clear color abrasion 506 onto the substrate 510 can be seen.

[0247] Figures 6a and 6b each show a photograph of a non-inventive polymer film 610 consisting of a coated bidirectionally stretched polypropylene (BOPP) from Example 6, onto which vertical lines 601 and 604, horizontal lines 602 and 605, and an oblique line 603 were printed, as described above under the printing process. Even if the general deviations at the indicated locations are no greater than for the inventive examples in Figures 1a, 1b, 2a, 2b, and 3a and 3b, it is clearly evident that the fluctuations in line width within the course of the line are considerably greater than in the inventive examples. Figure 6c shows a printed film according to non-inventive Example 6 according to the abrasion test method described above in the “Abrasion Test.” Lines 601 and 602 appear heavily abraded at abrasion point 606. A clear color abrasion 606 onto the substrate 610 can be seen.

[0248] In all photos, a scale of 10 out of 500 pm can be seen in the lower right corner, which was only clarified in Fig. 3d by enlarging photo 3a.

[0249] As can be seen from the width specifications within Figures 1a, 1b, 2a, 2b, 3a, 3b, 4a, 4b, 5a, 5b, 6a, 6b, the printed lines on Examples 1, 2 and 3 in particular show a particularly small deviation from the respective nominal line width.

[0250] Figure 7 shows a schematic of the process for producing a security document S. In step i) 710, a first polymer A1' was provided. In step ii) 712, a second polymer A2' was provided. The optional step iii) is not shown here. In step iv) 714, the polymers from step i) 10 and step ii) 12 were each melted in an extruder. Melting took place at a temperature of 250°C and at atmospheric pressure. In step v) 716, the polymer melts from step iv) were shaped as a coextrudate to form a first polymer film A1 and a second polymer film A2 made of the second polymer A2'. For this purpose, the melts from the extruders were allowed to flow through a nozzle onto two metal rollers. Parallel to the flow of the melts from the extruder, in step vi) 718, a security thread was threaded between the melt of the polymer A1' and the melt of the polymer A2'.After cooling the extrudate, in step vii) 720, the first outer layer AS1 of the polymer film A1 was printed with a blue offset ink according to the printing process described above. The result is shown in Figs. 1a and 1b.

Claims

Patent claims 1. A security document S with a first outer side AS1 and a second outer side AS2 opposite the first outer side AS1, comprising at least: A 1. a first polymer film A 1 , A2. optionally a second polymer film A2, A3. optionally at least one additional polymer film A3, A4. a print layer A4, wherein at least the first polymer film A1 comprises a thermoplastic polyurethane TPU having a hardness in a range from 80 Shore A to 95 Shore D, preferably from 85 Shore A to 90 Shore D, particularly preferably from 90 Shore A to 85 Shore D, in an amount in a range from 50 to 100 wt.%, based on the total weight of the first polymer film A1 and forms at least the outer side AS1 of the security document S, and wherein the print layer A4 covers the surface of the security document S in a range from 1 to 100%, preferably from 10 to 90%, based on the total surface area of the surface AS1.

2. The security document S according to claim 1, wherein the security document S comprises the second polymer film A2.

3. The security document S according to one of the preceding claims, wherein the printing layer A4 consists of printing inks selected from the group consisting of offset printing inks, flexographic printing inks, screen printing inks, digital printing inks or a combination thereof.

4. The security document S according to one of the preceding claims, wherein the print layer A4 has at least one, preferably at least two, particularly preferably at least three of the following properties: (Dl) that it consists of at least one line, wherein the at least one line has a shape selected from the group consisting of a circle, a polygon, an oval, a polygon or a combination of at least two thereof; (D2) that it has a line width of 20 pm to 500 pm, preferably of 50 to 400 pm, particularly preferably of 100 to 300 pm; (D3) that at least one line of the printing layer A4 is formed with a deviation from the nominal line width in a range of 2 to 20 pm, preferably 3 to 15 pm, particularly preferably 4 to 10 pm; (D4) has a height in a range of 0.5 pm to 15 pm (D5) increased abrasion resistance.

5. The security document S according to one of the preceding claims, wherein at least the first polymer film A1 has at least one of the following properties: a. a tear resistance in a range from 50 N / mm to 400 N / mm determined according to DIN 53363:2003-10; b. a tensile strength in a range from 20 MPa to 200 MPa determined according to ISO 527-3:1995; c. a light transmission in a range from 0% to 85%, determined according to ISO 13468-2:2019; d. a crease recovery angle in a range from 120 to 170°, more preferably from 130 to 160°, particularly preferably from 140 to 150° according to DIN 53 890 / 91; e. a Vicat softening temperature of 60°C to 105°C, particularly preferably 65°C to 85°C according to DIN EN ISO 306; f. a surface tension of 32 to 55 mN / m according to DIN ISO 8296:2003.

6. The security document S according to one of the preceding claims, wherein the security document S has at least one second polymer film A2, wherein the at least one second polymer film A2 contains a thermoplastic elastomer TPE in an amount in a range from 50 to 100 wt.%, preferably from 60 to 90 wt.%, particularly preferably from 70 to 80 wt.%, based on the total weight of the respective polymer film A2.

7. The security document S according to claim 5, wherein the thermoplastic elastomer TPE is selected from the group consisting of a thermoplastic polyamide elastomer, an olefin-based thermoplastic elastomer, preferably PP / EPDM, a thermoplastic styrene block copolymer SBS, SEBS, SEPS, SEEPS and MBS, a thermoplastic polyurethane TPU, a copolyester elastomer, a polyether block amide, a copolyester, a polycarbonate, a polyethylene terephthalate PET, a polyethylene terephthalate glycol PETG or a mixture of at least two thereof.

8. The security document S according to one of the preceding claims, wherein all polymer films A1, A2 and optionally A3 contain a polymer in an amount in a range from 50 to 100 wt.%, preferably from 60 to 90 wt.%, particularly preferably from 70 to 80 wt.%, based on the total weight of the respective polymer film A1, A2 or A3.

9. The security document S according to one of the preceding claims, wherein at least one of the polymer films selected from the group consisting of the second polymer film A2 or the at least one further polymer film A3 is a polymer selected from the group consisting of a thermoplastic polyurethane TPU, a copolyester or a mixture of at least two thereof or mixtures of TPU and at least one further TPE in a Amount in a range of 50 to 100 wt.%, preferably 60 to 90 wt.%, particularly preferably 70 to 80 wt.%, based on the total weight of the respective polymer film A2 or A3.

10. The security document S according to one of the preceding claims, wherein the security document S has at least one of the following properties: a. a tear resistance in a range from 50 N / mm to 400 N / mm determined according to DIN 53363:2003-10; b. a tensile strength in a range from 20 MPa to 200 MPa determined according to ISO 527-3:1995; c. a light transmission in a range from 0% to 85%, determined according to ISO 13468-2:2019; d. a security pigment content in a range from 0.1 to 10 wt.%, based on the total weight of the security document S; e. a crease recovery angle in a range from 120 to 170°, more preferably from 130 to 160°, particularly preferably from 140 to 150° according to DIN 53 890 / 91; f. a surface tension of 32 to 55 mN / m according to DIN ISO 8296:2003.

11. A method for producing a security document S with a first outer side AS1 and a second outer side AS2 opposite the first outer side AS1, comprising the steps: i) providing a first polymer Al', wherein the first polymer Al' is at least one TPU with a hardness in a range from 80 Shore A to 95 Shore D in an amount of 50 to 100 wt.-%, based on the total weight of the polymer A1'; ii) Optionally providing a second polymer A2'; iii) Optionally providing a further polymer A3'; iv) Melting the polymers from step i), optionally ii) and optionally iii); v) Either forming a first polymer film as an extrudate from the melt of the polymer A1' from step iv), or combining the polymer melts from step iv) to form a first polymer film A1 from the first polymer A1', a second polymer film A2 from the second polymer A2' and optionally a further polymer film A3 from the further polymer A3' as a coextrudate, or forming a laminate from a separate polymer film A1, A2 and optionally A3, which were formed from the melts in step iv), to obtain a layer structure with a first outer side AS1 formed by the first polymer film A1 and a second outer side AS2, which is opposite the first outer side AS1;. vi) Optionally, incorporating a security feature A5, selected from the group consisting of a hologram, a security thread, a fluorescent fiber, a dye, a pigment, carbon black, metallic or non-metallic micro- or nanoparticles, magnetic particles, or a combination of at least two of these into or onto one of the polymer films A1, A2, or A3; vii) Printing at least the outer side AS1 of the layer structure from step v), which is formed from the first polymer film A1, with an ink dissolved in organic solvents and optionally cured by UV light to obtain the security document S; viii) Optionally, joining, preferably by ultrasonic welding, vibration welding, or laser welding, a polymer layer A6 to one of the outer layers AS1 or AS2 over an area of at least 1 mm 2, wherein the second outer side AS2 is formed by one of the polymer films A1, A2 or A3, each of which contains or consists of a TPE.

12. The process according to claim 11, wherein at least one of the polymers is selected from the Group consisting of the polymer A2', optionally the polymer A3' a polymer selected from the group consisting of a thermoplastic polyamide elastomer, a thermoplastic elastomer based on olefins, preferably PP / EPDM, a thermoplastic styrene block copolymer, a thermoplastic polyurethane (TPU), a copolyester elastomer, a polyether block amide, a copolyester, a polycarbonate, a Polyethylene terephthalate (PET), a polyethylene terephthalate glycol (PETG) or a mixture of at least two thereof, preferably TPU.

13. Use of a thermoplastic polyurethane having a hardness in a range of 80 Shore A to 95 Shore D for the production of a polymer film Al which can be printed with dyes of the class offset printing inks, flexographic printing inks, screen printing inks, digital printing inks with a resolution of 20 pm to 500 pm.

14. Use of the security document S according to one of claims 1 to 10 or produced by a method according to one of claims 11 to 12 as a banknote, birth certificate, postage stamp, tax stamp, visa pages of a passport, hinge for the data page of a passport, carrier layer of an electromagnetic shield in the passport or a combination of at least two thereof.

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