Multi-layer foil

Abstract

The invention relates to a multi-layer film (1) for an artificial leather, comprising more than one layer (2, 3), wherein at least one layer (2, 3) has regions of a first cured digital printing ink (4) and regions of at least one second cured digital printing ink (5), wherein the first and at least one second cured digital printing ink (4, 5) are different from one another and wherein the multi-layer film (1) has a total thickness of at least 30 µm.

Description

[0001] The invention relates to a multilayer film, in particular for artificial leather, a multilayer composite structure comprising this film, a method for producing the multilayer film and the use of a digital printer for forming the multilayer composite structure.

[0002] For decorative surfaces on furniture or in vehicle interiors, a wide variety of single-layer or multi-layer composite structures containing polymeric materials are known, for example, based on polyurethane or polyvinyl chloride. Laminated with a textile carrier, such composite materials are used extensively, primarily in the form of artificial leather with a grained surface structure, as upholstery material for seats, furniture, or as cladding elements for walls or ceilings.

[0003] Typically, the individual layers of the composite structure are provided as sheet material made of a polymer mixture distributed over the entire surface of the layer. By stacking individual layers on top of each other, a layer is formed, which in turn, with additional layers, creates a composite structure. Composite structures are typically manufactured by extrusion, calendering, lamination, coating, casting, or painting, or a combination thereof.

[0004] The composition of the polymer mixture allows the material properties of each layer to be individually tailored. These material properties can affect, for example, hardness, abrasion resistance, or chemical resistance. These material properties can influence each other. In other words, an improvement in one material property can lead to the deterioration of another. Unfortunately, each material property within a layer or ply represents a compromise due to the interactions between the various material properties. The material properties within a layer or ply are therefore identical across the entire surface area of ​​the layer or ply.

[0005] For a visual and tactile impression, the top layer of the composite structure can have a textured surface. In the case of synthetic leather, the surface structure features elevations and / or depressions that can mimic the grain of genuine or natural leather. This structuring is typically created through thermal-mechanical surface structuring, also known as embossing. The disadvantage is that the thermal-mechanical treatment required to create the embossing can negatively influence or at least alter the material properties of the composite structure. The compression of the material caused by mechanical deformation must be considered in advance during the design process.

[0006] The invention is based on the object of providing a multi-layer film for an artificial leather which has different chemical and / or mechanical and / or physical material properties in certain regions within a layer.

[0007] A further object is to provide a process for producing such a multilayer film.

[0008] A further object is to provide a multilayer composite structure with such a multilayer film for use as a top layer in an artificial leather.

[0009] Additionally or alternatively, the composite structure should have a surface structure without the material properties of the film being negatively influenced by the creation of the surface structure.

[0010] The solution to this problem is provided by a multilayer film having the features of independent claim 1. A further solution to the problem is provided by a multilayer composite structure having the features of claim 9, as well as by a method for producing the multilayer film having the features of claim 14.

[0011] Further advantageous developments are disclosed in the dependent claims.

[0012] Claim 1 discloses a multi-layer film for an artificial leather comprising more than one layer, wherein at least one layer has regions of a first cured digital printing ink and regions of at least one second cured digital printing ink, wherein the first and at least one second cured digital printing ink are different from one another and wherein the multi-layer film has a total thickness of at least 30 µm.

[0013] Preferably, at least one layer of the multilayer film is produced using digital printing. Digital printing refers to a printing process in which the print image is transferred directly from a file or data stream from a computer to a printing press, without the use of a static printing form. To produce the multilayer film, one layer after another can be applied over the entire surface using digital printing. The additional layers of the film can be applied, for example, by doctoring or brushing. The film can also be referred to as a layered structure and is a flat structure consisting of several layers of a polymer composition.

[0014] A layer, within the meaning of the invention, is a flat, spread mass of a material. A layer consists of at least one material composition, e.g., a polymer composition or a varnish.

[0015] A layer, e.g., a carrier layer, underlayer, cover layer, or functional layer, within the meaning of the invention, is a flat, spread mass of a material. A layer can be formed from one or more plies, which can be arranged one above or one below the other. A layer formed from one ply can also be referred to as a ply, and vice versa. Multiple layers can, in principle, be arranged one above or one below the other.

[0016] The film according to the invention has the advantage that it has regions within a layer which can differ, for example, chemically and / or mechanically and / or physically from adjacent regions, by using more than one digital printing ink to create a layer. The film according to the invention differs from a purely decorative color print in the mechanical resilience, e.g. defined by abrasion resistance, strength and hardness, of the printed material. In order to meet these properties, e.g. for use in artificial leather, the film must have a minimum thickness of at least 30 µm, preferably 50 µm, particularly preferably 200 µm, most preferably 500 µm. The thickness can be achieved, for example, by applying more than 2 layers of the digital printing ink. The multi-layer film preferably has 5 or more layers, in particular 20 or more layers, most preferably 50 or more layers.Thus, the film according to the invention can have different material properties both within a plane of a layer and when several layers are arranged one above the other in the vertical direction.

[0017] Digital printing inks for use in digital printing processes are generally known to those skilled in the art. In preferred embodiments, the digital printing ink is a radiation-curable ink suitable for digital printing.

[0018] Such an ink typically includes photoinitiators, monomers, oligomers, thinners, and other additives, e.g. dyes, pigments, defoamers, etc.

[0019] Curing in this context means that an applied liquid undergoes polymerization induced by radiation, e.g., UV light, and thereby loses its plastic deformability. Preferred digital printing inks can contain polymerizable components containing monomers, oligomers, and higher-molecular-weight resins. By varying the type and number of functional groups, as well as the chain lengths and structure, a wide range of products with a broad spectrum of properties is accessible. The most important representatives of these products are (meth)acrylic ester compounds, followed by unsaturated polyesters and vinyl compounds, as well as compounds from cationic polymerization.

[0020] For example, the cured digital printing inks comprise a polymer selected from the group consisting of polyester (meth)acrylate, polyether (meth)acrylate, epoxy (meth)acrylate, urethane (meth)acrylate, amine-modified (meth)acrylate, acrylic (meth)acrylate, melamine (meth)acrylate, vinyl ether, vinyl ester, and mixtures thereof. The different digital printing inks of a layer can comprise the same or different polymers. Preferably, at least one of the cured digital printing inks within a layer of the multilayer film comprises a poly(meth)acrylate.

[0021] In advantageous embodiments, at least one layer of the film comprises different digital printing inks, so that the regions of the cured digital printing inks formed therefrom differ in their chemical and / or mechanical and / or physical properties. For example, a film can be produced which has a particularly abrasion-resistant material within one unit of layers (e.g. one layer or several layers arranged one above the other) and a particularly flexible material within another unit of layers. For example, alternatively or additionally, a film can be produced which has a thermally and / or electrically conductive material within one unit and a thermally and / or electrically insulating material within another unit of layers. In this way, alternatively or additionally to the aboveexemplary designs, color and / or gloss level and / or hardness and / or adhesion and / or material regeneration and / or material weakening can be individually adapted.

[0022] Preferred digital printing inks can comprise polymerizable components containing monomers, oligomers, higher molecular weight (meth)acrylic ester resins, vinyl-containing polymers, unsaturated polyesters, and mixtures thereof. Digital printing inks that comprise compounds based on electron-rich olefins and cyclic molecules with ring heteroatoms as products of cationic polymerization are also preferred. Electron-rich olefins as monomers for cationic polymerization can be, for example, isobutene, isoprene, and / or vinyl ethers. Examples of cyclic monomers with heteroatoms include epoxide, oxetane, tetrahydrofuran, 2-oxazoline, trioxane, lactide, and mixtures thereof.

[0023] Digital printing inks can also contain monomers as reactive diluents. These can primarily serve to reduce viscosity. They are incorporated into the polymer chain during polymerization and thus directly influence the properties of the cured ink. An important characteristic of monomers is their functionality. Mono- to hexafunctional monomers can be used. This functionality allows the crosslinking density and thus the chemical / physical film properties to be controlled.Examples of suitable monomers are trimethylolpropane triacrylate (TMPTA), butanediol diacrylate (BDDA), hexanediol diacrylate (HDDA), tripropylene glycol diacrylate (TPGDA), dipropylene glycol diacrylate (DPGDA), phenoxyethyl acrylate (POEA), 4-t-butylcyclohexyl acrylate (TBCH), isobornyl (meth)acrylate (IBOA), hydroxyethyl (meth)acrylate (HE(M)A), butyl (meth)acrylate, ethyl diglycol acrylate (EDGA), butanediol monoacrylate (BDMA), isodecyl acrylate, dipentaerythritol hexaacrylate (DPHA), pentaerythritol tri- / tetracrylate (TMPTA) and mixtures thereof. For example, a suitable digital printing ink may comprise 10 to 98 wt.%, preferably more than 50 wt.%, based on the total weight of the digital printing ink, of radiation-reactive (e.g., UV-reactive) monomers prior to curing.

[0024] The digital printing inks can also contain film-forming components. Film-forming components are oligomers and / or monomers and / or non-reactive polymers (those that do not take part in the polymerization reaction). These components influence the basic characteristics of the radiation-cured digital printing ink, such as hardness, scratch resistance, flexibility, adhesion, elasticity, etc. Compounds with free-radically polymerizable double bonds are preferably used, as these form a cured film through polymerization reactions (crosslinking). Particularly preferred film formers for free-radical polymerization, preferably through radiation-induced curing, particularly preferably through UV-induced curing, are epoxy (meth)acrylates, polyester (meth)acrylates, polyether (meth)acrylates, polyurethane (meth)acrylates, and silicone (meth)acrylates. Examples of these are Laromer® products from BASF, Ebecryl® products from Allnex, Genomer® products from Rahn, and Sartomer® products fromArkema, Photomer® products from IGM.

[0025] Epoxy (meth)acrylates are formed from the reaction of aromatic or aliphatic epoxy resins with free (meth)acrylic acid. The cured inks are characterized by high reactivity, high hardness, and good chemical resistance.

[0026] Polyester acrylates are reaction products of hydroxyl-terminated polyesters and acrylic acid. The cured inks are characterized by good hardness and weather resistance.

[0027] Polyether acrylates are products from the esterification of mostly linear polyethers with free hydroxyl groups and acrylic acid.

[0028] Polyurethane acrylates are obtained by reacting polyurethane prepolymers with terminal isocyanate groups with hydroxyalkyl acrylates. The simplest urethane acrylates are obtained by reacting a diisocyanate with a hydroxyl-containing monomer. The cured inks are characterized by excellent weather resistance, chemical resistance, and hardness, while maintaining good flexibility.

[0029] Silicone (meth)acrylates are formed either by reacting polydialkylsilanes with terminal silanol groups and hydroxyalkyl acrylates or by adding acrylic acid to polydialkylsilanes containing terminal epoxy groups.

[0030] For example, a suitable digital printing ink may comprise 2 to 90 wt.%, preferably less than 50 wt.%, based on the total weight of the digital printing ink, of oligomers prior to curing.

[0031] In addition to the above-mentioned components, a digital printing ink may contain 2 to 10 wt.% photoinitiators and 1 to 10 wt.% other additives, e.g., defoamers, UV absorbers, etc., each based on the total weight of the digital printing ink. In the case of electron beam curing or UV curing using wavelengths <250 nm, the photoinitiators can be omitted.

[0032] In some embodiments, the multilayer film is at least partially translucent. Preferably, the multilayer film has a light transmittance of 30% in a wavelength range for visible light between 380 nm and 780 nm. For an overall translucent composite, the individual layers of the film can be completely translucent, i.e. transparent, or partially translucent. Individual layers can also be opaque and have translucent segments or gaps at least in places, colloquially known as masking or masking layers. In this way, for example, symbols, letters or numbers can be reproduced on the surface of the film, the visibility of which only becomes apparent when the film is backlit or can at least be enhanced by backlighting.

[0033] Alternatively, the multilayer film may comprise at least one region of a cured digital printing ink comprising a dye and / or a pigment.

[0034] In another aspect of the present invention, a multilayer composite structure is claimed. The multilayer composite structure comprises a multilayer film as described above. The multilayer film has a front side and a back side, with the back side of the multilayer film being disposed on a single- or multi-layer backing layer.

[0035] In principle, any material suitable for forming a fully bonded composite with the multilayer film can be used as the underlayer. A suitable underlayer can be a substrate that can be completely and non-destructively separated from the multilayer film. Alternatively, a suitable underlayer can be a textile layer, a foam layer, a compact film, an adhesive layer, or a combination thereof.

[0036] In preferred embodiments, the multilayer composite structure is an artificial leather. In such embodiments, the underlayer can preferably be designed as a textile layer. The multilayer film preferably forms the upper layer or the visible side of the artificial leather. Alternatively, the multilayer composite structure can be a cladding element, e.g. a door panel or a dashboard for the vehicle interior, a floor laminate, a furniture film, a facade cladding, a coating of a window profile or a door, a protective or diving suit, a bellows, a printing blanket, a flexible container, e.g. a fuel tank, an enclosure or a decorative surface coating. In an embodiment in which the multilayer composite structure is designed as a multilayer film, e.g. as a furniture film or for decorative surface coating, the underlayer can preferably be designed as an adhesive layer or as a compact layer, i.e.as another multi-layer film.

[0037] Preferably, the multi-layer composite structure is no more than 20 cm thick in total.

[0038] In preferred embodiments of the multilayer composite structure, the multilayer film has a structure of elevations and / or depressions, in particular undercuts and / or cavities. The front side of the multilayer film preferably forms the visible side of the composite structure. By, for example, locally varying the layer thickness of at least one layer of the film, the composite structure can have a relief-like surface structure in the form of a grain, as is typically the case with a surface film or artificial leather. This can impart pleasant optical and tactile properties to the surface of the composite structure combined with high chemical and mechanical stability.

[0039] Advantageously, the multilayer film can also have cavities that can be filled with air, for example. The air inclusions can advantageously provide an additional cushioning function, at least in certain areas.

[0040] Additionally or alternatively, the layer thickness of the multilayer film can be varied locally, allowing for the creation of predetermined breaking points. For example, the composite structure can be used as an airbag cover, where the composite structure can tear open at defined locations when the airbag is deployed, ensuring the airbag's deployment. Varying the layer thickness advantageously provides a predetermined breaking point that does not undesirably affect the visual and tactile impression of the front of the composite structure, as has previously been the case with predetermined breaking points created by perforations or seams.

[0041] In a further aspect of the invention, a process for producing a multilayer film as described above is claimed. The process according to the invention comprises the steps: a) Providing a substrate, b) printing a first layer on the substrate using a first digital printing ink and at least one second digital printing ink, c) optional curing of the first layer, d) printing a second layer on the substrate surface according to step c) using a third and optionally at least a fourth digital printing ink, e) optional curing of the second layer, f) Repeat steps b) to e) until a fully formed film with a minimum thickness of 30 µm is produced, g) If necessary, remove the substrate.

[0042] The minimum thickness of the film is preferably 50 µm, particularly preferably 200 µm, most preferably 500 µm. In other words, the substrate surface after process step d) can be formed by the cured first layer. The third and / or fourth digital printing ink can correspond to the first and / or second digital printing ink or be different from them. In an advantageous manner, the process according to the invention can provide a multi-layer film for an artificial leather which, by arranging several digital printing inks with different properties within a layer, has different chemical and / or mechanical and / or physical material properties in certain regions. For example, byBy locally varying the layer thickness of at least one layer of the film, the film can have a relief-like surface structure in the form of a grain, as is typically the case with a surface film for artificial leather. Advantageously, the surface structuring can be carried out without further thermal-mechanical post-processing, so that the material properties of the film are not negatively affected by the creation of the surface structure.

[0043] In a further aspect of the invention, the use of a digital printer for producing a multilayer composite structure described above is claimed.

[0044] An embodiment and further advantages of the invention are schematically illustrated and explained in more detail below in connection with the following figure.

[0045] It shows Fig. 1 a schematic representation of a multilayer composite structure according to the invention according to a first embodiment in a sectional view.

[0046] The figure is described in Cartesian coordinates with a longitudinal direction X, a transverse direction Y perpendicular to the longitudinal direction X, and a vertical direction Z perpendicular to both the longitudinal direction X and the transverse direction Y. The longitudinal direction X can also be referred to as depth X, the transverse direction Y as width Y, and the vertical direction Z as height Z. The longitudinal direction X and the transverse direction Y together form the horizontal, X, Y, which can also be referred to as the horizontal plane X, Y. The longitudinal direction X, the transverse direction Y, and the vertical direction Z can together be referred to as the spatial directions X, Y, Z or as Cartesian spatial directions X, Y, Z.

[0047] The Fig.The multilayer composite structure 20 schematically illustrated in Figure 1 comprises a multilayer film 1 with a front side 6 and a back side 7, wherein the back side 7 of the multilayer film 1 is arranged on a base layer 30. The base layer 30 is formed as a foam layer. The film 1 has a first layer 2 and a second layer 3. The first layer 2 is formed from a cured first digital printing ink 4. A second layer 3 is arranged above the first layer 2, wherein the layer 3 has a region made of the first digital printing ink 4 and a further region made of a second digital printing ink 5. The layer 3 extends along the plane X, Y, wherein the plane X, Y of the layer 3 is formed from the cured first digital printing ink 4 and the cured second digital printing ink 5.By arranging the first digital printing ink 4 and the second digital printing ink 5 next to each other, the composite structure 20 exhibits different chemical and / or mechanical and / or physical material properties in certain regions along the X, Y plane. The front side 6 has a structure 8 consisting of elevations and depressions, which typically creates the visual and tactile impression of a grain on a surface film of artificial leather. List of reference symbols (part of the description) 1 multi-layer film 2 first layer 3 second layer 4 first digital printing ink 5 second digital printing ink 6 Front 7 Back 8 Structure 20 multilayer composite structure 30 Lower class X longitudinal direction; depth Y transverse direction; width Z vertical direction; height X, Y horizontals; horizontal plane

Claims

[1] Multi-layer film (1) for an artificial leather comprising more than one layer (2, 3), wherein at least one layer (2, 3) has areas of a first cured digital printing ink (4) and areas of at least one second cured digital printing ink (5), wherein the first and at least one second cured digital printing ink (4, 5) are different from one another and wherein the multi-layer film (1) has a total thickness of at least 30 µm. [2] Multilayer film (1) according to claim 1, wherein the multilayer film (1) is produced by digital printing. [3] Multilayer film (1) according to claim 1 or 2, wherein at least one of the cured digital printing inks (4, 5) comprises a poly(meth)acrylate. [4] Multi-layer film (1) according to one of claims 1 to 3, wherein the multi-layer film (1) is at least partially translucent. [5] Multilayer film (1) according to one of claims 1 to 4, wherein at least one of the cured digital printing inks (4, 5) comprises a dye and / or a pigment. [6] Multilayer film (1) according to one of claims 1 to 5, wherein the multilayer film (1) has a total thickness of at least 200 µm. [7] Multilayer film (1) according to one of claims 1 to 6, wherein the cured digital printing ink (4, 5) comprises a polymer selected from the group consisting of polyester (meth)acrylates, polyether (meth)acrylates, epoxy (meth)acrylates, urethane (meth)acrylates, vinyl ethers, vinyl esters and mixtures thereof. [8] Multi-layer film (1) according to one of claims 1 to 7, wherein the digital printing inks (4, 5) comprise polymers and wherein the regions of the cured digital printing inks (4, 5) within a layer differ in their mechanical properties, in particular hardness, abrasion and / or elasticity. [9] Multilayer composite structure (20) comprising a multilayer film (1) according to one of claims 1 to 8, with a front side (6) and a back side (7), wherein the back side (7) of the multilayer film (1) is arranged on a single- or multi-layer underlayer (30). [10] Multi-layer composite structure (20) according to claim 9, wherein the multi-layer composite structure (20) is at most 20 cm thick. [11] Multilayer composite structure (20) according to one of claims 9 to 10, wherein the underlayer (30) is a textile layer, a foam layer, a compact film or an adhesive layer. [12] Multi-layer composite structure (20) according to one of claims 9 to 11, wherein the multi-layer composite structure (20) is an artificial leather, a cladding element, a floor laminate, a furniture foil or a coating of a window profile or a door. [13] Multi-layer composite structure (20) according to one of claims 9 to 12, wherein the multi-layer film has a structure (8) of elevations and / or depressions, in particular undercuts and / or cavities. [14] A method for producing a multilayer film (1) according to any one of claims 1 to 8, comprising the steps: a) Providing a substrate, b) printing a first layer (2) on the substrate using a first digital printing ink (4) and at least one second digital printing ink (5), c) optionally curing the first layer (2), d) printing a second layer (3) on the substrate surface after step c) using a third digital printing ink and optionally at least a fourth digital printing ink, e) optionally curing the second layer (3), f) Repeat steps b) to e) until a fully formed film (1) with a minimum thickness of 30 µm is produced, g) If necessary, remove the substrate. [15] Use of a digital printer for producing a multilayer composite structure (20) according to claims 8 to 13.

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