Deep-drawable release film for fiber-reinforced plastic components

Description

[0001] The invention relates to a multilayer release film comprising a first surface layer based on a mixture of a thermoplastic elastomer and a polyolefin, a second surface layer based on at least one polypropylene or propylene copolymer, and an adhesion promoter layer, wherein the release film has a total layer thickness in the range of 10 to 250 µm. The release film according to the invention is suitable for the production of fiber-reinforced plastic components, in particular by a vacuum infusion process.

[0002] Using separating films or vacuum bags made from them, even complex fiber-reinforced plastic components can be manufactured for a wide variety of applications, such as in the aerospace, automotive, or wind energy industries. In this process, curable fiber-reinforced plastic semi-finished products, such as laminates made of carbon or glass fibers impregnated with a curing resin, are placed in a vacuum bag. The vacuum bag can, in principle, consist of a single separating film that completely surrounds the curable fiber-reinforced plastic semi-finished product. In practice, however, the vacuum bag often comprises several elements that are vacuum-sealed together.

[0003] In some technologies, the semi-finished products are already pre-impregnated with plastic resin (e.g. pre-impregnated fibers (prepregs), pre-impregnated metal grids, etc.), while in other technologies, non-pre-impregnated semi-finished products are used and subsequently impregnated with plastic resin inside the vacuum bags (e.g. in the infusion process).

[0004] The curable semi-finished product is then pressed into the vacuum-tight mold by evacuation and sufficiently compacted to allow any gas or air inclusions to escape and ensure the laminate is as free of voids as possible. The complete evacuable assembly, consisting of the vacuum bag, mold, and formed, curable fiber-reinforced plastic semi-finished product, is then heated under pressure in an autoclave until the resin reaches its curing temperature and has fully cured. After cooling, the cured fiber-reinforced plastic component can be removed from the vacuum bag and separated from the vacuum-tight mold.

[0005] Fiber-reinforced plastic components are often manufactured in molds using release agents to prevent the curable plastic resins from adhering to the molds. The use of such release agents is particularly time-consuming and costly when manufacturing large-area fiber-reinforced plastic components, such as wind turbine blades.

[0006] The production of wind turbine blades is mostly carried out using a vacuum infusion process in molds, each representing half of a blade. The molds are coated with a liquid release agent to create a separation between the cured resin of the fiber-reinforced plastic component and the mold after the curing of the liquid curable plastic resins, usually epoxy or, less frequently, polyester resin systems.

[0007] The use of these release agents has many disadvantages. For example, there is a risk of damaging the mold due to insufficient release agent coverage. Furthermore, the surface of the fiber-reinforced plastic component requires extensive post-processing before it can be coated with paint or varnish to achieve a sufficient surface finish. In particular, irregularities must be filled with fillers (so-called...). Pore ​​filler The surface of the fiber-reinforced plastic component must then be sealed and subsequently sanded. This surface treatment is very time-consuming and expensive. Furthermore, the resulting fine dust and the release agents themselves pose a health risk to employees.

[0008] WO 2014 124945 A1 relates to a siliconized release film for the production of plastic molded parts made of fiber composites using a mold, comprising a carrier film that is vacuum-formable at room temperature and a coating that can be applied in liquid form, which, if necessary after removal of any solvents, consists of more than 90 atomic% silicon, carbon and / or oxygen, more than 45 atomic% carbon, and more than 20 atomic% silicon, in each case based on the entire coating and measured by XPS, characterized in that the coating is cross-linked by addition reactions, condensation reactions or by radiation.

[0009] US 2017 0066218 A1 and US 2019 0322075 A1 relate to multilayer release films comprising a first outer layer consisting of polymethylpentene or a fluorinated polymer, which exhibits a first adhesion affinity, and a second outer layer consisting of polymethylpentene or a fluorinated polymer and an adhesion-modifying additive. The second outer layer exhibits a second adhesion affinity that differs from that of the first outer layer. The difference in adhesion affinity between the first and second outer layers of the release film enables the film to exhibit complete release properties from a mold.

[0010] EP 0 364 956 discloses a laminate comprising (A) a layer of a 4-methyl-1-pentene polymer, (B) a layer of a polymer composition comprising (a) 40 to 49 wt.% of a statistical ethylene / α-olefin copolymer containing 30 to 95 mol.% ethylene units, (b) 0.1 to 20 wt.% of a polyolefin modified with an unsaturated carboxylic acid or its derivative, and (d) 1 to 50 wt.% of a tackifier, wherein the proportions of components (a), (b) and (d) are based on the total weight of components (a), (b) and (d), and (d) a layer of a thermoplastic resin, wherein the layers (A), (B) and (d) are laminated in the specified order.

[0011] EP 0 376 681 discloses a separating film composed of a laminate comprising: (a) an intermediate layer comprising at least one layer of a flexible polyolefin, and (b) two outer layers of crystalline polymethylpentene, one on each side of the intermediate layer.

[0012] US patent 5,123,985 concerns vacuum bags made of thermoplastic elastomer films that easily conform to the surface contour of a workpiece at low pressures without interruption. The thermoplastic elastomer film can be processed into thin films that can withstand high pressures and temperatures.

[0013] WO 00 / 59720 discloses multilayer polymethylpentene-containing release films, processes for their production, and their use in the manufacture of articles, comprising hardened fiber-reinforced epoxy, phenolic, or polyacrylate compositions that can be used as structural elements for the aerospace industry. The films exhibit improved release properties when exposed to high temperatures. The films are non-oriented and multilayered, comprising a polyamide layer, a polymethylpentene layer, and an intervening adhesive layer. The release films have a total layer thickness of preferably 15 to 30 µm and are therefore neither dimensionally stable nor thermoformable.

[0014] US 2012 / 0175043 discloses a method for applying multiple polymeric coatings to a fiber substrate, in particular a method for applying multiple polymeric coatings to fibrous substrates, without regard to chemical or physical incompatibilities of the polymeric coating materials.

[0015] WO 2013 / 160437 discloses a composite comprising (i) a plastic molded part or (ii) a plastic semi-finished product with a protective layer system, wherein the protective layer system comprises a plastic film and a plasma-polymerized organosilicon layer. WO 2013 / 160437 further relates to the use of a temporary protective film as a release aid to the mold or between the mold and the emerging plastic molded part in a plastic molding process and to a method for producing a composite comprising a plastic molded part and a temporary protective film.

[0016] US 2015 / 0266276 discloses a composite comprising (i) a plastic component or (ii) a plastic semi-finished product with a protective layer system, wherein the protective layer system comprises a plastic film and an organosilicon plasma polymer layer, wherein the organosilicon plasma polymer layer is arranged between the (i) plastic component or the (ii) plastic semi-finished product and the plastic film; and wherein, after curing of the (i) plastic component or the (ii) plastic semi-finished product, the organosilicon plasma polymer layer adheres better to the plastic film than to the (i) plastic component or the (ii) plastic semi-finished product.

[0017] WO 2017 / 068152 discloses a composite component (10) characterized by the following layer structure: a) a layer (11) consisting at least partially of polyethylene, b) a layer (12) consisting at least partially of a polyurethane and / or elastomer, c) at least one layer (13) consisting at least partially of a plastic reinforced by fibers (14) or consisting at least partially of an adhesive, wherein the layer (12) is arranged directly between the layer (11) and the layer (13), wherein the layers (11) and (12) were joined to form a laminate composite in a first step and the layer (13) was joined to the laminate composite comprising the layers (11) and (12) in a second step.

[0018] DE 10 2007 010071 A1 relates to a layered composite comprising a coating layer and a release layer, as well as a coating-carrier arrangement for coating transfer. The layered composite comprises a coating layer and a release layer, wherein (a) the coating layer consists of an uncured and / or partially cured and / or cured coating, and (b) the release layer is a plasma-polymer layer consisting of carbon, silicon, oxygen, and hydrogen, as well as optionally usual impurities. WO 2021 / 094358 A1 discloses a carrier film for coating plastic molded parts with a coating material, wherein the carrier film is an adhesion-modified layer (2) based on a mixture comprising a polyolefin and a thermoplastic elastomer, wherein the weight fraction of the thermoplastic elastomer is in the range of 1.0 wt.% to 35 wt.%, preferably 5.0 wt.% to 15 wt.%.-%, based on the total weight of the adhesion-modified layer, and a further layer (4) based on polypropylene homopolymer and polypropylene copolymer, wherein the carrier film is provided with a coating material (1) on the adhesion-modified layer and the film has a total thickness of 40 to 250 µm. Furthermore, a method is disclosed comprising the steps: (a) providing a plastic film described above; (b) deep drawing the plastic film, preferably at room temperature, optionally.by applying a vacuum; in a tool for the production of plastic molded parts; (c) contacting the coating material with a curable plastic composition; and (d) curing the plastic composition; wherein the bond strength of the coating material to the cured composition is greater than the bond strength of the coating material to the adhesion-modified layer of the plastic film, and the carrier film is separated from the coated plastic molded part, i.e., acts as a release film, and wherein fiber composites are also referred to as the plastic composition.

[0019] There is a need for release films suitable for the production of fiber-reinforced plastic components, particularly via vacuum infusion, which offer advantages over the current state of the art. These release films should eliminate the need for liquid release agents in the production of fiber-reinforced plastic components. Furthermore, the release films should be producible from carrier films available through blown film coextrusion and offer intrinsic release properties. In addition, the release films should be thermoformable and able to withstand the temperatures generated during the exothermic curing process of the plastic resin. Moreover, the release films should be able to remain on the surfaces of the cured fiber-reinforced plastic components for a certain period of time to act as a protective film, but should also be easily removable when necessary to expose the surface of the fiber-reinforced plastic components.Furthermore, the release films on the side facing away from the fiber-reinforced plastic components, i.e., the outside, should have sufficient release properties against so-called . "Tacky tapes" exhibit features which are typically used for bonding strips of release film together or for fixing (bagging) films to the mold.

[0020] This problem is solved by the subject matter of the patent claims.

[0021] It was surprisingly discovered that deep-drawable release films can be provided which, after deep drawing, perfectly replicate the shape of a fiber-reinforced plastic component like a protective skin, so that damage to the mold surface is no longer possible.

[0022] Furthermore, it was surprisingly discovered that release films can be produced which, due to their comparatively high elongation, support the deep drawing of the release film at low forces. Using the release film according to the invention results in a very smooth surface of the hardened fiber-reinforced plastic component. This significantly reduces the need for surface rework, ideally eliminating it entirely. Process cost advantages can be achieved by saving on material (release agent, filler) and labor time for applying the filler and sanding the surface. At the same time, there are advantages in terms of employee health protection, as handling the release agent is no longer necessary and employees are no longer exposed to the fine dust from sanding the surface of the hardened fiber-reinforced plastic component.

[0023] Furthermore, it was surprisingly found that deep-drawable release films can be provided which do not require a release coating based on silicone compounds and have intrinsic release properties towards the plastic resins used, whereby the release properties are achieved solely through the composition of the release film.

[0024] A further advantage of the separating film according to the invention is that it can remain on the surface of the hardened fiber-reinforced plastic component outdoors for a longer period of time, depending on the climate zone, 3-6 months, thus providing protection of the surface against environmental influences during storage.

[0025] Furthermore, it was surprisingly found that the first surface layer, which faces the mold and is based on a thermoplastic polyester elastomer, exhibits sufficient release properties relative to the mold. This allows the release film according to the invention to be repositioned when inserted into the mold. The low force absorption and the plastic deformation of the release film according to the invention, which begins even at low elongations, offer the additional advantage that the release film, in its deep-drawn state, does not exert any horizontal tensile forces on the mold. "Tacky tape" exerts an effect; leaks are thereby avoided.

[0026] Furthermore, it was surprisingly found that the time required for post-processing the fiber-reinforced plastic component can be significantly reduced by using the release film according to the invention. This reduces costs that are usually incurred by post-processing the fiber-reinforced plastic component (e.g., the space required for processing, such as halls or hall areas, maintenance costs for surface processing equipment such as grinding machines, and disposal costs for grinding waste such as dust and sandpaper).

[0027] A first aspect of the invention relates to a multilayer separating film comprising a first surface layer based on a mixture of a thermoplastic elastomer and a polyolefin, wherein in the first surface layer the weight fraction of the thermoplastic elastomer is greater than the weight fraction of the polyolefin; an adhesion promoter layer; optionally a first intermediate layer; optionally a second intermediate layer; and a second surface layer based on at least one polypropylene or propylene copolymer; the separating film has a total layer thickness in the range of 10 to 250 µm.

[0028] The first surface layer and the second surface layer flank the two outer surfaces of the separating film according to the invention. Accordingly, the first surface layer and the second surface layer are each in direct contact with a further layer of the separating film according to the invention only on one of their two sides; the opposite layer forms the outer surface of the separating film according to the invention.

[0029] When the release film according to the invention is used to produce a fiber-reinforced plastic component in a mold, the first surface layer is intended to face the mold, whereas the second surface layer comes into contact with the curable plastic resin and adheres to it in a detachable manner. In the composite of release film and fiber-reinforced plastic component, the first surface layer of the release film then forms the outside of the composite, and the second surface layer of the release film forms the inside of the composite.

[0030] The first intermediate layer and the second intermediate layer are each independently optional.

[0031] In preferred embodiments (i) the release film according to the invention consists of the first surface layer, the adhesion promoter layer and the second surface layer; (ii) the release film according to the invention comprises or consists of the first surface layer, the adhesion promoter layer, the first intermediate layer and the second surface layer; or (iii) the release film according to the invention comprises or consists of the first surface layer, the adhesion promoter layer, the first intermediate layer, the second intermediate layer and the second surface layer; preferably in the aforementioned sequence of layers.

[0032] In principle, any number of additional layers may be present besides those mentioned above. The separating film according to the invention thus has at least three layers, but can in principle also have four, five, six, seven or more layers, with a five-layer structure being preferred.

[0033] Unless explicitly stated otherwise, percentages are percentages by weight. Unless explicitly stated otherwise, standards such as EN ISO, ASTM, FINAT, etc., as valid on January 1, 2021, apply.

[0034] Unless explicitly stated otherwise, the term "based on" means that the named component constitutes the main ingredient by weight, and this component may itself be a mixture of several ingredients. The main component does not necessarily have to constitute more than 50% by weight; it simply means that no other component is present with a greater weight percentage.

[0035] The first surface layer of the separating film according to the invention is based on a mixture of a thermoplastic elastomer and a polyolefin.

[0036] It was surprisingly found that the inventive mixture of a thermoplastic elastomer and a polyolefin offers particular advantages, especially when these materials are incompatible. This is the case, for example, when the thermoplastic elastomer is a thermoplastic polyester elastomer and the polyolefin is a polyethylene, particularly LLDPE. The polyethylene then acts as an antiblocking agent in the thermoplastic polyester elastomer, producing a surface roughness advantageous for blown film coextrusion, which cannot be achieved, or can only be achieved with great difficulty, using conventional antiblocking agents such as talc masterbatch. This prevents wrinkling and sticking to the rollers during the extrusion process, leading, for example, to an improvement in blown film coextrusion.

[0037] Furthermore, it was surprisingly found that the first surface layer provides sufficient separation against the butyl-coated "tacky tapes" used to seal the mold.

[0038] Thermoplastic elastomers are known to those skilled in the art and are commercially available. At room temperature, they behave similarly to conventional, i.e., non-thermoplastic elastomers, but can be plastically deformed upon the application of heat and thus exhibit thermoplastic behavior. According to the invention, preferred thermoplastic elastomers are selected from the group consisting of thermoplastic polyamide elastomers; thermoplastic polyester elastomers (copolyester elastomers); and thermoplastic olefin-based elastomers, e.g.Polypropylene / ethylene propylene diene rubber (PP / EPDM); thermoplastic styrene block copolymers (styrene-butadiene styrene block copolymer (SBS), styrene-ethylene butylene styrene block copolymer (SEBS), styrene-ethylene propylene styrene block copolymer (SEPS), styrene-ethylene propylene styrene block copolymer (SEEPS) and methyl acrylate-butadiene styrene copolymer (MBS), styrene-isoprene styrene block copolymer (SIS), styrene-isoprene butylene copolymer (SIBS)); urethane-based thermoplastic elastomers; and thermoplastic vulcanizates or cross-linked olefin-based thermoplastic elastomers, e.g. PP / EPDM.

[0039] Preferably, the thermoplastic elastomer is a thermoplastic polyester elastomer. Thermoplastic polyester elastomers are known to those skilled in the art and are commercially available, for example under the trade names Hytrel® (DuPont), Keyflex® (LG Chem), and Skypel® (SK Chemicals).

[0040] In particularly preferred embodiments, the thermoplastic elastomer in the first surface layer has a DSC melting temperature according to ISO 11357-3. of at least 150°C; preferably at least 155°C, more preferably at least 160°C, even more preferably at least 165°C; and / or of at most 190°C; preferably at most 185°C, more preferably at most 180°C, even more preferably at most 175°C; and / or in the range of 170±24°C; preferably 170±16°C, more preferably 170±8°C.

[0041] Thermoplastic elastomers, in particular thermoplastic polyester elastomers with such properties, are known to a person skilled in the art and are commercially available, for example as Hytrel ®< G4078 NC010.

[0042] Polyolefins are known to those skilled in the art and are commercially available. Preferably, the polyolefin is selected from the group consisting of polyethylene (PE), polypropylene (PP), polymethylpentene (PMP), polyisobutylene (PIB), polybutylene (PB, polybutene-1), their copolymers and / or mixtures.

[0043] Preferred polyethylenes include low-density polyethylene (LDPE / PE-LD), linear low-density polyethylene (LLDPE / PE-LLD), high-density polyethylene (HDPE / PE-HD), with LLDPE being particularly preferred.

[0044] Preferred polypropylenes include atactic polypropylene, isotactic polypropylene, syndiotactic polypropylene, and heterophasic polypropylene. Heterophasic polypropylene is typically a copolymer of ethylene and propylene, typically polymerized using Ziegler-Natta catalysts.

[0045] Preferably, the polyolefin in the first surface layer is a polyethylene or an ethylene copolymer; preferably an LLDPE.

[0046] In particularly preferred embodiments, the polyolefin in the first surface layer has a melt flow index MFI 190°C, 2.16 kg according to ISO 1133. of at least 0.7 g / 10 min; preferably at least 0.8 g / 10 min, more preferably at least 0.9 g / 10 min, even more preferably at least 1.0 g / 10 min; and / or of at most 1.5 g / 10 min; preferably at most 1.4 g / 10 min, more preferably at most 1.3 g / 10 min, even more preferably at most 1.2 g / 10 min; and / or in the range of 1.1 ± 0.3 g / 10 min; preferably 1.1 ± 0.2 g / 10 min, more preferably 1.1 ± 0.1 g / 10 min.

[0047] In particularly preferred embodiments, the polyolefin in the first surface layer has a VICAT softening temperature according to ASTM D1525. of at least 96°C; preferably at least 98°C, more preferably at least 100°C, even more preferably at least 102°C; and / or of at most 112°C; preferably at most 110°C, more preferably at most 108°C, even more preferably at most 106°C; and / or in the range of 104±9°C; preferably 104±6°C; more preferably 104±3°C.

[0048] In particularly preferred embodiments, the polyolefin in the first surface layer has a density according to ASTM D792. of at least 0.900 g / cm³; preferably at least 0.905 g / cm³, more preferably at least 0.910 g / cm³, even more preferably at least 0.915 g / cm³; and / or of at most 0.940 g / cm³; preferably at most 0.935 g / cm³, more preferably at most 0.930 g / cm³, even more preferably at most 0.925 g / cm³; and / or in the range of 0.919 ± 0.020 g / cm³; preferably 0.919 ± 0.015 g / cm³, more preferably 0.919 ± 0.010 g / cm³, even more preferably 0.919 ± 0.005 g / cm³.

[0049] Polyolefins, especially polyethylenes or ethylene copolymers such as LLDPE with such properties, are known to a person skilled in the art and are commercially available, for example as Dowlex ®< NG 5056 G.

[0050] According to the invention, in the first surface layer the weight fraction of the thermoplastic elastomer is greater than the weight fraction of the polyolefin.

[0051] Preferably, the weight fraction of the thermoplastic elastomer in the first surface layer is in the range of 72±25 wt.%, based on the total weight of the first surface layer; preferably 72±20 wt.%, more preferably 72±15 wt.%, even more preferably 72±10 wt.%, most preferably 72±5 wt.%.

[0052] Preferably, the weight fraction of the polyolefin in the first surface layer is in the range of 10±9 wt.%, based on the total weight of the first surface layer; preferably 10±8 wt.%, more preferably 10±7 wt.%, even more preferably 10±6 wt.%, most preferably 10±5 wt.%.

[0053] The thickness of the first surface layer preferably at least 5 µm; preferably at least 6 µm, more preferably at least 7 µm, even more preferably at least 8 µm; and / or preferably at most 13 µm; preferably at most 12 µm, more preferably at most 11 µm, even more preferably at most 10 µm; and / or preferably in the range of 9±7 µm; preferably 9±5 µm, more preferably 9±3 µm.

[0054] The second surface layer of the separating film according to the invention is based on at least one polypropylene or propylene copolymer.

[0055] Preferably, the second surface layer comprises at least one polypropylene or propylene copolymer, or at least one heterophasic polypropylene.

[0056] Preferably, the weight fraction of the at least one polypropylene or propylene copolymer in the second surface layer is in the range of 88±12 wt.%, based on the total weight of the second surface layer; preferably 88±10 wt.%, more preferably 88±8 wt.%, even more preferably 88±6 wt.%, most preferably 88±4 wt.%.

[0057] In particularly preferred embodiments, the at least one polypropylene or propylene copolymer in the second surface layer is a mixture of a first heterophasic polypropylene and a second heterophasic polypropylene different from it.

[0058] It was surprisingly found that the extrusion bubble in blown film coextrusion can be stabilized when a mixture of two different heterophasic polypropylenes is used.

[0059] Preferably, the weight fraction of the first heterophasic polypropylene in the second surface layer is at most 60 wt.%, based on the total weight of the second surface layer; preferably at most 50 wt.%, more preferably at most 40 wt.%, and even more preferably at most 30 wt.%.

[0060] Preferably, the weight fraction of the first heterophasic polypropylene in the second surface layer is in the range of 20±12 wt.%, based on the total weight of the second surface layer; preferably 20±10 wt.%, more preferably 20±8 wt.%, even more preferably 20±6 wt.%, most preferably 20±4 wt.%.

[0061] Preferably, the first heterophasic polypropylene has a lower melt flow rate and / or a lower DSC melting temperature than the second heterophasic polypropylene.

[0062] In particularly preferred embodiments, the first heterophasic polypropylene has a melt flow rate MFR 230°C, 2.16 kg according to ISO 1133-1. of at least 0.2 g / 10 min; preferably at least 0.3 g / 10 min, more preferably at least 0.4 g / 10 min, even more preferably at least 0.5 g / 10 min; and / or of at most 1.0 g / 10 min; preferably at most 0.9 g / 10 min, more preferably at most 0.8 g / 10 min, even more preferably at most 0.7 g / 10 min; and / or in the range of 0.6 ± 0.3 g / 10 min; preferably 0.6 ± 0.2 g / 10 min, more preferably 0.6 ± 0.1 g / 10 min;

[0063] In particularly preferred embodiments, the first heterophasic polypropylene has a DSC melting temperature according to ISO 11357-3. of at least 125°C; preferably at least 130°C, more preferably at least 135°C, even more preferably at least 140°C; and / or of at most 165°C; preferably at most 155°C, more preferably at most 150°C, even more preferably at most 145°C; and / or in the range of 142±24°C; preferably 142±16°C, more preferably 142±8°C.

[0064] Heterophasic polypropylenes with such properties are known to a person skilled in the art and are commercially available, for example as Adflex ®< Q 100 F.

[0065] Preferably, the weight fraction of the second heterophasic polypropylene in the second surface layer is at least 30 wt.%, based on the total weight of the second surface layer; preferably at least 40 wt.%, more preferably at least 50 wt.%, and even more preferably at least 60 wt.%.

[0066] Preferably, the weight fraction of the second heterophasic polypropylene in the second surface layer is in the range of 68±12 wt.%, based on the total weight of the second surface layer; preferably 68±10 wt.%, more preferably 68±8 wt.%, even more preferably 68±6 wt.%, most preferably 68±4 wt.%.

[0067] In particularly preferred embodiments, the second heterophasic polypropylene has a melt flow rate MFR 230°C, 2.16 kg according to ISO 1133-1. of at least 0.5 g / 10 min; preferably at least 0.6 g / 10 min, more preferably at least 0.7 g / 10 min, even more preferably at least 0.8 g / 10 min; and / or of at most 1.2 g / 10 min; preferably at most 1.1 g / 10 min, more preferably at most 1.0 g / 10 min, even more preferably at most 0.9 g / 10 min; and / or in the range of 0.85 ± 0.3 g / 10 min; preferably 0.85 ± 0.2 g / 10 min, more preferably 0.85 ± 0.1 g / 10 min.

[0068] In particularly preferred embodiments, the second heterophasic polypropylene has a DSC melting temperature according to ISO 11357-3. of at least 150°C; preferably at least 155°C, more preferably at least 160°C, even more preferably at least 165°C; and / or of at most 185°C; preferably at most 180°C, more preferably at most 175°C, even more preferably at most 170°C; and / or in the range of 166±24°C; preferably 166±16°C, more preferably 166±8°C.

[0069] Heterophasic polypropylenes with such properties are known to a person skilled in the art and are commercially available, for example as Borealis ®< BA110CF.

[0070] Preferably, the thickness of the second surface layer is greater than the thickness of the first surface layer.

[0071] The thickness of the second surface layer preferably at least 6 µm; preferably at least 8 µm, more preferably at least 10 µm, even more preferably at least 12 µm; and / or preferably at most 22 µm; preferably at most 20 µm, more preferably at most 18 µm, even more preferably at most 16 µm; and / or preferably in the range of 14±12 µm; preferably 14±9 µm, more preferably 14±6 µm.

[0072] The release film according to the invention comprises an adhesion promoter layer. This adhesion promoter layer is typically based on a material that is compatible with the materials of the two layers immediately adjacent to the adhesion promoter layer. Suitable materials are known to those skilled in the art and are commercially available.

[0073] Preferably, these two layers immediately adjacent to the adhesion promoter layer are the first surface layer and either the first intermediate layer or the second surface layer.

[0074] Accordingly, the adhesion promoter layer is preferably arranged between the first surface layer and the first intermediate layer. Preferably, the adhesion promoter layer is directly adjacent to the first surface layer. Preferably, the adhesion promoter layer (with its opposite side) is directly adjacent to the first intermediate layer.

[0075] Preferably, the adhesion promoter layer is based on an ethylene-acrylate copolymer. Ethylene-acrylate copolymers suitable for the production of such adhesion promoter layers are known to those skilled in the art and are commercially available.

[0076] Surprisingly, it was found that ethylene acrylate copolymers exhibit good adhesion-promoting properties, whereas conventional adhesion promoters, e.g. based on polyethylene, polypropylene or elastomers grafted with maleic anhydride, do not show sufficient adhesion-promoting properties.

[0077] The adhesion promoter layer is preferably non-reactive, i.e., it differs from conventional reactive adhesives and other conventional adhesion promoters. This ensures that the release film according to the invention can be thermoformed, in particular deep-drawn, or cold-formed. Preferably, the adhesion promoter layer is based essentially exclusively on thermoplastic polymers.

[0078] The separating film according to the invention preferably exhibits such high bond adhesion that the layers cannot be separated under the usual measurement conditions specified for determining the bond adhesion, thus preventing delamination under stress conditions. This is ensured, among other things, by the adhesion promoter layer.

[0079] In particularly preferred embodiments, the ethylene-acrylate copolymer has a melt flow index MFI 190°C, 2.16 kg according to ISO 1133. of at least 1.6 g / 10 min; preferably at least 1.7 g / 10 min, more preferably at least 1.8 g / 10 min, even more preferably at least 1.9 g / 10 min; and / or of at most 2.4 g / 10 min; preferably at most 2.3 g / 10 min, more preferably at most 2.2 g / 10 min, even more preferably at most 2.1 g / 10 min; and / or in the range of 2.0 ± 0.3 g / 10 min; preferably 2.0 ± 0.2 g / 10 min, more preferably 2.0 ± 0.1 g / 10 min;

[0080] In particularly preferred embodiments, the ethylene acrylate copolymer has a DSC melting temperature according to ISO 11357-3. of at least 75°C; preferably at least 80°C, more preferably at least 85°C, even more preferably at least 90°C; and / or of at most 110°C; preferably at most 105°C, more preferably at most 100°C, even more preferably at most 95°C; and / or in the range of 91 ± 12°C; preferably 91 ± 8°C, more preferably 91 ± 4°C;

[0081] In particularly preferred embodiments, the ethylene-acrylate copolymer has a VICAT softening temperature according to ASTM D1525. of at least 40°C; preferably at least 42°C, more preferably at least 44°C, even more preferably at least 46°C; and / or of at most 65°C; preferably at most 60°C, more preferably at most 55°C, even more preferably at most 50°C; and / or in the range of 48±12°C; preferably 48±8°C, more preferably 48±4°C.

[0082] Ethylene acrylate copolymers with such properties are known to a person skilled in the art and are commercially available, for example as Bynel ®< 22E 780.

[0083] Preferably, the weight fraction of the ethylene-acrylate copolymer in the adhesion promoter layer is at least 75 wt.%, based on the total weight of the adhesion promoter layer; preferably at least 80 wt.%, more preferably at least 85 wt.%, even more preferably at least 90 wt.%, most preferably at least 95 wt.%.

[0084] The thickness of the adhesion promoter layer preferably at least 0.5 µm; preferably at least 1.0 µm, more preferably at least 1.5 µm, even more preferably at least 2.0 µm; and / or preferably at most 7 µm; preferably at most 6 µm, more preferably at most 5 µm, even more preferably at most 4 µm; and / or preferably in the range of 3 ± 2 µm; preferably 3 ± 1 µm.

[0085] The release film according to the invention preferably has, in addition to the first surface layer and the second surface layer as well as the adhesion promoter layer, a first intermediate layer.

[0086] If the separating film according to the invention also has a second intermediate layer, the first intermediate layer preferably has a greater thickness than the second intermediate layer.

[0087] It was surprisingly found that the first intermediate layer, possibly in combination with the second intermediate layer, improves the properties of the release film according to the invention. It was also surprisingly found that comparatively soft, deep-drawable intermediate layers with a temperature resistance >140°C are advantageous, since temperature peaks of up to 135°C can be reached during the exothermic curing of the plastic resin, e.g., epoxy resin.

[0088] In preferred embodiments, the first intermediate layer is arranged between the adhesion promoter layer and the second intermediate layer. In preferred embodiments, the first intermediate layer is directly adjacent to the adhesion promoter layer. In preferred embodiments, the first intermediate layer is directly adjacent (on its opposite side) to the second intermediate layer.

[0089] The layer thickness of the first intermediate layer preferably at least 5 µm; preferably at least 6 µm, more preferably at least 7 µm, even more preferably at least 8 µm; and / or preferably at most 16 µm; preferably at most 14 µm, more preferably at most 12 µm, even more preferably at most 10 µm; and / or preferably in the range of 9±8 µm; preferably 9±6 µm, more preferably 9±4 µm.

[0090] Preferably, the first intermediate layer is based on at least one polypropylene or propylene copolymer, preferably on at least one heterophasic polypropylene.

[0091] In particularly preferred embodiments, the first intermediate layer is based on a mixture of a third heterophasic polypropylene and a fourth heterophasic polypropylene different from it.

[0092] In preferred embodiments, the third heterophasic polypropylene in the first intermediate layer has a lower melt flow rate and / or a higher DSC melting temperature than the fourth heterophasic polypropylene.

[0093] Preferably, the weight fraction of the third heterophasic polypropylene in the first interlayer is in the range of 0 to 83.5 wt.%, based on the total weight of the first interlayer. More preferably, the weight fraction of the third heterophasic polypropylene in the first interlayer is in the range of 34 ± 12 wt.%, based on the total weight of the first interlayer; preferably 34 ± 10 wt.%, more preferably 34 ± 8 wt.%, even more preferably 34 ± 6 wt.%, and most preferably 34 ± 4 wt.%.

[0094] In a further preferred embodiment, the weight fraction of the third heterophasic polypropylene in the first intermediate layer is in the range of 58±12 wt.%, based on the total weight of the first intermediate layer; preferably 58±10 wt.%, more preferably 58±8 wt.%, even more preferably 58±6 wt.%, most preferably 58±4 wt.%.

[0095] In a further preferred embodiment, the weight fraction of the third heterophasic polypropylene in the first intermediate layer, based on the total weight of the first intermediate layer, is at least 35 wt.%, preferably at least 40 wt.%, more preferably at least 45 wt.%, even more preferably at least 50 wt.%, most preferably at least 55 wt.%; and / or at most 55 wt.%, preferably at most 50 wt.%, more preferably at most 45 wt.%, even more preferably at most 40 wt.%, most preferably at most 35 wt.%.

[0096] Preferably, the weight fraction of the fourth heterophasic polypropylene in the first interlayer is in the range of 0 to 83.5 wt.%, based on the total weight of the first interlayer. More preferably, the weight fraction of the fourth heterophasic polypropylene in the first interlayer is in the range of 48 ± 12 wt.%, based on the total weight of the first interlayer; preferably 48 ± 10 wt.%, more preferably 48 ± 8 wt.%, even more preferably 48 ± 6 wt.%, and most preferably 48 ± 4 wt.%.

[0097] In a further preferred embodiment, the weight fraction of the fourth heterophasic polypropylene in the first intermediate layer is in the range of 40±6 wt.%, based on the total weight of the first intermediate layer; preferably 40±4 wt.%, more preferably 40±2 wt.%.

[0098] In a further preferred embodiment, the weight fraction of the fourth heterophasic polypropylene in the first intermediate layer, based on the total weight of the first intermediate layer, is at least 40 wt.%, preferably at least 45 wt.%; and / or at most 50 wt.%, preferably at most 45 wt.%, more preferably at most 40 wt.%.

[0099] The separating film according to the invention preferably has, in addition to the first surface layer, the second surface layer, the adhesion promoter layer and the first intermediate layer that may be present, a second intermediate layer.

[0100] In preferred embodiments, the second intermediate layer is arranged between the first intermediate layer and the second surface layer. In preferred embodiments, the second intermediate layer is directly adjacent to the first intermediate layer. In preferred embodiments, the second intermediate layer is directly adjacent (on its opposite side) to the second surface layer.

[0101] The thickness of the second intermediate layer preferably at least 1 µm; preferably at least 2 µm, more preferably at least 3 µm, even more preferably at least 4 µm; and / or preferably at most 9 µm; preferably at most 8 µm, more preferably at most 7 µm, even more preferably at most 6 µm; and / or preferably in the range of 5±4 µm; preferably 5±3 µm, more preferably 5±2 µm.

[0102] Preferably, the second intermediate layer is based on at least one polypropylene or propylene copolymer; preferably on at least one heterophasic polypropylene.

[0103] In particularly preferred embodiments, the second intermediate layer is based on a mixture of a fifth heterophasic polypropylene and a sixth heterophasic polypropylene different from it.

[0104] In preferred embodiments, the fifth heterophasic polypropylene in the second intermediate layer has a lower melt flow rate and / or a higher DSC melting temperature than the sixth heterophasic polypropylene.

[0105] Preferably, the weight fraction of the fifth heterophasic polypropylene in the second interlayer is in the range of 0 to 83.5 wt.%, based on the total weight of the second interlayer. More preferably, the weight fraction of the fifth heterophasic polypropylene in the second interlayer is in the range of 34 ± 12 wt.%, based on the total weight of the second interlayer; preferably 34 ± 10 wt.%, more preferably 34 ± 8 wt.%, even more preferably 34 ± 6 wt.%, and most preferably 34 ± 4 wt.%.

[0106] In a further preferred embodiment, the weight fraction of the fifth heterophasic polypropylene in the second intermediate layer is in the range of 56±12 wt.%, based on the total weight of the second intermediate layer; preferably 56±10 wt.%, more preferably 56±8 wt.%, even more preferably 56±6 wt.%, most preferably 56±4 wt.%.

[0107] In a further preferred embodiment, the weight fraction of the fifth heterophasic polypropylene in the second intermediate layer, based on the total weight of the second intermediate layer, is at least 35 wt.%, preferably at least 40 wt.%, more preferably at least 45 wt.%, even more preferably at least 50 wt.%, most preferably at least 55 wt.%; and / or at most 55 wt.%, preferably at most 50 wt.%, more preferably at most 45 wt.%, even more preferably at most 40 wt.%, most preferably at most 35 wt.%.

[0108] Preferably, the weight fraction of the sixth heterophasic polypropylene in the second interlayer is in the range of 0 to 83.5 wt.%, based on the total weight of the second interlayer. More preferably, the weight fraction of the sixth heterophasic polypropylene in the second interlayer is in the range of 50 ± 12 wt.%, based on the total weight of the second interlayer; preferably 50 ± 10 wt.%, more preferably 50 ± 8 wt.%, even more preferably 50 ± 6 wt.%, and most preferably 50 ± 4 wt.%.

[0109] In a further preferred embodiment, the weight fraction of the sixth heterophasic polypropylene in the second intermediate layer is in the range of 40±8 wt.%, based on the total weight of the second intermediate layer; preferably 40±6 wt.%, more preferably 40±4 wt.%, and even more preferably 40±2 wt.%.

[0110] In a further preferred embodiment, the weight fraction of the fourth heterophasic polypropylene in the first intermediate layer, based on the total weight of the first intermediate layer, is at least 40 wt.%, preferably at least 45 wt.%, more preferably at least 50 wt.%; and / or at most 50 wt.%, preferably at most 45 wt.%, more preferably at most 40 wt.%.

[0111] In a further preferred embodiment, the release film according to the invention has, in addition to the first surface layer and the second surface layer as well as the adhesion promoter layer, a first intermediate layer and a second intermediate layer, wherein The first intermediate layer is based on a mixture of a third heterophasic polypropylene and a fourth heterophasic polypropylene different from it; the second intermediate layer is based on a mixture of a fifth heterophasic polypropylene and a sixth heterophasic polypropylene different from it; the weight fraction of the third heterophasic polypropylene in the first intermediate layer is in the range of 34 ± 12 wt.%, based on the total weight of the first intermediate layer; preferably 34 ± 10 wt.%, more preferably 34 ± 8 wt.%, even more preferably 34 ± 6 wt.%, most preferably 34 ± 4 wt.%; the weight fraction of the fourth heterophasic polypropylene in the first intermediate layer is in the range of 48 ± 6 wt.%, based on the total weight of the first intermediate layer; preferably 48 ± 4 wt.%, more preferably 48 ± 2 wt.%; the weight fraction of the fifth heterophasic polypropylene in the second intermediate layer is in the range of 34 ± 12 wt.%.-%, based on the total weight of the second interlayer; preferably 34±10 wt.%, more preferably 34±8 wt.%, even more preferably 34±6 wt.%, most preferably 34±4 wt.%; the weight fraction of the sixth heterophasic polypropylene in the second interlayer is in the range of 50±8 wt.%, based on the total weight of the second interlayer; preferably 50±6 wt.%, more preferably 50±4 wt.%, even more preferably 50±2 wt.%.

[0112] In a further preferred embodiment, the release film according to the invention has, in addition to the first surface layer and the second surface layer as well as the adhesion promoter layer, a first intermediate layer and a second intermediate layer, wherein The first intermediate layer is based on a mixture of a third heterophasic polypropylene and a fourth heterophasic polypropylene different from it; the second intermediate layer is based on a mixture of a fifth heterophasic polypropylene and a sixth heterophasic polypropylene different from it; the weight fraction of the third heterophasic polypropylene in the first intermediate layer is in the range of 58 ± 12 wt.%, based on the total weight of the first intermediate layer; preferably 58 ± 10 wt.%, more preferably 58 ± 8 wt.%, even more preferably 58 ± 6 wt.%, most preferably 58 ± 4 wt.%; the weight fraction of the fourth heterophasic polypropylene in the first intermediate layer is in the range of 40 ± 6 wt.%, based on the total weight of the first intermediate layer; preferably 40 ± 4 wt.%, more preferably 40 ± 2 wt.%; the weight fraction of the fifth heterophasic polypropylene in the second intermediate layer is in the range of 56 ± 12 wt.%.-%, based on the total weight of the second interlayer; preferably 56±10 wt.%, more preferably 56±8 wt.%, even more preferably 56±6 wt.%, most preferably 56±4 wt.%; the weight fraction of the sixth heterophasic polypropylene in the second interlayer is in the range of 40±8 wt.%, based on the total weight of the second interlayer; preferably 40±6 wt.%, more preferably 40±4 wt.%, even more preferably 40±2 wt.%.

[0113] In preferred embodiments, the third heterophasic polypropylene in the first interlayer and / or the fifth heterophasic polypropylene in the second interlayer each independently exhibit a melt flow rate MFR 230°C, 2.16 kg according to ISO 1133-1. of at least 0.2 g / 10 min; preferably at least 0.3 g / 10 min, more preferably at least 0.4 g / 10 min, even more preferably at least 0.5 g / 10 min; and / or of at most 1.0 g / 10 min; preferably at most 0.9 g / 10 min, more preferably at most 0.8 g / 10 min, even more preferably at most 0.7 g / 10 min; and / or in the range of 0.6 ± 0.3 g / 10 min; preferably 0.6 ± 0.2 g / 10 min, more preferably 0.6 ± 0.1 g / 10 min;

[0114] In preferred embodiments, the third heterophasic polypropylene in the first interlayer and / or the fifth heterophasic polypropylene in the second interlayer each independently has a DSC melting temperature according to ISO 11357-3. of at least 125°C; preferably at least 130°C, more preferably at least 135°C, even more preferably at least 140°C; and / or of at most 165°C; preferably at most 155°C, more preferably at most 150°C, even more preferably at most 145°C; and / or in the range of 142±24°C; preferably 142±16°C, more preferably 142±8°C.

[0115] Heterophasic polypropylenes with such properties are known to a person skilled in the art and are commercially available, for example as Adflex ®< Q 100 F.

[0116] In preferred embodiments, the fourth heterophasic polypropylene in the first interlayer and / or the sixth heterophasic polypropylene in the second interlayer each independently exhibit a melt flow rate MFR 230°C, 2.16 kg according to ISO 1133-1. of at least 0.4 g / 10 min; preferably at least 0.5 g / 10 min, more preferably at least 0.6 g / 10 min, even more preferably at least 0.7 g / 10 min; and / or of at most 1.3 g / 10 min; preferably at most 1.2 g / 10 min, more preferably at most 1.1 g / 1.0 min, even more preferably at most 0.9 g / 10 min; and / or in the range of 0.8 ± 0.3 g / 10 min; preferably 0.8 ± 0.2 g / 10 min, more preferably 0.8 ± 0.1 g / 10 min;

[0117] In preferred embodiments, the fourth heterophasic polypropylene in the first interlayer and / or the sixth heterophasic polypropylene in the second interlayer each independently has a DSC melting temperature according to ISO 11357-3. of at least 120°C; preferably at least 125°C, more preferably at least 130°C, even more preferably at least 135°C; and / or of at most 165°C; preferably at most 155°C, more preferably at most 150°C, even more preferably at most 145°C; and / or in the range of 140±24°C; preferably 140±16°C, more preferably 140±8°C.

[0118] Heterophasic polypropylenes with such properties are known to a person skilled in the art and are commercially available, for example as Borsoft ®< SA 233 CF.

[0119] In preferred embodiments of the separating film according to the invention, (i) the first heterophasic polypropylene in the second surface layer and the third heterophasic polypropylene in the first intermediate layer are the same; and / or (ii) the first heterophasic polypropylene in the second surface layer and the fifth heterophasic polypropylene in the second intermediate layer are the same; and / or (iii) the third heterophasic polypropylene in the first intermediate layer and the fifth heterophasic polypropylene in the second intermediate layer are the same; and / or (iv) the fourth heterophasic polypropylene in the first intermediate layer and the sixth heterophasic polypropylene in the second intermediate layer are the same.

[0120] In preferred embodiments of the separating film according to the invention, (i) the first heterophasic polypropylene in the second surface layer and the fourth heterophasic polypropylene in the first intermediate layer are different; and / or (ii) the first heterophasic polypropylene in the second surface layer and the sixth heterophasic polypropylene in the second intermediate layer are different; and / or (iii) the second heterophasic polypropylene in the second surface layer and the third heterophasic polypropylene in the first intermediate layer are different; and / or (iv) the second heterophasic polypropylene in the second surface layer and the fourth heterophasic polypropylene in the first intermediate layer are different; and / or (v) the second heterophasic polypropylene in the second surface layer and the fifth heterophasic polypropylene in the second intermediate layer are different;and / or (vi) the second heterophasic polypropylene in the second surface layer and the sixth heterophasic polypropylene in the second intermediate layer are different; and / or (vii) the third heterophasic polypropylene in the first intermediate layer and the sixth heterophasic polypropylene in the second intermediate layer are different; and / or (viii) the fourth heterophasic polypropylene in the first intermediate layer and the fifth heterophasic polypropylene in the second intermediate layer are different.

[0121] Each layer of the separating film according to the invention can independently contain additives that are conventionally used in such films. Examples of such additives are pigments, dyes, lubricants, antistatic agents, fillers, nucleating agents, plasticizers, stabilizers, UV absorbers, etc., which can be used in usual quantities according to the invention.

[0122] In preferred embodiments of the separating film according to the invention, the first intermediate layer and / or the second intermediate layer does not comprise an antistatic agent.

[0123] In preferred embodiments of the separating film according to the invention, the first intermediate layer and / or the second intermediate layer independently comprise an antistatic agent. Suitable antistatic agents are known to a person skilled in the art and are commercially available.

[0124] The weight fraction of the antistatic agent is preferably in the range of 14±13 wt.%, more preferably 14±10 wt.%, more preferably 14±7 wt.%, and most preferably 14±4 wt.%, based on the total weight of the first intermediate layer and the second intermediate layer, respectively, independently of each other.

[0125] Preferably, the antistatic agent is based on a polyether-polyamide block copolymer. Such antistatic agents are commercially available, for example, as CESA-stat. For further details, reference can be made, for example, to DE 10 2010 025 938 A1. It was surprisingly found that the addition of an antistatic agent to the first or second intermediate layer reduces dust adhesion.

[0126] In preferred embodiments of the separating film according to the invention, neither the first surface layer nor the second surface layer contains silicon compounds.

[0127] Preferably, the separating film according to the invention is planar, in particular not embossed.

[0128] The separating film according to the invention is preferably not oriented.

[0129] The separating film according to the invention typically has a machine direction (MD) and a transverse direction (CD). These terms are known to those skilled in the art. The "machine direction" is typically the direction in which a film is transported during the production process, while the "transverse direction" is typically at an angle of 90° to the "machine direction".

[0130] The separating film according to the invention is preferably thermoplastic as such, i.e. it is preferably composed essentially entirely of thermoplastic polymers (and optionally additives), i.e. preferably does not contain thermosets, reactive adhesives, etc.

[0131] The separating film according to the invention is preferably thermoformable, preferably deep-drawable.

[0132] The term "deep-drawable" is known to those skilled in the art. For descriptive purposes, "deep-drawable" preferably means, as defined in the invention. a tensile strength of preferably at least 10 N, or at least 12 N, or at least 14 N, or at least 16 N, or at least 18 N, or at least 20 N, or at least 22 N, or at least 24 N, or at least 26 N, or at least 28 N, or at least 30 N; preferably in the machine direction (MD); or in the transverse direction (CD); or in both the machine direction and transverse direction (MD and CD); and / or a modulus of elasticity of preferably at least 350 MPa, or at least 370 MPa, or at least 390 MPa, or at least 410 MPa, or at least 430 MPa, or at least 450 MPa, or at least 470 MPa; preferably in both the machine direction (MD); or in the transverse direction (CD); or in both the machine direction and transverse direction (MD and CD);and / or an elongation at break of preferably at least 350%, or at least 375%, or at least 400%, or at least 425%, or at least 450%, or at least 475%, or at least 500%, or at least 525%, or at least 550%, or at least 575%, or at least 600%, or at least 625%, or at least 650%, or at least 675%, or at least 700%, or at least 725%, or at least 750%; preferably in the machine direction (MD); or in the transverse direction (CD); or in both the machine direction and the transverse direction (MD and CD); and / or a tensile force at 25% elongation of preferably less than 15 N, or less than 14 N, or less than 13 N, or less than 12 N, or less than 11 N, or less than 10 N, or less than 9 N, or less than 8 N, or less than 7 N, or less than 6 N, or less than 5 N; preferably in the machine direction (MD); or in the transverse direction (CD); or in both the machine direction and transverse direction (MD and CD); ; Each measured according to DIN EN ISO 527 on a 15 mm wide specimen with a clamping length of 100.00 mm, a pre-force of 100 mN and a test speed of 500 mm / min.

[0133] The separating film according to the invention is preferably cold-formable. The term "cold-formable" preferably refers to formability at room temperature (23°C).

[0134] The separating film according to the invention is preferably vacuum-tight. For the purposes of this description, "vacuum-tight" in the sense of the invention preferably means that a negative pressure created within a sealed casing made of the separating film is maintained for a sufficient period of time, optionally with continuous air extraction, so that a molded part can be produced from a semi-finished product located in the inner space under negative pressure (vacuum). If the production of the molded part according to the invention includes, for example, the curing of a plastic material in a vacuum and optionally with the application of heat, the vacuum tightness of the separating film according to the invention is sufficient to maintain the negative pressure in the inner space until the plastic material is at least partially, preferably completely, cured, optionally with continuous air extraction.

[0135] Preferably, the air permeability of the separating film according to the invention, as specified in ISO 15105-1:2007, is at most 2200 cm³ < mm / m² < Tag bar, more preferably at most 2100 cm³ < mm / m² < Tag bar, even more preferably at most 2000 cm³ < mm / m² < Tag bar, most preferably at most 1900 cm³ < mm / m² < Tag bar, and particularly at most 1800 cm³ < mm / m² < Tag bar. Preferably, the oxygen permeability and / or the nitrogen permeability are also within the aforementioned ranges.

[0136] Preferably, the separating film according to the invention has a total layer thickness in the range of 40±30 µm; preferably 40±25 µm, more preferably 40±20 µm, even more preferably 40±15 µm, even more preferably 40±10 µm, most preferably 40±5 µm.

[0137] Suitable methods for determining the total thickness of release films, as well as for determining the thickness of individual layers within the release film, are known to those skilled in the art. According to the invention, the determination is preferably carried out microscopically on a microtome section, with the measured value being given as the mean of a total of 10 measurements.

[0138] In preferred embodiments, the separating film according to the invention is transparent. The term "transparent" within the meaning of the invention means that a fiber-reinforced plastic semi-finished product can be viewed through the separating film according to the invention with the naked eye. The transparency is preferably quantified using densitometers. Such methods are familiar to those skilled in the art. Preferably, the turbidity can be measured as an optical value as a measure of the transparency. The turbidity is preferably measured according to ASTM test standard D 1003-61 m, Procedure A, after calibration of the measuring instrument with turbidity standards between 0.3 and 34% turbidity. For example, a hazemeter from Byk-Gardner with an integrating sphere is suitable as a measuring instrument, which allows an integrated measurement of diffuse light transmittances within a solid angle of 8° to 160°.The separating films according to the invention preferably have a haze of less than 100%, more preferably less than 96%, even more preferably less than 92%, most preferably less than 88% and in particular less than 84%, as determined by the method described above; and / or a transparency of more than 45%, more preferably more than 50%, more preferably more than 55%, even more preferably more than 60%, most preferably more than 65%; and / or a clarity of more than 8%, more preferably more than 10%, more preferably more than 12%, even more preferably more than 14%, most preferably more than 16%.

[0139] In other preferred embodiments, the separating film according to the invention is opaque.

[0140] The separating film according to the invention can be produced by conventional methods that are useful for producing multilayer films, preferably extrusion methods, in particular blown film coextrusion or cast film extrusion, with blown film coextrusion being particularly preferred.

[0141] Another aspect of the invention relates to a method for producing a fiber-reinforced plastic component from a curable fiber-reinforced plastic semi-finished product, comprising the steps of: (a) Providing a mold for producing a fiber-reinforced plastic component, wherein the mold has a design that corresponds, at least in one section, to the design of the fiber-reinforced plastic component to be produced with the mold; (b) Inserting the release film according to the invention, as described above, into the mold, wherein the release film lines the mold, at least in the section that corresponds to the design of the fiber-reinforced plastic component to be produced with the mold; and wherein the first surface layer of the release film faces the mold; (c) Optionally, deep drawing the release film; (d) Inserting the curable fiber-reinforced plastic semi-finished product into the mold, wherein the second surface layer of the release film faces the curable fiber-reinforced plastic semi-finished product; (e) Optionally, closing and / or evacuating the mold; (f) Heating the mold to a temperature at which the curable fiber-reinforced plastic semi-finished product cures; optionally,under pressure; (g) if necessary, cooling of the cured fiber-reinforced plastic component; (h) if necessary, removal of the cured fiber-reinforced plastic component together with the release film adhering to it from the mold; and (i) if necessary, peeling the release film from the cured fiber-reinforced plastic component.

[0142] In the production of the fiber-reinforced plastic component, the fiber-reinforced plastic semi-finished product, impregnated with the plastic resin to be cured, preferably a curable epoxy resin, is placed in the mold in step (d) and sealed vacuum-tight in step (e). By applying a vacuum, the release film according to the invention is compressed, thereby compacting the fiber material. While maintaining the vacuum, the mold with the formed laminate is heated in an autoclave to the curing temperature of the plastic resin to be cured and held there for the entire curing time, usually several hours.

[0143] Besides the autoclave method, curing can also be carried out using pressure or under atmospheric pressure (i.e., oven curing). Furthermore, curing can also be achieved by exposure to microwave radiation.

[0144] After the curing time and cooling in step (g), the fiber composite plastic component is removed from the mold in step (h) and packaged, if possible excluding exposure to moisture, until final application.

[0145] Preferably, the fiber-reinforced plastic component contains another material selected from balsa wood, technical foams, glass fleece, carbon fibers, glass fibers, and combinations thereof.

[0146] Preferably, the fiber-reinforced plastic semi-finished product contains a curable epoxy resin or a curable polyester resin; preferably a curable epoxy resin.

[0147] The fiber-reinforced plastic component is preferably intended for a means of transport, preferably for an aircraft, a spacecraft, a train or a motor vehicle, or for a wind turbine, preferably for a rotor blade.

[0148] Another aspect of the invention relates to a fiber-reinforced plastic component, on the outer surface of which the release film according to the invention, described above, adheres at least in a partial area and can be removed, preferably without leaving any residue, wherein the second surface layer of the release film faces the fiber-reinforced plastic component.

[0149] The fiber-reinforced plastic component is preferably intended for a means of transport, preferably for an aircraft, a spacecraft, a train or a motor vehicle, or for a wind turbine, preferably for a rotor blade.

[0150] Another aspect of the invention relates to the use of the separating film according to the invention, described above, as a separating film, preferably for the production of a fiber composite plastic component, particularly preferably in the method according to the invention, described above.

[0151] Figure 1 shows a separation film (1) according to the invention in cross-section with a schematic, preferred layer structure consisting of a first surface layer (2), adhesion promoter layer (3), first intermediate layer (4), second intermediate layer (5) and second surface layer (6).

[0152] Figure 2Figure 1 schematically shows how the release film (1) according to the invention is inserted into a mold (7) for the production of a fiber-reinforced plastic component, wherein the first surface layer (2) of the release film (1) faces the mold (7). A person skilled in the art will recognize that the release film (1) according to the invention does not typically have such pronounced rigidity that it completely seals the mold (7) as shown. Rather, the release film (1) according to the invention typically exhibits a certain degree of flexibility, so that it already adapts to the shape of the mold (7) to some extent without requiring any special measures. However, according to the invention, a precise fit of the release film (1) to the mold (7) is preferably achieved only by deep drawing, for example, after applying a vacuum between the mold (7) and the release film (1).

[0153] Figure 3Figure 1 schematically shows how the separating film (1) according to the invention can be used to produce a fiber composite plastic component from a curable fiber composite plastic semi-finished product (8). Figure 3A corresponds to the order according to Figure 2 , i.e., before the deep drawing of the release film. Figure 3B shows the deep-drawn separating film (1) in the form (7). Figure 3C shows how the curable fiber composite semi-finished product (8) is applied to the release film (1), wherein the second surface side of the release film (1) faces the curable fiber composite semi-finished product (8). 3D illustration shows how the cured fiber composite semi-finished product, together with the release film (1) adhering to it, is removed from the mold (7). Figure 3E shows how the release film (1) can be removed from the cured fiber composite semi-finished product. Figure 3E Finally, the finished, cured fiber-reinforced plastic semi-finished product with exposed surface is shown.

[0154] Reference symbol list: (1) Release film (2) First surface layer (3) Adhesion promoter layer (4) First intermediate layer (5) Second intermediate layer (6) Second surface layer (7) Mold for manufacturing a fiber-reinforced plastic component (8) Curable fiber-reinforced plastic semi-finished product

[0155] The following examples serve to illustrate the invention, but are not to be interpreted restrictively: Examples 1 - 3:

[0156] Three separating films with the following structure and composition were produced: Example 1 2 3 layer Polymer / Additive Trade name % µm % µm % µm first surface layer thermoplastic elastomer Hytrel® < G4078 NC010 72 9 72 9 72 14 Polyolefin Dowlex® < NG 5056 G 10 10 10 Additive mixture 18 18 18 Liability mediator layer Ethylene acrylate copolymer Bynel ®< 22E 780 98 3 98 3 98 3 Additive mixture 2 2 2 first intermediate shift 3. hetero PP Adflex® < Q100F 34 9 58 9 58 9 4. hetero PP Borsoft ®< SA 233 CF 48 40 40 Antistatic agent CESA® < stat 14 - - Additive mixture 4 2 2 second intermediate shift 5. hetero PP Adflex® < Q100F 34 5 56 5 56 5 6. hetero PP Borsoft ®< SA 233 CF 50 40 40 Antistatic agent CESA® < stat 14 - - Additive mixture 2 4 4 second surface layer 1. hetero PP Adflex® < Q 100 F 20 14 20 14 20 14 2. hetero PP Borealis ®< BA110CF 68 68 68 Additive mixture 12 12 12 All percentages are given as weight %.

[0157] The films according to Examples 1 and 2 showed no curling and lay flat. The mechanical properties of these two films were investigated in more detail. The following tables show the measurement results of the mechanical testing of the release films (Examples 1 and 2), each measured in the machine direction (MD) and transverse direction (CD), determined according to DIN EN ISO 527 on a 15 mm wide specimen; clamping length: 100.00 mm, preload: 100 mN, test speed: 500 mm / min: measurement results for modulus of elasticity, elongation at break, tensile strength, tensile strength, and thickness. Example E-modulus [MPa] Elongation at break [%] Tear strength [N] Tensile strength [MPa] Thickness [µm] Example 1 (MD) 411,9 ± 26,6 550,9 ± 32,9 29,6 ± 1,3 46 ± 1,8 43 ± 0,9 Example 1 (CD) 461,8 ± 16,3 737,5 ± 51,1 20,1 ± 1,5 31,3 ± 2,7 43 ± 1,4 Example 2 (MD) 400,1 ± 36,8 431,0 ± 15,3 21,4 ± 0,8 42,6 ± 3,0 33,7 ± 1,2 Example 2 (CD) 373,0 ± 20,3 645 ± 2,5 13,6 ± 0,6 26,7 ± 2,3 34,1 ± 1,7 Measurement results for tensile force and elongation Example F 1% [N] F 2.5% [N] F 5% [N] F 10% [N] F 25% [N] Example 1 (MD) 2,8 ± 0,2 5,9 ± 0,1 7,7 ± 0,1 9,5 ± 0,2 11,5 ± 0,3 Example 1 (CD) 3,5 ± 0,0 6,2 ± 0,0 7,7 ± 0,0 8,9 ± 0,1 9,3 ± 0,1 Example 2 (MD) 2,5 ± 0,1 4,5 ± 0,3 6,1 ± 0,4 7,9 ± 0,5 10,3 ± 0,6 Example 2 (CD) 2,4 ± 0,2 4,4 ± 0,2 5,7 ± 0,3 6,8 ± 0,3 7,2 ± 0,3

[0158] Additionally, the air permeability of the films was measured according to Example 1 and Example 2. The measurement was carried out according to ISO 15105-1 (2007-10) at 23°C with air. The relative humidity was 0%. The smooth side of the separating film was always facing the test gas (air). The measurement results are summarized in the following table: Measurement results for air permeability Example Measurement 1 Measurement 2 Test piece thickness measurement 1 [µm] Test piece thickness measurement 2 [µm] [cm3 mm / m 2< day bar] mean min max mean min max Example 1 1900 1700 42 40 44 42 39 43 Example 2 1800 1800 46 44 48 44 40 48

[0159] Furthermore, the transparency of the films according to Example 1 and Example 2 was also measured. The measurements were performed according to ISO and ASTM standards. The measurement results are summarized in the table below. Measurement results for turbidity [%] Haze Gard (according to ISO) Haze Gard (according to ASTM) transparency turbidity ( haze ) transparency turbidity ( haze ) Clarity ( clarity ) Example 1 64,7 86,6 66,5 94,1 13,0 Example 2 47,9 93,0 50,4 100,0 10,8

Claims

1. A multilayer release film (1) comprising - a first surface layer (2) based on a mixture of a thermoplastic elastomer and a polyolefin; wherein the weight proportion of the thermoplastic elastomer is greater than the weight proportion of the polyolefin; - an adhesive layer (3); - optionally, a first intermediate layer (4); - optionally, a second intermediate layer (5); and - a second surface layer (6) based on at least one polypropylene or propylene copolymer; wherein the release film (1) has a total layer thickness in the range of 10 to 250 µm.

2. The release film (1) according to claim 1, wherein the thermoplastic elastomer in the first surface layer (2) is a thermoplastic polyester elastomer.

3. The release film (1) according to claim 1 or 2, wherein the thermoplastic elastomer in the first surface layer (2) has a DSC melting temperature according to ISO 11357-3 of at least 150°C; preferably at least 155°C, more preferably at least 160°C, even more preferably at least 165°C.

4. The release film (1) according to one of the preceding claims, wherein the polyolefin in the first surface layer (2) is a polyethylene or an ethylene copolymer; preferably an LLDPE.

5. The release film (1) according to one of the preceding claims, wherein the at least one polypropylene or propylene copolymer in the second surface layer (6) is at least one heterophasic polypropylene.

6. The release film (1) according to one of the preceding claims, wherein the at least one polypropylene or propylene copolymer in the second surface layer (6) is a mixture of a first heterophasic polypropylene and a second heterophasic polypropylene different therefrom.

7. The release film (1) according to one of the preceding claims, which is thermoformable, preferably deep-drawable.

8. The release film (1) according to one of the preceding claims, which is cold-formable.

9. Use of the release film (1) according to one of the preceding claims as a release film.

10. The use according to claim 9, for the production of a fiber-reinforced plastic component from a curable fiber-reinforced plastic semi-finished product (8).

11. A method for producing a fiber-reinforced plastic component from a curable fiber-reinforced plastic semi-finished product (8), comprising the steps: (a) providing a mold (7) for manufacturing a fiber-reinforced plastic component, wherein the mold (7) has a configuration that corresponds at least in one section to the configuration of the fiber-reinforced plastic component to be manufactured with the mold (7); (b) inserting a release film (1) according to one of claims 1 to 8 into the mold (7), wherein the release film (1) lines the mold (7) at least in the section which corresponds to the configuration of the fiber-reinforced plastic component to be produced with the mold (7); and wherein the first surface layer (2) of the release film (1) faces the mold (7); (c) optionally, deep drawing of the release film (1); (d) inserting the curable fiber-reinforced plastic semi-finished product (8) into the mold (7), wherein the second surface layer (6) of the release film (1) faces the curable fiber-reinforced plastic semi-finished product (8); (e) optionally, sealing and / or evacuating the mold (7); optionally, deep drawing the release film (i); (f) heating the mold (7) to a temperature at which the curable fiber-reinforced plastic semi-finished product (8) cures; optionally, under pressure; (g) optionally, cooling the cured fiber-reinforced plastic component; (h) optionally, removing the cured fiber-reinforced plastic component together with the release film (1) adhering to it from the mold (7); and (i) optionally, removing the release film (1) from the cured fiber-reinforced plastic component.

12. The method according to claim 11, wherein the fiber-reinforced plastic component contains a further material selected from balsa wood, engineering foams, glass fleece, carbon fibers, glass fibers, and combinations thereof.

13. The method according to one of claims 11 or 12, wherein the fiber-reinforced plastic component is intended for a means of transport, preferably for an aircraft, a spacecraft, a train, or a motor vehicle, or is intended for a wind turbine, preferably for a rotor blade.

14. The method according to one of claims 11 to 13, wherein the curable fiber-reinforced plastic semi-finished product contains a curable epoxy resin or a curable polyester resin; preferably a curable epoxy resin.

15. A fiber-reinforced plastic component, on whose outer surface, at least in a partial area, a release film (1) according to one of claims 1 to 8 adheres and can be removed therefrom, wherein the second surface layer (6) of the release film (1) faces the fiber-reinforced plastic component.