Composite film for permanently equipping molds with a separating layer

Abstract

The invention relates to a composite film for simplifying the separation of a plastic body produced in a molding method from the mold, comprising a) a support film which is made of plastic and which can be vacuum-formed and b) a hot melt adhesive layer on one face of the support film, wherein the hot melt adhesive has a surface tackiness of <_ 2 N, preferably <_ 1 N, at 25°C, preferably even at 40°C, and the composite film face opposite the hot melt adhesive layer has a surface energy of <_ 30 mN / m, preferably <_ 28 mN / m, more preferably ≤ 26 mN / m, even more preferably ≤ 25 mN / m, and particularly preferably ≤ 24 mN / m. In a preferred embodiment, the hot melt adhesive is an adhesive based on a thermoplastic elastomer, such as a thermoplastic polyurethane or a thermoplastic polyester elastomer for example.

Description

[0001] Composite film for the permanent provision of moulds with a release layer

[0002] The present invention relates to a composite film for facilitating the separation of a plastic body produced in the primary forming process from the mold, comprising a) a vacuum-stretchable carrier film made of plastic and b) a hot melt adhesive layer on one side of the carrier film, wherein the hot melt adhesive has a surface tack of < 2 N at 25 °C and a surface energy of < 30 mN / m on the side of the composite film opposite the hot melt adhesive layer.

[0003] The invention further relates to an arrangement comprising a mold for a primary forming process and / or a composite film according to the invention vacuum-stretched therein, wherein the composite film a) is not fixed to the mold by means of the hot melt adhesive or b) is fixed to the mold by means of the hot melt adhesive. The invention also relates to the use of a hot melt adhesive for fixing and / or detaching, as needed, a vacuum-stretchable carrier film to facilitate the separation of a plastic body produced in the primary forming process from the mold, as well as to the use of a composite film according to the invention to facilitate the removal of a plastic body formed in the primary forming process from the mold. In this respect, the invention also includes the aspect of removing a used carrier film.

[0004] Furthermore, the invention relates to a method for producing a composite film according to the invention and to a method for producing an arrangement according to the invention.

[0005] State of the art

[0006] The use of release agents, which are applied in liquid or pasty form, is common practice in the production of plastic components made of reactive resins (e.g., for thermosets, elastomers, or fiber-reinforced plastics). All of these systems contain solvents, even those based on water.

[0007] Disadvantages of this procedure are the solvent emission, the time-consuming and labor-intensive separation of the mold, the risk of (local) failure of the release effect with the consequence of very high effort during demolding and possible damage to the component and mold, the mold occupancy time due to separation and evaporation, the cleaning effort for the mold and component due to cohesive failure within the release agent, the risk of exposing fibers if the component is cleaned too abrasively by grinding and the additional rework of the ground surface due to exposed pores, which are usually filled with filler, which then has to be sanded smooth.

[0008] In addition, plasma polymer release layers can be applied directly to the mold surface (cf. e.g. DE 10 2017 131 085 A1; DE 10 2013 219 331 B3). The advantages of this procedure are: no solvent emissions prior to production of the plastic components; during demolding, clean components are obtained due to adhesion failure on the release layer, from which no release agent residues need to be removed (e.g. by grinding); the release layer surface does not need to be cleaned as frequently, ideally not at all, of the mold structure (release agent and resin residues). Furthermore, the application of the plasma polymer release layers in a low-pressure (LP) plasma system is almost emission-free. A disadvantage of plasma polymer release layers is that coating the molds in LP plasma is complex, as the molds must be coated in an LP plasma reactor. This is not feasible for large / heavy molds.

[0009] Coating the molds in atmospheric pressure (AP) plasma is also complex; moreover, the AP plasma layers are not as durable as the LP plasma layers.

[0010] In some cases, fluoropolymer-based release films are bonded to the mold surface using pressure-sensitive adhesives (e.g., Tooltec® from Airtech). The advantages of this approach include no solvent emissions prior to the production of the plastic components, safe demolding, and clean mold surfaces.

[0011] Disadvantages of this procedure are: Complex application of the release film by draping a sticky film with low stretchability, and also a transfer of fluoropolymer residues to the component, so that the component still has to be cleaned before painting or gluing.

[0012] In some cases, fluoropolymer-based release films are applied to the mold surface as a single-use release film. The advantages of this approach include: no solvent emissions prior to the production of the plastic components, safe demolding, and clean mold surfaces, as long as the film is not damaged or resin penetrates between two release film sections.

[0013] Disadvantages of this approach include: high resource consumption (1. polymer film, which is not reusable or materially recyclable due to residues of matrix and vacuum sealing tape (tacky tape), among other things; 2. the so-called tacky tape), high material costs, and high application effort for each component. Furthermore, fluoropolymer residues are transferred to the component, so it still needs to be cleaned before painting or bonding.

[0014] In addition, stretchable polymer films with plasma-polymer release layers (see, for example, EP 2 841 269 B1) can be applied to the mold surface. The advantages of this approach are: no solvent emissions prior to the production of the plastic components, reliable demolding, and clean mold surfaces as long as the film is not damaged. Clean components are obtained from which no release agent residues need to be removed, and the adhesion between the plasma-polymer release layer and the matrix resin can be adjusted so that the polymer film can initially remain on the component after demolding as protection against contamination such as dust.

[0015] Disadvantages of this approach are: high resource consumption (1. polymer film, which is not reusable or materially recyclable due to residues of matrix and tacky tape, 2. the tacky tape), high material costs and high application effort for each component.

[0016] Against this background of the prior art, the object of the present invention was to provide a means that offers as many of the above-mentioned advantages as possible while simultaneously minimizing the aforementioned disadvantages. In particular, the means to be provided by the invention should ensure long-term and reliable release of plastic components from the mold. Preferably, molds with three-dimensionally irregular (complicated) surfaces should also be usable, and the introduction of the release agent into the mold should be reliable and as uncomplicated as possible.

[0017] According to the invention, this object is achieved by a composite film for facilitating the separation of a plastic body produced in the primary forming process from the mold, comprising a) a vacuum-stretchable carrier film made of plastic and b) a hot melt adhesive layer on one side of the carrier film, wherein the hot melt adhesive has a surface tack of < 2 N, preferably < 1 N, at 25 °C and preferably also at 40 °C and a surface energy of < 30 mN / m, preferably < 28 mN / m, more preferably < 26 mN / m, even more preferably < 25 mN / m and particularly preferably < 24 mN / m on the side of the composite film opposite the hot melt adhesive layer.

[0018] A primary forming process, as defined in this text, is a process in which a solid is formed from a formless mass, e.g., a viscous mass, a fiber structure impregnated with reactive resins, a powder arrangement, or a liquid. The primary forming process preferably takes place in the liquid, plastic, pasty, powder, or fibrous state. However, semi-finished products such as prepregs can also be used. Preferred primary forming processes, as defined in this text, are resin infusion processes, resin injection processes (particularly preferred is resin transfer molding (RTM)), compression molding, autoclave processes, foaming processes, reaction injection molding (RIM), and hand lay-up.

[0019] A vacuum stretch-formable "film" in the sense of this text means that for a 10% elongation at a test speed of 50 mm / min there is an elongation force of less than 25 N, preferably less than 20 N, more preferably less than 15 N and particularly preferably less than 10 N for a test specimen type 5 according to DIN EN ISO 527-3 (measured according to DIN EN ISO 527 at 23 °C) and in addition there is preferably an elongation at break of at least 120%.

[0020] In case of doubt, the elongation at break within the meaning of this text is measured according to DIN EN ISO 527-1 and 527-3.

[0021] "A hot melt adhesive, as defined in this text, is a thermoplastic polymer (preferably a thermoplastic elastomer) that is solid at room temperature (25 °C) and can be liquefied by heating for bonding purposes and can cure by cooling the molten material while simultaneously building up cohesive and adhesive forces. Preferred hot melt adhesives, as defined in this text, are also referred to as heat seal adhesives.

[0022] In case of doubt, the surface tackiness within the meaning of this text is measured as described in measurement example 2 (based on DIN EN 1719).

[0023] The determination of the surface energy of a solid and the polar component of the surface energy is measured as described in Example 1.

[0024] The present invention enables a release-assisting carrier film to be introduced into a mold by (vacuum) stretch forming or to be placed around a mold (male mold) in a surprisingly reliable manner, and, with the appropriate procedure, to ensure reliable fixation of the carrier film to the mold. In particular, it could not have been predicted that after (vacuum) stretch forming, the hot melt adhesive would still have sufficient distribution to fix the composite film to the mold, especially when the vacuum created for vacuum stretch forming is no longer present. Furthermore, it has been found that a hot melt adhesive as defined above is particularly well suited for (vacuum) stretch forming because, despite the mechanical stresses associated with this process, it retains sufficient lubricity relative to the mold and thus does not hinder the process.

[0025] Furthermore, it has surprisingly been found that the composite film according to the invention can be excellently vacuum-stretched into a female mold as well as stretched over a male mold. It may be preferable to evacuate the space beneath the composite film even in the male mold. Naturally, in both variants, the side of the carrier film coated with the hot-melt adhesive layer faces the mold surface.

[0026] By heating the composite film according to the invention at least to the beginning of the softening range, preferably at least to the average softening temperature of the hot melt adhesive, the composite film according to the invention can be fixed to the mold surface. At the latest after subsequent cooling, when the hot melt adhesive has cured, evacuation of any space beneath the composite film is no longer necessary. Ideally, however, the film according to the invention will be able to be fixed to the mold surface in a completely contour-mimicking manner.

[0027] Since fluorine compounds are not without problems, among other things for the reasons mentioned above, it is preferred according to the invention that the composite film according to the invention does not comprise fluorine.

[0028] A composite film according to the invention is preferred, wherein the hot melt adhesive is an adhesive based on a thermoplastic elastomer, more preferably based on a thermoplastic polyurethane or a thermoplastic polyester elastomer.

[0029] These materials have proven particularly suitable for a hot melt adhesive used according to the invention. For the purposes of this text, "based" on a substance or class of substances means that this substance or class of substances constitutes the predominant portion of any mixture present.

[0030] According to the invention, a composite film according to the invention is preferred, wherein the softening range of the hot melt adhesive begins at a temperature of > 40 °C, particularly preferably above > 50 °C, more preferably > 60 °C, > 70 °C, > 80 °C and most preferably > 90 °C. In case of doubt, the values ​​for the softening range within the meaning of this application are determined using a Kofler heating bench. In this case, (film) pieces ((Fi Im) samples) of the plastic to be tested or the hot melt adhesive to be tested (optionally also together) with a base area of ​​at least 1 mm 2placed on a Kofler heating bench. In case of doubt, the exact area specified is used. After these pieces have been placed on the Kofler heating bench for 60 seconds, a scalpel is used to determine at which position on the heating bench the plastic specimen can be plastically deformed without the application of a large lateral force. The position on the Kofler heating bench is then correlated with the temperature. The maximum and minimum values ​​determined on the test pieces indicate the upper and lower ends of the softening range.

[0031] The onset of the softening range at a relatively high temperature is advantageous for the intended use of the composite film according to the invention. Since elevated temperatures may occur or be desired during (vacuum) stretch forming, it is advantageous if the hot melt adhesive does not yet begin to soften at the temperatures then encountered. This ensures that surface tackiness does not increase, or does not increase excessively. Furthermore, an elevated temperature at the interface between the composite film according to the invention and the nascent plastic body can also be tolerated during subsequent primary forming (see also below).

[0032] In other words, the skilled person will preferably select a hot-melt adhesive that exhibits high cohesive strength in the range of the (later) process temperature. In principle, the skilled person will—depending on the plastic used for the subsequent primary forming process—select all materials of the composite film according to the invention such that the region of lowest adhesive strength exists between the side of the composite film according to the invention facing away from the hot-melt adhesive layer and the plastic body produced in the primary forming process (at the latest after cooling).This also means that the cohesion of the individual components of the composite film according to the invention, as well as the adhesion at the boundary layers, including the adhesion to the mold, must be adjusted so that, when force is applied to the composite of mold, composite film according to the invention, and plastic body, a separation occurs between the plastic body and the composite film according to the invention. Of course, it is also advisable to take measures to ensure that the composite film according to the invention maintains sufficient adhesion to itself and to the mold even during the actual primary forming process.

[0033] For this purpose, a composite film according to the invention is preferred, wherein the softening range of the carrier film begins > 20 °C, preferably > 30 °C, more preferably > 40 °C above the softening range of the hot melt adhesive.

[0034] Due to these preferred distances between the beginning of the softening range of the carrier film and the hot melt adhesive, it is possible to soften and thus activate the hot melt adhesive after (vacuum) stretch forming without subjecting the carrier film to further deformation.

[0035] To achieve the surface energy intended according to the invention on the side of the carrier film opposite the hot-melt adhesive layer, a multitude of options are available to the person skilled in the art. Firstly, the material selection for the carrier film is of course important, but in many cases it is preferable to implement further surface-modifying measures, such as an additional coating. Such additional layers are, of course, also encompassed by the composite film within the meaning of the present invention.

[0036] In this sense, a composite film according to the invention is preferred, wherein a silicon-containing, preferably an organosilicon, particularly preferably a plasma-polymer organosilicon coating is present on the side of the carrier film opposite the hot-melt adhesive layer.

[0037] Silicon-containing, in particular organosilicon layers, have the advantage that they can be excellently adjusted with regard to their degree of crosslinking and their surface properties, in particular with regard to their surface energies, so that they can develop an optimal release effect with high cohesive strength, in particular when they are matched by the person skilled in the art with regard to their surface properties to the plastic material which is to be formed into a plastic body in the primary forming process when the composite film according to the invention is later used.

[0038] In addition, organosilicon layers - if the layers are suitably designed, in particular in the form of plasma-polymer organosilicon layers - are stretchable together with the carrier film, so that premature detachment can be avoided even under tensile stress, in particular during vacuum stretch forming.

[0039] A plasma polymer silicon-organic layer is one that has been deposited using a PE-CVD process.

[0040] Plasma polymer silicon-organic layers also have the advantage—with a suitable coating design—of excellent adhesion to the carrier film through chemical bonding, allowing them to form cracks at a distance of less than 10 pm, even under very high tensile stress, without detaching from the carrier film. The desired release effect is largely retained. Furthermore, such layer systems are well cross-linked within themselves, thus possessing high cohesive strength.

[0041] Preferred within the meaning of the present invention is a composite film according to the invention, wherein on the side of the composite film opposite the hot melt adhesive layer there is a polar component of the surface energy of < 4.0 mN / m, preferably < 3.0 mN / m, more preferably < 2.0 mN / m and particularly preferably < 1.5 mN / m.

[0042] The polar component of the surface energy is a particularly useful parameter for setting a suitable release effect for a wide range of plastics.

[0043] Part of the invention is also an arrangement comprising a mold for a primary forming process and a composite film according to the invention stretch-drawn therein or therearound, wherein the composite film a) is not fixed to the mold by means of the hot-melt adhesive or b) is fixed to the mold by means of the hot-melt adhesive.

[0044] A mold for a primary forming process can be any suitable material capable of forming a plastic body to be molded using the primary forming process. The molds can be designed as either a female mold, meaning they have a recess, or a male mold, meaning they create a recess in the body to be formed.

[0045] Stretch forming, especially for female molds, preferably takes place using negative pressure, such as vacuum stretch forming. However, this may also be preferred for male molds.

[0046] If, in the arrangement according to the invention, the composite film according to the invention is not fixed to the mold by means of the hot-melt adhesive, this is a state before the hot-melt adhesive has been activated for bonding. This is a precursor to the (later) desired application situation.

[0047] If, in the arrangement according to the invention, the composite film according to the invention is fixed to the mold by means of the hot-melt adhesive, the fixing step in the form of heating the hot-melt adhesive has already been performed. The mold is then prepared for the primary forming process.

[0048] In this situation, the composite film according to the invention can function like a firmly and directly applied release coating. As long as the process temperature during the actual primary forming process does not cause the composite film according to the invention to detach from the mold surface, the composite film according to the invention will remain on the mold surface. How well and how durably the composite film according to the invention can then exert its release effect to separate a plastic body produced in the primary forming process depends on various factors that the expert can check and adjust before actual use:

[0049] The compatibility of the resin system with the composite film according to the invention - especially under the curing temperatures.

[0050] Particular care must be taken to ensure that the composite film does not swell.

[0051] Good release properties between the cured matrix (plastic) and the composite film surface

[0052] The release force remaining after stretching during composite film application to the mold surface.

[0053] For example, in the case of an elongation of more than 5% in a plasma polymer coating which is preferably provided according to the invention, a plasma process is selected which preferably provides a thin, well-adhering coating.

[0054] In the case of the production of fiber-reinforced plastics, sufficient resistance of the composite film to abrasive stresses or compressive stresses.

[0055] For this purpose, a composite film with sufficient hardness is preferably selected. If this is not possible, the composite film can preferably have a thin film thickness. Should the composite film according to the invention no longer exhibit sufficient release properties (over larger surface areas), e.g., after several demoldings, the composite film can simply be removed from the mold surface by heating the mold surface to temperatures above the lower softening temperature.

[0056] With composite films according to the invention, in particular with a plasma polymer coating as a release layer, it is also very easy to join prefabricated composite film pieces or corresponding film rolls in order to be able to equip mold surfaces that (possibly locally) require a composite film width that exceeds the width of the original film roll. For this purpose, two composite films according to the invention are placed side by side, each with the hot melt adhesive side facing down, preferably with an overlap, and heated to temperatures above the lower softening temperature in the overlap area and pressed together.

[0057] Furthermore, with composite films according to the invention, in particular with a plasma polymer release layer, it is possible to repair local defects that have arisen on the mold surface during use of the composite film according to the invention – both due to damage to the composite film according to the invention and due to a local reduction in the release effect – with the same composite film. To this end, for example, a patch of the composite film according to the invention can be placed over the defect and fixed with a projecting edge using vacuum sealing tape. The patch is then evacuated and heated to temperatures above the lower softening temperature of the hot melt adhesive. The patch thus laminated to the defect can be trimmed before the vacuum sealing tape. The vacuum sealing tape can then be removed.To facilitate trimming, a non-adherent medium to the lower composite film can be placed inside in front of the vacuum sealing tape—for example, an air distribution medium or a fluoropolymer film. In this case, trimming is performed in front of the non-adherent medium, and the non-adherent medium is removed along with the vacuum sealing tape.

[0058] Similar to covering local defects, larger areas of the mold surface can also be subsequently covered with the composite film. For example, large molds whose width exceeds the maximum film width can be covered with composite film strips in several steps.

[0059] According to the invention, an arrangement according to the invention comprising material for a primary forming process on the release film is preferred. This arrangement represents, in particular, the beginning of the primary forming process, in which the material (plastic) from which the plastic body to be produced in the primary forming process is then introduced onto the mold coated with the composite film according to the invention or into the mold coated with the composite film according to the invention.

[0060] An arrangement according to the invention is preferred, wherein the material for a primary forming process is a thermoset or elastomer, preferably comprising fibers for a fiber composite plastic and / or is preferably cured.

[0061] This preferred arrangement according to the invention comprises preferred materials for the primary forming process and / or preferred states of the corresponding material.

[0062] Part of the invention is also the use of a hot melt adhesive, preferably as defined in more detail above, for fixing and / or separating, as required, a vacuum-stretchable carrier film to facilitate the separation of a plastic body produced in the primary forming process from the mold, wherein the vacuum-stretchable carrier film is defined in more detail above.

[0063] For the purposes of this text, a “separation as required” is one that is deliberately brought about by the user, in particular to remove used composite films according to the invention from the mold.

[0064] The advantages of using hot melt adhesive have already been described above.

[0065] Part of the invention is also the use of a composite film according to the invention or an arrangement according to the invention to facilitate the removal of a plastic body formed in the primary forming process from the mold.

[0066] Ultimately, the use of the agent according to the invention (the composite film according to the invention) for precisely this purpose is the advantageous technical effect of the present invention.

[0067] Part of the invention is also a process for producing a composite film according to the invention, comprising the steps of a) providing a vacuum-stretchable carrier film made of plastic, b) providing a hot-melt adhesive and c) coating one side of the carrier film with the hot-melt adhesive.

[0068] It is possible for step c) to take place simultaneously with steps a) and b), for example, by coextrusion, preferably in a blown film line. It is therefore also possible according to the invention for steps a) to c) to take place together in a primary forming process, i.e., the vacuum-stretchable carrier film to be used according to the invention and the hot melt adhesive to be used according to the invention are formed together accordingly.

[0069] According to the invention, a method according to the invention is preferred, comprising as

[0070] Step d) Applying a silicon-containing, preferably an organosilicon, particularly preferably a plasma-polymer organosilicon coating on the side of the carrier film opposite the hot melt adhesive layer.

[0071] Preferably, step d) is carried out in a roll-to-roll plasma coating process, more preferably in a low-pressure process.

[0072] An advantage of this process technology is that corresponding coating processes are possible at or near room temperature. It is preferable that the back coating of the hot melt adhesive is largely suppressed by appropriate system-related covers behind the composite film.

[0073] Within the scope of the present invention, the plasma polymer (separation) layer to be used is preferably one that is applied to the carrier film in several steps, wherein the plasma polymer layer applied first preferably has a lower release effect than the outer plasma polymer layer, but the first applied layer ensures good adhesion to the carrier film. If more than two plasma polymer layers are provided, it is preferred that each layer, from the inside to the outside, has a greater release effect from the (later) plastic body than the layer before it. In case of doubt, the release effect is described by the surface energy, wherein the release effect increases with a decrease in the surface energy.

[0074] As an alternative to the layer structure of the plasma polymer coating, it may be preferable for the plasma polymer, in particular the organosilicon coating, to be a gradient layer. This means that it does not consist of several distinct layers, but rather exhibits a continuous material change from the boundary layer to the carrier film toward the outer surface. With the appropriate layer structures of the plasma polymer coatings, it is possible to ideally adjust the adhesion conditions and also optimally adapt the release properties (also with regard to the plastic to be used later).

[0075] Part of the invention is also a method for producing an arrangement according to the invention, comprising the steps: a1) providing a composite film according to the invention or a2) carrying out a method according to the invention for producing a composite film according to the invention and b) providing a mold and c) inserting the composite film into the mold via vacuum stretch forming or joining the composite film around the mold via stretch forming, preferably also via vacuum stretch forming and d) fixing the composite film to the mold by means of the hot melt adhesive by heating, preferably by heating to a temperature within the softening range of the hot melt adhesive and below the softening range of the carrier film.

[0076] As already described above, inserting the composite film into the mold is particularly useful for female molds, while joining it around the mold is used for male molds. It should be noted that it is not mandatory for the entire mold (this also applies to male molds) to be covered with the composite film according to the invention. However, it is naturally preferred according to the invention that all areas of the mold intended to come into contact with the material for the primary forming process be covered by the composite film according to the invention.

[0077] As already described above, the insertion or joining of the composite film according to the invention into or around the mold will generally and preferably take place below the lower softening temperature of the hot melt adhesive. With subsequent heating before the first primary forming process, the hot melt adhesive is activated such that the composite film according to the invention is fixed to the mold. It is preferable to select a heating temperature that is above the lower softening limit of the hot melt adhesive, preferably in the middle range of the softening range and more preferably close to the upper softening temperature of the softening range of the hot melt adhesive, while at the same time preferably the lower limit of the softening range of the carrier film is not exceeded. The heat required for this fixing can be provided by heating the mold or, preferably, an external heat source such as, for example,an infrared heater or a hot air blower on the side of the film opposite the mold.

[0078] For securing the composite film according to the invention to the mold, it is preferable that the mold be free of contamination and, in particular, free of release agent residues. Residues of so-called sealers (crosslinking agents) are particularly critical.

[0079] In general, the skilled person will adapt the materials for the composite film according to the invention - as already indicated above - to the planned primary forming process. Naturally, the tolerable temperatures are of great importance in this case. The carrier film according to the invention or the separating side of this film must be adapted to the plastic material with regard to its release properties. The selected hot melt adhesive (and naturally also the selected carrier film) must be adapted to the temperature requirements of the respective primary forming process insofar as the primary forming process must not generate temperatures that exceed the softening temperature of the carrier film. However, this only applies to the boundary layer between the composite film according to the invention and the material for the primary forming process during primary forming. Higher temperatures can of course also occur inside the nascent body.In addition, a relatively brief heating of the composite film according to the invention above the softening temperature of the hot melt adhesive can be tolerated, as long as the composite film according to the invention is sufficiently cooled to a temperature range below the softening range of the hot melt adhesive before removing the plastic body formed in the primary molding process. It has been found that in such a situation, the hot melt adhesive regains its adhesion in time to continue to fix the composite film according to the invention to the mold in a contour-mimicking manner.

[0080] Examples

[0081] Measurement example 1

[0082] Measurement of surface free energy or surface tension

[0083] A Mobile Surface Analyzer (MSA) from Krüss GmbH, Hamburg, was used to measure surface energies and their dispersed and polar fractions. This is a contact angle measuring device that dispenses two parallel drops onto the sample surface with a single click.

[0084] The test drop is dispensed contactlessly onto the sample surface at room temperature and has a volume of approximately 1 pl. Five seconds after dispensing the drop, an image is taken, and the static contact angle is automatically determined using the "sessile drop (double)" method. The automatic evaluation of the images is subsequently visually verified, and if necessary, the baseline is manually corrected and non-evaluable images are discarded.

[0085] To better describe the surface properties of the film, measurements are taken at at least ten different locations on the same sample using the test liquids water and diiodomethane, and the resulting surface energy calculations are performed. The average value is then calculated.

[0086] The test fluids used are water (surface tension: 72.80 mN / m; dispersed fraction: 21.80 mN / m; polar fraction: 51.00 mN / m) and diiodomethane (surface tension: 50.80 mN / m; dispersed fraction: 50.80 mN / m; polar fraction: 0.00 mN / m). In case of doubt, the expert will check the surface energy of the test fluids, for example, using a Wilhelmy balance, and always ensure that the test fluids are fresh and uncontaminated.

[0087] The measuring software used is the program “Advance” (version 1.6.2.0.) from Krüss GmbH.

[0088] The evaluation of the surface free energy with the dispersed and polar fractions is carried out according to the Owens, Wendt, Rabel & Kaelble (OWRK) method. The contact angle measurement is based on DIN 55660.

[0089] Measurement example 2

[0090] Measurement of surface stickiness

[0091] The surface tackiness of the composite films is measured in accordance with DIN EN 1719 (Measurement of the surface tackiness of pressure-sensitive adhesives / Determination of surface tackiness using the loop method). However, unlike the standard described in DIN EN 1719, a pressure-sensitive adhesive is not used on, for example, a 50 μm thick polyester film. Instead, the surface tackiness of the hot melt adhesives already present on the composite films, or in the case of reference measurements, the pressure-sensitive adhesives, is measured as part of the composite films. For this purpose, the composite films are backed on the carrier film side with a 0.050 mm thick stainless steel foil (Record metal foil, steel, stainless steel 18Cr9Ni, 0.050 mm). This means that the contact pressure is defined by the metal foil, allowing different composite films to be compared regardless of their stiffness.A glass plate is used as a flat, rigid plate, which is cleaned with a suitable solvent, such as acetone, before each test. If necessary, the specialist will replace the glass plate between measurements to prevent surface contamination.

[0092] Example 1: Front-side coating of composite films with a plasma polymer release layer

[0093] The composite films described in the following examples were coated with a plasma polymer release layer on the carrier film side using a low-pressure plasma system. The described films were used with a product width of 2 m, or smaller samples were affixed with the hot-melt adhesive backing of the carrier film to a 2 m wide polypropylene composite film with a thickness of 50 μm by affixing it laterally with a pressure-sensitive adhesive tape.

[0094] The plasma system has a cuboid-shaped plasma chamber made of stainless steel with the internal dimensions width: 1.7 m, height: 2.2 m and depth: 3.0 m. The two 3.0 m long side walls are dielectrically insulated with plastic. In the middle of each side wall, a cooled flat electrode with a width of 2.6 m and a height of 1.65 m is inserted into the plastic insulation. The plasma chamber is evacuated upwards using two vacuum pump trains with a total suction power of 750 sccm at 0.019 mbar. The wrapping device is electrically insulated from the chamber walls and floor and is placed into the plasma chamber on a retractable stainless steel base plate. The base plate and the front of the wrapping device are fixed to the grounded chamber door. The wrapping takes place between two drive rollers located inside the wrapping device that build up the fabric tension.

[0095] The foils were passed past the electrodes at a distance of 40 mm, with the outer surface facing first one electrode and then the other. Before the coating process, the foils were dried by wrapping them several times in a vacuum until a pressure of 0.012 mbar was achieved during the last wrapping before the coating process at a wrapping speed of 7 m / min.

[0096] During the coating process, oxygen at a flow rate of 100 sccm and hexamethyldisiloxane (HMDSO) at a flow rate of 380 sccm were introduced as working gases while evacuating from below. The gas flow was divided equally between the two electrode sides. Butterfly valves upstream of the vacuum pump lines regulated the pressure in the plasma chamber to 0.025 mbar. The plasma was excited at a high frequency of 13.56 MHz with 3000 W each (generator output power) via the two flat electrodes. The foils were wound at a speed of 8 m / min.

[0097] Implementation example 1 a: Contact angle measurements

[0098] The two plasma polymer-coated composite films according to the invention from Example 1 were measured and evaluated. The untreated composite films used for the plasma coating were also measured and evaluated as a reference. The results are listed in Table 1.

[0099] Table 1 : Results of contact angle measurements

[0100] Example 1 b: Measurements of surface tackiness

[0101] The two plasma polymer coated composite films according to the invention from the

[0102] Example 1 was measured and evaluated, along with two commercially available self-adhesive PTFE films as references. The results are listed in Table 2.

[0103] Table 2: Results of surface tackiness measurements

[0104] 1 ): PTFE film with silicone adhesive; Art.No.: SK 10 AD / PTFE.SFL.025.AD from Hightechflon GmbH & Co. KG, Konstanz

[0105] 2 ) Release film, 250 pm with acrylic pressure-sensitive adhesive; of composite films with a

[0106] The 100 μm thick thermoplastic polyester-polyurethane films Platilon HL 9007 and Platilon® HL 9074 (Covestro Deutschland AG, Leverkusen) were selected as composite films. These composite films are typically used as protective coatings for textiles and polyurethane foam components. Both films consist of a high-melting film (barrier layer) on the front side with a softening range of 155–175 °C, and a low-melting adhesive layer on the back side, which has a softening range of 85–130 °C for Platilon® HL 9007 and a softening range of 125–150 °C for Platilon® HL 9074. Both films were coated with a plasma polymer release layer on the high-melting film on the front side (according to Example 1).They were then stretched over a 5 mm thick glass plate (as a model for a mold), secured externally with vacuum sealing tape, vacuum drawn, and annealed for 10 minutes in an oven at 125 °C for Platilon® HL 9007 and 145 °C for Platilon® HL 9074. After subsequent cooling, the films adhered well to the glass plate, and the vacuum could be easily released. The surface was imaged evenly.

[0107] The film area outside the glass plate was discarded. A four-layer sample of the cyanate ester resin CFRP / GFRP prepreg PN900-C582-43 was then cured several times on the composite films laminated to the glass and subsequently removed without any problems. Curing took place in a typical autoclave setup at atmospheric pressure in an oven. The samples were placed in the oven at 60 °C under vacuum, heated to 125 °C at a heating rate of 3 K / min, annealed at 125 °C for 2 hours, and demolded after cooling to room temperature.

[0108] After 10 minutes of oven annealing at 130 °C for Platilon® HL 9007 and 150 °C for Platilon® HL 9074, the two composite films could be easily removed from the glass plates without leaving any visible residue. This allows the film to be replaced if defects occur.

[0109] Similarly, the composite films are stretch-formed over the mold surface of a press for the production of aircraft interior components made of fiber-reinforced plastics with an outer layer made of the cyanate ester resin CFRP / GFRP prepreg PN900-C582-43, and then fixed by heating. After 10 production cycles or demoldings, the mold surface is heated to 130 °C for Platilon® HL 9007 and 150 °C for Platilon® HL 9074, and the composite film is removed without residue. The mold surface is then cooled to below 70 °C, and a new composite film is vacuum-stretched onto the mold surface. with the composite films

[0110] Simple laboratory tests demonstrated that the TPU film Platilon® HL 9007, laminated with an overlap of 70 mm at a temperature of 130 °C and a pressure of 0.03 MPa, exhibited a maximum elongation of 107% (pure composite film > 300%). The tensile stress at 100% elongation for the laminated composite film deviated by less than 20% from the values ​​of the original composite film.

[0111] Embodiment 4: Production of fiber composite components for wind turbines using the composite films according to the invention

[0112] The composite films used are a 60 μm thick polymer film with a layer of a thermoplastic copolyester elastomer based on polybutylene terephthalate, a layer of approximately 7 μm polyamide 66, and on the back a layer of approximately 30 μm of a thermoplastic polyurethane hotmelt adhesive based on polyester polyurethanes with an average softening temperature of 110 °C. Instead of the simple film in Example 1, this film is used as a half-tube with an internal 50 μm thick polyethylene support layer. The composite film, with its back side resting on the support film, can be easily separated from the support film by hand at 23 °C. In this way, films according to the invention can be coated with twice the width.

[0113] The coating of the half-tube is carried out analogously to the coating of the film web in embodiment 1. Unlike described in embodiment 1, the half-tube is first guided along in front of one HF electrode at a speed of 4 m / min and then with the back side in front of the second electrode.

[0114] The described plasma polymer-coated film, with a half-tube width of 2000 mm, is positioned on the front side of the forming tool, a rotor blade half-shell. The film roll is positioned on a roll holder. The film is then unrolled and separated from the coil, so that the beginning of the web is located near the blade tip and the end of the web is near the blade root. The half-tube extends beyond the two front sides of the forming tool. The half-tube is then unfolded, and the polyethylene support layer is removed. The opened half-tube has a width of 4000 mm and is oriented with the side with the thermoplastic polyurethane hot melt adhesive toward the forming tool.

[0115] The composite film is then slightly pre-tensioned and fixed to the mold using vacuum sealing tape. Where the film width allows, the film is fixed to the tool edge outside the component area. In areas where the width of the component area in the mold exceeds the width of the film web, the film is only fixed to the tool edge on one side. The opposite film edge is fixed to the mold within the component area. The air volume between the film and the mold is then evacuated, and the film is vacuum-stretched into the mold. The mold is then heated to a temperature of 110 °C using the integrated mold heater. Once the tool has reached this temperature, it is held for 5 minutes before the heater is deactivated and the tool cools down to at least 40 °C.The softening and subsequent cooling of the hot melt adhesive bonds the composite film to the mold. The vacuum ports are then vented, leaving the composite film in a stretched state and adhering to the mold. The film is then cut all the way around the vacuum sealing tape frame with a sharp blade, and the severed edges are peeled off. Any parts of the cut edges still adhere to the mold, which are heated with a hot air gun to a temperature above the average softening temperature of the hot melt adhesive, can then be peeled off.

[0116] In order to apply the film to the remaining component area not covered by the film, a second film blank is spread over the remaining, exposed component area and prepared in the same way as the first film web. This second film blank is then slightly pre-tensioned and fixed to the mold using vacuum sealing tape. The vacuum tape runs on the previously applied film web within the component area so that the first and second film blanks overlap here. The second film blank is then vacuum-stretched into the mold by creating a vacuum between the film and the mold. The tool is heated again to a temperature of 110 °C in the area of ​​the second film blank. This temperature is maintained for 5 minutes before the heating is deactivated and the tool is allowed to cool again.This section of the composite film has also bonded to the one on the forming tool. After the vacuum is released, this section is severed all the way around within the vacuum sealing tape frame with a sharp blade. In the area of ​​overlap with the first film section, the separation is performed so that the two film webs are flush. Alternatively, the separation is possible so that the first film web remains undamaged on the tool and the second film web overlaps with it. The severed edges are peeled off.

[0117] After the composite film is applied over the entire surface of the mold, textile and hard semi-finished products are assembled on the mold. One of the hard semi-finished products is the hub connection, a semi-finished product made primarily of glass-fiber-reinforced, epoxy-based plastic and equipped with connection surfaces and connecting elements for connecting the future rotor blade to the hub.

[0118] Peel-off ply, perforated release film, flow aid, vacuum lines for infusion, and resin extraction are then inserted. Finally, vacuum film is applied and sealed to the mold using vacuum sealing tape. The injection line is then closed, and the layered structure is evacuated through the extraction line using a vacuum pump (absolute pressure: 50 mbar).

[0119] During evacuation, the mold is heated to 70 °C by the mold heater. Once this temperature is reached, 100 parts by mass of the epoxy resin EPIKOTE Resin MGS RIMR035c and 28 parts by mass of the hardener EPIKURE Curing Agent MGS RIMH037, both from Hexion, are mixed. The component is then infused through the injection line. The component cures at the set mold temperature of 70 °C. Eight hours after injection, the mold heater is deactivated, and the mold and component cool to room temperature.

[0120] After this cooling phase, the vacuum film, perforated release film, flow aid, and inserted hoses are removed before the component, with the remaining peel ply, is removed from the mold. The parting line runs between the composite film and the demolded component. The composite film remains on the mold during and after demolding. The composite film allows the production of additional components on the release film; its separating properties are retained after demolding, so that further analogous components can be manufactured using the same composite film. of fiber composite components for rbundfolien

[0121] The production of a rotor blade half-shell is analogous to example 4. However, in this example, the half-tube is spread out on a cutting table outside the mold, and the polyethylene support layer is removed there. Furthermore, the composite film is cut to the required contour for the rotor blade shape on the cutting table. Before spreading out in the rotor blade mold, a section of the composite film cut to the required contour is glued to the positions where the width of the composite film half-tube is insufficient. This section is placed with an overlap of approximately 3 cm next to the edge of the composite film. The overlap is then glued using pressure and heating for approximately 20 seconds to approximately 120°C.

[0122] The now prefabricated composite film is then folded, rolled up and transported to the rotor blade mold.

[0123] If local damage occurs after the composite film has been fixed according to embodiments 4 or 5, for example, due to the insertion of the above-described hard semi-finished products used in component production, the composite film can be repaired. To do this, the damaged area of ​​the film is cut out with a sharp blade, the damaged section of the composite film is heated with a hot air gun to a temperature above the average softening temperature of the hot melt adhesive, and then removed from the mold.

[0124] After the local exposure of the mold, a pre-cut piece of the composite film is secured with vacuum sealing tape, slightly pre-tensioned, to the mold section to be equipped. The vacuum sealing tape is secured to the adjacent mold section equipped with composite film. The composite film extends beyond the repair area and is oriented with the back side, containing the thermoplastic polyurethane hot melt adhesive, toward the mold. The air volume between the film and the mold is then evacuated, so that the pre-cut piece of film adheres to the mold. Evacuation occurs via a previously installed vacuum line. To fix the composite film to the mold surface, the film is heated to a temperature of 110 °C with a hot air blower.

[0125] The softening and subsequent cooling of the hot melt adhesive bonds the composite film to the mold. The vacuum is then released, leaving the composite film in a stretched state and adhering to the mold.

[0126] After the vacuum is released, this blank is cut all the way around the frame of vacuum sealing tape with a sharp blade. In the area of ​​overlap with the composite film to be repaired, the cut is made so that the two film webs are flush. Alternatively, the cut can be made so that the first film web remains undamaged on the tool and the second film web overlaps with it.

[0127] In the separated edge areas, the composite film is pulled off the forming tool, whereby the separation is supported by a hot air blower that heats the edge areas to a temperature close to the average softening temperature of the hot melt adhesive.

Claims

Claims 1. Composite film for facilitating the separation of a plastic body produced by a primary forming process from the mold, comprising a) a vacuum stretchable carrier film made of plastic and b) a hot melt adhesive layer on one side of the carrier film, wherein the hot melt adhesive has a surface tackiness of < 2 N at 25 °C and a surface energy of < 30 mN / m is present on the side of the composite film opposite the hot melt adhesive layer.

2. Composite film according to claim 1, wherein the hot melt adhesive is an adhesive based on a thermoplastic elastomer, more preferably based on a thermoplastic polyurethane or a thermoplastic polyester elastomer.

3. Composite film according to one of the preceding claims, wherein the softening range of the hot melt adhesive begins at a temperature > 40 °C, particularly preferably above > 50 °C, more preferably at > 60 °C, > 70 °C, > 80 °C and most preferably at > 90 °C.

4. Composite film according to one of the preceding claims, wherein the softening range of the carrier film begins > 20°C, preferably > 30°C, more preferably > 40°C above the softening range of the hot melt adhesive.

5. Composite film according to one of the preceding claims, wherein a silicon-containing, preferably a silicon-organic, particularly preferably a plasma-polymer silicon-organic coating is present on the side of the carrier film opposite the hot melt adhesive layer.

6. Composite film according to one of the preceding claims, wherein on the side of the composite film opposite the hot melt adhesive layer there is a polar component of the surface energy of < 4.0 mN / m preferably < 3.0 mN / m, more preferably < 2.0 mN / m and particularly preferably < 1.5 mN / m.

7. Arrangement comprising a mold for a primary forming process and a composite film according to one of the preceding claims stretched therein or around it, wherein the composite film is a) not fixed to the mold by means of the hot melt adhesive or b) fixed to the mold by means of the hot melt adhesive.

8. Arrangement according to claim 7, comprising in the form on the release film material for a primary forming process.

9. Arrangement according to claim 8, wherein the material for a primary forming process is a thermoset or elastomer, preferably comprising fibers for a fiber-reinforced plastic and / or preferably is cured.

10. Use of a hot melt adhesive, preferably as defined in more detail in one of the preceding claims, for fixing and / or releasing as required a vacuum stretchable carrier film to facilitate the separation of a plastic body produced by primary forming from the mold, wherein the vacuum stretchable carrier film is defined in more detail as in one of the preceding claims.

11. Use of a composite film as defined in any one of claims 1 to 6, or an arrangement as defined in any one of claims 7 to 9, to facilitate the removal of a plastic body formed by primary forming from the mold.

12. Method for producing a composite film according to any one of claims 1 to 6, comprising the steps: a) providing a vacuum stretchable carrier film made of plastic, b) providing a hot melt adhesive, c) coating one side of the carrier film with the hot melt adhesive.

13. The method of claim 12, comprising as step d) applying a silicon-containing, preferably an organosilicon, particularly preferably a plasma-polymer silicon-organic coating on the side of the carrier film opposite the hot melt adhesive layer.

14. A method according to claim 12 or 13, wherein step c) is performed in a blown film line.

15. A method for producing an arrangement according to any one of claims 7 to 9, comprising the steps of: a1) providing a composite film according to any one of claims 1 to 6, or a2) performing a method according to any one of claims 12 to 14, and b) providing a mold, and c) inserting the composite film into the mold by vacuum stretch forming or joining the composite film around the mold by stretch forming, preferably by vacuum stretch forming, and d) fixing the composite film to the mold by means of the hot melt adhesive by heating, preferably by heating to a temperature within the softening range of the hot melt adhesive and below the softening range of the carrier film.

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