DE102022103425A1 - Composite film for permanently equipping molds with a release layer - Google Patents

Abstract

Composite film for facilitating the separation of a plastic body produced in the original molding process from the mold, comprisinga) a vacuum stretch-drawable carrier film made of plastic andb) a hot-melt adhesive layer on one side of the carrier film, the hot-melt adhesive having a surface tack at 25°C and preferably also at 40°C ≤ 2 N, preferably ≤ 1 N, and has a surface energy of ≤ 30 mN/m, preferably ≤ 28 mN/m, more preferably ≤ 26 mN/m, even more preferably ≤ 25 mN/m on the side of the composite film opposite the hot-melt adhesive layer. m and particularly preferably ≦24 mN/m.

Description

1. a) eine vakuum-streckziehfähige Trägerfolie aus Kunststoff und
2. b) eine Schmelzklebstoffschicht auf einer Seite der Trägerfolie,

wobei der Schmelzklebstoff bei 25°C eine Oberflächenklebrigkeit von ≤ 2 N besitzt und auf der der Schmelzklebstoffschicht entgegengesetzten Seite der Verbundfolie eine Oberflächenenergie von ≤ 30 mN/m vorliegt.The present invention relates to a composite film for facilitating the separation of a plastic body produced in the primary molding process from the mold, comprising

1. a) a vacuum stretch-drawable carrier film made of plastic and
2. 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 there is a surface energy of ≦30 mN/m on the side of the composite film opposite the hot-melt adhesive layer.

1. a) nicht mittels des Schmelzklebstoffes an der Form fixiert ist oder
2. b) mittels des Schmelzklebstoffes an der Form fixiert ist.

The invention further relates to an arrangement comprising a mold for a primary shaping process and/or a composite film according to the invention vacuum stretch-drawn therein, wherein the composite film

1. a) is not fixed to the mold by means of the hot-melt adhesive or
2. 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 required, a vacuum stretch-drawable carrier film to facilitate the separation of a plastic body produced in the primary molding process from the mold and the use of a composite film according to the invention to facilitate the removal of a plastic body formed in the primary molding process from the mold . In this respect, the invention also includes the aspect of removing a used carrier film.

The invention also relates to a method for producing a composite film according to the invention and a method for producing an arrangement according to the invention.

State of the art

When manufacturing plastic components from reactive resins (e.g. for duroplastics, elastomers or fiber-reinforced plastics), it is common practice to use release agents that are applied in liquid or paste form. All of these systems contain solvents, including those that are water-based.

Disadvantages of this procedure are the emission of solvents, the time-consuming and labour-intensive parting of the mould, the risk of (local) failure of the parting effect with the consequence of very high effort when demolding and possible damage to the component and mould, the mold occupancy time due to parting and airing, the cleaning effort for the mold and component due to cohesive failure within the release agent, the risk of fibers being exposed if the component is cleaned too abrasively by grinding, and the additional reworking of the ground surface due to exposed pores, which are usually filled with filler, which in turn must then be ground smooth .

In addition, plasma polymer separating 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 before the production of the plastic components, during demolding due to adhesion failure on the separating layer, clean components are obtained from which no release agent residues have to be removed (e.g. by grinding), the separating layer surface does not have to be so frequently, Ideally, the mold structure (release agent and resin residues) should not be cleaned at all. In addition, the application of the plasma-polymer separating layers in a low-pressure (LP) plasma system is almost emission-free.

A disadvantage of plasma-polymer separating layers is that the coating of the molds in the LP plasma is complex, since the molds have to be coated in a LP plasma reactor. This is not possible with large/heavy moulds.

Coating the molds in atmospheric pressure (AP) plasma is also complex; in addition, the AD plasma layers are not as durable as the ND plasma layers.

In some cases, fluoropolymer-based release films are glued to the surface of the mold using pressure-sensitive adhesives (e.g. Tooltec® from Airtech). The advantages of this procedure are: no solvent emissions before the production of the plastic components, reliable demoulding and clean mold surfaces.

Disadvantages of this procedure are: time-consuming application of the release film by draping a sticky film with low elasticity, and there is also a transfer of fluoropolymer residues to the component, so that it must be cleaned before painting or gluing.

In some cases, fluoropolymer-based release films are applied to the mold surface as single-use release films. The advantages of this procedure are: no solvent emissions before the production of the plastic components, reliable demolding and clean mold surfaces as long as the foil is not damaged or resin penetrates between two release foil sections.

Disadvantages of this procedure are: High consumption of resources (1. polymer foil, which cannot be reused or materially recycled due to residues of matrix and vacuum sealing tape (tackytape), 2. the so-called tackytape), high material costs and high application effort for each component. In addition, there is a transfer of fluoropolymer residues to the component, so that it must still be cleaned before painting or gluing.

In addition, stretchable polymer films with plasma polymer separating layers (cf. e.g. EP 2 841 269 B1 ) are applied to the mold surface. The advantages of this procedure are: no solvent emissions before 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 have to be removed, and the adhesion between the plasma polymeric release layer and the matrix resin can be adjusted in such a way that the polymer film can initially remain on the component after demolding as protection against dirt such as dust.

Disadvantages of this procedure are: High consumption of resources (1. polymer film, which cannot be reused or materially recycled due to residues of matrix and tacky tape, 2. the tacky tape), high material costs and high application effort for each component.

Against this background of the prior art, it was an object of the present invention to provide an agent which has as many of the advantages mentioned above as possible and at the same time as few as possible of the disadvantages mentioned. In particular, the means to be provided by the invention should ensure a long-term and reliable separation of plastic components from the mold, with molds with three-dimensionally irregular (complicated) surfaces preferably also being able to be used and the introduction of the separating agent into the mold should be possible in a reliable and as uncomplicated manner as possible .

1. a) eine vakuum-streckziehfähige Trägerfolie aus Kunststoff und
2. b) eine Schmelzklebstoffschicht auf einer Seite der Trägerfolie,

wobei der Schmelzklebstoff bei 25°C und bevorzugt auch bei 40°C eine Oberflächenklebrigkeit von ≤ 2 N, bevorzugt ≤ 1 N, besitzt und auf der der Schmelzklebstoffschicht entgegengesetzten Seite der Verbundfolie eine Oberflächenenergie von ≤ 30 mN/m, bevorzugt ≤ 28 mN/m, weiter bevorzugt ≤ 26 mN/m, noch weiter bevorzugt ≤ 25 mN/m und besonders bevorzugt ≤ 24 mN/m vorliegt.According to the invention, this object is achieved by a composite film for facilitating the separation of a plastic body produced in the original molding process from the mold, comprising

1. a) a vacuum stretch-drawable carrier film made of plastic and
2. b) a hot-melt adhesive layer on one side of the carrier film,

where the hot-melt adhesive has a surface tack of ≦2 N, preferably ≦1 N, at 25° C. and preferably also at 40° C. m, more preferably ≦26 mN/m, even more preferably ≦25 mN/m and particularly preferably ≦24 mN/m.

A prototyping process within the meaning of the present text is a process in which a shapeless mass, e.g. B. a viscous mass, a fibrous structure impregnated with reaction resins, a powder arrangement or a liquid, a solid is formed. The primary shaping process preferably takes place in the liquid, plastic, pulpy, powdery or fibrous state. But semi-finished products can also be used, such as prepregs.

Preferred original molding processes within the meaning of the present text are resin infusion processes, resin injection processes (particularly preferably resin transfer molding (RTM)), pressing processes, autoclave processes, foaming processes, reaction injection molding (RIM) and hand lamination.

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

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

"A hot-melt adhesive in the sense of this text is a thermoplastic polymer (preferably a thermoplastic elastomer) that is solid at room temperature (25°C), which can be liquefied by heating for bonding and can be hardened by cooling the molten material while simultaneously building up cohesive and adhesive forces can. Preferred hot-melt adhesives within the meaning of this present text are also referred to as hot-melt adhesives.

In case of doubt, the surface tack in the sense of this text is measured as described in measurement example 2 (based on DIN EN 1719).

The determination of the surface energy of a solid and the polar part of the surface energy is measured as described in measurement example 1.

The present invention makes it possible, surprisingly reliably, to introduce a separation-supporting carrier film into a mold by (vacuum) stretch-forming or to place it around a mold (male mold), and with a corresponding procedure to ensure reliable fixing of the carrier film to the mold. In particular, it could not be predicted that after (vacuum) stretch-forming the hot-melt adhesive would still have sufficient distribution for fixing the composite film to the mold, in particular even if the vacuum applied for vacuum stretch-forming is no longer present.

It has also been found that a hot-melt adhesive as defined above is particularly suitable for (vacuum) stretch-forming, since it - despite the mechanical stresses that this method entails - maintains sufficient lubricity over the mold and so the process is not hindered.

Furthermore, it has surprisingly been found that the composite film according to the invention can be excellently vacuum stretch-drawn into a female shape as well as stretch-drawn over a male shape. In this case, it may be preferable to evacuate the space under the composite film in the case of the male form as well. In both variants, of course, the side of the carrier film coated with the hot-melt adhesive layer faces the mold surface.

The composite film according to the invention can be fixed on the mold surface by heating the composite film according to the invention at least up to the start of the softening range, preferably at least up to the average softening point of the hot-melt adhesive. At the latest after subsequent cooling, when the hot-melt adhesive has hardened, it is no longer necessary to evacuate any space that may be present under the composite film. In the ideal case, however, the film according to the invention can in any case be fixed to the surface of the mold completely in a manner that reproduces the contour.

Since fluorine compounds are not unproblematic, inter alia for the reasons mentioned above, it is preferred according to the invention that the composite film according to the invention does not comprise any fluorine.

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

These materials have proven to be particularly suitable for a hot-melt adhesive to be used according to the invention. In the sense of this text, "on the basis" of a substance or a substance class means that this substance or this substance class is the predominant part of a mixture that may be present.

According to the invention, a composite film according to the invention is preferred, the softening range of the hot-melt adhesive starting at a temperature ≧40° C., particularly preferably above ≧50° C., more preferably ≧60° C., ≧70° C., ≧80° C. and very particularly preferably ≥ 90°C begins.

In case of doubt, the values for the softening range within the meaning of this application are determined using a Kofler heating bench. (Foil) pieces ((film) samples) of the plastic to be examined or of the hot-melt adhesive to be examined (possibly also together) with a base area of at least 1 mm ² are placed on a Kofler heating bench. In case of doubt, the specified area is used. After these pieces have been on the Kofler heating bench for 60 seconds, a scalpel is used to determine the position of the heating bench in which the plastic specimen can be plastically deformed from the side without the application of a large force. The position on the Kofler hot bench is then correlated with the temperature. The maximum and minimum values determined on the test pieces indicate the upper and lower end of the softening range.

The beginning of the softening range at a relatively high temperature is advantageous in terms of the intended use for the composite film according to the invention. Since elevated temperatures can already occur or be desirable during (vacuum) stretch-forming, it is advantageous if the hot-melt adhesive does not yet begin to soften at the temperatures then occurring. This can ensure that the surface tack does not increase or does not increase too much. In addition, an elevated temperature at the interface between the composite film according to the invention and the nascent plastic body can also be tolerated during the later primary shaping (see also below).

In other words, the person skilled in the art will preferably select a hot-melt adhesive that has high cohesive strength in the (later) process temperature range. In principle, the person skilled in the art - depending on the plastic used for the later primary forming process - will select all materials of the composite film according to the invention in such a way that the area of the lowest adhesive strength 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) consists. At the same time, this means that the cohesion of the individual components of the composite film according to the invention and the adhesion to the boundary layers, including adhesion to the mold, must be adjusted in such a way that when force is applied to the composite of mold, composite film according to the invention and plastic body, a separation between the plastic body occurs and the composite film according to the invention.

Of course, it is also sensible to take measures to ensure that the composite film according to the invention has sufficient adhesive strength in itself and to the mold during the actual primary shaping.

A composite film according to the invention is preferred for this purpose, the softening range of the carrier film beginning ≧20° C., preferably ≧30° C., more preferably ≧40° C. above the softening range of the hot-melt adhesive.

These preferred distances between the start of the softening area of the carrier film and the hot-melt adhesive make it possible to soften and thus activate the hot-melt adhesive after (vacuum) stretching without subjecting the carrier film to further deformations.

In order to achieve the surface energy provided according to the invention on the side of the carrier film opposite the layer of hot-melt adhesive, a large number of possibilities are available to the person skilled in the art. On the one hand, the choice of material for the carrier film should of course be mentioned here, but in many cases it is preferable to use further surface-modifying measures such as e.g. B. to make an additional coating. Such additional layers are of course included in the composite film in the sense of the present invention.

In this sense, a composite film according to the invention is preferred, with a silicon-containing, preferably a silicon-organic, particularly preferably a plasma-polymeric silicon-organic coating being present on the side of the carrier film opposite the hot-melt adhesive layer.

Silicon-containing, in particular silicon-organic layers, have the advantage that they can be excellently adjusted in terms of 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, especially when they are characterized by their surface properties the person skilled in the art can be matched to the plastic material that is to be formed into a plastic body in the original molding process when the composite film according to the invention is later used.

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

A plasma-polymer silicon-organic layer is one that has been deposited in a PE-CVD process.

Plasma polymer silicon-organic layers have - with a suitable design of the coating - also the advantage that they have excellent adhesion to the carrier film due to chemical bonding, which means that they form cracks at a distance of less than 10 µm even under very high stretching loads without being separated from the substrate Carrier film to be detached. The desired separating effect is largely retained. Furthermore, such layer systems are well crosslinked in themselves, so that they have high cohesive strength.

A composite film according to the invention is preferred for the purposes of the present invention, wherein on the side of the composite film opposite the hot-melt adhesive layer a polar component of the surface energy of ≦4.0 mN/m, preferably ≦3.0 mN/m, more preferably ≦2.0 mN/m m and particularly preferably ≦1.5 mN/m.

The polar portion of the surface energy is a particularly helpful variable for setting a suitable release effect for a large number of plastics.

Part of the invention is also an arrangement comprising a mold for a primary shaping process and a composite film according to the invention stretched in or around it, the composite film a) not being fixed to the mold by means of the hot-melt adhesive or b) being fixed to the mold by means of the hot-melt adhesive.

A mold for a molding process can be any suitable material suitable for forming a plastic body to be molded in the molding process. The molds can be designed both as a female shape, that is, with a depression, and as a male shape, that is, that they produce a depression in the body to be molded.

The stretch-forming, particularly in the case of the female shapes, preferably takes place using negative pressure as vacuum stretch-forming. However, this may also be preferred in the case of the male forms.

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, a state exists before the hot-melt adhesive was activated for bonding. This is a preliminary stage to the (later) desired operational situation.

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 has already been carried out in the form of heating the hot-melt adhesive. Then the mold is prepared for the primary molding process.

• - Der Kompatibilität des Harzsystems mit der erfindungsgemäßen Verbundfolie - insbesondere auch unter den Aushärtetemperaturen. Hierbei ist besonders darauf zu achten, dass die Verbundfolie nicht quillt.
• - Gute Trenneigenschaften zwischen der ausgehärteten Matrix (Kunststoff) und der Verbundfolienoberfläche
• - Der nach der Dehnung bei der Verbundfolienapplikation auf die Formoberfläche verbleibenden Trennkraft. Beispielsweise wird im Falle einer Dehnung über 5 % bei einer erfindungsgemäß bevorzugt vorzusehenden plasmapolymeren Beschichtung ein Plasmaprozess gewählt, der bevorzugt eine dünne, gut haftende Beschichtung bereitstellt.
• - Im Falle der Herstellung von Faserverbundkunststoffen eine ausreichende Beständigkeit der Verbundfolie gegenüber abrasiven Beanspruchungen oder Druckbeanspruchungen. Hierfür wird bevorzugt eine Verbundfolie mit ausreichender Härte gewählt. Ist dies nicht möglich, kann die Verbundfolie bevorzugt eine geringe Folienstärke aufweisen. Sollte die erfindungsgemäße Verbundfolie (auf größeren Flächenanteilen), z. B. nach mehreren Entformungen keine ausreichende Trennwirkung mehr zeigen, kann die Verbundfolie einfach von der Formoberfläche abgelöst werden, indem die Formoberfläche auf Temperaturen oberhalb der unteren Erweichungstemperatur erwärmt wird.

In this situation, the composite film of the present invention can function as a firmly and directly applied release liner. As long as the process temperature during the actual primary shaping process does not ensure that the composite film according to the invention detaches itself from the mold surface again, 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 separating effect for separating a plastic body produced in the primary molding process depends on various factors that the person skilled in the art can check and adjust before actual use:

• - The compatibility of the resin system with the composite film according to the invention - especially under the curing temperatures. It is particularly important to ensure that the composite film does not swell.
• - Good release properties between the hardened matrix (plastic) and the composite film surface
• - The release force remaining after stretching during composite film application to the mold surface. For example, in the case of an elongation of more than 5%, it is preferable to provide one according to the invention For the plasma polymeric coating, a plasma process is chosen, which preferably provides a thin, well-adhering coating.
• - In the case of the production of fiber composite plastics, sufficient resistance of the composite film to abrasive stresses or pressure stresses. A composite film with sufficient hardness is preferably selected for this purpose. If this is not possible, the composite film can preferably have a small film thickness. If the composite film according to the invention (on larger surface areas), z. B. no longer show a sufficient release effect after several removals from the mold, the composite film can be easily detached from the mold surface by heating the mold surface to temperatures above the lower softening point.

With composite films according to the invention, in particular with a plasma polymer coating as a separating layer, it is also very easy to connect 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 Foil roll goes out. To this end, two composite films according to the invention are each placed next to one another with the hot-melt adhesive side down, preferably with an overlap, and are heated to temperatures above the lower softening point and pressed together in the overlapping area.

In addition, with composite films according to the invention, in particular with a plasma-polymer separating 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 through damage to the composite film according to the invention and through a local reduction in the separating effect - with the same composite film . For this purpose, for example, a patch of the composite film according to the invention can be placed over the defect and fixed with a protruding edge with vacuum sealing tape. The patch is then evacuated and heated to temperatures above the lower softening point of the hot-melt adhesive. The patch laminated to the defect in this way can be trimmed in front of the vacuum sealing tape. The vacuum sealing tape can then be removed. To facilitate trimming, a non-adherent medium can be placed on the bottom composite film in front of the vacuum sealing tape - for example, an air distribution medium or a fluoropolymer film. In this case the trimming will be done before the non-adhesive media and the non-adhesive media will be removed along with the vacuum sealing tape

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

According to the invention, an arrangement according to the invention is preferred, comprising material for a primary shaping process on the separating film.

This arrangement represents in particular the beginning of the primary shaping process, in which the material (plastic) is 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, from which the plastic body to be produced in the primary shaping process is then to be produced.

An arrangement according to the invention is preferred, in which the material for a primary shaping process is a duroplastic or elastomer, preferably comprising fibers for a fiber-reinforced plastic and/or is preferably cured.

This preferred arrangement according to the invention includes preferred materials for the primary shaping process and/or preferred states of the corresponding material.

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 stretch-drawable carrier film to facilitate the separation of a plastic body produced in the original molding process from the mold, the vacuum stretch-drawable carrier film being defined in more detail above is.

For the purposes of this text, a “needs-based separation” is one that is consciously brought about by the user, in particular in order to remove used composite films according to the invention from the mold.

The advantages of using the hot-melt adhesive have already been described above.

Part of the invention is also the use of a composite film according to the invention or an arrangement according to the invention for facilitating the removal of a plastic body formed in the original molding process from the mold.

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.

1. a) Bereitstellen einer vakuum-streckziehfähigen Trägerfolie aus Kunststoff,
2. b) Bereitstellen eines Schmelzklebstoffes und
3. c) Beschichten einer Seite der Trägerfolie mit dem Schmelzklebstoff.

Part of the invention is also a method for producing a composite film according to the invention, comprising the steps

1. a) providing a vacuum stretch-drawable carrier film made of plastic,
2. b) providing a hot-melt adhesive and
3. c) Coating one side of the carrier film with the hot-melt adhesive.

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 shaping process, ie the vacuum stretch-drawable carrier film to be used according to the invention and the hot-melt adhesive to be used according to the invention are correspondingly shaped together.

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

Step d) Application of a silicon-containing, preferably an organosilicon, particularly preferably a plasma-polymeric, organosilicon coating to the side of the carrier film opposite the hot-melt adhesive layer.

Step d) preferably takes place in a roll-to-roll plasma coating process, more preferably in the low-pressure process.

An advantage of this process technology is that corresponding coating processes are possible close to or at room temperature. In this case, it is preferred that the rear-side coating of the hot-melt adhesive is largely suppressed with corresponding plant-construction coverings behind the composite film.

In the context of the present invention, the plasma polymeric (separation) layer to be used is preferably one that is applied to the carrier film in several steps, with the plasma polymeric layer applied first preferably having a lower separating effect than the outer plasma polymeric layer, but with the first applied layer ensures good adhesion to the carrier film. If more than two plasma polymer layers are provided, it is preferable for each layer to have a greater separating effect on the (subsequent) plastic body from the inside to the outside than the layer in front of it. In case of doubt, the separating effect is described by the surface energy, with the separating effect increasing as the surface energy decreases.

As an alternative to the layer structure of the plasma polymer coating, it can be preferred that the plasma polymer, in particular silicon-organic coating is a gradient layer, i.e. does not consist of several distinct layers, but has a constant material change from the area of the boundary layer to the carrier film to the outside.

With the appropriate layer structures of the plasma polymer coatings, it is possible to set the adhesion conditions ideally and also to optimally adjust the release properties (also with regard to the plastic to be used later).

• a1) Bereitstellen einer erfindungsgemäßen Verbundfolie oder
• a2) Durchführen eines erfindungsgemäßen Verfahrens zur Herstellung einer erfindungsgemäßen Verbundfolie und
• b) Bereitstellen einer Form und
• c) Einfügen der Verbundfolie in die Form via Vakuum-Streckziehen oder Fügen der Verbundfolie um die Form via Streckziehen, bevorzugt ebenfalls via Vakuum-Streckziehen und
• d) Fixieren der Verbundfolie mittels des Schmelzklebstoffes an der Form durch Erwärmung, bevorzugt durch Erwärmung auf eine Temperatur innerhalb des Erweichungsbereiches des Schmelzklebstoffes und unterhalb des Erweichungsbereichs der Trägerfolie.

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.

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

As already described above, the insertion or joining of the composite film according to the invention in or around the mold will generally and preferably take place below the lower softening point of the hot-melt adhesive. With subsequent heating before the first primary shaping process, the hot-melt adhesive is activated in such a way that the composite film according to the invention is fixed to the mold. It is preferred to choose a heating temperature that is above the lower softening limit of the hot-melt adhesive, preferably in the middle of the softening range and more preferably in the vicinity of the upper softening temperature of the softening range of the hot-melt adhesive, while preferably not at the same time the lower limit of the softening range of the carrier film is exceeded. The heat required for this fixation can be obtained by heating the mold or preferably an external heat source such as e.g. B. an infrared radiator or a hot air blower on the opposite side of the mold.

For fixing the composite film according to the invention to the mold, it is preferred that the mold is free of dirt and in particular free of release agent residues. Residues of so-called sealers (founding agents that crosslink) are particularly critical.

In general, as already indicated above, the person skilled in the art will adapt the materials for the composite film according to the invention to the planned primary shaping process. Of course, the tolerable temperatures are of great importance. The carrier film according to the invention or the separating side of this film must be adapted to the plastic material in terms of its separating properties. The selected hot-melt adhesive (and of course also the selected carrier foil) must be adapted to the temperature requirements in the respective primary forming process insofar as the primary forming process must not generate temperatures that exceed the softening point of the carrier foil. 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 short-term 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 the plastic body formed in the original molding process is removed. It has been found that in such a situation the hot-melt adhesive develops its adhesion again in good time in order to continue to fix the composite film according to the invention on the mold in a contour-simulating manner.

examples

Measurement example 1

Measurement of the free surface energy or surface tension

A "Mobile Surface Analyzer (MSA)" from Krüss GmbH, Hamburg, was used to measure the surface energies and their disperse and polar components. This is a contact angle measuring device in which two parallel drops are dosed onto the sample surface with one click.

The test drop is dispensed contact-free onto the sample surface at room temperature and has a volume of approx. 1 µl. 5 seconds after dosing the drop, a recording is made and the static contact angle is first determined automatically using the “lying drop (double)” method. The automatic evaluation of the recordings is checked visually later and, if necessary, the baseline is corrected manually and recordings that cannot be evaluated are sorted out.

In order to be able to better describe the surface properties of the film, measurements with the test liquids water and diiodomethane and the resulting calculations of the surface energy are carried out at at least ten different positions of the same sample. The mean value is formed from this.

The test liquids used are water (surface tension: 72.80 mN/m; disperse fraction: 21.80 mN/m; polar fraction: 51.00 mN/m) and diiodomethane (surface tension: 50.80 mN/m; disperse fraction: 50 .80 mN/m; polar component: 0.00 mN/m). In case of doubt, the specialist will check the surface energy of the test liquids, e.g. with a Wilhelmy balance, and always ensure that the test liquids are fresh and uncontaminated.

The "Advance" program (version 1.6.2.0.) from Krüss GmbH is used as the measuring software.

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

Measurement example 2

Measurement of surface tack

The surface tack of the composite films is measured in accordance with DIN EN 1719 (measurement of the surface tack of pressure-sensitive adhesives/determination of the surface tack using the loop method).

In contrast to what is described in DIN EN 1719, however, a pressure-sensitive adhesive is not used on, for example, a polyester film with a thickness of 50 μm. Instead, the surface tack of the hot-melt adhesives already on the composite films, or the pressure-sensitive adhesives in the reference measurements, is measured as part of the composite films. For this purpose, the composite foils are underlaid on the carrier foil side with a 0.050mm thick stainless steel foil (Record metal foil, steel, rustproof 18Cr9Ni, 0.050mm). The contact pressure is thus defined by the metal foil, which means that different composite foils can 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 exchange the glass plate between different measurements in order to rule out contamination of the surface.

Exemplary embodiment 1 Front-side coating of composite films with a plasma-polymer separating layer

The composite films described in the examples below were provided with a plasma-polymer separating layer on the carrier film side using a low-pressure plasma system. The films described were used with a product width of 2 m, or smaller samples were fixed 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 lateral adhesion with a pressure-sensitive adhesive tape.

The plasma system has a cuboid 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 equipped with dielectric plastic insulation. A cooled flat electrode with a width of 2.6 m and a height of 1.65 m is inserted in the middle of the plastic insulation. The plasma chamber is evacuated upwards with 2 vacuum pump trains with a total suction capacity of 750 sccm at 0.019 mbar. The wrapping device is installed in the plasma chamber, electrically isolated from the chamber wall and floor, on a removable stainless steel floor 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, which are arranged inside the wrapping device and build up the fabric tension.

The foils were fed past the electrodes at a distance of 40 mm, with the outside pointing first to one electrode and then to the other. Before the coating process, the foils were dried by repeated wrapping in a vacuum for so long that the last wrapping before the coating process resulted in a pressure of 0.012 mbar at a wrapping speed of 7 m/min.

During the coating process, oxygen with a gas flow of 100 sccm and hexamethyldisiloxane (HMDSO) with a gas flow of 380 sccm were introduced as working gases from below with ongoing evacuation. The amount of gas was divided equally between the two electrode sides. The pressure in the plasma chamber was regulated to 0.025 mbar with the help of butterfly valves in front of the vacuum pump lines. The plasma was excited with a high frequency of 13.56 MHz with 3000 W each (generator output power) via the two flat electrodes. The films were rewound at a speed of 8 m/min.

Exemplary embodiment 1a: Contact angle measurements

The two plasma polymer-coated composite films according to the invention from exemplary embodiment 1 were measured and evaluated. Likewise, the untreated composite foils used for plasma coating as a reference. The results are shown in Table 1. Table 1: Results of the contact angle measurements foil pattern Water diiodomethane disperse part polar part total surface energy side facing away from the hot melt adhesive (°) (°) (mN/m) (mN/m) (mN/m) Example film 1 (coated PLATILON HL 9007) 101.0 72.8 21.3 1.3 22.6 Example film 2 (coated PLATILON HL 9074) 103.2 76.2 19.5 1.2 20.6 Reference film PLATILON 9007 ("barrier side") 102.0 55.4 31.2 0.2 31:4 Reference film PLATILON 9007 ("barrier side") 99.4 55.2 31:3 0.4 31:8

Example 1b: Measurements of the surface tack

The two plasma polymer-coated composite films according to the invention from exemplary embodiment 1 were measured and evaluated. Also two commercial self-adhesive PTFE sheets for reference. The results are shown in Table 2. Table 2: Results of surface tack measurements foil pattern Surface tack by loop method (N) Average smallest force greatest power Example film 1 (coated PLATILON HL 9007) 0.11 0.09 0.13 Example film 2 (coated PLATILON HL 9074) 0.08 0.08 0.08 Reference film PTFE virgin film 0.25 V self-adhesive ¹ ) 27.55 22.6 31.2 Reference film Release film with acrylate adhesive, self-adhesive ² ) 33.28 29.26 36.66
¹ ): PTFE film with silicone pressure-sensitive adhesive; Item No.: SK 10 AD / PTFE.SFL.025.AD from Hightechflon GmbH & Co. KG, Constance
² ) release film, 250 µm with acrylate adhesive;

Embodiment 2 Use of composite foils with a plasma-polymer separating layer for permanently providing molds with a separating layer in relation to cyanate ester prepregs

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 commonly used as protective equipment for textiles and polyurethane foam components. The two films consist of a high-melting film (barrier layer) on the front, with a softening range of 155 - 175°C, and a low-melting adhesive layer on the back, which has a softening range of 85 - 130°C for the Platilon ^® HL 9007 and for the Platilon ^® HL 9074 has a softening range of 125 - 150°C. Both foils were equipped with a plasma-polymer separating layer on the front side of the high-melting film (according to exemplary embodiment 1). They were then stretched over a 5 mm thick glass plate (as a model for a mould), fixed on the outside with vacuum sealing tape, vacuum stretch-drawn and 10 minutes in the oven at 125°C in the case of the Platilon® HL 9007 and 145°C in the case of the Platilon® HL 9074 tempered. After the subsequent cooling, the films adhered well to the glass plate and the vacuum could be released without any problems. The surface was mapped evenly.

The foil area outside the glass plate was discarded. A four-layer sample of the cyanate ester resin CFRP/GFRP prepreg PN900-C582-43 could now be cured several times on the composite foils laminated to the glass and then removed without any problems. Curing took place with a typical autoclave setup at atmospheric pressure in the oven. The samples were evacuated and placed in the oven at 60° C., heated to 125° C. at a heating rate of 3 K/min, tempered at 125° C. for 2 hours and, after cooling to room temperature, removed from the mold.

After 10 minutes of tempering in the oven at 130°C in the case of Platilon® HL 9007 and 150°C in the case of Platilon® HL 9074, the two composite films could then be easily pulled from the glass plates without any visible residue. If necessary, the film can be replaced in the event of defects.

Analogously, the composite foils are stretch-drawn over the mold surface of a press for the production of aircraft interior components from fiber-reinforced plastics with an outer layer made from the cyanate ester resin CFRP/GFRP prepregs PN900-C582-43 and fixed by heating. After 10 production cycles or demoulding, the mold surface is heated to 130°C in the case of the Platilon® HL 9007 and to 150°C in the case of the Platilon® HL 9074 and the composite film is removed without leaving any residue. The mold surface is then cooled to below 70°C and a new composite film is vacuum stretch-drawn onto the mold surface.

Exemplary embodiment 3: Possibility of widening the composite foils

Using simple laboratory tests, it was possible to show that the TPU film Platilon® HL 9007, which was laminated in an overlap area of 70 mm at a temperature of 130°C and a pressure of 0.03 MPa, has a maximum elongation of 107% ( pure composite foil > 300 %). The tensile stress to 100% elongation of the laminated composite sheet differed by less than 20% from the values of the original composite sheet.

Example 4 Production of fiber composite components for wind turbines using the composite foils according to the invention

A 60 μm thick polymer film with a layer of a thermoplastic co-polyester elastomer based on polybutylene terephthalate, a layer of approx. 7 μm polyamide 66 and on 30 µm of a thermoplastic polyurethane hot-melt adhesive based on polyester-polyurethanes with an average softening point of 110°C is used on the back of a layer. In this case, instead of the simple film in embodiment 1, this film is used as a half-tube with an inner 50 μm thick polyethylene support layer. The composite film lying with the back on the supporting film can be easily separated from the supporting film by hand at 23 °C. In this way, films according to the invention can be coated with twice the width.

The half-tube is coated analogously to the coating of the film web in exemplary embodiment 1. Unlike described in exemplary 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 in front of the second electrode.

The plasma polymer-coated film described, with a half-tube width of 2000 mm, is positioned on the face of the mold, a rotor blade half-shell. The film roll is provided on a roll holder. The film is then unrolled and separated from the roll so that the start of the web is in the area of the blade tip and the end of the web is in the area of the blade root. The half tube protrudes beyond the two end faces of the mold. The half-tube is then unfolded and the polyethylene support layer removed. The opened half-tube has a width of 4000 mm and is oriented with the side with thermoplastic polyurethane hot-melt adhesive in the direction of the mold.

The composite film is then slightly pretensioned and fixed to the mold with vacuum sealing tape. Where the foil width allows, the foil is fixed to the edge of the tool 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 on one side at the edge of the tool. The opposite edge of the film is fixed on the mold within the component area. The volume of air between the film and the mold is then evacuated and the film is thus vacuum-stretched into the mold. The mold is then heated to a temperature of 110°C by the integrated mold heater. After the tool has reached the temperature, it is held for 5 minutes before the heating is deactivated and the tool cools down to at least 40°C. As a result of the softening and subsequent cooling of the hot-melt adhesive, the composite film has connected to the mold. The vacuum connections are then vented, the composite film remains in the stretched state and adheres to the mold. The film is then cut through all the way around inside the frame made of vacuum sealing tape with a sharp blade and the severed edge areas are pulled off. If parts of the cut-off edge areas are still sticking to the mold, they are heated with a hot-air blower to a temperature above the average softening point of the hot-melt adhesive and can then be removed.

In order to apply the film to the remaining component area not covered by the film, a second film cut is spread out over the remaining, exposed component area and prepared analogously to the first film web. This second film cut is then again slightly pretensioned and fixed on the mold with vacuum sealing tape. The vacuum belt runs in the area within the component area on the previously applied foil web, so that the first and the second foil cut overlap here. The second film cut is then vacuum-stretched into the mold by applying a vacuum between the film and the mold. The tool is again heated to a temperature of 110°C in the area of the second film cut, this temperature is maintained for 5 minutes before the heating is deactivated and the tool is allowed to cool down again. This cut of the composite foil has also connected to the one with the forming tool. After the vacuum has been released, this blank is cut through with a sharp blade all the way around inside the frame made of vacuum sealing tape. In the area of the overlap with the first foil cut, the separation takes place in such a way that a flush joint of the two foil webs is created. Alternatively, a separation is possible so that the first film web remains undamaged on the tool and the second film web overlaps with it. The separated edge areas are deducted.

After the composite film has been applied to the entire surface of the mold, textile and hard semi-finished products are built up on the mold. One of the tough semi-finished products is the hub connection, a semi-finished product that consists primarily of glass fiber reinforced epoxy-based plastic and is equipped with connection surfaces and connecting elements for connecting the subsequent rotor blade to the hub.

The tear-off fabric, perforated release film, flow aid, vacuum lines for infusion and suction of the resin are then inserted. Finally, vacuum film is applied and applied airtight to the mold using vacuum sealing tape. The injection line is then closed and the layer structure is evacuated by means of a vacuum pump through the suction line (absolute pressure: 50 mbar).

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

After this cooling phase, the vacuum film, perforated separating film, flow aid and the inserted hoses are removed before the component with the peel-off fabric remaining on it 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 demoulding. The composite film allows the production of further components on the separating film, their separating properties are retained after demolding, so that further analogous components can be produced with the same composite film.

Example 5 Production of fiber composite components for wind turbines using the composite foils according to the invention

A rotor blade half-shell is produced analogously to exemplary embodiment 4. Deviating from this, in this example the half-tube is spread out outside the mold on a cutting table and the polyethylene supporting layer is removed there. In addition, the composite foil is already cut to size on the cutting table to the contour required for the shape of the rotor blade. Also, before spreading in the rotor blade mold, a section of the composite foil cut to the required contour is glued to the positions where the width of the composite foil half-tube is not sufficient by arranging it with an overlap of approx. 3 cm next to the composite foil edge and the overlap glued with pressure and heating for approx. 20 seconds to approx. 120°C.

The now prefabricated composite foil is then folded together, rolled up and transported to the rotor blade mold.

Exemplary embodiment Example 6: Repair of local damage to the composite film in the mold

If local damage occurs after fixing the composite film according to exemplary embodiment 4 or 5, for example due to the insertion of the hard semi-finished products described above, which are 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 area of the composite film is heated with a hot air blower to a temperature above the average softening point of the hot-melt adhesive and then removed from the mold.

After the local exposure of the tool mold, a foil cut of the composite foil is fixed with vacuum sealing tape, slightly pretensioned, on the partial area of the mold to be equipped. The vacuum sealing tape is fixed to the adjoining mold area equipped with composite film, the composite film protrudes over the repair area and is oriented with the thermoplastic polyurethane hot-melt adhesive on the back in the direction of the mold. The volume of air between the film and the mold is then evacuated, so that the film blank is in contact with the mold. The evacuation takes place through a previously installed vacuum line. To fix the composite film on the mold surface, the film is heated to a temperature of 110°C with a hot air blower.

As a result of the softening and subsequent cooling of the hot-melt adhesive, the composite film has connected to the mold. The vacuum is then vented, the composite film remains in the stretched state and adheres to the mold.

After the vacuum has been released, this blank is cut through with a sharp blade all the way around inside the frame made of vacuum sealing tape. In the area of the overlap with the composite foil to be repaired, the separation takes place so that a flush joint of the two foil webs is created. Alternatively the separation takes place in such a way that the first film web remains undamaged on the tool and the second film web overlaps with it. In the separated edge areas, the composite film is pulled off the mold, the separation being supported with a hot air blower that heats the edge areas to a temperature close to the mean softening point of the hot-melt adhesive.

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• DE 102017131085 A1 [0007]
• DE 102013219331 B3 [0007]
• EP 2841269 B1 [0014]

Non-patent Literature Cited

• DIN EN ISO 527-3 [0020]
• DIN EN ISO 527 [0020]
• DIN EN ISO 527-1 [0021]

Claims (15)

Composite film for facilitating the separation of a plastic body produced in the primary molding process from the mould, comprising a) a vacuum stretch-drawable carrier film made of plastic and b) a hot-melt adhesive layer on one side of the carrier film, the hot-melt adhesive having a surface tack of ≦2 N at 25° C. and a surface energy of ≦30 mN/m being present on the side of the composite film opposite the hot-melt adhesive layer. composite foil 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. Composite film according to one of the preceding claims, wherein the softening range of the hot-melt adhesive from a temperature ≥ 40 ° C, particularly preferably above ≥ 50 ° C, more preferably ≥ 60 ° C, ≥ 70 ° C, ≥ 80 ° C and very particularly preferred ≥ 90°C begins. 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. Composite film according to one of the preceding claims, wherein a silicon-containing, preferably a silicon-organic, particularly preferably a plasma-polymeric silicon-organic coating is present on the side of the carrier film opposite the hot-melt adhesive layer. Composite film according to one of the preceding claims, wherein on the side of the composite film opposite the hot-melt adhesive layer 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 preferred ≤ 1.5 mN/m. Arrangement comprising a mold for a primary forming process and stretch-drawn therein or around it a composite film according to any one of the preceding claims, 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. arrangement according to claim 7 , comprising in the mold on the release film material for an original molding process. arrangement according to claim 8 , Wherein the material for a primary molding process is a duroplastic or elastomer, preferably comprising fibers for a fiber-reinforced plastic and/or is preferably cured. Use of a hot-melt adhesive, preferably as defined in more detail in one of the preceding claims, for fixing and/or detaching a vacuum stretch-drawable carrier film as required to facilitate the separation of a plastic body produced in the original molding process from the mold, the vacuum stretch-drawable carrier film being defined in more detail as in one of the preceding claims. Use of a composite film as in any of Claims 1 until 6 defined, or an arrangement as in any of Claims 7 until 9 defined to facilitate the removal of a plastic body formed in the primary molding process from the mold. Method for producing a composite film according to one of Claims 1 until 6 , comprising the steps: a) providing a vacuum stretch-drawable carrier film made of plastic b) providing a hot-melt adhesive, c) coating one side of the carrier film with the hot-melt adhesive. procedure after claim 12 , comprising as step d) application of a silicon-containing, preferably a silicon-organic, particularly preferably a plasma-polymeric silicon-organic coating on the opposite side of the hot-melt adhesive layer of the carrier film. procedure after claim 12 or 13 , wherein step c) takes place in a blown film line. Method for producing an arrangement according to one of Claims 7 until 11 , comprising the steps of: a1) providing a composite film according to one of Claims 1 until 7 or a2) performing a method according to any one of Claims 13 until 15 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 via vacuum stretch-forming, and d) fixing the composite film by means of the hot-melt adhesive to the mold by heating, preferably by heating a temperature within the softening range of the hot melt adhesive and below the softening range of the backing film.