Method for producing a prepreg layer, prepreg layer and use thereof

Abstract

The invention relates to a method for producing a prepreg layer (1), comprising at least the following steps: a) providing a wire structure (2) having a specified basis weight, b) adding a water-polyolefin mixture (3) into the wire structure (2) such that the basis weight is increased by at least 30%, c) dewatering the wire structure (2) having the water-polyolefin mixture (3), d) consolidating the wire structure (2) with a polyolefin.

Description

Technical Field

[0001] The invention relates to a method for producing a prepreg layer, a prepreg layer and use thereof. Background Art

[0002] In particular, components (eg vehicle components, aircraft components, ship components, train interior components, electronic components, etc.) can be produced with fiber-reinforced materials on the basis of fiber-based semi-finished products, the best-known representative of which is "prepreg".

[0003] Prepregs generally contain a fiber material made of one or more types of fibers, such as carbon fibers, glass fibers, aramid fibers, basalt, boron fibers, ceramic fibers, silica fibers, steel fibers, polyester fibers, nylon fibers, polyethylene fibers, organic glass fibers, natural fibers and / or other types of fibers, wherein the fiber material is impregnated with a matrix plastic. The fibers of the fiber material can be present in the prepreg as continuous fibers with a preferred direction (unidirectional layer), as an ordered fabric surface (e.g. woven fabric, knitted fabric, scrim, interlaced knitted fabric...) or as a disordered fabric surface such as wool or a random fiber mat.

[0004] Polymer materials (also called "resin systems") are usually used as matrix plastics for prepregs, such as thermosets (also called duromers; synthetic resins, epoxy resins, phenolic resins, polyester resins), thermoplastics or elastomers. When the prepregs are delivered, thermosets and elastomers have not yet reacted completely and are therefore still plastically deformable. Special storage conditions must be observed here, such as very low storage temperatures. It is well known that thermoplastics can be repeatedly put into a plastically deformable state by heating.

[0005] Prepregs are usually manufactured as layers, sheets, tapes or webs, with the webs usually being delivered in rolls.

[0006] To produce an object or component, a piece large enough is usually separated from the prepreg in order to line the surface of a pressing tool (mold). By pressing the prepreg in a pressing tool under the influence of heat (or more generally by applying a pressure greater than atmospheric pressure to the prepreg), the thermosetting or elastomeric matrix plastic reacts and the object or component is shaped. In the case of a thermoplastic matrix plastic, it acquires plasticity through the action of heat and the shape of the object or component can be achieved by pressing the prepreg under the action of heat and then cooling the shaped prepreg to below the softening temperature of the thermoplastic.

[0007] The requirements for prepregs can be very different, especially with regard to their end use for the production of injection-molded components and / or the preparation of the injection-molding process. In particular, it may be desirable to achieve a particularly uniform, complete and / or strong adhesion of the matrix plastic to the textile surface structure. In particular when considering continuous production, it is necessary to find suitable, cost-effective and fast methods for producing such prepregs.

[0008] A particular challenge is to provide lightweight prepregs with high deformation and strength properties and, if required, uniform surface reflectivity. Summary of the invention

[0009] The object of the present invention is to at least partially overcome the disadvantages described with reference to the prior art and also to produce in a simple manner prepregs of high and variable practical value, in this case ensuring that the composite structure stabilizes the final product as uniformly as possible over the entire planar design of the final product. In particular, a simple possibility of providing prepregs is to be created, wherein the method is suitable for further processing using manufacturing technologies existing on the market that require intensive shaping.

[0010] The objects are solved by the features of the independent claims. Advantageous further developments are specified in detail in the dependent claims. The description, in particular the drawings, illustrate the invention and show further exemplary embodiments. The features listed individually in the claims can be combined with features of other claims and / or the description.

[0011] A method for producing a prepreg layer contributes to this, the method comprising at least the following steps:

[0012] a. providing a wire structure having a basis weight,

[0013] b. adding the water-polyolefin mixture to the thread structure so that the basis weight increases by at least 30%,

[0014] c) dehydrating the thread structure with the water-polyolefin mixture,

[0015] d) Consolidation of the wire structure with polyolefins.

[0016] Steps a), b), c) and d) can be carried out in the order given here. However, some steps can also be carried out simultaneously or overlappingly. This means in particular that the steps are carried out (partially) simultaneously but still (spatially) independently, for example in the case of continuous production, in which the (infinite) line structure is transferred to different stations in sequence to carry out steps b), c) and d). Therefore, the steps are not carried out simultaneously on the same section of the line structure.

[0017] In the context of step a), a large number of threads (also called filaments or (continuous) fibers) can be provided. These can be provided individually, directionally and / or (partially) in combination with each other. Alternatively or cumulatively, a bundle of threads, i.e. a (separate or separate) strand made of a large number of threads, can also be provided. The bundle of threads can be designed as a so-called roving, i.e. a (multi) filament yarn made of parallel arranged threads (or also called filaments). It is particularly preferred that all threads and / or bundles of threads are arranged to be essentially unidirectionally aligned with each other, in particular in the direction of a common conveying or transport direction. The thread can consist of at least one or more of the above-mentioned fiber materials.

[0018] The thread preferably comprises a glass fiber bundle, in particular a glass fiber bundle having a fineness in the range of 300 to 1200 tex. The thread preferably comprises or is formed by a plurality of glass fiber filaments, which extend substantially parallel to each other and thus form a bundle. The glass fiber bundle may comprise internal holes, which can be used as a reservoir for the application of the plastic matrix.

[0019] The threads are arranged relative to one another in such a way that they provide a (separate) thread structure, for example in the manner of a fleece, a woven fabric, a knitted fabric, a cross-knitted fabric or a scrim.

[0020] The thread structure is preferably designed as a fabric. The fabric preferably has a regular and / or uniform design. The fabric is essentially formed only by threads and / or thread bundles. This can be provided in the form of a web and / or a plate and / or a layer. The fabric has a very high ratio of surface area to material thickness. The fabric can be windable and / or stackable and / or (elastic) deformable. The fabric can be designed open, wherein the open fabric has a large number of (transparent) holes.

[0021] The open or grid-like wire structure can have holes with an opening width in the range of up to 200 mm [millimeter], wherein the opening width is particularly preferably in the range of 1 to 150 mm. The opening width is understood to be the maximum extent of the hole (perpendicular to the thickness of the wire structure), for example the maximum free diagonal in the case of square holes. It is preferred to produce small opening widths, for example in the range of 1 to 10 mm, for processes / components with a high oriented fiber content. In injection molded reinforcement, these hole sizes are advantageous for achieving good embedding in the injection molding compound. However, larger opening widths (for example 30 to 100 mm) are suitable for large-area applications with low force absorption, for example in the construction sector for use with reinforced insulation materials or masonry facings (so-called "strips"), so that the individual elements form a larger mat, which makes manual work easier. If there are square holes, such applications preferably have an edge length (maximum) of about 100 mm.

[0022] According to step a), a predetermined basis weight is assigned to the thread structure. The basis weight can be adjusted, for example, by appropriate choice of the material and structure of the threads and the arrangement of the threads relative to one another, in particular also taking into account the design of the holes. The basis weight is usually expressed in grams per square meter [g / m 2 ] and can be, for example, from 50 to 500 g / m 2 The basis weight is selected or set in a range of 10 cm x 10 cm [centimeter] in particular, wherein the basis weight value remains within such a size range. If the surface structure is larger than this size range, the value of the surface structure can preferably be maintained in all size ranges, in particular if the thread structure has the same thickness or structure. According to step a), it is a "dry" basis weight, which means that it contains practically no (separated or unbound) water.

[0023] According to step b) the water-polyolefin mixture is added to the thread structure such that the basis weight is increased by at least 30%.

[0024] In particular, polyolefin copolymers are used in water-polyolefin mixtures. Polyolefins (also called "polyalkene") are compounds of the formula C n H 2n Polyolefins are polymers composed of hydrocarbons (ethylene, propylene, 1-butene, isobutylene). Polyolefins are semicrystalline thermoplastics. Polyolefins are currently usually produced from oil or natural gas. This process is called polymerization, in which short chains of chemical substances (monomers) are linked to long chains (polymers) using catalysts. Polyolefin copolymers are therefore polyolefins composed of two different types of monomer units. The polyolefins used are applied via aqueous solutions, for example by spraying or dipping. The water-polyolefin mixture can be added particularly concentratedly or comprehensively, so that the thread structure is completely wetted or even saturated. This can be supported by capillary forces, for example due to the choice of thread and / or the shape of the thread structure.

[0025] According to step b), it is the "wet" basis weight, which therefore includes in particular the supplied water or part of the water-polyolefin mixture, which in particular adheres to the surface structure and / or is in the surface structure or is transported with it. The amount added is adjusted so that the basis weight increases by at least 30%. The basis weight after the predetermined addition of the water-polyolefin mixture can also be referred to as the "wet basis weight". This increase in basis weight must be adjusted in particular taking into account the absorption capacity of the fabric and / or the composition of the polyolefin copolymer and / or the required properties of the prepreg layer. In particular, the additional carrier or wet basis weight is set in a targeted manner and, if necessary, is also immediately monitored or corrected. For example, in step b), more water-polyolefin mixture can first be added than corresponds to the target, and then part of the carrier can be removed again in order to set the target. Obviously, the predetermined increase in basis weight exists at the end of step b), followed by the addition of plastic until the end of step d).

[0026] After the addition of the water-polyolefin mixture, the (wet) thread structure is dehydrated according to step c). In other words, this means in particular that the water content or water adhering to the thread structure is removed, in particular evaporated. Therefore, the (dry) basis weight of the thread structure after step c) is generally less than the (wet) basis weight after step b), but also greater than the (dry) basis weight after step a). When step c) is carried out, the basis weight can be reduced by at least 9%, in particular in the range of 9% to 27%. Preferably, when step c) is carried out, the basis weight is reduced by 10% to 24%, in particular 13% to 22%, particularly preferably 15% to 20%. Water has in particular the function of uniformly distributing the polyolefin particles in or on the thread structure, which is supported by its flow properties. It can therefore be assumed that this will reach an acceptable level at a given time and the water can be removed. In order to maintain the distribution of the polyolefin particles in or on the thread structure to a large extent during this process, the evaporation of water is particularly advantageous. Therefore, at the end of step c), there is in particular a (completely) dry thread structure.

[0027] Preferably, step c) is carried out thermally, wherein the temperature (of the thread structure comprising the water-polyolefin mixture) is set in the range between 100° C. and the melting temperature of the polyolefin. Step c) is preferably carried out using electromagnetic radiation in the wavelength range of 0.78 μm to 100 μm [micrometers], in particular in the wavelength range of 1 μm to 10 μm, or using infrared radiation. This obviously requires that the carrier (possibly with the thread structure) is heated to a dehydration temperature which is above the evaporation temperature of water but (significantly or definitely) below the melting temperature of the polyolefin used. In other words, this means in particular that (significant) melting of the polyolefin used is prevented during step c). The thermal dehydration can more preferably be carried out for a time of 0.2 to 4.0 min [minutes]. The predetermined time period can be set taking into account the amount of water to be removed per square meter, the action distance, the heating power and / or the feed speed of the thread structure. In the case of a woven thread structure in the context of step a), the feed speed depends significantly on, for example, the weft insertion power (β / min) and the weft yarn density (β / cm), so that other parameters can be adjusted on this basis.

[0028] The dried thread structure is then consolidated with the polyolefin in step d). In particular, thermal consolidation takes place here. The (dry) basis weight of the thread structure after step d) corresponds (substantially) to the (dry) basis weight after step c). As part of this step, a permanent connection or fixation of the polyolefin particles to each other and to the thread is achieved by melting or fusing the polyolefin particles and connecting them to the thread or to each other during a subsequent curing process. The thread structure may be present at a temperature at or below the dehydration temperature at the start of step d). Step d) leads to a significant, possibly sudden increase in the ambient temperature, wherein the thread structure and the polyolefin can achieve the greatest possible heating rate. In particular, step c) takes place in a first oven and step d) takes place in a second oven, wherein the thread structure is preferably guided or moved directly from the first oven into the second oven or the ovens are seamlessly merged into each other or the oven is treated as an oven with two different areas.

[0029] Step d) is preferably carried out thermally, wherein the temperature (of the thread structure comprising the water-polyolefin mixture) is set in a range above the melting temperature of the polyolefin. The thermal consolidation may more preferably be carried out for a time of 0.2 to 4.0 min [minutes]. The predetermined time period may be set taking into account the amount of polyolefin to be melted per square meter, the heating power and / or the feed speed of the thread structure.

[0030] Preferably, the basis weight increase in step b) is 35 to 65 wt.-% [percent by weight]. In the case of a weight loading of 35% of the water-polyolefin mixture, sufficient polyolefin is added to the product in order to achieve a favorable fiber-matrix ratio in the final product. A loading of 35 wt.-% or more ensures that the fibers in the final product are adequately covered with the polyolefin matrix, thereby giving the product sufficient dimensional stability so that it can be easily handled using conventional fixture systems and can therefore be easily processed automatically. In addition, a sufficient amount of polyolefin matrix ensures good bonding properties during further processing in subsequent processes. With a weight loading of the water-polyolefin mixture exceeding 65%, economics are at risk, since there is a significant excess of polyolefin in the product and at the same time a large amount of water is introduced that must be evaporated. Since the evaporation of water is a very energy-intensive process, excessive exposure of the product to the water-polyolefin mixture is disadvantageous from an economic point of view.

[0031] Preferably, in step b), a water-polyolefin mixture is added, wherein the water content is in the range of 40 to 60 wt % [weight percent]. Within the scope of this regulation, it can be achieved or guaranteed that the mixture remains stable for a long time and can still be processed economically. The lower limit of 40 wt % of regulation can, for example, ensure that the described manufacturing process can operate economically. At lower values, the water content is too high, meaning that excessive energy must be used to dry. With significantly higher polyolefin weight percentages, for example, when exceeding 60 wt %, the mixture may be unstable, i.e. phase separation occurs, so that the polyolefin and water are separated, i.e. separated. Therefore, the uniform distribution of the polyolefin in the linear structure is no longer guaranteed.

[0032] Preferably, the wire structure is immersed in the water-polyolefin mixture during step b). Thus, the wire structure can be supplied to the groove, for example, by means of a roller device, so that it is immersed below the surface of the water-polyolefin mixture (the so-called "float") located in the groove. In the region of the groove, rollers can also be provided, over which the wire structure is guided and / or between which the rollers are located. The rollers can have roller surfaces that adjust or influence the application or introduction of the water-polyolefin mixture toward the wire structure. The viscosity can typically or preferably be less than 5000 mPas, preferably between 500 and 3000 mPas, for example during dipping. In this way, the water-polyolefin mixture can be added to the wire structure quickly, evenly and / or comprehensively.

[0033] The wire structure with the water-polyolefin mixture may be subjected to a (subsequent) roller extrusion process during or after the impregnation process. In the roller extrusion process, the wire structure passes between two or more rollers or rollers, wherein the water-polyolefin mixture is pressed between the individual wires and their filaments by the pressure between at least two rollers. In order to adjust the carrier weight, the distance between the rollers may be set to a defined gap, or the rollers may be placed in a movable manner relative to each other. The adjustment or setting of the basis weight may be adjusted, for example, by at least one of the following measures:

[0034] - Varying the contact pressure of the rollers, for example by using rollers with higher / lower intrinsic mass, varying the external pressure application, for example by pneumatics or similar.

[0035] - Adjust the wrap angle (the angular range of the rollers where the wire structure lies).

[0036] - Modification of the roller surface(s), for example the optional use of smooth, (substance-) covered and / or structured rollers.

[0037] -Adjust the feed speed of the wire structure.

[0038] - Extend the distance below the surface of the floating body.

[0039] As part of the rolling process, the wire structure can also be flattened and / or embossed.

[0040] The polyolefin used here is preferably a copolymer selected from the group consisting of random copolymers, gradient copolymers, alternating copolymers, block copolymers, polymer mixtures, graft polymers.

[0041] In a random copolymer, the monomers are randomly distributed in the chain, for example as follows:

[0042] AABBABBBBAAAABAABBBAAABBABBAAAABBBABAABBAB….

[0043] Gradient copolymers have a structure similar to random copolymers but have variable monomer ratios along the chain, for example in the following manner:

[0044] AAAAAAAAABAAAABBBAAABBABBBAABBBBBBABBBBBBBB….

[0045] In an alternating copolymer, the monomers are arranged regularly along the chain, for example in the following manner:

[0046] ABABABABABABABAB...

[0047] Block copolymers are characterized by longer blocks or sequences of each monomer, which may also repeat, for example in one of the following ways:

[0048] AAAAAAAAABBBBBBBBBBBB

[0049] or

[0050] AAAAAAAAABBBBBBBBBBBAAAAAAAAAAAAABBBBBBBBB...

[0051] Mixed polymers are characterized by the presence of different polymers without chemically reactive connections between them, such as the following types:

[0052] AAAAAAA+BBBBBBBB.

[0053] Graft copolymers consist of a backbone composed of a polymer of one monomer onto which are grafted blocks / "side arms" of a polymer of another monomer, such as the following types:

[0054] BBB

[0055] BBBBB

[0056] BBBBB

[0057] AAAAAAAAAAAAAAAAA...

[0058] BBBBB

[0059] BBBB

[0060] B

[0061] B

[0062] In all cases mentioned, the molecular chain may be linear or (slightly) branched.

[0063] This allows the polymeric material to be blended with other substances, in particular for functionalization (e.g. stabilizers, flame retardants, ...) and / or cost reduction (fillers). The copolymers can be selected to provide different properties to different plastics.

[0064] The polyolefin copolymer is preferably a polymer mixture of (especially) polymers with different particle sizes and / or molecular chain lengths. Smaller particles / molecules can penetrate better between the threads or individual filaments and form good bonds between the threads. On the other hand, larger particles / molecules tend to penetrate less and can therefore influence or adjust the surface properties of the prepreg, such as the connection to the subsequent composite material. In addition, by mixing polymers with different melting points, the melting point of the mixture can be easily adjusted to suit the respective application.

[0065] According to another aspect, a wet prepreg layer is proposed, comprising a thread structure wetted with a water-polyolefin mixture, wherein the water-polyolefin mixture represents 35% to 65% of the (wet) layer weight.

[0066] Particularly preferably, the wet prepreg layer is produced using steps a) and b) of the method proposed herein. In any case, the listed properties of the "wet" wire structure can also be used alone to characterize the wet prepreg layer, in particular with regard to subsequent use.

[0067] On the other hand, the use of wet prepreg layers for thermal aftertreatment and production of prepreg layers with a solid polyolefin matrix is ​​proposed.

[0068] Wet prepreg layers are particularly preferably suitable for thermal aftertreatment and the production of prepreg layers according to steps c) and d) of the method proposed herein. Regardless, the listed specific features of dehydration and / or consolidation can be used to characterize the wet prepreg layers.

[0069] Finally, a prepreg layer is also proposed, which is produced using the method disclosed herein, wherein the minimum bending radius of the prepreg layer can be up to 30 mm [millimeters]. The minimum bending radius is understood to be the bending radius at which (under normal room conditions, in particular below room temperature) the plastic matrix does not (significantly) separate and / or kink the threads. In particular, it is in the range of 10 to 20 mm (e.g., a fabric thickness of up to 1.0 mm). The structure of the prepreg layer proposed herein thus allows surprisingly small bending radii without damaging it and / or significantly impairing further use.

[0070] The prepreg layer is designed in particular such that the threads are embedded in a polyolefin matrix or plastic matrix. This means in particular that the matrix surrounds substantially the entire thread. If filament bundles are present, these are also substantially penetrated by the matrix or the filaments themselves are (mostly) surrounded by the matrix. The matrix in particular forms the entire surface of the prepreg layer.

[0071] Most preferably, the prepreg layer is designed with a plurality of holes or as an (open) grid and has a layer density of up to a maximum of 1.0 g / cm3 [grams per cubic centimeter]. The layer density is determined in particular in this case by measuring the weight of the layer and setting it relative to its (envelope) volume (length x width x thickness of the layer). In other words, this means in particular that the layer density corresponds to the quotient of the basis weight of the (consolidated) prepreg layer and the thickness of the (consolidated) prepreg layer.

[0072] The thickness of a layer is measured as the distance between a reference plate on which the layer is located and a parallel circular pressure die (preferably a die diameter of about 50 mm) which applies a fixed pressure (preferably about 1 kPa) to the layer to be measured. The distance between the reference plate and the printing die is measured and recorded. The usual climatic conditions apply here. The thickness measurements are preferably made at different points on the layer and an average value is then formed from these measurements. The thickness of the layer must be determined in particular in accordance with DIN EN ISO 5084.

[0073] The upper limit of the layer density specified here is 1.0 g / cm3, which ensures high deformation and strength properties of the lightweight prepreg. The layer density can be achieved in particular by a more open shape of the line arrangement, wherein the provision of the polyolefin copolymer plastic matrix enables the line arrangement to have specific bonding properties.

[0074] The layer density is preferably between 0.45 and 0.9 g / cm 3 In the range of 0.55 to 0.75 g / cm 3 The range of 0.45 to 0.9 g / cm3 is considered to be particularly advantageous for, for example, a grid-like prepreg layer, wherein the range of 0.55 to 0.75 g / cm3 is a particularly advantageous application amount for a polyolefin copolymer plastic matrix, which is particularly advantageous for further processing, in particular for complex and highly stressed components.

[0075] Preferably, at least a slight gloss can be observed in the prepreg layer, which is achieved in particular by consolidation. In particular, the prepreg layer does not have a matte, diffusely reflecting surface. With sufficient consolidation, the structural features of the rough surface combine to form a relatively smooth, reflective, shiny film, whereby the structure of the thread material can also influence the surface structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0076] The present invention and its technical environment are described below in conjunction with the accompanying drawings. It should be noted that the present invention is not limited to the embodiments shown. The features shown in the accompanying drawings can be extracted and, if necessary, combined with other features of the specification or other drawings, unless this is explicitly excluded below.

[0077] Schematically in the accompanying drawings:

[0078] Figure 1 A top view of a prepreg layer is shown;

[0079] Figure 2 shows a cross-sectional view of a prepreg layer;

[0080] Figure 3 An overview of embodiment variations of the method disclosed herein is shown;

[0081] Figure 4 Exemplary embodiments of different designs of step b) are shown. DETAILED DESCRIPTION

[0082] Figure 1 and Figure 2 By way of example, a (finished or consolidated) woven prepreg layer 1 is shown having a plurality of threads 2 arranged to form a thread structure 2 (woven fabric or open grid). They are embedded in a polyolefin matrix 9. However, a plurality of holes 4 with a predetermined opening width 5 are provided. In this case, the polyolefin matrix 9 comprises a polyolefin copolymer and the prepreg layer 1 has a maximum of 1.0 g / cm 3 The layer density can be determined by the envelope volume, which can be determined based on the predetermined length 6, width 7 and thickness 8 of the prepreg layer 1.

[0083] Figure 3 By way of example and schematically a possible manufacturing process of such a prepreg layer 1 is shown, wherein from left to right a sequential production is shown and comprises the following steps:

[0084] a) A thread structure 2 having a predetermined basis weight is provided, here by means of a weaving machine 10. The produced thread structure 2 is further conveyed along a predetermined feed direction 16.

[0085] b) adding the water-polyolefin mixture 3 to the thread structure 2 so that the basis weight increases by at least 30%. This step is carried out in the tank 11, wherein this step can be carried out in particular according to Figure 4 is carried out according to one of the embodiment variants.

[0086] c) Dehydration of the thread structure 2 with the water-polyolefin mixture 3 , wherein this takes place in a first oven 12 .

[0087] d) Consolidation of the thread structure 2 with the polyolefin, wherein this takes place in a second oven 13 .

[0088] e) Cooling the line structure 2 along the cooling section 14 .

[0089] f) Winding up the prepreg layer 1 in a winding station 15 .

[0090] Figure 4 Different embodiment variants of step b) are disclosed by way of example and schematically, in which a water-polyolefin mixture 3 is added to the thread structure 2 such that the basis weight is increased by at least 30%.

[0091] In the different variants (I) to (V) shown, the filamentary structure 2 is fed to a tank 11 in which a water-polyolefin mixture 3 is stored. The (lowest) roller 17 is always immersed in the water-polyolefin mixture 3 and is in contact with the wire structure 2 when the wire structure is guided past along the feed direction 16. The roller 17 can have a roller surface that can adjust or enable the application or introduction of the water-polyolefin mixture 3 toward the wire structure 2.

[0092] As can be seen from the variants, the rollers used, their number and shape and / or the contact path or wrap angle of the wire structure 2 can be adjusted differently to ensure the desired increase in basis weight in this step. Figure 4 The essential differences between the variants shown are obvious and can be briefly summarized here:

[0093] Variant (I): The wire structure 2 passes (substantially straight) through the gap between two rollers 17 , wherein the lower roller is not completely immersed in the bath of the water-polyolefin mixture 3 .

[0094] Variant (II): The wire structure 2 passes (essentially straight) through the gap between two (upper and middle) rollers 17, wherein the lower roller is not completely immersed in the bath of water-polyolefin mixture 3. The lower roller 17 transfers a portion of the absorbed water-polyolefin mixture 3 to the middle roller 17, which is completely outside the bath of water-polyolefin mixture 3.

[0095] Variant (III): The wire structure 2 is guided under the lower roller 17, which is not completely immersed in the bath of the water-polyolefin mixture 3. The wire structure 2 then further passes around the lower roller 17 and (adjacent thereto) passes through the gap between the lower roller and the upper roller 17. The wire structure 2 is then further guided around the upper roller 17 (adjacent thereto) and is finally conveyed away again in the original feed direction 16.

[0096] Variant (IV): Here, the roller arrangement and the guide arrangement are as in variant (III), but here a third (upper) roller 17 is also provided and the wire structure 2 is finally guided through the gap between the two upper rollers 17 .

[0097] Variant (V): This figure shows that, in order to set the desired carrier weight, the distance between the rollers can be set to a defined gap or the rollers can be placed in a movable manner relative to each other. For example, the setting of the basis weight can be adjusted by at least one of the measures indicated here: adjusting the contact pressure of the roller 17 (+p, -p, 0); adjusting the wrap angle (+q, -q, 0); adjusting the feed speed (v) of the wire structure 2.

[0098] This shows that the solution proposed herein at least partially overcomes the disadvantages described with reference to the prior art and also produces in a simple manner prepregs of high and variable practical value, in which case it is possible to ensure that the composite structure stabilizes the final product as uniformly as possible over the entire planar design of the final product. In particular, a simple possibility is created to provide prepregs, wherein the method is suitable for further processing using manufacturing technologies existing on the market that require intensive shaping.

[0099] Reference numerals list

[0100] 1 Prepreg layer

[0101] 2-wire structure

[0102] 3 Water-polyolefin mixture

[0103] 4 holes

[0104] 5. Opening Width

[0105] 6 Length

[0106] 7 Width

[0107] 8 Thickness

[0108] 9 Polyolefin matrix

[0109] 10. Loom

[0110] 11 slots

[0111] 12. First Oven

[0112] 13. Second Oven

[0113] 14 Cooling section

[0114] 15 Winding Station

[0115] 16 Feed direction

[0116] 17 Roller

Claims

1. A method for producing a prepreg layer (1), comprising at least the following steps: a) providing a thread structure (2) having a specified basis weight, b) adding the water-polyolefin mixture (3) to the thread structure (2) such that the basis weight is increased by at least 30%, c) dehydrating the thread structure (2) with the water-polyolefin mixture (3), d) Consolidating the thread structure (2) with polyolefin.

2. The method according to claim 1, wherein step c) is performed thermally, wherein the temperature is set in the range between 100°C and the melting temperature of the polyolefin. 3 . The method according to claim 2 , wherein step c) is performed using electromagnetic radiation in the wavelength range of 0.78 μm to 100 μm.

4. The process according to any one of the preceding claims, wherein in step d) the temperature is set in a range above the melting temperature of the polyolefin.

5. A process according to any one of the preceding claims, wherein the basis weight is increased in step b) by 35% to 65%.

6. The process according to any of the preceding claims, wherein in step b) a water-polyolefin mixture (3) is added, wherein the water content is in the range of 40% to 60%.

7. The method according to any one of the preceding claims, wherein in step b) the thread structure is immersed in the water-polyolefin mixture (3).

8. The method according to any of the preceding claims, wherein the viscosity of the added water-polyolefin mixture is below 5000 mPas, preferably between 500 and 3000 mPas.

9. A method according to any one of the preceding claims, wherein when performing step c), the basis weight is reduced by 9% to 27%.

10. The method according to any one of the preceding claims, wherein the polyolefin comprises a copolymer selected from the group consisting of random copolymers, gradient copolymers, alternating copolymers, block copolymers, polymer blends, grafted polymers.

11. The method according to claim 10, wherein the polyolefin copolymer comprises a polymer mixture of polymers having different crystallite sizes and / or molecular chain lengths.

12. A wet prepreg layer comprising a thread structure (2) wetted with a water-polyolefin mixture (3), wherein the water-polyolefin mixture (3) represents 35% to 65% of the layer weight.

13. A wet prepreg layer according to claim 12, designed with an open or grid-like wire structure (2) having holes with an opening width in the range of 1 to 150 mm.

14. Use of a wet prepreg layer according to claim 12 for thermal post-treatment and production of a prepreg layer (1) having a solid polyolefin matrix (4).

15. A prepreg layer (1) produced using the method according to any one of the preceding claims 1 to 11, wherein the prepreg layer has a minimum bending radius of at most 30 mm.

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