WO2023213724A1 - Method for producing a prepeg layer, prepeg layers and use thereof - Google Patents

Abstract

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

Description

Process for producing a prepreg layer, prepreg layers and their use

The present invention relates to methods for producing a prepreg layer, prepreg layers and their use.

The production of components (such as vehicle components, aircraft components, boat components, interior parts of trains, components in electronics, etc.) from fiber-reinforced materials can, among other things. based on a fiber-matrix semi-finished product, the best-known representative of which is a “prepreg”.

Prepregs regularly contain a fibrous material made of one or more types of fiber, such as carbon, fiberglass, aramid, basalt, boron, ceramic, silica, steel, polyester, nylon, polyethylene, plexiglass, natural fiber and/or another type of fiber, the fibrous material being impregnated with a matrix plastic. The fibers of the fibrous material can be present within the prepreg as continuous fibers with a preferred direction (unidirectional layer), as an ordered textile surface (e.g. woven, knitted fabric, scrim, knitted fabric, ...) or as a disordered textile surface as a fleece or random fiber mat.

Polymer materials (also called “resin systems”) are generally 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, the thermosets and elastomers have not yet fully reacted and are therefore still plastically deformable. Special storage conditions must be observed, such as very low storage temperatures. As is known, thermoplastics can be repeatedly brought into a plastically deformable state by applying heat.

Prepregs are usually manufactured as a layer, plate, tape or web-shaped material, with web-shaped material often being delivered rolled up into rolls. To produce an object or component, a piece is conventionally separated from the prepreg that is sufficiently large to line a surface of a pressing tool (mold). By pressing the prepreg (or, more generally, by applying pressure to the prepreg greater than atmospheric pressure) in the pressing tool under the influence of heat, the thermoset or elastomeric matrix plastic reacts and the object or component is shaped. In the case of a thermoplastic matrix plastic, it acquires plastic properties 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 below the softening temperature of the thermoplastic.

The requirements for a prepreg can be very different, especially with regard to its final use to produce an injection molded component and/or the preparation of the injection molding process. In particular, it may be desirable to achieve a particularly uniform, complete and/or intensive adhesion of the matrix plastic to the textile fabric. Particularly when continuous production is taken into account, suitable, cost-efficient and quick processes for producing such prepregs are sought.

A particular challenge lies in providing lightweight prepregs with high deformation and strength properties and, if necessary, even surface reflection properties.

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 prepregs with a high and variable utility value in a simple manner, ensuring that the composite structure covers the end product over the entire flat design of the end product is stabilized as evenly as possible. In particular, a simple way to provide prepregs should be created, with these being included in relation to further processing are suitable for manufacturing technologies currently available on the market, which may require a lot of forming.

These tasks are solved with the features of the independent claims. Advantageous further developments are specified in the respective dependent claims. The description, especially with the figures, illustrates the invention and gives further exemplary embodiments. The features listed individually in the claims can be combined with features of other claims and/or the description.

A method for producing a prepreg layer contributes to this, which comprises at least the following steps: a) providing a thread structure with a basis weight, b) adding a water-polyolefin mixture to the thread structure so that the basis weight increases by at least 30% is, c) dewatering the thread structure with a water-polyolefin mixture, d) consolidating the thread structure with the polyolefin.

Steps a), b), c) and d) can be carried out in the order given here. However, it is also possible for some of the steps to be carried out simultaneously or overlapping. This means in particular that the steps are carried out (partially) at the same time but nevertheless (spatially) separately, for example as in the context of continuous production, with the (endless) thread structure successively passing to different stations for carrying out steps b), c) and d). is supplied. These steps are therefore not carried out at the same time on the same section of the thread structure.

As part of step a), a large number of threads (also called filaments or (continuous) fibers) can be provided. These can be provided individually, directed and/or (partially) in combination with one another. Alternatively or cumulatively, thread bundles can also be provided, i.e. (separate or separate) strands made of a large number of threads. The thread bundles can be designed as so-called rovings, i.e. as (multi) filament yarn made from parallel threads. ordered threads (or also called filaments). It is particularly preferred that all threads and/or thread bundles are provided essentially unidirectionally aligned with one another, in particular in the direction of a common conveying or transport direction. The threads can consist of at least one or more of the fibrous materials mentioned above.

The threads preferably comprise fiberglass bundles, in particular with a titer in the range from 300 to 1,200 tex. The threads are preferably formed with or from a large number of glass fiber filaments, which run essentially parallel to one another and thus form a bundle. The fiberglass bundle can include internal pores that can serve as a reservoir for the application of the plastic matrix.

These threads are arranged relative to one another in such a way that they provide an (independent) thread structure, for example in the manner of a fleece, woven fabric, knitted fabric, knitted fabric or scrim.

The thread structure is preferably designed as a fabric. The fabric preferably has a regular and/or uniform shape. Fabric can essentially only be formed with threads and/or thread bundles. This can be provided in strips and/or plates and/or in one layer. The fabric has a very high ratio of surface area to material thickness. The fabric can be wrapable and/or stackable and/or (elastically) deformable. The fabric can be designed to be open, with an open fabric having a large number of (see-through) holes.

An open or grid-like thread structure can have holes with an opening width in the range of up to a maximum of 200 mm [millimeters], with the opening width particularly preferably in the range from 1 to 150 mm. The opening width is understood to be the maximum extent of the hole (perpendicular to the thickness of the thread structure), for example the largest free diagonal in the case of a square hole. Small opening widths, for example in the range of 1 to 10 mm, are preferably created for processes/components with a high, oriented fiber content. In the spray For casting reinforcement, these hole sizes are advantageous in order to achieve good embedding in the injection molding compound. Large opening widths, e.g. in the range of 30 to 100 mm, are, however, suitable for large-area applications with lower force absorption, e.g. in the construction sector for use with insulation materials for reinforcement or with masonry facings (so-called “strips”) in order to make individual elements larger To combine mats and thus make manual work easier. If there is a square hole, an edge length of (maximum) approx. 100 mm is preferred for such applications.

According to step a), a predetermined basis weight is assigned to the thread structure. The basis weight can be adjusted, for example, through a suitable choice of material and structure of the threads as well as the arrangement of the threads relative to one another, in particular also taking into account the design of holes. The basis weight is usually given in the unit grams per square meter [g/m ² ] and can be selected or set here, for example, from a range of 50 to 500 g/m ^z . The basis weight is considered in particular with a dimension of 10 cm x 10 cm [centimeters], with a value of the basis weight being maintained in such a dimension field. If the fabric is larger than this dimensional field, the value of the fabric can preferably be maintained in all dimensional fields, in particular if the thickness or structure of the thread structure is the same. According to step a), it is a “dry” basis weight, meaning it contains practically no (separated or unbound) water.

According to step b), a water-polyolefin mixture is then added to the thread structure so that the basis weight is increased by at least 30%.

In particular, a polyolefin copolymer is used in the water-polyolefin mixture. Polyolefins (also called “polyalkenes”) are polymers that are made up of hydrocarbons of the formula C _n H _2n with a double bond (ethylene, propylene, butene-1, isobutene). Polyolefins are semi-crystalline thermoplastics. Polyolefins are currently generally produced from oil or natural gas. The The process is called polymerization, whereby short chains of chemicals (monomers) are linked into long chains (polymers) using a catalyst. Polyolefin copolymers are therefore polyolefins that are composed of two different types of monomer units. The polyolefin used is applied with an aqueous solution, for example by spraying or dipping. The water-polyolefin mixture can be added particularly intensively 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 selection of threads and/or the shape of the thread structure.

According to step b), it is a “wet” basis weight, i.e. it includes in particular a part of the supplied water or water-polyolefin mixture, which in particular adheres to and/or in the flat structure or is transported with it. The addition is adjusted so that the basis weight is increased by at least 30%. The basis weight after the predefined addition of the water-polyolefin mixture can also be referred to as “wet basis weight”. This increase in the 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 desired properties of the prepreg layer. In particular, the additional support or the wet weight per unit area is set specifically and, if necessary, also monitored or corrected immediately. For example, in step b), it is possible to initially add more water-polyolefin mixture than corresponds to the target, with part of the layer then being removed again so that the target is set. Obviously, the predetermined increase in basis weight is present at the end of step b) - no subsequent addition of plastic takes place until the end of step d).

After the water-polyolefin mixture has been added, the (wet) thread structure is drained according to step c). In other words, this means in particular that the water content or the water adhering to the thread structure is removed, in particular evaporated. The (dry) basis weight of the Thread structure after step c) is therefore regularly smaller than the (wet) basis weight after step b) but also larger than the (dry) basis weight after step a). When carrying out step c), the basis weight can decrease by at least 9%, in particular in the range from 9 to 27%. It is preferred that the basis weight when carrying out step c) is reduced in the range from 10 to 24%, in particular 13 to 22% and particularly preferably in the range from 15 to 20%. The water has the particular function of arranging the polyolefin particles in or on the thread structure evenly distributed, which is supported by its flow properties. It can therefore be assumed that this will be achieved to an acceptable extent at a given time and that the water can be removed. In order to largely maintain the distribution of the polyolefin particles in or on the thread structure during this process, evaporation of the water is particularly advantageous. Thus, at the end of step c), in particular, there is a (completely) dry thread structure.

It is preferred that step c) takes place thermally, with a temperature (of the thread structure including the water-polyolefin mixture) being 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 0.78 pm to 100 pm [micrometers], in particular in the wavelength range 1 pm to 10 pm, or using infrared radiation. This obviously requires heating the support (possibly with the thread structure) to a dewatering temperature that is above the evaporation temperature of the water but (significantly or certainly) 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 dewatering can more preferably be carried out over a period of 0.2 to 4.0 minutes [minutes]. The predefined period can be set taking into account the amount of water to be removed per square meter, the exposure distance, the heating power and/or the feed speed of the thread structure. In the event that the thread structure is woven in step a), the feed speed, for example, depends largely on the weft insertion performance. tension (ß/min) and the weft thread density (ß/cm), so that the other parameters can be adjusted based on this.

The dried thread structure with the polyolefin is then consolidated in step d). In particular, thermal consolidation takes place here. The (dry) basis weight of the thread structure after step d) corresponds (essentially) to the (dry) basis weight after step c). As part of this step, a permanent connection or fixation of the polyolefin particles to one another and to the threads is achieved by melting them onto or melting them and connecting them to the threads or to one another during subsequent solidification. It is possible that the thread structure is present at the dewatering temperature or a temperature lower than the dewatering temperature at the beginning of step d). Step d) leads to a significant, possibly sudden increase in the ambient temperature, with the greatest possible heating speed of the thread structure being possible with the polyolefin. In particular, step c) takes place in a first oven, while step d) takes place in a second oven, wherein the thread structure is preferably guided or moved from the first oven directly into the second oven or the ovens merge seamlessly into one another or the oven as one with two different zones.

Step d) is preferably carried out thermally, with a temperature (of the thread structure including the water-polyolefin mixture) being set in the range above the melting temperature of the polyolefin. The (thermal) consolidation can further preferably be carried out over a period of 0.2 to 4.0 minutes [minutes]. The predefined period can 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.

It is preferred that the basis weight in step b) is increased by 35 to 65% by weight [% by weight]. With a 35% weight loading of water-polyolefin mixture, just enough polyolefin is added to the product so that a favorable fiber-matrix ratio is achieved in the end product. With an exposure of 35% by weight or more, it is ensures that the fibers in the end product are sufficiently covered with polyolefin matrix to give the product sufficient dimensional stability so that it can be easily handled with conventional gripper systems and can therefore be easily processed automatically. In addition, this sufficient amount of polyolefin matrix ensures good bonding properties during further processing in subsequent processes. Above 65% weight loading with a water-polyolefin mixture, economic viability is at risk because there is a significant excess of polyolefin in the product, which is accompanied by large amounts of water introduced that has to be evaporated. Since the evaporation of water is a very energy-intensive process, excessive exposure of the product to a water-polyolefin mixture is unfavorable from an economic point of view.

It is preferred if a water-polyolefin mixture is added in step b), in which the water content is in the range from 40 to 60% by weight [percentage by weight]. In the range specified here, it can be achieved or guaranteed that the mixture remains stable in the long term and can still be processed economically. The specified lower limit of 40% by weight can, for example, ensure that the manufacturing process described can be operated economically. At lower values, the water content is too high, meaning an excessive amount of energy would have to be used for drying. With significantly higher polyolefin weight percentages, e.g. B. at more than 60% by weight, the mixture can be unstable, i.e. phase separation takes place so that polyolefins and water separate, i.e. segregate. A uniform distribution of the polyolefins in the thread structure is therefore no longer guaranteed.

The thread structure is preferably soaked in the water-polyolefin mixture during step b). The thread structure can thus be fed to a trough, for example by means of a roller arrangement, so that it is immersed under a surface of the water-polyolefin mixture (so-called “float”) located in the trough. In the area of the trough, rollers can (also) be provided over which and/or between which the thread structure is guided. The rollers can have a roller surface that adjusts or effects the application or entry of the water-polyolefin mixture towards the thread structure. The viscosity can generally or for example when soaking, preferably below 5,000 mPas, preferably between 500 and 3,000 mPas. In this way, water-polyolefin mixture can be added to the thread structure quickly, uniformly and/or comprehensively.

It is possible that during or after this impregnation process the thread structure provided with a water-polyolefin mixture is subjected to a (subsequent) roller squeezing process. In a roller squeezing process, the thread structure is passed between two or more rollers or rollers, the water-polyolefin mixture being pressed between the individual threads and their filaments by the pressure between at least two rollers. In order to adjust the support weight, the distances between the rollers can be set to a defined gap or the rollers can rest on one another in a movable manner. The adjustment or setting of the basis weight can be adjusted, for example, by at least one of the following measures:

The contact pressure of the roller(s) is varied, for example by using rollers with a higher/lower mass, varying an external pressure application, for example by means of pneumatics, or similar.

- The wrap angle (angle range of the roll over which the thread structure lies) is adjusted.

- The roll surface(s) is changed, for example the optional use of smooth, (fabric) covered and/or structured rolls.

- Adjusting the feed speed of the thread structure.

- Extension of the dwell distance below the fleet surface.

As part of the roll squeezing process, the thread structure can also be taped and/or padded.

The polyolefin used here is preferably a copolymer selected from the following group: random copolymer, gradient copolymer, alternating copolymer, block copolymer, polymer mixture, graft polymer.

In a random copolymer, a random distribution of monomers in the chain occurs, e.g. B. in the following way: AABBABBBBAAAABAABBBAAABBABBAAAABBBABAABBAB....

A gradient copolymer is structured similarly to a random copolymer, but with a variable monomer proportion along the chain, for example in the following way:

AAAAAAAAABAAABBBAAABBABBBAABBBBBBABBBBBBBB. ...

In an alternating copolymer there is a regular arrangement of the monomers along the chain, for example in the following way:

ABABABAB AB AB ABAB ...

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

AAAAAAAAABBBBBBBBBBBB or

AAAAAAAAABBBBBBBBBBBAAAAAAAAAAAAAABBBBBBBBBBB...

Mixture polymers are characterized by the fact that different polymers are present without a chemically reactive connection between the polymers, for example of the following type:

AAAAAAA + BBBBBBBB.

Graft copolymers consist of a framework consisting of the polymer of one monomer onto which blocks/"side arms" of a polymer of another monomer are grafted, e.g. B. of the following type:

B B B

B B B B B

B B B B B

AAAAAAAAAAAAAAAAA...

B B B B B

BBBB b

b

In all of the cases mentioned, the molecular chains can be linear or (slightly) branched.

This makes it possible for polymeric materials to be mixed with other substances, which serve in particular for functionalization (e.g. stabilizers, flame retardants, ...) and/or cost reduction (fillers). The copolymers can be selected so that different properties of different plastics are provided.

The polyolefin copolymer is preferably a polymer mixture (in particular) with polymers of different grain sizes and/or molecular chain lengths. Smaller particles/molecules can penetrate better between the threads or individual filaments and create a good bond between the threads. Larger particles/molecules, on the other hand, tend to penetrate less and can therefore influence or adjust the surface properties of the prepreg, e.g. the connection to later material composites. Furthermore, by mixing polymers with different melting points, the melting point of the mixture can be easily adjusted to the respective application.

According to a further aspect, a wet prepreg layer is proposed, comprising a thread structure which is wetted with a water-polyolefin mixture, the water-polyolefin mixture being 35 to 65% of the (wet) layer weight.

It is particularly preferred for the wet prepreg layer to have been produced using steps a) and b) of the method proposed here. Regardless of this, the listed properties of the “wet” thread structure can also be used individually to characterize the wet prepreg layer, especially with a view to subsequent use. Following a further aspect, the use of a wet prepreg layer for thermal aftertreatment and production of a prepreg layer with a solid polyolefi n matrix is proposed.

The wet prepreg layer is particularly preferably suitable for thermal aftertreatment and production of a prepreg layer according to steps c) and d) of the method proposed here. Regardless of this, the listed special features of dewatering and/or consolidation can be used to characterize the wet prepreg layer.

Finally, a prepreg layer is also proposed, which is produced using a method disclosed here, with a smallest bending radius of the prepreg layer being up to a maximum of 30 mm [millimeters]. The smallest bending radius is understood to be the bending radius at which (under normal room conditions, in particular below room temperature) no (significant) detachment of the plastic matrix and/or kinking of the threads occurs. It is in particular in the range of 10 to 20 mm (for example with a fabric thickness of a maximum of 1.0 millimeters). The structure of the prepreg layer proposed here therefore allows surprisingly small bending radii without damaging it and/or significantly impairing further use.

The prepreg layer is designed in particular in such a way that the threads are embedded in a polyolefin or plastic matrix. This means in particular that the matrix essentially encloses the entire threads. If bundles of filaments are present, they are essentially also penetrated by the matrix or the filaments themselves are (largely) surrounded by the matrix. The matrix in particular forms all surfaces of the prepreg layer.

Very particularly preferably, the prepreg layer is designed with a large number of holes or as an (open) grid and has a layer density of up to a maximum of 1.0 g/cm ³ [grams per cubic centimeter]. The layer density is to be determined in particular in such a way that the weight of the layer is measured and placed in relation 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 area weight of the (consolidated) prepreg layer and the thickness of the (consolidated) prepreg layer corresponds.

The thickness of a layer is defined as the distance between a reference plate on which the layer rests and a parallel, circular pressure stamp (preferably with a stamp diameter of approx. 50 mm), which applies a fixed pressure (preferably approx. 1 kPa) exerts, measured. The distance between the reference plate and the printing stamp is measured and recorded. Normal climate conditions prevail. The thickness measurement is preferably carried out at different points on the layer and then an average value is formed from these measurements. The thickness of the layer must be determined in particular in accordance with DIN EN ISO 5084.

The upper limit value for the layer density of 1.0 g/cm ³ specified here ensures light prepregs with high deformation and strength properties. The layer density can be achieved in particular by the more open shape of the thread arrangement, with the provision of the polyolefin copolymer plastic matrix enabling particular adhesion properties for this thread arrangement.

The layer density is preferably in a range from 0.45 to 0.9 g/cm ³ , in particular in a range from 0.55 to 0.75 g/cm ³ . The range from 0.45 to 0.9 g/cm ³ was identified as particularly advantageous for, for example, grid-like prepreg layers, with the range 0.55 to 0.75 g/cm ³ being a particularly advantageous application amount of the polyolefin copolymer -Plastic matrix, which particularly favors further processing, especially for complex and highly stressed components.

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 matt, diffusely reflecting surface. With sufficient consolidation, the structural features of the rough surface combine to form a relatively smooth, reflectively shiny film, whereby the structure of the thread material can also influence the surface structure. The invention and the technical environment are explained below using figures. It should be noted that the invention is not limited to the embodiments shown. The features illustrated in the figures can be extracted and, if necessary, combined with other features of the description or other figures, unless this is explicitly excluded below.

It shows schematically:

Fig. 1: a top view of a prepreg layer,

Fig. 2: a sectional view of a prepreg layer,

Fig. 3: an overview of an embodiment variant of the method disclosed here, and

Fig. 4: Embodiments for different versions of step b).

Figures 1 and 2 illustrate by way of example that the (finished or consolidated) woven prepreg layer 1 has a large number of threads, which are arranged to form a thread structure 2 (fabric or open grid). These are embedded in a polyolefin matrix 9. Nevertheless, a plurality of holes 4 with a predetermined opening width 5 are provided. The polyolefin matrix 9 comprises a polyolefin copolymer and the prepreg layer 1 has a preferred layer density of up to a maximum of 1.0 g/cm ³ . The layer density can be determined by means of the envelope volume, which can be determined based on a predetermined length 6, width 7 and thickness 8 of the prepreg layer 1.

3 illustrates by way of example and schematically a possible manufacturing process for such a prepreg layer 1, with continuous production being shown here from left to right and comprising the following steps: a) Providing a thread structure 2 with a predetermined basis weight, here by means of a weaving machine 10. The thread structure 2 produced is further transported along a predetermined feed direction 16. b) Adding a water-polyolefin mixture 3 to the thread structure 2 so that the basis weight is increased by at least 30%. This step is carried out here in a trough 11, which can be carried out in particular according to one of the embodiment variants from FIG. c) dewatering the thread structure 2 with water-polyolefin mixture 3, this being done here in a first oven 12. d) Consolidating the thread structure 2 with the polyolefin, this taking place in a second oven 13. e) cooling the thread structure 2 along a cooling section 14. f) winding up the prepreg layer 1 in a winding station 15.

4 discloses, by way of example and schematically, different embodiment variants of step b), in which the water-polyolefin mixture 3 is added to the thread structure 2 so that the basis weight is increased by at least 30%.

It is illustrated in different variants (I) to (V) that the thread structure 2 is fed to a trough 11 in which a water-polyolefin mixture 3 is stored. A (lowermost) roller 17 is always immersed in the water-polyolefin mixture 3 and is in contact with the thread structure 2 when it is guided past along the feed direction 16. The rollers 17 can have a roller surface that can adjust or effect the application or entry of the water-polyolefi n mixture 3 towards the thread structure 2.

As can be seen from the variants, the rollers used, their number and shape and/or the contact path or wrap angle of the thread structure 2 can be adjusted differently in order to ensure the desired increase in the basis weight in this step. The essential differences between the variants illustrated in FIG. 4 are evident when looking at them and are briefly summarized here: Variant (I): The thread structure 2 is passed (essentially straight) through a gap between two rollers 17, the lower roller not being completely submerged in the bath of water-polyolefin mixture 3.

Variant (II): The thread structure 2 is passed (essentially straight) through a gap between two (an upper and a middle) rollers 17, with a lower roller not being completely submerged in the bath of water-polyolefin mixture 3. The lower roller 17 transfers a portion of the absorbed water-polyolefin mixture 3 to a middle roller 17, which is positioned completely outside the bath of water-polyolefin mixture 3.

Variant (III): The thread structure 2 is guided under the lower roller 17, which is not completely submerged in the bath of water-polyolefin mixture 3. Then the thread structure 2 is passed further around this lower roller 17 and (adjacent to it) through a gap between it and an upper roller 17. Then the thread structure 2 is guided further around this upper roller 17 (adjacent) and finally transported away again with the original feed direction 16.

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

Variant (V): This illustration illustrates that in order to set the desired support weight, the distances between the rollers can be set to a defined gap or the rollers can rest on one another in a movable manner. The setting of the basis weight can be adjusted, for example, by at least one of the measures indicated here: Adjusting the contact pressure (+p, -p, 0) regarding roles 17; Adjusting the wrap angle (+q, -q, 0); Adjusting the feed speed (v) of the thread structure 2.

This shows that the solutions proposed here at least partially overcome the disadvantages described with reference to the prior art and, moreover, that prepregs with a high and variable utility value can be produced in a simple manner, whereby it can be ensured that the composite structure covers the end product over the entire Flat design of the end product is stabilized as evenly as possible. In particular, a simple way to provide prepregs has been created, which is suitable for further processing using manufacturing technologies currently available on the market, which may require a lot of forming.

Reference symbol list

1 prepreg layer

2 thread structures

3 Water-polyolefin mixture

4 hole

5 opening width

6 length

7 width

8 thickness

9 polyolefin matrix

10 weaving machine

11 trough

12 First oven

13 Second oven

14 cooling section

15 changing station

16 feed direction

17 role

Claims

Claims Method for producing a prepreg layer (1), at least comprising the following steps: a) providing a thread structure (2) with a basis weight, b) adding a water-polyolefin mixture (3) to the thread structure (2), so that the basis weight is increased by at least 30%, c) dewatering the thread structure (2) with water-polyolefin mixture (3), d) consolidating the thread structure (2) with the polyolefin. Method according to claim 1, in which step c) takes place thermally, a temperature being set in the range between 100 ° C and the melting temperature of the polyolefin. Method according to claim 2, in which step c) is carried out using electromagnetic radiation in the wavelength range 0.78 pm to 100 pm. Method according to one of the preceding claims, in which in step d) a temperature is set in the range above the melting temperature of the polyolefin. Method according to one of the preceding claims, in which the basis weight in step b) is increased by 35 to 65%. Method according to one of the preceding claims, in which in step b) a water-polyolefin mixture (3) is added, in which the water content is in the range from 40 to 60%. Method according to one of the preceding claims, in which the thread structure is soaked in the water-polyolefin mixture (3) in step b). Method according to one of the preceding claims, in which a viscosity of the added water-polyolefin mixture is below 5,000 mPas, preferably between 500 and 3,000 mPas. Method according to one of the preceding claims, in which the basis weight is reduced in the range from 9 to 27% when carrying out step c). Method according to one of the preceding claims, in which the polyolefin comprises a copolymer selected from the following group: random copolymer, gradient copolymer, alternating copolymer, block copolymer, polymer mixture, graft polymer. The method according to claim 10, wherein the polyolefin copolymer comprises a polymer mixture with polymers of different grain sizes and/or molecular chain lengths. Wet prepreg layer comprising a thread structure (2) which is wetted with a water-polyolefin mixture (3), the water-polyolefin mixture (3) being 35 to 65% of the layer weight. Wet prepreg layer according to claim 12, which is designed with an open or grid-like thread structure (2) which has holes with an opening width in the range of 1 to 150 mm. Use of a wet prepreg layer according to claim 12 for thermal aftertreatment and production of a prepreg layer (1) with a solid polyolefin matrix (4). Prepreg layer (1), produced using a method according to one of the preceding claims 1 to 11, wherein it has a smallest bending radius of up to a maximum of 30 mm.