Method for producing a recyclable winding body and recycling method therefor

Abstract

The present invention relates to a method for producing a recyclable wound body from a fiber composite material comprising a quasi-endless fiber material and a matrix material embedding the fiber material in a winding process, the method comprising the following steps: - Providing the quasi-endless fiber material and a winding system with a winding core onto which the quasi-endless fiber material is wound in multiple layers, - Winding the quasi-endless fiber material onto the winding core of the winding system in such a way that a multi-layer laminate structure is created on the winding core, and - Consolidating the matrix material of the laminate structure to produce the winding body, where - a release agent is introduced between the fiber layers of the multi-layer laminate structure, which causes a structural weakening between the fiber layers either permanently or after activation.

Description

The invention relates to a method for producing a recyclable wound body from a fiber composite material comprising a quasi-endless fiber material and a matrix material embedding the fiber material in a winding process.The invention also relates to a recycling method for this purpose.Due to the weight-specific strength and rigidity of fiber composite components which are produced from fiber composite materials, such components are no longer to be considered as being available today from aircraft and space travel and from the automotive sector. In the production of a fiber composite component, a matrix material infused into a fiber material is usually cured under the action of temperature and pressure and thus forms an integral unit with the fiber material after curing. The reinforcing fibers of the fiber material are thereby forced (fixed) in the predetermined direction and can remove the loads occurring in the predetermined direction.Fiber composites from which such fiber composite components are produced generally have two main components, namely, on the one hand, a fiber material and, on the other hand, a matrix material. In addition to this, further secondary constituents can be used here, such as binder materials, particles or additional functional elements, for example, which are intended to be integrated into the component.In addition to dry fiber materials which are infused with the matrix material in a subsequent infusion process, already preimpregnated fiber materials (so-called prepregs) are often also used in which the fiber material is already preimpregnated with the matrix material. A subsequent infusion process is then generally no longer necessary. Before the matrix material cures, the fiber material is generally introduced into a molding tool, such as wound around a winding core, in order to define the geometry of the component.It is known to produce pressure tanks from a fiber composite material. Such pressure tanks must generally be capable of absorbing considerable forces. In order to ensure this, when using an isotropic material, for example a metallic material, the load-bearing capacity is therefore achieved by a high wall thickness, as a result of which such tanks have a relatively high weight. A more favorable ratio with a lightweight construction potential can be realized if a fiber composite material is used.It is known to produce pressure tanks as reservoirs for gaseous or liquid fluids, such as natural gas, air or hydrogen, for example, from such fiber composites. In order to achieve an optimum load limit with respect to weight in such, in particular rotationally symmetrical hollow bodies, such pressure tanks are generally produced in a winding process. In this case, a quasi-endless fiber material is deposited on a rotating winding core or shaping core as a shaping tool, in which the fiber material is wound onto the winding core or the shaping body is wound around with the fiber material. By changing the fiber orientation, a laminate construction adapted to the load can be realized. Such pressure tanks made of a fiber composite material are particularly efficient because the fibers of the fiber material can be laid down on the molded body in the load directions according to an isotensoid structure and the fiber stiffness and fiber strength are thus exploited in the best possible manner. Thus, the weight of a pressure tank made of a fiber composite material can be lowered more than ten times compared to a pressure tank made of aluminum. The production of hollow bodies of this type as a braid is also known.DE 10 2010 043 645 A1 discloses a method for producing a pressure tank for receiving a fluid under pressure, which is formed from a plurality of elements made of a textile sheet material made of reinforcing fibers. The sheet material is placed on a molded body and can be impregnated, for example, with a thermosetting or thermoplastic plastic. The molded body, on which the sheet material is deposited, can be subjected to an overpressure in order to easily expand the molded body and thus improve the form fit between the molded body and the fiber material. This is intended to prevent excess resin, for example, from accumulating in intermediate spaces between the molded body and the fiber material and thus possibly forming so-called resin esters. In addition, the fiber volume content of the composite material can optionally be increased as a result.DE 10 2016 109 116 B4 discloses winding a fiber material onto a liner and then infusing it with a matrix material. A separate infusion device infuses the wound fiber material with the matrix material. It is provided here that the liner rotates alternately, i.e. the direction of rotation changes alternately, in order to distribute the infused matrix material in the fiber material in the best possible manner. A disadvantage here is that, depending on the tensile stress during deposition, the matrix material distributes itself only insufficiently.From post-published DE 10 2022 103 036.9, a method for producing a hollow body from a fiber composite material is known, in which a hollow mould core is first provided, the mould core surface of which is formed from an infunable matrix material. After the fibrous material has been deposited on the mould core surface, an internal pressure is generated in the interior of the mould core and the fibrous material is tempered, the internal pressure and the temperature being selected such that the outer mould core surface is infused into the fibrous material of the fibre preform produced on the mould core.One aspect which is becoming more and more prominent is the recycling of hollow bodies or wound bodies of this type which are produced from a fiber composite material. In this case, inter alia, two essential options for recycling fiber composite components are known: mechanical recycling and chemical recycling (pyrolysis, solvolysis, solvent-based).The fibers recovered by currently used recycling processes have a completely different form than the endless fibers originally used for production. The reduction in the recycling process greatly shortens the fiber lengths. Furthermore, the orientation of the fibers is lost in the recycling process and the fibers are usually present as a type of vault. The combination of shortening and orientation loss means strong downcycling. This is associated with both a loss of value and a greatly restricted re-usability of the recycled material.It is therefore the object of the present invention to specify an improved method for producing a recyclable wound body and a recycling method for recycling such wound bodies.The object is achieved according to the invention by the method for producing a recyclable wound body according to claim 1. Advantageous embodiments of the invention are then found in the corresponding dependent claims.According to claim 1, a method for producing a recyclable wound body from a fiber composite material comprising a quasi-endless fiber material and a matrix material embedding the fiber material in a winding process is proposed, wherein the method comprises the following steps:providing the quasi-endless fiber material and a winding installation having a winding core, onto which the quasi-endless fiber material is wound in multiple layers,winding the quasi-endless fiber material onto the winding core of the winding system in such a way that a multilayer laminate structure is produced on the winding core, andconsolidating the matrix material of the laminate structure in order to produce the winding body,wherein a release agent is introduced between the fiber layers of the multilayer laminate structure, which release agent permanently or after activation causes a structure weakening between the fiber layers.Accordingly, the production of a winding body from a fiber composite material is proposed, wherein the winding body is produced in a winding process on a mould core or winding core by winding a quasi-endless fiber material. The quasi-endless fiber material can be a preimpregnated fiber material that is already impregnated with at least one matrix material. The quasi-endless fiber material can, however, also be a dry fiber material which, after the production of the multilayer laminate structure on the winding core, is infused with the matrix material. Such a laminate construction is thus a multilayer fiber preform formed on the winding body.The quasi-endless fiber material is preferably a semi-finished product consisting of a plurality of individual filaments, which is wound onto the wound body due to a relative movement between the material supply and the surface of the wound body. It is conceivable that the winding body rotates, whereby the fiber material is pulled from the material supply onto the surface of the winding body and wound up. However, it is also conceivable for the material supply to be moved with respect to the stationary and non-moving surface of the winding body, as a result of which the fiber material is likewise wound onto the winding body. After the production of the laminate construction, the matrix material is consolidated, i.e. consolidated. For this purpose, the matrix material can be cured if it carries out a chemical crosslinking reaction for this purpose (for example. Resins, thermosetting plastics) or it is solidified by lowering the temperature, for example in the case of thermoplastic plastics.According to the invention, it is now provided that a separating agent is introduced between the individual layers of fiber material, which causes a structure weakening between the fiber layers permanently or after an activation (for example chemical, optical, electromechanical and / or thermal activation). Such a permanent or activatable structure weakening has the consequence that the adhesion of a layer relative to the lower layer is weakened, as a result of which, in the recycling process, detachment of the quasi-endless fiber material from the produced wound body is possible without destroying the quasi-endless fiber.The separating agent can be introduced continuously during the winding of the quasi-endless fiber material onto the winding body. It is conceivable that the separating agent is already a component of the quasi-endless fiber material or is introduced into the winding structure in a targeted manner. The separating agent can be sprayed between the individual fiber layers, for example onto a lower, first fiber layer, wherein a second fiber layer is then used up on this lower, first fiber layer and the separating agent sprayed onto the first, lower fiber layer is then between the first and the second fiber layer.It has been recognized that in wound packages a targeted weakening between the individual fiber layers as far as possible does not cause any effects on the load distribution of the package, since in such packages the loads are substantially absorbed by the fibers and the matrix plays only a subordinate role here in terms of structural mechanics. However, the targeted weakening leads to a later recycling capability of the wound body produced without causing strong downcycling by shortening the fibers used. Rather, the useful value of the fibers can be maintained, since in a recycling process these can be completely unwound and recovered due to the structural weakening between the fiber layers introduced by the separating agent. This makes it possible to recover the valuable fibers in their quasi-endless length.According to one embodiment, it is provided that a separating film, a mesh and / or a grid is introduced at least partially between the individual fiber layers during the winding of the quasi-endless fiber material onto the winding core, in order to bring about a permanent or activatable structure weakening between the fiber layers.Such a separating film, mesh or grid can be introduced over the entire surface between each individual fiber layer. However, it is also conceivable for such a separating film, mesh or lattice to be provided only in sections between the fiber layers, for example transversely to the fiber-laying direction in individual sections, so that a structure weakening is partially effected only at these points. It has been found that this is sufficient to recycle the wound body in a later recycling process while maintaining the quasi-endless length of the fiber material. Such a separating film, mesh or grid is thus a thin sheet-like structure.Accordingly, the concept of the invention includes the separating means for causing the structure weakening being partially introduced or introduced between the fiber layers in selected sections of the wound body.According to one embodiment, it is provided that a quasi-endless 2-component fiber material is provided, which is impregnated with a first matrix material and sheathed with a second matrix material, wherein the second matrix material as a separating agent brings about a structure weakening between the fiber layers by an activation.The fiber material is provided as a prepreg fiber material with a 2-component matrix system which contains a first matrix material and a second matrix material. The second matrix material is configured such that it brings about a structure weakening between the fiber layers by an activation (for example a chemical, optical, electromechanical and / or thermal activation) when both matrix materials are consolidated and the winding body is completely produced. The second matrix material thus forms a selective separating agent, which serves as a structural mechanical matrix in a first phase of use of the wound body (and in this case does not have the function of a separating agent) and serves as a separating agent for a structural weakening between the fiber layers in a second recycling phase when it is activated accordingly.Thermal activation can be effected by a corresponding heating device, such as e.g. laser, xenon lamps, induction, resistance heating).According to one embodiment for this purpose, it is provided that the first matrix material directly impregnates the fiber material, while the second matrix material coats the fiber material impregnated with the first matrix material.In this embodiment of a 2-component fiber, the fibers themselves are impregnated with the first matrix material and preferably completely enclosed by the first matrix material, while the second matrix material in turn surrounds and preferably completely encloses the fiber material impregnated with the first matrix material. However, it is also conceivable here that the second matrix material is provided only in sections along the quasi-endless fiber material.According to one embodiment, it is provided that the second matrix material is a polymer, a thermoplastic and / or a particle-modified polymer and / or that the first matrix material is a thermosetting plastic or thermoplastic.In this embodiment of a 2-component fiber, the fibers themselves are impregnated with a duromer or thermoplastic resin, which serves to hold the individual filaments of the fiber or roving together in the winding process. The degree of impregnation can be adjusted and reduced to the minimum necessary, for example. The use of flexible matrix materials gives rise to the potential for improving the mechanical properties of the wound winding body. This impregnated core is then wetted or coated with a second material and can be activated in a targeted manner in the recycling process. This layer serves as a binder material to fix the generous layer, but allows some flexibility if needed to allow better load distribution to many fibers. In the recycling process, only the coating has to be activated in order to unwind the quasi-continuous fiber material in an uncutated manner.The particles may be activated to reduce adhesion. For example, particles expanding upon activation are conceivable, for example. Expandable graphite. However, the particles can also contribute to locally very limited heating between the layers by excitation by light or by alternating electromagnetic fields, in order to reduce adhesion in this way.According to one embodiment, it is provided that during the winding of the quasi-endless fiber material onto the winding core, a specific porosity between the fiber layers is produced by the specific inclusion of air as a separating agent, in order to bring about a permanent structural weakening between the fiber layers.Since the matrix material has only a small proportion of the total load transfer by structure-mechanical means, a recyclable pressure tank can be produced as a result, the porosity introduced in a targeted manner causing permanent structure weakening between the fiber layers, which structure weakening improves the recycling process when the fibers are unwound.A further aspect of the present invention is a recycling method for recycling a recyclable wound body which has been produced from a fiber composite material comprising a quasi-endless fiber material and a matrix material embedding the fiber material in a winding process. According to the invention, the method comprises the following steps- providing a recyclable winding body produced according to one of the preceding claims,activating the introduced separating agent and / or tempering the wound body at least in regions, anddrawing off the quasi-endless fiber material from the winding body.Firstly, a recyclable wound body is provided which has been produced according to the method according to the invention as described above. Subsequently, for recycling this wound body, the introduced separating agent is activated in order to bring about a targeted structure weakening. Subsequently, the quasi-endless fiber material is drawn off from the winding body. The fiber material is preferably removed without severing the fiber material into individual blanks. Rather, the fiber material wound up quasi-endless previously for producing the wound body is also unwound again as a whole from the wound body. The activation takes place in particular when the separating agent in the recyclable wound body is an activatable separating agent which, after activation, causes a structural weakening between the fiber layers.It is conceivable that the recyclable wound body is basically tempered in order to make the wound body flexible.According to one embodiment, it is provided that the separating means is activated in such a way that the winding body is tempered at least in regions.According to one embodiment, it is provided that the wound body is tempered at least in regions via the glass transition temperature of a thermosetting matrix material of the wound body.By heating a thermosetting matrix material, in particular above the glass transition temperature, the thermosetting resin system becomes compliant, but holds the filaments of the fiber material together and thus prevents the roving from splicing or fraying.According to one embodiment, it is provided that the separating agent introduced into the winding body is activated at least in regions before the pulling off.The invention is explained in more detail by way of example with reference to the appended figures. The following are shown: FIG. 1 is a schematic illustration of a multiply impregnated fiber material; FIG. 2 shows a schematic illustration of a plant for producing a recyclable wound body; FIG. 3 shows a schematic illustration of a plant for recycling a recyclable wound body.FIG. 1 shows a schematically very simplified illustration of a multiply impregnated fiber material 10 which is formed from a plurality of filaments 11. The fiber material 10 can be, for example, a roving.The fiber material 10 is now directly impregnated with a first matrix material 12 in such a way that the fiber material 10 is completely surrounded by the first matrix material 12 and in particular fills the hollow spaces between the individual filaments 11. This arrangement of fiber material 10 and first matrix material 12 is now wetted or sheathed with a second matrix material 13, which is formed from an activatable (thermally, electromagnetically or chemically) plastic, in order to thus form an activatable separating agent between the individual layers of fiber material.FIG. 2 shows a production plant 100 with which a recyclable wound body can be produced. For this purpose, a fiber material 120 is wound onto a winding core or shaping core 110, in that the winding core 110 is permanently rotated about its axis 112. A fiber laying head 130, which can move axially with respect to the axis 112, continuously supplies the fiber material 120 from a fiber magazine, not shown, so that this fiber material 120 is drawn off during the rotation of the winding core 110 and wound onto the surface of the winding core 110.After a first layer of fiber material 120 has been wound directly onto the surface of the winding core 110, the fiber material 120 is preferably wound further onto the winding core 110 in geodetic tracks, so that now a further, second layer of fiber material 120 is formed on the winding core 110. This results in a multi-layer laminate structure 122 on the winding core 110.The fiber material 120 used can be the multiply impregnated fiber material from FIG. 1. As a result, a separating agent is introduced between the individual fiber layers of the laminate structure 122 by the second matrix material, which separating agent does not act permanently but is activated thermally, for example, during recycling. This achieves a structural weakening between the individual fiber layers, as a result of which the fiber material 120 can be unwound from the structure again.After the laminate assembly 122 has been completely manufactured from multiple layers of fiber material 120, the matrix material which infuses or impregnates the fiber material 120 is cured or consolidated, in order to thus produce a wound body. This can then be recycled later.The process of recycling a winding body 200 is shown schematically by way of example in FIG. 3. The structural weakening (whether it is permanent or activated) and / or tempering of the wound body 200 brought about by the separating means between the individual fiber layers leads to a reduction in the bond between the individual layers of the fiber material, so that the fiber material can be unwound from the wound body 200 in the form of a quasi-endless fiber material 220. It can then be wound onto a suitable reel 230 and stored for further use.Reference numerals denote reference numerals10 Quasi-endless fiber material 11 filaments 12 first matrix material 13 second matrix material 100 manufacturing plant 110 winding core 112 axis of rotation 120 fiber material 122 laminate structure 130 laying head 200 winding body 220 recyclable quasi-endless fiber material 230 rollReferences included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedDE 10 2010 043 645 A1

[0008] DE 10 2016 109 116 B4

[0009] DE 10 2022 103 036.9

[0010]

Claims

Method for producing a recyclable wound body (200) from a fiber composite material having a quasi-endless fiber material (10) and a matrix material (12, 13) embedding the fiber material (120) in a winding process, wherein the method comprises the following steps: - providing the quasi-endless fiber material (10) and a winding installation having a winding core (110), onto which the quasi-endless fiber material (10) is wound in multiple layers, - winding the quasi-endless fiber material (10) onto the winding core (110) of the winding installation in such a way that a multilayer laminate structure (122) is produced on the winding core (110), and - consolidating the matrix material (12, 13) of the laminate structure (122) in order to produce the wound body (200), characterized in that - a separating agent is introduced between the fiber layers of the multilayer laminate structure (122), which causes a structure weakening between the fibre layers permanently or after activation.Method according to claim 1, characterised in that a separating film, a mesh and / or a grid is introduced at least partially between the individual fibre layers during the winding of the quasi-endless fibre material (10) onto the winding core (110), in order to effect a permanent or activatable structure weakening between the fibre layers.Method according to Claim 1 or 2, characterized in that a quasi-endless 2-component fiber material is provided, which is impregnated with a first matrix material (12) and sheathed with a second matrix material (13), wherein the second matrix material (13), as a separating agent, brings about a structure weakening between the fiber layers by activation.Method according to claim 3, characterised in that the first matrix material (12) directly impregnates the fibre material (120), while the second matrix material (13) surrounds the fibre material (120) impregnated with the first matrix material (12).Method according to claim 3 or 4, characterised in that the second matrix material (13) is a polymer, a thermoplastic and / or a particle-modified polymer and / or that the first matrix material (12) is a thermosetting plastic or thermoplastic.Method according to one of the preceding claims, characterized in that during the winding of the quasi-endless fibre material (10) onto the winding core (110), a specific porosity is produced between the fibre layers by the specific inclusion of air as a separating agent in order to bring about a permanent structure weakening between the fibre layers.Recycling method for recycling a recyclable wound body (200) which has been produced from a fiber composite material comprising a quasi-endless fiber material (10) and a matrix material (12, 13) embedding the fiber material (120) in a winding process, wherein the method comprises the following steps: - providing a recyclable wound body (200) which has been produced according to one of the preceding claims, - activating the introduced separating agent and / or tempering the wound body at least in regions, and - removing the quasi-endless fiber material (10) from the wound body (200) after the activated separating agent has brought about a structural weakening.Recycling method according to Claim 7, characterized in that the separating means is activated in such a way that the winding body (200) is tempered at least in regions.Recycling method according to Claim 7 or 8, characterized in that the winding body (200) is tempered at least in regions via the glass transition temperature of a thermosetting matrix material of the winding body (200).Recycling method according to one of Claims 7 to 9, characterized in that the separating agent introduced into the wound body (200) is activated at least in regions before the pulling-off.

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