Method for producing a wind turbine blade and a wind turbine blade produced corresponding and a

Abstract

A method of producing a wind turbine blade or a component thereof is described, the method comprising providing a mold containing a compound having a chemical structure of general formula I or general formula II (depicted hereinafter), applying a resin into the mold, and curing the resin. Furthermore, a correspondingly produced wind turbine blade or a component thereof, a method of recirculating a wind turbine blade or a component thereof, a compound useful for producing a wind turbine blade or a component thereof, in particular as a flow regulator and / or a hot melt adhesive, is described. # imgabs0 # wherein R1, R2, R3, R4, R5 and R6, independently of each other, represent a linear or branched, saturated or unsaturated, substituted or unsubstituted alkyl group; a linear or branched, saturated or unsaturated, substituted or unsubstituted heteroalkyl group; a saturated or unsaturated, substituted or unsubstituted cycloalkyl group; a saturated or unsaturated, substituted or unsubstituted heterocycloalkyl group; a substituted or unsubstituted aryl group; a substituted or unsubstituted heteroaryl group; a linear or branched, substituted or unsubstituted aralkyl group; or a linear or branched, substituted or unsubstituted alkaryl group; and n represents an integer of 1 to 10.

Description

Field of the Invention

[0001] The present invention relates to the field of wind turbine blades, in particular to methods for producing wind turbine blades or components thereof and the correspondingly produced wind turbine blades or components thereof, as well as methods for recycling wind turbine blades or components thereof. Furthermore, the present invention relates to compounds that can be used for producing wind turbine blades or components thereof, in particular as flow regulators and / or hot melt adhesives. BACKGROUND OF THE INVENTION

[0003] Wind power generation is considered to be one of the cleanest and most environmentally friendly energy sources currently available, and wind turbines have received increasing attention for harnessing this energy. Modern wind turbines typically include a tower, a generator, a gearbox, a nacelle, and one or more rotor blades. The rotor blades capture the kinetic energy of the wind and transfer the kinetic energy in the form of rotational energy, thereby rotating the shaft that couples the rotor blades to the gearbox or directly to the generator. The generator then converts the mechanical energy into electrical energy that can be fed into the power grid.

[0004] For many years, the recycling of wind turbines has become an increasingly important topic in terms of sustainability. In particular, the recycling of wind turbine blades remains an unsolved problem. The most widely used technology for producing wind turbine blades, especially longer blades, is resin infusion technology. In resin infusion technology, fiber materials are typically placed in a mold, and resin is infused into the cavity containing the fibers and optionally a core material under pressure. Thereby, fiber-reinforced composite materials that may include balsa wood and / or foam core materials are used to manufacture wind turbine blades. The composite materials used in this case are typically glass fibers, carbon fibers, or aramid fibers reinforced in a resin (such as epoxy resin or polyester), and these resins are difficult to recycle because they are most commonly thermosetting resins and cannot be remolded. Therefore, in addition to the reuse of the resin, the reuse of the fiber materials and / or core materials (such as balsa wood or foam core materials) has proven to be difficult, if not impossible, because the thermosetting resins used are difficult to separate from such blade materials.

[0005] Recently, resin technologies for manufacturing wind turbine blades have been introduced, which are based on acetal or ketal groups in the crosslinking of thermosetting resin networks, enabling chemical cleavage and recycling under mild (acidic) conditions. Conventionally, however, in addition to fiber layers and optional core materials in the blade, there are materials that cannot be degraded and dissolved together with the bulk resin, such as flow regulators placed in the lay-up or adhesives in the blade. If fibers and optional core materials are used in the blade lay-up, flow regulators in the form of, for example, a web, a cloth, a felt, or a veil can be placed under such materials and / or between layers of such materials, for example, between the layers in a stacked arrangement of fiber layers. In fact, adhesives and flow regulators that are compatible with the recycling process and soluble during the recycling process have not been used to date. Instead, materials that do not degrade in a controlled manner during the recycling process are conventionally used. These materials can contaminate the recycled polymers and complicate the separation and further processing of the recycled materials. It is desirable to avoid this problem and / or improve the total percentage of components used in blades that can be recycled.

[0006] Accordingly, there may be a need for adhesives and flow regulators that can degrade in a controlled manner, such as dissolve, during the recycling process of an acetal- or ketal-based recyclable resin, thereby enabling substantially complete recycling of wind turbine blades, which is not only advantageous in terms of sustainability but also reduces the process costs during the recycling process and enables the reuse of the recycled materials. SUMMARY OF THE INVENTION

[0008] This need can be met by the subject matter of the independent claims. Advantageous embodiments of the invention are described by the dependent claims.

[0009] According to one aspect of the invention, there is provided a method for producing a wind turbine blade or a component thereof, the method comprising providing a mold (having a cavity) containing a compound having a chemical structure of general formula I or general formula II (depicted below) therein, applying (e.g., injecting) a resin (in particular, an infusion resin) into the mold, and curing (hardening) the (infusion) resin;

[0010]

[0011]

[0012] wherein

[0013] R 1 、R 2 、R 3 、R 4 、R 5 and R 6each independently represents a straight-chain or branched-chain, saturated or unsaturated, substituted or unsubstituted alkyl group; a straight-chain or branched-chain, saturated or unsaturated, substituted or unsubstituted heteroalkyl group; a saturated or unsaturated, substituted or unsubstituted cycloalkyl group; a saturated or unsaturated, substituted or unsubstituted heterocycloalkyl group; a substituted or unsubstituted aryl group; a substituted or unsubstituted heteroaryl group; a straight-chain or branched-chain, substituted or unsubstituted aralkyl group; or a straight-chain or branched-chain, substituted or unsubstituted alkaryl group; and

[0014] n represents an integer from 1 to 10.

[0015] According to another aspect of the present invention, there is provided a wind turbine blade or a component thereof (recyclable, in particular substantially completely recyclable) that can be obtained (or has been obtained) by the method described herein.

[0016] According to another aspect of the present invention, there is provided the use of a compound having a chemical structure of general formula I or general formula II (depicted above) as a flow regulator for a casting resin.

[0017] According to yet another aspect of the present invention, there is provided a method for recycling a wind turbine blade or a component thereof, in particular a wind turbine blade or a component thereof as described herein, the method comprising contacting the wind turbine blade or the component thereof with an acidic aqueous liquid containing an acid at a temperature of 70°C to 100°C (such as placing the wind turbine blade or the component thereof in a bath of the acidic aqueous liquid) and / or for a time of 1 hour to 10 hours (such that the wind turbine blade or the component thereof degrades and the soluble portion of the wind turbine blade or the component thereof dissolves substantially completely).

[0018] These aspects of the present invention are particularly based on the concept that specific compounds having a chemical structure of general formula I or general formula II as described herein are suitable for use as flow regulators (such as flow promoting materials or flow restricting materials) and / or as adhesives in the production of wind turbine blades. In addition, these compounds can be degraded in a controlled manner (such as dissolved) during the recycling process of an acetal- or ketal-based recyclable resin (such as under mild (acidic) conditions at elevated temperatures), thereby enabling substantially complete recycling of the wind turbine blade and reuse of the material. DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, the details, other features and advantages of the present invention will be described. However, the present invention is not limited to the following specific descriptions, which are for illustrative purposes only.

[0021] It should be noted that, unless otherwise specifically stated, features described in connection with an exemplary embodiment or aspect can be combined with any other exemplary embodiment or aspect. In particular, features described in connection with any exemplary embodiment of a manufacturing method can be combined with any other exemplary embodiment of a manufacturing method, with any exemplary embodiment of a wind turbine blade, with any exemplary embodiment of a use, and with any exemplary embodiment of a recycling method, and vice versa.

[0022] Unless otherwise explicitly stated, when using an indefinite or definite article (such as "a", "an", or "the") in reference to a singular term, the plural of that term is also included, and vice versa.

[0023] As used herein, the expression "comprising" not only includes the meanings of "including", "containing", or "having", but can also cover "consisting essentially of" and "consisting of".

[0024] Unless otherwise specifically stated, the expressions "at least partially", "at least part of", or "at least a portion" as used herein can refer to at least 5% thereof, particularly at least 10% thereof, particularly at least 15% thereof, particularly at least 20% thereof, particularly at least 25% thereof, particularly at least 30% thereof, particularly at least 35% thereof, particularly at least 40% thereof, particularly at least 45% thereof, particularly at least 50% thereof, particularly at least 55% thereof. Particularly at least 60%, particularly at least 65%, particularly at least 70%, particularly at least 75%, particularly at least 80%, particularly at least 85%, particularly at least 90%, particularly at least 95%, particularly at least 98%, and can also refer to 100% thereof.

[0025] In a first aspect, a method of producing a wind turbine blade or a component thereof includes providing a mold (inside which) contains a compound having a chemical structure of general formula I or general formula II (depicted below), applying (injecting) a resin (particularly an infusion resin) into the mold, and curing (hardening) the (infused) resin.

[0026] The mold generally forms a cavity and can thus also be referred to as a cavity mold. The mold can be adapted to the profile of the turbine blade or component to be manufactured. For example, the mold can be designed as a blade half-shell or a component thereof.

[0027] In one embodiment, a compound having a chemical structure of general formula I or general formula II, as described in more detail below, can be arranged or placed inside the mold.

[0028] The compound of general formula I has the following chemical structure:

[0029]

[0030] And the compound of general formula II has the following chemical structure:

[0031]

[0032] Wherein

[0033] R 1 、R 2 、R 3 、R 4 、R 5 and R 6 each independently represent a straight-chain or branched-chain, saturated or unsaturated, substituted or unsubstituted alkyl group; a straight-chain or branched-chain, saturated or unsaturated, substituted or unsubstituted heteroalkyl group; a saturated or unsaturated, substituted or unsubstituted cycloalkyl group; a saturated or unsaturated, substituted or unsubstituted heterocycloalkyl group; a substituted or unsubstituted aryl group; a substituted or unsubstituted heteroaryl group; a straight-chain or branched-chain, substituted or unsubstituted aralkyl group; or a straight-chain or branched-chain, substituted or unsubstituted alkaryl group; and

[0034] n represents an integer from 1 to 10.

[0035] As used herein, the terms "straight-chain", "branched-chain", "saturated", "unsaturated" and "unsubstituted" have their respective generally recognized meanings, as known to those skilled in the art. As used herein, the term "substituted" means that one or more, particularly 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 hydrogen atoms of the corresponding group are replaced by substituents. Examples of suitable substituents include halogen atoms such as -F, -Cl, -Br, -I; -OH, hydroxyalkyl (ether), -SH, thioalkyl (thioether), ═O, carboxyl (-COOH) and its salts, esters and amides, -NH2, secondary amino group, tertiary amino group, nitrile group, nitro group, alkyl group, heteroalkyl group, cycloalkyl group, heterocycloalkyl group, aryl group and heteroaryl group. If there are two or more substituents, they may be the same or different, and they may be bonded to each other to form a ring. The terms "heteroalkyl", "heterocycloalkyl" or "heteroaryl" respectively mean an alkyl group, cycloalkyl group or aryl group in which one or more, particularly 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 carbon atoms are replaced by heteroatoms such as O, N or S, particularly O and / or N. If the group contains more than one heteroatom, these heteroatoms may be the same or different.

[0036] Suitable examples of alkyl groups include C1 to C 20 alkyl groups, particularly C2 to C 10 alkyl groups, particularly C3 to C8 alkyl groups, particularly C4 to C6 alkyl groups.

[0037] Suitable examples of cycloalkyl groups include C3 to C 20Cycloalkyl, especially C4 to C 15 Cycloalkyl, especially C5 to C 10 Cycloalkyl, especially C6 to C8 cycloalkyl.

[0038] Suitable examples of aryl include C6 to C 20 Aryl, especially C6 to C 16 Aryl, especially C6 to C 14 Aryl, especially C6 to C 10 Aryl. In particular, the aryl may be phenyl.

[0039] As used herein, "aralkyl" denotes a group having an aliphatic and an aromatic moiety, wherein the aliphatic moiety is bonded to the oxygen or nitrogen atom of the corresponding compound represented by formula (I) or (II), respectively, and wherein the aromatic moiety and / or the aliphatic moiety may optionally contain a heteroatom. In other words, "aralkyl" denotes an alkyl or cycloalkyl (or heteroalkyl or heterocycloalkyl) having an aryl (or heteroaryl) as a substituent. Suitable aliphatic and aromatic moieties of aralkyl correspond to alkyl, cycloalkyl and aryl (or heteroalkyl, heterocycloalkyl and heteroaryl, respectively) as defined above.

[0040] As used herein, "alkaryl" denotes a group having an aliphatic and an aromatic moiety, wherein the aromatic moiety is bonded to the oxygen or nitrogen atom of the corresponding compound represented by formula (I) or (II), respectively, and wherein the aliphatic moiety and / or the aromatic moiety may optionally contain a heteroatom. In other words, "alkaryl" denotes an aryl (or heteroaryl) having an alkyl or cycloalkyl (or heteroalkyl or heterocycloalkyl) as a substituent. Suitable aliphatic and aromatic moieties of alkaryl correspond to alkyl, cycloalkyl and aryl (or heteroalkyl, heterocycloalkyl and heteroaryl, respectively) as defined above.

[0041] In one embodiment, R 1 and / or R 2 — together with the oxygen atom bonded to R 1 and / or R 2 — comprises a bisphenol moiety, such as a bisphenol A moiety and / or a bisphenol F moiety, butanediol, hexanediol, neopentyl glycol, C 12 -C 14 alcohol, 2-ethylhex-2-ol, fatty alcohols (such as C 14 -C 26 alcohol) and / or cardanol.

[0042] In one embodiment, one or more of R 3 、R 4 、R 5 and R 6 comprise hydrogen, methyl, ethyl, n-propyl, isopropyl and / or straight-chain or branched hydroxyalkyl.

[0043] In general formula (II), "n" represents an integer from 1 to 10, particularly from 1 to 5, more particularly from 1 to 3, such as 1 or 2.

[0044] In one embodiment, the compounds of general formula I can be synthesized by the reaction of a difunctional epoxy resin (i.e., containing two epoxy groups) and a monofunctional primary amine compound (which can react with two epoxy groups) according to the following reaction scheme:

[0045]

[0046] In another embodiment, the compounds of general formula I can also be recovered from the recycling of epoxy-amine resins containing acetals or ketals, as illustrated by the following reaction scheme:

[0047]

[0048] In one embodiment, the compounds of general formula II can be synthesized by the reaction of a difunctional epoxy resin (i.e., containing two epoxy groups) and a difunctional secondary amine compound (where each amine group can react with one epoxy group) according to the following reaction scheme:

[0049]

[0050] In one embodiment, mixtures of the above components can be used, such as mixtures of compounds of general formula I and compounds of general formula II or mixtures of the above isolates.

[0051] In one embodiment, when synthesizing the compounds of general formula I and / or the compounds of general formula I, in addition to the difunctional epoxy resin (i.e., containing two epoxy groups), a monofunctional epoxy resin (i.e., containing only one epoxy group) can be added to control the molecular weight of the polymer chain (particularly to terminate the growth of the polymer chain).

[0052] In one embodiment, the compounds having the chemical structure of general formula I or general formula II are thermoplastic materials, i.e., having thermoplastic properties. The term "thermoplastic" as used herein means that, compared with thermosetting materials, the material becomes flexible or moldable at a certain elevated temperature and solidifies upon cooling.

[0053] In one embodiment, a compound having a chemical structure of general formula I or general formula II is present (e.g., having been placed in or applied to a mold) in the form of at least one selected from a film, a web, a fabric, a fleece (non-woven), a veil, and a felt (having the above-mentioned shape). It may be advantageous that the compound having a chemical structure of general formula I or general formula II is not present in powder or granule form, but has a specific shape, such as the shape of a film, a web, a fabric, a fleece (non-woven), a veil, or a felt, in order to perform its desired function (e.g., as an adhesive and / or as a flow regulator) during the production of a wind turbine blade or its components. The production of these specific shapes (such as films, webs, fleeces, or veils) can be accomplished by standard processing techniques for thermoplastic materials, such as extrusion or melt spinning. For example, a fleece, a veil, or a felt can be produced by melt spinning, and a film or fibers (which can subsequently be further processed into a web or a fabric) can be obtained by extrusion.

[0054] In one embodiment, a compound having a chemical structure of general formula I or general formula II or a material based on this chemical nature can be used as a flow regulator and / or an adhesive, in particular a hot melt adhesive. A flow regulator can include a flow promoting material (i.e., a material that increases the flow of a resin, such as a casting resin) and a flow restricting material (i.e., a material that reduces the flow of a resin, such as a casting resin). The regulation of the flow may be important for avoiding or at least suppressing the occurrence of runs when a casting resin is applied. A run is an area and space in a laminate where the resistance to the casting resin is reduced. The resin flows much faster in these spaces, and as a result, air inclusions and reduced part quality may occur. Runs may be caused by incorrect design, curved shapes (including rigid materials in the laminate), wrinkles in the material or the vacuum bag, poor sealing along the sides, etc.

[0055] In one embodiment, a compound having a chemical structure of general formula I or general formula II has a coverage rate of less than 50%, particularly less than 40%, particularly less than 30%, particularly less than 20% of, for example, the inner surface of a mold. As used herein, the term "coverage rate" represents the ratio between the area covered by the material (e.g., the inner surface of a mold) and the area not covered by the material (i.e., the area of the open space therebetween). With such a relatively low coverage rate, which can result in high in-plane and through-plane permeability, the compound having a chemical structure of general formula I or general formula II can represent a flow promoting (enhancing, improving, increasing) material. For this purpose, it may be advantageous if the thickness of a web, a fleece, a felt, or a veil made of a compound having a chemical structure of general formula I or general formula II is higher than 1 mm and / or if the compound having a chemical structure of general formula I or general formula II is an incompressible material.

[0056] In one embodiment, a compound having a chemical structure of general formula I or general formula II has a mold (e.g., inner surface) coverage of greater than 50%, particularly greater than 60%, particularly greater than 70%. With such a relatively high coverage, the compound having a chemical structure of general formula I or general formula II can represent a flow-restricting (inhibiting, reducing) material. For this purpose, it may be advantageous if the web, flannel, felt or veil made of the compound having a chemical structure of general formula I or general formula II has a thickness higher than 1 mm and / or if the compound having a chemical structure of general formula I or general formula II is a compressible material.

[0057] In one embodiment, particularly after the step of applying an infusion resin into a mold, the method further comprises heating the compound having a chemical structure of general formula I or general formula II to a temperature of 80 to 200 °C, particularly 100 to 180 °C, particularly 120 to 160 °C. By taking this measure, the compound having a chemical structure of general formula I or general formula II can be used as an adhesive, particularly a hot-melt adhesive.

[0058] In one embodiment, particularly in the previous embodiment, the compound having a chemical structure of general formula I or general formula II is present in the form of at least one selected from a web, flannel and veil, wherein the web, flannel and / or veil satisfy at least one of the following characteristics: a thickness of 100 μm or less, particularly 50 μm or less, and / or a surface weight (mass per unit area) of 75 g / m 2 or less, particularly 50 g / m 2 or less, particularly 25 g / m 2 or less, and / or a mold coverage of less than 50%, particularly less than 20%. By taking this measure, the compound having a chemical structure of general formula I or general formula II can be particularly suitable for use as an adhesive, particularly a hot-melt adhesive.

[0059] In one embodiment, the step of applying a resin into a mold includes the step of injecting an infusion resin into the mold, for example, by a vacuum infusion method. In the context of this specification, the term "vacuum infusion method" can particularly denote a molding technique in which a liquid or flowable resin is injected into a mold under a vacuum. In particular, vacuum-assisted resin transfer molding (VARTM) can be used. The infusion resin can particularly be a liquid or flowable composition that contains a plurality of components, usually at least two different types of components, which can react with each other to form a cured or hardened product.

[0060] In one embodiment, the (infusion) resin comprises an epoxyamine (infusion) resin (epoxyamine-based resin or epoxy-based resin). The epoxyamine resin can, for example, comprise an epoxy component and an amine component.

[0061] In one embodiment, the (infusion) resin contains cleavable functional groups, particularly at least one of acetal and ketal functional groups. In the context of the present application, the term "cleavable functional group" may particularly refer to a functional group having a covalent bond that can be cleaved under certain conditions (such as temperature, pH value, reagent). For example, the cleavable functional group may particularly be an acid-cleavable functional group, that is, a functional group having a covalent bond that can be cleaved by an acid or cleaved under acidic conditions (such as a pH less than 7).

[0062] In one embodiment, the (infusion) resin comprises an epoxyamine (infusion) resin containing cleavable functional groups, particularly at least one of acetal and ketal functional groups. Commercial examples thereof are, for example, based on (from Aditya Birla Chemicals) or (from Adesso Advanced Materials) technology.

[0063] In one embodiment, the curing (or hardening) of the infusion resin is not particularly limited and can be carried out at room temperature or at an elevated temperature (i.e., heating may be involved) depending on the type of infusion resin.

[0064] In one embodiment, the method further includes removing the manufactured wind turbine blade or its component from the mold after curing the infusion resin.

[0065] On the other hand, a (recyclable, particularly substantially fully recyclable) wind turbine blade or its component can be obtained by the method described above or by the method described above. Compounds having a chemical structure of general formula I or general formula II for producing a wind turbine blade (or its component) may still be contained in the wind turbine blade (or its component) thus obtained and form its component. In fact, compounds having a chemical structure of general formula I or general formula II can be degraded in a controlled manner (such as dissolved) during the recycling process of an acetal- or ketal-based recyclable resin (such as at an elevated temperature under mild (acidic) conditions), thereby enabling the substantially complete recycling of the wind turbine blade and the reuse of the material.

[0066] On the other hand, compounds having a chemical structure of general formula I or general formula II are used as flow regulators for the infusion resin.

[0067] In one embodiment, a compound having a chemical structure of general formula I or general formula II is used as a flow-promoting (enhancing, improving, increasing) material (i.e., a material that increases the flow of a casting resin). For this purpose, the compound having a chemical structure of general formula I or general formula II has a mold (inner surface) coverage of less than 50%, particularly less than 40%, particularly less than 30%, particularly less than 20%.

[0068] In another embodiment, a compound having a chemical structure of general formula I or general formula II is used as a flow-restricting (inhibiting, reducing) material (i.e., a material that reduces the flow of a resin, such as a casting resin). For this purpose, the compound having a chemical structure of general formula I or general formula II has a mold (inner surface) coverage of more than 50%, particularly more than 60%, particularly more than 70%.

[0069] As described above, when applying a casting resin, regulating the flow of the casting resin may be important for avoiding or at least suppressing the occurrence of runs.

[0070] On the other hand, a method of recycling a wind turbine blade or a component thereof, particularly a wind turbine blade or a component thereof as described herein, includes contacting the wind turbine blade or a component thereof with an acidic aqueous liquid containing an acid at an elevated temperature above ambient temperature, such as at a temperature of 70 °C to 100 °C, and / or for a time of 1 hour to 10 hours (such that the wind turbine blade or a component thereof degrades and the soluble portion of the wind turbine blade or a component thereof is substantially completely dissolved). Depending on the size of the blade or blade component, such a blade or blade component may also be divided into smaller workpieces (pieces) (components) for processing. For example, separation by mechanical means including cutting or shredding, thereby dividing the process into several intermediate steps.

[0071] In one embodiment, the step of contacting the wind turbine blade or a component thereof with an acidic aqueous liquid containing an acid includes placing the wind turbine blade or a component thereof in an acidic aqueous liquid bath. Alternatively, the wind turbine blade or a component thereof to be recycled may also be sprayed with an acidic aqueous liquid containing an acid or otherwise contacted with an acidic aqueous liquid containing an acid.

[0072] In one embodiment, the acidic aqueous liquid has a pH value of less than 7, particularly less than 6, particularly less than 5, particularly less than 4. Additionally, the acidic aqueous liquid may have a pH value greater than 0, particularly greater than 1.

[0073] In one embodiment, the acid is preferably an organic acid or a carboxylic acid rather than an inorganic acid. Organic acids or carboxylic acids are not only particularly suitable for adjusting the appropriate pH but can also additionally act as solvents for the recyclate.

[0074] In one embodiment, the acid comprises monocarboxylic acid, dicarboxylic acid, tricarboxylic acid, and / or polycarboxylic acid, particularly selected from acetic acid, lactic acid, citric acid, oxalic acid, and tartaric acid. Combinations of two or more of these acids are also suitable. In particular, the acid may comprise acetic acid, which has proven to be particularly suitable.

[0075] In one embodiment, the wind turbine blade or a component thereof to be recycled is contacted with an acidic aqueous liquid comprising an acid (such as 20 - 30% acetic acid) at a temperature of 70°C to 100°C, such as 80°C to 90°C, and / or for a time of 1 hour to 10 hours, such as 3 hours to 6 hours.

[0076] In one embodiment, the wind turbine blade or a component thereof to be recycled comprises or is made of a resin containing at least one cleavable functional group, particularly at least one of acetal and ketal functional groups. As a result of the contacting step, at least a part of the cleavable functional groups of the resin of the wind turbine blade or a component thereof are cleaved, such that the cleaved resin becomes dissolved in the acidic aqueous liquid. At the same time, a compound having a chemical structure of Formula I or Formula II is also dissolved in the acidic aqueous liquid and can form a substantially homogeneous blend or mixture with the cleaved resin, enabling the recovery of the compound having a chemical structure of Formula I.

[0077] The invention or embodiments of the invention described herein can be descriptively summarized as follows:

[0078] The flow promoting or restricting materials and adhesives used in the laminate (such as for enhancing flow, reducing runways, or consolidating preforms) are based on linear polymers, which are based on epoxy - amine type chemistry and thus have thermoplastic properties. The materials have chemical properties similar to or the same as the thermoplastic recycled materials that can be recovered from the recycling of ketal - or acetal - based resins.

[0079] The novel flow materials and adhesives are based on the chemical structure of Formula I or Formula II. The compound having a chemical structure of Formula I can be recovered from the recycling of an epoxy - amine resin containing acetal or ketal (thus the starting materials used can be cleaved to provide new chemical entities), or can be synthesized by the reaction of a difunctional epoxy resin and a monofunctional primary amine hardener (which can react with 2 epoxy groups). The compound having a chemical structure of Formula II can be synthesized by the reaction of a difunctional epoxy resin and a difunctional secondary amine hardener (each amine can react with one epoxy group) and can contain heteroatoms in the main chain and side chains. It can also be a mixture of the above components. In addition to the difunctional epoxy resin, a monofunctional epoxy resin can be added to control the molecular weight of the polymer chain.

[0080] The above specific chemical structure enables the adhesive layer of the flow material to be dissolved together with the body blade matrix (infusion resin and repair resin) during the recycling process based on acid solvent decomposition. Examples of infusion resin and repair resin technologies compatible with the present invention are, for example, commercially available products Recyclamine and Cleavamine, but are not limited to these.

[0081] The preferred form of the product is a film, web, fabric, flannel, veil or felt. For webs, flannels and veils for adhesive use, the thickness should not exceed 100 μm, preferably 50 μm or less, and the weight is 75 g / m 2 , preferably 25 g / m 2 or less, and the coverage (or covering factor) is less than 50%, preferably less than 20%, to achieve high in-plane and through-plane permeability. The production of films, webs, flannels or veils can be carried out by standard processing techniques for thermoplastic materials such as extrusion or melt spinning.

[0082] For use as a flow regulator, the thickness and aerial weight of the web, flannel, felt or veil can be higher than 1 mm or more. The flow-promoting material should be incompressible and have a coverage of less than 50%, preferably less than 20%, to achieve high in-plane and through-plane permeability, and the flow-restricting material should have a coverage higher than 50% and be compressible. Potential manufacturing techniques for wool, veils or felts can be melt spinning, but are not limited to this, and fibers and films can be manufactured by extrusion. The coverage is the ratio between the area covered by the material and the area of the open space therebetween.

[0083] The films, flannels, veils, etc. can be applied to the blade during the lamination process and before infusion. The resin system for infusion should be recyclable under acidic conditions and elevated temperatures, such as an infusion resin based on Recyclamine. After the end of the life of the blade, the composite structure can be recycled under acidic conditions. The flow material and the adhesive layer are dissolved together with the resin under these conditions and become part of the recycled thermoplastic material of general formula I. To some extent, wind turbine blades contain fiber materials and optionally core materials, such as balsa wood or foam core materials (usually this is the case), and these materials can be separated and reused in subsequent wind turbine blade manufacturing or used for other purposes suitable for them.

[0084] Although the present invention has been described in detail by specific embodiments and examples, it should be understood that the present invention is not limited thereto, and various changes and modifications can be made without departing from the scope of the present invention.

Claims

1. A method for producing a wind turbine blade or a component thereof, the method comprising: providing a mold containing a compound having a chemical structure of general formula I or general formula II depicted below, applying a resin into the mold, curing the resin; wherein R 1 、R 2 、R 3 、R 4 、R 5 and R 6 each independently represents a straight-chain or branched-chain, saturated or unsaturated, substituted or unsubstituted alkyl group; a straight-chain or branched-chain, saturated or unsaturated, substituted or unsubstituted heteroalkyl group; a saturated or unsaturated, substituted or unsubstituted cycloalkyl group; a saturated or unsaturated, substituted or unsubstituted heterocycloalkyl group; a substituted or unsubstituted aryl group; a substituted or unsubstituted heteroaryl group; a straight-chain or branched-chain, substituted or unsubstituted aralkyl group; or a straight-chain or branched-chain, substituted or unsubstituted alkaryl group; and n represents an integer from 1 to 10.

2. The method according to claim 1, wherein the compound having a chemical structure of general formula I or general formula II is present in at least one form selected from a film, a web, a fabric, a flannel, a veil, and a felt.

3. The method according to any one of the preceding claims, wherein the compound having a chemical structure of general formula I or general formula II has a mold coverage of less than 50%, particularly less than 20%.

4. The method according to any one of claims 1 or 2, wherein the compound having a chemical structure of general formula I or general formula II has a mold coverage of more than 50%.

5. The method according to any one of the preceding claims, particularly after the step of applying the infusion resin into the mold, further comprising heating the compound having a chemical structure of general formula I or general formula II to a temperature of 80 to 200 °C, particularly 100 to 180 °C.

6. The method according to claim 5, wherein the compound having a chemical structure of general formula I or general formula II is present in at least one form selected from a web, a flannel, and a veil, wherein the fabric web, the flannelette and / or the veil has a thickness of 100 μm or less, in particular 50 μm or less, and / or a surface weight of 75 g / m 2 or less, in particular 25 g / m 2 or less.

7. The method according to any one of the preceding claims, wherein the resin comprises an epoxy amine resin.

8. The method according to any one of the preceding claims, wherein the resin contains a cleavable functional group, particularly at least one of an acetal and a ketal functional group.

9. The method according to any one of the preceding claims, wherein the method further comprises removing the mold after curing the infusion resin.

10. A wind turbine blade or a component thereof obtainable by the method according to any one of claims 1 to 9.

11. Use of a compound having a chemical structure of general formula I or general formula II depicted below as a flow regulator for an infusion resin; wherein R 1 、R 2 、R 3 、R 4 、R 5 and R 6 each independently represents a straight-chain or branched-chain, saturated or unsaturated, substituted or unsubstituted alkyl group; a straight-chain or branched-chain, saturated or unsaturated, substituted or unsubstituted heteroalkyl group; a saturated or unsaturated, substituted or unsubstituted cycloalkyl group; a saturated or unsaturated, substituted or unsubstituted heterocycloalkyl group; a substituted or unsubstituted aryl group; a substituted or unsubstituted heteroaryl group; a straight-chain or branched-chain, substituted or unsubstituted aralkyl group; or a straight-chain or branched-chain, substituted or unsubstituted alkaryl group; and n represents an integer from 1 to 10.

12. The use according to claim 11, wherein the compound is used as a flow promoting material.

13. The use according to claim 11, wherein the compound is used as a flow restricting material.

14. A method for recycling a wind turbine blade or a component thereof, particularly a wind turbine blade or a component thereof according to claim 10, the method comprising: contacting the wind turbine blade or the component thereof with an acidic aqueous liquid containing an acid at an elevated temperature, for example at a temperature of 70 °C to 100 °C, and / or for a time of 1 hour to 10 hours, which is elevated compared to the ambient temperature.

15. The method according to claim 14, wherein the acid comprises at least one selected from acetic acid, lactic acid, citric acid, oxalic acid, and tartaric acid.

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