Method of producing a wind turbine blade, a correspondingly produced wind turbine blade and a resin composition suitable for said production

Abstract

A resin composition is described, suitable for producing wind turbine blades or any of the aforementioned components by means of a vacuum infusion method. The resin composition comprises an epoxy component, a sterically hindered amine component, and a polyfunctional (meth)acrylate component. Furthermore, a method for producing wind turbine blades, nacelles, or any of the aforementioned components, and the corresponding produced wind turbine blades, nacelles, or any of the aforementioned components, as well as a method for recirculating wind turbine blades, nacelles, or any of the aforementioned components, are described.

Description

Invention Field

[0001] This invention relates to the field of wind turbine blades, and particularly to resin compositions suitable for methods of producing wind turbine blades or nacelles by means of vacuum infusion, and methods for producing wind turbine blades, nacelles or any of the aforementioned components. Background Technology

[0002] Wind power is considered one of the cleanest and most environmentally friendly energy sources available today, and wind turbines have received increasing attention in order to utilize this energy. A modern wind turbine typically consists of a tower, generator, gearbox, nacelle, and one or more rotor blades. The rotor blades capture the kinetic energy of the wind and transfer it as rotational energy to rotate the shaft that connects 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.

[0003] Various components of wind turbines, such as turbine blades or nacelles, are typically made of composite materials of (glass) fiber-reinforced polymer resins. Commonly used methods for producing such composites include vacuum-assisted resin transfer molding (VARTM), in which liquid or flowable resin is injected into a mold under a vacuum. For this purpose, low-viscosity resins are typically used, which reduces the cycle time for component manufacturing. Furthermore, the recycling and reprocessing of composite materials are becoming increasingly important issues.

[0004] Epoxyamine resins are commonly used as resin starting materials in industry. Their chemical properties are versatile for applications in wind turbine blades and components because of their outstanding mechanical properties, and their physical properties can be tuned to suit vacuum infusion processes that require low viscosity and long pot life, ideally combined with rapid curing. A disadvantage of epoxyamine resins is their reaction enthalpy and its release mechanism. This can lead to very high temperatures in thick components and insulating areas.

[0005] Despite the numerous advantages of ethylene oxide-based resins, challenges exist in the handling, post-treatment, maintenance, and end-of-life of cured structures.

[0006] For example, if geometric deviations exist, they must be accepted; defects such as dry areas or cracks must be removed and reconstructed with specialized resin for post-processing. The same applies to damage occurring during operation. End-of-life disposal is also difficult. Few recycling technologies are available, but those are less suitable for recycling glass-reinforced composite structures because the cost of the recycling process exceeds the value of the recycled materials.

[0007] As a first step, resins containing acetals or ketals have been introduced, which can be recycled under mildly acidic conditions. Acetals and ketals are described in the literature as exhibiting dynamic behavior, but the very densely cross-linked infusion resins used for recyclable blades show only very little weldability and generally almost no dynamic behavior.

[0008] Furthermore, Dow (WO 2012 / 148815 A1) has described a combination of small amounts of acrylate in an epoxy-amine resin. This patent application describes the use of several percentages (up to 4%) of acrylate in the epoxy moiety. This reference describes the reaction products (primary amine and secondary amine of acrylate) being able to further react with epoxy groups to form tertiary amines. However, such epoxy-acrylate amine resins still have disadvantages, particularly in terms of pot life and network density, hindering their application in the production of composites of fiber-reinforced polymer resins for wind turbine blades or other components of wind turbines.

[0009] Therefore, it may be necessary to further improve amine-based resins used in the production of composites of fiber-reinforced polymer resins for wind turbine blades or other components of wind turbines, particularly in terms of manageability (such as sufficiently long service life), reprocessability and / or recyclability. Invention Overview This need can be met by the subject matter of the independent claims. Advantageous embodiments of the invention are described in the dependent claims.

[0011] According to one aspect of the invention, a resin composition is provided (suitable for the production of wind turbine blades, nacelles or components thereof by means of vacuum infusion) comprising an epoxy component, a sterically hindered amine component and a polyfunctional (meth)acrylate component (comprising two or more (meth)acrylate functional groups).

[0012] According to a further aspect of the invention, a method for producing a wind turbine blade, nacelle, or any of the aforementioned components is provided, the method comprising applying a resin composition as described herein into a mold by vacuum infusion, particularly vacuum-assisted resin transfer molding, and curing the resin composition.

[0013] According to a further aspect of the invention, wind turbine blades, nacelles, or any of the foregoing components are provided that can be obtained (or acquired) by means of the methods described herein.

[0014] According to a further aspect of the invention, a method for recycling a wind turbine blade, nacelle, or any of the aforementioned components is provided, wherein the method comprises contacting a portion of the surface of the wind turbine blade, nacelle, or any of the aforementioned components with an acidic aqueous liquid containing an acid (having a pH of less than 7).

[0015] These aspects of the invention are particularly based on the discovery that if an epoxy acrylate amine resin contains an excess of sterically hindered amine component, this component reacts only once with the acrylate or epoxy component (because each amine group reacts only once, the resulting secondary amine does not react further). As a result, a polymer network with a lower network density is obtained compared to (sterically unhindered) amines that react twice. Furthermore, reactivity is reduced and the system provides a longer pot life.

[0016] Surprisingly, it was also found that sterically hindered amines reacted only once offered reprocessability at much lower acrylate levels compared to (non-sterically hindered) amines that reacted twice.

[0017] The combination of sterically hindered amines with acrylates and epoxy resins solves the challenges of acrylate-amine reactions. Reduced reactivity results in a significantly longer pot life. Furthermore, dynamic behavior is achieved with lower acrylate concentrations compared to other amines.

[0018] As a distinctive feature, the resulting polymer readily disintegrates (decomposes) in aqueous acetic acid, even at room temperature. This is an interesting characteristic because it allows for the recycling of the polymer portion of fiber-reinforced polymer resin composites under mild conditions. This is advantageous for the industrialization of recycling processes, as they are compatible with a wider range of resins. Invention Details The details of the invention and its other features and advantages will be described below. However, the invention is not limited to the specific description below, but is used for illustrative purposes only.

[0020] It should be noted that features described in connection with one 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 the resin composition can be combined with any other exemplary embodiment of the resin composition and with any exemplary embodiment of the method of producing a wind turbine blade, nacelle or any of the aforementioned components and with any exemplary embodiment of the method of producing a wind turbine blade, nacelle or any of the aforementioned components, or a recirculating wind turbine blade, nacelle or any of the aforementioned components, and vice versa, unless otherwise expressly stated.

[0021] When referring to a singular term, the use of an indefinite or definite article, such as “a,” “an,” or “the,” also includes the plural form of the term, and vice versa, unless otherwise explicitly stated.

[0022] As used in this article, the word "contains" includes not only the meaning of "containing", "including", or "containing", but also "basically composed of" and "composed of".

[0023] Unless otherwise expressly stated, the expressions “at least partially”, “at least partially” or “at least (a) part” as used herein may refer to at least 5%, in particular at least 10%, in particular at least 15%, in particular at least 20%, in particular at least 25%, in particular at least 30%, in particular at least 35%, in particular at least 40%, in particular at least 45%, in particular at least 50%, in particular at least 55%, in particular at least 60%, in particular at least 65%, in particular at least 70%, in particular at least 75%, in particular at least 80%, in particular at least 85%, in particular at least 90%, in particular at least 95%, in particular at least 98%, and may also refer to 100%.

[0024] In a first aspect, a resin composition is provided. This resin composition is particularly suitable for vacuum infusion methods and is therefore also referred to as an infusion resin. Furthermore, this resin composition is particularly suitable for producing wind turbine blades, nacelles, or any of the foregoing components or any other components of a wind turbine that comprise a composite material containing a (glass) fiber reinforced polymer resin.

[0025] As used herein, the term "composition" can specifically refer to a composition in which the components (ingredients) are close to each other and / or the components are (vigorously) mixed, for example, by using a mixer, agitator, and / or by shaking, thereby forming the composition. In particular, the components of the composition can be uniformly distributed or dispersed throughout the composition. The composition can be, in particular, a semi-solid (paste) or liquid, especially a liquid solution or a semi-solid or liquid suspension.

[0026] As used herein, the term "resin composition" may specifically refer to a composition comprising or consisting primarily of a resin or resin component that may chemically react with some of each other (e.g., polymerization or crosslinking) to cure or harden, which is typically induced by thermal energy (e.g., heating) or electromagnetic radiation.

[0027] The resin composition contains an epoxy component. There are no particular limitations on the epoxy component, and any suitable example conventional in the field of epoxy-amine infusion resins can be used. The epoxy component is characterized in particular by containing one or more epoxy functional groups.

[0028] In one embodiment, the epoxy component is selected from glycidyl ethers, glycidyl esters, glycidyl amines, divinylbenzene dioxide, alicyclic epoxides, and combinations thereof.

[0029] In one embodiment, the epoxy component is selected from bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, bisphenol S diglycidyl ether, bisphenol E diglycidyl ether, bisphenol Z diglycidyl ether, bisphenol C diglycidyl ether, bisphenol AP diglycidyl ether, triphenol PA triglycidyl ether, 4,4'-dihydroxydiphenyl diglycidyl ether, 4,4'-dihydroxybenzophenone diglycidyl ether, and hydrogenated forms of the listed substances (versions) and combinations thereof.

[0030] In one embodiment, the epoxy component is selected from butanediol diglycidyl ether, hexanediol diglycidyl ether, neopentyl glycol diglycidyl ether, fatty alcohol glycidyl ethers (saturated, unsaturated, C8-C24, straight-chain or branched, single substance or mixture), 2-ethylhexyl glycidyl ether, glycidyl tert-carbonate and similar fatty acid glycidyl esters (saturated, unsaturated, C8-C24, straight-chain or branched, single substance or mixture), epoxidized phenolic varnish, epoxidized cresol varnish, triglycidyl-p-aminophenol, trimethylolpropane triglycidyl ether, diglycidyl ether of cyclohexanediol, and polyoxypropylene. Diglycidyl ether, diglycidyl ether of polyoxyethylene, triglycidyl ether of propoxylated glycerol, monoglycidyl ether of p-tert-butylphenol, diglycidyl hexahydrophthalic acid, phenol glycidyl ether, cashew phenol glycidyl ether, cresol glycidyl ether, resorcinol diglycidyl ether, vanillin-based epoxy resins and their dimers or oligomers, eugenol epoxy resins and their dimers or oligomers, limonene oxide or dioxide, epoxidized sorbitol, epoxidized fatty acids, 2,5-bis(hydroxymethyl)furan diglycidyl ether, difurandiol diglycidyl ether, triglycidyl ether of castor oil, tetraglycidyl ether of m-phenylenediamine, and combinations thereof.

[0031] In one embodiment, the epoxy component is a combination of epoxy components mentioned in this application.

[0032] The resin composition also contains an amine component. The amine component is characterized by being a sterically hindered amine component. In other words, the amine functional groups are sterically hindered or partially shielded, reducing or limiting their accessibility (e.g., to potential reactants). Therefore, the reactivity of sterically hindered amines is generally reduced compared to non-sterically hindered amines. In particular, the inventors have discovered that the sterically hindered amine component can react with only one (meth)acrylate component or epoxy component, instead of reacting with both (meth)acrylate and epoxy components as in the case of a non-sterically hindered amine component. As a result, a polymer network with a lower network density can be obtained compared to (non-sterically hindered) amines that react twice.

[0033] In one embodiment, the sterically hindered amine component comprises at least one functional group selected from: H2N-C(CH3)2- (i.e., having two methyl groups at the carbon atom bonded to the amino group), H2N-C(CH(CH3)2)2- (i.e., having two isopropyl groups at the carbon atom bonded to the amino group), H2N-C(C(CH3)3)2- (i.e., having two tert-butyl groups at the carbon atom bonded to the amino group), and an amino group bonded to a cyclic carbon atom (i.e., forming part of an alicyclic ring, such as in 1,8-diamino-p-menthane). The sterically hindered amine component may further comprise at least one functional group wherein the amino group is bonded to a carbon atom bonded to a combination of at least two of the methyl, isopropyl, and cyclic carbon atoms. As those skilled in the art will understand, the steric hindrance of the amino group increases with the volume of the adjacent group; that is, the H2N-C(C(CH3)3)2- functional group provides an amine component with higher steric hindrance than the H2N-C(CH3)2- functional group. This sterically hindered amine component may also contain combinations of the functional groups H2N-C(CH3)2-, H2N-C(CH(CH3)2)2-, and / or H2N-C(C(CH3)3)2- in a molecule and in individual components.

[0034] In one embodiment, the sterically hindered amine component comprises at least one H2N-C(CH3)2- functional group. It has been shown that a structure with two methyl groups at the carbon atom bonded to the amino group may provide sufficient steric hindrance for the amino group to achieve the desired effect. The sterically hindered amine component may comprise one, two, or three H2N-C(CH3)2- functional groups, particularly two H2N-C(CH3)2- functional groups.

[0035] In one embodiment, the sterically hindered amine component is selected from aliphatic polyamines, aryl aliphatic polyamines, alicyclic polyamines, alkanolamines, polyether polyamines, and combinations thereof, wherein each component contains at least one sterically hindered amine functional group.

[0036] In one embodiment, the amine component, particularly the sterically hindered amine component, is selected from cyclohexylamine, methylcyclohexylamine, dimethylcyclohexylamine, isophorone diamine, cyclohexane diamine, methylcyclohexane diamine, N-aminoethylpiperazine, menthane diamine, 1,3-bis(aminomethyl)cyclohexane, diaminodicyclohexylmethane, diaminodimethyldicyclohexylmethane, N-(3-aminopropyl)cyclohexylamine, and combinations thereof.

[0037] In one embodiment, the amine component, particularly the sterically hindered amine component, is selected from diethylenetriamine, triethylenetetramine, tetraethylenepentamine, dipropylenediamine, diethylaminopropylamine, alkane diamines (propylenediamine, butanediamine, pentanediamine, hexanediamine, heptanediamine, octanediamine, nonanediamine, decanedanediamine, undecanediamine, dodecanediamine and longer-chain diamines and isomers, such as neopentanediamine, isobutanediamine) and combinations thereof.

[0038] In one embodiment, the amine component, particularly the sterically hindered amine component, is selected from polyamide amines, polyamide imidazoles, polyaminoimidazoliums, Mannich base amines, phenalkamines, and combinations thereof.

[0039] In one embodiment, the amine component, particularly the sterically hindered amine component, is selected from amine-terminated polyethylene glycol, amine-terminated polypropylene glycol, amine-terminated polybutane glycol, amine-terminated mixed polyalkylene glycols, dioxadodecanediamine, amine-terminated glyceryl polyethylene glycol, and combinations thereof.

[0040] In one embodiment, the amine component, particularly the sterically hindered amine component, is a combination of the amine components mentioned in this application.

[0041] The resin composition also comprises a polyfunctional (meth)acrylate component. The polyfunctional (meth)acrylate component is characterized in that it contains two or more (meth)acrylate functional groups. A polyfunctional acrylate component, i.e., containing two or more acrylate functional groups, is preferred, but a polyfunctional methacrylate component, i.e., containing two or more methacrylate functional groups, can also be used. A mixed polyfunctional (meth)acrylate component containing one or more acrylate functional groups and one or more methacrylate functional groups may also be used.

[0042] The term “(meth)acrylate” encompasses acrylates and / or methacrylates. As used herein, the terms “acrylate” and “methacrylate” correspond to their generally accepted meanings. Acrylates may be represented by the general formula “H₂C=CH-C(=O)-”, and methacrylates may be represented by the general formula “H₂C=C(CH₃)-C(=O)-”. Acrylates may also encompass itaconic acid esters.

[0043] In one embodiment, the multifunctional (meth)acrylate component comprises two, three, four or more (meth)acrylate functional groups.

[0044] In one embodiment, the polyfunctional (meth)acrylate component is selected from diol diacrylate, butanediol diacrylate, dipropylene glycol diacrylate, diethylene glycol diacrylate, neopentyl glycol diacrylate, bisphenol A diglycidyl ether diacrylate, trimethylolpropane triacrylate, pentaerythritol tetraacrylate, tricyclo[5.2.1.0(2,6)]decanediethanol diacrylate, and combinations thereof.

[0045] In one embodiment, the (meth)acrylate component is selected from methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, isobutyl acrylate, pentyl acrylate, isoamyl acrylate, neopentyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, decyl acrylate and longer-chain alkyl acrylates and their isomers, hydroxypropyl acrylate, hydroxyethyl acrylate, 2-phenoxyethyl acrylate, tert-butylcyclohexyl acrylate, 3-methyl-1,5-pentanediol diacrylate, tricyclodecane methanol acrylate, caprolactone acrylate, cyclotrimethylolpropane methyl acetal acrylate, 2-(2-ethoxyethoxy)ethyl acrylate, and isobornyl.

[0046] In one embodiment, the (meth)acrylate component is selected from glycol diacrylate, butanediol diacrylate, neopentyl glycol diacrylate, decanediol diacrylate, ethylene glycol diacrylate, diethylene glycol diacrylate, triethylene glycol diacrylate, polyethylene glycol diacrylate, propylene glycol diacrylate, dipropylene glycol diacrylate, tripropylene glycol diacrylate, tricyclodecanediethanol diacrylate, and urethaneacrylates.

[0047] In one embodiment, (meth)acrylate is a combination of (meth)acrylates mentioned in this application.

[0048] In one embodiment, the (meth)acrylate is an epoxy acrylate. In another embodiment, the (meth)acrylate is an acrylated epoxy component derived from the epoxy component mentioned in this application.

[0049] In one embodiment, the (meth)acrylate component is selected from trimethylolpropane triacrylate, triglyceride triacrylate, tri(2-hydroxyethyl)isocyanurate triacrylate, soybean oil epoxy acrylate, dipentaerythritol hexaacrylate, pentaerythritol triacrylate, dipentaerythritol pentaacrylate, and pentaerythritol tetraacrylate.

[0050] In one embodiment, the (meth)acrylate component is a combination of the (meth)acrylate components mentioned in this application, particularly the aforementioned (meth)acrylate components.

[0051] In one embodiment, the epoxy component and / or amine component and / or (meth)acrylate component are provided and / or present in the presence or absence of a catalyst, such as, but not limited to, imidazole-based catalysts, tertiary amines, metal and metal salt catalysts, organometallic catalysts, enzyme and protein catalysts, and combinations thereof.

[0052] In one embodiment, the resin composition comprises at least one catalyst selected from imidazole-based catalysts, tertiary amines, metal and metal salt catalysts, organometallic catalysts, enzyme and protein catalysts, and combinations thereof.

[0053] In one embodiment, the epoxy component and / or amine component and / or (meth)acrylate component are provided and / or present in the presence of additives, such as, but not limited to, wetting agents, coupling agents, nano and micro fillers, defoamers, degassing agents, and combinations thereof.

[0054] In one embodiment, the resin composition comprises at least one additive, which is a wetting agent, a coupling agent, a nano- or micro-sized filler, a defoamer, or a degassing agent. The at least one additive may be a combination of the above-mentioned additives.

[0055] In one embodiment, the epoxy component comprises bisphenol A diglycidyl ether and / or the sterically hindered amine component comprises 1,8-diamino-p-menthane and / or the polyfunctional (meth)acrylate component comprises trimethylolpropane triacrylate or pentaerythritol tetraacrylate. In other words, the epoxy component may particularly comprise bisphenol A diglycidyl ether. The sterically hindered amine component may particularly comprise 1,8-diamino-p-menthane. The polyfunctional (meth)acrylate component may particularly comprise trimethylolpropane triacrylate or pentaerythritol tetraacrylate. Using two or three of these preferred compounds may be advantageous, as they have proven particularly suitable for achieving the desired effects and properties.

[0056] In one embodiment, the molar ratio of the polyfunctional (meth)acrylate component ranges from 10 to 50 mol%, and the molar ratio of the epoxy component ranges from 50 to 90 mol%, each based on 100 mol% of the sterically hindered amine component. In other words, for every 100 mol% of the sterically hindered amine component, the resin composition may contain 50 to 90 mol% of the epoxy component and 10 to 50 mol% of the polyfunctional (meth)acrylate component. The total amount of the epoxy component and the polyfunctional (meth)acrylate component may specifically be 100 mol%. An excess of the sterically hindered amine component may also be present compared to the total amount of the epoxy component and the polyfunctional (meth)acrylate component. For example, the composition may also contain 100 to 200 mol% of the sterically hindered amine component, 50 to 90 mol% of the epoxy component, and 10 to 50 mol% of the polyfunctional (meth)acrylate component.

[0057] In one embodiment, the molar ratio of the polyfunctional (meth)acrylate component to the epoxy component is in the range of 1:9 to 1:1, particularly in the range of 1:5 to 1:2.

[0058] In one embodiment, the resin composition further comprises an amine curing agent. Specifically, the amine curing agent can be an amine component that does not contain sterically hindered amine functional groups, i.e., conventional amine curing agents in the epoxy-amine infusion resin field, such as isophorone diamine (IPDA) or polyether amines such as Jeffamine D-230. Since the epoxy component is partially replaced by a polyfunctional (meth)acrylate component, particularly in the case of a higher amount of polyfunctional (meth)acrylate component, such conventional amine curing agents can replace a portion of the sterically hindered amine component, which provides the effect of increased reactivity of the resin composition and increased network density of the resulting polymer. Since these improvements are desired only in some cases and only to a certain extent, the content of the amine curing agent should generally be limited to, for example, 1 to 20 parts by weight, particularly 5 to 15 parts by weight, per 100 parts by weight of the sterically hindered amine component. However, as those skilled in the art will understand, the reactivity of the resin composition and the network density of the resulting polymer can be appropriately adjusted as needed by adding only a relatively small amount of conventional amine curing agent.

[0059] The resin composition according to the first aspect can be advantageously used in the method according to the second aspect as described below.

[0060] In a second aspect, a method for producing wind turbine blades, nacelles, or any of the aforementioned components is provided.

[0061] In this method, the resin composition as described herein is applied, particularly injected, into a mold by vacuum infusion. In the context of this specification, the term "vacuum infusion" may specifically refer to a molding technique in which a liquid or flowable resin is injected into a mold under an applied vacuum. In particular, vacuum-assisted resin transfer molding (VARTM) may be used. The infused resin may be, in particular, a liquid or flowable composition comprising components that can react with each other to form a cured or hardened product, typically at least two different types of components.

[0062] The mold into which the resin composition is applied typically forms a cavity, and is therefore also called a mold cavity. The mold can be adapted to the contours of the turbine blade, nacelle, or any of the aforementioned components to be produced.

[0063] In one embodiment, the step of curing the resin composition includes heating the resin composition to a temperature in the range of 60 to 150°C, particularly 70 to 120°C.

[0064] In one embodiment, the method further includes removing the mold after curing the resin composition, thereby obtaining the produced wind turbine blade, nacelle, or component thereof.

[0065] In a further aspect, wind turbine blades, nacelles, or any of the aforementioned components can be obtained or acquired by means of the methods described above.

[0066] In a further aspect, a method for recycling a wind turbine blade, nacelle, or any of the aforementioned components as described herein, wherein the method includes contacting a portion of the surface of the wind turbine blade, nacelle, or any of the aforementioned components with an acidic aqueous liquid containing an acid.

[0067] 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. Furthermore, the acidic aqueous liquid may have a pH value greater than 0, particularly greater than 1.

[0068] In one embodiment, the acid is preferably an organic acid or 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 reaction products following the reaction of the resin with the acid. Furthermore, it may be advantageous if the organic acid or carboxylic acid has good miscibility with water or water / solvent mixtures, and can also dissolve nonpolar substances.

[0069] In one embodiment, the acid includes monocarboxylic acids, dicarboxylic acids, tricarboxylic acids, and / or polycarboxylic acids, particularly selected from aliphatic monocarboxylic acids, aliphatic dicarboxylic acids, aliphatic tricarboxylic acids, and aliphatic polycarboxylic acids. For example, the acid may be selected from acetic acid, lactic acid, maleic acid, fumaric acid, tartaric acid, oxalic acid, malonic acid, succinic acid, adipic acid, and citric acid. Combinations of two or more of these acids are also suitable.

[0070] In one embodiment, the acid comprises at least one selected from acetic acid, lactic acid, citric acid, oxalic acid, tartaric acid, or a combination of two or more of the foregoing. In particular, the acid may comprise acetic acid (e.g., at a concentration of 25% by mass of an acidic aqueous liquid), which has proven particularly suitable for the purposes of this invention.

[0071] Acids, such as acetic acid, may have already reacted with the resin at room temperature. Therefore, no additional heating step is required. However, to increase the reaction rate, it may be advantageous to apply heat, for example by preheating the acidic aqueous liquid and / or a portion of the surface of the wind turbine blade, nacelle, or any of the aforementioned components, and / or by heating after the acidic aqueous liquid has been applied to a portion of the surface of the wind turbine blade, nacelle, or any of the aforementioned components.

[0072] Although the invention has been described in detail with reference to specific embodiments and examples, it should be understood that the invention is not limited thereto, and various changes and modifications are possible without departing from the scope of the invention.

Claims

1. A resin composition comprising: Epoxy components; sterically hindered amine components; Multifunctional (meth)acrylate component.

2. The resin composition of claim 1, wherein the epoxy component is selected from glycidyl ether, glycidyl ester, glycidylamine, divinylbenzene dioxide, alicyclic epoxides, and combinations thereof.

3. The resin composition according to any one of the preceding claims, wherein the sterically hindered amine component comprises at least one functional group selected from H2N-C(CH3)2-, H2N-C(CH(CH3)2)2-, H2N-C(C(CH3)3)2- and an amino group bonded to a ring carbon atom.

4. The resin composition according to any one of the preceding claims, wherein the sterically hindered amine component comprises at least one H2N-C(CH3)2-functional group, particularly one, two or three H2N-C(CH3)2-functional groups.

5. The resin composition according to any one of the preceding claims, wherein the sterically hindered amine component is selected from aliphatic polyamines, aryl aliphatic polyamines, alicyclic polyamines, alkanolamines, polyether polyamines, and combinations thereof, wherein each component comprises at least one sterically hindered amine functional group.

6. The resin composition of any of the preceding claims, wherein the polyfunctional (meth)acrylate component comprises two, three, four or more (meth)acrylate functional groups.

7. The resin composition according to any one of the preceding claims, wherein the polyfunctional (meth)acrylate component is selected from bis(2-diol) diacrylate, butanediol diacrylate, dipropylene glycol diacrylate, diethylene glycol diacrylate, neopentyl glycol diacrylate, bisphenol A diglycidyl ether diacrylate, trimethylolpropane triacrylate, pentaerythritol tetraacrylate, tricyclo[5.2.1.0(2,6)]decanediethanol diacrylate, and combinations thereof.

8. The resin composition of any of the preceding claims, wherein the epoxy component comprises bisphenol A diglycidyl ether and / or the sterically hindered amine component comprises 1,8-diamino-p-menthane and / or the polyfunctional (meth)acrylate component comprises trimethylolpropane triacrylate or pentaerythritol tetraacrylate.

9. The resin composition according to any one of the preceding claims, wherein the molar ratio of the polyfunctional (meth)acrylate component is in the range of 10 to 50 mol%, and the molar ratio of the epoxy component is in the range of 50 to 90 mol%, each based on 100 mol% of the sterically hindered amine component.

10. The resin composition according to any one of the preceding claims, wherein the resin composition further comprises an amine curing agent, particularly in an amount of 1 to 20 parts by weight per 100 parts by weight of the sterically hindered amine component.

11. A method for producing a wind turbine blade, nacelle, or any of the aforementioned components, the method comprising: The resin composition according to any one of the preceding claims is applied into a mold by vacuum infusion, particularly by vacuum-assisted resin transfer molding. The resin composition is cured.

12. The method of claim 11, wherein the step of curing the resin composition comprises heating the resin composition to a temperature in the range of 60 to 150°C, particularly 70 to 120°C.

13. The method of any one of claims 11 to 12, wherein the method further comprises removing the mold after curing the resin composition.

14. A wind turbine blade, nacelle, or any of the aforementioned components, which can be obtained by the method according to any one of claims 11 to 13.

15. A method for recycling a wind turbine blade, nacelle, or any of the components described in claim 14, wherein the method comprises: The acidic aqueous liquid containing acid is brought into contact with a portion of the surface of the wind turbine blade, nacelle, or any of the aforementioned components.