Method for producing wind turbine blade, wind turbine blade produced accordingly and resin composition suitable for said production

Abstract

A resin composition suitable for producing a wind turbine blade or a component of any of the foregoing by means of a vacuum infusion process is described. The resin composition includes an epoxy component, an amine component further including at least one imine functional group, and a multifunctional (meth) acrylate component. Furthermore, a method of producing a wind turbine blade, a nacelle or a component of any of the foregoing and a correspondingly produced wind turbine blade, nacelle or a component of any of the foregoing is 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 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 gained 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.

[0004] Furthermore, the recycling and reprocessing of composite materials are becoming increasingly important issues. One potential solution involves covalent adaptive networks (CANs), also known as dynamic networks or vitrimers. One of the most promising technologies is imine-based CANs. As an example, this technology has been patented and marketed by Mallinda (see, for example, WO 2020 / 051506 and WO 2022 / 187451). It is based on readily available, known components. The concept is built upon imine-containing structural units crosslinked by different reactive groups, with epoxy groups being the preferred component.

[0005] However, the imine-containing hardeners used in epoxy resins are high-viscosity bulk molecules. Therefore, this system is unsuitable for vacuum infusion systems for wind turbine blades because it is not feasible to achieve sufficiently low viscosity, long open time, and rapid curing.

[0006] Other CAN technologies, such as disulfide-based networks or aza-Michael networks, are described in the literature. Disulfide-based CANs are of interest, but the necessary curing agents are not industrialized. Aza-Michael CANs are described in the literature (Christian Taplan, Marc Guerre, and Filip E. Du Prez; Journal of the American Chemical Society 2021 143 (24), 9140-9150; DOI: 10.1021 / jacs.1c03316) and are reaction products of different acrylate-based and amine components. However, the reaction of the (already reacted) secondary amine with another acrylate is not favorable, as it affects the achievable network density. Furthermore, the reaction rate is very high and problematic for achieving high-quality vacuum infusion of large components.

[0007] Dow (WO 2012 / 148815 A1) has described the combination of small amounts of acrylate in epoxy-amine resins. 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.

[0008] Imine-based CAN technology cannot yet be applied to vacuum infusion; it is only used in other processes, such as pre-impregnation. Other CAN technologies are not yet commercialized and do not yet provide the expected and required set of properties for vacuum infusion of wind turbine blades.

[0009] Therefore, it may be necessary to apply imine-based CAN technology to vacuum infusion, particularly imine-based resin compositions with appropriate (especially sufficiently low) viscosity, so that they can be used in vacuum infusion methods for the production of wind turbine blades or other components of wind turbines. 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 producing wind turbine blades or components thereof by means of a vacuum infusion method), comprising an epoxy component, an amine component further comprising at least one imine functional group, 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] These aspects of the invention are particularly based on the discovery that the viscosity and reactivity problems of imine-based epoxy-amine resin systems can be solved by partially replacing the epoxy component with (meth)acrylates, more specifically, polyfunctional (meth)acrylates. While not wishing to be bound by any theory, the inventors hypothesize that replacing a portion of the epoxy resin with (meth)acrylates can further contribute to reducing viscosity and, since (meth)acrylates are more reactive than epoxy groups, can increase the overall reaction rate while simultaneously lowering the peak temperature of the exothermic reaction.

[0015] The combination of the imine groups in the backbone of the amine curing agent and the aza-Michael adduct formed in the polymerization reaction of acrylates and amines introduces two kinetic components: a) The imine group exhibits association or dissociation kinetics as shown in the following exemplary reaction diagram: Ar represents the aromatic moiety, and R1 and R2 represent any residues.

[0016] b) The aza-Michael adduct exhibits a dissociation kinetic mechanism via the reverse aza-Michael reaction as shown in the following exemplary reaction diagram: Where EWG represents an electron-withdrawing group, and R represents any residue.

[0017] There is a synergistic effect because the amine groups released in the reverse azirmono-Michael reaction increase the number of free amine groups in the network, which can then interact with imine groups (this is a very rapid exchange reaction). This additional kinetic mechanism allows large imine-containing curing agent molecules to be partially replaced by amine curing agents with much lower viscosity, such as polyetheramines like Jeffamine D-230 or IPDA (depending on the desired reinforcing properties other than viscosity).

[0018] Combinations of different reactions and mechanisms broaden the range of applicable components and enable much better fine-tuning to overcome the inherent problems of individual technologies. This leads to better curing control, improved viscosity adjustment, and tunability of bond exchange kinetics.

[0019] Detailed Explanation The details of the invention and its other features and advantages will be described below. However, the invention is not limited to the specific descriptions below, which are for illustrative purposes only.

[0020] It should be noted that features described in connection with one exemplary embodiment or aspect may be combined with any other exemplary embodiment or aspect. In particular, features described in connection with any exemplary embodiment of the resin composition may 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 vice versa, unless otherwise expressly stated.

[0021] When referring to a singular term, the use of an indefinite or definite article, such as “a,” “a kind,” 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 "comprising" includes not only the meaning of "containing", "including", or "including", 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 glass fiber reinforced polymer resin.

[0025] As used herein, the term "composition" may specifically refer to a composition in which the components (ingredients) are close to each other and / or the components are (vigorously) mixed together, for example by using a mixer, agitator, and / or by shaking, thereby forming the composition. In particular, the components of the composition may be uniformly distributed or dispersed throughout the composition. The composition may 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 of a resin or resin component, which may chemically react with some of each other (e.g., polymerization or crosslinking reaction), thereby curing or hardening, which is typically induced by thermal energy (e.g., heating) or electromagnetic radiation.

[0027] This 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 that it contains 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] The resin composition also comprises an amine component. The amine component is characterized in that, in addition to one or more amine functional groups, it further comprises at least one imine functional group, i.e., a functional group containing a carbon-nitrogen double bond. By comprising at least one imine functional group, the amine component is capable of undergoing imine bond exchange reactions, thereby contributing to a covalently adaptive network.

[0030] In one embodiment, the amine component comprises one, two, or three imine functional groups.

[0031] In one embodiment, the amine component is selected from aliphatic polyamines, aryl aliphatic polyamines, alicyclic polyamines, alkanolamines, polyether polyamines, and combinations thereof, wherein each component further comprises at least one imine functional group.

[0032] 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 can also be used.

[0033] "(Meth)acrylates" includes 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 include itaconic acid esters.

[0034] In one embodiment, the multifunctional (meth)acrylate component comprises two or three (meth)acrylate functional groups.

[0035] 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, and combinations thereof.

[0036] In one embodiment, the weight ratio of the polyfunctional (meth)acrylate component to the epoxy component is from 1:9 to 1:1. In other words, 10 to 50% by weight of the epoxy component can be replaced by the polyfunctional (meth)acrylate component. Particularly when a high amount of polyfunctional (meth)acrylate is used compared to the amount of epoxy component, at least a portion of the bulky amine component containing at least one imine functional group can be replaced by a conventional amine curing agent. This makes it possible to obtain a resin composition with a lower viscosity, which is very advantageous (if not necessary) for application in vacuum infusion methods.

[0037] In one embodiment, the molar ratio of the polyfunctional (meth)acrylate component to the epoxy component is from 1:9 to 1:1. In other words, in this embodiment, 10 to 50 mol% of the epoxy component is replaced by the polyfunctional (meth)acrylate component.

[0038] In one embodiment, the ratio (by weight or molar) of the polyfunctional (meth)acrylate component to the epoxy component is between 1:5 and 1:2.

[0039] 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 at least one imine functional group, i.e., a conventional amine curing agent in the epoxy-amine infusion resin field, such as isophorone diamine (IPDA) or a polyether amine 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 a conventional amine curing agent can replace a portion of the amine component containing at least one imine functional group, which provides the advantage of reducing the viscosity of the resin composition.

[0040] In one embodiment, the resin composition has a viscosity of less than 300 mPa·s at 25°C. Specifically, the resin composition may have a viscosity of less than 200 mPa·s at 25°C, preferably less than 150 mPa·s. The resin composition may also have a viscosity of greater than 50 mPa·s at 25°C. The viscosity of the resin composition or the infused resin can be determined, for example, using a falling ball viscometer according to ISO 12058-1:2018. It has been surprisingly demonstrated that such low viscosity can be achieved by means of the techniques described herein, particularly by partially replacing the epoxy component with a polyfunctional (meth)acrylate component, despite the use of bulky and high-viscosity amine curing agents containing at least one imine functional group.

[0041] The resin composition according to the first aspect can be advantageously used in the method according to the second aspect as described below.

[0042] In a second aspect, a method for producing wind turbine blades, nacelles, or any of the aforementioned components is provided.

[0043] 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.

[0044] In one embodiment, the resin composition (before its application) has a viscosity of less than 300 mPa·s at the infusion temperature (e.g., at 25°C), particularly less than 150 mPa·s, such as less than 100 mPa·s. Such a low-viscosity resin is advantageous in reducing the cycle time of products manufactured by vacuum infusion. As explained above, an imino-epoxyamine resin composition with such low viscosity can be achieved by partially replacing the epoxy component with a polyfunctional (meth)acrylate component.

[0045] 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.

[0046] In one embodiment, the step of curing the resin composition includes heating the resin composition to a temperature of 60 to 150°C, particularly 70 to 120°C.

[0047] In one embodiment, the method further includes removing the mold after curing the resin composition, thereby obtaining the manufactured wind turbine blade, nacelle, or component thereof.

[0048] In a further aspect, wind turbine blades, nacelles, or any of the aforementioned components can be obtained or acquired through the methods described above.

[0049] 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; Further comprising an amine component containing at least one imine functional group; Multifunctional (meth)acrylate component.

2. The resin composition according to 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 amine component comprises one, two, or three imine functional groups.

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

5. The resin composition according to any one of the preceding claims, wherein the polyfunctional (meth)acrylate component comprises two or three (meth)acrylate functional groups.

6. The resin composition according to any one of the preceding claims, wherein the polyfunctional (meth)acrylate component is selected from diethylene glycol diacrylate, butanediol diacrylate, dipropylene glycol diacrylate, diethylene glycol diacrylate, neopentyl glycol diacrylate, bisphenol A diglycidyl ether diacrylate, trimethylolpropane triacrylate, and combinations thereof.

7. The resin composition according to any one of the preceding claims, wherein the weight ratio of the polyfunctional (meth)acrylate component to the epoxy component is from 1:9 to 1:

1.

8. The resin composition according to any one of the preceding claims, wherein the resin composition further comprises an amine curing agent.

9. The resin composition according to any one of the preceding claims, wherein the resin composition has a viscosity of less than 300 mPa·s at 25°C.

10. The resin composition according to any one of the preceding claims, wherein the resin composition has a viscosity of less than 150 mPa·s at 25°C.

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 infusion resin has a viscosity of less than 300 mPa·s at the infusion temperature.

13. The method according to any one of claims 11 to 12, wherein the step of curing the resin composition comprises heating the resin composition to a temperature of 60 to 150°C, particularly 70 to 120°C.

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

15. 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 14.

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