Gasket for a transition piece of a wind turbine and method for installing such a gasket

Abstract

A gasket for form-fitting a lower portion of a superstructure of a wind turbine, such as a transition piece or a turbine tower, to one or more foundation piles, the gasket being formed as an elongated hollow body for surrounding at least a portion of the pile structure when attached between the superstructure and the pile structure, the gasket stabilizing the position of the superstructure relative to the pile structure by absorbing compressive, tensile and shear stresses resulting from movements of the superstructure and / or the pile structure, the gasket comprising: (a) an organic polyisocyanate; (b) an isocyanate-reactive hydrogen atom-containing polyisocyanate; (c) one or more chain extenders in an amount of 1 to 12% by weight, based on the total weight of components (a) to (c), (d) a catalyst, and (e) optionally a filler and / or polyurethane additive, to result in a reaction mixture and to cure the reaction mixture, characterized in that the polymer compound (b) having at least two isocyanate-reactive hydrogen atoms comprises a polyetherol (b1) obtained by alkoxylation of a difunctional starter molecule and a polyetherol (b2) obtained by alkoxylation of a trifunctional starter molecule.Furthermore, the present invention relates to a method for attaching a transition piece of a wind turbine to a monopile, comprising the steps of attaching a gasket according to the present invention to a lower part of the transition piece and assembling the transition piece on the monopile such that the gasket is sandwiched between the transition piece and the monopile.

Description

[Technical field]

[0001] A gasket for form-fitting a lower part of a superstructure of a wind turbine, such as a transition piece or a turbine tower, to one or more foundation piles, the gasket being formed as an elongated hollow body for surrounding at least a part of the pile structure when mounted between the superstructure and the pile structure, the gasket stabilizing the position of the superstructure relative to the pile structure by absorbing compressive, tensile and shear stresses arising due to movements of the superstructure and / or the pile structure, the gasket comprising: (a) an organic polyisocyanate; (b) an isocyanate of a difunctional starter molecule; The gasket, characterized in that it comprises a polyurethane obtained by mixing a polymeric compound having at least two isocyanate-reactive hydrogen atoms, comprising at least one polyetherol (b1) obtained by alkoxylation and at least one polyetherol (b2) obtained by alkoxylation of a trifunctional starter molecule, (c) one or more chain extenders in an amount of 1 to 12% by weight, based on the total weight of components (a) to (c), (d) a catalyst, and (e) optionally a filler and / or a polyurethane additive, to obtain a reaction mixture and curing the reaction mixture.Furthermore, the present invention relates to a method for mounting a transition piece of a wind turbine to a monopile, comprising the steps of mounting a gasket according to the present invention at the bottom of the transition piece and assembling the transition piece on the monopile such that the gasket is sandwiched between the transition piece and the monopile.

[0002] Large structures, such as wind turbines and especially offshore wind turbines, are attached to the ground, for example by monopiles driven into the seabed. As well as monopiles, large structures can be attached on jacket foundations, for example tripod or tetrapod foundations, and sometimes on floating platforms. Jacket foundations can provide a stronger and more flexible foundation, because the weight of the structure is supported by multiple piles or legs, rather than a single monopile. The superstructure is typically attached on top of an assembly of the wind turbine superstructure as a turbine tower or transition piece and one or more foundation piles, for example monopiles. In many cases, monopiles are used. One end of the pile is fixed into the ground or into the seabed, and at the other (upper) end of the pile, the transition piece or tower structure is attached. The assembly thus provides a level platform for mounting the turbine itself. The assembly of the superstructure, for example the transition piece, and the piles, for example monopiles, supports the load of the wind turbine. It is therefore essential that the assembly is stable and that the transition piece does not move relative to the monopile. Particularly at sea level, the connection is further influenced by sea water, weather conditions such as wind, sun and oxygen.

[0003] Traditionally, the superstructure, often the transition piece, is fixed or stabilized relative to the monopile by grouting or by bolting the two together or a combination thereof. The monopile and transition piece are cylindrical bodies arranged concentrically with a space between them, and the two bodies are attached and fixed together by a grout seal formed in the annular space between the monopile and the transition piece and / or by bolting the transition piece and the monopile together, e.g. by bolting the corresponding flanges of the two parts. This set-up is time-consuming and expensive, since the conditions for installation require low wind motion and near calm. In particular, grouting and bolting cannot be scaled up to future size wind turbines. Furthermore, grouted assemblies have been found not to be durable over the life of the turbine.

[0004] WO2017178657 proposes a form-fitting of the pile structure and the top of the turbine by placing a gasket between the pile structure and the superstructure, said gasket being formed as an elongated hollow body for surrounding at least a part of the pile structure when it is attached between the superstructure and the pile structure, said gasket stabilizing the position of the superstructure relative to the pile structure by absorbing compressive, tensile and shear stresses arising due to the movements of the superstructure and / or the pile structure. As a material for the gasket, WO2017 / 178657 proposes an elastomeric material, or even a viscoelastic material. Polymeric materials, such as polyurea, polyurethane, rubber, nylon, polyoxymethylene, polyethylene and combinations thereof, are mentioned as preferred materials for the gasket, so that the use of mortar, grout, sand, gravel, cement and / or concrete can be avoided. Thus, gasket failure due to high compressive forces is critical and must be avoided. According to WO 2017 / 178657, the gaskets disclosed further act as a seal against seawater and preferably have a resistance of 15 N / mm 2 and has a hardness of 70 to 120 Shore A. WO 2017 / 178657 does not describe a material that meets these requirements. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2017 / 178657 Summary of the Invention [Problem to be solved by the invention]

[0006] The object of the present invention is therefore to provide a gasket with high elasticity for the form-fitting of the lower part of the superstructure of a wind turbine, for example the transition piece or the turbine tower, with one or more foundation piles. In particular, the elastomer must be suitable for compensating for irregularities on the piles and the superstructure, for example the transition piece. Due to the manufacturing, it is not possible to achieve a sufficiently flat surface on the two large steel members, but air pockets between the elastomer and the steel members must be avoided as far as possible in order to be able to achieve a form-fitting. The elongation / elasticity of the material is therefore important and must be maintained even under ageing in seawater. A further requirement is that the compression set of the material forming the gasket is low and does not change under ageing conditions in seawater. [Means for solving the problem]

[0007] The object of the present invention is to provide a gasket for the positive connection of a lower part of a superstructure of a wind turbine, for example a transition piece or a turbine tower, to one or more foundation piles, said gasket being formed as an elongated hollow body for surrounding at least a part of the pile structure when it is attached between the superstructure and the pile structure, said gasket stabilizing the position of the superstructure relative to the pile structure by absorbing compressive, tensile and shear stresses arising due to the movements of the superstructure and / or the pile structure, said gasket being composed of (a) an organic polyisocyanate, (b) an aryl group of bifunctional starter molecules, The problem is solved by the gasket, characterized in that it comprises a polymeric compound having at least two isocyanate-reactive hydrogen atoms, comprising at least one polyetherol (b1) obtained by alkoxylation and at least one polyetherol (b2) obtained by alkoxylation of a trifunctional starter molecule, (c) 1 to 12% by weight, based on the total weight of components (a) to (c), of one or more chain extenders, (d) a catalyst, and (e) optionally a filler and / or a polyurethane additive, to obtain a reaction mixture, and curing the reaction mixture.

[0008] The present invention relates to a gasket for mounting onshore and preferably offshore wind turbine structures, for example a gasket adapted to be placed between a transition piece and a pile structure, for example a monopile of a wind turbine or a pile for a tripod or tetrapod of a wind turbine. The gasket is further suitable for mounting other offshore wind turbine related structures having a corresponding structural shape, for example multiple tower sections. The sections may include a tubular or conical assembly shape similar to the transition piece to the pile structure. The gasket may thus be suitable for mounting multiple parts of a transition piece or for mounting multiple tower sections.

[0009] In a preferred embodiment of the invention, the gasket comprises at least 80% by weight, more preferably at least 90% by weight, of a polyurethane according to the invention and particularly preferably consists of a polyurethane according to the invention.

[0010] The organic and / or modified polyisocyanates (a) used to prepare the polyurethanes of the present invention can be selected from the organic and / or modified polyisocyanates known in the field of polyurethane chemistry and include aliphatic, cycloaliphatic and aromatic di- or polyfunctional isocyanates (component a-1) known from the prior art, and any desired mixtures thereof. Examples are diphenylmethane 4,4'-diisocyanate, diphenylmethane 2,4'-diisocyanate, mixtures of monomeric diphenylmethane diisocyanate with the higher polycyclic homologues of diphenylmethane diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate (HDI), mixtures of hexamethylene diisocyanate with the higher polycyclic homologues of hexamethylene diisocyanate (polycyclic HDI), isophorone diisocyanate (IPDI), tolylene 2,4- or 2,6-diisocyanate (TDI), or mixtures of the abovementioned isocyanates. It is preferred to use tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), such as 2,4'-MDI and 4,4'-MDI, and mixtures of diphenylmethane diisocyanate with polyphenylene polymethylene polyisocyanate (crude MDI). The isocyanates may be modified, for example, by the incorporation of uretdione, carbamate, isocyanurate, carbodiimide, allophanate, and especially urethane groups. In a preferred embodiment, the organic and / or modified polyisocyanate (a) comprises MDI or modified MDI.

[0011] In a preferred embodiment of the present invention, the isocyanate component (a) is used in the form of an isocyanate group-containing polyisocyanate prepolymer. These polyisocyanate prepolymers are obtained by reacting the above-mentioned polyisocyanates (a-1) with polyols (a-2) at temperatures of, for example, 30 to 100°C, preferably about 80°C, to give prepolymers. It is preferred to use 4,4'-MDI together with uretonimine-modified MDI and commercial polyols based, for example, on polyethers containing ethylene glycol, propylene glycol and / or butanediol, or on oligomers containing ethylene glycol, propylene glycol and / or butanediol as building blocks, to prepare the prepolymers of the present invention. Particularly preferred polyethers (a2) are propylene glycol, dipropylene glycol, tripropylene glycol, and oligomeric propylene glycols having 4 to 20, preferably 4 to 15, and more preferably 4 to 10 propylene glycol building blocks, and mixtures thereof.

[0012] In a preferred embodiment, the isocyanate (a) is an MDI prepolymer having an NCO content of 6 to 30% by weight, preferably 10 to 29% by weight and particularly preferably 20 to 2% by weight, based on the weight of the prepolymer, and is obtained by reacting 4,4'-MDI with oligomeric polypropylene glycol to give the prepolymer.

[0013] The polymeric compound (b) having at least two isocyanate-reactive hydrogen atoms has a molecular weight of at least 400 g / mol. It is possible to use all compounds known for the preparation of polyurethanes and having at least two reactive hydrogen atoms and a molecular weight of at least 400 g / mol. They have, for example, a functionality of 2 to 8 and a molecular weight of 400 to 12000 g / mol. For example, it is possible to use polyether polyamines and / or polyols selected from the group of polyether polyols, polyester polyols or mixtures thereof.

[0014] The polyols preferably used are polyether polyols, polycarbonate polyols and / or polyesterols having a molecular weight of 500 to 12000, preferably 500 to 6000, in particular 500 to less than 4000, and preferably an average functionality of 2 to 6, preferably 2 to 4, in particular 2 to 3. The polyols used are preferably exclusively polyether polyols and polycarbonate polyols, more preferably exclusively polyether polyols. The average hydroxyl number of the polymeric compound (b) having at least two isocyanate-reactive hydrogen atoms is in a preferred embodiment 20 to 80, more preferably 20 to 50 mg KOH / g. In the context of the present invention, the functionality of the polyether polyol is to be understood as the functionality of the starter molecule or the average functionality of a mixture of starter molecules, even if in reality the functionality is reduced by side reactions compared to the functionality of the starter molecule.

[0015] The polyetherols usable according to the invention are prepared by known methods. For example, they can be prepared by anionic polymerization using an alkali metal hydroxide, such as sodium hydroxide or potassium hydroxide, or an alkali metal alkoxide, such as sodium methoxide, sodium or potassium ethoxide, or potassium isopropoxide, as catalyst and adding at least one starter molecule having 2 to 8, preferably 2 to 6, reactive hydrogen atoms, or by cationic polymerization using a Lewis acid, such as, inter alia, antimony pentachloride, boron fluoride etherate, or bleaching earth, as catalyst. It is likewise possible to prepare polyether polyols from one or more alkylene oxides having 2 to 4 carbon atoms in the alkylene group by double metal cyanide catalysis. It is also possible to use tertiary amines, such as triethylamine, tributylamine, trimethylamine, dimethylethanolamine, imidazole or dimethylcyclohexylamine, as catalysts. For certain end uses, it is also possible to incorporate monofunctional starters into the polyether structure.

[0016] Suitable alkylene oxides are, for example, tetrahydrofuran, 1,3-propylene oxide, 1,2- or 2,3-butylene oxide, styrene oxide, and preferably ethylene oxide and 1,2-propylene oxide. The alkylene oxides can be used individually, alternatingly in succession or as mixtures.

[0017] Examples of useful starter molecules include water, aliphatic and aromatic, optionally N-mono-, N,N- and N,N'-dialkyl-substituted diamines having 1 to 4 carbon atoms in the alkyl group, such as optionally mono- and dialkyl-substituted ethylenediamine, diethylenetriamine, triethylenetetramine, 1,3-propylenediamine, 1,3- or 1,4-butylenediamine, 1,2-, 1,3-, 1,4-, 1,5- and 1,6-hexamethylenediamine, phenylenediamine, 2,3-, 2,4- and 2,6-tolylenediamine (TDA), and 4,4'-, 2,4'- and 2,2'-diaminodiphenylmethane (MDA), and polymeric MDA. Useful starter molecules also include alkanolamines such as ethanolamine, N-methyl- and N-ethylethanolamine, dialkanolamines such as diethanolamine, N-methyl- and N-ethyldiethanolamine, trialkanolamines such as triethanolamine, and ammonia. It is preferred to use polyhydric alcohols such as ethanediol, 1,2- and 2,3-propanediol, diethylene glycol, dipropylene glycol, 1,4-butanediol, 1,6-hexanediol, glycerol, trimethylolpropane, pentaerythritol, and mixtures thereof. The polyether polyols can be used individually or in the form of mixtures.

[0018] The polymeric compound (b) having at least two isocyanate-reactive hydrogen atoms comprises a polyether polyol (b1) obtained from the alkoxylation of a difunctional starter molecule and a polyether polyol (b2) obtained from the alkoxylation of a trifunctional starter molecule. In a preferred embodiment of the present invention, the polymeric compound (b) having at least two isocyanate-reactive hydrogen atoms comprises at least 80% by weight, more preferably at least 90% by weight, even more preferably at least 95% by weight of polyols (b1) and (b2), each based on the total weight of compound (b), and particularly preferably consists of polyols (b1) and (b2).

[0019] The difunctional starter molecules used to prepare component (b1) can be, for example, ethanediol, propanediol-1,2- and -1,3-diethylene glycol, dipropylene glycol, butanediol-1,4 or hexanediol-1,6, or mixtures thereof. It is preferred to use diethylene glycol or dipropylene glycol, particularly preferably dipropylene glycol.

[0020] The trifunctional starter molecule used to prepare component (b2) is preferably glycerol, trimethylolpropane, or a mixture thereof.

[0021] In a preferred embodiment of the present invention, the alkoxylation of the difunctional and trifunctional starter molecules is carried out with ethylene oxide and propylene oxide as alkoxylating agents, respectively. The polyols (b1) and (b2) contain ethylene oxide and propylene oxide as building blocks. In a preferred embodiment of the present invention, the weight ratio of ethylene oxide and propylene oxide in the polyetherol (b1) and in the polyetherol (b2) is in the range of 50:50 to 5:95, more preferably 70:30 to 90:10, and particularly preferably 75:25 to 85:15. Preferably, the alkoxylation is carried out such that the polyols (b1) and (b2) each have ethylene oxide end blocks of at least 5% by weight, based on the total amount of alkylene oxide in the polyols (b1) or (b2), respectively.

[0022] Generally, the alkoxylation of component (b1) is carried out so that component (b1) has a hydroxyl number of 20 to 40 mg KOH / g, preferably 22 to 35 mg KOH / g, and more preferably 24 to 32 mg KOH / g.

[0023] Generally, the alkoxylation of component (b2) is carried out so that component (b2) has a hydroxyl number of 20 to 40 mg KOH / g, preferably 22 to 35 mg KOH / g, and more preferably 24 to 32 mg KOH / g.

[0024] In a preferred embodiment of the present invention, the content of polyol (b1) is 35-60 mass% and the content of polyol (b2) is 35-60 mass% based on the total mass of polymer compound (b) each having at least two isocyanate-reactive hydrogen atoms. Preferably, polymer compound (b) having at least two isocyanate-reactive hydrogen atoms contains less than 10 mass% of a polymer compound having at least two isocyanate-reactive hydrogen atoms different from polyol (b1) and polyol (b2), more preferably consisting of polyol (b1) and polyol (b2).

[0025] The chain extenders used may be substances having a molecular weight of less than 400 g / mol, more preferably from 60 to 350 g / mol, and having two isocyanate-reactive hydrogen atoms. They may be used individually or, preferably, in the form of a mixture. It is preferred to use diols. Examples of useful substances include aliphatic, cycloaliphatic and / or araliphatic or aromatic diols having 2 to 14, preferably 2 to 10, carbon atoms, such as ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, 1,10-decanediol and bis(2-hydroxyethyl)hydroquinone, 1,2-, 1,3-, 1,4-dihydroxycyclohexane, diethylene glycol, dipropylene glycol, tripropylene glycol, and low molecular weight hydroxyl-containing polyalkylene oxides based on ethylene oxide and / or 1,2-propylene oxide, and the diols mentioned above as starter molecules.

[0026] Preferably, the chain extender (c) is selected from the group consisting of propylene glycol, dipropylene glycol, tripropylene glycol, butanediol, and mixtures of two or more thereof, and particularly preferably, the chain extender (c) is 1,4-butanediol.

[0027] According to the invention, the chain extender (c) is used in an amount of 1 to 12% by weight, preferably 4 to 11% by weight, and particularly preferably 7 to 10% by weight, based on the total weight of components (a) to (c).

[0028] The catalysts (d) used for the production of the polyurethane moldings are preferably compounds which significantly accelerate the reaction of the hydroxyl-containing compounds of components (b) and optionally (c) with the organic, optionally modified polyisocyanates (a). Examples include amidines such as 2,3-dimethyl-3,4,5,6-tetrahydropyrimidine, tertiary amines such as triethylamine, tributylamine, dimethylbenzylamine, N-methyl-, N-ethyl-, N-cyclohexylmorpholine, N,N,N',N'-tetramethylethylenediamine, N,N,N',N'-tetramethylbutanediamine, N,N,N',N'-tetramethylhexanediamine, pentamethyldiethylenetriamine, tetramethyldiaminoethyl ether, bis(dimethylaminopropyl)urea, dimethylpiperazine, 1,2-dimethylimidazole, 1-azabicyclo[3.3.0]octane, and preferably 1,4-diazabicyclo[2.2.2]octane, and alkanolamine compounds such as triethanolamine, triisopropanolamine, N-methyl- and N-ethyldiethanolamine and dimethylethanolamine. Organometallic compounds, preferably organotin compounds, such as tin(II) salts of organic carboxylic acids, such as tin(II) acetate, tin(II) octanoate, tin(II) ethylhexanoate and tin(II) laurate, and dialkyltin(IV) salts of organic carboxylic acids, such as dibutyltin diacetate, dibutyltin dilaurate, dibutyltin maleate and dioctyltin diacetate, and also bismuth carboxylates, such as bismuth(III) neodecanoate, bismuth 2-ethylhexanoate and bismuth octanoate, or mixtures thereof, are also useful. Organometallic compounds can be used alone or, preferably, in combination with a strongly basic amine. When component (b) contains an ester, it is preferred to use only amine catalysts.

[0029] It is preferred to use 0.001 to 5% by weight, especially 0.05 to 2% by weight, of the catalyst or catalyst combination, based on the weight of component (b).

[0030] Optionally, fillers and / or polyurethane additives (e) may be added to the mixture of components (a)-(d), examples of which include surfactants, dyes, pigments, flame retardants, hydrolytic stabilizers, oxidative stabilizers, and UV stabilizers.

[0031] Furthermore, as additive (f), it is possible to add blowing agents known from the prior art. However, it is preferred not to use blowing agents, more preferably not to add water. Thus, components (a) and (b) more preferably do not contain any blowing agent other than the residual water present in the industrially produced polyol.

[0032] Furthermore, it is particularly preferred if the residual water content is reduced by adding a water scavenger. Suitable water scavengers are, for example, zeolites. These water scavengers are used, for example, in an amount of 0.1 to 10% by weight, based on the total weight of the polyol component (b).

[0033] As mentioned above, if no blowing agent is used, the product of the present invention is not a polyurethane foam but a dense polyurethane. In a preferred embodiment, the gasket according to the present invention contains less than 5% by volume, preferably less than 3% by volume, and particularly preferably less than 1% by volume of trapped air bubbles.

[0034] The starting components are typically mixed and reacted at temperatures between 0°C and 100°C, preferably between 15°C and 60°C. Mixing can be carried out using conventional PUR processing machines. In a preferred embodiment, mixing is carried out by low pressure or high pressure machines. Preferably, mixing is carried out at an isocyanate index of 85-130, more preferably 90-120, even more preferably 95-110, and particularly preferably 98-102, and most preferably 99-101. The isocyanate index is defined as the ratio of the NCO groups of the isocyanate to the total number of reactive hydrogen atoms, with an isocyanate index of 100 relating to a ratio of the NCO groups of the isocyanate to the total number of reactive hydrogen atoms of 1:1.

[0035] The gasket according to the invention preferably has a Shore A hardness of 75 to 100 Shore A, more preferably 80 to 95, and particularly preferably 82 to 92 Shore A. It is well known to the skilled person to adjust the hardness, for example by varying the amount of filler or chain extender.

[0036] The gasket according to the invention has excellent properties. The elongation at break according to DIN 53504 is more than 400%, preferably more than 450% and especially more than 500%, while the compression set after 90 days of storage in artificial seawater at 50°C according to DIN ISO 815 (72 h, 23°C, 30 min) is less than 50%, preferably less than 40% and particularly preferably less than 30%. Furthermore, the gasket shows high tear strength and low wear. The mechanical properties of the gasket according to the invention remain high even after 90 days of storage in artificial seawater at 50°C compared to the properties before storage in artificial seawater. Thus, the Shore A hardness preferably changes less than 5%, more preferably less than 4% and particularly preferably less than 3% relative to the initial hardness, and the tear strength and tear resistance also preferably do not change more than 10%, more preferably less than 5%, respectively, relative to their initial values. Furthermore, the swelling rate after storage in artificial seawater at 50° C. for 90 days is preferably less than 3%, more preferably less than 2.5%.

[0037] The gasket according to the invention preferably has a wall thickness of at least 10 mm, more preferably at least 15 mm, even more preferably at least 20 mm, still more preferably at least 25 mm, or from 10 to 80 mm, more preferably from 20 to 60 mm, and most preferably from 25 to 50 mm, and the elongated hollow body has a height of at least 2 m, or at least 3 m, or at least 5 m, or at least 7 m, or at least 8 m, or from 5 to 60 m, more preferably from 10 to 50 m, and most preferably from 15 to 40 m.

[0038] The gaskets disclosed herein may be used to attach any onshore or offshore wind turbine related structure, including being suitable for attaching a transition piece to a pile structure, such as attaching a transition piece to a monopile, or attaching a transition piece to any other type of foundation structure that contacts the seabed, such as a pile for a tripod or tetrapod, where each of the three or four piles or legs of a tripod or tetrapod, respectively, may be considered equivalent to a monopile.

[0039] The invention further relates to a method for attaching a transition piece of a wind turbine to a monopile, said method comprising the steps of attaching a gasket according to the invention to a lower part of a transition piece and assembling said transition piece on said monopile such that said gasket is sandwiched between said transition piece and said monopile. Preferably, the wind turbine superstructure is attached to the monopile at the location where the monopile is fixed to the ground, e.g. at an offshore location.

[0040] The gasket can be attached to the underside of the superstructure by spraying or pouring a reaction mixture onto the portion of the superstructure where the gasket is to be placed. Alternatively, the gasket can be fully or partially molded, placed and attached. Fixing of the gasket is preferably performed by adhering the gasket, preferably by applying an adhesive or adhesive tape. If an adhesive is used, polyurethane, epoxy or acrylate adhesives or adhesive tapes may be used. EXAMPLES

[0041] The invention is illustrated by the following examples.

[0042] Starting materials: Polyol 1: Polyether polyol obtained by alkoxylation of propylene glycol with propylene oxide and ethylene oxide, where 80% by weight of propylene oxide and 20% by weight of ethylene oxide are used and has a hydroxyl number of 30 mg KOH / g.

[0043] Polyol 2: Polyether polyol obtained by alkoxylation of glycerol with propylene oxide and ethylene oxide, where 80% by weight of propylene oxide and 20% by weight of ethylene oxide are used and has a hydroxyl number of 26 mg KOH / g.

[0044] Isocyanate: Isocyanate prepolymer of 4,4'-MDI and dipropylene glycol and oligomers of propylene glycol having an NCO content of 23% by weight.

[0045] Catalyst Mixture: A mixture containing an amine catalyst, an acid blocked amine catalyst, and a metal catalyst.

[0046] Water scavenger: Zeolite.

[0047] A polyol component containing 46% by weight of polyol 1, 44% by weight of polyol 2, 8% by weight of butanediol and 0.17% by weight of a catalyst mixture, 2% of a water scavenger was mixed with an isocyanate with an isocyanate index of 100. The component temperature was 40° C. and the mold temperature was 90° C. The reaction mixture was introduced into a mold (800×400×30 mm, 10-12 kg / part) and the reaction mixture was allowed to harden.

[0048] The resulting molded polyurethanes were stored in artificial seawater [ASTM D1141-98(2013)] at 50°C for 49 and 91 days. The following properties were measured initially, after 49 days, and after 91 days: swelling ratio (volume and mass) according to ASTM D570, Shore hardness according to DIN ISO 7619-1, tensile strength and elongation at break according to DIN EN ISO 527 with reference to DIN 53504, tear resistance according to DIN ISO 34,1,B(b), and compression set according to DIN ISO 815-1 (72 hours at 23°C). After storage in artificial seawater, the samples were wiped and measured directly. Before the abrasion measurements, the samples were dried for 16 hours at 50°C.

[0049] The measurement results are shown in Table 1: [Table 1]

[0050] As shown in Table 1, the polyurethane according to the invention exhibits good mechanical properties even after aging in artificial seawater and is perfectly suitable for producing a gasket for the form-fitting of the lower part of the wind turbine superstructure to one or more foundation piles.

Claims

1. 1. A gasket for positively coupling a lower part of a wind turbine superstructure, such as a transition piece or a turbine tower, to one or more foundation piles, the gasket being formed as an elongated hollow body for surrounding at least a part of the pile structure when attached between the superstructure and the pile structure, the gasket stabilizing the position of the superstructure relative to the pile structure by absorbing compressive, tensile and shear stresses arising from movements of the superstructure and / or the pile structure, The gasket is (a) an organic polyisocyanate; (b) polymeric compounds having at least two isocyanate-reactive hydrogen atoms, comprising at least one polyetherol (b1) obtained by alkoxylation of a difunctional starter molecule and at least one polyetherol (b2) obtained by alkoxylation of a trifunctional starter molecule; (c) 1 to 12 wt. % of one or more chain extenders, based on the total weight of components (a) to (c); (d) a catalyst, and (e) optionally mixing fillers and / or polyurethane additives to form a reaction mixture, and curing the reaction mixture to form a polyurethane.

2. 2. The gasket according to claim 1, wherein the polyetherol (b1) and the polyetherol (b2) each contain ethylene oxide and propylene oxide as building blocks.

3. 2. The gasket according to claim 1, wherein the mass ratio of ethylene oxide to propylene oxide in the polyetherol (b1) and the polyetherol (b2), respectively, is 50:50 to 5:

95.

4. 2. The gasket according to claim 1, wherein the hydroxyl number of the polyetherol (b1) and the polyetherol (b2) is each 20 to 40 mg KOH / g.

5. 2. The gasket according to claim 1, wherein the content of polyol (b1) is 35 to 60 mass% and the content of polyol (b2) is 35 to 60 mass%, each relative to the total mass of the polymer compound (b) having at least two isocyanate-reactive hydrogen atoms.

6. 2. The gasket of claim 1, wherein the chain extender (c) is selected from the group consisting of propylene glycol, dipropylene glycol, tripropylene glycol, butanediol, and mixtures of two or more thereof.

7. 2. The gasket of claim 1, wherein the isocyanate (a) comprises MDI or modified MDI.

8. 8. The gasket of claim 7, wherein the isocyanate (a) is an MDI prepolymer having an NCO content of 6 to 30% by weight, based on the weight of the prepolymer.

9. 9. The gasket according to claim 8, characterized in that the MDI prepolymer is obtained by reacting MDI (a-1) with oligomeric propylene glycol to give a prepolymer.

10. 2. The gasket according to claim 1, wherein the compounds (a) to (e) react with each other at an isocyanate index of 85 to 130.

11. 10. The gasket of claim 1, wherein the gasket contains less than 5% by volume of trapped air bubbles.

12. 2. The gasket of claim 1, wherein the gasket has a hardness of 80 to 95 Shore A.

13. 2. The gasket according to claim 1, wherein the pile structure is a monopile, tripod or tetrapod pile.

14. 1. A method of attaching a transition piece of a wind turbine to a monopile, comprising: Attaching a gasket according to any one of claims 1 to 13 to a lower part of a transition piece; and assembling the transition piece onto the monopile such that the gasket is sandwiched between the transition piece and the monopile. The method comprising:

15. 15. A method according to claim 14, characterized in that the transition piece of the wind turbine is attached to the monopile at a location where the monopile is fixed to the ground, e.g. at an offshore location.