RU2819364C2 - Use of coating compositions for wind turbine blades - Google Patents

Abstract

FIELD: machine building.

SUBSTANCE: group of inventions can be used to protect the leading edge of wind turbine blades. Disclosed is use of a coating composition containing a base composition and a curing agent for applying a coating on a wind turbine blade. Base composition contains a polyester-containing aspartic acid ester of formula (I)

where each R is a linear or branched C₁-C₁₀ alkyl residue, X is a polyester. Wind turbine blade is also disclosed.

EFFECT: group of inventions makes it possible to increase flexibility, strength, resistance to abrasion and resistance to rain erosion of coating of a wind turbine blade.

17 cl, 6 tbl

Description

Field of technology

The present invention relates to coating compositions for wind turbine blades. The compositions are particularly suitable as either topcoat compositions or leading edge protection (LEP) compositions. The present invention also relates to a wind blade, such as a leading edge of a wind blade, coated with the coating compositions of the present invention, and a method for applying the coating composition, and a method for restoring and/or replacing an existing coating layer on a wind blade by applying the coating composition of the present invention. The present invention also relates to a kit of components containing a base composition and a curing agent used in coating compositions.

State of the art

In recent years, wind energy has become an important source of electricity generation and makes a significant contribution to reducing CO ₂ emissions. Wind energy represents the use of air flow through wind turbines to provide mechanical force to turn electric generators.

Wind turbines typically have a windward rotor with three blades attached to a fairing on top of a tall tubular support. Wind turbine blades or "wind blades" are typically designed to withstand operation for approximately 20 to 25 years. Blades are constantly exposed to atmospheric conditions and are ideally designed to withstand temperature extremes, wind shear, precipitation and/or other environmental hazards with minimal failure. Coating failure due to erosion is often observed at the leading edge of the blade. Rain, hail, ice, UV radiation, water absorption and other weather conditions erode the leading edge of the blade. This affects the aerodynamics of the blade and can cause serious damage.

Common concepts for protecting the leading edge of wind turbine blades are, for example, the application of anti-erosion tape or the application of a suitable coating composition (see, for example, Herring, 25 Dyer, Martin and Ward. Renewable and Sustainable Energy reviews 115 (2019) 109382). For both concepts, good adhesion to the blade and good elastic properties are of paramount importance. For coating compositions, material properties also play a significant role in obtaining the right balance between, for example, durability, hardness and elasticity of the coating. In addition, it is desirable that the coating compositions can be easily applied to the wind blade.

Various types of coating compositions are used in protective coatings of wind blades to minimize erosion, including compositions formed from aliphatic polyaspartic acid esters and isocyanate-based curing agents. For example, WO 2015/136018 proposes the use of aliphatic polyaspartic acid esters in wind blade coating compositions, and WO 2015/049260 discloses coating compositions containing an aliphatic polyaspartic acid ester and a polyisocyanate-based curing agent and further containing particulate matter. polymer based on amino resin. WO 2015/120941 discloses coating compositions containing aliphatic polyaspartic acid esters and at least one polycarbonate diol in a paint binder.

The essence of the invention

The present invention provides new coating compositions for wind turbine blades. It is within the scope of the present invention to provide coating compositions that are suitable for leading edge protection (LEP) and compositions that are suitable as topcoat compositions for wind turbine blades.

Therefore, in one embodiment, the present invention relates to the use of a coating composition containing

a) a base composition containing a polyester-containing aspartic acid ester having formula (I) below

,

where each R represents a linear or branched C ₁ -C ₁₀ alkyl residue, such as a linear or branched C ₁ -C ₆ alkyl residue, such as, for example, a methyl, ethyl, propyl or butyl residue; And

where X represents polyester;

And

b) hardening agent;

for coating wind turbine blades.

In one embodiment, the present invention relates to a wind turbine blade having at least a portion of its outer surface coated with a coating composition as described above.

Definitions

In the context of the present invention, the "leading edge" of a wind blade refers to the part of the blade that first enters the wind. The opposite edge may be referred to as the trailing edge.

The term "leading edge protection" is commonly abbreviated as "LEP". As used herein, the terms "leading edge protective coating composition" or "LEP composition" are used interchangeably and indicate a coating composition applied to at least a portion of the wind blade, including at least the leading edge or at least at least part of the leading edge of a wind blade to provide protection against erosion caused by, for example, rain, hail, ice, UV radiation, water absorption and other weather conditions. One way to achieve the effectiveness of leading edge protective coating is the Rain Erosion Test (RET), described in the experimental section of this document. Preferably said LEP is applied on top of the topcoat, but can also be applied under the topcoat, then preferably on top of the primer layer.

As used herein, the term "topcoat" refers to a coating layer applied to at least a portion of a wind blade, preferably the entire wind blade. Preferably, said topcoat coating composition (or "topcoat composition") is applied to the primer layer. Various wind blade primer compositions are known in the art.

In this context, the term "outermost layer" refers to the final coating system applied to the wind turbine blade, i.e. the outermost layer when the wind turbine blade is operating. The "outermost layer" of the leading edge is typically a coating derived from a LEP coating composition, while the outermost layer of other portions of the wind blade is typically a coating derived from a topcoat composition.

As for the overall coating composition, it typically consists of a "base composition" (in which the base component is included) and a "curing agent" (in which the curing agent component is included). Typically, the coating composition also contains a number of other constituents, such as fillers and pigments, additives and solvents. It should be understood that when reference is made to a “coating composition,” it is a mixed composition containing both a base composition and a curing agent ready for application to a wind blade.

As used herein, “polyester aspartic acid ester mixture” or “polyester aspartic acid ester mixture” refers to a mixture of at least two different polyester aspartic acid esters.

As used herein, a "kit of components" refers to a kit of components containing two or more containers, one container containing the base composition and the other container containing a curing agent. Other components that may be present in the coating composition of the present invention, as defined herein, such as fillers, pigments, solvents and additives, can be contained in either of the two containers of the kit of components, typically the container containing said base composition. Alternatively, these other components may be contained in one or more additional containers.

The term "polyester" refers to a polymer made by joining together or polymerizing many molecules of simpler compounds (monomers) by establishing ester bonds between them. In the context of the present invention, the term "polyester" preferably indicates a polymer in which the repeating unit contains an alkyl moiety of one or more carbon atoms connected by an oxygen atom, such as an alkyl moiety between two to six carbon atoms connected by an oxygen atom, such as an alkyl moiety made of two carbon atoms joined by an oxygen atom. One or more of these carbon atoms may be replaced by a small alkyl such as, for example, methyl, ethyl or propyl; preferably methyl.

Detailed Description of the Invention

The present invention relates to new coating compositions for wind turbine blades, in which the base composition contains a polyester-containing aspartic acid ester having formula (I) below

,

where each R represents a linear or branched C ₁ -C ₁₀ alkyl residue, such as a linear or branched C ₁ -C ₆ alkyl residue, such as, for example, a methyl, ethyl, propyl or butyl residue; and where X is a polyester. The coating composition also contains a curing agent.

Polyester-containing aspartic acid esters differ from more conventional aliphatic polyaspartic acid esters in that X in an aliphatic polyaspartic acid ester is typically an aliphatic straight-chain or branched alkyl and/or cycloalkyl moiety rather than a polyester.

In one embodiment, the present invention relates to coating compositions containing a mixture of polyester-containing aspartic acid esters, where X is a polyester with a repeating unit structure:

,

where m is in the range 2-35.

The mixture of polyester aspartic acid esters may contain at least two different polyester aspartic acid esters that have different numbers of repeat units in X. In one embodiment, the mixture is such that the average value of m is in the range of 2-10, for example, 2 -6, for example, 2-4, for example, 2.5-3.

Polyester-containing aspartic acid esters can be prepared by reacting one or more polyester polyamines with a dialkyl maleate, such as, for example, a linear or branched C ₁ -C ₁₀ dialkyl maleate, such as a linear or branched C ₁ -C ₆ dialkyl maleate, such as, for example, diethyl maleate. These polyester-containing aspartic acid esters can be prepared, for example, by using the reactants in such amounts that there is at least one equivalent, and in some embodiments approximately one equivalent, of olefinic double bonds for each equivalent of primary amine groups. Examples of processes for preparing polyester-containing aspartic acid esters can be found in WO 2014/151307 and Chen et al., RSC Advances (2018), 8: 13474-13481.

Suitable polyester polyamines that can react with dialkyl maleates in Michael addition reactions to produce polyester aspartic acid esters for the coating compositions of the present invention include JEFFAMINE polyester amines, commercially available from Huntsman Corporation, The Woodlands, Texas; for example, polyesteramines from the Jeffamine D series, such as, for example, Jeffamine D-230. In one embodiment, the mixture of polyester polyamines includes a mixture of polyester polyamines according to formula (II) below, where p represents a number with an average value of at least 2, such as 2-35, or 2-8, or 2.5-6.1,

(II)

wherein the mixture contains: (1) approximately 50-99 wt. %, for example, 50-90 wt. % or in some cases 80-90 wt. %, polyester polyamines according to the formula, where p has an average value of 2.5; and (2) approximately 1-50 wt. %, for example 10-50 wt. % or in some cases 10-20 wt. %, polyester polyamines according to the formula where p has a mean value of 6.1.

An example of a mixture of polyester-containing aspartic acid esters that is suitable for use in the present invention is Desmophen NH 2850 XP from Covestro Deutschland AG, Leverkusen, Germany, which has an equivalent weight of approximately 295, a viscosity at 25°C of approximately 170-210 mPa.s and amine number 170-210 mg KOH/g.

The use of polyester aspartic acid esters in coating compositions is known from WO 2014/151307, which discloses a coating composition with a resin containing a polyester aspartic acid ester in combination with an aliphatic polyaspartic acid ester, manufactured by Jeffamines. In particular, WO 2014/151307 discloses a polyester aspartic acid ester produced using an aliphatic trifunctional polyester polyamine. WO 2014/151307 does not disclose or propose the use of polyester aspartic acid esters in wind blade coating compositions, nor does WO 2014/151307 propose the use of a difunctional polyester aspartic acid ester.

Mixtures of polyester aspartic esters have further been proposed for use in sealant compositions in WO 2016/049104, where mixtures of polyester aspartic esters are used in combination with an aliphatic polyaspartic ester and/or a polyester diol. These compositions of sealing materials are intended for application, for example, to expansion joints, expansion joints and perimeter joints of substrates, such as concrete substrates.

Blends of polyester-containing aspartic esters have also been proposed, for example, for use in automotive release coatings (EP3495403) and for use in floor coverings and kitchen countertops in combination with an acrylate-containing compound (US 2018/0362801).

In one aspect, the coating composition of the present invention containing one or more polyester-containing aspartic acid esters is a LEP coating composition for wind blades. The specified LEP coating provides good erosion protection as demonstrated by the rain erosion test. The LEP composition is capable of providing protection in the particularly severe rain erosion conditions experienced by wind turbine blades.

In another aspect, the coating composition of the present invention is for a topcoat composition for wind turbine blades. Both the topcoat composition and the LEP composition have good mechanical and physical properties, including a high degree of elasticity, which can, for example, be determined by tapered rod or tensile stress tests. In addition, both the topcoat and the LEP provide protection against rain erosion.

The compositions of the present invention can be applied using standard techniques, for example, brush and roller, and can even be applied by spraying, for example, conventional air spray application (topcoat composition) or airless spray application (both topcoat compositions and LEP). Suitability for spray application is advantageous both for the original coating of a wind blade and for the restoration and/or replacement or partial replacement of an existing coating layer on a wind blade.

The coating compositions of the present invention may also contain some amounts of one or more aliphatic polyaspartic acid esters, which are an optional ingredient when the composition is intended for use as a LEP coating composition. Aliphatic esters of polyaspartic acid are well known in the art. For a typical aliphatic polyaspartic acid ester, X, as shown in formula (I), represents a straight-chain or branched alkyl and/or cycloalkyl moiety. Typical examples of aliphatic polyaspartic acid esters include those sold under the trade names Desmophen NH 1220, Desmophen NH 1420, Desmophen NH 1423, Desmophen 1520 and Desmophen NH 1521, commercially available from Covestro Deutschland AG, Leverkusen, Germany.

If the coating composition is intended for use as a topcoat, the composition contains one or more aliphatic polyaspartic acid esters in addition to a mixture of polyester-containing aspartic acid esters. The mixture ratio of polyester-containing aspartic acid esters to aliphatic polyaspartic acid esters is typically in the range of 40:60 to 60:40, for example in the range of 45:55 to 55:45, for example about 50:50.

Preferably, if the coating composition is for use in leading edge protection and contains one or more aliphatic polyaspartic acid esters, the mixture ratio of polyester aspartic acid esters to aliphatic polyaspartic acid esters is in the range of 70:30 to 99:1, for example, in the range from 80:20 to 99:1, for example in the range from 85:15 to 99:1, most preferably in the range from 90:10 to 99:1, for example from 95:5 to 99:1. In a preferred embodiment, the base composition contains less than 20%, for example less than 15%, for example less than 10%, for example less than 5%, for example less than 1%, by weight of said base composition, any aliphatic polyaspartic acid esters . In one embodiment, said LEP composition is substantially free of any aliphatic polyaspartic acid esters.

Hardening agent

The coating composition of the present invention also contains a curing agent. In a preferred embodiment, said curing agent contains one or more polyisocyanates. As used herein, "polyisocyanate" refers to any organic compound that has two or more reactive isocyanate (-NCO) groups in a single molecule, such as diisocyanates, triisocyanates, tetraisocyanates, etc., and mixtures thereof. Cyclic and/or linear polyisocyanate molecules can be used effectively. The number of isocyanate groups per molecule is easily determined by the isocyanate content and the number average molecular weight of the corresponding polyisocyanate. The isocyanate content can be determined, for example, according to DIN EN ISO 11909 by reacting the corresponding sample with an excess of dibutylamine and back-titrating the excess with hydrochloric acid against bromophenol blue.

Examples of the polyisocyanates according to the present invention are compounds that are known per se, preferably aliphatic polyisocyanates, with specific mention of diisocyanates and their dimers and trimers, such as urethdiones and isocyanurates. Examples include derivatives of hexamethylene-1,6-diisocyanate (also referred to as hexamethylene diisocyanate or HDI), octamethylene diisocyanate, decamethylene diisocyanate, dodecamethylene diisocyanate, tetradecamethylene diisocyanate, trimethylhexane diisocyanate, memtramethylhexane diisocyanate, isophorone diisocyanate (IPDI), 2-isocyanatopropylcyclohexyl isocyanate, dicyclohexylmethane-2,4'-diisocyanate, dicyclohexylmethane -4,4'-diisocyanate, 1,4- or 1,3-bis(isocyanatomethyl)cyclohexane, 1,4-or 1,3-or 1,2-diisocyanatocyclohexane and 2,4- or 2,6- diisocyanato-1-methylcyclohexane, and mixtures thereof. Most preferred is hexamethylene diisocyanate (HDI).

Reaction products or prepolymers of aliphatic polyisocyanates can also be used. Particular mention may be made of biuret, allophochanate, urethdione and isocyanurate of said polyisocyanates. Here, preference is given to the use of dimers and/or trimers of these polyisocyanates, preferably hexamethylene diisocyanate. In particular, urethdiones and isocyanurates of the above polyisocyanates, which are known per se and are also available on the market.

Isocyanurates can be prepared from any of a very wide variety of isocyanurates, in the presence of specific catalysts, examples being sodium formate, potassium acetate, tertiary amines or triphenylphosphines. The isocyanurate ring system constitutes a trimer consisting of three isocyanate groups in each case, is very stable, maintaining its integrity even at high temperatures of more than 100°C, for example. Each of these three isocyanate groups is derived from three different molecules of the respective isocyanates used; in other words, trimeric structures are formed. If polyisocyanates are used, examples being diisocyanates such as HDI, intermediate cross-linking may occur and thus multiple isocyanurate rings may become connected to each other. It is also known that it is possible to add fractions of cross-linking diols, such as hexanediol, in the preparation of isocyanurates, to modify their reactivity, for example, and thus a plurality of isocyanurate ring systems can become linked to each other. Similarly, urethdiones, consisting of two isocyanate groups, can be prepared by a similar catalytic reaction.

In one embodiment, said curing agent comprises a prepolymer based on an aliphatic polyisocyanate, preferably hexamethylene diisocyanate. "Prepolymers" in the context of the present invention are reaction products with NCO-functional groups of isocyanates and polyols, such as polyesters or polyesters.

A typical prepolymer is a polyisocyanate containing aliphatic polyester groups that contain repeating structural units —R—C(=O)—O—C—, where R is a divalent aliphatic radical. Preferred aliphatic polyester groups are polylactone groups, more particularly polycaprolactone groups. For example, polycaprolactones and their preparation by the reaction of a monohydric alcohol with epsilon-caprolactone are known. They can be introduced, for example, by known methods by reacting an isocyanate group with at least one of the hydroxyl groups they contain. Due to the polyester groups present and intermediate cross-linking where present, polyisocyanates such as, for example, hexamethylene diisocyanate (HDI) isocyanurates containing aliphatic polyester groups have a lower isocyanate content than pure HDI trimer. Although the latter has an isocyanate content of approximately 25% (molecular weight 3×NCO = 126 g/mol; molecular weight of pure HDI trimeric isocyanurate = 504.6 g/mol), polyisocyanate containing aliphatic ester groups typically has an isocyanate content of 5-20% eg 5-15%, preferably 6-14%, eg 6-11% or 8-14% or 10-12%, such as about 11%. A commercially available polyisocyanate prepolymer containing aliphatic polyester groups is Desmodur E 2863. Another typical HDI-based prepolymer is XP 2599 containing ester groups. Both prepolymers mentioned above are available from Covestro Deutschland AG, Leverkusen, Germany.

Preferred polyisocyanates are solvent-free and substantially free of isocyanate monomer, i.e. contain less than 0.5% and more preferably less than 0.3% isocyanate monomer, as measured according to DIN EN ISO 10 283.

When polyisocyanates are used as curing agents, functionality is defined as the number of isocyanate groups present in the molecule. For practical purposes, the number of isocyanate groups is provided as an average due to the presence of various related types of polyisocyanate molecules in the commercial product. The expression "medium functionality" refers to the functionality of a combination of two or more polyisocyanates. "Average functionality" is calculated as the total number of reactive (isocyanate groups) divided by the total number of polyisocyanate molecules. Generally, lower functionality gives less cross-linking, resulting in more flexible, softer products, while higher functionality gives more cross-linking, resulting in stiffer, harder products. In a preferred embodiment, the average functionality of the polyisocyanates used in the composition of the present invention is in the range of 2-4, for example in the range of 3-4 or 2-3, for example in the range of 2-2.5.

Examples of commercially available polyisocyanates that are useful in the present invention include Desmodur N 3900, Desmodur E 2863 XP, Desmodur N 3800, Desmodur XP 2860 and Desmodur XP 2599; all available from Covestro Deutschland AG, Leverkusen, Germany. In one embodiment, the curing agent according to the present invention contains one or more polyisocyanates selected from the group consisting of Desmodur N 3900, Desmodur E 2863 XP, Desmodur N 3800, Desmodur XP 2860 and Desmodur XP 2599.

The selection of one or more polyisocyanates to be contained in the curing agent may be based on the desired properties of the coating composition, for example, the preferred degree of viscosity of the coating composition and the flexibility of the coating layer. The term "one or more polyisocyanates" indicates that a mixture of polyisocyanates can be used.

For both the topcoat composition and the LEP of the present invention, the total number of isocyanate groups in the curing agent component to the number of amino groups in the base component will typically be in the range of 80:100 to 160:100, for example, 90:100 to 125:100, for example, 95:100 to 120:100, preferably in the range of 100:100 to 120:100, for example 100:100 to 110:100 or 105:100 to 110:100. Preferably, the number of isocyanate groups is in excess relative to the number of amino groups, preferably only in slight excess, to facilitate complete reaction of the amino groups.

Preparation of the coating compositions of the present invention

The coating composition can be prepared from commercially available components. The base composition (including one or more polyester-containing aspartic acid esters and potentially one or more aliphatic polyaspartic acid esters) and curing agent (including one or more polyisocyanates) typically may contain one or more other constituents, for example, fillers and pigments, solvents and additives (e.g. thickeners, wetting agents, dispersants, anti-drip agents, anti-settling agents, anti-foam agents and stabilizers).

Examples of fillers and pigments are calcium carbonate, dolomite, talc, mica, barium sulfate, kaolin, silica, titanium dioxide, red iron oxide, yellow iron oxide, black iron oxide, carbon black, phthalocyanine blue and phthalocyanine green. In the LEP coating composition, the total amount of filler(s) and pigment(s) is preferably 5-30 wt. %, for example 10-25 wt. % of the coating composition, while the topcoat composition preferably contains approximately 20-40 wt. %, for example approximately 25-30 wt. % of filler(s) and pigment(s) of the coating composition.

Examples of additives include diluents, wetting agents, smoothing agents and dispersants; antifoaming agents such as silicone oils; stabilizers such as light stabilizers and heat stabilizers, for example hindered amine light stabilizers (HALS); moisture stabilizers (water scavengers) such as substituted isocyanates, substituted silanes, trialkyl orthoformic esters and synthetic zeolites; oxidation stabilizers such as butylated hydroxyanisole and butylated hydroxytoluene; Thickeners and anti-settling agents such as organomodified clays (Bentone), polyamide waxes and polyethylene waxes.

In addition, the base and/or curing agent may be supplemented with one or more solvents. Preferable examples of suitable solvents include organic solvents such as toluene, xylene and naphtha solvent; ketones such as methyl ethyl ketone, methyl isobutyl ketone, diacetone alcohol and cyclohexanone; esters such as methoxypropyl acetate, n-butyl acetate and 2-ethoxyethyl acetate; and mixtures thereof. However, with respect to the inventive coating composition, when used in LEP, a solvent may not be necessary due to the low viscosity of the remaining components of the coating composition due to the combined properties of the polyester aspartic esters and the polyisocyanate curing agent. For example, the LEP coating composition of the present invention can be produced in a solvent-free form and thus provides good environmental properties. Thus, in the LEP coating composition, preferably one or more solvents are included (or not included) in an amount of less than 25 wt. %, for example, less than 15 wt. %, for example, less than 10 wt. %, preferably less than 5 wt. %, for example, less than 2.5 wt. % coating composition. Most preferably, when used as a LEP coating composition, the composition is substantially free of any solvents, meaning that one or more organic solvents have not been explicitly added, for example, to control the viscosity of the composition, "substantially free of any solvents" means, that, if this occurs, only small amounts of one or more organic solvents are present in the coating composition as a result of the use of, for example, conventional coating additives that may optionally be prepared commercially in solution of organic solvents.

When the inventive coating composition is intended for use as a topcoat, said composition preferably contains one or more added solvents in addition to solvents that may be contained in the coating composition through the use of, for example, coating additives, which may optionally be prepared commercially in a solution of organic solvents . Preferably, the added solvent is present in an amount in the range of 10-30 wt. % of the coating composition, for example in the range of 15-25%, for example approximately 20% of the specified coating composition.

The coating composition can be prepared by suitable techniques commonly used in the coating art. The coating composition can be prepared by mixing two or more components, for example, two pre-mixes, one containing the base composition and the other containing a curing agent. Before mixing, one or both premixes may be pre-treated to meet specific temperature requirements. It should be understood that when reference is made to a coating composition, it is a mixed coating composition.

Mixing the base composition (containing one or more polyester aspartic acid esters) and the curing agent (containing one or more polyisocyanates) provides a chemical reaction between the amino groups of the polyester aspartic acid esters, and optionally the aliphatic polyaspartic acid esters when present, and the isocyanate groups polyisocyanates. The mixing ratio between the two components must therefore be precisely controlled to obtain a coating composition with the correct physical properties. The mixing ratio is defined as the volumetric or mass ratio between the base composition and the curing agent. In the context of the present invention, the volumetric mixing ratio between the base composition and the curing agent is usually from 1:5 to 5:1, for example from 1:4 to 4:1, for example from 1:3 to 3:1, preferably from 1: 2 to 2:1, for example 1:1.5 to 1.5:1, for example approximately 1:1.

Application of the coating compositions of the present invention

Application of the coating compositions can be accomplished by standard application methods, such as by brush or roller. In addition, the inventive coating composition can be applied to the wind blade by spray application, such as, for example, conventional air spray (topcoat) or airless spray application (both topcoat and LEP). In practical embodiments, the base composition and curing agent are mixed either in one batch for normal spray application, or as a continuous process when using multi-component spray equipment.

In order to provide ease of application of the coating composition (eg, spray, brush or roller application techniques), the LEP composition typically has a viscosity in the range of 150-5000 mPa.s, for example 250-3000 mPa.s, preferably in the range 500-2500 mPa.s. , for example, 500-2000 mPa⋅s; whereas the topcoat composition typically has a viscosity in the range of 50-500 mPas, for example about 50-300 mPas, for example about 50-200 mPas. Typically, the LEP composition has a higher viscosity than the topcoat composition.

Preferably, the coating composition is applied in one or more layers, and the total dry film thickness of the coating composition is from 50 to 1000 microns.

Also preferably, the portion of the outer surface of the wind turbine blade coated with the coating composition comprises at least a predominant portion of the leading edge of the blade, but the overall surface of the wind turbine blade may be coated with the coating composition.

In the context of the present invention, the wind blade to which the topcoat composition is applied is typically pre-coated with one or more layers of a coating comprising a primer to which the topcoat composition is applied. Preferably, the wind blade to which the topcoat composition is applied is pre-coated with at least one or more layers of primer.

In the context of the present invention, a wind blade to which the LEP coating composition is applied may be pre-coated with one or more coating layers comprising a primer and/or topcoat to which the coating composition is applied. Preferably, the wind blade to which the LEP coating composition is applied is pre-coated with at least one or more layers of primer and/or topcoat.

In one embodiment, the present invention relates to a wind blade having at least a portion of its outer surface coated with one or more coating layers derived from a topcoat composition of the present invention, and thereon one or more LEP coating layers derived from the coating composition LEP of the present invention, wherein said LEP coating composition is applied to at least a portion of the leading edge of the wind blade. Optionally, the wind blade has been previously coated with one or more coat layers containing a primer.

Thus, the present invention also provides a method of coating a wind blade, the method comprising applying a coating composition as defined herein to at least a portion of the surface of said wind blade and allowing the coating composition to cure.

Since the use of the coating compositions of the present invention includes both topcoat use and leading edge protection use, a further embodiment of the present invention provides a method of coating a wind blade comprising the steps of i) applying the coating composition of the present invention for use as a topcoat. coating at least a portion of a wind turbine blade and allowing the composition to cure, followed by ii) applying a coating composition according to the present invention for use in leading edge protection to at least a leading edge of the wind blade and allowing the composition to cure.

In another embodiment, the present invention provides a method of coating a wind blade, comprising the steps of i) applying a coating composition according to the present invention for use in leading edge protection to at least the leading edge of a wind blade and allowing the composition to cure, followed by ii) applying the composition coatings according to the present invention for use as a topcoat on at least a portion of a wind blade and allowing the composition to cure.

Said wind blade may be pre-coated with a primer prior to application of the topcoat and/or LEP coating composition.

After applying the coating composition to the wind blade, the coating composition is allowed to cure under controlled ambient temperature and humidity. The coating composition is preferably cured at a temperature not exceeding 70°C, in particular at a temperature in the range of 0-45°C, for example a temperature in the range of 15-35°C. The actual temperature at which the coating composition can be cured is generally set at the lower limit by the temperature at which the coating composition is substantially curable, and at the upper limit by the temperature at which the integrity of the wind blade and any underlying coatings will be degraded.

The coating compositions of the present invention can also be used in a wind blade restoration method. A method for restoring a wind blade will include the step of applying a coating composition of the present application to at least a portion of the wind blade. The coating may be applied to substantially the entire wind blade or only to a portion of the wind blade, such as the leading edge of the wind blade. In some embodiments, one or more layers of coating may be applied to at least a portion of the wind blade. A wind turbine blade repaired in this manner may have a pre-existing coating or coating layers, some or all of which may be removed prior to application of the inventive coating composition. Alternatively, the inventive coating composition may be applied to the existing coating layer(s). Thus, the present invention also relates to a method for restoring and/or replacing or partially replacing an existing coating layer on a wind blade. In one embodiment, if the coating composition is applied to existing coating layer(s), an adhesion promoter may be applied to the existing coating layer prior to application of the coating composition of the present invention to improve adhesion of the coating composition. In another embodiment, no adhesion promoter is applied. Adhesion promoters and their use are known in the art.

Preferred features of the inventive coating compositions (both topcoat compositions and LEP compositions) are - in addition to a high degree of flexibility - film cohesion (as a result of crosslink density), UV resistance, gloss retention and adhesion to underlying coatings. In addition, preferably the coating composition, in particular the LEP composition, provides a coating that provides good protection against erosion caused by harsh weather conditions.

Embodiments of the Present Invention

The following describes embodiments of the present invention. The first embodiment is designated as E1, the second embodiment is designated as E2, etc.

It should be understood that various aspects, embodiments, embodiments and features of the present invention mentioned herein may be claimed alone or in any combination.

E1. Application of a coating composition containing:

a) a base composition containing a polyester-containing aspartic acid ester having formula (I) below

,

where each R represents a linear or branched C ₁ -C ₁₀ alkyl residue, such as a linear or branched C ₁ -C ₆ alkyl residue, preferably a methyl, ethyl, propyl or butyl residue; And

where X represents polyester;

And

b) hardening agent;

for coating wind turbine blades.

E2. Use according to embodiment 1, provided that said coating composition is not:

a coating composition containing:

(a) an isocyanate-reactive component containing:

(a1) at least one polyaspartic acid ester, and

(a2) optionally a polyester containing aspartic acid ester;

(b) an isocyanate component containing:

(b1) at least one isocyanate prepolymer, wherein the isocyanate prepolymer is the reaction product of components containing at least one aliphatic isocyanate and at least one polyester polyol, wherein the polyester polyol has a weight average molecular weight of 400-6000 and a structure of formula I:

HO-R ¹ _n -R ²

I,

where R ¹ has one or more of the following structures:

R ² represents one or more of the following: hydrogen and an organic group inert to the isocyanate group,

n represents an integer from 6 to 100,

the amount of structure -R ¹ _n - is at least 40 wt. % based on the weight of the polyester polyol;

And

(b2) at least one isocyanate oligomer containing at least two isocyanate groups,

wherein the weight ratio of the isocyanate prepolymer (b1) to the isocyanate oligomer (b2) is greater than 1:4 and less than 4:1;

(c) catalyst and

(d) optionally an additive;

wherein the molar ratio of isocyanate groups to isocyanate-reactive groups in the coating composition is from 1.5:1 to 4:1.

E3. Use according to any of embodiments 1-2, wherein X is a polyester, wherein the repeating unit contains an alkyl moiety of one or more carbon atoms connected by an oxygen atom, such as an alkyl moiety between two to six carbon atoms connected by an oxygen atom, such as an alkyl residue of two carbon atoms connected by an oxygen atom;

wherein one or more of said carbon atoms may be replaced by a small alkyl such as, for example, methyl, ethyl or propyl.

E4. Use according to any one of embodiments 1-3, wherein X has a repeating unit structure below

,

where m is in the range from 2 to 35, for example in the range from 2 to 10, for example in the range from 2 to 6, for example in the range from 2 to 4.

E5. Use according to any one of embodiments 1-4, wherein said base composition contains a mixture of polyester aspartic acid esters having formula (I) containing at least two polyester aspartic acid esters,

where X has a repeating link of the structure below

,

where the mixture is such that the average value of m is in the range from 2 to 35, for example in the range from 2 to 10, for example in the range from 2 to 6, for example in the range from 2 to 4, for example in the range from 2 .5 to 3.

E6. Use according to any one of embodiments 1 to 5, wherein each R in formula (I) represents an ethyl radical.

E7. Use according to any one of embodiments 1-4, wherein said polyester-containing aspartic acid ester is a reaction product of a dialkyl maleate, preferably a linear or branched C ₁ -C ₁₀ dialkyl maleate, such as a linear or branched C ₁ -C ₆ dialkyl maleate, for example diethyl maleate; and polyester polyamine according to formula (II) below

(II),

where p is in the range from 2 to 35, for example in the range from 2 to 10, for example in the range from 2 to 6, for example in the range from 2 to 4.

E8. Use according to any one of embodiments 1-5, wherein said base composition comprises a mixture of polyester aspartic acid esters containing at least two polyester aspartic acid esters, each of which is a reaction product of a dialkyl maleate, preferably a linear or branched C ₁ -C ₁₀ dialkyl maleate, such as a linear or branched C ₁ -C ₆ dialkyl maleate, for example diethyl maleate; and at least two polyester polyamines according to formula (II) below

(II),

where the mean p value is in the range from 2 to 35, for example in the range from 2 to 10, for example in the range from 2 to 6, for example in the range from 2 to 4, for example in the range from 2.5 to 3.

E9. Use according to any one of embodiments 7-8, wherein said dialkyl maleate is diethyl maleate.

E10. Use according to any of embodiments 1-9, wherein said curing agent b) contains one or more polyisocyanates.

E11. Use according to any one of embodiments 1-2, wherein said coating composition comprises

a) a base composition containing a polyester-containing aspartic acid ester having the formula below

,

where X has a repeating link of the structure below

,

where m is in the range from 2 to 35, for example in the range from 2 to 10, for example in the range from 2 to 6, for example in the range from 2 to 4;

And

b) a curing agent containing one or more polyisocyanates.

E12. Use according to any one of embodiments 1 or 11, wherein said coating composition contains

a) a base composition containing a mixture of polyester containing aspartic acid ester having the formula below

,

where X has a repeating link of the structure below

,

where the mixture is such that the average value of m is in the range from 2 to 35, for example in the range from 2 to 10, for example in the range from 2 to 6, for example in the range from 2 to 4, for example in the range from 2 .5 to 3;

And

b) a curing agent containing one or more polyisocyanates.

E13. Use according to any one of embodiments 10-12, wherein one or more of said one or more polyisocyanates is based on hexamethylene diisocyanate (HDI).

E14. Use according to any one of embodiments 10-12, wherein one or more of said one or more polyisocyanates is based on a hexamethylene diisocyanate (HDI) trimer.

E15. Use according to any one of embodiments 10-14, wherein said one or more polyisocyanates contain less than 0.5% isocyanate monomer, preferably less than 0.3% isocyanate monomer, for example less than 0.1% isocyanate monomer; according to DIN EN ISO 10 283.

E16. Use according to any one of embodiments 10-15, wherein the average functionality of said one or more polyisocyanates is in the range of 2-4, for example in the range of 3-4 or 2-3, for example in the range of 2-2.5.

E17. Use according to any one of embodiments 10-16, wherein a) and b) are present in said coating composition in such an amount that the stoichiometric ratio of the number of isocyanate groups in the curing agent component to the number of amino groups in the base component is in the range of 80:100 to 160:100, for example 90:100 to 125:100, for example 95:100 to 120:100, preferably in the range from 100:100 to 120:100, for example 100:100 to 110:100 or 105:100 to 110:100; for example approximately 100:100.

E18. Use according to any one of embodiments 1-17, wherein said coating composition further comprises

c) one or more additional components selected from fillers, pigments, solvents and additives.

E19. Use according to embodiment 18, wherein said one or more additional components include one or more components selected from the group consisting of calcium carbonate, dolomite, talc, mica, barium sulfate, kaolin, silica, titanium dioxide, red iron oxide, yellow iron oxide, black iron oxide, carbon black, phthalocyanine blue and phthalocyanine green.

E20. Use according to any of embodiments 18-19, wherein the total amount of filler(s) and pigment(s) is 5-30 wt. %, for example 10-25 wt. % coating composition.

E21. Use according to any one of embodiments 1-20, wherein said coating composition has a viscosity in the range of 150-5000 mPa⋅s, for example 250-3000 mPa⋅s, preferably in the range of 500-2500 mPa⋅s, for example 500-2000 mPa⋅s, for example approximately 1500 mPa⋅s.

E22. Use according to any one of embodiments 1-21, wherein said coating composition is cured at a temperature below 90°C, for example below 70°C, such as a temperature in the range of 0-45°C, for example in the range of 15-35°C .

E23. Use according to any of embodiments 1-22, wherein said base composition a) contains less than 20%, for example less than 15%, for example less than 10%, for example less than 5%, for example less than 1% any aliphatic esters of polyaspartic acid by weight of the specified base composition.

E24. Use according to any of embodiments 1-22, wherein said base composition a) optionally further contains one or more aliphatic polyaspartic acid esters,

wherein the mixture ratio of polyester-containing aspartic acid esters to aliphatic polyaspartic acid esters is in the range of 70:30 to 99:1, preferably in the range of 80:20 to 99:1, for example in the range of 85:15 to 99:1 , most preferably in the range from 90:10 to 99:1, for example from 95:5 to 99:1.

E25. Use according to any of embodiments 1-22, wherein said coating composition is substantially free of any aliphatic polyaspartic acid esters.

E26. Use according to any of embodiments 1-22, wherein said base composition a) optionally further contains one or more aliphatic polyaspartic acid esters,

wherein the mixture ratio of polyester-containing aspartic acid esters to aliphatic polyaspartic acid esters is in the range of 70:30 to 99:1, preferably in the range of 80:20 to 99:1, for example in the range of 85:15 to 99:1 , most preferably in the range of 90:10 to 99:1, such as 95:5 to 99:1; or

wherein said coating composition is substantially free of any aliphatic polyaspartic acid esters.

E27. Use according to any of embodiments 1-26, wherein said coating composition contains one or more solvents, wherein the total amount of solvent is less than 25 wt. %, for example, less than 15 wt. %, for example, less than 10 wt. %, for example, less than 5 wt. %, for example, less than 2.5 wt. % coating composition.

E28. Use according to any of embodiments 1-26, wherein said coating composition is substantially free of any solvents.

E29. Use according to any one of embodiments 10-28, wherein said one or more polyisocyanates have an isocyanate content of 5-25%, for example 5-20%, for example 5-15%, preferably 6-14%, for example 6-11 % or 8-14% or 10-12%; or, for example, about 6%, or about 7%, or about 8%, or about 9%, or about 10%, or about 11%.

E30. Use according to any one of embodiments 10-29, wherein each of the one or more polyisocyanates contains aliphatic polyester groups.

E31. Use according to any of embodiments 1-19 and 29-30, wherein the total amount of filler(s) and pigment(s) is 20-40 wt. %, for example, 25-30 wt. % coating composition.

E32. Use according to any one of embodiments 1-19 and 29-31, wherein said coating composition has a viscosity in the range of 50-1000 mPa⋅s, for example, in the range of 50-500 mPa⋅s.

E33. Use according to any one of embodiments 1-19 and 29-32, wherein said coating composition is cured at a temperature below 50°C, for example below 30°C, for example a temperature in the range of -10-30°C.

E34. Use according to any of embodiments 1-19 and 29-33, wherein said base composition a) further comprises one or more aliphatic polyaspartic acid esters,

wherein the ratio of the mixture of polyester-containing aspartic acid esters to aliphatic polyaspartic acid esters is in the range of 40:60 to 60:40, for example in the range of 45:55 to 55:45, for example about 50:50.

E35. Use according to any one of embodiments 1-19 and 29-34, wherein said coating composition contains one or more solvents, the total amount of solvent being in the range of 10-30 wt. % of the coating composition, for example in the range of 15-25 wt. %, for example approximately 20 wt. % of the specified coating composition.

E36. Use according to any of embodiments 1-19 and 29-35, wherein said curing agent further comprises a polyisocyanate as defined in any of embodiments 13-16 and having an isocyanate content of 20-26 w/w. %, for example 15-30 wt./mass. %, for example 22-24 w/w. %, for example approximately 23 wt./mass. %.

E37. Use according to any one of embodiments 1-30, wherein said composition is for use as a protective coating on the leading edge of said wind turbine blade.

E38. Use according to any one of embodiments 1-30, wherein said coating composition is applied to at least a leading edge of said wind turbine blade.

E39. Application according to any one of embodiments 1-30, wherein said coating composition is applied to the leading edge of said wind turbine blade.

E40. Use according to any of embodiments 1-19 and 29-36; wherein said coating is for use as a top coating for said wind turbine blade.

E41. A wind turbine blade having at least a portion of its outer surface coated with a coating composition as defined in any of embodiments 1-36.

E42. A wind turbine blade according to embodiment 41, having at least on a leading edge of said wind turbine blade a coating obtained from a coating composition as defined in any of embodiments 1-36.

E43. A wind turbine blade according to any one of embodiments 41-42, having on a leading edge of said wind turbine blade a coating derived from a coating composition as defined in any one of embodiments 1-30.

E44. A wind turbine blade according to any one of embodiments 41-43, wherein said coating constitutes the outermost coating layer.

E45. The wind turbine blade according to any one of embodiments 43-44, wherein said coating is a leading edge protective coating.

E46. The wind turbine blade according to any one of embodiments 43-45, wherein said coating is a leading edge protective coating, and

wherein said coating was applied on top of the top coating, or

wherein said coating was applied under the top coat, preferably on top of the primer layer.

E47. A wind turbine blade according to Embodiment 41, having a first coating layer that is a top coating obtained from a coating composition as defined in any of Embodiments 1-19 and 29-36; and on top of said first coating layer, having a second coating that is a LEP coating derived from a coating composition as defined in any of embodiments 1-30 applied to the first coating layer on at least a portion of the outer surface of said wind turbine blade, for example, onto the leading edge of said wind turbine blade.

E48. A wind turbine blade according to embodiment 41, having a first coating layer, which is a LEP coating obtained from a coating composition as defined in any of embodiments 1-30, applied to at least a portion of the surface of said wind turbine blade, for example , onto the leading edge of said wind turbine blade; and on top of said first coating layer, having a second coating which is a top coating derived from a coating composition as defined in any one of embodiments 1-19 and 29-36 applied to the outer surface of said wind turbine blade and to the first coating layer of said wind turbine blades.

E49. The wind turbine blade according to any one of embodiments 41-44, wherein said wind turbine blade has a primer layer applied under the topcoat and/or the leading edge protective coating layer.

E50. A set of components containing

i) a container containing a) a base composition containing a polyester-containing aspartic acid ester having formula (I) below

,

where each R represents a linear or branched C ₁ -C ₁₀ alkyl residue, such as a linear or branched C ₁ -C ₆ alkyl residue, preferably a methyl, ethyl, propyl or butyl residue; And

where X represents polyester; And

ii) a container containing b) a curing agent.

E51. The kit of Embodiment 50, wherein X is a polyester, wherein the repeating unit contains an alkyl moiety of one or more carbon atoms connected by an oxygen atom, such as an alkyl moiety between two to six carbon atoms connected by an oxygen atom, such as an alkyl moiety of two carbon atoms connected by an oxygen atom;

wherein one or more of said carbon atoms may be replaced by a small alkyl such as, for example, methyl, ethyl or propyl.

E52. The set according to any one of embodiments 50-51, wherein X has a repeating unit structure below

,

where m is in the range from 2 to 35, for example in the range from 2 to 10, for example in the range from 2 to 6, for example in the range from 2 to 4.

E53. The kit according to any one of 50-52, wherein said base composition contains a mixture of polyester aspartic acid esters having formula (I) containing at least two polyester aspartic acid esters,

where X has a repeating link of the structure below

,

where the mixture is such that the average value of m is in the range from 2 to 35, for example in the range from 2 to 10, for example in the range from 2 to 6, for example in the range from 2 to 4, for example in the range from 2 .5 to 3.

E54. The kit according to any one of embodiments 50-53, wherein each R in formula (I) represents an ethyl moiety.

E55. The kit according to any one of embodiments 50-54, wherein said polyester-containing aspartic acid ester is a reaction product of a dialkyl maleate, preferably a linear or branched C ₁ -C ₆ dialkyl maleate, for example diethyl maleate; and polyester polyamine according to formula (II) below

(II),

where p is in the range from 2 to 35, for example in the range from 2 to 10, for example in the range from 2 to 6, for example in the range from 2 to 4.

E56. The kit according to any one of embodiments 50-54, wherein said base composition comprises a mixture of polyester aspartic acid esters containing at least two polyester aspartic acid esters, each of which is a reaction product of a dialkyl maleate, preferably a linear or branched C ₁ -C ₁₀ dialkyl maleate, such as a linear or branched C ₁ -C ₆ dialkyl maleate, for example diethyl maleate; and at least two polyester polyamines according to formula (II) below

(II),

where the mean p value is in the range from 2 to 35, for example in the range from 2 to 10, for example in the range from 2 to 6, for example in the range from 2 to 4, for example in the range from 2.5 to 3.

E57. The coating kit or composition according to any one of embodiments 55-56, wherein said dialkyl maleate is diethyl maleate.

E58. The kit according to any one of embodiments 50-57, wherein said curing agent contains one or more polyisocyanates.

E59. The kit of Embodiment 50, wherein said kit comprises

i) a container containing a) a base composition containing a polyester-containing aspartic acid ester having the formula below

,

where X has a repeating link of the structure below

,

where when m is in the range from 2 to 35, for example in the range from 2 to 10, for example in the range from 2 to 6, for example in the range from 2 to 4;

And

ii) a container containing b) a curing agent containing one or more polyisocyanates.

E60. The kit according to any one of embodiments 50 or 59, wherein said kit comprises

i) a container containing a) a base composition containing a mixture of polyester-containing aspartic acid esters having the formula below

,

where X has a repeating link of the structure below

,

where the mixture is such that the average value of m is in the range from 2 to 35, for example in the range from 2 to 10, for example in the range from 2 to 6, for example in the range from 2 to 4, for example in the range from 2 ,5 to3;

And

ii) a container containing b) a curing agent containing one or more polyisocyanates.

E61. The kit according to any one of embodiments 58-60, wherein one or more of said one or more polyisocyanates is based on hexamethylene diisocyanate (HDI).

E62. The kit according to any one of embodiments 58-61, wherein one or more of the one or more polyisocyanates is based on a hexamethylene diisocyanate (HDI) trimer.

E63. The kit according to any one of embodiments 55-62, wherein said one or more polyisocyanates contain less than 0.5% isocyanate monomer, preferably less than 0.3% isocyanate monomer, for example, less than 0.1% isocyanate monomer; according to DIN EN ISO 10 283.

E64. The kit according to any one of embodiments 58-63, wherein the average functionality of said one or more polyisocyanates is in the range of 2-4, for example in the range of 3-4 or 2-3, for example in the range of 2-2.5.

E65. The kit according to any one of embodiments 58-64, wherein said one or more polyisocyanates have an isocyanate content of 5-20%, for example 5-15%, preferably 6-14%, for example 6-11% or 8-14% or 10-12%; or, for example, about 6%, or about 7%, or about 8%, or about 9%, or about 10%, or about 11%.

E66. The kit according to any one of embodiments 58-65, wherein each of the one or more polyisocyanates contains aliphatic polyester groups.

E67. The kit according to any one of embodiments 50-67, wherein said base composition a) in container i) optionally further contains one or more aliphatic polyaspartic acid esters,

wherein the ratio of the mixture of polyester-containing aspartic acid esters to aliphatic polyaspartic acid esters is in the range from 70:30 to 99:1, for example in the range from 80:20 to 99:1, for example in the range from 85:15 to 99: 1, most preferably in the range of 90:10 to 99:1, such as 95:5 to 99:1, or

wherein said base composition a) in container i) is substantially free of any polyaspartic acid esters.

E68. The kit according to any one of embodiments 50-66, wherein said base composition in container i) contains less than 20%, such as less than 15%, such as less than 10%, such as less than 5%, such as less than 1% of any aliphatic polyaspartic acid esters by weight of the specified base composition.

E69. The kit according to any one of embodiments 50-66, wherein said base composition in container i) contains less than 20%, such as less than 15%, such as less than 10%, such as less than 5%, such as less than 1% of any acrylate-containing compounds by weight of the specified base composition.

E70. The kit according to any one of embodiments 50-69, wherein said base composition in container i) contains less than 20%, such as less than 15%, such as less than 10%, such as less than 5%, such as less than 1% of any silane-containing compounds by weight of the coating composition.

E71. The set according to any one of embodiments 50-70, wherein:

the total amount of solvent in said base composition in container i) is less than 25 wt. %, for example, less than 15 wt. %, for example, less than 10 wt. %, for example, less than 5 wt. %, for example, less than 2.5 wt. % of said base composition, or said base composition is substantially free of any solvents;

and/or

the total amount of solvent in said curing agent in container i) is less than 25 wt. %, for example, less than 15 wt. %, for example, less than 10 wt. %, for example, less than 5 wt. %, for example, less than 2.5 wt. % of said curing agent, or said curing agent is substantially free of any solvents.

E72. The kit according to any one of embodiments 50-66, wherein said base composition in the container i) further contains one or more aliphatic polyaspartic acid esters,

wherein the ratio of the mixture of polyester-containing aspartic acid esters to aliphatic polyaspartic acid esters is in the range of 40:60 to 60:40, for example in the range of 45:55 to 55:45, for example about 50:50.

E73. The kit according to any one of embodiments 50-72, wherein said base composition a) in container i) and/or said curing agent b) in container ii) further comprises one or more additional components selected from fillers, pigments, solvents and additives .

E74. The kit of embodiment 73, wherein said one or more additional components includes one or more components selected from the group consisting of calcium carbonate, dolomite, talc, mica, barium sulfate, kaolin, silica, titanium dioxide, red iron oxide, yellow iron oxide, black iron oxide, carbon black, phthalocyanine blue and phthalocyanine green.

E75. The kit of any one of embodiments 50-74, further comprising instructions for using said base composition and said curing agent.

E76. A method of coating a wind blade, comprising the step of applying a coating composition as defined in any of embodiments 1-36 to at least a portion of the wind blade, such as a leading edge of the wind blade.

E77. The method of Embodiment 76, wherein said wind blade has been pre-coated with a layer of primer before applying the coating composition as defined in any of Embodiments 1-36.

E78. Method of coating a wind blade, comprising stages

i) applying a coating composition as defined in any of embodiments 1-19 and 29-36 to at least a portion of the wind blade and allowing the composition to cure; followed by

ii) applying a coating composition, as defined in any of embodiments 1-30, to at least a portion of the wind blade, such as at least a leading edge of the wind blade, and allowing the composition to cure.

E79. Method of coating a wind blade, comprising stages

i) applying a coating composition as defined in any of embodiments 1-30 to at least a portion of the wind blade, such as at least the leading edge of the wind blade, and allowing the composition to cure;

ii) applying a coating composition as defined in any of embodiments 1-19 and 29-36 to at least a portion of the wind blade and allowing the composition to cure.

E80. The method according to any one of embodiments 78-79, wherein said wind blade has been pre-coated with a layer of primer before step i).

E81. A method of restoring a wind blade, comprising the step of applying a coating composition as defined in any of embodiments 1-36 to at least a portion of the wind blade, such as a leading edge of the wind blade.

E82. A method of restoring and/or replacing or partially replacing an existing coating layer on a wind blade, comprising the step of applying a coating composition as defined in any of embodiments 1-36 to at least a portion of the wind blade, such as a leading edge of the wind blade.

E83. The method of any one of embodiments 81-82, wherein said wind blade has one or more pre-existing coating layers;

wherein said one or more existing coating layers are applied to said coating composition, or

wherein said one or more pre-existing coating layers are at least partially removed prior to application of said coating composition, or

wherein said one or more pre-existing coating layers are completely removed prior to application of said coating composition.

E84. The method according to any one of embodiments 81-83, wherein said wind blade has a pre-existing coating layer, which is a leading edge protective coating layer;

wherein said leading edge protective coating layer is applied to said coating composition, or

wherein said leading edge protective coating layer is at least partially removed prior to application of said coating composition, or

wherein said leading edge protective coating layer is completely removed prior to application of said coating composition.

E85. The method of any one of embodiments 74-84, wherein said coating composition is applied by brush or roller or spray application, for example, by airless spray application to said wind blade.

All references, including publications, patent applications and patents cited herein, are hereby incorporated by reference in their entirety and to the same extent as if each reference had been separately and specifically identified as being incorporated by reference and had been cited in their entirety in herein (to the maximum extent permitted by law), notwithstanding any express inclusion of specific documents made elsewhere herein.

The use of singular terms and similar references in the context of the description of the invention should be construed to cover both the singular and plural forms, unless otherwise specified herein or clearly inconsistent with the context. For example, the phrase “composition” should be understood to refer to various “compositions” of the present invention or the specifically described aspect unless otherwise indicated.

The description herein of any aspect or aspect of the present invention, using terms such as “comprising,” “having,” “including,” or “comprising,” with reference to an element or elements, is intended to provide evidence of a similar aspect or aspect of the present invention that “ consists of," "consists primarily of," or "essentially contains" that particular element or elements, unless otherwise indicated or clearly inconsistent with the context (e.g., a composition described herein as containing a specific element should also be understood to describe the composition consisting of this element unless otherwise indicated or clearly inconsistent with the context).

The use of any or all examples or an introductory word before an example (including “for example,” “for example,” “as an example,” and “such as”) in this specification is intended only to better illuminate the present invention and does not constitute a limitation on the scope of the present invention , unless otherwise specified.

Headings and subheadings are used herein for convenience only and should not be construed as limiting the present invention in any way. The use of any or all examples or an introductory word before an example (including “for example,” “for example,” “as an example,” and “such as”) in this specification is intended only to better illuminate the present invention and does not constitute a limitation on the scope of the present invention , unless otherwise specified. The citation and inclusion of patent documents herein is for convenience only and does not reflect any kind of validity, patentability and/or enforceability of such patent documents.

It should be understood that various aspects, embodiments, embodiments and features of the present invention mentioned herein may be claimed separately or in any combination.

experimental part

The present invention will be illustrated by the following non-limiting examples.

Rain Erosion Test

The Rain Erosion Test (RET) is widely accepted as the most suitable test for assessing the erosion control properties of wind turbine blade leading edge coatings. The idea is to simulate the erosive action of impacting raindrops, dust particles, hailstones and the like by creating a controlled area of rain in which the coated surface moves at high speed.

The Rain Erosion Test (RET) was carried out using a rotary test rig, which was developed for this purpose by R&D A/S. The test was carried out according to DNVGL-RP-0171 Guidelines, Testing of rotor blade erosion protection systems.

Erosion damage was reproduced on samples mounted on a bracket that rotates horizontally through an area of artificial rain. Rain impacts the surface of the test piece and erodes the surface that is protected by the coating to be tested. The extent of erosion damage caused by droplets was checked and recorded. This was carried out by visual inspection and documentation with photographs at certain intervals. Detailed documentation with images allows for investigation of the initial damage at the end of the incubation period, as well as the progression of the damage. The time required for a surface to erode to a certain limit was a measure that was used to compare the performance of protection systems with each other. There are two stages of erosion that are commonly used to determine the durability of specimens:

1. End of incubation period: The incubation period is defined as the exposure time until the first damage becomes visually detectable on the outer surface of the test sample. The incubation period depends on the speed of exposure and thus, for a rotary test setup, on the position of the sample.

2. Breakthrough to the underlying substrate: Breakdown to the underlying substrate: Breakthrough is defined as the point in time when erosion breaks through the protective layer to the underlying substrate. The breakdown time depends on the speed of exposure and thus for a rotary test setup it also depends on the location of the sample.

45 cm long U-shaped test pieces based on NACA 634-021 airfoil geometry simulating the leading edge of a wind turbine blade (as described in Appendix A.1, DNVGL-RP-0171), consisting of a composite substrate, were coated with 200-600 µm (dry film thickness) coating compositions to be tested. The coating compositions were cured under controlled laboratory conditions, typically 25°C and 50% RH, for at least 7 days to ensure complete cure of the binder system.

Three test specimens were then mounted on the horizontal rotor arms with a radial position of 1 m for the center of the specimen. The rotor rotated at a controlled radial speed, giving a range of speeds for the test sample.

Tables 1a and 1b below indicate the test condition parameters defined and/or controlled for each test.

Table 1a. Rain erosion test conditions for experiments in Table 4a and Table 5

Test parameter Unit Nominal condition Speed (tip - center - base) m/s 155 - 130 - 105 Rain area mm/h 29-33 Water temperature °C 8 Water quality μS <5 Test chamber temperature °C 8-10 Average droplet size, diameter, d mm 2.2

Table 1b. Rain erosion test conditions for experiments in Table 4b and table 6

Test parameter Unit Nominal condition Speed (tip - center - base) m/s 140 - 115 - 95 Rain area mm/h 29-33 Water temperature °C 8 Water quality μS <5 Test chamber temperature °C 8-10 Average droplet size, diameter, d mm 2.2

General procedure for preparing coating compositions

The components of each of the base composition a) and the curing agent b) were prepared by mixing said ingredients for each of a) and b) in a manner known to one skilled in the art.

Component a) was then sequentially mixed with component b) before application.

The mixed coating composition was applied to composite test samples, which were primed in advance by brush application. The examples below show six coating compositions within the scope of the present invention and one comparative coating composition wherein the polyester aspartic acid ester has been replaced by an aliphatic aspartic acid ester.

The LEP coating compositions in Tables 4a and 5 were applied directly to primed test pieces, while the LEP coating compositions in Table 4b were applied to primed test pieces coated with a topcoat.

Tables 2 and 3 below show the identity of the aspartic acid ester and polyisocyanates used in the examples.

Table 2: Aspartic acid esters used in the examples (available from Covestro Deutschland AG, Leverkusen, Germany).

Aspartic acid ester Description Amine number (mg KOH/g) Aliphatic polyaspartic acid ester 1: Desmophen NH 1420 Amino-functional coreagent for polyisocyanates. 199-203 Aliphatic polyaspartic acid ester 2: Desmophen NH 1423 Amino-functional coreagent for polyisocyanates. 202-208 Polyester containing aspartic acid ester:
Desmophen NH 2850 XP Amino-functional coreagent for polyisocyanates. 170-210

Table 3: Polyisocyanates used in the examples (available from Covestro Deutschland AG, Leverkusen, Germany)

Compound Polyisocyanate Description Isocyanate content(%) Functionality (n) Viscosity (mPa*s) LEP Polyisocyanate 1:
Desmodur E 2863 XP Polyester modified polyisocyanate prepolymer based on hexamethylene-1,6-diisocyanate (HDI) 11.0 2.2 1350 LEP Polyisocyanate 2:
Desmodur N 3800 Aliphatic polyisocyanate that improves the flexibility of the HDI trimer. 11.0 3.8 6000 LEP Polyisocyanate 3:
Desmodur XP 2860 Aliphatic polyisocyanate based on hexamethylene diisocyanate 20.0 2.5 500 LEP Polyisocyanate 4:
Desmodur XP 2599 Aliphatic prepolymer containing ester groups and based on hexamethylene-1,6-diisocyanate (HDI) 6.0 4.0 2500 Top coating Polyisocyanate 5:
Desmodur N 3900 Aliphatic polyisocyanate resin based on hexamethylene diisocyanate 23.5 3.2 730

Tables 4 and 5 show the compositions and RET results for the coating compositions of the present invention and for comparative coating compositions with an aliphatic polyaspartic acid ester replacing, in whole or in part, the polyester-containing aspartic acid ester.

The amounts of each component indicated in the coating compositions in Tables 4 and 5 are given as a percentage by weight of each of the entire coating composition.

The RET results are listed in Table 4a as follows:

End of incubation period:

≥ 30 min: *

≥ 60 min: **

≥ 120 min: ***

Breakdown to the underlying substrate:

≥ 30 min: +

≥ 60 min: ++

≥ 120 min: +++

Table 4a: LEP coating compositions and RET results, comparative example

Model coating 1 LEP Comparative composition of LEP coating Component a) Aspartic acid ester: Aliphatic polyaspartic acid ester 1 33.8 Polyester containing aspartic acid ester 34.9 Additives: Wetting and dispersing agent 0.2 0.2 Thixotropic additive 1.8 1.9 Antifoam 0.3 0.3 Light stabilizer 0.8 0.8 Pigments and fillers: Pigments 5.1 5.3 Fillers 8.7 8.1 Component b) Polyisocyanate: Polyisocyanate 1 48.2 49.7 Stoichiometric ratio of isocyanate groups in b) to amino groups in a) 107:100 107:100 Rain Erosion Test (RET) End of incubation period ** * Breakdown to the underlying substrate +++ ++

Table 4b: LEP coating compositions and RET results, examples with increasing amounts of aliphatic polyaspartic acid ester

Component Coating A Coating B Coating C Coating D Coating E Coating F Component a) Aspartic acid ester: Aliphatic polyaspartic acid ester 2 0.0 6.3 12.5 18.7 24.9 31.0 Polyester containing aspartic acid ester 31.7 24.4 18.2 12.1 6.0 0.0 Additives: Wetting and dispersing agent 0.1 0.1 0.1 0.1 0.1 0.1 Thixotropic additive 0.7 0.6 0.5 0.4 0.3 0.2 Antifoam 0.3 0.3 0.3 0.3 0.3 0.3 Leveling agent 1.0 1.0 1.0 1.0 1.0 1.0 Light stabilizer 0.6 0.6 0.6 0.6 0.6 0.6 Pigments and fillers: Pigments 9.1 9.0 9.0 9.0 9.0 8.9 Fillers 11.9 13.6 13.8 14.0 14.1 14.3 Component b) Polyisocyanate: Polyisocyanate 1 44.6 44.1 44.0 43.8 43.7 43.6 Stoichiometric ratio of isocyanate groups in b) to amino groups in a) 111:100 109:100 107:100 105:100 103:100 101:100 Rain Erosion Test (RET) End of incubation period ≥ 9 h ≥ 6 h ≥ 4 h ≥ 3 h ≥ 2 h ≥ 2 h Breakdown to the underlying substrate ≥12h ≥7 h ≥ 6 h ≥ 6 h ≥ 6 h ≥ 4 h

Table 5: LEP Coating Compositions and RET Results Model Coatings of the Present Invention

Model coating 2 Model coating 3 Model coating 4 Model coating 5 Model coating 6 Component a) Aspartic acid ester: Polyester containing aspartic acid ester 32.4 30.5 32.8 41.4 23.8 Additives: Wetting and dispersing agent 0.6 - 0.6 0.8 0.5 Thixotropic additive 2.2 2.2 2.2 2.8 1.6 Antifoam 0.5 0.3 0.5 0.6 0.4 Light stabilizer 0.6 - 0.6 0.8 0.5 Pigments and fillers: Pigments 5.1 10.6 5.1 6.5 3.7 Fillers 12.9 12.3 11.3 14.3 8.2 Component b) Polyisocyanates Polyisocyanate 1 45.7 44.1 Polyisocyanate 2 46.7 Polyisocyanate 3 32.8 Polyisocyanate 4 61.4 Stoichiometric ratio of isocyanate groups in b) to amino groups in a) 109:100 109:100 110:100 109:100 109:100 Rain Erosion Test (RET) End of incubation period *** *** ** * ** Breakdown to the underlying substrate +++ +++ +++ + +++

The viscosities of the model LEP coating compositions are in the range of 800-2500 mPa⋅s, while the comparative LEP coating has a viscosity of approximately 5500 mPa⋅s.

Table 6: Topcoat composition and RET results, model coatings of the present invention

Component Component a) Aspartic acid ester: Aliphatic polyaspartic acid ester 1 13.6 Polyester containing aspartic acid ester 13.3 Additives: Leveling agent 0.4 Light stabilizer 0.5 Thixotropic agent 2.5 Mattifying agent 2.6 Wetting and dispersing agent 0.4 Solvents, pigments and fillers: Filler 16.5 Pigment 8.9 Solvent 23.0 Component b) Polyisocyanate Polyisocyanate 5 18.4 Stoichiometric ratio of isocyanate groups in b) to amino groups in a) 107:100 Rain Erosion Test (RET) End of incubation period ≥ 2 h Breakdown to the underlying substrate ≥ 3 h

The composition in Table 6 showed excellent properties for use as a topcoat in wind turbine blades. The topcoat provides a protective effect against rain erosion on its own, even without leading edge protection. In addition, the topcoat has very high abrasion resistance (60 mg, ASTM D4060, 23°C and 50% RH CS10, 1000 g, 1000 rpm), flexibility (<8 mm diameter cylindrical rod test at 23°C and 50% RH, ISO 1519), tensile strength (18% breaking stress) and accelerated weathering (ΔE<1 at 3000 hours, ISO 16474-3 Type 1A (UVA-340), Method 1) .

The topcoat composition has a viscosity in the range of 80-150 mPa⋅s.

Characterization of various properties of coating compositions can be carried out, for example, by the following methods.

Viscosity

The viscosity of the coating compositions was determined using a cone-plate viscometer according to ISO 2884-1:1999, using a cone-plate viscometer set at 25°C and providing a viscosity measurement range of 0-5000 mPa⋅s.

Solid content

The solids content of coating compositions can be calculated according to ASTM D5201 or by determining the percentage solids volume, dry film density and spreading rate of coating materials according to ISO 3233-1.

Calculation of volatile organic compounds content

The volatile organic compound (VOC) content of coating compositions can be calculated according to ASTM D5201.

Bend test

The procedure according to ISO 6860 or ISO 1519 can be followed. A wet film of 150-250 microns is applied to a 0.8 mm thick sanded and degreased steel panel and, after curing, the coated metal panel is bent around a cylindrical rod and the flexibility is assessed by observing cracking.

Impact resistance

Impact resistance can be tested according to ISO 6272-2, which specifies a method for assessing the resistance of a dry film of varnish or related product to cracking or peeling from a substrate when subjected to deformation caused by a falling weight falling under standard conditions applied to a small area spherical indenter.

Taber abrasion

Taber abrasion was tested according to ASTM D 4060. A weight of 1 kg was applied to a coated steel panel. We used a CS-10 grinding wheel and used 2 x 500 rpm. Results are presented in terms of film loss in mg.

Drying time

Drying times can be estimated using the Beck-Koller method according to ISO 9117-4, which establishes a test to determine the time required to reach various stages of drying of organic coatings using a mechanical flow or circular drying time recorder.

Artificial climate aging

The resistance of coatings to UV degradation can be tested by artificial climate aging according to ISO 16474-3, following Test Cycle 1. Test Cycle 1: 4 hours of UV light at 60°C with UVA-340 lamps , 0.83 W/m ² irradiation at 340 nm) followed by 4 hours of condensation at 50°C for a total of 1000-3000 hours.

Glass transition temperature

The glass transition temperature (Tg) of the binder and/or coating composition can be obtained by differential scanning calorimetry (DSC) and/or DMA glass transition temperature (Tg) measurements of cured paint films determined by a dynamic mechanical analyzer (DMA).

Tensile strength

Tensile modulus and other aspects of the tensile stress/strain relationship can be measured according to ISO 527.

Claims (31)

1. Application of a coating composition containing: a) a base composition containing a polyester-containing aspartic acid ester having formula (I) below where each R represents a linear or branched C ₁ -C ₁₀ alkyl residue; And where X represents polyester; And b) hardening agent; for coating wind turbine blades. 2. Use according to claim 1, wherein said base composition a) optionally further comprises one or more aliphatic polyaspartic acid esters, wherein the mixture ratio of polyester-containing aspartic acid esters to aliphatic polyaspartic acid esters is in the range of 70:30 to 99 :1, preferably in the range from 80:20 to 99:1, for example in the range from 85:15 to 99:1, most preferably in the range from 90:10 to 99:1, for example from 95:5 to 99:1; or wherein said coating composition does not contain any aliphatic polyaspartic acid esters. 3. Use according to claim 1, wherein said base composition a) contains less than 20%, for example less than 15%, for example less than 10%, for example less than 5%, for example less than 1% of any aliphatic esters of polyaspartic acid by weight of the specified base composition. 4. Application according to any one of paragraphs. 1-3, wherein X is a polyester, wherein the repeating unit contains an alkyl moiety of one or more carbon atoms connected by an oxygen atom, such as an alkyl moiety between two to six carbon atoms connected by an oxygen atom, such as a two-atom alkyl moiety carbon connected by an oxygen atom; wherein one or more of said carbon atoms may be replaced by methyl, ethyl or propyl. 5. Application according to any one of paragraphs. 1-4, in which X has a repeating structure link below where m is in the range from 2 to 35, for example in the range from 2 to 10, for example in the range from 2 to 6, for example in the range from 2 to 4. 6. Application according to any one of paragraphs. 1-5, in which each R in formula (I) represents a linear or branched C ₁ -C ₆ alkyl residue. 7. Application according to any one of paragraphs. 1-5, in which each R in formula (I) represents a methyl, ethyl, propyl or butyl radical. 8. Application according to any one of paragraphs. 1-5, in which each R in formula (I) represents an ethyl radical. 9. Application according to any one of paragraphs. 1-5, wherein said curing agent contains one or more polyisocyanates. 10. Use according to claim 9, wherein said one or more polyisocyanates in said coating composition have an isocyanate content of 5-20%, for example 5-15%, preferably 6-14%, for example 6-11%, or 8-14% , or 10-12%, for example approximately 11%, and/or wherein the average functionality of said one or more polyisocyanates is in the range of 2-4, for example in the range of 2-3, for example in the range of 2-2.5. 11. Application according to any one of paragraphs. 9, 10, wherein each of said one or more polyisocyanates optionally contains aliphatic polyester groups. 12. Application according to any one of paragraphs. 1-11, in which a) and b) are present in the specified coating composition in such an amount that the stoichiometric ratio of the number of isocyanate groups in the curing agent component to the number of amino groups in the base component is in the range from 80:100 to 160:100, for example from 90:100 to 125:100, for example 95:100 to 120:100, preferably in the range of 100:100 to 120:100, for example 100:100 to 110:100 or 105:100 to 110:100. 13. Application according to any one of paragraphs. 1-12, wherein said coating composition further comprises c) one or more additional components selected from fillers, pigments, solvents and additives; wherein said one or more additional components include one or more components selected from the group consisting of calcium carbonate, dolomite, talc, mica, barium sulfate, kaolin, silica, titanium dioxide, red iron oxide, yellow iron oxide, black iron oxide , carbon black, phthalocyanine blue and phthalocyanine green. 14. Application according to any one of paragraphs. 1-13, wherein said coating application is for use as a protective coating on the leading edge of said wind turbine blade. 15. A wind turbine blade having at least a portion of its outer surface coated with a coating composition as defined in any one of claims. 1-14. 16. The wind turbine blade of claim 15, wherein said coating is a leading edge protective coating. 17. Wind turbine blade according to any one of paragraphs. 15, 16, wherein said coating is a leading edge protective coating, and wherein said coating was applied on top of the topcoat, or wherein said coating was applied under the topcoat, preferably on top of the primer layer.