A coating composition, a coating prepared therefrom, and use thereof

Abstract

The present invention relates to a coating composition comprising: a) a base composition comprising a polyetheraspartic ester having the formula (I) wherein each R represents a linear or branched C1-C10 alkyl residue, such as a linear or branched C1-C6 alkyl residue; and wherein X is a polyether; and an aminosilane with at least one amino group, wherein the amount of aminosilane is at least 0.5 wt.% based on the overall amount of the base composition; and b) a curing agent.

Description

[0001] A COATING COMPOSITION, A COATING PREPARED THEREFROM, AND USE THEREOF

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to a coating composition, a coating prepared from a coating composition and the use of a coating composition. The present invention further relates to a wind turbine blade and an article having a coating according to the present invention.

[0004] BACKGROUND OF THE INVENTION

[0005] Coating compositions and coatings are important for protecting materials such as surfaces which are exposed to various hazards such as rain or sun light.

[0006] In recent years, wind energy has become an important source of electricity production, and contributes significantly to reducing CO2 emissions. Wind power is the use of air flow through wind turbines to provide the mechanical power to turn electric generators.

[0007] Wind turbine blades are usually designed to last around 20 to 25 years. The leading edge is the part of the wind turbine blade that first cuts the wind. The blades are constantly exposed to the elements and are ideally designed to endure temperature extremes, wind shears, precipitation, and / or other environmental hazards with minimal failure. Coating failure due to erosion is often observed on the leading edge of the blade. Rain, hail, ice, UV, water absorption and other weather conditions erode the leading edge of the blade. This affects the aerodynamic of the blade and could cause severe damages.

[0008] Common concepts for protecting the leading edge of wind turbine blades are for example application of an anti-erosive tape or application of a suitable coating composition. For both concepts good adhesion to the blade and good resilience properties are of outmost importance. For coating compositions the material properties also play a significant role in order to obtain the right balance between e.g. robustness, hardness and elasticity of the coating. Furthermore, it is desirable that the coating compositions can be easily applied to the wind turbine blade.

[0009] Various types of coating compositions are used in protective coatings of wind turbine blades for minimizing erosion including compositions formed from aliphatic polyaspartic esters and isocyanate curing agents. For example WO 2015 / 136018 suggests the use of aliphatic polyaspartic esters in formulations for wind turbine blade coating and WO 2015 / 049260 discloses coating compositions comprising an aliphatic polyaspartic ester and a polyisocyanate curing agent and further comprising solid particles of an amino resin based polymer. WO 2015 / 120941 discloses coating compositions comprising aliphatic polyaspartic esters and at least one polycarbonate diol in the paint base. WO 2020 / 260578 discloses coating compositions for wind turbine blades comprising a base composition comprising a polyetheraspartic ester.

[0010] However, known poly(ether)aspartic coating compositions regularly used for e.g. coating wind turbine blades benefit by providing a high flexibility but have long drying times. This is particularly disadvantageous when a coating needs to be repaired. It is regularly found that coating compositions with faster drying times have decreased mechanical properties which make them less useful for coatings, especially for coatings for wind turbine blades.

[0011] Hence, there is a need for a coating composition with an advantageous drying time which concomittantly has acceptable mechanical properties.

[0012] SUMMARY OF THE INVENTION

[0013] In one aspect, the present invention concerns a coating composition comprising: a) a base composition comprising a polyetheraspartic ester having the formula (I) below wherein each R represents a linear or branched C1-C10 alkyl residue, such as a linear or branched C1-C6 alkyl residue, preferably a methyl, ethyl, propyl or butyl residue; and wherein X is a polyether; and an aminosilane with at least one amino group, preferably at least two amino groups, wherein the amount of aminosilane is at least 0.5 wt.%, preferably at least 1.0 wt.%, and more preferably at least 1 .5 wt.% based on the overall amount of the base composition; and b) a curing agent.

[0014] In a further aspect, the present invention concerns a coating prepared from a coating composition according to the present invention.

[0015] In another aspect, the present invention concerns a use of a coating composition according to the invention for coating of a floor, a glass fibre substrate and / or a wind turbine blade, preferably a wind turbine blade made of a glass fibre substrate.

[0016] In yet another aspect, the present invention concerns the use of a coating composition according to the invention as repair coat. In a further aspect of the invention, it concerns the use of a coating composition according to the invention for coating a wind turbine blade or a part of a wind turbine blade such as the leading edge of a wind turbine blade.

[0017] In yet a further aspect, the present invention concerns a wind turbine blade having on at least a part of the outer surface thereof, a coating prepared from a coating composition according to the present invention and / or a coating according to the present invention. In another aspect, the present invention concerns an article having a coating according to the present invention.

[0018] In another aspect, the present invention concerns a kit-of-parts comprising the base composition and the curing agent used in the coating compositions.

[0019] DETAILED DESCRIPTION OF THE INVENTION

[0020] Definitions

[0021] In terms of the “coating composition”, it typically consists of a “base composition” (in which the polyetheraspartic ester and the aminosilane is included) and a “curing agent” (in which the curing agent component is included). Typically the coating composition further includes one or more of other constituents such as fillers, pigments, additives and / or solvents. The other consituents may be present in the base composition and / or the curing agent and / or separately. It should be understood that when reference is made to the “coating composition”, it is the mixed composition ready to be applied to e.g. a wind turbine blade.

[0022] The term “curing” indicates a process in which a solid layer of the coating system is obtained from the liquid components. It may take place, for example, via a chemical reaction and / or via evaporation of solvent. It will be understood that the curing reaction may not always be complete, for example, there may be unreacted functional groups, such as isocyanate groups, remaining after "curing" has taken place. Thus, by “curing”, “cured” or “allowing to cure” we cover both the scenarios of partial and complete curing.

[0023] In the present invention the term “coating” is used for a coating composition after curing. The terms coating and coating composition after curing can be used interchangeably.

[0024] The term “polyether” indicates a polymer prepared by joining together or polymerizing many molecules of simpler compounds (monomers) by establishing ether links between them. In the context of the present invention, the term “polyether” preferably indicates a polymer in which the repeating unit contains an alkyl residue of one or more carbon atoms linked by an oxygen atom, such as an alkyl residue of between two to six carbon atoms linked by an oxygen atom, such as an alkyl residue of two carbon atoms linked by an oxygen atom. One or more of said carbon atoms may be substituted with a small alkyl such as for example methyl, ethyl or propyl, preferably methyl.

[0025] According to the present invention a “blend of polyetheraspartic esters” or “a polyetheraspartic ester blend” indicates a blend of at least two different polyetheraspartic esters.

[0026] In the context of the invention, the “leading edge” of a wind turbine blade indicates the portion of the blade that first cuts into the wind. The opposite edge can be denoted “the trailing edge”.

[0027] The term “Leading Edge Protection” is typically abbreviated “LEP”. In the present context the terms “Leading Edge Protective coating (composition)” or “LEP coating (composition)” are used interchangeably and indicate a coating composition applied to at least a part of a wind turbine blade including at least to the leading edge or at least to a part of the leading edge of a wind turbine blade to provide protection against erosion caused by for example rain, hail, ice, UV, water absorption and other weather conditions. One way to assess the effectiveness of a Leading Edge Protective Coating is the Rain Erosion Test (RET) described in the experimental section herein. Preferably said coating composition is applied as the outermost layer on top of a topcoat, but can also be applied on top of e.g. a primer layer or on top of a primer layer but under a topcoat.

[0028] In the present invention, the term “topcoat” refers to a coating layer applied to at least a part of a wind turbine blade, preferably to the entire wind turbine blade. Preferably, said topcoat coating composition (or “topcoat composition”) is applied on top of a primer layer. Various primer compositions for wind turbine blades are known in the art. The topcoat may be the outermost layer. In an embodiment the topcoat is applied below the LEP coating on the leading edge and as the outermost layer on the remaining parts of the wind blade.

[0029] In the present context, the term “outermost layer” refers to the final coating applied to the wind turbine blade, i.e. the outermost layer when the wind turbine blade is in operation. The “outermost layer” of the leading edge is typically a coating made from a LEP coating composition while the outermost layer of other parts of the wind turbine blade typically refers to a coating made from a topcoat composition.

[0030] In the present invention, the term “repair coat” or “repair coating” refers to a coating layer applied to at least a part of a wind turbine blade, preferably to the leading edge of the wind turbine blade. Preferably, said repair coating composition is applied as the outermost layer.

[0031] In the present invention, a “kit of parts” concerns a kit of parts comprising two or more containers, wherein one container comprises the base composition (in which the polyetheraspartic ester and the aminosilane is included) and another container comprises the curing agent. The one or more other constituents that might be present in the coating composition of the invention as defined herein e.g. fillers, pigments, solvents and / or additives, may be contained in either of the two containers of the kit of parts. Typically the majority or all of the other constituents are contained in the container comprising said base composition. Alternatively, part of said other constituents may be contained in the curing agent or one or more further containers. The present invention relates to a coating composition comprising, or consisting of,: a) a base composition comprising a polyetheraspartic ester having the formula (I) below wherein each R represents a linear or branched C1-C10 alkyl residue, such as a linear or branched Ci-Ce alkyl residue, preferably a methyl, ethyl, propyl or butyl residue; and wherein X is a polyether; and an aminosilane with at least one amino group, preferably at least two amino groups, wherein the amount of aminosilane is at least 0.5 wt.%, preferably at least 0.7 wt.%, more preferably at least 1.0 wt.%, and even more preferably at least 1.5 wt.% based on the overall amount of the base composition; and b) a curing agent.

[0032] It has surprisingly been found that coating compositions according to the present invention have a faster drying time and a improved “dry-to-walk-on”-time. Hence, the addition of aminosilanes to the formulation leads to significant improvements in the performance, including faster drying times without compromising the pot life or working time of the wet coating.

[0033] It has also been found that the coating compositions are useful for repair applications, enabling a quicker return to operation. Hence the coating compositions may be used e.g. as LEP coatings for wind turbine blades, and / or as repair coatings for e.g. wind turbine blades and Leading Edge Protection (LEP). Hence, such coating compositions are useful as coatings applied to wind turbine blades and / or the leading edge of a wind turbine blade not yet installed or which is already installed. Due to the improved drying time and exposure time (determined by the “dry-to-walk-on” time) the return to operation interval of the wind turbine blade can be shortened.

[0034] It has also been surprisingly found that the mechanical properties are kept at a satisfactory level. It is usually the case in coating compositions that there is a trade off between drying time and mechanical properties. The balance of these properties is important. Base composition

[0035] Polyetheraspartic esters are distinguished from the more conventional aliphatic polyaspartic esters in that X in formula (I) is a polyether instead of an aliphatic straight or branched alkyl and / or cycloalkyl residue.

[0036] Polyetheraspartic esters can be prepared by reacting one or more polyether polyamines with a dialkylmaleate, such as for example a linear or branched C1-C10 dialkyl maleate, such as linear or branched Ci-Ce dialkyl maleate, such as for example diethyl maleate. Said polyetheraspartic esters may be prepared, for example, by employing the reactants in amounts such that there is at least one equivalent, and in some embodiments approximately one equivalent, of olefinic double bonds for each equivalent of primary amino groups. Examples of methods for the preparation of polyetheraspartic esters are known in the art and can e.g. be found in WO 2014 / 151307.

[0037] Suitable polyether polyamines that may be reacted with dialkylmaleates in Michael addition reactions to produce polyetheraspartic esters for the coating compositions of the invention include the Jeffamine polyetheramines commercially available from Huntsman Corporation, The Woodlands, TX; for example polyetheramines from the Jeffamine D series, such as for example Jeffamine D-230.

[0038] In one embodiment, the blend of polyether polyamines comprises, or consists of, a blend of polyether polyamines according to formula (II) below, wherein p is a number having an average value of at least 2, such as 2 to 35, or 2 to 8, or 2.5 to 6.1 wherein the blend comprises: (1 ) about 50 to 99 wt.%, such as 50 to 90 wt.%, or, in some cases, 80 to 90 wt.%, of polyether polyamines according to the formula wherein p has an average value of 2.5; and (2) about 1 to 50 wt.%, such as 10 to 50 wt.%, or, in some cases, 10 to 20 wt.%, of polyether polyamines according to the formula wherein p has an average value of 6.1.

[0039] Examples of commercially available polyetheraspartic esters suitable for use in the present invention include Desmophen NH 1720 (Covestro Deutschland AG) which has an equivalent weight of about 290- 295 g mol-1, a viscosity at 25°C of > 80 mPa-s, and an amine value between 170-210 mg KOH / g and Desmophen NH 1723 (Covestro Deutschland AG) which has an equivalent weight of about 290-295 g mol-1, a viscosity at 25°C of > 80 mPa-s, and an amine value between 170-210 mg KOH / g.

[0040] The use of polyetheraspartic esters in coating compositions is known from WO 2014 / 151307 which discloses a coating composition with a resin comprising a polyetheraspartic ester in combination with an aliphatic polyaspartic ester made with Jeffamines. Polyetheraspartic ester blends have furthermore been suggested for use in sealant compositions in WO 2016 / 049104 wherein polyetheraspartic ester blends are used in combination with an aliphatic polyaspartic ester and / or polyether diol. Said sealant compositions are intended for application at for example, expansion joints, control joints, and perimeter joints, of substrates, such as concrete substrates.

[0041] In a preferred embodiment X in formula (I) is a polyether wherein the repeating unit contains an alkyl residue of one or more carbon atoms linked by an oxygen atom, preferably an alkyl residue of between two to six carbon atoms linked by an oxygen atom, and more preferably an alkyl residue of two carbon atoms linked by an oxygen atom; and wherein one or more of said carbon atoms may be substituted with a small alkyl, preferably methyl, ethyl, propyl or butyl, and more preferably methyl, ethyl or propyl.

[0042] In another preferred embodiment X according to formula (I) has a repeating unit of the structure according to the formula (III) below wherein m is in the range of 2 to 35, preferably in the range of 2 to 10, more preferably in the range of 2 to 6, and even more preferably in the range of 2 to 4.

[0043] In a further preferred embodiment, the invention relates to coating compositions comprising, or consisting of, a blend of polyetheraspartic esters wherein X according to formula (I) is a polyether having a repeat unit of the structure according to the formula (III): wherein m is in the range of 2 to 35, preferably in the range of 2 to 10, more preferably in the range of 2 to 6, and even more preferably in the range of 2 to 4.

[0044] The blend of polyetheraspartic esters may comprise at least two different polyetheraspartic esters which have a different number of repeating units in X. In one embodiment, the blend is such that the average value of m is in the range of 2 to 10, preferably 2 to 6, more preferably 2 to 4, and even more preferably 2.5 to 3.

[0045] In another preferred embodiment each R in formula (I) represents an ethyl residue. According to another embodiment the polyetheraspartic ester is the reaction product of a dialkylmaleate, preferably a linear or branched C1-C10 dialkyl maleate, more preferably a linear or branched Ci-Ce dialkyl maleate, and even more preferably diethyl maleate; and of a polyether polyamine according to the formula (II) wherein p is in the range of 2 to 35, preferably in the range of 2 to 10, more preferably in the range of 2 to 6, and even more preferably in the range of 2 to 4.

[0046] In another embodiment the base composition comprises a blend of polyetheraspartic esters comprising at least two polyetheraspartic esters which are each the reaction product of a dialkyl maleate, preferably a linear or branched C1-C10 dialkyl maleate, more preferably a linear or branched Ci-Ce dialkyl maleate, even more preferably diethyl maleate; and of at least two polyether polyamines according to the formula (II) wherein the average value of p is in the range of 2 to 35, preferably is in the range of 2 to 10, more preferably in the range of 2 to 6, even more preferably in the range of 2 to 4, and still more preferably in the range of 2.5 to 3.

[0047] In another embodiment the base composition a) further comprises one or more aliphatic polyaspartic esters. Aliphatic polyaspartic esters are well known in the art. Typical examples of aliphatic polyaspartic esters include substances 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.

[0048] In a preferred embodiment the base composition a) further comprises one or more aliphatic polyaspartic esters, wherein the ratio of polyetheraspartic ester to aliphatic polyaspartic esters is in the range of 70:30 to 99:1 , preferably in the range of 80:20 to 99:1 , such as in the range of 85:15 to 99:1 , and more preferably in range of 90:10 to 99:1 such as 95:5 to 99:1 .

[0049] According to a further preferred embodiment the base composition a) has a viscosity in the range of 50 - 3000 mPa*s, preferably in the range of 250 to 2500 mPa*s, and more preferably in the range of 500- 2000 mPa*s, and even more preferably in the range of 750-1800 mPa*s.

[0050] In another preferred embodiment the coating composition is substantially free of any aliphatic polyaspartic esters, i.e. contains less than 5 wt.%, such as less than 3 wt.%, such as less than 1 wt.%, or such as less than 0.5 wt.% of any aliphatic polyaspartec esters. In another embodiment the coating composition is free of any aliphatic polyaspartic esters.

[0051] Aminosilane

[0052] The coating composition of the invention further comprises an aminosilane.

[0053] According to a preferred embodiment the aminosilane comprises at least one primary amino group, preferably at least two amino groups, and more preferably at least one primary and at least one secondary amino group.

[0054] According to another preferred embodiment the aminosilane has the structure according to the formula (IV), wherein R1, R2, R3independently are hydrogen, linear or branched alkyl or cycloalkyl residue with 1 to 10 carbon atoms, which optionally comprise heteroatoms, preferably R1, R2, R3independently are hydrogen, linear or branched alkyl or cycloalkyl residue with 1 to 10 carbon atoms, which comprise nitrogen, oxygen, and / or sulphur atoms, more preferably R1, R2, R3indepedently are hydrogen or alkoxy residues with 1 to 6 carbon atoms; wherein R4is a linear or branched alkyl or cycloalkyl residue having 1 to 20 carbon atoms, optionally with aromatic moieties, and having one or more heteroatoms, wherein at least one of the heteroatoms is a nitrogen atom, preferably present as primary or secondary amino group, and preferably R4is a linear or branched alkyl or cycloalkyl residue having 1 to 10 carbon atoms having one or more heteroatoms, wherein at least one of the heteroatoms is a nitrogen atom, preferably present as primary or secondary amino group.

[0055] Preferred aminosilanes are aminoalkyl silanes comprising at least two alkoxy groups, preferably three alkoxy groups, bonded to silicon.

[0056] Examples of suitable aminoalkyl silanes are primary amines such as 3-aminopropyltriethoxysilane, 3- aminopropyltrimethoxysilane, 3-aminobutyltriethoxysilane, 3-aminobutyltrimethoxysilane 3- aminopropylmethyldimethoxysilane, and 3-aminopropylmethyldiethoxysilane, primary secondary amines such as N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, secondary amines such as N-methyl- or N-phenyl-3-aminopropyltrimethoxysilane, polyglycolether-modified aminosilanes, and triaminofunctional propyltrimethoxysilanes. Similar aminosilanes having two or three silicon atoms can also be used.

[0057] According to a preferred embodiment the aminosilane can be selected from the group consisting of 3- aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminobutyltriethoxysilane, 3- aminobutyltrimethoxysilane 3-aminopropylmethyldimethoxy-silane, 3- aminopropylmethyldiethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, 3-(2- aminoethylamino)propyltriethoxysilane, N-methyl- or N-phenyl-3-aminopropyltrimethoxy-silane, polyglycolether-modified aminosilanes, and triamino-functional propyltrimethoxy-silanes.

[0058] In a further preferred embodiment the aminosilane is selected from the group consisting of N(2- aminoethyl)-3-aminopropyltrimethoxysilane, 3-(2-aminoethylamino)propyltriethoxy-silane, 3- aminopropyltriethoxysilane or combinations thereof, preferably N(2-aminoethyl)-3- aminopropyltrimethoxysilane, 3-(2-aminoethylamino)propyltriethoxysilane or combinations thereof. In an embodiment the coating composition of the invention comprises two or more different aminosilanes, such as two different aminosilanes.

[0059] In another embodiment the coating composition of the invention comprises only one aminosilane.

[0060] According to another preferred embodiment the total amount of aminosilane is 5.0 wt.% or less, preferably 4.0 wt.% or less, and more preferably 3.5 wt.% or less based on the overall amount of the base composition. It is preferred that the amount of aminosilane is at least 0.05 wt.%, such as at least 0.3 wt.%, such as at least 0.5 wt%, such as at least 0.7 wt%, such as at least 1.0 wt% or such as at least 1 .5 wt.% based on the overall amount of the base composition.

[0061] According to another preferred embodiment the total amount of aminosilane is 4.0 wt.% or less, preferably 3.0 wt.% or less, and more preferably 2.5 wt.% or less based on the overall amount of the coating composition. It is preferred that the amount of aminosilane is at least 0.1 wt.%, such as at least 0.2 wt.%, such as at least 0.3 wt%, such as at least 0.4 wt, such as at least 0.6 wt%, such as at least 0.8 wt%, or such as at least 1.0 wt% based on the overall amount of the coating composition. In another preferred embodiment the amount of aminosilane in the coating composition is in the range of from 0.2 to 3.0 wt.%, preferably of from 0.3 to 2.5 wt.% and more preferably of from 0.4 to 2.2 wt.% or 0.6 to 2.1 wt.% or 0.8 to 1 .5 wt.% or 1 .0 to 2.0 wt.% or 1 .1 to 1 .7 wt.% based on the overall amount of the coating composition.

[0062] Curing agent

[0063] The coating composition of the invention further comprises a curing agent.

[0064] In a preferred embodiment, the curing agent comprises, or consists of, one or more polyisocyanates.

[0065] The term “one or more polyisocyanates” indicates that a blend of polyisocyanates can be used.

[0066] In the present context, “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 may usefully be employed. The number of isocyanate groups per molecule is readily determinable via the isocyanate content and the number-average molecular weight of the respective polyisocyanate. The isocyanate content can be determined for example in accordance with DIN EN ISO 11909 by reaction of the respective sample with excess dibutylamine and back-titration of the excess with hydrochloric acid against bromophenol blue.

[0067] Examples of polyisocyanates according to the invention are compounds that are known per se, preferably aliphatic polyisocyanates with particular mention of diisocyanates and their dimers and trimers such as uretdiones and isocyanurates. Examples include derivatives of hexamethylene-1 ,6- diisocyanate (also denoted hexamethylene diisocyanate or HDI), octamethylene diisocyanate, decamethylene diisocyanate, dodecamethylene diisocyanate, tetradecamethylene diisocyanate, trimethylhexane diisocyanate, tetramethyl-hexane diisocyanate, isophorone diisocyanate (IPDI), 2- isocyanatopropylcyclohexyl isocyanate, dicyclohexylmethane 2,4'-diisocyanate, dicyclohexylmethane 4,4'-diisocyanate, 1 ,4- or 1 ,3-bis(isocyanato-methyl)cyclohexane, 1 ,4- or 1 ,3- or 1 ,2-diisocyanato- cyclohexane, and 2,4- or 2,6-diisocyanato-1-methyl-cyclohexane, and mixtures of these. Most preferred is hexamethylene diisocyanate (HDI).

[0068] According to a preferred embodiment the curing agent comprises, preferably consists of, one or more polyisocyanates wherein one or more of said one or more polyisocyanates is based on hexamethylene diisocyanate (HDI).

[0069] According to another preferred embodiment the curing agent comprises, preferably consists of, one or more polyisocyanates wherein one or more of said one or more polyisocyanates is based on a trimer of hexamethylene diisocyanate (HDI).

[0070] Also, reaction products or prepolymers of aliphatic polyisocyanates may be utilized. Particular mention is made of biurets, allophohanates, uretdiones and isocyanurates of the stated polyisocyanates. Preference here is given to using the dimers and / or trimers of the stated polyisocyanates, preferably of hexamethylene diisocyanate. Thus, in particular, the uretdiones and isocyanurates of the abovementioned polyisocyanates, that are known per se and also available commercially.

[0071] Isocyanurates can be prepared from any of a very wide variety of isocyanates, in the presence of particular 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, are very stable, retaining their integrity even at high temperatures of more than 100° C, for example. Each of these three isocyanate groups originates from three different molecules of the respective isocyanate used; in other words trimeric structures are formed. If polyisocyanates are used, examples being diisocyanates such as HDI, it is possible for an intermediate crosslinking to occur, and hence a plurality of isocyanurate rings may become linked to one another. It is known also to be possible for fractions of bridging diols, as for example hexanediol, to be added during the preparation of the isocyanurates, in order to modify their reactivity, for example, and in this way for a plurality of isocyanurate ring systems to become joined to one another. Likewise uretdiones, consisting of two isocyanate groups can be prepared by catalytic reaction.

[0072] In one embodiment, the curing agent comprises a prepolymer based on an aliphatic polyisocyanate, preferably hexamethylene diisocyanate. “Prepolymers” in the context of the invention, are NCO- functional reaction products of isocyanates and polyols, such as polyethers or polyesters.

[0073] An exemplary prepolymer is a polyisocyanate containing aliphatic polyester groups which comprises 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. Polycaprolactones and their preparation, by reaction of a monoalcohol with epsilon-caprolactone, for example, are known. They may be introduced, for example, by common methods, via reaction of an isocyanate group with at least one of the hydroxyl groups they contain. As a result of the polyester groups present and of the intermediate crosslinking, where it occurs, polyisocyanates such as for example hexamethylene diisocyanate (HDI) isocyanurates containing aliphatic polyester groups have a lower isocyanate content than a pure HDI trimer. While the latter has an isocyanate content of about 25% (molecular weight 3*NCO=126 g / mol; molecular weight of the purely trimeric isocyanurate of HDI=504.6 g / mol), the polyisocyanate containing aliphatic ester groups typically possesses an isocyanate content of 5-20%, such as 5-15%, preferably 6-14%, such as 6-1 1% or 8-14% or 10-12%, such as about 11 %. A commercially available polyisocyanate prepolymer containing aliphatic polyester groups is Desmodur E 30700 (Covestro Deutschland AG, Leverkusen, Germany). Another exemplary prepolymer based on HDI is Desmodur XP 2599 containing ether groups (Covestro Deutschland AG, Leverkusen, Germany).

[0074] Preferred polyisocyanates are solvent-free and are substantially free of isocyanate monomer, i.e. contains less than 0.5 % and more preferably less than 0.3 % of isocyanate monomer as measured according to DIN EN ISO 10 283.

[0075] According to a preferred embodiment the curing agent comprises, preferably consists of, one or more polyisocyanates wherein said one or more polyisocyanates contains less than 0.5% isocyanate monomer, preferably less than 0.3% isocyanate monomer such as less than 0.1% isocyanate monomer; according to DIN EN ISO 10 283.

[0076] When polyisocyanates are used as curing agents, the functionality is defined as the number of isocyanate groups present per 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 within a commercial product. The expression “average functionality” refers to the functionality of a combination of two or more polyisocyanates. The “average functionality” is calculated as the total number of reactive (isocyanate groups) divided by the total number of polyisocyanate molecules. Typically, lower functionality yields less crosslinking, which results in more flexible, softer products, and higher functionality yields higher crosslinking and resulting 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, such as in the range of 3-4 or 2-3, and preferably in the range of 2-2.5.

[0077] Examples of commercially available polyisocyanates which are useful within the present invention include Desmodur N 3900, Desmodur E 2863 XP, Desmodur N 3800, Desmodur XP 2860, Desmodur E 30700 and Desmodur XP 2599 (all available from Covestro Deutschland AG, Leverkusen, Germany). In one embodiment, the curing agent according to the present invention comprises one or more polyisocyanates selected from the group consisting of Desmodur N 3900, Desmodur E30700, Desmodur N 3800, Desmodur XP 2860, Desmodur E 30700 and Desmodur XP 2599.

[0078] The choice of the one or more polyisocyanates to be comprised in the curing agent may be based on the desired properties of the coating composition, such as the preferred degree of viscosity of the coating composition and flexibility of the coating layer.

[0079] In the coating composition the total number of isocyanate groups in the curing agent component to the number of amine groups in the base component will typically be in the range of 80: 100 to 160: 100, such as 90: 100 to 125: 100, such as 95: 100 to 120: 100, preferably in the range of 100: 100 to 120: 100, such as 100: 100 to 110: 100 or 105: 100 to 110: 100. Preferably, the number of isocyanate groups is in excess of the number of amino groups. According to a preferred embodiment the curing agent comprises, preferably consists of, one or more polyisocyanates wherein said one or more polyisocyanates in said coating composition has an isocyanate content of 5-20%, such as 5-15%, preferably 6-14%, such as 6-1 1% or 8-14% or 10-12%, such as about 1 1%.

[0080] According to a preferred embodiment the curing agent comprises, preferably consists of, one or more polyisocyanates wherein the average functionality of said one or more polyisocyanates is in the range of 2-4, such as in the range of 2-3, and preferably in the range of 2-2.5.

[0081] According to a preferred embodiment the curing agent comprises, preferably consists of, one or more polyisocyanates wherein said one or more polyisocyanates contains aliphatic polyester groups.

[0082] The curing agent may further comprise one or more other substituents such as e.g. solvents, fillers, pigments and additives.

[0083] According to a preferred embodiment the coating composition has a pot life of at least 5 minutes, preferably of at least 8 minutes, and more preferably of at least 10 minutes and even more preferably of at least 12 minutes.

[0084] The coating composition

[0085] The coating compositions can be prepared from commercially available components. The base composition (including polyetheraspartic ester(s) and aminosilane) and the curing agent (including polyisocyanate(s)) may typically also comprise one or more other constituents, such as fillers, pigments, solvents and additives.

[0086] In a preferred embodiment the coating composition further comprises c) one or more components selected from fillers, pigments, solvents and / or additives.

[0087] In one embodiment the coating composition comprises at least one filler.

[0088] In another embodiment the coating composition comprises at least one pigment.

[0089] In another embodiment the coating composition comprises at least one filler and / or at least one pigment.

[0090] Examples of fillers include calcium carbonate, (di)dolomite, talc, mica, diatomite, barium sulfate, kaolin and silica.

[0091] In the coating composition the total amount of filler(s) is preferably between 2-40 wt.%, more preferably between 5-20 wt.% and even more preferably 6-18 wt.% or 7-15 wt % based on the overall amount of the coating composition.

[0092] Examples of pigment(s) include titanium dioxide, red iron oxide, yellow iron oxide, black iron oxide, carbon black, phthalocyanine blue and phthalocyanine green. In the coating composition the total amount of pigment(s) is preferably between 2-22 wt.%, more preferably between 5-20 wt.% and even more preferably 6-18 wt.% or 7-15 wt % based on the overall amount of the coating composition. According to a preferred embodiment the at least one filler and / or at least one pigment is selected from the group consisting of calcium carbonate, dolomite, talc, mica, diatomite, barium sulphate, kaolin, silica, titanium dioxide, red iron oxide, yellow iron oxide, black iron oxide, carbon black, phthalocyanine blue and phthalocyanine green.

[0093] In the coating composition the total amount of filler(s) and pigment(s) is preferably between 5-35 wt.%, more preferably between 7-30 wt.% and even more preferably 10-25 wt.% based on the overall amount of the coating composition.

[0094] Examples of additives are diluents, wetting agents, levelling agents and dispersants; defoaming agents such as silicone oils; stabilisers such as stabilisers against light and heat, e.g. hindered amine light stabilisers (HALS); stabilisers against moisture (water scavengers) such as substituted isocyanates, substituted silanes, ortho formic acid trialkyl esters and synthetic zeolites; stabilisers against oxidation such as butylated hydroxyanisole and butylated hydroxytoluene; thickeners and anti-settling agents such as organo-modified clays (Bentone), fumed silicas, polyamide waxes and polyethylene waxes.

[0095] The coating composition may further comprise cycloaliphatic diamine aldimines, such as Vestamin A- 139 from Evonik.

[0096] In the coating composition the total amount of additive(s) is preferably below 10 wt.%, such as below 8 wt.%, or such as below 7 wt.%.

[0097] In one embodiment the coating composition comprises at least 1 wt.% of additive(s).

[0098] Moreover, the base and / or the curing agent may be supplemented with one or more solvents. Preferable examples of suitable solvents are 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 as regards the claimed coating composition when for use in LEP, a solvent may not even be necessary due to the low viscosity of the remaining constituents of the coating composition because of the combined properties of the polyetheraspartic esters and polyisocyanate curing agent. For example the coating composition of the invention may be prepared in solvent-free form and thus, provide a good environmental profile.

[0099] Hence, in the coating composition preferably one or more solvents are included (or not included) in an amount of less than 25 wt.%, such as less than 15 wt.%, such as less than 10 wt.%, preferably less than 5 wt.%, such as less than 2.5 wt.% based on the overall amount of the coating composition. More preferably, when for use as an LEP coating composition, the composition is substantially free of any solvents meaning that one or more organic solvents has not been explicitly added in order, for example, to adapt the viscosity of the composition. “Substantially free of any solvents” means that, if at all, only small amounts of one or more organic solvents, are present in the coating composition as a result of the use of for example typical coatings additives, which may be optionally obtained commercially in solution in organic solvents.

[0100] When the claimed coating composition is for use as a topcoat, said composition preferably contains one or more added solvents in addition to the solvents that might be comprised in the coating composition as a result of the use of for example coating additives, which may be optionally obtained commercially in solution in organic solvents. Preferably the total amount of solvent present is in the range of 10-30 wt.% of the topcoat coating composition, such as in a range of 15-25 wt.%, such as about 20 wt.% based on the overall amount of the coating composition.

[0101] In a preferred embodiment the coating composition comprises one or more solvents in a total amount of less than 30 wt.%, preferably less than 20 wt.%, more preferably less than 10 wt.%, even more preferably less than 5 wt.%, and even more preferably less than 2.5 wt.%, such as less than 1 wt.% or less than 0.5 wt.% of the overall amount of the coating composition, or is free of any solvents.

[0102] The coating composition may be prepared by suitable techniques that are commonly used within the field of coating production. The coating composition may be prepared by mixing two or more components e.g. two pre-mixtures whereof one pre-mixture comprises the base composition and one pre-mixture comprises the curing agent. Prior to mixing one or both of the pre-mixtures may be preconditioned to meet specific temperature requirements. It should be understood that when reference is made to the coating composition, it is the mixed coating composition.

[0103] Mixing of the base composition (comprising polyetheraspartic ester(s) and aminosilane(s)) and the curing agent (comprising poiyisocyanate(s)) allows a chemical reaction between the amino groups of the polyetheraspartic esters and the isocyanate groups of the polyisocyanates. The mixing ratio between the two components must therefore be carefully controlled in order to obtain a coating composition with the right physical properties. The mixing ratio is defined as the volumetric or weight 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 typically between 1 :5 and 5:1 , such as between 1 :4 and 4:1 , such as between 1 :3 and 3:1 , preferably between 1 :2 and 2:1 , such as between 1 : 1 .5 and 1.5:1 , such as about 1 :1.

[0104] In a further preferred embodiment the coating composition comprises a) a base composition comprising a polyetheraspartic ester having the formula below wherein X has a repeat unit of the structure below wherein m is in the range of 2 to 35, preferably in the range of 2 to 10, more preferably in the range of 2 to 6, and even more preferably in the range of 2 to 4; and an aminosilane with at least one amino group, preferably at least two amino groups, wherein the amount of aminosilane in the coating composition is in the range of from 0.2 to 3.0 wt.%, preferably of from 0.3 to 2.5 wt.% and more preferably of from 0.4 to 2.2 wt.% based on the overall amount of the coating composition, and preferably the aminosilane comprises at least two alkoxy groups, more preferably three alkoxy groups, bonded to silicon; b) a curing agent comprising one or more polyisocyanates; and c) optionally one or more further components selected from fillers, pigments, solvents and additives.

[0105] In another preferred embodiment the coating composition comprises a) a base composition comprising a polyetheraspartic ester blend having the formula below wherein X has a repeat unit of the structure below wherein the blend is such that the average value of m is in the range of 2 to 35, such as in the range of 2 to 10, such as in the range of 2 to 6, such as in the range of 2 to 4 such as in the range of 2.5 to 3; an aminosilane with at least one amino group, preferably at least two amino groups, wherein the amount of aminosilane in the coating composition is in the range of from 0.2 to 3.0 wt.%, preferably of from 0.3 to 2.5 wt.% and more preferably of from 0.4 to 2.2 wt.% based on the overall amount of the coating composition, and preferably the aminosilane comprises at least two alkoxy groups, more preferably three alkoxy groups, bonded to silicon; b) a curing agent comprising one or more polyisocyanates; and c) optionally one or more further components selected from fillers, pigments, solvents and additives.

[0106] According to a further preferred embodiment the coating composition has a viscosity in the range of 50- 5000 mPa*s, preferably in the range of 250-4600 mPa*s, more preferably in the range of 300-4500 mPa*s, even more preferably in the range of 400-4300 mPa*s, and even more preferably in the range of 500-4100 mPa*s.

[0107] In another preferred embodiment the coating composition is cured at a temperature below 90°C, and preferably below 70°C. Preferably the temperature is in the range of 0-45°C, more preferably in the range of 5-40°C and even more preferably in the range of 10-30°C.

[0108] Application of the coating compositions of the invention

[0109] Application of the coating compositions can be done by standard application methods such as by brush, spatula or roller.

[0110] The coating composition of the present invention can be used for coating a floor, a glass fibre substrate and / or a wind turbine blade, preferably a wind turbine blade made of a glass fibre substrate.

[0111] The coating composition of the present invention can be a repair coat.

[0112] The claimed coating composition can, hence, be applied to a wind turbine blade by spray application such as for example by conventional air-atomized spray application or by airless spray application. In practical embodiments, the base composition and the curing agent are mixed either in a single batch for normal spray application or as a continuous process when plural component spray equipment is used.

[0113] With the aim of facilitating easy application of the coating composition (e.g. by spray, brush or roller application techniques), the LEP composition typically has a viscosity in the range of 150-5000 mPa*s, such as 250-4600 mPa*s, preferably in the range of 500-4300 mPa*s, such as 500-4100 mPa*s, such as about 4000 mPa*s; while the topcoat composition typically has a viscosity in the range of 50-500 mPa*s, such as about 50-300 mPa*s, such as about 50-200 mPa*s, such as about 100 mPa*s.

[0114] Preferably, the coating composition is applied in one or more layers, such as 1 , 2 or 3 layers and the total dry film thickness (DFT) of the coating composition is typically between 50 and 1000 pm , such as 100-800 pm or 200-600 pm. If the coating composition is used as repair coat typically only one layer is applied. The repair coat may be applied by brush, spatula, roller and / or spraying. Thus in a preferred embodiment the coating composition is used as a repair coat applied in a single layer. In one preferred embodiment the total dry film thickness of the repair coat layer is between 100 and 600 pm.

[0115] Also preferred, the part of the outer surface of a wind turbine blade coated with the coating composition comprises at least a predominant portion of the leading edge of the blade, but the total surface of the wind turbine blade can be coated with the coating composition.

[0116] In the context of the invention, the wind turbine blade to which the coating composition is applied is typically pre-coated with one or more coating layers comprising e.g. a primer to which the coating composition is applied. Preferably, the wind turbine blade to which the coating composition is applied is pre-coated with at least one or more layers of a primer.

[0117] In the context of the invention, the wind turbine blade to which the coating composition is applied can be pre-coated with one or more coating layers comprising a primer and / or a topcoat. Preferably, the wind turbine blade to which the coating composition is applied is pre-coated with at least one or more layers of a primer and / or a topcoat.

[0118] In one embodiment, the invention relates to a wind turbine blade having on at least a part of the outer surface thereof one or more coating layers prepared from a topcoat coating composition according to the invention and thereon one or more layers of an LEP coating prepared from a coating composition according to the invention, wherein said coating composition is applied to at least a part of the leading edge of the wind turbine blade. Optionally, the wind turbine blade has been be pre-coated with one or more coating layers comprising a primer.

[0119] In yet an embodiment, the invention relates to a wind turbine blade comprising: an outer surface, and at least one coating applied to one part of the outer surface the at least one coating including a first coating prepared from a coating composition according to the present invention. Hence, the present invention also provides a method of coating a floor, a glass fibre substrate and / or a wind turbine blade, preferably a wind turbine blade made of a glass fibre substrate, said method comprising applying a coating composition as defined herein to at least a part of the surface of a floor, a glass fibre substrate and / or a wind turbine blade, preferably a wind turbine blade made of a glass fibre substrate; and allowing the coating composition to cure.

[0120] Since the use of the coating compositions according to the invention includes the use for floors, glass fibre substrates and / or wind turbine blades, preferably use in topcoats and / or use in LEP of wind turbine blades, a further embodiment of the invention provides a method for coating comprising the steps, i) applying a coating composition according to the invention for use as coating for floors, glass fibre substrates and / or wind turbine blades, preferably use as topcoat to at least a portion of the wind blade and allowing the composition to cure; followed by ii) applying a coating composition according to the invention for use as coating for floors, glass fibre substrates and / or wind turbine blades, preferably use in LEP, to at least a portion of the leading edge of a wind blade and allowing the composition to cure. A substrate to be coated, preferably a wind turbine blade, may be pre-coated with a primer before applying the coating composition.

[0121] After application of the coating composition, the coating composition is allowed to cure under controlled ambient temperature (23°C) and humidity (50%RH). The coating composition is preferably cured at a temperature not exceeding 70°C, preferably at a temperature in the range of 0-45°C, more preferably in the range of 5-40°C and even more preferably in the range of 10-30°C. The actual temperature at which the coating composition can be cured is normally set at the lower limit by the temperature at which the coating composition is practically curable and at the upper limit by the temperature at which the integrity of the wind turbine blade and any underlying coats will be compromised.

[0122] The coating compositions of the present invention may also be used in a method for repairing, preferably repairing a wind turbine blade. The method for repairing, preferably repairing a wind turbine blade, would comprise a step of applying the coating composition of the present application to at least a portion of the substrate, preferably the wind turbine blade.

[0123] In case of repairing a wind turbine blade the coating can be applied to substantially all of the wind turbine blade, or just to a portion of the wind turbine blade, such as the leading edge of the wind turbine blade. In certain embodiments, one or more of the coating layers can be applied to at least a portion of the wind turbine blade. The wind turbine blade repaired in this manner can have a pre-existing coating or coating layers, some or all of which may be removed prior to application of the claimed coating composition. Alternatively, the claimed coating composition could be painted over the existing coating layer(s). Thus, the invention also relates to a method for repairing and / or replacing or partly replacing an existing coating layer on a wind turbine blade.

[0124] Preferred features of the claimed coating compositions, in particular for repair coating compositions, are - in addition to the fast curing, good pot life and the good mechanical properties - cohesion of the film (as a result of the cross-linking density), UV-resistance, gloss retention and adhesion to underlying coatings. Furthermore, preferably the coating composition provides a coating that provides good protection against erosion caused by harsh weather conditions.

[0125] The above described method can also be applied to a floor or a glass fibre substrate.

[0126] In another aspect the invention relates to a coating prepared from a coating composition according to the invention.

[0127] It should be understood that any feature and / or aspect discussed above in connection with the coating composition and the application of the coating composition according to the invention apply by analogy to coating prepared from a coating composition according to the invention described herein.

[0128] According to a preferred embodiment the coating has a tensile strength (E-modulus) of at least 1.50 N / mm2, preferably of at least 2.0 N / mm2, and more preferably of at least 2.5 N / mm2. The tensile strength regularly does not exceed 15.0 N / mm2 In another preferred embodiment the coating is ready for Rain Erosion Test (RET) exposure after less than 48 hours determined by the “dry-to-walk-on”-time.

[0129] It is preferred that the coating has an RET incubation time at 1 127 rpm (1 layer) of at least 5 hours, preferably at least 8 hours and more preferably at least 11 hours.

[0130] According to another preferred embodiment the coating has a drying time BK I, determined according to ASTM D5895-03, of 2.5 hours or less, preferably of 2.0 hours or less. The drying time is preferably more than 0.01 hour.

[0131] It is preferred that the coating has a drying time BK II, determined according to ASTM D5895-03, of 4.5 hours or less, preferably of 4.0 hours or less.

[0132] It is further preferred the coating has a drying time BK III, determined according to ASTM D5895-03, of 5.5 hours or less, preferably of 5.0 hours or less.

[0133] It is also preferred the coating has a drying time BK IV, determined according to ASTM D5895-03, of 7.0 hours or less, preferably 6.0 hours or less.

[0134] According to another preferred embodiment the coating has a dry film thickness per layer of at least 50 pm, preferably at least 100 pm and more preferably in the range of from 150 to 400 pm.

[0135] In another aspect the present invention relates to the use of a coating composition according to the invention for coating of a floor, a glass fibre substrate and / or a wind turbine blade, preferably a wind turbine blade made of a glass fibre substrate.

[0136] It should be understood that any feature and / or aspect discussed above in connection with the coating composition, the application of the coating composition and the coating according to the invention apply by analogy to the use of the coating according to the invention described herein.

[0137] According to a preferred embodiment the coating is for use as a leading edge protective coating of the wind turbine blade.

[0138] In yet another aspect of the invention, it concerns a use of a coating composition according to the invention as repair coat.

[0139] It should be understood that any feature and / or aspect discussed above in connection with the coating composition, the application of the coating composition and the coating according to the invention apply by analogy to the use of the coating composition according to the invention described herein.

[0140] In another aspect the present invention relates to a wind turbine blade having on at least a part of the outer surface thereof, a coating prepared from a coating composition according to the invention and / or a coating according to the present invention. It should be understood that any feature and / or aspect discussed above in connection with the coating composition, the application of the coating composition and the coating according to the invention apply by analogy to the wind turbine blade according to the invention described herein.

[0141] In a preferred embodiment, the coating is a leading edge protective coating or a repair coat.

[0142] It is preferred that the coating is a leading edge protective coating, and the coating has been applied on top of a topcoat or wherein the coating has been applied on top of a primer layer.

[0143] In another aspect the invention relates to an article having a coating according to the invention.

[0144] It should be understood that any feature and / or aspect discussed above in connection with the coating composition, the application of the coating composition and the coating according to the invention apply by analogy to the article according to the invention described herein.

[0145] In another aspect the present invention relates to a kit-of-parts comprising, or consisting of, i) a container comprising a base composition comprising a polyetheraspartic ester having the formula (I) below wherein each R represents a linear or branched C1-C10 alkyl residue, such as a linear or branched Ci-Ce alkyl residue, preferably a methyl, ethyl, propyl or butyl residue; and wherein X is a polyether; and an aminosilane with at least one amino group, preferably at least two amino groups, wherein the amount of aminosilane is at least 0.5 wt.%, preferably at least 1.0 wt.%, and more preferably at least 1.1 wt.% based on the overall amount of the base composition; and ii) a container comprising a curing agent.

[0146] It should be understood that any feature and / or aspect discussed above in connection with the coating composition, the application of the coating composition and the coating according to the invention apply by analogy to the kit-of-parts according to the invention described herein. The following examples are provided below to illustrate the present invention. They are intended to be illustrative and are not to be construed as limiting in any way.

[0147] EXPERIMENTAL

[0148] Materials

[0149] Aminosilane 1 : N(2-Aminoethyl)-3-aminopropyltrimethoxysilane purchased under the tradename DAMO-T from Evonik (Germany)

[0150] Aminosilane 2: 3-(2-Aminoethylamino)propyltriethoxysilane purchased under the tradename Geniosil DAPTE from Wacker (Germany)

[0151] Aminosilane 3: 3-Aminopropyltriethoxysilane purchased under the tradename Dynasylan AMEO from Evonik (Germany).

[0152] Polyetheraspartic ester 1 : Desmophen NH 1720, amine value 170-210 mg KOH / g (Covestro)

[0153] Polyisocyanate 1 : Desmodur E 30700 (former Desmodur E 2863 XP) , aliphatic ester groups containing prepolymer based on hexamethylene-1 ,6-diisocyanate (HDI), (Covestro).

[0154] Pigments: Titanium dioxide

[0155] Light stabilizers: HALS, UV-absorber

[0156] Additives contain defoamer, wetting agent, levelling agent, rheology modifiers, moisture scavenger.

[0157] Methods

[0158] Tensile strength test

[0159] The tensile strength test is a fast method to determine certain material properties such as the behavior of the material when it is subject to a constant load. It is performed at a constant temperature. For polymeric materials the specimen is typically of rectangular shape. Its dimensions have to be determined, not only clamping distance Io but also its cross-sectional area. The sample is clamped into the machine and held in place by two jaws. One of the jaws is fixed in place, while the other can be moved with a defined speed. The sample is elongated and the course of force F and length change of the sample is tracked during the test, until the sample eventually breaks. The corresponding elongation is called strain at break. As a result of the tensile strength test one obtains stress / strain-curves.

[0160] The following parameters are chosen for the tensile strength test that is carried out according to ISO 527-1 :

[0161] Sample preparation for tensile strength test

[0162] Component a and component b of the paint are mixed prior to the application carefully so there is no air entrapment. The coating is applied by drawdown bar on a suitable plastic foil (the film has to be detachable) and cured one week in conditions of 23°C and 50%RH. The specimen is cut out of the free film with a sample cutting press to dimensions of 10mm by 200mm and the film thickness is determined according to ISO 2808. For the tensile strength test in the present invention a “Zwick Tensile testing Machine Z2.5 / TS1 S - 2000” was used. The higher a tensile strength (N / mm2) obtained the better.

[0163] Drying time using the BK drying time recorder

[0164] The drying time of the paint is measured according to ASTM D5895-03. BK-I, BK-II, BK-III and BK-IV are reported in hours, while BK-III is the relevant parameter for QC purposes. The applicator’s gap size is 280 pm. The test is carried out at 23 °CZ 50% RH. A needle is running across the surface of the freshly applied paint in a known speed and leaves a mark, which is evaluated as follows:

[0165] Stage I (BK I): The point when the film stops flowing together in the track.

[0166] Stage II (BK II): The point when the continuous track stops and the needle starts to tear the film or leave a discontinuous cutting of the film.

[0167] Stage III (BK III): The point when the needle stops tearing or cutting the film, leaving a visible track on the film surface.

[0168] Stage IV (BK IV): The point when the needle does not leave any track.

[0169] Determination of the “dry-to-walk-on”-time

[0170] The “dry-to-walk-on” test method is used to determine the “dry-to-walk-on”-time. A pressure of 25 kg / cm2is used. This pressure is applied in order to simulate the pressure applied by the shoes or boots of a person walking on the surface coated with the primer composition.

[0171] Hence, the freshly painted panels have a wet film thickness of 350-400 pm and a pressure of 25 kg / cm2is applied for 3 minutes after the application of the primer layer. A Teflon-coated steel block (base area 25 cm2) was pressed towards the painted surface by means of a pneumatic compression machine with a mobile arm. If the paint is not “dry-to-walk-on”, the paint will ooze out from underneath the pressure block resulting in visible indentation marks.

[0172] The appearance of the painted surface, resulting from the pressure applied, is rated on a scale from 0 to 5, where 1 is unsatisfactory and 5 is perfect with no visible mark after testing. The pressure is applied at intervals of 1 hour after application of the primer (starting a full number of hours after application when the panel was considered ready for testing) (a new panel for each test) and until a rating of 5 is obtained, or until no more panels are available.

[0173] The definition of “dry-to-walk-on” time according to this test is the time after application of the outermost coat required in order to obtain a rating of 5. After this period of time, the paint surface is sufficiently hardened to be walked on without coming off / being damaged.

[0174] Rain Erosion Test (RET)

[0175] The Rain Erosion Test (RET) is widely accepted as being the most suitable test for evaluating anti- erosive properties of coatings on the leading edge of wind turbine blades. The idea is to simulate the erosive effect from collision with raindrops, dust particles, hailstone and the like by creating a controlled rain field in which the coated surface moves at high speed.

[0176] Rain Erosion Test (RET) was carried out using a rotating arms test rig. The test was carried out according to the DNVGL-RP-0171 Recommended Practice, Testing of Rotor Blade Erosion Protection Systems.

[0177] The erosion damage was reproduced on specimens mounted on an arm which rotates horizontally, through an artificial rain field. The rain impacts the surface of the test specimen and erodes the surface, which is protected with the coating to be tested. The degree of erosion damage caused by the droplet impacts was inspected and documented. This was performed by visual inspection and picture documentation at defined intervals. Detailed picture documentation enables the investigation of the initial damage at the end of the incubation period, as well as the damage progress. The time needed to erode the surface to a specified limit, was the measure which is used to compare the performance of the protection systems with each other. There are two erosion stages which are commonly used to specify the survival time of the specimens:

[0178] End of incubation period: The incubation period is defined as the exposure time until the first damage is visually detectable on the outer surface of the test specimen. The incubation period depends on the impact speed and thus, for rotating arm test rigs, on the position on the specimen.

[0179] Breakthrough to the underlying substrate: Breakthrough is defined as the point in time when the erosion breaks through the protective layer to the underlying substrate. The time of breakthrough depends on the impact velocity and thus, for rotating arm test rigs it also depends on the location on the specimen.

[0180] 45 cm long U-shaped test specimens based on NACA 634-021 aerofoil geometry simulating the leading edge of a wind turbine blade (as described in Appendix A.1 , DNVGL-RP-0171 ), consisting of a composite substrate initially coated with a system of porefiller + primer (total dry film thickmness of porefiller and primer 300 pm) were coated with 200-600 pm (dry film thickness) of the coating compositions to be tested. The coating compositions were cured at controlled laboratory conditions, typically 25°C and 50% RH, for at least 7 days to secure 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 was spun at a controlled radial velocity resulting in a range of test subject velocities.

[0181] Table 1 below indicates the test condition parameters specified and / or monitored during each test.

[0182] Table 1 : Rain Erosion Test conditions for experiments

[0183] Viscosity and Pot Life

[0184] The viscosity of the coating compositions was determined using a Cone and Plate viscosimeter according to ISO 2884-1 :1999 set at a temperature of 23°C in a viscosity measurement range of 50- 5000 mPa*s.

[0185] The pot life is determined as the time until the viscosity doubles compared to the first value measured right after mixing. Hence, the paint is mixed and viscosity measurements are performed in certain time differences, for example every minute until the viscosity is twice the initial value.

[0186] Examples

[0187] General procedure for preparation of coating compositions

[0188] The components of each of the base composition a) and the curing agent b) were produced by mixing the indicated ingredients for each of a) and b) in a conventional manner known to the person skilled in the art. The coating compositions are described in Table 2 and listed in percent by weight.

[0189] Component a) was then subsequently mixed with Component b) prior to application. CE are comparative examples and IE are examples according to the invention.

[0190] The mixed coating composition was applied to the composite test specimens in one or two layers, (see table 3) which were primed in advance, by roller / brush application or spatula application. The primer is a 2-component polyaspartic ester and applied on the substrate with a brush. Overcoating interval between primer and LEP is between 1 and 4 hours. Table 2: Coating compositions

[0191] As evident from Table 3 below, addition of an aminosilane leads to faster drying time without compromising the pot life, incubation time or working time of the wet coating. Also a faster “dry-to-walk- on” time is observed. The tensile strength is also favourable for the inventive examples. Table 3: Experimental results n.m.: not measured

Claims

CLAIMS1. Coating composition comprising: a) a base composition comprising a polyetheraspartic ester having the formula (I) belowwherein each R represents a linear or branched C1-C10 alkyl residue, such as a linear or branched Ci-Ce alkyl residue, preferably a methyl, ethyl, propyl or butyl residue; and wherein X is a polyether; and an aminosilane with at least one amino group, preferably at least two amino groups, wherein the amount of aminosilane is at least 0.5 wt.%, preferably at least 0.7 wt.%, more preferably at least 1.0 wt.%, and even more preferably at least 1.5 wt.% based on the overall amount of the base composition; and b) a curing agent.

2. Coating composition according to claim 1 , wherein the aminosilane comprises at least one primary amino group, preferably at least two amino groups, and more preferably at least one primary and at least one secondary amino group.

3. Coating composition according to claims 1 or 2, wherein the aminosilane has the structure according to the formula (IV),R1R4— Si — R2R3(IV)wherein R1, R2, R3independently are hydrogen, linear or branched alkyl or cycloalkyl residue with 1 to 10 carbon atoms, which optionally comprise heteroatoms, preferably R1, R2, R3independently are hydrogen, linear or branched alkyl or cycloalkyl residue with 1 to 10 carbon atoms, which comprise nitrogen, oxygen, and / or sulphur atoms, more preferably R1, R2, R3indepedently are hydrogen or alkoxy residues with 1 to 6 carbon atoms; and wherein R4is a linear or branched alkyl or cycloalkyl residue having 1 to 20 carbon atoms, optionally with aromatic moieties, and having one or more heteroatoms, wherein at least one of the heteroatoms is a nitrogen atom, preferably R4is a linear or branched alkyl or cycloalkyl residue having 1 to 10 carbon atoms having one or more heteroatoms, wherein at least one of the heteroatoms is a nitrogen atom.

4. Coating composition according to any of the previous claims, wherein the aminosilane is selected from the group consisting of N(2-aminoethyl)-3- aminopropyltrimethoxysilane, 3-(2-aminoethylamino)propyltriethoxysilane, 3- aminopropyltriethoxysilane or combinations thereof, preferably N(2-aminoethyl)-3- aminopropyltrimethoxysilane, 3-(2-aminoethylamino)propyltriethoxysilane or combations thereof; and / or wherein the amount of aminosilane is 5.0 wt.% or less, preferably 4.0 wt.% or less, and more preferably 3.5 wt.% or less based on the overall amount of the base composition; and / or wherein the amount of aminosilane in the coating composition is in the range of from 0.2 to 3.0 wt.%, preferably of from 0.3 to 2.5 wt.% and more preferably of from 0.4 to 2.2 wt.% based on the overall amount of the coating composition; and / or wherein said coating composition comprises one or more solvents with a total amount of less than 20 wt.%, preferably less than 15 wt.%, more preferably less than 10 wt.%, even more preferably less than 5 wt.%, and even more preferably less than 2.5 wt.% of the overall amount of the coating composition, or is free of any solvents.

5. Coating composition according to any of the previous claims, wherein said base composition a) further comprises one or more aliphatic polyaspartic esters, wherein the ratio of polyetheraspartic ester to aliphatic polyaspartic esters is in the range of 70:30 to 99:1 , preferably in the range of 80:20 to 99:1 , such as in the range of 85:15 to 99:1 , most preferably in 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 esters.

6. Coating composition according to any of the previous claims, wherein said curing agent comprises one or more polyisocyanates; orwherein said curing agent comprises one or more polyisocyanates, wherein said one or more polyisocyanates in said coating composition has an isocyanate content of 5-20%, such as 5-15%, preferably 6-14%, such as 6-11% or 8-14% or 10-12%, such as about 11%.

7. Coating composition according to claim 6, wherein the average functionality of said one or more polyisocyanates is in the range of 2-4, such as in the range of 2-3, such as in the range of 2-2.5; and / or wherein said one or more polyisocyanates contains aliphatic polyester groups.

8. Coating composition according to any of the previous claims, wherein said coating composition further comprises c) one or more components selected from fillers, pigments, solvents and / or additives; and / or wherein a) and b) are present in said coating composition in an amount so that the stoichiometric ratio of the number of isocyanate groups in the curing agent component to the number of amine groups in the base component is in the range of 80: 100 to 160: 100, such as 90: 100 to 125: 100, such as 95: 100 to 120: 100, preferably in the range of 100: 100 to 120: 100, such as 100: 100 to 1 10: 100 or 105: 100 to 110: 100; and / or wherein the coating composition has a pot life of at least 5 minutes, preferably of at least 8 minutes, and more preferably of at least 10 minutes, and even more preferably of at least 12 minutes.

9. A coating prepared from a coating composition as defined in any one of claims 1 to 8.

10. Coating according to claim 9, wherein the coating has a tensile strength (E-modulus) of at least 1.50 N / mm2, preferably of at least 2.00 N / mm2, and more preferably of at least 2.50 N / mm2; and / or wherein the coating is ready for Rain Erosion Test (RET) exposure after less than 48 hours determined by the “dry-to-walk-on”-time as defined herein.

11. Coating according to claims 9 or 10, wherein the coating has a drying time BK I, determined according to ASTM D5895-03, of 2.5 hours or less, preferably of 2.0 hours or less; and / orwherein the coating has a drying time BK II, determined according to ASTM D5895-03, of 4.5 hours or less, preferably of 4.0 hours or less; and / or wherein the coating has a drying time BK III, determined according to ASTM D5895-03, of 5.5 hours or less, preferably of 5.0 hours or less; and / or wherein the coating has a drying time BK IV, determined according to ASTM D5895-03, of 7.0 hours or less, preferably 6.0 hours or less.

12. Coating according to claims 9 to 11 , wherein the coating has a dry film thicknes per layer of at least 50 pm, preferably at least 100 pm and more preferably in the range of from 150 to 400 pm.

13. Use of a coating composition according to claims 1 to 8 for coating of a floor, a glass fibre substrate and / or a wind turbine blade, preferably a wind turbine blade made of a glass fibre substrate.

14. The use according to claim 13, wherein said coating composition use is for use as a leading edge protective coating of the wind turbine blade, preferably a wind turbine blade made of a glass fibre substrate.

15. Use of a coating composition according to claims 1 to 8 as repair coat.

16. A wind turbine blade having on at least a part of the outer surface thereof, a coating prepared from a coating composition according to any one of claims 1 to 8.

17. A wind turbine blade having on at least a part of the outer surface thereof, a coating according to any one of claims 9 to 12.

18. The wind turbine blade according to claims 16 or 17, wherein said coating is a leading edge protective coating.

19. The wind turbine blade according to any of claims 16 to 18, wherein said coating is a leading edge protective coating, and wherein said coating has been applied on top of a topcoat, orwherein said coating has been applied on top of a primer layer.

20. Article having a coating according to any of claims 9 to 12.

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