Protective coating composition

Abstract

A protective coating composition comprising a urethane resin having a urethane structure and a carbonate structure in the same molecule, and an ethylenically unsaturated compound, wherein the urethane resin is a urethane (meth)acrylate resin, and the erosion resistance of cured products of the protective coating composition is 1.5 hours or more.

Description

Protective Coating Composition

[0001] The present disclosure relates to protective coating compositions.

[0002] Wind turbine blades are becoming larger in order to maximize power generation efficiency. As wind turbine blades become larger, damage or wear (erosion) of the leading edge of the blade due to rain or sand becomes a problem. Erosion reduces the aerodynamic characteristics of the wind turbine blade, resulting in a decrease in power generation efficiency. To prevent erosion, leading edge protection (LEP) is attached to the wind turbine blade. To date, various types of LEPs have been developed, including sheet-type, paint-type, and molded-type LEPs.

[0003] US Patent Application Publication No. 2020 / 0040869 describes a method for applying a protective layer to the outer surface of a wind turbine rotor blade, the method including the steps of preparing a protective layer for application to the outer surface of the rotor blade, providing an air outlet channel between the rotor blade and the protective layer, attaching the protective layer to the outer surface of the rotor blade, and extracting air through the air outlet channel.

[0004] Patent Document 2 (WO 2012 / 102294) describes a blade body made of fiber-reinforced plastic (FRP), in which a laminated protective sheet is adhered to at least a portion of the leading edge of the blade body body, and the laminated protective sheet has, in order from the blade body side, an adhesive layer, an intermediate base fabric layer, and a durable surface layer.

[0005] U.S. Patent Application Publication No. 2021 / 0130647 describes a coating material composition used to produce an erosion-stable coating used as erosion protection, particularly edge protection for rotor blades. The composition includes a stock component and a curing agent component, where the stock component includes at least one trifunctional polycaprolactone polyol, at least one polycarbonate diol, or at least one trifunctional polycaprolactone polyol and polycarbonate diol, and the curing agent component includes at least one crystallization-resistant isocyanate-functional prepolymer.

[0006] WO 2016 / 075619 describes a method for making protective covers for wind turbine blades, the method comprising: a) mixing a polyol and a butanediol; b) conditioning and degassing the mixture according to a); c) conditioning and degassing an isocyanate; d) pumping the degassed mixture according to b) and the degassed isocyanate according to c) through a mix head into a mold; e) curing in the mold; and f) removing the cured article from the mold.

[0007] Non-patent document 1 (Wind Energy Utilization Symposium, 2021, Vol. 43, p. 210) describes that when an erosion protection sheet is applied to a wind turbine blade, the aerodynamic characteristics of the wind turbine blade are reduced due to a step that occurs at the boundary between the wind turbine blade and the protection sheet.

[0008] U.S. Patent Application Publication No. 2020 / 0040869 WO 2012 / 102294 U.S. Patent Application Publication No. 2021 / 0130647 WO 2016 / 075619

[0009] Hirokazu Kawabata, "Aerodynamic Performance Evaluation of Blades with Erosion Protection Sheets," Wind Energy Utilization Symposium, 2021, Vol. 43, p. 210

[0010] The protective layer described in Patent Document 1 is a sheet that is applied in a post-process after blade manufacturing, and application is time-consuming. Furthermore, if the protective layer is applied in a post-process, as described in Non-Patent Document 1, there is a risk that the aerodynamic characteristics of the blade will be reduced due to a step that occurs at the boundary between the protective layer and the blade. The laminated protective sheet described in Patent Document 2 is attached to the blade with an adhesive layer, and therefore there is a risk that the laminated protective sheet will peel off from the blade over long-term use, resulting in reduced aerodynamic characteristics or noise generation. If the thickness of the protective layer or laminated protective sheet is set to, for example, 300 μm or more in order to ensure erosion resistance over a long period of time, the aerodynamic characteristics of the blade will be significantly reduced.

[0011] The coating material composition described in Patent Document 3 has excellent workability, but its curability is low, making it difficult to obtain a sufficient level of erosion resistance.

[0012] The method described in Patent Document 4 requires that the protective cover be molded in advance to match the shape of the blade, which limits the blades that can be applied. The thickness of the molded protective cover also tends to increase, which can easily lead to a deterioration in the aerodynamic characteristics of the blade.

[0013] Furthermore, when applying a sheet, coating or molding to a blade, it may be necessary to strip or remove coatings, such as gel coats, from the blade surface to improve adhesion.

[0014] The present disclosure provides a protective coating composition that requires little effort in application, can avoid a decrease in aerodynamic characteristics, and can form an LEP that has excellent erosion resistance.

[0015] The inventors have discovered that by using a resin composition containing a urethane resin having a urethane structure and a carbonate structure in the same molecule as a gel coat and leading edge protectant during the manufacture of wind power generation blades, it is possible to reduce the effort required for application, avoid a decrease in aerodynamic characteristics, and impart an LEP with excellent erosion resistance to various types of wind power generation blades, and have completed the present invention.

[0016] The present disclosure encompasses the following aspects.

[0017] [Aspect 1] A protective coating composition comprising a urethane resin having a urethane structure and a carbonate structure in the same molecule, and an ethylenically unsaturated compound, wherein the urethane resin is a urethane (meth)acrylate resin, and the cured product of the protective coating composition has an erosion resistance of 1.5 hours or more. [Aspect 2] The protective coating composition of Aspect 1, further comprising an epoxy (meth)acrylate resin. [Aspect 3] The protective coating composition of Aspect 1 or 2, comprising 10% to 90% by mass of the urethane resin. [Aspect 4] The protective coating composition of any one of Aspects 1 to 3, wherein the urethane resin is a reaction product of a composition comprising a polycarbonate polyol and a polyisocyanate, and the molar ratio of hydroxyl groups of the polycarbonate polyol to isocyanato groups of the polyisocyanate (OH [mol] / NCO [mol]) is 0.5 to 0.9. [Aspect 5] The protective coating composition according to Aspect 4, wherein the polycarbonate polyol has a number average molecular weight of 500 to 10,000. [Aspect 6] The protective coating composition according to Aspect 4 or 5, wherein the polyisocyanate comprises an alicyclic polyisocyanate. [Aspect 7] The protective coating composition according to any one of Aspects 1 to 6, wherein the urethane resin has a number average molecular weight of 500 to 30,000. [Aspect 8] The protective coating composition according to any one of Aspects 1 to 7, wherein the protective coating composition is a leading edge protectant for wind power generation blades. [Aspect 9] The protective coating composition according to Aspect 8, wherein the wind power generation blade has a blade length of 10 m or more.

[0018] According to the present disclosure, LEPs with excellent erosion resistance can be formed on various types of wind power blades with minimal application effort, while avoiding deterioration of aerodynamic characteristics. The protective coating composition of the present disclosure can also be used for various protective purposes other than protecting the leading edge of wind power blades.

[0019] Fig. 1 is a schematic cross-sectional view of a wind power generation blade according to one embodiment, and Fig. 2 is an explanatory diagram of a method for manufacturing a wind power generation blade according to one embodiment using a vacuum-assisted impregnation method.

[0020] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. The present disclosure is not limited to the following embodiments, and various modifications can be made within the scope of the present invention.

[0021] In the present disclosure, when a range of values ​​is given, the numerical values ​​at both ends are the upper and lower limits, respectively, and are included in the range.

[0022] In this disclosure, "(meth)acrylic" means acrylic or methacrylic, "(meth)acrylate" means acrylate or methacrylate, and "(meth)acryloyloxy" means acryloyloxy or methacryloyloxy.

[0023] In the present disclosure, the term "ethylenically unsaturated bond" refers to a double bond formed between carbon atoms excluding carbon atoms forming an aromatic ring, and the term "ethylenically unsaturated monomer" refers to a monomer having an ethylenically unsaturated bond.

[0024] In the present disclosure, the "weight average molecular weight" and "number average molecular weight" refer to values ​​measured using gel permeation chromatography (GPC) at room temperature (23°C) under the following conditions and determined using a standard polystyrene calibration curve. Apparatus: Shodex™ GPC-101 (Resonac Inc.) Column: Shodex™ LF-804 (Resonac Inc.) Column temperature: 40°C Sample: 0.2% by mass solution of sample in tetrahydrofuran Flow rate: 1 mL / min Eluent: Tetrahydrofuran Detector: Shodex™ RI-71S (Resonac Inc.)

[0025] [Protective Coating Composition] In one embodiment, a protective coating composition is provided that includes a urethane resin having a urethane structure and a carbonate structure in the same molecule, and an ethylenically unsaturated compound. In this embodiment, the urethane resin is a urethane (meth)acrylate resin, and the erosion resistance of the cured product of the protective coating composition is 1.5 hours or more. The erosion resistance is measured by forming the cured product of the protective coating composition into a film having a thickness of 2 mm and evaluating it according to the procedure described in the examples. The erosion resistance of the cured product of the protective coating composition is preferably 0.5 hours or more, more preferably 1.0 hour or more, and even more preferably 1.5 hours or more.

[0026] In one embodiment, the protective coating composition is a leading edge protectant for wind power blades. By using the protective coating composition, the formation and application of a coating that can be used as a leading edge protectant can be performed during the manufacturing process of the wind power blade, thereby shortening the process and enabling coatings to be applied to wind power blades of various shapes. Furthermore, since the coating can be heat-cured during the heating step for curing the matrix resin, a coating with high mechanical strength and bonding strength can be applied to the wind power blade. Furthermore, since the coating is formed to conform to the shape of the mold surface, it does not affect the aerodynamic characteristics of the wind power blade and can prevent a decrease in power generation efficiency. However, the use of the protective coating composition of the present disclosure is not limited to the formation of a leading edge protectant for wind power blades.

[0027] Fig. 1 is a schematic cross-sectional view of a wind power generation blade according to one embodiment. In Fig. 1, the wind power generation blade 10 is shown as a component, and includes a fiber-containing substrate 14 and a coating 12 partially disposed on the leading edge side of the fiber-containing substrate 14. The surfaces of the coating 12 and the fiber-containing substrate 14 are continuous along the surface of the mold used in manufacturing the wind power generation blade 10, and there is no step at the boundary between the coating 12 and the fiber-containing substrate 14.

[0028] [Protective Coating Composition] In one embodiment, the protective coating composition comprises a urethane resin having a urethane structure and a carbonate structure in the same molecule. The urethane resin having a urethane structure and a carbonate structure in the same molecule has both high mechanical strength and excellent elongation properties. These properties of the urethane resin contribute to the excellent erosion resistance of the cured product of the protective coating composition.

[0029] <Urethane Resin> A urethane resin having a urethane structure and a carbonate structure in the same molecule can be obtained by polyaddition reaction of at least a polyisocyanate and a polyol, and at least one of the polyisocyanate and the polyol has a carbonate structure. One type of urethane resin may be used alone, or two or more types may be used in combination.

[0030] Examples of polyisocyanates include aromatic polyisocyanates such as 4,4'-diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 1,5-naphthalene diisocyanate, 3,3'-dimethyl-4,4'-biphenylene diisocyanate, polymethylene polyphenyl diisocyanate, xylylene diisocyanate, phenylene diisocyanate, and triphenylmethane triisocyanate; alicyclic polyisocyanates such as 4,4'-methylenebiscyclohexyl diisocyanate, isophorone diisocyanate, and cyclohexane-1,3-diylbis(methylene)diisocyanate; and aliphatic polyisocyanates such as hexamethylene diisocyanate and trimethylhexamethylene diisocyanate; as well as adducts, isocyanurates, and biurets of these polyisocyanates. The polyisocyanate may be used alone or in combination of two or more kinds.

[0031] From the viewpoint of the mechanical strength and weather resistance of the coating, the polyisocyanate preferably contains an alicyclic polyisocyanate, and more preferably contains at least one selected from the group consisting of 4,4'-methylenebiscyclohexyldiisocyanate and isophorone diisocyanate.

[0032] As the polyol, a polycarbonate polyol capable of introducing a carbonate structure into a urethane resin is generally used. Polycarbonate polyol can be synthesized using an alkanediol and a carbonate diester as raw materials in the presence of an ester exchange catalyst. Examples of alkanediols include 1,6-hexanediol, 1,5-pentanediol, 1,4-butanediol, and 2-methyl-1,3-propanediol. Polycarbonate polyols can form coatings with excellent mechanical strength and elongation properties. One type of polyol may be used alone, or two or more types may be used in combination.

[0033] From the viewpoint of the mechanical strength and elongation properties of the coating, the number average molecular weight (Mn) of the polycarbonate polyol is preferably 500 or more, more preferably 600 or more, even more preferably 700 or more, and preferably 10,000 or less, more preferably 8,000 or less, and even more preferably 5,000 or less. Any combination of these lower limit and upper limit values ​​may be used. The number average molecular weight of the polycarbonate polyol is preferably 500 to 10,000, more preferably 600 to 8,000, and even more preferably 700 to 5,000. When Mn is 500 or more, a coating having excellent mechanical strength can be formed. When Mn is 10,000 or less, a coating having excellent elongation properties can be formed.

[0034] The polyol may contain a low molecular weight polyol as a chain extender. The low molecular weight polyol increases the molecular weight of the urethane resin, thereby further improving the mechanical strength of the coating. Examples of low molecular weight polyols include ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, 1,10-decanediol, 1,1-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, tricyclodecane dimethanol, xylylene glycol, bis(p-hydroxy)diphenyl, bis(p-hydroxyphenyl)propane, 2,2-bis[4-(2-hydroxyethoxy)phenyl]propane, bis[4-(2-hydroxyethoxy)phenyl]sulfone, and 1,1-bis[4-(2-hydroxyethoxy)phenyl]cyclohexane. One type of low molecular weight polyol may be used alone, or two or more types may be used in combination.

[0035] The amount of polyisocyanate used can be designed based on the molar ratio (OH [mol] / NCO [mol]) of the hydroxyl groups of the polyol to the isocyanato groups of the polyisocyanate. This molar ratio is preferably 0.5 or more. This molar ratio is preferably 0.9 or less, more preferably 0.8 or less, and even more preferably 0.7 or less. Any combination of these lower and upper limits is acceptable. This molar ratio is preferably 0.5 to 0.9, more preferably 0.5 to 0.8, and even more preferably 0.5 to 0.7. When this molar ratio is 0.9 or less, the mechanical strength of the coating can be increased. When this molar ratio is 0.5 or more, the elongation properties of the coating can be increased.

[0036] In an embodiment in which the urethane resin is a reaction product of a composition containing a polycarbonate polyol and a polyisocyanate, the molar ratio of hydroxyl groups of the polycarbonate polyol to isocyanato groups of the polyisocyanate (OH [mol] / NCO [mol]) is preferably 0.5 or more. This molar ratio is preferably 0.9 or less, more preferably 0.8 or less, and even more preferably 0.7 or less. Any combination of these lower and upper limits may be used. The molar ratio is preferably 0.5 to 0.9, more preferably 0.5 to 0.8, and even more preferably 0.5 to 0.7.

[0037] The reaction temperature for the polyaddition reaction is not particularly limited, but is preferably 20°C to 200°C, more preferably 50°C to 150°C, and even more preferably 80°C to 120°C.

[0038] The polyaddition reaction may be carried out using a catalyst. Examples of the catalyst include amine compounds such as triethylamine, N-ethylmorpholine, triethylenediamine, and diazabicycloundecene; organotin compounds such as trimethyltin laurate and dibutyltin dilaurate; organotitanium compounds; and organolead compounds such as lead octoate. One type of catalyst may be used alone, or two or more types may be used in combination.

[0039] The polyaddition reaction may be carried out substantially in the absence of a solvent, or in the presence of a solvent. Examples of the solvent include dimethylformamide, diethylformamide, dimethylacetamide, dimethyl sulfoxide, tetrahydrofuran, methyl isobutyl ketone, dioxane, cyclohexanone, benzene, toluene, and ethyl cellosolve. One solvent may be used alone, or two or more solvents may be used in combination.

[0040] The urethane resin is a urethane (meth)acrylate resin. The urethane (meth)acrylate resin can form a coating with high mechanical strength by heat curing. As the urethane (meth)acrylate resin, for example, a resin obtained by introducing a (meth)acryloyl group into the terminal hydroxyl group or isocyanato group of the urethane resin obtained by reacting the polyisocyanate with the polyalcohol can be used. One type of urethane (meth)acrylate resin may be used alone, or two or more types may be used in combination.

[0041] In the synthesis of a urethane (meth)acrylate resin, when a (meth)acryloyl group is introduced, for example, a method of reacting a terminal isocyanato group with a hydroxyl group-containing (meth)acrylic compound, or a method of reacting a terminal hydroxyl group with an isocyanato group-containing (meth)acrylic compound can be used. The hydroxyl group-containing (meth)acrylic compound and the isocyanato group-containing (meth)acrylic compound may each be used alone or in combination of two or more.

[0042] Examples of the hydroxyl group-containing (meth)acrylic compound include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, caprolactone-modified hydroxyalkyl (meth)acrylate, polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, tris(hydroxyethyl)isocyanuric acid di(meth)acrylate, pentaerythritol tri(meth)acrylate, glycerin mono(meth)acrylate, and hydroxyethyl acrylamide, of which 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, caprolactone-modified hydroxyalkyl (meth)acrylate, and hydroxyethyl acrylamide are preferred.

[0043] Examples of the isocyanato group-containing (meth)acrylic compound include 2-(meth)acryloyloxyethyl isocyanate, 2-(meth)acryloyloxypropyl isocyanate, and 1,1-bis(acryloyloxymethyl)ethyl isocyanate.

[0044] After synthesis of the urethane (meth)acrylate resin, the unreacted hydroxyl group-containing (meth)acrylic compound or the unreacted isocyanato group-containing (meth)acrylic compound can be used as the ethylenically unsaturated monomer described below.

[0045] The number average molecular weight (Mn) of the urethane resin is preferably 500 or more, more preferably 700 or more, even more preferably 1,000 or more, and preferably 30,000 or less, more preferably 25,000 or less, and even more preferably 20,000 or less. Any combination of these lower and upper limits may be used. The number average molecular weight of the urethane resin is preferably 500 to 30,000, more preferably 700 to 25,000, and even more preferably 1,000 to 20,000. If the number average molecular weight of the urethane resin is 500 to 30,000, the mechanical strength and erosion resistance of the coating will be better.

[0046] The protective coating composition preferably contains 10% by mass or more of a urethane resin, more preferably 20% by mass or more, and even more preferably 30% by mass or more. The protective coating composition preferably contains 90% by mass or less of a urethane resin, more preferably 80% by mass or less, and even more preferably 70% by mass or less. Any combination of these lower and upper limits may be used. The protective coating composition preferably contains 10% to 90% by mass of a urethane resin, more preferably 20% to 80% by mass, and even more preferably 30% to 70% by mass. When the urethane resin content is 10% by mass or more, the erosion resistance of the coating film is improved. When the urethane resin content is 90% by mass or less, the coatability of the protective coating composition is good. In the present disclosure, the urethane resin content is calculated as solids content.

[0047] <Epoxy (meth)acrylate resin> In one embodiment, the protective coating composition further comprises an epoxy (meth)acrylate resin. The epoxy (meth)acrylate resin is generally a compound having an ethylenically unsaturated bond obtained by a ring-opening reaction between the epoxy group of an epoxy compound having two or more epoxy groups and the carboxy group of an unsaturated monobasic acid having an ethylenically unsaturated bond and a carboxy group. The epoxy (meth)acrylate resin may be used alone or in combination of two or more.

[0048] The epoxy compound is not particularly limited as long as it has two or more epoxy groups. For example, at least one selected from bisphenol-type epoxy compounds, hydrogenated bisphenol-type epoxy compounds, and novolac phenol-type epoxy compounds can be used. These epoxy compounds can further improve the mechanical strength and erosion resistance of the coating.

[0049] Examples of bisphenol-type epoxy compounds include those obtained by reacting a bisphenol compound such as bisphenol A, bisphenol F, bisphenol S, and tetrabromobisphenol A with epichlorohydrin or methylepichlorohydrin, and those obtained by reacting one or more glycidyl ethers of the above bisphenol compounds, one or more condensates of the above bisphenol compounds, and epichlorohydrin or methylepichlorohydrin.

[0050] Examples of hydrogenated bisphenol epoxy compounds include those obtained by reacting hydrogenated bisphenol with epichlorohydrin or methylepichlorohydrin, and those obtained by reacting a glycidyl ether of hydrogenated bisphenol A with a bisphenol compound such as bisphenol A, bisphenol F, bisphenol S, or tetrabromobisphenol A.

[0051] Examples of novolak phenol type epoxy compounds include those obtained by reacting phenol novolak or cresol novolak with epichlorohydrin or methyl epichlorohydrin.

[0052] From the viewpoint of the mechanical strength of the coating, the epoxy compound is preferably at least one selected from the group consisting of bisphenol A epoxy resins and hydrogenated bisphenol A epoxy resins.

[0053] The unsaturated monobasic acid is not particularly limited as long as it is a monocarboxylic acid having an ethylenically unsaturated bond. Examples of the unsaturated monobasic acid include (meth)acrylic acid, crotonic acid, and cinnamic acid. From the viewpoint of the mechanical strength and erosion resistance of the coating, the unsaturated monobasic acid is more preferably (meth)acrylic acid, and from the viewpoint of the mechanical strength of the coating, methacrylic acid is more preferably.

[0054] The amount of the unsaturated monobasic acid used is preferably 0.3 to 1.5 mol, more preferably 0.4 to 1.2 mol, and particularly preferably 0.5 to 1.0 mol, of the total carboxyl groups of the unsaturated monobasic acid relative to 1 mol of the total epoxy groups of the epoxy compound. If the amount of the unsaturated monobasic acid used is within the above range, a coating having high hardness can be obtained.

[0055] The epoxy (meth)acrylate resin can be synthesized by a known synthesis method, for example, by dissolving an epoxy compound and an unsaturated monobasic acid in a solvent as needed in the presence of an esterification catalyst and reacting them at 70 to 150°C, preferably 80 to 140°C, and more preferably 90 to 130°C.

[0056] Examples of the esterification catalyst include tertiary amines such as triethylamine, N,N-dimethylbenzylamine, N,N-dimethylaniline, 2,4,6-tris(dimethylaminomethyl)phenol, and diazabicyclooctane; phosphorus compounds such as triphenylphosphine and benzyltriphenylphosphonium chloride; and diethylamine hydrochloride. One type of esterification catalyst may be used alone, or two or more types may be used in combination.

[0057] Any unreacted unsaturated monobasic acid remaining after synthesis of the epoxy (meth)acrylate resin can be used as an ethylenically unsaturated monomer, as described below.

[0058] The number average molecular weight (Mn) of the epoxy (meth)acrylate resin is not particularly limited, but is preferably 500 to 30,000, more preferably 700 to 25,000, and even more preferably 1,000 to 20,000. If the number average molecular weight of the epoxy (meth)acrylate resin is 500 to 30,000, the mechanical strength and erosion resistance of the coating film will be better.

[0059] In one embodiment, the protective coating composition contains 1% to 80% by weight, preferably 3% to 70% by weight, and more preferably 5% to 60% by weight of an epoxy (meth)acrylate resin. When the content of the epoxy (meth)acrylate resin is 1% by weight or more, the mechanical strength of the coating can be increased. When the content of the epoxy (meth)acrylate resin is 80% by weight or less, the elongation properties of the coating can be increased. In the present disclosure, the content of the epoxy (meth)acrylate resin is calculated as solid content.

[0060]

[0023] The protective coating composition includes an ethylenically unsaturated monomer as a diluent monomer. The diluent monomer adjusts the viscosity of the protective coating composition, thereby improving workability and coatability. The diluent monomer may be used alone or in combination of two or more.

[0061] Examples of the ethylenically unsaturated monomer include vinyl compounds such as styrene, vinyltoluene, t-butylstyrene, methoxystyrene, divinylbenzene, vinylnaphthalene, and acenaphthylene; diene compounds such as butadiene, 2,3-dimethylbutadiene, isoprene, and chloroprene; methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, t-butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate. (Meth)acrylate compounds such as acrylate, isodecyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, stearyl (meth)acrylate, cyclohexyl (meth)acrylate, furfuryl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, phenyl (meth)acrylate, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, allyl (meth)acrylate, isobornyl (meth)acrylate, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, tricyclodecanol di(meth)acrylate, and trimethylolpropane tri(meth)acrylate; (meth)acrylamide, N,N-dimethyl (meth)acrylamide unsaturated fatty acids such as oleic acid, linoleic acid, linolenic acid, arachidonic acid, eicosapentaenoic acid, docosahexaenoic acid, and sorbic acid; unsaturated dicarboxylic acids such as fumaric acid and maleic acid; unsaturated dicarboxylic acid diesters such as diethyl citraconic acid; monomaleimide compounds such as N-phenylmaleimide; N-(meth)acryloylphthalimide; cinnamic acid; and dihydroxycinnamic acid.

[0062] From the viewpoints of the curing rate and the mechanical strength of the coating, the ethylenically unsaturated monomer is preferably at least one selected from the group consisting of styrene, vinyltoluene, methyl(meth)acrylate, ethyl(meth)acrylate, propyl(meth)acrylate, t-butyl(meth)acrylate, phenyl(meth)acrylate, isobornyl(meth)acrylate, and benzyl(meth)acrylate, and more preferably at least one selected from the group consisting of styrene, vinyltoluene, t-butyl methacrylate, and isobornyl acrylate.

[0063] The content of the ethylenically unsaturated monomer is preferably 10% by mass to 95% by mass, more preferably 30% by mass to 90% by mass, and even more preferably 50% by mass to 80% by mass, based on the total of the urethane resin, the epoxy (meth)acrylate resin, and the ethylenically unsaturated monomer. When the content of the ethylenically unsaturated monomer is within the above range, the mechanical strength of the coating can be further increased.

[0064] <Curing Agent> The protective coating composition may contain a radical polymerization initiator as a curing agent to promote curing. Adding the radical polymerization initiator to the protective coating composition initiates curing of the protective coating composition. Therefore, for example, when storing the protective coating composition, it is desirable to add the radical polymerization initiator to the protective coating composition immediately before curing of the protective coating composition. When the protective coating composition is stored under conditions that do not initiate a radical polymerization reaction, from the perspective of work efficiency, a curing agent can also be incorporated into the protective coating composition in advance. One type of curing agent may be used alone, or two or more types may be used in combination.

[0065] The radical polymerization initiator is not particularly limited and can be appropriately selected depending on the application, curing conditions, etc. Examples of the radical polymerization initiator include a thermal radical initiator and a photoradical initiator, and a thermal radical initiator is preferred from the viewpoint of workability.

[0066] Examples of the thermal radical initiator include organic peroxides such as diacyl peroxides such as benzoyl peroxide; peroxyesters such as t-butyl peroxybenzoate; hydroperoxides such as cumene hydroperoxide; dialkyl peroxides such as dicumyl peroxide; ketone peroxides such as methyl ethyl ketone peroxide and acetylacetone peroxide; peroxyketals such as 1,1-dialkylperoxycyclohexane; alkyl peresters such as alkyl peroxydecanoate; and percarbonates such as peroxydicarbonate.

[0067] The amount of radical polymerization initiator used is preferably 0.1 to 10 parts by mass, more preferably 0.5 to 8 parts by mass, and even more preferably 0.5 to 5 parts by mass, per 100 parts by mass of the total of the urethane resin, epoxy (meth)acrylate resin, and ethylenically unsaturated monomer. When the content of the radical polymerization initiator is 0.1 part by mass or more, curing of the protective coating composition can proceed quickly. When the content of the radical polymerization initiator is 10 parts by mass or less, a good balance between productivity and cost can be achieved.

[0068] The protective coating composition may contain a curing accelerator to accelerate the radical polymerization reaction of the protective coating composition. The curing accelerators may be used alone or in combination of two or more.

[0069] Examples of the curing accelerator include salts of metal elements and organic acids. Examples of the metal elements include cobalt, vanadium, and manganese. Specific examples of the curing accelerator include manganese octoate, cobalt octoate, zinc octoate, vanadium octoate, cobalt naphthenate, copper naphthenate, barium naphthenate, vanadium acetoacetate, cobalt acetoacetate, and iron acetoacetate. Preferred curing accelerators are manganese octoate, cobalt octoate, and cobalt naphthenate.

[0070] The amount of the curing accelerator used is preferably 0.01 to 6.0 parts by mass, more preferably 0.02 to 4.0 parts by mass, and even more preferably 0.03 to 3.0 parts by mass, per 100 parts by mass of the total of the urethane resin, epoxy (meth)acrylate resin, and ethylenically unsaturated monomer. By using an amount of the curing accelerator within this range, the radical polymerization reaction of the protective coating composition can proceed rapidly at low to room temperature, for example, in the temperature range of 5°C to 40°C.

[0071] <Solvent> The protective coating composition may contain a solvent. The solvent may be derived from the solvent used in the synthesis of the urethane resin or epoxy (meth)acrylate resin. Examples of solvents include esters such as n-butyl acetate and n-propyl acetate; and aromatic hydrocarbons such as benzene, toluene, and xylene. In the present disclosure, the solvent does not include the diluent monomer. The content of the solvent can be determined appropriately depending on the application and application method. For example, the content of the solvent can be set so that the solids content of the protective coating composition is 10% to 90% by mass, 20% to 80% by mass, or 30% to 70% by mass.

[0072] Additives The protective coating composition may further comprise additives, such as dispersants, fillers, thixotropic agents, thixotropic aids, colorants, and polymerization inhibitors.

[0073] An example of the dispersant is DISPERBYK-2152 (manufactured by BYK Japan Co., Ltd.).

[0074] Examples of fillers include calcium carbonate, aluminum hydroxide, fly ash, barium sulfate, talc, clay, glass flakes, glass powder, and wood flour. Hollow fillers such as glass microballoons, saran resin microballoons, acrylonitrile microballoons, and shirasu balloons can also be used as fillers.

[0075] Examples of thixotropic agents include inorganic powders such as silica and clay. The thixotropic agent can adjust the rheological properties of the protective coating composition to improve its coatability. When the protective coating composition contains particles such as fillers and pigments, the thixotropic agent can also inhibit the settling of these particles, thereby improving the storage stability of the protective coating composition.

[0076] Examples of thixotropy-imparting aids include polyethylene glycol, glycerin, polyhydroxycarboxylic acid amide, organic quaternary ammonium salt, and BYK-R-605 (manufactured by BYK Japan Co., Ltd.).

[0077] Examples of colorants include organic pigments, inorganic pigments such as titanium oxide, and dyes.

[0078] Examples of the polymerization inhibitor include hydroquinone, trimethylhydroquinone, p-benzoquinone, naphthoquinone, tert-butylhydroquinone, catechol, p-tert-butylcatechol, and 2,6-di-tert-butyl-4-methylphenol.

[0079] Other additives include, for example, antifoaming agents, ultraviolet absorbers, light stabilizers, thickeners, and plasticizers.

[0080] <Viscosity> The viscosity of the protective coating composition is preferably 10 mPa·s to 20,000 mPa·s, more preferably 50 mPa·s to 15,000 mPa·s, and even more preferably 100 mPa·s to 10,000 mPa·s. By setting the viscosity of the protective coating composition within the above range, workability and coatability can be improved. In the present disclosure, the viscosity of the protective coating composition is defined as the shear viscosity at 25°C and a rotation speed of 100 rpm using a cone and plate viscometer in accordance with JIS K 5600-2-3:2014.

[0081] Each step of the method for manufacturing a wind power generation blade will be described below with reference to FIG.

[0082] <Coating Step> In the coating step, the protective coating composition is applied to at least a portion of the mold surface to form a film.

[0083] Figure 2(a) shows a cross-sectional view of a mold 20. The mold 20 has a mold surface 22 and includes an internal heater 24 for heating the stack during the heating process. The mold 20 in Figure 2 is shown forming a portion of a wind power blade. As shown in Figure 2(b), a protective coating composition is applied to a portion of the mold surface 22 to form a coating 12. The coating 12 is formed on a portion of the mold surface 22 that corresponds to the leading edge of the wind power blade.

[0084] The protective coating composition can be applied to the surface of the mold using known application means, such as a spray, a brush, a roll, a trowel, a spatula, or a syringe.

[0085] The coating formed by application may be pre-cured, for example, at 5° C. to 40° C. for 10 minutes to 72 hours.

[0086] The thickness of the coating may vary depending on the shape of the wind power blade, the required mechanical strength, etc. In one embodiment, the thickness of the coating on the wind power blade is 0.5 mm or more. In one embodiment, the thickness of the coating is 2 mm or less. Any combination of these lower limit values ​​and upper limit values ​​may be used. In one embodiment, the thickness of the coating is 0.5 mm to 2 mm. By setting the thickness of the coating to 0.5 mm or more and 2 mm or less, a coating with high mechanical strength can be imparted to the wind power blade.

[0087] In one embodiment, the coating is partially formed on the mold surface. The coating is, for example, a leading edge protector for a wind turbine blade. In this embodiment, the leading edge protector can also be a gel coat. That is, the coating functions as both a leading edge protector and a gel coat.

[0088] A separate coating may be formed on the mold surface other than the coating. In one embodiment, the coating is a leading edge protectant and the separate coating is a gel coat used on typical wind turbine blades.

[0089] After the protective coating composition is partially applied to the mold surface to form a film, another coating composition may be applied to cover the film and at least a portion of the mold surface to form a second coating, such as a gel coat agent typically used on wind power blades.

[0090] In the placement step, a fiber-containing substrate impregnated with a matrix resin is placed on the coating to form a stack. Examples of the fiber-containing substrate impregnated with a matrix resin include prepregs containing glass fibers or carbon fibers.

[0091] The disposing step may include impregnating the fibrous substrate with a matrix resin on the coating to form a fibrous substrate. Impregnation can be performed using, for example, a hand lay-up method or a vacuum-assisted impregnation method.

[0092] Examples of fibrous substrates include substrates containing fibers such as glass fiber, carbon fiber, polyester fiber, aramid fiber, vinylon fiber, and cellulose nanofiber. Examples of fibrous substrates that can be used include short fibers, long fibers, twisted yarns, chopped strand mats, continuous strand mats, rovings, nonwoven fabrics, roving cloths, woven fabrics, braided fabrics, three-dimensional woven fabrics, and three-dimensional braided fabrics. Examples of nonwoven fabrics include spunbond nonwoven fabrics and meltblown nonwoven fabrics. Examples of woven fabrics include plain weaves, satin weaves, and twill weaves.

[0093] The matrix resin may be any resin commonly used in FRP molding, such as a thermosetting epoxy resin.

[0094] 2(c) and 2(d), a method for forming a fiber-containing substrate by impregnating a fiber substrate with a matrix resin on a coating using a vacuum-assisted impregnation method is described. As shown in FIG. 2(c), a fiber substrate 142 is placed to cover the coating 12 and the mold surface 22. As shown in FIG. 2(d), a sheet 26 is placed on the fiber substrate 142, creating an airtight space between the sheet 26 and the mold surface 22. An exhaust port 28 is provided at one end of the sheet 26. The exhaust port 28 is connected to a vacuum pump, and by operating the vacuum pump, the space between the sheet 26 and the mold surface 22 can be reduced in pressure. A matrix resin supply device 30 containing a matrix resin 144 is installed at the other end of the sheet. By opening a valve 32 and operating the vacuum pump to reduce the pressure in the space between the sheet 26 and the mold surface 22, the fiber substrate 142 is impregnated with the matrix resin 144, thereby forming a fiber-containing substrate 14 on the coating 12. The fiber-containing substrate 14 is mated with the coating 12 to form a stack 16 .

[0095] <Heating Step> In the heating step, the stack is heated to form a molded article in which the coating and the fiber-containing substrate are bonded. The coating includes a cured product of the protective coating composition, i.e., a cured coating. The cured coating is more firmly bonded to the fiber-containing substrate, resulting in a molded article with superior erosion resistance.

[0096] As shown in Fig. 2(e), the heater 24 is operated to heat the stack 16. As a result, the coating 12 and the fiber-containing substrate 14 are bonded together to form the wind power generation blade 10 shown in Fig. 1.

[0097] The heating temperature can be, for example, 50° C. to 200° C. The heating time can be, for example, 30 minutes to 24 hours.

[0098] When the fiber-containing substrate is a prepreg, for example, autoclave molding or press molding can be used.

[0099] In one embodiment, the coating is disposed at least on the tip portion of the leading edge of the wind power blade. The tip portion of the leading edge refers to, for example, a portion of the leading edge extending from the end of the wind power blade farthest from the rotation axis by 1% to 50%, 5% to 40%, or 10% to 30% of the blade length of the wind power blade. In this embodiment, the coating functions as a leading edge protection material. This embodiment is suitable for large wind power blades, whose tip portions move at high speeds and are therefore prone to erosion. The coating can also be disposed on the entire leading edge, including the tip portion, or on the entire surface of the wind power blade.

[0100] The blade length of the wind power generation blade is preferably 10 m or more, more preferably 20 m or more, and even more preferably 30 m or more. The blade length of the wind power generation blade may be, for example, 140 m or less, 100 m or less, or 80 m or less. Any combination of these lower limit values ​​and upper limit values ​​may be used. In one embodiment, the blade length of the wind power generation blade is 10 m to 140 m, 20 m to 100 m, or 30 m to 80 m.

[0101] The protective coating composition of the present disclosure can be suitably used to form leading edge protective materials for wind power blades.The protective coating composition of the present disclosure can also be suitably used in a variety of applications where erosion resistance is desired, such as airplane propellers, fins for coolers, high-speed railway vehicle components, pipes in chemical plants, chemical storage tanks, and concrete repair materials.

[0102] Examples, comparative examples, and reference examples related to the present invention are shown below, but the present invention is not limited to these.

[0103] [Viscosity at 25°C] The viscosity of the protective coating composition was evaluated by the following procedure: Shear viscosity was measured at 25°C and a rotation speed of 100 rpm using a cone-plate viscometer (RE-215U, manufactured by Toki Sangyo Co., Ltd., rotor: 1°34' x R24) in accordance with JIS K 5600-2-3:2014 "General test methods for paints - Part 2: Properties and stability of paints - Section 3: Viscosity (cone-plate viscometer method)."

[0104] The physical properties of the molded articles were evaluated according to the following procedures.

[0105] [Erosion Resistance] Using a high-pressure washer (SH-0807, manufactured by Super Kogyo Co., Ltd.), a water pressure of 6.0 MPa, a water flow rate of 6 L / min, and a test piece-to-nozzle distance of 7 cm were used to directly hit a 50 mm × 60 mm × 2 mm (thickness) test piece with a continuous water flow at 23°C for 30 minutes, and the test piece was then visually inspected for damage. The time required for damage to occur was taken as the erosion resistance.

[0106] [Adhesion strength] In accordance with JIS K 5600-5-7:2014 "General test methods for paints - Part 5: Mechanical properties of coating films - Section 7: Adhesion (pull-off method)", a coating was formed to a thickness of 0.5 mm on a standard glass epoxy plate (60 mm x 150 mm x 2 mm (thickness), manufactured by Nippon Test Panel Co., Ltd.), and a dolly (diameter 20 mm, made of aluminum) was fixed to the coating using an adhesive (Metallock (trademark), manufactured by Cemedine Co., Ltd.), and the adhesive strength was measured using an adhesion tester (Positest AT-A, manufactured by COTEC Co., Ltd.). The adhesive strength was defined as the average value measured with N = 3.

[0107] [Heat and humidity cycle resistance] A test piece (50 mm x 80 mm x 2 mm (thickness)) was placed in a thermo-humidistat chamber (PL-2J, manufactured by Espec Corporation) and subjected to 100 cycles of repeated heat and humidity cycles at -40°C for 6 hours and at 60°C and 98% relative humidity for 6 hours. After this, the appearance was visually inspected for the presence or absence of chalking, blisters, and cracks. A: None of chalking, blisters, or cracks was observed. B: No cracks were observed, and neither chalking nor blisters were observed. C: No cracks were observed. D: Cracks were observed.

[0108] The materials used in the synthesis of the urethane (meth)acrylate resin and the epoxy (meth)acrylate resin are shown in Table 1.

[0109]

[0110] The materials used in preparing the protective coating compositions are as follows: Dry silica Reolosil PM-20L (Tokuyama Corporation) Titanium oxide PFC-105 (Ishihara Sangyo Kaisha, Ltd.) Glass powder CF0033 (Takara Standard Co., Ltd.) Glass Flake™ RCF-160N (Nippon Sheet Glass Co., Ltd.) DISPERBYK-2152 (BYK Japan Co., Ltd.) 8% cobalt octoate (8% cobalt hexoate, Toei Kako Co., Ltd.) Hardener 328E (t-butyl peroxybenzoate, cumene hydroperoxide mixture, Kayaku Nouryon Co., Ltd.) Percumyl™ H-80 (cumene hydroperoxide, NOF Corporation)

[0111] Urethane (meth)acrylate resin and epoxy (meth)acrylate resin were synthesized by the following procedure.

[0112] Synthesis Example 1 Urethane (meth)acrylate Resin UAc-1 A flask equipped with a stirrer, reflux condenser, thermometer, and gas inlet tube was charged with 142 g of 4,4'-methylenebiscyclohexyl diisocyanate (Desmodur W, manufactured by Sumika Covestro Urethane Co., Ltd.), 411 g of polycarbonate diol (ETERNACOLL PH-100, manufactured by UBE Corporation), and 0.4 g of dibutyltin dilaurate, and the mixture was reacted for 4 hours at 80°C with heating and stirring. Thereafter, 46 g of 2-hydroxyethyl methacrylate was charged, and the mixture was reacted for 4 hours at 80°C with heating and stirring while blowing in dry air, to obtain urethane (meth)acrylate resin UAc-1.

[0113] [Synthesis Examples 2 to 7: Urethane (meth)acrylate resins UAc-2 to UAc-7] Urethane (meth)acrylate resins UAc-2 to UAc-7 were obtained in the same manner as in Synthesis Example 1, except that the raw materials and their blending amounts were as shown in Table 2.

[0114] Synthesis Example 8 Epoxy (meth)acrylate resin EAc-1 A flask equipped with a stirrer, a reflux condenser, a thermometer, and a gas inlet tube was charged with 683 g of bisphenol A-type epoxy resin (Epomic R140, manufactured by Mitsui Fine Chemicals, Inc.), 313 g of methacrylic acid, 3.0 g of triethylamine, and 0.6 g of hydroquinone, and the mixture was reacted at 120°C while blowing air into it. When the acid value reached 5 mgKOH / g or less, the mixture was cooled, yielding epoxy (meth)acrylate resin EAc-1.

[0115] Synthesis Example 9 Epoxy (meth)acrylate resin EAc-2 Epoxy (meth)acrylate resin EAc-2 was obtained in the same manner as in Synthesis Example 8, except that the raw materials and their amounts were as shown in Table 2.

[0116]

[0117] A protective coating composition was prepared by the following procedure.

[0118] Example 1 A protective coating composition of Example 1 was obtained by adding 40 g of the urethane (meth)acrylate resin UAc-1 obtained in Synthesis Example 1 above, 60 g of vinyl toluene, 0.5 g of 8% cobalt octylate, and 1.5 g of curing agent 328E, and stirring the mixture at 2000 rpm for 1 minute using a planetary centrifugal mixer.

[0119] The protective coating composition was poured into a 2 mm deep silicone mold and left for 3 hours at 23°C for pre-cure and 6 hours at 70°C for post-cure to obtain a molded product of the protective coating composition. The pre-cure corresponds to the process of applying the protective coating composition to the mold surface to form a coating, and the post-cure corresponds to the process of heating the stack of the coating and the fiber-containing substrate. The evaluation results of the protective coating composition and the molded product are shown in Table 3.

[0120] [Examples 2 to 15, Comparative Examples 1 to 4] Protective coating compositions were obtained in the same manner as in Example 1, except that the raw materials and their blending amounts were as shown in Table 3. Molded articles were obtained from the obtained protective coating compositions in the same manner as in Example 1. The evaluation results of the protective coating compositions and the molded articles are shown in Table 3.

[0121] [Reference Examples 1 to 3] Using the protective coating composition of Example 1, molded articles were obtained by pre-curing only, without post-curing, under the conditions shown in Table 3. The evaluation results of the molded articles are shown in Table 3.

[0122] Example 16 A molded article was obtained in the same manner as in Example 1, except that the protective coating composition of Example 1 was poured into a silicone mold with a depth of 0.1 mm. The evaluation results of the molded article are shown in Table 3.

[0123]

[0124]

[0125]

[0126] The protective coating compositions of the present disclosure can be suitably used in the manufacture of leading edge protection for wind power blades.

[0127] REFERENCE SIGNS LIST 10 Wind power generation blade 12 Coating 14 Fiber-containing substrate 142 Fiber substrate 144 Matrix resin 16 Stack 20 Mold 22 Mold surface 24 Heater 26 Sheet 28 Exhaust port 30 Matrix resin supply device 32 Valve

Claims

1. A protective coating composition comprising a urethane resin having a urethane structure and a carbonate structure in the same molecule, and an ethylenically unsaturated compound, wherein the urethane resin is a urethane (meth)acrylate resin, and the cured product of the protective coating composition has an erosion resistance of 1.5 hours or more.

2. The protective coating composition of claim 1 further comprising an epoxy (meth)acrylate resin.

3. The protective coating composition according to claim 1 or 2, comprising 10% to 90% by weight of the urethane resin.

4. The protective coating composition according to claim 1 or 2, wherein the urethane resin is a reaction product of a composition containing a polycarbonate polyol and a polyisocyanate, and the molar ratio (OH [mol] / NCO [mol]) of the hydroxyl groups of the polycarbonate polyol to the isocyanato groups of the polyisocyanate is 0.5 to 0.

9.

5. The protective coating composition of claim 4, wherein said polycarbonate polyol has a number average molecular weight of from 500 to 10,000.

6. The protective coating composition of claim 4, wherein said polyisocyanate comprises a cycloaliphatic polyisocyanate.

7. The protective coating composition of claim 1 or 2, wherein the urethane resin has a number average molecular weight of 500 to 30,000.

8. The protective coating composition of claim 1 or 2, wherein the protective coating composition is a leading edge protectant for a wind power blade.

9. The protective coating composition of claim 8, wherein the wind power blade has a blade length of 10 m or more.

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