Protective film for blade of wind turbine generator, blade of wind turbine generator, and wind turbine generator

Abstract

To provide a protective film for a blade of a wind turbine generator by which it is possible to reduce environmental load.SOLUTION: A protective film for a blade of a wind turbine generator includes a protective layer containing a biodegradable resin, and an adhesive layer disposed on one surface of the protective layer.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a protective film for wind turbine blades, a wind turbine blade, and a wind turbine. [Background technology]

[0002] The blades of wind turbines are exposed to ultraviolet rays from sunlight, wind, rain, snow, hail, sleet, lightning, seawater, gas, sand, dust, and other elements. They can also be affected by collisions with birds, insects, and flying objects. Because the blades are exposed to such harsh environments, they can suffer from problems such as damage, deformation, surface contamination, and surface peeling over time. Furthermore, because the blades rotate at high speeds, the likelihood of damage, deformation, surface contamination, and surface peeling increases. These problems can lead to a decrease in power generation efficiency. In the worst case scenario, the blades can break or even fall off.

[0003] Therefore, in order to protect the blade, a technique has been proposed in which a protective film or protective cover is placed on the surface of the blade (Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2012 / 102294 [Patent Document 2] Special Publication No. 2018-503775 Summary of the Invention [Problem to be solved by the invention]

[0005] It is important to inspect the blades of wind turbines regularly and, if necessary, perform maintenance such as repairs. Therefore, when the protective film deteriorates, it is replaced. The protective film is made of resins such as polyurethane, and is discarded after being peeled off from the blades. Furthermore, because wind turbines are installed outdoors, the protective film is often already deteriorated when it is replaced. Therefore, when the protective film is peeled off, some of the protective film breaks into small pieces, making it difficult to completely recover the protective film after peeling. Furthermore, deterioration of the protective film can cause parts of the protective film to peel off from the blade surface.

[0006] In recent years, environmental problems caused by waste plastics and microplastics have been attracting attention. In particular, marine pollution caused by waste plastics and microplastics is serious, and the widespread use of biodegradable resins is expected.

[0007] The present disclosure has been made in view of the above circumstances, and a main object of the present disclosure is to provide a protective film for wind turbine blades that can reduce the environmental load. [Means for solving the problem]

[0008] One embodiment of the present disclosure provides a protective film for wind turbine blades, the protective film having a protective layer containing a biodegradable resin and an adhesive layer disposed on one surface of the protective layer.

[0009] Another embodiment of the present disclosure provides a blade for a wind turbine generator having the above-described blade protective film on its surface.

[0010] Another embodiment of the present disclosure provides a wind turbine generator including the blade described above. [Effects of the Invention]

[0011] The protective film for wind turbine blades according to the present disclosure has the effect of reducing the environmental load. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a schematic cross-sectional view illustrating a protective film for wind turbine blades according to the present disclosure. [Figure 2] 1A and 1B are a schematic plan view and a cross-sectional view illustrating a protective film for wind turbine blades according to the present disclosure. [Figure 3] 1A and 1B are a schematic plan view and a cross-sectional view illustrating a protective film for wind turbine blades according to the present disclosure. [Figure 4] 1 is a schematic cross-sectional view illustrating a protective film for wind turbine blades according to the present disclosure. [Figure 5] 1A and 1B are schematic perspective and cross-sectional views illustrating blades of a wind turbine generator according to the present disclosure. [Figure 6] 1 is a schematic diagram illustrating a wind turbine generator according to the present disclosure; DETAILED DESCRIPTION OF THE INVENTION

[0013] Embodiments of the present disclosure will be described below with reference to the drawings and the like. However, the present disclosure can be implemented in many different forms and should not be construed as being limited to the description of the embodiments exemplified below. Furthermore, to clarify the explanation, the drawings may show the width, thickness, shape, etc. of each part schematically compared to the actual form, but these are merely examples and should not be construed as limiting the interpretation of the present disclosure. Furthermore, in this specification and each drawing, elements similar to those described above with reference to the previous drawings may be designated by the same reference numerals, and detailed descriptions may be omitted as appropriate.

[0014] In this specification, when describing a mode in which another component is placed on a certain component, the term "above" or "below" is used, unless otherwise specified, to include both a case in which another component is placed directly above or below a certain component so as to be in contact with the component, and a case in which another component is placed above or below a certain component with another component interposed therebetween. Also, in this specification, when describing a mode in which another component is placed on the surface of a certain component, the term "on the surface side" or "on the surface" is used, unless otherwise specified, to include both a case in which another component is placed directly above or below a certain component so as to be in contact with the component, and a case in which another component is placed above or below a certain component with another component interposed therebetween.

[0015] In this specification, the term "film" also includes a member called a "sheet."

[0016] The protective film for wind turbine blades, the wind turbine blades, and the wind turbine according to the present disclosure will be described in detail below.

[0017] A. Protective film for wind turbine blades A protective film for wind turbine blades according to the present disclosure includes a protective layer containing a biodegradable resin and an adhesive layer disposed on one surface of the protective layer.

[0018] In this specification, the "protective film for wind turbine blades" may be abbreviated to simply "protective film".

[0019] 1 is a schematic cross-sectional view illustrating a protective film according to the present disclosure. The protective film 10 in FIG. 1 has a protective layer 1 containing a biodegradable resin and an adhesive layer 2 disposed on one side of the protective layer 1.

[0020] In the present disclosure, the protective layer contains a biodegradable resin, thereby reducing the environmental impact. As described above, it is important to regularly inspect the blades of wind turbine generators and, if necessary, perform maintenance such as repairs. Therefore, the protective film is replaced as needed. The protective film peeled off from the blade for replacement is discarded. However, in the present disclosure, the protective layer contains a biodegradable resin, thereby reducing the environmental impact of the discarded protective film. Furthermore, because wind turbine generators are installed outdoors, the protective film is often deteriorated when replaced. Therefore, when peeled off, part of the protective film breaks into small pieces, which may make it difficult to completely recover the protective film after peeling. Furthermore, deterioration of the protective film may cause part of the protective film to peel off from the blade surface. Even in such cases, the protective layer contains a biodegradable resin, thereby reducing the environmental impact.

[0021] Hereinafter, the protective film according to the present disclosure will be described in detail for each component.

[0022] 1.Protective layer (1) Protective layer material (a) Biodegradable resin The protective layer in the present disclosure contains a biodegradable resin. The biodegradable resin may be a resin that is biodegradable itself, or a resin that is non-biodegradable itself but has been given biodegradability by an additive. Hereinafter, the additive that gives biodegradability may be referred to as a biodegradable additive.

[0023] In this specification, biodegradable resins do not include oxidatively degradable plastics, which are also called oxo-degradable plastics.

[0024] When the resin itself is biodegradable, examples of the biodegradable resin include polylactic acid resins, polyhydroxyalkanoate resins, 3-hydroxybutyric acid-3-hydroxyhexanoic acid copolymer polyester resins, polybutylene succinate resins, polybutylene adipate terephthalate resins, starch polyester resins, cellulose acetate resins, polyvinyl alcohol resins, polyglycolic acid resins, polybutylene succinate-co-adipate resins, polybutylene adipate terephthalate resins, and polyethylene terephthalate succinate resins.

[0025] When biodegradability is imparted by a biodegradable additive, the resin is not particularly limited, and examples thereof include polyolefin-based resins, polyurethane-based resins, polyethylene-based resins, polypropylene-based resins, polyethylene terephthalate-based resins, polytrimethylene terephthalate-based resins, polyvinyl chloride-based resins, polystyrene-based resins, acrylonitrile-butadiene-styrene-based resins, polycarbonate-based resins, polybutylene terephthalate-based resins, polyacetal-based resins, polymethyl methacrylate-based resins, polyphenylene sulfide-based resins, polyamide-based resins, phenol-based resins, and epoxy-based resins.

[0026] When biodegradability is imparted by a biodegradable additive, the biodegradable additive is not particularly limited, and examples thereof include polylactic acid, fatty acid polyester, polyamino acid, adipic acid, and dithiodipropionic acid.

[0027] The biodegradable resin may be a soil biodegradable resin or a marine biodegradable resin. For example, when the wind power generation device is installed on land, a soil biodegradable resin is preferably used. On the other hand, when the wind power generation device is installed offshore, a marine biodegradable resin is preferably used.

[0028] The content of the biodegradable resin in the protective layer is, for example, preferably 0.1 parts by mass or more, more preferably 1 part by mass or more, and even more preferably 10 parts by mass or more, relative to 100 parts by mass of the resin component in the protective layer. The content of the biodegradable resin in the protective layer may be 100 parts by mass relative to 100 parts by mass of the resin component in the protective layer.

[0029] When biodegradability is imparted by an additive, the resin is preferably a polyolefin-based resin. Polyolefin-based resins have high durability, so that deterioration of the performance of the protective film due to aging can be suppressed. Polyolefin-based resins will be described below.

[0030] (Polyolefin resin) The polyolefin-based resin may be obtained by polymerizing only an olefin, or may be obtained by copolymerizing an olefin with a monomer other than an olefin. That is, the polyolefin-based resin may be composed of only an olefin, or may be composed of an olefin and a monomer other than an olefin. Among these, the polyolefin-based resin is preferably composed of only an olefin.

[0031] Examples of polyolefin resins include polyethylene resins and polypropylene resins, with polyethylene resins being preferred.

[0032] The polyethylene resin may be a homopolymer of ethylene, a copolymer of ethylene and an α-olefin, or a copolymer of ethylene and a monomer other than an olefin.

[0033] In the copolymer of ethylene and an α-olefin, the α-olefin is preferably an α-olefin having 3 to 12 carbon atoms. Specific examples include propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-heptene, 4-methyl-pentene-1, 4-methyl-hexene-1, and 4,4-dimethylpentene-1. The α-olefin may be used alone or in combination of two or more. Among these, unbranched α-olefins are preferred, and unbranched α-olefins having 3 to 8 carbon atoms are more preferred. Specific examples include 1-propene, 1-butene, 1-pentene, 1-hexene, 1-heptene, and 1-octene. An α-olefin having 3 to 8 carbon atoms can impart good flexibility and good strength.

[0034] Specific examples of copolymers of ethylene and α-olefins include ethylene-propylene copolymer, ethylene-1-butene copolymer, ethylene-1-hexene copolymer, ethylene-1-octene copolymer, and ethylene-4-methyl-pentene-1 copolymer.

[0035] A specific example of a copolymer of ethylene and a monomer other than an olefin is an ethylene-vinyl acetate copolymer.

[0036] Examples of polyethylene resins include high-density polyethylene (HDPE), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), metallocene linear low-density polyethylene (M-LLDPE), and very low-density polyethylene (VLDPE). One type of polyethylene resin may be used alone, or two or more types may be used in combination.

[0037] Among these, low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), metallocene linear low-density polyethylene (M-LLDPE), and very low-density polyethylene (VLDPE) are preferred. They offer good flexibility, transparency, and processability. Because they can impart good flexibility to the protective layer, the protective layer of the protective film can absorb the impact of a collision with the blade, suppressing the occurrence of erosion. They can also improve conformability to the curved surface of the blade.

[0038] Metallocene linear low-density polyethylene (M-LLDPE) is synthesized using a single-site metallocene catalyst. This type of polyethylene resin has little branching in the side chains and a uniform distribution of comonomers. This allows for a narrow molecular weight distribution and low density, imparting flexibility and strength. In addition, the crystallinity distribution is narrow and the crystal size is uniform, so not only are there no large crystals, but the low density also means that the crystallinity itself is low. This results in excellent transparency.

[0039] The density of the polyethylene resin is not particularly limited. For example, the density of the polyethylene resin is 0.950 g / cm. 3 is less than or equal to 0.930 g / cm 3 It may be less than 0.925 g / cm 3 It may be less than 0.920 g / cm 3 or less. When the density of the polyethylene-based resin is in the above range, flexibility, transparency, and processability can be improved. Since good flexibility can be imparted to the protective layer, the protective layer of the protective film can absorb the impact caused by collision with the blade, and the occurrence of erosion can be suppressed. In addition, the ability to conform to the curved surface of the blade can be improved. Furthermore, when the density of the polyethylene-based resin is in the above range, the unit weight of the protective layer can be reduced, and the weight of the protective film can be reduced. On the other hand, the density of the polyethylene-based resin is, for example, 0.850 g / cm 3 or more, 0.870 g / cm 3 That is, the density of the polyethylene resin may be, for example, 0.850 g / cm 3More than 0.950g / cm 3 less than or equal to 0.850 g / cm 3 More than 0.930g / cm 3 It may be less than 0.870 g / cm 3 More than 0.925g / cm 3 It may be less than 0.870 g / cm 3 More than 0.920g / cm 3 It may be the following:

[0040] The density of polyethylene resins is measured by the pycnometer method in accordance with ISO 1183:2019.

[0041] The melting point of the polyethylene resin is not particularly limited. The melting point of the polyethylene resin is, for example, 130°C or lower. Polyolefin resins tend to become softer when their melting point is low. Therefore, if the melting point is within the above range, the protective layer can be imparted with good flexibility, and the protective layer of the protective film can absorb the impact caused by collision with the blade and suppress the occurrence of erosion. In addition, the ability to conform to the curved surface of the blade can be improved. On the other hand, the melting point of the polyethylene resin is, for example, 50°C or higher, and may be 60°C or higher. If the melting point is too low, heat resistance may be reduced.

[0042] The melting point of the resin is measured using a differential scanning calorimeter (DSC) in accordance with ISO 3146: 2000. If two or more melting point peaks are present, the higher temperature is taken as the melting point.

[0043] The melt mass flow rate (MFR) of the polyethylene resin at a temperature of 190°C is, for example, preferably 0.1 g / 10 min or more and 30 g / 10 min or less, more preferably 0.1 g / 10 min or more and 25 g / 10 min or less, and even more preferably 0.1 g / 10 min or more and 20 g / 10 min or less. When the MFR of the polyethylene resin is a predetermined value or less, the strength can be improved. Furthermore, when the MFR of the polyethylene resin is within the above range, the film-forming properties and flexibility can be improved.

[0044] The melt mass flow rate (MFR) of polyethylene resins is measured in accordance with ISO 1133-1:2011. The measurement conditions are Method A, temperature 190°C, and load 2.16 kg.

[0045] The polyolefin resin may be a crosslinked polyolefin resin or a non-crosslinked polyolefin resin, and the polyethylene resin may be a crosslinked polyethylene resin or a non-crosslinked polyethylene resin.

[0046] The cross-linked polyolefin resin refers to a cross-linked polyolefin resin, i.e., a polyolefin resin having cross-linked bonds, while the non-cross-linked polyolefin resin refers to a polyolefin resin that is not cross-linked.

[0047] Furthermore, the term "crosslinked polyethylene resin" refers to a polyethylene resin that has been crosslinked, i.e., a polyethylene resin having crosslinked bonds, while the term "non-crosslinked polyethylene resin" refers to a polyethylene resin that has not been crosslinked.

[0048] As a crosslinking method for crosslinking the polyolefin resin, a general crosslinking method can be applied, for example, a crosslinking method using a crosslinking agent, a silane crosslinking method using silanol condensation, and a crosslinking method using ionizing radiation. Among these, a crosslinking method using a crosslinking agent is preferred.

[0049] As the crosslinking agent, a general crosslinking agent can be used, for example, organic peroxides. Examples of organic peroxides include peroxycarbonates, peroxyketals, and dialkyl peroxides. Examples of peroxycarbonates include t-amyl-peroxy-2-ethylhexyl carbonate and t-butylperoxy-2-ethylhexyl carbonate. Examples of peroxyketals include n-butyl 4,4-di(t-butylperoxy)valerate, ethyl 3,3-di(t-butylperoxy)butyrate, and 2,2-di(t-butylperoxy)butane. Examples of dialkyl peroxides include di-t-butyl peroxide, t-butylcumyl peroxide, dicumyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, and 2,5-dimethyl-2,5-di(t-peroxy)hexyne-3. The crosslinking agent may be used alone or in combination of two or more.

[0050] In the resin composition used to form the protective layer, the content of the crosslinking agent is appropriately selected depending on the desired degree of crosslinking and the like.

[0051] In addition, in the crosslinking method using a crosslinking agent, a crosslinking aid may be used. By using the crosslinking aid, it is possible to promote an appropriate crosslinking reaction. Furthermore, the crosslinking aid reduces the crystallinity of the polyolefin resin, so that transparency can be maintained. As the crosslinking aid, a general crosslinking aid can be used, and for example, a polyfunctional monomer having a polymerizable functional group can be mentioned.

[0052] Among these, from the viewpoint of improving reactivity, the crosslinking aid is preferably a nurate ring-containing compound having two or more polymerizable functional groups in one molecule.

[0053] In the crosslinking aid, the number of polymerizable functional groups per molecule is, for example, preferably 2 to 6, and more preferably 2 to 3. If the number of polymerizable functional groups is too small, the crosslinking density may not be increased sufficiently. On the other hand, if the number of polymerizable functional groups is too large, the physical properties of the protective layer may be adversely affected, such as the protective layer becoming brittle after crosslinking treatment.

[0054] The polymerizable functional group is not particularly limited as long as it can react with the polyolefin resin as the base resin and impart a crosslinked structure, but among them, a group having a carbon-carbon double bond, an epoxy group, etc. Examples of the group having a carbon-carbon double bond include a vinyl group, a (meth)acryloyl group, a (meth)acryloyloxy group, and an allyl group.

[0055] Examples of crosslinking aids include polyallyl compounds, poly(meth)acryloxy compounds, and epoxy compounds. Examples of polyallyl compounds include triallyl isocyanurate (TAIC), triallyl cyanurate, diallyl phthalate, diallyl fumarate, and diallyl maleate. Examples of poly(meth)acryloxy compounds include trimethylolpropane trimethacrylate (TMPT), trimethylolpropane triacrylate (TMPTA), ethylene glycol diacrylate, ethylene glycol dimethacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, and 1,9-nonanediol diacrylate. Examples of epoxy compounds include epoxy compounds containing a double bond and an epoxy group, and epoxy compounds containing two or more epoxy groups. Examples of epoxy compounds containing a double bond and an epoxy group include glycidyl methacrylate and 4-hydroxybutyl acrylate glycidyl ether. Examples of epoxy compounds containing two or more epoxy groups include 1,6-hexanediol diglycidyl ether, 1,4-butanediol diglycidyl ether, cyclohexanedimethanol diglycidyl ether, and trimethylolpropane polyglycidyl ether. The crosslinking aids may be used alone or in combination of two or more.

[0056] Among these, triallyl isocyanurate (TAIC) is preferably used as a crosslinking aid. TAIC has good compatibility with linear low-density polyethylene and can reduce crystallinity by crosslinking to maintain transparency. Furthermore, triallyl isocyanurate (TAIC) can impart flexibility to the protective layer at low temperatures.

[0057] In the resin composition used to form the protective layer, the content of the crosslinking aid is appropriately selected depending on the desired degree of crosslinking and the like.

[0058] The content of the polyolefin resin is, for example, preferably 90 parts by mass or more, more preferably 95 parts by mass or more, relative to 100 parts by mass of all resin components contained in the protective layer, which can improve transparency and flexibility.

[0059] The proportion of each resin component contained in the protective layer is analyzed from the peak ratio detected by differential scanning calorimetry (DSC).

[0060] (b) Other resins The protective layer may contain a resin other than the above-mentioned biodegradable resin. When a biodegradable resin that is itself biodegradable is used, the resin other than the biodegradable resin may be, for example, a polyolefin-based resin or a polyurethane-based resin.

[0061] (c) Additives The protective layer may contain additives as needed. Examples of additives include light stabilizers, ultraviolet absorbers, antioxidants, heat stabilizers, nucleating agents, dispersants, leveling agents, plasticizers, antifoaming agents, flame retardants, and fillers. Among these, the protective layer preferably contains a weathering agent. Examples of weathering agents include light stabilizers, ultraviolet absorbers, and antioxidants.

[0062] Examples of light stabilizers include hindered amine light stabilizers (HALS). Hindered amine light stabilizers are broadly divided into three types based on the bonding partner of the nitrogen atom in the piperidine skeleton: NH type (hydrogen bonded to the nitrogen atom), NR type (an alkyl group (R) bonded to the nitrogen atom), and N-OR type (an alkoxy group (OR) bonded to the nitrogen atom). Among these, N-OR type hindered amine light stabilizers are preferred. N-OR type stabilizers capture radicals faster than NH type and NR type stabilizers. Furthermore, N-OR type low molecular weight HALS migrate to the surface faster than polymeric HALS, and capture radicals in a shorter period of time than NH type and N-CH3 type HALS. This can suppress deterioration of the protective layer.

[0063] The weather-resistant agents such as the above-mentioned light stabilizers, ultraviolet absorbers, and antioxidants may be dispersed in a resin to form a weather-resistant masterbatch and added to the resin composition. The weather-resistant masterbatch may be prepared as appropriate, or a commercially available product may be used. The resin used in the weather-resistant masterbatch may be the above-mentioned polyolefin resin or another resin.

[0064] The content of the additive in the protective layer is, for example, 5% by mass or less.

[0065] (2) Shape of the protective layer (a) a recess or groove In the present disclosure, a plurality of recesses or grooves may be arranged on the surface of the protective layer opposite the adhesive layer side. For example, in FIGS. 2(a) and 2(b), a plurality of recesses 11 are arranged on the surface of the protective layer 1 opposite the adhesive layer 2 side. For example, in FIGS. 3(a) and 3(b), a plurality of grooves 12 are arranged on the surface of the protective layer 1 opposite the adhesive layer 2 side. FIG. 2(b) is a cross-sectional view taken along line AA in FIG. 2(a). FIG. 3(b) is a cross-sectional view taken along line AA in FIG. 3(a). If a protective film after use, or a portion of a protective film that has peeled off from a blade, has a plurality of recesses or grooves on the surface of the protective layer opposite the adhesive layer side, these recesses or grooves are likely to cause tears or holes as the protective film breaks down into small pieces. This makes the protective layer more likely to break down into small pieces, accelerating its decomposition.

[0066] When generating power, air moves relatively along the blade surface from the leading edge of the blade. At this time, the air flow may separate from the leading edge to the blade surface, creating turbulence. Depending on the rotation speed of the blade, this turbulence may regularly create large vortices (Kármán vortices), which not only generate wind noise but also increase air resistance.

[0067] In contrast, if multiple recesses or grooves are arranged on the surface of the protective layer opposite the adhesive layer, new small turbulences are irregularly generated upwind of the area where Karman vortices are generated, thereby suppressing the generation of larger turbulences such as Karman vortices. This reduces wind noise and prevents an increase in air resistance.

[0068] Furthermore, as will be described later, when the recesses are through-holes that penetrate the protective layer in the thickness direction, or when the recessed grooves are through-grooves that penetrate the protective layer in the thickness direction, air bubbles trapped between the blade and the protective film can be removed by the through-holes or through-grooves when the protective film is attached to the blade, thereby improving the ease of application of the protective film.

[0069] The recesses or grooves may be arranged regularly or irregularly.

[0070] The cross-sectional shape of the recess or groove is not particularly limited, and examples thereof include a rectangle, a trapezoid, a triangle, a semicircle, and a semi-ellipse.

[0071] The shape of the recess in plan view is not particularly limited, and examples thereof include a circle, an ellipse, a rectangle, a polygon, etc. Among these, a circle is preferable.

[0072] The size of the recess is not particularly limited. In particular, the size of the recess is preferably a size that allows new small turbulence to be generated irregularly. Specifically, the maximum diameter of the recess is 0.2 cm or more and 5 cm or less, or may be 0.2 cm or more and 2.5 cm or less, or may be 0.2 cm or more and 0.5 cm or less.

[0073] The width of the groove is not particularly limited. In particular, the width of the groove is preferably a width that can irregularly generate new small turbulences. Specifically, the width of the groove is 0.2 cm to 5 cm, or may be 0.2 cm to 2.5 cm, or may be 0.2 cm to 0.5 cm. The size of the recess is indicated by the symbol W1 in FIG. 2(b), for example. The width of the groove is indicated by the symbol W2 in FIG. 3(b), for example.

[0074] The pitch of the recesses or grooves is not particularly limited. It is preferable that the pitch of the recesses or grooves be a pitch that can irregularly generate new small turbulences. Specifically, the pitch of the recesses or grooves is 0.001 cm to 10 cm or less, or may be 0.001 cm to 5 cm, or 0.001 cm to 1 cm. The pitch of the recesses is the distance between the centers of adjacent recesses. The pitch of the grooves is the distance between the centers of adjacent grooves.

[0075] In the protective layer, the recesses may be recesses that do not penetrate the protective layer in the thickness direction, or may be through-holes that penetrate the protective layer in the thickness direction. When the recesses are recesses that do not penetrate the protective layer in the thickness direction, the depth of the recesses is not particularly limited. Specifically, the depth of the recesses is 1 μm or more and 1000 μm or less, or may be 10 μm or more and 900 μm or less, or may be 30 μm or more and 800 μm or less.

[0076] In the protective layer, the grooves may be grooves that do not penetrate the protective layer in the thickness direction, or may be through grooves that penetrate the protective layer in the thickness direction. When the grooves do not penetrate the protective layer in the thickness direction, the depth of the grooves is not particularly limited. Specifically, the depth of the grooves is 1 μm or more and 1000 μm or less, or may be 10 μm or more and 900 μm or less, or may be 30 μm or more and 800 μm or less.

[0077] Furthermore, when the recess is a through hole that penetrates the protective layer in the thickness direction, the recess may be a through hole that penetrates not only the protective layer but also the adhesive layer in the thickness direction. Similarly, when the groove is a through groove that penetrates the protective layer in the thickness direction, the groove may be a through groove that penetrates not only the protective layer but also the adhesive layer in the thickness direction.

[0078] The number of recesses or grooves is plural. In particular, the number of recesses or grooves is preferably a number that can irregularly generate new small turbulences as described above. Specifically, the number of recesses or grooves may be any number that can be formed on the surface of the protective layer at a predetermined pitch and having the predetermined size described above.

[0079] (b) Through hole In the present disclosure, the protective layer may have through holes. For example, in FIG. 4(a), the protective layer 1 has through holes 13. For example, in FIG. 4(b), the protective layer 1 is multi-layered as described below, and has two biodegradable resin films 1a and 1b, each of which has a through hole 13. If the protective layer has through holes in the protective film after use or in a portion of the protective film that has peeled off from the blade, the protective layer is more likely to break down into small pieces, which can promote decomposition of the protective layer.

[0080] Furthermore, when the protective film is attached to the blade, the through holes allow air bubbles trapped between the blade and the protective film to be removed. Furthermore, the protective layer having through holes makes the protective film easier to bend. Therefore, the application of the protective film can be improved.

[0081] The through holes may be arranged regularly or irregularly.

[0082] (3) Physical properties of the protective layer (a) Tensile modulus In the present disclosure, the tensile modulus of the protective layer is, for example, 35 MPa or less, or may be 30 MPa or less, 20 MPa or less, or 15 MPa or less. When the tensile modulus of the protective layer is within the above range, the protective layer tends to be soft, stretchable, and resistant to deformation. Therefore, when wind, rain, snow, hail, sleet, seawater, sand, dust, dirt, birds, insects, flying objects, etc. collide with the surface of a blade having the protective film, the protective layer of the protective film can absorb the impact. This can suppress the occurrence of erosion. Furthermore, the ability to conform to the curved surface of the blade can be improved. Meanwhile, the tensile modulus of the protective layer is, for example, 5 MPa or more, or may be 7 MPa or more, or 10 MPa or more. If the tensile modulus of the protective layer is too low, the protective layer may become too soft, which may result in reduced erosion resistance or difficulty in handling the protective film. Specifically, the tensile modulus of the protective layer is 5 MPa or more and 35 MPa or less, or may be 5 MPa or more and 30 MPa or less, or 7 MPa or more and 20 MPa or less, or may be 10 MPa or more and 15 MPa or less.

[0083] The tensile modulus is measured using a tensile testing machine in accordance with ISO 527-3:2018. The tensile modulus is the slope of the stress-strain curve, calculated by the least squares method, between the two points of 5% strain and 10% strain. The specific measurement conditions are shown below.

[0084] <Measurement conditions> Test piece: rectangular Test piece size: width 10mm, length 80mm ·Distance between gauge lines: 25mm Pulling speed: 100mm / min Test conditions: Temperature 25°C, humidity 50%RH Number of test pieces: Measurement is performed on three test pieces, and the arithmetic mean value is used.

[0085] When measuring the tensile modulus of the protective layer, the adhesive layer is removed from the protective film, and the protective layer is taken out. A method for removing the adhesive layer includes dissolving the adhesive layer in a solvent. The solvent may be the same as that contained in the adhesive composition used to form the adhesive layer.

[0086] (b) Tensile breaking stress In the present disclosure, the tensile breaking stress of the protective layer is, for example, 5 MPa or more, or may be 7 MPa or more, or 10 MPa or more. Having the tensile breaking stress of the protective layer in the above range can improve durability. On the other hand, the tensile breaking stress of the protective layer is, for example, 35 MPa or less, or may be 30 MPa or less, or may be 20 MPa or less. If the tensile breaking stress of the protective layer is too high, the protective film may be difficult to stretch, and its ability to conform to the curved surface of the blade may be reduced. Specifically, the tensile breaking stress of the protective layer is 5 MPa or more and 35 MPa or less, or may be 7 MPa or more and 30 MPa or less, or may be 10 MPa or more and 20 MPa or less.

[0087] The tensile stress at break is measured using a tensile tester in accordance with ISO 527-3:2018. The tensile stress at break is the stress at which the test piece breaks. The tensile test for measuring the tensile stress at break is the same as the tensile test for measuring the tensile modulus.

[0088] (c) Tensile elongation at break In the present disclosure, the tensile elongation at break of the protective layer is, for example, 800% or more, optionally 1000% or more, or even 1200% or more. Having the tensile elongation at break of the protective layer in the above range can improve durability. Meanwhile, the upper limit of the tensile elongation at break of the protective layer is not particularly limited, but may be, for example, 3500% or less, optionally 3000% or less, or optionally 2500% or less. Specifically, the tensile elongation at break of the protective layer is 800% or more and 3500% or less, optionally 1000% or more and 3000% or less, or optionally 1200% or more and 2500% or less.

[0089] The tensile elongation at break is measured using a tensile tester in accordance with ISO 527-3:2018. The tensile elongation at break is the elongation at break of the test piece. The tensile test for measuring the tensile elongation at break is the same as the tensile test for measuring the tensile modulus described above.

[0090] (d) Type A durometer hardness In the present disclosure, the Type A durometer hardness of the protective layer is, for example, 95 or less, or may be 90 or less, or may be 85 or less. When the Type A durometer hardness of the protective layer is within the above range, the protective layer tends to be relatively soft. Therefore, the protective layer of the protective film can absorb the impact caused by collision with the blade, thereby suppressing the occurrence of erosion. Furthermore, the conformability to the curved surface of the blade can be improved. On the other hand, the Type A durometer hardness of the protective layer is, for example, 60 or more, or may be 65 or more, or may be 70 or more. If the durometer A hardness of the protective layer is too low, the protective layer may become too soft, which may result in reduced erosion resistance or difficulty in handling the protective film. Specifically, the Type A durometer hardness of the protective layer is 60 or more and 95 or less, or may be 65 or more and 90 or less, or may be 70 or more and 85 or less.

[0091] Type A durometer hardness is measured using a hardness tester in accordance with JIS K6253-3:2012. However, when measuring by stacking test pieces, there is no limit to the number of test pieces stacked. For example, if the protective layer thickness is 300 μm, 20 test pieces are stacked. The specific measurement conditions are shown below.

[0092] <Measurement conditions> Test piece thickness: 6 mm Test conditions: 23°C, 50% RH Measurement time: 3 seconds

[0093] (4) Layer structure of the protective layer The protective layer may be a single layer or multiple layers. When the protective layer is multiple layers, it is sufficient that the protective layer has at least a biodegradable resin film containing a biodegradable resin. When the protective layer is multiple layers and has multiple biodegradable resin films, the biodegradable resin contained in each biodegradable resin film may be the same or different. Furthermore, when the protective layer is multiple layers and has multiple biodegradable resin films, the content of the biodegradable resin in each biodegradable resin film may be the same or different.

[0094] When a protective film is applied to the blades of a wind turbine generator, deterioration may progress from the surface on the protective layer side of the protective film. Therefore, when the protective layer is multilayered, it is preferable that the protective layer has a biodegradable resin film on the outermost surface opposite the adhesive layer side. Even if the protective film deteriorates from the surface on the protective layer side and the outermost biodegradable resin film peels off, the environmental load can be reduced. In this case, the film in the protective layer that is arranged between the adhesive layer and the biodegradable resin film may or may not contain a biodegradable resin.

[0095] (5) Thickness of the protective layer The thickness of the protective layer is not particularly limited. The thickness of the protective layer is, for example, 50 μm or more, or may be 80 μm or more, or 100 μm or more. A protective layer thickness within the above range provides sufficient erosion resistance. On the other hand, the thickness of the protective layer is, for example, 1000 μm or less, or may be 700 μm or less, or may be 500 μm or less. Having a protective layer thickness within the above range makes the protective film more stretchable, improving adhesion and conformability to uneven and curved surfaces. Furthermore, depending on the material of the protective layer, a protective layer thickness within the above range can ensure sufficient transparency. Specifically, the thickness of the protective layer is 50 μm or more and 1000 μm or less, or may be 80 μm or more and 700 μm or less, or may be 100 μm or more and 500 μm or less. When the protective layer is multilayered, the thickness of the protective layer refers to the thickness of the entire protective layer.

[0096] (6) Method for forming protective layer The protective layer can be obtained, for example, by mixing the above components to prepare a resin composition, melting the resin composition, and forming the resin composition into a sheet-like film. Furthermore, a crosslinking treatment may be performed after film formation. The melt molding method may be any common molding method, such as injection molding, extrusion molding, blow molding, compression molding, or rotational molding. The molding temperature may be a temperature above the melting point of the resin composition. Depending on the crosslinking agent, the molding temperature may be a temperature at which crosslinking does not initiate during film formation, i.e., a temperature at which the gel fraction of the resin composition can be maintained at 0%. The molding temperature is, for example, 80°C or higher and 250°C or lower. Examples of crosslinking treatment include, as described above, crosslinking treatment using a crosslinking agent and crosslinking treatment using ionizing radiation.

[0097] Methods for forming recesses or grooves in the protective layer include, for example, etching and mechanical processing. In the case of an extrusion molding method, a method in which the film is pressed against a roll having a plurality of protrusions or ridges immediately after film formation is also included.

[0098] The surface of the protective layer facing the adhesive layer may be subjected to an adhesion enhancing treatment, if necessary, to improve adhesion to the adhesive layer. Examples of adhesion enhancing treatments include corona discharge treatment, plasma treatment, and ozone treatment.

[0099] 2.Adhesive layer The adhesive layer in the present disclosure is a member for attaching the protective film to the blades of the wind turbine generator.

[0100] The adhesive layer is not particularly limited as long as it can attach the protective film to the blade, and can be appropriately selected depending on the material of the blade, etc. A common adhesive can be used for the adhesive layer. Examples include ultraviolet-curable adhesives, two-component curable adhesives, and pressure-sensitive adhesives. Ultraviolet-curable adhesives and two-component curable adhesives can increase adhesive strength. Pressure-sensitive adhesives also have good workability.

[0101] Examples of pressure-sensitive adhesives include acrylic adhesives, urethane adhesives, and silicone adhesives. Among these, acrylic adhesives are preferred because of their excellent transparency, weather resistance, heat resistance, etc.

[0102] The adhesive layer also preferably contains a biodegradable resin, which can further reduce the environmental impact. The biodegradable resin may be a resin that is biodegradable itself, or a resin that is non-biodegradable itself but has been given biodegradability by a biodegradable additive.

[0103] When the resin itself is biodegradable, the biodegradable resin is not particularly limited, but examples thereof include polylactic acid resins, polyhydroxyalkanoate resins, 3-hydroxybutyric acid-3-hydroxyhexanoic acid copolymer polyester resins, polybutylene succinate resins, polybutylene adipate terephthalate resins, starch polyester resins, cellulose acetate resins, polyvinyl alcohol resins, polyglycolic acid resins, polybutylene succinate-co-adipate resins, polybutylene adipate terephthalate resins, and polyethylene terephthalate succinate resins.

[0104] When biodegradability is imparted by a biodegradable additive, the resin is not particularly limited, and examples thereof include acrylic resins, urethane resins, and silicone resins.

[0105] When biodegradability is imparted by a biodegradable additive, the biodegradable additive is not particularly limited, and examples thereof include polylactic acid, fatty acid polyester, polyamino acid, adipic acid, and dithiodipropionic acid.

[0106] The biodegradable resin may be a soil biodegradable resin or a marine biodegradable resin. For example, when the wind power generation device is installed on land, a soil biodegradable resin is preferably used. On the other hand, when the wind power generation device is installed offshore, a marine biodegradable resin is preferably used.

[0107] When the adhesive layer contains a biodegradable resin, the content of the biodegradable resin in the adhesive layer is, for example, preferably 0.1 parts by mass or more, more preferably 1 part by mass or more, and even more preferably 10 parts by mass or more, relative to 100 parts by mass of the resin component in the adhesive layer. The content of the biodegradable resin in the adhesive layer may be 100 parts by mass relative to 100 parts by mass of the resin component in the adhesive layer.

[0108] The thickness of the adhesive layer is not particularly limited as long as it can bond the protective film and the blade, and is appropriately selected depending on the application. The thickness of the adhesive layer is, for example, 25 μm or more, and may be 25 μm or more, or 30 μm or more. The thickness of the adhesive layer is, for example, 120 μm or less, or may be 90 μm or less, or may be 80 μm or less. That is, the thickness of the adhesive layer is, for example, 25 μm or more and 120 μm or less, or may be 25 μm or more and 90 μm or less, or may be 30 μm or more and 80 μm or less.

[0109] 3. Other configurations The protective film of the present disclosure may have other configurations depending on the application. The protective film of the present disclosure may have a separator on the surface of the adhesive layer opposite to the protective layer.

[0110] 4.Properties of protective film In the protective film of the present disclosure, the adhesive strength to a SUS plate is, for example, preferably 3 N / 10 mm or more, or may be 7 N / 10 mm or more, or may be 10 N / 10 mm or more. Having the adhesive strength in the above range improves durability. Meanwhile, the upper limit of the adhesive strength to a SUS plate is not particularly limited, but is, for example, preferably 30 N / 10 mm or less, or may be 25 N / 10 mm or less, or may be 20 N / 10 mm or less. If the adhesive strength is too high, the workability when replacing the protective film may be reduced. Specifically, the adhesive strength to a SUS plate is preferably 3 N / 10 mm or more and 30 N / 10 mm or less, or may be 7 N / 10 mm or more and 25 N / 10 mm or less, or may be 10 N / 10 mm or more and 20 N / 10 mm or less.

[0111] Adhesion strength to SUS plates is measured in accordance with Method 6 of JIS Z0237:2009. Specific measurement conditions are shown below. The tensile tester used is, for example, the "Tensilon RTF1150" manufactured by A&D Co., Ltd. The SUS plate used is a SUS304 steel plate with a surface finish of BA.

[0112] <Measurement conditions> Tape width: 10mm Peeling speed: 300mm / min Peeling angle: 90 degrees Test conditions: 23°C, 50% RH Number of tests: Measurements are performed on three test pieces, and the arithmetic mean value is used.

[0113] In the protective film of the present disclosure, the adhesive strength to the fluororesin layer is, for example, preferably 2.5 N / 10 mm or more, or may be 4 N / 10 mm or more, or may be 5 N / 10 mm or more. Having the adhesive strength in the above range can improve durability. Meanwhile, the upper limit of the adhesive strength to the fluororesin layer is not particularly limited, but is, for example, preferably 30 N / 10 mm or less, or may be 25 N / 10 mm or less, or may be 20 N / 10 mm or less. If the adhesive strength is too high, the workability when replacing the protective film may be impaired. Specifically, the adhesive strength to the fluororesin layer is preferably 2.5 N / 10 mm or more and 30 N / 10 mm or less, or may be 4 N / 10 mm or more and 25 N / 10 mm or less, or may be 5 N / 10 mm or more and 20 N / 10 mm or less.

[0114] The adhesive strength to the fluororesin layer is measured in accordance with Method 6 of JIS Z0237:2009. The specific measurement conditions are the same as those for measuring the adhesive strength to the SUS plate described above. As a tensile tester, for example, a "Tensilon RTF1150" manufactured by A&D Co., Ltd. is used. Instead of a SUS plate, a test plate prepared by the following method is used. A fluororesin paint ("Wind Hullo Topcoat F" manufactured by Nippon Tokushu Toryo Co., Ltd.) is applied to one side of the SUS substrate using a roller to form a fluororesin layer with a thickness of 100 μm to 150 μm, which is used as the test plate.

[0115] Furthermore, in the protective film of the present disclosure, the adhesive strength (N / 10 mm) to the fluororesin layer is preferably equal to or greater than the tensile load (N) at 10% elongation of the protective layer, thereby improving durability.

[0116] The tensile load at 10% elongation of the protective layer is measured using a tensile tester in accordance with ISO 527-3:2018. The measurement conditions are the same as those for measuring the tensile modulus. For example, an A&D "Tensilon RTF1150" tensile tester is used.

[0117] 5.Applications The protective film of the present disclosure is attached to the surface of the blade of a wind turbine generator. For example, as shown in Figures 5(a) and 5(b), the protective film 10 is disposed on the tip 22 of the leading edge 21 of the blade 20. The protective film may be disposed over the entire leading edge of the blade, or may be disposed on the blade portion other than the leading edge.

[0118] B. Wind turbine blades The blades of the wind turbine generator in the present disclosure have the above-described protective film on their surfaces.

[0119] Fig. 5(a) is a schematic perspective view showing an example of a blade according to the present disclosure, and Fig. 5(b) is a cross-sectional view taken along line AA in Fig. 5(a). As shown in Fig. 5(a) and Fig. 5(b), a blade 20 has a protective film 10 on its surface. In Fig. 5(a) and Fig. 5(b), the protective film 10 is disposed on a tip 22 of a leading edge 21 of the blade 20.

[0120] The protective film is preferably disposed on the leading edge of the blade, and more preferably on the tip of the leading edge of the blade, because erosion mainly occurs at the tip of the leading edge.

[0121] The structure and materials of the blade are the same as those of a general blade, so a description thereof will be omitted here.

[0122] C. Wind power generation equipment The wind turbine generator of the present disclosure includes the blade described above.

[0123] Fig. 6 is a schematic diagram showing an example of a wind turbine generator according to the present disclosure. As shown in Fig. 6, the wind turbine generator 30 includes a rotor 32 having blades 20 and a hub 31 supporting the blades 20, a nacelle 33, and a tower 34 supporting the rotor 32 and the nacelle 33. Although not shown, the nacelle 33 houses a main shaft connected to the hub 31 and rotating together with the hub 31, a step-up gear connected to the main shaft for increasing the rotational speed, and a generator that generates electricity by rotating the rotor at the rotational speed increased by the step-up gear. In Fig. 8, a protective film 10 is disposed on the tip of the leading edge of the blade 20.

[0124] The components that make up the wind turbine generator are similar to those of a general wind turbine generator, and therefore a description thereof will be omitted here.

[0125] The present disclosure is not limited to the above-described embodiments. The above-described embodiments are merely examples, and any configuration that is substantially identical to the technical idea described in the claims of the present disclosure and that provides similar effects is included within the technical scope of the present disclosure. [Explanation of symbols]

[0126] 1 … protective layer 2 … Adhesive layer 10... Protective film 20... Blade 30... Wind power generation equipment

Claims

1. A protective film for wind turbine blades, comprising a protective layer containing a biodegradable resin and an adhesive layer disposed on one side of the protective layer.

2. The protective film for blades according to claim 1 , wherein the adhesive layer contains a biodegradable resin.

3. A blade for a wind turbine generator, having the blade protective film according to claim 1 or 2 on its surface.

4. A wind turbine generator comprising the blade according to claim 3.

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