Alkali-resistant and weather-resistant water-based wind turbine blade topcoat and preparation method thereof

Abstract

The present application relates to the field of paint technology, and particularly relates to a water-based wind power blade finish paint with excellent alkali resistance and weather resistance and a preparation method thereof.The paint comprises a component A and a component B, the component A comprises water, a first water-based hydroxyl acrylic emulsion, a film forming aid, a wear-resistant filler, a water-based polyurethane dispersion, a hybrid emulsion, a wax emulsion and other aids; the component B comprises a water-based isocyanate curing agent and propylene glycol diacetate.The paint has good flexibility and strength, high wear resistance and fast drying characteristics, and at the same time, has excellent acid and alkali resistance, water resistance, oil resistance and weather resistance, effectively improves the alkali resistance and weather resistance of the water-based wind power blade finish paint with a high content of low-hydroxyl polyurethane resin component, and can realize long-term protection of onshore or offshore wind power blades.

Description

Technical Field

[0001] This invention relates to the field of coating technology, and in particular to a water-based wind turbine blade topcoat with excellent alkali resistance and weather resistance, and its preparation method. Background Technology

[0002] In recent years, my country's wind energy industry has developed rapidly, and its share of global wind power manufacturing has been increasing year by year.

[0003] As an important protective material in the wind power industry chain, wind turbine blade coatings protect blades from environmental factors such as ultraviolet light, dust, rain, and icing, ensuring the long-term, efficient, and safe operation of wind turbines, and have broad market prospects.

[0004] With continuous technological advancements, wind turbine blade coating systems are increasingly adopting environmentally friendly approaches. Water-based coatings, such as those from brands like Mega and Jotun, are commonly used for the topcoat of wind turbine blades. Water-based coatings offer advantages such as ease of application, safety, and environmental friendliness, making them popular among wind turbine blade manufacturers.

[0005] Currently, low-hydroxyl polyurethanes (HHPPs) are favored for their fast drying and high flexibility, which contribute to improved coating efficiency, wind and sand resistance, and rain erosion resistance. Therefore, this type of resin is incorporated as a film-forming component in waterborne topcoats for wind turbine blades. However, waterborne polyurethane coatings are inherently susceptible to hydrolysis under alkaline conditions, exhibiting generally poor alkali resistance. Furthermore, the low hydroxyl content of HHPPs leads to a lower crosslinking density in the coating, further reducing its alkali resistance. This lower crosslinking density also results in decreased UV aging performance of the topcoat. Existing literature and related research lacks reports on how to enhance the alkali resistance and weather resistance of HHPP coatings. Therefore, developing a waterborne topcoat for wind turbine blades that combines excellent alkali resistance and weather resistance with fast drying and high flexibility is a pressing issue requiring resolution in this field. Summary of the Invention

[0006] To address the problems of the prior art mentioned in the background section, the present invention provides a water-based wind turbine blade topcoat with excellent alkali resistance and weather resistance, the purpose of which is to improve the alkali resistance and weather resistance of the water-based wind turbine blade topcoat with a high content of low-hydroxyl polyurethane resin components.

[0007] This waterborne wind turbine blade topcoat, exhibiting excellent alkali resistance and weather resistance, comprises component A and component B. Component A includes water, a first waterborne hydroxy acrylic emulsion, a film-forming aid, abrasion-resistant filler, a waterborne polyurethane dispersion, a hybrid emulsion, a wax emulsion, and other additives. Component B includes a waterborne isocyanate curing agent and propylene glycol diacetate. The hybrid emulsion is prepared by mixing a second waterborne hydroxy acrylic emulsion, an amphiphilic silane coupling agent, and L-lysine and heating them to obtain mixture M. Then, tetraethyl orthosilicate is added to mixture M and heated to obtain the hybrid emulsion.

[0008] In some embodiments, the other additives include aqueous dispersants, aqueous defoamers, aqueous thickeners, titanium dioxide, matting agents, and aqueous color pastes; by weight, component A includes 6-10 parts water, 9.6-14.4 parts of a first aqueous hydroxy acrylic emulsion, 2-6 parts film-forming aid, 0.4-0.6 parts aqueous dispersant, 0.2-0.3 parts aqueous defoamer, 0.2-0.4 parts aqueous thickener, 17-25 parts titanium dioxide, 5-10 parts abrasion-resistant filler, 1.5-2.5 parts matting agent, 9.6-14.4 parts hybrid emulsion, 20-28 parts aqueous polyurethane dispersion, 3-5 parts wax emulsion, and 0-0.730 parts aqueous color paste; component B includes 50-75 parts aqueous isocyanate curing agent and 25-50 parts propylene glycol diacetate.

[0009] In some embodiments, the preparation process of the hybrid emulsion is as follows:

[0010] A second aqueous hydroxy acrylic emulsion, an amphiphilic silane coupling agent, and L-lysine were mixed and subjected to a first-stage heating reaction to obtain mixture M.

[0011] Tetraethyl orthosilicate was added dropwise to the mixture M, and a second-stage heating reaction was carried out. After the reaction was completed, the mixture was cooled to room temperature to obtain a hybrid emulsion.

[0012] The mass ratio of the second aqueous hydroxy acrylic emulsion, the amphiphilic silane coupling agent, tetraethyl orthosilicate, and L-lysine is (80-90):(2-5):(8-16):(0.03-0.06).

[0013] In some embodiments, the first stage heating reaction temperature is (45-60)℃, and the reaction time is (0.5-1.5)h; the dropping rate of the tetraethyl orthosilicate is (0.5-1) drops / second; the second stage heating reaction temperature is (45-60)℃, and the reaction time is (4-6)h.

[0014] In some embodiments, the mass ratio of component A to component B is (5-10):1.

[0015] In some embodiments, the solid content of the first and second aqueous hydroxy acrylic emulsions is (40-55)%, wherein the hydroxyl content is (2-4.2)% of the total mass of the hydroxy acrylic resin; the film-forming aid is one or a mixture of dipropylene glycol butyl ether and diethylene glycol monobutyl ether; the wear-resistant filler includes one or a combination of feldspar powder, benzoic acid powder, wollastonite powder, quartz powder, and quartz sand; the aqueous polyurethane dispersion is a low-hydroxyl aqueous polyurethane dispersion, wherein the hydroxyl content is (0-2)% of the total mass of the aqueous polyurethane resin, the solid content is (35-55)%, and its surface drying time at room temperature is <20 min, and its actual drying time is <1 h; the wax emulsion is one or a combination of aqueous polytetrafluoroethylene dispersions PTFE-1004A and PTFE-1008, and its solid content is 50-55 wt%.

[0016] In some embodiments, the aqueous isocyanate curing agent is a polyether-modified HD I trimer oligomer with high NCO- group content, wherein the NCO- content is 18-22% of the total molecular weight, and its structural formula is:

[0017]

[0018] The structure of R is as follows:

[0019] Where n = 10 to 100.

[0020] In some embodiments, the aqueous dispersant is one or more combinations of BYK-180, BYK-190, UCAR 690w, SN5040, and X-405; the aqueous defoamer is one or more combinations of BYK-024, Tego810, Tego901w, Tego902w, UCAR 290w, and UCAR 295w; the aqueous thickener is one or more combinations of WT-105A, U805, 812W, COATEXXS71, RM2020, and BR125P; the titanium dioxide is rutile titanium dioxide, including one or more combinations of R706, R996, and R5566; and the matting agent is a modified silica matting agent with a wax-treated surface, having a porosity of 1.8 mL / g, an oil absorption value of 260–300 g, a particle size of 4.5–5.5 μm, and a pH of 6.0–7.0.

[0021] In some embodiments, the color paste includes one or more combinations of water-based iron yellow paste, water-based iron black paste, and water-based royal blue paste.

[0022] This invention also provides a method for preparing the water-based wind turbine blade topcoat with excellent alkali resistance and weather resistance as described above, wherein:

[0023] The preparation of component A includes the following steps:

[0024] According to the formula ratio, water, first aqueous hydroxy acrylic emulsion, film-forming aid, aqueous dispersant, aqueous defoamer and aqueous thickener are added into a stainless steel tank with condensate water and dispersed to obtain mixture N;

[0025] According to the formula ratio, titanium dioxide, wear-resistant filler and matting powder are added to mixture N, and sand milling is carried out until the fineness is <30 microns. Then, the paint is produced by filtration.

[0026] After weighing the paint, add wax emulsion, waterborne polyurethane dispersion, hybrid emulsion and waterborne color paste to the paint according to the formula ratio, and disperse at high speed to obtain component A.

[0027] The preparation of component B includes the following steps:

[0028] According to the formulation ratio, the water-based isocyanate curing agent and propylene glycol diacetate are dispersed evenly to obtain component B.

[0029] Based on the above, compared with the prior art, the water-based wind turbine blade topcoat with excellent alkali resistance and weather resistance provided by the present invention has the following technical effects:

[0030] This invention provides a water-based wind turbine blade topcoat, which features good flexibility and strength, high abrasion resistance, and rapid drying. Simultaneously, it exhibits excellent acid and alkali resistance, water resistance, oil resistance, and weather resistance, effectively improving the alkali resistance and weather resistance of water-based wind turbine blade topcoats with high content of low-hydroxyl polyurethane resin components. Its fast drying rate and short application interval between two topcoats help wind turbine blade manufacturers improve coating efficiency and reduce costs. Furthermore, the coating's excellent abrasion resistance, alkali resistance, and weather resistance provide long-term protection for onshore or offshore wind turbine blades.

[0031] Other features and beneficial effects of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. The objects of the invention and other beneficial effects may be realized and obtained by means of the structures and / or components pointed out in the description and claims. Attached Figure Description

[0032] Figure 1 The images show actual samples after alkali resistance tests, as provided in the embodiments and comparative examples of this invention. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. The technical features designed in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0034] In the description of this invention, it should be noted that all terms used in this invention (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains, and should not be construed as limiting the invention; it should be further understood that the terms used in this invention should be understood to have the same meaning as those in the context of this specification and in the relevant field, and should not be understood in an idealized or overly formal sense, except as expressly defined in this invention.

[0035] This invention provides a method for preparing a water-based wind turbine blade topcoat with excellent alkali resistance and weather resistance, comprising the following steps:

[0036] 1. The preparation of component A includes the following steps:

[0037] According to the formula ratio, water, first aqueous hydroxy acrylic emulsion, film-forming aid, aqueous dispersant, aqueous defoamer and aqueous thickener are added into a stainless steel tank with condensate water and dispersed to obtain mixture N;

[0038] According to the formula ratio, titanium dioxide, wear-resistant filler and matting powder are added to mixture N, and sand milling is carried out until the fineness is <30 microns. Then, the paint is produced by filtration.

[0039] After weighing the paint, add wax emulsion, waterborne polyurethane dispersion, hybrid emulsion and waterborne color paste to the paint according to the formula ratio, and disperse at high speed to obtain component A.

[0040] 2. The preparation of component B includes the following steps:

[0041] According to the formula ratio, the water-based isocyanate curing agent and propylene glycol diacetate are dispersed evenly to obtain component B.

[0042] The formulations of components A and B are as follows:

[0043] By weight, component A comprises 6-10 parts water, 9.6-14.4 parts first aqueous hydroxy acrylic emulsion, 2-6 parts film-forming aid, 0.4-0.6 parts aqueous dispersant, 0.2-0.3 parts aqueous defoamer, 0.2-0.4 parts aqueous thickener, 17-25 parts titanium dioxide, 5-10 parts wear-resistant filler, 1.5-2.5 parts matting agent, 9.6-14.4 parts hybrid emulsion, 20-28 parts aqueous polyurethane dispersion, 3-5 parts wax emulsion, and 0-0.730 parts aqueous color paste;

[0044] The B component comprises 50-75 parts of water-based isocyanate curing agent and 25-50 parts of propylene glycol diacetate; wherein the mass ratio of the A component to the B component is (5-10):1.

[0045] The hybrid emulsion is prepared in-house, and its preparation process is as follows:

[0046] A second aqueous hydroxy acrylic emulsion, an amphiphilic silane coupling agent, and L-lysine were mixed and subjected to a first-stage heating reaction to obtain mixture M.

[0047] Tetraethyl orthosilicate was added dropwise to the mixture M to carry out a second-stage heating reaction. After the reaction was completed, the mixture was cooled to room temperature to obtain a hybrid emulsion. The first-stage heating reaction temperature was (45-60)℃ and the reaction time was (0.5-1.5)h. The dropping rate of the tetraethyl orthosilicate was (0.5-1) drops / second. The second-stage heating reaction temperature was (45-60)℃ and the reaction time was (4-6)h.

[0048] The mass ratio of the second aqueous hydroxy acrylic emulsion, the amphiphilic silane coupling agent, tetraethyl orthosilicate, and L-lysine is (80-90):(2-5):(8-16):(0.03-0.06).

[0049] The present invention also provides the following embodiments and comparative examples of formulations (unit: parts by weight), as shown in Table 1 below:

[0050] Table 1

[0051]

[0052]

[0053] Specifically, the raw materials used in the examples and comparative examples in Table 1 are:

[0054] (1) The water is deionized water;

[0055] (2) The first waterborne hydroxyl acrylic emulsion has a solid content of 45% and a hydroxyl content of 4.2% of the total mass of the hydroxyl acrylic resin;

[0056] (3) The film-forming aid is dipropylene glycol butyl ether;

[0057] (4) The aqueous dispersant is BYK-190;

[0058] (5) The water-based defoamer is BYK-024;

[0059] (6) The water-based thickener is U805;

[0060] (7) The titanium dioxide is rutile titanium dioxide, specifically R996;

[0061] (8) The wear-resistant filler is feldspar powder;

[0062] (9) The matting powder is a modified silica matting powder with a wax-treated surface. Its porosity is 1.8 mL / g, its oil absorption value is 260 g (based on 100 g sample), its particle size is 5.0 μm, and its pH is 7.0.

[0063] (10) The waterborne polyurethane dispersion is a low-hydroxyl waterborne polyurethane dispersion with a hydroxyl content of 1.5% of the total mass of the waterborne polyurethane resin, a solid content of 35%, a surface drying time of <20 min at room temperature, and a hard drying time of <1 h.

[0064] (11) The hybrid emulsion was prepared in the laboratory.

[0065] In Examples 1 and 2 and Comparative Examples 1, 2 and 3, the method for preparing the hybrid emulsion includes the following steps:

[0066] S1: Mix the second aqueous hydroxy acrylic emulsion, KH-570 and L-lysine, and carry out the first stage of heating reaction;

[0067] S2: Tetraethyl orthosilicate is added dropwise to the mixture to carry out the second-stage heating reaction. After the reaction is completed, it is cooled to room temperature to obtain a hybrid emulsion. The first-stage heating reaction temperature is 45°C and the reaction time is 1.5 h; the "dropwise addition" rate is 1 drop / second; the second-stage heating reaction temperature is 45°C and the reaction time is 6 h.

[0068] The first aqueous hydroxyl acrylic emulsion has a solid content of 45% and a hydroxyl content of 4.2% of the total resin mass. The aqueous hydroxyl acrylic emulsion is added in 90 parts by weight. KH-570 is an amphiphilic silane coupling agent, added in 2 parts. Tetraethyl orthosilicate is a commercially available analytical grade product, added in 8 parts. L-Lysine is a commercially available analytical grade product, added in 0.05 parts.

[0069] In Comparative Example 4, the preparation method of the hybrid emulsion includes the following steps:

[0070] S1: Mix the second aqueous hydroxy acrylic emulsion, KH-560 and L-lysine, and carry out the first stage of heating reaction;

[0071] S2: Tetraethyl orthosilicate is added dropwise to the mixture to carry out the second-stage heating reaction. After the reaction is completed, it is cooled to room temperature to obtain a hybrid emulsion. The first-stage heating reaction temperature is 45°C and the reaction time is 1.5 h; the "dropwise addition" rate is 1 drop / second; the second-stage heating reaction temperature is 45°C and the reaction time is 6 h.

[0072] The first aqueous hydroxyl acrylic emulsion has a solid content of 45% and a hydroxyl content of 4.2% of the total resin mass. The aqueous hydroxyl acrylic emulsion is added in 90 parts by weight. KH-560 is a hydrophilic silane coupling agent, added in 2 parts. Tetraethyl orthosilicate is a commercially available analytical grade product, added in 8 parts. L-Lysine is a commercially available analytical grade product, added in 0.05 parts.

[0073] In Comparative Example 5, the method for preparing the hybrid emulsion includes the following steps:

[0074] S1: The second aqueous hydroxy acrylic emulsion and L-lysine are mixed, and tetraethyl orthosilicate is added dropwise to the mixture. The mixture is heated to react, and after the reaction is complete, it is cooled to room temperature to obtain a hybrid emulsion. The "dropwise addition" rate is 1 drop / second; the heating reaction temperature is 45°C, and the reaction time is 6 hours. The first aqueous hydroxy acrylic emulsion has a solid content of 45% and a hydroxyl content of 4.2% of the total resin mass; the amount of aqueous hydroxy acrylic emulsion added is 90 parts by weight; tetraethyl orthosilicate is a commercially available analytical grade product, added in an amount of 8 parts; and L-lysine is a commercially available analytical grade product, added in an amount of 0.05 parts.

[0075] (12) The wax emulsion is PTFE-1004A with a solid content of 50wt%.

[0076] (13) The aqueous isocyanate curing agent is a polyether-modified HD I trimer oligomer with high NCO- content, the NCO- content being 20% ​​of the total molecular weight, and its structural formula is:

[0077]

[0078] The structural formula for R is:

[0079] Where n = 10 to 100.

[0080] The preparation process of the coatings in the examples and comparative examples is as follows:

[0081] Add the prescribed amounts of deionized water, diethylene glycol butyl ether, first aqueous hydroxy acrylic emulsion, aqueous dispersant, aqueous defoamer, and aqueous thickener to a stainless steel tank with condensate flowing through it, and disperse at 500 r / min for 5 min.

[0082] Add the prescribed amounts of titanium dioxide, feldspar powder, and matting powder, along with 1000g of zirconium beads, and mill at 1600r / min for 90min until the fineness is <30 microns.

[0083] Subsequently, the paint was filtered out using a 100-mesh filter, weighed, and placed in an iron can. The formulated amounts of wax emulsion, waterborne polyurethane dispersion, hybrid emulsion, and waterborne color paste were added, and the mixture was dispersed at 1000 r / min for 10 min to obtain component A.

[0084] Add the prescribed amounts of water-based isocyanate curing agent and propylene glycol diacetate to an iron can and disperse at 400 r / min for 4 min to obtain component B.

[0085] The products obtained in the above embodiments and the products obtained in the comparative examples were mixed according to the ratio of component A and component B in Table 1, and the following performance tests were conducted to obtain the test results:

[0086] (1) Components A and B of the comparative and examples were mixed according to the formula, stirred evenly, and mechanical and wear resistance tests were conducted. The test results are shown in Table 2.

[0087] Table 2 Results of Mechanical and Abrasion Resistance Tests

[0088]

[0089] (2) Components A and B of the comparative and examples were mixed according to the formula, stirred evenly, and subjected to media resistance tests. The test results are shown in Table 3. Photos of the samples after alkali resistance are shown in the figure. Figure 1 As shown:

[0090] Table 3 Resistance to Media

[0091]

[0092] Among them, such as Figure 1 As shown, Comparative Example 1 showed a large number of bubbles on its surface after 240 hours of alkali resistance, while the surfaces of Comparative Example 2, Example 1, Example 2 and Comparative Example 3 remained intact after 240 hours of alkali resistance.

[0093] (3) Components A and B of the comparative and examples were mixed according to the formula, stirred evenly, and subjected to artificial accelerated aging resistance test. The test results are shown in Table 4:

[0094] Table 4 Weather Resistance

[0095]

[0096]

[0097] (4) Components A and B of the comparative example were mixed according to the formula, stirred evenly, and a roller coating process test was conducted to test the wet film thickness and drying time, and the surface condition of the paint film was observed. The results are shown in Table 5.

[0098] Table 5. Test Results of Roller Coating Application Process

[0099]

[0100]

[0101] The diluent is deionized water.

[0102] (5) Analysis of the above test data shows that:

[0103] 1) As shown in Table 2:

[0104] In Examples 1-2 and Comparative Examples 1-3, when the coupling agent in the hybrid emulsion was KH 570, as the amount of hybrid emulsion added increased from 0 wt% to 40 wt%, the tensile strength of the coating film gradually increased from 10.65 to 14.21 MPa, the elongation at break decreased from 163.8% to 61.97%, and the abrasion resistance increased from 65 to 37.8 mg.

[0105] In Comparative Example 4, when the coupling agent in the hybrid emulsion was KH560, precipitation occurred in the hybrid emulsion;

[0106] In Comparative Example 5, when there was no coupling agent in the hybrid emulsion, the tensile strength of the coating film was 8.4 MPa, the elongation at break was 71.03%, and the abrasion resistance was 81.7 mg.

[0107] Therefore, it can be seen that when the coupling agent in the hybrid emulsion is KH 570, the hybrid emulsion improves the strength and wear resistance of the coating film, but reduces the flexibility to a certain extent. This is mainly because the silanol groups on the surface of the silica shell in the hybrid emulsion undergo dehydration and cross-linking, forming an inorganic silica network structure, which increases the hardness and cross-linking density of the coating film, thereby improving the strength and wear resistance. However, the short chain segments and poor toughness in the inorganic silica network structure lead to a decrease in the flexibility of the coating film. Overall, except for Comparative Example 3 where the flexibility is below 70%, the tensile strength, elongation at break, and wear resistance of the formulations in Examples 1-2 and Comparative Examples 1-2 are all excellent.

[0108] In addition, in Comparative Example 4, the hybrid emulsion prepared using KH 560 hydrophilic coupling agent flocculated. This may be because KH 560 could not spread evenly on the surface of latex particles, resulting in uneven silica polymerization and growth, which in turn led to flocculation and precipitation of the hybrid emulsion.

[0109] In Comparative Example 5, when the hybrid emulsion lacked the coupling agent KH570, the film strength, flexibility, and abrasion resistance all decreased compared to Examples 1-2. This was mainly due to the low degree of polymerization of silica and its poor compatibility with organic resins.

[0110] 2) As shown in Table 3:

[0111] Comparative Example 1 did not add any hybrid emulsion, and its water resistance, acid resistance, and oil resistance all met the requirements. However, after alkali resistance, a large amount of foaming occurred. This was mainly because the low hydroxyl polyurethane content in the formula was high, and the crosslinking density was low. At the same time, the urethane groups in the polyurethane molecular structure were partially hydrolyzed under long-term erosion in the alkaline environment, which further reduced the crosslinking density of the paint film and caused foaming.

[0112] Furthermore, no bubbling occurred in Comparative Example 2, Example 1, Example 2, and Comparative Example 3 after 240 hours of alkali resistance, indicating that the introduction of the hybrid emulsion prepared in this application improved the alkali resistance of the coating film. The reasons for the improved alkali resistance of the coating film by the hybrid emulsion are mainly twofold. Firstly, the introduction of the hybrid emulsion forms an organic-inorganic covalently bonded network structure. The relatively stable inorganic silica network structure provides support for the hydrolyzable organic network structure, thereby improving alkali resistance. Secondly, the silica shell structure encapsulates and protects the internally embedded polyurethane molecules, delaying the erosion of the internal polyurethane molecules by the medium in the external environment, further slowing down hydrolysis, and thus improving alkali resistance.

[0113] In Comparative Example 5, the hybrid emulsion without coupling agent exhibited significant foaming after alkali resistance. This was mainly due to the low degree of polymerization and free distribution of silica formed in the hybrid emulsion, resulting in severe separation between the inorganic silica network and the polyurethane structural phase, thus providing poor protection for the polyurethane network structure.

[0114] 3) As shown in Table 4:

[0115] In Examples 1-2 and Comparative Examples 1-3, when the coupling agent in the hybrid emulsion was KH570, and the amount of hybrid emulsion added was increased from 0 to 40%, the chalking grade of the paint film after 1500 hours of UV aging decreased from grade 2 to grade 0, with no cracking or discoloration. The adhesion after aging was between 13.7 and 16.4 MPa, and the elongation at break after aging decreased from 23.7% to 13.3%.

[0116] In Comparative Example 5, when KH 570 coupling agent was not added to the hybrid emulsion, the paint film exhibited grade 2 chalking after 1500 hours of UV aging, with no cracking or discoloration. The adhesion after aging was 9.2 MPa, and the elongation at break after aging was 8.3%.

[0117] Therefore, it can be seen that the introduction of the hybrid emulsion with added KH 570 coupling agent prepared in this application improves the weather resistance of the paint film. When the amount of hybrid emulsion added reaches 20 wt%, the paint film does not chalk after aging. This is mainly because the higher the amount of hybrid emulsion added, the higher the proportion of the inorganic silica network structure formed. The silicon-oxygen-silicon bond energy in the inorganic network structure is high and the stability is good, which plays a certain supporting role in the structure of the film-forming material, thereby improving the weather resistance of the paint film. However, in Comparative Example 5, when no KH 570 coupling agent was added to the hybrid emulsion, the chalking of the paint film after aging was not improved compared with Comparative Example 1, and the adhesion and fracture productivity both decreased after aging. This further indicates that the coupling agent KH 570 in the hybrid emulsion plays a key role in forming a unique organic-inorganic shell-core structure.

[0118] 4) As shown in Table 5:

[0119] In Examples 1-2 and Comparative Examples 1-3, the coupling agent in the hybrid emulsion was KH 570. When the amount of hybrid emulsion added increased from 0 to 40 wt%, the surface drying time of the coating decreased from 22 min to 17 min, and the complete drying time decreased from 40 min to 30 min. The roller-coated surface of the paint film was smooth and free of defects such as blistering and pinholes. This indicates that the introduction of the hybrid emulsion did not adversely affect the drying rate and surface condition of the paint film. In Comparative Example 5, when the hybrid emulsion did not contain KH 570, the surface drying time of the coating was 20 min, and the complete drying time was 40 min, slightly lower than in Example 1.

[0120] In summary:

[0121] Overall, Examples 1 and 2 exhibit excellent comprehensive performance. Compared to the scheme without the addition of hybrid emulsion, their abrasion resistance, alkali resistance, aging resistance, and drying speed are significantly improved, while flexibility and strength remain at a good level, meeting application requirements. They are suitable for roller coating, with a surface drying time of 17 minutes and a complete drying time of 35 minutes at room temperature; tensile strength is 12.74–13.47 MPa, elongation at break is 9641–111.28%, and abrasion resistance is 40–41.8 mg. They show no blistering or peeling after 240 hours of acid resistance, 240 hours of water resistance, 96 hours of oil resistance, and 240 hours of alkali resistance. After 1500 hours of UVA-313 aging, there is no cracking, chalking grade 0, discoloration grade 0, and the adhesion after aging is 13.7–14.2 MPa, with an elongation at break of 18.5–21.4%.

[0122] In summary, the technical solution of the water-based wind turbine blade topcoat with excellent alkali resistance and weather resistance provided by the present invention includes at least the following design concept, mechanism of action, and beneficial effects:

[0123] In this invention, a self-assembly technique is used to construct a silica shell on the surface of hydroxyl acrylic latex particles, forming a hybrid emulsion. Using this hybrid emulsion and a low-hydroxyl polyurethane dispersion as film-forming materials, and an aqueous polyisocyanate oligomer as a curing agent, a two-component waterborne polyurethane coating is prepared. In this system, the silica shell structure surface contains a large number of silanol groups, which can self-crosslink or undergo crosslinking reactions with residual isocyanate groups. The introduction of the silica shell enhances the crosslinking density of the coating, increases the bond energy of the film-forming material, and provides a certain degree of protection for the polyurethane structure, improving the alkali resistance and weather resistance of waterborne wind turbine blade topcoats with high content of low-hydroxyl polyurethane resin components. Specifically, the hybrid emulsion in this invention employs a particular design:

[0124] This application describes a hybrid emulsion prepared using a self-assembly technique. The raw material selected is a specific amphiphilic silane coupling agent, which spreads on the surface of latex particles by extending its hydrophobic end into the particle and its hydrophilic end towards the aqueous phase. This results in numerous silanol sites on the particle surface, further generating silica nanoparticles in situ. A silica shell is then formed on the surface of the hydroxyl acrylic latex particles, thereby improving the coating's alkali resistance and weather resistance. If an amphiphilic silane coupling agent is not used, and a non-amphiphilic coupling agent like KH-560 is selected, a silica shell cannot form on the latex particle surface, leading to flocculation and precipitation in the hybrid emulsion. This may be due to uneven interaction between the coupling agent groups in the formed silica and the emulsion. While no flocculation or precipitation occurs in the hybrid emulsion without a coupling agent, the silica exists freely in the emulsion, making it difficult to form seeds for growth. The resulting silica has low cross-linking degree and poor compatibility with the resin, leading to severe phase separation and no significant improvement in the coating's alkali resistance and weather resistance. Meanwhile, the temperatures of the first and second stage heating reactions are controlled within a limited range, which is conducive to the formation of the silica shell. If the temperature exceeds the limited range, the hybrid emulsion particles may agglomerate, and the storage stability of the coating will decrease.

[0125] The coating provided by this invention has the following effects:

[0126] (1) Excellent alkali resistance and weather resistance:

[0127] In this invention, a hybrid emulsion, low-hydroxyl polyurethane, and isocyanate trimer are used as film-forming materials. The hybrid emulsion is prepared by constructing a silica shell on the surface of hydroxyl acrylic latex particles using a self-assembly technique. The silica shell surface of the hybrid emulsion has a large number of silanol groups distributed on it. On one hand, the silanol groups can self-crosslink at room temperature during the film drying process, forming covalent bonds between the particles. On the other hand, a small number of silanol groups react chemically with isocyanate groups during the curing reaction, causing the inorganic silica network structure and the organic polyurethane network structure to form chemical crosslinks. Therefore, the introduction of the silica shell in the hybrid emulsion significantly increases the crosslinking density of the film-forming material, improves the alkali resistance of the coating, and, due to the stable chemical properties of the formed silicon-oxygen-silicon bonds, the introduction of the silica shell also improves the weather resistance of the coating.

[0128] (2) High wear resistance:

[0129] Typically, the wear resistance of a material is related to its hardness, toughness, and surface friction coefficient. In this invention, the presence of the low-hydroxyl polyurethane component gives the coating high toughness, while the presence of the inorganic network structure gives the coating high hardness; the introduction of the wax emulsion gives the coating surface a low friction coefficient. Therefore, under the synergistic effect of the low-hydroxyl polyurethane, the inorganic network structure, and the wax emulsion, the coating film exhibits high wear resistance.

[0130] (3) Fast drying rate:

[0131] The drying process of two-component waterborne coatings generally includes two steps: moisture evaporation and chemical crosslinking. Low-hydroxyl polyurethane resin can be used as a single-component film-forming material, naturally drying to form a film without undergoing a chemical reaction, eliminating the need for a chemical crosslinking drying process. In this invention, the low-hydroxyl polyurethane resin has a high content in the film-forming material, thus giving it the characteristics of single-component drying film formation. After moisture evaporation, the paint film surface reaches a dry, non-sticky state, meeting the drying conditions for the next topcoat. Simultaneously, the silanol groups on the silica shell surface enable room temperature self-crosslinking and curing, and the introduction of the silica shell further enhances the physical drying rate of the coating to a certain extent.

[0132] Experiments show that the obtained coating can be applied by roller coating. At room temperature, it is surface dry in 17 minutes and fully dry in 35 minutes. The tensile strength is 12.74–13.47 MPa, the elongation at break is 96.41–111.28%, and the abrasion resistance is 40–41.8 mg. It does not blister or peel off after 240 hours of acid resistance, 240 hours of water resistance, 96 hours of oil resistance, or 240 hours of alkali resistance. It does not crack after 1500 hours of UVA-313 aging, and has a chalking grade of 0 and a discoloration grade of 0. After aging, the adhesion is 13.7–14.2 MPa, and the elongation at break is 18.5–21.4%. Through the above technical route, the water-based topcoat for wind turbine blades developed by this invention has the characteristics of high flexibility, high strength, high abrasion resistance, and fast drying. At the same time, it has excellent alkali resistance and weather resistance, solving related technical problems.

[0133] In summary, this invention provides a water-based wind turbine blade topcoat that can be applied by roller coating. It features good flexibility and strength, high abrasion resistance, and rapid drying. Furthermore, it exhibits excellent acid and alkali resistance, water resistance, oil resistance, and weather resistance, effectively improving the alkali resistance and weather resistance of water-based wind turbine blade topcoats with high-content, low-hydroxyl polyurethane resin components. Its fast drying rate and short application interval between coats help wind turbine blade manufacturers improve coating efficiency and reduce costs. Additionally, the coating's excellent abrasion resistance, alkali resistance, and weather resistance provide long-term protection for onshore or offshore wind turbine blades.

[0134] It should be noted that:

[0135] The specific parameters or commonly used reagents in the above embodiments are specific or preferred embodiments under the concept of the present invention, and are not intended to limit it; those skilled in the art can make adaptive adjustments within the concept and protection scope of the present invention.

[0136] In addition, unless otherwise specified, the raw materials used may be commercially available products in the field or prepared by conventional methods in the field.

[0137] Furthermore, those skilled in the art should understand that although many problems exist in the prior art, each embodiment or technical solution of the present invention can be improved in only one or a few aspects, without necessarily solving all the technical problems listed in the prior art or the background art simultaneously. Those skilled in the art should understand that any content not mentioned in a claim should not be construed as a limitation on that claim.

[0138] Although this document frequently uses terms such as aqueous hydroxy acrylic emulsion, film-forming aid, abrasion-resistant filler, aqueous polyurethane dispersion, hybrid emulsion, and wax emulsion, the possibility of using other terms is not excluded. These terms are used merely for the convenience of describing and explaining the essence of the invention; interpreting them as any additional limitation would be contrary to the spirit of the invention.

[0139] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A water-based wind turbine blade topcoat with excellent alkali resistance and weather resistance, comprising component A and component B, characterized in that: The first component includes water, a first aqueous hydroxy acrylic emulsion, a film-forming aid, abrasion-resistant filler, an aqueous polyurethane dispersion, a hybrid emulsion, a wax emulsion, and other additives; the other additives include aqueous dispersants, aqueous defoamers, aqueous thickeners, titanium dioxide, matting agents, and aqueous color pastes; By weight, component A comprises 6-10 parts water, 9.6-14.4 parts first aqueous hydroxy acrylic emulsion, 2-6 parts film-forming aid, 0.4-0.6 parts aqueous dispersant, 0.2-0.3 parts aqueous defoamer, 0.2-0.4 parts aqueous thickener, 17-25 parts titanium dioxide, 5-10 parts wear-resistant filler, 1.5-2.5 parts matting agent, 9.6-14.4 parts hybrid emulsion, 20-28 parts aqueous polyurethane dispersion, 3-5 parts wax emulsion, and 0-0.730 parts aqueous color paste; The B component comprises 50-75 parts of an aqueous isocyanate curing agent and 25-50 parts of propylene glycol diacetate. The preparation process of the hybrid emulsion is as follows: A second aqueous hydroxy acrylic emulsion, an amphiphilic silane coupling agent, and L-lysine were mixed and subjected to a first-stage heating reaction to obtain mixture M. Tetraethyl orthosilicate was added dropwise to the mixture M, and a second-stage heating reaction was carried out. After the reaction was completed, the mixture was cooled to room temperature to obtain a hybrid emulsion. The mass ratio of the second aqueous hydroxy acrylic emulsion, the amphiphilic silane coupling agent, tetraethyl orthosilicate, and L-lysine is (80-90):(2-5):(8-16):(0.03-0.06). The first stage heating reaction temperature is (45~60)℃, and the reaction time is (0.5~1.5)h; the dropping rate of the tetraethyl orthosilicate is (0.5~1) drops / second; the second stage heating reaction temperature is (45~60)℃, and the reaction time is (4~6)h. The mass ratio of component A to component B is (5-10):

1.

2. The water-based wind turbine blade topcoat with excellent alkali resistance and weather resistance according to claim 1, characterized in that: The solid content of the first and second aqueous hydroxy acrylic emulsions is (40-55)%, wherein the hydroxyl content is (2-4.2)% of the total mass of the hydroxy acrylic resin. The film-forming aid is one or a mixture of two of dipropylene glycol butyl ether and diethylene glycol monobutyl ether; The wear-resistant filler includes one or more combinations of feldspar powder, diatomite powder, wollastonite powder, quartz powder, and quartz sand. The waterborne polyurethane dispersion is a low-hydroxyl waterborne polyurethane dispersion, wherein the hydroxyl content is (0-2)% of the total mass of the waterborne polyurethane resin, the solid content is (35-55)%, and its surface drying time at room temperature is <20 min, and its actual drying time is <1 h. The wax emulsion is one or more of the aqueous polytetrafluoroethylene dispersions PTFE-1004A and PTFE-1008, with a solid content of 50-55 wt%.

3. The water-based wind turbine blade topcoat with excellent alkali resistance and weather resistance according to claim 1, characterized in that: The aqueous isocyanate curing agent is a polyether-modified HDI trimer oligomer with high NCO- group content, wherein the NCO- content is 18-22% of the total molecular weight, and its structural formula is: The structure of R is as follows: Where n = 10 to 100.

4. The water-based wind turbine blade topcoat with excellent alkali resistance and weather resistance as described in claim 1, characterized in that: The aqueous dispersant is one or more combinations of BYK-180, BYK-190, Eucalyptus 690w, SN5040, and X-405; The aqueous defoamer is one or more of the following: BYK-024, Tego810, Tego901w, Tego902w, Ucar290w, and Ucar295w. The aqueous thickener is one or a combination of WT-105A, U805, 812W, COATEX XS71, RM2020, and BR125P; The titanium dioxide is rutile titanium dioxide, which includes one or more combinations of R706, R996, and R5566. The matting powder is a modified silica matting powder with a wax-treated surface, having a porosity of 1.8 mL / g, an oil absorption value of 260–300 g, a particle size of 4.5–5.5 µm, and a pH of 6.0–7.

0.

5. The water-based wind turbine blade topcoat with excellent alkali resistance and weather resistance as described in claim 1, characterized in that: The colorant includes one or more combinations of water-based iron yellow colorant, water-based iron black colorant, and water-based royal blue colorant.

6. A method for preparing a water-based wind turbine blade topcoat with excellent alkali resistance and weather resistance as described in claim 1, characterized in that: The preparation of component A includes the following steps: According to the formula ratio, water, first aqueous hydroxy acrylic emulsion, film-forming aid, aqueous dispersant, aqueous defoamer and aqueous thickener are added into a stainless steel tank with condensate water and dispersed to obtain mixture N; According to the formula ratio, titanium dioxide, wear-resistant filler and matting powder are added to mixture N, and sand milling is carried out until the fineness is <30 microns. Then, the paint is produced by filtration. After weighing the paint, add wax emulsion, waterborne polyurethane dispersion, hybrid emulsion and waterborne color paste to the paint according to the formula ratio, and disperse at high speed to obtain component A. The preparation of component B includes the following steps: According to the formulation ratio, the water-based isocyanate curing agent and propylene glycol diacetate are dispersed evenly to obtain component B.

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