Polyester polyol for weather-resistant wind power coating and preparation method of polyester polyol

Abstract

The invention discloses polyester polyol for a weather-resistant wind power coating and a preparation method of the polyester polyol. The polyester polyol comprises polybasic acid, polyol and a catalyst, the polybasic acid comprises at least one of sebacic acid, 1, 4-cyclohexanedicarboxylic acid and terephthalic acid; the polyol comprises at least one of neopentyl glycol, trimethylolpropane, 1, 4-butanediol, diethylene glycol or 1, 6-hexanediol. The preparation method comprises the following steps: dehydrating at normal pressure; performing prepolymerization; and performing condensation polymerization. Through the formula design of the micromolecular polybasic acid and the polyhydric alcohol and the design of process conditions, the gloss retention rate of the prepared polyester polyol is larger than or equal to 90% after QUV-B accelerated aging is conducted for 2500 h, and the weather resistance is good; the acid value is less than or equal to 0.6 mgKOH / g, so that the electrochemical corrosion to the metal blade is reduced; the adhesive force of the coating is greater than or equal to 8MPa, and the use requirements of the coating for the wind power blade can be met.

Description

Technical Field

[0001] This invention relates to the field of coating preparation technology, and in particular to a weather-resistant polyester polyol for wind power coatings and its preparation method. Background Technology

[0002] In recent years, with the development and utilization of new energy sources such as wind power, wind power equipment and related products have experienced rapid growth. Wind turbine blades, being exposed to the natural environment for extended periods, require protective coatings to extend their service life.

[0003] Currently, wind turbine coatings prepared using traditional adipic acid-based polyester polyols have significant defects: gloss retention is <50% after 1000 hours of QUV-B aging; acid value >1.0 mgKOH / g, leading to coating powdering and peeling. The industry commonly uses the addition of antioxidants and physically blended UV absorbers to improve weather resistance, but the improvement effect is limited. Furthermore, physically blended additives are prone to migration, volatilization, and precipitation, resulting in insufficient durability and adhesion dropping to <5 MPa, failing to meet the long-term protection requirements of wind turbine blades. Summary of the Invention

[0004] This invention provides a weather-resistant polyester polyol for wind power coatings and its preparation method. The polyester polyol achieves durable, efficient and stable weather resistance by covalently bonding ultraviolet absorbing functional groups in its molecular chain, while maintaining excellent adhesion and low acid value.

[0005] To solve the above-mentioned technical problems, the present invention provides a polyester polyol for weather-resistant wind power coating, characterized in that it comprises polyacid, polyol, catalyst and ultraviolet absorption functional monomer. The amount of catalyst used is 50-80 ppm of the total mass of the polyacid and polyol; The amount of the ultraviolet-absorbing functional monomer is 3-5 wt% of the total mass of the polybasic acid; The polyacids include at least one of sebacic acid, 1,4-cyclohexanedicarboxylic acid and terephthalic acid; The polyol includes at least one of neopentyl glycol, trimethylolpropane, 1,4-butanediol, diethylene glycol, or 1,6-hexanediol; The ultraviolet absorption functional monomer is 2-(2'-hydroxy-5'-methylphenyl)benzotriazole-acrylate.

[0006] In a preferred embodiment of the present invention, the polyacids include sebacic acid and 1,4-cyclohexanedicarboxylic acid, and the mass ratio of sebacic acid to 1,4-cyclohexanedicarboxylic acid is 3-4:1.

[0007] In a preferred embodiment of the present invention, the polyol comprises neopentyl glycol and trimethylolpropane, and the mass ratio of neopentyl glycol to trimethylolpropane is 6-8:1.

[0008] In a preferred embodiment of the present invention, the catalyst is tetraisopropyl titanate.

[0009] In a preferred embodiment of the present invention, the preparation method of the ultraviolet absorption functional monomer includes the following steps: (a) Under inert gas protection, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole and an organic base are dissolved in an anhydrous organic solvent and cooled to 0-5°C; (b) While stirring, slowly add an organic solvent solution of acryloyl chloride. After the addition is complete, raise the temperature to room temperature and react for 6-8 hours. (c) After the reaction is complete, the by-product salt is removed by filtration, and the solvent is removed by vacuum distillation of the filtrate to obtain the crude product; (d) The crude product was recrystallized from the ethanol-water mixture to obtain purified 2-(2'-hydroxy-5'-methylphenyl)benzotriazole-acrylate.

[0010] In a preferred embodiment of the present invention, the molar ratio of 2-(2'-hydroxy-5'-methylphenyl)benzotriazole to acryloyl chloride is 1:1.0~1.2; and the molar ratio of the organic base to acryloyl chloride is 1.2~1.5:1.

[0011] To address the aforementioned technical problems, the present invention also provides a method for preparing polyester polyols, comprising the following steps: (1) Functional monomer pretreatment: The UV absorption functional monomer and part of the polyol in the formulation are stirred and pre-dissolved at 60-70°C to form a homogeneous solution; (2) Dehydration under normal pressure: Add the prescribed amount of the polyacid, the remaining polyol and the pretreatment solution obtained in step (1) into the reaction vessel and heat to complete the dehydration reaction; (3) Prepolymerization: Heat the dehydrated material to 210-220℃, add the amount of catalyst specified in the formula, and carry out the prepolymerization reaction under vacuum; (4) Polycondensation reaction: The prepolymerized mixture is heated to 230-240℃ and polycondensation reaction is carried out in an inert gas environment. During the polycondensation reaction, the hydroxyl value and acid value are monitored simultaneously. When the hydroxyl value reaches 50-60mgKOH / g and the acid value is ≤0.6mgKOH / g, the reaction is terminated, the material is cooled and discharged to obtain the polyester polyol.

[0012] In a preferred embodiment of the present invention, in step (1), the polyol used for pre-dissolving is neopentyl glycol, and its amount accounts for 10-15% of the total mass of the polyol.

[0013] In a preferred embodiment of the present invention, in step (2), the process conditions for the dehydration reaction are: atmospheric pressure, 130-140℃, 30-60min.

[0014] In a preferred embodiment of the present invention, in step (3), the prepolymerization process conditions are: absolute vacuum of 0.003-0.008 MPa and time of 2-2.5 h.

[0015] The beneficial effects of this invention are as follows: This invention provides a weather-resistant polyester polyol for wind turbine coatings and its preparation method. Through specific formulation and process design, and by covalently bonding ultraviolet absorption functional groups in the molecular chain, the prepared polyester polyol achieves a gloss retention rate of ≥92% after 3000 hours of accelerated QUV-B aging, exhibiting extremely excellent weather resistance; an acid value ≤0.6mgKOH / g, reducing electrochemical corrosion of metal blades; and a coating adhesion ≥8MPa, meeting the requirements for coatings used on wind turbine blades. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the process flow for preparing a weather-resistant wind power coating polyester polyol according to the present invention. Detailed Implementation

[0017] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby providing a clearer and more explicit definition of the scope of protection of the present invention.

[0018] This invention discloses a weather-resistant polyester polyol for wind power coating, comprising polyacid, polyol, catalyst and ultraviolet absorption functional monomer.

[0019] The catalyst is tetraisopropyl titanate, which has good environmental performance. Its dosage is 50-80 ppm of the total mass of polybasic acid and polyol, covering all carboxyl groups and preventing insufficient reaction rate from causing the acid value to exceed the standard.

[0020] The UV-absorbing functional monomer is 2-(2'-hydroxy-5'-methylphenyl)benzotriazole-acrylate (hereinafter referred to as HMPBT-AA), and its amount is 3-5 wt% of the total mass of the polybasic acid. The acrylate bond at the end of this monomer can undergo a polycondensation reaction with the polybasic acid and polyol, thereby firmly embedding itself into the polyester polyol molecular chain in the form of a covalent bond, realizing the "bulk" UV protection function.

[0021] Specifically, the preparation method of the ultraviolet absorption functional monomer includes the following steps: (a) Under inert gas protection, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole and an organic base are dissolved in an anhydrous organic solvent and cooled to 0-5°C; (b) While stirring, slowly add an organic solvent solution of acryloyl chloride. After the addition is complete, raise the temperature to room temperature and react for 6-8 hours. (c) After the reaction is complete, the by-product salt is removed by filtration, and the solvent is removed by vacuum distillation of the filtrate to obtain the crude product; (d) The crude product obtained is recrystallized twice with an ethanol-water mixed solvent to obtain purified 2-(2'-hydroxy-5'-methylphenyl)benzotriazole-acrylate with a concentration of not less than 99.0%, wherein the volume ratio of ethanol to water in the ethanol-water mixed solvent is 3:1 to 5:1.

[0022] The polycarboxylic acid includes at least one selected from sebacic acid, 1,4-cyclohexanedicarboxylic acid, and terephthalic acid. Preferably, the polycarboxylic acid includes sebacic acid and 1,4-cyclohexanedicarboxylic acid, and the mass ratio of sebacic acid to 1,4-cyclohexanedicarboxylic acid is 3-4:1. Sebacic acid is a long-chain dicarboxylic acid, which imparts flexibility to the polyester polyol molecular chain, while 1,4-cyclohexanedicarboxylic acid has a rigid alicyclic structure, which improves the UV degradation resistance of the polyester polyol.

[0023] The polyol includes at least one selected from neopentyl glycol, trimethylolpropane, 1,4-butanediol, diethylene glycol, or 1,6-hexanediol. Preferably, the polyol comprises neopentyl glycol and trimethylolpropane, and the mass ratio of neopentyl glycol to trimethylolpropane is 6-8:1. This amount of neopentyl glycol can reduce the crystallinity of the polyester polyol and reduce the brittleness of the polyester polyol film. The trimethylolpropane is used to improve the degree of crosslinking.

[0024] The specific steps for preparing the above-mentioned polyester polyol are as follows: (1) Dehydration under normal pressure: Add the prescribed amount of polyacid and polyol to the reaction vessel, heat to 130-140℃ under normal pressure, and dehydrate for 30-60 min to reduce the water content of the system to less than 0.05%; (2) Prepolymerization: Heat the dehydrated material to 210-220℃, add the catalyst of the formula amount, and evacuate to an absolute vacuum of 0.003-0.008MPa. The prepolymerization reaction is carried out for 2-2.5h. (3) Polycondensation reaction: The prepolymerized mixture is heated to 230-240℃ and polycondensation reaction is carried out in an inert gas environment. During the polycondensation stage, the hydroxyl value and acid value are monitored simultaneously. When the hydroxyl value reaches 50-60mgKOH / g and the acid value is ≤0.6mgKOH / g, the reaction is terminated and the material is discharged after cooling to below 120℃.

[0025] The polyester polyol of this invention achieves high weather resistance without the need for additional antioxidants.

[0026] The technical solution of the present invention will be described in detail below through specific embodiments.

[0027] Example 1: Preparation of the UV-absorbing functional monomer HMPBT-AA Nitrogen gas was introduced into a 1000 mL three-necked flask equipped with a stirrer, thermometer, and constant-pressure dropping funnel. 50.0 g (0.22 mol) of 2-(2'-hydroxy-5'-methylphenyl)benzotriazole and 33.4 g (0.33 mol) of triethylamine were added, dissolved in 400 mL of anhydrous tetrahydrofuran. The mixture was cooled to 0–5 °C in an ice-water bath. With stirring, 27.0 g (0.24 mol) of acryloyl chloride dissolved in 100 mL of tetrahydrofuran was slowly added dropwise, completing the addition over approximately 1 hour. The ice bath was removed, and the reaction was continued at room temperature for 7 hours. After the reaction was complete, the white triethylamine hydrochloride precipitate was removed by filtration. The filtrate was distilled under reduced pressure to recover the tetrahydrofuran, yielding a pale yellow viscous substance. Recrystallization from this substance using an ethanol-water (4:1 v / v) mixture yielded 58.2 g of white flaky crystals, with a yield of 91.5%. HPLC analysis showed a purity of 99.2%. FT-IR (KBr) cm⁻¹: 1725 (C=O, acrylate), 1630 (C=C, acrylate), 1600, 1550 (benzene ring and triazole ring).

[0028] Example 2 Preparation of Polyester Polyols Weigh 75 kg of sebacic acid and 25 kg of 1,4-cyclohexanedicarboxylic acid as the polyacid component. Weigh 72 kg of neopentyl glycol and 12 kg of trimethylolpropane as the polyol component. Separately weigh 3.0 kg (3 wt% of the total mass of the polyacid) of HMPBT-AA prepared in Example 1 and 10 kg of neopentyl glycol (approximately 11.9% of the total mass of the polyol) and stir at 65°C to pre-dissolve and form a homogeneous solution.

[0029] The pretreated solution was added to the reactor along with the remaining polyacid and polyol. Under normal pressure, the reactor was heated to 135°C and dehydrated for 60 minutes until the water content was less than 0.05%.

[0030] Then, heat to 220°C, add 60 ppm (based on the total mass of polyacids and polyols) of tetraisopropyl titanate catalyst, evacuate to an absolute vacuum of 0.008 MPa, and prepolymerize for 2 hours.

[0031] Continue heating to 230℃ and carry out polycondensation reaction at a constant temperature for 2 hours under nitrogen protection. During the process, samples are taken for testing. When the hydroxyl value of the material reaches 55mgKOH / g and the acid value drops to 0.48mgKOH / g, the reaction is terminated, the temperature is lowered to 120℃ and the material is discharged to obtain the target polyester polyol.

[0032] Example 3 Preparation of Polyester Polyols Weigh 80 kg of sebacic acid and 20 kg of 1,4-cyclohexanedicarboxylic acid as the polyacid component. Weigh 75 kg of neopentyl glycol and 10.7 kg of trimethylolpropane as the polyol component. Separately weigh 5.0 kg (5 wt% of the total mass of the polyacid) of HMPBT-AA prepared in Example 1 and 12 kg of neopentyl glycol (approximately 14.0% of the total mass of the polyol) and stir at 65°C to pre-dissolve and form a homogeneous solution.

[0033] The subsequent steps were the same as in Example 2. The final product had a hydroxyl value of 52 mgKOH / g and an acid value of 0.47 mgKOH / g.

[0034] Comparative Example 1 Compared to Example 2, HMPBT-AA was not added to the raw materials, but the remaining components and process conditions were exactly the same.

[0035] Comparative Example 2 Compared to Example 2, the raw materials were physically blended, that is, after the polycondensation reaction was completed and the temperature was lowered to 120°C, a conventional commercial UV absorber (Tinuvin 234) of the same mass as HMPBT-AA was added, and the mixture was stirred for 30 minutes. The remaining components and process conditions were the same as in Example 2.

[0036] Performance testing The polyester polyols prepared in Examples 2, 3, Comparative Example 1, and Comparative Example 2 were formulated with polyisocyanate curing agents to form coatings. The coatings underwent QUV-B aging tests according to GB / T 23987-2009, acid value determination according to GB / T 6743-2008, and adhesion determination according to the pull-off method in GB / T 5210-2006. Infrared spectral analysis was performed on the coatings after 3000 hours of aging to observe changes in the characteristic peaks of benzotriazole. The results are shown in Table 1 below.

[0037] Table 1 As shown in Table 1, the polyester polyols prepared in Examples 2 and 3 of this invention maintained a gloss retention rate of over 93% after 3000 hours of QUV-B aging, and the infrared spectrum showed extremely high retention of ultraviolet absorbing functional groups, proving the long-term stability of the chemical bonding method. In contrast, Comparative Example 1 (without additives) showed a significant performance decline after long-term aging. Comparative Example 2 (physical blend) exhibited lower long-term weather resistance and adhesion than the present invention due to the migration loss of the ultraviolet absorber, and the retention rate of ultraviolet absorbing groups was significantly reduced.

[0038] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A polyester polyol for weather-resistant wind power coatings, characterized in that, Including polyacids, polyols, catalysts, and UV-absorbing functional monomers; The amount of catalyst used is 50-80 ppm of the total mass of the polyacid and polyol; The amount of the ultraviolet-absorbing functional monomer is 3-5 wt% of the total mass of the polybasic acid; The polyacids include at least one of sebacic acid, 1,4-cyclohexanedicarboxylic acid and terephthalic acid; The polyol includes at least one of neopentyl glycol, trimethylolpropane, 1,4-butanediol, diethylene glycol, or 1,6-hexanediol; The ultraviolet absorption functional monomer is 2-(2'-hydroxy-5'-methylphenyl)benzotriazole-acrylate.

2. The polyester polyol according to claim 1, characterized in that, The polyacids include sebacic acid and 1,4-cyclohexanedicarboxylic acid, and the mass ratio of sebacic acid to 1,4-cyclohexanedicarboxylic acid is 3-4:

1.

3. The polyester polyol according to claim 1, characterized in that, The polyol includes neopentyl glycol and trimethylolpropane, and the mass ratio of neopentyl glycol to trimethylolpropane is 6-8:

1.

4. The polyester polyol according to claim 1, characterized in that, The catalyst is tetraisopropyl titanate.

5. The polyester polyol according to claim 1, characterized in that, The preparation method of the ultraviolet absorption functional monomer is as follows: (a) Under inert gas protection, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole and an organic base are dissolved in an anhydrous organic solvent and cooled to 0-5°C; (b) While stirring, slowly add an organic solvent solution of acryloyl chloride. After the addition is complete, raise the temperature to room temperature and react for 6-8 hours. (c) After the reaction is complete, the by-product salt is removed by filtration, and the solvent is removed by vacuum distillation of the filtrate to obtain the crude product; (d) The crude product was recrystallized from the ethanol-water mixture to obtain purified 2-(2'-hydroxy-5'-methylphenyl)benzotriazole-acrylate.

6. The polyester polyol according to claim 5, characterized in that, The molar ratio of 2-(2'-hydroxy-5'-methylphenyl)benzotriazole to acryloyl chloride is 1:1.0~1.2; the molar ratio of the organic base to acryloyl chloride is 1.2~1.5:

1.

7. A method for preparing a polyester polyol according to any one of claims 1-6, characterized in that, Includes the following steps: (1) Functional monomer pretreatment: The UV absorption functional monomer and part of the polyol in the formulation are stirred and pre-dissolved at 60-70°C to form a homogeneous solution; (2) Dehydration under normal pressure: Add the prescribed amount of the polyacid, the remaining polyol and the pretreatment solution obtained in step (1) into the reaction vessel and heat to complete the dehydration reaction; (3) Prepolymerization: Heat the dehydrated material to 210-220℃, add the amount of catalyst specified in the formula, and carry out the prepolymerization reaction under vacuum; (4) Polycondensation reaction: The prepolymerized mixture is heated to 230-240℃ and polycondensation reaction is carried out in an inert gas environment. During the polycondensation reaction, the hydroxyl value and acid value are monitored simultaneously. When the hydroxyl value reaches 50-60mgKOH / g and the acid value is ≤0.6mgKOH / g, the reaction is terminated, the material is cooled and discharged to obtain the polyester polyol.

8. The preparation method according to claim 7, characterized in that, In step (1), the polyol used for pre-dissolution is neopentyl glycol, and its amount accounts for 10-15% of the total mass of the polyol.

9. The preparation method according to claim 7, characterized in that, In step (2), the process conditions for the dehydration reaction are: atmospheric pressure, 130-140℃, 30-60min.

10. The preparation method according to claim 7, characterized in that, In step (3), the prepolymerization process conditions are: absolute vacuum of 0.003-0.008 MPa and time of 2-2.5 h.

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