Polyester core material and preparation method therefor, wind turbine blade skin and wind turbine blade

Abstract

Provided in the present application are a polyester core material and a preparation method therefor, a wind turbine blade skin and a wind turbine blade. The polyester core material comprises a modified polyester, wherein the modified polyester material is obtained by introducing a chain segment of bisphenol A diglycidyl ether and a chain segment of methyl tetrahydrophthalic acid into a PET material, and controlling the molar ratio of the chain segment of bisphenol A diglycidyl ether to the chain segment of ethylene glycol to be 1: (10-50). A relatively high content of a group having a rigid structure and larger spatial internal resistance can be introduced into the PET material, such that the number-average molecular weight and the molecular-weight distribution of the PET material are in an appropriate range, the modified polyester molecules are difficult to move, and the heat resistance and mechanical properties of PET are also improved.

Description

Polyester core material and preparation method thereof, wind power blade skin and wind power blade

[0001] Cross-reference to related applications

[0002] The present application claims priority to Chinese Patent Application No. 202411303423.0, filed on September 18, 2024, entitled "Polyester Core Material and Preparation Method Thereof, Wind Power Blade Skin and Wind Power Blade", the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0003] The present application belongs to the technical field of polyester materials, and specifically relates to a polyester core material and a preparation method thereof, a wind power blade skin and a wind power blade. BACKGROUND

[0004] Polyethylene terephthalate (PET) core material is mainly obtained by mixing polyethylene terephthalate resin with a foaming agent and foaming. The performance of the polyethylene terephthalate core material mainly depends on the properties of the PET resin used. PET resin is one of the most cost-effective plastic resins due to its low price, small wear, high hardness, non-toxicity, good weather resistance, good chemical stability, low water absorption, and resistance to weak acids and organic solvents, and is widely used.

[0005] However, the heat resistance and mechanical properties of PET resin are not ideal, especially it is difficult to obtain PET resin with good heat resistance and mechanical properties. Although, the PET resin can be modified by increasing the molecular weight of PET or introducing functional additives, but these methods still cannot well improve the heat resistance and mechanical properties, such as tensile strength and yield strength, at the same time. SUMMARY

[0006] The present application provides a polyester core material and a preparation method thereof, a wind power blade skin and a wind power blade, aiming to simultaneously improve the heat resistance and mechanical properties of the polyester core material.

[0007] The first aspect of the present application provides a polyester core material, comprising a modified polyester, wherein the modified polyester comprises a chain segment represented by Formula 1, Formula 2, Formula 3 and Formula 4,

[0008] The chain segment represented by Formula 1 is connected to the chain segment represented by Formula 3 or Formula 4; the chain segment represented by Formula 4 is connected to the chain segment represented by Formula 1 or Formula 2; and the molar ratio of the chain segments represented by Formula 1 and Formula 2 is 1:(10-50).

[0009] In an implementable embodiment of the first aspect of the present application, the modified polyester at least meets one of the following conditions:

[0010] a. the molar ratio of the segments represented by Formula 4 to Formula 3 is 1:(10-50);

[0011] b. the ratio of the total molar amount of the segments represented by Formula 1 and Formula 2 to the total molar amount of the segments represented by Formula 3 and Formula 4 is 1:(0.6-2), optionally 1:(1.0-1.5);

[0012] c. the segments represented by Formula 1 and Formula 4 account for 1%-20% of the total weight of the modified polyester.

[0013] In an implementable embodiment of the first aspect of the present application, the modified polyester at least meets one of the following conditions:

[0014] d. the number average molecular weight of the modified polyester is 20000 Da-30000 Da;

[0015] e. the molecular weight distribution of the modified polyester is 1.5-2.2;

[0016] f. the hydroxyl value of the modified polyester is 50 mgKOH / g-150 mgKOH / g.

[0017] In an implementable embodiment of the first aspect of the present application, the melt viscosity of the modified polyester is 250 Pa·s-520 Pa·s; and / or, the heat distortion temperature of the modified polyester is 100°C-120°C.

[0018] In an implementable embodiment of the first aspect of the present application, the ultimate tensile strength of the modified polyester is 40 MPa-55 MPa; and / or, the yield strength of the modified polyester is 35 MPa-50 MPa.

[0019] In an implementable embodiment of the first aspect of the present application, the polyester core material further comprises a foaming agent, and the mass ratio of the modified polyester to the foaming agent is 1:(0.2-0.8); optionally, the foaming agent comprises one or more of azodicarbonamide, azobisisobutyronitrile and azodicarboxylic ester.

[0020] The second aspect of the present application provides a preparation method of the polyester core material provided by the first aspect of the present application, comprising:

[0021] providing a degradation product of a wind turbine blade pultruded sheet, the degradation product of the wind turbine blade pultruded sheet comprising components of segments represented by Formula 1 and Formula 4;

[0022] mixing the degradation product of the wind turbine blade pultruded sheet and terephthalic acid, ethylene glycol to obtain a modified polyester;

[0023] mixing the modified polyester and a foaming agent, and expanding to obtain a polyester core material.

[0024] In an embodiment of the second aspect of the present application, in the step of providing the degradation product of the wind turbine blade pultrusion plate, the hydroxyl value of the degradation product of the wind turbine blade pultrusion plate is 300 mg KOH / g to 400 mg KOH / g.

[0025] In an embodiment of the second aspect of the present application, in the step of mixing the degradation product of the wind turbine blade pultrusion plate with terephthalic acid and ethylene glycol to obtain a modified polyester, the degradation product of the wind turbine blade pultrusion plate is mixed with terephthalic acid and ethylene glycol under an inert atmosphere and at a vacuum degree of 0 Pa to 10 Pa, and subjected to polycondensation reaction at 240°C to 300°C for 5 h to 12 h to obtain the modified polyester.

[0026] In an embodiment of the second aspect of the present application, in the step of mixing the modified polyester and the foaming agent and expanding to obtain the polyester core material, the modified polyester and the foaming agent are mixed and stirred at a mass ratio of 1:(0.2 to 0.8), and stirred under a nitrogen atmosphere at 240°C to 260°C for 2 h to 10 h, and then cooled to room temperature to obtain the PET core material.

[0027] The third aspect of the present application provides a wind turbine blade skin comprising the polyester core material provided by the first aspect of the present application.

[0028] The fourth aspect of the present application provides a wind turbine blade comprising the wind turbine blade skin provided by the third aspect of the present application.

[0029] The polyester core material of the present application comprises a modified polyester, wherein the modified polyester is obtained by replacing part of the ethylene glycol with a component comprising a segment represented by Formula 1 (e.g., a degradation product of a wind turbine blade pultrusion resin hydrolyzed into a hydroxyl-terminated bisphenol A diglycidyl ether) and replacing part of the terephthalic acid with a component comprising a segment represented by Formula 4 (e.g., a degradation product of a wind turbine blade pultrusion resin hydrolyzed into a carboxyl-containing methyltetrahydrophthalic acid), and then subjecting the hydroxyl groups and the carboxyl groups to polycondensation reaction, so as to introduce the segments represented by Formula 1 and Formula 4 (segments represented by Formula 2 and Formula 3) into the PET material. The introduction of a higher content of rigid structural groups and a larger steric hindrance into the PET material can make the modified polyester molecules difficult to move, so as to simultaneously improve the heat resistance and the mechanical properties of the PET.

[0030] Further, by controlling the molar ratio of the segments represented by Formula 1 and Formula 2 to be 1:(10 to 50), the PET material can be controlled to be less prone to degradation, so as to make the number average molecular weight, the molecular weight distribution, and the hydroxyl value of the PET material be in a suitable range, improve the problem of the number average molecular weight of the PET material being too low, the molecular weight distribution being too wide, and the viscosity being too low, and simultaneously improve the heat resistance and the mechanical properties of the PET. DETAILED DESCRIPTION

[0031] In order to make the inventive purposes, technical solutions and beneficial technical effects of the present application clearer, the present application will be further described in detail below in combination with embodiments. It should be understood that the embodiments described in the specification are only for the purpose of explaining the present application and are not intended to limit the present application.

[0032] For the sake of simplicity, only some numerical ranges are explicitly disclosed herein. However, any lower limit can be combined with any upper limit to form a range not explicitly recited; and any lower limit can be combined with other lower limits to form a range not explicitly recited, as can any upper limit be combined with any other upper limit to form a range not explicitly recited. Furthermore, although a range of endpoints is recited, each point or individual number within the range is also included in the range. Thus, each point or individual number can be combined with any other point or individual number to form a range not explicitly recited.

[0033] In the description herein, when a composition is described as containing, including, or comprising a particular component, or when a process is described as having, including, or comprising a particular step, it is contemplated that the present compositions also consist essentially of, or consist of, the recited components, and that the present processes also consist essentially of, or consist of, the recited steps.

[0034] The use of the terms "including," "containing," "having," "with" and variations thereof, is meant to encompass the items listed thereafter and equivalents thereof as well as additional items.

[0035] In the description herein, it is to be understood that the terms "above," "below," "upper," "lower," "upwardly," "downwardly," and variations thereof, refer to the specification in relation to the drawings, and not necessarily to the position of the described item in relation to the gravity.

[0036] The above summary of the application is not intended to describe each disclosed embodiment or every implementation of the present application. The description which follows more particularly exemplifies illustrative embodiments. In the description, reference is made to a series of embodiments, which can be used individually or in various combinations. In each instance, illustrative combinations are listed only as representative of the many combinations that are possible.

[0037] The inventors found that the performance of PET can be improved by increasing the molecular weight of PET, such as introducing chain extenders to increase the diversification of branches, or adding other resins or functional additives. However, the modification effect of these methods is limited, and since they usually extend the molecular weight of the original PET, it is easy to cause the molecular weight distribution to be too large, at least 3 or 4 or more. A large molecular weight distribution of PET material will cause the viscosity of the polyester material to be high, and the glass transition temperature to be low, resulting in limited improvement in the mechanical properties and heat resistance.

[0038] In view of this, the application provides a polyester core material and a preparation method thereof, a wind power blade skin and a wind power blade, aiming to simultaneously improve the heat resistance and mechanical properties of the PET core material.

[0039] In an embodiment of the first aspect of the application, a polyester core material is provided, comprising a modified polyester, wherein the modified polyester comprises segments represented by the following formula 1, formula 2, formula 3 and formula 4,

[0040] The segment represented by formula 1 is connected to the segment represented by formula 3 or formula 4; the segment represented by formula 4 is connected to the segment represented by formula 1 or formula 2; and the molar ratio of the segments represented by formula 1 and formula 2 is 1:(10-50).

[0041] In the polyester core material of the application, the modified polyester material uses a component comprising the segment represented by formula 1 (for example, a hydroxyl-terminated bisphenol A diglycidyl ether degradation product obtained by hydrolysis of a wind power blade pultrusion resin) to replace part of ethylene glycol, and a component comprising the segment represented by formula 4 (for example, a carboxyl-containing methyltetrahydrophthalic acid obtained by hydrolysis of a wind power blade pultrusion resin) to replace part of terephthalic acid, and the segments represented by formula 1 and formula 4 are introduced into the PET material (segments represented by formula 2 and formula 3) by polycondensation of the hydroxyl and carboxyl groups. This can introduce a higher content of rigid structural groups and a larger spatial resistance into the PET material, making it difficult for the modified polyester molecules to move, and thus simultaneously improving the heat resistance and mechanical properties of the PET.

[0042] Further, by controlling the molar ratio of the segments represented by formula 1 and formula 2 to be 1:(10-50), the PET material is less likely to degrade, and the number average molecular weight, molecular weight distribution and hydroxyl value of the PET material are within a suitable range, thereby improving the problem of a decrease in the number average molecular weight, a wide molecular weight distribution and a decrease in viscosity of the PET material, and simultaneously improving the heat resistance and mechanical properties of the PET.

[0043] In addition, the modification is performed at the front end of the preparation of the PET material, and part of the ethylene glycol and terephthalic acid is replaced, which avoids chain extension on the original PET molecular weight, thereby better improving the heat resistance and mechanical properties of the PET.

[0044] At the same time, since the application introduces a plurality of hydrophobic groups of benzene rings, the water resistance of the modified PET material can be enhanced, and the comprehensive performance of the PET resin can be improved.

[0045] Exemplarily, the connection mode of the segments represented by Formula 1, Formula 2, Formula 3 and Formula 4 in the modified polyester can be one or more of Formula 1-Formula 3-Formula 2-Formula 4, Formula 1-Formula 3-Formula 4-Formula 2, Formula 1-Formula 4-Formula 3-Formula 2, Formula 1-Formula 4-Formula 2-Formula 3, Formula 1-Formula 3-Formula 1-Formula 4-Formula 2, Formula 1-Formula 3-Formula 2-Formula 3-Formula 4 and Formula 2-Formula 4-Formula 2-Formula 3-Formula 1-Formula 3. For example, the reaction formula of the modified polyester can be as shown in Formula 5 below.

[0046] The raw materials including the segments represented by Formula 1, Formula 2, Formula 3 and Formula 4 in the polyester core material in the present application can be from recycled wind turbine blade related materials, such as wind turbine blade pultrusion plates, wind turbine blade skins, or from other materials.

[0047] For example, the substances including the segments represented by Formula 1 and Formula 4 described above in the polyester material of the present application can both be from the degradation products of thermosetting resins in recycled wind turbine blade pultrusion plates. For example, they can be from the degradation products of hydroxyl-terminated bisphenol A diglycidyl ether and methyl tetrahydrophthalic acid, respectively.

[0048] Developing renewable energy, reducing fossil energy consumption and building a green and low-carbon energy system are important measures to control global warming and achieve carbon emission reduction targets. Wind turbine blades, as the key core components of wind turbines for capturing wind energy, lead the development of wind turbines towards high power and large scale. The pultrusion plates of wind turbine blades usually use continuous fibers (such as glass fibers, carbon fibers) as reinforcing materials, which are impregnated with a resin matrix to obtain higher mechanical properties than vacuum infusion molding process, especially the compression performance in the 0° direction can be improved by nearly one time. The application of pultrusion plates makes the design and manufacture of super large wind turbine blades possible.

[0049] Pultruded panels are usually made of thermosetting resins and glass fiber or carbon fiber yarns by pultrusion process. It is reported in the literature [Dissolution of epoxy thermosets via mild alcoholysis: the mechanism and kinetics study.], [Recycling of Epoxy Thermoset and Composites via Good Solvent Assisted and Small Molecules Participated Exchange Reactions], [Bona fide upcycling strategy of anhydride cured epoxy and reutilization of decomposed dual monomers into multipurpose applications, Lin Shao, Yu-Chung Chang, Baoming Zhao, Xinyan Yan, Brian J. Bliss, Ming-en Fei, Chenhao Yu, Jinwen Zhang, Chemical Engineering Journal, Volume 464, 2023, 142735] that the method of alkaline hydrolysis can degrade anhydride-cured epoxy resins with similar structure to pultruded resins, which can theoretically separate the fibers and resins in the pultruded panels. However, the degradation products of wind turbine blade panels, such as bisphenol A diglycidyl ether and methyl tetrahydrophthalic acid, have not been high-value utilized. Therefore, developing high-value application scenarios for pultruded panel degradation resin products is a key problem faced by pultruded panel alkaline hydrolysis degradation schemes.

[0050] The inventors analyzed that the reason why the degradation products of wind turbine blade pultruded panels, such as bisphenol A diglycidyl ether and methyl tetrahydrophthalic acid, have not been high-value utilized may be that 1) wind turbine blade pultruded panels currently belong to a relatively advanced technical field, and the degradation of wind turbine blade pultruded panels is more advanced, and the cost of degrading wind turbine blade pultruded panels is relatively high, which is poor in economy, resulting in less research data; 2) the content of epoxy resin in wind turbine blade pultruded panels is relatively low, and the mass content is only about 10% to 20%, which is difficult to be high-value utilized; 3) the degradation products of wind turbine blade pultruded panels are complex, and it is difficult to find a suitable parameter and range or standard to evaluate whether they can be utilized; 4) due to the complexity of the degradation products, and almost no past research data, whether they can produce application value when added to other materials is a blank technical field, which is difficult.

[0051] The present application overcomes the defect that the degradation products of the thermosetting resin in the wind turbine blade pultruded plate are difficult to be high-value utilization by controlling the hydroxyl value of the degradation products of the wind turbine blade pultruded plate within a suitable range, for example, 300 mg KOH / g to 400 mg KOH / g, successfully introducing the degradation products of bisphenol A diglycidyl ether and methyl tetrahydrophthalic acid in the wind turbine blade pultruded plate into the PET material, combining the wind turbine blade pultruded plate with the application of the PET material, not only realizing the high-value application of the degradation products of the wind turbine blade pultruded plate, but also comprehensively improving the performance of the PET material, for example, simultaneously improving the heat resistance and mechanical strength of the PET material, and having high application value.

[0052] Further, the present application can control the introduction amount of the degradation products of bisphenol A diglycidyl ether and methyl tetrahydrophthalic acid, for example, the weight percentage of the chain segments contained in the modified PET material accounts for the total weight of the modified PET material within a suitable range, for example, the molar ratio of the chain segments represented by formula 4 and formula 3, the total molar amount of the chain segments represented by formula 1 and formula 2 to the total molar amount of the chain segments represented by formula 3 and formula 4, to affect the content of the terminal carboxyl group and the ester group in the modified polyester, so that the content of the two is lower, thereby further improving the mechanical properties, thermal stability and water resistance of the PET.

[0053] For example, in some embodiments, the modified polyester at least meets one of the following conditions:

[0054] a. The molar ratio of the chain segments represented by formula 4 and formula 3 is 1:(10-50);

[0055] b. The ratio of the total molar amount of the chain segments represented by formula 1 and formula 2 to the total molar amount of the chain segments represented by formula 3 and formula 4 is 1:(0.6-2), and optionally 1:(1.0-1.5);

[0056] c. The weight of the chain segments represented by formula 1 and formula 4 accounts for 1% to 20% of the total weight of the modified polyester.

[0057] In the present application, the PET material is modified at the front end, and the number average molecular weight of the obtained modified PET material is 20000 Da to 30000 Da, and the molecular weight distribution is small, which can be 1.5 to 2.2, and the small hydroxyl value can make the heat resistance and mechanical properties of the modified polyester more excellent, such as tensile strength and yield strength. And, it can also improve the water resistance, curing speed, hardness and mechanical properties of the PET material.

[0058] For example, in some embodiments, the modified polyester at least meets one of the following conditions:

[0059] d. the number average molecular weight of the modified polyester is 20,000 Da to 30,000 Da, optionally 25,000 Da to 29,000 Da;

[0060] e. the molecular weight distribution of the modified polyester is 1.5 to 2.2;

[0061] f. the hydroxyl value of the modified polyester is 50 mgKOH / g to 150 mgKOH / g.

[0062] The modified PET material of the present application has excellent heat resistance. For example, in some embodiments, the melt viscosity of the modified polyester is 250 Pa-s to 520 Pa-s; and / or, the heat distortion temperature of the modified polyester is 100°C to 120°C, optionally 109°C to 120°C.

[0063] The modified PET material of the present application not only has excellent heat resistance, but also has high mechanical strength. For example, in some embodiments, the ultimate tensile strength of the modified polyester is 40 MPa to 55 MPa, optionally 43 MPa to 55 MPa; and / or, the yield strength of the modified polyester is 35 MPa to 50 MPa, optionally 36 MPa to 50 MPa.

[0064] In some embodiments, the polyester core material further comprises a foaming agent, and the mass ratio of the modified polyester to the foaming agent is 1:(0.2 to 0.8); optionally, the foaming agent comprises one or more of azodicarbonamide, azobisisobutyronitrile, and azobisacetate.

[0065] In the embodiments of the second aspect of the present application, the preparation method of the polyester core material provided by the first aspect of the present application is provided, comprising:

[0066] Providing a degradation product of a wind turbine blade pultruded sheet, the degradation product of the wind turbine blade pultruded sheet comprising components respectively having structures shown in Formula 1 and Formula 4;

[0067] Mixing the degradation product of the wind turbine blade pultruded sheet and terephthalic acid, ethylene glycol to obtain a modified polyester;

[0068] Mixing the modified polyester and a foaming agent, and expanding to obtain a polyester core material.

[0069] The inventors found that when the hydroxyl value of the degradation product of the wind turbine blade pultruded sheet is controlled within a certain range, such as 300 mg KOH / g to 400 mg KOH / g, the degradation product of the thermosetting resin in the wind turbine blade pultruded sheet, i.e., bisphenol A diglycidyl ether and methyl tetrahydrophthalic acid, can be introduced into the PET material to improve the heat resistance and mechanical strength of the PET material, and realize high-value application of the degradation product of the wind turbine blade pultruded sheet.

[0070] In some embodiments, in the step of providing a degradation product of a wind power blade pultrusion sheet, the degradation product of the wind power blade pultrusion sheet comprises components having structures shown in Formula 1 and Formula 4 respectively, the hydroxyl value of the degradation product of the wind power blade pultrusion sheet is 300 mg KOH / g to 400 mg KOH / g.

[0071] In some embodiments, in the step of mixing the degradation product of the wind power blade pultrusion sheet with terephthalic acid and ethylene glycol to obtain a modified polyester, the degradation product of the wind power blade pultrusion sheet is mixed with terephthalic acid and ethylene glycol under an inert atmosphere and at a vacuum degree of 0 Pa to 10 Pa, and subjected to polycondensation reaction at 240°C to 300°C for 5 h to 12 h to obtain the modified polyester.

[0072] In some embodiments, in the step of mixing the modified polyester and the foaming agent and expanding to obtain a polyester core material, the modified polyester and the foaming agent are mixed and stirred at a mass ratio of 1:(0.2 to 0.8), and stirred under a nitrogen atmosphere at 240°C to 260°C for 2 h to 10 h, and then cooled to room temperature to obtain the PET core material.

[0073] In some embodiments of the third aspect of the present application, a wind power blade skin is provided, which comprises the polyester core material provided by the first aspect of the present application.

[0074] In some embodiments of the fourth aspect of the present application, a wind power blade skin is provided, which comprises the wind power blade skin provided by the third aspect of the present application.

[0075] The present application can first obtain a degradation product by degrading a waste wind power blade pultrusion sheet, then control the hydroxyl value of the degradation product within a certain range, and apply the degradation product of the wind power blade pultrusion sheet to PET to obtain a PET core material having excellent heat resistance and mechanical properties, and then the PET core material can be prepared into a wind power blade skin, and the wind power blade skin can be further assembled into a wind power blade, thereby realizing long cycle utilization of wind power blade materials, effectively integrating the resources of wind power blades, and having very important significance for environmental protection, production cost, and resource utilization, and being conducive to sustainable development.

[0076] Examples

[0077] The following examples more specifically describe the present disclosure, which are merely illustrative and not restrictive, because various modifications and changes can be made within the scope of the present disclosure, which will be apparent to those skilled in the art. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are based on weight, and all reagents used in the examples are commercially available or synthesized according to conventional methods and used directly without further treatment, and the instruments used in the examples are commercially available.

[0078] Example 1

[0079] The present embodiment provides a preparation method of a modified PET core material, comprising: taking a degradation product of a wind turbine blade pultruded sheet with a hydroxyl value of ~350 mg KOH / g, the degradation product including bisphenol A diglycidyl ether degradation product and methyl tetrahydrophthalic acid, and subjecting the degradation product of the wind turbine blade pultruded sheet to polycondensation reaction with terephthalic acid and ethylene glycol under inert atmosphere and at a vacuum degree of 10 Pa at 300℃ for 5h to obtain a modified PET resin.

[0080] The molar ratio of bisphenol A diglycidyl ether to ethylene glycol is 1:30, the molar ratio of methyl tetrahydrophthalic acid to terephthalic acid is 1:25, the total molar amount of bisphenol A diglycidyl ether and ethylene glycol to the total molar amount of methyl tetrahydrophthalic acid and terephthalic acid is 1:1, and the weight of bisphenol A diglycidyl ether and methyl tetrahydrophthalic acid accounts for 8% of the total weight of the modified PET resin.

[0081] The above modified PET resin and azodicarbonamide are mixed at a mass ratio of 1:0.5, stirred at 250℃ under nitrogen atmosphere for 4h, and cooled to room temperature to shape, to obtain a PET core material.

[0082] Examples 2-8

[0083] Example 2, compared with Example 1, the main difference is that the molar ratio of methyl tetrahydrophthalic acid to terephthalic acid is changed to 1:50, and other conditions such as the molar ratio of bisphenol A diglycidyl ether to ethylene glycol is 1:30, the total molar amount of bisphenol A diglycidyl ether and ethylene glycol to the total molar amount of methyl tetrahydrophthalic acid and terephthalic acid is 1:1, and the weight percentage of bisphenol A diglycidyl ether and methyl tetrahydrophthalic acid in the total weight of the modified PET resin is adjusted adaptively.

[0084] Example 3, compared with Example 1, the main difference is that the molar ratio of methyl tetrahydrophthalic acid to terephthalic acid is changed to 1:10, and other conditions such as the molar ratio of bisphenol A diglycidyl ether to ethylene glycol is 1:30, the total molar amount of bisphenol A diglycidyl ether and ethylene glycol to the total molar amount of methyl tetrahydrophthalic acid and terephthalic acid is 1:1, and the weight percentage of bisphenol A diglycidyl ether and methyl tetrahydrophthalic acid in the total weight of the modified PET resin is adjusted adaptively.

[0085] Example 4, the main difference compared to Example 1 is that the ratio of the total moles of bisphenol A diglycidyl ether and ethylene glycol to the total moles of methyltetrahydrophthalic acid and terephthalic acid is changed to 1:1.5, other conditions are that the molar ratio of bisphenol A diglycidyl ether to ethylene glycol is 1:30, the molar ratio of methyltetrahydrophthalic acid to terephthalic acid is 1:25, and the percentage of the weight of bisphenol A diglycidyl ether and methyltetrahydrophthalic acid in the total weight of the modified PET resin is adaptively changed.

[0086] Example 5, the main difference compared to Example 1 is that the ratio of the total moles of bisphenol A diglycidyl ether and ethylene glycol to the total moles of methyltetrahydrophthalic acid and terephthalic acid is changed to 1:1.5, other conditions are that the molar ratio of bisphenol A diglycidyl ether to ethylene glycol is 1:30, the molar ratio of methyltetrahydrophthalic acid to terephthalic acid is 1:25, and the percentage of the weight of bisphenol A diglycidyl ether and methyltetrahydrophthalic acid in the total weight of the modified PET resin is adaptively changed.

[0087] Example 6, the main difference compared to Example 1 is that the ratio of the total moles of bisphenol A diglycidyl ether and ethylene glycol to the total moles of methyltetrahydrophthalic acid and terephthalic acid is changed to 1:0.67, other conditions are that the molar ratio of bisphenol A diglycidyl ether to ethylene glycol is 1:30, the molar ratio of methyltetrahydrophthalic acid to terephthalic acid is 1:25, and the percentage of the weight of bisphenol A diglycidyl ether and methyltetrahydrophthalic acid in the total weight of the modified PET resin is adaptively changed.

[0088] Example 7, the main difference compared to Example 1 is that the degradation product of the wind turbine blade pultruded sheet with a hydroxyl value of ~500 mg KOH / g is used in the preparation method.

[0089] Example 8, the main difference compared to Example 1 is that in the preparation method, commercial PET pellets are used instead of terephthalic acid and ethylene glycol, and then the degradation product of the wind turbine blade pultruded sheet with a hydroxyl value of ~350 mg KOH / g is added for modification to obtain the modified PET material.

[0090] Comparative Examples 1-3

[0091] Comparative Example 1, the main difference compared to Example 1 is that only the segment shown in Formula 1 is introduced into the modified PET resin, and only bisphenol A diglycidyl ether is introduced.

[0092] Comparative Example 2, the main difference compared to Example 1 is that only the segment shown in Formula 4 is introduced into the modified PET resin, and only methyltetrahydrophthalic acid is introduced.

[0093] Comparative Example 3, compared with Example 1, the main difference is that the molar ratio of bisphenol A diglycidyl ether to ethylene glycol in the modified PET resin is changed to 1:55, and the other conditions are that the molar ratio of methyltetrahydrophthalic acid to terephthalic acid is 1:25, the total molar amount of bisphenol A diglycidyl ether and ethylene glycol to the total molar amount of methyltetrahydrophthalic acid and terephthalic acid is 1:1, and the weight percentage of bisphenol A diglycidyl ether and methyltetrahydrophthalic acid in the total weight of the modified PET resin is adaptively changed.

[0094] The properties of the modified PET resins prepared in each example and comparative example were tested, and the test results are shown in Tables 1-2 below.

[0095] Measurement method

[0096] Number average molecular weight: tested according to ASTM D5296 / ASTM D6226 standards.

[0097] Molecular weight distribution: tested according to ASTM D5296 / ASTM D6226 standards.

[0098] Hydroxyl value: tested according to ASTM D4274 standards.

[0099] Melt viscosity: tested according to ASTM D3835 / ISO 11443 standards.

[0100] Heat distortion temperature: tested according to ASTM D648 standards.

[0101] Ultimate tensile strength: tested according to ISO 527 standards.

[0102] Yield strength: tested according to ISO 527 standards.

[0103] Table 1: Test data of physical and chemical properties of PET resins in each example and comparative example

[0104] Table 2: Test data of heat resistance and mechanical properties of PET resins in each example and comparative example

[0105] As can be seen from Tables 1-2, the modified PET resin of the embodiments of the present application obtains samples with excellent heat resistance and mechanical properties by introducing the chain segments shown in Formula 1 and Formula 4 and controlling the proportion of the introduced amount. Among them, the comparative examples 1-2 do not simultaneously introduce the chain segments shown in Formula 1 and Formula 2, and the heat resistance and mechanical strength are both decreased, especially the heat distortion temperature and the ultimate tensile strength and yield strength. Although the comparative example 3 introduces the chain segments shown in Formula 1 and Formula 2, the introduced amount of the chain segment shown in Formula 1 is small and the ethylene glycol is more, which may cause the polymerization reaction of the PET material to be poor, the number average molecular weight to decrease, the molecular distribution to increase, and the heat resistance and mechanical properties to be significantly decreased, indicating that the introduction of the chain segments shown in Formula 1 and Formula 4 and the proportion of the introduced amount are important for improving the heat resistance and mechanical properties of the modified PET resin.

[0106] In addition, the inventors have also found through experimental research that the heat resistance and mechanical properties of PET can be further improved by controlling the introduced amount of the chain segment shown in Formula 4, the total introduced amount of the chain segments shown in Formula 1 and Formula 4, and the total amount of the chain segments shown in Formula 1 and Formula 2 and the total amount of the chain segments shown in Formula 3 and Formula 4. As can be seen from the embodiments 1-3, the increase of the introduced amount of the chain segment shown in Formula 4 can increase the rigid groups in the polymer molecular structure, and the heat resistance and mechanical properties are improved. As can be seen from the embodiments 1, 4-6, the proportion of the total introduced amount of the chain segments shown in Formula 1 and Formula 4 and the proportion of the total amount of the chain segments shown in Formula 1 and Formula 2 and the total amount of the chain segments shown in Formula 3 and Formula 4 can be controlled in a suitable range, the number average molecular weight, the molecular weight distribution and the hydroxyl value of the modified polyester are controlled in a suitable range, the number average molecular weight is increased, the molecular weight distribution is reduced, and the performance of PET is further improved.

Claims

1. A polyester core material, wherein, The polyester core material includes a modified polyester, wherein the modified polyester includes segments represented by Formula 1, Formula 2, Formula 3, and Formula 4 below, The segment of the formula 1 is connected with the segment of the formula 3 or the formula 4; the segment of the formula 4 is connected with the segment of the formula 1 or the formula 2. The molar ratio of the segment of the formula 1 to the segment of the formula 2 is 1:(10-50).

2. The polyester core material according to claim 1, wherein, The modified polyester at least meets one of the following characteristics: a. The molar ratio of the segment of the formula 4 to the segment of the formula 3 is 1:(10-50); b. The total molar amount of the segment of the formula 1 and the formula 2 to the total molar amount of the segment of the formula 3 and the formula 4 is 1:(0.6-2), optionally 1:(1.0-1.5); c. The weight of the segment of the formula 1 and the formula 4 accounts for 1%-20% of the total weight of the modified polyester.

3. The polyester core material according to claim 1, wherein, The modified polyester at least meets one of the following characteristics: d. The number average molecular weight of the modified polyester is 20000 Da-30000 Da; e. The molecular weight distribution of the modified polyester is 1.5-2.2; f. The hydroxyl value of the modified polyester is 50 mgKOH / g-150 mgKOH / g.

4. The polyester core material according to claim 1, wherein, The melt viscosity of the modified polyester is 250 Pa·s-520 Pa·s; and / or, the heat distortion temperature of the modified polyester is 100℃-120℃.

5. The polyester core material according to claim 1, wherein, The ultimate tensile strength of the modified polyester is 40 MPa-55 MPa; and / or, the yield strength of the modified polyester is 35 MPa-50 MPa.

6. The polyester core material according to claim 1, wherein, The polyester core material further comprises a foaming agent, and the mass ratio of the modified polyester to the foaming agent is 1:(0.2-0.8); optionally, the foaming agent comprises one or more of azodicarbonamide, azobisisobutyronitrile and azodicarboxylic ester.

7. The method of producing a polyester core material according to any one of claims 1 to 6, wherein It comprises: Providing a degradation product of a wind power blade pultruded sheet, wherein the degradation product of the wind power blade pultruded sheet comprises components of the segment of the formula 1 and the formula 4; Mixing the degradation product of the wind power blade pultruded sheet with terephthalic acid and ethylene glycol to obtain a modified polyester; Mixing the modified polyester with a foaming agent and expanding to obtain the polyester core material.

8. The method of producing a polyester core material according to claim 7, wherein In the step of providing the degradation product of the wind power blade pultruded sheet, the hydroxyl value of the degradation product of the wind power blade pultruded sheet is 300 mg KOH / g-400 mg KOH / g.

9. The method of producing a polyester core material according to claim 7, wherein In the step of mixing the degradation product of the wind power blade pultruded sheet with terephthalic acid and ethylene glycol to obtain a modified polyester, the degradation product of the wind power blade pultruded sheet is mixed with terephthalic acid and ethylene glycol under the conditions of inert atmosphere, vacuum degree 0 Pa-10 Pa, reaction temperature 240℃-300℃ and reaction time 5 h-12 h to obtain the modified polyester.

10. The method of producing a polyester core material according to claim 7, wherein In the step of mixing the modified polyester with a foaming agent and expanding to obtain the polyester core material, the modified polyester and the foaming agent are mixed and stirred at the mass ratio of 1:(0.2-0.8), under the conditions of nitrogen atmosphere, stirring temperature 240℃-260℃ and stirring time 2 h-10 h, and then cooled to room temperature to obtain the polyester core material.

11. A wind turbine blade skin, wherein, A polyester core material comprising any one of claims 1 to 6.

12. A wind turbine blade, wherein, A wind turbine blade skin comprising the claim 11.

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