High-weather-resistance polyester resin and preparation method thereof

Abstract

The invention belongs to the technical field of polyester resin preparation, and provides high-weather-resistance polyester resin and a preparation method thereof. Firstly, neopentyl glycol, maleic anhydride and benzoic acid are used as raw materials to synthesize a polyester matrix, the steric hindrance effect of neopentyl glycol reduces the hydrolysis sensitivity of ester bonds, and the end group blocking effect of benzoic acid reduces the carboxyl content; the weather resistance of the material is further enhanced through high chemical stability and oxidation resistance of a phosphorus-nitrogen main chain of polyphosphazene, and the ultraviolet resistance and the light aging resistance are enhanced by introducing 2, 6-di-tert-butylphenol; in addition, PDMS-PEG is synthesized and polymerized with 4-vinylpyridine, a PDMS-PEG block copolymer with high flexibility and oxidation resistance is prepared, PDMS provides hydrophobicity and flexibility, a pyridine group inhibits oxidative degradation by capturing free radicals, and a polyphosphazene hybrid, a polyester matrix and the PDMS-PEG block copolymer are mixed to obtain the high-weather-resistance polyester resin.

Description

Technical Field

[0001] The present invention belongs to the technical field of polyester resin preparation, and relates to a highly weather-resistant polyester resin and a preparation method thereof. Background Art

[0002] As an important polymer material, polyester resin has been widely used due to its excellent comprehensive properties. Polyester resin has good mechanical strength, chemical corrosion resistance, and high thermal stability, and occupies an important position in fields such as coatings, fibers, composites, and packaging materials. However, despite the significant advantages shown by polyester resin in many applications, the inherent defects in its chemical structure result in relatively poor weather resistance, which limits its service life under long-term exposure to harsh environmental conditions. The weather resistance problem of polyester resin mainly stems from the chemical activity and instability of ester bonds in the molecular chain. In a humid or acidic / alkaline environment, ester bonds are vulnerable to nucleophilic attack by water molecules and undergo hydrolysis reactions. Such hydrolysis reactions can cause the polyester chain to break, resulting in a decrease in the molecular weight of the material, thereby leading to a significant deterioration in performance, manifested as a decrease in mechanical strength and toughness. In addition, the photo-degradation and oxidative degradation processes of polyester resin are usually accompanied by the generation and propagation of free radicals, and this chain reaction will further accelerate the degradation rate of the material. Especially in polyester-based products used outdoors, such as coatings, building materials, and outdoor fiber products, long-term exposure to sunlight and the atmospheric environment makes their photo-degradation and oxidative degradation behaviors inevitable. This problem not only reduces the service life of polyester resin but also restricts its promotion in high-performance and high-durability applications.

[0003] Therefore, how to effectively improve the weather resistance of polyester resin has become the focus of current research. Summary of the Invention

[0004] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a highly weather-resistant polyester resin and a preparation method thereof. First, through esterification and polycondensation reactions, a polyester matrix is prepared, and end-capping benzoic acid further reduces the carboxyl end group content. Subsequently, through the high-temperature polymerization of hexachlorocyclotriphosphazene and phenolic substitution reactions, a polyphosphazene hybrid with antioxidant and ultraviolet-resistant functions is prepared; PDMS and PEG monomethyl ether are catalytically polymerized to prepare PDMS-PEG with both flexible and polar functions, and the mechanical properties and photo-oxidation stability of the material are enhanced by the introduction of 4-vinylpyridine. Finally, the polyphosphazene hybrid and the PDMS-PEG block copolymer are dispersed in the polyester matrix to meet the actual production needs.

[0005] To achieve this purpose, the present invention adopts the following technical solutions:

[0006] In the first aspect, the present invention provides a preparation method of a highly weather-resistant polyester resin, and the preparation method includes:

[0007] S1, Mix terephthalic acid, isophthalic acid, ethylene glycol, neopentyl glycol, and 1,6 - hexanediol, and add tetrabutyl titanate, maleic anhydride, and benzoic acid to obtain a polyester matrix;

[0008] S2, Place hexachlorocyclotriphosphazene in a nitrogen atmosphere, heat it to obtain polyphosphazene. Disperse the polyphosphazene in DMF, add 2,6 - di - tert - butylphenol and potassium carbonate, react to obtain a phenolic - substituted product, and then add light stabilizer 1577, N,N'-dicyclohexylcarbodiimide, and 4 - dimethylaminopyridine to the phenolic - substituted product to obtain a polyphosphazene hybrid;

[0009] S3, Mix polydimethylsiloxane, methoxypolyethylene glycol, and p - toluenesulfonic acid, react to obtain PDMS - PEG. Then disperse PDMS - PEG, 4 - vinylpyridine, and azobisisobutyronitrile in toluene and react to obtain a PDMS - PEG block copolymer;

[0010] S4, Add the polyphosphazene hybrid to the polyester matrix, and then add the PDMS - PEG block copolymer to obtain a highly weather - resistant polyester resin;

[0011] The mass ratio of terephthalic acid, tetrabutyl titanate, maleic anhydride, and benzoic acid is (450 - 460):2:(5 - 6):(8 - 9);

[0012] The mass ratio of polyphosphazene, 2,6 - di - tert - butylphenol, and potassium carbonate is (20 - 25):(30 - 35):20;

[0013] The mass ratio of PDMS - PEG, 4 - vinylpyridine, and azobisisobutyronitrile is (30 - 35):50:(1 - 2).

[0014] Specifically include:

[0015] S1, In a nitrogen atmosphere, mix terephthalic acid, isophthalic acid, ethylene glycol, neopentyl glycol, and 1,6 - hexanediol, adjust the temperature to the first temperature, add tetrabutyl titanate, react until the acid value ≤ 30 mg KOH / g, raise the temperature to the second temperature, add maleic anhydride, adjust the temperature to the third temperature, reduce the pressure to 10 KPa and continue to react. When the acid value drops to 15 mg KOH / g, add benzoic acid and continue to react until the acid value ≤ 5 mg KOH / g, then cool down to 160 °C for standby to obtain a polyester matrix;

[0016] S2. Place hexachlorocyclotriphosphazene in a nitrogen atmosphere, heat it to the fourth temperature and hold for a certain time, cool it, and disperse it in tetrahydrofuran to obtain polyphosphazene. Then disperse the polyphosphazene in DMF, add 2,6-di-tert-butylphenol and potassium carbonate, react under a nitrogen atmosphere by adjusting the temperature to the fifth temperature. After the reaction, filter to remove potassium carbonate, wash with hydrochloric acid solution, and then wash with water until neutral to obtain a phenol-substituted product. Then add light stabilizer 1577, N,N'-dicyclohexylcarbodiimide and 4-dimethylaminopyridine to the phenol-substituted product, react at the fifth temperature, and dry to obtain a polyphosphazene hybrid;

[0017] S3. Mix polydimethylsiloxane, polyethylene glycol monomethyl ether and p-toluenesulfonic acid, adjust the temperature to the fifth temperature under a nitrogen atmosphere, and after the reaction, wash and dry to obtain PDMS-PEG. Then disperse PDMS-PEG, 4-vinylpyridine and azobisisobutyronitrile in toluene, adjust the temperature to the sixth temperature and react under a nitrogen atmosphere, precipitate and dry to obtain a PDMS-PEG block copolymer;

[0018] S4. Add the polyphosphazene hybrid to the polyester matrix, mix evenly, adjust the temperature to the seventh temperature, then add the PDMS-PEG block copolymer, mix evenly and extrude to obtain a highly weather-resistant polyester resin;

[0019] The mass ratio of terephthalic acid, tetrabutyl titanate, maleic anhydride and benzoic acid is (450 - 460):2:(5 - 6):(8 - 9);

[0020] The mass ratio of the polyphosphazene, 2,6-di-tert-butylphenol and potassium carbonate is (20 - 25):(30 - 35):20;

[0021] The mass ratio of PDMS-PEG, 4-vinylpyridine and azobisisobutyronitrile is (30 - 35):50:(1 - 2).

[0022] The weather resistance improvement of the polyester matrix depends on the stability of the main-chain chemical structure. In the reaction formulation design, terephthalic acid is selected as the main dibasic acid monomer, while isophthalic acid is introduced in a small amount as a comonomer. The benzene ring structure of terephthalic acid provides extremely high chemical stability through the conjugated π-electron system. The rigidity of the benzene ring makes the main chain not easily undergo molecular chain breakage when exposed to ultraviolet radiation, and at the same time, the benzene ring can partially absorb the energy of ultraviolet radiation, thereby reducing the destructive effect of ultraviolet rays on the ester bond. In addition, the introduction of isophthalic acid forms a certain distortion in the molecular chain. This distorted structure can not only effectively reduce the packing density between polyester chains, but also delay the occurrence of oxidative degradation and hydrolysis by hindering the diffusion of oxygen and moisture. Secondly, in the selection of diols, the synergistic effect of ethylene glycol, neopentyl glycol and 1,6-hexanediol also significantly improves the weather resistance of the polyester. As a short-chain diol, the high reactivity of ethylene glycol ensures the efficient progress of the esterification reaction, but its rigidity is relatively high, and its flexibility and weather resistance are relatively insufficient. The introduction of neopentyl glycol makes up for this defect. The two methyl groups bonded to the central carbon atom of neopentyl glycol provide a significant steric hindrance effect. This steric hindrance can effectively protect the ester bond from the attack of moisture or acids and bases in the external environment, thereby improving the hydrolysis stability of the polyester. In addition, the symmetry and molecular stability of neopentyl glycol also enhance the thermal stability and antioxidant properties of the polyester chain. The long-chain structure of 1,6-hexanediol introduces flexibility to the molecular chain, making the polyester more ductile under long-term environmental stress and able to resist embrittlement caused by heat or mechanical action. The anhydride group structure of maleic anhydride can undergo a ring-opening reaction with the hydroxyl groups in the system to form ester bonds and introduce unsaturated double bonds at the same time. This process not only further reduces the concentration of free hydroxyl groups in the system and reduces the hydrolysis sensitivity, but also provides the possibility of chemical modification for the polyester chain. The unsaturated double bonds of maleic anhydride have high chemical activity and can undergo cross-linking reactions in subsequent processing to form a certain degree of three-dimensional network structure. The cross-linked network effectively restricts the free movement of the molecular chain, improves the thermal aging stability of the polyester, and enhances its resistance to ultraviolet rays and oxidative environment at the same time. The introduction of benzoic acid plays a dual role of capping and enhancing weather resistance. As a terminal regulator, the monofunctional carboxyl group of benzoic acid can only undergo an esterification reaction with the terminal hydroxyl group of the polyester chain to form a benzoyl end group. This capping process significantly reduces the content of free hydroxyl groups and carboxyl groups in the polyester molecular chain, thereby greatly reducing the possibility of attack on the ester bond by external moisture or acids and bases and improving the hydrolysis stability of the polyester. At the same time, the benzene ring structure in the benzoyl group has excellent ultraviolet absorption and antioxidant capabilities. The conjugated effect of the benzene ring can effectively absorb the high-energy radiation of ultraviolet rays, thereby protecting the ester bond from photo-degradation. In addition, the benzoyl group has high thermal stability and can significantly delay the thermal degradation and oxidative degradation processes of the molecular chain when exposed to high temperature or oxidative environment. The acid value of the polyester reflects the content of free carboxyl groups in the system, and the free carboxyl groups are the main active sites for the hydrolysis of the polyester.In the gradual polycondensation reaction, the acid value is gradually reduced by controlling the acid value to eventually reach an extremely low level, ensuring that the carboxyl groups in the polyester molecular chain are almost completely involved in the reaction, thereby minimizing the hydrolysis sensitivity.

[0023] During the synthesis of polyphosphazene, hexachlorocyclotriphosphazene undergoes ring-opening polymerization under high temperature conditions to generate linear polyphosphazene chains. The ring tension of hexachlorocyclotriphosphazene causes it to cleave under high temperature conditions. At the same time, the high polarity and high reactivity of the phosphorus-nitrogen bond enable the cyclic monomer to further open the ring to form a linear long chain structure. The alternating phosphorus-nitrogen main chain structure gives the material itself excellent weather resistance. The presence of phosphorus provides strong flame retardancy and antioxidant properties, while the lone pair of electrons of nitrogen enhances the chemical stability of the main chain through interaction with phosphorus. This chemical stability is reflected in its high resistance to ultraviolet radiation, because there are no double bonds or other functional groups that are easily excited by ultraviolet rays in the main chain, thereby reducing the possibility of photodegradation. In addition, the high polarity of the phosphorus-nitrogen main chain also makes it resistant to oxidants to a certain extent, which can slow down the degradation rate of the material in a high-oxygen environment. The reaction of polyphosphazene with 2,6-di-tert-butylphenol and potassium carbonate causes some of the chlorine atoms on the polyphosphazene chain to be replaced by phenolic groups. Potassium carbonate, as a weak alkaline reagent, can activate the protons of the phenolic hydroxyl group and convert it into a more reactive phenolic anion, thereby promoting the nucleophilic substitution reaction with the chlorine atoms on the polyphosphazene chain. The benzene ring in the 2,6-di-tert-butylphenol molecule effectively absorbs ultraviolet radiation through a conjugated π electron system, reducing the direct damage of ultraviolet light to the polyphosphazene chain. This ultraviolet shielding ability enables the polyphosphazene hybrid after phenolic group substitution to maintain high chemical stability under long-term ultraviolet irradiation environment. Secondly, the two tert-butyl substituents on the benzene ring provide a significant steric hindrance effect, further protecting the chemical environment around the phenolic group, making it less likely to be oxidized or decomposed under oxidative stress conditions, thereby improving the antioxidant properties of the material. In addition, the presence of tert-butyl groups also increases the hydrophobicity of the polyphosphazene material, reduces the risk of water molecules corroding the material, and thus improves its hydrolysis stability. After the phenol substitution reaction is completed, light stabilizers, carbodiimides and catalysts are finally added for hybrid modification. By introducing additional chemical modifications, the stability of polyphosphazene hybrids under light aging and heat aging conditions is improved. The main function of the light stabilizer is to further reduce the destructive effect of ultraviolet rays on the polyphosphazene main chain by absorbing or scattering ultraviolet energy. At the same time, the antioxidant groups in its molecular structure can capture free radicals triggered by ultraviolet radiation, thereby inhibiting the occurrence of photooxidation chain reactions. Carbodiimides act as crosslinkers and react with phenolic groups or other active sites in the polyphosphazene molecular chain to form a partially crosslinked structure. The crosslinking reaction restricts the free movement of the polyphosphazene chain segments at the molecular scale, improves the thermal stability of the material, and enhances the durability of the material under high temperature or oxidative environments.

[0024] In the synthesis process of the PDMS-PEG block copolymer, polydimethylsiloxane and methoxypolyethylene glycol are used for an acid-catalyzed reaction to form a block structure. The main chain of PDMS is composed of silicon-oxygen bonds, which have a high bond energy and extremely strong chemical stability, and have a very high resistance to heat, oxidants, and ultraviolet radiation. This chemical stability is the basis for improving the weather resistance of the material. In the reaction, the acid catalyst promotes the condensation reaction between the silanol groups at the ends of PDMS and the hydroxyl groups at the ends of PEG-ME to form silicon-oxygen bonds. The controllability of the condensation reaction is achieved through the optimization of reaction conditions and time, ensuring that the segments of PDMS and PEG are connected in a block form to form a copolymer with a well-defined phase-separated structure. The formation of the block copolymer realizes the synergistic effect of PDMS and PEG at the molecular level. The presence of the PDMS segment endows the material with excellent ultraviolet resistance and flexibility. The silicon-oxygen main chain of PDMS not only has a high bond energy and can resist degradation caused by ultraviolet radiation, but also its high flexibility makes the material less likely to undergo irreversible structural damage when subjected to mechanical stress or environmental stress. On the other hand, the PEG segment provides the material with a certain degree of hydrophilicity and interfacial wettability through its ether bonds, and this hydrophilicity can be used to improve the interfacial compatibility of the material with other components. In terms of weather resistance, the conjugated structure of the pyridine ring in 4-vinylpyridine can effectively absorb ultraviolet radiation and reduce the damage of ultraviolet rays to the material. In addition, the electronic structure of the pyridine ring can capture free radicals generated in an oxidative environment, thereby inhibiting the progress of the chain oxidation reaction. This antioxidant ability is crucial for improving the long-term weather resistance of the material. At the same time, the introduction of the polypyridine chain also provides the material with additional mechanical strength and thermal stability, enabling the polymer to maintain stable performance in high-temperature and high-stress environments. The combination of PDMS-PEG and the polypyridine chain further enhances the weather resistance of the material through intermolecular synergy. The flexibility and stability of the PDMS segment are complementary to the rigidity and antioxidant ability of the polypyridine segment, forming a PDMS-PEG block copolymer structure with both flexibility and chemical tolerance. In addition, the low surface energy property of PDMS makes the material surface have a certain degree of hydrophobicity, which can effectively reduce the erosion of water and pollutants on the material, thereby further improving its weather resistance performance.

[0025] As a preferred technical solution of the present invention, in S1, the mass ratio of terephthalic acid, isophthalic acid, ethylene glycol, neopentyl glycol, and 1,6-hexanediol is (450-460):(50-55):(160-170):(120-125):(20-25), for example, it can be (450, 451, 452, 453, 454, 455, 456, 457, 458, 459 or 460):(50.0, 50.5, 51.0, 51.5, 52.0, 52.5, 53.0, 53.5, 54.0, 54.5 or 55.0):(160, 161, 162, 163, 164, 165, 166, 167, 168, 169 or 170):(120.0, 120.5, 121.0, 121.5, 122.0, 122.5, 123.0, 123.5, 124.0, 124.5 or 125.0):(20.0, 20.5, 21.0, 21.5, 22.0, 22.5, 23.0, 23.5, 24.0, 24.5 or 25.0), but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0026] In some alternative examples, the first temperature is 190-195 °C, for example, it can be 190.0 °C, 190.5 °C, 191.0 °C, 191.5 °C, 192.0 °C, 192.5 °C, 193.0 °C, 193.5 °C, 194.0 °C, 194.5 °C or 195.0 °C, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0027] In some alternative examples, the second temperature is 210-215 °C, for example, it can be 210.0 °C, 210.5 °C, 211.0 °C, 211.5 °C, 212.0 °C, 212.5 °C, 213.0 °C, 213.5 °C, 214.0 °C, 214.5 °C or 215.0 °C, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0028] In some alternative examples, the third temperature is 240-245 °C, for example, it can be 240.0 °C, 240.5 °C, 241.0 °C, 241.5 °C, 242.0 °C, 242.5 °C, 243.0 °C, 243.5 °C, 244.0 °C, 244.5 °C or 245.0 °C, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0029] As a preferred technical solution of the present invention, in S2, the fourth temperature is 280 - 285 °C, for example, it can be 280.0 °C, 280.5 °C, 281.0 °C, 281.5 °C, 282.0 °C, 282.5 °C, 283.0 °C, 283.5 °C, 284.0 °C, 284.5 °C or 285.0 °C, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0030] In some alternative examples, the holding time at the fourth temperature is 2 - 3 h, for example, it can be 2.0 h, 2.1 h, 2.2 h, 2.3 h, 2.4 h, 2.5 h, 2.6 h, 2.7 h, 2.8 h, 2.9 h or 3.0 h, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0031] In some alternative examples, the mass ratio of the polyphosphazene, light stabilizer 1577, N,N'-dicyclohexylcarbodiimide to 4-dimethylaminopyridine is (20 - 25):(40 - 45):(2 - 3):(2 - 3), for example, it can be (20.0, 20.5, 21.0, 21.5, 22.0, 22.5, 23.0, 23.5, 24.0, 24.5 or 25.0):(40.0, 40.5, 41.0, 41.5, 42.0, 42.5, 43.0, 43.5, 44.0, 44.5 or 45.0):(2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9 or 3.0):(2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9 or 3.0).

[0032] In some alternative examples, the fifth temperature is 80 - 85 °C, for example, it can be 80.0 °C, 80.5 °C, 81.0 °C, 81.5 °C, 82.0 °C, 82.5 °C, 83.0 °C, 83.5 °C, 84.0 °C, 84.5 °C or 85.0 °C, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0033] In some alternative examples, the reaction time at the fifth temperature is 12 - 13 h, for example, it can be 12.0 h, 12.1 h, 12.2 h, 12.3 h, 12.4 h, 12.5 h, 12.6 h, 12.7 h, 12.8 h, 12.9 h or 13.0 h, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0034] In some alternative examples, the mass fraction of the hydrochloric acid solution is 5 - 8 wt.%, for example, it can be 5.0 wt.%, 5.3 wt.%, 5.6 wt.%, 5.9 wt.%, 6.2 wt.%, 6.5 wt.%, 6.8 wt.%, 7.1 wt.%, 7.4 wt.%, 7.7 wt.% or 8.0 wt.%, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0035] As a preferred technical solution of the present invention, in S3, the mass ratio of polydimethylsiloxane, polyethylene glycol monomethyl ether and p-toluenesulfonic acid is (100 - 110):(20 - 25):(0.5 - 1), for example, it can be (100, 101, 102, 103, 104, 105, 106, 107, 108, 109 or 110):(20.0, 20.5, 21.0, 21.5, 22.0, 22.5, 23.0, 23.5, 24.0, 24.5 or 25.0):(0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95 or 1), but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0036] In some alternative examples, the sixth temperature is 70 - 75 °C, for example, it can be 70.0 °C, 70.5 °C, 71.0 °C, 71.5 °C, 72.0 °C, 72.5 °C, 73.0 °C, 73.5 °C, 74.0 °C, 74.5 °C or 75.0 °C, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0037] In some alternative examples, the reaction time at the sixth temperature is 10 - 11 h, for example, it can be 10.0 h, 10.1 h, 10.2 h, 10.3 h, 10.4 h, 10.5 h, 10.6 h, 10.7 h, 10.8 h, 10.9 h or 11.0 h, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0038] As a preferred technical solution of the present invention, in S4, the mass ratio of the polyphosphazene hybrid, polyester matrix and PDMS-PEG block copolymer is (2.5 - 3):100:(3 - 4), for example, it can be (2.5, 2.55, 2.6, 2.65, 2.7, 2.75, 2.8, 2.85, 2.9, 2.95 or 3):100:(3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9 or 4.0), but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0039] In some alternative embodiments, the seventh temperature is 135 - 140 °C. For example, it can be 135.0 °C, 135.5 °C, 136.0 °C, 136.5 °C, 137.0 °C, 137.5 °C, 138.0 °C, 138.5 °C, 139.0 °C, or 139.5 °C, 140.0 °C. However, it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0040] In a second aspect, the present invention provides a highly weather-resistant polyester resin prepared by the preparation method described in the first aspect.

[0041] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) In the polyester matrix, a benzene ring structure and benzoyl end groups are introduced. The conjugated π-electron system can absorb ultraviolet light, protecting the ester bonds in the main chain from photo-degradation. The 2,6-di-tert-butylphenol introduced by phenolic substitution further enhances the anti-ultraviolet ability. Its benzene ring structure absorbs ultraviolet light, while the steric hindrance of the tert-butyl group stabilizes the molecular structure, avoiding decomposition caused by ultraviolet radiation. The PDMS segment also has extremely high ultraviolet stability, and the pyridine groups formed by the polymerization of 4-vinylpyridine disperse the ultraviolet energy through the conjugation effect and simultaneously capture the free radicals generated during the photo-oxidation process, preventing the chain degradation reaction triggered by ultraviolet light; (2) In the polyester matrix, the symmetric structure of neopentyl glycol and the two methyl groups on the central carbon provide significant steric hindrance, reducing the probability of water molecules attacking the ester bonds. The capping effect of benzoic acid significantly reduces the carboxyl group content at the ends of the polyester chains, improving the hydrolysis stability of the polyester. The hydrophobicity of the polyphosphazene material is significantly enhanced after phenolic substitution, and the hydrophobicity of the tert-butyl group further reduces the possibility of water molecules eroding the material. The PDMS segment in the PDMS-PEG block copolymer exhibits excellent hydrophobicity due to the chemical inertness and low polarity of its silicon-oxygen bonds, effectively preventing the penetration of water. Specific Embodiments

[0042] The technical solutions of the present invention will be described in detail below with reference to specific embodiments. The embodiments described herein are specific specific embodiments of the present invention and are used to illustrate the concept of the present invention; these descriptions are all explanatory and exemplary, and should not be construed as limiting the embodiments of the present invention and the protection scope of the present invention. Except for the embodiments described herein, those skilled in the art can also adopt other obvious technical solutions based on the content disclosed in the claims and the specification of the present application. These technical solutions include technical solutions that make any obvious substitutions and modifications to the embodiments described herein.

[0043] The chemical reagents used in the examples and comparative examples of the present invention are all commercially available products and have not been further purified.

[0044] Example 1

[0045] This embodiment provides a highly weather-resistant polyester resin and a preparation method thereof. The preparation method specifically includes the following steps:

[0046] S1, Under a nitrogen atmosphere, 450 parts of terephthalic acid, 50 parts of isophthalic acid, 160 parts of ethylene glycol, 120 parts of neopentyl glycol, and 20 parts of 1,6-hexanediol are mixed. The temperature is adjusted to 190 °C, 2 parts of tetrabutyl titanate are added, and the reaction is carried out until the acid value ≤ 30 mgKOH / g. Then the temperature is raised to 210 °C, 5 parts of maleic anhydride are added, the temperature is adjusted to 240 °C, and the pressure is reduced to 10 KPa for continuous reaction. When the acid value drops to 15 mgKOH / g, 8 parts of benzoic acid are added, and the reaction is continued until the acid value ≤ 5 mgKOH / g. Then it is cooled to 160 °C and reserved to obtain a polyester matrix.

[0047] S2, Hexachlorocyclotriphosphazene is placed under a nitrogen atmosphere and heated to 280 °C for heat preservation for 2 h. After cooling, it is dispersed in tetrahydrofuran to obtain polyphosphazene. 20 parts of polyphosphazene are dispersed in DMF, 30 parts of 2,6-di-tert-butylphenol and 20 parts of potassium carbonate are added, and the reaction is carried out at 80 °C for 12 h under a nitrogen atmosphere. After the reaction is completed, potassium carbonate is removed by filtration, washed with a 5.0 wt.% hydrochloric acid solution, and then washed with water until neutral to obtain a phenolic-substituted product. Then 40 parts of light stabilizer 1577, 2 parts of N,N'-dicyclohexylcarbodiimide, and 2 parts of 4-dimethylaminopyridine are added to the phenolic-substituted product, and the reaction is carried out at 80 °C. After drying, a polyphosphazene hybrid is obtained.

[0048] S3, 100 parts of polydimethylsiloxane, 20 parts of polyethylene glycol monomethyl ether, and 0.5 part of p-toluenesulfonic acid are mixed. The temperature is adjusted to 80 °C under a nitrogen atmosphere, and after the reaction is completed, it is washed and dried to obtain PDMS-PEG. Then 30 parts of PDMS-PEG, 50 parts of 4-vinylpyridine, and 1 part of azobisisobutyronitrile are dispersed in toluene, and the temperature is adjusted to 70 °C under a nitrogen atmosphere for reaction for 10 h. After precipitation and drying, a PDMS-PEG block copolymer is obtained.

[0049] S4, 2.5 parts of the polyphosphazene hybrid are added to 100 parts of the polyester matrix. After mixing evenly, the temperature is adjusted to 135 °C, and then 3 parts of the PDMS-PEG block copolymer are added. After mixing evenly, it is extruded to obtain a highly weather-resistant polyester resin.

[0050] Example 2

[0051] This embodiment provides a highly weather-resistant polyester resin and a preparation method thereof. The preparation method specifically includes the following steps:

[0052] S1, Under a nitrogen atmosphere, 460 parts of terephthalic acid, 55 parts of isophthalic acid, 163 parts of ethylene glycol, 122 parts of neopentyl glycol, and 25 parts of 1,6 - hexanediol were mixed. The temperature was adjusted to 191°C, and 2 parts of tetrabutyl titanate were added. The reaction was carried out until the acid value ≤ 30 mgKOH / g. Then the temperature was raised to 211°C, 5.3 parts of maleic anhydride were added, and the temperature was adjusted to 244°C. The pressure was reduced to 10 KPa and the reaction continued. When the acid value dropped to 15 mg KOH / g, 8.4 parts of benzoic acid were added, and the reaction continued until the acid value ≤ 5 mg KOH / g. Then the temperature was lowered to 160°C for standby to obtain the polyester matrix;

[0053] S2, Hexachlorocyclotriphosphazene was placed under a nitrogen atmosphere and heated to 285°C for insulation for 2.3 h. After cooling, it was dispersed in tetrahydrofuran to obtain polyphosphazene. 25 parts of polyphosphazene were dispersed in DMF, 35 parts of 2,6 - di - tert - butylphenol and 20 parts of potassium carbonate were added. Under a nitrogen atmosphere, the temperature was adjusted to 85°C and the reaction was carried out for 12.6 h. After the reaction ended, potassium carbonate was removed by filtration, washed with 8.0 wt.% hydrochloric acid solution, and then washed with water until neutral to obtain the phenol - substituted product. Then 43 parts of light stabilizer 1577, 2.3 parts of N,N'-dicyclohexylcarbodiimide, and 2.4 parts of 4 - dimethylaminopyridine were added to the phenol - substituted product, and the reaction was carried out at 85°C. After drying, the polyphosphazene hybrid was obtained;

[0054] S3, 102 parts of polydimethylsiloxane, 24 parts of polyethylene glycol monomethyl ether, and 1 part of p - toluenesulfonic acid were mixed. Under a nitrogen atmosphere, the temperature was adjusted to 82°C. After the reaction ended, it was washed and dried to obtain PDMS - PEG. Then 35 parts of PDMS - PEG, 50 parts of 4 - vinylpyridine, and 1.4 parts of azobisisobutyronitrile were dispersed in toluene. Under a nitrogen atmosphere, the temperature was adjusted to 73°C and the reaction was carried out for 10.4 h. After precipitation and drying, the PDMS - PEG block copolymer was obtained;

[0055] S4, 3 parts of the polyphosphazene hybrid were added to 100 parts of the polyester matrix. After mixing evenly, the temperature was adjusted to 137°C, and then 3.4 parts of the PDMS - PEG block copolymer were added. After mixing evenly, it was extruded to obtain a highly weather - resistant polyester resin.

[0056] Example 3

[0057] This example provides a highly weather - resistant polyester resin and its preparation method. The preparation method specifically includes the following steps:

[0058] S1. Under a nitrogen atmosphere, 455 parts of terephthalic acid, 54 parts of isophthalic acid, 170 parts of ethylene glycol, 125 parts of neopentyl glycol, and 23 parts of 1,6 - hexanediol were mixed. The temperature was adjusted to 194°C, and 2 parts of tetrabutyl titanate were added. The reaction was carried out until the acid value ≤ 30 mgKOH / g. Then the temperature was raised to 215°C, 5.7 parts of maleic anhydride were added, and the temperature was adjusted to 245°C. The pressure was reduced to 10 KPa and the reaction continued. When the acid value dropped to 15 mgKOH / g, 9.0 parts of benzoic acid were added, and the reaction continued until the acid value ≤ 5 mgKOH / g. Then the temperature was lowered to 160°C for standby to obtain the polyester matrix;

[0059] S2. Hexachlorocyclotriphosphazene was placed under a nitrogen atmosphere and heated to 281°C for 3 h of insulation. After cooling, it was dispersed in tetrahydrofuran to obtain polyphosphazene. 21 parts of polyphosphazene were dispersed in DMF, 33 parts of 2,6 - di - tert - butylphenol and 20 parts of potassium carbonate were added. Under a nitrogen atmosphere, the temperature was adjusted to 84°C and the reaction was carried out for 13.0 h. After the reaction ended, potassium carbonate was removed by filtration, washed with 6.0 wt.% hydrochloric acid solution, and then washed with water until neutral to obtain the phenol - substituted product. Then, 45 parts of light stabilizer 1577, 2.7 parts of N,N'-dicyclohexylcarbodiimide, and 3.0 parts of 4 - dimethylaminopyridine were added to the phenol - substituted product, and the reaction was carried out at 84°C. After drying, the polyphosphazene hybrid was obtained;

[0060] S3. 110 parts of polydimethylsiloxane, 25 parts of polyethylene glycol monomethyl ether, and 0.7 part of p - toluenesulfonic acid were mixed. Under a nitrogen atmosphere, the temperature was adjusted to 85°C. After the reaction ended, it was washed and dried to obtain PDMS - PEG. Then, 33 parts of PDMS - PEG, 50 parts of 4 - vinylpyridine, and 2.0 parts of azobisisobutyronitrile were dispersed in toluene. Under a nitrogen atmosphere, the temperature was adjusted to 71°C and the reaction was carried out for 11.0 h. After precipitation and drying, the PDMS - PEG block copolymer was obtained;

[0061] S4. 2.7 parts of the polyphosphazene hybrid were added to 100 parts of the polyester matrix. After mixing evenly, the temperature was adjusted to 140°C, and then 4.0 parts of the PDMS - PEG block copolymer were added. After mixing evenly, it was extruded to obtain a highly weather - resistant polyester resin.

[0062] Example 4

[0063] This example provides a highly weather - resistant polyester resin and its preparation method. The preparation method specifically includes the following steps:

[0064] S1, Under a nitrogen atmosphere, 452 parts of terephthalic acid, 52 parts of isophthalic acid, 167 parts of ethylene glycol, 121 parts of neopentyl glycol, and 21 parts of 1,6 - hexanediol were mixed. The temperature was adjusted to 195°C, and 2 parts of tetrabutyl titanate were added. The reaction was carried out until the acid value ≤ 30 mgKOH / g. Then the temperature was raised to 214°C, 6.0 parts of maleic anhydride were added, and the temperature was adjusted to 242°C. The pressure was reduced to 10 KPa and the reaction continued. When the acid value dropped to 15 mgKOH / g, 8.7 parts of benzoic acid were added, and the reaction continued until the acid value ≤ 5 mgKOH / g. Then the temperature was lowered to 160°C for standby to obtain the polyester matrix;

[0065] S2, Hexachlorocyclotriphosphazene was placed under a nitrogen atmosphere and heated to 284°C for insulation for 2.7 h. After cooling, it was dispersed in tetrahydrofuran to obtain polyphosphazene. 23 parts of polyphosphazene were dispersed in DMF, 31 parts of 2,6 - di - tert - butylphenol and 20 parts of potassium carbonate were added. Under a nitrogen atmosphere, the temperature was adjusted to 81°C and the reaction was carried out for 12.2 h. After the reaction ended, potassium carbonate was removed by filtration, washed with a 7.0 wt.% hydrochloric acid solution, and then washed with water until neutral to obtain the phenol - substituted product. Then, 41 parts of light stabilizer 1577, 3.0 parts of N,N'-dicyclohexylcarbodiimide, and 2.8 parts of 4 - dimethylaminopyridine were added to the phenol - substituted product, and the reaction was carried out at 81°C. After drying, the polyphosphazene hybrid was obtained;

[0066] S3, 107 parts of polydimethylsiloxane, 21 parts of polyethylene glycol monomethyl ether, and 0.6 part of p - toluenesulfonic acid were mixed. Under a nitrogen atmosphere, the temperature was adjusted to 84°C. After the reaction ended, it was washed and dried to obtain PDMS - PEG. Then, 31 parts of PDMS - PEG, 50 parts of 4 - vinylpyridine, and 1.7 parts of azobisisobutyronitrile were dispersed in toluene. Under a nitrogen atmosphere, the temperature was adjusted to 75°C and the reaction was carried out for 10.9 h. After precipitation and drying, the PDMS - PEG block copolymer was obtained;

[0067] S4, 2.9 parts of the polyphosphazene hybrid were added to 100 parts of the polyester matrix. After mixing evenly, the temperature was adjusted to 138°C, and then 3.7 parts of the PDMS - PEG block copolymer were added. After mixing evenly, it was extruded to obtain a highly weather - resistant polyester resin.

[0068] Comparative Example 1

[0069] This comparative example provides a highly weather - resistant polyester resin and its preparation method. The difference from Example 1 is that the mass part of benzoic acid is 1, which is 7 parts less than that in Example 1, and other process parameters and operating conditions are exactly the same as those in Example 1.

[0070] Comparative Example 2

[0071] This comparative example provides a highly weather-resistant polyester resin and its preparation method. The difference from Example 1 is that the mass portion of 2,6-di-tert-butylphenol is 5, which is 25 parts less than that in Example 1, and other process parameters and operating conditions are exactly the same as those in Example 1.

[0072] Comparative Example 3

[0073] This comparative example provides a highly weather-resistant polyester resin and its preparation method. The difference from Example 1 is that the mass portion of 4-vinylpyridine is 10, which is 40 parts less than that in Example 1, and other process parameters and operating conditions are exactly the same as those in Example 1.

[0074] Comparative Example 4

[0075] This comparative example provides a highly weather-resistant polyester resin and its preparation method. The difference from Example 1 is that the mass portion of maleic anhydride is 1, which is 4 parts less than that in Example 1, and other process parameters and operating conditions are exactly the same as those in Example 1.

[0076] Take equal amounts of the highly weather-resistant polyester resins prepared in the examples and comparative examples, melt-extrude the polyester resin raw materials, and cool and form them on a casting drum to make polyester resin films, and conduct weather resistance tests on these polyester resin films. The test method for ultraviolet resistance is GB / T 14522-2008; the test method for comprehensive aging is GB / T 16422.2-2014; the test method for hydrolysis resistance is IEC 60068-2-78:2012; the test method for yellowing index is ASTM E313-20; the test method for tensile test is GB / T1040.3-2006. The test results are shown in Table 1.

[0077] Table 1 Test Results of Highly Weather-Resistant Polyester Resins in Examples 1-4 and Comparative Examples 1-4

[0078]

[0079] As can be seen from Table 1, in Comparative Example 1, the amount of benzoic acid is insufficient. As a capping agent, its insufficiency will lead to an increase in the residual carboxyl end groups in the material, a decrease in hydrolysis resistance, and more prone to degradation during photooxidation, resulting in an increase in the yellowing index. In Comparative Example 2, 2,6-di-tert-butylphenol is insufficient, and its insufficiency leads to a decrease in ultraviolet resistance, a decrease in hydrolysis stability, and an increase in the yellowing index. In Comparative Example 3, 4-vinylpyridine is insufficient. The conjugated structure of the pyridine ring in 4-vinylpyridine can effectively absorb ultraviolet radiation, and at the same time, the electronic structure of the pyridine ring can capture free radicals generated in the oxidative environment. Therefore, the ultraviolet resistance decreases and the yellowing index increases. In Comparative Example 4, the amount of maleic anhydride is insufficient. Maleic anhydride is an active site in the molecular structure, and its insufficiency will lead to a decrease in the crosslinking degree. Therefore, the ultraviolet resistance decreases, the comprehensive aging test performance decreases, and the yellowing index increases.

[0080] The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by any person skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A preparation method of a highly weather-resistant polyester resin, characterized in that, The preparation method includes: S1. Mix terephthalic acid, isophthalic acid, ethylene glycol, neopentyl glycol, and 1,6 - hexanediol, and add tetrabutyl titanate, maleic anhydride, and benzoic acid to obtain a polyester matrix; S2. Place hexachlorocyclotriphosphazene in a nitrogen atmosphere, keep warm to obtain polyphosphazene, disperse the polyphosphazene in DMF, add 2,6 - di - tert - butylphenol and potassium carbonate, react to obtain a phenolic - substituted product, and then add light stabilizer 1577, N,N'-dicyclohexylcarbodiimide, and 4 - dimethylaminopyridine to the phenolic - substituted product to obtain a polyphosphazene hybrid; S3. Mix polydimethylsiloxane, methoxypolyethylene glycol, and p - toluenesulfonic acid, react to obtain PDMS - PEG, and then disperse PDMS - PEG, 4 - vinylpyridine, and azobisisobutyronitrile in toluene, react to obtain a PDMS - PEG block copolymer; S4. Add the polyphosphazene hybrid to the polyester matrix, and then add the PDMS - PEG block copolymer to obtain a highly weather - resistant polyester resin; The mass ratio of terephthalic acid, tetrabutyl titanate, maleic anhydride, and benzoic acid is (450 - 460):2:(5 - 6):(8 - 9); The mass ratio of polyphosphazene, 2,6 - di - tert - butylphenol, and potassium carbonate is (20 - 25):(30 - 35):20; The mass ratio of PDMS - PEG, 4 - vinylpyridine, and azobisisobutyronitrile is (30 - 35):50:(1 - 2).

2. The preparation method of a highly weather-resistant polyester resin according to claim 1, characterized in that, In S1: The mass ratio of terephthalic acid, isophthalic acid, and ethylene glycol is (450 - 460):(50 - 55):(160 - 170).

3. The preparation method of a highly weather-resistant polyester resin according to claim 1, characterized in that, In S1: The mass ratio of terephthalic acid, neopentyl glycol, and 1,6 - hexanediol is (450 - 460):(120 - 125):(20 - 25).

4. The preparation method of a highly weather-resistant polyester resin according to claim 1, characterized in that, In S2: The mass ratio of polyphosphazene, light stabilizer 1577, N,N'-dicyclohexylcarbodiimide, and 4 - dimethylaminopyridine is (20 - 25):(40 - 45):(2 - 3):(2 - 3).

5. The preparation method of a highly weather-resistant polyester resin according to claim 1, characterized in that, In S3: The mass ratio of polydimethylsiloxane, methoxypolyethylene glycol, and p - toluenesulfonic acid is (100 - 110):(20 - 25):(0.5 - 1).

6. The preparation method of a highly weather-resistant polyester resin according to claim 1, characterized in that, In S4: The mass ratio of the polyphosphazene hybrid, polyester matrix, and PDMS - PEG block copolymer is (2.5 - 3):100:(3 - 4).

7. A highly weather - resistant polyester resin obtained by the preparation method according to any one of claims 1 - 6.

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